Tool wear mechanisms in turning titanium-aluminum-vanadium using tungsten carbide and polycrystalline diamond inserts

NASA Astrophysics Data System (ADS)

Schrock, David James

The objective of this work is to identify some of the tool wear mechanisms at the material level for the machining of titanium and to provide some understanding of these mechanisms for use in physics based tool wear models. Turning experiments were conducted at cutting speeds of 61m/min, 91m/min, and 122m/min on Ti-6Al-4V, an alloy of titanium, using two different grades of tungsten carbide cutting inserts and one grade of polycrystalline diamond inserts. Three-dimensional wear data and two-dimensional wear profiles of the rake face were generated using Confocal Laser Scanning Microscopy to quantify the tool wear mechanisms. Additionally, the microstructure of the deformed work material (chip) and un-deformed parent material (work piece) were studied using Orientation Imaging Microscopy (OIM). Observations from tool wear studies on the PCD inserts revealed the presence of two fundamentally different wear mechanisms operating at the different cutting speeds. Microstructural analyses of the chip and the work material showed phase dependent tool wear mechanisms for machining titanium. There is a high likelihood of phase change occurring in the work material during machining, with a transformation from the alpha phase to the beta phase. The observed dramatic increase in wear is attributed to a combination of increased diffusivity in the beta phase of the titanium alloy in conjunction with a higher degree of recrystallization of the prior beta phase upon cooling. Results of other observations such as the influence of carbide grain size on tool wear are also discussed.

Effect of bionic coupling units' forms on wear resistance of gray cast iron under dry linear reciprocating sliding condition

NASA Astrophysics Data System (ADS)

Pang, Zuobo; Zhou, Hong; Xie, Guofeng; Cong, Dalong; Meng, Chao; Ren, Luquan

2015-07-01

In order to get close to the wear form of guide rails, the homemade linear reciprocating wear testing machine was used for the wear test. In order to improve the wear-resistance of gray cast iron guide rail, bionic coupling units of different forms were manufactured by a laser. Wear behavior of gray-cast-iron with bionic-coupling units has been studied under dry sliding condition at room temperature using the wear testing machine. The wear resistance was evaluated by means of weight loss measurement and wear morphology. The results indicated that bionic coupling unit could improve the wear resistance of gray cast iron. The wear resistance of gray cast iron with reticulation bionic coupling unit is the best. When the load and speed changed, reticulation bionic coupling unit still has excellent performance in improving the wear resistance of gray cast iron.

Wear of human enamel: a quantitative in vitro assessment.

PubMed

Kaidonis, J A; Richards, L C; Townsend, G C; Tansley, G D

1998-12-01

Many factors influence the extent and rate at which enamel wears. Clinical studies in humans are limited by difficulties in the accurate quantification of intra-oral wear and by a lack of control over the oral environment. The purpose of this study was to determine the wear characteristics of human dental enamel under controlled experimental conditions. An electro-mechanical tooth wear machine, in which opposing enamel surfaces of sectioned, extracted teeth were worn under various conditions, was used to simulate tooth grinding or bruxism. Enamel surface wear was quantified by weight to an accuracy of 0.1 mg, with water uptake and loss controlled. The variables considered included the structure and hardness of enamel, facet area, duration of tooth contact, relative speed of opposing surfaces, temperature, load, pH, and the nature of the lubricant. Enamel wear under non-lubricated conditions increased with increasing load over the range of 1.7 to 16.2 kg. The addition of a liquid lubricant (pH = 7) reduced enamel wear up to 6.7 kg, but when the load increased above this threshold, the rate of wear increased dramatically. With the viscosity of the lubricant constant and pH = 3, the rate of wear was further reduced to less than 10% of the non-lubricated rate at 9.95 kg, after which the rate again increased substantially. Under more extreme conditions (pH = 1.2, simulating gastric acids), the wear was excessive under all experimental loads. When saliva was used as a lubricant, the amount of wear was relatively low at 9.95 kg, but rapid wear occurred at 14.2 kg and above. These results indicate that under non-lubricated conditions, enamel wear remains low at high loads due to the dry-lubricating capabilities of fine enamel powder. Under lubricated conditions, low loads with an acidic lubricant lead to little enamel wear, whereas very low pH results in a high rate of wear under all loads.

Real-Time Closed Loop Modulated Turbine Cooling

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Culley, Dennis E.; Eldridge, Jeffrey; Jones, Scott; Woike, Mark; Cuy, Michael

2014-01-01

It has been noted by industry that in addition to dramatic variations of temperature over a given blade surface, blade-to-blade variations also exist despite identical design. These variations result from manufacturing variations, uneven wear and deposition over the life of the part as well as limitations in the uniformity of coolant distribution in the baseline cooling design. It is proposed to combine recent advances in optical sensing, actuation, and film cooling concepts to develop a workable active, closed-loop modulated turbine cooling system to improve by 10 to 20 the turbine thermal state over the flight mission, to improve engine life and to dramatically reduce turbine cooling air usage and aircraft fuel burn. A reduction in oxides of nitrogen (NOx) can also be achieved by using the excess coolant to improve mixing in the combustor especially for rotorcraft engines. Recent patents filed by industry and universities relate to modulating endwall cooling using valves. These schemes are complex, add weight and are limited to the endwalls. The novelty of the proposed approach is twofold 1) Fluidic diverters that have no moving parts are used to modulate cooling and can operate under a wide range of conditions and environments. 2) Real-time optical sensing to map the thermal state of the turbine has never been attempted in realistic engine conditions.

MS212--A Homogeneous Sputtered Solid Lubricant Coating for Use to 800 C

NASA Technical Reports Server (NTRS)

Sliney, Harold E.; Waters, William J.; Soltis, Richard

1997-01-01

Composite coatings containing chromium carbide, stable fluorides and silver were prepared by magnetron sputtering. The microstructure of the coatings is very homogeneous compared to that of plasma sprayed and sintered versions of the same chemical composition. Friction and wear of MS212-coated and baseline uncoated aluminum and Inconel X-750 are compared. At room temperature, the friction and wear of coated aluminum is dramatically better compared to the baseline. The acceptable load is limited by deformation of the soft aluminum substrate. In the case of the nickel alloy, lower friction is observed for the coated alloy at all temperatures up to the maximum test temperature of 800 C. Pin wear factors for sliding against the coated alloy are lower than the baseline at room temperature and 350 C, and comparable to baseline wear at higher test temperatures. Low baseline wear at high temperatures is due to the lubricious nature of the natural oxides formed on nickel-chromium alloys in a hot, oxidizing atmosphere. No load limit was found for coated Inconel X-750 at loads up to five times the load limit for coated aluminum.

Reconstructing cultural behavior from dental wear studies: is para-facets analysis approach scientifically valid?

PubMed

Sarig, Rachel; Tillier, Anne-marie

2014-06-01

It is common knowledge, that in archaic populations teeth were used as tools, this behavior can be studied by evaluating attrition patterns. Parafacets were defined as nonmasticatory wear areas that have no antagonist matching wear facets. The presence of the parafacets led to far-reaching conclusions regarding cultural interactions between Near Eastern Neanderthals and anatomically modern humans. This study was aimed to examine the identification of parafacets in some of the Qafzeh specimens. Based on findings of our research we suggest that the attrition facets mistakenly considered as parafacets are in fact the result of the static and dynamic occlusion. Therefore the observations induce much less dramatic interpretation. We here propose several guidelines that would be beneficial in that they aim to evaluate the parafacets with heightened accuracy. Copyright © 2014 Elsevier GmbH. All rights reserved.

Development of wear resistant NFSS-HA novel biocomposites and study of their tribological properties for orthopaedic applications.

PubMed

Younesi, M; Bahrololoom, M E; Fooladfar, H

2010-02-01

Implants made of nickel free austenitic stainless steel can reduce the toxic effect of released nickel ion and compounds from the conventional stainless steels. On the other hand, hydroxyapatite is a ceramic which has been used in orthopaedic applications due to its good osteoconductivity, biocompatibility and bioactivity. However, there is no evidence in the literature up to now on producing composites based on nickel free stainless steel and hydroxyapatite and study of their tribology. The aim of this work was to produce novel biocomposites made up of nickel free stainless steel with hydroxyapatite (prepared by heat treating bone ash) and studying their tribology under various loads in air and in Ringer's physiological solution. Different amounts of hydroxyapatite powder (10, 20, 30 and 40% Vol.) were added to this nickel free stainless steel powder to get the biocomposites. Variation of their density, hardness, wear resistance and friction with the ceramic (hydroxyapatite) content and wear load were investigated in air and in Ringer's solution. The density of the composites was decreased by increasing the volume percentage of the hydroxyapatite, while wear resistance of the composites was increased. The wear mechanism of these composites was changed by increasing the wear load and consequently the volume loss was enhanced dramatically. Furthermore, by increasing the sliding distance, the rate of volume loss was decreased slightly. The friction coefficient of the composites was also decreased by increasing the weight percentage of hydroxyapatite. Effect of the physiological Ringer's solution on wear resistance and friction coefficient of the composites was nearly negligible. The wear mechanisms of the samples were identified by studying the SEM images of the worn surfaces of the tested samples in different wear loads and HA contents. Copyright 2009 Elsevier Ltd. All rights reserved.

Skew And Twist Resistant Hydrodynamic Rotary Shaft Seal

DOEpatents

Dietle, Lannie; Kalsi, Manmohan Singh

2000-03-14

A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. Compared to prior art, this invention provides a dramatic reduction of seal and shaft wear in abrasive environments and provides a significant increase in seal life.

Commercialization of NASA's High Strength Cast Aluminum Alloy for High Temperature Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2003-01-01

In this paper, the commercialization of a new high strength cast aluminum alloy, invented by NASA-Marshall Space Flight Center, for high temperature applications will be presented. Originally developed to meet U.S. automotive legislation requiring low- exhaust emission, the novel NASA aluminum alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (450 F-750 F), which can lead to reducing part weight and cost as well as improving performance for automotive engine applications. It is an ideal low cost material for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. NASA alloy also offers greater wear resistance, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys, and the new alloy can be produced economically from sand, permanent mold and investment casting. Since 2001, this technology was licensed to several companies for automotive and marine internal combustion engines applications.

Understanding the differences between the wear of metal-on-metal and ceramic-on-metal total hip replacements.

PubMed

Figueiredo-Pina, C G; Yan, Y; Neville, A; Fisher, J

2008-04-01

Hip simulator studies have been carried out extensively to understand and test artificial hip implants in vitro as an efficient alternative to obtaining long-term results in vivo. Recent studies have shown that a ceramic-on-metal material combination lowers the wear by up to 100 times in comparison with a typical metal-on-metal design. The reason for this reduction remains unclear and for this reason this study has undertaken simple tribometer tests to understand the fundamental material loss mechanisms in two material combinations: metal-on-metal and ceramic-on-ceramic. A simple-configuration reciprocating pin-on-plate wear study was performed under open-circuit potential (OCP) and with applied cathodic protection (CP) in a serum solution using two tribological couples: firstly, cobalt-chromium (Co-Cr) pins against Co-Cr plates; secondly, Co-Cr pins against alumina (Al2O3) plates. The pin and plate surfaces prior to and after testing were examined by profilometry and scanning electron microscopy. The results showed a marked reduction in wear when CP was applied, indicating that total material degradation under the OCP condition was attributed to corrosion processes. The substitution of the Co-Cr pin with an Al2O3 plate also resulted in a dramatic reduction in wear, probably due to the reduction in the corrosion-wear interactions between the tribological pair.

The production and tribology of hard facing coatings for agricultural applications

NASA Astrophysics Data System (ADS)

Roffey, Paul

Abrasive wear is a significant issue in many industries but is of particular significance in agriculture. This research is being carried out due to the demand for a hard wearing, economical coating for use in the agricultural industry.A primary objective has been to review and develop an in depth understanding of the type of wear suffered by metal shares in agricultural soils. The affect of soil properties and abrasive wear environments on the amount of wear that occurs, and the way in which material properties can be used to reduce or prevent this has also been investigated. A review of the diverse range of soil properties, such as the mineral content, moisture content, soils strengths has been carried out in order to create an appropriate wear test procedure.The coatings developed for testing were modifications to an existing powder metallurgy coating. The modifications were made by the addition of selected hard phases to the powder prior to sintering. The resulting materials were characterised in terms of sinterability, hardness and abrasive wear resistance. Prior to commencing this work little or no data existed on the wear performance of the pre-existing coating. Wear resistance has been measured using a fixed ball micro-scale abrasive wear test (also known as the ball-cratering wear test) with SiC and SiO2 abrasives and also using a modified version of the ASTM G65 abrasive wear test which allowed testing in dry and wet modes. Limited field trials were performed to determine the abrasive wear resistance in real soil. Results from wear testing have determined that the optimum modification to the coating can improve performance compared to the unmodified coating.Detailed scanning electron microscopy (SEM) has been performed on the wear scars and has revealed the resultant wear mechanisms and role that the hard phase additions play in improving the wear resistance. The influence of the hard phase addition on the microstructure has also been studied.The wear volume and corresponding wear coefficient from laboratory studies have been used to determine the optimum level of addition that can be added to produce an improved wear resistance. The results show the optimum hard phase addition to be 100mum WC/W[2]C particles at around 10wt.% with 15 mum WC at 5wt.% also providing improved wear resistance.

An Overview of the Nuclear Electric Xenon Ion System (NEXIS) Activity

NASA Technical Reports Server (NTRS)

Randolph, Thomas M.; Polk, James E., Jr.

2004-01-01

The Nuclear Electric Xenon Ion System (NEXIS) research and development activity within NASA's Project Prometheus, was one of three proposals selected by NASA to develop thruster technologies for long life, high power, high specific impulse nuclear electric propulsion systems that would enable more robust and ambitious science exploration missions to the outer solar system. NEXIS technology represents a dramatic improvement in the state-of-the-art for ion propulsion and is designed to achieve propellant throughput capabilities >= 2000 kg and efficiencies >= 78% while increasing the thruster power to >= 20 kW and specific impulse to >= 6000 s. The NEXIS technology uses erosion resistant carbon-carbon grids, a graphite keeper, a new reservoir hollow cathode, a 65-cm diameter chamber masked to produce a 57-cm diameter ion beam, and a shared neutralizer architecture to achieve these goals. The accomplishments of the NEXIS activity so far include performance testing of a laboratory model thruster, successful completion of a proof of concept reservoir cathode 2000 hour wear test, structural and thermal analysis of a completed development model thruster design, fabrication of most of the development model piece parts, and the nearly complete vacuum facility modifications to allow long duration wear testing of high power ion thrusters.

Improved Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway

DTIC Science & Technology

2008-11-21

Research Laboratory (NSMRL) is seeking information from the eyewear industry that will provide prescription eyewear frames for use when wearing an EAB...Improved Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway by Alison America, MA Wayne G. Horn, MD...Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway Authors: Alison America, MA Wayne G. Horn, MD Naval Submarine Medical Research

High Strength and Wear Resistant Aluminum Alloy for High Temperature Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.; Chen, Po Shou

2003-01-01

Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent thermal growth stability, surface hardness and wear resistant properties.

An investigation of the microstructure, mechanical properties, and tribological performance of ultra high molecular weight polyethylene for applications in total joint arthroplasty

NASA Astrophysics Data System (ADS)

van Citters, Douglas W.

Ultra high molecular weight polyethylene (UHMWPE) is the most common bearing material in joint arthroplasty due to its biocompatibility, its wear resistance, and its mechanical toughness. Despite the favorable properties of UHMWPE and its success as a biomaterial, billions of dollars are spent annually to revise tens of thousands of failed artificial joints. Over half of these revision procedures are related to mechanical failure of the polymer bearing or osteolysis resulting from polymer wear. Contemporary material processing steps involving thermal treatment and/or radiation treatment seek to improve outcomes through improving the tribological properties of UHMWPE. However, it is widely recognized that achieving wear resistance through radiation-induced crosslinking comes at the cost of reduced mechanical properties. Moreover, current wear theories for orthopaedic UHMWPE are incomplete in that they predict zero wear in the absence of crossing motion. Wear nonetheless occurs in linear reciprocation, necessitating an alternate theory. The present work explains the effects of thermal treatments and radiation treatments on the properties of GUR1050 UHMWPE. A test matrix allows comparisons of different treatments across different test platforms. Characterization techniques include DSC, FTIR spectroscopy, tensile testing, x-ray diffraction, and electron microscopy. A novel quantitative stereology technique is developed to quantify crystallite size in the semicrystalline material. Seven clinically relevant materials are subjected to rolling-sliding tribotesting to determine polyethylene wear behavior in linear reciprocation. The multi-station tribotester employed for this work enables high throughput testing, and the specimen geometry allows direct measurement of wear rates without a gravimetric soak control. The results of the material characterization tests can be used to accurately predict the rolling-sliding wear behavior of UHMWPE. Wear rate is directly related to crystallite size divided by the material yield strength. A modification of the delamination theory of wear is proposed to explain the wear mechanism. The results and conclusions of the present study can be used to specify future UHMWPE treatments that might eliminate a toughness-reducing radiation dose while improving the wear properties of the polymer. Such treatments would improve the in vivo performance of UHMWPE and hence would improve orthopaedic surgery outcomes.

Comparative wear resistance of reinforced glass ionomer restorative materials.

PubMed

Yap, A U; Teo, J C; Teoh, S H

2001-01-01

This study investigated the wear resistance of three restorative reinforced glass ionomer cements (Fuji IX GP FAST [FJ], Miracle Mix [MM] and Ketac Silver [KS]). Microfilled (Silux [SX]) and mini-filled (Z100 [ZO]) composites were used for comparison. Six specimens were made for each material. The specimens were conditioned for one week in distilled water at 37 degrees C and subjected to wear testing at 20 MPa contact stress against SS304 counterbodies using a reciprocal compression-sliding wear instrumentation. Distilled water was used as lubricant. Wear depth (microm) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe's test (p<0.05). After 10,000 cycles of wear testing, ranking was as follows: KS>ZO>MM>FJ>SX. Wear ranged from 26.1 microm for SX to 71.5 microm for KS. The wear resistance of KS was significantly lower than FJ, MM and SX at all wear intervals. Although KS had significantly more wear than ZO at 2,000 to 6,000 cycles, no significant difference in wear was observed between these two materials at 8,000 and 10,000 cycles. Sintering of silver particles to glass ionomer cement (KS) did not appear to improve wear resistance. The simple addition of amalgam alloy to glass ionomer may improve wear resistance but results in poor aesthetics (silver-black color). FJ, which relies on improved chemistry instead of metal fillers, showed comparable wear resistance to the composites evaluated and is tooth-colored. It may serve as a potential substitute for composites in low-stress situations where fluoride release is desirable and aesthetic requirements are not high.

Influence of Laser Shock Texturing on W9 Steel Surface Friction Property

NASA Astrophysics Data System (ADS)

Fan, Yujie; Cui, Pengfei; Zhou, Jianzhong; Dai, Yibin; Guo, Erbin; Tang, Deye

2017-09-01

To improve surface friction property of high speed steel, micro-dent arrays on W9Mo3Cr4V surface were produced by laser shock processing. Friction test was conducted on smooth surface and texturing surface and effect of surface texturing density on friction property was studied. The results show that, under the same condition, friction coefficient of textured surface is lower than smooth surface with dent area density less than 6%, wear mass loss, width and depth of wear scar are smaller; Wear resistance of the surface is the best and the friction coefficient is the smallest when dent area density is 2.2%; Friction coefficient, wear mass loss, width and depth of wear scar increase correspondingly as density of dent area increases when dent area density is more than 2.2%. Abrasive wear and adhesive wear, oxidative wear appear in the wear process. Reasonable control of geometric parameters of surface texturing induced by laser shock processing is helpful to improve friction performance.

Association Between Adherence to Glasses Wearing During Amblyopia Treatment and Improvement in Visual Acuity.

PubMed

Maconachie, Gail D E; Farooq, Shegufta; Bush, Glen; Kempton, Julie; Proudlock, Frank A; Gottlob, Irene

2016-12-01

Occlusion dose monitors have helped establish that better adherence to occlusion is associated with improved visual outcomes in patients undergoing amblyopia treatment. However, the role of adherence to glasses wearing is unknown. To establish the feasibility and reliability of objectively monitoring adherence to glasses wearing using age-based norms, establish the association between adherence to glasses wearing and improvement in visual acuity (VA) after optical treatment and occlusion therapy, and analyze the effect of age, sex, refractive errors, type of amblyopia, and adherence to glasses wearing on improvement in VA. A prospective, observational, nonmasked, cohort study was conducted between June 8, 2008, and June 30, 2013, among patients at a pediatric ophthalmology clinic of a tertiary care hospital who were newly diagnosed with anisometropic and/or strabismic amblyopia and had not undergone previous treatment. The study consisted of a glasses phase (18 weeks) and a patching phase (glasses and occlusion for 10 hours per day for 12 weeks). Reliability of the glasses monitors was assessed by comparing diary entries and monitor recordings in adults. Objective monitoring of glasses wearing and occlusion. Adherence to glasses wearing (hours per day) and effect on VA. Among 20 children with anisometropia (mean [SD] age, 6.20 [2.16] years; 11 boys and 9 girls) and 20 with strabismic or mixed amblyopia (mean [SD] age, 4.90 [1.36] years; 10 boys and 10 girls), adherence to glasses wearing was successfully monitored in all but 1 patient. Agreement between diaries and monitored times wearing glasses in adults was high (intraclass correlation coefficient, 1.00; 95% CI, 0.999-1.00). Median (SD) adherence to glasses wearing was 70% (25.3%). A moderate correlation was observed between adherence to glasses wearing and percentage improvement in VA during the glasses phase (r = 0.462; P = .003). Multiple regression revealed that age (β = -0.535; P = .001), type of amblyopia (β = -0.347; P = .02), and adherence to glasses wearing (β = 0.287; P = .04) were independently associated with improvement in VA after the glasses phase and explained 42% of the variability (F3,35 = 8.457; P < .001). A strong correlation between glasses wearing and occlusion adherence was observed (r = 0.719; P < .001). The results suggest that adherence to glasses wearing is less than optimal and highly variable but is important in achieving good VA. This study emphasizes the importance of encouraging children to not only have good adherence to occlusion therapy but also to glasses wearing.

Gasification Slag and the Mechanisms by Which Phosphorous Additions Reduce Slag Wear and Corrosion in High Cr2O3 Refractories

NASA Astrophysics Data System (ADS)

Bennett, James; Nakano, Anna; Nakano, Jinichiro; Thomas, Hugh

Gasification is a high-temperature/high-pressure process that converts carbonaceous materials such as coal and/or petcoke into CO and H2, feedstock materials used in power generation and chemical production. Gasification is considered an important technology because of its high process efficiency and the ability to capture environmental pollutants such as CO2, SO3 and Hg. Ash impurities in the carbon feedstock materials melt and coalesce during gasification (1325-1575 °C), becoming slag that attaches to and flows down the gasifier sidewall, corroding and eroding the high Cr2O3 refractory liner used to protect the gasification chamber. Phosphate additions to high Cr2O3 refractory have been found to alter slag/refractory interactions and dramatically reduce refractory wear by the following mechanisms: a) spinel formation, b) slag chemistry changes, c) two phase liquid formation, and d) oxidation state changes. The mechanisms and how they work together to impact material wear/corrosion will be discussed.

The effects of wearing undersized lower-body compression garments on endurance running performance.

PubMed

Dascombe, Ben J; Hoare, Trent K; Sear, Joshua A; Reaburn, Peter R; Scanlan, Aaron T

2011-06-01

To examine whether wearing various size lower-body compression garments improves physiological and performance parameters related to endurance running in well-trained athletes. Eleven well-trained middle-distance runners and triathletes (age: 28.4 ± 10.0 y; height: 177.3 ± 4.7 cm; body mass: 72.6 ± 8.0 kg; VO2max: 59.0 ± 6.7 mL·kg-1·min-1) completed repeat progressive maximal tests (PMT) and time-to-exhaustion (TTE) tests at 90% VO2max wearing either manufacturer-recommended LBCG (rLBCG), undersized LBCG (uLBCG), or loose running shorts (CONT). During all exercise testing, several systemic and peripheral physiological measures were taken. The results indicated similar effects of wearing rLBCG and uLBCG compared with the control. Across the PMT, wearing either LBCG resulted in significantly (P < .05) increased oxygen consumption, O2 pulse, and deoxyhemoglobin (HHb) and decreased running economy, oxyhemoglobin, and tissue oxygenation index (TOI) at low-intensity speeds (8-10 km·h-1). At higher speeds (12-18 km·h-1), wearing LBCG increased regional blood flow (nTHI) and HHb values, but significantly lowered heart rate and TOI. During the TTE, wearing either LBCG significantly (P < .05) increased HHb concentration, whereas wearing uLBCG also significantly (P < .05) increased nTHI. No improvement in endurance running performance was observed in either compression condition. The results suggest that wearing LBCG facilitated a small number of cardiorespiratory and peripheral physiological benefits that appeared mostly related to improvements in venous flow. However, these improvements appear trivial to athletes, as they did not correspond to any improvement in endurance running performance.

Fretting wear study of surface modified Ni-Ti shape memory alloy.

PubMed

Tan, L; Crone, W C; Sridharan, K

2002-05-01

A combination of shape memory characteristics, pseudoelasticity, and good damping properties make near-equiatomic nickel-titanium (Ni-Ti) alloy a desirable candidate material for certain biomedical device applications. The alloy has moderately good wear resistance, however, further improvements in this regard would be beneficial from the perspective of reducing wear debris generation, improving biocompatibility, and preventing failure during service. Fretting wear tests of Ni-Ti in both austenitic and martensitic microstructural conditions were performed with the goal of simulating wear which medical devices such as stents may experience during surgical implantation or service. The tests were performed using a stainless steel stylus counter-wearing surface under dry conditions and also with artificial plasma containing 80 g/L albumen protein as lubricant. Additionally, the research explores the feasibility of surface modification by sequential ion implantation with argon and oxygen to enhance the wear characteristics of the Ni-Ti alloy. Each of these implantations was performed to a dose of 3 x 10(17) atom/cm(2) and an energy of 50 kV, using the plasma source ion implantation process. Improvements in wear resistance were observed for the austenitic samples implanted with argon and oxygen. Ion implantation with argon also reduced the surface Ni content with respect to Ti due to differential sputtering rates of the two elements, an effect that points toward improved biocompatibility.

Tooth wear and feeding ecology in mountain gorillas from Volcanoes National Park, Rwanda.

PubMed

Galbany, Jordi; Imanizabayo, Olive; Romero, Alejandro; Vecellio, Veronica; Glowacka, Halszka; Cranfield, Michael R; Bromage, Timothy G; Mudakikwa, Antoine; Stoinski, Tara S; McFarlin, Shannon C

2016-03-01

Ecological factors have a dramatic effect on tooth wear in primates, although it remains unclear how individual age contributes to functional crown morphology. The aim of this study is to determine how age and individual diet are related to tooth wear in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. We calculated the percent of dentine exposure (PDE) for all permanent molars (M1-M3) of known-age mountain gorillas (N = 23), to test whether PDE varied with age using regression analysis. For each molar position, we also performed stepwise multiple linear regression to test the effects of age and percentage of time spent feeding on different food categories on PDE, for individuals subject to long-term observational studies by the Dian Fossey Gorilla Fund International's Karisoke Research Center. PDE increased significantly with age for both sexes in all molars. Moreover, a significant effect of gritty plant root consumption on PDE was found among individuals. Our results support prior reports indicating reduced tooth wear in mountain gorillas compared to western gorillas, and compared to other known-aged samples of primate taxa from forest and savanna habitats. Our findings corroborate that mountain gorillas present very low molar wear, and support the hypothesis that age and the consumption of particular food types, namely roots, are significant determinants of tooth wear variation in mountain gorillas. Future research should characterize the mineral composition of the soil in the Virunga habitat, to test the hypothesis that the physical and abrasive properties of gritty foods such as roots influence intra- and interspecific patterns of tooth wear. © 2015 Wiley Periodicals, Inc.

Grading technologies for the manufacture of innovative cutting blades

NASA Astrophysics Data System (ADS)

Rostek, Tim; Homberg, Werner

2018-05-01

Cutting blades for harvesting applications are used in a variety of agricultural machines. These parts are in contact with highly abrasive lawn clippings and often wear out within hours which results in high expensive re-sharpening maintenance. This paper relates to manufacturing techniques enhancing the durability of cutting blades based on a structural analysis of the prevailing wear mechanisms containing chipping and abrasive wear. Each mechanism results in specific demands on the cutting edge's mechanical characteristics. The design of evaluation methods respectively is one issue of the paper. This is basis for approaches to improve the cutting edge performance on purpose. On option to improve abrasive wear resistance and, thus, service life is the application of locally graded steel materials as semi-finished products for self-sharpening cutting blades. These materials comprise a layered structure consisting of a hard, wear resistant layer and a relatively softer layer which is lesser wear resistant. As the cutting blade is subjected to wear conditions, the less wear resistant layer wears faster than the relatively more wear resistant harder layer revealing a durable cross section of the cutting edge and, thus, cutting performance. Anyways, chipping is another key issue on the cutting edge's lifetime. Here, the cutting edges cross section by means of geometry and grind respectively as well as its mechanical properties matter. FEM analysis reveal innovative options to optimize the cross section of the blade as well as thermomechanical strengthening add further strength to reduce chipping. This paper contains a comprehensive strategy to improve cutting blades with use of innovative manufacturing technologies which apply application-specific graded mechanical characteristics and, thus, significantly improved performance characteristics.

Oxidized zirconium on ceramic; Catastrophic coupling.

PubMed

Ozden, V E; Saglam, N; Dikmen, G; Tozun, I R

2017-02-01

Oxidized zirconium (Oxinium™; Smith & Nephew, Memphis, TN, USA) articulated with polyethylene in total hip arthroplasty (THA) appeared to have the potential to reduce wear dramatically. The thermally oxidized metal zirconium surface is transformed into ceramic-like hard surface that is resistant to abrasion. The exposure of soft zirconium metal under hard coverage surface after the damage of oxidized zirconium femoral head has been described. It occurred following joint dislocation or in situ succeeding disengagement of polyethylene liner. We reported three cases of misuse of Oxinium™ (Smith & Nephew, Memphis, TN, USA) heads. These three cases resulted in catastrophic in situ wear and inevitable failure although there was no advice, indication or recommendation for this use from the manufacturer. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Influences of die channel angles on microstructures and wear behaviors of AZ61 wrought magnesium alloy fabricated by extrusion-shear process

NASA Astrophysics Data System (ADS)

Hu, Hong-J.; Sun, Z.; Ou, Z.-W.

2016-12-01

Extrusion-shear (ES) process for magnesium alloy is a newly developed plastic deformation process, and ES process combines direct extrusion and two steps of ECAE (equal channel angular extrusion). To investigate the effects of the die channel angles on the microstructures and wear behaviors of AZ61 wrought magnesium alloy, the samples used in this study were fabricated by ES process with different die channel angles (120° and 135°). The microstructures of the samples were characterized by optical microscopy (OM), X-ray diffraction (XRD) and (SEM). The cumulative strains in the ES process were predicted by approaches of numerical simulation and theoretical calculation. To characterize the wear resistance of the samples, pin-on-disk tests under dry sliding conditions with various normal loads and reciprocating frequencies were conducted. To define the wear mechanisms of AZ61 magnesium alloy, the worn surfaces after wear tests were analyzed by SEM and energy-dispersive X-ray spectrometer (EDS). Based on the results obtained, die channel angles have significant influences on the grain refinements and wear behaviors of the samples. Decreasing channel angles of the ES die will not only refine the microstructures of magnesium alloys effectively and improve their harnesses, but also improve their wear resistance as decreasing channel angles results in higher friction coefficients and wear rates. With the increase in applied loads and frequencies, wear mechanisms change from mild wear (adhesion, abrasion and oxidation) to severe wear (delamination, plastic deformation and melting). In summary, the wear resistance of ES-processed AZ61 magnesium alloy could be improved by decreasing channel angles of ES dies.

Rasagiline for dysexecutive symptoms during wearing-off in Parkinson's disease: a pilot study.

PubMed

Rinaldi, Domiziana; Assogna, Francesca; Sforza, Michela; Tagliente, Stefania; Pontieri, Francesco E

2018-01-01

Wearing-off refers to the predictable worsening of motor and sometimes non-motor symptoms of Parkinson's disease occurring at the end of levodopa dose that improves with the next drug dose. Here, we investigated the efficacy of rasagiline on executive functions at the end of levodopa dose in patients displaying symptoms of wearing-off. Rasagiline was well-tolerated and produced a significant improvement at the Frontal Assessment Battery, together with improvement of motor symptoms at the end of levodopa dose. These results suggest that treatment of motor symptoms of wearing-off with rasagiline may be accompanied by improvement of executive functions, and further support the need for optimizing dopamine replacement therapy in fluctuating Parkinson's disease patients.

Effect of Copper Coated SiC Reinforcements on Microstructure, Mechanical Properties and Wear of Aluminium Composites

NASA Astrophysics Data System (ADS)

Kori, P. S.; Vanarotti, Mohan; Angadi, B. M.; Nagathan, V. V.; Auradi, V.; Sakri, M. I.

2017-08-01

Experimental investigations are carried out to study the influence of copper coated Silicon carbide (SiC) reinforcements in Aluminum (Al) based Al-SiC composites. Wear behavior and mechanical Properties like, ultimate tensile strength (UTS) and hardness are studied in the present work. Experimental results clearly revealed that, an addition of SiC particles (5, 10 and 15 Wt %) has lead in the improvement of hardness and ultimate tensile strength. Al-SiC composites containing the Copper coated SiC reinforcements showed better improvement in mechanical properties compared to uncoated ones. Characterization of Al-SiC composites are carried out using optical photomicrography and SEM analysis. Wear tests are carried out to study the effects of composition and normal pressure using Pin-On Disc wear testing machine. Results suggested that, wear rate decreases with increasing SiC composition, further an improvement in wear resistance is observed with copper coated SiC reinforcements in the Al-SiC metal matrix composites (MMC’s).

Inspection of wear particles in oils by using a fuzzy classifier

NASA Astrophysics Data System (ADS)

Hamalainen, Jari J.; Enwald, Petri

1994-11-01

The reliability of stand-alone machines and larger production units can be improved by automated condition monitoring. Analysis of wear particles in lubricating or hydraulic oils helps diagnosing the wear states of machine parts. This paper presents a computer vision system for automated classification of wear particles. Digitized images from experiments with a bearing test bench, a hydraulic system with an industrial company, and oil samples from different industrial sources were used for algorithm development and testing. The wear particles were divided into four classes indicating different wear mechanisms: cutting wear, fatigue wear, adhesive wear, and abrasive wear. The results showed that the fuzzy K-nearest neighbor classifier utilized gave the same distribution of wear particles as the classification by a human expert.

The Effect of Coatings on the Wear Behavior of Ti6Al4V Alloy Used in Biomedical Applications

NASA Astrophysics Data System (ADS)

Danışman, Ş.; Odabas, D.; Teber, M.

2018-01-01

The properties expected from implant materials are biocompatibility, long service life and wear resistance. The wear resistance of the implant materials varies according to the type of implant, usage area and the movement. The ability of implant material to be more compatible with biological tissues and to increase the useful life depends on the surface properties. Today many different kind of surface modification techniques are applying on medical and dental implant surfaces to improve surface specifications and wear resistance. In this study TiN, TiAlN, TiCN coatings were applied on Ti6Al4V alloy used as implant material by reactive magnetron sputtering method. The wear resistances of uncoated Ti6Al4V alloy and TiN, TiAlN, TiCN coatings were investigated at room temperature under dry conditions. The wear resistance at different load and different sliding rates were compared using an wear tester. The wear losses, wear track widths and friction coefficients of coated and uncoated Ti6Al4V alloys are taken into account for comparison. The results show that a significant improvement in wear resistance of the alloy with the coating is achieved and TiN-coated Ti6Al4V alloy has the highest wear resistance.

Pin on disk against ball on disk for the evaluation of wear improvement on cryo-treated metal cutting shears

NASA Astrophysics Data System (ADS)

Jimbert, P.; Iturrondobeitia, M.; Ibarretxe, J.; Fernandez-Martinez, R.

2015-03-01

When talking about trybology, the election of the laboratory experiment type is a common problem of discussion. Laboratory wear methods are not designed to exactly reproduce the real working conditions of the analyzed part itself but serve to engineers and researcher to extrapolate the laboratory results to the real application. In order to shed some light on this issue, two wear tests have been analyzed following an ASTM standard and using the same experimental parameters and testing pair-materials in order to be able to make a comparison: Pin-on-Disk (PoD) against Ball-on-Disk (BoD). Three different tool steel have been analyzed in this study, AISI D2, AISI A8 and AISI H13, used to produce metal cutting shears. Metal on metal dry sliding tests were designed in order to reproduce the tool working conditions. These three materials were cryogenically treated and compared against no cryogenically treated ones to measure the improvement on their wear resistance due to cryogenic treatment. Finally, the wear rates obtained with both laboratory tests were compared against some real production metal cutting tools wear data. Results revealed an improvement of the wear resistance for cryo-treated samples of around 20% with the BoD test and around 6% with the PoD test. Real production tools wear was calculated for one of the tool steels and for two different applications. The improvement was approximately the one revealed by the BoD test. So, for the studied case, the BoD laboratory test gives more realistic prediction of real tool life improvement due to the cryogenic treatment.

Validation of accelerometer wear and nonwear time classification algorithm.

PubMed

Choi, Leena; Liu, Zhouwen; Matthews, Charles E; Buchowski, Maciej S

2011-02-01

the use of movement monitors (accelerometers) for measuring physical activity (PA) in intervention and population-based studies is becoming a standard methodology for the objective measurement of sedentary and active behaviors and for the validation of subjective PA self-reports. A vital step in PA measurement is the classification of daily time into accelerometer wear and nonwear intervals using its recordings (counts) and an accelerometer-specific algorithm. the purpose of this study was to validate and improve a commonly used algorithm for classifying accelerometer wear and nonwear time intervals using objective movement data obtained in the whole-room indirect calorimeter. we conducted a validation study of a wear or nonwear automatic algorithm using data obtained from 49 adults and 76 youth wearing accelerometers during a strictly monitored 24-h stay in a room calorimeter. The accelerometer wear and nonwear time classified by the algorithm was compared with actual wearing time. Potential improvements to the algorithm were examined using the minimum classification error as an optimization target. the recommended elements in the new algorithm are as follows: 1) zero-count threshold during a nonwear time interval, 2) 90-min time window for consecutive zero or nonzero counts, and 3) allowance of 2-min interval of nonzero counts with the upstream or downstream 30-min consecutive zero-count window for detection of artifactual movements. Compared with the true wearing status, improvements to the algorithm decreased nonwear time misclassification during the waking and the 24-h periods (all P values < 0.001). the accelerometer wear or nonwear time algorithm improvements may lead to more accurate estimation of time spent in sedentary and active behaviors.

Effects of bionic units on the fatigue wear of gray cast iron surface with different shapes and distributions

NASA Astrophysics Data System (ADS)

Chen, Zhi-kai; Lu, Shu-chao; Song, Xi-bin; Zhang, Haifeng; Yang, Wan-shi; Zhou, Hong

2015-03-01

To improve the fatigue wear resistance of gray cast iron (GCI), GCI samples were modified by a laser to imitate the unique structure of some soil animals alternating between soft and hard phases; the hard phase resists the deformation and the soft phase releases the deformation. Using the self-controlled fatigue wear test method, the fatigue wear behaviors of treated and untreated samples were investigated and compared experimentally. The results show that the bionic non-smooth surface obtains a beneficial effect on improving the fatigue wear resistance of a sample, and the fatigue wear resistance of the bionic sample assembled with reticulate units (60°+0°), whose mass loss was reduced by 62%, was superior to the others. Meanwhile, a finite element (FE) was used to simulate the compression and the distributions of strain and stress on the non-smooth surface was inferred. From these results, we understood that the functions of the bionic unit such as reducing strain and stress, and also obstructing the closure and propagation of cracks were the main reasons for improving the fatigue wear property of GCI.

Experimental Study of Tool Wear and Grinding Forces During BK-7 Glass Micro-grinding with Modified PCD Tool

NASA Astrophysics Data System (ADS)

Pratap, A.; Sahoo, P.; Patra, K.; Dyakonov, A. A.

2017-09-01

This study focuses on the improvement in grinding performance of BK-7 glass using polycrystalline diamond micro-tool. Micro-tools are modified using wire EDM and performance of modified tools is compared with that of as received tool. Tool wear of different types of tools are observed. To quantify the tool wear, a method based on weight loss of tool is introduced in this study. Modified tools significantly reduce tool wear in comparison to the normal tool. Grinding forces increase with machining time due to tool wear. However, modified tools produce lesser forces thus can improve life of the PCD micro-grinding tool.

Microstructures and Dry Sliding Wear Resistance of the Laser Ceramics Composite Coating on Pure Ti

NASA Astrophysics Data System (ADS)

Liu, Peng; Zhang, Yuanbin; Luo, Hui; Huo, Yushuang

2012-06-01

In this study, Al-Ti-Co was used to improve the surface performance of pure Ti. Laser cladding is an important surface modification technique, which can be used to improve the surface performance of pure Ti. Laser cladding of the Al-Ti-Co + TiB2 pre-placed powders on pure Ti can form ceramics reinforced the composite coating, which improved the wear resistance of the substrate. Characteristics of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness and wear tests. And the laser-cladded coating can also have major dilution from the substrate. Due to the action of the fine grain strengthening and the phase constituent, the wear resistance and microhardness of pure Ti surface were greatly improved.

Open System Tribology and Influence of Weather Condition.

PubMed

Lyu, Yezhe; Bergseth, Ellen; Olofsson, Ulf

2016-08-30

The tribology of an open system at temperatures ranging between 3 °C and -35 °C, with and without snow, was investigated using a pin-on-disc tribometer mounted in a temperature-controlled environmental chamber. The relationship between the microstructure and ductility of the materials and the tribology at the contacting surfaces was investigated. The study shows that during continuous sliding, pressure causes snow particles to melt into a liquid-like layer, encouraging the generation of oxide flakes on the contact path. The friction coefficient and wear rate are dramatically reduced through an oxidative friction and wear mechanism. In the absence of snow, the tribological process is controlled by the low temperature brittleness of steel in the temperature range from 3 °C to -15 °C. At these temperatures, cracks are prone to form and extend on the worn surfaces, resulting in the spalling of bulk scraps, which are crushed into debris that increases the friction coefficient and wear rate due to strong abrasion. When the temperature falls to -25 °C, an ice layer condenses on the metal surfaces and relaxes the tribological process in the same way as the added snow particles, which significantly decreases the friction and wear.

Open System Tribology and Influence of Weather Condition

PubMed Central

Lyu, Yezhe; Bergseth, Ellen; Olofsson, Ulf

2016-01-01

The tribology of an open system at temperatures ranging between 3 °C and −35 °C, with and without snow, was investigated using a pin-on-disc tribometer mounted in a temperature-controlled environmental chamber. The relationship between the microstructure and ductility of the materials and the tribology at the contacting surfaces was investigated. The study shows that during continuous sliding, pressure causes snow particles to melt into a liquid-like layer, encouraging the generation of oxide flakes on the contact path. The friction coefficient and wear rate are dramatically reduced through an oxidative friction and wear mechanism. In the absence of snow, the tribological process is controlled by the low temperature brittleness of steel in the temperature range from 3 °C to −15 °C. At these temperatures, cracks are prone to form and extend on the worn surfaces, resulting in the spalling of bulk scraps, which are crushed into debris that increases the friction coefficient and wear rate due to strong abrasion. When the temperature falls to −25 °C, an ice layer condenses on the metal surfaces and relaxes the tribological process in the same way as the added snow particles, which significantly decreases the friction and wear. PMID:27573973

Combinatorial Study of Gradient Ag-Al Thin Films: Microstructure, Phase Formation, Mechanical and Electrical Properties.

PubMed

Mao, Fang; Taher, Mamoun; Kryshtal, Oleksandr; Kruk, Adam; Czyrska-Filemonowicz, Aleksandra; Ottosson, Mikael; Andersson, Anna M; Wiklund, Urban; Jansson, Ulf

2016-11-09

A combinatorial approach is applied to rapidly deposit and screen Ag-Al thin films to evaluate the mechanical, tribological, and electrical properties as a function of chemical composition. Ag-Al thin films with large continuous composition gradients (6-60 atom % Al) were deposited by a custom-designed combinatorial magnetron sputtering system. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), nanoindentation, and four-point electrical resistance screening were employed to characterize the chemical composition, structure, and physical properties of the films in a time-efficient way. For low Al contents (<13 atom %), a highly (111)-textured fcc phase was formed. At higher Al contents, a (002)-textured hcp solid solution phase was formed followed by a fcc phase in the most Al-rich regions. No indication of a μ phase was observed. The Ag-Al films with fcc-Ag matrix is prone to adhesive material transfer leading to a high friction coefficient (>1) and adhesive wear, similar to the behavior of pure Ag. In contrast, the hexagonal solid solution phase (from ca. 15 atom %Al) exhibited dramatically reduced friction coefficients (about 15% of that of the fcc phase) and dramatically reduced adhesive wear when tested against the pure Ag counter surface. The increase in contact resistance of the Ag-Al films is limited to only 50% higher than a pure Ag reference sample at the low friction and low wear region (19-27 atom %). This suggests that a hcp Ag-Al alloy can have a potential use in sliding electrical contact applications and in the future will replace pure Ag in specific electromechanical applications.

The effect of processing and compositional changes on the tribology of PM212 in air

NASA Technical Reports Server (NTRS)

Bogdanski, Michael S.; Sliney, Harold E.; Dellacorte, Christopher

1993-01-01

The effects of processing and compositional variations on the tribological performance of PM212 were studied. PM212 is a self lubricating powder metallurgy composite, comprised of a wear resistant metal bonded chromium carbide matrix, containing the solid lubricants barium fluoride/calcium fluoride eutectic and silver. Several composites were formulated which had lubricant, matrix, and processing variations. Processing variations included sintering and hot isostatic pressing. Pins fabricated from the composites were slid against superalloys disks in a pin-on-disk tribometer to study the tribological properties. Several composites exhibited low friction and wear in sliding against a nickel based superalloy. The tribological performance by several different composites showed that the composition of PM212 can be altered without dramatically affecting performance.

EVALUATION AND RECOMMENDATION OF SALTSTONE MIXER AUGER/PADDLES MATERIALS OF CONSTRUCTION FOR IMPROVED WEAR RESISTANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickalonis, J.; Torres, R.

2012-08-15

Wear and corrosion testing were conducted to evaluate alternate materials of construction for the Saltstone mixer auger and paddles. These components have been degraded by wear from the slurry processed in the mixer. Material test options included PVD coatings (TiN, TiCN, and ZrN), weld overlays (Stellite 12 and Ultimet) and higher hardness steels and carbides (D2 and tungsten carbide). The corrosion testing demonstrated that the slurry is not detrimental to the current materials of construction or the new candidates. The ASTM G75 Miller wear test showed that the high hardness materials and the Stellite 12 weld overlay provide superior wearmore » relative to the Astralloy and CF8M stainless steel, which are the current materials of construction, as well as the PVD coatings and Ultimet. The following recommendations are made for selecting new material options and improving the overall wear resistance of the Saltstone mixer components: A Stellite 12 weld overlay or higher hardness steel (with toughness equivalent to Astralloy) be used to improve the wear resistance of the Saltstone mixer paddles; other manufacturing specifications for the mixer need to be considered in this selection. The current use of the Stellite 12 weld overlay be evaluated so that coverage of the 316 auger can be optimized for improved wear resistance of the auger. The wear surfaces of the Saltstone mixer auger and paddles be evaluated so that laboratory data can be better correlated to actual service. The 2-inch Saltstone mixer prototype be used to verify material performance.« less

Improved Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway

DTIC Science & Technology

2010-01-15

information. 2.0 DESCRIPTION Naval Submarine Medical Research Laboratory (NSMRL) is seeking information from the eyewear industry that will provide...Improved Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway by Alison America, MA Wayne G. Horn, MD...Submariner Eyewear for Routine Wear and Emergency Equipment Use Underway 50818 Alison America, MA Wayne G. Horn, MD Naval Submarine Medical Research

The Wear Behavior of Textured Steel Sliding against Polymers

PubMed Central

Wang, Meiling; Zhang, Changtao; Wang, Xiaolei

2017-01-01

Artificially fabricated surface textures can significantly improve the friction and wear resistance of a tribological contact. Recently, this surface texturing technique has been applied to polymer materials to improve their tribological performance. However, the wear behavior of textured tribo-pairs made of steel and polymer materials has been less thoroughly investigated and is not well understood; thus, it needs further research. The aim of this study is to investigate the wear properties of tribological contacts made of textured stainless steel against polymer surfaces. Three polymer materials were selected in this study, namely, ultrahigh molecular weight polyethylene (UHMWPE), polyoxymethylene (POM) and (polyetheretherketone) PEEK. Wear tests were operated through a ring-on-plane mode. The results revealed that the texture features and material properties affected the wear rates and friction coefficients of the textured tribo-pairs. In general, PEEK/textured steel achieved the lowest wear rate among the three types of tribo-pairs investigated. Energy dispersive x-ray spectroscopy (EDX) analysis revealed that the elements of C and O on the contacting counterfaces varied with texture features and indicated different wear behavior. Experimental and simulated results showed differences in the stress distribution around the dimple edge, which may influence wear performance. Wear debris with different surface morphologies were found for tribo-pairs with varying texture features. This study has increased the understanding of the wear behavior of tribo-pairs between textured stainless steel and polymer materials. PMID:28772688

Let the Games Begin--Again: HBCU Coaches and Administrators Give Their Play-by-Play Accounts of the Benefits of Reviving College Football Programs

ERIC Educational Resources Information Center

Keels, Crystal L.

2004-01-01

It's the pageantry, the precision, the rhythm and the music. It's wave after wave of energetic flute, trumpet, tuba and drum players wearing colorful uniforms and executing intricate steps. It's the dramatic dance moves and megawatt smiles of majorettes in short pleated skirts. It's the drum major whose kinetic energy electrifies them all. And…

Switch Panel wear loading - a parametric study regarding governing train operational factors

NASA Astrophysics Data System (ADS)

Hiensch, E. J. M.; Burgelman, N.

2017-09-01

The acting forces and resulting material degradation at the running surfaces of wheels and rail are determined by vehicle, track, interface and operational characteristics. To effectively manage the experienced wear, plastic deformation and crack development at wheels and rail, the interaction between vehicle and track demands a system approach both in maintenance and in design. This requires insight into the impact of train operational parameters on rail- and wheel degradation, in particular at switches and crossings due to the complex dynamic behaviour of a railway vehicle at a turnout. A parametric study was carried out by means of vehicle-track simulations within the VAMPIRE® multibody simulation software, performing a sensitivity analysis regarding operational factors and their impact on expected switch panel wear loading. Additionally, theoretical concepts were cross-checked with operational practices by means of a case study in response to a dramatic change in lateral rail wear development at specific switches in Dutch track. Data from train operation, track maintenance and track inspection were analysed, providing further insight into the operational dependencies. From the simulations performed in this study, it was found that switch rail lateral wear loading at the diverging route of a 1:9 type turnout is significantly influenced by the level of wheel-rail friction and to a lesser extent by the direction of travel (facing or trailing). The influence of other investigated parameters, being vehicle speed, traction, gauge widening and track layout is found to be small. Findings from the case study further confirm the simulation outcome. This research clearly demonstrates the contribution flange lubrication can have in preventing abnormal lateral wear at locations where the wheel-rail interface is heavily loaded.

A new methodology for predictive tool wear

NASA Astrophysics Data System (ADS)

Kim, Won-Sik

An empirical approach to tool wear, which requires a series of machining tests for each combination of insert and work material, has been a standard practice for industries since early part of the twentieth century. With many varieties of inserts and work materials available for machining, the empirical approach is too experiment-intensive that the demand for the development of a model-based approach is increasing. With a model-based approach, the developed wear equation can be extended without additional machining experiments. The main idea is that the temperatures on the primary wear areas are increasing such that the physical properties of the tool material degrade substantially and consequently tool wear increases. Dissolution and abrasion are identified to be the main mechanisms for tool wear. Flank wear is predominantly a phenomenon of abrasion as evident by the presence of a scoring mark on the flank surface. Based on this statement, it is reasonable to expect that the flank-wear rate would increase with the content of hard inclusions. However, experimental flank wear results did not necessary correspond to the content of cementite phase present in the steels. Hence, other phenomena are believed to significantly affect wear behavior under certain conditions. When the cutting temperature in the flank interface is subjected to high enough temperatures, pearlitic structure austenizes. During the formation of a new austenitic phase, the existing carbon is dissolved into the ferrite matrix, which will reduce the abrasive action. To verify the austenitic transformation, turning tests were conducted with plain carbon steels. The machined surface areas are imaged using X-ray diffraction the Scanning Electron Microscope (SEM) and the Transmission Electron Microscope (TEM). On the other hand, crater wear occurs as a result of dissolution wear and abrasive wear. To verify the wear mechanisms of crater wear, various coating inserts as well as uncoated inserts were turned with various cutting conditions and the results were compared with the proposed analytical wear models. The crater surfaces after machining have been carefully studied to shed light on the physics behind the crater wear. In addition, the abrasive wear mechanism plays a major role in the development of crater wear. Laser shock processing (LSP) has been applied to locally relieve the deleterious tensile residual stresses on the crater surface of a coated tool, thus to improve the hardness of the coating. This thesis shows that LSP has indeed improve wear resistance of CVD coated alumina tool inserts, which has residual stress due to high processing temperature. LSP utilizes a very short laser pulse with high energy density, which induces high-pressure stress wave propagation. The residual stresses are relieved by incident shock waves on the coating surface. Residual stress levels of LSP CVD alumina-coated carbide insert were evaluated by the X-ray diffractometer. Based on these results, LSP parameters such as number of laser pulses and laser energy density can be controlled to reduce residual stress. Crater wear shows that the wear resistance increase with LSP treated tool inserts. Because the hardness data are used to predict the wear, the improvement in hardness and wear resistance shows that the mechanism of crater wear also involves abrasive wear.

Effects of EVA gloves on grip strength and fatigue under low temperature and low pressure.

PubMed

Tian, Yinsheng; Ding, Li; Liu, Heqing; Li, Yan; Li, Deyu; Wang, Li

2016-03-01

To study the effects of wearing extravehicular activity (EVA) gloves on grip strength and fatigue in low temperature, low pressure and mixing of two factors (low temperature and low pressure). The maximum grip strength and fatigue tests were performed with 10 healthy male subjects wearing gloves in a variety of simulated environments. The data was analysed using the normalization method. The results showed that wearing gloves significantly affected the maximum grip strength and fatigue. Pressure (29.6, 39.2 kPa) had more influence on the maximum grip compared with control group while low temperatures (-50, -90, -110 °C) had no influence on grip but affected fatigue dramatically. The results also showed that the maximum grip strength and fatigue were influenced significantly in a compound environment. Space environment remarkably reduced strength and endurance of the astronauts. However, the effects brought by the compound environment cannot be understood as the superimposition of low temperature and pressure effects. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Behaviors of 40Cr steel treated by laser quenching on impact abrasive wear

NASA Astrophysics Data System (ADS)

Chen, Zhikai; Zhu, Qinghai; Wang, Jing; Yun, Xiao; He, Bing; Luo, Jingshuai

2018-07-01

In present work, laser quenching had been carried out to improve the impact abrasive wear resistance of 40Cr steel. The distinct microstructure between original and quenched region was demonstrated after laser quenching. Since the effect of temperature and cooling rate, the phase combinations were apparently different for quenched layer in depth. The impact abrasive wear resistance of sample was experimentally investigated and the improved level was assessed in light of the average mass loss of three repetitive tests. Worn surface was detected by means of SEM, OM and EDS, and results showed that three typical failure modes were performed during the processing of impact abrasive wear, including abrasive wear, impact effect and rolling contact fatigue. Basing on the different worn surface profile, the mainly failure mode was respectively pointed out for matrix and quenched sample, which was significantly in accordance with the result of impact abrasive wear.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panwar, Ranvir Singh, E-mail: ranvir.panwar@thapar.edu; Pandey, O.P., E-mail: oppandey@thapar.edu

Particulate reinforced aluminum metal matrix composite is in high demand in automobile industry where the operational conditions vary from low to high temperature. In order to understand the wear mode at elevated temperature, this study was planned. For this purpose we developed a metal matrix composite containing aluminum alloy (LM13) as matrix and zircon sand as particulate reinforcement by stir casting process. Different amounts of zircon sand (5, 10, 15 and 20 wt.%) were incorporated in the matrix to study the effect of reinforcement on the wear resistance. Dispersion of zircon sand particles in the matrix was confirmed by usingmore » optical microscopy. Sliding wear tests were done to study the durability of the composite with respect to the base alloy. The effects of load and temperature on wear behavior from room temperature to 300 Degree-Sign C were studied to understand the wear mechanism deeply. Surface morphology of the worn surfaces after the wear tests as well as wear debris was observed under scanning electron microscope. Mild to severe wear transition was noticed in tests at high temperature and high load. However, there is interesting change in wear behavior of the composite near the critical temperature of the composite. All the observed behavior has been explained with reference to the observed microstructure of the wear track and debris. - Highlights: Black-Right-Pointing-Pointer Good interfacial bonding between zircon sand particles and Al matrix was observed. Black-Right-Pointing-Pointer The effect of temperature on the wear behavior of LM13/Zr composites was studied. Black-Right-Pointing-Pointer Wear resistance of the composite was improved with addition of zircon sand. Black-Right-Pointing-Pointer Transition temperature from mild to severe wear also improved in composite. Black-Right-Pointing-Pointer SEM analysis of the tracks and debris was done to establish wear mechanism.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Xiaodong; Wu, Hong, E-mail: wuhong927@126.com

Metallic glass composite coatings Ti{sub 45}Cu{sub 41}Ni{sub 9}Zr{sub 5} and Ti{sub 45}Cu{sub 41}Ni{sub 6}Zr{sub 5}Sn{sub 3} (at.%) on a Ti-30Nb-5Ta-7Zr (wt.%) (TNTZ) alloy were prepared by laser cladding. The microstructures of the coatings were characterized by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDXA), and transmission electron microscopy (TEM). Results indicated that the coatings have an amorphous structure embedded with a few nanocrystalline phases and dendrites. A partial substitution of Ni by Sn can improve the glass forming ability of Ti-base metallic glass system, and induce the formation of nano-sized Ni{sub 2}SnTimore » phase during the cyclic laser heating. The tribological behavior of both the substrate and the coatings was investigated in detail. A significant improvement in both the hardness and the wear resistance of the coatings was achieved with the addition of Sn. The relationship between the wear resistance and the microstructures of the coatings was discussed. - Highlights: •Ti-based metallic glass composite coatings were prepared by laser cladding. •The wear resistance is greatly improved by laser cladding of composite coatings. •Substitution of Ni by Sn increases GFA and wear resistance of the coatings. •A good balance of crystalline/amorphous phases improves the wear resistance. •Adhesive wear serves as the dominant wear mechanism of the composite coatings.« less

Wear Mechanism Maps for Magnesium Alloy AM60 and Composite AM60-9% (Al2O3)f

NASA Astrophysics Data System (ADS)

Ullah Khan, Muhammad Zafar

The purpose of this work was to study the tribological behaviour of squeeze cast Mg alloy AM60 and its composite AM60-9% (Al2O3) f. Dry sliding wear tests were performed on specimens of these materials using a block-on-ring tribometer which was equipped with a COF and temperature measurement system. Wear, COF and temperature maps were constructed to illustrate the effect of temperature and COF on the wear behaviour of the Mg alloy and it's composite. Four wear regimes namely low, mild, transient and severe wear were identified. The transition from mild to severe wear regime was found to be dependent on the bulk temperature of the specimen. Oxidational wear prevailed in low and mild wear whereas plastic deformation induced wear and melt wear controlled the wear rates in transient and severe wear regimes, respectively. This study shows that the incorporation of Al2O3 fibres in AM60 alloy improved the wear resistance of the resulting composite by delaying the transition from mild to severe wear.

Developing and Characterizing Bulk Metallic Glasses for Extreme Applications

NASA Astrophysics Data System (ADS)

Roberts, Scott Nolan

Metallic glasses have typically been treated as a "one size fits all" type of material. Every alloy is considered to have high strength, high hardness, large elastic limits, corrosion resistance, etc. However, similar to traditional crystalline materials, properties are strongly dependent upon the constituent elements, how it was processed, and the conditions under which it will be used. An important distinction which can be made is between metallic glasses and their composites. Charpy impact toughness measurements are performed to determine the effect processing and microstructure have on bulk metallic glass matrix composites (BMGMCs). Samples are suction cast, machined from commercial plates, and semi-solidly forged (SSF). The SSF specimens have been found to have the highest impact toughness due to the coarsening of the dendrites, which occurs during the semi-solid processing stages. Ductile to brittle transition (DTBT) temperatures are measured for a BMGMC. While at room temperature the BMGMC is highly toughened compared to a fully glassy alloy, it undergoes a DTBT by 250 K. At this point, its impact toughness mirrors that of the constituent glassy matrix. In the following chapter, BMGMCs are shown to have the capability of being capacitively welded to form single, monolithic structures. Shear measurements are performed across welded samples, and, at sufficient weld energies, are found to retain the strength of the parent alloy. Cross-sections are inspected via SEM and no visible crystallization of the matrix occurs. Next, metallic glasses and BMGMCs are formed into sheets and eggbox structures are tested in hypervelocity impacts. Metallic glasses are ideal candidates for protection against micrometeorite orbital debris due to their high hardness and relatively low density. A flat single layer, flat BMG is compared to a BMGMC eggbox and the latter creates a more diffuse projectile cloud after penetration. A three tiered eggbox structure is also tested by firing a 3.17 mm aluminum sphere at 2.7 km/s at it. The projectile penetrates the first two layers, but is successfully contained by the third. A large series of metallic glass alloys are created and their wear loss is measured in a pin on disk test. Wear is found to vary dramatically among different metallic glasses, with some considerably outperforming the current state-of-the-art crystalline material (most notably Cu43Zr 43Al7Be7). Others, on the other hand, suffered extensive wear loss. Commercially available Vitreloy 1 lost nearly three times as much mass in wear as alloy prepared in a laboratory setting. No conclusive correlations can be found between any set of mechanical properties (hardness, density, elastic, bulk, or shear modulus, Poisson's ratio, frictional force, and run in time) and wear loss. Heat treatments are performed on Vitreloy 1 and Cu43Zr43Al7Be7. Anneals near the glass transition temperature are found to increase hardness slightly, but decrease wear loss significantly. Crystallization of both alloys leads to dramatic increases in wear resistance. Finally, wear tests under vacuum are performed on the two alloys above. Vitreloy 1 experiences a dramatic decrease in wear loss, while Cu43Zr43Al7Be7 has a moderate increase. Meanwhile, gears are fabricated through three techniques: electrical discharge machining of 1 cm by 3 mm cylinders, semisolid forging, and copper mold suction casting. Initial testing finds the pin on disk test to be an accurate predictor of wear performance in gears. The final chapter explores an exciting technique in the field of additive manufacturing. Laser engineered net shaping (LENS) is a method whereby small amounts of metallic powders are melted by a laser such that shapes and designs can be built layer by layer into a final part. The technique is extended to mixing different powders during melting, so that compositional gradients can be created across a manufactured part. Two compositional gradients are fabricated and characterized. Ti 6Al-4V to pure vanadium was chosen for its combination of high strength and light weight on one end, and high melting point on the other. It was inspected by cross-sectional x-ray diffraction, and only the anticipated phases were present. 304L stainless steel to Invar 36 was created in both pillar and as a radial gradient. It combines strength and weldability along with a zero coefficient of thermal expansion material. Only the austenite phase is found to be present via x-ray diffraction. Coefficient of thermal expansion is measured for four compositions, and it is found to be tunable depending on composition.

How patient-selected colors for removable appliances are reflected in electronically tracked compliance (wear times and wear behavior).

PubMed

Schott, Timm C; Menne, Dieter

2018-07-01

A broad spectrum of colors for removable appliances, intended to optimize acceptance of treatment and patient cooperation, have been available on the dental market for years. This is the first study to analyze how patient-selected colors are reflected in wear times and wear behavior of removable appliances. The study included 117 children (55 girls and 62 boys) who were treated with active removable plate or functional appliances. All patients were offered to choose from 11 different colors, which were pooled into six groups (black, blue, green, yellow, pink, red) for analysis, or to combine any two to four colors ("multicolored" group) for their appliances. All appliances featured a built-in microsensor (TheraMon; MC Technology, Hargelsberg, Austria) for objective wear-time tracking. Differences between wear times were analyzed using pairwise t tests and Tukey correction. The longest median wear times were recorded in the blue and green groups (≈11 h/d) and the shortest ones in the red and pink groups (≈9 h/d), but they were not significantly influenced by the patient-selected colors. The median wear times involved an age-related decrease by 0.56 h/y that was statistically significant ( P = .00005). No gender-specific patterns of wear behavior were observed. Patient-selected colors for removable appliances can presumably improve acceptance of treatment, but they are not associated with statistically significant improvements in wear time or wear behavior.

Effect of motion inputs on the wear prediction of artificial hip joints

PubMed Central

Liu, Feng; Fisher, John; Jin, Zhongmin

2013-01-01

Hip joint simulators have been largely used to assess the wear performance of joint implants. Due to the complexity of joint movement, the motion mechanism adopted in simulators varies. The motion condition is particularly important for ultra-high molecular weight polyethylene (UHMWPE) since polyethylene wear can be substantially increased by the bearing cross-shear motion. Computational wear modelling has been improved recently for the conventional UHMWPE used in total hip joint replacements. A new polyethylene wear law is an explicit function of the contact area of the bearing and the sliding distance, and the effect of multidirectional motion on wear has been quantified by a factor, cross-shear ratio. In this study, the full simulated walking cycle condition based on a walking measurement and two simplified motions, including the ISO standard motion and a simplified ProSim hip simulator motion, were considered as the inputs for wear modelling based on the improved wear model. Both the full simulation and simplified motions generated the comparable multidirectional motion required to reproduce the physiological wear of the bearing in vivo. The predicted volumetric wear of the ProSim simulator motion and the ISO motion conditions for the walking cycle were 13% and 4% lower, respectively, than that of the measured walking condition. The maximum linear wear depths were almost the same, and the areas of the wear depth distribution were 13% and 7% lower for the ProSim simulator and the ISO condition, respectively, compared with that of the measured walking cycle motion condition. PMID:25540472

Tribological investigation of oriented HDPE.

PubMed

Hoseini, Mohammed; Lausmaa, Jukka; Boldizar, Antal

2002-09-15

The possibility to control the wear properties of high-density polyethylene (HDPE) material at an early processing stage is explored. Wear measurements of cold roll-drawn HDPE with two different draw ratios were carried out for three sliding planes, each in two directions. The dependence of the wear properties on the degree and direction of orientation was investigated. The experiments were performed in a pin-on-disc machine in a dry environment. The tribo-couple consisted of HDPE plates versus a standardised diamond coated steel disc. The results show that the wear resistance of cold roll-drawn HDPE differ widely, by a factor up to 6, depending on the sliding direction relative to the drawing direction. The material has a significantly better wear resistance when the sliding direction was perpendicular to the processing direction. The best wear resistance was in the end plane and it was improved by a factor up to 3.6 when the draw ratio was increased from 2 to 4. These results indicate that molecular orientation by polymer processing is a promising method to improve the wear properties and decrease the wear debris production of HDPE. Copyright 2002 Wiley Periodicals, Inc.

2005 survey of seat belt wearing rates

DOT National Transportation Integrated Search

2005-01-01

The 2005 seat belt survey showed a minor improvement in driver wearing : rates. Over the 2003 2005 period, estimated wearing rates for male drivers : increased by one percentage point to 83 per cent, and for female drivers : increased by two perc...

Effects of Laser Energies on Wear and Tensile Properties of Biomimetic 7075 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Yuan, Yuhuan; Zhang, Peng; Zhao, Guoping; Gao, Yang; Tao, Lixi; Chen, Heng; Zhang, Jianlong; Zhou, Hong

2018-03-01

Inspired by the non-smooth surface of certain animals, a biomimetic coupling unit with various sizes, microstructure, and hardness was prepared on the surface of 7075 aluminum alloy. Following experimental studies were conducted to investigate the wear and tensile properties with various laser energy inputs. The results demonstrated that the non-smooth surface with biomimetic coupling units had a positive effect on both the wear resistance and tensile property of 7075 aluminum alloy. In addition, the sample with the unit fabricated by the laser energy of 420.1 J/cm2 exhibited the most significant improvement on the wear and tensile properties owing to the minimum grain size and the highest microhardness. Also, the weight loss of the sample was one-third of the untreated one's, and the yield strength, the ultimate tensile strength, and the elongation improved by 20, 20, and 34% respectively. Moreover, the mechanisms of wear and tensile properties improvement were also analyzed.

Microstructure and wear property of the Ti5Si3/TiC reinforced Co-based coatings fabricated by laser cladding on Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Weng, Fei; Yu, Huijun; Liu, Jianli; Chen, Chuanzhong; Dai, Jingjie; Zhao, Zhihuan

2017-07-01

Ti5Si3/TiC reinforced Co-based composite coatings were fabricated on Ti-6Al-4V titanium alloy by laser cladding with Co42 and SiC mixture. Microstructure and wear property of the cladding coatings with different content of SiC were investigated. During the cladding process, the original SiC dissolved and reacted with Ti forming Ti5Si3 and TiC. The complex in situ formed phases were found beneficial to the improvement of the coating property. Results indicated that the microhardness of the composite coatings was enhanced to over 3 times the substrate. The wear resistance of the coatings also showed distinct improvement (18.4-57.4 times). More SiC gave rise to better wear resistance within certain limits. However, too much SiC (20 wt%) was not good for the further improvement of the wear property.

Improved wear resistance by phase transformation of surface nanocrystalline 1090 steel prepared by sandblasting technique

NASA Astrophysics Data System (ADS)

Peng, Rong; Fu, Licai; Zhou, Lingping

2016-12-01

A surface nanocrystalline 1090 steel has been fabricated by using sandblasting technique. The surface average grain size was about 78 nm. The high strain rate and strain in sandblasting were main reasons for surface nanocrystallization. The wear resistance of 1090 steel was considerably enhanced as grain size decreased. The microstructure and hardness of contact zones before and after wear tests have been examined by XRD, SEM and TEM. Except the higher hardness, the results demonstrated that parts of ferrite transferred to cementite and martensite. It was additional beneficial for improving the wear resistance of 1090 steel as the grain size decreased.

Stoichiometry and tribological behavior of thick Ta(N) coatings produced by direct current magnetron sputtering (DCMS)

NASA Astrophysics Data System (ADS)

Guo, Xiaotong; Niu, Yunsong; Chen, Minghui; Sun, Wenyao; Zhu, Shenglong; Wang, Fuhui

2018-01-01

Thick Ta(N) coating of 51 μm has been successfully obtained by DCMS technology. Ta(N) is a kind of distorted Ta matrix, which is inter-soluble with N-defect lattice structure, forming the disabled bcc structure. From the XRD and XPS investigations, the composition of Ta(N) coating is consisted of bcc-Ta and bcc-TaN0.06, while that of Ta coating mainly contains β-Ta phase. It can be concluded from wear test, nanoindentation test and SEM observations, wear resistance of Ta(N) coating is much better than that of Ta coating, due to its high hardness, H/E, H3/E2 value and low COF value. The wear mechanism of Ta coating is the compound fatigue and abrasive wear, while that of Ta(N) coating is transformed into adhesive wear mechanism. The secondary adhesion of the plastic deformation for the Ta(N) coating can reinforce the coated surface, to improve the load-bearing and anti-wear capacities, and thus improve the wear resistance.

Plasma immersion ion implantation on 15-5PH stainless steel: influence on fatigue strength and wear resistance

NASA Astrophysics Data System (ADS)

Bonora, R.; Cioffi, M. O. H.; Voorwald, H. J. C.

2017-05-01

Surface improvement in steels is of great interest for applications in industry. The aim of this investigation is to study the effect of nitrogen ion implantation on the axial fatigue strength and wear resistance of 15-5 PH stainless steel. It is well know that electroplated coatings, which are used to improve abrasive wear and corrosion properties, affects negatively the fatigue strength. It is also important to consider requirements to reduce the use of coated materials with electroplated chromium and cadmium, that produce waste, which is harmful to health and environment. The HVOF (High velocity oxygen fuel) process provides hardness, wear strength and higher fatigue resistance in comparison to electroplated chromium. Plasma immersion ion implantation has been used to enhance the hardness, wear, fatigue and corrosion properties of metals and alloys. In the present research the fatigue life increased twice for 15-5 PH three hours PIII treated in comparison to base material. From the abrasive wear tests a lower pin mass reduction was observed, associated to the superficial treatments. The improvement of fatigue and mechanical performance is attributed to a combination of nitrides phase structure and compressive residual stresses during the PIII treatment.

Tumor Suppression by BRCA-1: A Critical Role at DNA Replication Forks

DTIC Science & Technology

2006-10-01

replication defect. We wished to test the hypothesis that BRCA1/BARD1 function during DNA replication supporting DNA transactions at replication forks. We...are using cell-free extracts derived from Xenopus laevis eggs that support: 1. Semi-conservative, cell-cycle regulated DNA replication ; 2. Many facets...complex assembles to chromatin in a DNA replication -dependent manner. Finally, we show that BRCA1/BARD1 loading to chromatin does not dramatically

Effect of CeO₂ on Microstructure and Wear Resistance of TiC Bioinert Coatings on Ti6Al4V Alloy by Laser Cladding.

PubMed

Chen, Tao; Liu, Defu; Wu, Fan; Wang, Haojun

2017-12-31

To solve the lack of wear resistance of titanium alloys for use in biological applications, various prepared coatings on titanium alloys are often used as wear-resistant materials. In this paper, TiC bioinert coatings were fabricated on Ti6Al4V by laser cladding using mixed TiC and ZrO₂ powders as the basic pre-placed materials. A certain amount of CeO₂ powder was also added to the pre-placed powders to further improve the properties of the TiC coatings. The effects of CeO₂ additive on the phase constituents, microstructures and wear resistance of the TiC coatings were researched in detail. Although the effect of CeO₂ on the phase constituents of the coatings was slight, it had a significant effect on the microstructure and wear resistance of the coatings. The crystalline grains in the TiC coatings, observed by a scanning electron microscope (SEM), were refined due to the effect of the CeO₂. With the increase of CeO₂ additive content in the pre-placed powders, finer and more compact dendrites led to improvement of the micro-hardness and wear resistance of the TiC coatings. Also, 5 wt % content of CeO₂ additive in the pre-placed powders was the best choice for improving the wear properties of the TiC coatings.

Rapid Analyses of Polyetheretherketone Wear Characteristics by Accelerated Wear Testing with Microfabricated Surfaces for Artificial Joint Systems

PubMed Central

Kuo, Chien-Wei

2017-01-01

Wear particle-induced biological responses are the major factors resulting in the loosening and then failure of total joint arthroplasties. It is feasible to improve the lubrication and reduce the wear of artificial joint system. Polyetheretherketone (PEEK) is considered as a potential bearing material due to its mechanical characteristics of resistance to fatigue strain. The PEEK wear particles have been indicated to be involved in biological responses in vitro, and further studies regarding the wear phenomena and wear particle generation are needed. In this study, we have established an accelerated wear testing system with microfabricated surfaces. Various contact pressures and lubricants have been utilized in the accelerated wear tests. Our results showed that increasing contact pressure resulted in an increase of wear particle sizes and wear rate, and the size of PEEK wear particles can be controlled by the feature size of microfabricated surfaces. These results provided the information rapidly about factors that affect the morphology and amount of PEEK wear particles and can be applied in the future for application of PEEK on the biological articulation system. PMID:29230411

Rapid Analyses of Polyetheretherketone Wear Characteristics by Accelerated Wear Testing with Microfabricated Surfaces for Artificial Joint Systems.

PubMed

Su, Chen-Ying; Kuo, Chien-Wei; Fang, Hsu-Wei

2017-01-01

Wear particle-induced biological responses are the major factors resulting in the loosening and then failure of total joint arthroplasties. It is feasible to improve the lubrication and reduce the wear of artificial joint system. Polyetheretherketone (PEEK) is considered as a potential bearing material due to its mechanical characteristics of resistance to fatigue strain. The PEEK wear particles have been indicated to be involved in biological responses in vitro, and further studies regarding the wear phenomena and wear particle generation are needed. In this study, we have established an accelerated wear testing system with microfabricated surfaces. Various contact pressures and lubricants have been utilized in the accelerated wear tests. Our results showed that increasing contact pressure resulted in an increase of wear particle sizes and wear rate, and the size of PEEK wear particles can be controlled by the feature size of microfabricated surfaces. These results provided the information rapidly about factors that affect the morphology and amount of PEEK wear particles and can be applied in the future for application of PEEK on the biological articulation system.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Mulligan, Anthony C.; Rigali, Mark J.; Sutaria, Manish P.; Popovich, Dragan; Halloran, Joseph P.; Fulcher, Michael L.; Cook, Randy C.

2005-12-13

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Mulligan, Anthony C.; Rigali, Mark J.; Sutaria, Manish P.; Popovich, Dragan; Halloran, Joseph P.; Fulcher, Michael L.; Cook, Randy C.

2009-04-14

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Rigali, Mark J.; Sutaria, Manish P.; Mulligan, Anthony C.; Popovich, Dragan

2004-03-23

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Friction and wear properties of three hard refractory coatings applied by radiofrequency sputtering

NASA Technical Reports Server (NTRS)

Brainard, W. A.

1977-01-01

The adherence, friction, and wear properties of thin hard refractory compound coatings applied to 440C bearing steel by radiofrequency sputtering were investigated. Friction and wear tests were done with nonconforming pin on disk specimens. The compounds examined were chromium carbide, molybdenum silicide, and titanium carbide. The adherence, friction, and wear were markedly improved by the application of a bias voltage to the bearing steel substrate during coating deposition. Analysis by X-ray photoelectron spectroscopy indicated that the improvement may be due to a reduction in impurities in bias deposited coatings. A fivefold reduction in oxygen concentration in MoSi2 coating by biasing was noted. Chromium carbide was not effective as an antiwear coating. Molybdenum silicide provided some reduction in both friction and wear. Titanium carbide exhibited excellent friction and antiwear properties at light loads. Plastic flow and transfer of the coating material onto the pin specimen appears to be important in achieving low friction and wear.

Effects of potassium titanate fiber on the wear of automotive brake linings

NASA Technical Reports Server (NTRS)

Halberstadt, M. L.; Mansfield, J. A.; Rhee, S. K.

1977-01-01

Asbestos reinforcing fiber in an automotive friction material was replaced by an experimental ingredient having better thermal stability, and the effects on wear and friction were studied. A friction materials test machine (SAE J661a) was used to determine friction and wear, under constant energy output conditions, as a function of temperature between 121 and 343 C (250 and 650 F). When potassium titanate fiber replaced one half of the asbestos in a standard commercial lining, with a 40 percent upward adjustment of phenolic resin content, wear above 204 C (400 F) was improved by 40% and friction by 30%. Tests on a full-scale inertial dynamometer supported the findings of the sample dynamometer tests. It was demonstrated that the potassium titanate fiber contributes directly to the improvement in wear and friction.

Effect of load on the tribological properties of hypereutectic Al-Si alloy under boundary lubrication conditions

NASA Astrophysics Data System (ADS)

Kumar, Parveen; Wani, M. F.

2017-11-01

Researchers reported that the IC engine components (piston, cylinder liner etc) fail due to the friction losses (~45%) and wear losses (~25-40%). So the demand of light weight, low friction and wear resistance alloys increases day by day, which reduces the emission and increases the efficiency of the IC engine. In this connection, tribological tests on hypereutectic Al-25Si alloy were performed using a ball-on-disk configuration under dry and lubricated sliding conditions. Hypereutectic Al-25Si alloy was prepared by rapid solidification process with T6 condition. T6 condition improves the friction, wear and mechanical properties of the alloy. Friction coefficient and wear rate of the alloy was measured under high loads ranging from 100 to 300 N. It was found that the friction coefficient (COF) and wear rate of hypereutectic Al-25Si alloy/steel tribo pair increased with increase in load. Significant reduction in COF and wear rate was accomplished with SAE20W50 engine oil and Si particles act as solid lubricant. Optical microscope, 3D surface profilometer and scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) were used for characterization the worn surface morphologies. The morphology, size and distribution of high Si particles due to its fabrication process caused the improvements in COF and wear rate under lubricated conditions. Adhesive wear, abrasive wear and plastic deformation acted as the dominant wear mechanism for hypereutectic Al-25Si alloy.

The association between refractive cutoffs for spectacle provision and visual improvement among school-aged children in South Africa.

PubMed

Congdon, Nathan G; Patel, Nita; Esteso, Paul; Chikwembani, Florence; Webber, Fiona; Msithini, Robert Bongi; Ratcliffe, Amy

2008-01-01

To evaluate different refractive cutoffs for spectacle provision with regards to their impact on visual improvement and spectacle compliance. Prospective study of visual improvement and spectacle compliance. South African school children aged 6-19 years receiving free spectacles in a programme supported by Helen Keller International. Refractive error, age, gender, urban versus rural residence, presenting and best-corrected vision were recorded for participants. Spectacle wear was observed directly at an unannounced follow-up examination 4-11 months after initial provision of spectacles. The association between five proposed refractive cutoff protocols and visual improvement and spectacle compliance were examined in separate multivariate models. Refractive cutoffs for spectacle distribution which would effectively identify children with improved vision, and those more likely to comply with spectacle wear. Among 8520 children screened, 810 (9.5%) received spectacles, of whom 636 (79%) were aged 10-14 years, 530 (65%) were girls, 324 (40%) had vision improvement > or = 3 lines, and 483 (60%) were examined 6.4+/-1.5 (range 4.6 to 10.9) months after spectacle dispensing. Among examined children, 149 (31%) were wearing or carrying their glasses. Children meeting cutoffs < or = -0.75 D of myopia, > or = +1.00 D of hyperopia and > or = +0.75 D of astigmatism had significantly greater improvement in vision than children failing to meet these criteria, when adjusting for age, gender and urban versus rural residence. None of the proposed refractive protocols discriminated between children wearing and not wearing spectacles. Presenting vision and improvement in vision were unassociated with subsequent spectacle wear, but girls (p < or = 0.0006 for all models) were more likely to be wearing glasses than were boys. To the best of our knowledge, this is the first suggested refractive cutoff for glasses dispensing validated with respect to key programme outcomes. The lack of association between spectacle retention and either refractive error or vision may have been due to the relatively modest degree of refractive error in this African population.

Improved Wear Resistance of Low Carbon Steel with Plasma Melt Injection of WC Particles

NASA Astrophysics Data System (ADS)

Liu, Aiguo; Guo, Mianhuan; Hu, Hailong

2010-08-01

Surface of a low carbon steel Q235 substrate was melted by a plasma torch, and tungsten carbide (WC) particles were injected into the melt pool. WC reinforced surface metal matrix composite (MMC) was synthesized. Dry sliding wear behavior of the surface MMC was studied and compared with the substrate. The results show that dry sliding wear resistance of low carbon steel can be greatly improved by plasma melt injection of WC particles. Hardness of the surface MMC is much higher than that of the substrate. The high hardness lowers the adhesion and abrasion of the surface MMC, and also the friction coefficient of it. The oxides formed in the sliding process also help to lower the friction coefficient. In this way, the dry sliding wear resistance of the surface MMC is greatly improved.

Unique Tuft Test Facility Dramatically Reduces Brush Seal Development Costs

NASA Technical Reports Server (NTRS)

Fellenstein, James A.

1997-01-01

Brush seals have been incorporated in the latest turbine engines to reduce leakage and improve efficiency. However, the life of these seals is limited by wear. Studies have shown that optimal sealing characteristics for a brush seal occur before the interference fit between the brush and shaft is excessively worn. Research to develop improved tribopairs (brush and coating) with reduced wear and lower friction has been hindered by the lack of an accurate, low-cost, efficient test methodology. Estimated costs for evaluating a new material combination in an engine company seal test program are on the order of $100,000. To address this need, the NASA Lewis Research Center designed, built, and validated a unique, innovative brush seal tuft tester that slides a single tuft of brush seal wire against a rotating shaft under controlled loads, speeds, and temperatures comparable to those in turbine engines. As an initial screening tool, the brush seal tuft tester can tribologicaly evaluate candidate seal materials for 1/10th the cost of full-scale seal tests. Previous to the development of the brush seal tuft tester facility, most relevant tribological data had been obtained from full-scale seal tests conducted primarily to determine seal leakage characteristics. However, from a tribological point of view, these tests included the confounding effects of varying contact pressures, bristle flaring, high-temperature oxidation, and varying bristle contact angles. These confounding effects are overcome in tuft testing. The interface contact pressures can be either constant or varying depending on the tuft mounting device, and bristle wear can be measured optically with inscribed witness marks. In a recent cooperative program with a U.S. turbine engine manufacturer, five metallic wire candidates were tested against a plasma-sprayed Nichrome-bonded chrome carbide. The wire materials used during this collaboration were either nickel-chrome- or cobaltchrome-based superalloys. These tests corroborated full-scale seal test results and provided insight into previously untested combinations. As the cycle temperature for improved efficiency turbine engines increases, new brush seal materials combinations must be considered. Future brush seal tuft testing will include both metallic and ceramic bristles versus commercial and NASA-developed shaft coatings. The ultimate goal of this work is to expand the current data base so that seal designers can tailor brush seal materials to specific applications.

An improved automotive brake lining using fibrous potassium titanate

NASA Technical Reports Server (NTRS)

Mansfield, J. A.; Halberstadt, M. L.; Riccitiello, S. R.; Rhee, S. K.

1976-01-01

Simultaneous fade reduction and wear improvement of a commercial automotive brake lining were achieved by adding fibrous potassium titanate. The dependence of friction and wear characteristics on quantitative variations in potassium titanate, asbestos, phenolic binder, and organic and inorganic modifiers was evaluated.

Technology for improving the wear resistance of aggregates by materials impregnation

DOT National Transportation Integrated Search

1981-08-01

The use of impregnation as a means of improving the wear resistance of natural aggregates was investigated. A series of tests were conducted using four aggregates of varying quality, selected from a sampling of 40 different aggregates. Tests performe...

Effect of friction stir processing on tribological properties of Al-Si alloys

NASA Astrophysics Data System (ADS)

Aktarer, S. M.; Sekban, D. M.; Yanar, H.; Purçek, G.

2017-02-01

As-cast Al-12Si alloy was processed by single-pass friction stir processing (FSP), and its effect on mainly friction and wear properties of processed alloy was studied in detail. The needle-shaped eutectic silicon particles were fragmented by intense plastic deformation and dynamic recrystallization during FSP. The fragmented and homogenously distributed Si particles throughout the improve the mechanical properties and wear behavior of Al-12Si alloy. The wear mechanisms for this improvement were examined and the possible reasons were discussed.

Tooth wear and wear investigations in dentistry.

PubMed

Lee, A; He, L H; Lyons, K; Swain, M V

2012-03-01

Tooth wear has been recognised as a major problem in dentistry. Epidemiological studies have reported an increasing prevalence of tooth wear and general dental practitioners see a greater number of patients seeking treatment with worn dentition. Although the dental literature contains numerous publications related to management and rehabilitation of tooth wear of varying aetiologies, our understanding of the aetiology and pathogenesis of tooth wear is still limited. The wear behaviour of dental biomaterials has also been extensively researched to improve our understanding of the underlying mechanisms and for the development of restorative materials with good wear resistance. The complex nature of tooth wear indicates challenges for conducting in vitro and in vivo wear investigations and a clear correlation between in vitro and in vivo data has not been established. The objective was to critically review the peer reviewed English-language literature pertaining to prevalence and aetiology of tooth wear and wear investigations in dentistry identified through a Medline search engine combined with hand-searching of the relevant literature, covering the period between 1960 and 2011. © 2011 Blackwell Publishing Ltd.

Effect of medium on friction and wear properties of compacted graphite cast iron processed by biomimetic coupling laser remelting process

NASA Astrophysics Data System (ADS)

Guo, Qing-chun; Zhou, Hong; Wang, Cheng-tao; Zhang, Wei; Lin, Peng-yu; Sun, Na; Ren, Luquan

2009-04-01

Stimulated by the cuticles of soil animals, an attempt to improve the wear resistance of compact graphite cast iron (CGI) with biomimetic units on the surface was made by using a biomimetic coupled laser remelting process in air and various thicknesses water film, respectively. The microstructures of biomimetic units were examined by scanning electron microscope and X-ray diffraction was used to describe the microstructure and identify the phases in the melted zone. Microhardness was measured and the wear behaviors of biomimetic specimens as functions of different mediums as well as various water film thicknesses were investigated under dry sliding condition, respectively. The results indicated that the microstructure zones in the biomimetic specimens processed with water film are refined compared with that processed in air and had better wear resistance increased by 60%, the microhardness of biomimetic units has been improved significantly. The application of water film provided finer microstructures and much more regular grain shape in biomimetic units, which played a key role in improving the friction properties and wear resistance of CGI.

Sensor of total hip arthoplasty wear designed on principle of scanning profilometry

NASA Astrophysics Data System (ADS)

Rössler, Tomas; Mandat, Dusan; Gallo, Jiri; Hrabovsky, Miroslav; Pochmon, Michal; Havranek, Vitezslav

2008-12-01

Total hip arthroplasty significantly improves the quality of life in majority of patients with osteoarthritis. However, prosthetic wear is a problem because of inducing the development of aseptic loosening and periprosthetic osteolysis which needs the revision surgery. Thus, the polyethylene wear measurement is the central to contemporary orthopaedics and this interesting has encouraged the development and improvement of both radiologic (in vivo) and non-radiologic (in vitro) methods for polyethylene wear quantification. The principles of polyethylene liner wear measurements are predominantly geometric; nevertheless, the realization of individual types of in vivo measurements brings with it the necessity of many simplifications and compromising steps to acquire approximately accurate values. In fact, the volumetric wear can be obtained by mathematical conversion based on the most linear shift of femoral head in the cup. However, such approach is understood to be somewhat insufficient. Our ongoing research pointed to the development of optical non-contact method for wear measurement and its results are introduced in this paper including the methodology designed for the usability validation of the method for the given purpose and the description of sensor, its principle, technical realization, design and parameters.

Tribological properties of coal slurries

NASA Technical Reports Server (NTRS)

Fusaro, Robert L.; Schrubens, Dale L.

1987-01-01

A pin-on-disk tribometer was used to study the tribological properties of methyl alcohol-coal slurries. Friction coefficients, steel pin wear rates and wear surface morphological studies were conducted on AISI 440C HT and M-50 bearing steels which were slid dry and in solutions of methyl alcohol, methyl alcohol-fine coal particles, and methyl alcohol-fine coal particles-flocking additive. The latter was an oil derived from coal and originally intended to be added to the coal slurry to improve the sedimentation and rheology properties. The results of this study indicated that the addition of the flocking additive to the coal slurry markedly improved the tribological properties, especially wear. In addition, the type of steel was found to be very important in determining the type of wear that took place. Cracks and pits were found on the M-50 steel pin wear surfaces that slid in the coal slurries while 440C HT steel pins showed none.

A novel method for isolation and recovery of ceramic nanoparticles and metal wear debris from serum lubricants at ultra-low wear rates.

PubMed

Lal, S; Hall, R M; Tipper, J L

2016-09-15

Ceramics have been used to deliver significant improvements in the wear properties of orthopaedic bearing materials, which has made it challenging to isolate wear debris from simulator lubricants. Ceramics such as silicon nitride, as well as ceramic-like surface coatings on metal substrates have been explored as potential alternatives to conventional implant materials. Current isolation methods were designed for isolating conventional metal, UHMWPE and ceramic wear debris. In this paper, we describe a methodology for isolation and recovery of ceramic or ceramic-like coating particles and metal wear particles from serum lubricants under ultra-low and low wear performance. Enzymatic digestion was used to digest the serum proteins and sodium polytungstate was used as a novel density gradient medium to isolate particles from proteins and other contaminants by ultracentrifugation. This method demonstrated over 80% recovery of particles and did not alter the size or morphology of ceramic and metal particles during the isolation process. Improvements in resistance to wear and mechanical damage of the articulating surfaces have a large influence on longevity and reliability of joint replacement devices. Modern ceramics have demonstrated ultra-low wear rates for hard-on-hard total hip replacements. Generation of very low concentrations of wear debris in simulator lubricants has made it challenging to isolate the particles for characterisation and further analysis. We have introduced a novel method to isolate ceramic and metal particles from serum-based lubricants using enzymatic digestion and novel sodium polytungstate gradients. This is the first study to demonstrate the recovery of ceramic and metal particles from serum lubricants at lowest detectable in vitro wear rates reported in literature. Copyright © 2016. Published by Elsevier Ltd.

Effect of CeO2 on Microstructure and Wear Resistance of TiC Bioinert Coatings on Ti6Al4V Alloy by Laser Cladding

PubMed Central

Wang, Haojun

2017-01-01

To solve the lack of wear resistance of titanium alloys for use in biological applications, various prepared coatings on titanium alloys are often used as wear-resistant materials. In this paper, TiC bioinert coatings were fabricated on Ti6Al4V by laser cladding using mixed TiC and ZrO2 powders as the basic pre-placed materials. A certain amount of CeO2 powder was also added to the pre-placed powders to further improve the properties of the TiC coatings. The effects of CeO2 additive on the phase constituents, microstructures and wear resistance of the TiC coatings were researched in detail. Although the effect of CeO2 on the phase constituents of the coatings was slight, it had a significant effect on the microstructure and wear resistance of the coatings. The crystalline grains in the TiC coatings, observed by a scanning electron microscope (SEM), were refined due to the effect of the CeO2. With the increase of CeO2 additive content in the pre-placed powders, finer and more compact dendrites led to improvement of the micro-hardness and wear resistance of the TiC coatings. Also, 5 wt % content of CeO2 additive in the pre-placed powders was the best choice for improving the wear properties of the TiC coatings. PMID:29301218

Autophagy mediated CoCrMo particle-induced peri-implant osteolysis by promoting osteoblast apoptosis

PubMed Central

Wang, Zhenheng; Liu, Naicheng; Liu, Kang; Zhou, Gang; Gan, Jingjing; Wang, Zhenzhen; Shi, Tongguo; He, Wei; Wang, Lintao; Guo, Ting; Bao, Nirong; Wang, Rui; Huang, Zhen; Chen, Jiangning; Dong, Lei; Zhao, Jianning; Zhang, Junfeng

2015-01-01

Wear particle-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for THA (total hip arthroplasty) failure and revision surgery. Although existing studies suggest that osteoblast apoptosis induced by wear debris is involved in aseptic loosening, the underlying mechanism linking wear particles to osteoblast apoptosis remains almost totally unknown. In the present study, we investigated the effect of autophagy on osteoblast apoptosis induced by CoCrMo metal particles (CoPs) in vitro and in a calvarial resorption animal model. Our study demonstrated that CoPs stimulated autophagy in osteoblasts and PIO (particle-induced osteolysis) animal models. Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts. Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models. Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model. Collectively, these results suggest that autophagy plays a key role in CoPs-induced osteolysis and that targeting autophagy-related pathways may represent a potential therapeutic approach for treating particle-induced peri-implant osteolysis. PMID:26566231

Improved adaptability of polyaryl-ether-ether-ketone with texture pattern and graphite-like carbon film for bio-tribological applications

NASA Astrophysics Data System (ADS)

Ren, Siming; Huang, Jinxia; Cui, Mingjun; Pu, Jibin; Wang, Liping

2017-04-01

With the development of surface treatment technology, an increasing number of bearings, seals, dynamic friction drive or even biomedical devices involve a textured surface to improve lubrication and anti-wear. The present investigation has been conducted in order to evaluate the friction and wear behaviours of textured polyaryl-ether-ether-ketone (PEEK) coated with a graphite-like carbon (GLC) film sliding against stainless steel pin in biological medium. Compared with pure PEEK, the PEEK coated with GLC film shows excellent tribological performance with a low friction of 0.08 and long lifetime (wear volumes are about 3.78 × 10-4 mm3 for un-textured one and 2.60 × 10-4 mm3 for textured GLC film after 36,000 s of sliding) under physiological saline solution. In particular, the GLC film with appropriate dimple area density is effective to improve friction reduction and wear resistance properties of PEEK substrate under biological solution, which is attributed to the entrapment of wear debris in the dimples to inhibit the graphitization and the fluid dynamic pressure effect derived from the texture surface to increase the thickness in elastohydrodynamic lubrication (EHL) film during sliding motions. Moreover, the friction coefficient of GLC film under physiological saline solution decreases with the increase in the applied load. With the increasing applied load, the texture surface is responsible for accounting the improved wear resistance and a much lower graphitization of the GLC film during whole test.

Characteristics of highly cross-linked polyethylene wear debris in vivo

PubMed Central

Baxter, Ryan M.; MacDonald, Daniel W.; Kurtz, Steven M.; Steinbeck, Marla J.

2014-01-01

Despite the widespread implementation of highly cross-linked polyethylene (HXLPE) liners to reduce the clinical incidence of osteolysis, it is not known if the improved wear resistance will outweigh the inflammatory potential of HXLPE wear debris generated in vivo. Thus, we asked: What are the differences in size, shape, number, and biological activity of polyethylene wear particles obtained from primary total hip arthroplasty revision surgery of conventional polyethylene (CPE) versus remelted or annealed HXLPE liners? Pseudocapsular tissue samples were collected from revision surgery of CPE and HXLPE (annealed and remelted) liners, and digested using nitric acid. The isolated polyethylene wear particles were evaluated using scanning electron microscopy. Tissues from both HXLPE cohorts contained an increased percentage of submicron particles compared to the CPE cohort. However, the total number of particles was lower for both HXLPE cohorts, as a result there was no significant difference in the volume fraction distribution and specific biological activity (SBA; the relative biological activity per unit volume) between cohorts. In contrast, based on the decreased size and number of HXLPE wear debris there was a significant decrease in total particle volume (mm3/g of tissue). Accordingly, when the SBA was normalized by total particle volume (mm3/gm tissue) or by component wear volume rate (mm3/year), functional biological activity of the HXLPE wear debris was significantly decreased compared to the CPE cohort. Indications for this study are that the osteolytic potential of wear debris generated by HXLPE liners in vivo is significantly reduced by improvements in polyethylene wear resistance. PMID:23436587

Improvement in the assessment of wear of total knee replacements using coordinate-measuring machine techniques.

PubMed

Blunt, L A; Bills, P J; Jiang, X-Q; Chakrabarty, G

2008-04-01

Total joint replacement is one of the most common elective surgical procedures performed worldwide, with an estimate of 1.5x 10(6) operations performed annually. Currently joint replacements are expected to function for 10-15 years; however, with an increase in life expectancy, and a greater call for knee replacement due to increased activity levels, there is a requirement to improve their function to offer longer-term improved quality of life for patients. Wear analysis of total joint replacements has long been an important means in determining failure mechanisms and improving longevity of these devices. The effectiveness of the coordinate-measuring machine (CMM) technique for assessing volumetric material loss during simulated life testing of a replacement knee joint has been proved previously by the present authors. The purpose of the current work is to present an improvement to this method for situations where no pre-wear data are available. To validate the method, simulator tests were run and gravimetric measurements taken throughout the test, such that the components measured had a known wear value. The implications of the results are then discussed in terms of assessment of joint functionality and development of standardized CMM-based product standards. The method was then expanded to allow assessment of clinically retrieved bearings so as to ascertain a measure of true clinical wear.

Plasma deposition and surface modification techniques for wear resistance

NASA Technical Reports Server (NTRS)

Spalvins, T.

1982-01-01

The ion-assisted or plasma coating technology is discussed as it applies to the deposition of hard, wear resistant refractory compound films. Of the many sputtering and ion plating modes and configurations the reactive magnetron sputtering and the reactive triode ion plating techniques are the preferred ones to deposit wear resistant coatings for tribological applications. Both of these techniques incorporate additional means to enhance the ionization efficiency and chemical reaction to precision tailor desirable tribological characteristics. Interrelationships between film formation, structure, and ribological properties are strictly controlled by the deposition parameters and the substrate condition. The enhanced ionization contributes to the excellent adherence and coherence, reduced internal stresses and improved structural growth to form dense, cohesive, equiaxed grain structure for improved wear resistance and control.

Texturing of UHMWPE surface via NIL for low friction and wear properties

NASA Astrophysics Data System (ADS)

Suryadi Kustandi, Tanu; Choo, Jian Huei; Low, Hong Yee; Sinha, Sujeet K.

2010-01-01

Wear is a major obstacle limiting the useful life of implanted ultra-high molecular weight polyethylene (UHMWPE) components in total joint arthroplasty. It has been a continuous effort in the implant industry to reduce the frictional wear problem of UHMWPE by improving the structure, morphology and mechanical properties of the polymer. In this paper, a new paradigm that utilizes nanoimprint lithography (NIL) in producing textures on the surface of UHMWPE is proposed to efficiently improve the tribological properties of the polymer. Friction and wear experiments were conducted on patterned and controlled (non-patterned) UHMWPE surfaces using a commercial tribometer, mounted with a silicon nitride ball, under a dry-sliding condition with normal loads ranging from 60 to 200 mN. It has been shown that the patterned UHMWPE surface showed a reduction in the coefficient of friction between 8% and 35% as compared with the controlled (non-patterned) surface, depending on the magnitude of the normal load. Reciprocating wear experiments also showed that the presence of surface textures on the polymer resulted in lower wear depth and width, with minimal material transfer to the sliding surface.

Sliding seal materials for adiabatic engines

NASA Technical Reports Server (NTRS)

Lankford, J.

1985-01-01

The sliding friction coefficients and wear rates of promising carbide, oxide, and nitride materials were measured under temperature, environmental, velocity, loading conditions that are representative of the adiabatic engine environment. In order to provide guidance needed to improve materials for this application, the program stressed fundamental understanding of the mechanisms involved in friction and wear. Microhardness tests were performed on the candidate materials at elevated temperatures, and in atmospheres relevant to the piston seal application, and optical and electron microscopy were used to elucidate the micromechanisms of wear following wear testing. X-ray spectroscopy was used to evaluate interface/environment interactions which seemed to be important in the friction and wear process. Electrical effects in the friction and wear processes were explored in order to evaluate the potential usefulness of such effects in modifying the friction and wear rates in service. However, this factor was found to be of negligible significance in controlling friction and wear.

Friction and wear life properties of polyimide thin films

NASA Technical Reports Server (NTRS)

Fusaro, R. L.

1972-01-01

A transition in the friction coefficient and wear life properties of Pyralin polyimide (PI) thin films was found to exist at a temperature between 25 deg and 100 deg C. Above this transition, PI thin films gave long wear lives and low friction coefficients. The presence of H2O in air improved the friction and wear life properties at 25 deg C; but at 100 deg C, H2O had a detrimental effect. At 100 deg C and above, a dry argon atmosphere gave lower friction coefficients and longer wear lives than did a dry air atmosphere.

Dry sliding wear of heat treated hybrid metal matrix composites

NASA Astrophysics Data System (ADS)

Naveed, Mohammed; Khan, A. R. Anwar

2016-09-01

In recent years, there has been an ever-increasing demand for enhancing mechanical properties of Aluminum Matrix Composites (AMCs), which are finding wide applications in the field of aerospace, automobile, defence etc,. Among all available aluminium alloys, Al6061 is extensively used owing to its excellent wear resistance and ease of processing. Newer techniques of improving the hardness and wear resistance of Al6061 by dispersing an appropriate mixture of hard ceramic powder and whiskers in the aluminium alloy are gaining popularity. The conventional aluminium based composites possess only one type of reinforcements. Addition of hard reinforcements such as silicon carbide, alumina, titanium carbide, improves hardness, strength and wear resistance of the composites. However, these composites possessing hard reinforcement do posses several problems during their machining operation. AMCs reinforced with particles of Gr have been reported to be possessing better wear characteristics owing to the reduced wear because of formation of a thin layer of Gr particles, which prevents metal to metal contact of the sliding surfaces. Further, heat treatment has a profound influence on mechanical properties of heat treatable aluminium alloys and its composites. For a solutionising temperature of 5500C, solutionising duration of 1hr, ageing temperature of 1750C, quenching media and ageing duration significantly alters mechanical properties of both aluminium alloy and its composites. In the light of the above, the present paper aims at developing aluminium based hybrid metal matrix composites containing both silicon carbide and graphite and characterize their mechanical properties by subjecting it to heat treatment. Results indicate that increase of graphite content increases wear resistance of hybrid composites reinforced with constant SiC reinforcement. Further heat treatment has a profound influence on the wear resistance of the matrix alloy as well as its hybrid composites. For all the heat treatment processes studied ice quenching with ageing duration of 6hrs resulted in improved wear resistance of both the unreinforced matrix alloy and its hybrid composites.

Wear Behavior and Microstructure of Mg-Sn Alloy Processed by Equal Channel Angular Extrusion

PubMed Central

Chen, Jung-Hsuan; Shen, Yen-Chen; Chao, Chuen-Guang; Liu, Tzeng-Feng

2017-01-01

Mg-5wt.% Sn alloy is often used in portable electronic devices and automobiles. In this study, mechanical properties of Mg-5wt.% Sn alloy processed by Equal Channel Angular Extrusion (ECAE) were characterized. More precisely, its hardness and wear behavior were measured using Vickers hardness test and a pin-on-disc wear test. The microstructures of ECAE-processed Mg-Sn alloys were investigated by scanning electron microscope and X-ray diffraction. ECAE process refined the grain sizes of the Mg-Sn alloy from 117.6 μm (as-cast) to 88.0 μm (one pass), 49.5 μm (two passes) and 24.4 μm (four passes), respectively. Meanwhile, the hardness of the alloy improved significantly. The maximum wear resistance achieved in the present work was around 73.77 m/mm3, which was obtained from the Mg-Sn alloy treated with a one-pass ECAE process with a grain size of 88.0 μm. The wear resistance improvement was caused by the grain size refinement and the precipitate of the second phase, Mg2Sn against the oxidation of the processed alloy. The as-cast Mg-Sn alloy with the larger grain size, i.e., 117.6 μm, underwent wear mechanisms, mainly adhesive wear and abrasive wear. In ECAE-processed Mg-Sn alloy, high internal energy occurred due to the high dislocation density and the stress field produced by the plastic deformation, which led to an increased oxidation rate of the processed alloy during sliding. Therefore, the oxidative wear and a three-body abrasive wear in which the oxide debris acted as the three-body abrasive components became the dominant factors in the wear behavior, and as a result, reduced the wear resistance in the multi-pass ECAE-processed alloy. PMID:29144414

The Wear Behavior of HVOF Sprayed Near-Nanostructured WC-17%Ni(80/20)Cr Coatings in Dry and Slurry Wear Conditions

NASA Astrophysics Data System (ADS)

Ben Mahmud, Tarek A.; Atieh, Anas M.; Khan, Tahir I.

2017-07-01

The ability to deposit nanostructured feedstock by using high-velocity oxygen-fuel (HVOF) spray offers potential improvements in coating hardness, wear resistance and toughness for applications in the oil sands industry. In this study, the wear behavior of a near-nanostructured coating was compared under dry and slurry abrasive wear test using an uncoated AISI-1018 low-carbon steel substrate as a reference. The coating microstructures were analyzed in the as-sprayed, dry and slurry test conditions using scanning electron microscopy, x-ray diffraction and microhardness measurements. Wear behavior of the steel and coating surfaces were assessed using a pin-on-plate wear test under various loads. The results showed that a coating could be successfully deposited using the HVOF spraying technique and with retention of the near-nanosized WC dispersion within the coating structure. The wear rate under dry test conditions was greater for the steel and coating compared to tests performed under slurry conditions. Examination of the wear tracks revealed that the wear mechanism was different for the two test conditions. Wear in the dry test condition resulted from 2-body abrasion, while 3-body abrasion dominated wear in slurry conditions. The latter showed lower wear rates due to a lubricating effect of the oil.

[Stop the annual firework disaster--a plea for medical scientific associations to take a clear-cut position].

PubMed

Stilma, J S

2009-01-01

Every year people sustain serious injuries when they let off fireworks on New Year's Eve. Public education and protective eye wear do not solve this problem. Experience from other countries shows that the number of injuries decreases dramatically when fireworks are handled only by experienced specialists. Medical scientific associations are invited to promote a ban on ordinary citizens letting off fireworks and for fireworks to be reserved for firework specialists only.

Friction and wear properties of novel HDPE--HAp--Al2O3 biocomposites against alumina counterface.

PubMed

Bodhak, Subhadip; Nath, Shekhar; Basu, Bikramjit

2009-03-01

In an effort to enhance physical properties of biopolymers (high-density polyethylene, HDPE) in terms of elastic modulus and hardness, various ceramic fillers, like alumina (Al2O3) and hydroxyapatite (HAp) are added, and therefore it is essential to assess the friction and wear resistance properties of HDPE biocomposites. In this perspective, HDPE composites with varying ceramic filler content (upto 40 vol%) were fabricated under the optimal compression molding conditions and their friction and wear properties were evaluated against Al2O3 at fretting contacts. All the experiments were conducted at a load of 10 N for duration of 100,000 cycles in both dry as well as simulated body fluid (SBF). Such planned set of experiments has been designed to address three important issues: (a) whether the improvement in physical properties (hardness, E-modulus) will lead to corresponding improvement in friction and wear properties; (b) whether the fretting in SBF will provide sufficient lubrication in order to considerably enhance the tribological properties, as compared to that in ambient conditions; and (c) whether the generation of wear debris particles be reduced for various compositionally modified polymer composites, in comparison to unreinforced HDPE. The experimental results indicate the possibility of achieving extremely low coefficient of friction (COF approximately 0.047) as well as higher wear resistance (wear rate in the order of approximately 10(-7) mm3 N(-1) m(-1)) with the newly developed composites in SBF. A low wear depth of 3.5-4 microm is recorded, irrespective of fretting environment. Much effort has been put forward to correlate the friction and wear mechanisms with abrasion, adhesion, and wear debris formation.

Effects of Deep Cryogenic Treatment on the Wear Resistance and Mechanical Properties of AISI H13 Hot-Work Tool Steel

NASA Astrophysics Data System (ADS)

Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, Ergün; Uygur, İlyas

2015-11-01

In this study, a number of wear and tensile tests were performed to elucidate the effects of deep cryogenic treatment on the wear behavior and mechanical properties (hardness and tensile strength) of AISI H13 tool steel. In accordance with this purpose, three different heat treatments (conventional heat treatment (CHT), deep cryogenic treatment (DCT), and deep cryogenic treatment and tempering (DCTT)) were applied to tool steel samples. DCT and DCTT samples were held in nitrogen gas at -145 °C for 24 h. Wear tests were conducted on a dry pin-on-disk device using two loads of 60 and 80 N, two sliding velocities of 0.8 and 1 m/s, and a wear distance of 1000 m. All test results showed that DCT improved the adhesive wear resistance and mechanical properties of AISI H13 steel. The formation of small-sized and uniformly distributed carbide particles and the transformation of retained austenite to martensite played an important role in the improvements in the wear resistance and mechanical properties. After cleavage fracture, the surfaces of all samples were characterized by the cracking of primary carbides, while the DCT and DCTT samples displayed microvoid formation by decohesion of the fine carbides precipitated during the cryo-tempering process.

Increasing the wear resistance of ultra-high molecular weight polyethylene by adding solid lubricating fillers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panin, S. V., E-mail: svp@ispms.tsc.ru; Kornienko, L. A.; Poltaranin, M. A.

2014-11-14

In order to compare effectiveness of adding solid lubricating fillers for polymeric composites based on ultra-high molecular weight polyethylene (UHMWPE) with graphite, molybdenum disulfide and polytetrafluoroethylene, their tribotechnical characteristics under dry friction, boundary lubrication and abrasive wearing were investigated. The optimal weight fractions of fillers in terms of improving wear resistance have been determined. The supramolecular structure and topography of wear track surfaces of UHMWPE-based composites with different content of fillers have been studied.

New Challenges in Tribology: Wear Assessment Using 3D Optical Scanners

PubMed Central

Valigi, Maria Cristina; Logozzo, Silvia; Affatato, Saverio

2017-01-01

Wear is a significant mechanical and clinical problem. To acquire further knowledge on the tribological phenomena that involve freeform mechanical components or medical prostheses, wear tests are performed on biomedical and industrial materials in order to solve or reduce failures or malfunctions due to material loss. Scientific and technological advances in the field of optical scanning allow the application of innovative devices for wear measurements, leading to improvements that were unimaginable until a few years ago. It is therefore important to develop techniques, based on new instrumentations, for more accurate and reproducible measurements of wear. The aim of this work is to discuss the use of innovative 3D optical scanners and an experimental procedure to detect and evaluate wear, comparing this technique with other wear evaluation methods for industrial components and biomedical devices. PMID:28772905

New Challenges in Tribology: Wear Assessment Using 3D Optical Scanners.

PubMed

Valigi, Maria Cristina; Logozzo, Silvia; Affatato, Saverio

2017-05-18

Wear is a significant mechanical and clinical problem. To acquire further knowledge on the tribological phenomena that involve freeform mechanical components or medical prostheses, wear tests are performed on biomedical and industrial materials in order to solve or reduce failures or malfunctions due to material loss. Scientific and technological advances in the field of optical scanning allow the application of innovative devices for wear measurements, leading to improvements that were unimaginable until a few years ago. It is therefore important to develop techniques, based on new instrumentations, for more accurate and reproducible measurements of wear. The aim of this work is to discuss the use of innovative 3D optical scanners and an experimental procedure to detect and evaluate wear, comparing this technique with other wear evaluation methods for industrial components and biomedical devices.

Concrete surface with nano-particle additives for improved wearing resistance to increasing truck traffic.

DOT National Transportation Integrated Search

2012-07-01

This study focused on the use of nanotechnology in concrete to improve the wearing resistance of concrete. The nano : materials used were polymer cross-linked aerogels, carbon nanotubes, and nano-SiO2, nano-CaCO3, and nano-Al2O3 : particles. As an in...

Two-body and three-body wear of glass ionomer cements.

PubMed

Kunzelmann, K H; Bürkle, V; Bauer, C

2003-11-01

Glass ionomer cements (GIC) have been modified in an attempt to improve their mechanical properties. The objective of the present paper was to compare the two-body and three-body wear of four modified GIC. The tested materials were Fuji IX (GC Corporation), Hi-Fi (Shofu) and Ketac Molar Aplicap (3M/ESPE). The cermet cement Ketac Silver Maxicap (3M/ESPE) was used as reference material. Two-body wear tests were carried out in the computer controlled 'artificial mouth' of the Munich Dental School, three-body wear was tested with the ACTA wear machine. The resulting average two-body wear rates (in microm) were: Fuji IX 327 (SD +/- 82) < Ketac Molar 379 (SD +/- 94) < Hi-Fi 376 (SD +/- 90) < Ketac silver 449 (SD +/- 127). The differences between the materials were significant (P < 0.05, ANOVA, modified LSD-test) with the exception of Ketac Molar and Hi-Fi. The average three-body wear rates (in microm) were: Hi-Fi 30 (SD +/- 10) < Ketac Molar +/- 42 (SD +/- 12) < Fuji IX 49 (SD +/- 14) < Ketac silver 73 (SD +/- 23). The difference between Ketac silver and the three other materials was significant (P < 0.05, ANOVA, modified LSD-test). No significant difference was calculated between Hi-Fi, Ketac Molar and Fuji IX. As Ketac Molar, Hi-Fi and Fuji IX show better wear resistance compared to Ketac silver both in occlusal-contact and contact-free areas, it may be assumed that the wear resistance of a glass ionomer cement may be improved more by changing the powder: liquid ratio than by incorporating silver particles into the glass powder.

A hybrid floating brush seal (HFBS) for improved sealing and wear performance in turbomachinery applications

NASA Astrophysics Data System (ADS)

Lattime, Scott Byran

A conceptually new type of seal has been developed for gas turbine applications which dramatically reduces wear and leakage associated with current labyrinth and brush seal technologies. The Hybrid Floating Brush Seal (HFBS) combines brush seal and film riding face seal technologies to create a hybrid seal that allows both axial and radial excursions of the sealed shaft, while simultaneously eliminating interface surface speeds (friction and heat) between the rotor and the brush material that characterize standard brush seal technology. A simple test rig was designed to evaluate feasibility of the HFBS under relatively low pressures and rotational speeds (50psig, 5krpm). A second test stand was created to study the effects of centrifugal force on bristle deflection. A third test facility was constructed for prototype development and extensive room temperature testing at moderate pressures and fairly high rotational speeds (100psig, 40krpm). This test rig also allowed the evaluation of the HFBS during axial movement of a rotating shaft. An analytical model to predict the effects of centrifugal force on the bristles of a rotating brush seal was developed. Room temperature analysis of the HFBS proved successful for relatively high operating rotational velocities at moderate pressures with very acceptable leakage rates for gas turbine engines. Brush seals were able to track rotor speeds up to 24krpm while maintaining sealing integrity. The HFBS's ability to function under axial shaft displacement and synchronous dynamic radial loading was also proven successful. Hydrodynamic performance of the face seal was proven to provide adequate stiffness and load carrying capacity to keep the brush seal from contacting the face seal at pressure drops across the brush of up to 100psi. Leakage performance over standard brush seal and labyrinth technology was quite dramatic. The HFBS showed its sealing advantage using much higher radial interference between the rotor and the bristle bore over standard brush seal designs. Experimental results of the HFBS showed leakage reductions of 6 to 7 times that of a standard brush seal at the same operating pressure ratios and rotational speed and an order of magnitude less than numerical predictions of a standard labyrinth seal. (Abstract shortened by UMI.)

Effect of deep cryogenic treatment on the formation of nano-sized carbides and the wear behavior of D2 tool steel

NASA Astrophysics Data System (ADS)

Amini, Kamran; Akhbarizadeh, Amin; Javadpour, Sirus

2012-09-01

The effect of deep cryogenic treatment on the microstructure, hardness, and wear behavior of D2 tool steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), hardness test, pin-on-disk wear test, and the reciprocating pin-on-flat wear test. The results show that deep cryogenic treatment eliminates retained austenite, makes a better carbide distribution, and increases the carbide content. Furthermore, some new nano-sized carbides form during the deep cryogenic treatment, thereby increasing the hardness and improving the wear behavior of the samples.

Wear measurement of the cutting edge of superhard turning tools using TLA technique

NASA Astrophysics Data System (ADS)

Vasváry, L.; Ditrói, F.; Takács, S.; Szabó, Z.; Szűcs, J.; Kundrák, J.; Mahunka, I.

1994-03-01

Wear measurement on superhard boron nitride and artificial diamond turning tools was performed using thin layer activation (TLA) technique. The samples were irradiated in two different geometries to improve the sensitivity of the method and change the region of wear to be investigated. The most proper irradiation parameters and nuclear reactions were investigated for both kind of tools.

Recent advances in the mechanical durability of superhydrophobic materials.

PubMed

Milionis, Athanasios; Loth, Eric; Bayer, Ilker S

2016-03-01

Large majority of superhydrophobic surfaces have very limited mechanical wear robustness and long-term durability. This problem has restricted their utilization in commercial or industrial applications and resulted in extensive research efforts on improving resistance against various types of wear damage. In this review, advances and developments since 2011 in this field will be covered. As such, we summarize progress on fabrication, design and understanding of mechanically durable superhydrophobic surfaces. This includes an overview of recently published diagnostic techniques for probing and demonstrating tribo-mechanical durability against wear and abrasion as well as other effects such as solid/liquid spray or jet impact and underwater resistance. The review is organized in terms of various types of mechanical wear ranging from substrate adhesion, tangential surface abrasion, and dynamic impact to ultrasonic processing underwater. In each of these categories, we highlight the most successful approaches to produce robust surfaces that can maintain their non-wetting state after the wear or abrasive action. Finally, various recommendations for improvement of mechanical wear durability and its quantitative evaluation are discussed along with potential future directions towards more systematic testing methods which will also be acceptable for industry. Copyright © 2015 Elsevier B.V. All rights reserved.

Wear Improvement of Tools in the Cold Forging Process for Long Hex Flange Nuts.

PubMed

Hsia, Shao-Yi; Shih, Po-Yueh

2015-09-25

Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life.

Wear Improvement of Tools in the Cold Forging Process for Long Hex Flange Nuts

PubMed Central

Hsia, Shao-Yi; Shih, Po-Yueh

2015-01-01

Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life. PMID:28793589

Coating glass-ionomer cements with a nanofilled resin.

PubMed

Bonifácio, Clarissa Calil; Werner, Arie; Kleverlaan, Cornelis Johanes

2012-12-01

The objective of this study was to investigate the effect of a nanofilled resin coat on the flexural strength (FS) and the early wear (after 50,000 and 200,000 cycles) of the glass-ionomer cements Fuji IX GP Extra (FIXE) and Ketac Molar Aplicap (KM). Specimens were prepared and half of them were coated with G-Coat plus. The uncoated specimens were used as controls. Flexural strength (n = 10) was evaluated after 24 h using a 3-point bending test on a universal testing machine (ISO 9917-2). Wear (n = 20) was evaluated after 50,000 and 200,000 cycles using the ACTA wear machine. One-way, two-way ANOVA and Tukey post-hoc tests were used to analyze differences in FS and wear. For FIXE the coat significantly increased the FS and the wear along the two time spans. KM did not show a significant difference in FS with the coat. Improvements in wear were observed only after 50,000 cycles. Based on these laboratory results, it is concluded that G-coat Plus is indicated in association with GP IX Extra with the aim to improve the mechanical properties of the former. However, this study is limited to a short-term observation.

Surface Modifications for Improved Wear Performance in Artificial Joints: A Review

NASA Astrophysics Data System (ADS)

Sullivan, Stacey J. L.; Topoleski, L. D. Timmie

2015-11-01

Artificial joint replacement is one of the most successful treatments for arthritis. Excellent wear and corrosion resistance, together with high strength and fracture toughness, are fundamental requirements for implant materials. Wear and/or corrosion of the materials used in artificial joints may lead to implant failure. Therefore, hard and wear-resistant materials, like cobalt-chromium-molybdenum and ceramic, are currently used as bearing surfaces. However, even using such hard materials, wear and/or corrosion related failure of artificial joints remains a central concern. One primary goal in orthopedic biomaterials research is to create more wear-resistant surfaces. Different technologies have been used to create new surfaces, or to modify existing surfaces, to prevent wear. It is the intent of this overview first to provide a summary of materials currently used as bearing surfaces in artificial joints, their functions, and their contributions to device longevity. Then, we will discuss advancements in modifying those bearing surfaces to produce more wear-resistant artificial joints.

Wear mechanisms and improvements of wear resistance in cobalt-chromium alloy femoral components in artificial total knee joints

NASA Astrophysics Data System (ADS)

Que, Like

Wear is one of the major causes of artificial total knee arthroplasty (TKA) failure. Wear debris can cause adverse reactions to the surrounding tissue which can ultimately lead to loosening of the prosthesis. The wear behavior of UHMWPE tibial components have been studied extensively, but relatively little attention has been paid to the CoCrMo femoral component. The goal of the present study was to investigate the wear mechanisms of CoCrMo femoral components, to study the effect of CoCrMo alloy surface roughness on the wear of UHMWPE, and to determine the effect of heat treatments on the wear resistance of the CoCrMo implant alloys. The surface roughness of twenty-seven retrieved CoCrMo femoral components was analyzed. A multiple station wear testing machine and a wear fixture attached to an MTS 858 bionix system were built and used for in vitro wear studies of the CoCrMo/UHMWPE bearing couple. Solution and aging treatments were applied to the CoCrMo alloys. A white light interference surface profilometer (WLISP) and a scanning electron microscope (SEM) were used to measure the surface roughness and to study wear mechanisms of CoCrMo alloy. An optical microscope was used for alloy microstructure study. X-ray diffraction tests were performed to identify alloy phase transformation after aging. The micro-structure, hardness, and wear resistance of the alloys were studied. Surface roughness was used to quantify alloy wear, and the minimum number of surface roughness measurements required to obtain a reliable and repeatable characterization of surface roughness for a worn alloy surface was determined. The surfaces of the retrieved CoCrMo femoral components appeared to be damaged by metal particles embedded in the UHMWPE tibial component and metal-on-metal wear due to UHMWPE tibial component through-wear. Surface roughness of the femoral components was not correlated with patient age, weight, sex, or length of implantation. In vitro wear tests showed that when the CoCrMo alloy surface roughness was higher than 0.022 mum Ra (surface roughness average), UHMWPE wear increased with increasing CoCrMo alloy surface roughness. Bone and poly(methyl methacrylate) (PMMA) bone cement abrasive particles created scratches on the alloy via a ploughing mechanism, and resulted in significantly rougher surfaces than controls without particles (P < 0.01). Solution treatments at 1230sp°C and 1245sp°C reduced the hardness and wear resistance of the as-cast F75 CoCrMo alloy. Aging at 700sp°C caused recrystallization of the forged F799 alloy and improved wear resistance. Thermo-mechanical treatments have the potential to increase the lifetime of artificial joints by increasing the wear resistance of CoCrMo components.

Improvement of wear resistance of plasma-sprayed molybdenum blend coatings

NASA Astrophysics Data System (ADS)

Ahn, Jeehoon; Hwang, Byoungchul; Lee, Sunghak

2005-06-01

The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl2 and Cu9Al4 formed inside the coating.

Friction and wear of radiofrequency-sputtered borides, silicides, and carbides

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1978-01-01

The friction and wear properties of several refractory compound coatings were examined. These compounds were applied to 440 C bearing steel surfaces by radiofrequency (RF) sputtering. The refractory compounds were the titanium and molybdenum borides, the titanium and molybdenum silicides, and the titanium, molybdenum, and boron carbides. Friction testing was done with a pin-on-disk wear apparatus at loads from 0.1 to 5.0 newtons. Generally, the best wear properties were obtained when the coatings were bias sputtered onto 440 C disks that had been preoxidized. Adherence was improved because of the better bonding of the coatings to the iron oxide formed during preoxidation. As a class the carbides provided wear protection to the highest loads. Titanium boride coatings provided low friction and good wear properties to moderate loads.

Robotic-assisted percutaneous coronary intervention--filling an unmet need.

PubMed

Carrozza, Joseph P

2012-02-01

Percutaneous coronary intervention (PCI) has undergone a remarkable evolution over the past 25 years. Initially, the procedure was limited to relatively straightforward lesions and was associated with significant risk and unpredictable long-term efficacy. With the incorporation of new technologies such as stents, the safety and efficacy of the procedure has improved dramatically. However, the fundamental way in which the procedure is performed has changed little since the time of Gruntzig's first successful case. Cumulative exposure to ionizing radiation, orthopedic injuries resulting from wearing shielding aprons, and fatigue from standing for hours at the table have made the catheterization laboratory a "high-risk workplace" for the interventional cardiologist. Robotic-assisted PCI was developed to allow the operator to precisely manipulate angioplasty guidewires, balloons, and stents from a radiation-shielded cockpit. A small first-in-man study demonstrated that PCI can be performed with robotic assistance. The pivotal Percutaneous Robotically Enhanced Coronary Intervention Study trial is currently enrolling patients and evaluating the safety and efficacy of the CorPath® robotically assisted PCI system.

Wear behavior of AISI 1090 steel modified by pulse plasma technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayday, Aysun; Durman, Mehmet

2012-09-06

AISI 1090 steel was pulse plasma treated (PPT) using a Molybdenum electrode. Two different pulse numbers were chosen to obtain modified layers of 20{+-}5 {mu}m thickness. The dry sliding wear studies performed on this steel with and without PPT against an alumina ball counterpart showed that the PPT improved the wear resistance. The pulse number of the PPT modified layer was found to be highly influential in imparting the wear resistance to this steel, due to enhancement of surface hardness depending on treatment time.

Effect of ion-plated films of germanium and silicon on friction, wear, and oxidation of 52100 bearing steel

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Spalvins, T.

1977-01-01

Friction and wear experiments were conducted with ion plated films of germanium and silicon on the surface of 52100 bearing steel both dry and in the presence of mineral oil. Both silicon and germanium were found to reduce wear, with germanium being more effective than silicon. An optimum film thickness of germanium for minimum wear without surface crack formation was found to be approximately 400 nanometers (4000 A). The presence of silicon and germanium on the 52100 bearing steel surface improved resistance to oxidation.

Wear of seal materials used in aircraft propulsion systems

NASA Technical Reports Server (NTRS)

Bill, R. C.; Ludwig, L. P.

1978-01-01

The various types of seal locations in a gas turbine engine are described, and the significance of wear to each type is reviewed. Starting with positive contact shaft seals, existing material selection guidelines are reviewed, and the existing PV (contact pressure X sliding velocity) criteria for selecting seal materials are discussed, along with the theoretical background for these criteria. Examples of wear mechanisms observed to operate in positive contact seals are shown. Design features that can extend the operating capabilities of positive contact seals, including pressure balancing and incorporation of hydrodynamic lift are briefly discussed. It is concluded that, despite the benefits arising from these design features, improved positive contact seal materials from the standpoint of wear, erosion and oxidation resistance will be necessary for further improvements in seal performance and durability, and to meet stringent future challenges.

Wear Characteristics of Ni-Based Hardfacing Alloy Deposited on Stainless Steel Substrate by Laser Cladding

NASA Astrophysics Data System (ADS)

Awasthi, Reena; Limaye, P. K.; Kumar, Santosh; Kushwaha, Ram P.; Viswanadham, C. S.; Srivastava, Dinesh; Soni, N. L.; Patel, R. J.; Dey, G. K.

2015-03-01

In this study, dry sliding wear characteristics of the Ni-based hardfacing alloy (Ni-Mo-Cr-Si) deposited on stainless steel SS316L substrate by laser cladding have been presented. Dry sliding wear behavior of the laser clad layer was evaluated against two different counter bodies, AISI 52100 chromium steel (~850 VHN) and tungsten carbide ball (~2200 VHN) to study both adhesive and abrasive wear characteristics, in comparison with the substrate SS316L using ball on plate reciprocating wear tester. The wear resistance was evaluated as a function of load and sliding speed for a constant sliding amplitude and sliding distance. The wear mechanisms were studied on the basis of wear surface morphology and microchemical analysis of the wear track using SEM-EDS. Laser clad layer of Ni-Mo-Cr-Si on SS316L exhibited much higher hardness (~700 VHN) than that of substrate SS316L (~200 VHN). The laser clad layer exhibited higher wear resistance as compared to SS316L substrate while sliding against both the counterparts. However, the improvement in the wear resistance of the clad layer as compared to the substrate was much higher while sliding against AISI 52100 chromium steel than that while sliding against WC, at the same contact stress intensity.

Plasma-assisted physical vapor deposition surface treatments for tribological control

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis

1990-01-01

In any mechanical or engineering system where contacting surfaces are in relative motion, adhesion, wear, and friction affect reliability and performance. With the advancement of space age transportation systems, the tribological requirements have dramatically increased. This is due to the optimized design, precision tolerance requirements, and high reliability expected for solid lubricating films in order to withstand hostile operating conditions (vacuum, high-low temperatures, high loads, and space radiation). For these problem areas the ion-assisted deposition/modification processes (plasma-based and ion beam techniques) offer the greatest potential for the synthesis of thin films and the tailoring of adherence and chemical and structural properties for optimized tribological performance. The present practices and new approaches of applying soft solid lubricant and hard wear resistant films to engineering substrates are reviewed. The ion bombardment treatments have increased film adherence, lowered friction coefficients, and enhanced wear life of the solid lubricating films such as the dichalcogenides (MoS2) and the soft metals (Au, Ag, Pb). Currently, sputtering is the preferred method of applying MoS2 films; and ion plating, the soft metallic films. Ultralow friction coefficients (less than 0.01) were achieved with sputtered MoS2. Further, new diamond-like carbon and BN lubricating films are being developed by using the ion assisted deposition techniques.

Skin Health Connected to the Use of Absorbent Hygiene Products: A Review.

PubMed

Bender, Johanna Karlsson; Faergemann, Jan; Sköld, Maria

2017-09-01

Over the past 50 years, absorbent hygiene products such as baby diapers and incontinence products have become essential features of modern day life. Through innovation and enhanced technology, their design, composition and performance have been dramatically upgraded from their early forms, and they have transformed the lives of millions of people, improving their quality of life. Skin health related to the use of absorbent hygiene products has accordingly also greatly improved. Still, the wearing of absorbent hygiene products will affect the skin, and for some users the changes in microclimate, mechanical interactions and the exposure to urine and faeces may result in irritant contact dermatitis, i.e. diaper dermatitis (DD) or incontinence-associated dermatitis (IAD). Babies with developing skin and the elderly with deteriorating skin functions who are the most frequent users of absorbent hygiene products are more vulnerable to the causal factors. Although irritant reactions are the most common, allergic contact dermatitis should be considered if a DD/IAD fails to improve by recommended actions. There is also a connection between IAD and pressure ulcer development of which it is important to be aware. A holistic approach of using high-quality absorbent hygiene products in combination with appropriate skin care will help maintaining good skin health.

Investigation of Accelerated Life Prediction Techniques

DTIC Science & Technology

1975-10-01

26, No. 1, 1974, ;). 13. 116. Krukar, M., et al, STUDDED TIRE PAVEMENT WEAR REDUCTION AND REPAIR, Washington State Dept. of Highways, Highway...167. Okushlma, K., and Kakino, Y., STUD * ON INFLUENCE OF GROOVE WEAR OF A TOOL TO SURFACE ROUGHNESS DURING FINISHING TURNING OF CARBON STEEL, Journal...MODIFICATION OF ASPHALT CEMENTS FOR IMPROVE- MENT OF WEAR RESISTANCE OF PAVEMENT SURFACES, Materials Research «nd Development, Inc., Oakland

Cryogenic Cooling of Infrared Electronics

DTIC Science & Technology

1986-05-01

thermally driven, offers the potential of reducing operating and maintenance costs over the entire life cycle because of advan- tages in reduced wear due to...on demand. In addition to conventional mechanical cycles, it is possible to incorporate thermal, thermoelectric, and magnetic processes avoiding wear ...Considerable effort has been expended in improving the components of the Stirling cryocooler, especially in terms of minimizing the wear of the

Ceramic roadway aggregates with improved polish- and wear-resistance

DOT National Transportation Integrated Search

1981-08-01

Through a cooperative program between the Bureau of Mines, Tuscaloosa Research Center and the Federal Highway Administration, synthetic ceramic aggregates having high wear- and polish-resistance were developed. Three hundred aggregate compositions, i...

Day vs. day-night use of ankle-foot orthoses in young children with spastic diplegia: a randomized controlled study.

PubMed

Zhao, Xiaoke; Xiao, Nong; Li, Hongying; Du, Senjie

2013-10-01

The aim of this study was to compare the effectiveness of treatment with hinged ankle-foot orthoses (AFOs) during the day vs. during both the day and the night in young ambulant children with spastic diplegia. In this prospective randomized controlled trial, 112 ambulatory children (70 boys and 42 girls; mean age, 2 yrs 6.93 mos; range, 1 yr 1 mo to 4 yrs 0 mo) with spastic diplegia participated. Forty-eight were classified at level I of the Gross Motor Function Classification System; the remaining 64 were at level II. Using stratified randomization, all children were assigned to either the day AFO-wearing group (n = 56, wearing AFOs all day) or the day-night AFO-wearing group (n = 56, wearing AFOs all day and all night). The two groups underwent conventional rehabilitative treatments five times a week for 8 wks. The primary outcomes measured were passive ankle dorsiflexion angle and sections D and E of the 66-item Gross Motor Function Measure; the root mean square of surface electromyography in the ventral and dorsal lower limb muscles was compared in a subgroup (ten from each group). Seven children did not complete the full intervention: three in the day AFO-wearing group and four in the day-night AFO-wearing group. Significant baseline-postintervention improvements were found for passive ankle dorsiflexion angle and the 66-item Gross Motor Function Measure in both groups (P < 0.05). On the basis of the score changes, there was no significant difference between these two groups with respect to passive ankle dorsiflexion angle; however, the improvements in the 66-item Gross Motor Function Measure were significantly better in the day AFO-wearing group (P < 0.01). A significant root mean square decrease in gastrocnemius (P < 0.05) was present after the intervention in the day AFO-wearing group, whereas the muscles affected in the day-night AFO-wearing group were the gastrocnemius (P < 0.05) and the tibialis anterior (P < 0.001). The results demonstrate that the daytime use of AFOs was more effective in improving Gross Motor Function Measure scores than the day-night use. In addition, the prolonged wearing of AFOs may influence muscle activity, which should be monitored in the clinic.

Studies on the Biotribological and Biological Behavior of Thermally Oxidized Ti6Al4V for Use in Artificial Cervical Disk

NASA Astrophysics Data System (ADS)

Wang, Song; Li, Junhui; Lu, Junzhe; Tyagi, Rajnesh; Liao, Zhenhua; Feng, Pingfa; Liu, Weiqiang

2017-05-01

The artificial cervical disk was simplified and considered as a ball-on-socket model with the material configuration of ultra-high molecular weight polyethylene and Ti6Al4V (PE-on-TC4). In order to improve the wear resistance, an optimized thermal oxidation (TO) coating was applied on TC4 component. The long-term wear behavior of the model was assessed in vitro using a wear simulator under 10 million cycles (MC) testing intervals. The biological behavior was investigated by bone marrow-derived mesenchymal stem cells (BMSCs) cell attachment and cell viability/proliferation assays, respectively. The total average wear rate for PE/TC4 pair was found to be 0.81 mg/MC, whereas the same was about 0.96 mg/MC for PE/TO pair. The wear rate of the metal has been neglected in comparison with that of the mating polymer. PE component was found to suffer severe damage characterized by scratches, fatigue cracks and arc-shaped wear grooves on the edge zone of ball. The dominant wear mechanism was abrasion for metal component while the dominant failure mechanism was a mix of plowing, fatigue and plastic deformation for polymer component. TO coating improved the cell attachment property of TC4, and the cell viability results were also quite good. TO coating protected TC4 from being plowed and avoided the release of toxic metal ions. However, this intensified the wear of PE component. Considering the biotribological and biological behavior in totality, TO coating could still be promising when applied in articulation surfaces.

Experimental Evaluation of Oxide Nanoparticles as Friction and Wear Improvement Additives in Motor Oil

DOE PAGES

Demas, Nicholaos G.; Erck, Robert A.; Lorenzo-Martin, Cinta; ...

2017-01-30

The effect of two nanoparticle oxides on friction and wear was studied under laboratory test conditions using a reciprocating test machine and two test configurations. The addition of these nanoparticles in base stock oil under certain conditions reduced the coefficient of friction and improved wear, but that depended on the test configuration. Examination of the rubbed surfaces showed the pronounced formation of a tribofilm in some cases, while polishing on the surface was also observed in other cases. Contact configuration is important when oxide nanoparticles are being evaluated and the conclusions about their efficacy can be vastly different.

Sliding friction and wear behaviors of surface-coated natural serpentine mineral powders as lubricant additive

NASA Astrophysics Data System (ADS)

Zhang, Baosen; Xu, Yi; Gao, Fei; Shi, Peijing; Xu, Binshi; Wu, Yixiong

2011-01-01

This work aims to investigate the friction and wear properties of surface-coated natural serpentine powders (SP) suspended in diesel engine oil using an Optimal SRV oscillating friction and wear tester. The worn surface was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Results indicated that the additives can improve the wear resistance and decrease friction coefficient of carbon steel friction couples. The 0.5 wt% content of serpentine powders is found most efficient in reducing friction and wear at the load of 50 N. The SEM and XPS analysis results demonstrate that a tribofilm forms on the worn surface, which is responsible for the decrease in friction and wear, mainly with iron oxides, silicon oxides, graphite and organic compounds.

The lexicon of polyethylene wear in artificial joints.

PubMed

McKellop, Harry A

2007-12-01

The analysis of wear on polyethylene components that have been retrieved after use in patients has provided invaluable understanding of how wear occurs in vivo, and how it may be minimized through improved materials and implant design. The great number of such studies that have been published over the past three decades has lead to an extensive vocabulary to describe the tribology of prosthetic joints. However, these also have led to some confusion, due to the occasional misuse of terms from classical tribology, along with the use of multiple terms to describe the same wear phenomenon, and vice versa. The author has proposed that our understanding of wear in artificial joints may be enhanced by recognizing that there are four general subject areas: Modes, Mechanisms, Damage and Debris. Wear Mode 1 occurs when the two bearing surfaces are articulating against each other in the manner intended by the implant designer. Mode 2 occurs when a bearing surface articulates against a non-bearing surface. Mode 3 occurs when third-body abrasive particles have become entrapped between the two bearing surfaces, and Mode 4 occurs when two non-bearing surfaces are wearing against each other. The least wear occurs in Mode 1, whereas severe wear typically occurs in Modes 2, 3 and 4. The classical wear mechanisms that apply to prosthetic joints include adhesion, abrasion and fatigue. These can occur in varying amounts in either of the four wear modes. As used in the literature for the past three decades, wear "damage" can best be defined as the change surface texture or morphology that is caused by the action of the wear mechanisms. Although a wide variety of terms have been used, an overview of the literature indicates that about eight terms have been sufficient to describe the types of damage that occur on retrieved polyethylene components, i.e., burnishing, abrasion, scratches, plastic deformation, cracks, pits, delamination, and embedded third bodies. The author suggests that, as far as possible, investigators endeavor to limit their descriptions of surface damage to these terms and, importantly, to clearly and consistently distinguish the classical wear mechanisms from the types of damage produced by those mechanisms. Wear debris refers to the billions of particles, some measuring in nanometers, that are generated by the wear mechanisms, and that initiate biological reactions, such as osteolysis, that may lead to the failure of the implant. As the methods for recovering wear debris from joint fluids and tissues are improved, investigators are using a growing number of terms to describe them. As with the types of damage, it will be important in the coming years to maximize clarity and minimize redundancy of the vocabulary in this important area of research.

Characterization of ion beam modified ceramic wear surfaces using Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Wei, W.; Lankford, J.

1987-01-01

An investigation of the surface chemistry and morphology of the wear surfaces of ceramic material surfaces modified by ion beam mixing has been conducted using Auger electron spectroscopy and secondary electron microscopy. Studies have been conducted on ceramic/ceramic friction and wear couples made up of TiC and NiMo-bonded TiC cermet pins run against Si3N4 and partially stabilized zirconia disc surfaces modified by the ion beam mixing of titanium and nickel, as well as ummodified ceramic/ceramic couples in order to determine the types of surface changes leading to the improved friction and wear behavior of the surface modified ceramics in simulated diesel environments. The results of the surface analyses indicate that the formation of a lubricating oxide layer of titanium and nickel, is responsible for the improvement in ceramic friction and wear behavior. The beneficial effect of this oxide layer depends on several factors, including the adherence of the surface modified layer or subsequently formed oxide layer to the disc substrate, the substrate materials, the conditions of ion beam mixing, and the environmental conditions.

Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator.

PubMed

Raabe, D; Harrison, A; Ireland, A; Alemzadeh, K; Sandy, J; Dogramadzi, S; Melhuish, C; Burgess, S

2012-03-01

This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator. Experimental studies of wear using this simulator demonstrate that integrating the biological feature of combined force/position hybrid control in dental material testing improves the linearity and reduces the variability of results. In addition, it has been shown that present biaxially operated dental wear simulators are likely to provide misleading results in comparative in vitro/in vivo one-contact studies due to neglecting the occlusal sliding motion in one plane which could introduce an error of up to 49% since occlusal sliding motion D and volumetric wear loss V(loss) are proportional.

The electrodeposition of silver composites using deep eutectic solvents.

PubMed

Abbott, Andrew P; El Ttaib, Khalid; Frisch, Gero; Ryder, Karl S; Weston, David

2012-02-21

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.

Characterization and tribology of PEG-like coatings on UHMWPE for total hip replacements.

PubMed

Kane, Sheryl R; Ashby, Paul D; Pruitt, Lisa A

2010-03-15

A crosslinked hydrogel coating similar to poly(ethylene glycol) (PEG) was covalently bonded to the surface of ultrahigh molecular weight polyethylene (UHMWPE) to improve the lubricity and wear resistance of the UHWMPE for use in total joint replacements. The chemistry, hydrophilicity, and protein adsorption resistance of the coatings were determined, and the wear behavior of the PEG-like coating was examined by two methods: pin-on-disk tribometry to evaluate macroscale behavior, and atomic force microscopy (AFM) to simulate asperity wear. As expected, the coating was found to be highly PEG-like, with approximately 83% ether content by x-ray photoelectron spectroscopy and more hydrophilic and resistant to protein adsorption than uncoated UHMWPE. Pin-on-disk testing showed that the PEG-like coating could survive 3 MPa of contact pressure, comparable to that experienced by total hip replacements. AFM nanoscratching experiments uncovered three damage mechanisms for the coatings: adhesion/microfracture, pure adhesion, and delamination. The latter two mechanisms appear to correlate well with wear patterns induced by pin-on-disk testing and evaluated by attenuated total reflection Fourier transform infrared spectroscopy mapping. Understanding the mechanisms by which the PEG-like coatings wear is critical for improving the behavior of subsequent generations of wear-resistant hydrogel coatings. (c) 2009 Wiley Periodicals, Inc.

Tribological Characteristics of Submicron SiC(p)-GR(p)/Zn-35Al-1Mg Composites in Semisolidification Casting process

NASA Astrophysics Data System (ADS)

Liu, S.; Fang, Z. W.; Li, L. X.

2018-05-01

Uniform SiC(p)-GR(p)/Zn-35Al-1Mg composites were prepared by powder pressing and semisolidification stirring-casting process by adding submicron silicon carbide and graphite reinforcement particles in an aluminum-zinc alloy matrix. Micro Vickers hardness and microstructures of the novel composites were studied, and their wear properties and wear temperature were measured for different load and friction conditions. The results show that silicon carbide and graphite particles homogeneously mix in the matrix, while contained silicon carbide particles improve the matrix hardness to 8.4%, graphite improves the matrix hardness to 16.8%, but two of them, combined, reduce the matrix hardness to 7.6%; the rate of temperature rise of the zinc-aluminum matrix alloy is the highest than the other three composites and is up to 48.5° C/s at 1.69MPa. At 0.56MPa and sliding 26.4km, the graphite composite anti-wear effect is optimal, while at 1.13MPa, the wear resistance of silicon carbide and graphite compound particles is the best; in the other case of only silicon carbide particles, the wear resistance is increased to 35% at 1.69MPa and 26.4km, and its anti-wear effects are excellent.

Wear Properties of ECAP-Processed AM80 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Gopi, K. R.; Shivananda Nayaka, H.; Sahu, Sandeep

2017-07-01

AM80 magnesium alloy was subjected to equal-channel angular pressing (ECAP), and microstructural evolution was studied using scanning electron microscope (SEM). Grain size was found to decrease up to 3 µm after four passes. An increase in number of ECAP passes led to a corresponding increase in hardness of the processed samples. Unprocessed and ECAP-processed samples were subjected to wear test using pin-on-disk wear test machine to study the wear behavior. Effects of varying loads (30 and 40 N) with sliding distances (2500 and 5000 m) were studied. The results showed reduction in wear mass loss for the ECAP-processed samples in comparison with unprocessed condition. Coefficient of friction (COF) was studied for different loads, and improvement in COF values was observed for ECAP-processed samples compared to unprocessed condition. Worn surfaces were studied using SEM and energy-dispersive x-ray spectrometer, and they exhibited plastic deformation, delamination, plowing, wear debris and oxidation in the sliding direction. X-ray diffraction analysis was conducted on the worn surfaces to identify the phases. It revealed the presence of magnesium oxide and magnesium aluminum oxide which led to oxidation wear in the sliding direction. Wear mechanism was found to be abrasive and oxidation wear.

Steady-state wear and friction in boundary lubrication studies

NASA Technical Reports Server (NTRS)

Loomis, W. R.; Jones, W. R., Jr.

1980-01-01

A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.

Prediction Of Abrasive And Diffusive Tool Wear Mechanisms In Machining

NASA Astrophysics Data System (ADS)

Rizzuti, S.; Umbrello, D.

2011-01-01

Tool wear prediction is regarded as very important task in order to maximize tool performance, minimize cutting costs and improve the quality of workpiece in cutting. In this research work, an experimental campaign was carried out at the varying of cutting conditions with the aim to measure both crater and flank tool wear, during machining of an AISI 1045 with an uncoated carbide tool P40. Parallel a FEM-based analysis was developed in order to study the tool wear mechanisms, taking also into account the influence of the cutting conditions and the temperature reached on the tool surfaces. The results show that, when the temperature of the tool rake surface is lower than the activation temperature of the diffusive phenomenon, the wear rate can be estimated applying an abrasive model. In contrast, in the tool area where the temperature is higher than the diffusive activation temperature, the wear rate can be evaluated applying a diffusive model. Finally, for a temperature ranges within the above cited values an adopted abrasive-diffusive wear model furnished the possibility to correctly evaluate the tool wear phenomena.

A high sensitivity wear debris sensor using ferrite cores for online oil condition monitoring

NASA Astrophysics Data System (ADS)

Zhu, Xiaoliang; Zhong, Chong; Zhe, Jiang

2017-07-01

Detecting wear debris and measuring the increasing number of wear debris in lubrication oil can indicate abnormal machine wear well ahead of machine failure, and thus are indispensable for online machine health monitoring. A portable wear debris sensor with ferrite cores for online monitoring is presented. The sensor detects wear debris by measuring the inductance change of two planar coils wound around a pair of ferrite cores that make the magnetic flux denser and more uniform in the sensing channel, thereby improving the sensitivity of the sensor. Static testing results showed this wear debris sensor is capable of detecting 11 µm and 50 µm ferrous debris in 1 mm and 7 mm diameter fluidic pipes, respectively; such a high sensitivity has not been achieved before. Furthermore, a synchronized sampling method was also applied to reduce the data size and realize real-time data processing. Dynamic testing results demonstrated that the sensor is capable of detecting wear debris in real time with a high throughput of 750 ml min-1 the measured debris concentration is in good agreement with the actual concentration.

Classification of accelerometer wear and non-wear events in seconds for monitoring free-living physical activity

PubMed Central

Zhou, Shang-Ming; Hill, Rebecca A; Morgan, Kelly; Stratton, Gareth; Gravenor, Mike B; Bijlsma, Gunnar; Brophy, Sinead

2015-01-01

Objective To classify wear and non-wear time of accelerometer data for accurately quantifying physical activity in public health or population level research. Design A bi-moving-window-based approach was used to combine acceleration and skin temperature data to identify wear and non-wear time events in triaxial accelerometer data that monitor physical activity. Setting Local residents in Swansea, Wales, UK. Participants 50 participants aged under 16 years (n=23) and over 17 years (n=27) were recruited in two phases: phase 1: design of the wear/non-wear algorithm (n=20) and phase 2: validation of the algorithm (n=30). Methods Participants wore a triaxial accelerometer (GeneActiv) against the skin surface on the wrist (adults) or ankle (children). Participants kept a diary to record the timings of wear and non-wear and were asked to ensure that events of wear/non-wear last for a minimum of 15 min. Results The overall sensitivity of the proposed method was 0.94 (95% CI 0.90 to 0.98) and specificity 0.91 (95% CI 0.88 to 0.94). It performed equally well for children compared with adults, and females compared with males. Using surface skin temperature data in combination with acceleration data significantly improved the classification of wear/non-wear time when compared with methods that used acceleration data only (p<0.01). Conclusions Using either accelerometer seismic information or temperature information alone is prone to considerable error. Combining both sources of data can give accurate estimates of non-wear periods thus giving better classification of sedentary behaviour. This method can be used in population studies of physical activity in free-living environments. PMID:25968000

Nanoclay-Reinforced Glass-Ionomer Cements: In Vitro Wear Evaluation and Comparison by Two Wear-Test Methods

PubMed Central

Fareed, Muhammad A.; Stamboulis, Artemis

2017-01-01

Glass ionomer cement (GIC) represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task. The aim of this paper was to evaluate the wear resistance of novel glass ionomer cement by two wear-test methods and to compare the two wear methods.The wear resistance of a conventional glass ionomer cement (HiFi Advanced Health Care Kent, UK) and cements modified by including various percentages of nanoclays (1, 2 and 4 wt %) was measured by a reciprocating wear test (ball-on-flat) and Oregon Health and Sciences University’s (OHSU) wear simulator. The OHSU wear simulation subjected the cement specimens to three wear mechanisms, namely abrasion, three-body abrasion and attrition using a steatite antagonist. The abrasion wear resulted in material loss from GIC specimen as the steatite antagonist forced through the exposed glass particles when it travelled along the sliding path.The hardness of specimens was measured by the Vickers hardness test. The results of reciprocation wear test showed that HiFi-1 resulted in the lowest wear volume 4.90 (0.60) mm3 (p < 0.05), but there was no significant difference (p > 0.05) in the wear volume in comparison to HiFi, HiFi-2 and HiFi-4. Similarly, the results of OHSU wear simulator showed that the total wear volume of HiFi-4 1.49 (0.24) was higher than HiFi-1 and HiFi-2. However, no significant difference (p > 0.05) was found in the OHSU total wear volume in GICs after nanoclay incorporation. The Vickers hardness (HV) of the nanoclay-reinforced cements was measured between 62 and 89 HV. Nanoclay addition at a higher concentration (4%) resulted in higher wear volume and wear depth. The total wear volumes were less dependent upon abrasion volume and attrition volume. The total wear depths were strongly influenced by attrition depth and to some extent by abrasion depth. The addition of nanoclay in higher wt % to HiFi did not result in significant improvement in wear resistance and hardness. Nonetheless, wear is a very complex phenomenon because it is sensitive to a wide number of factors that do not necessarily act in the same way when compared using different parameters. PMID:29563434

Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying

NASA Astrophysics Data System (ADS)

Guo, Lili; Qin, Lin; Kong, Fanyou; Yi, Hong; Tang, Bin

2016-12-01

Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000 °C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000 °C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.

The psychosocial benefits of secondary hydroxyapatite orbital implant insertion and prosthesis wearing for patients with anophthalmia.

PubMed

Wang, Junming; Zhang, Hong; Chen, Wei; Li, Guigang

2012-01-01

Anophthalmia is associated with a range of psychosocial difficulties and hydroxyapatite orbital implant insertion and prosthesis wearing is the predominant rehabilitation therapy for anophthalmia. However, few articles have compared preoperative and postoperative psychosocial outcomes using standardized questionnaires. This study aimed to investigate the psychosocial benefits of hydroxyapatite orbital implant insertion and prosthesis wearing in this patient population. In all, 36 participants were tested preoperatively and 6-months postoperatively using standardized measures of anxiety and depression (Hospital Anxiety and Depression Scale), social anxiety and social avoidance (Derriford Appearance Scale-Short Form), and quality of life (World Health Organization Quality of Life Scale-Short Form). Before treatment, levels of depression were comparable with population norms; however, levels of general anxiety were slightly raised, levels of social anxiety, social avoidance, and quality of life were significantly poorer than population norms. Treatment resulted in significant improvement in psychosocial adjustment with improvements in all study variables for the participant group as a whole. Hydroxyapatite orbital implant insertion and prosthesis wearing offers significant improvements in psychological and physical functioning for patients with anophthalmia.

Effect of deep cryogenic treatment on the microstructure and wear performance of Cr-Mn-Cu white cast iron grinding media

NASA Astrophysics Data System (ADS)

Vidyarthi, M. K.; Ghose, A. K.; Chakrabarty, I.

2013-12-01

The phase transformation and grinding wear behavior of Cr-Mn-Cu white cast irons subjected to destabilization treatment followed by air cooling or deep cryogenic treatment were studied as a part of the development program of substitute alloys for existing costly wear resistant alloys. The microstructural evolution during heat treatment and the consequent improvement in grinding wear performance were evaluated with optical and scanning electron microscopy, X-ray diffraction analysis, bulk hardness, impact toughness and corrosion rate measurements, laboratory ball mill grinding wear test etc. The deep cryogenic treatment has a significant effect in minimizing the retained austenite content and converts it to martensite embedded with fine M7C3 alloy carbides. The cumulative wear losses in cryotreated alloys are lesser than those with conventionally destabilized alloys followed by air cooling both in wet and dry grinding conditions. The cryotreated Cr-Mn-Cu irons exhibit comparable wear performance to high chromium irons.

Wear resistance of metals and alloys; Proceedings of the Conference, Chicago, IL, Sept. 24-30, 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kingsbury, G.R.

1988-01-01

Techniques for characterizing and improving the wear properties of metals and composites are discussed in reviews and reports. Topics addressed include the use of interatomic potentials to study the relationship between abrasive wear and other mechanical properties, gas-detonation powder spraying of diamond coatings, a fluidized-bed test method for erosion resistance, the wear behavior of Al and Al-Si-Cu alloys, and abrasive wear of bronze and ZA alloys with and without lubrication. Consideration is given to continuously cast vs sand-cast Zn-Al alloys for bearings, sintered 6061 Al-alloy-based particulate composites with dry lubricants, Cu-based particulate composites, high-temperature friction and wear of X-750 andmore » X-188 superalloys for low-heat-rejection engines, a new metallurgical conception of wear-resistant steels, and the effect of matrix microstructure on the abrasion resistance of high-Cr white cast irons. Extensive graphs and micrographs are provided.« less

Optical 3D methods for measurement of prosthetic wear of total hip arthroplasty: principles, verification and results.

PubMed

Rossler, Tomas; Mandat, Dusan; Gallo, Jiri; Hrabovsky, Miroslav; Pochmon, Michal; Havranek, Vitezslav

2009-07-20

Total hip arthroplasty (THA) significantly improves the quality of life in majority of patients with severe osteoarthritis. However, long-term outcomes of THAs are compromised by aseptic loosening and periprosthetic osteolysis which needs revision surgery. Both of these are causally linked to a prosthetic wear deliberated from the prosthetic articulating surfaces. As a result, there is a need to measure the mode and magnitude of wear. The paper evaluates three optical methods proposed for construction of a device for the non-contact prosthetic wear measurement. Of them, the scanning profilometry achieved promising combination of accuracy and repeatability. Simultaneously, it is time efficient to enable the development of a sensor for wear measurement.

Wear and Friction Behavior of Metal Impregnated Microporous Carbon Composites

NASA Technical Reports Server (NTRS)

Goller, Gultekin; Koty, D. P.; Tewari, S. N.; Singh, M.; Tekin, A.

1996-01-01

Metal-matrix composites have been prepared by pressure-infiltration casting of copper-base alloy melts into microporous carbon preforms. The carbon preforms contained varying proportions of amorphous carbon and graphite. Load dependence of the wear and friction behavior of the composite pins has been examined under ambient conditions against cast-iron plates, using a pin-on-plate reciprocating wear tester. The wear resistance of the composite is significantly improved, as compared with the base alloy. Contrary to the normally expected behavior, the addition of graphite to the amorphous carbon does not reduce the friction coefficient, especially at high loads. The wear and friction behavior of the composites is very sensitive to the size and distribution of the microstructural constituents.

Microstructure and wear property of Fe-Cr13-C hardfacing alloy reinforced by WC particles

NASA Astrophysics Data System (ADS)

Yang, Ke; Li, Jiaqi; Bao, Yefeng; Jiang, Yongfeng

2017-07-01

Tungsten as the most effective carbide-forming element was added in the Fe-Cr13-C hardfacing alloy to precipitate WC particles. Optical microscope (OM), scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) were used to investigate the microstructures of the hardfacing alloy. The wear resistance was tested through a slurry rubber wheel abrasion test machine, and the wear behavior was also studied. The results indicate that the microstructures of the hardfacing alloy consist of lath martensite, residual austenite and WC particles. The wear resistance can be significantly improved through the addition of tungsten element being provided by the precipitation of WC particles. And the predominant wear mechanism was microcutting with shallow grooves and spalling.

Corrosion and wear properties of Zn-Ni and Zn-Ni-Al2O3 multilayer electrodeposited coatings

NASA Astrophysics Data System (ADS)

Shourgeshty, M.; Aliofkhazraei, M.; Karimzadeh, A.; Poursalehi, R.

2017-09-01

Zn-Ni and Zn-Ni-Al2O3 multilayer coatings with 32, 128, and 512 layers were electroplated on a low carbon steel substrate by pulse electrodeposition under alternative changes in the duty cycle between 20% and 90% and a constant frequency of 250 Hz. Corrosion behavior was investigated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) and wear behavior of the coatings was evaluated by a pin on disk test. The results showed that the corrosion resistance of coatings was improved by increasing the number of layers (the decrease in layer thickness) as well as the presence of alumina nanoparticles. The lowest corrosion current density corresponds to Zn-Ni-Al2O3 with 512 layers equal to 3.74 µA cm-2. Increasing the number of layers in the same total thickness and the presence of alumina nanoparticles within the coating also leads to the improvement in wear resistance of the samples. The coefficient of friction decreased with increasing number of layers and the lowest coefficient of friction (0.517) corresponds to Zn-Ni-Al2O3 coating with 512 layers. Wear mechanism of Zn-Ni coatings with a different number of layers is adhesive while in the Zn-Ni-Al2O3 coatings wear mechanism is a combination of adhesive and abrasive wear, where by increasing the number of the layers to 512 abrasive wear mechanism becomes dominant.

Wear mechanisms in hybrid composites of Graphite-20 Pct SiC in A356 Aluminum Alloy (Al-7 Pct Si-0.3 Pct Mg)

NASA Astrophysics Data System (ADS)

Ames, W.; Alpas, A. T.

1995-01-01

The wear behavior of A356 aluminum alloy (Al-7 Pct Si-0.3 Pct Mg) matrix composites reinforced with 20 vol Pct SiC particles and 3 or 10 vol Pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X-ray diffractometry (XRD). The wear resistance of 3 Pct graphite-20 Pct SiC-A356 hybrid composite was comparable to 20 Pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 Pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 Pct graphite 20 Pct SiC-A356 was 1 to 2 times higher than 10 Pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 Pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 Pct and 10 Pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites. Tribolayers, mainly consisting of a compacted mixture of graphite, iron oxides, and aluminum, were generated on the surfaces of the hybrid composites. In the hybrid composites, the elimination of the severe wear (and hence the improvement in seizure resistance) was attributed to the reduction in friction-induced surface heating due to the presence of graphite- and iron-oxide-containing tribolayers.

3D FEM Simulation of Flank Wear in Turning

NASA Astrophysics Data System (ADS)

Attanasio, Aldo; Ceretti, Elisabetta; Giardini, Claudio

2011-05-01

This work deals with tool wear simulation. Studying the influence of tool wear on tool life, tool substitution policy and influence on final part quality, surface integrity, cutting forces and power consumption it is important to reduce the global process costs. Adhesion, abrasion, erosion, diffusion, corrosion and fracture are some of the phenomena responsible of the tool wear depending on the selected cutting parameters: cutting velocity, feed rate, depth of cut, …. In some cases these wear mechanisms are described by analytical models as a function of process variables (temperature, pressure and sliding velocity along the cutting surface). These analytical models are suitable to be implemented in FEM codes and they can be utilized to simulate the tool wear. In the present paper a commercial 3D FEM software has been customized to simulate the tool wear during turning operations when cutting AISI 1045 carbon steel with uncoated tungsten carbide tip. The FEM software was improved by means of a suitable subroutine able to modify the tool geometry on the basis of the estimated tool wear as the simulation goes on. Since for the considered couple of tool-workpiece material the main phenomena generating wear are the abrasive and the diffusive ones, the tool wear model implemented into the subroutine was obtained as combination between the Usui's and the Takeyama and Murata's models. A comparison between experimental and simulated flank tool wear curves is reported demonstrating that it is possible to simulate the tool wear development.

Assessment of variations in wear test methodology.

PubMed

Gouvêa, Cresus V D; Weig, Karin; Filho, Thales R M; Barros, Renata N

2010-01-01

The properties of composite resin for dental fillings were improved by development, but its weakness continues to be its wear strength. Several tests have been proposed to evaluate wear in composite resin materials. The aim of this study was to verify how polishing and the type of abrasive can influence the wear rate of composite resin. The test was carried out on two groups. In one group we employed an ormocer and a hybrid composite that was polished group the composite was polished with the same abrasive paper plus a 1 microm and 0.25 microm grit diamond paste. A three-body wear test was performed using the metal sphere of the wear test machine, the composite and an abrasive. A diamond paste and aluminum oxide dispersion were used as abrasive. Analysis of the results showed that there was no difference between polishing techniques, but revealed a difference between abrasives.

Biologically Based Restorative Management of Tooth Wear

PubMed Central

Kelleher, Martin G. D.; Bomfim, Deborah I.; Austin, Rupert S.

2012-01-01

The prevalence and severity of tooth wear is increasing in industrialised nations. Yet, there is no high-level evidence to support or refute any therapeutic intervention. In the absence of such evidence, many currently prevailing management strategies for tooth wear may be failing in their duty of care to first and foremost improve the oral health of patients with this disease. This paper promotes biologically sound approaches to the management of tooth wear on the basis of current best evidence of the aetiology and clinical features of this disease. The relative risks and benefits of the varying approaches to managing tooth wear are discussed with reference to long-term follow-up studies. Using reference to ethical standards such as “The Daughter Test”, this paper presents case reports of patients with moderate-to-severe levels of tooth wear managed in line with these biologically sound principles. PMID:22315608

Tribological improvements of carbon-carbon composites by infiltration of atomic layer deposited lubricious nanostructured ceramic oxides

NASA Astrophysics Data System (ADS)

Mohseni, Hamidreza

A number of investigators have reported enhancement in oxidation and wear resistant of carbon-carbon composites (CCC) in the presence of protective coating layers. However, application of a surface and subsurface coating system that can preserve its oxidation and wear resistance along with maintaining lubricity at high temperature remains unsolved. To this end, thermodynamically stable protective oxides (ZnO/Al2O3/ZrO2) have been deposited by atomic layer deposition (ALD) to infiltrate porous CCC and graphite foams in order to improve the thermal stability and wear resistance in low and high speed sliding contacts. Characterization of microstructural evolution was achieved by using energy dispersive x-ray spectroscopy (EDS) mapping in scanning electron microscope (SEM) coupled with focused ion beam (FIB), x-ray tomography, high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD). Evaluation of the tribological properties of CCC coated with abovementioned ALD thin films were performed by employing low speed pure sliding tribometer and a high speed/frequency reciprocating rig to simulate the fretting wear behavior at ambient temperature and elevated temperatures of 400°C. It was determined with x-ray tomography imaging and EDS mapping that ALD ZnO/Al2O3/ZrO2 nanolaminates and baseline ZrO2 coatings exhibited excellent conformality and pore-filling capabilities down to ˜100 microm and 1.5 mm in the porous CCC and graphite foam, respectively, which were dependent on the exposure time of the ALD precursors. XRD and HRTEM determined the crystalline phases of {0002} textured ZnO (wurtzite), amorphous Al2O3, and {101}-tetragonal ZrO2. Significant improvements up to ˜65% in the sliding and fretting wear factors were determined for the nanolaminates in comparison to the uncoated CCC. A tribochemical sliding-induced mechanically mixed layer (MML) was found to be responsible for these improvements. HRTEM confirmed the presence of a high density of ZnO shear-induced basal stacking faults inside the wear tracks responsible for intrafilm shear velocity accommodation that mitigated friction and wear.

Linking Tribofilm Nanomechanics to the Origin of Low Friction and Wear

DTIC Science & Technology

2013-08-08

34Improving Wind Turbine Gearbox Reliability," National Renewable Energy Laboratory, Boulder, CO USA. [3] De Groh, K. K., Banks, B. A., McCarthy, C. E...the development of advanced lubrication strategies for improved friction and wear management. For example, increased size and power output of wind ... turbines reduce specific costs, but also contribute to stresses and temperatures that exceed the capabilities of existing gearbox lubrication

Polyethylene wear of mobile-bearing unicompartmental knee replacement at 20 years.

PubMed

Kendrick, B J L; Simpson, D J; Kaptein, B L; Valstar, E R; Gill, H S; Murray, D W; Price, A J

2011-04-01

The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively. The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year). The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

Analysis of factors associated with seatbelt wearing among rear passengers in Malaysia.

PubMed

Mohamed, Norlen; Mohd Yusoff, Muhammad Fadhli; Isah, Noradrenalina; Othman, Ihamah; Syed Rahim, Sharifah-Allyana; Paiman, Noorfaradilla

2011-03-01

A cross-sectional survey using a self-administered questionnaire was conducted among 793 rear passengers in Malaysia. Logistic regression was performed to analyse the association of rear seatbelt wearing with 12 independent variables. Seven factors were significantly associated with rear seatbelt wearing. Experience of being stopped by an enforcement officer for not wearing rear seatbelt yielded the highest odds ratio 2.3 (p = 0.002) followed by self-consciousness (odds ratio 1.7; p = 0.004), attitude (odds ratio 1.5, p = 0.001), and knowledge (odds ratio 1.4, p = 0.004). Age of participants and their perception of being caught by an enforcement officer were also significantly associated with rear seatbelt wearing, odds ratios were 1.03 (p = 0.004) and 1.1 (p = 0.004), respectively. In contrast, level of education was negatively associated with rear seatbelt wearing (odds ratio 0.59, p = 0.003). It was concluded that enforcement activities, knowledge and attitude on seatbelt wearing play a very important role in improving the rate of rear seatbelt wearing. Thus, efforts to increase these factors should be the special focus in designing education and social marketing activities to advocate rear seatbelt wearing.

Multi-objective optimization of swash plate forging process parameters for the die wear/service life improvement

NASA Astrophysics Data System (ADS)

Hu, X. F.; Wang, L. G.; Wu, H.; Liu, S. S.

2017-12-01

For the forging process of the swash plate, the author designed a kind of multi-index orthogonal experiment. Based on the Archard wear model, the influences of billet temperature, die temperature, forming speed, top die hardness and friction coefficient on forming load and die wear were numerically simulated by DEFORM software. Through the analysis of experimental results, the best forging process parameters were optimized and determined, which could effectively reduce the die wear and prolong the die service life. It is significant to increase the practical production of enterprise, especially to reduce the production cost and to promote enterprise profit.

Enhanced wear performance of ultra high molecular weight polyethylene crosslinked by organosilane.

PubMed

Tang, C Y; Xie, X L; Wu, X C; Li, R K Y; Mai, Y W

2002-11-01

Ultra high molecular weight polyethylene (UHMWPE) crosslinked by organosilane was thermal compression molded. The organosilane used was the tri-ethyloxyl vinyl silane. Its gelation, melting behavior, crystallinity, mechanical and wear-resisting properties were systematically investigated. The results showed that the gel ratio of UHMWPE increases with the incorporation of organosilane. At a low content of organosilane, the melting point and crystallinity of the crosslinked UHMWPE increase, and hence the mechanical and wear-resisting properties are improved. However, at a high content of organosilane, these performances of the crosslinked UHMWPE become worse. At 0.4 phr silane, the wear resistance of crosslinked UHMWPE reaches its optimum value.

Comprehensive process maps for synthesizing high density aluminum oxide-carbon nanotube coatings by plasma spraying for improved mechanical and wear properties

NASA Astrophysics Data System (ADS)

Keshri, Anup Kumar

Plasma sprayed aluminum oxide ceramic coating is widely used due to its outstanding wear, corrosion, and thermal shock resistance. But porosity is the integral feature in the plasma sprayed coating which exponentially degrades its properties. In this study, process maps were developed to obtain Al2O3-CNT composite coatings with the highest density (i.e. lowest porosity) and improved mechanical and wear properties. Process map is defined as a set of relationships that correlates large number of plasma processing parameters to the coating properties. Carbon nanotubes (CNTs) were added as reinforcement to Al2O 3 coating to improve the fracture toughness and wear resistance. Two novel powder processing approaches viz spray drying and chemical vapor growth were adopted to disperse CNTs in Al2O3 powder. The degree of CNT dispersion via chemical vapor deposition (CVD) was superior to spray drying but CVD could not synthesize powder in large amount. Hence optimization of plasma processing parameters and process map development was limited to spray dried Al2O3 powder containing 0, 4 and 8 wt. % CNTs. An empirical model using Pareto diagram was developed to link plasma processing parameters with the porosity of coating. Splat morphology as a function of plasma processing parameter was also studied to understand its effect on mechanical properties. Addition of a mere 1.5 wt. % CNTs via CVD technique showed ˜27% and ˜24% increase in the elastic modulus and fracture toughness respectively. Improved toughness was attributed to combined effect of lower porosity and uniform dispersion of CNTs which promoted the toughening by CNT bridging, crack deflection and strong CNT/Al2O3 interface. Al2O 3-8 wt. % CNT coating synthesized using spray dried powder showed 73% improvement in the fracture toughness when porosity reduced from 4.7% to 3.0%. Wear resistance of all coatings at room and elevated temperatures (573 K, 873 K) showed improvement with CNT addition and decreased porosity. Such behavior was due to improved mechanical properties, protective film formation due to tribochemical reaction, and CNT bridging between the splats. Finally, process maps correlating porosity content, CNT content, mechanical properties, and wear properties were developed.

Effects of Heat Treatment on Tribological Behavior of Electroless Ni-B Coating at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Arkadeb; Barman, Tapan Kumar; Sahoo, Prasanta

The present work investigates the effects of heat treatment on friction and wear behavior of electroless Ni-B coatings at elevated temperatures. Coating is deposited on AISI 1040 steel specimens and subjected to heat treatments at 350∘C, 400∘C and 450∘C. Coating characterization is done using scanning electron microscope, energy dispersive X-Ray analysis and X-Ray diffraction analysis. Improvement in microhardness is observed for the heat treated deposits. Further, the effect of heat treatment on the tribological behavior of the coatings at room temperature, 100∘C, 300∘C and 500∘C are analyzed on a pin-on-disc setup. Heat treatment at 350∘C causes a significant improvement in the tribological behavior at elevated temperatures. Higher heat treatment temperatures cause deterioration in the wear resistance and coefficient of friction. The wear mechanism at 100∘C is observed to be predominantly adhesive along with abrasion. While at 300∘C, abrasive wear is seen to be the governing wear phenomenon. Formation of mechanically mixed layers is noticed at both the test temperatures of 100∘C and 300∘C for the coatings heat treated at 400∘C and 450∘C test temperature. The predominant wear mechanisms at 500∘C are abrasive and fatigue for as-deposited and heat treated coatings, respectively.

Online detecting system of roller wear based on laser-linear array CCD technology

NASA Astrophysics Data System (ADS)

Guo, Yuan

2010-10-01

Roller is an important metallurgy tool in the rolling mill. And the surface of a roller affects the quantity of the rolling product directly. After using a period of time, roller must be repaired or replaced. Examining the profile of a working roller between the intervals of rolling is called online detecting for roller wear. The study of online detecting roller wear is very important for selecting the grinding time in reason, reducing the exchanging times of rollers, improving the quality of the product and realizing online grinding rollers. By applying the laser-linear array CCD detective technology, a method for online non-touch detecting roller wear was brought forward. The principle, composition and the operation process of the linear array CCD detecting system were expatiated. And an error compensation algorithm is exactly calculated to offset the shift of the roller axis in this measurement system. So the stability and the accuracy were improved remarkably. The experiment proves that the accuracy of the detecting system reaches to the demand of practical production process. It can provide a new method of high speed and high accuracy online detecting for roller wear.

Mechanical properties of nitrogen-rich surface layers on SS304 treated by plasma immersion ion implantation

NASA Astrophysics Data System (ADS)

Fernandes, B. B.; Mändl, S.; Oliveira, R. M.; Ueda, M.

2014-08-01

The formation of hard and wear resistant surface regions for austenitic stainless steel through different nitriding and nitrogen implantation processes at intermediate temperatures is an established technology. As the inserted nitrogen remains in solid solution, an expanded austenite phase is formed, accounting for these surface improvements. However, experiments on long-term behavior and exact wear processes within the expanded austenite layer are still missing. Here, the modified layers were produced using plasma immersion ion implantation with nitrogen gas and had a thickness of up to 4 μm, depending on the processing temperature. Thicker layers or those with higher surface nitrogen contents presented better wear resistance, according to detailed microscopic investigation on abrasion, plastic deformation, cracking and redeposition of material inside the wear tracks. At the same time, cyclic fatigue testing employing a nanoindenter equipped with a diamond ball was carried out at different absolute loads and relative unloadings. As the stress distribution between the modified layer and the substrate changes with increasing load, additional simulations were performed for obtaining these complex stress distributions. While high nitrogen concentration and/or thicker layers improve the wear resistance and hardness, these modifications simultaneously reduce the surface fatigue resistance.

Effect of MoSi2 Content on Dry Sliding Tribological Properties of Zr-Based Bulk Metallic Glass Composites

NASA Astrophysics Data System (ADS)

Liu, Longfei; Yang, Jun

2017-12-01

Zr55Cu30Al10Ni5 bulk metallic glass and its composites were prepared by suction casting into a copper mold. The effect of MoSi2 content on the tribological behavior of Zr55Cu30Al10Ni5 BMG was studied by using a high-speed reciprocating friction and wear tester. The results indicate that the friction coefficient and wear resistance of the BMGs can be improved by a certain amount of crystalline phase induced by MoSi2 content from 1 to 3% and deteriorated with MoSi2 content of 4%. The wear mechanism of both the metallic glass and its composite is abrasive wear. The mechanism of crystalline phase-dependent tribological properties of the composite was discussed based on the wear track and mechanical properties in the present work. The wear behavior of Zr55Cu30Al10Ni5 BMG and its composite indicates that a good combination of the toughness and the hardness can make the composite be well wear resistant.

Protection of 310l Stainless Steel from Wear at Elevated Temperatures using Conicraly Thermal Spray Coatings with and without Sic Addition

NASA Astrophysics Data System (ADS)

Zhang, Yan; Zhang, Tao; Li, Kaiyang; Li, Dongyang

2017-10-01

Due to its high oxidation resistance, 310L stainless steel is often used for thermal facilities working at high-temperatures. However, the steel may fail prematurely at elevated temperatures when encounter surface mechanical attacks such as wear. Thermal spray coatings have been demonstrated to be effective in protecting the steel from wear at elevated temperatures. In this study, we investigated the effectiveness of high velocity oxy-fuel(HVOF) spraying CoNiCrAlY/SiC coatings in resisting wear of 310L stainless steel at elevated temperature using a pin-on-disc wear tester. In order to further improve the performance of the coating, 5%SiC was added to the coating. It was demonstrated that the CoNiCrAlY/SiC coating after heat treatment markedly suppressed wear. However, the added SiC particles did not show benefits to the wear resistance of the coating. Microstructures of CoNiCrAlY coatings with and without the SiC addition were characterized in order to understand the mechanism responsible for the observed phenomena.

Coupling mechanism between wear and oxidation processes of 304 stainless steel in hydrogen peroxide environments.

PubMed

Dong, Conglin; Yuan, Chengqing; Bai, Xiuqin; Li, Jian; Qin, Honglin; Yan, Xinping

2017-05-24

Stainless steel is widely used in strongly oxidizing hydrogen peroxide (H 2 O 2 ) environments. It is crucial to study its wear behaviour and failure mode. The tribological properties and oxidation of 304 stainless steel were investigated using a MMW-1 tribo-tester with a three-electrode setup in H 2 O 2 solutions with different concentrations. Corrosion current densities (CCDs), coefficients of frictions (COFs), wear mass losses, wear surface topographies, and metal oxide films were analysed and compared. The results show that the wear process and oxidation process interacted significantly with each other. Increasing the concentration of H 2 O 2 or the oxidation time was useful to form a layer of integrated, homogeneous, compact and thick metal oxide film. The dense metal oxide films with higher mechanical strengths improved the wear process and also reduced the oxidation reaction. The wear process removed the metal oxide films to increase the oxidation reaction. Theoretical data is provided for the rational design and application of friction pairs in oxidation corrosion conditions.

Gear Tooth Wear Detection Algorithm

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.

2015-01-01

Vibration-based condition indicators continue to be developed for Health Usage Monitoring of rotorcraft gearboxes. Testing performed at NASA Glenn Research Center have shown correlations between specific condition indicators and specific types of gear wear. To speed up the detection and analysis of gear teeth, an image detection program based on the Viola-Jones algorithm was trained to automatically detect spiral bevel gear wear pitting. The detector was tested using a training set of gear wear pictures and a blind set of gear wear pictures. The detector accuracy for the training set was 75 percent while the accuracy for the blind set was 15 percent. Further improvements on the accuracy of the detector are required but preliminary results have shown its ability to automatically detect gear tooth wear. The trained detector would be used to quickly evaluate a set of gear or pinion pictures for pits, spalls, or abrasive wear. The results could then be used to correlate with vibration or oil debris data. In general, the program could be retrained to detect features of interest from pictures of a component taken over a period of time.

High productivity machining of holes in Inconel 718 with SiAlON tools

NASA Astrophysics Data System (ADS)

Agirreurreta, Aitor Arruti; Pelegay, Jose Angel; Arrazola, Pedro Jose; Ørskov, Klaus Bonde

2016-10-01

Inconel 718 is often employed in aerospace engines and power generation turbines. Numerous researches have proven the enhanced productivity when turning with ceramic tools compared to carbide ones, however there is considerably less information with regard to milling. Moreover, no knowledge has been published about machining holes with this type of tools. Additional research on different machining techniques, like for instance circular ramping, is critical to expand the productivity improvements that ceramics can offer. In this a 3D model of the machining and a number of experiments with SiAlON round inserts have been carried out in order to evaluate the effect of the cutting speed and pitch on the tool wear and chip generation. The results of this analysis show that three different types of chips are generated and also that there are three potential wear zones. Top slice wear is identified as the most critical wear type followed by the notch wear as a secondary wear mechanism. Flank wear and adhesion are also found in most of the tests.

The safety and efficacy of contact lens wear in the industrial and chemical workplace.

PubMed

Tyhurst, Keith; McNett, Ryan; Bennett, Edward

2007-11-01

The use and safety of contact lenses in the industrial and chemical workplace has often been questioned since the 1960s because of many unconfirmed reports of ocular injury resulting from contact lens wear. Because of these urban legends, contact lens wear has been banned or wearers have been required to wear additional personal protective equipment (PPE) not required of non-contact lens wearers. Literature review via Medline and Google search. Research has shown that contact lenses typically provide protective benefits that decrease the severity of ocular injury and improve worker performance. While contact lens wear contraindications do exist, in most cases, and with proper precautions, contact lens wear is still possible. Industrial and chemical companies need to establish written contact lens use policies based on current studies that have shown the safety of workplace contact lens wear when combined with the same PPE required of non-contact lens wearers. Practitioners need to discuss, with their contact lens patients, the additional responsibilities required to maintain proper lens hygiene and proper PPE in the workplace.

Evaluating lubricating capacity of vegetal oils using Abbott-Firestone curve

NASA Astrophysics Data System (ADS)

Georgescu, C.; Cristea, G. C.; Dima, C.; Deleanu, L.

2017-02-01

The paper presents the change of functional parameters defined on the Abbott-Firestone curve in order to evaluate the surface quality of the balls from the four ball tester, after tests done with several vegetable oils. The tests were done using two grades of rapeseed oil (degummed and refined) and two grades of soybean oil (coarse and degummed) and a common transmission oil (T90). Test parameters were 200 N and 0.576 m/s (1500 rpm) for 60 minutes. For the refined rapeseed oil, the changes in shape of the Abbott-Firestone curves are more dramatic, these being characterized by high values of Spk (the average value for the wear scars on the three balls), thus being 40% of the sum Svk + Sk + Spk, percentage also obtained for the soybean oil, but the value Spk being lower. For the degummed soybean oil, the profile height of the wear scars are taller than those obtained after testing the coarse soybean oil, meaning that the degumming process has a negative influence on the worn surface quality and the lubricating capacity of this oil. Comparing the surface quality of the wear scars on fixed tested balls is a reliable method to point out the lubricant properties of the vegetable oils, especially if they are compared to a “classical” lubricant as a non-additivated transmission mineral oil T90. The best surface after testing was obtained for the soybean oil, followed by T90 oil and the degummed grades of the soybean oil and rapeseed oil (these three giving very close values for the functional parameters), but the refined rapeseed oil generated the poorest quality of the wear scars on the balls, under the same testing conditions.

Fundamental interfacial studies of advanced solid lubricants and their operating environments

NASA Astrophysics Data System (ADS)

Gilley, Kevin

Solid lubricants are a class of materials that are utilized in applications and environments where traditional lubrication schemes cannot be implemented. A variety of materials display solid lubrication, and in this study a number of solid lubricants were investigated. Firstly, electrolessly deposited nickel boride alloys were annealed at different temperatures under a flow of oxygen. The surface chemistry, friction, and wear behavior of the coating were then investigated. It was found that when annealed above 550°C the coatings had a dramatic change in surface chemistry, where the Ni 3B had formed a thick layer of B2O3 on the surface. This oxide then reacted at ambient temperatures with moist air to form the lubricious compound H3BO3. This led to a coefficient of friction below 0.1 and a slight increase of the wear rate from 10 -8 mm3/Nm to 10-7 mm3/Nm. Secondly, the surface chemistry of advanced MoS2 based coatings that had been exposed to low earth orbit was investigated. It was found that this exposure produced the complete oxidation of the coatings. Also, exposure to the unique space environments resulted in the deposition of large amounts of contaminant SiO2 on the surface. Lastly the tribological properties of single crystal cadmium sulfide were investigated. There is nearly no knowledge of the tribological activity of cadmium sulfide in the literature, so the study was performed as an initial investigation into the material. It was discovered that cadmium sulfide did not show low friction, with a coefficient of friction of approximately 0.25, but did show low wear, with a wear rate of approximately 3x10-7 mm3/Nm.

Classification of accelerometer wear and non-wear events in seconds for monitoring free-living physical activity.

PubMed

Zhou, Shang-Ming; Hill, Rebecca A; Morgan, Kelly; Stratton, Gareth; Gravenor, Mike B; Bijlsma, Gunnar; Brophy, Sinead

2015-05-11

To classify wear and non-wear time of accelerometer data for accurately quantifying physical activity in public health or population level research. A bi-moving-window-based approach was used to combine acceleration and skin temperature data to identify wear and non-wear time events in triaxial accelerometer data that monitor physical activity. Local residents in Swansea, Wales, UK. 50 participants aged under 16 years (n=23) and over 17 years (n=27) were recruited in two phases: phase 1: design of the wear/non-wear algorithm (n=20) and phase 2: validation of the algorithm (n=30). Participants wore a triaxial accelerometer (GeneActiv) against the skin surface on the wrist (adults) or ankle (children). Participants kept a diary to record the timings of wear and non-wear and were asked to ensure that events of wear/non-wear last for a minimum of 15 min. The overall sensitivity of the proposed method was 0.94 (95% CI 0.90 to 0.98) and specificity 0.91 (95% CI 0.88 to 0.94). It performed equally well for children compared with adults, and females compared with males. Using surface skin temperature data in combination with acceleration data significantly improved the classification of wear/non-wear time when compared with methods that used acceleration data only (p<0.01). Using either accelerometer seismic information or temperature information alone is prone to considerable error. Combining both sources of data can give accurate estimates of non-wear periods thus giving better classification of sedentary behaviour. This method can be used in population studies of physical activity in free-living environments. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

An evaluation of 1-day disposable contact lens wear in a population of allergy sufferers.

PubMed

Hayes, Valérie Y; Schnider, Cristina M; Veys, Jane

2003-06-01

This was a multi-site, 128-subject, bilateral crossover study to evaluate subjective comfort and slit-lamp findings with 1-day disposable contact lenses in a population of allergy sufferers during periods when allergen levels were elevated. The study involved 1-month of single-use daily wear with a 1-day disposable test lens (1. DAY ACUVUE Brand Contact Lenses, Johnson & Johnson Vision Care) and 1-month of daily wear with subjects' habitual lenses replaced to their usual replacement schedule. Pollen and mould counts were obtained for each site 1 week prior to the study and twice weekly throughout the study period. Subjective comfort and slit-lamp findings were recorded at baseline and after 1-month's wear of each modality. Sixty-seven percent of subjects agreed that the 1-day disposable lenses provided improved comfort when compared to the lenses they wore prior to the study, compared with 18% agreeing that the new pair of habitual lenses provided improved comfort. The 1-day disposable lenses showed greater improvement in slit-lamp findings from baseline than new habitual lenses. The use of 1-day disposable lenses is an effective strategy for managing allergy-suffering contact lens wearers.

Application of powder metallurgy techniques to produce improved bearing elements for liquid rocket engines

NASA Technical Reports Server (NTRS)

Moracz, D. J.; Shipley, R. J.; Moxson, V. S.; Killman, R. J.; Munson, H. E.

1992-01-01

The objective was to apply powder metallurgy techniques for the production of improved bearing elements, specifically balls and races, for advanced cryogenic turbopump bearings. The materials and fabrication techniques evaluated were judged on the basis of their ability to improve fatigue life, wear resistance, and corrosion resistance of Space Shuttle Main Engine (SSME) propellant bearings over the currently used 440C. An extensive list of candidate bearing alloys in five different categories was considered: tool/die steels, through hardened stainless steels, cobalt-base alloys, and gear steels. Testing of alloys for final consideration included hardness, rolling contact fatigue, cross cylinder wear, elevated temperature wear, room and cryogenic fracture toughness, stress corrosion cracking, and five-ball (rolling-sliding element) testing. Results of the program indicated two alloys that showed promise for improved bearing elements. These alloys were MRC-2001 and X-405. 57mm bearings were fabricated from the MRC-2001 alloy for further actual hardware rig testing by NASA-MSFC.

Characterization of the Micro-Abrasive Wear in Coatings of TaC-HfC/Au for Biomedical Implants

PubMed Central

Guzmán, Pablo; Yate, Luis; Sandoval, Mercy; Caballero, Jose

2017-01-01

The object of this work was the deposition of a Ta-Hf-C thin film with a gold interlayer on stainless steel, via the physical vapor deposition (PVD) technique, in order to evaluate the properties of different systems subjected to micro-abrasive wear phenomena generated by alumina particles in Ringer's solution. The surface characterization was performed using a scanning electron microscope (SEM) and atomic force microscope (AFM). The crystallographic phases exhibited for each coating were obtained by X-ray diffraction (XRD). As a consequence of modifying the composition of Ta-Hf there was evidence of an improvement in the micro-abrasive wear resistance and, for each system, the wear constants that confirm the enhancement of the surface were calculated. Likewise, these surfaces can be bioactive, generating an alternative to improve the biological fixation of the implants, therefore, the coatings of TaC-HfC/Au contribute in the development of the new generation of orthopedic implants. PMID:28773207

Effects of Ti and TiC ceramic powder on laser-cladded Ti-6Al-4V in situ intermetallic composite

NASA Astrophysics Data System (ADS)

Ochonogor, O. F.; Meacock, C.; Abdulwahab, M.; Pityana, S.; Popoola, A. P. I.

2012-12-01

Titanium metal matrix composite (MMCs) was developed on titanium alloy (Ti-6Al-4V) substrate with the aim of improving the hardness and wear properties by laser cladding technique using a Rofin Sinar 4 kW Nd: YAG laser. Wear investigations were carried out with the aid of three body abrasion tester. The resultant microstructure show homogeneous distribution of TiC particles free from cracks and pores. Multiple track deposited systems with 50% overlap revealed micro-hardness increase from 357.3 HV0.1for the substrate reaching a peak as high as 922.2 HV0.1 for 60%Ti + 40%TiC and the least 665.3 HV0.1 for 80%Ti + 20%TiC MMCs. The wear resistance of the materials improved significantly, indicating a fifteen-fold wear rate reduction due to the proper distribution of ceramic particles thereby forming interstitial carbides as revealed by the X-ray diffraction spectrum.

Effect of nitrogen-containing plasma on adherence, friction, and wear of radiofrequency-sputtered titanium carbide coatings

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1979-01-01

Friction and wear experiments on 440C steel surfaces that were rf sputtered with titanium carbide when a small percentage of nitrogen was added to the plasma were conducted. Both X-ray photoelectron spectroscopy and X-ray diffraction were used to analyze the resultant coatings. Results indicate that the small partial pressure of nitrogen (approximately 0.5 percent) markedly improves the adherence, friction, and wear properties when compared with coatings applied to sputter-etched surfaces, oxidized surfaces, or in the presence of a small oxygen partial pressure. The improvements are related to the formation of an interface containing a mixture of the nitrides of titanium and iron, which are harder than their corresponding oxides.

Improvement of Wearable Power Assist Wear for Low Back Support using Pneumatic Actuator

NASA Astrophysics Data System (ADS)

Cho, Feifei; Sugimoto, Riku; Noritsugu, Toshiro; Li, Xiangpan

2017-10-01

This study focuses on developing a safe, lightweight, power assist device that can be worn by people who like caregivers during lifting or static holding tasks to prevent low back pain (LBP). Therefore in consideration of their flexibility, light weight, and large force to weight ratio we have developed a Wearable Power Assist Wear for caregivers, two types of pneumatic actuators are employed in assisting low back movement for their safety and comfort. The device can be worn directly on the body like normal clothing. Because there is no rigid exoskeleton frame structure, it is lightweight and user friendly. In this paper, we proposed the new type of the wearable power assist wear and improved the controller of control system.

Research into properties of wear resistant ceramic metal plasma coatings

NASA Astrophysics Data System (ADS)

Ivancivsky, V. V.; Skeeba, V. Yu; Zverev, E. A.; Vakhrushev, N. V.; Parts, K. A.

2018-03-01

The study considers one of the promising ways to improve the quality of wear resistant plasma ceramic coatings by implementing various powder mixtures. The authors present the study results of the nickel-ceramic and cobalt-ceramic coating properties and describe the specific character of the investigated coatings composition. The paper presents the results of the coating microhardness, chemical and adhesive strength studies. The authors conducted wear resistance tests of composite coatings in comparison with the plasma coatings of initial powder components.

Influence of conformity on the wear of total knee replacement: An experimental study

PubMed Central

Brockett, Claire L; Carbone, Silvia; Fisher, John; Jennings, Louise M

2017-01-01

Wear of total knee replacement continues to be a significant factor influencing the clinical longevity of implants. Historically, failure due to delamination and fatigue directed design towards more conforming inserts to reduce contact stress. As new generations of more oxidatively stable polyethylene have been developed, more flexibility in bearing design has been introduced. The aim of this study was to investigate the effect of insert conformity on the wear performance of a fixed bearing total knee replacement through experimental simulation. Two geometries of insert were studied under standard gait conditions. There was a significant reduction in wear with reducing implant conformity. This study has demonstrated that bearing conformity has a significant impact on the wear performance of a fixed bearing total knee replacement, providing opportunities to improve clinical performance through enhanced material and design selection. PMID:29251167

Using goggles to increase periocular humidity and reduce dry eye symptoms.

PubMed

Korb, Donald R; Blackie, Caroline A

2013-07-01

To investigate the use of goggles to increase periocular humidity and reduce dry eye symptoms. Noncontact lens wearing patients, previously diagnosed with and symptomatic for dry eye, were recruited. All patients, test (n = 100) and control (n = 25) patients, were required to fill out a simple questionnaire to assess their ocular comfort at three time points during the study: immediately before wearing goggles, after 20 minutes of continuous goggle wear, and 15 minutes after the goggles were removed. The test group consisted of 100 patients who wore swim goggles. The randomly selected control group consisted of 25 patients who wore goggles with the central lens cut out. Ninety-nine percent of the patients in the test group reported a decrease in their symptoms after the goggles had been worn for 20 minutes. After the goggles had been removed for 15 minutes, the symptoms returned in 88% of the test patients. In the control group, only 24% experienced an improvement in symptoms during goggle wear; 76% experienced no improvement. Increasing the periocular humidity has a significant positive impact on ocular comfort in patients with dry eye. This effect is transient. However, the significance of the improvement is such that the use of goggles should be revisited to help patients suffering from chronic discomfort and other dry eye sequelae. Furthermore, the response of an individual patient to short-term goggle wear may help streamline treatment options for both physicians and patients.

Enhancement of the Wear Particle Monitoring Capability of Oil Debris Sensors Using a Maximal Overlap Discrete Wavelet Transform with Optimal Decomposition Depth

PubMed Central

Li, Chuan; Peng, Juan; Liang, Ming

2014-01-01

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements. PMID:24686730

Low-Velocity Impact Wear Behavior of Ball-to-Flat Contact Under Constant Kinetic Energy

NASA Astrophysics Data System (ADS)

Wang, Zhang; Cai, Zhen-bing; Chen, Zhi-qiang; Sun, Yang; Zhu, Min-hao

2017-11-01

The impact tests were conducted on metallic materials with different bulk hardness and Young's moduli. Analysis of the dynamics response during the tribological process showed that the tested materials had similar energy absorption, where the peak contact force increased as the tests continued. Moreover, wear volume decreased with the increase in Young's modulus of metals, except for Cr with a relatively low hardness. Wear rate was gradually reduced to a steady stage with increasing cycles, which was attributed to the decrease in contact stress and work-hardening effect. The main wear mechanism of impact was characterized by delamination, and the specific surface degradation mechanisms were depending on the mechanical properties of materials. The absorbed energy was used to the propagation of micro-cracks in the subsurface instead of plastic deformation, when resistance of friction wear and plastic behavior was improved. Hence, both the hardness and Young's modulus played important roles in the impact wear of metallic materials.

Evaluation of boundary lubricants using steady-state wear and friction

NASA Technical Reports Server (NTRS)

Loomis, W. R.; Jones, W. R., Jr.

1981-01-01

A friction and wear study was made at 20 C to establish operating limits and procedures for obtaining improved reproducibility and reliability in boundary lubrication testing. Ester base and C-other base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a pin-on-disk apparatus. Results of a parametric study with varying loads and speeds slowed that satisfactory test conditions for studying the direction and wear characteristics in the boundary lubrication regime with this test device were found to be 1 kilogram load; 7 to 9 meters-per-minute (50 rpm) surface speed; dry air test atmosphere (less than 100 ppm H2O); and use of a time stepwise procedure for measuring wear. Highly reproducible steady-state wear rates resulted from the two fluid studies which had a linearity of about 99 percent after initially higher wear rates and friction coefficients during run-in periods of 20 to 40 minutes.

Enhancement of the wear particle monitoring capability of oil debris sensors using a maximal overlap discrete wavelet transform with optimal decomposition depth.

PubMed

Li, Chuan; Peng, Juan; Liang, Ming

2014-03-28

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements.

Effect of design factors on surface temperature and wear in disk brakes

NASA Technical Reports Server (NTRS)

Santini, J. J.; Kennedy, F. E.; Ling, F. F.

1976-01-01

The temperatures, friction, wear and contact conditions that occur in high energy disk brakes are studied. Surface and near surface temperatures were monitored at various locations in a caliper disk brake during drag type testing, with friction coefficient and wear rates also being determined. The recorded transient temperature distributions in the friction pads and infrared photographs of the rotor disk surface both showed that contact at the friction surface was not uniform, with contact areas constantly shifting due to nonuniform thermal expansion and wear. The effect of external cooling and of design modifications on friction, wear and temperatures was also investigated. It was found that significant decreases in surface temperature and in wear rate can be achieved without a reduction in friction either by slotting the contacting face of the brake pad or by modifying the design of the pad support to improve pad compliance. Both design changes result in more uniform contact conditions on the friction surface.

Influence of Cryogenic Treatments on the Wear Behavior of AISI 420 Martensitic Stainless Steel

NASA Astrophysics Data System (ADS)

Prieto, G.; Tuckart, W. R.

2017-11-01

The objective of the present work is to characterize the wear behavior of a cryogenically treated low-carbon AISI 420 martensitic stainless steel, by means of ball-on-disk tribological tests. Wear tests were performed under a range of applied normal loads and in two different environments, namely a petrolatum bath and an argon atmosphere. Wear tracks were analyzed by both optical and scanning electron microscopy and Raman spectroscopy to evaluate wear volume, track geometry, surface features and the tribolayers generated after testing. This paper is an extension of the work originally reported in the VIII Iberian Conference of Tribology (Prieto and Tuckart, in: Ballest Jiménez, Rodríguez Espinosa, Serrano Saurín, Pardilla Arias, Olivares Bermúdez (eds) VIII Iberian conference of tribology, Cartagena, 2015). In this study, it has been experimentally demonstrated that cryogenically treated specimens showed a wear resistance improvement ranging from 35 to 90% compared to conventionally treated ones.

Laser scanning stereomicroscopy for fast volumetric imaging with two-photon excitation and scanned Bessel beams

NASA Astrophysics Data System (ADS)

Yang, Yanlong; Zhou, Xing; Li, Runze; Van Horn, Mark; Peng, Tong; Lei, Ming; Wu, Di; Chen, Xun; Yao, Baoli; Ye, Tong

2015-03-01

Bessel beams have been used in many applications due to their unique optical properties of maintaining their intensity profiles unchanged during propagation. In imaging applications, Bessel beams have been successfully used to provide extended focuses for volumetric imaging and uniformed illumination plane in light-sheet microscopy. Coupled with two-photon excitation, Bessel beams have been successfully used in realizing fluorescence projected volumetric imaging. We demonstrated previously a stereoscopic solution-two-photon fluorescence stereomicroscopy (TPFSM)-for recovering the depth information in volumetric imaging with Bessel beams. In TPFSM, tilted Bessel beams were used to generate stereoscopic images on a laser scanning two-photon fluorescence microscope; upon post image processing we could successfully provide 3D perception of acquired volume images by wearing anaglyph 3D glasses. However, tilted Bessel beams were generated by shifting either an axicon or an objective laterally; the slow imaging speed and severe aberrations made it hard to use in real-time volume imaging. In this article, we report recent improvements of TPFSM with newly designed scanner and imaging software, which allows 3D stereoscopic imaging without moving any of the optical components on the setup. This improvement has dramatically improved focusing qualities and imaging speed so that the TPFSM can be performed potentially in real-time to provide 3D visualization in scattering media without post image processing.

Evaluation of Personal Cooling Systems in Conjunction with Explosive Ordnance Disposal Suits

DTIC Science & Technology

1992-06-01

of thermal comfort and perceived exertion. The results indicated that wearing the EOD suit produces significant increases in thermal physiological...indicated reduced perceived exertion levels and improved thermal comfort when wearing the liquid-cooling garment with a EOD suit. In contrast, the ribbed

Comparison of Wear Resistance of Hawley and Vacuum Formed Retainers: An in-vitro Study.

PubMed

V, Moshkelgosha; M, Shomali; M, Momeni

2016-06-01

As a physical property, wear resistance of the materials used in the fabrication of orthodontic retainers play a significant role in the stability and long term use of the appliances. To evaluate the wear resistance of two commonly used materials for orthodontic retainers: Acropars OP, i.e. a polymethyl methacrylate based material, and 3A-GS060, i.e. a polyethylene based material. For each material, 30 orthodontic retainers were made according to the manufacturers' instructions and a 30×30×2 mm block was cut out from the mid- palatal area of each retainer. Each specimen underwent 1000 cycles of wear stimulation in a pin on disc machine. The depth of wear of each specimen was measured using a Nano Wizard II atomic force microscope in 3 random points of each specimen's wear trough. The average of these three measurements was calculated and considered as mean value wear depth of each specimen (µm). The mean wear depth was 6.10µm and 2.15µm for 3A-GS060 and Acropars OP groups respectively. Independent t-test showed a significant difference between the two groups ( p < 0.001). The results show Polymethyl methacrylate base (Acropars) is more wear resistance than the polyethylene based material (3A-GS060). As the higher wear resistance of the fabrication material can improve the retainers' survival time and its cost-effectiveness, VFRs should be avoided in situations that the appliance needs high wear resistance such as bite blocks opposing occlusal forces.

Comparison of Wear Resistance of Hawley and Vacuum Formed Retainers: An in-vitro Study

PubMed Central

V, Moshkelgosha; M, Shomali; M, Momeni

2016-01-01

Statement of Problem: As a physical property, wear resistance of the materials used in the fabrication of orthodontic retainers play a significant role in the stability and long term use of the appliances. Objectives: To evaluate the wear resistance of two commonly used materials for orthodontic retainers: Acropars OP, i.e. a polymethyl methacrylate based material, and 3A-GS060, i.e. a polyethylene based material. Materials and Methods: For each material, 30 orthodontic retainers were made according to the manufacturers’ instructions and a 30×30×2 mm block was cut out from the mid- palatal area of each retainer. Each specimen underwent 1000 cycles of wear stimulation in a pin on disc machine. The depth of wear of each specimen was measured using a Nano Wizard II atomic force microscope in 3 random points of each specimen’s wear trough. The average of these three measurements was calculated and considered as mean value wear depth of each specimen (µm). Results: The mean wear depth was 6.10µm and 2.15µm for 3A-GS060 and Acropars OP groups respectively. Independent t-test showed a significant difference between the two groups (p < 0.001). The results show Polymethyl methacrylate base (Acropars) is more wear resistance than the polyethylene based material (3A-GS060). Conclusions: As the higher wear resistance of the fabrication material can improve the retainers’ survival time and its cost-effectiveness, VFRs should be avoided in situations that the appliance needs high wear resistance such as bite blocks opposing occlusal forces. PMID:28959750

Surface Design and Engineering Toward Wear-Resistant, Self-Lubricating Diamond Films and Coatings

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

The tribological properties of chemical-vapor-deposited (CVD) diamond films vary with the environment, possessing a Jekyll-and-Hyde character. CVD diamond has low coefficient of friction and high wear resistance in air but high coefficient of friction and low wear resistance in vacuum. Improving the tribological functionality of materials (such as achieving low friction and good wear resistance) was an aim of this investigation. Three studies on the surface design, surface engineering, and tribology of CVD diamond have shown that its friction and wear are significantly reduced in ultrahigh vacuum. The main criteria for judging whether diamond films are an effective wear-resistant, self-lubricating material were coefficient of friction and wear rate, which must be less than 0.1 and on the order of 10(exp 6) cu mm/N(dot)m, respectively. In the first study the presence of a thin film (less than 1 micron thick) of amorphous, nondiamond carbon (hydrogenated carbon, also called diamondlike carbon or DLC) on CVD diamond greatly decreased the coefficient of friction and the wear rate. Therefore, a thin DLC film on CVD diamond can be an effective wear-resistant, lubricating coating in ultrahigh vacuum. In the second study the presence of an amorphous, nondiamond carbon surface layer formed on CVD diamond by ion implantation significantly reduced the coefficient of friction and the wear rate in ultrahigh vacuum. Therefore, such surface layers are acceptable for effective self-lubricating, wear-resistant applications of CVD diamond. In the third study CVD diamond in contact with cubic boron nitride exhibited low coefficient of friction in ultra high vacuum. Therefore, this materials combination can provide an effective self-lubricating, wear-resistant couple in ultrahigh vacuum.

Three-body wear of resin denture teeth with and without nanofillers.

PubMed

Stober, Thomas; Henninger, Moritz; Schmitter, Marc; Pritsch, Maria; Rammelsberg, Peter

2010-02-01

The wear behavior of newly developed denture teeth with nanofillers may be different from teeth with other chemical formulations. The purpose of this study was to examine the 3-body wear resistance of 11 different commercially available resin denture teeth. The materials tested were conventional (SR Orthotyp PE, Orthognath) and cross-linked acrylic resin teeth without inorganic fillers (Premium 8, SR Postaris DCL, Trubyte Portrait, Artiplus), composite resin teeth with inorganic fillers (SR Orthosit PE, Vitapan), and composite resin teeth (experimental materials) with inorganic nanofillers (NC Veracia Posterior, e-Ha, Mondial). Human enamel and a ceramic denture tooth (Lumin Vacuum) were used as reference materials. The 3-body wear test was performed in a wear machine developed by the Academic Center for Dentistry Amsterdam (ACTA), with millet suspension acting as an abrasive medium (n=10, test load: 15 N, slip rate: 20%, number of cycles: 100,000). Wear was determined with the aid of a profilometer. Data were analyzed with the Kruskal-Wallis test and Mann-Whitney U test using the closed testing approach (significance level for familywise error rate, alpha=.05). None of the acrylic and composite resin materials tested in this study demonstrated the 3-body wear resistance of ceramic teeth or human enamel. Teeth with inorganic fillers demonstrated significantly lower wear values than conventional or cross-linked acrylic resin teeth without fillers. Composite resin teeth with traditional fillers showed significantly lower wear than composite resin teeth with nanofillers. Denture teeth with and without inorganic fillers differed significantly with regard to the degree of wear generated in the ACTA wear simulator. The incorporation of nanofillers did not improve the wear resistance compared to teeth with traditional fillers.

Time series analysis of tool wear in sheet metal stamping using acoustic emission

NASA Astrophysics Data System (ADS)

Vignesh Shanbhag, V.; Pereira, P. Michael; Rolfe, F. Bernard; Arunachalam, N.

2017-09-01

Galling is an adhesive wear mode that often affects the lifespan of stamping tools. Since stamping tools represent significant economic cost, even a slight improvement in maintenance cost is of high importance for the stamping industry. In other manufacturing industries, online tool condition monitoring has been used to prevent tool wear-related failure. However, monitoring the acoustic emission signal from a stamping process is a non-trivial task since the acoustic emission signal is non-stationary and non-transient. There have been numerous studies examining acoustic emissions in sheet metal stamping. However, very few have focused in detail on how the signals change as wear on the tool surface progresses prior to failure. In this study, time domain analysis was applied to the acoustic emission signals to extract features related to tool wear. To understand the wear progression, accelerated stamping tests were performed using a semi-industrial stamping setup which can perform clamping, piercing, stamping in a single cycle. The time domain features related to stamping were computed for the acoustic emissions signal of each part. The sidewalls of the stamped parts were scanned using an optical profilometer to obtain profiles of the worn part, and they were qualitatively correlated to that of the acoustic emissions signal. Based on the wear behaviour, the wear data can be divided into three stages: - In the first stage, no wear is observed, in the second stage, adhesive wear is likely to occur, and in the third stage severe abrasive plus adhesive wear is likely to occur. Scanning electron microscopy showed the formation of lumps on the stamping tool, which represents galling behavior. Correlation between the time domain features of the acoustic emissions signal and the wear progression identified in this study lays the basis for tool diagnostics in stamping industry.

Effect of Alloying Elements on Nano-ordered Wear Property of Magnesium Alloys

NASA Astrophysics Data System (ADS)

Yagi, Takahiro; Hirayama, Tomoko; Matsuoka, Takashi; Somekawa, Hidetoshi

2017-03-01

The effect of alloying elements on nano-ordered wear properties was investigated using fine-grained pure magnesium and several types of 0.3 at. pct X (X = Ag, Al, Ca, Li, Mn, Y, and Zn) binary alloys. They had an average grain size of 3 to 5 μm and a basal texture due to their production by the extrusion process. The specific wear rate was influenced by the alloying element; the Mg-Ca and Mg-Mn alloys showed the best and worst wear property, respectively, among the present alloying elements, which was the same trend as that for indentation hardness. Deformed microstructural observations revealed no formation of deformation twins, because of the high activation of grain boundary-induced plasticity. On the contrary, according to scratched surface observations, when grain boundary sliding partially contributed to deformation, these alloys had large specific wear rates. These results revealed that the wear property of magnesium alloys was closely related to the plastic deformation mechanism. The prevention of grain boundary sliding is important to improve the wear property, which is the same as that of a large-scale wearing configuration. One of the influential factors is the change in the lattice parameter with the chemical composition, i.e., ∂( c/ a)/∂ C. An alloying element that has a large value of ∂( c/ a)/∂ C effectively enhances the wear property.

New developments in ophthalmic coatings on plastic lenses

NASA Astrophysics Data System (ADS)

Eigenmann, H. P.; Lobsiger, W.; Suter, R.

1998-02-01

The origin of vision aids such as eyeglasses, magnifying glasses, telescopes and so forth lies in the distant past and cannot be dated with precision. However, such aids certainly came into use at different times in different cultures. Early portraits and other pictures prove to a certainty, however, that remarkable well-made spectacles were in use by the end of the Middle Ages. Glass was employed for optical lenses from the very beginning, and quality improved continuously with advances in glassmaking and polishing techniques. Starting around 1970, this continuing development received new impetus from the introduction of plastics as a new material for ophthalmic lenses. Rapid progress in plastics chemistry had epoch-making effects on lens technology, and today a wide variety of materials such as CR39, PMMA and polycarbonates, with refractive indices ranging from 1.52 to 1.65, are used for this purpose. Eyeglasses have long been important on other grounds than vision correction; people wear them as adornment, because they are fashionable, to express their personality, and for other reasons. This dramatic history shows no signs of coming to an end, and more innovations are definitely ahead.

Microstructure and Antiwear Property of Laser Cladding Ni-Co Duplex Coating on Copper.

PubMed

Wang, Yiyong; Liang, Zhipeng; Zhang, Junwei; Ning, Zhe; Jin, Hui

2016-07-28

Ni-Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al₂O₃/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni-Co duplex coatings comprised a Co-based solid solution, Cr₇C₃, (Fe,Ni) 23 C₆, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni-Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni-Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.

Nano- and Macro-wear of Bio-carbo-nitrided AISI 8620 Steel Surfaces

NASA Astrophysics Data System (ADS)

Arthur, Emmanuel Kwesi; Ampaw, Edward; Zebaze Kana, M. G.; Adetunji, A. R.; Olusunle, S. O. O.; Adewoye, O. O.; Soboyejo, W. O.

2015-12-01

This paper presents the results of an experimental study of nano- and macro-scale wear in a carbo-nitrided AISI 8620 steel. Carbo-nitriding is carried out using a novel method that involves the use of dried, cyanide-containing cassava leaves, as sources of carbon and nitrogen. These are used in a pack cementation that is used to diffuse carbon and nitrogen into case layers at intermediate temperatures [673.15 K, 723.15 K, 773.15 K, and 823.15 K (400 °C, 450 °C, 500 °C, and 550 °C)]. Nano- and macro-scale wear properties are studied in the case-hardened surfaces, using a combination of nano-scratch and pin-on-disk experiments. The measured wear volumes (at both nano- and macro-length scales) are shown to increase with decreasing pack cyaniding temperature. The nano- and macro-wear resistances are also shown to be enhanced by the in situ diffusion of carbon and nitrogen from cyanide-containing bio-processed waste. The underlying wear mechanisms are also elucidated via atomic force microscopy and scanning electron microscopy observations of the wear tracks. The implications of the results are discussed for the design of hardened carbo-nitrided steel surfaces with improved wear resistance.

Effect of cobalt content on wear and corrosion behaviors of electrodeposited Ni-Co/WC nano-composite coatings.

PubMed

Amadeh, A; Ebadpour, R

2013-02-01

Metal-ceramic composite coatings are widely used in automotive and aerospace industries as well as micro-electronic systems. Electrodeposition is an economic method for application of these coatings. In this research, nickel-cobalt coatings reinforced by nano WC particles were applied on carbon steel substrate by pulse electrodeposition from modified Watts bath containing different amounts of cobalt sulphate as an additive. Saccharin and sodium dodecyl sulphate (SDS) were also added to electroplating bath as grain refiner and surfactant, respectively. The effect of cobalt content on wear and corrosion behavior of the coatings was investigated. Wear and corrosion properties were assessed by pin-on-disk and potentiodynamic polarization methods, respectively. Phase analysis was performed by X-ray diffraction (XRD) using CuK(alpha) radiation and the worn surfaces were studied by means of Scanning Electron Microscopy (SEM). The results showed that the addition of cobalt improved the wear resistance of the coatings. In the presence of 18 g/L cobalt in electrodeposition bath, the wear rate of the coating decreased to 0.002 mg/m and the coefficient of friction reduced to 0.695 while they were 0.004 mg/m and 0.77 in the absence of cobalt, respectively. This improvement in wear properties can be attributed to the formation of hcp phase in metallic matrix. Meanwhile, the corrosion resistance of the coatings slightly reduced because cobalt is more active metal with respect to nickel.

Wear and Corrosion Properties of 316L-SiC Composite Coating Deposited by Cold Spray on Magnesium Alloy

NASA Astrophysics Data System (ADS)

Chen, Jie; Ma, Bing; Liu, Guang; Song, Hui; Wu, Jinming; Cui, Lang; Zheng, Ziyun

2017-08-01

In order to improve the wear and corrosion resistance of commonly used magnesium alloys, 316L stainless steel coating and 316L-SiC composite coating have been deposited directly on commercial AZ80 magnesium alloy using cold spraying technology (CS). The microstructure, hardness and bonding strength of as-sprayed coatings were studied. Their tribological properties sliding against Si3N4 and GCr15 steel under unlubricated conditions were evaluated by a ball-on-disk tribometer. Corrosion behaviors of coated samples were also evaluated and compared to that of uncoated magnesium alloy substrate in 3.5 wt.% NaCl solution by electrochemical measurements. Scanning electron microscopy was used to characterize the corresponding wear tracks and corroded surfaces to determine wear and corrosion mechanisms. The results showed that the as-sprayed coatings possessed higher microhardness and more excellent wear resistance than magnesium alloy substrate. Meanwhile, 316L and 316L-SiC coating also reduced the corrosion current density of magnesium alloy and the galvanic corrosion of the substrates was not observed after 200-h neutral salt spray exposure, which demonstrated that corrosion resistance of a magnesium alloy substrate could be greatly improved by cold-sprayed stainless steel-based coatings.

Porosity and wear resistance of flame sprayed tungsten carbide coatings

NASA Astrophysics Data System (ADS)

Winarto, Winarto; Sofyan, Nofrijon; Rooscote, Didi

2017-06-01

Thermal-sprayed coatings offer practical and economical solutions for corrosion and wear protection of components or tools. To improve the coating properties, heat treatment such as preheat is applied. The selection of coating and substrate materials is a key factor in improving the quality of the coating morphology after the heat treatment. This paper presents the experimental results regarding the effect of preheat temperatures, i.e. 200°C, 300°C and 400°C, on porosity and wear resistance of tungsten carbide (WC) coating sprayed by flame thermal coating. The powders and coatings morphology were analyzed by a Field Emission Scanning Electron Microscope equipped with Energy Dispersive Spectrometry (FE-SEM/EDS), whereas the phase identification was performed by X-Ray diffraction technique (XRD). In order to evaluate the quality of the flame spray obtained coatings, the porosity, micro-hardness and wear rate of the specimens was determined. The results showed that WC coating gives a higher surface hardness from 1391 HVN up to 1541 HVN compared to that of the non-coating. Moreover, the wear rate increased from 0.072 mm3/min. to 0.082 mm3/min. when preheat temperature was increased. Preheat on H13 steel substrate can reduce the percentage of porosity level from 10.24 % to 3.94% on the thermal spray coatings.

Sliding Seal Materials for Adiabatic Engines, Phase 2

NASA Technical Reports Server (NTRS)

Lankford, J.; Wei, W.

1986-01-01

An essential task in the development of the heavy-duty adiabatic diesel engine is identification and improvements of reliable, low-friction piston seal materials. In the present study, the sliding friction coefficients and wear rates of promising carbide, oxide, and nitride materials were measured under temperature, environmental, velocity, and loading conditions that are representative of the adiabatic engine environment. In addition, silicon nitride and partially stabilized zirconia disks were ion implanted with TiNi, Ni, Co, and Cr, and subsequently run against carbide pins, with the objective of producing reduced friction via solid lubrication at elevated temperature. In order to provide guidance needed to improve materials for this application, the program stressed fundamental understanding of the mechanisms involved in friction and wear. Electron microscopy was used to elucidate the micromechanisms of wear following wear testing, and Auger electron spectroscopy was used to evaluate interface/environment interactions which seemed to be important in the friction and wear process. Unmodified ceramic sliding couples were characterized at all temperatures by friction coefficients of 0.24 and above. The coefficient at 800 C in an oxidizing environment was reduced to below 0.1, for certain material combinations, by the ion implanation of TiNi or Co. This beneficial effect was found to derive from lubricious Ti, Ni, and Co oxides.

The influence of machining condition and cutting tool wear on surface roughness of AISI 4340 steel

NASA Astrophysics Data System (ADS)

Natasha, A. R.; Ghani, J. A.; Che Haron, C. H.; Syarif, J.

2018-01-01

Sustainable machining by using cryogenic coolant as the cutting fluid has been proven to enhance some machining outputs. The main objective of the current work was to investigate the influence of machining conditions; dry and cryogenic, as well as the cutting tool wear on the machined surface roughness of AISI 4340 steel. The experimental tests were performed using chemical vapor deposition (CVD) coated carbide inserts. The value of machined surface roughness were measured at 3 cutting intervals; beginning, middle, and end of the cutting based on the readings of the tool flank wear. The results revealed that cryogenic turning had the greatest influence on surface roughness when machined at lower cutting speed and higher feed rate. Meanwhile, the cutting tool wear was also found to influence the surface roughness, either improving it or deteriorating it, based on the severity and the mechanism of the flank wear.

Coated carbide drill performance under soluble coconut oil lubricant and nanoparticle enhanced MQL in drilling AISI P20

NASA Astrophysics Data System (ADS)

Jamil, N. A. M.; Azmi, A. I.; Fairuz, M. A.

2016-02-01

This research experimentally investigates the performance of a TiAlN coated carbide drill bit in drilling AISI P20 through two different kinds of lubricants, namely; soluble coconut oil (SCO) and nanoparticle-enhanced coconut oil (NECO) under minimum quantity lubrication system. The tool life and tool wear mechanism were studied using various cutting speeds of 50, 100 and 150 m/min with a constant feed of 0.01 mm/rev. Since the flank wear land was not regular along the cutting edge, the average flank wear (VB) was measured at several points using image analysis software. The drills were inspected using a scanning electron microscope to further elucidate the wear mechanism. The result indicates that drilling with the nanoparticle- enhanced lubricant was better in resisting the wear and improving the drill life to some extent

Improvement in Microstructure Performance of the NiCrBSi Reinforced Coating on TA15 Titanium Alloy

NASA Astrophysics Data System (ADS)

Peng, Li

2012-10-01

This work is based on the dry sliding wear of NiCrBSi reinforced coating deposited on TA15 titanium alloy using the laser cladding technique, the parameters of which were such as to provide almost crack-free coatings with minimum dilution and very low porosity. SEM results indicated that a laser clad coating with metallurgical joint to the substrate was formed. Compared with TA15 substrate, an improvement of the micro-hardness and wear resistance was observed for this composite coating. Rare earth oxide Y2O3 was beneficial in producing of the amorphous phases in laser clad coating. With addition of Y2O3, more amorphous alloys were produced, which increased the micro-hardness and wear resistance of the coating.

Abrasive wear of Hilong BoTN hardfacings

NASA Astrophysics Data System (ADS)

Fedorova, L.; Fedorov, S.; Sadovnikov, A.; Ivanova, Y.; Voronina, M.

2018-02-01

The spread of steels, which are used to produce locks of steel drill pipes, adversely affects their wear resistance, which, in combination with low hardness of HV 2400 ... 2800 MPa as well as of the thread of screw, results in low wear resistance and the need for their reconstruction at the pipe control shop. An efficient way of improving the quality of drill pipe jonts is to hard-face them by the outside diameter with wear-resistant materials (hardbanding). One of the companies engaged in the development of hardfacing materials and hardbanding is Hilong (China) with weld seams of the brand BoTn. According to the results of the studies the following conclusion can be made: hardfacing increases the durability of the hardware, contributing to an increase in wear resistance of locks of DP under the conditions of abrasive action of aggressive geological formations; the usage of DP without wear-resistant weld seams is impermissible, because their further operation, as part of the drill-stem, can lead to emergency consequences; application of the pipes with the hardfacing collars together with the collars without hardfacing, due to varying degree of wear of jonts in the drill-stem, is also impermissible.

Improved wear resistance of functional diamond like carbon coated Ti-6Al-4V alloys in an edge loading conditions.

PubMed

Choudhury, Dipankar; Lackner, Jürgen M; Major, Lukasz; Morita, Takehiro; Sawae, Yoshinori; Bin Mamat, Azuddin; Stavness, Ian; Roy, Chanchal K; Krupka, Ivan

2016-06-01

This study investigates the durability of functional diamond-like carbon (DLC) coated titanium alloy (Ti-6Al-4V) under edge loading conditions for application in artificial hip joints. The multilayered (ML) functional DLC coatings consist of three key layers, each of these layers were designed for specific functions such as increasing fracture strength, adapting stress generation and enhancing wear resistance. A 'ball-on-disk' multi-directional wear tester was used in the durability test. Prior to the wear testing, surface hardness, modulus elasticity and Raman intensity were measured. The results revealed a significant wear reduction to the DLC coated Ti-6Al-4V disks compared to that of non-coated Ti-6Al-4V disks. Remarkably, the counterpart Silicon Nitride (Si3N4) balls also yielded lowered specific wear rate while rubbed against the coated disks. Hence, the pairing of a functional multilayered DLC and Si3N4 could be a potential candidate to orthopedics implants, which would perform a longer life-cycle against wear caused by edge loading. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microstructure and Wear Resistance of Composite Coating by Laser Cladding Al/TiN on the Ti-6Al-4V Substrate

NASA Astrophysics Data System (ADS)

Zhang, H. X.; Yu, H. J.; Chen, C. Z.

2015-05-01

The composite coatings were fabricated by laser cladding Al/TiN pre-placed powders on Ti-6Al-4V substrate for enhancing wear resistance and hardness of the substrate. The composite coatings were analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The sliding wear tests were performed by MM200 wear test machine. The hardness of the coatings was tested by HV-1000 hardness tester. After laser cladding, it was found that there was a good metallurgical bond between the coating and the substrate. The composite coatings were mainly composed of the matrix of β-Ti (Al) and the reinforcements of titanium nitride (TiN), Ti3Al, TiAl and Al3Ti. The hardness and wear resistance of the coatings on four samples were greatly improved, among which sample 4 exhibited the highest hardness and best wear resistance. The hardness of the coating on sample 4 was approximately 2.5 times of the Ti-6Al-4V substrate. And the wear resistance of sample 4 was four times of the substrate.

Nanomechanical properties, wear resistance and in-vitro characterization of Ta2O5 nanotubes coating on biomedical grade Ti-6Al-4V.

PubMed

Sarraf, Masoud; Razak, Bushroa Abdul; Nasiri-Tabrizi, Bahman; Dabbagh, Ali; Kasim, Noor Hayaty Abu; Basirun, Wan Jefrey; Bin Sulaiman, Eshamsul

2017-02-01

Tantalum pentoxide nanotubes (Ta 2 O 5 NTs) can dramatically raise the biological functions of different kinds of cells, thus have promising applications in biomedical fields. In this study, Ta 2 O 5 NTs were prepared on biomedical grade Ti-6Al-4V alloy (Ti64) via physical vapor deposition (PVD) and a successive two-step anodization in H 2 SO 4 : HF (99:1)+5% EG electrolyte at a constant potential of 15V. To improve the adhesion of nanotubular array coating on Ti64, heat treatment was carried out at 450°C for 1h under atmospheric pressure with a heating/cooling rate of 1°Cmin - 1 . The surface topography and composition of the nanostructured coatings were examined by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS), to gather information about the corrosion behavior, wear resistance and bioactivity in simulated body fluids (SBF). From the nanoindentation experiments, the Young's modulus and hardness of the 5min anodized sample were ~ 135 and 6GPa, but increased to ~ 160 and 7.5GPa, respectively, after annealing at 450°C. It was shown that the corrosion resistance of Ti64 plates with nanotubular surface modification was higher than that of the bare substrate, where the 450°C annealed specimen revealed the highest corrosion protection efficiency (99%). Results from the SBF tests showed that a bone-like apatite layer was formed on nanotubular array coating, as early as the first day of immersion in simulated body fluid (SBF), indicating the importance of nanotubular configuration on the in-vitro bioactivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Abrasive wear of resin composites as related to finishing and polishing procedures.

PubMed

Turssi, Cecilia P; Ferracane, Jack L; Serra, Mônica C

2005-07-01

Finishing and polishing procedures may cause topographical changes and introduce subsurface microcracks in dental composite restoratives. Since both of these effects may contribute toward the kinetics of wear, the purpose of this study was to assess and correlate the wear and surface roughness of minifilled and nanofilled composites finished and polished by different methods. Specimens (n=10) made of a minifilled and a nanofilled composite were finished and polished with one of the four sequences: (1) tungsten carbide burs plus Al(2)O(3)-impregnated brush (CbBr) or (2) tungsten carbide burs plus diamond-impregnated cup (CbCp), (3) diamond burs plus brush (DmBr) or (4) diamond burs plus cup (DmCp). As a control, abrasive papers were used. After surface roughness had been quantified, three-body abrasion was simulated using the OHSU wear machine. The wear facets were then scanned to measure wear depth and post-testing roughness. All sets of data were subjected to ANOVA and Tukey's tests (alpha=0.05). Pearson's correlation test was applied to check for the existence of a relationship between pre-testing roughness and wear. Significantly smoother surfaces were attained with the sequences CbBr and CbCp, whereas DmCp yielded the roughest surface. Regardless of the finishing/polishing technique, the nanofilled composite exhibited the lowest pre-testing roughness and wear. There was no correlation between the surface roughness achieved after finishing/polishing procedures and wear (p=0.3899). Nano-sized materials may have improved abrasive wear resistance over minifilled composites. The absence of correlation between wear and surface roughness produced by different finishing/polishing methods suggests that the latter negligibly influences material loss due to three-body abrasion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyazgin, Alexander, E-mail: lyazgin@list.ru; Shugurov, Artur, E-mail: shugurov@ispms.tsc.ru; Sergeev, Viktor, E-mail: retc@ispms.tsc.ru

The effect of bombardment of the Ni-B sublayer by Zr ion beams on the surface morphology and tribomechanical properties of Au-Ni coatings was investigated. It was found that the treatment has no significant effect on the surface roughness and grain size of the Au-Ni coatings, while it provides essential reducing of their friction coefficient and improvement of wear resistance. It is shown that increased wear resistance of these coatings was caused by their strain hardening resulted from localization of plastic strain. The optimal Zr fluence were determined that provide the maximum reduction of linear wear of the coatings.

Dramatic impact of using protective equipment on the level of hurling-related head injuries: an ultimately successful 27-year programme.

PubMed

Crowley, Patrick J; Crowley, Michael J

2014-01-01

Major head injuries are not uncommon in the Irish national game of hurling. Historically, helmets were not worn. We report a multistage campaign to facilitate and encourage the use of appropriate headgear among the estimated 100 000 hurling players in Ireland. This campaign lasted for 27 years between 1985 and 2012, and involved a number of different stages including: (1) facilitating the establishment of a business dedicated to developing head protection equipment suitable for hurling, (2) placing a particular emphasis on continual product enhancement to the highest industrial standards, (3) engaging continually with the game's controlling body, the Gaelic Athletic Association (GAA), with the ultimate objective of securing a mandatory usage policy for protective helmets and faceguards, (4) longitudinal research to monitor hurling injury, equipment usage and players' attitudes and (5) widely communicating key research findings to GAA leaders and members, as well as to 1000 clubs and schools. One of our three relevant studies included 798 patients and identified a dramatic association between the type of head protection used by a player, if any, and the site of the injury requiring treatment. While 51% of the injured players without head protection suffered head trauma, this rate was only 35% among the players wearing helmets and 5% among players who were wearing full head protection (both a helmet and faceguard). The GAA responded in three stages to the accumulating evidence: (1) they introduced a mandatory regulation for those aged less than 18 years in 2005; (2) this ruling was extended to all players under 21 years in 2007 and (3) finally extended to all players irrespective of age, gender or grade from January 2010. The latter ruling applied to both games and organised training sessions.

Effect of Groove Surface Texture on Tribological Characteristics and Energy Consumption under High Temperature Friction.

PubMed

Wu, Wei; Chen, Guiming; Fan, Boxuan; Liu, Jianyou

2016-01-01

Energy consumption and tribological properties could be improved by proper design of surface texture in friction. However, some literature focused on investigating their performance under high temperature. In the study, different groove surface textures were fabricated on steels by a laser machine, and their tribological behaviors were experimentally studied with the employment of the friction and wear tester under distinct high temperature and other working conditions. The friction coefficient was recorded, and wear performance were characterized by double light interference microscope, scanning electron microscope (SEM) and x-ray energy dispersive spectrometry (EDS). Then, the performances of energy consumptions were carefully estimated. Results showed that friction coefficient, wear, and energy consumption could almost all be reduced by most textures under high temperature conditions, but to a different extent which depends on the experimental conditions and texture parameters. The main improvement mechanisms were analyzed, such as the hardness change, wear debris storage, thermal stress release and friction induced temperature reduction by the textures. Finally, a scattergram of the relatively reduced ratio of the energy consumption was drawn for different surface textures under four distinctive experimental conditions to illustrate the comprehensive energy consumption improving ability of textures, which was of benefit for the application of texture design.

Effect of Groove Surface Texture on Tribological Characteristics and Energy Consumption under High Temperature Friction

PubMed Central

Wu, Wei; Chen, Guiming; Fan, Boxuan; Liu, Jianyou

2016-01-01

Energy consumption and tribological properties could be improved by proper design of surface texture in friction. However, some literature focused on investigating their performance under high temperature. In the study, different groove surface textures were fabricated on steels by a laser machine, and their tribological behaviors were experimentally studied with the employment of the friction and wear tester under distinct high temperature and other working conditions. The friction coefficient was recorded, and wear performance were characterized by double light interference microscope, scanning electron microscope (SEM) and x-ray energy dispersive spectrometry (EDS). Then, the performances of energy consumptions were carefully estimated. Results showed that friction coefficient, wear, and energy consumption could almost all be reduced by most textures under high temperature conditions, but to a different extent which depends on the experimental conditions and texture parameters. The main improvement mechanisms were analyzed, such as the hardness change, wear debris storage, thermal stress release and friction induced temperature reduction by the textures. Finally, a scattergram of the relatively reduced ratio of the energy consumption was drawn for different surface textures under four distinctive experimental conditions to illustrate the comprehensive energy consumption improving ability of textures, which was of benefit for the application of texture design. PMID:27035658

Surface Design and Engineering Toward Wear-Resistant, Self-Lubricant Diamond Films and Coatings. Chapter 10

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

This chapter describes three studies on the surface design, surface engineering, and tribology of chemical-vapor-deposited (CVD) diamond films and coatings toward wear-resistant, self-lubricating diamond films and coatings. Friction mechanisms and solid lubrication mechanisms of CVD diamond are stated. Effects of an amorphous hydrogenated carbon on CVD diamond, an amorphous, nondiamond carbon surface layer formed on CVD diamond by carbon and nitrogen ion implantation, and a materials combination of cubic boron nitride and CVD diamond on the adhesion, friction, and wear behaviors of CVD diamond in ultrahigh vacuum are described. How surface modification and the selected materials couple improved the tribological functionality of coatings, giving low coefficient of friction and good wear resistance, is explained.

Effect of T6 treatment on the coefficient of friction of Al25Mg2Si2Cu4Fe alloy

NASA Astrophysics Data System (ADS)

Sondur, D. G.; Mallapur, D. G.; Udupa, K. Rajendra

2018-04-01

Effect of T6 treatment on the coefficient of friction of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting wear test on pin on disc wear testing machine. Wear test parameters such as the load and the speed were varied by keeping one constant and varying the other respectively. It was observed that the coefficient of friction is high for as cast condition due to the brittle microstructure. After T6 heat treatment the precipitates formed such as the Chinese scripts and the Mg2Si blocks got modified that lead to improvement in the hardness and the wear resistance. This reduces the coefficient of friction.

Shuttle landing runway modification to improve tire spin-up wear performance

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Yager, Thomas J.; Stubbs, Sandy M.

1988-01-01

This paper presents the results of a series of tire spin-up wear tests on a simulated Kennedy Space Center (KSC) runway that were carried out to investigate the tire wear problem for Space Shuttle landings on the KSC runway and to test several modifications of the runway surface designed to alleviate the problem. It was found that the runway surface produced by a concrete smoothing machine using cutters spaced one and three-quarters blades per centimeter provided adequate wet cornering while limiting spin-up wear. Based on the test results, the KSC runway was smoothed for about 1066 m at each end, leaving the original high friction surface, for better wet steering and braking, in the 2438-m central section.

Wear and corrosion resistance of electroforming layer after WEDM for 7075 aluminum alloy

NASA Astrophysics Data System (ADS)

Xu, Jinkai; Qiu, Rongxian; Lian, Zhongxu; Yu, Zhanjiang; Yu, Peng; Ren, Wanfei; Yu, Huadong

2018-06-01

In order to investigate the influence of the recast layer obtained by wire electrical discharge machining (WEDM) for 7075 aluminum alloy on the mechanical physical properties of the workpiece, we carried out research on the geometry parameters, microstructure, adhesion, wear resistance and corrosion resistance of the recast layer. The results show that the unit thermal power density decreases, the surface roughness Ra value increases, and the amount of the electric erosion craters and the micro/nano pits decrease with the increase of current and voltage. In the meantime, the thickness and hardness of the recast layer are increased, so the wear resistance and corrosion resistance are significantly improved. In addition, the surface hardness plays a major role in increasing wear resistance.

Characterization of Ti and Co based biomaterials processed via laser based additive manufacturing

NASA Astrophysics Data System (ADS)

Sahasrabudhe, Himanshu

Titanium and Cobalt based metallic materials are currently the most ideal materials for load-bearing metallic bio medical applications. However, the long term tribological degradation of these materials still remains a problem that needs a solution. To improve the tribological performance of these two metallic systems, three different research approaches were adapted, stemming out four different research projects. First, the simplicity of laser gas nitriding was utilized with a modern LENS(TM) technology to form an in situ nitride rich later in titanium substrate material. This nitride rich composite coating improved the hardness by as much as fifteen times and reduced the wear rate by more than a magnitude. The leaching of metallic ions during wear was also reduced by four times. In the second research project, a mixture of titanium and silicon were processed on a titanium substrate in a nitrogen rich environment. The results of this reactive, in situ additive manufacturing process were Ti-Si-Nitride coatings that were harder than the titanium substrate by more than twenty times. These coatings also reduced the wear rate by more than two magnitudes. In the third research approach, composites of CoCrMo alloy and Calcium phosphate (CaP) bio ceramic were processed using LENS(TM) based additive manufacturing. These composites were effective in reducing the wear in the CoCrMo alloy by more than three times as well as reduce the leaching of cobalt and chromium ions during wear. The novel composite materials were found to develop a tribofilm during wear. In the final project, a combination of hard nitride coating and addition of CaP bioceramic was investigated by processing a mixture of Ti6Al4V alloy and CaP in a nitrogen rich environment using the LENS(TM) technology. The resultant Ti64-CaP-Nitride coatings significantly reduced the wear damage on the substrate. There was also a drastic reduction in the metal ions leached during wear. The results indicate that the three tested approaches for reducing the wear damage in Ti and Co based were successful. These approaches and the associated research investigations could pave the way for future work in alleviating wear and corrosion related damage, especially via the additive manufacturing route.

Effect of Nano-Si3N4 Additives and Plasma Treatment on the Dry Sliding Wear Behavior of Plasma Sprayed Al2O3-8YSZ Ceramic Coatings

NASA Astrophysics Data System (ADS)

Gou, Junfeng; Zhang, Jian; Zhang, Qiwen; Wang, You; Wang, Chaohui

2017-04-01

In this paper, the effect of nano-Si3N4 additives and plasma treatment on the wear behavior of Al2O3-8YSZ ceramic coatings was studied. Nano-Al2O3, nano-8YSZ (8 wt.% Y2O3-stabilized ZrO2) and nano-Si3N4 powders were used as raw materials to fabricate four types of sprayable feedstocks. Plasma treatment was used to improve the properties of the feedstocks. The surface morphologies of the ceramic coatings were observed. The mechanical properties of the ceramic coatings were measured. The dry sliding wear behavior of the Al2O3-8YSZ coatings with and without Si3N4 additives was studied. Nano-Si3N4 additives and plasma treatment can improve the morphologies of the coatings by prohibiting the initiation of micro-cracks and reducing the unmelted particles. The hardness and bonding strength of AZSP (Al2O3-18 wt.% 8YSZ-10 wt.% Si3N4-plasma treatment) coating increased by 79.2 and 44% compared to those of AZ (Al2O3-20 wt.% 8YSZ) coating. The porosity of AZSP coating decreased by 85.4% compared to that of AZ coating. The wear test results showed that the addition of nano-Si3N4 and plasma treatment could improve the wear resistance of Al2O3-8YSZ coatings.

Use of a Textured Insole to Improve the Association Between Postural Balance and Ankle Discrimination in Young Male and Female Dancers.

PubMed

Steinberg, Nili; Waddington, Gordon; Adams, Roger; Karin, Janet; Tirosh, Oren

2015-12-01

Ballet dancers require a high level of postural balance (PB) and proprioception ability during performance. As textured insoles inserted into ballet shoes were found to improve proprioception ability, and better proprioceptive acuity was associated with better PB, the aim of the present study was to investigate whether the association between ankle inversion movement discrimination (AIMD) and PB changed following wearing textured insoles in young male and female dancers. Forty-four dancers from the Australian Ballet School, ages 14-19 yrs, were tested for static and dynamic PB and AIMD under two conditions: in ballet shoes, and in ballet shoes with textured insoles inserted. Female dancers demonstrated a significant inverse relationship between AIMD and static PB in the medio-lateral direction when wearing ballet shoes, but not when wearing textured insoles. Male dancers showed a non-monotonic relationship when tested with ballet shoes only, but a significant inverse relationship between AIMD and dynamic PB in the vertical direction and with the waist/head cross-correlation acceleration in the three movement directions when they were tested with textured insoles. Male dancers demonstrated an improved association between dynamic PB and proprioception ability when using textured insoles, suggesting that the increased afferent information from the plantar surface had a beneficial effect on proprioception feedback about their PB. Conversely, for female dancers, that association was present when wearing ballet shoes, but not when using textured insoles, suggesting that the increased afferent information for female dancers who already had high proprioception ability was "overloaded" by wearing the textured insoles.

New Effective Material Couple--Oxide Ceramic and Carbon Nanotube-- Developed for Aerospace Microsystem and Micromachine Technologies

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; VanderWal, Randall L.; Tomasek, Aaron J.; Sayir, Ali; Farmer, Serene C.

2004-01-01

The prime driving force for using microsystem and micromachine technologies in transport vehicles, such as spacecraft, aircraft, and automobiles, is to reduce the weight, power consumption, and volume of components and systems to lower costs and increase affordability and reliability. However, a number of specific issues need to be addressed with respect to using microsystems and micromachines in aerospace applications--such as the lack of understanding of material characteristics; methods for producing and testing the materials in small batches; the limited proven durability and lifetime of current microcomponents, packaging, and interconnections; a cultural change with respect to system designs; and the use of embedded software, which will require new product assurance guidelines. In regards to material characteristics, there are significant adhesion, friction, and wear issues in using microdevices. Because these issues are directly related to surface phenomena, they cannot be scaled down linearly and they become increasingly important as the devices become smaller. When microsystems have contacting surfaces in relative motion, the adhesion and friction affect performance, energy consumption, wear damage, maintenance, lifetime and catastrophic failure, and reliability. Ceramics, for the most part, do not have inherently good friction and wear properties. For example, coefficients of friction in excess of 0.7 have been reported for ceramics and ceramic composite materials. Under Alternate Fuels Foundation Technologies funding, two-phase oxide ceramics developed for superior high-temperature wear resistance in NASA's High Operating Temperature Propulsion Components (HOTPC) project and new two-layered carbon nanotube (CNT) coatings (CNT topcoat/iron bondcoat/quartz substrate) developed in NASA's Revolutionary Aeropropulsion Concepts (RAC) project have been chosen as a materials couple for aerospace applications, including micromachines, in the nanotechnology lubrication task because of their potential for superior friction and wearf properties in air and in an ultrahigh vacuum, spacelike environment. At the NASA Glenn Research Center, two-phase oxide ceramic eutectics, Al2O3/ZrO2(Y2O3), were directionally solidified using the laser-float-zone process, and carbon nanotubes were synthesized within a high-temperature tube furnace at 800 C. Physical vapor deposition was used to coat all quartz substrates with 5-nm-thick iron as catalyst and bondcoat, which formed iron islands resembling droplets and serving as catalyst particles on the quartz. A series of scanning electron micrographs showing multiwalled carbon nanotubes directionally grown as aligned "nanograss" on quartz is presented. Unidirectional sliding friction eperiments were conducted at Glenn with the two-layered CNT coatings in contact with the two-phase Al2O3/ZrO2(Y2O3) eutectics in air and in ultrachigh vacuum. The main criteria for judging the performance of the materials couple for solid lubrication and antistick applications in a space environment were the coefficient of friction and the wear resistance (reciprocal of wear rate), which had to be less than 0.2 and greater than 10(exp 5) N(raised dot)/cubic millimetes, respectively, in ultrahigh vacuum. In air, the coefficient of friction for the CNT coatings in contact with Al2O3/ZrO2 (Y2O3) eutectics was 0.04, one-fourth of that for quartz. In an ultrahigh vacuum, the coefficient of friction for CNT coatings in contact with Al2O3/ZrO2 (Y2O3) was one-third of that for quartz. The two-phase Al2O3/ZrO2 (Y2O3) eutectic coupled with the two-layered CNT coating met the coefficient of friction and wear resistance criteria both in air and in an ultrahigh vacuum, spacelike environment. This material's couple can dramatically improve the stiction (or adhesion), friction, and wear resistance of the contacting surfaces, which are major issues for microdevices and micromachines.

Electrochemical corrosion, wear and cell behavior of ZrO2/TiO2 alloyed layer on Ti-6Al-4V.

PubMed

Li, Jianfang; He, Xiaojing; Zhang, Guannan; Hang, Ruiqiang; Huang, Xiaobo; Tang, Bin; Zhang, Xiangyu

2018-06-01

Ti-6Al-4V (TC4) has received increasing attention as biomaterial but also raised concerns about the long-term safety of releasing of metal ions and poor wear resistance. In this work, an ZrO 2 /TiO 2 alloyed layer was prepared on TC4 by plasma surface alloying with Zr and subsequently annealed in the air for improved corrosion and wear resistant. To assess the corrosion performance of the alloyed layer, the specimens were measured by open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid solution. The result shows that the ZrO 2 /TiO 2 alloyed layer exhibits strikingly high polarization resistance, wide passive region and very low current density, indicating the excellent corrosion resistance. The layer also displays significant improvement of wear resistance. Furthermore, the alloyed layer restricts cell adhesion and spreading. We infer that the ZrO 2 /TiO 2 alloyed layer might be potentially useful implanted devices such as biosensors, bioelectronics or drug delivery devices. Copyright © 2018 Elsevier B.V. All rights reserved.

Sputtered silver films to improve chromium carbide based solid lubricant coatings for use to 900 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Sliney, Harold E.; Deadmore, Daniel L.

1988-01-01

Thin silver films, 250 to 3500 A thick, were sputtered onto PS200, a plasma sprayed, chromium carbide based solid lubricant coating, to reduce run-in wear and improve tribological properties. The coating contains bonded chromium carbide as the wear resistant base stock with silver and barium fluoride/calcium fluoride eutectic added as low and high temperature lubricants, respectively. Potential applications for the PS200 coating are cylinder wall/piston ring lubrication for Stirling engines and foil bearing journal lubrication. In this preliminary program, the silver film overlay thickness was optimized based on tests using a pin-on-disk tribometer. The friction and wear studies were performed in a helium atmosphere at temperatures from 25 to 760 C with a sliding velocity of 2.7 m/s under a 4.9 N load. Films between 1000 and 1500 A provide the best lubrication of the counterface material. The films enrich the sliding surface with lubricant and reduce the initial abrasiveness of the as ground, plasma-sprayed coating surface, thus reducing wear.

Sputtered silver films to improve chromium carbide based solid lubricant coatings for use to 900 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Sliney, Harold E.; Deadmore, Daniel L.

1988-01-01

Thin silver films, 250 to 3500 A thick, were sputtered onto PS200, a plasma sprayed, chromium carbide based solid lubricant coating, to reduce run-in wear and improve tribological properties. The coating contains bonded chromium carbide as the wear resistant base stock with silver and barium fluoride/calcium fluoride eutectic added as low and high temperature lubricants respectively. Potential applications for the PS200 coating are cylinder wall/piston ring lubrication for Stirling engines and foil bearing journal lubrication. In this preliminary program, the silver film overlay thickness was optimized based on tests using a pin-on-disk tribometer. The friction and wear studies were performed in a helium atmosphere at temperatures from 25 to 760 C with a sliding velocity of 2.7 m/s under a 4.9 N load. Films between 1000 and 1500 A provide the best lubrication of the counterface material. The films enrich the sliding surface with lubricant and reduce the initial abrasiveness of the as ground, plasma-sprayed coating surface, thus reducing wear.

Improved piston ring materials for 650 deg C service

NASA Technical Reports Server (NTRS)

Bjorndahl, W. D.

1986-01-01

A program to develop piston ring material systems which will operate at 650C was performed. In this program, two candidate high temperature piston ring substrate materials, Carpenter 709-2 and 440B, were hot formed into the piston ring shape and subsequently evaluated. In a parallel development effort ceramic and metallic piston ring coating materials were applied to cast iron rings by various processing techniques and then subjected to thermal shock and wear evaluation. Finally, promising candidate coatings were applied to the most thermally stable hot formed substrate. The results of evaluation tests of the hot formed substrate show that Carpenter 709-2 has greater thermal stability than 440B. Of the candidate coatings, plasma transferred arc (PTA) applied tungsten carbide and molybdenum based systems exhibit the greatest resistance to thermal shock. For the ceramic based systems, thermal shock resistance was improved by bond coat grading. Wear testing was conducted to 650C (1202F). For ceramic systems, the alumina/titania/zirconia/yttria composition showed highest wear resistance. For the PTA applied systems, the tungsten carbide based system showed highest wear resistance.

Mechanical Properties and Wear Behavior of AA5182/WC Nanocomposite Fabricated by Friction Stir Welding at Different Tool Traverse Speeds

NASA Astrophysics Data System (ADS)

Paidar, Moslem; Asgari, Ali; Ojo, Olatunji Oladimeji; Saberi, Abbas

2018-03-01

Grain growth inhibition at the heat-affected zone, improved weld strength and superior tribological properties of welds are desirable attributes of modern manufacturing. With the focused on these attributes, tungsten carbide (WC) nanoparticles were employed as reinforcements for the friction stir welding of 5-mm-thick AA5182 aluminum alloy by varying tool traverse speeds. The microstructure, microhardness, ultimate tensile strength, fracture and wear behavior of the resultant WC-reinforced welds were investigated, while unreinforced AA5182 welds were employed as controls for the study. The result shows that the addition of WC nanoparticles causes substantial grain refinement within the weld nugget. A decrease in traverse speed caused additional particle fragmentation, improved hardness value and enhanced weld strength in the reinforced welds. Improved wear rate and friction coefficient of welds were attained at a reduced traverse speed of 100 mm/min in the WC-reinforced welds. This improvement is attributed to the effects of reduced grain size/grain fragmentation and homogeneous dispersion of WC nanoparticles within the WC-reinforced weld nugget.

Friction and wear of oxide-ceramic sliding against IN-718 nickel base alloy at 25 to 800 C in atmospheric air

NASA Technical Reports Server (NTRS)

Sliney, Harold E.; Deadmore, Daniel L.

1989-01-01

The friction and wear of oxide-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C were measured. The oxide materials tested were mullite (3Al2O3.2SiO2); lithium aluminum silicate (LiAlSi(x)O(y)); polycrystalline monolithic alpha alumina (alpha-Al2O3); single crystal alpha-Al2O3 (sapphire); zirconia (ZrO2); and silicon carbide (SiC) whisker-reinforced Al2O3 composites. At 25 C the mullite and zirconia had the lowest friction and the polycrystalline monolithic alumina had the lowest wear. At 800 C the Al2O3-8 vol/percent SiC whisker composite had the lowest friction and the Al2O3-25 vol/percent SiC composite had the lowest wear. The friction of the Al2O3-SiC whisker composites increased with increased whisker content while the wear decreased. In general, the wear-resistance of the ceramics improve with their hardness.

Motion-Blurred Particle Image Restoration for On-Line Wear Monitoring

PubMed Central

Peng, Yeping; Wu, Tonghai; Wang, Shuo; Kwok, Ngaiming; Peng, Zhongxiao

2015-01-01

On-line images of wear debris contain important information for real-time condition monitoring, and a dynamic imaging technique can eliminate particle overlaps commonly found in static images, for instance, acquired using ferrography. However, dynamic wear debris images captured in a running machine are unavoidably blurred because the particles in lubricant are in motion. Hence, it is difficult to acquire reliable images of wear debris with an adequate resolution for particle feature extraction. In order to obtain sharp wear particle images, an image processing approach is proposed. Blurred particles were firstly separated from the static background by utilizing a background subtraction method. Second, the point spread function was estimated using power cepstrum to determine the blur direction and length. Then, the Wiener filter algorithm was adopted to perform image restoration to improve the image quality. Finally, experiments were conducted with a large number of dynamic particle images to validate the effectiveness of the proposed method and the performance of the approach was also evaluated. This study provides a new practical approach to acquire clear images for on-line wear monitoring. PMID:25856328

Psychosocial impact on anophthalmic patients wearing ocular prosthesis.

PubMed

Goiato, M C; dos Santos, D M; Bannwart, L C; Moreno, A; Pesqueira, A A; Haddad, M F; dos Santos, E G

2013-01-01

The aim of this study was to assess the improvement in psychosocial awareness of anophthalmic patients wearing ocular prostheses and its relationship with demographic characteristics, factors of loss/treatment, social activity, and relationship between professional and patient. Surveys including a form for evaluation of psychosocial pattern were conducted with 40 anophthalmic patients rehabilitated with ocular prosthesis at the Center of Oral Oncology in the authors' dental school from January 1998 to November 2010. The improvement in psychosocial awareness was assessed by comparing the perception of some feelings reported in the period of eye loss and currently. Wilcoxon tests were applied for comparison of patients' perception between the periods. χ(2) tests were used to assess the relationship between the improvement in psychosocial awareness and the variables of the study. In addition, the logistic regression model measured this relationship with the measure of odds ratio. The feelings of shame, shyness, preoccupation with hiding it, sadness, insecurity and fear were significant for improvement in psychosocial awareness. It was concluded that the anophthalmic patients wearing an ocular prosthesis has significant improvement in psychosocial awareness after rehabilitation. Copyright © 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Current Pressure Transducer Application of Model-based Prognostics Using Steady State Conditions

NASA Technical Reports Server (NTRS)

Teubert, Christopher; Daigle, Matthew J.

2014-01-01

Prognostics is the process of predicting a system's future states, health degradation/wear, and remaining useful life (RUL). This information plays an important role in preventing failure, reducing downtime, scheduling maintenance, and improving system utility. Prognostics relies heavily on wear estimation. In some components, the sensors used to estimate wear may not be fast enough to capture brief transient states that are indicative of wear. For this reason it is beneficial to be capable of detecting and estimating the extent of component wear using steady-state measurements. This paper details a method for estimating component wear using steady-state measurements, describes how this is used to predict future states, and presents a case study of a current/pressure (I/P) Transducer. I/P Transducer nominal and off-nominal behaviors are characterized using a physics-based model, and validated against expected and observed component behavior. This model is used to map observed steady-state responses to corresponding fault parameter values in the form of a lookup table. This method was chosen because of its fast, efficient nature, and its ability to be applied to both linear and non-linear systems. Using measurements of the steady state output, and the lookup table, wear is estimated. A regression is used to estimate the wear propagation parameter and characterize the damage progression function, which are used to predict future states and the remaining useful life of the system.

Tooth wear risk assessment and care-planning in general dental practice.

PubMed

O'Toole, S; Khan, M; Patel, A; Patel, N J; Shah, N; Bartlett, D; Movahedi, S

2018-03-09

Objective To assess charting, risk assessment and treatment-planning of tooth wear between recently qualified and experienced dentists in general dental practice.Design Service evaluation.Setting Multi-setting evaluation of three mixed NHS/Private general dental practices in North-East London.Methods The clinical notes of new patient examinations on dentate adults presenting from the 1 October 2016 to 31 December 2016 were audited collecting data on tooth wear charting, risk assessment and treatment planning. Data were analysed using descriptives, chi square and logistic regressions in SPSS. Significance was inferred at p <0.05.Results Foundation dentists and experienced dentists performed 85 and 200 new patient examinations, respectively, during the evaluation period. Tooth wear was charted for 48% of those attending foundation dentists and 5% of those attending experienced dentists. Diet was assessed in 50.6% of patients examined by foundation dentists and 1.0% of patients examined by experienced dentists. Foundation dentists were more likely to chart tooth wear, risk assess and preventively manage tooth wear compared to experienced dentists (p <0.001).Conclusion This service evaluation highlights that improvements are required in recording, risk assessing and preventive treatment planning of erosive tooth wear. Experienced dentists were less likely to risk assess tooth wear and less likely to provide preventive treatment. Experienced GDPs may benefit from re-training in this area.

Wear Behavior of Plasma Spray Deposited and Post Heat-Treated Hydroxyapatite (HA)-Based Composite Coating on Titanium Alloy (Ti-6Al-4V) Substrate

NASA Astrophysics Data System (ADS)

Kumari, Renu; Majumdar, Jyotsna Dutta

2018-04-01

The present study concerns a detailed evaluation of wear resistance property of plasma spray deposited composite hydroxyapatite (HA)-based (HA-50 wt pct TiO2 and HA-10 wt pct ZrO2) bioactive coatings developed on Ti-6Al-4V substrate and studying the effect of heat treatment on it. Heat treatment of plasma spray deposited samples has been carried out at 650 °C for 2 hours (for HA-50 wt pct TiO2 coating) and at 750 °C for 2 hours (for HA-10 wt pct ZrO2 coating). There is significant deterioration in wear resistance for HA-50 wt pctTiO2 coating and a marginal deterioration in wear resistance for HA-10 wt pct ZrO2 coating in as-sprayed state (as compared to as-received Ti-6Al-4V) which is, however, improved after heat treatment. The coefficient of friction is marginally increased for both HA-50 wt pct TiO2 and HA-10 wt pct ZrO2 coatings in as-sprayed condition as compared to Ti-6Al-4V substrate. However, coefficient of friction is decreased for both HA-50 wt pct TiO2 and HA-10 wt pct ZrO2 coatings after heat-treated condition as compared to Ti-6Al-4V substrate. The maximum improvement in wear resistance property is, however, observed for HA-10 wt pct ZrO2 sample after heat treatment. The mechanism of wear has been investigated.

Development of fuel wear tests using the Cameron-Plint High-Frequency reciprocating machine. Interim report, March 1988-May 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanakia, M.D.; Cuellar, J.P.; Lestz, S.J.

The objectives of this program were to develop laboratory bench fuel-wear test methodology using JP-8 and to evaluate the effects of additives to improve load-carrying capacity of JP-8 for use in diesel-powered ground equipment. A laboratory test using the Cameron-Plint High-Frequency Reciprocating machine evaluated the effects of various chemical and physical parameters influencing the lubricity of the distillate fuels. The test conditions were determined sufficient to eliminate the effect of fluid physical properties such as viscosity. It was shown that the differences in the intrinsic lubricity of the fuels were due to small amounts of chemical additives. Under such conditions,more » the test can be used as a screening tool to find additives for enhancement of JP-8 lubricity. The test has potential to ascertain minimum lubricity level for diesel-powered ground equipment if these requirements are verified with field performance data and determined to be different from the Air Force JP-8 specifications. The dimensionless wear coefficients of Reference No. 2 diesel fuel were shown to be an order of magnitude lower than the jet fuels. In all cases, the wear rates of jet fuels and isoparaffinic solvents were improved by addition of a corrosion inhibitor or antiwear additive to match the lower wear rates of the diesel fuels. Although there was no measurable change in the viscosities of the jet fuel due to the additives, the wear rates changed by an order of magnitude.« less

Effects of orthopedic insoles on static balance of older adults wearing thick socks.

PubMed

Ma, Christina Zong-Hao; Wong, Duo Wai-Chi; Wan, Anson Hong-Ping; Lee, Winson Chiu-Chun

2018-06-01

The wearing of socks and insoles may affect the ability of the foot to detect tactile input influencing postural balance. The aim of this study was to investigate whether (1) thick socks adversely affected the elderly postural balance and (2) orthopedic insoles could improve the elderly postural balance while wearing thick socks. Repeated-measures study design. In total, 14 healthy older adults were recruited. A monofilament test was conducted to evaluate foot plantar sensation with and without thick socks. Subjects then performed the Romberg tests under three conditions: (1) barefoot, (2) with socks only, and (3) with both socks and insoles. Postural balance was assessed by measuring the center of pressure movement during standing in each experimental condition. Thick socks significantly decreased the monofilament score ( p < 0.001), suggesting reduction in ability to detect external forces. All center of pressure parameters increased significantly while wearing thick socks ( p < 0.017), implying reduction of postural stability. They then decreased significantly with the additional use of insoles ( p < 0.017). Previous studies have documented the changes in plantar pressure distribution with the use of orthopedic insoles. This study further suggests that such changes in contact mechanics could produce some balance-improving effects, which appears not to have been reported earlier. Clinical relevance Wearing thick socks reduces plantar pressure sensitivity and increases postural sway which may increase risk of falls. Orthopedic insoles and footwear with similar design could potentially be a cost-effective method in maintaining postural balance when wearing thick socks.

Microstructure and Antiwear Property of Laser Cladding Ni–Co Duplex Coating on Copper

PubMed Central

Wang, Yiyong; Liang, Zhipeng; Zhang, Junwei; Ning, Zhe; Jin, Hui

2016-01-01

Ni–Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al2O3/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni–Co duplex coatings comprised a Co-based solid solution, Cr7C3, (Fe,Ni)23C6, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni–Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni–Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties. PMID:28773755

A Novel Method to Assess Wear Rates of Retrieved Tibial Inserts Following in-vivo Use

NASA Astrophysics Data System (ADS)

Paniogue, Tanille J.

Ultra-high molecular weight polyethylene (UHMWPE) on cobalt chrome is the bearing couple of choice for total knee arthroplasty. The number of patients undergoing total knee arthroplasty has been steadily growing and is projected to continue increasing rapidly in the near future. Many of these patients are younger and more active and therefore need a longer lasting device. However, many of these devices fail prematurely and often the primary reason for failure and ultimately revision is due to wear related issues. Therefore, examining how wear rates of the UHMWPE tibial insert change during in-vivo use can help elucidate the mechanisms of accelerated wear and hopefully aid in finding solutions to combat wear related failures. Different crosslinking treatments have been employed by manufacturers to improve wear resistance of the polyethylene. While this has been shown to be an effective way to reduce wear, crosslinking has led to other issues such as oxidative instability and a decline in mechanical properties. The purpose of this body of work is to examine how changes in oxidation, after in-vivo use, affect wear resistance. A novel testing method was developed to test the native articular surface from retrieved tibial inserts in a laboratory Pin-on-Disk (POD) simulator. The method was validated using short-duration implant articular surfaces and non-articular control pins. In the absence of high surface oxidation or severe surface damage, the articular surface pins had comparable steady state wear rates to their bulk counterparts. Tests of devices with longer in-vivo service show chemical changes consistent with a free-radical mediated oxidation mechanism. Tribological assessment of the articular surfaces shows increasing wear rates as a function of oxidation. While this relationship has been hypothesized in the literature, these experiments represent the first physical demonstration of the phenomenon. The wear mechanism is further explored through infrared spectroscopy, assessment of the wear scar, and documentation of evolution of the contact surfaces in the articulation.

Microstructural studies of wear mechanisms in cast aluminum alloys

NASA Astrophysics Data System (ADS)

Elmadagli, Mustafa

2005-07-01

The microstructural basis of wear and surface degradation mechanisms in Al-Si alloys has been investigated in order to improve the current understanding of the requirements for wear resistant aluminum alloy design. The wear behaviour of three commercial alloys namely: a sand cast A390 (Al-18.4%Si), a spray formed Al-25%Si, and a die cast 383 (Al-9.5%Si) have been investigated. Dry sliding wear tests were performed using a block on ring type tribometer under controlled environments. The experiments were performed in a load range between 0.2 N and 300 N at a constant speed of 1 m/s. The testing environments were a dry air (5% RH), a humid air (95% RH), and an argon atmosphere. In dry air (5% RH), two main wear regimes namely, mild wear (MW), and severe wear (SW) were identified. The (MW) regime consisted of two sub-regimes: first and second regimes of mild wear, (MW-1) and (MW-2). The mild wear was controlled by the formation and destruction (spallation) of hardened tribolayers composed of Fe, Al, Si, and O which gave rise to steady state wear rates in both sub-regimes. The transition to second sub-regime was attributed to the destabilization and partial removal of the tribolayers on the contact surfaces. Severe wear occurred at loads exceeding 150 N irrespective of the alloy when the contact surface temperature reached a critical value (210-240°C). The wear rates (W) in each sub-regime of the MW obeyed the relation, W=CLn, where C and n were the wear coefficient and the wear exponent, respectively. The wear exponents, n, were similar in each of the sub-regimes for all three alloys, indicating that the same mechanisms controlled the wear rates. However, the wear coefficients, C, and the transition loads to the second sub-regime were considerably different for each alloy. A method of analyzing the wear coefficients and the transition loads of the alloys, based on pair-wise comparison between them, was developed. This method demonstrated that small equiaxed silicon particles, high alloy hardness, and high silicon content promoted a better wear resistance in the Al-Si alloys by delaying MW-1 to MW-2 transition, and reducing the wear coefficients. Wear tests performed on A390 in air with 95% RH and in argon atmospheres resulted in a 10-fold reduction of wear rates and formation of an ultra mild wear (UMW) regime at loads less than 10 N. UMW in an argon atmosphere was due to the formation of highly deformed Al-(Si) tribolayers, which were less brittle and were not removed as easily as Fe-Al-Si-O tribolayers formed in dry air (5% RH). UMW of A390 samples could be also achieved in dry air (5% RH) when the tests were performed against a diamond-like carbon (DLC) coated counterface at loads less than 10 N. The analysis showed that DLC reduced the wear and friction significantly through preventing the formation of Fe rich oxidized tribolayers and Al transfer to the counterface.

Gaussian process regression for tool wear prediction

NASA Astrophysics Data System (ADS)

Kong, Dongdong; Chen, Yongjie; Li, Ning

2018-05-01

To realize and accelerate the pace of intelligent manufacturing, this paper presents a novel tool wear assessment technique based on the integrated radial basis function based kernel principal component analysis (KPCA_IRBF) and Gaussian process regression (GPR) for real-timely and accurately monitoring the in-process tool wear parameters (flank wear width). The KPCA_IRBF is a kind of new nonlinear dimension-increment technique and firstly proposed for feature fusion. The tool wear predictive value and the corresponding confidence interval are both provided by utilizing the GPR model. Besides, GPR performs better than artificial neural networks (ANN) and support vector machines (SVM) in prediction accuracy since the Gaussian noises can be modeled quantitatively in the GPR model. However, the existence of noises will affect the stability of the confidence interval seriously. In this work, the proposed KPCA_IRBF technique helps to remove the noises and weaken its negative effects so as to make the confidence interval compressed greatly and more smoothed, which is conducive for monitoring the tool wear accurately. Moreover, the selection of kernel parameter in KPCA_IRBF can be easily carried out in a much larger selectable region in comparison with the conventional KPCA_RBF technique, which helps to improve the efficiency of model construction. Ten sets of cutting tests are conducted to validate the effectiveness of the presented tool wear assessment technique. The experimental results show that the in-process flank wear width of tool inserts can be monitored accurately by utilizing the presented tool wear assessment technique which is robust under a variety of cutting conditions. This study lays the foundation for tool wear monitoring in real industrial settings.

Strength and wear resistance of a dental glass-ionomer cement with a novel nanofilled resin coating.

PubMed

Lohbauer, Ulrich; Krämer, Norbert; Siedschlag, Gustavo; Schubert, Edward W; Lauerer, Brigitte; Müller, Frank A; Petschelt, Anselm; Ebert, Johannes

2011-04-01

To evaluate the influence of different resin coating protocols on the fracture strength and wear resistance of a commercial glass-ionomer cement (GIC). A new restorative concept [Equia (GC Europe)] has been introduced as a system application consisting of a condensable GIC (Fuji IX GP Extra) and a novel nanofilled resin coating material (G-Coat Plus). Four-point fracture strength (FS, 2 x 2 x 25 mm, 14-day storage, distilled water, 37 degrees C) were produced and measured from three experimental protocols: no coating GIC (Group 1), GIC coating before water contamination (Group 2), GIC coating after water contamination (Group 3). The strength data were analyzed using Weibull statistics. Three-body wear resistance (Group 1 vs. Group 2) was measured after each 10,000 wear cycles up to a total of 200,000 cycles using the ACTA method. GIC microstructure and interfaces between GIC and coating materials were investigated under SEM and CLSM. The highest FS of 26.1 MPa and the most homogenous behavior (m = 7.7) has been observed in Group 2. The coated and uncoated GIC showed similar wear resistance until 90,000 cycles. After 200,000 wear cycles, the coated version showed significantly higher wear rate (ANOVA, P< 0.05). The coating protocol has been shown to determine the GIC fracture strength. Coating after water contamination and air drying is leading to surface crack formation thus significantly reducing the FS. The resin coating showed a proper sealing of GIC surface porosities and cracks. In terms of wear, the coating did not improve the wear resistance of the underlying cement as similar or higher wear rates have been measured for Group 1 versus Group 2.

Causes of wear of PDC bits and ways of improving their wear resistance

NASA Astrophysics Data System (ADS)

Timonin, VV; Smolentsev, AS; Shakhtorin, I. O.; Polushin, NI; Laptev, AI; Kushkhabiev, AS

2017-02-01

The scope of the paper encompasses basic factors that influence PDC bit efficiency. Feasible ways of eliminating the negatives are illustrated. The wash fluid flow in a standard bit is modeled, the resultant pattern of the bit washing is analyzed, and the recommendations are made on modification of the PDC bit design.

Laser engineered net shaping of quasi-continuous network microstructural TiB reinforced titanium matrix bulk composites: Microstructure and wear performance

NASA Astrophysics Data System (ADS)

Hu, Yingbin; Ning, Fuda; Wang, Hui; Cong, Weilong; Zhao, Bo

2018-02-01

Titanium (Ti) and its alloys have been successfully applied to the aeronautical and biomedical industries. However, their poor tribological properties restrict their fields of applications under severe wear conditions. Facing to these challenges, this study investigated TiB reinforced Ti matrix composites (TiB-TMCs), fabricated by in-situ laser engineered net shaping (LENS) process, through analyzing parts quality, microstructure formation mechanisms, microstructure characterizations, and workpiece wear performance. At high B content areas (original B particle locations), reaction between Ti and B particles took place, generating flower-like microstructure. At low B content areas, eutectic TiB nanofibers contacted with each other with the formation of crosslinking microstructure. The crosslinking microstructural TiB aggregated and connected at the boundaries of Ti grains, forming a three-dimensional quasi-continuous network microstructure. The results show that compared with commercially pure Ti bulk parts, the TiB-TMCs exhibited superior wear performance (i.e. indentation wear resistance and friction wear resistance) due to the present of TiB reinforcement and the innovative microstructures formed inside TiB-TMCs. In addition, the qualities of the fabricated parts were improved with fewer interior defects by optimizing laser power, thus rendering better wear performance.

Cerium Addition Improved the Dry Sliding Wear Resistance of Surface Welding AZ91 Alloy

PubMed Central

Zhao, Zhihao; Zhu, Qingfeng; Wang, Gaosong; Tao, Kai

2018-01-01

In this study, the effects of cerium (Ce) addition on the friction and wear properties of surface welding AZ91 magnesium alloys were evaluated by pin-on-disk dry sliding friction and wear tests at normal temperature. The results show that both the friction coefficient and wear rate of surfacing magnesium alloys decreased with the decrease in load and increase in sliding speed. The surfacing AZ91 alloy with 1.5% Ce had the lowest friction coefficient and wear rate. The alloy without Ce had the worst wear resistance, mainly because it contained a lot of irregularly shaped and coarse β-Mg17Al12 phases. During friction, the β phase readily caused stress concentration and thus formed cracks at the interface between β phase and α-Mg matrix. The addition of Ce reduced the size and amount of Mg17Al12, while generating Al4Ce phase with a higher thermal stability. The Al-Ce phase could hinder the grain-boundary sliding and migration and reduced the degree of plastic deformation of subsurface metal. Scanning electron microscopy observation showed that the surfacing AZ91 alloy with 1.5% Ce had a total of four types of wear mechanism: abrasion, oxidation, and severe plastic deformation were the primary mechanisms; delamination was the secondary mechanism. PMID:29415492

Introducing loupes to clinical practice: dental hygienists experiences and opinions.

PubMed

Hayes, M J; Taylor, J A; Smith, D R

2016-08-01

Recent literature has identified a number of potential advantages in wearing loupes for dental hygienists, including improved quality of care and ergonomics. The aim of the study was to determine dental hygienists' opinions about wearing loupes. A short online survey was distributed to all dental hygienists who had recently participated in a study investigating the efficacy of loupes on musculoskeletal disorders; all had only worn loupes for a 6-month period, and prior to the study had not worn loupes. All of those invited completed the survey (n = 12), achieving a 100% response rate. The majority of respondents noted that the loupes were adaptable to wear; however, only one-quarter of hygienists surveyed were wearing them often following the study. Respondents identified that the biggest advantage to loupes was calculus removal (91.7%), and most indicated that they felt the quality of their work increased when wearing loupes (75%). The biggest disadvantage to wearing loupes was the adjustment period (50%), with limited depth of vision, headache, vertigo and infection control noted by at least one-third of respondents. This study revealed that hygienists identify both benefits and limitations to wearing loupes, and therefore, ongoing support may be required for hygienists adopting their use in clinical practice. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Multidirectional wear and impact-to-wear tests of phospholipid-polymer-grafted and vitamin E-blended crosslinked polyethylene: a pilot study.

PubMed

Kyomoto, Masayuki; Moro, Toru; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko

2015-03-01

Modifying the surface and substrate of a crosslinked polyethylene (CLPE) liner may be beneficial for high wear resistance as well as high oxidative stability and excellent mechanical properties, which would be useful in contributing to the long-term performance of orthopaedic bearings. A grafted poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on a vitamin E-blended crosslinked PE (HD-CLPE[VE]) surface may provide hydrophilicity and lubricity without compromising the oxidative stability or mechanical properties. (1) Will the modifications (PMPC grafting and vitamin E blending) affect the lubrication characteristics of the CLPE surface? (2) Will the modifications affect wear resistance? (3) Will the modifications affect fatigue resistance? We investigated the effects of surface and substrate modifications (PMPC grafting and vitamin E blending) on the wear and fatigue fracture of thin CLPE samples. For each of the untreated and PMPC-grafted CLPE surfaces with and without vitamin E blended (four groups), wettability and lubricity surface analyses were conducted as well as multidirectional wear and impact-to-wear tests using a pin-on-disk testing machine. The water wettability and lubricity (CLPE [mean ± 95% confidence interval]: 23.2° ± 1.8°, 0.005 ± 0.001; HD-CLPE[VE]: 26.0° ± 2.3°, 0.009 ± 0.003) of the PMPC-grafted surfaces were greater (p < 0.001) than that (CLPE: 90.3° ± 1.2°, 0.067 ± 0.015; HD-CLPE[VE]: 90.8° ± 2.0°, 0.063 ± 0.008) of the untreated surface regardless of vitamin E additives. It was observed that the PMPC grafting (CLPE: 0.23 ± 0.06 mg; HD-CLPE[VE]: 0.05 ± 0.10 mg) was associated with reduced gravimetric wear (CLPE: 0.53 ± 0.08 mg, p = 0.004 HD-CLPE[VE]: 0.23 ± 0.07 mg, p = 0.038) in the multidirectional wear test. The PMPC-grafted surface characteristics did not appear to affect the impact fatigue resistance regardless of vitamin E blending. PMPC grafting improved the surface hydrophilicity and lubricity, and it reduced the gravimetric wear in terms of multidirectional sliding. It did not result in differences in terms of the impact-to-unidirectional sliding regardless of vitamin E blending. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo. Our preliminary in vitro findings suggest that some improvement in the wear performance of crosslinked polyethylene acetabular liners in total hip arthroplasty could be obtained using PMPC grafting. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo.

Improvement of Scratch and Wear Resistance of Polymers by Fillers Including Nanofillers

PubMed Central

Brostow, Witold; Lobland, Haley E. Hagg; Hnatchuk, Nathalie; Perez, Jose M.

2017-01-01

Polymers have lower resistance to scratching and wear than metals. Liquid lubricants work well for metals but not for polymers nor for polymer-based composites (PBCs). We review approaches for improvement of tribological properties of polymers based on inclusion of fillers. The fillers can be metallic or ceramic—with obvious consequences for electrical resistivity of the composites. Distinctions between effectiveness of micro- versus nano-particles are analyzed. For example, aluminum nanoparticles as filler are more effective for property improvement than microparticles at the same overall volumetric concentration. Prevention of local agglomeration of filler particles is discussed along with a technique to verify the prevention. PMID:28336900

Vacuum Sputtered and Ion-Plated Coatings for Wear and Corrosion Protection

NASA Technical Reports Server (NTRS)

Spalvins, T.

1982-01-01

The plasma or ion-assisted coating techniques such as sputtering and ion plating are discussed in view of wear and corrosion protection. The basic processes and the unique features of the technique are discussed in regard to the synthesis and development of high reliability wear and corrosion resistant films. The ions of the plasma which transfer energy, momentum, and charge to the substrate and the growing films can be beneficially used. As a result, coating adherence and cohesion is improved. Favorable morphological growth such as high density and porosity-free films can be developed, and residual stresses can be reduced.

Influence of lithium slag from lepidolite on the durability of concrete

NASA Astrophysics Data System (ADS)

Qi, Luo; Shaowen, Huang; Yuxuan, Zhou; Jinyang, Li; Weiliang, Peng; Yufeng, Wen

2017-04-01

This paper mainly studies the effect of lithium slag from lepidolite on the property of concrete including dry shrinkage, anti-carbonation, wear resistance and chloride ion resistance. Concrete interface structure has been observed with SEM. The results show that adding lithium slag to concrete can improve concrete property including dry shrinkage, wear resistance and chloride ion resistance. However, the wear resistance tends to decrease when the amount of lithium slag reach 20%. Lithium slag also has negative effect on anti-carbonation property. With the increasing amount of lithium slag, anti-carbonation property of concrete decrease gradually.

High Chromium Cast Irons: Destabilized-Subcritical Secondary Carbide Precipitation and Its Effect on Hardness and Wear Properties

NASA Astrophysics Data System (ADS)

Guitar, María Agustina; Suárez, Sebastián; Prat, Orlando; Duarte Guigou, Martín; Gari, Valentina; Pereira, Gastón; Mücklich, Frank

2018-05-01

This work evaluates the effect of a destabilization treatment combined with a subcritical diffusion (SCD) and a subsequent quenching (Q) steps on precipitation of secondary carbides and their influence on the wear properties of HCCI (16%Cr). The destabilization of the austenite at high temperature leads to a final microstructure composed of eutectic and secondary carbides, with an M7C3 nature, embedded in a martensitic matrix. An improved wear resistance was observed in the SCD + Q samples in comparison with the Q one, which was attributed to the size of secondary carbides.

Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application

PubMed Central

Ganapathy, Perumal; Manivasagam, Geetha; Rajamanickam, Asokamani; Natarajan, Alagumurthi

2015-01-01

This paper presents the wear characteristics of the composite ceramic coating made with Al2O3-40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma parameters was performed using response surface methodology to obtain dense coating. The tribological behaviors of the coated and uncoated substrates were evaluated using a ball-on-plate sliding wear tester at 37°C in simulated body-fluid conditions. The microstructure of both the titanium alloy and coated specimen were examined using an optical microscope and scanning electron microscope. The hardness of the plasma-sprayed alumina–zirconia composite coatings was 2.5 times higher than that of the Ti-6Al-4V alloy, while the wear rate of Ti-6Al-4V alloy was 253 times higher than that of the composite-coated Ti-6Al-4V alloy. The superior wear resistance of the alumina–zirconia coated alloy is attributed to its enhanced hardness and intersplat bonding strength. Wear-track examination showed that the predominant wear mechanism of Ti-6Al-4V alloy was abrasive and adhesive wear, whereas, in the case of alumina–zirconia composite coated alloy, the wear was dominated by microchipping and microcracking. PMID:26491323

The wear of cross-linked polyethylene against itself.

PubMed

Joyce, T J; Ash, H E; Unsworth, A

1996-01-01

Cross-linked polyethylene (XLPE) may have an application as a material for an all-plastic surface replacement finger joint. It is inexpensive, biocompatible and can be injection-moulded into the complex shapes that are found on the ends of the finger bones. Further, the cross-linking of polyethylene has significantly improved its mechanical properties. Therefore, the opportunity exists for an all-XLPE joint, and so the wear characteristics of XLPE sliding against itself have been investigated. Wear tests were carried out on both reciprocating pin-on-plate machines and a finger function simulator. The reciprocating pin-on-plate machines had pins loaded at 10 N and 40 N. All pin-on-plate tests show wear factors from the plates very much greater than those of the pins. After 349 km of sliding, a mean wear factor of 0.46 x 10(-6) mm3/N m was found for the plates compared with 0.021 x 10(-6) mm3/N m for the pins. A fatigue mechanism may be causing this phenomenon of greater plate wear. Tests using the finger function simulator give an average wear rate of 0.22 x 10(-6) mm3/N m after 368 km. This sliding distance is equivalent to 12.5 years of use in vivo. The wear factors found were comparable with those of ultra-high molecular weight polyethylene (UHMWPE) against a metallic counterface and, therefore, as the loads across the finger joint are much less than those across the knee or the hip, it is probable that an all-XLPE finger joint will be viable from a wear point of view.

Microstructural Evaluation of Inductively Sintered Aluminum Matrix Nanocomposites Reinforced with Silicon Carbide and/or Graphene Nanoplatelets for Tribological Applications

NASA Astrophysics Data System (ADS)

Islam, Mohammad; Khalid, Yasir; Ahmad, Iftikhar; Almajid, Abdulhakim A.; Achour, Amine; Dunn, Theresa J.; Akram, Aftab; Anwar, Saqib

2018-04-01

Silicon carbide (SiC) nanoparticles (NP) and/or graphene nanoplatelets (GNP) were incorporated into the aluminum matrix through colloidal dispersion and mixing of the powders, followed by consolidation using a high-frequency induction heat sintering process. All the nanocomposite samples exhibited high densification (> 96 pct) with a maximum increase in Vickers microhardness by 92 pct relative to that of pure aluminum. The tribological properties of the samples were determined at the normal frictional forces of 10 and 50 N. At relatively low load of 10 N, the adhesive wear was found to be the predominant wear mechanism, whereas in the case of a 50 N normal load, there was significant contribution from abrasive wear possibly by hard SiC NP. From wear tests, the values for the coefficient of friction (COF) and the normalized wear rate were determined. The improvement in hardness and wear resistance may be attributed to multiple factors, including high relative density, uniform SiC and GNP dispersion in the aluminum matrix, grain refinement through GNP pinning, as well as inhibition of dislocation movement by SiC NP. The nanocomposite sample containing 10 SiC and 0.5 GNP (by wt pct) yielded the maximum wear resistance at 10 N normal load. Microstructural characterization of the nanocomposite surfaces and wear debris was performed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The synergistic effect of the GNP and SiC nanostructures accounts for superior wear resistance in the aluminum matrix nanocomposites.

Microstructural Evaluation of Inductively Sintered Aluminum Matrix Nanocomposites Reinforced with Silicon Carbide and/or Graphene Nanoplatelets for Tribological Applications

NASA Astrophysics Data System (ADS)

Islam, Mohammad; Khalid, Yasir; Ahmad, Iftikhar; Almajid, Abdulhakim A.; Achour, Amine; Dunn, Theresa J.; Akram, Aftab; Anwar, Saqib

2018-07-01

Silicon carbide (SiC) nanoparticles (NP) and/or graphene nanoplatelets (GNP) were incorporated into the aluminum matrix through colloidal dispersion and mixing of the powders, followed by consolidation using a high-frequency induction heat sintering process. All the nanocomposite samples exhibited high densification (> 96 pct) with a maximum increase in Vickers microhardness by 92 pct relative to that of pure aluminum. The tribological properties of the samples were determined at the normal frictional forces of 10 and 50 N. At relatively low load of 10 N, the adhesive wear was found to be the predominant wear mechanism, whereas in the case of a 50 N normal load, there was significant contribution from abrasive wear possibly by hard SiC NP. From wear tests, the values for the coefficient of friction (COF) and the normalized wear rate were determined. The improvement in hardness and wear resistance may be attributed to multiple factors, including high relative density, uniform SiC and GNP dispersion in the aluminum matrix, grain refinement through GNP pinning, as well as inhibition of dislocation movement by SiC NP. The nanocomposite sample containing 10 SiC and 0.5 GNP (by wt pct) yielded the maximum wear resistance at 10 N normal load. Microstructural characterization of the nanocomposite surfaces and wear debris was performed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The synergistic effect of the GNP and SiC nanostructures accounts for superior wear resistance in the aluminum matrix nanocomposites.

Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus.

PubMed

Morita, Yusuke; Nakata, Kenichi; Kim, Yoon-Ho; Sekino, Tohru; Niihara, Koichi; Ikeuchi, Ken

2004-01-01

While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.

Computational wear assessment of hard on hard hip implants subject to physically demanding tasks.

PubMed

Nithyaprakash, R; Shankar, S; Uddin, M S

2018-05-01

Hip implants subject to gait loading due to occupational activities are potentially prone to failures such as osteolysis and aseptic loosening, causing painful revision surgeries. Highly risky gait activities such as carrying a load, stairs up or down and ladder up or down may cause excessive loading at the hip joint, resulting in generation of wear and related debris. Estimation of wear under the above gait activities is thus crucial to design and develop a new and improved implant component. With this motivation, this paper presents an assessment of wear generation of PCD-on-PCD (poly crystalline diamond) hip implants using finite element (FE) analysis. Three-dimensional (3D) FE model of hip implant along with peak gait and peak flexion angle for each activity was used to estimate wear of PCD for 10 million cycles. The maximum and minimum initial contact pressures of 206.19 MPa and 151.89 MPa were obtained for carrying load of 40 kg and sitting down or getting up activity. The simulation results obtained from finite element model also revealed that the maximum linear wear of 0.585 μm occurred for the patients frequently involved in sitting down or getting up gait activity and maximum volumetric wear of 0.025 mm 3 for ladder up gait activity. The stair down activity showed the least linear and volumetric wear of 0.158 μm and 0.008 mm 3 , respectively, at the end of 10 million cycles. Graphical abstract Computational wear assessment of hip implants subjected to physically demanding tasks.

Investigation of the Effect of Residual Stress Gradient on the Wear Behavior of PVD Thin Films

NASA Astrophysics Data System (ADS)

Tlili, B.; Nouveau, C.; Guillemot, G.; Besnard, A.; Barkaoui, A.

2018-02-01

The control of residual stresses has been seldom investigated in multilayer coatings dedicated to improvement of wear behavior. Here, we report the preparation and characterization of superposed structures composed of Cr, CrN and CrAlN layers. Nano-multilayers CrN/CrAlN and Cr/CrN/CrAlN were deposited by Physical Vapor Deposition (PVD) onto Si (100) and AISI4140 steel substrates. The Cr, CrN and CrAlN monolayers were developed with an innovative approach in PVD coatings technologies corresponding to deposition with different residual stresses levels. Composition and wear tracks morphologies of the coatings were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and 3D-surface analyzer. The mechanical properties (hardness, residual stresses and wear) were investigated by nanoindentation, interferometry and micro-tribometry (fretting-wear tests). Observations suggest that multilayer coatings are composed mostly of nanocrystalline. The residual stresses level in the films has practically affected all the physicochemical and mechanical properties as well as the wear behavior. Consequently, it is demonstrated that the coating containing moderate stresses has a better wear behavior compared to the coating developed with higher residual stresses. The friction contact between coated samples and alumina balls shows also a large variety of wear mechanisms. In particular, the abrasive wear of the coatings was a combination of plastic deformation, fine microcracking and microspallation. The application of these multilayers will be wood machining of green wood.

Microstructure and Tribological Properties of Mo–40Ni–13Si Multiphase Intermetallic Alloy

PubMed Central

Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong

2016-01-01

Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo–40Ni–13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo–Ni–Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy—including wear resistance, friction coefficient, and metallic tribological compatibility—were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear. PMID:28774106

Occurrence and effects of tire wear particles in the environment--a critical review and an initial risk assessment.

PubMed

Wik, Anna; Dave, Göran

2009-01-01

This review summarizes the existing knowledge on the occurrence of tire wear particles in the environment, and their ecotoxicological effects. A meta-analysis on tire components in the environment revealed that tire wear particles are present in all environmental compartments, including air, water, soils/sediments, and biota. The maximum Predicted Environmental Concentrations (PECs) of tire wear particles in surface waters range from 0.03 to 56 mg l(-1) and the maximum PECs in sediments range from 0.3 to 155 g kg(-1) d.w. The results from our previous long-term studies with Ceriodaphnia dubia and Pseudokirchneriella subcapitata were used to derive Predicted No Effect Concentrations (PNECs). The upper ranges for PEC/PNEC ratios in water and sediment were >1, meaning that tire wear particles present potential risks for aquatic organisms. We suggest that management should be directed towards development and production of more environmentally friendly tires and improved road runoff treatment.

The solid film lubrication by carbon ion implantation into α-Al 2O 3

NASA Astrophysics Data System (ADS)

Jun, Tian; Qizu, Wang; Qunji, Xue

1998-10-01

Improvement in tribological performance by C +110 keV implantation can be achieved by having a more graphite-like carbon structure on Al 2O 3. It was shown that fracture toughness and critical peeling load increased for a fluence of 5 × 10 17C +/cm 2 because of residual compression stress and amorphism of surface. The testing in a different implantation dose indicated that the friction and wear mechanism in Optimol fretting wear machine (SRV) was a combination of surface structure and its abrasive wear. Raman shift shows that the amorphous graphite with 5 × 10 17-1 × 10 18 C +/cm 2 implantation dose was formed on Al 2O 3 surface, so that it reduced friction coefficient and wear of Al 2O 3, also it is noticed that the failure of lubrication due to graphite-like film wear is much earlier in the implantation sample with 1 × 10 17C +/cm 2 dose.

Study of wear mechanism of chopped fiber reinforced epoxy composite filled with graphite and bronze

NASA Astrophysics Data System (ADS)

Patil, Nitinchand; Prasad, Krishna

2018-04-01

The combined effect of graphite and sintered bronze with a short glass fiber reinforced epoxy composites was investigated in this work. A pin on disc wear test was carried out to study the wear behaviour and mechanism of the composites. The objective of this work is to develop an alternate friction resistance material for the application of sliding bearing. It was observed that the addition of sintered bronze improved mechanical and thermal stability of the composites as bronze has low contact resistance with graphite and has high thermal conductivity. It was observed from the test results that increased volume percentage of graphite and presence of bronze are play significant role in wear mechanism of the composites. It was observed from the scanning electronic microscopes (SEM) that the abrasive and adhesive wear mechanism was prominent in this study. It was also evident from the result that the frictional force remains stable irrespective of the applied normal load.

Microstructure and Tribological Properties of Mo-40Ni-13Si Multiphase Intermetallic Alloy.

PubMed

Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong

2016-12-06

Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo-40Ni-13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo-Ni-Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy-including wear resistance, friction coefficient, and metallic tribological compatibility-were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear.

Multidimensional esthetic evaluation of patients with a cleft lip and palate wearing a maxillary partial removable dental prosthesis: A 5-year retrospective study.

PubMed

Yu, Dedong; Xing, Guofang; Nie, Ping; Zhang, Xiuyin; Steve Shen, Guofang

2016-04-01

No published quantitative or qualitative studies are available of the 2-dimensional (2D) and 3D esthetic evaluation of patients with a cleft lip and palate (CLP) wearing a maxillary partial removable dental prosthesis (MPRDP). The purpose of this retrospective clinical study was to qualitatively and quantitatively evaluate the facial esthetic improvements of patients with CLP wearing an MPRDP for 5 years by using 2D cephalometric and 3D photogrammetry methods. Six patients, 2 men and 4 women, with CLP deformity were recruited and treated with an MPRDP by the same dentist over 5 years. Results of the clinical examination were recorded before and after wearing the MPRDP. Sella-nasion-A (SNA) point, the U1-SN, 0-meridian to SN, nasolabial angle, and maxillary incisor exposure were measured by 2D cephalometric analysis before and after wearing the MPRDP. 3D photographs were captured by 3dMD software. Geomagic Spark Studio software was also used to measure the patients' improved upper lip projection after the MPRDP was worn. The paired sample t test was used to compare the participants (α=.05). U1-SN (P<.05) and 0-meridian to SN (P<.01) had significant deviation statistically. After patients underwent clinical examination, SNA and nasiolabial angles were found to have improved, although no statistical significance was observed. A maxillary partial removable dental prosthesis (MPRDP) can advance the upper lip forward, restoring the subnasal and upper lip projection. Patients' nasiolabial angles with MPRDPs were decreased, which led to a more harmonious facial contour. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Rheumatoid arthritis patients' experiences of wearing therapeutic footwear - A qualitative investigation

PubMed Central

Williams, Anita E; Nester, Christopher J; Ravey, Michael I

2007-01-01

Background Specialist 'therapeutic' footwear is recommended for patients with diseases such as rheumatoid arthritis (RA) as a beneficial intervention for reducing foot pain, improving foot health, and increasing general mobility. However, many patients choose not to wear this footwear. Recommendations from previous studies have been implemented but have had little impact in improving this situation. The aim of this study was to explore RA patients' experiences of this footwear to ascertain the factors which influence their choice to wear it or not. Method Ten females and three males with RA and experience of wearing specialist footwear were recruited from four National Health Service orthotic services. Semi-structured interviews were carried out in the participants own homes. A hermeneutic phenomenological analysis of the transcripts was carried out to identify themes. Results The analysis revealed two main themes from both the female and male groups. These were the participants' feelings about their footwear and their experiences of the practitioner/s involved in providing the footwear. In addition, further themes were revealed from the female participants. These were feelings about their feet, behaviour associated with the footwear, and their feelings about what would have improved their experience. Conclusion Unlike any other intervention specialist therapeutic footwear replaces something that is normally worn and is part of an individual's body image. It has much more of a negative impact on the female patients' emotions and activities than previously acknowledged and this influences their behaviour with it. The patients' consultations with the referring and dispensing practitioners are pivotal moments within the patient/practitioner relationship that have the potential to influence whether patients choose to wear the footwear or not. PMID:17976235

Effect of Laser Remelting on Friction-Wear Behaviors of Cold Sprayed Al Coatings in 3.5% NaCl Solution

PubMed Central

Jing, Zhang; Dejun, Kong

2018-01-01

A cold sprayed Al coating on S355 structural steel was processed using a laser remelting (LR). The surface and cross-section morphologies, chemical compositions, and phases of as-obtained Al coating before and after LR were analyzed using a scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively, and their hardness was measured using a micro-hardness tester. The friction-wear behaviors of Al coating before and after LR in 3.5% NaCl solution were conducted to simulate the sand and gravel scouring on its surface in seawater, the effects of wear loads and speeds on the tribological properties of Al coating were analyzed, and the wear mechanisms under different wear loads and speeds were also discussed. The results show that the Al coating after LR is primarily composed of an Al phase and its hardness is 104.66 HV, increasing 54.70 HV than the cold sprayed Al coating. The average coefficient of friction (COF) of cold sprayed Al coating at the wear load of 0.5, 1.0 and 1.5 N is 0.285, 0.239, and 0.435, respectively, while that after LR is 0.243, 0.227, and 0.327, respectively, decreased by 14.73%, 5.02% and 24.83% compared to the cold sprayed Al coating. The wear rate of cold sprayed Al coating at the wear load of 0.5, 1.0 and 1.5 N is 1.60 × 10−4, 2.36 × 10−4, and 2.40 × 10−4 mm3/m·N, respectively, while that after LR is 1.59 × 10−4, 1.70 × 10−4, and 1.94 × 10–4 mm3/m·N, respectively, decreased by 1%, 32%, and 23%, respectively, indicating that LR has high anti-friction performance. Under the wear load action of 1.0 N, the average COF of laser remelted Al coating at the wear speeds of 300, 400 and 500 times/min is 0.294, 0.279, and 0.239, respectively, and the corresponding wear rate is 1.06 × 10−4, 1.24 × 10−4, and 1.70 × 10−4 mm3/m·N, respectively. The wear mechanism of cold sprayed Al coating is primarily corrosion wear at the loads of 0.5 and 1.0 N, and that at the load of 1.5 N is abrasive wear and fatigue wear; while that after LR is abrasive wear and fatigue wear, with no corrosion wear, showing that LR improves its corrosion and wear resistance. PMID:29439485

Effect of Laser Remelting on Friction-Wear Behaviors of Cold Sprayed Al Coatings in 3.5% NaCl Solution.

PubMed

Jing, Zhang; Dejun, Kong

2018-02-11

A cold sprayed Al coating on S355 structural steel was processed using a laser remelting (LR). The surface and cross-section morphologies, chemical compositions, and phases of as-obtained Al coating before and after LR were analyzed using a scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively, and their hardness was measured using a micro-hardness tester. The friction-wear behaviors of Al coating before and after LR in 3.5% NaCl solution were conducted to simulate the sand and gravel scouring on its surface in seawater, the effects of wear loads and speeds on the tribological properties of Al coating were analyzed, and the wear mechanisms under different wear loads and speeds were also discussed. The results show that the Al coating after LR is primarily composed of an Al phase and its hardness is 104.66 HV, increasing 54.70 HV than the cold sprayed Al coating. The average coefficient of friction (COF) of cold sprayed Al coating at the wear load of 0.5, 1.0 and 1.5 N is 0.285, 0.239, and 0.435, respectively, while that after LR is 0.243, 0.227, and 0.327, respectively, decreased by 14.73%, 5.02% and 24.83% compared to the cold sprayed Al coating. The wear rate of cold sprayed Al coating at the wear load of 0.5, 1.0 and 1.5 N is 1.60 × 10 -4 , 2.36 × 10 -4 , and 2.40 × 10 -4 mm³/m·N, respectively, while that after LR is 1.59 × 10 -4 , 1.70 × 10 -4 , and 1.94 × 10 -4 mm³/m·N, respectively, decreased by 1%, 32%, and 23%, respectively, indicating that LR has high anti-friction performance. Under the wear load action of 1.0 N, the average COF of laser remelted Al coating at the wear speeds of 300, 400 and 500 times/min is 0.294, 0.279, and 0.239, respectively, and the corresponding wear rate is 1.06 × 10 -4 , 1.24 × 10 -4 , and 1.70 × 10 -4 mm³/m·N, respectively. The wear mechanism of cold sprayed Al coating is primarily corrosion wear at the loads of 0.5 and 1.0 N, and that at the load of 1.5 N is abrasive wear and fatigue wear; while that after LR is abrasive wear and fatigue wear, with no corrosion wear, showing that LR improves its corrosion and wear resistance.

Oral omega-3 fatty acid treatment for dry eye in contact lens wearers.

PubMed

Bhargava, Rahul; Kumar, Prachi

2015-04-01

The aim of this study was to evaluate the effect of dietary omega-3 fatty acid (O3FA) supplementation on dry eye symptoms, tear film tests, and conjunctival impression cytology in patients with contact lens wear-associated dry eye. In this randomized, double-blind, multicentric trial, contact lens wearers (n = 496) were randomized to receive either O3FAs or placebo capsules (corn oil) twice daily for 6 months. Subjects underwent examinations at baseline, 3 months, and 6 months. At each visit, a questionnaire of dry eye symptoms and lens wear comfort was administered. Subjects further underwent measurement of tear film break-up time (TBUT) and a Schirmer test. Conjunctival impression cytology was performed by the transfer method. Improvement in symptoms and lens wear comfort were primary outcome measures. Changes from baseline in TBUT, Schirmer, and Nelson grade at 6 months were secondary outcome measures. The mean improvement in symptom score in the O3FA group was 4.7 ± 2 (2.0) as compared with 0.5 ± 2 (0.9) in the placebo group (P < 0.0001). Lens wear comfort levels improved significantly (P < 0.0001) from baseline. There was a significant increase in TBUT [3.3 ± 2 (1.5)] and Nelson grade [0.7 ± 2 (0.6)] in the O3FA group (P < 0.0001) as compared with 0.3 ± 2 (0.6) and 0.1 ± 2 (0.4) in the placebo group (P = 0.164 and 0.094, respectively). However, the magnitude of increase in Schirmer score [2.0 ± 2 (1.5)] was relatively small (P = 0.08). The results of this study point toward benefits of orally administered O3FAs in alleviating dry eye symptoms, improving lens wear comfort, and cytological changes in contact lens wearers.

Over 25 years survival after Charnley's total hip arthroplasty.

PubMed

Caton, Jacques; Prudhon, Jean Louis

2011-02-01

Since 1962, the low friction arthroplasty (LFA) developed by Sir John Charnley has spread widely throughout the world. Many series have reported long-term results. Polyethylene (PE) wear is well known. The average wear ratio is about 0.1 mm a year. Many factors may influence that wear process. The authors describe two different series of patients operated upon with Charnley's total hip arthroplasty (THA) using the original cemented stem and a non modular 22.2-mm head, with a cemented full polyethylene acetabular socket. Outcomes confirm excellent patient function after 25 years. They emphasise the fact that PE is the weak point of total hip arthroplasty. Function may be excellent even though PE wear is significant. In several cases, no wear at the maximum follow-up was detectable. This study confirms different publications relating long-term follow-up with LFA. During a Charnley meeting in Lyon, we published a survival curve of 85% after 25 years. Berry et al. published a 86.5% survival curve (J Bone Joint Surg Am 84:171-177, 2002). In 1995, Luc and Marcel Kerboul published a 77% survival rate after 20 years in young patients under 40 years old at the time of the surgery. In 2009, Callaghan et al. published a series of 35 years follow-up with a ratio of 78% survivorship (J Bone Joint Surg Br 91:2617-2621). Could the long-term results be improved? Through recent decades, many solutions have been introduced to improve the survivorship of THA including bearing surfaces such as alumina-on-alumina and metal-on-metal. Different problems have occurred with these solutions. LFA might be improved by working on the nature and the quality of the head. Improvements might also be obtained by working on the quality and the hardness of the acetabular socket.

Integrated experimental and theoretical approach for corrosion and wear evaluation of laser surface nitrided, Ti-6Al-4V biomaterial in physiological solution.

PubMed

Vora, Hitesh D; Shanker Rajamure, Ravi; Dahotre, Sanket N; Ho, Yee-Hsien; Banerjee, Rajarshi; Dahotre, Narendra B

2014-09-01

A laser based surface nitriding process was adopted to further enhance the osseo-integration, corrosion resistance, and tribological properties of the commonly used bioimplant alloy, Ti-6Al-4V. Earlier preliminary osteoblast, electrochemical, and corrosive wear studies of laser nitrided titanium in simulated body fluid clearly revealed improvement of cell adhesion as well as enhancement in corrosion and wear resistance but mostly lacked the in-depth fundamental understanding behind these improvements. Therefore, a novel integrated experimental and theoretical approach were implemented to understand the physical phenomena behind the improvements and establish the property-structure-processing correlation of nitrided surface. The first principle and thermodynamic calculations were employed to understand the thermodynamic, electronic, and elastic properties of TiN for enthalpy of formation, Gibbs free energy, density of states, and elastic properties of TiN were investigated. Additionally, open circuit potential and cyclic potentio-dynamic polarization tests were carried out in simulated body fluid to evaluate the corrosion resistance that in turn linked with the experimentally measured and computationally predicted surface energies of TiN. From these results, it is concluded that the enhancement in the corrosion resistance after laser nitriding is mainly attributed to the presence of covalent bonding via hybridization among Ti (p) and N (d) orbitals. Furthermore, mechanical properties, such as, Poisson׳s ratio, stiffness, Pugh׳s ductility criteria, and Vicker׳s hardness, predicted from first principle calculations were also correlated to the increase in wear resistance of TiN. All the above factors together seem to have contributed to significant improvement in both wear and corrosion performance of nitride surface compared to the bare Ti-6Al-4V in physiological environment indicating its suitability for bioimplant applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Study on torsional fretting wear behavior of a ball-on-socket contact configuration simulating an artificial cervical disk.

PubMed

Wang, Song; Wang, Fei; Liao, Zhenhua; Wang, Qingliang; Liu, Yuhong; Liu, Weiqiang

2015-10-01

A ball-on-socket contact configuration was designed to simulate an artificial cervical disk in structure. UHMWPE (ultra high molecular weight polyethylene) hot pressed by powders and Ti6Al4V alloy were selected as the material combination of ball and socket. The socket surface was coated by a ~500 nm C-DLC (carbon ion implantation-diamond like carbon) mixed layer to improve its surface nano hardness and wear resistance. The torsional fretting wear behavior of the ball-on-socket model was tested at different angular displacements under 25% bovine serum lubrication with an axial force of 100 N to obtain more realistic results with that in vivo. The fretting running regimes and wear damage characteristics as well as wear mechanisms for both ball and socket were studied based on 2D (two dimension) optical microscope, SEM (scanning electron microscope) and 3D (three dimension) profiles. With the increase of angular displacement amplitude from 1° to 7°, three types of T-θ (Torsional torque-angular displacement amplitude) curves (i.e., linear, elliptical and parallelogram loops) corresponding to running regimes of PSR (partial slip regime), MR (mixed regime) and SR (slip regime) were observed and analyzed. Both the central region and the edge zone of the ball and socket were damaged. The worn surfaces were characterized by wear scratches and wear debris. In addition, more severe wear damage and more wear debris appeared on the central region of the socket at higher angular displacement amplitude. The dominant damage mechanism was a mix of surface scratch, adhesive wear and abrasive wear for the UHMWPE ball while that for the coated socket was abrasive wear by PE particles and some polishing and rolling process on the raised overgrown DLC grains. The frictional kinetic behavior, wear type, damage region and damage mechanism for the ball-on-socket model revealed significant differences with those of a ball-on-flat contact while showing better consistency with that of in vitro cervical prosthesis simulations according to the literature. Copyright © 2015. Published by Elsevier B.V.

Does Wearing Textured Insoles during Non-class Time Improve Proprioception in Professional Dancers?

PubMed

Steinberg, N; Tirosh, O; Adams, R; Karin, J; Waddington, G

2015-11-01

This study sought to determine whether textured insoles inserted in the sports shoes of young dancers improved their inversion and eversion ankle movement discrimination. 26 ballet dancers (14 female, 12 male) from the Australian Ballet School, ages 14-19 years, were divided into 2 groups according to sex and class levels. During the first 4 weeks, the first intervention group (GRP1) was asked to wear textured insoles in their sports shoes during non-class periods, and the second intervention group (GRP2) followed standard practice. In the next 4 weeks, GRP2 was asked to wear the textured insoles and GRP1 did not wear the textured insoles. Participants were tested pre-intervention, after 4 weeks, and at 8 weeks for both inversion and eversion ankle discrimination. In both inversion and eversion testing positions, interaction was found between the 2 groups and the 3 testing times (p<0.001), with significant differences between the first testing and the second testing (p=0.038 and p=0.019, respectively), and between the third testing and the second testing (p=0.003 and p=0.029, respectively). In conclusion, the stimulation to the proprioceptive system arising from textured insoles worn for 4 weeks was sufficient to improve the ankle proprioception of ballet dancers, in both inversion and eversion movements. © Georg Thieme Verlag KG Stuttgart · New York.

Limits of Stability and Adaptation to Wearing Rocker Bottom Shoes.

PubMed

Vieira, Edgar Ramos; Guerrero, Gerardo; Holt, Daniel; Arreaza, Monica; Veroes, Valentina; Brunt, Denis

2014-06-01

Stability and balance are fundamental during static and dynamic activities. The effects of wearing rocker bottom sole (RBS) shoes on the limits of stability (LOS) and adaptation to wearing RBS shoes need to be investigated. The objectives of this study were to evaluate the LOS when wearing RBS shoes, and to evaluate if people improve their stability while wearing RBS shoes over time. Eleven female subjects with no lower extremity impairments participated in the study. The LOS were tested at baseline and weeks 3 and 6 using a Neurocom SMART EquiTest equipment. Center of pressure (CoP) was determined using force plates, and the center of gravity (CoG) position was estimated from the CoP measures and subjects' anthropometry. Subjects performed a series of tasks that involved leaning in different directions so as to move the vertical projection of their CoG. End-point excursions of the CoG floor projection were calculated as a percentage of the distance between the starting position and the target. Considering the body as an inverted pendulum, we recorded the average angular velocity of the inverted pendulum during the movements and quantified directional control as a percentage of movement toward versus away from the target. Shoe types were compared using paired t tests, and sessions were compared using repeated measures ANOVA. The angular velocities of the inverted pendulum (ie, CoG velocity) were not significantly different between shoe conditions in the front and back directions at baseline (4 ± 3 with RBS vs 5 ± 2 deg/sec with regular shoes, and 4 ± 1 vs 6 ± 4 deg/sec). Front directional control of the CoG was significantly worse with RBS shoes at weeks 3 and 6 ( P < .015). Front end-point excursions were also lower with RBS shoes both at baseline and week 6 ( P < .014). There were no significant changes over time. The findings indicate that the LOS were negatively affected by wearing RBS shoes and that people do not improve their stability while wearing these shoes even after a 6-week period of use. This study shows that wearing RBS shoes increase instability and the instability remains even after wearing these shoes for six weeks.

Characterization of Microstructure and Wear Resistance of PEO Coatings Containing Various Microparticles on Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Li, Xinyi; Dong, Chaofang; Zhao, Qing; Pang, Yu; Cheng, Fasong; Wang, Shuaixing

2018-02-01

Titania-based composite coatings were prepared by plasma electrolytic oxidation (PEO) treatment of Ti6Al4V alloy in electrolyte with α-Al2O3, Cr2O3 or h-BN microparticles in suspension. The microstructure, composition of PEO composite coatings were analyzed by SEM, EDS and XRD. The wear resistance of composite ceramic coatings was studied by ball-on-disk wear test at ambient temperature and 300 °C. The results showed that the addition of microparticles accelerated the growth rate of PEO coating and changed the microstructure and composition of PEO coating. PEO coating was porous and mainly composed of rutile-TiO2, anatase-TiO2 and Al2TiO5. PEO/α-Al2O3 (Cr2O3 or h-BN) composite coating only had small micropores and appeared some α-Al2O3 (Cr2O3 or h-BN) phase. Besides, the addition of α-Al2O3 (Cr2O3 or h-BN) microparticles greatly improved the wear resistance of PEO coating. At ambient temperature, abrasive wear dominated the wear behavior of PEO coating, but abrasive wear and adhesive peel simultaneously happened at 300 °C. Whether at ambient temperature or 300 °C, PEO composite coating had better wear resistance than PEO coating. Besides, PEO/h-BN composite coating outperformed other composite coatings regardless of the temperature.

Wear behavior of carbide tool coated with Yttria-stabilized zirconia nano particles.

NASA Astrophysics Data System (ADS)

Jadhav, Pavandatta M.; Reddy, Narala Suresh Kumar

2018-04-01

Wear mechanism takes predominant role in reducing the tool life during machining of Titanium alloy. Challenges of wear mechanisms such as variation in chip, high pressure loads and spring back are responsible for tool wear. In addition, many tool materials are inapt for machining due to low thermal conductivity and volume specific heat of these materials results in high cutting temperature during machining. To confront this issue Electrostatic Spray Coating (ESC) coating technique is utilized to enhance the tool life to an acceptable level. The Yttria Stabilized Zirconia (YSZ) acts as a thermal barrier coating having high thermal expansion coefficient and thermal shock resistance. This investigation focuses on the influence of YSZ nanocoating on the tungsten carbide tool material and improve the machinability of Ti-6Al-4V alloy. YSZ nano powder was coated on the tungsten carbide pin by using ESC technique. The coatings have been tested for wear and friction behavior by using a pin-on-disc tribological tester. The dry sliding wear test was performed on Titanium alloy (Ti-6Al-4V) disc and YSZ coated tungsten carbide (pin) at ambient atmosphere. The performance parameters like wear rate and temperature rise were considered upon performing the dry sliding test on Ti-6Al-4V alloy disc. The performance parameters were calculated by using coefficient of friction and frictional force values which were obtained from the pin on disc test. Substantial resistance to wear was achieved by the coating.

Effect of consolidation on adhesive and abrasive wear of ultra high molecular weight polyethylene.

PubMed

Gul, Rizwan M; McGarry, Frederick J; Bragdon, Charles R; Muratoglu, Orhun K; Harris, William H

2003-08-01

Total hip replacement (THR) is widely performed to recover hip joint functions lost by trauma or disease and to relieve pain. The major cause of failure in THR is the wear of the ultra high molecular weight polyethylene (UHMWPE) component. The dominant wear mechanism in THR occurs through adhesion and abrasion. While poor consolidation of UHMWPE is known to increase the incidence of a different damage mode, delamination, which is the dominant wear mechanism in tibial inserts but uncommon in THR, the effect of consolidation on adhesive and abrasive wear of UHMWPE is not clear. In this study UHMWPE resin was subjected to hot isostatic pressing under a pressure of 138MPa at different temperatures (210 degrees C, 250 degrees C, and 300 degrees C) to achieve varying degrees of consolidation. The extent of consolidation was determined by optical microscopy using thin sections, and by scanning electron microscopy using cryofractured and solvent etched specimens. Wear behavior of the samples with varying degree of consolidation was determined using a bi-directional pin-on-disc machine simulating conditions in a hip joint. Increasing the processing temperature decreased the incidence of fusion defects and particle boundaries reflecting the powder flakes of the virgin resin, improving the consolidation. However, the bi-directional pin-on-disc wear rate did not change with the processing temperature, indicating that adhesive and abrasive wear is independent of the extent of consolidation in the range of parameters studied here.

Comparison of the wear and flexural characteristics of flowable resin composites for posterior lesions.

PubMed

Sumino, Natsu; Tsubota, Keishi; Takamizawa, Toshiki; Shiratsuchi, Koji; Miyazaki, Masashi; Latta, Mark A

2013-01-01

To determine the localized wear and flexural properties of flowable resin composites for posterior lesions compared with universal resin composites produced by the same manufacturers. Ten specimens of each of three flowable resins, G-ænial Universal Flo, G-ænial Flo and Clearfil Majesty Flow, and the corresponding resin composite materials, Kalore and Clearfil Majesty Esthetics, were prepared in custom fixtures and subjected to 400,000 wear machine cycles to simulate localized wear. The total maximum depth and volume loss of the wear facets was calculated for each specimen using a profilometer. A three-point bending test was performed to determine the flexural strength, modulus of elasticity and resilience. Values were statistically compared using one-way analysis of variance (ANOVA) followed by Tukey's Honestly Significant Difference (HSD) test. The wear depth ranged from 58.3-126.9 m and the volumetric loss ranged from 0.019-0.049 mm(3), with significant differences observed between restorative materials. The wear depth of G-ænial Universal Flo was significantly smaller than those of the other resin composites tested. The flexural strengths and elastic modulus ranged from 90.5-135.1 MPa and from 4.7-7.6 GPa, respectively. A significantly greater flexural strength and higher elastic modulus was found for G-ænial Universal Flo than the other composites. The wear and mechanical properties of the flowable resin composites tested suggested improved performance compared with universal resin composites.

Attritional wear and abrasive surface alterations of composite resin materials in vitro.

PubMed

Göhring, T N; Besek, M J; Schmidlin, P R

2002-01-01

A laboratory study was performed with 232 specimens and 72 human enamel, 24 gold, 24 ceramic and 12 composite antagonists in 22 groups to test attritional and abrasive wear behavior of composite materials compared to wear behavior of human enamel. Belleglass HP, Concept Inlay/Onlay, Targis and Targis Upgrade 99 composite resin for lab-made restorations was tested as well as Tetric Ceram and FHC Merz light as resins for direct restorations. Natural human enamel specimens served as control. All specimens were subjected to long-term thermo-mechanical loading in a computer-controlled masticator, chemical degradation and toothbrush/toothpaste abrasion. Wear of specimen in occlusal contact area (OCA), contact-free occlusal area and wear of natural enamel cusps as well as antagonists made of gold, ceramic and composite in identical form was measured after 120,000, 240,000, 640,000 and 1200,000 load cycles. A qualitative SEM analysis was performed to support quantitative data. Belleglass HP and Targis Upgrade 99 restorative materials showed wear resistance comparable to human enamel when loaded with enamel cusps. Wear of Targis versus composite and gold antagonists was significantly higher (p<0.0001). Analysis of surface alterations showed hygroscopic expansion in all composite resins during the test. As a consequence of this study, necessity to further improve physical properties of composites for long lasting restorations was obvious. Beside of attritional wear in OCA, attention must be given to stable filler-matrix interfaces and prevention of water sorption.

Tooth wear and erosion: methodological issues in epidemiological and public health research and the future research agenda.

PubMed

Ganss, C; Young, A; Lussi, A

2011-09-01

This paper addresses methodological issues in the field of tooth wear and erosion research including the epidemiological indices, and identifies future work that is needed to improve knowledge about tooth wear and erosion. The paper is result of the work done at the meetings of the Special Interest Group "Tooth Surface Loss and Erosion" at the 2008, 2009 and 2010 conferences of the European Association for Dental Public Health, and the Workshop "Current Erosion indices- flawed or valid" which took place in Basel in 2007. Although there is consensus about the definition and the diagnostic criteria of various forms of tooth wear, gaps in research strategies have been identified. A basic problem is that fundamental concepts of wear and erosion as an oral health problem, have not yet been sufficiently defined. To a certain extent, tooth wear is a physiological condition, and there is no consensus as to whether it can be regarded as a disease. Furthermore, the multitude of indices and flaws in existing indices, make published data difficult to interpret. Topics for the research agenda are: the initiation of a consensus process towards an internationally accepted index, and the initiation of data collection on the prevalence of various forms of wear on a population-based level. There should be an emphasis on promoting communication between basic and clinical sciences, and the area of Public Health Dentistry. Furthermore, the question of whether tooth wear is a public health problem remains open for debate.

Surface amorphization of NiTi alloy induced by Ultrasonic Nanocrystal Surface Modification for improved mechanical properties.

PubMed

Ye, Chang; Zhou, Xianfeng; Telang, Abhishek; Gao, Hongyu; Ren, Zhencheng; Qin, Haifeng; Suslov, Sergey; Gill, Amrinder S; Mannava, S R; Qian, Dong; Doll, Gary L; Martini, Ashlie; Sahai, Nita; Vasudevan, Vijay K

2016-01-01

We report herein the effects of Ultrasonic Nano-crystal Surface Modification (UNSM), a severe surface plastic deformation process, on the microstructure, mechanical (hardness, wear), wettability and biocompatibility properties of NiTi shape memory alloy. Complete surface amorphization of NiTi was achieved by this process, which was confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The wear resistance of the samples after UNSM processing was significantly improved compared with the non-processed samples due to increased surface hardness of the alloy by this process. In addition, cell culture study demonstrated that the biocompatibility of the samples after UNSM processing has not been compromised compared to the non-processed sample. The combination of high wear resistance and good biocompatibility makes UNSM an appealing process for treating alloy-based biomedical devices. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Effect of Boronizing on Metallic Alloys for Automotive Applications

NASA Astrophysics Data System (ADS)

Petrova, Roumiana S.; Suwattananont, Naruemon; Samardzic, Veljko

2008-06-01

In this study the wear resistance, corrosion resistance, and oxidation resistance of boronized metallic alloys were investigated. Thermochemical treatment was performed by powder pack boronizing process at temperature 850-950 °C for 4 h. Saw-tooth morphology and smooth interface microstructures were observed with an optical microscope; microhardness was measured across the coating depth. The phases present in the boron coatings depend on the substrate material. High-temperature oxidation resistance was investigated and it was found that boron coating on ferrous alloys can resist temperatures up to 800 °C. The corrosion resistance of the boronized samples was improved and the corrosion rate was calculated for boronized and plain specimens. Wear testing was conducted by following the procedures of ASTM G99, ASTM D2526, and ASTM D4060. The obtained experimental results revealed that boronizing significantly improves the wear-resistance, corrosion-resistance, and oxidation resistance of metallic alloys.

Wear behaviour of the couple polyethylene Ti6Al4V: Effects of the metallic surface preparation and nitrogen implantation

NASA Astrophysics Data System (ADS)

Martinella, R.; Giovanardi, S.; Palombarini, G.; Corchia, M.; Delogu, P.; Giorgi, R.; Tosello, C.

The wear behaviour improvement of the tribological couple Ti6Al4V-UHMWPE is of great interest to the medical field. Wear tests were carried out in water on a reciprocating UHMWPE annulus on implanted Ti6Al4V disc tribotestcr, with loads and velocities simulating those of hip joints. A comparison of wear behaviours was also carried out between untreated Ti6Al4V samples and Ti6Al4V subjected to a special lapping procedure. UHMWPE worn against ion-implanted and especially lapped Ti alloy showed the lowest wear rate, while, the highest (about one order of magnitude) was shown by the UHMWPE against untreated Ti6Al4V samples. XPS and AES surface analyses were carried out on metallic discs to examine the chemical composition of the surface before wear tests. Moreover depth distribution of nitrogen in implanted samples was determined using the same techniques. SEM observations displayed a polyethylene transfer film on all metallic surfaces, particularly on untreated Ti6Al4V samples. A discussion about uselessness of more conventional surface treatments for the Ti alloy is also reported.

Tribological and Mechanical Behaviors of Polyamide 6/Glass Fiber Composite Filled with Various Solid Lubricants

PubMed Central

Li, Duxin; Xie, Ying; Li, Wenjuan; You, Yilan; Deng, Xin

2013-01-01

The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study. PMID:23766687

Effect of SiC particle impact nano-texturing on tribological performance of 304L stainless steel

NASA Astrophysics Data System (ADS)

Lorenzo-Martin, C.; Ajayi, O. O.

2014-10-01

Topographical features on sliding contact surfaces are known to have a significant impact on friction and wear. Indeed, various forms of surface texturing are being used to improve and/or control the tribological performance of sliding surfaces. In this paper, the effect of random surface texturing produced by a mechanical impact process is studied for friction and wear behavior of 304L stainless steel (SS) under dry and marginal oil lubrication. The surface processing was applied to 304L SS flat specimens and tested under reciprocating ball-on-flat sliding contact, with a 440C stainless steel ball. Under dry contact, the impact textured surface exhibited two order of magnitude lower wear than the isotropically ground surface of the same material. After 1500 s of sliding and wearing through of the processed surface layer following occurring of scuffing, the impact textured surface underwent a transition in wear and friction behavior. Under marginal oil lubrication, however, no such transition occurred, and the wear for the impact textured surface was consistently two orders of magnitude lower than that for the ground material. Mechanisms for the tribological performance enhancement are proposed.

Effect of Deep Cryogenic treatment on AISI A8 Tool steel & Development of Wear Mechanism maps using Fuzzy Clustering

NASA Astrophysics Data System (ADS)

Pillai, Nandakumar; Karthikeyan, R., Dr.

2018-04-01

Tool steels are widely classified according to their constituents and type of thermal treatments carried out to obtain its properties. Viking a special purpose tool steel coming under AISI A8 cold working steel classification is widely used for heavy duty blanking and forming operations. The optimum combination of wear resistance and toughness as well as ease of machinability in pre-treated condition makes this material accepted in heavy cutting and non cutting tool manufacture. Air or vacuum hardening is recommended as the normal treatment procedure to obtain the desired mechanical and tribological properties for steels under this category. In this study, we are incorporating a deep cryogenic phase within the conventional treatment cycle both before and after tempering. The thermal treatments at sub zero temperatures up to -195°C using cryogenic chamber with liquid nitrogen as medium was conducted. Micro structural changes in its microstructure and the corresponding improvement in the tribological and physical properties are analyzed. The cryogenic treatment leads to more conversion of retained austenite to martensite and also formation of fine secondary carbides. The microstructure is studied using the micrographs taken using optical microscopy. The wear tests are conducted on DUCOM tribometer for different combinations of speed and load under normal temperature. The wear rates and coefficient of friction obtained from these experiments are used to developed wear mechanism maps with the help of fuzzy c means clustering and probabilistic neural network models. Fuzzy C means clustering is an effective algorithm to group data of similar patterns. The wear mechanisms obtained from the computationally developed maps are then compared with the SEM photographs taken and the improvement in properties due to this additional cryogenic treatment is validated.

Effect of alumina on grain refinement of Al-Si hypereutectic alloys

NASA Astrophysics Data System (ADS)

Majhi, J.; Sahoo, S. K.; Patnaik, S. C.; Sarangi, B.; Sachan, N. K.

2018-03-01

The size, volume fraction and distribution of primary as well as eutectic silicon affect the mechanical properties of the Al-Si hypereutectic alloys. It is very difficult for the simultaneous refinement and modification of primary and secondary Si particles in hypereutectic Al-Si alloys through traditional processes. This paper explores the role of γ-Al2O3 nanoparticles on Si particles in the course of solidification in hypereutectic Al-Si alloys at particular pouring temperature. The present study involves incorporation of varying contents dispersed γ-Al2O3 nanoparticles into a molten base metal during stir casting and followed by solidification. It has been reported that the synthesized composites having good interfacial bonding (wetting) between the dispersed phase and the liquid matrix was achieved in order to provide improved mechanical properties of the composite. The cast product of hypereutectic Al-16Si alloy with the reinforcement of nanoparticles, illustrated a significant improvement in both wear behaviour and hardness. The dry sliding wear test has been performed on a group of specimens with varying parameters (different loads and sliding velocities) in a pin on disc wear testing machine. Moreover, the wear rate and specific wear rate also affected in different load and different sliding velocities. However in XRD analysis of the samples, the enhancement of wear resistance as well as hardness was due to the formation of brittle phases like SiO2, Al2O3 and Al-rich intermetallic compounds. The hardness value of the materials increases nearly 6% in addition to increase in the density of only 0.8%. As per literature, the large plate eutectic Si particles were modified in to the fine core particles and it acquires enough potential for various applications.

The Tribological Performance of Surface Treated Ti6A14V as Sliding Against Si3N4 Ball and 316L Stainless Steel Cylinder

NASA Astrophysics Data System (ADS)

Kao, W. H.; Su, Y. L.; Horng, J. H.; Huang, H. C.

2016-12-01

Closed field unbalanced magnetron sputtering was used to deposit diamond-like carbon (Ti-C:H) coatings on Ti6Al4V alloy and gas nitrided Ti6Al4V alloy. Four different specimens were prepared, namely untreated Ti6Al4V alloy (Ti6Al4V), gas nitrided Ti6Al4V alloy (N-Ti6Al4V), Ti-C:H-coated Ti6Al4V alloy (Ti-C:H/Ti6Al4V) and Ti-C:H-coated gas nitrided Ti6Al4V alloy (Ti-C:H/N-Ti6Al4V). The tribological properties of the four specimens were evaluated using a reciprocating wear tester sliding against a Si3N4 ball (point contact mode) and 316L stainless steel cylinder (line contact mode). The wear tests were performed in a 0.89 wt.% NaCl solution. The results showed that the nitriding treatment increased the surface roughness and hardness of the Ti6Al4V alloy and improved the wear resistance as a result. In addition, the Ti-C:H coating also improved the tribological performance of Ti6Al4V. For example, compared to the untreated Ti6Al4V sample, the Ti-C:H coating reduced the wear depth and friction coefficient by 340 times and 10 times, respectively, in the point contact wear mode, and 151 times and 9 times, respectively, in the line contact wear mode. It is thus inferred that diamond-like carbon coatings are of significant benefit in extending the service life of artificial biomedical implants.

Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

NASA Astrophysics Data System (ADS)

Agrawal, Neha; Pandey, Akanksha; Parihar, A. S.; Mishra, A. K.; Gandhi, M. N.; Bhattacharyya, A. R.; Mukhopadhyay, K.; Prasad, N. E.

2016-05-01

Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS2) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and aging effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS2 and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS2 and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.

Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Neha, E-mail: neha87bhu@gmail.com; Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra; Pandey, Akanksha

Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS{sub 2}) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and agingmore » effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS{sub 2} and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS{sub 2} and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.« less

Comparison of joint angles and electromyographic activity of the lower extremities during standing with wearing standard and revised high-heeled shoes: A pilot study.

PubMed

Bae, Young-Hyeon; Ko, Mansoo; Lee, Suk Min

2016-04-29

Revised high-heeled shoes (HHSs) were designed to improve the shortcomings of standard HHSs. This study was conducted to compare revised and standard HHSs with regard to joint angles and electromyographic (EMG) activity of the lower extremities during standing. The participants were five healthy young women. Data regarding joint angles and EMG activity of the lower extremities were obtained under three conditions: barefoot, when wearing revised HHSs, and when wearing standard HHSs. Lower extremity joint angles in the three dimensional plane were confirmed using a VICON motion capture system. EMG activity of the lower extremities was measured using active bipolar surface EMG. Kruskal-Wallis one-way analysis of variance by rank applied to analyze differences during three standing conditions. Compared with the barefoot condition, the standard HHSs condition was more different than the revised HHSs condition with regard to lower extremity joint angles during standing. EMG activity of the lower extremities was different for the revised HHSs condition, but the differences among the three conditions were not significant. Wearing revised HHSs may positively impact joint angles and EMG activity of the lower extremities by improving body alignment while standing.

Influence of Surface Features for Increased Heat Dissipation on Tool Wear

PubMed Central

Beno, Tomas; Hoier, Philipp; Wretland, Anders

2018-01-01

The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life and surface quality of the machined surface, which in turn, contributes to higher manufacturing costs. This paper investigates improved heat dissipation from the cutting zone on the tool wear through surface features on the cutting tools. Firstly, the objective was to increase the available surface area in high temperature regions of the cutting tool. Secondly, multiple surface features were fabricated for the purpose of acting as channels in the rake face to create better access for the coolant to the proximity of the cutting edge. The purpose was thereby to improve the cooling of the cutting edge itself, which exhibits the highest temperature during machining. These modified inserts were experimentally investigated in face turning of Alloy 718 with high-pressure coolant. Overall results exhibited that surface featured inserts decreased flank wear, abrasion of the flank face, cutting edge deterioration and crater wear probably due to better heat dissipation from the cutting zone. PMID:29693579

Ceramic on ceramic arthroplasty of the hip: new materials confirm appropriate use in young patients.

PubMed

Sentuerk, U; von Roth, P; Perka, C

2016-01-01

The leading indication for revision total hip arthroplasty (THA) remains aseptic loosening owing to wear. The younger, more active patients currently undergoing THA present unprecedented demands on the bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest rates of wear. The recent advances, especially involving alumina/zirconia composite ceramic, have led to substantial improvements and good results in vitro. Alumina/zirconia composite ceramics are extremely hard, scratch resistant and biocompatible. They offer a low co-efficient of friction and superior lubrication and lower rates of wear compared with other bearings. The major disadvantage is the risk of fracture of the ceramic. The new composite ceramic has reduced the risk of fracture of the femoral head to 0.002%. The risk of fracture of the liner is slightly higher (0.02%). Assuming that the components are introduced without impingement, CoC bearings have major advantages over other bearings. Owing to the superior hardness, they produce less third body wear and are less vulnerable to intra-operative damage. The improved tribology means that CoC bearings are an excellent choice for young, active patients requiring THA. ©2016 The British Editorial Society of Bone & Joint Surgery.

Tungsten coating for improved wear resistance and reliability of microelectromechanical devices

DOEpatents

Fleming, James G.; Mani, Seethambal S.; Sniegowski, Jeffry J.; Blewer, Robert S.

2001-01-01

A process is disclosed whereby a 5-50-nanometer-thick conformal tungsten coating can be formed over exposed semiconductor surfaces (e.g. silicon, germanium or silicon carbide) within a microelectromechanical (MEM) device for improved wear resistance and reliability. The tungsten coating is formed after cleaning the semiconductor surfaces to remove any organic material and oxide film from the surface. A final in situ cleaning step is performed by heating a substrate containing the MEM device to a temperature in the range of 200-600 .degree. C. in the presence of gaseous nitrogen trifluoride (NF.sub.3). The tungsten coating can then be formed by a chemical reaction between the semiconductor surfaces and tungsten hexafluoride (WF.sub.6) at an elevated temperature, preferably about 450.degree. C. The tungsten deposition process is self-limiting and covers all exposed semiconductor surfaces including surfaces in close contact. The present invention can be applied to many different types of MEM devices including microrelays, micromirrors and microengines. Additionally, the tungsten wear-resistant coating of the present invention can be used to enhance the hardness, wear resistance, electrical conductivity, optical reflectivity and chemical inertness of one or more semiconductor surfaces within a MEM device.

Development and characterization of laser surface cladding (Ti,W)C reinforced Ni-30Cu alloy composite coating on copper

NASA Astrophysics Data System (ADS)

Yan, Hua; Zhang, Peilei; Yu, Zhishui; Li, Chonggui; Li, Ruidi

2012-07-01

To improve the wear resistance of copper components, laser surface cladding (LSC) was applied to deposit (Ti,W)C reinforced Ni-30Cu alloy composite coating on copper using a cladding interlayer of Ni-30Cu alloy by Nd:YAG laser. The microstructure and phases of the composite coating were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray energy dispersive microanalysis (EDX). Microhardness tester and pin-on-disc wear tester were employed to evaluate the hardness and dry-sliding wear resistance. The results show that crack-free composite coating with metallurgical bonding to the copper substrate is obtained. Phases identified in the (Ti,W)C-reinforced Ni-30Cu alloy composite layer are composed of TiWC2 reinforcements and (Ni,Cu) solid solution. TiWC2 reinforcements are distributed uniformly in the (Ni,Cu) solid solution matrix with dendritic morphology in the upper region and with particles in the mid-lower region. The microhardness and wear properties of the composite coating are improved significantly in comparison to the as-received copper substrate due to the addition of 50 wt% (Ti,W)C multicarbides.

Alternative materials to improve total hip replacement tribology.

PubMed

Santavirta, Seppo; Böhler, Max; Harris, William H; Konttinen, Yrjö T; Lappalainen, Reijo; Muratoglu, Orhun; Rieker, Claude; Salzer, Martin

2003-08-01

An improvement in tribology of bearing surfaces is an effective means of increasing the longevity of total hip replacement (THR). Currently, 3 approaches are available to achieve this aim: first, use of highly cross-linked UHMWPE; second, aluminum oxide ceramic bearings, and third, metal-on-metal bearings. Cross-linking reduces the wear resistance of UHMWPE markedly without impairment of other significant properties of the material. Simulator studies and some clinical long-term (10-22 years) follow-up surveys suggest an almost immeasurable wear of the highly cross-linked UHMWPE-based acetabular components during an expected clinical life span. Bioinert alumina ceramic (aluminum oxide) was introduced 3 decades ago for THR-bearing surfaces to improve performance and longevity. Alumina ceramic is entirely biostable and bioinert and has good mechanical properties. For correctly positioned alumina-on-alumina bearings, the annual linear wear rate has been reported to be 3.9 microm. Alumina heads have been successfully used in combination with polyethylene sockets, but as regards wear, the best results have been obtained with alumina-on-alumina bearings. In ceramic THR bearings, precise manufacture and contact surface geometry, including optimal clearance, are most important. For the currently available products, the component fracture risk is almost nonexistent (less than 1 per 1000). Metal-on-metal bearings were used in the early stage of THR surgery, although not all old designs were successful. More recent analyses of the early series have shown the advantages of metal-on-metal to be better and have led to a renaissance of this articulation. Initially, stainless steel was used because it was easy to manufacture and polish. Current metal-on-metal bearings are based on cobalt-chromium-molybdenum alloys with varying carbon contents. Such bearings are self-polishing. Linear wear rates remain at the level of a few microm a year. An improvement in technology has increased the life span of the above three THR-bearing systems. Although the technical solutions differ considerably, they all seem to improve clearly the tribology and longevity of the THR. Each of these bearing concepts will probably permit the use of larger head sizes, to reduce the risk of impingement and luxations.

Microstructural Characterisation and Wear Behaviour of Diamond Composite Materials

PubMed Central

Boland, James N.; Li, Xing S.

2010-01-01

Since the initial research leading to the production of diamond composite materials, there have been several important developments leading to significant improvements in the properties of these superhard composite materials. Apart from the fact that diamonds, whether originating from natural resources or synthesised commercially, are the hardest and most wear-resistant materials commonly available, there are other mechanical properties that limit their industrial application. These include the low fracture toughness and low impact strength of diamond. By incorporating a range of binder phases into the sintering production process of these composites, these critically important properties have been radically improved. These new composites can withstand much higher operating temperatures without markedly reducing their strength and wear resistance. Further innovative steps are now being made to improve the properties of diamond composites by reducing grain and particle sizes into the nano range. This review will cover recent developments in diamond composite materials with special emphasis on microstructural characterisation. The results of such studies should assist in the design of new, innovative diamond tools as well as leading to radical improvements in the productivity of cutting, drilling and sawing operations in the exploration, mining, civil construction and manufacturing industries.

Performance of aseptic technique during neuraxial analgesia for labor before and after the publication of international guidelines on aseptic technique

PubMed Central

2014-01-01

Background Aseptic technique and handwashing have been shown to be important factors in perioperative bacterial transmission, however compliance often remains low despite guidelines and educational programs. Infectious complications of neuraxial (epidural and spinal) anesthesia are severe but fortunately rare. We conducted a survey to assess aseptic technique practices for neuraxial anesthesia in Israel before and after publication of international guidelines (which focused on handwashing, jewelry/watch removal and the wearing of a mask and cap). Methods The sampling frame was the general anesthesiology workforce in hospitals selected from each of the four medical faculties in Israel. Data was collected anonymously over one week in each hospital in two periods: April 2006 and September 2009. Most anesthesiologists received the questionnaires at departmental staff meetings and filled them out during these meetings; additionally, a local investigator approached anesthesiologists not present at these staff meetings individually. Primary endpoint questions were: handwashing, removal of wristwatch/jewelry, wearing mask, wearing hat/cap, wearing sterile gown; answering options were: "always", "usually", "rarely" or "never". Primary endpoint for analysis: respondents who both always wash their hands and always wear a mask ("handwash-mask composite") - "always" versus "any other response". We used logistic regression to perform the analysis. Time (2006, 2009) and hospital were included in the analysis as fixed effects. Results 135/160 (in 2006) and 127/164 (in 2009) anesthesiologists responded to the surveys; response rate 84% and 77% respectively. Respondents constituted 23% of the national anesthesiologist workforce. The main outcome "handwash-mask composite" was significantly increased after guideline publication (33% vs 58%; p = 0.0003). In addition, significant increases were seen for handwashing (37% vs 63%; p = 0.0004), wearing of mask (61% vs 78%; p < 0.0001), hat/cap (53% vs 76%; p = 0.0011) and wearing sterile gown (32% vs 51%; p < 0.0001). An apparent improvement in aseptic technique from 2006 to 2009 is noted across all hospitals and all physician groups. Conclusion Self-reported aseptic technique by Israeli anesthesiologists improved in the survey conducted after the publication of international guidelines. Although the before-after study design cannot prove a cause-effect relationship, it does show an association between the publication of international guidelines and significant improvement in self-reported aseptic technique. PMID:24661425

Inorganic-organic nanocomposites formed using porous ceramic particles

NASA Astrophysics Data System (ADS)

Luo, Jiazhong

Inorganic-organic nanocomposites are expected to be of great significance in new material technologies impacting many different fields. We develop new nanomaterials of this type that have an interpenetrating network structure via in-situ polymerization of monomer within the nanopores of inorganic gel particles (porosity 20-80 vol.%). Due to strong nanomechanical bonding, these thermosetting polymer composites are expected to exhibit improved mechanical performance. Particle porosity is a primary factor. In contrast to HCl-catalyzed gels, more porous HF-catalyzed gels (porosity 62 vol.%) produced higher composite wear-resistance. At the same loading, the wear rates decrease linearly with increasing filler porosity. Better wear resistance is associated with fine-scale plastic deformation as opposed to brittle fracture and particle pull-out. For the coupling of HF-catalyzed particles with gamma-methacryloxypropyl trimethoxysilane, FTIR and solid-state sp{13}C/sp{29}Si NMR show that the use of a catalyst (n-propylamine) and a nonpolar solvent (cyclohexane), causes the degree of coupling and self-condensation to increase. Ethanol competes with the silane for the surface and results in less silane self-condensation. Surprisingly, the silane diminishes the composite wear resistance due to its pore-filling effect and the subsequent decrease in polymer interpenetration. A transition from plastic deformation to brittle fracture is involved. A new sol-gel technique was found to prepare porous (up to 76.54 vol.%) silica nanoparticles from solution via sodium fluoride (NaF) salt catalysis. Full interpenetration is achieved without the use of silane coupling agents. The resulting composites displayed improved wear resistance, toughness, modulus, hardness and high compressive strength. Toughening and reinforcement can be explained by pore confinement. DMA and DEA were combined with TEM to investigate related structure and property issues. The filler matrix effect on composite wear was evaluated utilizing the phase transformation of porous alumina gels from the stable monohydrate to the gamma-alumina form between 300 and 400sp°C; conveniently the total amount of porosity remains the same. gamma-alumina is more efficient than the monohydrate in improving wear resistance. The susceptibility of the monohydrate to 'transgranular' deformation and the crack-deflection of gamma-alumina in an 'intergranular' mode are responsible for the similar toughening effect of these two reinforcements.

Improvements in Microstructure and Wear Resistance of Plasma-Sprayed Fe-Based Amorphous Coating by Laser-Remelting

NASA Astrophysics Data System (ADS)

Jiang, Chaoping; Chen, Hong; Wang, Gui; Chen, Yongnan; Xing, Yazhe; Zhang, Chunhua; Dargusch, Matthew

2017-04-01

Amorphous coating technology is an attractive way of taking advantage of the superior properties of amorphous alloys for structural applications. However, the limited bonds between splats within the plasma-sprayed coatings result in a typically lamellar and porous coating structure. To overcome these limitations, the as-sprayed coating was treated by a laser-remelting process. The microstructure and phase composition of two coatings were analyzed using scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and x-ray diffraction. The wear resistance of the plasma-sprayed coating and laser-remelted coating was studied comparatively using a pin-on-disc wear test under dry friction conditions. It was revealed that the laser-remelted coating exhibited better wear resistance because of its defect-free and amorphous-nanocrystalline composited structure.

Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

NASA Astrophysics Data System (ADS)

Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

2018-04-01

Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

Investigation of Selective Laser Melting Surface Alloyed Aluminium Metal Matrix Dispersive Reinforced Layers

NASA Astrophysics Data System (ADS)

Kamburov, V. V.; Dimitrova, R. B.; Kandeva, M. K.; Sofronov, Y. P.

2018-01-01

The aim of the paper is to investigate the improvement of mechanical properties and in particular wear resistance of laser surface alloyed dispersive reinforced thin layers produced by selective laser melting (SLM) technology. The wear resistance investigation of aluminium matrix composite layers in the conditions of dry friction surface with abrasive particles and nanoindentation tests were carried out. The process parameters (as scan speed) and their impact on the wear resistant layers have been evaluated. The alloyed layers containing metalized SiC particles were studied by Optical and Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray microanalysis (EDX). The obtained experimental results of the laser alloyed thin layers show significant development of their wear resistance and nanohardness due to the incorporated reinforced phase of electroless nickel coated SiC particles.

A probabilistic-based approach to monitoring tool wear state and assessing its effect on workpiece quality in nickel-based alloys

NASA Astrophysics Data System (ADS)

Akhavan Niaki, Farbod

The objective of this research is first to investigate the applicability and advantage of statistical state estimation methods for predicting tool wear in machining nickel-based superalloys over deterministic methods, and second to study the effects of cutting tool wear on the quality of the part. Nickel-based superalloys are among those classes of materials that are known as hard-to-machine alloys. These materials exhibit a unique combination of maintaining their strength at high temperature and have high resistance to corrosion and creep. These unique characteristics make them an ideal candidate for harsh environments like combustion chambers of gas turbines. However, the same characteristics that make nickel-based alloys suitable for aggressive conditions introduce difficulties when machining them. High strength and low thermal conductivity accelerate the cutting tool wear and increase the possibility of the in-process tool breakage. A blunt tool nominally deteriorates the surface integrity and damages quality of the machined part by inducing high tensile residual stresses, generating micro-cracks, altering the microstructure or leaving a poor roughness profile behind. As a consequence in this case, the expensive superalloy would have to be scrapped. The current dominant solution for industry is to sacrifice the productivity rate by replacing the tool in the early stages of its life or to choose conservative cutting conditions in order to lower the wear rate and preserve workpiece quality. Thus, monitoring the state of the cutting tool and estimating its effects on part quality is a critical task for increasing productivity and profitability in machining superalloys. This work aims to first introduce a probabilistic-based framework for estimating tool wear in milling and turning of superalloys and second to study the detrimental effects of functional state of the cutting tool in terms of wear and wear rate on part quality. In the milling operation, the mechanisms of tool failure were first identified and, based on the rapid catastrophic failure of the tool, a Bayesian inference method (i.e., Markov Chain Monte Carlo, MCMC) was used for parameter calibration of tool wear using a power mechanistic model. The calibrated model was then used in the state space probabilistic framework of a Kalman filter to estimate the tool flank wear. Furthermore, an on-machine laser measuring system was utilized and fused into the Kalman filter to improve the estimation accuracy. In the turning operation the behavior of progressive wear was investigated as well. Due to the nonlinear nature of wear in turning, an extended Kalman filter was designed for tracking progressive wear, and the results of the probabilistic-based method were compared with a deterministic technique, where significant improvement (more than 60% increase in estimation accuracy) was achieved. To fulfill the second objective of this research in understanding the underlying effects of wear on part quality in cutting nickel-based superalloys, a comprehensive study on surface roughness, dimensional integrity and residual stress was conducted. The estimated results derived from a probabilistic filter were used for finding the proper correlations between wear, surface roughness and dimensional integrity, along with a finite element simulation for predicting the residual stress profile for sharp and worn cutting tool conditions. The output of this research provides the essential information on condition monitoring of the tool and its effects on product quality. The low-cost Hall effect sensor used in this work to capture spindle power in the context of the stochastic filter can effectively estimate tool wear in both milling and turning operations, while the estimated wear can be used to generate knowledge of the state of workpiece surface integrity. Therefore the true functionality and efficiency of the tool in superalloy machining can be evaluated without additional high-cost sensing.

Wear resistance of machine tools' bionic linear rolling guides by laser cladding

NASA Astrophysics Data System (ADS)

Wang, Yiqiang; Liu, Botao; Guo, Zhengcai

2017-06-01

In order to improve the rolling wear resistance (RWR) of linear rolling guides (LRG) as well as prolong the life of machine tools, various shape samples with different units spaces ranged from 1 to 5 mm are designed through the observation of animals in the desert and manufactured by laser cladding. Wear resistance tests reproducing closely the real operational condition are conducted by using a homemade linear reciprocating wear test machine, and wear resistance is evaluated by means of weight loss measurement. Results indicate that the samples with bionic units have better RWR than the untreated one, of which the reticulate treated sample with unit space 3 mm present the best RWR. More specifically, among the punctuate treated samples, the mass loss increases with the increase of unit space; among the striate treated samples, the mass loss changes slightly with the increase of unit space, attaining a minimum at the unit space of 4 mm; among the reticulate treated samples, with the increase of unit space, the mass loss initially decreases, but turns to increase after reaching a minimum at the unit space of 3 mm. Additionally, the samples with striate shape perform better wear resistance than the other shape groups on the whole. From the ratio value of laser treated area to contacted area perspective, that the samples with ratio value between 0.15 and 0.3 possess better wear resistance is concluded.

High-speed microprobe for roughness measurements in high-aspect-ratio microstructures

NASA Astrophysics Data System (ADS)

Doering, Lutz; Brand, Uwe; Bütefisch, Sebastian; Ahbe, Thomas; Weimann, Thomas; Peiner, Erwin; Frank, Thomas

2017-03-01

Cantilever-type silicon microprobes with an integrated tip and a piezoresistive signal read out have successfully proven to bridge the gap between scanning force microscopy and stylus profilometry. Roughness measurements in high-aspect-ratio microstructures (HARMS) with depths down to 5 mm and widths down to 50 µm have been demonstrated. To improve the scanning speed up to 15 mm s-1, the wear of the tip has to be reduced. The atomic layer deposition (ALD) technique with alumina (Al2O3) has been tested for this purpose. Repeated wear measurements with coated and uncoated microprobe cantilevers have been carried out on a roughness standard at a speed of 15 mm s-1. The tip shape and the wear have been measured using a new probing tip reference standard containing rectangular silicon grooves with widths from 0.3 µm to 3 µm. The penetration depth of the microprobe allows one to measure the wear of the tip as well as the tip width and the opening angle of the tip. The roughness parameters obtained on the roughness standard during wear experiments agree well with the reference values measured with a calibrated stylus instrument, nevertheless a small amount of wear still is observable. Further research is necessary in order to obtain wear resistant microprobe tips for non-destructive inspection of microstructures in industry and microform measurements, for example in injection nozzles.

Tread wear and footprint geometrical characters of truck bus radial tires

NASA Astrophysics Data System (ADS)

Liang, Chen; Wang, Guolin; An, Dengfeng; Ma, Yinwei

2013-05-01

Wear and mileage performance are the foremost performances for truck bus radial (TBR) tires. There are a lot of researches about the tire wear performance as well as the contact patch phenomenon by using finite element analysis (FEA) method or testing. But there is little published data on the correlations between the footprint geometry and the tread wear performance of tires. In this paper, an experiment on tire-ground performance of TBR tires is carried out by using Tekscan. The real-time changes of contact-area pressure distribution that occurred during the process of continuous load and unload are recorded. Three types of tires that act differently in behavior under normal usage are analyzed. A new method of researching in tire tread wear, which focuses on the geometrical characters of the footprint, is put forward. The experimental results of the three tires are described by using footprint geometrical characters. On the basis of studying the changing laws of footprint geometrical characters during the loading process and considering consumer survey and factory feedback information, the correlations between the geometrical character of footprints and tread destruction form are built. The analyzed results show that a greater contact area coefficient and a steady coefficient of contact result in a better wear performance for TBR tires. The footprint-shape coefficient changing laws in the process of loading are found to have a very good coincidence with the tread wear of the three types of tires. Tires with a smaller footprint-shape coefficient are likely to have an average tread wear while avoiding the shoulder wear first. The proposed research provides a new solution to predict tire-ground performance at the point of footprint and several useful references for improving tire design.

Friction and Wear of Monolithic and Fiber Reinforced Silicon-Ceramics Sliding Against IN-718 Alloy at 25 to 800 C in Atmospheric Air at Ambient Pressure

NASA Technical Reports Server (NTRS)

Deadmore, Daniel L.; Sliney, Harold E.

1988-01-01

The friction and wear of monolithic and fiber reinforced Si-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C was measured. The monolithic materials tested were silicon carbide (SiC), fused silica (SiO2), syalon, silicon nitride (Si3N4) with W and Mg additives, and Si3N4 with Y2O3 additive. At 25 C fused silica had the lowest friction while Si3N4 (W,Mg type) had the lowest wear. At 800 C syalon had the lowest friction while Si3N4 (W,Mg type) and syalon had the lowest wear. The SiC/IN-718 couple had the lowest total wear at 25 C. At 800 C the fused silica/IN-718 couple exhibited the least total wear. SiC fiber reinforced reaction bonded silicon nitride (RBSN) composite material with a porosity of 32 percent and a fiber content of 23 vol percent had a lower coefficient of friction and wear when sliding parallel to the fiber direction than in the perpendicular at 25 C. The coefficient of friction for the carbon fiber reinforced borosilicate composite was 0.18 at 25 C. This is the lowest of all the couples tested. Wear of this material was about two decades smaller than that of the monolithic fused silica. This illustrates the large improvement in tribological properties which can be achieved in ceramic materials by fiber reinforcement. At higher temperatures the oxidation products formed on the IN-718 alloy are transferred to the ceramic by sliding action and forms a thin, solid lubricant layer which decreases friction and wear for both the monolithic and fiber reinforced composites.

Nurse uniform wearing practices and associated factors among nurses working in Northwest Ethiopia: a cross-sectional institution based study.

PubMed

Desta, Etaferahu Alamaw; Gebrie, Mignote Hailu; Dachew, Berihun Assefa

2015-01-01

Wearing uniforms help in the formation of professional identity in healthcare. It fosters a strong self image and professional identity which can lead to good confidence and better performance in nursing practice. However, most nurses in Ethiopia are not wearing nursing uniforms and the reasons remain unclear. Therefore, the aim of this research is to assess nurse uniform wearing practices among nurses and factors associated with such practice in hospitals in Northwest Ethiopia. A hospital based cross-sectional study was conducted from March to April, 2014 in five hospitals located in Northwest Ethiopia. A total 459 nurses participated in the study. Data was collected using a pre-tested self-administered questionnaire. Descriptive statistics were analyzed in order to characterize the study population. Bivariate and multiple logistic regression models were fitted. Odds ratios with 95 % confidence intervals were computed to identify factors associated with nursing uniform practice. Nurse uniform wearing practice was found to be 49.2 % of the total sample size. Around 35 % of the respondents that did not implement nurse uniform wearing practices stated that there was no specific uniform for nurses recommended by hospital management. In addition to this, nurse uniform wearing practices were positively associated with being female [AOR = 1.58, 95 % CI (1.02, 2.44)], studying nursing by choice [AOR =3.16, 95 % CI (2.03, 4.92)], and the appeal of nursing uniforms to nurses [AOR = 3.43 95 % CI (1.96, 5.98)]. Nurse uniform wearing practices were not exceptionally prevalent in Northwest Ethiopian hospitals. However, encouraging students to pursue interest-based careers and implementing a nurse uniform wearing policy may have the potential to improve such practices.

The Effects of Acid Passivation, Tricresyl Phosphate Pre-Soak, and UV/Ozone Treatment on the Tribology of Perfluoropolyether-Lubricated 440C Stainless Steel Couples

NASA Technical Reports Server (NTRS)

Shogrin, Bradley A.; Jones, William R., Jr.; Herrera-Fierro, Pilar

1997-01-01

The boundary-lubrication performance of perfluoropolyether (PFPE) thin films in the presence of passivated 440 C stainless steel is presented. The study utilized a standard ball-on-disc tribometer. Stainless steel surfaces were passivated with one of four techniques: 1) submersion in a chromic acid bath for 30 minutes at 46 C, 2) submersion in a chromic acid bath for 60 minutes at 56 C, 3) submersion in a tricresyl phosphate (TCP) bath for 2 days at 107 C, or 4) UV/Ozone treated for 15 minutes. After passivation, each disc had a 400 A film of PFPE (hexafluoropropene oxide) applied to it reproducibly (+/- 20%) and uniformly (+/- 15%) using a film deposition device. The lifetimes of these films were quantified by measuring the number of sliding wear cycles required to induce an increase in the friction coefficient from an initial value characteristic of the lubricated wear couple to a final, or failure value, characteristic of an unlubricated, unpassivated wear couple. The lubricated lifetime of the 440 C couple was not altered as a result of the various passivation techniques. The resulting surface chemistry of each passivation technique was examined using X-ray Photoelectron Spectroscopy (XPS). It was found that chromic acid passivation altered the Cr to Fe ratio of the surface. TCP passivation resulted in a FePO4 layer on the surface, while UV/Ozone passivation only removed the carbonaceous contamination layer. None of the passivation techniques were found to dramatically increase the oxide film thickness.

Method and apparatus for reducing cleaning blade wear

DOEpatents

Grannes, Steven G.; Rhoades, Charles A.; Hebbie, Terry L.

1992-01-01

An improved cleaning blade construction (10) for eliminating erosion troughs (6) in the upper surface (15) of a cleaning blade member (14) by introducing pressurized fluid through a pressure manifold chamber (16) formed in the upper surface (15) of the cleaning blade member (14). The pressurized fluid will prevent carryback material (7) from passing through a wear groove (6) formed in the cleaning blade member.

Recent Religious Accommodations: Have We Gone Too Far Too Fast?

DTIC Science & Technology

2012-03-12

de corps, eventually colorful fighting uniforms gave way to drab colors as weapons improved in precision and camouflaging with the environment...and the Army provides gear for soldiers use. In garrisons, soldiers wear their uniforms unless the commander allows for the wear of civilian clothes ...provides an appeal process .39 Commanders, often in conjunction with their command or post chaplain, routinely address requests for religious

Erosion-corrosion resistance properties of 316L austenitic stainless steels after low-temperature liquid nitriding

NASA Astrophysics Data System (ADS)

Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Pan, Dong

2018-05-01

The low-temperature liquid nitriding of stainless steels can result in the formation of a surface zone of so-called expanded austenite (S-phase) by the dissolution of large amounts of nitrogen in the solid solution and formation of a precipitate-free layer supersaturated with high hardness. Erosion-corrosion measurements were performed on low-temperature nitrided and non-nitrided 316L stainless steels. The total erosion-corrosion, erosion-only, and corrosion-only wastages were measured directly. As expected, it was shown that low-temperature nitriding dramatically reduces the degree of erosion-corrosion in stainless steels, caused by the impingement of particles in a corrosive medium. The nitrided 316L stainless steels exhibited an improvement of almost 84% in the erosion-corrosion resistance compared to their non-nitrided counterparts. The erosion-only rates and synergistic levels showed a general decline after low-temperature nitriding. Low-temperature liquid nitriding can not only reduce the weight loss due to erosion but also significantly reduce the weight loss rate of interactions, so that the total loss of material decreased evidently. Therefore, 316L stainless steels displayed excellent erosion-corrosion behaviors as a consequence of their highly favorable corrosion resistances and superior wear properties.

Mechanics

NASA Astrophysics Data System (ADS)

Maestro, P.; Gaffet, E.; Le Caër, G.; Mocellin, A.; Reynaud, E.; Rouxel, T.; Soulard, M.; Patarin, J.; Thilly, L.; Lecouturier, F.

Inorganic reinforcements are used in rubber, and in particular in tyre treads for light vehicles, in order to improve the compromise between three key features of tyres: road holding performance or road adherence, especially when the road is wet or snow-covered (road safety), roll resistance (petrol consumption), and resistance to wear (lifetime of the tyre). Over the last ten years, highly dispersible silicas (HDS) developed by Rhodia have been more and more widely used as a substitute for the traditionally used carbon black. The advantage with HDS materials is that they improve road holding and reduce roll resistance, while maintaining the same level of resistance to wear.

Analysis of Hard Thin Film Coating

NASA Technical Reports Server (NTRS)

Shen, Dashen

1998-01-01

Marshall Space Flight Center (MSFC) is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) to deposit hard thin film on stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

Analysis of Hard Thin Film Coating

NASA Technical Reports Server (NTRS)

Shen, Dashen

1998-01-01

MSFC is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using electron cyclotron resonance chemical vapor deposition (ECRCVD) to deposit hard thin film an stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

Laser surface modification of Ti--6Al--4V: wear and corrosion characterization in simulated biofluid.

PubMed

Singh, Raghuvir; Kurella, A; Dahotre, Narendra B

2006-07-01

Laser surface melting (LSM) of Ti-6Al-4V is performed in argon to improve its properties, such as microstructure, corrosion, and wear for biomedical applications. Corrosion behavior is investigated by conducting electrochemical polarization experiments in simulated body fluid (Ringer's solution) at 37 C. Wear properties are evaluated in Ringer's solution using pin-on-disc apparatus at a slow speed. Untreated Ti-6Al-4V contains alpha+beta phase. After laser surface melting, it transforms to acicular alpha embedded in the prior beta matrix. Grain growth in the range of 65-89 microm with increase in laser power from 800 to 1500 W due to increase in associated temperature is observed. The hardness of as-laserprocessed Ti-6Al-4V alloy is more (275-297 HV) than that of the untreated alloy (254 HV). Passivation currents are significantly reduced to < 4.3 microA/cm2 after laser treatment compared to untreated Ti-6Al-4V (approximately 12 microA/cm2). The wear resistance of laser-treated Ti-6Al-4V in simulated body fluid is enhanced compared to that of the untreated one. It is the highest for the one that is processed at a laser power of 800 W. Typical micro-cutting features of abrasive wear is the prominent mechanism of wear in both untreated and as-laser-treated Ti-6Al-4V. Fragmentation of wear debris assisted by microcracking was responsible for mass loss during the wear of untreated Ti-6Al-4V in Ringer's solution.

Tribological Behavior and Corrosion Resistance of Electroless Ni-B-W Coatings

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Arkadeb; Barman, Tapan Kumar; Sahoo, Prasanta

The present study considers the tribological behavior and corrosion resistance of electroless Ni-B-W coatings deposited on AISI 1040 steel substrates. Coating is characterized using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction technique. In as-deposited condition, coatings are found to be amorphous. On heat treatment, precipitation of crystalline Ni (1 1 1) and its borides take place. For as-deposited coating, the microhardness is obtained as ˜759HV100 which increases to ˜1181HV100 and ˜1098HV100 when heat treated at 350∘C and 450∘C, respectively. Incorporation of W in Ni-B coating results in an increase of hardness by 89HV100 in as-deposited condition. Heat treatment also results in increase in crystallite size of Ni (1 1 1). Wear rate and coefficient of friction (COF) of the coatings are evaluated on a pin-on-disc setup under both dry and lubricated sliding conditions. Wear resistance is observed to improve on heat treatment with an increase in crystallite size while COF deteriorates. However, in as-deposited condition, wear rate and COF of Ni-B-W coatings improve by ˜5 and ˜3 times, respectively, compared with Ni-B coatings. Wear and friction performance of the coatings are enhanced under lubrication due to the columnar structure of the coatings that retain lubricants. Corrosion resistance of Ni-B-W coating in 3.5% NaCl solution gets improved on heat treatment.

Influence of Bond Coat on HVOF-Sprayed Gradient Cermet Coating on Copper Alloy

NASA Astrophysics Data System (ADS)

Ke, Peng; Cai, Fei; Chen, Wanglin; Wang, Shuoyu; Ni, Zhenhang; Hu, Xiaohong; Li, Mingxi; Zhu, Guanghong; Zhang, Shihong

2017-06-01

Coatings are required on mold copper plates to prolong their service life through enhanced hardness, wear resistance, and oxidation resistance. In the present study, NiCr-30 wt.%Cr3C2 ceramic-metallic (cermet) layers were deposited by high velocity oxy-fuel (HVOF) spraying on different designed bond layers, including electroplated Ni, HVOF-sprayed NiCr, and double-decker Ni-NiCr. Annealing was also conducted on the gradient coating (GC) with NiCr bond layer to improve the wear resistance and adhesion strength. Coating microstructure was investigated by scanning electron microscopy and x-ray diffraction analysis. Mechanical properties including microhardness, wear resistance, and adhesion strength of the different coatings were evaluated systematically. The results show that the types of metallic bond layer and annealing process had a significant impact on the mechanical properties of the GCs. The GCs with electroplated Ni bond layer exhibited the highest adhesion strength (about 70 MPa). However, the GC with HVOF-sprayed NiCr bond layer exhibited better wear resistance. The wear resistance and adhesion strength of the coating with NiCr metallic bond layer were enhanced after annealing.

High Temperature Brush Seal Tuft Testing of Selected Nickel-Chrome and Cobalt-Chrome Superalloys

NASA Technical Reports Server (NTRS)

Fellenstein, James A.; DellaCorte, Christopher; Moore, Kenneth D.; Boyes, Esther

1997-01-01

The tribology of brush seals is of considerable interest to turbine engine designers because bristle wear continues to limit long term seal performance and life. To provide better materials characterization and foster the development of improved seals, NASA Lewis has developed a brush seal tuft tester. In this test, a 'paintbrush' sample tuft is loaded under constant contact pressure against the outside diameter of a rotating journal. With this configuration, load and friction are directly measured and accurate wear measurements are possible. Previously reported research using this facility showed excellent data repeatability and wear morphology similar to published seal data and dynamic rig tests. This paper is an update of the ongoing research into the tribology of brush seals. The effects of wire materials processing on seal wear and the tribological results for three journal coatings are discussed. Included in the materials processing were two nickel-chrome superalloys each processed to two different yield strengths. The results suggest that seal wear is dependent more on material composition than processing conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ajayi, O. O.; Lorenzo-Martin, Cinta

This study presents results of an experimental study to evaluate friction stir processing (FSP) with and without hard second-phase particle incorporation as a means to enhance surface properties and wear performance of C86300 manganese bronze alloy. FSP of flat bronze alloy specimens was conducted with hardened H-13 tool steel to create a 3-mm-thick processed surface layer. The process was also used to incorporate B 4C particles, thereby creating a metal-matrix composite layer on the alloy surface. FSP alone was observed to produce substantial reduction in grain size (from an initial value of 350 mu m to 1-5 μm). FSP withoutmore » particle incorporation resulted in modest surface hardening due to grain refinement and dispersion hardening. Under lubricated contact in block-on-ring testing with a hardened steel counter face, FSP produced substantial reduction (about 3X) in bronze wear after polishing of processing surface roughening. FSP with hard B 4C second-phase particle incorporation further reduced wear by up to 20X. The improvement in wear behavior is attributed to grain refinement and load shielding by second-phase particles, as determined by wear mechanism analysis.« less

Effect of frequency on fretting wear behavior of Ti/TiN multilayer film on depleted uranium

PubMed Central

Zhu, Sheng-Fa; Lu, Lei; Cai, Zhen-Bing

2017-01-01

The Ti/TiN multi-layer film was prepared on the depleted uranium (DU) substrate by cathodic arc ion plating equipment. The character of multi-layer film was studied by SEM, XRD and AES, revealed that the surface was composed of small compact particle and the cross-section had a multi-layer structure. The fretting wear performance under different frequencies was performed by a MFT-6000 machine with a ball-on-plate configuration. The wear morphology was analyzed by white light interferometer, OM and SEM with an EDX. The result shows the Ti/TiN multi-layer film could greatly improve the fretting wear performance compared to the DU substrate. The fretting wear running and damaged behavior are strongly dependent on the film and test frequency. The fretting region of DU substrate and Ti/TiN multi-layer under low test frequency is gross slip. With the increase of test frequency, the fretting region of Ti/TiN multi-layer change from gross slip to mixed fretting, then to partial slip. PMID:28384200

Effect of frequency on fretting wear behavior of Ti/TiN multilayer film on depleted uranium.

PubMed

Wu, Yan-Ping; Li, Zheng-Yang; Zhu, Sheng-Fa; Lu, Lei; Cai, Zhen-Bing

2017-01-01

The Ti/TiN multi-layer film was prepared on the depleted uranium (DU) substrate by cathodic arc ion plating equipment. The character of multi-layer film was studied by SEM, XRD and AES, revealed that the surface was composed of small compact particle and the cross-section had a multi-layer structure. The fretting wear performance under different frequencies was performed by a MFT-6000 machine with a ball-on-plate configuration. The wear morphology was analyzed by white light interferometer, OM and SEM with an EDX. The result shows the Ti/TiN multi-layer film could greatly improve the fretting wear performance compared to the DU substrate. The fretting wear running and damaged behavior are strongly dependent on the film and test frequency. The fretting region of DU substrate and Ti/TiN multi-layer under low test frequency is gross slip. With the increase of test frequency, the fretting region of Ti/TiN multi-layer change from gross slip to mixed fretting, then to partial slip.

Effects of grain size and humidity on fretting wear in fine-grained alumina, Al{sub 2}O{sub 3}/TiC, and zirconia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krell, A.; Klaffke, D.

Friction and wear of sintered alumina with grain sizes between 0.4 and 3 {micro}m were measured in comparison with Al{sub 2}O{sub 3}/TiC composites and with tetragonal ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effectmore » reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al{sub 2}O{sub 3}/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 {micro}m.« less

Effect of counterface material type and its topography on the tribological properties of polyimide composites

NASA Technical Reports Server (NTRS)

Fusaro, R. L.

1985-01-01

Graphite fiber reinforced polyimide composite pins were slid against seven different counterfaces to determine the effect of material type on the tribological properties of polymer composites. In addition, the effect of sliding a new pin on a pre-established transfer film was investigated. The results indicated that almost a five order of magnitude difference in composite wear rate can occur just by varying the counterface material. An attempt to make all surfaces as smooth as possible was made, but due to differences in material composition this was not possible and a range of surface roughnesses were obtained. The results indicate that the smoother the surface, the lower the composite wear rate; but that small protrusions (not discernible with arithmetic surface roughness measurements) can markedly increase wear rates. A pre-established transfer film improved both run in and steady state wear rates.

Development and fabrication of patient-specific knee implant using additive manufacturing techniques

NASA Astrophysics Data System (ADS)

Zammit, Robert; Rochman, Arif

2017-10-01

Total knee replacement is the most effective treatment to relief pain and restore normal function in a diseased knee joint. The aim of this research was to develop a patient-specific knee implant which can be fabricated using additive manufacturing techniques and has reduced wear rates using a highly wear resistant materials. The proposed design was chosen based on implant requirements, such as reduction in wear rates as well as strong fixation. The patient-specific knee implant improves on conventional knee implants by modifying the articulating surfaces and bone-implant interfaces. Moreover, tribological tests of different polymeric wear couples were carried out to determine the optimal materials to use for the articulating surfaces. Finite element analysis was utilized to evaluate the stresses sustained by the proposed design. Finally, the patient-specific knee implant was successfully built using additive manufacturing techniques.

Abrasive wear behavior of in-situ RZ5-10wt%TiC composite

NASA Astrophysics Data System (ADS)

Mehra, Deepak; Mahapatra, M. M.; Harsha, S. P.

2018-05-01

RZ5 Magnesium alloys containing zinc, rare earth and zirconium are well-known to have high specific strength, good creep resistance widely used in aerospace components. The incorporation of hard ceramic strengthens RZ5 mg alloy. The RZ5-10wt%TiC composite has been fabricated in situ using RZ5 mg alloy as matrix and TiC as reinforcement by self propagating high temperature synthesis (SHS) technique. This paper investigates the abrasive wear behavior of RZ5-10wt%TiC. Tests were performed using pin-on-disc apparatus against 600 grit abrasive paper by varying the sliding distance and applied load. The results showed improvement in the wear resistance of testing composite as compared to the unreinforced RZ5 Mg alloy. The coefficient of friction and weight loss increased linearly as applied load and sliding distance increased. The field emission scanning electron microscopic (FESEM) showed dominate wear mechanisms: abrasion, ploughing grooves.

Correlating mechanical properties and anti-wear performance of tribofilms formed by ionic liquids, ZDDP and their combinations

DOE PAGES

Landauer, Alexander K.; Barnhill, William C.; Qu, Jun

2016-03-10

Here we examine the elasticity, hardness, and resistance-to-plastic-deformation (P/S 2) measured via nanoindentation of several tribofilms and correlates these properties to friction and wear behavior. The tribofilms were generated by ball-on-plate reciprocating sliding lubricated by a base oil containing an ionic liquid, phosphonium-organophosphate or ammonium-organophosphate, zinc dialkyldithiophosphate (ZDDP), or combination of IL and ZDDP. Nanoindentation was conducted at room and elevated temperatures. While there seems little correlation between the tribofilm hardness and tribological behavior, a higher modulus generally leads to better friction and wear performance. Interestingly, a lower P/S 2 ratio tends to reduce friction and improve wear protection, whichmore » is in an opposite trend as reported for bulk materials. Ultimately, this is likely attributable to the dynamic, self-healing characteristics of tribofilms.« less

Cast Aluminum Alloy for High Temperature Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2003-01-01

Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties.

Nonlinear dynamics of a rack-pinion-rack device powered by the Casimir force.

PubMed

Miri, MirFaez; Nekouie, Vahid; Golestanian, Ramin

2010-01-01

Using the lateral Casimir force-a manifestation of the quantum fluctuations of the electromagnetic field between objects with corrugated surfaces-as the main force transduction mechanism, a nanomechanical device with rich dynamical behaviors is proposed. The device is made of two parallel racks that are moving in the same direction and a pinion in the middle that couples with both racks via the noncontact lateral Casimir force. The built-in frustration in the device causes it to be very sensitive and react dramatically to minute changes in the geometrical parameters and initial conditions of the system. The noncontact nature of the proposed device could help with the ubiquitous wear problem in nanoscale mechanical systems.

New Oxide Ceramic Developed for Superior High-Temperature Wear Resistance

NASA Technical Reports Server (NTRS)

Sayir, Ali; Miyoshi, Kazuhisa; Farmer, Serene C.

2003-01-01

Ceramics, for the most part, do not have inherently good tribological properties. For example friction coefficients in excess of 0.7 have been reported for silicon nitride sliding on silicon nitride or on bearing steel (ref. 1). High friction is always accompanied by considerable wear. Despite their inherently poor tribological properties, the high strength and high toughness of silicon nitride (Si3N4) ceramics has led to their successful use in tribological applications (refs. 1 to 4). The upper temperature limit for the application of Si3N4 as wear-resistant material is limited by reaction with the tribological environment (ref. 3). Silicon nitride is known to produce a thin silicon dioxide film with easy shear capability that results in low friction and low wear in a moist environment (ref. 5). At elevated temperatures, the removal of the reaction product that acts as lubricant causes the friction coefficient to increase and, consequently, the wear performance to become poor. New materials are sought that will have wear resistance superior to that of Si3N4 at elevated temperatures and in harsh environments. A new class of oxide ceramic materials has been developed with potential for excellent high-temperature wear resistance. The new material consists of a multicomponent oxide with a two-phase microstructure, in which the wear resistance of the mixed oxide is significantly higher than that of the individual constituents. This is attributed to the strong constraining effects provided by the interlocking microstructures at different length scales, to the large aspect ratio of the phases, to the strong interphase bonding, and to the residual stresses. Fretting wear tests were conducted by rubbing the new ceramic material against boron carbide (B4C). The new ceramic material produced a wear track groove on B4C, suggesting significantly higher wear resistance for the oxide ceramic. The new material did not suffer from any microstructural degradation after the wear test. The wear rate of the new ceramic material at 600 C was determined to be on the order of 10-10 mm3/N-m, which is 3 to 5 orders of magnitude lower than that for the current state-of-theart wear-resistant materials (Si3N4and B4C). The friction coefficient of the new ceramic materials is on the order of 0.4, which is significantly lower than that of silicon nitride. This new class of oxide materials has shown considerable potential for applications requiring high wear resistance at high temperatures and in harsh environments. New understanding of the wear behavior of ceramic materials is emerging as a result of the surprisingly high wear resistance of two-phase oxide ceramics. There is excellent potential for further improvements in the wear resistance of oxide ceramics through optimizing the microstructure and altering the crystallographic properties of specific oxide materials as a second phase to reduce the coefficient of friction at elevated temperatures.

Sliding wear and corrosion behaviour of alloyed austempered ductile iron subjected to novel two step austempering treatment

NASA Astrophysics Data System (ADS)

Sethuram, D.; Srisailam, Shravani; Rao Ponangi, Babu

2018-04-01

Austempered Ductile Iron(ADI) is an exciting alloy of iron which offers the design engineers the best combination high strength-to-weight ratio, low cost design flexibility, good toughness, wear resistance along with fatigue strength. The two step austempering procedure helps in simultaneously improving the tensile strength as-well as the ductility to more than that of the conventional austempering process. Extensive literature survey reveals that it’s mechanical and wear behaviour are dependent on heat treatment and alloy additions. Current work focuses on characterizing the two-step ADI samples (TSADI) developed by novel heat treatment process for resistance to corrosion and wear. The samples of Ductile Iron were austempered by the two-Step Austempering process at temperatures 300°C to 450°C in the steps of 50°C.Temperaturesare gradually increased at the rate of 14°C/Hour. In acidic medium (H2SO4), the austempered samples showed better corrosive resistance compared to conventional ductile iron. It has been observed from the wear studies that TSADI sample at 350°C is showing better wear resistance compared to ductile iron. The results are discussed in terms of fractographs, process variables and microstructural features of TSADI samples.

Microstructure and wear resistance of laser cladded Ni-Cr-Co-Ti-V high-entropy alloy coating after laser remelting processing

NASA Astrophysics Data System (ADS)

Cai, Zhaobing; Cui, Xiufang; Liu, Zhe; Li, Yang; Dong, Meiling; Jin, Guo

2018-02-01

An attempt, combined with the technologies of laser cladding and laser remelting, has been made to develop a Ni-Cr-Co-Ti-V high entropy alloy coating. The phase composition, microstructure, micro-hardness and wear resistance (rolling friction) were studied in detail. The results show that after laser remelting, the phase composition remains unchanged, that is, as-cladded coating and as-remelted coatings are all composed of (Ni, Co)Ti2 intermetallic compound, Ti-rich phase and BCC solid solution phase. However, after laser remelting, the volume fraction of Ti-rich phase increases significantly. Moreover, the micro-hardness is increased, up to ∼900 HV at the laser remelting parameters: laser power of 1 kW, laser spot diameter of 3 mm, and laser speed of 10 mm/s. Compared to the as-cladded high-entropy alloy coating, the as-remelted high-entropy alloy coatings have high friction coefficient and low wear mass loss, indicating that the wear resistance of as-remelted coatings is improved and suggesting practical applications, like coatings on brake pads for wear protection. The worn surface morphologies show that the worn mechanism of as-cladded and as-remelted high-entropy alloy coatings are adhesive wear.

The effect of firefighter protective garments, self-contained breathing apparatus and exertion in the heat on postural sway.

PubMed

White, Scott C; Hostler, David

2017-08-01

Fire suppression wearing thermal protective clothing (TPC) and self-contained breathing apparatus (SCBA) challenges a firefighter's balance and may explain firefighter falls. Postural control based on force plate centre of pressure (COP) was compared for healthy subjects wearing TPC and SCBA before and after 20 min of heavy physical exertion in hot conditions. Baseline measures with and without TPC and SCBA (two different SCBA cylinder masses) were compared before and after exertion that included elements of fire suppression activities in an environmental chamber. COP excursion and variability increased with exertion for TPC and SCBA conditions compared to non-stressed conditions. The two different cylinder masses had no significant effect. Wearing TPC and SCBA when physically stressed in a hot environment increases postural sway and exacerbates postural control. Subjects compensated for the extra mass and adjusted to control postural sway with the addition of TPC and SCBA, but the stress protocol amplified these adjustments. Practitioner Summary: Firefighters wear thermal protective clothing (TPC) and self-contained breathing apparatus (SCBA) when heat-stressed and fatigued. Wearing TPC and SCBA was found to negatively impact balance when stressed, but not for non-stressed or two different sized SCBA tanks. Simulating fire-ground conditions wearing TPC and SCBA should be considered for improving balance.

Influence of Ultrasonic Surface Rolling on Microstructure and Wear Behavior of Selective Laser Melted Ti-6Al-4V Alloy

PubMed Central

Wang, Zhen; Xiao, Zhiyu; Huang, Chuanshou; Wen, Liping; Zhang, Weiwen

2017-01-01

The present article studied the effect of ultrasonic surface rolling process (USRP) on the microstructure and wear behavior of a selective laser melted Ti-6Al-4V alloy. Surface characteristics were investigated using optical microscope, nano-indentation, scanning electron microscope, transmission electron microscope and laser scanning confocal microscope. Results indicated that the thickness of pore-free surfaces increased to 100~200 μm with the increasing ultrasonic surface rolling numbers. Severe work hardening occurred in the densified layer, resulting in the formation of refined grains, dislocation walls and deformation twins. After 1000 N 6 passes, about 15.5% and 14.1% increment in surficial Nano-hardness and Vickers-hardness was obtained, respectively. The hardness decreased gradually from the top surface to the substrate. Wear tests revealed that the friction coefficient declined from 0.74 (polished surface) to 0.64 (USRP treated surface) and the wear volume reduced from 0.205 mm−3 to 0.195 mm−3. The difference in wear volume between USRP treated and polished samples increased with sliding time. The enhanced wear resistance was concluded to be associated with the improvement of hardness and shear resistance and also the inhibition of delamination initiation. PMID:29048344

Hydroxyapatite-nanotube composites and coatings for orthopedic applications

NASA Astrophysics Data System (ADS)

Lahiri, Debrupa

Hydroxyapatite (HA) has received wide attention in orthopedics, due to its biocompatibility and osseointegration ability. Despite these advantages, the brittle nature and low fracture toughness of HA often results in rapid wear and premature fracture of implant. Hence, there is a need to improve the fracture toughness and wear resistance of HA without compromising its biocompatibility. The aim of the current research is to explore the potential of nanotubes as reinforcement to HA for orthopedic implants. HA- 4 wt.% carbon nanotube (CNT) composites and coatings are synthesized by spark plasma sintering and plasma spraying respectively, and investigated for their mechanical, tribological and biological behavior. CNT reinforcement improves the fracture toughness (>90%) and wear resistance (>66%) of HA for coating and free standing composites. CNTs have demonstrated a positive influence on the proliferation, differentiation and matrix mineralization activities of osteoblasts, during in-vitro biocompatibility studies. In-vivo exposure of HA-CNT coated titanium implant in animal model (rat) shows excellent histocompatibility and neobone integration on the implant surface. The improved osseointegration due to presence of CNTs in HA is quantified by the adhesion strength measurement of single osteoblast using nano-scratch technique. Considering the ongoing debate about cytotoxicity of CNTs in the literature, the present study also suggests boron nitride nanotube (BNNT) as an alternative reinforcement. BNNT with the similar elastic modulus and strength as CNT, were added to HA. The resulting composite having 4 wt.% BNNTs improved the fracture toughness (˜85%) and wear resistance (˜75%) of HA in the similar range as HA-CNT composites. BNNTs were found to be non-cytotoxic for osteoblasts and macrophages. In-vitro evaluation shows positive role of BNNT in osteoblast proliferation and viability. Apatite formability of BNNT surface in ˜4 days establishes its osseointegration ability.

In-Service Evaluation of HVOF Coated Main Landing Gear on Navy P-3 Aircraft

NASA Technical Reports Server (NTRS)

Devereaux, jon L.; Forrest, Clint

2008-01-01

Due to the environmental and health concerns with Electroplated Hard Chrome (EHC), the Hard Chrome Alternatives Team (HCAT) has been working to provide an alternative wear coating for EHC. The US Navy selected Tungsten-Carbide Cobalt (WC- 17Co) High Velocity Oxy-Fuel (HVOF) thermal spray coating for this purpose and completed service evaluations on select aircraft components to support the HCAT charter in identifying an alternative wear coating for chrome plating. Other benefits of WC-Co thermal spray coatings over EHC are enhanced corrosion resistance, improved durability, and exceptional wear properties. As part of the HCAT charter and to evaluate HVOF coatings on operational Navy components, the P-3 aircraft was selected for a service evaluation to determine the coating durability as compared to chrome plating. In April 1999, a VP-30 P-3 aircraft was outfitted with a right-hand Main Landing Gear (MLG) shock strut coated with WCCo HYOF thermal spray applied to the piston barrel and four axle journals. The HVOF coating on the piston barrel and axle journals was applied by Southwest United Industries, Inc. This HVOF coated strut assembly has since completed 6,378 landings. Teardown analysis .for this WC-Co HVOF coated MLG asset is significant in assessing the durability of this wear coating in service relative to EHC and to substantiate Life Cycle Cost (LCC) data to support a retrograde transition from EHC to HVOF thermal spray coatings. Findings from this teardown analysis may also benefit future transitions to HVOF thermal spray coatings by identifying enhancements to finishing techniques, mating bearing and liner material improvements, improved seal materials, and improvements in HVOF coating selection.

Design of improved ceramic/polymeric composites

NASA Astrophysics Data System (ADS)

Seghi, Steven Monte

This thesis describes an optimized approach for fabrication of boron nitride matrix composites reinforced with carbon fibers. The boron nitride was introduced via liquid infiltration of borazine oligomer to obtain high density (rho ˜ 1.75g/cc) composites and d002 spacings of 3.35A, which afforded excellent hydrolytic stability. The friction and wear properties were explored using an inertial dynamometer for potential replacement of current C/C in aircraft brakes. One set of tested composites provided outstanding wear resistance, incurring nearly zero wear across the entire range tested. In contrast to C/C, the coefficient of friction (COF) was relatively stable with respect to energy level, varying only 0.2 to 0.3. The wear surface morphologies were examined and it was found that low volume BN composites wore by a mechanism similar to C/C. The wear rates were controlled by the formation of a friction film from the wear debris. In the case of BN composites, this film incurred wear via an abrasive and brittle fracture mechanism while C/C exhibited only abrasive wear. As the BN content increased, a film still formed from the debris but large particles of BN emerged that limited direct contact of the surfaces thus effectively eliminating abrasive wear so the underlying film wore via brittle fracture. The removed wear debris was easily reincorporated into the film, with the suspected aid of boron oxide, thus keeping the wear rates low. The last chapter deals with the design, fabrication, and evaluation of a new coupling agent for glass fiber/epoxy matrix composites. This interface consisted of a thin coating of activated carbon (ACI) with high surface area to take advantage of mechanical interlocking. Furthermore, the surface chemistry was modified to provide varying degrees of bonding to the resin. These ACI provided equivalent moduli when compared to similar composites using commercial coupling agents. Hygrothermal aging showed the basic surface chemistry ACI to be extremely resistant to mechanical property degradation. The ACI systems displayed two distinct failure modes, fiber/matrix fracture and fiber debonding, controlled by the interface strength and thus the surface chemistry. These different failure modes led to a damage evolution study via thermoelastic stress analysis.

Effects of crystal refining on wear behaviors and mechanical properties of lithium disilicate glass-ceramics.

PubMed

Zhang, Zhenzhen; Guo, Jiawen; Sun, Yali; Tian, Beimin; Zheng, Xiaojuan; Zhou, Ming; He, Lin; Zhang, Shaofeng

2018-05-01

The purpose of this study is to improve wear resistance and mechanical properties of lithium disilicate glass-ceramics by refining their crystal sizes. After lithium disilicate glass-ceramics (LD) were melted to form precursory glass blocks, bar (N = 40, n = 10) and plate (N = 32, n = 8) specimens were prepared. According to the differential scanning calorimetry (DSC) of precursory glass, specimens G1-G4 were designed to form lithium disilicate glass-ceramics with different crystal sizes using a two-step thermal treatment. In the meantime, heat-pressed lithium disilicate glass-ceramics (GC-P) and original ingots (GC-O) were used as control groups. Glass-ceramics were characterized using X-ray diffraction (XRD) and were tested using flexural strength test, nanoindentation test and toughness measurements. The plate specimens were dynamically loaded in a chewing simulator with 350 N up to 2.4 × 10 6 loading cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 300,000 wear cycles. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pairwise comparisons of means were performed by Tukey's post-hoc test. Materials with different crystal sizes (p < 0.05) exhibited different properties. Specifically, G3 with medium-sized crystals presented the highest flexural strength, hardness, elastic modulus and fracture toughness. G1 and G2 with small-sized crystals showed lower flexural strength, whereas G4, GC-P, and GC-O with large-sized crystals exhibited lower hardness and elastic modulus. The wear behaviors of all six groups showed running-in wear stage and steady wear stage. G3 showed the best wear resistance while GC-P and GC-O exhibited the highest wear volume loss. After crystal refining, lithium disilicate glass-ceramic with medium-sized crystals showed the highest wear resistance and mechanical properties. Copyright © 2018 Elsevier Ltd. All rights reserved.

Wear in Fluid Power Systems.

DTIC Science & Technology

1979-11-30

the detection and analysis of this wear is extremely important. In this study, it was determined that ferrography is an effective tool for this...dealt with the practical applications of ferrography to fluid power systems. The first two phases were investigations of the life improvements of...damning evidence that ferrography is not the beneficial tool it was originally thought to be. However, a further analysis of the entire program and the

Materials as additives for advanced lubrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pol, Vilas G.; Thackeray, Michael M.; Mistry, Kuldeep

This invention relates to carbon-based materials as anti-friction and anti-wear additives for advanced lubrication purposes. The materials comprise carbon nanotubes suspended in a liquid hydrocarbon carrier. Optionally, the compositions further comprise a surfactant (e.g., to aid in dispersion of the carbon particles). Specifically, the novel lubricants have the ability to significantly lower friction and wear, which translates into improved fuel economies and longer durability of mechanical devices and engines.

Comparative Analysis of Cutting Efficiency and Surface Maintenance Between Different Types of Implant Drills: An In Vitro Study.

PubMed

Hochscheidt, Celso João; Shimizu, Roberto Hideo; Andrighetto, Augusto Ricardo; Pierezan, Rodrigo; Thomé, Geninho; Salatti, Rafael

2017-10-01

This study evaluated cutting efficiency (CE) and linear wear of dental implant drills after 450 standardized osteotomies on bovine ribs. Diamond-like carbon-coated steel drills (SG), acid-treated steel drills (EG), and ceramic drills (ZG) were divided into 6 subgroups according to the number of uses. A robot-controlled program performed systematic instrumentation, timing, axial loading, and managed feed rate. CE was recorded in a polyurethane resin blank and end wear (VBBmax) was analyzed under stereo microscopy. After osteotomies in beef ribs, CE for the Ø2.0-mm drill decreased 10.2% in SG and 10.9% in ZG; for the Ø3.0-mm drill, CE decreased 30.6% in SG, 8.5% in ZG, and improved in EG. The greatest wear occurred in Ø2.0-mm drills; ZG drills (Ø3.0 mm) exhibited only edge frittering, as confirmed on scanning electron microscopy. After 50 exposures to mechanical loads, steel and ceramic drills lost CE. Whereas cutting and thermal performance improved in experimental drills, the Ø2.0-mm drill exhibited the most signs of wear proportional to use. These findings suggest that, with the methodology employed, the life of these drills exceeds 50 osteotomies.

Enhancing Corrosion and Wear Resistance of AA6061 by Friction Stir Processing with Fe78Si9B13 Glass Particles

PubMed Central

Guo, Lingyu; Liu, Yan; Shen, Kechang; Song, Chaoqun; Yang, Min; Kim, Kibuem; Wang, Weimin

2015-01-01

The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix. The XRD results indicated that the lattice parameter of α-Al increases and the preferred orientation factors F of (200) plane of α-Al reduces after friction stir processing. The coefficient of thermal expansion (CTE) for FSP samples increases at first with the temperature but then decreases as the temperature further increased, which can be explained by the dissolving of Mg and Si from β phase and Fe78Si9B13 particles. The corrosion and wear resistance of FSP samples have been improved compared with that of base metal, which can be attributed to the reduction of grain size and the CTE mismatch between the base metal and reinforced particles by FSP, and the lubrication effect of Fe78Si9B13 particles also plays a role in improving wear resistance. In particular, the FSP sample with reinforced particles in amorphous state exhibited superior corrosion and wear resistance due to the unique metastable structure. PMID:28793492

Investigation of surface finishing of carbon based coated tools for dry deep drawing of aluminium alloys

NASA Astrophysics Data System (ADS)

Steiner, J.; Andreas, K.; Merklein, M.

2016-11-01

Global trends like growing environmental awareness and demand for resource efficiency motivate an abandonment of lubricants in metal forming. However, dry forming evokes increased friction and wear. Especially, dry deep drawing of aluminum alloys leads to intensive interaction between tool and workpiece due to its high adhesion tendency. One approach to improve the tribological behavior is the application of carbon based coatings. These coatings are characterized by high wear resistance. In order to investigate the potential of carbon based coatings for dry deep drawing, friction and wear behavior of different coating compositions are evaluated in strip drawing tests. This setup is used to model the tribological conditions in the flange area of deep drawing operations. The tribological behavior of tetrahedral amorphous (ta-C) and hydrogenated amorphous carbon coatings with and without tungsten modification (a-C:H:W, a-C:H) is investigated. The influence of tool topography is analyzed by applying different surface finishing. The results show reduced friction with decreased roughness for coated tools. Besides tool topography the coating type determines the tribological conditions. Smooth tools with ta-C and a-C:H coatings reveal low friction and prevent adhesive wear. In contrast, smooth a-C:H:W coated tools only lead to slight improvement compared to rough, uncoated specimen.

Micro-Abrasion Wear Resistance of Borided 316L Stainless Steel and AISI 1018 Steel

NASA Astrophysics Data System (ADS)

Reséndiz-Calderon, C. D.; Rodríguez-Castro, G. A.; Meneses-Amador, A.; Campos-Silva, I. E.; Andraca-Adame, J.; Palomar-Pardavé, M. E.; Gallardo-Hernández, E. A.

2017-11-01

The 316L stainless steel has high corrosion resistance but low tribological performance. In different industrial sectors (biomedical, chemical, petrochemical, and nuclear engineering), improvement upon wear resistance of 316L stainless steel components using accessible and inexpensive methods is critical. The AISI 1018 steel is widely used in industry, but its tribological performance is not the best among steels. Therefore, in this study the behavior of the borided 316L stainless steel and 1018 steel is evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over 6 h of exposure time, resulting in a biphase layer composed of FeB/Fe2B phases. In order to evaluate Fe2B phase with no influence from FeB phase, AISI 1018 steel samples were borided at 1273 K for over 20 min and then diffusion annealed at 1273 K over 2 h to obtain a Fe2B mono-phase layer. Micro-abrasion wear resistance was evaluated by a commercial micro-abrasion testing rig using a mix of F-1200 SiC particles with deionized water as abrasive slurry. The obtained wear rates for FeB and Fe2B phases and for the 316L stainless steel were compared. Wear resistance of 316L stainless steel increases after boriding. The wear mechanisms for both phases and for the stainless steel were identified. Also, transient conditions for rolling and grooving abrasion were determined for the FeB and Fe2B phases.

Effect of structure on the tribology of ultrathin graphene and graphene oxide films.

PubMed

Chen, Hang; Filleter, Tobin

2015-03-27

The friction and wear properties of graphene and graphene oxide (GO) with varying C/O ratio were investigated using friction force microscopy. When applied as solid lubricants between a sliding contact of a silicon (Si) tip and a SiO2/Si substrate, graphene and ultrathin GO films (as thin as 1-2 atomic layers) were found to reduce friction by ∼6 times and ∼2 times respectively as compared to the unlubricated contact. The differences in measured friction were attributed to different interfacial shear strengths. Ultrathin films of GO with a low C/O ratio of ∼2 were found to wear easily under small normal load. The onset of wear, and the location of wear initiation, is attributed to differences in the local shear strength of the sliding interface as a result of the non-homogeneous surface structure of GO. While the exhibited low friction of GO as compared to SiO2 makes it an economically viable coating for micro/nano-electro-mechanical systems with the potential to extend the lifetime of devices, its higher propensity for wear may limit its usefulness. To address this limitation, the wear resistance of GO samples with a higher C/O ratio (∼4) was also studied. The higher C/O ratio GO was found to exhibit much improved wear resistance which approached that of the graphene samples. This demonstrates the potential of tailoring the structure of GO to achieve graphene-like tribological properties.

Randomized trial of the effect of contact lens wear on self-perception in children.

PubMed

Walline, Jeffrey J; Jones, Lisa A; Sinnott, Loraine; Chitkara, Monica; Coffey, Bradley; Jackson, John Mark; Manny, Ruth E; Rah, Marjorie J; Prinstein, Mitchell J

2009-03-01

To determine whether contact lens wear affects children's self-perceptions. The Adolescent and Child Health Initiative to Encourage Vision Empowerment Study was a randomized, single-masked trial conducted at five clinical centers in the United States. Subjects were 8- to 11-year-old myopic children randomly assigned to wear spectacles (n = 237) or soft contact lenses (n = 247) for 3 years. The primary endpoint was the Self-Perception Profile for Children Global Self-Worth scale. Secondary outcomes included the Physical Appearance, Athletic Competence, Scholastic Competence, Behavioral Conduct, and Social Acceptance Self-Perception Profile for Children scales. Global self-worth was not affected by contact lens wear [analysis of variance (ANOVA), difference = 0.06; 95% CI, -0.004 to 0.117]. Physical appearance (ANOVA, difference = 0.15; 95% CI, 0.07 to 0.22), athletic competence (ANOVA, difference = 0.08; 95% CI, 0.01 to 0.15), and social acceptance (ANOVA, difference = 0.10; 95% CI, 0.03 to 0.17) were all greater for contact lens wearers. Although contact lens wear does not affect global self-perceptions of 8- to 11-year-old myopic children their physical appearance, athletic competence, and social acceptance self-perceptions are likely to improve with contact lens wear. Eye care practitioners should consider the social and visual benefits of contact lens wear when choosing the most appropriate vision correction modality for children as young as 8 years of age.

Clinical study of the influence of preoperative wearing time on postoperative effects in children with partially accommodative esotropia.

PubMed

Jiang, Danni; Han, Dong; Zhang, Jiahuan; Pei, Tianxu; Zhao, Qi

2018-05-01

The aim of this study was to evaluate the influence of the preoperative wearing time on the postoperative effect in children with partially accommodative esotropia.Sixty children with partially accommodative esotropia who visited our hospital were placed in full cycloplegic refraction by using 1% Atropine eye gel and then wore full hyperopic correction glasses. Children were divided into groups A and B according to the preoperative wearing time. The visual acuity, eye position, and results of the synoptophore and Titmus stereoacuity tests were recorded before and half a year after the surgery in each group, and appropriate statistical analyses were conducted.Half a year after the operation, 54 cases achieved orthotropia when wearing full hyperopic correction glasses. One case was overcorrected. Five cases were undercorrected. The results of the synoptophore and Titmus stereoacuity test showed that there was no significant difference between postoperative outcomes for patients who wore glasses for half a year and for 1 year before the operation.For children with partially accommodative esotropia, surgery should be used to correct the eye position after wearing full hyperopic correction glasses for half a year to improve the eye position and binocular vision as early as possible. If the operation cannot be completed after the patient wears full hyperopic correction glasses for half a year due to various subjective and objective factors, a good postoperative effect can be obtained if the patients receive surgery after wearing full hyperopic correction glasses for 1 year.

Dynamic and wear study of an extremely bidisperse magnetorheological fluid

NASA Astrophysics Data System (ADS)

Iglesias, G. R.; Fernández Ruiz-Morón, L.; Durán, J. D. G.; Delgado, A. V.

2015-12-01

In this work the friction and wear properties of five magnetorheological fluids (MRFs) with varying compositions are investigated. Considering that many of the proposed applications for these fluids involve lubricated contact between mobile metal-metal or polymer-metal parts, the relationship between MR response and wear behavior appears to be of fundamental importance. One of the fluids (MR#1) contains only the iron microparticles and base oil; the second and third ones (MR#2 and MR#3) contain an anti-wear additive as well. The fourth one (MR#4) is a well known commercial MRF. Finally, MR#5 is stabilized by dispersing the iron particles in a magnetite ferrofluid. The MR response of the latter fluid is better (higher yield stress and post-yield viscosity) than that of the others. More importantly, it remains (and even improves) after the wear test: the pressure applied in the four-ball apparatus produces a compaction of the magnetite layer around the iron microparticles. Additionally, the friction coefficient is larger, which seems paradoxical in principle, but can be explained by considering the stability of MR#5 in comparison to the other four MRs, which appear to undergo partial phase separation during the test. In fact, electron and optical microscope observations confirm a milder wear effect of MR#5, with almost complete absence of scars from the steel test spheres and homogeneous and shallow grooves on them. Comparatively, MR#2, MR#3 and, particularly, MR#1 produce a much more significant wear.

Experimental Evaluation and Optimization of Flank Wear During Turning of AISI 4340 Steel with Coated Carbide Inserts Using Different Cutting Fluids

NASA Astrophysics Data System (ADS)

Lawal, S. A.; Choudhury, I. A.; Nukman, Y.

2015-01-01

The understanding of cutting fluids performance in turning process is very important in order to improve the efficiency of the process. This efficiency can be determined based on certain process parameters such as flank wear, cutting forces developed, temperature developed at the tool chip interface, surface roughness on the work piece, etc. In this study, the objective is to determine the influence of cutting fluids on flank wear during turning of AISI 4340 with coated carbide inserts. The performances of three types of cutting fluids were compared using Taguchi experimental method. The results show that palm kernel oil based cutting fluids performed better than the other two cutting fluids in reducing flank wear. Mathematical models for cutting parameters such as cutting speed, feed rate, depth of cut and cutting fluids were obtained from regression analysis using MINITAB 14 software to predict flank wear. Experiments were conducted based on the optimized values to validate the regression equations for flank wear and 5.82 % error was obtained. The optimal cutting parameters for the flank wear using S/N ratio were 160 m/min of cutting speed (level 1), 0.18 mm/rev of feed (level 1), 1.75 mm of depth of cut (level 2) and 2.97 mm2/s palm kernel oil based cutting fluid (level 3). ANOVA shows cutting speed of 85.36 %; and feed rate 4.81 %) as significant factors.

Effect of microstructure of superalloy guide plate on its surface wear resistance

NASA Astrophysics Data System (ADS)

Zhou, Jianbo; Zhang, Xizhen

2018-03-01

The microstructure had been observed for guide plate, the guide plate be made of casting for groove controlling of hot rolled seamless tube, be produced for the production of 1600 seamless steel pipe,which cause obvious surface deformation and can not be normally produced. The alloy elements in matrix and precipitate phase of the guide plate were analyzed with the help of EDS. The results show that the wear resistance of the guide plate is directly affected by the fact that the guide plate is unable to form typical carbides, it shows that the formation of typical carbide strengthening plays an important role in improving the surface wear resistance of the guide plate.

Coatings for wear and lubrication

NASA Technical Reports Server (NTRS)

Spalvins, T.

1978-01-01

Recent advances in the tribological uses of rf-sputtered and ion plated films of solid film lubricants (laminar solids, soft metals, organic polymers) and wear resistant refractory compounds (carbides, nitrides, silicides) are reviewed. The sputtering and ion plating potentials and the corresponding coatings formed were evaluated relative to the friction coefficient, wear endurance life and mechanical properties. The tribological and mechanical properties for each kind of film are discussed in terms of film adherence, coherence, density, grain size, morphology, internal stresses, thickness, and substrate conditions such as temperature, topography, chemistry and dc-biasing. The ion plated metallic films in addition to improved tribological properties also have better mechanical properties such as tensile strength and fatigue life.

Effects of Synchronous Rolling on Microstructure, Hardness, and Wear Resistance of Laser Multilayer Cladding

NASA Astrophysics Data System (ADS)

Zhao, W.; Zha, G. C.; Xi, M. Z.; Gao, S. Y.

2018-03-01

A synchronous rolling method was proposed to assist laser multilayer cladding, and the effects of this method on microstructure, microhardness, and wear resistance were studied. Results show that the microstructure and mechanical properties of the traditional cladding layer exhibit periodic inhomogeneity. Synchronous rolling breaks the columnar dendrite crystals to improve the uniformity of the organization, and the residual plastic energy promotes the precipitation of strengthening phases, as CrB, M7C3, etc. The hardness and wear resistance of the extruded cladding layer increase significantly because of the grain refinement, formation of dislocations, and dispersion strengthening. These positive significances of synchronous rolling provide a new direction for laser cladding technology.

Investigation of Wear and Corrosion of a High-Carbon Stellite Alloy for Hip Implants

NASA Astrophysics Data System (ADS)

Hu, P. S.; Liu, R.; Liu, J.; McRae, G.

2014-04-01

Low-carbon Stellite 21 has been used as hip implant material for a number of decades; however, its limited metal-on-metal bearing has resulted in loosening between the femoral head and the acetabular cup of hip implants. In order to improve the metal-on-metal bearing, it is proposed that a high-carbon alloy, Stellite 720, surface coating be applied on Stellite 21 hip implants to improve mechanical and tribological performance. For this coating to be practical, it must also meet the requirements of corrosion resistance for orthopedic implant materials. In this research, Stellite 720 is investigated with pin-on-disk wear tests, and electrochemical and immersion corrosion tests in simulated human body fluid (Hank's solution; pH 7.4 at temperature of 37°C). The experimental results demonstrate that Stellite 720 exhibits much better wear resistance than Stellite 21, and has the potential for better corrosion resistance as well. The applicability of coating Stellite 21 hip implants with Stellite 720 is discussed.

Compliance with removable orthodontic appliances.

PubMed

Shah, Nirmal

2017-12-22

Data sourcesMedline via OVID, PubMed, Cochrane Central Register of Controlled Trials, Web of Science Core Collection, LILACS and BBO databases. Unpublished clinical trials accessed using ClinicalTrials.gov, National Research Register, ProQuest Dissertation and Thesis database.Study selectionTwo authors searched studies from inception until May 2016 without language restrictions. Quantitative and qualitative studies incorporating objective data on compliance with removable appliances, barriers to appliance wear compliance, and interventions to improve compliance were included.Data extraction and synthesisQuality of research was assessed using the Cochrane Collaboration's risk of bias tool, the risk of bias in non-randomised studies of interventions (ROBINS-I), and the mixed methods appraisal tool. Statistical heterogeneity was investigated by examining a graphic display of the estimated compliance levels in conjunction with 95% confidence intervals and quantified using the I-squared statistic. A weighted estimate of objective compliance levels for different appliances in relation to stipulated wear and self-reported levels was also calculated. Risk of publication bias was assessed using funnel plots. Meta-regression was undertaken to assess the relative effects of appliance type on compliance levels.ResultsTwenty-four studies met the inclusion criteria. Of these, 11 were included in the quantitative synthesis. The mean duration of objectively measured wear was considerably lower than stipulated wear time amongst all appliances. Headgear had the greatest discrepancy (5.81 hours, 95% confidence interval, 4.98, 6.64). Self-reported wear time was consistently higher than objectively measured wear time amongst all appliances. Headgear had the greatest discrepancy (5.02 hours, 95% confidence interval, 3.64, 6.40). Two studies found an increase in compliance with headgear and Hawley retainers when patients were aware of monitoring. Five studies found younger age groups to be more compliant than older groups. Three studies also found compliance to be better in the early stages of treatment. Integration between quantitative and qualitative studies was not possible.ConclusionsCompliance with removable orthodontic appliances is suboptimal. Patients wear appliances for considerably less time than stipulated and self-reported. Compliance may be increased when patients are aware of monitoring; however, further research is required to identify effective interventions and possible barriers in order to improve removable orthodontic appliance compliance.

Effect of triangular texture on the tribological performance of die steel with TiN coatings under lubricated sliding condition

NASA Astrophysics Data System (ADS)

Chen, Ping; Xiang, Xin; Shao, Tianmin; La, Yingqian; Li, Junling

2016-12-01

The friction and wear of stamping die surface can affect the service life of stamping die and the quality of stamping products. Surface texturing and surface coating have been widely used to improve the tribological performance of mechanical components. This study experimentally investigated the effect of triangular surface texture on the friction and wear properties of the die steel substrate with TiN coatings under oil lubrication. TiN coatings were deposited on a die steel (50Cr) substrate through a multi-arc ion deposition system, and then triangular surface texturing was fabricated by a laser surface texturing. The friction and wear test was conducted by a UMT-3 pin-on-disk tribometer under different sliding speeds and different applied loads, respectively. The adhesion test was performed to evaluate the effectiveness of triangular texturing on the interfacial bonding strength between the TiN coating and the die steel substrate. Results show that the combination method of surface texturing process and surface coating process has excellent tribological properties (the lowest frictional coefficient and wear volume), compared with the single texturing process or the single coating process. The tribological performance is improved resulting from the high hardness and low elastic modulus of TiN coatings, and the generation of hydrodynamic pressure, function of micro-trap for wear debris and micro-reservoirs for lubricating oil of the triangular surface texture. In addition, the coating bonding strength of the texturing sample is 3.63 MPa, higher than that of the single coating sample (3.48 MPa), but the mechanisms remain to be further researched.

Modeling and Investigation of the Wear Resistance of Salt Bath Nitrided Aisi 4140 via ANN

NASA Astrophysics Data System (ADS)

Ekinci, Şerafettin; Akdemir, Ahmet; Kahramanli, Humar

2013-05-01

Nitriding is usually used to improve the surface properties of steel materials. In this way, the wear resistance of steels is improved. We conducted a series of studies in order to investigate the microstructural, mechanical and tribological properties of salt bath nitrided AISI 4140 steel. The present study has two parts. For the first phase, the tribological behavior of the AISI 4140 steel which was nitrided in sulfinuz salt bath (SBN) was compared to the behavior of the same steel which was untreated. After surface characterization using metallography, microhardness and sliding wear tests were performed on a block-on-cylinder machine in which carbonized AISI 52100 steel discs were used as the counter face. For the examined AISI 4140 steel samples with and without surface treatment, the evolution of both the friction coefficient and of the wear behavior were determined under various loads, at different sliding velocities and a total sliding distance of 1000 m. The test results showed that wear resistance increased with the nitriding process, friction coefficient decreased due to the sulfur in salt bath and friction coefficient depended systematically on surface hardness. For the second part of this study, four artificial neural network (ANN) models were designed to predict the weight loss and friction coefficient of the nitrided and unnitrided AISI 4140 steel. Load, velocity and sliding distance were used as input. Back-propagation algorithm was chosen for training the ANN. Statistical measurements of R2, MAE and RMSE were employed to evaluate the success of the systems. The results showed that all the systems produced successful results.

Scratch and wear behaviour of plasma sprayed nano ceramics bilayer Al2O3-13 wt%TiO2/hydroxyapatite coated on medical grade titanium substrates in SBF environment

NASA Astrophysics Data System (ADS)

Palanivelu, R.; Ruban Kumar, A.

2014-10-01

Among the various coating techniques, plasma spray coating is an efficient technique to protect the metal surface from the various surface problems like wear and corrosion. The aim of this present work is to design and produce a bilayer coating on the non- toxic commercially pure titanium (denoted as CP-Ti) implant substrate in order to improve the biocompatibility and surface properties. To achieve that, Al2O3-13 wt%TiO2 (AT13) and hydroxyapatite (HAP) were coated on CP-Ti implant substrate using plasma spray coating technique. Further, the coated substrates were subjected to various characterization techniques. The crystallite size of coated HAP and its morphological studies were carried out using X-ray diffractometer (XRD) and scanning electron microscopy (SEM) respectively. The wear test on the bilayer (AT13/HAP) coated CP-Ti implant surface was conducted using ball-on-disc tester under SBF environment at 37 °C, in order to determine the wear rate and the coefficient of friction. The adhesion strength of the bilayer coated surface was evaluated by micro scratch tester under the ramp load conditions with load range of 14-20 N. The above said studies were repeated on the single layer coated HAP and AT13 implant surfaces. The results reveal that the bilayer (AT13/HAP) coated CP-Ti surface has the improved wear rate, coefficient of friction in compared to single layer coated HAP and AT13 surfaces.

Tribological investigation of novel HDPE-HAp-Al2O3 hybrid biocomposites against steel under dry and simulated body fluid condition.

PubMed

Nath, Shekhar; Bodhak, Subhadip; Basu, Bikramjit

2007-10-01

Among various biocompatible polymers, polyethylene based materials have received wider attention because of its excellent stability in body fluid, inertness, and easy formability. Attempts have been made to improve their physical properties (modulus/strength) to enable them to be used as load bearing hard tissue replacement applications. Among such attempts, high density polyethylene (HDPE)-hydroxyapatite (HAp) composite (HAPEX), has already been developed for total hip replacement (THR) acetabular cup and low load bearing bone tissue replacement. In the present work, alumina has been added as a partial replacement of HAp phase to improve the mechanical and tribological properties of the HAPEX composite. In an attempt to assess the suitability of the developed composite in THR application, the tribological properties against steel counterbody under both in air and simulated body fluid (SBF), have been investigated and efforts have been made to understand the wear mechanisms. The fretting wear study indicates the possibility of achieving extremely low COF (Coefficient of Friction approximately 0.09) as well as higher wear resistance (order of 10(-6) mm(3)/N m) with the newly developed composites in SBF. A low wear depth of approximately 4.6-5.3 microm is recorded, irrespective of fretting environment. The implication of the work is that optimal and combined addition of bioactive and bioinert ceramic filler to HDPE can provide a good opportunity to obtain hybrid biocomposites with better combination of physical properties (modulus, hardness) as well as low friction and high wear resistance.

Energy and wear optimisation of train longitudinal dynamics and of traction and braking systems

NASA Astrophysics Data System (ADS)

Conti, R.; Galardi, E.; Meli, E.; Nocciolini, D.; Pugi, L.; Rindi, A.

2015-05-01

Traction and braking systems deeply affect longitudinal train dynamics, especially when an extensive blending phase among different pneumatic, electric and magnetic devices is required. The energy and wear optimisation of longitudinal vehicle dynamics has a crucial economic impact and involves several engineering problems such as wear of braking friction components, energy efficiency, thermal load on components, level of safety under degraded or adhesion conditions (often constrained by the current regulation in force on signalling or other safety-related subsystem). In fact, the application of energy storage systems can lead to an efficiency improvement of at least 10% while, as regards the wear reduction, the improvement due to distributed traction systems and to optimised traction devices can be quantified in about 50%. In this work, an innovative integrated procedure is proposed by the authors to optimise longitudinal train dynamics and traction and braking manoeuvres in terms of both energy and wear. The new approach has been applied to existing test cases and validated with experimental data provided by Breda and, for some components and their homologation process, the results of experimental activities derive from cooperation performed with relevant industrial partners such as Trenitalia and Italcertifer. In particular, simulation results are referred to the simulation tests performed on a high-speed train (Ansaldo Breda Emu V250) and on a tram (Ansaldo Breda Sirio Tram). The proposed approach is based on a modular simulation platform in which the sub-models corresponding to different subsystems can be easily customised, depending on the considered application, on the availability of technical data and on the homologation process of different components.

Effects of working gas pressure on zirconium dioxide thin film prepared by pulsed plasma deposition: roughness, wettability, friction and wear characteristics.

PubMed

Berni, M; Marchiori, G; Gambardella, A; Boi, M; Bianchi, M; Russo, A; Visani, A; Marcacci, M; Pavan, P G; Lopomo, N F

2017-08-01

In joint arthroplasty one of the main issues related to the failure of prosthetic implants is due to the wear of the ultra-high molecular weight polyethylene (UHMWPE) component. Surface treatments and coatings have been recognized as enhancing methods, able to improve the tribological properties of the implants. Therefore, the main objective of this work was to investigate the possibility to fabricate yttria-stabilized zirconia (YSZ) coatings on a metal (AISI 316-L) substrate by means of Pulsed Electron Deposition, in order to improve the tribological behavior of the polymer-metal coupling, by reducing the initial wear of the UHMWPE component. In order to optimize the coating characteristics, the effects of working gas pressure on both its morphological and tribological properties were analyzed. Morphological characterization of the films was evaluated by Atomic Force Microscopy (AFM). Coating wettability was also estimated by contact angle (CA) measurement. Tribological performance (coupling friction and wear of UHMWPE) was evaluated by using a ball-on-disc tribometer during highly-stressing tests in dry and lubricated (i.e. NaCl and serum) conditions; friction and wear were specifically evaluated at the initial sliding distances - to highlight the main effect of coating morphology - and after 100m - where the influence of the intrinsic materials properties prevails. AFM analysis highlighted that the working pressure heavily affected the morphological characteristics of the realized films. The wettability of the coating at the highest and lowest deposition pressures (CA ~ 60°, closed to substrate value) decreased for intermediate pressures, reaching a maximum CA of ~ 90°. Regarding tribological tests, a strong correlation was found in the initial steps between friction coefficient and wettability, which decreased as the distance increased. Concerning UHMWPE wear associated to coated counterpart, at 100m a reduction rate of about 7% in dry, 12% in NaCl and 5% in presence of serum was obtained compared to the uncoated counterpart. Differently from what highlighted for friction, no correlation was found between wear rate and morphological parameters. These findings, in agreement with literature, underlined the effect of the deposition pressure on the morphological properties, but suggested that physical characteristics are influenced too. Further research on the deposition process will be required in order to improve the tribological performance of the coating at long distances, addressing - above all - orthopedic applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

The influence of simulator input conditions on the wear of total knee replacements: An experimental and computational study

PubMed Central

Brockett, Claire L; Abdelgaied, Abdellatif; Haythornthwaite, Tony; Hardaker, Catherine; Fisher, John; Jennings, Louise M

2016-01-01

Advancements in knee replacement design, material and sterilisation processes have provided improved clinical results. However, surface wear of the polyethylene leading to osteolysis is still considered the longer-term risk factor. Experimental wear simulation is an established method for evaluating the wear performance of total joint replacements. The aim of this study was to investigate the influence of simulation input conditions, specifically input kinematic magnitudes, waveforms and directions of motion and position of the femoral centre of rotation, on the wear performance of a fixed-bearing total knee replacement through a combined experimental and computational approach. Studies were completed using conventional and moderately cross-linked polyethylene to determine whether the influence of these simulation input conditions varied with material. The position of the femoral centre of rotation and the input kinematics were shown to have a significant influence on the wear rates. Similar trends were shown for both the conventional and moderately cross-linked polyethylene materials, although lower wear rates were found for the moderately cross-linked polyethylene due to the higher level of cross-linking. The most important factor influencing the wear was the position of the relative contact point at the femoral component and tibial insert interface. This was dependent on the combination of input displacement magnitudes, waveforms, direction of motion and femoral centre of rotation. This study provides further evidence that in order to study variables such as design and material in total knee replacement, it is important to carefully control knee simulation conditions. This can be more effectively achieved through the use of displacement control simulation. PMID:27160561

Effects of nano-LaF3 on the friction and wear behaviors of PTFE-based bonded solid lubricating coatings under different lubrication conditions

NASA Astrophysics Data System (ADS)

Jia, Yulong; Wan, Hongqi; Chen, Lei; Zhou, Huidi; Chen, Jianmin

2016-09-01

Influence of nanometer lanthanum fluoride (nano-LaF3) on the tribological behaviors of polytetrafluoroethylene (PTFE) bonded solid lubricating coatings were investigated using a ring-on-block friction-wear tester under dry friction and RP-3 jet fuel lubrication conditions. The worn surfaces and transfer films formed on the counterpart steel rings were observed by scanning electron microscope (SEM) and optical microscope (OM), respectively. The microstructures of the nano-LaF3 modified coatings and the distribution states of nano-LaF3 were studied by field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM), respectively. The results show that incorporation of nano-LaF3 improves the microhardness and the friction-reduced and anti-wear abilities of PTFE bonded solid lubricating coatings. The wear life of the modified coating is about 6 times longer than that of the coating without nano-LaF3 filler at a relatively low applied load (200 N) and rotary speed (1000 rev/min) under dry friction condition. The friction coefficient and wear life of the modified coating decrease with increase of applied load under dry friction, but the friction coefficient has hardly any variation and wear life decreases under RP-3 jet fuel lubrication condition. In addition, the friction coefficient of the modified coating reduces with the rotary speed increasing under dry sliding but has little change under RP-3 lubrication, the wear life increases firstly and then decreases. The results indicated that the wear failure mechanism is dominated by applied load, which plays an important role in guidance of application of nano-LaF3 modified PTFE bonded coating under different working environment.

Prevalence of ocular surface symptoms, signs, and uncomfortable hours of wear in contact lens wearers: the effect of refitting with daily-wear silicone hydrogel lenses (senofilcon a).

PubMed

Riley, Colleen; Young, Graeme; Chalmers, Robin

2006-12-01

Many soft contact lens wearers have symptoms or signs that compromise successful lens wear. This study estimated the prevalence of problems in current wearers of soft contact lenses and tested the effect of refitting patients with senofilcon A silicone hydrogel lenses (ACUVUE Oasys). Prevalence was estimated from 1,092 current lens wearers for frequent or constant discomfort or dryness, at least 2 hours of uncomfortable wear, at least grade 2 limbal or bulbar hyperemia (0-4), or at least grade 3 corneal staining (0-15). In the second part of the study, 112 of the 564 wearers classified as problem patients were refitted with senofilcon A lenses and reassessed 2 weeks later. Fifty-two percent (564 of 1,092) had some qualifying criteria, with dryness reported by 23%, discomfort by 13%, and at least 2 hours of uncomfortable wear by 27%. Six percent of subjects had qualifying limbal hyperemia; 10% had bulbar hyperemia; and 12% had corneal staining. After refitting 112 problem patients, 75% had less dryness; 88% had better comfort (P<0.0001 each); and 76% had fewer uncomfortable hours of wear (P=0.004). Although the average wearing time was unchanged, comfortable wearing time increased significantly (10.4 to 11.6 hours) (P=0.004). All (35 of 35) eyes with qualifying limbal hyperemia before the refit also improved (P<0.0001), as did 80% (40 of 50) of those with bulbar hyperemia (P<0.0001) and 76% (26 of 34) of those with corneal staining (P=0.005). Most soft lens wearers encounter clinically significant signs or symptoms with their current contact lenses. Refitting with new-generation silicone hydrogel lenses (senofilcon A) can alleviate some of these common problems.

Spectacle-wear compliance in school children in Concepción Chile.

PubMed

von-Bischhoffshausen, Fernando Barria; Muñoz, Beatriz; Riquelme, Ana; Ormeño, Maria Jose; Silva, Juan Carlos

2014-12-01

Although international policies promote programs for correction of refractive errors in school children, recent studies report low compliance with respect to spectacle wear. Our aim was to assess spectacle-wear compliance and identify associated visual factors among children participating in Chile's school spectacle provision program. A total of 270 school children were prescribed spectacles and monitored after 1 year. Visual acuity, refractive error, reasons for not wearing spectacles, and self-reported visual function were assessed. Compliance is reported as the proportion of children wearing spectacles at the 1-year visit. Factors associated with compliance and reasons for not wearing spectacles were examined using contingency table analyses. Logistic models were constructed to assess independently associated factors. Only 204 children (76%) participated in the 1-year follow-up. Mean age was 10 years (range 4-19 years); 58% were girls, 42% boys. Overall compliance was 58%. Spectacle use was independently associated with age and refractive error. Older children were less likely to be compliant (odds ratio, OR, 0.8, 95% confidence interval, CI, 0.76-0.92/year of increasing age). Compared with children with refractions of -0.75 to +0.75 diopters, both myopic and hyperopic children were more compliant (OR 4.93, 95% CI 2.28-10.67 and OR 2.37, 95% CI 1.06-5.31, respectively). Primary reasons for not wearing spectacles included breakage/loss in younger children, and disliking the appearance in teenagers. We found greater compliance in spectacle wear than that reported in most published studies. Guidelines for provision of children's spectacles should consider excluding children with mild refractive error and improving spectacle quality and appearance.

Using a surrogate contact pair to evaluate polyethylene wear in prosthetic knee joints.

PubMed

Sanders, Anthony P; Lockard, Carly A; Weisenburger, Joel N; Haider, Hani; Raeymaekers, Bart

2016-01-01

With recent improvements to the properties of ultra-high molecular weight polyethylene (UHMWPE) used in joint replacements, prosthetic knee and hip longevity may extend beyond two decades. However, it is difficult and costly to replicate such a long in vivo lifetime using clinically relevant in vitro wear testing approaches such as walking gait joint simulators. We advance a wear test intermediate in complexity between pin-on-disk and knee joint simulator tests. The test uses a surrogate contact pair, consisting of a surrogate femoral and tibial specimen that replicate the contact mechanics of any full-scale knee condyle contact pair. The method is implemented in a standard multi-directional pin-on-disk wear test machine, and we demonstrate its application via a two-million-cycle wear test of three different UHMWPE formulations. Further, we demonstrate the use of digital photography and image processing to accurately quantify fatigue damage based on the reduced transmission of light through a damage area in a UHMWPE specimen. The surrogate contact pairs replicate the knee condyle contact areas within -3% to +12%. The gravimetric wear test results reflect the dose of crosslinking radiation applied to the UHMWPE: 35 kGy yielded a wear rate of 7.4 mg/Mcycles, 55 kGy yielded 1.0 mg/Mcycles, and 75 kGy (applied to a 0.1% vitamin E stabilized UHMWPE) yielded 1.5 mg/Mcycles. A precursor to spalling fatigue is observed and precisely measured in the radiation-sterilized (35 kGy) and aged UHMWPE specimen. The presented techniques can be used to evaluate the high-cycle fatigue performance of arbitrary knee condyle contact pairs under design-specific contact stresses, using existing wear test machines. This makes the techniques more economical and well-suited to standardized comparative testing. © 2015 Wiley Periodicals, Inc.

Advances in tribological testing of artificial joint biomaterials using multidirectional pin-on-disk testers

PubMed Central

Baykal, D.; Siskey, R.S.; Haider, H.; Saikko, V.; Ahlroos, T.; Kurtz, S.M.

2013-01-01

The introduction of numerous formulations of Ultra-high molecular weight polyethylene (UHMWPE), which is widely used as a bearing material in orthopedic implants, necessitated screening of bearing couples to identify promising iterations for expensive joint simulations. Pin-on-disk (POD) testers capable of multidirectional sliding can correctly rank formulations of UHMWPE with respect to their predictive in vivo wear behavior. However, there are still uncertainties regarding POD test parameters for facilitating clinically relevant wear mechanisms of UHMWPE. Studies on the development of POD testing were briefly summarized. We systematically reviewed wear rate data of UHMWPE generated by POD testers. To determine if POD testing was capable of correctly ranking bearings and if test parameters outlined in ASTM F732 enabled differentiation between wear behavior of various formulations, mean wear rates of non-irradiated, conventional (25–50 kGy) and highly crosslinked (≥90 kGy) UHMWPE were grouped and compared. The mean wear rates of non-irradiated, conventional and highly crosslinked UHMWPEs were 7.03, 5.39 and 0.67 mm3/MC. Based on studies that complied with the guidelines of ASTM F732, the mean wear rates of non-irradiated, conventional and highly crosslinked UHMWPEs were 0.32, 0.21 and 0.04 mm3/km, respectively. In both sets of results, the mean wear rate of highly crosslinked UHMPWE was smaller than both conventional and non-irradiated UHMWPEs (p<0.05). Thus, POD testers can compare highly crosslinked and conventional UHMWPEs despite different test parameters. Narrowing the allowable range for standardized test parameters could improve sensitivity of multi-axial testers in correctly ranking materials. PMID:23831149

Microhardness and wear resistance of PEO-coated 5754 aluminum alloy

NASA Astrophysics Data System (ADS)

Vyaliy, I. E.; Egorkin, V. S.; Sinebryukhov, S. L.; Minaev, A. N.; Gnedenkov, S. V.

2017-09-01

We present results of the study aimed at assessing the effect of duty cycle (D) during plasma electrolytic oxidation (PEO) on protective properties of the coatings produced on 5754 aluminum alloy. It is shown that increasing the duty cycle of a microsecond current pulses leads to increased hardness and reduced abrasive wear of the PEO-layers, improving mechanical properties. The obtained data allowed confirming, that increasing the amount of energy consumed for coating growth leads to the formation of thicker PEO-layers with improved tribological properties. The effect of duty cycle during plasma electrolytic oxidation on protective properties of the produced coatings was assessed.

Microstructure evolution and tribological properties of acrylonitrile-butadiene rubber surface modified by atmospheric plasma treatment

NASA Astrophysics Data System (ADS)

Shen, Ming-xue; Zhang, Zhao-xiang; Peng, Xu-dong; Lin, Xiu-zhou

2017-09-01

For the purpose of prolonging the service life for rubber sealing elements, the frictional behavior of acrylonitrile-butadiene rubber (NBR) surface by dielectric barrier discharge plasma treatments was investigated in this paper. Surface microstructure and chemical composition were measured by atomic force microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. Water contact angles of the modified rubber surface were also measured to evaluate the correlation between surface wettability and tribological properties. The results show that plasma treatments can improve the properties of the NBR against friction and wear effectively, the surface microstructure and roughness of plasma-modified NBR surface had an important influence on the surface tribological behavior, and the wear depth first decreased and then increased along with the change of plasma treatment time. It was found that the wettability of the modified surface was gradually improved, which was mainly due to the change of the chemical composition after the treatment. This study suggests that the plasma treatment could effectively improve the tribological properties of the NBR surface, and also provides information for developing wear-resistant NBR for industrial applications.

Improvement in wear and corrosion resistance of AISI 1020 steel by high velocity oxy-fuel spray coating containing Ni-Cr-B-Si-Fe-C

NASA Astrophysics Data System (ADS)

Prince, M.; Thanu, A. Justin; Gopalakrishnan, P.

2012-04-01

In this investigation, AISI 1020 low carbon steel has been selected as the base material. The Ni based super alloy powder NiCrBSiFeC was sprayed on the base material using high velocity oxy-fuel spraying (HVOF) technique. The thickness of the coating was approximately 0.5 mm (500 μm). The coating was characterized using optical microscopy, Vickers microhardness testing, X-ray diffraction technique and scanning electron microscopy. Dry sliding wear tests were carried out at 3 m/s sliding speed under the load of 10 N for 1000 m sliding distance at various temperatures i.e., 35° C, 250° C and 350° C. The corrosion test was carried out in 1 M copper chloride in acetic acid solution. The polarization studies were also conducted for both base material and coating. The improvement in microhardness from 1.72 GPa (175 HV0.05) to 10.54 GPa (1075 HV0.05) was observed. The coatings exhibited 3-6 times improved wear resistance as compared with base material. Also, the corrosion rate was reduced by 3.5 times due to the presence of coatings.

Immediate-term effects of use of an ankle-foot orthosis with an oil damper on the gait of stroke patients when walking without the device.

PubMed

Yamamoto, Sumiko; Ibayashi, Setsuro; Fuchi, Masako; Yasui, Tadashi

2015-04-01

An ankle-foot orthosis using an oil damper is designed to enable natural movement of the ankle joint. Wearing an ankle-foot orthosis using an oil damper has been demonstrated to assist the first rocker in stroke patients, but its effect on their gait when not wearing it is unclear. To determine the effect of use of ankle-foot orthosis using an oil damper on the gait of stroke patients with hemiparesis when not wearing the ankle-foot orthosis. Crossover study. The gait of eight stroke patients in the chronic phase when not wearing an ankle-foot orthosis was measured, using a three-dimensional motion analysis system, before using the ankle-foot orthosis using an oil damper and then without and with using the ankle-foot orthosis using an oil damper after 3 weeks of use. Differences in gait were compared between the three measurement conditions. Use of ankle-foot orthosis using an oil damper significantly decreased preswing time and significantly increased the positive ankle joint power in stance when not wearing the ankle-foot orthosis using an oil damper. These changes indicate the promising therapeutic effects of ankle-foot orthosis using an oil damper use and suggest the ankle-foot orthosis using an oil damper's potential as a therapeutic device. After 3 weeks of use of an ankle-foot orthosis using an oil damper, which assists the first rocker, the gait of stroke patients in the chronic phase when not wearing the ankle-foot orthosis using an oil damper was improved. Preswing time was significantly decreased and positive ankle joint power was significantly increased. The ankle-foot orthosis using an oil damper, which assists the first rocker function with natural movement of the ankle joint during gait, has the potential to improve the gait of stroke patients after immediate-term use. © The International Society for Prosthetics and Orthotics 2014.

The Effects of Liquid Cooling Garments on Post-Space Flight Orthostatic Intolerance

NASA Technical Reports Server (NTRS)

Billica, Roger; Kraft, Daniel

1997-01-01

Post space flight orthostatic intolerance among Space Shuttle crew members following exposure to extended periods of microgravity has been of significant concern to the safety of the shuttle program. Following the Challenger accident, flight crews were required to wear launch and entry suits (LES). It was noted that overall, there appeared to be a higher degree of orthostatic intolerance among the post-Challenger crews (approaching 30%). It was hypothesized that the increased heat load incurred when wearing the LES, contributed to an increased degree of orthostatic intolerance, possibly mediated through increased peripheral vasodilatation triggered by the heat load. The use of liquid cooling garments (LCG) beneath the launch and entry suits was gradually implemented among flight crews in an attempt to decrease heat load, increase crew comfort, and hopefully improve orthostatic tolerance during reentry and landing. The hypothesis that the use of the LCG during reentry and landing would decrease the degree of orthostasis has not been previously tested. Operational stand-tests were performed pre and post flight to assess crewmember's cardiovascular system's ability to respond to gravitational stress. Stand test and debrief information were collected and databased for 27 space shuttle missions. 63 crewpersons wearing the LCG, and 70 crewpersons not wearing the LCG were entered into the database for analysis. Of 17 crewmembers who exhibited pre-syncopal symptoms at the R+O analysis, 15 were not wearing the LCG. This corresponds to a 21% rate of postflight orthostatic intolerance among those without the LCG, and a 3% rate for those wearing LCG. There were differences in these individual's average post-flight maximal systolic blood pressure, and lower minimal Systolic Blood pressures in those without LCG. Though other factors, such as type of fluid loading, and exercise have improved concurrently with LCG introduction, from this data analysis, it appears that LCG usage provided a significant degree of protection from post-flight orthostatic intolerance.

Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints.

PubMed

Koseki, Hironobu; Tomita, Masato; Yonekura, Akihiko; Higuchi, Takashi; Sunagawa, Sinya; Baba, Koumei; Osaki, Makoto

2017-01-01

Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses.

Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints

PubMed Central

Koseki, Hironobu; Tomita, Masato; Yonekura, Akihiko; Higuchi, Takashi; Sunagawa, Sinya; Baba, Koumei; Osaki, Makoto

2017-01-01

Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses. PMID:28615939

Sliding Wear and Fretting Wear of DLC-Based, Functionally Graded Nanocomposite Coatings

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Pohlchuck, B.; Street, Kenneth W.; Zabinski, J. S.; Sanders, J. H.; Voevodin, A. a.; Wu, R. L. C.

1999-01-01

Improving the tribological functionality of diamondlike carbon (DLC) films--developing, good wear resistance, low friction, and high load-carrying capacity-was the aim of this investigation. Nanocomposite coatings consisting of an amorphous DLC (a-DLC) top layer and a functionally graded titanium-titanium carbon-diamondlike carbon (Ti-Ti(sub x) C(sub y)-DLC) underlayer were produced on AISI 440C stainless steel substrates by the hybrid technique of magnetron sputtering and pulsed-laser deposition. The resultant DLC films were characterized by Raman spectroscopy, scanning electron microscopy, and surface profilometry. Two types of wear experiment were conducted in this investioation: sliding friction experiments and fretting wear experiments. Unidirectional ball-on-disk sliding friction experiments were conducted to examine the wear behavior of an a-DLC/Ti-Ti(sub x) C(sub y)-DLC-coated AISI 440C stainless steel disk in sliding contact with a 6-mm-diameter AISI 440C stainless steel ball in ultrahigh vacuum, dry nitrogen, and humid air. Although the wear rates for both the coating and ball were low in all three environments, the humid air and dry nitrogen caused mild wear with burnishing, in the a-DLC top layer, and the ultrahigh vacuum caused relatively severe wear with brittle fracture in both the a-DLC top layer and the Ti-Ti(sub x) C(sub y)-DLC underlayer. For reference, amorphous hydrogenated carbon (H-DLC) films produced on a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coatings by using an ion beam were also examined in the same manner. The H-DLC films markedly reduced friction even in ultrahigh vacuum without sacrificing wear resistance. The H-DLC films behaved much like the a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coating in dry nitrogen and humid air, presenting low friction and low wear. Fretting wear experiments were conducted in humid air (approximately 50% relative humidity) at a frequency of 80 Hz and an amplitude of 75 micron on an a-DLC/Ti-Ti(sub x) C(sub y)-DLC-coated AISI 440C disk and on a titanium-6 wt % aluminum-4 wt% vanadium (Ti-6Al-4V) flat, both in contact with a 9.4-mm-diameter, hemispherical Ti-6Al-4V pin. The resistance to fretting wear and damage of the a-DLC/Ti-6Al-4V materials pair was superior to that of the Ti-6Al-4V/Ti-6AI-4V materials pair.

Enhancement of bronze alloy surface properties by FSP second-phase particle incorporation

DOE PAGES

Ajayi, O. O.; Lorenzo-Martin, Cinta

2017-06-15

This study presents results of an experimental study to evaluate friction stir processing (FSP) with and without hard second-phase particle incorporation as a means to enhance surface properties and wear performance of C86300 manganese bronze alloy. FSP of flat bronze alloy specimens was conducted with hardened H-13 tool steel to create a 3-mm-thick processed surface layer. The process was also used to incorporate B 4C particles, thereby creating a metal-matrix composite layer on the alloy surface. FSP alone was observed to produce substantial reduction in grain size (from an initial value of 350 mu m to 1-5 μm). FSP withoutmore » particle incorporation resulted in modest surface hardening due to grain refinement and dispersion hardening. Under lubricated contact in block-on-ring testing with a hardened steel counter face, FSP produced substantial reduction (about 3X) in bronze wear after polishing of processing surface roughening. FSP with hard B 4C second-phase particle incorporation further reduced wear by up to 20X. The improvement in wear behavior is attributed to grain refinement and load shielding by second-phase particles, as determined by wear mechanism analysis.« less

Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher

PubMed Central

Amanov, Auezhan; Ahn, Byungmin; Lee, Moon Gu; Jeon, Yongho; Pyun, Young-Sik

2016-01-01

An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc. PMID:28774070

Wear resistance of polypropylene-SiC composite

NASA Astrophysics Data System (ADS)

Abenojar, J.; Enciso, B.; Martínez, MA; Velasco, F.

2017-05-01

In this work, the wear resistance of thermoplastic composites with a high amount of ceramic is evaluated. Composites made of polypropylene (PP) and silicon carbide (SiC) powder at 50 wt% were used with the final objective of manufacturing ablative materials. This is the first part of a project studying the wear resistance and the mechanical properties of those composites, to be used in applications like habitat industry. In theory, the exposure to high temperature of ablative materials involves the elimination of thermal energy by the sacrifice of surface polymer. In our case, PP will act as a heat sink, up to the reaction temperature (melting or sublimation), where endothermic chemical decomposition into charred material and gaseous products occurs. As the surface is eroded, it is formed a SiC like-foam with improved insulation performance. Composites were produced by extrusion and hot compression. The wear characterization was performed by pin-on-disk test. Wear test was carried out under standard ASTM G99. The parameters were 120 rpm speed, 15 N load, a alumina ball with 6 mm as pin and 1000 m sliding distance. The tracks were also observed by opto-digital microscope.

Evaluation for Bearing Wear States Based on Online Oil Multi-Parameters Monitoring

PubMed Central

Hu, Hai-Feng

2018-01-01

As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been proposed based on an improved gray k-means clustering model (G-KCM). First, an online monitoring system with multiple sensors for bearings is established, obtaining oil multi-parameter data and vibration signals for bearings through the whole lifetime. Secondly, a gray correlation degree distance matrix is generated using a gray correlation model (GCM) to express the relationship of oil monitoring samples at different times and then a KCM is applied to cluster the matrix. Analysis and experimental results show that there is an obvious correspondence that state changing coincides basically in time between the lubricants’ multi-parameters and the bearings’ wear states. It also has shown that online oil samples with multi-parameters have early wear failure prediction ability for bearings superior to vibration signals. It is expected to realize online oil monitoring and evaluation for bearing health condition and to provide a novel approach for early identification of bearing-related failure modes. PMID:29621175

Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher.

PubMed

Amanov, Auezhan; Ahn, Byungmin; Lee, Moon Gu; Jeon, Yongho; Pyun, Young-Sik

2016-11-22

An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties-microstructure, surface hardness, surface roughness, etc.

Novel biological strategies for treatment of wear particle-induced periprosthetic osteolysis of orthopaedic implants for joint replacement

PubMed Central

Goodman, S. B.; Gibon, E.; Pajarinen, J.; Lin, T.-H.; Keeney, M.; Ren, P.-G.; Nich, C.; Yao, Z.; Egashira, K.; Yang, F.; Konttinen, Y. T.

2014-01-01

Wear particles and by-products from joint replacements and other orthopaedic implants may result in a local chronic inflammatory and foreign body reaction. This may lead to persistent synovitis resulting in joint pain and swelling, periprosthetic osteolysis, implant loosening and pathologic fracture. Strategies to modulate the adverse effects of wear debris may improve the function and longevity of joint replacements and other orthopaedic implants, potentially delaying or avoiding complex revision surgical procedures. Three novel biological strategies to mitigate the chronic inflammatory reaction to orthopaedic wear particles are reported. These include (i) interference with systemic macrophage trafficking to the local implant site, (ii) modulation of macrophages from an M1 (pro-inflammatory) to an M2 (anti-inflammatory, pro-tissue healing) phenotype in the periprosthetic tissues, and (iii) local inhibition of the transcription factor nuclear factor kappa B (NF-κB) by delivery of an NF-κB decoy oligodeoxynucleotide, thereby interfering with the production of pro-inflammatory mediators. These three approaches have been shown to be viable strategies for mitigating the undesirable effects of wear particles in preclinical studies. Targeted local delivery of specific biologics may potentially extend the lifetime of orthopaedic implants. PMID:24478281

Evaluation for Bearing Wear States Based on Online Oil Multi-Parameters Monitoring.

PubMed

Wang, Si-Yuan; Yang, Ding-Xin; Hu, Hai-Feng

2018-04-05

As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been proposed based on an improved gray k-means clustering model (G-KCM). First, an online monitoring system with multiple sensors for bearings is established, obtaining oil multi-parameter data and vibration signals for bearings through the whole lifetime. Secondly, a gray correlation degree distance matrix is generated using a gray correlation model (GCM) to express the relationship of oil monitoring samples at different times and then a KCM is applied to cluster the matrix. Analysis and experimental results show that there is an obvious correspondence that state changing coincides basically in time between the lubricants' multi-parameters and the bearings' wear states. It also has shown that online oil samples with multi-parameters have early wear failure prediction ability for bearings superior to vibration signals. It is expected to realize online oil monitoring and evaluation for bearing health condition and to provide a novel approach for early identification of bearing-related failure modes.

The effect of runway surface and braking on Shuttle Orbiter main gear tire wear

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.

1992-01-01

In 1988, a 1067 m long touchdown zone on each end of the Kennedy Space Center (KSC) Shuttle Landing Facility (SLF) was modified from its original heavy-broom finish with transverse grooves configuration to a longitudinal corduroy surface texture with no transverse grooves. The intent of this modification was to reduce the spin-up wear on the Orbiter main gear tires and provide for somewhat higher crosswind capabilities at that site. The modification worked well, so it was proposed that the remainder of the runway be modified as well to permit even higher crosswind landing capability. Tests were conducted at the NASA Langley Aircraft Landing Dynamics Facility (ALDF) to evaluate the merit of such a modification. This paper discusses the results of these tests, and explains why the proposed modification did not provide the expected improvement and thus was not implemented. Also, in an ongoing program to evaluate the origin of various tire wear phenomenon, a series of tests was conducted to evaluate the effect of braking on tire wear. Finally, a modified tire is discussed in terms of its wear performance under rollout and braking operations.

Field observations of display placement requirements and character size for presbyopic and prepresbyopic computer users.

PubMed

Bartha, Michael C; Allie, Paul; Kokot, Douglas; Roe, Cynthia Purvis

2015-01-01

Computer users continue to report eye and upper body discomfort even as workstation flexibility has improved. Research shows a relationship between character size, viewing distance, and reading performance. Few reports exist regarding text height viewed under normal office work conditions and eye discomfort. This paper reports self-selected computer display placement, text characteristics, and subjective comfort for older and younger computer workers under real-world conditions. Computer workers were provided with monitors and adjustable display support(s). In Study 1, older workers wearing progressive-addition lenses (PALs) were observed. In study 2, older workers wearing multifocal lenses and younger workers were observed. Workers wearing PALs experienced less eye and body discomfort with adjustable displays, and less eye and neck discomfort for text visual angles near or greater than ergonomic recommendations. Older workers wearing multifocal correction positioned displays much lower than younger workers. In general, computer users did not adjust character size to ensure that fovial images of text fell within the recommended range. Ergonomic display placement recommendations should be different for computer users wearing multifocal correction for presbyopia. Ergonomic training should emphasize adjusting text size for user comfort.

Effect of Ti3SiC2 on Tribological Properties of M50 Matrix Self-Lubricating Composites from 25 to 450 °C

NASA Astrophysics Data System (ADS)

Deng, Xiaobin; Shi, Xiaoliang; Liu, Xiyao; Huang, Yuchun; Yan, Zhao; Yang, Kang; Wang, Yufu

2017-09-01

The tribological performance is a key factor for M50 steel that is widely used in aero-engine main-shaft bearings. In this study, the tribological properties of M50 matrix self-lubricating composites with different contents of Ti3SiC2 against Si3N4 ceramic counterpart are investigated at 15 N-0.2 m/s from 25 to 450 °C. The results showed that M50 with 10 wt.% Ti3SiC2 (MT10) exhibits the lower friction coefficients (0.21-0.78) and less wear rates (1.78-3.14 × 10-6 mm3 N-1 m-1) at 25-450 °C. Especially at 350 °C, MT10 shows the lowest friction coefficient and wear rate owing to the formation of smooth lubricating layer containing Ti3SiC2 and oxides. Ti3SiC2 and compacted Ti-Si-oxides are uniformly distributed in the lubricating layer, which can well improve the anti-friction and anti-wear performance of MT10. The mechanically mixed layer containing massive Ti3SiC2 can sustain the lubricating layer, resulting in the increase of anti-wear performance of MT10. MT10 could be applied under the practical conditions of friction and wear for its outstanding anti-friction and anti-wear performance.

A dramatic, objective antiandrogen withdrawal response: case report and review of the literature.

PubMed

Lau, Yiu-Keung; Chadha, Manpreet K; Litwin, Alan; Trump, Donald L

2008-11-05

Antiandrogen withdrawal response is an increasingly recognized entity in patients with metastatic prostate cancer. To our knowledge, there have been no reports describing a durable radiologic improvement along with prostate-specific antigen (PSA) with discontinuation of the antiandrogen agent bicalutamide. We report a case in which a dramatic decline of serum PSA levels associated with a dramatic improvement in radiologic disease was achieved with bicalutamide discontinuation.

Mutant monocyte chemoattractant protein 1 protein attenuates migration of and inflammatory cytokine release by macrophages exposed to orthopedic implant wear particles.

PubMed

Yao, Zhenyu; Keeney, Michael; Lin, Tzu-Hua; Pajarinen, Jukka; Barcay, Katherine; Waters, Heather; Egashira, Kensuke; Yang, Fan; Goodman, Stuart

2014-09-01

Wear particles generated from total joint replacements can stimulate macrophages to release chemokines, such as monocyte chemoattractant protein 1 (MCP-1), which is the most important chemokine regulating systemic and local cell trafficking and infiltration of monocyte/macrophages in chronic inflammation. One possible strategy to curtail the adverse events associated with wear particles is to mitigate migration and activation of monocyte/macrophages. The purpose of this study is to modulate the adverse effects of particulate biomaterials and inflammatory stimuli such as endotoxin by interfering with the biological effects of the chemokine MCP-1. In the current study, the function of MCP-1 was inhibited by the mutant MCP-1 protein called 7ND, which blocks its receptor, the C-C chemokine receptor type 2 (CCR2) on macrophages. Addition of 7ND decreased MCP-1-induced migration of THP-1 cells in cell migration experiments in a dose-dependent manner. Conditioned media from murine macrophages exposed to clinically relevant polymethylmethacrylate (PMMA) particles with/without endotoxin [lipopolysaccharide (LPS)] had a chemotactic effect on human macrophages, which was decreased dramatically by 7ND. 7ND demonstrated no adverse effects on the viability of macrophages, and the capability of mesenchymal stem cells (MSCs) to form bone at the doses tested. Finally, proinflammatory cytokine production was mitigated when macrophages were exposed to PMMA particles with/without LPS in the presence of 7ND. Our studies confirm that the MCP-1 mutant protein 7ND can decrease macrophage migration and inflammatory cytokine release without adverse effects at the doses tested. Local delivery of 7ND at the implant site may provide a therapeutic strategy to diminish particle-associated periprosthetic inflammation and osteolysis. © 2013 Wiley Periodicals, Inc.

Identifying Safer Anti-Wear Triaryl Phosphate Additives for Jet Engine Lubricants

PubMed Central

Baker, Paul E.; Cole, Toby B.; Cartwright, Megan; Suzuki, Stephanie M.; Thummel, Kenneth E.; Lin, Yvonne S.; Co, Aila L.; Rettie, Allan E.; Kim, Jerry H.; Furlong, Clement E.

2013-01-01

Individuals aboard jet aircraft may be exposed to potentially toxic triaryl organophosphate anti-wear lubricant additives (TAPs) that are converted by cytochromes P450 into toxic metabolites. Consequences of exposure could be reduced by using less toxic TAPs. Our goal was to determine whether an in vitro assay for inhibition of butyrylcholinesterase (BChE) by bioactivated TAPs would be predictive of inhibition of serine active-site enzymes in vivo. The in vitro assay involved TAP bioactivation with liver microsomes and NADPH, followed by incubation with human BChE and measurement of BChE activity. Of 19 TAPs tested, tert-butylated isomers produced the least BChE inhibition. To determine the relevance of these results in vivo, mice were exposed to Durad 125 (D125; a commercial mixture of TAP esters) or to TAPs demonstrating low or no BChE inhibition when assayed in vitro. Inhibition of BChE by bioactivated TAPs in vitro correlated well with inhibition of other serine active-site enzymes in vivo, with the exception of brain acetylcholinesterase and neuropathy target esterase (NTE), which were not inhibited by any TAP tested following single exposures. A recombinant catalytic domain of NTE (rNEST) exhibited classical kinetic properties of NTE. The metabolite of tri-(o-cresyl) phosphate (ToCP), 2-(o-cresyl)-4H-1,3,2-benzodioxaphosphoran-2-one (CBDP), inhibited rNEST in vitro, but with an IC50 value almost 6-times higher than for inhibition of BChE. Physiologically-relevant concentrations of the flavonoid, naringenin, dramatically reduced D125 bioconversion in vitro. The in vitro assay should provide a valuable tool for prescreening candidate TAP anti-wear additives, identifying safer additives and reducing the number of animals required for in vivo toxicity testing. PMID:23085349

Identifying safer anti-wear triaryl phosphate additives for jet engine lubricants.

PubMed

Baker, Paul E; Cole, Toby B; Cartwright, Megan; Suzuki, Stephanie M; Thummel, Kenneth E; Lin, Yvonne S; Co, Aila L; Rettie, Allan E; Kim, Jerry H; Furlong, Clement E

2013-03-25

Individuals aboard jet aircraft may be exposed to potentially toxic triaryl organophosphate anti-wear lubricant additives (TAPs) that are converted by cytochromes P450 into toxic metabolites. Consequences of exposure could be reduced by using less toxic TAPs. Our goal was to determine whether an in vitro assay for inhibition of butyrylcholinesterase (BChE) by bioactivated TAPs would be predictive of inhibition of serine active-site enzymes in vivo. The in vitro assay involved TAP bioactivation with liver microsomes and NADPH, followed by incubation with human BChE and measurement of BChE activity. Of 19 TAPs tested, tert-butylated isomers produced the least BChE inhibition. To determine the relevance of these results in vivo, mice were exposed to Durad 125 (D125; a commercial mixture of TAP esters) or to TAPs demonstrating low or no BChE inhibition when assayed in vitro. Inhibition of BChE by bioactivated TAPs in vitro correlated well with inhibition of other serine active-site enzymes in vivo, with the exception of brain acetylcholinesterase and neuropathy target esterase (NTE), which were not inhibited by any TAP tested following single exposures. A recombinant catalytic domain of NTE (rNEST) exhibited classical kinetic properties of NTE. The metabolite of tri-(o-cresyl) phosphate (ToCP), 2-(o-cresyl)-4H-1,3,2-benzodioxaphosphoran-2-one (CBDP), inhibited rNEST in vitro, but with an IC(50) value almost 6-times higher than for inhibition of BChE. Physiologically-relevant concentrations of the flavonoid naringenin dramatically reduced D125 bioconversion in vitro. The in vitro assay should provide a valuable tool for prescreening candidate TAP anti-wear additives, identifying safer additives and reducing the number of animals required for in vivo toxicity testing. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Oxide Ceramic Films Grown on 55Ni-45Ti for NASA and Department of Defense Applications: Unidirectional Sliding Friction and Wear Evaluation

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Lukco, Dorothy; Cytron, Sheldon J.

2004-01-01

An investigation was conducted to examine the friction and wear behavior of the two types of oxide ceramic films furnished by the U.S. Army Research Laboratory, Development and Engineering Center (ARDEC) under Space Act Agreement SAA3 567. These two types of oxide ceramics were grown on 55Ni-45Ti (60 wt% Ni and 40 wt% Ti) substrates: one was a TiO2 with no other species (designated the B film) and the other was a TiO2 with additional species (designated the G film). Unidirectional ball-on-disk sliding friction experiments were conducted with the oxide films in contact with sapphire at 296 K (23 C) in approx. 50-percent relative humidity laboratory air in this investigation. All material characterization and sliding friction experiments were conducted at the NASA Glenn Research Center. The results indicate that both films greatly improve the surface characteristics of 55Ni-45Ti, enhancing its tribological characteristics. Both films decreased the coefficient of friction by a factor of 4 and increased wear resistance by a two-figure factor, though the B film was superior to the G film in wear resistance and endurance life. The levels of coefficient of friction and wear resistance of both films in sliding contact with sapphire were acceptable for NASA and Department of Defense tribological applications. The decrease in friction and increase in wear resistance will contribute to longer wear life for parts, lower energy consumption, reduced related breakdowns, decreased maintenance costs, and increased reliability.

Genipin crosslinking decreases the mechanical wear and biochemical degradation of impacted cartilage in vitro.

PubMed

Bonitsky, Craig M; McGann, Megan E; Selep, Michael J; Ovaert, Timothy C; Trippel, Stephen B; Wagner, Diane R

2017-03-01

High energy trauma to cartilage causes surface fissures and microstructural damage, but the degree to which this damage renders the tissue more susceptible to wear and contributes to the progression of post-traumatic osteoarthritis (PTOA) is unknown. Additionally, no treatments are currently available to strengthen cartilage after joint trauma and to protect the tissue from subsequent degradation and wear. The purposes of this study were to investigate the role of mechanical damage in the degradation and wear of cartilage, to evaluate the effects of impact and subsequent genipin crosslinking on the changes in the viscoelastic parameters of articular cartilage, and to test the hypothesis that genipin crosslinking is an effective treatment to enhance the resistance to biochemical degradation and mechanical wear. Results demonstrate that cartilage stiffness decreases after impact loading, likely due to the formation of fissures and microarchitectural damage, and is partially or fully restored by crosslinking. The wear resistance of impacted articular cartilage was diminished compared to undamaged cartilage, suggesting that mechanical damage that is directly induced by the impact may contribute to the progression of PTOA. However, the decrease in wear resistance was completely reversed by the crosslinking treatments. Additionally, the crosslinking treatments improved the resistance to collagenase digestion at the impact-damaged articular surface. These results highlight the potential therapeutic value of collagen crosslinking via genipin in the prevention of cartilage degeneration after traumatic injury. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:558-565, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Wear measurement of dental tissues and materials in clinical studies: A systematic review.

PubMed

Wulfman, C; Koenig, V; Mainjot, A K

2018-06-01

This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently. An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered. After duplicates' removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results. There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Contact lens wearers' experiences while trekking in the Khumbu region/Nepal: a cross-sectional survey.

PubMed

Bauer, Irmgard L

2015-01-01

Safe contact lens wear depends on a hygiene regime and lens-appropriate wear patterns which may be compromised during travel in remote and wilderness areas. The purpose of this study was to describe the experience of contact lens wearers while trekking at high-altitude in Nepal. For this descriptive study, trekkers with contact lenses were recruited in Lukla and invited to complete an online-questionnaire on trip preparation, contact lens use, care and experiences, and possible changes for future travel. Quantitative data were analysed using SurveyMonkey; content analysis applied to qualitative responses. The majority of the 158 participants (124; 78.48%) reported no problems with their lenses (daily disposables, soft lenses, extended-wear lenses, hard/rigid lenses) during their stay although dry air, dust, wind, cold temperatures, and difficult hygiene maintenance were challenging. Freezing lenses and freezing solutions were additional challenges. Thirty-four (21.52%) experienced a variety of problems. Improvements were requested from manufacturers. Lodges should provide better access to clean water, mirrors and lighting. Almost 60% of participants had not sought any pre-travel health advice. Remote and wilderness areas provide a challenge for appropriate contact lens wear and care. The decision between the potential risk of infection due to touching lenses (daily disposables, soft/hard lenses) and the potential risk of corneal erosion (extended-wear lenses) needs to be made in pre-travel consultations. Travel health professionals and travel agencies should remind CL-wearing trekkers to carefully assess their wear and care routine to accommodate potentially challenging conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

An Additive to Improve the Wear Characteristics of Perfluoropolyether Based Greases

NASA Technical Reports Server (NTRS)

Jones, David G. V.; Fowzy, Mahmoud A.; Landry, James F.; Jones, William R., Jr.; Shogrin, Bradley A.; Nguyen, QuynhGiao

1999-01-01

The friction and wear characteristics of two formulated perfluoropolyether based greases were compared to their non-additive base greases. One grease was developed for the electronics industry (designated as GXL-296A) while the other is for space applications (designated as GXL-320A). The formulated greases (GXL-296B and GXL-320B) contained a proprietary antiwear additive at an optimized concentration. Tests were conducted using a vacuum four-ball tribometer. AISI 52100 steel specimens were used for all GXL-296 tests. Both AISI 52100 steel and 440C stainless steel were tested with the GXL-320 greases. Test conditions included: a pressure less than 6.7 x 10(exp )-4 Pa, a 200N load, a sliding velocity of 28.8 mm/sec (100 rpm) and room temperature (approximately equal to 23 C). Wear rates for each grease were determined from the slope of the wear volume as a function of sliding distance. Both non-additive base greases yielded relatively high wear rates on the order of 10(exp -8) cu mm using AISI 52100 steel specimens. Formulated grease GXL-296B yielded a reduction in wear rate by a factor of approximately 21, while grease GXL-320B had a reduction of approximately 12 times. Lower wear rates (-50%) were observed with both GXL-320 greases using 440C stainless steel. Mean friction coefficients were slightly higher for both formulated greases compared to their base greases. The GXL-296 series (higher base oil viscosity) yielded much higher friction coefficients compared to their GXL-320 series (lower base oil viscosity) counterparts.

Threading on ADI Cast Iron, Developing Tools and Conditions

NASA Astrophysics Data System (ADS)

Elósegui, I.; de Lacalle, L. N. López

2011-01-01

The present work is focussed on the improvement of the design and performance of the taps used for making threaded holes in ADI (Austempered Ductile Iron). It is divided in two steps: a) The development of a method valid to compare the taps wear without reaching the end of their life, measuring the required torque to make one threaded hole, after having made previously a significant number of threaded holes. The tap wear causes some teeth geometrical changes, that supposes an increase in the required torque and axial force. b) The taps wear comparison method is open to apply on different PVD coated taps, AlTiN, AlCrSiN, AlTiSiN, , and to different geometries.

Precision of computer vision systems for real-time inspection of contact wire wear in railways

NASA Astrophysics Data System (ADS)

Borromeo, Susana; Aparicio, Jose L.

2005-02-01

This paper is oriented to study techniques to improve the precision of the systems for wear measurement of contact wire in the railways. The problematic of wear measurement characterized by some important determining factors like rate of sampling and auscultation conditions is studied in detail. The different solutions to resolve the problematic successfully are examined. Issues related to image acquisition and image processing are discussed. Type of illumination and sensors employed, image processing hardware and image processing algorithms are some topics studied. Once analyzed each one factor which have influence on the precision of the measurement system, there are proposed an assembly of solutions that allow to optimize the conditions under which the inspection can be carried out.

Evaluating lubricant performance by 3D profilometry of wear scars

NASA Astrophysics Data System (ADS)

Georgescu, C.; Deleanu, L.; Pirvu, C.

2016-08-01

Due to improvement in analysing surface texture and optical instruments for investigating the texture surface, the authors propose to evaluate the lubricant performance by analysing the change in several 3D parameters in comparison to an analysis on 2D profile. All the surface of the wear scar generated on the four ball machine is investigated and the conclusion is that from the tribological point of view, the 3D parameters reflect better the surface quality evolution after testing. Investigation was done on the wear scars generated on the three fixed balls, for five lubricants: a non-additivated transmission mineral oil (T90), two grades of rapeseed oil (coarse degummed and refined) and two grades of soybean oil (coarse and degummed).

Nut Cracking Tools Used by Captive Chimpanzees (Pan troglodytes) and Their Comparison with Early Stone Age Percussive Artefacts from Olduvai Gorge.

PubMed

Arroyo, Adrián; Hirata, Satoshi; Matsuzawa, Tetsuro; de la Torre, Ignacio

2016-01-01

We present the results of a series of experiments at the Kumamoto Sanctuary in Japan, in which captive chimpanzees (Pan troglodytes) performed several nut cracking sessions using raw materials from Olduvai Gorge, Tanzania. We examined captive chimpanzee pounding tools using a combination of technological analysis, use-wear distribution, and micro-wear analysis. Our results show specific patterns of use-wear distribution across the active surfaces of pounding tools, which reveal some similarities with traces on archaeological percussive objects from the Early Stone Age, and are consistent with traces on other experimental pounding tools used by modern humans. The approach used in this study may help to stablish a framework with which to interpret archaeological assemblages and improve understanding of use-wear formation processes on pounding tools used by chimpanzees. This study represents the first direct comparison of chimpanzee pounding tools and archaeological material, and thus may contribute to a better understanding of hominin percussive activities.

Mechanical properties enhancement and microstructure study of Al-Si-TiB2 in situ composites

NASA Astrophysics Data System (ADS)

Sahoo, S. K.; Majhi, J.; Pattnaik, A. B.; Sahoo, J. K.; Das, Swagat

2018-03-01

Al–Si alloy-based composite is one of the most promising MMC materials owing to its outstanding mechanical properties, wear and corrosion resistance, low cost and ability to be synthesized via conventional casting routes. Challenges in achieving clean interface between reinforced particles and matrix alloy have been overcome by means of in-situ techniques of fabrication. Present investigation is concerned with synthesizing Al-Si-TiB2 in-situ composites through stir casting route using K2TiF6 and KBF4 halide salts for exothermic salt metal reaction. X-Ray diffraction analysis revealed the existence of TiB2 in the prepared samples. Effect of TiB2in-situ particles in the Al-Si base alloy has been investigated from the results obtained from optical microscopy as well as SEM study and wear analysis with a pin on disc wear testing apparatus. Improved hardness and wear properties were observed with addition of TiB2.

Preparation and tribological behaviors of poly (ether ether ketone) nanocomposite films containing graphene oxide nanosheets

NASA Astrophysics Data System (ADS)

Song, Hao-Jie; Li, Na; Yang, Jin; Min, Chun-Ying; Zhang, Zhao-zhu

2013-02-01

The composite films of poly (ether ether ketone) (PEEK) filled with different proportions of graphene oxide (GO) nanosheets were prepared by the cast method. The tribological behaviors of the composite films under boundary lubrication (water and liquid paraffin oil lubrication) were investigated and compared with that under dry sliding on an UMT-2 friction and wear machine, by running a steel sphere against the composite films. The results were as follows: GO nanosheets as the filler greatly improve the wear resistance of PEEK under boundary lubrication, though the composites show a different dependence of wear resistance on the filler content. Scanning electron microscopy and optical microscopy performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of GO could be attributed to their small size and extremely thin laminated structure, which allow the GO to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

A tri-layer thin film containing graphene oxide to protect zinc substrates from wear

NASA Astrophysics Data System (ADS)

Wang, Ying; Gu, Zhengpeng; Yuan, Ningyi; Chu, Fuqiang; Cheng, Guanggui; Ding, Jianning

2018-06-01

Due to its excellent properties, Zn alloy is widely used in daily life. However, the poor wear-resisting properties of Zn alloys limits their application. In this paper, a tri-layer thin film consisting of 3-aminopropyltriethoxysilane (APS), graphene oxide (GO) and perfluoropolyethers (PFPE) were successfully prepared on the surface of Zn alloy to improve the wear-resisting properties. The as-prepared tri-layer thin films were characterized by atomic force microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy and contact angle measurement. In addition, the tribological properties of the as-prepared tri-layer thin films were studied on a ball-on-plate tribometer and the morphologies of worn surfaces were observed using 3D noncontact interferometric microscope. Compared with the control samples, the tri-layer thin films showed excellent friction-reducing and wear-resisting properties, which was attributed to the synergistic effect of the GO as the load-carrying layer and the PFPE as the lubricating layer.

Effects of rare earth oxide additive on surface and tribological properties of polyimide composites

NASA Astrophysics Data System (ADS)

Pan, Zihe; Wang, Tianchang; Chen, Li; Idziak, Stefan; Huang, Zhaohui; Zhao, Boxin

2017-09-01

Rare earth oxide La2O3 microparticles-reinforced polyimide (PI) composites (La-PI-Cs) were fabricated, aiming to improve the tribological property of PI. Surface roughness, surface composition, bulk structure, friction force (Ff) and coefficient of friction (COF) at macro/micro preload, and anti-wear performances of La-PI-Cs were studied and compared with neat PI. With La2O3 microparticles, La-PI-Cs showed larger surface roughness, lower surface energy, and higher hydrophobicity than neat PI, and displayed beneficial layered structure different from the compact structure of PI. Owing to these advantages, La-PI-Cs were found to show a 70% reduction in Ff and COF, and a 30% reduction in wear rate, indicating significantly lowered friction and enhanced anti-wear properties after adding La2O3 microparticles. Our research findings demonstrated an easy and low cost method to fabricate polymer composites with low friction and high wear resistance, and help meet the demanding of polymer composites with high tribological performances in broaden applications.

Synthesis and characterization of in situ TiC-TiB2 composite coatings by reactive plasma spraying on a magnesium alloy

NASA Astrophysics Data System (ADS)

Zou, Binglin; Tao, Shunyan; Huang, Wenzhi; Khan, Zuhair S.; Fan, Xizhi; Gu, Lijian; Wang, Ying; Xu, Jiaying; Cai, Xiaolong; Ma, Hongmei; Cao, Xueqiang

2013-01-01

TiC-TiB2 composite coatings were successfully synthesized using the technique of reactive plasma spraying (RPS) on a magnesium alloy. Phase composition, microstructure and wear resistance of the coatings were characterized by using X-ray diffraction, scanning electron microscopy and pin-on-disk wear test, respectively. The results showed that the resultant product in the RPS coatings was composed of TiC and TiB2. Depending on the ignition of self-propagating high-temperature synthesis reaction in the agglomerate particles, the RPS coatings displayed porous and dense microstructures. The porosity of the RPS coatings, to some extent, decreased when the feed powders were plasma sprayed with Ni powders. The RPS coatings provided good wear resistance for the substrate under various loads. For high loads (e.g., ≥15 N), the wear resistance could be significantly improved by the proper addition of Ni into the RPS coatings.

Nut Cracking Tools Used by Captive Chimpanzees (Pan troglodytes) and Their Comparison with Early Stone Age Percussive Artefacts from Olduvai Gorge

PubMed Central

Arroyo, Adrián; Hirata, Satoshi; Matsuzawa, Tetsuro; de la Torre, Ignacio

2016-01-01

We present the results of a series of experiments at the Kumamoto Sanctuary in Japan, in which captive chimpanzees (Pan troglodytes) performed several nut cracking sessions using raw materials from Olduvai Gorge, Tanzania. We examined captive chimpanzee pounding tools using a combination of technological analysis, use-wear distribution, and micro-wear analysis. Our results show specific patterns of use-wear distribution across the active surfaces of pounding tools, which reveal some similarities with traces on archaeological percussive objects from the Early Stone Age, and are consistent with traces on other experimental pounding tools used by modern humans. The approach used in this study may help to stablish a framework with which to interpret archaeological assemblages and improve understanding of use-wear formation processes on pounding tools used by chimpanzees. This study represents the first direct comparison of chimpanzee pounding tools and archaeological material, and thus may contribute to a better understanding of hominin percussive activities. PMID:27870877

Sintering Process and Mechanical Property of MWCNTs/HDPE Bulk Composite.

PubMed

Ming-Wen, Wang; Tze-Chi, Hsu; Jie-Ren, Zheng

2009-08-01

Studies have proved that increasing polymer matrices by carbon nanotubes to form structural reinforcement and electrical conductivity have significantly improved mechanical and electrical properties at very low carbon nanotubes loading. In other words, increasing polymer matrices by carbon nanotubes to form structural reinforcement can reduce friction coefficient and enhance anti-wear property. However, producing traditional MWCNTs in polymeric materix is an extremely complicated process. Using melt-mixing process or in situ polymerization leads to better dispersion effect on composite materials. In this study, therefore, to simplify MWCNTs /HDPE composite process and increase dispersion, powder was used directly to replace pellet to mix and sinter with MWCNTs. The composite bulks with 0, 0.5, 1, 2 and 4% nanotube content by weight was analyzed under SEM to observe nanotubes dispersion. At this rate, a MWCNTs/HDPE composite bulk with uniformly dispersed MWCNTs was achieved, and through the wear bench (Pin-on-Disk), the wear experiment has accomplished. Accordingly, the result suggests the sintered MWCNTs/HDPE composites amplify the hardness and wear-resist property.

Effect of In-Situ Titanium Boride Particle Addition and Friction Stir Processing on Wear Behavior of Aluminum Alloy 2219

NASA Astrophysics Data System (ADS)

Sampath, V.; Rajasekaran, N. R.

There is paucity of data on the effect of in-situ TiB2 particles on the different behavior of 2219 Al alloy. In the present work, therefore, composites with 2219 Al alloy matrix reinforced with in-situ TiB2 particles were produced by flux-assisted synthesis. Different amounts (5 and 10 wt.%) of TiB2 were incorporated. The base alloy and the composites were subjected to friction stir processing to reduce particle clustering. The wear behavior of the materials was studied. The base alloy showed considerable improvement in the wear behavior due to the in-situ particle addition which is attributed to the presence of finer particles with good interfacial bonding and high hardness. Uniform distribution of TiB2 particles and good interface between the matrix and the particles led to reduction in the wear of friction stir processed composites by 30%. The results are analyzed and discussed in detail in the paper.

Friction behavior of network-structured CNT coating on pure titanium plate

NASA Astrophysics Data System (ADS)

Umeda, Junko; Fugetsu, Bunshi; Nishida, Erika; Miyaji, Hirofumi; Kondoh, Katsuyoshi

2015-12-01

Friction behavior of the network-structured CNTs coated pure Ti plate was evaluated by ball-on-disk wear test using SUS304 ball specimen under dry condition. The friction coefficient was significantly low and stable compared to the as-received Ti plate with no coating film. CNTs coating film had two important roles; self-lubrication and bearing effects to reduce the friction coefficient and carbon solid-solution hardening to improve the abrasive wear property of Ti plate. The annealing treatment at higher temperature (1123 K) was more effective to reduce the friction coefficient than that at lower temperature (973 K) because the Ti plate surface was uniformly covered with CNTs film even after sliding wear test. This is due to TiC interlayer formation via a reaction between Ti plate and carbon elements originated from CNTs during annealing. As a result, a strong interface bonding between CNTs film and Ti plate surface was obtained by higher temperature annealing treatment, and obstructed the detachment of CNTs film during wear test.

Study on the Correlation Between Dynamical Behavior and Friction/Wear Mechanism Under the Effect of Grooves

NASA Astrophysics Data System (ADS)

Zhu, Z. Y.; Mo, J. L.; Wang, D. W.; Zhao, J.; Zhu, M. H.; Zhou, Z. R.

2018-04-01

In this work, the interfacial friction and wear and vibration characteristics are studied by sliding a chromium bearing steel ball (AISI 52100) over both multi-grooved and single-grooved forged steel disks (20CrMnMo) at low and high rotating speeds in order to reveal the effect mechanism of groove-textured surface on tribological behaviors. The results show that the grooves modify the contact state of the ball and the disk at the contact interface. This consequently causes variations in the normal displacement, normal force, and friction force signals. The changes in these three signals become more pronounced with increasing groove width at a low speed. The collision behavior between the ball and the groove increase the amplitude of vibration acceleration at a high speed. The test results suggest that grooves with appropriate widths could trap wear debris on the ball surface while avoiding a strong collision between the disk and the ball, resulting in an improvement in the wear states.

Large-scale Manufacturing of Nanoparticulate-based Lubrication Additives for Improved Energy Efficiency and Reduced Emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erdemir, Ali

This project was funded under the Department of Energy (DOE) Lab Call on Nanomanufacturing for Energy Efficiency and was directed toward the development of novel boron-based nanocolloidal lubrication additives for improving the friction and wear performance of machine components in a wide range of industrial and transportation applications. Argonne's research team concentrated on the scientific and technical aspects of the project, using a range of state-of-the art analytical and tribological test facilities. Argonne has extensive past experience and expertise in working with boron-based solid and liquid lubrication additives, and has intellectual property ownership of several. There were two industrial collaboratorsmore » in this project: Ashland Oil (represented by its Valvoline subsidiary) and Primet Precision Materials, Inc. (a leading nanomaterials company). There was also a sub-contract with the University of Arkansas. The major objectives of the project were to develop novel boron-based nanocolloidal lubrication additives and to optimize and verify their performance under boundary-lubricated sliding conditions. The project also tackled problems related to colloidal dispersion, larger-scale manufacturing and blending of nano-additives with base carrier oils. Other important issues dealt with in the project were determination of the optimum size and concentration of the particles and compatibility with various base fluids and/or additives. Boron-based particulate additives considered in this project included boric acid (H{sub 3}BO{sub 3}), hexagonal boron nitride (h-BN), boron oxide, and borax. As part of this project, we also explored a hybrid MoS{sub 2} + boric acid formulation approach for more effective lubrication and reported the results. The major motivation behind this work was to reduce energy losses related to friction and wear in a wide spectrum of mechanical systems and thereby reduce our dependence on imported oil. Growing concern over greenhouse gas emissions was also a major reason. The transportation sector alone consumes about 13 million barrels of crude oil per day (nearly 60% of which is imported) and is responsible for about 30% of the CO{sub 2} emission. When we consider manufacturing and other energy-intensive industrial processes, the amount of petroleum being consumed due to friction and wear reaches more than 20 million barrels per day (from official energy statistics, U.S. Energy Information Administration). Frequent remanufacturing and/or replacement of worn parts due to friction-, wear-, and scuffing-related degradations also consume significant amounts of energy and give rise to additional CO{sub 2} emission. Overall, the total annual cost of friction- and wear-related energy and material losses is estimated to be rather significant (i.e., as much as 5% of the gross national products of highly industrialized nations). It is projected that more than half of the total friction- and wear-related energy losses can be recovered by developing and implementing advanced friction and wear control technologies. In transportation vehicles alone, 10% to 15% of the fuel energy is spent to overcome friction. If we can cut down the friction- and wear-related energy losses by half, then we can potentially save up to 1.5 million barrels of petroleum per day. Also, less friction and wear would mean less energy consumption as well as less carbon emissions and hazardous byproducts being generated and released to the environment. New and more robust anti-friction and -wear control technologies may thus have a significant positive impact on improving the efficiency and environmental cleanliness of the current legacy fleet and future transportation systems. Effective control of friction in other industrial sectors such as manufacturing, power generation, mining and oil exploration, and agricultural and earthmoving machinery may bring more energy savings. Therefore, this project was timely and responsive to the energy and environmental objectives of DOE and our nation. In this project, most of the boron-based materials with known and potential anti-friction and -wear properties have been manufactured as colloidal additives and tested for their effectiveness in controlling friction and wear. Unlike other anti-friction and -wear additives, which consist of zinc, molybdenum, sulfur, phosphorus, and even chlorine, lubricious boron compounds considered in this project are made of boron, oxygen, nitrogen, and hydrogen, which are more environmentally benign. Among others, boric acid is a natural mineral (known in mineralogy as "sassolite"). Based on our earlier exploratory research, it was found to offer the best overall prospect in terms of performance improvements, environmental friendliness, and ease of manufacturing and, hence, cost effectiveness. Hexagonal boron nitride and borax also offered good prospects for improving the tribological properties of lubricated sliding surfaces. Boron oxide particles were found to be rather hard and somewhat abrasive and, hence, were not considered beyond the initial screening studies. In our bench-top tribological evaluation, we also demonstrated that those additives which worked well with engine oils could work equally well with very common gear oils. When added at appropriate concentrations, such gear oils were found to provide significant resistance to micropitting and scuffing failures in bench-top tribological test systems. Their traction coefficients were also reduced substantially and their scuffing limits were improved considerably. Such impressive tribological behavior of boron-based additives may have been due to their high chemical affinities to interact with sliding contact surfaces and to form slick and protective boundary films. Indeed, our surface studies have confirmed that most of the boron-based nanoparticulate additives prepared in our project possess a strong tendency to form a boron-rich boundary film on sliding contact surfaces. It is believed that the formation of such slick and highly durable boundary films is perhaps one of the fundamental reasons for their superior anti-friction, -wear, and -scuffing performance. Boron-based additives developed under this project have shown potential to reduce or replace the uses of environmentally unsafe sulfur- and phosphorus-bearing anti-wear and friction additives, such as zinc dialkyl dithiophosphate (ZDDP) and molybdenum dialkyl dithiocarbamate (MoDTC), in current lubricating oils. Because ZDDP and MoDTC were suspected of adversely impacting the performance of after-treatment catalysts in current engines, the Environmental Protection Agency (EPA) and other regulatory agencies are demanding that the concentrations of these catalysts in current oils be curtailed drastically. The boron-based nano-additives developed in this project may help reduce the use of ZDDP and MoDTC additives and, hence, help ease the poisoning effects on after-treatment catalysts. When used as lubricity additives, these boron additives can chemically interact with sliding or contacting surfaces and form a protective and slick boundary film, which can, in turn, help reduce friction and wear and increase resistance to scuffing. In the cases of traditional anti-friction and -wear additives mentioned, such protective boundary films result from phosphorus, sulfur, and other elements in the additive package, and again they have been under increased scrutiny in recent years, mainly because of their adverse effects on after-treatment devices. Overall, the boron-based nano-additive technology of this project was shown to hold promise for a broad range of industrial and transportation applications where lower friction and higher resistance to wear and scuffing are needed. Due to more stringent operating conditions of modern machinery, rolling, rotating, and sliding components have been failing to meet the projected lifetimes, mainly because of failures related to mechanical wear, corrosion, and scuffing. The novel boron-based additive technology developed under this project may help such machine components to function reliably by cutting down the friction and wear losses and by increasing resistance to scuffing.« less

[The development of research in tribology of artificial joints].

PubMed

Dai, Zhendong; Gong, Juanqing

2006-06-01

Aseptic loosening of the prosthesis is a major form for the failure of artificial joints, which results in the conglomeration of wear particles at the bone-implant interface. This paper briefly reviews the recent development of tribology of artificial joints preserving good lubrication, enhancing the wear resistance of materials for the joints, reducing the generation of sensitive-size particles and depressing the debris-tissue reactions. Suggestion for improvement in the design of artificial joints is presented.

Antiwear Additive Mechanisms in Sliding Contacts

NASA Technical Reports Server (NTRS)

Baldwin, B. A.

1984-01-01

The possible mechanisms associated with wear in a sliding contact and how an oil and antiwear additive can mitigate wear or prevent catastropic seizure of the contacting parts was examined. The various load and temperature regimes are examined and the mechanisms which are predominant under these conditions are determined. The critical mechanism(s) depend on the test parameters, particularly load and temperature, although sliding speed is also a factor. Different ways to improve the efficiency of antiwear additives are suggested.

Microstructure, mechanical and tribological characterization of CrN/DLC/Cr-DLC multilayer coating with improved adhesive wear resistance

NASA Astrophysics Data System (ADS)

Sui, Xudong; Liu, Jinyu; Zhang, Shuaituo; Yang, Jun; Hao, Junying

2018-05-01

Adhesive wear is one of the major reasons for the failure of components during various tribological application, especially for rubbing with viscous materials. This study presents CrN/DLC/Cr-DLC multilayer composite coatings prepared on a plasma enhanced chemical vapor deposition (PECVD) device with the close field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique. SEM, XRD and Raman spectroscopy were used to determine the structure of multilayer coatings. It was found that the multilayer coatings are composed by the alternating CrN and DLC layers. Compared with the single CrN coatings, the friction coefficient of the CrN/DLC/Cr-DLC multilayer coating decreases about more than seven times after sliding a distance of 500 m. This helps to reduce the adhesive wear of multilayer coatings. Compared with the single CrN and DLC coating, the wear rate of the CrN/DLC/Cr-DLC multilayer coating is reduced by an order of magnitude to 7.10 × 10-17 (sliding with AISI 440C) and 2.64 × 10-17 (sliding with TC4) m3/(N m). The improved tribological performance of multilayer coatings mainly attributes to the introduction of lubricant DLC and hard support CrN layers, the enhancement of crack propagation inhibition, and the increment of elastic recovery value We (71.49%) by multilayer design method.

Enhancement of wear and corrosion resistance of beta titanium alloy by laser gas alloying with nitrogen

NASA Astrophysics Data System (ADS)

Chan, Chi-Wai; Lee, Seunghwan; Smith, Graham; Sarri, Gianluca; Ng, Chi-Ho; Sharba, Ahmed; Man, Hau-Chung

2016-03-01

The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family, the quaternary Ti-Nb-Zr-Ta (TNZT) alloys have received the highest attention as a promising replacement for Ti6Al4V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must be resolved before commercialising in the orthopaedic market. In this work, a newly developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface structure and composition of the laser-treated TNZT surface were examined by grazing incidence X-ray diffraction (GI-XRD) and X-ray photoelectron spectroscopy (XPS). The wear and corrosion resistance were evaluated by pin-on-plate sliding test and anodic polarisation test in Hanks' solution. The experimental results were compared with the untreated (or base) TNZT material. The research findings showed that the laser surface treatment technique reported in this work can effectively improve the wear and corrosion resistance of TNZT.

Tribological characterisation of UHMWPE used in dual mobility total hip prosthesis

NASA Astrophysics Data System (ADS)

Essefi, I.; Hakkouna, H.; Ouenzerfi, G.; Mollon, G.; Hamza, S.; Renault, E.; Berthier, Y.; Trunfio-Sfarghiu, A.-M.

2016-08-01

Total hip arthroplasty represents an effective solution for bone and joint diseases. Nevertheless, the hip prosthesis has a limited lifetime, in the average around fifteen years. Their improvement, especially their dual mobility is the objective of this study. Therefore, our strategy is focused on improving the material by comparing three types of polyethylene to determine the best one from a friction mechanism and wear rate minimization standpoint. A dual mobility hip prosthesis, containing a two-sided steel and cobalt chrome cup, was tested with a TORNIER hip joint simulator in calf serum. The rubbed surfaces were characterized using scanning electron microscopy (SEM), contact angle measurements, atomic force microscopy (AFM) and confocal fluorescence microscopy. All these multiscale characterization techniques (from nanoscale to millimeter and micro- scale) showed that the velocity accommodation mechanism is different from one type of polyethylene to another. The wear in the case of standard polyethylene was noticeable and the particles were large and scattered between the surface of polyethylene, the surface of the cup and in the calf serum. For the crosslinked polyethylene, the particles coming from the wear, were not as large, but they were spread the same way as the first case. Even though it shares the same accommodation principle on the detachment of the material with the crosslinked polyethylene the wear particles for the crosslinked vitaminized polyethylene were large and they were only found on the surface of the polyethylene.

Evaluation of Wear on Macro-Surface Textures Generated by ns Fiber Laser

NASA Astrophysics Data System (ADS)

Harish, V.; Soundarapandian, S.; Vijayaraghavan, L.; Bharatish, A.

2018-03-01

The demand for improved performance and long term reliability of mechanical systems dictate the use of advanced materials and surface engineering techniques. A small change in the surface topography can lead to substantial improvements in the tribological behaviour of the contact surfaces. One way of altering the surface topography is by surface texturing by introducing dimples or channels on the surfaces. Surface texturing is already a successful technique which finds a wide area of applications ranging from heavy industries to small scale devices. This paper reports the effect of macro texture shapes generated using a nanosecond fiber laser on wear of high carbon chromium steel used in large size bearings having rolling contacts. Circular and square shaped dimples were generated on the surface to assess the effect of sliding velocities on friction coefficient. Graphite was used as solid lubricant to minimise the effect of wear on textured surfaces. The laser parameters such as power, scan speed and passes were optimised to obtain macro circular and square dimples which was characterised using a laser confocal microscope. The friction coefficients of the circular and square dimples were observed to lie in the same range due to minimum wear on the surface. On the contrary, at medium and higher sliding velocities, square dimples exhibited lower friction coefficient values compared to circular dimples. The morphology of textured specimen was characterised using Scanning Electron Microscope.

Swimming performances in long distance open-water events with and without wetsuit

PubMed Central

2014-01-01

Background Existing literature showed improved swimming performances for swimmers wearing wetsuits competing under standardized conditions in races held in pools on short to middle distances. Data about the influence of wetsuits on swimming performances in long and ultra-long open-water swimming races are missing. It is unknown whether the benefit of wearing wetsuits is comparable in men and women. The aim of this study was to investigate the influence of wearing a wetsuit on open-water swimming performances at the 26.4 km ‘Marathon Swim in Lake Zurich’ in Lake Zurich, Switzerland, and the 3.8 km Lake Ontario Swim Team-Race (LOST-Race) in Lake Ontario, Canada. Methods Race times of the fastest female and male swimmers competing with and without wetsuit were compared using multi-level regression analyses and analysis of variance. Results In the ‘Marathon Swim’ in Lake Zurich, wearing a wetsuit had no effect on race time regarding the gender where athletes wearing a wetsuit were not faster than athletes without wetsuit. However, the ten fastest men wearing a wetsuit (410.6 ± 26.7 min) were faster (32.7%, p < 0.01) than the ten fastest women without wetsuit (544.9 ± 81.3 min). In the ‘LOST-Race’, the top ten men wearing a wetsuit (51.7 ± 2.5 min) were faster (13.2%, p < 0.01) than the top ten women wearing a wetsuit (58.5 ± 3.2 min). Additionally, the top ten men without wetsuit (52.1 ± 2.4 min) were faster (19.6%, p < 0.01) than the top ten women without wetsuit (62.3 ± 2.5 min). The top ten women wearing a wetsuit (58.5 ± 3.2 min) were faster (6.5%, p < 0.01) than top ten women without a wetsuit (62.3 ± 25 min). Conclusions These results suggest that wearing a wetsuit had a positive influence on swimming speed for both women and men but the benefit of the use of wetsuits seemed to depend on additional factors (i.e. race distance). Women seemed to benefit more from wearing wetsuits than men in longer open-water ultra-distance swimming races. PMID:24891942

Properties of crosslinked ultra-high-molecular-weight polyethylene.

PubMed

Lewis, G

2001-02-01

Substantially reducing the rate of generation of wear particles at the surfaces of ultra-high-molecular-weight polyethylene (UHMWPE) orthopedic implant bearing components, in vivo, is widely regarded as one of the most formidable challenges in modern arthroplasty. In the light of this, much research attention has been paid to the myriad of endogenous and exogenous factors that have been postulated to affect this wear rate, one such factor being the polymer itself. In recent years, there has been a resurgence of interest in crosslinking the polymer as a way of improving its properties that are considered relevant to its use for fabricating bearing components. Such properties include wear resistance, fatigue life, and fatigue crack propagation rate. Although a large volume of literature exists on the topic on the impact of crosslinking on the properties of UHMWPE, no critical appraisal of this literature has been published. This is one of the goals of the present article, which emphasizes three aspects. The first is the trade-off between improvement in wear resistance and depreciation in other mechanical and physical properties. The second aspect is the presentation of a method of estimating the optimal value of a crosslinking process variable (such as dose in radiation-induced crosslinking) that takes into account this trade-off. The third aspect is the description of a collection of under- and unexplored research areas in the field of crosslinked UHMWPE, such as the role of starting resin on the properties of the crosslinked polymer, and the in vitro evaluation of the wear rate of crosslinked tibial inserts and other bearing components that, in vivo, are subjected to nearly unidirectional motion.

A dramatic, objective antiandrogen withdrawal response: case report and review of the literature

PubMed Central

Lau, Yiu-Keung; Chadha, Manpreet K; Litwin, Alan; Trump, Donald L

2008-01-01

Antiandrogen withdrawal response is an increasingly recognized entity in patients with metastatic prostate cancer. To our knowledge, there have been no reports describing a durable radiologic improvement along with prostate-specific antigen (PSA) with discontinuation of the antiandrogen agent bicalutamide. We report a case in which a dramatic decline of serum PSA levels associated with a dramatic improvement in radiologic disease was achieved with bicalutamide discontinuation. PMID:18986533

Layered Double Hydroxide Nanoplatelets with Excellent Tribological Properties under High Contact Pressure as Water-Based Lubricant Additives

PubMed Central

Wang, Hongdong; Liu, Yuhong; Chen, Zhe; Wu, Bibo; Xu, Sailong; Luo, Jianbin

2016-01-01

High efficient and sustainable utilization of water-based lubricant is essential for saving energy. In this paper, a kind of layered double hydroxide (LDH) nanoplatelets is synthesized and well dispersed in water due to the surface modification with oleylamine. The excellent tribological properties of the oleylamine-modified Ni-Al LDH (NiAl-LDH/OAm) nanoplatelets as water-based lubricant additives are evaluated by the tribological tests in an aqueous environment. The modified LDH nanoplatelets are found to not only reduce the friction but also enhance the wear resistance, compared with the water-based cutting fluid and lubricants containing other particle additives. By adding 0.5 wt% LDH nanoplatelets, under 1.5 GPa initial contact pressure, the friction coefficient, scar diameter, depth and width of the wear track dramatically decrease by 83.1%, 43.2%, 88.5% and 59.5%, respectively. It is considered that the sufficiently small size and the excellent dispersion of NiAl-LDH/OAm nanoplatelets in water are the key factors, so as to make them enter the contact area, form a lubricating film and prevent direct collision of asperity peaks. Our investigations demonstrate that the LDH nanoplatelet as a water-based lubricant additive has a great potential value in industrial application. PMID:26951794

Layered Double Hydroxide Nanoplatelets with Excellent Tribological Properties under High Contact Pressure as Water-Based Lubricant Additives.

PubMed

Wang, Hongdong; Liu, Yuhong; Chen, Zhe; Wu, Bibo; Xu, Sailong; Luo, Jianbin

2016-03-08

High efficient and sustainable utilization of water-based lubricant is essential for saving energy. In this paper, a kind of layered double hydroxide (LDH) nanoplatelets is synthesized and well dispersed in water due to the surface modification with oleylamine. The excellent tribological properties of the oleylamine-modified Ni-Al LDH (NiAl-LDH/OAm) nanoplatelets as water-based lubricant additives are evaluated by the tribological tests in an aqueous environment. The modified LDH nanoplatelets are found to not only reduce the friction but also enhance the wear resistance, compared with the water-based cutting fluid and lubricants containing other particle additives. By adding 0.5 wt% LDH nanoplatelets, under 1.5 GPa initial contact pressure, the friction coefficient, scar diameter, depth and width of the wear track dramatically decrease by 83.1%, 43.2%, 88.5% and 59.5%, respectively. It is considered that the sufficiently small size and the excellent dispersion of NiAl-LDH/OAm nanoplatelets in water are the key factors, so as to make them enter the contact area, form a lubricating film and prevent direct collision of asperity peaks. Our investigations demonstrate that the LDH nanoplatelet as a water-based lubricant additive has a great potential value in industrial application.

EFFECTS OF EPISODIC SUBLUXATION EVENTS ON THIRD BODY INGRESS AND EMBEDMENT IN THE THA BEARING SURFACE

PubMed Central

Heiner, Anneliese D.; Lundberg, Hannah J.; Baer, Thomas E.; Pedersen, Douglas R.; Callaghan, John J.; Brown, Thomas D.

2008-01-01

In total joint arthroplasty, third body particle access to the articulating surfaces results in accelerated wear. Hip joint subluxation is an under-recognized means by which third body particles could potentially enter the otherwise closely conforming articular bearing space. The present study was designed to test the hypothesis that, other factors being equal, even occasional events of femoral head subluxation greatly increase the number of third body particles that enter the bearing space and become embedded in the acetabular liner, as compared to level walking cycles alone. Ten metal-on-polyethylene hip joint head-liner pairs were tested in a multi-axis joint motion simulator, with CoCrMo third body particles added to the synovial fluid analog. All component pairs were tested for two hours of level walking; half also were subjected to twenty intermittent subluxation events. The number and location of embedded particles on the acetabular liners were then determined. Subluxation dramatically increased the number of third body particles embedded in the acetabular liners, and it considerably increased the amount of scratch damage on the femoral heads. Since both third body particles and subluxation frequently occur in contemporary total hip arthroplasty, their potent synergy needs to be factored prominently into strategies to minimize wear. PMID:18561936

Dramatic pretend play games uniquely improve emotional control in young children.

PubMed

Goldstein, Thalia R; Lerner, Matthew D

2017-09-15

Pretense is a naturally occurring, apparently universal activity for typically developing children. Yet its function and effects remain unclear. One theorized possibility is that pretense activities, such as dramatic pretend play games, are a possible causal path to improve children's emotional development. Social and emotional skills, particularly emotional control, are critically important for social development, as well as academic performance and later life success. However, the study of such approaches has been criticized for potential bias and lack of rigor, precluding the ability to make strong causal claims. We conducted a randomized, component control (dismantling) trial of dramatic pretend play games with a low-SES group of 4-year-old children (N = 97) to test whether such practice yields generalized improvements in multiple social and emotional outcomes. We found specific effects of dramatic play games only on emotional self-control. Results suggest that dramatic pretend play games involving physicalizing emotional states and traits, pretending to be animals and human characters, and engaging in pretend scenarios in a small group may improve children's emotional control. These findings have implications for the function of pretense and design of interventions to improve emotional control in typical and atypical populations. Further, they provide support for the unique role of dramatic pretend play games for young children, particularly those from low-income backgrounds. A video abstract of this article can be viewed at: https://youtu.be/2GVNcWKRHPk. © 2017 John Wiley & Sons Ltd.

Corrosion-wear of β-Ti alloy TMZF (Ti-12Mo-6Zr-2Fe) in simulated body fluid.

PubMed

Yang, Xueyuan; Hutchinson, Christopher R

2016-09-15

Titanium alloys are popular metallic implant materials for use in total hip replacements. Although, α+β titanium alloys such as Ti-6Al-4V have been the most commonly used alloys, the high Young's modulus (∼110GPa) leads to an undesirable stress shielding effect. An alternative is to use β titanium alloys that exhibit a significantly lower Young's modulus (∼70GPa). Femoral stems made of a β titanium alloy known as TMZF (Ti-12Mo-6Zr-2Fe (wt.%)) have been used as part of modular hip replacements since the early 2000's but these were recalled in 2011 by the US Food & Drug Administration (FDA) due to unacceptable levels of 'wear debris'. The wear was caused by small relative movement of the stem and neck at the junction where they fit together in the modular hip replacement design. In this study, the corrosion and wear properties of the TMZF alloy were investigated in simulated body fluid to identify the reason for the wear debris generation. Ti64 was used as a control for comparison. It is shown that the interaction between the surfaces of Ti64 and TMZF with simulated body fluid is very similar, both from the point of view of the products formed and the kinetics of the reaction. The dry wear behaviour of TMZF is also close to that of Ti64 and consistent with expectations based on Archard's law for abrasive wear. However, wear of Ti64 and TMZF in simulated body fluid show contrasting behaviours. A type of time-dependent wear test is used to examine the synergy between corrosion and wear of TMZF and Ti64. It is shown that the wear of TMZF accelerated rapidly in SBF whereas that of Ti64 is reduced. The critical role of the strain hardening capacity of the two materials and its role in helping the surface resist abrasion by hydroxyapatite particles formed as a result of the reaction with the SBF is discussed and recommendations are made for modifications that could be made to the TMZF alloy to improve the corrosion-wear response. TMZF is a low modulus β-Ti alloy that has been used as the femoral stem in the Stryker modular design total hip replacement. It went into service in the early 2000's but was recalled by the FDA in 2011 due to unacceptable levels of wear debris released in the body which led to adverse physiological reactions. A large number of these implants remain in patients today. In this contribution, we investigate the corrosion (interaction of the alloy with simulated body fluid (SBF)), dry wear and then corrosion-wear in SBF to identify the origin of the unacceptable levels of wear that led to the FDA recall of this material. We use Ti-6Al-4V as a control and demonstrate that the reaction between Ti64 and TMZF with SBF is very similar in terms of both products formed and kinetics. We also show that the dry wear behaviour of TMZF is very similar to that of Ti64 and exactly as should be expected for the hardness of this material. However, the wear behaviours of TMZF and Ti64 are completed different in SBF and wear of TMZF is significantly accelerated in SBF. A type of time-dependent wear test is used to demonstrate the synergy between corrosion and wear and the key role of the strain hardening capacity (or lack thereof in the case of β-Ti) is discussed. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High Current Plasma Electrolytic Oxidation Coating Processes for Wear and Corrosion Prevention of Al 2024

NASA Astrophysics Data System (ADS)

Wang, Rui

Plasma electrolytic oxidation (PEO) treatments have been used in the aerospace and automotive industries because the coating formed on light metals or alloys has great hardness, high wear, corrosion, and oxidation resistance, and a low friction coefficient that improves lifetime length and provide a higher surface quality. However, the PEO treatments that are presently used for industrial applications require a long period of time to confirm the quality of the coating. For this reason, the present study seeks to increase the current density of PEO treatments to improve their efficiency and explore the performance of the obtained coatings. It was found that for high current density (0.18A/cm2) PEO treatments, smaller ratio, such as 50% and 70%, is beneficial to obtaining a better performance coating. When compared with the coating of a "normal" (current density: 0.09A/cm2) PEO treatment, it had better wear resistance; however, for corrosion resistance, it had a lower performance than the coatings obtained by the "normal" current density PEO treatment which was attributed to the negative influence of porosity increase.

Body awareness training in the treatment of wearing-off related anxiety in patients with Parkinson's disease: Results from a pilot randomized controlled trial.

PubMed

Ghielen, Ires; van Wegen, Erwin E H; Rutten, Sonja; de Goede, Cees J T; Houniet-de Gier, Marieke; Collette, Emma H; Burgers-Bots, Ingrid A L; Twisk, Jos W R; Kwakkel, Gert; Vermunt, Kees; van Vliet, Bep; Berendse, Henk W; van den Heuvel, Odile A

2017-12-01

In Parkinson's disease (PD) patients, fluctuations in symptoms commonly occur after many years of dopamine replacement therapy. The so-called wearing-off phenomenon exists of both motor and non-motor symptoms, such as rigidity and anxiety. Current treatment options are limited and an integrated approach is needed to address the complex interactions between motor and non-motor symptoms. Since wearing-off is eventually inevitable, treatment needs to focus on coping, acceptance and self-efficacy. We developed the body awareness training, named BEWARE, combining physical therapy with acceptance and commitment therapy to help PD patients deal better with wearing-off related anxiety (WRA). This was an investigator-blinded randomized controlled trial. Forty PD patients with WRA were randomly assigned to the BEWARE or to the treatment as usual (TAU) condition. Assessments were performed prior to and immediately after the treatment period, and at 3-months follow up. The primary outcome was self-efficacy, secondary outcomes focused on mobility, daily functioning, anxiety, depression and quality of life. There was no significant improvement in self-efficacy in the BEWARE treatment condition when compared to TAU. However, standing balance and emotional wellbeing showed a significant improvement, and feelings of stigmatization showed a trend-significant decrease in the BEWARE condition. We consider the BEWARE training to be a promising therapeutic approach to address WRA. Improvement points from the participants included 1) less frequent but longer therapy sessions; 2) active involvement of caregivers; and 3) the development of a supportive workbook. The optimized treatment protocol needs further evaluation in a phase III RCT. ClinicalTrials.gov identifier: NCT02054845. Copyright © 2017 Elsevier Inc. All rights reserved.

Ammonia-treated phosphate glasses useful for sealing to metals metals

DOEpatents

Brow, Richard K.; Day, Delbert E.

1991-01-01

A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.

Ammonia-treated phosphate glasses useful for sealing to metals

DOEpatents

Brow, R.K.; Day, D.E.

1991-09-03

A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.

A hybrid method based on Band Pass Filter and Correlation Algorithm to improve debris sensor capacity

NASA Astrophysics Data System (ADS)

Hong, Wei; Wang, Shaoping; Liu, Haokuo; Tomovic, Mileta M.; Chao, Zhang

2017-01-01

The inductive debris detection is an effective method for monitoring mechanical wear, and could be used to prevent serious accidents. However, debris detection during early phase of mechanical wear, when small debris (<100 um) is generated, requires that the sensor has high sensitivity with respect to background noise. In order to detect smaller debris by existing sensors, this paper presents a hybrid method which combines Band Pass Filter and Correlation Algorithm to improve sensor signal-to-noise ratio (SNR). The simulation results indicate that the SNR will be improved at least 2.67 times after signal processing. In other words, this method ensures debris identification when the sensor's SNR is bigger than -3 dB. Thus, smaller debris will be detected in the same SNR. Finally, effectiveness of the proposed method is experimentally validated.

Friction and Wear of Ion-Beam-Deposited Diamondlike Carbon on Chemical-Vapor-Deposited, Fine-Grain Diamond

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Wu, Richard L. C.; Lanter, William C.

1996-01-01

Friction and wear behavior of ion-beam-deposited diamondlike carbon (DLC) films coated on chemical-vapor-deposited (CVD), fine-grain diamond coatings were examined in ultrahigh vacuum, dry nitrogen, and humid air environments. The DLC films were produced by the direct impact of an ion beam (composed of a 3:17 mixture of Ar and CH4) at ion energies of 1500 and 700 eV and an RF power of 99 W. Sliding friction experiments were conducted with hemispherical CVD diamond pins sliding on four different carbon-base coating systems: DLC films on CVD diamond; DLC films on silicon; as-deposited, fine-grain CVD diamond; and carbon-ion-implanted, fine-grain CVD diamond on silicon. Results indicate that in ultrahigh vacuum the ion-beam-deposited DLC films on fine-grain CVD diamond (similar to the ion-implanted CVD diamond) greatly decrease both the friction and wear of fine-grain CVD diamond films and provide solid lubrication. In dry nitrogen and in humid air, ion-beam-deposited DLC films on fine-grain CVD diamond films also had a low steady-state coefficient of friction and a low wear rate. These tribological performance benefits, coupled with a wider range of coating thicknesses, led to longer endurance life and improved wear resistance for the DLC deposited on fine-grain CVD diamond in comparison to the ion-implanted diamond films. Thus, DLC deposited on fine-grain CVD diamond films can be an effective wear-resistant, lubricating coating regardless of environment.

Wear resistance of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted carbon fiber reinforced poly(ether ether ketone) liners against metal and ceramic femoral heads.

PubMed

Yamane, Shihori; Kyomoto, Masayuki; Moro, Toru; Hashimoto, Masami; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko

2018-04-01

Younger, active patients who undergo total hip arthroplasty (THA) have increasing needs for wider range of motion and improved stability of the joint. Therefore, bearing materials having not only higher wear resistance but also mechanical strength are required. Carbon fiber-reinforced poly(ether ether ketone) (CFR-PEEK) is known as a super engineering plastic that has great mechanical strength. In this study, we focused on poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-grafted CFR-PEEK and investigated the effects of PMPC grafting and the femoral heads materials on the wear properties of CFR-PEEK liners. Compared with untreated CFR-PEEK, the PMPC-grafted CFR-PEEK surface revealed higher wettability and lower friction properties under aqueous circumstances. In the hip simulator wear test, wear particles generated from the PMPC-grafted CFR-PEEK liners were fewer than those of the untreated CFR-PEEK liners. There were no significant differences in the size and the morphology of the wear particles between the differences of PMPC-grafting and the counter femoral heads. Zirconia-toughened alumina (ZTA) femoral heads had significantly smoother surfaces compared to cobalt-chromium-molybdenum alloy femoral heads after the hip simulator test. Thus, we conclude that the bearing combination of the PMPC-grafted CFR-PEEK liner and ZTA head is expected to be a lifelong bearing interface in THA. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1028-1037, 2018. © 2017 Wiley Periodicals, Inc.

Polyethylene wear debris in modular acetabular prostheses.

PubMed

Chen, P C; Mead, E H; Pinto, J G; Colwell, C W

1995-08-01

The longevity of total hip arthroplasty has brought forth the recognition of aseptic loosening of prosthetic components as the leading cause of implant failure. Modularity of implants, although a significant improvement in versatility, may increase debris formation, a recognized cause of implant failure. This study was designed to measure the relative motion, and to assess the polyethylene wear debris production at the interface between the metal acetabular shell and the back side of the polyethylene liner, in modular hip prostheses. Five models from 4 manufacturers with different locking mechanisms and acetabular shell surface treatments were tested under long-term simultaneous sinusoidal and static loading (10(7) cycles at 3 Hz with +/- 2.5 Nmeter and 220 N static load). Results showed that there were marked differences in the security of the acetabular shell and polyethylene liner locking mechanism, wear pattern, damage sites, and amount of polyethylene debris on the acetabular shell and polyethylene liner surfaces. The range of polyethylene liner motion observed among the 5 models during 1 cycle of testing varied from an average of 0.96 degrees to movement too small to be detected by the test machines. Image and scanning electron microscopy analysis showed different wear patterns and a wide range in the average polyethylene liner surface wear area (0.26 cm2-4.61 cm2). In general, a stable locking mechanism and a smooth acetabular shell surface are essential in minimizing polyethylene liner wear and polyethylene debris production.

Increasing Wear Resistance of Titanium Alloys by Anode Plasma Electrolytic Saturation with Interstitial Elements

NASA Astrophysics Data System (ADS)

Belkin, P. N.; Kusmanov, S. A.; Dyakov, I. G.; Silkin, S. A.; Smirnov, A. A.

2017-05-01

In our previous studies, we have shown that anode plasma electrolytic saturation of titanium alloys with nitrogen and carbon can improve their tribological properties. Obtained structure containing oxide layer and solid solution of diffused element in titanium promotes the enhancement of running-in ability and the decrease in the wear rate in some special cases. In this paper, further investigations are reported regarding the tribological properties of alpha- and beta-titanium alloys in wear test against hardened steel (50 HRC) disk using pin-on-disk geometry and balls of Al2O3 (6.25 mm in diameter) or bearing steel (9.6 mm in diameter) with ball-on-plate one and normal load from 5 to 209 N. Reproducible results were obtained under testing samples treated by means of the plasma electrolytic nitriding (PEN) with the mechanical removal of the oxide layer. Friction coefficient of nitrided samples is 0.5-0.9 which is somewhat higher than that for untreated one (0.48-0.75) during dry sliding against Al2O3 ball. An increase in the sliding speed results in the polishing of nitrided samples and reduction of their wear rate by 60 times. This result is obtained for 5 min at 850 °C using PEN in electrolyte containing 5 wt.% ammonia and 10 wt.% ammonium chloride followed by quenching in solution. Optical microscope was employed to assist in the evaluation of the wear behavior. Sizes of wear tracks were measured by profilometer TR200.

An analysis of the wear behavior of SiC whisker reinforced alumina from 25 to 1200 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher

1991-01-01

A model is described for predicting the wear behavior of whisker reinforced ceramics. The model was successfully applied to a silicon carbide whisker reinforced alumina ceramic composite subjected to sliding contact. The model compares the friction forces on the whiskers due to sliding, which act to pull or push them out of the matrix, to the clamping or compressive forces on the whiskers due to the matrix, which act to hold the whiskers in the composite. At low temperatures, the whiskers are held strongly in the matrix and are fractured into pieces during the wear process along with the matrix. At elevated temperatures differential thermal expansion between the whiskers and matrix can cause loosening of the whiskers and lead to pullout during the wear process and to higher wear. The model, which represents the combination of elastic stress analysis and a friction heating analysis, predicts a transition temperature at which the strength of the whiskers equals the clamping force holding them in the matrix. Above the transition the whiskers are pulled out of the matrix during sliding, and below the transition the whiskers are simply fractured. The existence of the transition gives rise to a dual wear mode or mechanism behavior for this material which was observed in laboratory experiments. The results from this model correlate well with experimentally observed behavior indicating that the model may be useful in obtaining a better understanding of material behavior and in making material improvements.

An analysis of the wear behavior of SiC whisker-reinforced alumina from 25 to 1200 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher

1993-01-01

A model is described for predicting the wear behavior of whisker reinforced ceramics. The model was successfully applied to a silicon carbide whisker reinforced alumina ceramic composite subjected to sliding contact. The model compares the friction forces on the whiskers due to sliding, which act to pull or push them out of the matrix, to the clamping or compressive forces on the whiskers due to the matrix, which act to hold the whiskers in the composite. At low temperatures, the whiskers are held strongly in the matrix and are fractured into pieces during the wear process along with the matrix. At elevated temperatures differential thermal expansion between the whiskers and matrix can cause loosening of the whiskers and lead to pullout during the wear process and to higher wear. The model, which represents the combination of elastic stress analysis and a friction heating analysis, predicts a transition temperature at which the strength of the whiskers equals the clamping force holding them in the matrix. Above the transition the whiskers are pulled out of the matrix during sliding, and below the transition the whiskers are simply fractured. The existence of the transition gives rise to a dual wear mode or mechanism behavior for this material which was observed in laboratory experiments. The results from this model correlate well with experimentally observed behavior indicating that the model may be useful in obtaining a better understanding of material behavior and in making material improvements.

A Multidirectional Tribo-System: Wear of UHMWPE under Sliding, Rolling, and Rotation

NASA Astrophysics Data System (ADS)

Patten, Elias Wolfgang

Total knee replacements (TKR) have become a successful surgical procedure for addressing end-stage osteoarthritis, with ultra-high molecular weight polyethylene and cobalt chrome alloy (UHMWPE/Co-Cr) serving as the bearing materials of choice for decades. However, more than 10% of TKRs fail and require revision surgery. The predominant challenge with UHMWPE is the particulate debris generated through wear-mediated processes; wear debris from the UHMWPE tibial bearing surface leading to loosening is still the main cause for post-fifth-year revisions. UHMWPE wear in hip arthroplasty has been linked to microstructural evolution at the surface from multidirectional sliding in the hip joint but little is known about how the microstructure responds to clinically relevant sliding conditions in the knee. This is likely because wear tests are typically performed under basic motion parameters with simplified geometry (pin-on-disk tests) while the knee has more complex kinematics: it is neither a ball-and-socket joint nor a simple hinge joint, but has 2D sliding, rolling/slip motion, and rotation. There is also disagreement over how to best quantify cross-shear and how to model how much wear it will cause. A custom multidirectional tribo-system was used to investigate the individual and combined effects of the different motions in TKR: 2D sliding, rolling, and rotation, for a total of eight separate kinematic conditions. The trends in wear rates and wear factors for these different motions were compared with many different definitions for magnitudes and ratios of cross-shear. Additionally, the wear surfaces were examined for wear mechanism and the microstructural changes in lamellae orientation for the different motions were analyzed. To mimic the tribological conditions of a condyle in a TKR, polished Co-Cr spheres were articulated against flat, smooth UHMWPE disks with physiologically relevant loading, speed, and lubrication conditions. The motion parameters were selected based on the lowest and highest reasonable amounts of cross-shear that each motion type would generate during a realistic gait cycle: a reciprocating line or a "figure 8" with a 15° crossing angle, no rolling or a 0.4 slide-to-roll ratio, and no rotation or a 1°/mm of rotation. The amount of wear was measured with optical profilometry of the cross-section at the middle of the wear scar, after allowing for a resting period for the material creep to recover. To calculate the amount of cross-shear at this cross-section, the sliding interface was simulated with a computer Matlab model. Multiple definitions of cross-shear were used, including the traditional, cycle-based approaches and newer, memory-based approaches. The wear surfaces were examined using optical microscopy and scanning electron microscopy (SEM). The lamellar microstructure at the wear surface and below the wear surface was examined using an oxidizing etch to remove the amorphous phase. The remaining lamellae were imaged using SEM and their orientations and alignment was quantified using an image analysis program. Wear factors were between 0.3 and 8.7 µm2/(Nm/mm), significantly increasing with motion complexity and cross-shear, with the "figure 8" sliding path having the greatest effect. Volumetric wear rates correlated linearly with the total amount of cross-shear, while wear factors correlated linearly with ratios of cross-shear. The best predictors of the wear factor were the normalized crossing intensity and normalized, memory-based cross-shear ratios, with R2 values of 0.98 and 0.97, although many of the cross-shear ratios also had a good linear fits with wear factor. The kinematic parameters in this experiment did not differentiate the various cross-shear parameters enough to conclusively determine which are most appropriate, although some have a stronger theoretical foundation than others. SEM analysis of the wear scar surface revealed slight scratching and instances of rippling and surface cracking perpendicular to the primary sliding directions. These are consistent with abrasive wear, plastic flow and adhesive wear, and fatigue wear mechanisms reported in other in vitro and in vivo wear studies. The orientations of the lamellae at the wear surfaces were not discernibly different from the lamellae of an unworn section of the disk surface. Similarly, the near-surface regions of the disk cross-section were not discernibly different from the subsurface regions. Previous studies have demonstrated orientation of the microstructure during wear using transmission electron microscopy, X-ray scattering, and Fourier transform infrared spectroscopy techniques, and such methods may be necessary for texture characterization. These results demonstrate that knee kinematics have a significant effect on the cross-shear and wear of UHMWPE and should not be neglected when designing TKR. A better theoretical understanding of how kinematics contribute to wear can lead to better UHMWPE formulations, improved computer simulations of wear, and optimized TKR designs with longer life-spans.

Compliance With Protective Lens Wear in Anophthalmic Patients.

PubMed

Neimkin, Michael G; Custer, Philip L

To evaluate the frequency of protective lens wear by anophthalmic patients and identify factors that influence compliance. An IRB approved descriptive retrospective chart review of patients undergoing surgery with the senior author (PLC) with an anophthalmic orbit and one remaining sighted eye. Results were tabulated and analyzed using age, indication for procedure, duration of visual symptoms, safety glasses wear, number of postoperative visits, and evidence of new trauma to the remaining eye. All patients underwent counseling on the importance of protective lens wear preoperatively and each subsequent visit. Etiologies for loss of the eye in the 132 study patients included trauma (33.3%), blind painful eye (33.3%), congenital disorders (14.4%), adult-onset malignancy (14.4%), and retinoblastoma (4.5%). At the final visit, protective lenses were worn in the following patterns: full-time (55.3%), frequently (11.4%), occasional (6%), and never (28.8%). The regular use of protective eyewear at last visit was more common in patients wearing glasses at presentation (79.7%), than in those who did not (32.9%; p ≤ 0.001). Increased number of office encounters correlated with more frequent use of protective eyewear (p ≤ 0.01). Patient age (p = 0.95), indication for surgery (p = 0.97), and duration of visual loss (p = 0.85) were not predictive of safety glasses wear. Three patients had evidence of subsequent ocular trauma to the remaining eye, with 2 having resultant decrease in acuity; none of these 3 patients wore safety glasses full-time. A significant number of anopthalmic patients were not wearing protective lenses at presentation. Overall compliance was poor; but repeated education on the importance of safety glasses appears to improve compliance. Educating referring providers and primary care physicians about the importance of early and repeated counseling is vital to increasing compliance.

The Tribological Difference between Biomedical Steels and CoCrMo-Alloys

PubMed Central

Fischer, Alfons; Weiß, Sabine; Wimmer, Markus A.

2012-01-01

In orthopedic surgery different self-mating metal couples are used for sliding wear applications. Despite the fact that in mechanical engineering self-mating austenitic alloys often lead to adhesion and seizure in biomedical engineering the different grades of Co-base alloys show good clinical results e.g. as hip joints. The reason stems from the fact that they generate a so-called tribomaterial during articulation, which consists of a mixture of nanometer small metallic grains and organic substances from the interfacial medium, which act as boundary lubricant. Even though stainless steels also generate such a tribomaterial they were ruled out from the beginning already in the 1950 as “inappropriate”. On the basis of materials with a clinical track record this contribution shows that the cyclic creep characteristics within the shear zone underneath the tribomaterial are another important criterion for a sufficient wear behavior. By means of sliding wear and torsional fatigue tests followed by electron microscopy it is shown, that austenitic materials generate wear particles of either nano- or of microsize. The latter are produced by crack initiation and propagation within the shear fatigue zone which is related to the formation of subsurface dislocation cells and, therefore, by the fact that a Ni-containing CrNiMo solid solution allows for wavy-slip. In contrast to this a Ni-free CrMnMo solid solution with further additions of C and N only shows planar slip. This leads to the formation of nanosize wear particles and distinctly improves the wear behavior. Still the latter does not fully achieve that of CoCrMo, which also shows solely planar-slip behavior. This explains why for metallurgical reasons the Ni-containing 316L-type of steels had to fail in such boundary lubricated sliding wear tribosystems. PMID:22498283

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landauer, Alexander K.; Barnhill, William C.; Qu, Jun

Here we examine the elasticity, hardness, and resistance-to-plastic-deformation (P/S 2) measured via nanoindentation of several tribofilms and correlates these properties to friction and wear behavior. The tribofilms were generated by ball-on-plate reciprocating sliding lubricated by a base oil containing an ionic liquid, phosphonium-organophosphate or ammonium-organophosphate, zinc dialkyldithiophosphate (ZDDP), or combination of IL and ZDDP. Nanoindentation was conducted at room and elevated temperatures. While there seems little correlation between the tribofilm hardness and tribological behavior, a higher modulus generally leads to better friction and wear performance. Interestingly, a lower P/S 2 ratio tends to reduce friction and improve wear protection, whichmore » is in an opposite trend as reported for bulk materials. Ultimately, this is likely attributable to the dynamic, self-healing characteristics of tribofilms.« less

Design of crusher liner based on time - varying uncertainty theory

NASA Astrophysics Data System (ADS)

Tang, J. C.; Shi, B. Q.; Yu, H. J.; Wang, R. J.; Zhang, W. Y.

2017-09-01

This article puts forward the time-dependent design method considering the load fluctuation factors for the liner based on the time-varying uncertainty theory. In this method, the time-varying uncertainty design model of liner is constructed by introducing the parameters that affect the wear rate, the volatility and the drift rate. Based on the design example, the timevarying design outline of the moving cone liner is obtained. Based on the theory of minimum wear, the gap curve of wear resistant cavity is designed, and the optimized cavity is obtained by the combination of the thickness of the cone and the cavity gap. Taking the PYGB1821 multi cylinder hydraulic cone crusher as an example, it is proved that the service life of the new liner is improved by more than 14.3%.

Ultra-High Molecular Weight Polyethylene: Influence of the Chemical, Physical and Mechanical Properties on the Wear Behavior. A Review

PubMed Central

Bellare, Anuj; Bistolfi, Alessandro

2017-01-01

Ultra-high molecular weight polyethylene (UHMWPE) is the most common bearing material in total joint arthroplasty due to its unique combination of superior mechanical properties and wear resistance over other polymers. A great deal of research in recent decades has focused on further improving its performances, in order to provide durable implants in young and active patients. From “historical”, gamma-air sterilized polyethylenes, to the so-called first and second generation of highly crosslinked materials, a variety of different formulations have progressively appeared in the market. This paper reviews the structure–properties relationship of these materials, with a particular emphasis on the in vitro and in vivo wear performances, through an analysis of the existing literature. PMID:28773153

Surface Nb-ALLOYING on 0.4C-13Cr Stainless Steel: Microstructure and Tribological Behavior

NASA Astrophysics Data System (ADS)

Yu, Shengwang; You, Kai; Liu, Xiaozhen; Zhang, Yihui; Wang, Zhenxia; Liu, Xiaoping

2016-02-01

0.4C-13Cr stainless steel was alloyed with niobium using double glow plasma surface alloying and tribological properties of Nb-alloyed steel such as hardness, friction and wear were measured. Effects of the alloying temperature on microstructure and the tribological behavior of the alloyed steel were investigated compared with untreated steel. Formation mechanisms of Nb-alloyed layers and increased wear resistance were also studied. The result shows that after surface Nb-alloying treatment, the 0.4C-13Cr steel exhibits a diffusion adhesion at the alloyed layer/substrate interface and improved tribological property. The friction coefficient of Nb-alloyed steel is decreased by about 0.3-0.45 and the wear rate after Nb-alloying is only 2-5% of untreated steel.

Design of Wear-Resistant Austenitic Steels for Selective Laser Melting

NASA Astrophysics Data System (ADS)

Lemke, J. N.; Casati, R.; Lecis, N.; Andrianopoli, C.; Varone, A.; Montanari, R.; Vedani, M.

2018-03-01

Type 316L stainless steel feedstock powder was modified by alloying with powders containing carbide/boride-forming elements to create improved wear-resistant austenitic alloys that can be readily processed by Selective Laser Melting. Fe-based alloys with high C, B, V, and Nb contents were thus produced, resulting in a microstructure that consisted of austenitic grains and a significant amount of hard carbides and borides. Heat treatments were performed to modify the carbide distribution and morphology. Optimal hard-phase spheroidization was achieved by annealing the proposed alloys at 1150 °C for 1 hour followed by water quenching. The total increase in hardness of samples containing 20 pct of C/B-rich alloy powder was of 82.7 pct while the wear resistance could be increased by a factor of 6.

Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part.

PubMed

Ahmed, Yassmin Seid; Fox-Rabinovich, German; Paiva, Jose Mario; Wagg, Terry; Veldhuis, Stephen Clarence

2017-10-25

During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool-chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear.

Synergistic effect between nano-ceramic lubricating additives and electroless deposited Ni-W-P coating

NASA Astrophysics Data System (ADS)

Chen, Min; Cheng, Wushan; Zhao, Zuxin; Huang, Xiaobo

2013-01-01

The major solving ways for the material wear are surface modification and lubrication. Currently, the researches at home and abroad are all limited to the single study of either nano-lubricating oil additive or electroless deposited coating. The surface coating has high hardness and high wear resistance, however, the friction reduction performance of the coating with high hardness is not good, the thickness of the coating is limited, and the coating can not regenerate after wearing. The nano-lubricating additives have good tribological performance and self-repair function, but under heavy load, the self-repair rate to the worn surface with the nano-additives is smaller than the wearing rate of the friction pair. To solve the above problems, the Ni-W-P alloy coating and deposition process with excellent anti-wear, and suitable for industrial application were developed, the optimum bath composition and process can be obtained by studying the influence of the bath composition, temperature and PH value to the deposition rate and the plating solution stability. The tribological properties as well as anti-wear and friction reduction mechanism of wear self-repair nano-ceramic lubricating additives are also studied. The ring-block abrasion testing machine and energy dispersive spectrometer are used to explore the internal relation between the coating and the nano-lubricating oil additives, and the tribology mechanism, to seek the synergetic effect between the two. The test results show that the wear resistance of Ni-W-P alloy coating (with heat treatment and in oil with nano-ceramic additives) has increased hundreds times than 45 steel as the metal substrate in basic oil, the friction reduction performance is improved. This research breaks through the bottleneck of previous separate research of the above-mentioned two methods, and explores the combination use of the two methods in industrial field.

Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part

PubMed Central

Fox-Rabinovich, German; Wagg, Terry

2017-01-01

During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear. PMID:29068405

Impact of removable dentures on oral health-related quality of life among elderly adults in Taiwan.

PubMed

Yen, Yea-Yin; Lee, Huey-Er; Wu, Yi-Min; Lan, Shou-Jen; Wang, Wen-Chen; Du, Je-Kang; Huang, Shun-Te; Hsu, Kun-Jung

2015-01-05

Although the use of removable dentures can improve oral function and esthetics for elderly people, compared to those who do not wear removable dentures, those wearing removable dentures could have worse oral health related-quality of life (OHRQoL). Additional information is required to assess which factors related to denture wearing influence the OHRQoL of elderly individuals. The purpose of this study is to evaluate the association between denture wearing and OHRQoL in a sample of elderly individuals in Taiwan. The study population included 277 elderly people wearing removable dentures (mean age = 76.0 years). Using face-to-face interviews, we collected data on the participants' socio-demographic characteristics, dental care service usage (regular dental checkups, treatment during toothache, dental visits in the last year), and factors related to denture wearing (perceived oral pain, perceived loose denture, perceived oral ulcer, perceived halitosis, perceived dry mouth, and perceived total denture satisfaction scores). OHRQoL was measured using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The location and number of remaining natural teeth and the type of denture were also recorded. Hierarchical multiple regression analysis was performed using GOHAI-T scores as the dependent variable. All the predictors together accounted for 50% of the variance in GOHAI-T scores. Further, education level, number of natural teeth, denture status, perceived loose denture, perceived oral ulcer, and perceived total denture satisfaction scores had statistically significant influences on OHRQoL. When compared with other variables, factors related to denture wearing, especially perceived total denture satisfaction scores, had the greatest impact on GOHAI-T scores. Of the factors analyzed in this study, denture satisfaction was the strongest predictor of OHRQoL. This suggests that denture satisfaction is useful for assessing the effect of denture treatment on the OHRQoL of elderly individuals wearing removable dentures.

Development of wear resistant ceramic coatings for diesel engine components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haselkorn, M.H.

1992-04-01

Improved fuel economy and a reduction of emissions can be achieved by insulation of the combustion chamber components to reduce heat rejection. However, insulating the combustion chamber components will also increase the operating temperature of the piston ring/cylinder liner interface from approximately 150{degree}C to over 300{degree}C. Existing ring/liner materials can not withstand these higher operating temperatures and for this reason, new materials need to be developed for this critical tribological interface. The overall goal of this program is the development of piston ring/cylinder liner material pairs which would be able to provide the required friction and wear properties at thesemore » more severe operating conditions. More specifically, this program first selected, and then evaluated, potential d/wear resistant coatings which could be applied to either piston rings an or cylinder liners and provide, at 350{degree}C under lubricated conditions, coefficients of friction below 0.1 and wear rates of less than 25 {times} lO{sup {minus}6} mm/hour. The processes selected for applying the candidate wear resistant coatings to piston rings and/or cylinder liners were plasma spraying, chemical vapor, physical vapor and low temperature arc vapor deposition techniques as well as enameling techniques.« less

Development of wear resistant ceramic coatings for diesel engine components. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haselkorn, M.H.

1992-04-01

Improved fuel economy and a reduction of emissions can be achieved by insulation of the combustion chamber components to reduce heat rejection. However, insulating the combustion chamber components will also increase the operating temperature of the piston ring/cylinder liner interface from approximately 150{degree}C to over 300{degree}C. Existing ring/liner materials can not withstand these higher operating temperatures and for this reason, new materials need to be developed for this critical tribological interface. The overall goal of this program is the development of piston ring/cylinder liner material pairs which would be able to provide the required friction and wear properties at thesemore » more severe operating conditions. More specifically, this program first selected, and then evaluated, potential d/wear resistant coatings which could be applied to either piston rings an or cylinder liners and provide, at 350{degree}C under lubricated conditions, coefficients of friction below 0.1 and wear rates of less than 25 {times} lO{sup {minus}6} mm/hour. The processes selected for applying the candidate wear resistant coatings to piston rings and/or cylinder liners were plasma spraying, chemical vapor, physical vapor and low temperature arc vapor deposition techniques as well as enameling techniques.« less

Hybrid ABC Optimized MARS-Based Modeling of the Milling Tool Wear from Milling Run Experimental Data

PubMed Central

García Nieto, Paulino José; García-Gonzalo, Esperanza; Ordóñez Galán, Celestino; Bernardo Sánchez, Antonio

2016-01-01

Milling cutters are important cutting tools used in milling machines to perform milling operations, which are prone to wear and subsequent failure. In this paper, a practical new hybrid model to predict the milling tool wear in a regular cut, as well as entry cut and exit cut, of a milling tool is proposed. The model was based on the optimization tool termed artificial bee colony (ABC) in combination with multivariate adaptive regression splines (MARS) technique. This optimization mechanism involved the parameter setting in the MARS training procedure, which significantly influences the regression accuracy. Therefore, an ABC–MARS-based model was successfully used here to predict the milling tool flank wear (output variable) as a function of the following input variables: the time duration of experiment, depth of cut, feed, type of material, etc. Regression with optimal hyperparameters was performed and a determination coefficient of 0.94 was obtained. The ABC–MARS-based model's goodness of fit to experimental data confirmed the good performance of this model. This new model also allowed us to ascertain the most influential parameters on the milling tool flank wear with a view to proposing milling machine's improvements. Finally, conclusions of this study are exposed. PMID:28787882

Hybrid ABC Optimized MARS-Based Modeling of the Milling Tool Wear from Milling Run Experimental Data.

PubMed

García Nieto, Paulino José; García-Gonzalo, Esperanza; Ordóñez Galán, Celestino; Bernardo Sánchez, Antonio

2016-01-28

Milling cutters are important cutting tools used in milling machines to perform milling operations, which are prone to wear and subsequent failure. In this paper, a practical new hybrid model to predict the milling tool wear in a regular cut, as well as entry cut and exit cut, of a milling tool is proposed. The model was based on the optimization tool termed artificial bee colony (ABC) in combination with multivariate adaptive regression splines (MARS) technique. This optimization mechanism involved the parameter setting in the MARS training procedure, which significantly influences the regression accuracy. Therefore, an ABC-MARS-based model was successfully used here to predict the milling tool flank wear (output variable) as a function of the following input variables: the time duration of experiment, depth of cut, feed, type of material, etc . Regression with optimal hyperparameters was performed and a determination coefficient of 0.94 was obtained. The ABC-MARS-based model's goodness of fit to experimental data confirmed the good performance of this model. This new model also allowed us to ascertain the most influential parameters on the milling tool flank wear with a view to proposing milling machine's improvements. Finally, conclusions of this study are exposed.

Tribological behavior of Al-WC nano-composites fabricated by ultrasonic cavitation assisted stir-cast method

NASA Astrophysics Data System (ADS)

Pal, Arpan; Poria, Suswagata; Sutradhar, Goutam; Sahoo, Prasanta

2018-03-01

In the present study, the effects of WC nano-particles content on the microstructure, hardness, wear, and friction behavior of aluminum matrix composites are investigated. Al-WC nano composites with varying wt% of WC (0, 1, 1.5, and 2) are fabricated using ultrasonic cavitation assisted stir-cast method. The microstructure of the nano-composite samples is analyzed using optical microscopy and scanning electron microscopy. Elemental composition is determined by energy dispersive x-ray analysis. Vicker’s microhardness test is performed in different locations on the composite sample surface with a load of 50 gf and 10s dwell time. Wear and friction of the composites under dry sliding is studied using a pin-on-disk tribotester for varying normal load (10–40 N) and sliding speed (0.1–0.4 m/s). Uniform distribution of nano-WC is observed over composite surface without noticeable clustering. Reinforcement of nano-WC particles improves wear resistance and frictional behavior of the composite. Hardness is seen to increase with increase in wt% of nano-particles. Wear behavior of composites depends on formation of layers over the surface mixed with oxidized debris and counter-face particles. Wear mechanism changes from adhesion to abrasion with increase in wt% of hard nano particles.

Microstructure and Dry Sliding Wear Resistance of Laser Cladding Ti-Al-Si Composite Coating

NASA Astrophysics Data System (ADS)

Zhang, H. X.; Yu, H. J.; Chen, C. Z.; Dai, J. J.

In order to improve the wear resistance of Ti alloys, different mass ratios of Ti-Si-Al powders were designed to fabricate hard phases reinforced intermetallic matrix composite coatings on the Ti-6Al-4V substrate by laser cladding. The corresponding coatings were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and high resolution transmission microscopy (HRTEM). The HV-1000 hardness tester and MM200 wear test machine were employed to test the hardness and the wear resistance of the composite coatings, respectively. The composite coatings mainly consisted of the reinforcements of Ti5Si3, Ti3AlC2 and Ti7Al5Si12 and the matrix of Ti3Al, TiAl, TiAl3 and α-Ti. The micro-hardness of the Ti-35Al-15Si coating was from 956 HV0.2 to 1130 HV0.2, which was approximately 3-4 times of the substrate and the highest in the three samples. The wear rate of the Ti-35Al-15Si coating was 0.023cm3ṡmin-1, which was about 1/4 of the Ti-6Al-4V substrate. It was the lowest in the three samples.

The Sliding Wear and Friction Behavior of M50-Graphene Self-Lubricating Composites Prepared by Laser Additive Manufacturing at Elevated Temperature

NASA Astrophysics Data System (ADS)

Liu, Xiyao; Shi, Xiaoliang; Huang, Yuchun; Deng, Xiaobin; Lu, Guanchen; Yan, Zhao; Zhou, Hongyan; Xue, Bing

2018-03-01

M50 steel is widely applied to manufacture aircraft bearings where service lives are mainly determined by the friction and wear behaviors. The main purpose of this study is to investigate the tribological behaviors and wear mechanisms of M50-1.5 wt.% graphene composites (MGC) prepared by laser additive manufacturing (LAM) (MGC-LAM) sliding against Si3N4 ball from 25 to 550 °C at 18 N-0.2 m/s. XRD, EPMA, FESEM, and EDS mapping were conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MGC-LAM. The results indicated that MGC-LAM showed the excellent friction and wear performance at 25-550 °C for the lower friction coefficient of 0.16-0.52 and less wear rate of 6.1-9.5 × 10-7 mm3 N-1 m-1. Especially at 350 °C, MGC-LAM obtained the best tribological performance (0.16, 6.1 × 10-7mm3 N-1 m-1). It was attributed to the dense coral-like microstructure, as well as the formed surface lubricating structure which is composed of the upper uniform lubricating film with massive graphene and the underneath compacted layer.

Interfacing superhydrophobic silica nanoparticle films with graphene and thermoplastic polyurethane for wear/abrasion resistance.

PubMed

Naderizadeh, Sara; Athanassiou, Athanassia; Bayer, Ilker S

2018-06-01

Nanoparticle films are one of the most suitable platforms for obtaining sub-micrometer and nanometer dual-scale surface texture required for liquid repellency. The assembly of superhydrophobic nanoparticles into conformal and strongly adherent films having abrasion-induced wear resistance still poses a significant challenge. Various techniques have been developed over the years to render nanoparticle films with good liquid repellent properties and transparency. However, forming abrasion resistant superhydrophobic nanoparticle films on hard surfaces is challenging. One possibility is to partially embed or weld nanoparticles in thin thermoplastic primers applied over metals. Hexamethyldisilazane-functionalized fumed silica nanoparticle films spray deposited on aluminum surfaces were rendered abrasion resistant by thermally welding them into thermoplastic polyurethane (TPU) primer applied a priori over aluminum. Different solvents, nanoparticle concentrations and annealing temperatures were studied to optimize nanoparticle film morphology and hydrophobicity. Thermal annealing at 150 °C enhanced stability and wear resistance of nanoparticle films. A thin thermal interface layer of graphene nanoplatelets (GnPs) between the primer and the nanoparticle film significantly improved superhydrophobic wear resistance after annealing. As such, superhydrophobic nanocomposite films with the GnPs thermal interface layer displayed superior abrasion-induced wear resistance under 20 kPa compared to films having no GnPs-based thermal interface. Copyright © 2018 Elsevier Inc. All rights reserved.

Microstructural characterization and tribological behavior of surface plasma Zr-Er alloying on TC11 alloy

NASA Astrophysics Data System (ADS)

Wei, Dongbo; Zhang, Pingze; Liu, Yingchao; Chen, Xiaohu; Ding, Feng; Li, Fengkun

2018-02-01

The Zr coating and Zr-Er coating are grown on TC11 substrate by double-glow plasma surface metallurgy technique, followed by the wear tests at ambient temperature and 500 °C. The data of nanohardness and elastic modulus of the samples are collected by the nano-indentation test. The adhesion strength of coatings is investigated by means of the scratch test. The study of wear resistance is performed using a ball-on-disc wear test system by running against the Si3N4 ball and measured by scanning electron microscope (SEM) and X-ray diffraction (XRD). Experimental results indicate that the nanohardness of the Zr coating and Zr-Er coating are 5.94 GPa and 7.98 GPa, respectively, which are 1.79 times and 2.41 times greater than that of TC11 substrate. Zr coating and Zr-Er coating realize the metallurgical bonding with TC11 substrate with continuous and compact structure. Compared with the Zr coating and TC11, the Zr-Er coating presents the lowest specific wear rates, which are 1.689 × 10-6 mm3 Nm-1 and 1.851 × 10-6 mm3 Nm-1 at ambient temperature and 500 °C respectively, indicating the excellent and improved wear resistance of TC11.

Ion implantation method for preparing polymers having oxygen erosion resistant surfaces

DOEpatents

Lee, Eal H.; Mansur, Louis K.; Heatherly, Jr., Lee

1995-01-01

Hard surfaced polymers and the method for making them are generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface, improved wear resistance, and improved oxygen erosion resistance.

Individual 3D measurements of end users to personalize work wear clothing

NASA Astrophysics Data System (ADS)

Mielicka, E.; Napieralska, L.; Jasińska, I.; Jarzyna, V.

2017-10-01

Body silhouette 3D measurements need to be performed separately in each country due to significant ethnic differences in body silhouette which preclude the transfer of European data to particular countries. Systematic research allows to update information on the population body silhouette and body proportions as well as select the size changes possible to implement in clothing construction modifications. The diversity in body silhouettes and sizes as well as the issue of clothing fitting encourage clothing producers to provide work wear clothing based on individual measurements of the end users’ bodies. In the framework of the carried research, the group of construction workers was selected as the target group of the analysed work wear clothing users. 42 construction workers, men only, were measured. The body silhouette measurement process was non-contact and was carried out with the use of 3D body scanner. The collected data on the body silhouette allowed to select sizes used to construct the work wear clothing and identify the clothing size. The selected measurement points of the body silhouette underwent statistical analysis to determine the distribution of random variables, here body sizes. The variables distribution characteristics were calculated. On that basis, the fitting appraisal of work wear clothing with respect to the size of the finished product corresponding to the adequate size of individually measured worker/end user was performed. The size overview of the work wear clothing used by the specific professional group and the appraisal of the size fitting to the body silhouette took into consideration the work wear clothing ergonomic functionality with respect to the body posture when performing the tasks, design and clothing construction. The analysis based on the currently gathered end users’ remarks and objections concerning the clothing fitting and performed body silhouette measurements allows to modify the existing work wear clothing for the selected group of end users. The research was aimed at the improvement of the work wear clothing fitting thanks to personalization based on individual body measurements at the stage of construction design.

Wear resistance of a modified polymethyl methacrylate artificial tooth compared to five commercially available artificial tooth materials.

PubMed

Kamonwanon, Pranithida; Yodmongkol, Sirasa; Chantarachindawong, Rojcharin; Thaweeboon, Sroisiri; Thaweeboon, Boonyanit; Srikhirin, Toemsak

2015-08-01

Wear resistance is a limitation of artificial denture teeth. Improving the wear resistance of conventional artificial denture teeth is of value to prosthodontic patients. The purpose of this in vitro study was to evaluate the wear resistance and hardness of modified polymethyl methacrylate artificial denture teeth compared to 5 commercially available artificial tooth materials. This study evaluated 180 artificial denture teeth (6 groups) that included 3 groups of conventional artificial teeth (MajorDent, Cosmo HXL, and Gnathostar), 2 groups of composite resin artificial teeth (Endura and SR Orthosit PE), and 1 group of modified surface artificial teeth. The flattened buccal surface of each tooth (n=15) was prepared for investigation with the Vickers hardness test and the elucidate wear test (n=15) by using a brushing machine. Each group was loaded for 18,000 cycles, at 2 N, and 150 rpm. The wear value was identified with a profilometer. The data were statistically analyzed by using 1-way ANOVA and post hoc Turkey honestly significant difference tests (α=.001). The tribologies were observed under a scanning electron microscope, and the cytotoxicities were evaluated by MTT assay. The Vickers hardnesses ranged from 28.48 to 39.36. The wear depths and worn surface area values ranged from 1.12 to 10.79 μm and from 6.74 to 161.95 μm(2). The data revealed that the modified artificial denture teeth were significantly harder and exhibited significantly higher wear resistance than did the conventional artificial teeth (P<.001). The scanning electron microscopic images revealed cross sections of the conventional artificial denture teeth with intensively worn surface areas after brushing. The cytotoxicity test revealed 97.85% cell viability, which indicates the nontoxicity of the modified surface of this material. Within the limitations of this study, the polymethyl methacrylate modified surface artificial denture teeth was not significantly different from that of the composite resin artificial denture teeth, with the exceptions that the surface was harder and more wear resistant. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Old stones' song: use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya).

PubMed

Lemorini, Cristina; Plummer, Thomas W; Braun, David R; Crittenden, Alyssa N; Ditchfield, Peter W; Bishop, Laura C; Hertel, Fritz; Oliver, James S; Marlowe, Frank W; Schoeninger, Margaret J; Potts, Richard

2014-07-01

Evidence of Oldowan tools by ∼2.6 million years ago (Ma) may signal a major adaptive shift in hominin evolution. While tool-dependent butchery of large mammals was important by at least 2.0 Ma, the use of artifacts for tasks other than faunal processing has been difficult to diagnose. Here we report on use-wear analysis of ∼2.0 Ma quartz and quartzite artifacts from Kanjera South, Kenya. A use-wear framework that links processing of specific materials and tool motions to their resultant use-wear patterns was developed. A blind test was then carried out to assess and improve the efficacy of this experimental use-wear framework, which was then applied to the analysis of 62 Oldowan artifacts from Kanjera South. Use-wear on a total of 23 artifact edges was attributed to the processing of specific materials. Use-wear on seven edges (30%) was attributed to animal tissue processing, corroborating zooarchaeological evidence for butchery at the site. Use-wear on 16 edges (70%) was attributed to the processing of plant tissues, including wood, grit-covered plant tissues that we interpret as underground storage organs (USOs), and stems of grass or sedges. These results expand our knowledge of the suite of behaviours carried out in the vicinity of Kanjera South to include the processing of materials that would be 'invisible' using standard archaeological methods. Wood cutting and scraping may represent the production and/or maintenance of wooden tools. Use-wear related to USO processing extends the archaeological evidence for hominin acquisition and consumption of this resource by over 1.5 Ma. Cutting of grasses, sedges or reeds may be related to a subsistence task (e.g., grass seed harvesting, cutting out papyrus culm for consumption) and/or a non-subsistence related task (e.g., production of 'twine,' simple carrying devices, or bedding). These results highlight the adaptive significance of lithic technology for hominins at Kanjera. Copyright © 2014 Elsevier Ltd. All rights reserved.

Improved tribocorrosion performance of bio-functionalized TiO2 nanotubes under two-cycle sliding actions in artificial saliva.

PubMed

Alves, Sofia A; Rossi, André L; Ribeiro, Ana R; Toptan, Fatih; Pinto, Ana M; Shokuhfar, Tolou; Celis, Jean-Pierre; Rocha, Luís A

2018-04-01

After insertion into bone, dental implants may be subjected to tribocorrosive conditions resulting in the release of metallic ions and solid wear debris, which can induce to peri-implant inflammatory reactions accompanied by bone loss, and ultimately implant loosening. Despite the promising ability of TiO 2 nanotubes (NTs) to improve osseointegration and avoid infection-related failures, the understanding of their degradation under the simultaneous action of wear and corrosion (tribocorrosion) is still very limited. This study aims, for the first time, to study the tribocorrosion behavior of bio-functionalized TiO 2 NTs submitted to two-cycle sliding actions, and compare it with conventional TiO 2 NTs. TiO 2 NTs grown by anodization were doped with bioactive elements, namely calcium (Ca), phosphorous (P), and zinc (Zn), through reverse polarization anodization treatments. Characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM), were used to characterize the films. Tribocorrosion tests were carried out in artificial saliva (AS) by applying two cycles of reciprocating sliding actions. The open circuit potential (OCP) was monitored before, during, and after both cycles of sliding, during which the coefficient of friction (COF) was calculated. The resulting wear scars were analyzed by SEM and EDS, and wear volume measurements were performed by 2D profilometry. Finally, the mechanical features of TiO 2 NTs were accessed by nanoindentation. The results show that bio-functionalized TiO 2 NTs display an enhanced tribocorrosion performance, ascribed to the growth of a nano-thick oxide film at Ti/TiO 2 NTs interface, which significantly increased their adhesion strength to the substrate and consequently their hardness. Furthermore, it was discovered that during tribo-electrochemical solicitations, the formation of a P-rich tribofilm takes place, which grants both electrochemical protection and resistance to mechanical wear. This study provides fundamental and new insights for the development of multifunctional TiO 2 NTs with long-term biomechanical stability and improved clinical outcomes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guang Jie; Li, Jun, E-mail: jacob_lijun@sina.com; Luo, Xing

2014-12-15

Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900 °C for 1 h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni{sub 3}Ti; some unknown rich Ni-more » and Ti-rich particles with sizes ranging from 10 nm to 50 nm were precipitated and uniformly distributed in the Ni{sub 3}Ti phase to form a thin granular layer after heat treatment at 700 °C. The granular layer spread from the edge toward the center of the Ni{sub 3}Ti phase with increasing temperature. A large number of fine equiaxed Cr{sub 23}C{sub 6} particles with 0.2–0.5 μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900 °C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900 °C presented the most excellent wear resistance. - Highlights: • TiC + WC reinforced intermetallic compound matrix composite coatings were produced. • The formation mechanism of the reinforcements was analyzed. • Two precipitates were generated at elevated temperature. • Cracking susceptibility and microhardness of the coatings were improved. • Post-heat treatment enhances wear resistance of the coatings.« less

Clinical efficacy of toric orthokeratology in myopic adolescent with moderate to high astigmatism.

PubMed

Luo, Ming; Ma, Shengsheng; Liang, Na

2014-12-01

To observe the efficacy of toric design orthokera- tology (ortho-k) for correcting myopia and astigmatism in myopic adolescents with moderate to high astigmatism. This was a self-controlled clinical study. Twenty-four subjects (42 eyes) aged 9 to 16 years with myopia of 2.50-6.00 D complicated with rule astigmatism of 1.50-3.50 D were fitted with Lucid Night Toric Ortho-k Lenses (LUCID,KO- REA). The changes in uncorrected visual acuity (UCVA), spherical degree, refraction, axial length (AL), and corneal status were assessed at baseline, 1 night, 1 week, 1 month, 3 months, 6 months, and 1 year after the commencement of ortho-k lens wear. The success rate of the first lens fit was 92.8%. The UCVA after ortho-k wearing was improved significantly compared to the baseline during each visit (all P < 0.01), and became stable 1 month after ortho-k. The manifest myopia was significantly reduced from (-3.41 ± 1.27) D to (-0.41 ± 0.37) D by toric ortho-k and the degree of astigmatism from (-1.81 ± 0.53)D to (-0.41 ± 0.39) D after 1 month of lens wear (P < 0.01). The mean AL was (24.47 ± 0.91) mm at baseline, which did not significantly differ from (24.49 ± 0.87) mm and (24.48 ± 0.94) mm after 6 months and 1 year, respectively, of lens wear (both P > 0.05). Grade 1 corneal staining was observed at 1 week (23.8%), 1 month (21.4%), and 1 year (16.7%) following lens wear, and was improved by lens cleaning, discontinuing lens wear, and moistening the cornea with eye drops. No severe adverse events were reported. The toric ortho-k lens was effective and safe for correction of low to moderate myopia in children with moderate to high astigmatism. The lens also effectively controlled axial length elongation during 1 year of observation. However, the long-term efficacy remains to be elucidated.

Development of new duplex treatments on 100Cr6steel combining Thermochemical Treatments, Laser Shock Peening and Physical Vapour Deposition

NASA Astrophysics Data System (ADS)

Osés, J.; Fuentes, G. G.; Santo Domingo, S.; Miguel, I.; Gimeno, S.; Carreras, L.; Peyre, P.; Gorny, C.

2017-05-01

100Cr6 steel (AISI 52100) is one of the most used steel grades in the manufacturing of through hardening bearings mainly due to its properties: controlled impurities during steel making process, high hardenability and well known mechanical properties such as wear and fatigue resistance on clean environments. These characteristics play an important role on the performance of a bearing together with the bearing design, loads and environment. However, there is an increasing set of demanding applications where the above mentioned steel does not fulfil the required needs and thus, bearing manufacturers continuously work on the development of technologies to improve the bearing performance. Nowadays thermochemical treatments (TCT), such as carbonitriding are being applied to this steel in order to enhance the performance of such pieces in contaminated environment, where particles can produce defects on the raceway, increasing the onset of defects that eventually lead to premature fail. These treatments induce the formation of carbides and nitrides which are directly related to the enhancement of the wear resistance and also to increasing the amount of Retained Austenite (RA) in the surface which may have a beneficial effect as it delays the crack propagation on subsurface regions, then increasing bearing fatigue life. In this work, different TCTs have been applied to 100Cr6 steel flat samples. Using a tribometer (ball-on-disc configuration) and a grinding machine, surface and in-depth wear resistance measurements have been carried out, obtaining wear resistance profiles that have been correlated with the microstructure, microhardness profiles and RA content. The most promising TCT has been combined either with Laser Shock Peening (LSP) treatments or carbonaceous Physical Vapour Deposition (PVD) coatings with the aim of improving not only the wear resistance but also the CoF of the duplex treated sample. The results obtained on flat samples are promising; the combination of treatments produces long-lasting low CoF and a reduction of 60% in the wear rate. However, the treatments should be applied on real pieces and tested in a test bench in order to obtain more appropriate data about the lifespan of duplex treated bearings.

Effects of thermal underwear on thermal and subjective responses in winter.

PubMed

Choi, Jeong-Wha; Lee, Joo-Young; Kim, So-Young

2003-01-01

This study was conducted to obtain basic data in improving the health of Koreans, saving energy and protecting environments. This study investigated the effects of wearing thermal underwear for keeping warm in the office in winter where temperature is not as low as affecting work efficiency, on thermoregulatory responses and subjective sensations. In order to create an environment where every subject feels the same thermal sensation, two experimental conditions were selected through preliminary experiments: wearing thermal underwear in 18 degrees C air (18-condition) and not wearing thermal underwear in 23 degrees C air (23-condition). Six healthy male students participated in this study as experiment subjects. Measurement items included rectal temperature (T(re)), skin temperature (T(sk)), clothing microclimate temperature (T(cm)), thermal sensation and thermal comfort. The results are as follows: (1) T(re) of all subjects was maintained constant at 37.1 degrees C under both conditions, indicating no significant differences. (2) (T)(sk) under the 18-condition and the 23-condition were 32.9 degrees C and 33.7 degrees C, respectively, indicating a significant level of difference (p<0.05). (3) Among local skin temperature, trunk part (forehead and abdomen) did not show significant differences. After 90-min exposure, the skin temperature of hands and feet under the 18-condition was significantly lower than that under the 23-condition (p<0.001). (4) More than 80% of all the respondents felt comfortable under both conditions. It was found (T)(sk) decreased due to a drop in the skin temperature of hands and feet, and the subjects felt cooler wearing only one layer of normal thermal underwear at 18 degrees C. Yet, the thermal comfort level, T(re) and T(cm) of chest part under the 18-condition were the same as those under the 23-condition. These results show that the same level of comfort, T(re) and T(cm) can be maintained as that of an environment about 5 degrees C higher in the office in winter, by wearing one layer of thermal underwear. In this regard, this study suggests that lowering indoor temperature by wearing thermal underwear in winter can contribute to saving energy and improving health.

Alternate paddle configuration for improved wear resistance in the saltstone mixer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reigel, M.; Fowley, M.

The Saltstone Production Facility has a 10-inch Readco-Kurimoto continuous mixer that mixes the premix dry feeds and low-level waste salt solution to make fresh (uncured) saltstone. Inspection of the mixer in January 2013 showed significant wear on the third, fourth and fifth paddle pairs after the conveying augers. A 2-inch Readco-Kurimoto continuous mixer was used to test alternate paddle configurations for use in the 10-inch mixer to decrease the wear rate on the paddles. Two wear tests were conducted to investigate a method of reducing wear on the mixer paddles. The first test (wear test 2a) had a paddle configurationmore » similar to the currently installed 10-inch mixer in the SPF. This test established baseline wear. The second test (wear test 2b) had a reconfigured paddle arrangement that replaced the flat paddles with helical paddles for paddle pairs 2 - 6 and aligned paddle pair 1 with the augers. The intent of the reconfiguration was to more effectively convey the partially wetted dry feeds through the transition region and into the liquid feed where paddle wear is reduced due to dry feeds and salt solution being mixed at the intended water to premix ratio. The design of the helical paddles provides conveyance through the transition region to the liquid feed inlet. The alignment with the auger is aimed to provide a smoother transition (minimizing the discontinuity between the auger and paddle pair 1) into the downstream paddles. A soft metal with low wear resistance (6000 series aluminum) was used for the wear testing paddles to determine wear patterns while minimizing run time and maximizing wear rate. For the two paddle configurations tested using the scaled 2-inch Readco-Kurimoto continuous mixer, with the first six paddles after the augers replaced by the wear paddles and the remaining paddles were stainless steel. Since the 10-inch SPF mixer is designed with the liquid inlet centered over paddle pairs 5 and 6, the scaled 2-inch mixer was configured the same way. The wear rate from wear test 2a was approximately double the wear rate from wear test 2b for paddle pairs 4 and 5. For both configurations, there was little or no wear on paddle pairs 1, 2, 3 and 6 based on mass change, indicating that the un-wetted and fully wetted premix materials cause less wear than the partially wetted premix. Additionally, inspection of the wear surface of the paddles showed more deformation on the flat paddles than the helical paddles which was consistent with the wear rates. Aligning of the auger discharge flight with paddle pair 1 resulted in a lower wear rate paddle pair 1 rather than having them misaligned with the feed augers. During the paddle wear tests, polishing wear was observed on the inside barrel of the mixer. The polishing wear is evident on the upper housing clamshell and the lower housing clamshell primarily at paddle pairs 4 and 5, which is the transition region of the mixer. Wear on the mixer barrel increases the space between the paddles and the barrel, resulting in increased grout build up on the barrel. Since the mixer barrel cannot be reconfigured or replaced in the SPF, the method for mitigating wear on the barrel is to move the more viscous grout through the transition region as quickly as possible. In addition, the location of the liquid inlet does not allow for sufficient cleaning of the mixer since residual grout remains on paddle pairs 1 - 4. As the paddles continue to wear and the self-cleaning capability of the paddles is lost, the lack of sufficient flushing would aid in grout build up between the barrel and the paddles which could eventually lead to decreased throughput capacity of the dry feeds. Changing the paddle configuration from flat to helical resulted in no change to the rheological properties of the grout mixture. Both tests produced a grout that is within the processing range of the SPF. Based on the results of this testing, it is recommended for the currently installed SPF mixer that paddle pairs 1 through 6 be helical rather than flat, with the paddle pair 1 aligned with the feed augers in order to minimize the wear occurring in the SPF mixer. Based on the results of this testing, it is recommended that the mixer be inspected and critical measurements be taken whenever the SPF processing schedule allows in order to establish a wear rate of the 10-inch mixer paddles.5 Based on these measurements, the lifetime of paddles in the transition region can be established in order to set up a maintenance schedule for the mixer. Since replacing the entire mixer is very expensive and time intensive, replacing the worn paddles after a specific time period would allow for planned shutdowns as well as process optimization such that the mixer throughput is not compromised. In addition, further testing should be performed to determine an alternate liquid inlet location to better flush the mixer of residual grout at the end of processing. Sufficiently cleaning the mixer will help eliminate another potential source of wear. Another potential method for reducing the wear rate in the mixer is to reduce the mixer speed without affecting the throughput capacity. Since wear rate is a function of impact velocity of the grout and mixing paddles, testing could be done using the 2-inch mixer determine the optimum mixer speed to reduce wear but not adversely impact facility operations (e.g. throughput capacity and grout properties).« less

Four Months of Wearing a Balance Orthotic Improves Measures of Balance and Mobility Among a Cohort of Community-Living Older Adults.

PubMed

Noah, Sean; Gibson-Horn, Cynthia; Vincenzo, Jennifer L

2018-01-18

The Centers for Disease Control and Prevention estimated that there were 29 million falls and 7 million injuries in 2014 in the United States. Falls, decreased balance, and mobility disability are common in older adults and often result in loss of independence. Finding interventions to address these issues is important, as this age group is growing exponentially. Prior studies indicate balance and mobility can be improved by the balance-based torso-weighting (BBTW) assessment implemented through wear of a balance orthotic (BO). This study sought to determine the impact of wearing a BO on balance, mobility, and fall risk over time. This quasiexperimental, 1-group pre-/posttest study investigated the effect of 4 months of daily wear (4 hours per day) of a BO on mobility, balance, and falls efficacy in 30 older adults living in a retirement community with limited mobility defined by a Short Physical Performance Battery (SPPB) score range between 4 and 9 out of a maximum of 12 points. Pre- and posttreatment tests included the Timed Up and Go (TUG), Functional Gait Assessment (FGA), Falls Efficacy Scale (FES), and SPPB. Participants received the BBTW assessment, consisting of individualized assessment of 3-dimensional balance loss, and treatment with a strategically weighted and fitted BO to control balance loss. The BO was worn twice a day for 2 hours (4 hours per day) for 4 months. Participants continued regular activity and no other interventions were provided. All posttests were conducted after 4 months and at least 8 hours after removal of the BO. Subitems from the SPPB (gait speed [GS], 5-time sit-to-stand [FTSST], and tandem stance time [TST]) were analyzed as separate outcome measures. Data were analyzed with paired t tests with a Bonferroni correction (SPPB, GS, FGA, and FES) when statistical assumptions were met. Data that did not meet the statistical assumptions of the paired t test (FTSST, TST, and TUG) were analyzed with Wilcoxon signed rank tests with a Bonferroni correction. Twenty-four subjects, average age 87 (5.7) years, completed the study. Paired t tests indicated that mean group scores on the SPPB, GS, and FGA significantly improved from pre- to posttests. The SPPB improved by 1.3 points (P = .001). GS improved by 0.09 m/s (P = .004) and both mean values improved beyond fall risk cutoffs. The FGA also improved by 2.6 points (P = .001). There were no significant changes in FES scores (P = .110). Wilcoxon signed rank tests indicated median group scores of the FTSST significantly improved from pre- to posttests by 7.4 seconds (P = .002) and median TUG times improved by 3.5 seconds (P = .004). There were no changes in TST (P = .117). This study suggests that wearing a BO for 4 hours per day for 4 months results in improvements in functional assessments related to fall risk (SPPB, GS, FGA, TUG, and FTSST) in a group of older adult participants with limited mobility.

Investigation of microstructural and physical characteristics of nano composite tin oxide-doped Al3+ in Zn2+ based composite coating by DAECD technique

NASA Astrophysics Data System (ADS)

Anawe, P. A. L.; Fayomi, O. S. I.; Popoola, A. P. I.

In other to overcome the devastating deterioration of mild steel in service, Zn-based embedded Al/SnO2 composite coatings have been considered as reinforcing alternative replacements to the more traditional deposition for improved surface properties by using Dual Anode Electrolytic Co-deposition (DAECD) technique from chloride bath. The structural characterization of the starting materials and deposited coating are evaluated using scanning electron microscopy (SEM), equipped with energy dispersive X-ray spectroscopy (EDX) elemental analysis and atomic force microscope (AFM). The hardness behaviour, wear and intermetallic distribution was examined by diamond based microhardness tester, CETR reciprocating sliding test rig and X-ray diffractometer (XRD) respectively. The corrosion properties of the developed coating were examined in 3.5% NaCl. The microstructure of the deposited sample obtained at 7% SnO2, revealed fine-grains deposit of the Al/SnO2 on the mild steel surface. The results showed that the Al/SnO2 strengthening alloy plays a significant role in impelling the wear and corrosion behaviour of Zn-Al/SnO2 coatings in an aggressive saline environment. Interestingly Zn-30Al-7Sn-chloride showed the highest wear and improved corrosion resistance due to Al/SnO2 oxide passive film that forms during anodic polarization. This work established that co-deposition of mild steel with Al/SnO2 is auspicious in increasing the anti-wear and corrosion progression.

A novel anti-frictional multiphase layer produced by plasma nitriding of PVD titanium coated ZL205A aluminum alloy

NASA Astrophysics Data System (ADS)

Lu, C.; Yao, J. W.; Wang, Y. X.; Zhu, Y. D.; Guo, J. H.; Wang, Y.; Fu, H. Y.; Chen, Z. B.; Yan, M. F.

2018-02-01

The heat treatment (consisting of solid solution and aging), is integrated with the nitriding process of titanium coated ZL205A aluminum alloy to improve the surface and matrix mechanical properties simultaneously. Two-step duplex treatment is adopted to prepare the gradient multiphase layer on a magnesium-free ZL205A aluminum-copper based alloy. Firstly, pure titanium film is deposited on the aluminum alloy substrate using magnetron sputtering. Secondly, the Ti-coated specimen is nitrided at the solid solution temperature of the substrate alloying elements in a gas mixture of N2 and H2 and aged at 175 °C. The microstructure evolution, microhardness as well as the wear resistance of obtained multiphase layers are investigated by means of scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), microhardness tester and pin-on-disc tribometer. The multiphase layer, dominated by TiN0.3 or Al3Ti, is prepared with significantly increased layer depth after duplex treatment. The surface hardness of multiphase layer is remarkably improved from 23.7HV to 457HV. The core matrix hardness is also increased to 65HV after aging. The wear rate of the multiphase layer decreases about 55.22% and 49.28% in comparison with the aged and Ti coated specimens, respectively. The predominant wear mechanism for the multiphase layer is abrasive and oxidation, but severe adhesive wear for the aged and Ti coated specimens.

Evaluation of load tracks and wear of two sets of bearings from space shuttle main engine high pressure oxygen turbopumps

NASA Technical Reports Server (NTRS)

Kannel, J. W.; Dufrane, K. F.

1985-01-01

Bearings supporting the rotor in the High Pressure Oxygen Turbopump (HPOTP) were examined. The No. 1 bearings from both units were in good condition and had successfully completed 5000 seconds of operation. The No. 2 bearings, which were in service the same length of time, were significantly degraded in the form of ball wear, race pitting, and damage from high axial loads. The No. 3 and 4 bearings were in generally acceptable condition. The general conclusion from the examinations was that improved cooling on the No. 2 bearings and further improvements in controlling axial and radial load would likely result in the HPOTP meeting the qualification test results.

Nicotine patches improve mood and response speed in a lexical decision task.

PubMed

Gentry, M V; Hammersley, J J; Hale, C R; Nuwer, P K; Meliska, C J

2000-01-01

The effects of smoking a cigarette or wearing a transdermal nicotine patch on mood and lexical decision-making were tested in eight smokers. Each participant was tested after 4 hours of smoking abstinence, under 4 conditions: placebo (very low nicotine) cigarette, nicotine cigarette, placebo patch, and nicotine patch. Relative to placebo, wearing the nicotine patch reduced Profile of Mood States (POMS) Total Mood Disturbance and Fatigue/Inertia scores, while increasing the speed of some types of lexical decisions. Smoking a nicotine cigarette did not affect reaction times, but unexpectedly decreased the accuracy of Word/ Nonword lexical decisions. Thus, transdermal nicotine may improve mood and facilitate longterm memory search and/or attentional processes in nicotine-deprived smokers.

Improved Dental Implant Drill Durability and Performance Using Heat and Wear Resistant Protective Coatings.

PubMed

Er, Nilay; Alkan, Alper; Ilday, Serim; Bengu, Erman

2018-06-01

The dental implant drilling procedure is an essential step for implant surgery, and frictional heat in bone during drilling is a key factor affecting the success of an implant. The aim of this study was to increase the dental implant drill lifetime and performance by using heat- and wear-resistant protective coatings to decrease the alveolar bone temperature caused by the dental implant drilling procedure. Commercially obtained stainless steel drills were coated with titanium aluminum nitride, diamond-like carbon, titanium boron nitride, and boron nitride coatings via magnetron-sputter deposition. Drilling was performed on bovine femoral cortical bone under the conditions mimicking clinical practice. Tests were performed under water-assisted cooling and under the conditions when no cooling was applied. Coated drill performances and durabilities were compared with those of three commonly used commercial drills with surfaces made from zirconia, black diamond. and stainless steel. Protective coatings with boron nitride, titanium boron nitride, and diamond-like carbon have significantly improved drill performance and durability. In particular, boron nitride-coated drills have performed within safe bone temperature limits for 50 drillings even when no cooling is applied. Titanium aluminium nitride coated drills did not show any improvement over commercially obtained stainless steel drills. Surface modification using heat- and wear-resistant coatings is an easy and highly effective way to improve implant drill performance and durability, which can improve the surgical procedure and the postsurgical healing period. The noteworthy success of different types of coatings is novel and likely to be applicable to various other medical systems.

Investigation of material improvements to mitigate the abrasive wear mechanism of concrete crosstie rail seat deterioration (RSD).

DOT National Transportation Integrated Search

2014-11-01

To meet the increasingly stringent design and performance requirements due to increasing cumulative : gross tonnages from heavy-haul freight operations, along with increased high-speed inter-city passenger : rail development, improvements in concrete...

Ion implantation method for preparing polymers having oxygen erosion resistant surfaces

DOEpatents

Lee, E.H.; Mansur, L.K.; Heatherly, L. Jr.

1995-04-18

Hard surfaced polymers and the method for making them are generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface, improved wear resistance, and improved oxygen erosion resistance. 8 figs.

Surface Modification of C17200 Copper-Beryllium Alloy by Plasma Nitriding of Cu-Ti Gradient Film

NASA Astrophysics Data System (ADS)

Zhu, Y. D.; Yan, M. F.; Zhang, Y. X.; Zhang, C. S.

2018-03-01

In the present work, a copper-titanium film of gradient composition was firstly fabricated by the dual magnetron sputtering through power control and plasma nitriding of the film was then conducted to modify C17200 Cu alloy. The results showed that the prepared gradient Cu-Ti film by magnetron sputtering was amorphous. After plasma nitriding at 650 °C, crystalline Cu-Ti intermetallics appeared in the multi-phase coating, including CuTi2, Cu3Ti, Cu3Ti2 and CuTi. Moreover, even though the plasma nitriding duration of the gradient Cu-Ti film was only 0.5 h, the mechanical properties of the modified Cu surface were obviously improved, with the surface hardness enhanced to be 417 HV0.01, the wear rate to be 0.32 × 10-14 m3/Nm and the friction coefficient to be 0.075 at the load of 10 N, which are all more excellent than the C17200 Cu alloy. In addition, the wear mechanism also changed from adhesion wear for C17200 Cu substrate to abrasive wear for the modified surface.

Natural fibre reinforced non-asbestos organic non-metallic friction composites: effect of abaca fibre on mechanical and tribological behaviour

NASA Astrophysics Data System (ADS)

Liu, Yucheng; Ma, Yunhai; Che, Junjian; Duanmu, Lingjian; Zhuang, Jian; Tong, Jin

2018-05-01

To obtain a natural fibre reinforced non-asbestos organic non-metallic friction composite with good wear resistance and environmental-friendly performances, friction composites reinforced with different lengths of abaca fibre were fabricated by a compression molder equipment and evaluated by using a constant-speed friction test machine. The worn surface morphologies were observed and analyzed using a Scanning Electron Microscopy (SEM). Experimental results show that the length of abaca fibre had no significant effect on the density and hardness, but was obvious on impact strength. The impact strength increased and then decreased with the increasing of length of abaca fibres. Abaca fibres, especially short fibre (lengths of 5 mm, 10 mm), could improve the wear resistance of the friction composites. Meanwhile, the increase of test temperature could result in the increasing of wear rates of the friction composites. A large amount of secondary plateaux presented on the worn surface of specimens FC1 and FC2 which showe relatively smooth worn surfaces and yield the better wear resistance performance.

Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites

PubMed Central

Alajmi, Mahdi; Shalwan, Abdullah

2015-01-01

The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR) and coefficient of friction (COF) of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs), as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites. PMID:28793431

Tribological Analysis of Copper-Coated Graphite Particle-Reinforced A359 Al/5 wt.% SiC Composites

NASA Astrophysics Data System (ADS)

Lin, C. B.; Wang, T. C.; Chang, Z. C.; Chu, H. Y.

2013-01-01

Copper-coated graphite particles can be mass-produced by the cementation process using simple equipment. Graphite particulates that were coated with electroless copper and 5 wt.% SiC particulates were introduced into an aluminum alloy by compocasting to make A359 Al/5 wt.% SiC(p) composite that contained 2, 4, 6, and 8 wt.% graphite particulate composite. The effects of SiC particles, quantity of graphite particles, normal loading, sliding speed and wear debris on the coefficient of friction, and the wear rate were investigated. The results thus obtained indicate that the wear properties were improved by adding small amounts of SiC and graphite particles into the A359 Al alloy. The coefficient of friction of the A359 Al/5 wt.% SiC(p) composite that contained 6.0 wt.% graphite particulates was reduced to 0.246 and the amount of graphite film that was released on the worn surface increased with the graphite particulate content. The coefficient of friction and the wear rate were insensitive to the variation in the sliding speed and normal loading.

Microstructure analysis and wear behavior of titanium cermet femoral head with hard TiC layer.

PubMed

Luo, Yong; Ge, Shirong; Liu, Hongtao; Jin, Zhongmin

2009-12-11

Titanium cermet was successfully synthesized and formed a thin gradient titanium carbide coating on the surface of Ti6Al4V alloy by using a novel sequential carburization under high temperature, while the titanium cermet femoral head was produced. The titanium cermet phase and surface topography were characterized with X-ray diffraction (XRD) and backscattered electron imaging (BSE). And then the wear behavior of titanium cermet femoral head was investigated by using CUMT II artificial joint hip simulator. The surface characterization indicates that carbon effectively diffused into the titanium alloys and formed a hard TiC layer on the Ti6Al4V alloys surface with a micro-porous structure. The artificial hip joint experimental results show that titanium cermet femoral head could not only improve the wear resistance of artificial femoral head, but also decrease the wear of UHMWPE joint cup. In addition, the carburized titanium alloy femoral head could effectively control the UHMWPE debris distribution, and increase the size of UHMWPE debris. All of the results suggest that titanium cermet is a prospective femoral head material in artificial joint.

Sintering Process and Mechanical Property of MWCNTs/HDPE Bulk Composite

PubMed Central

Tze-Chi, Hsu; Jie-Ren, Zheng

2009-01-01

Studies have proved that increasing polymer matrices by carbon nanotubes to form structural reinforcement and electrical conductivity have significantly improved mechanical and electrical properties at very low carbon nanotubes loading. In other words, increasing polymer matrices by carbon nanotubes to form structural reinforcement can reduce friction coefficient and enhance anti-wear property. However, producing traditional MWCNTs in polymeric materix is an extremely complicated process. Using melt-mixing process or in situ polymerization leads to better dispersion effect on composite materials. In this study, therefore, to simplify MWCNTs /HDPE composite process and increase dispersion, powder was used directly to replace pellet to mix and sinter with MWCNTs. The composite bulks with 0, 0.5, 1, 2 and 4% nanotube content by weight was analyzed under SEM to observe nanotubes dispersion. At this rate, a MWCNTs/HDPE composite bulk with uniformly dispersed MWCNTs was achieved, and through the wear bench (Pin-on-Disk), the wear experiment has accomplished. Accordingly, the result suggests the sintered MWCNTs/HDPE composites amplify the hardness and wear-resist property. PMID:19730688

Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding.

PubMed

Wu, Fan; Chen, Tao; Wang, Haojun; Liu, Defu

2017-09-06

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening.

Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding

PubMed Central

Chen, Tao; Wang, Haojun

2017-01-01

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening. PMID:28878190

Titanium carbide nanoparticles reinforcing nickel matrix for improving nanohardness and fretting wear properties in wet conditions

NASA Astrophysics Data System (ADS)

Dănăilă, Eliza; Benea, Lidia; Caron, Nadège; Raquet, Olivier

2016-09-01

In this study Ni/nano-TiC functional composite coatings were produced by electro-codeposition of TiC nanoparticles (50 nm mean diameter) with nickel on 304L stainless steel support. Coatings were obtained from a Watts classical solution in which TiC nanoparticles were added. The surface morphology, chemical composition, structure, roughness and thickness, were evaluated in relation to the effect of TiC nanoparticles incorporation into Ni matrix. It was found that incorporation of TiC nanoparticles into the nickel matrix produces morphological changes in the deposit and increases the roughness. The fretting wear behavior in wet conditions of the obtained coatings was evaluated on a ball-on-plate configuration. To evaluate the wet fretting wear (tribocorrosion) behavior the open circuit potential was measured before, during and after the fretting tests at room temperature in the solution that simulates the primary water circuit of Pressurized Water Reactors. The results show that Ni/nano-TiC composite coatings exhibited a low friction coefficient, high nanohardness and fretting wear resistance in wet conditions compared with pure Ni coatings.

Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites.

PubMed

Alajmi, Mahdi; Shalwan, Abdullah

2015-07-08

The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR) and coefficient of friction (COF) of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs), as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites.

Tribological Behaviour of Ti:Ta-DLC Films Under Different Tribo-Test Conditions

NASA Astrophysics Data System (ADS)

Efeoglu, İhsan; Keleş, Ayşenur; Totik, Yaşar; Çiçek, Hikmet; Emine Süküroglu, Ebru

2018-01-01

Diamond-like carbon (DLC) films are suitable applicants for cutting tools due to their high hardness, low friction coefficient and wear rate. Doping metals in DLC films have been improved its tribological properties. In this study, titanium and tantalum doped hydrogenated DLC films were deposited by closed-field unbalanced magnetron sputtering system onto M2 high speed steels in Ar/N2/C2H2 atmosphere. The friction and wear properties of Ti:Ta-DLC film were investigated under different tribo-test conditions including in atmospheric pressure, distilled water, commercial oil and Ar atmosphere. The coated specimens were characterized by SEM and X-ray diffraction techniques. The bonding state of C-C (sp3) and C=C (sp2) were obtained with XPS. The tribological properties of Ti:Ta-DLC were investigated with pin-on-disc wear test. Hardness measurements performed by micro-indentation. Our results suggest that Ti:Ta-doped DLC film shows very dense columnar microstructure, high hardness (38.2 GPa) with low CoF (µ≈0.02) and high wear resistance (0.5E-6 mm3/Nm).

Effect of wear of bearing surfaces on elastohydrodynamic lubrication of metal-on-metal hip implants.

PubMed

Liu, F; Jin, Z M; Hirt, F; Rieker, C; Roberts, P; Grigoris, P

2005-09-01

The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 microm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul bearing to achieve a fluid film lubrication regime during this period, and this was consistent with the minimal wear observed between 1 and 5 million cycles. However, under adverse in vivo conditions associated with start-up and stopping and depleted lubrication, wear of the bearing surfaces can still occur. An increase in the wear depth beyond a certain limit was shown to lead to the constriction of the lubricant film around the edge of the contact conjunction and consequently to a decrease in the lubricant film thickness. Continuous cycles of a running-in wear period followed by a steady state wear period may be inevitable in MOM hip implants. This highlights the importance of minimizing the wear in these devices during the initial running-in period, particularly from design and manufacturing points of view.

Dramatically Improve How and Where Academic Content Is Taught

ERIC Educational Resources Information Center

Hyslop, Alisha

2007-01-01

The fourth recommendation in ACTE's high school reform position statement is to dramatically improve how and where academic content is taught. Even as advanced academic course-taking and high school graduation requirements have increased, student achievement on national benchmarks has remained flat, and college remediation rates continue to…

Firmware Development Improves System Efficiency

NASA Technical Reports Server (NTRS)

Chern, E. James; Butler, David W.

1993-01-01

Most manufacturing processes require physical pointwise positioning of the components or tools from one location to another. Typical mechanical systems utilize either stop-and-go or fixed feed-rate procession to accomplish the task. The first approach achieves positional accuracy but prolongs overall time and increases wear on the mechanical system. The second approach sustains the throughput but compromises positional accuracy. A computer firmware approach has been developed to optimize this point wise mechanism by utilizing programmable interrupt controls to synchronize engineering processes 'on the fly'. This principle has been implemented in an eddy current imaging system to demonstrate the improvement. Software programs were developed that enable a mechanical controller card to transmit interrupts to a system controller as a trigger signal to initiate an eddy current data acquisition routine. The advantages are: (1) optimized manufacturing processes, (2) increased throughput of the system, (3) improved positional accuracy, and (4) reduced wear and tear on the mechanical system.