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Sample records for high wear applications

  1. Elastomer Compound Developed for High Wear Applications

    NASA Technical Reports Server (NTRS)

    Crawford, D.; Feuer, H.; Flanagan, D.; Rodriguez, G.; Teets, A.; Touchet, P.

    1993-01-01

    The U.S. Army is currently spending 300 million dollars per year replacing rubber track pads. An experimental rubber compound has been developed which exhibits 2 to 3 times greater service life than standard production pad compounds. To improve the service life of the tank track pads various aspects of rubber chemistry were explored including polymer, curing and reinforcing systems. Compounds that exhibited superior physical properties based on laboratory data were then fabricated into tank pads and field tested. This paper will discuss the compounding studies, laboratory data and field testing that led to the high wear elastomer compound.

  2. High Temperature Solid Lubricant Coating for High Temperature Wear Applications

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher (Inventor); Edmonds, Brian J (Inventor)

    2014-01-01

    A self-lubricating, friction and wear reducing composite useful over a wide temperature range is described herein. The composite includes metal bonded chromium oxide dispersed in a metal binder having a substantial amount of nickel. The composite contains a fluoride of at least one Group I, Group II, or rare earth metal, and optionally a low temperature lubricant metal.

  3. Nano Structured Plasma Spray Coating for Wear and High Temperature Corrosion Resistance Applications

    NASA Astrophysics Data System (ADS)

    Ghosh, D.; Shukla, A. K.; Roy, H.

    2014-04-01

    The nano structured coating is a major challenge today to improve the different mechanical properties, wear and high temperature corrosion resistance behaviour of different industrial alloys. This paper is a review on synthesis of nano powder, plasma spraying methods, techniques of nano structured coating by plasma spray method, mechanical properties, tribological properties and high temperature corrosion behaviour of nano structured coating. Nano structured coatings of ceramic powders/composites are being developed for wide variety of applications like boiler, turbine and aerospace industries, which requires the resistance against wear, corrosion, erosion etc. The nano sized powders are subjected to agglomeration by spray drying, after which nano structured coating can be successfully applied over the substrate. Nano structured coating shows improved mechanical wear resistance and high temperature corrosion resistance. The significant improvement of wear and corrosion resistance is mainly attributed to formation of semi molten nano zones in case of nano structured coatings. The future scope of application of nano structured coating has also been highlighted in this paper.

  4. 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.

  5. Characterization of thermally sprayed coatings for high-temperature wear-protection applications

    SciTech Connect

    Li, C.C.

    1980-03-01

    Under normal high-temperature gas-cooled reactor (HTGR) operating conditions, faying surfaces of metallic components under high contact pressure are prone to friction, wear, and self-welding damage. Component design calls for coatings for the protection of the mating surfaces. Anticipated operating temperatures up to 850 to 950/sup 0/C (1562 to 1742/sup 0/F) and a 40-y design life require coatings with excellent thermal stability and adequate wear and spallation resistance, and they must be compatible with the HTGR coolant helium environment. Plasma and detonation-gun (D-gun) deposited chromium carbide-base and stabilized zirconia coatings are under consideration for wear protection of reactor components such as the thermal barrier, heat exchangers, control rods, and turbomachinery. Programs are under way to address the structural integrity, helium compatibility, and tribological behavior of relevant sprayed coatings. In this paper, the need for protection of critical metallic components and the criteria for selection of coatings are discussed. The technical background to coating development and the experience with the steam cycle HTGR (HTGR-SC) are commented upon. Coating characterization techniques employed at General Atomic Company (GA) are presented, and the progress of the experimental programs is briefly reviewed. In characterizing the coatings for HTGR applications, it is concluded that a systems approach to establish correlation between coating process parameters and coating microstructural and tribological properties for design consideration is required.

  6. NASA PS400: A New Temperature Solid Lubricant Coating for High Temperature Wear Applications

    NASA Technical Reports Server (NTRS)

    DellaCorte, C.; Edmonds, B. J.

    2009-01-01

    A new solid lubricant coating, NASA PS400, has been developed for high temperature tribological applications. This plasma sprayed coating is a variant of the patented PS304 coating and has been formulated to provide higher density, smoother surface finish and better dimensional stability than PS304. PS400 is comprised of a nickel-molybdenum binder that provides strength, creep resistance and extreme oxidative and dimensional stability. Chromium oxide, silver and barium-calcium fluoride eutectic are added to the binder to form PS400.Tribological properties were evaluated with a pin-on-disk test rig in sliding contact to 650 C. Coating material samples were exposed to air, argon and vacuum at 760 C followed by cross section microscopic analysis to assess microstructure stability. Oil-Free microturbine engine hot section foil bearing tests were undertaken to assess PS400 s suitability for hot foil gas bearing applications. The preliminary results indicate that PS400 exhibits tribological characteristics comparable to the PS304 coating but with enhanced creep resistance and dimensional stability suitable for demanding, dynamic applications.

  7. Wear of highly crosslinked polyethylene acetabular components

    PubMed Central

    Callary, Stuart A; Solomon, Lucian B; Holubowycz, Oksana T; Campbell, David G; Munn, Zachary; Howie, Donald W

    2015-01-01

    Background and purpose Wear rates of highly crosslinked polyethylene (XLPE) acetabular components have varied considerably between different published studies. This variation is in part due to the different techniques used to measure wear and to the errors inherent in measuring the relatively low amounts of wear in XLPE bearings. We undertook a scoping review of studies that have examined the in vivo wear of XLPE acetabular components using the most sensitive method available, radiostereometric analysis (RSA). Methods A systematic search of the PubMed, Scopus, and Cochrane databases was performed to identify published studies in which RSA was used to measure wear of XLPE components in primary total hip arthroplasty (THA). Results 18 publications examined 12 primary THA cohorts, comprising only 260 THAs at 2–10 years of follow-up. The mean or median proximal wear rate reported ranged from 0.00 to 0.06 mm/year. However, differences in the manner in which wear was determined made it difficult to compare some studies. Furthermore, differences in RSA methodology between studies, such as the use of supine or standing radiographs and the use of beaded or unbeaded reference segments, may limit future meta-analyses examining the effect of patient and implant variables on wear rates. Interpretation This scoping review confirmed the low wear rates of XLPE in THA, as measured by RSA. We make recommendations to enhance the standardization of reporting of RSA wear results, which will facilitate early identification of poorly performing implants and enable a better understanding of the effects of surgical and patient factors on wear. PMID:25301435

  8. Consideration of wear rates at high velocity

    NASA Astrophysics Data System (ADS)

    Hale, Chad S.

    The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models

  9. Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites.

    PubMed

    Liu, Tian; Wood, Weston; Zhong, Wei-Hong

    2011-12-01

    We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.

  10. Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites

    PubMed Central

    2011-01-01

    We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials. PMID:27502631

  11. Friction, wear, transfer and wear surface morphology of ultra-high-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1983-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  12. Wear performance of garnet aluminium composites at high contact pressure

    NASA Astrophysics Data System (ADS)

    Sharma, Anju; Arora, Rama; Kumar, Suresh; Singh, Gurmel; Pandey, O. P.

    2016-05-01

    To satisfy the needs of the engineering sector, researchers and material scientists in this area adopted the development of composites with tailor made properties to enhance efficiency and cost savings in the manufacturing sector. The technology of the mineral industry is shaping the supply and demand of minerals derived materials. The composites are best classified as high performance materials have high strength-to-weight ratios, and require controlled manufacturing environments for optimum performance. Natural mineral garnet was used as the reinforcement of composite because of satisfactory mechanical properties as well as an attractive ecological alternative to others ceramics. For this purpose, samples have been prepared with different sizesof the garnet reinforcement using the mechanical stirring method to achieve the homogeneously dispersed strengthening phase. A systematic study of the effect of high contact pressure on the sliding wear behaviour of garnet reinforced LM13 alloy composites is presented in this paper. The SEM analysis of the worn samples and debris reveals the clues about the wear mechanism. The drastic improvement in the wear resistance of the composites at high contact pressure shows the high potential of the material to be used in engineering applications.

  13. Wear Testing of Moving Components in Ultra-High Vacuum

    NASA Astrophysics Data System (ADS)

    Short, Arnelia; McAlister, T.; Ellis, R.; Mosleh, M.

    2010-11-01

    Wear and friction in moving parts in an Ultra-High Vacuum (UHV) environment is a fundamental challenge in the design of mechanical assemblies in fusion experiments. In a reactor-scale experiment, constraints have been placed on the material choices and mechanical motions within the system due to their vacuum environment. Wear and friction only serve to complicate these constraints. Textured surfaces, bonded lubricants, and vacuum compatible greases have shown promise as possible means of reducing friction and wear. We have designed a machine for testing wear in a UHV environment, at room temperature, and elevated temperatures. This poster describes the design of the wear test machine and its operating parameters. We have presented an outline of the material test program along with a discussion of the pros and cons of anti-friction and anti-wear treatments.

  14. A review on nozzle wear in abrasive water jet machining application

    NASA Astrophysics Data System (ADS)

    Syazwani, H.; Mebrahitom, G.; Azmir, A.

    2016-02-01

    This paper discusses a review on nozzle wear in abrasive water jet machining application. Wear of the nozzle becomes a major problem since it may affect the water jet machining performance. Design, materials, and life of the nozzle give significance effect to the nozzle wear. There are various parameters that may influence the wear rate of the nozzle such as nozzle length, nozzle inlet angle, nozzle diameter, orifice diameter, abrasive flow rate and water pressure. The wear rate of the nozzle can be minimized by controlling these parameters. The mechanism of wear in the nozzle is similar to other traditional machining processes which uses a cutting tool. The high pressure of the water and hard abrasive particles may erode the nozzle wall. A new nozzle using a tungsten carbide-based material has been developed to reduce the wear rate and improve the nozzle life. Apart from that, prevention of the nozzle wear has been achieved using porous lubricated nozzle. This paper presents a comprehensive review about the wear of abrasive water jet nozzle.

  15. Consideration of Wear Rates at High Velocities

    DTIC Science & Technology

    2010-03-01

    evaluations were performed for different velocity ranges depending on the interest of the individual researcher. As a result, an inconsistency 4 W L...together will produce heat. The slipper-rail interaction being studied is no different . The amount of heat generated is a function of the frictional...the one which provides the highest wear rate. To correlate specimens from different sources and of varying sizes and shapes, the wear rate, normal

  16. Consideration of Wear Rates at High Velocity

    DTIC Science & Technology

    2010-03-01

    Mild wear “involves the relatively slow removal of the tops of the highest contacting asperities with little substrate distortion”. They indicated...introduced pressure velocity, the product of bearing pressure and slid- ing velocity, Pv, as a parameter for presenting results. Units for Pv are (Pa)(m...the pin. Length loss was measured for each test. However, the soft copper pins had a tendency to “ mushroom ” during sliding under the applied load

  17. Evaluation of the wear properties of high interstitial stainless steels

    SciTech Connect

    Tylczak, J.H.; Rawers, J.C.; Alman, D.E.

    2007-04-01

    Adding carbon to high nitrogen steels increases interstitial concentrations over what can be obtained with nitrogen addition alone. This can results in an increase in hardness, strength, and wear resistance. The alloys produced for this study were all based on commercially available high-nitrogen Fe-18Cr-18Mn stainless steel. This study is the first significant wear study of these new high interstitial nitrogen-carbon stainless steel alloys. Wear tests included: scratch, pin-on-disk abrasion, dry sand/rubber wheel abrasion, impeller impact, and jet erosion. Increasing interstitial concentration increased strength and hardness and improved wear resistance under all test conditions. The results are discussed in terms of overall interstitial alloy concentration.

  18. Experiment on wear behavior of high pressure gas seal faces

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Peng, Xudong; Bai, Shaoxian; Meng, Xiangkai; Li, Jiyun

    2014-11-01

    Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%-25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures.

  19. An Evaluation of High Velocity Wear

    DTIC Science & Technology

    2007-03-01

    x10F~ -4 [18:18-19]. Authors such as Hutchings and Rabinowicz however, do not explicitly limit equation (12) to plastic wear. They suggest that...2:0; K=11604.5; %Constant for converting from Kelvin to eV for CTH N=size(y,1); T0=T(1); Tf=T(N); [C,I]=max(T); %Find the Maximum...package rail * normal level rail height material 2 numsub 100 temperature = 2.55935e-2 * eV = 74.93F = 297 K xvel 0.0 yvel 0.0

  20. 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

  1. WEAR BEHAVIOR OF CARBON NANOTUBE/HIGH DENSITY POLYETHYLENE COMPOSITES

    PubMed Central

    Johnson, Brian B.; Novotny, John E.; Advani, Suresh G.

    2009-01-01

    Carbon Nanotube/High Density Polyethylene (CNT/HDPE) composites were manufactured and tested to determine their wear behavior. The nanocomposites were made from untreated multi-walled carbon nanotubes and HDPE pellets. Thin films of the precursor materials were created with varying weight percentages of nanotubes (1%, 3%, and 5%), through a process of mixing and extruding. The precursor composites were then molded and machined to create test specimens for mechanical and wear tests. These included small punch testing to compare stiffness, maximum load and work-to-failure and block-on-ring testing to determine wear behavior. Each of the tests was conducted for the different weight percentages of composite as well as pure HDPE as the baseline. The measured mechanical properties and wear resistance of the composite materials increased with increasing nanotube content in the range studied. PMID:20161101

  2. Surface texture measurement for dental wear applications

    NASA Astrophysics Data System (ADS)

    Austin, R. S.; Mullen, F.; Bartlett, D. W.

    2015-06-01

    The application of surface topography measurement and characterization within dental materials science is highly active and rapidly developing, in line with many modern industries. Surface measurement and structuring is used extensively within oral and dental science to optimize the optical, tribological and biological performance of natural and biomimetic dental materials. Although there has historically been little standardization in the use and reporting of surface metrology instrumentation and software, the dental industry is beginning to adopt modern areal measurement and characterization techniques, especially as the dental industry is increasingly adopting digital impressioning techniques in order to leverage CAD/CAM technologies for the design and construction of dental restorations. As dental treatment becomes increasingly digitized and reliant on advanced technologies such as dental implants, wider adoption of standardized surface topography and characterization techniques will become evermore essential. The dental research community welcomes the advances that are being made in surface topography measurement science towards realizing this ultimate goal.

  3. Wear measurement of highly cross-linked UHMWPE using a 7Be tracer implantation technique.

    PubMed

    Wimmer, Markus A; Laurent, Michel P; Dwiwedi, Yasha; Gallardo, Luis A; Chipps, Kelly A; Blackmon, Jeffery C; Kozub, Raymond L; Bardayan, Daniel W; Gross, Carl J; Stracener, Daniel W; Smith, Michael S; Nesaraja, Caroline D; Erikson, Luke; Patel, Nidhi; Rehm, Karl E; Ahmad, Irshad; Greene, John P; Greife, Uwe

    2013-04-01

    The very low wear rates achieved with the current highly cross-linked ultrahigh molecular weight polyethylenes (UHMWPE) used in joint prostheses have proven to be difficult to measure accurately by gravimetry. Tracer methods are therefore being explored. The purpose of this study was to perform a proof-of-concept experiment on the use of the radioactive tracer beryllium-7 ((7)Be) for the determination of in vitro wear in a highly cross-linked orthopedic UHMWPE. Three cross-linked and four conventional UHMWPE pins made from compression-molded GUR 1050, were activated with 10(9) to 10(10) (7)Be nuclei using a new implantation setup that produced a homogenous distribution of implanted nuclei up to 8.5 μm below the surface. The pins were tested for wear in a six-station pin-on-flat apparatus for up to 7.1 million cycles (178 km). A Germanium gamma detector was employed to determine activity loss of the UHMWPE pins at preset intervals during the wear test. The wear of the cross-linked UHMWPE pins was readily detected and estimated to be 17 ± 3 μg per million cycles. The conventional-to-cross-linked ratio of the wear rates was 13.1 ± 0.8, in the expected range for these materials. Oxidative degradation damage from implantation was negligible; however, a weak dependence of wear on implantation dose was observed limiting the number of radioactive tracer atoms that can be introduced. Future applications of this tracer technology may include the analysis of location-specific wear, such as loss of material in the post or backside of a tibial insert.

  4. Carbon-Based Wear Coatings: Properties and Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    2003-01-01

    The technical function of numerous engineering systems - such as vehicles, machines, and instruments - depends on the processes of motion and on the surface systems. Many processes in nature and technology depend on the motion and dynamic behavior of solids, liquids, and gases. Smart surface systems are essential because of the recent technological push toward higher speeds, loads, and operating temperatures; longer life; lighter weight and smaller size (including nanotechnology); and harsh environments in mechanical, mechatronic, and biomechanical systems. If proper attention is not given to surface systems, then vehicles, machines, instruments, and other technical systems could have short lives, consume excessive energy, experience breakdowns, result in liabilities, and fail to accomplish their missions. Surface systems strongly affect our national economy and our lifestyles. At the NASA Glenn Research Center, we believe that proper attention to surface systems, especially in education, research, and application, could lead to economic savings of between 1.3 and 1.6 percent of the gross domestic product. Wear coatings and surface systems continue to experience rapid growth as new coating and surface engineering technologies are discovered, more cost-effective coating and surface engineering solutions are developed, and marketers aggressively pursue, uncover, and exploit new applications for engineered surface systems in cutting tools and wear components. Wear coatings and smart surface systems have been used widely in industrial, consumer, automotive, aerospace, and biomedical applications. This presentation expresses the author's views of and insights into smart surface systems in wear coatings. A revolution is taking place in carbon science and technology. Diamond, an allotrope of carbon, joins graphite, fullerenes, and nanotubes as its major pure carbon structures. It has a unique combination of extreme properties: hardness and abrasion resistance; adhesion

  5. Tribology: Wear test selection for design and application

    SciTech Connect

    Ruff, A.W.; Bayer, R.G.

    1993-01-01

    One important area of concern that has not been covered in previous symposia by the ASTM's Committee on Wear and Erosion is the connection between laboratory testing and actual operating performance of systems or components. This connection between laboratory testing, test results, and final design and performance is a crucial one in the practical application of tribology science and engineering. One of the aims of this symposium was to show by example how successful simulative testing has been accomplished. Specific examples are presented from a number of applications involving different forms of wear, including some from such specialized areas as computer peripherals, engines, and prosthetic devices. An important consideration in all the presentations was the identification of critical use conditions. Nine of the papers have been processed separately for inclusion on the data base.

  6. Wear Characteristics of Oleophobic Coatings in Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Shams, Hamza; Basit, Kanza

    2016-05-01

    This paper investigates the wear characteristics of oleophobic coatings when applied over Inconel 718, which has widespread applications in the aerospace industry. Coatings once applied were selectively exposed to controlled uni-and then multi-directional stand storm conditions. Size and speed of sand particles colliding with the work surface were carefully moderated to simulate sand storm conditions. Study of friction was performed using Lateral Force Microscopy (LFM) coupled with standard optical microscopy. The analysis has been used to devise a coefficient of friction value and in turn suggest wear behavior of the coated surface including the time associated with exposure of the base substrate. The analysis after validation aims to suggest methods for safe usage of these coatings for aerospace applications.

  7. Wear Characteristics of Oleophobic Coatings in Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Shams, Hamza; Siddiqui, Bilal A.; Saleem, Sajid

    This paper investigates the wear characteristics of oleophobic coatings when applied over Inconel 718, which has widespread applications in the aerospace industry. Coatings once applied were selectively exposed to controlled uni-and then multi-directional stand storm conditions. Size and speed of sand particles colliding with the work surface were carefully moderated to simulate sand storm conditions. Study of friction was performed using Lateral Force Microscopy (LFM) coupled with standard optical microscopy. The analysis has been used to devise a coefficient of friction value and in turn suggest wear behavior of the coated surface including the time associated with exposure of the base substrate. The analysis after validation aims to suggest methods for safe usage of these coatings for aerospace applications.

  8. Friction and wear of hydroxyapatite reinforced high density polyethylene against the stainless steel counterface.

    PubMed

    Wang, M; Chandrasekaran, M; Bonfield, W

    2002-06-01

    Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) was invented as a biomaterial for skeletal applications. In this investigation, tribological properties (e.g. wear rate and coefficient of friction) of unfilled HDPE and HA/HDPE composites were evaluated against the duplex stainless steel in dry and lubricated conditions, with distilled water or aqueous solutions of proteins (egg albumen or glucose) being lubricants. Wear tests were conducted in a custom-built test rig for HDPE and HA/HDPE containing up to 40 vol % of HA. It was found that HA/HDPE composites had lower coefficients of friction than unfilled HDPE under certain conditions. HA/HDPE also exhibited less severe fatigue failure marks than HDPE. The degradation and fatigue failure of HDPE due to the presence of proteins were severe for low speed wear testing (100 rpm) as compared to high speed wear testing (200 rpm). This was due possibly to the high shear rate at the contact which could remove any degraded film instantaneously at high sliding speed, while with a low sliding speed the build-up of a degraded layer of protein could occur. The degraded protein layer would stay at the contact for a longer time and mechanical activation would induce adverse reactions, weakening the surface layer of HDPE. Both egg albumen and glucose were found to be corrosive to steel and adversely reactive for HDPE and HA/HDPE composites. The wear modes observed were similar to that of ultra-high molecular weight polyethylene. Specimens tested with egg albumen also displayed higher wear rates, which was again attributed to corrosion accelerated wear.

  9. Wear-resistant ball bearings for space applications

    NASA Technical Reports Server (NTRS)

    Boving, H.; Hintermann, H. E.; Hanni, W.; Bondivenne, E.; Boeto, M.; Conde, E.

    1977-01-01

    Ball bearings consisting of steel parts of which the rings are coated with hard, wear resistant, chemical vapor deposited TiC are described. Experiments conducted in ultrahigh vacuum, using cages of various materials with self-lubricating properties, show that such bearings are suitable for space applications. The results of laboratory tests on the ESA Meteosat Radiometer Focalizing mechanism, which contains six coated bearings, are summarized.

  10. Development of an extremely wear-resistant ultra high molecular weight polyethylene for total hip replacements.

    PubMed

    McKellop, H; Shen, F W; Lu, B; Campbell, P; Salovey, R

    1999-03-01

    Osteolysis induced by ultra high molecular weight polyethylene wear debris is one of the primary factors limiting the lifespan of total hip replacements. Crosslinking polyethylene is known to improve its wear resistance in certain industrial applications, and crosslinked polyethylene acetabular cups have shown improved wear resistance in two clinical studies. In the present study, crosslinked polyethylene cups were produced by two methods. Chemically crosslinked cups were produced by mixing a peroxide with ultra high molecular weight polyethylene powder and then molding the cups directly to shape. Radiation-crosslinked cups were produced by exposing conventional extruded ultra high molecular weight polyethylene bar stock to gamma radiation at various doses from 3.3 to 100 Mrad (1 Mrad = 10 kGy), remelting the bars to extinguish residual free radicals (i.e., to minimize long-term oxidation), and then machining the cups by conventional techniques. In hip-joint simulator tests lasting as long as 5 million cycles, both types of cross-linked cups exhibited dramatically improved resistance to wear. Artificial aging of the cups by heating for 30 days in air at 80 degrees C induced oxidation of the chemically crosslinked cups. However, a chemically crosslinked cup that was aged 2.7 years at room temperature had very little oxidation. Thus, whether substantial oxidation of chemically crosslinked polyethylene would occur at body temperature remains unclear. The radiation-crosslinked remelted cups exhibited excellent resistance to oxidation. Because crosslinking can reduce the ultimate tensile strength, fatigue strength, and elongation to failure of ultra high molecular weight polyethylene, the optimal crosslinking dose provides a balance between these physical properties and the wear resistance of the implant and might substantially reduce the incidence of wear-induced osteolysis with total hip replacements.

  11. The research on tool wear of high speed milling titanium alloy TC4

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Wang, Zhichao; Ren, Huanhuan; Yuan, Haoteng

    2017-01-01

    In this paper, carbide cutting tools with physical vapor deposition (PVD) coating was used to high speed milling α+β phase TC4 titanium alloy. The PVD tool was used to study the process of milling TC4 titanium alloy tool wear patterns and wear mechanisms. The results showed that the PVD coating surface wear was small after cutter blade. The cutting life was long, it was suitable for processing of titanium alloy TC4, the wear of rake face was mainly adhesion wear and oxidation wear, the flank face was mainly boundary wear. That was because the adhesion wear of the rake face and the boundary wear of the flank face had a weakening effect on the cutting edge , which made the micro crack blade of the main cutting edge.

  12. Improvement in high stress abrasive wear property of steel by hardfacing

    SciTech Connect

    Kumar, S.; Mondal, D.P.; Khaira, H.K.; Jha, A.K.

    1999-12-01

    High stress abrasive wear behavior of mild steel, medium carbon steel, and hardfacing alloy has been studied to ascertain the extent of improvement in the wear properties after hardfacing of steel. High stress abrasive wear tests were carried out by sliding the specimen against the abrasive media consisting of silicon carbide particles, rigidly bonded on paper base and mounted on disk. Maximum wear was found in the case of mild steel followed by a medium carbon alloy steel and a hardfacing alloy. Different compositions of steels and constituent phases present led to different wear rates of the specimen. The extent of improvement in wear performance of steel due to hardfacing is quite appreciable (twice compared to mild steel). Microstructural examination of the wear surface has been carried out to understand the wear mechanism.

  13. Controlled tip wear on high roughness surfaces yields gradual broadening and rounding of cantilever tips

    NASA Astrophysics Data System (ADS)

    Vorselen, Daan; Kooreman, Ernst S.; Wuite, Gijs J. L.; Roos, Wouter H.

    2016-11-01

    Tip size in atomic force microscopy (AFM) has a major impact on the resolution of images and on the results of nanoindentation experiments. Tip wear is therefore a key limitation in the application of AFM. Here we show, however, how wear can be turned into an advantage as it allows for directed tip shaping. We studied tip wear on high roughness polycrystalline titanium and diamond surfaces and show that tip wear on these surfaces leads to an increased tip size with a rounded shape of the apex. Next, we fitted single peaks from AFM images in order to track the changes in tip radius over time. This method is in excellent agreement with the conventional blind tip reconstruction method with the additional advantage that we could use it to demonstrate that the increase in tip size is gradual. Moreover, with our approach we can shape and control the tip size, while retaining identical chemical and cantilever properties. This significantly expands the reproducibility of AFM force spectroscopy data and is therefore expected to find a wide applicability.

  14. Controlled tip wear on high roughness surfaces yields gradual broadening and rounding of cantilever tips

    PubMed Central

    Vorselen, Daan; Kooreman, Ernst S.; Wuite, Gijs J. L.; Roos, Wouter H.

    2016-01-01

    Tip size in atomic force microscopy (AFM) has a major impact on the resolution of images and on the results of nanoindentation experiments. Tip wear is therefore a key limitation in the application of AFM. Here we show, however, how wear can be turned into an advantage as it allows for directed tip shaping. We studied tip wear on high roughness polycrystalline titanium and diamond surfaces and show that tip wear on these surfaces leads to an increased tip size with a rounded shape of the apex. Next, we fitted single peaks from AFM images in order to track the changes in tip radius over time. This method is in excellent agreement with the conventional blind tip reconstruction method with the additional advantage that we could use it to demonstrate that the increase in tip size is gradual. Moreover, with our approach we can shape and control the tip size, while retaining identical chemical and cantilever properties. This significantly expands the reproducibility of AFM force spectroscopy data and is therefore expected to find a wide applicability. PMID:27833143

  15. Unified wear model for highly crosslinked ultra-high molecular weight polyethylenes (UHMWPE).

    PubMed

    Muratoglu, O K; Bragdon, C R; O'Connor, D O; Jasty, M; Harris, W H; Gul, R; McGarry, F

    1999-08-01

    Crosslinking has been shown to improve the wear resistance of ultra-high molecular weight polyethylene in both in vitro and clinical in vivo studies. The molecular mechanisms and material properties that are responsible for this marked improvement in wear resistance are still not well understood. In fact, following crosslinking a number of mechanical properties of UHMWPE are decreased including toughness, modulus, ultimate tensile strength, yield strength, and hardness. In general, these changes would be expected to constitute a precursor for lower wear resistance, presenting a paradox in that wear resistance increases with crosslinking. In order to understand better and to analyze this paradoxical behaviour of crosslinked UHMWPE, we investigated the wear behavior of (i) radiation-crosslinked GUR 1050 resin, (ii) peroxide-crosslinked GUR 1050 resin and (iii) peroxide-crosslinked Himont 1900 resin using a bi-directional pin-on-disk (POD) machine. Wear behavior was analyzed as a function of crystallinity, ultimate tensile strength (UTS), yield strength (YS), and molecular weight between crosslinks (Mc). The crosslink density increased with increasing radiation dose level and initial peroxide content. The UTS, YS, and crystallinity decreased with increasing crosslink density. While these variations followed the same trend, the absolute changes as a function of crosslink density were different for the three types of crosslinked UHMWPE studied. There was no unified correlation for the wear behavior of the three types of crosslinked UHMWPE with the crystallinity, UTS and YS. However, the POD wear rate showed the identical linear dependence on Mc with all three types of crosslinked UHMWPEs studied. Therefore, we have strong evidence to propose that Mc or crosslink density is a fundamental material property that governs the lubricated adhesive and abrasive wear mechanisms of crosslinked UHMWPEs, overriding the possible effects of other material properties such as UTS, YS

  16. Application of ion implantation to wear protection of materials

    NASA Astrophysics Data System (ADS)

    Hubler, O. K.; Smidt, F. A.

    1985-03-01

    Key results from the literature for the wear behavior of N- and Ti-implanted steels are reviewed. A qualitative model which rationalizes the mechanisms producing improvements in the sliding wear resistance of steels is presented. In the limited regime of low sliding velocities the model provides guidelines for choosing the experimental conditions of applied load, composition, hardness and heat treatment of the steel under which implantation will improve wear resistance.

  17. A new application of dental wear analyses: estimation of duration of hominid occupations in archaeological localities.

    PubMed

    Rivals, Florent; Schulz, Ellen; Kaiser, Thomas M

    2009-04-01

    Characterization of settlement patterns is one of the core concepts in archeological research. The duration of an occupation is usually estimated through zooarchaeology (e.g., density of remains, cementochronology) and is limited by taphonomic processes and sample size. We propose a new application of dental wear methods for estimating the relative duration of hominid settlements in Paleolithic sites. Dental microwear is known to be sensitive to seasonal changes in diet. In this new application we use microwear scratch counts to estimate the variation in the dietary signal of various ungulate species. We propose that this variation is correlated to the duration of site occupation. Each season presents a limited and different set of food resources available in the environment. If animals are sampled only during a specific season (i.e., during a short term occupation) then they would be expected to have a dental wear signal with little variation. On the other hand, a greater diversity of food is available across different seasons. Therefore, if game animals are hunted through various seasons during long occupation periods, then they would be expected to have more variable dental wear. The application of this technique to the Middle Paleolithic site of Arago Cave (France), where various types of occupations occurred, supports this hypothesis. When combined with multidisciplinary studies of archaeological localities (seasonality in particular), this new application of dental wear analysis presents valuable information about hominid settlements and behavior. We contextualize our data with results from lithic and zooarchaeological analyses from Arago. These results reveal the presence of both high and low mobility groups of Homo heidelbergensis throughout the sequence of the Arago Cave.

  18. Application of an X-ray Fluorescence Instrument to Helicopter Wear Debris Analysis

    DTIC Science & Technology

    2008-04-01

    Application of an X-ray Fluorescence Instrument to Helicopter Wear Debris Analysis Andrew Becker Air Vehicles Division...instrument to determine the composition of wear debris collected from helicopter magnetic chip detectors and oil filters. The Twin-X XRF (assessed in this...report) is a commercially produced bench-top XRF and has not previously been applied to wear debris analysis of Australian Defence Force aircraft

  19. Online Wear Detection Using High-Speed Imaging.

    PubMed

    Soleimani, Seyfollah; Sukumaran, Jacob; Douterloigne, Koen; De Baets, Patrick; Philips, Wilfried

    2016-08-01

    In this paper, the change detection of a fast turning specimen is studied at micro-level, whereas the images are acquired without stopping the rotation. In the beginning of the experiment, the imaging system is focused on the surface of the specimen. By starting the rotation of the specimen, the diameter of the specimen changes due to wear, which results in de-focusing of the imaging system. So the amount of blur in the images can be used as evidence of the wear phenomenon. Due to the properties of the microscope, the corners of the frames were dark and had to be cropped. So, each micrograph reflects only a small area of the surface. Nevertheless, techniques like stitching of multiple images can provide a significant surface area for micro-level investigation which increases the effectiveness of analyzing the material modification. Based on the results computer vision could detect a change of about 1.2 µm in the diameter of the specimen. More important is that we could follow the same locations of the surface in the microscopic images despite blurring, uneven illumination, change on the surface, and relatively a high-speed rotation.

  20. Wear of PEEK-OPTIMA® and PEEK-OPTIMA®-Wear Performance articulating against highly cross-linked polyethylene.

    PubMed

    East, Rebecca H; Briscoe, Adam; Unsworth, Anthony

    2015-03-01

    The idea of all polymer artificial joints, particularly for the knee and finger, has been raised several times in the past 20 years. This is partly because of weight but also to reduce stress shielding in the bone when stiffer materials such as metals or ceramics are used. With this in mind, pin-on-plate studies of various polyetheretherketone preparations against highly cross-linked polyethylene were conducted to investigate the possibility of using such a combination in the design of a new generation of artificial joints. PEEK-OPTIMA(®) (no fibre) against highly cross-linked polyethylene gave very low wear factors of 0.0384 × 10(-6) mm(3)/N m for the polyetheretherketone pins and -0.025 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates. The carbon-fibre-reinforced polyetheretherketone (PEEK-OPTIMA(®)-Wear Performance) also produced very low wear rates in the polyetheretherketone pins but produced very high wear in the highly cross-linked polyethylene, as might have been predicted since the carbon fibres are quite abrasive. When the fibres were predominantly tangential to the sliding plane, the mean wear factor was 0.052 × 10(-6) mm(3)/N m for the pins and 49.3 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates; a half of that when the fibres ran axially in the pins (0.138 × 10(-6) mm(3)/N m for the pins and 97.5 × 10(-6) mm/ N m for the cross-linked polyethylene plates). PEEK-OPTIMA(®) against highly cross-linked polyethylene merits further investigation.

  1. Wear resistance properties of austempered ductile iron

    NASA Astrophysics Data System (ADS)

    Lerner, Y. S.; Kingsbury, G. R.

    1998-02-01

    A detailed review of wear resistance properties of austempered ductile iron (ADI) was undertaken to examine the potential applications of this material for wear parts, as an alternative to steels, alloyed and white irons, bronzes, and other competitive materials. Two modes of wear were studied: adhesive (frictional) dry sliding and abrasive wear. In the rotating dry sliding tests, wear behavior of the base material (a stationary block) was considered in relationship to countersurface (steel shaft) wear. In this wear mode, the wear rate of ADI was only one-fourth that of pearlitic ductile iron (DI) grade 100-70-03; the wear rates of aluminum bronze and leaded-tin bronze, respectively, were 3.7 and 3.3 times greater than that of ADI. Only quenched DI with a fully martensitic matrix slightly outperformed ADI. No significant difference was observed in the wear of steel shafts running against ADI and quenched DI. The excellent wear performance of ADI and its countersurface, combined with their relatively low friction coefficient, indicate potential for dry sliding wear applications. In the abrasive wear mode, the wear rate of ADI was comparable to that of alloyed hardened AISI 4340 steel, and approximately one-half that of hardened medium-carbon AISI 1050 steel and of white and alloyed cast irons. The excellent wear resistance of ADI may be attributed to the strain-affected transformation of high-carbon austenite to martensite that takes place in the surface layer during the wear tests.

  2. Laboratory evaluation of low cobalt wear materials for nuclear applications

    SciTech Connect

    Shiels, S.A.; Wilson, W.L.; Rosengarth, K.W.; Wire, G.L.

    1994-09-01

    Laboratory wear and corrosion screening tests were conducted on several commercially available, low-cobalt and cobalt-free hardsurfacing alloys to evaluate their relative wear and corrosion performance under simulated Pressurized Water Reactor (PWR) primary heat transport circuit conditions. Wear tests were performed under reciprocating, sliding contact. Corrosion performance was evaluated in both steady state and off-normal chemistry conditions. The wear behavior of the candidate hardsurfacing alloys was generally comparable to or better than that of Stellite 6, a material of proven wear performance under PWR operating conditions. With the exception of Tristelle 5183, the iron base alloys exhibited unacceptable corrosion behavior under wet layup conditions. The Tristelle 5183 experienced minor corrosion attack in primary coolant having elevated oxygen levels. The twelve percent cobalt alloy, Tristelle TS-2, performed well but exhibited some attack after a simulated decontamination treatment.

  3. High stress abrasive wear behavior of some hardfaced surfaces produced by thermal spraying

    NASA Astrophysics Data System (ADS)

    Jha, A. K.; Gachake, Arati; Prasad, B. K.; Dasgupta, Rupa; Singh, M.; Yegneswaran, A. H.

    2002-02-01

    Steel surfaces were thermally sprayed with nickel chromium boron (NCB) powder (with and without tungsten carbide) using an oxy-acetylene torch. The sprayed (hard) surfaces and substrate were characterized for abrasive wear properties. Test parameters such as load and sliding distance were varied. A significant improvement in the abrasive wear resistance (inverse of wear rate) was noted for the thermally sprayed surfaces as compared to that of the substrate. Wear surfaces, subsurface regions, and debris were examined in order to ascertain the operating wear mechanisms. Substrate (mild steel), because of its low hardness, suffered severe wear through the cutting, ploughing, and wedging action of the hard abrasive (silicon carbide). Deep cuts on the worn surface, a bulky transfer layer, subsurface cracks, and large-size debris were observed. However, wear was reduced due to high hardness of the layer of NCB powder on the substrate, which resisted the penetration of abrasive into the surface. Presence of tungsten carbide in the layer of NCB powder further reduced the wear of the corresponding specimen because of very high hardness of the tungsten carbide. Shallow wear grooves and finer debris were observed for the NCB coating with and without tungsten carbide. Cutting was the predominating wear mechanism in the case of coatings.

  4. Wear Measurement of Highly Cross-linked UHMWPE using a 7Be Tracer Implantation Technique

    SciTech Connect

    Wimmer, Markus A.; Laurent, Michael P.; Dwivedi, Yasha; Gallardo, Luis A.; Chipps, K.; Blackmon, Jeffery C; Kozub, R. L.; Bardayan, Daniel W; Gross, Carl J; Stracener, Daniel W; Smith, Michael Scott; Nesaraja, Caroline D; Erikson, Luke; Patel, Nidhi; Rehm, Karl E.; Ahmad, Irshad; Greene, John P.; Greife, Uwe

    2013-01-01

    The very low wear rates achieved with the current highly cross-linked ultrahigh molecular weight polyethylenes (UHMWPE) used in joint prostheses have proven to be difficult to measure accurately by gravimetry. Tracer methods are there- fore being explored. The purpose of this study was to perform a proof-of-concept experiment on the use of the radioactive tracer beryllium-7 (7Be) for the determination of in vitro wear in a highly cross-linked orthopedic UHMWPE. Three cross-linked and four conventional UHMWPE pins made from compression- molded GUR 1050, were activated with 109 to 1010 7Be nuclei using a new implantation setup that produced a homogenous distribution of implanted nuclei up to 8.5 lm below the surface. The pins were tested for wear in a six-station pin-on-flat appara- tus for up to 7.1 million cycles (178 km). A Germanium gamma detector was employed to determine activity loss of the UHMWPE pins at preset intervals during the wear test. The wear of the cross-linked UHMWPE pins was readily detected and esti- mated to be 17 6 3 lg per million cycles. The conventional-to- cross-linked ratio of the wear rates was 13.1 6 0.8, in the expected range for these materials. Oxidative degradation dam- age from implantation was negligible; however, a weak depend- ence of wear on implantation dose was observed limiting the number of radioactive tracer atoms that can be introduced. Future applications of this tracer technology may include the analysis of location-specific wear, such as loss of material in the post or backside of a tibial insert.

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

    SciTech Connect

    Panin, S. V.; Kornienko, L. A.; Poltaranin, M. A.; Ivanova, L. R.; Suan, T. Nguen

    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.

  6. High Density Infrared (HDI) Transient Liquid Coatings for Improved Wear and Corrosion Resistance

    SciTech Connect

    Ronald W. Smith

    2007-07-05

    This report documents a collaborative effort between Oak Ridge National Laboratory (ORNL), Materials Resources International and an industry team of participants to develop, evaluate and understand how high density infrared heating technology could be used to improve infiltrated carbide wear coatings and/or to densify sprayed coatings. The research included HDI fusion evaluations of infiltrated carbide suspensions such (BrazeCoat® S), composite suspensions with tool steel powders, thermally sprayed Ni-Cr- B-Si (self fluxing alloy) and nickel powder layers. The applied work developed practical HDI / transient liquid coating (TLC) procedures on test plates that demonstrated the ability to fuse carbide coatings for industrial applications such as agricultural blades, construction and mining vehicles. Fundamental studies helped create process models that led to improved process understanding and control. The coating of agricultural blades was demonstrated and showed the HDI process to have the ability to fuse industrial scale components. Sliding and brasive wear tests showed that high degree of wear resistance could be achieved with the addition of tool steel powders to carbide particulate composites.

  7. The Friction and Wear of Copper in High-Load, Low-Speed, Small-Amplitude Reciprocating Sliding

    DTIC Science & Technology

    1982-08-01

    carbon, medium chromium and nickel steel Inconel 718 Nickel-chromium based alloy k Wear constant, commonly called Archard wear coefficient n Wear...nickel-chromium based alloy ( Inconel 718 ) and (c) high-purity copper. These metals hereafter are identified as (a) steel, (b) Inconel , and (c) copper. I...22 WEAR RESULTS ........... . ............................. 23 Stages of Wear for Copper Sliding on Steel or Inconel .......... . 26

  8. Wear Consideration in Gear Design for Space Applications

    DTIC Science & Technology

    1989-01-01

    profile. The Archard 1/2 wear equation ( Rabinowicz , 1965) will be used to calcu- late depth wear (h) as follows b " ’ (5) h= (2) 3pAa where where =rltv aiso...This can be calculated from: e5 =h5/Rb where h5 KWNPy EV . 0.005671 e h I ( 3PF I rad e5 . 0.005671/1.1746 - 0.0048 rad, or 0.280 3 also the top...Subtract 0.0018 in. for initial backlash plus Handbook, ASME, New York. tooth-to-tooth composite error (when new) to get Rabinowicz , E., 1965, Friction and

  9. Wear Resistance of H13 and a New Hot-Work Die Steel at High temperature

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Wu, Xiaochun; Chen, Shihao; Li, Junwan

    2016-07-01

    The friction and wear behaviors of a new hot-work die steel, SDCM-SS, were studied at high temperature under dry air conditions. The wear mechanism and microstructural characteristics of the SDCM-SS steel were also investigated. The results showed that the SDCM-SS steel had greater wear resistance compared with H13 steel; this was owed to its high oxidizability and temper stability. These features facilitate the generation, growth, and maintenance of a tribo-oxide layer at high temperature under relatively stable conditions. The high oxidizability and thermal stability of the SDCM-SS steel originate from its particular alloy design. No chromium is added to the steel; this ensures that the material has high oxidizability, and facilitates the generation of tribo-oxides during the sliding process. Molybdenum, tungsten, and vanadium additions promote the high temper resistance and stability of the steel. Many fine Mo2C and VC carbides precipitate during the tempering of SDCM-SS steel. During sliding, these carbides can delay the recovery process and postpone martensitic softening. The high temper stability postpones the transition from mild to severe wear and ensures that conditions of mild oxidative wear are maintained. Mild oxidative wear is the dominant wear mechanism for SDCM-SS steel between 400 and 700 °C.

  10. Wear Analysis of Second-generation Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty.

    PubMed

    Samujh, Christopher; Bhimani, Samrath; Smith, Langan; Malkani, Arthur L

    2016-11-01

    A major limiting factor in the longevity of total hip replacement is the wear rate of the hip bearing. As manufacturing technology has improved during the past several decades, much attention has been focused on developing newer generations of polyethylene that have lower rates of wear while minimizing free radical formation and subsequent osteolysis. The turning point for the manufacture of polyethylene was moving from gamma irradiation in air to irradiation in a low oxygen environment, which reduced free radical formation while increasing the wear resistance. New polyethylene manufacturing methods, including multiple cycles of irradiation and annealing, have resulted in greater wear resistance. Wear analysis studies are essential to determine if these new liners actually show a benefit from prior generations of polyethylene and, more importantly, if they are safe to use. This study involved a single center retrospective review of 60 patients with a mean follow-up of 5.5 years who underwent primary total hip arthroplasty with a second-generation highly cross-linked polyethylene manufactured by 3 cycles of sequential irradiation and annealing. Linear and volumetric wear rates were determined from digitized radiographs using contemporary wear analysis software. The mean linear wear rate for the entire group was 0.025 millimeters per year (mm/y). This value represents a linear wear rate 2.7 times less than that of a first-generation highly cross-linked polyethylene and 4.2 times less than that of a conventional polyethylene. At an average of 5 years, compared with a first-generation highly cross-linked polyethylene, a second-generation highly cross-linked polyethylene appears to show significant improvement regarding wear. [Orthopedics. 2016; 39(6):e1178-e1182.].

  11. Wear and creep of highly crosslinked polyethylene against cobalt chrome and ceramic femoral heads.

    PubMed

    Galvin, A L; Jennings, L M; Tipper, J L; Ingham, E; Fisher, J

    2010-10-01

    The wear and creep characteristics of highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) articulating against large-diameter (36mm) ceramic and cobalt chrome femoral heads have been investigated in a physiological anatomical hip joint simulator for 10 million cycles. The crosslinked UHMWPE/ceramic combination showed higher volume deformation due to creep plus wear during the first 2 million cycles, and a steady-state wear rate 40 per cent lower than that of the crosslinked UHMWPE/cobalt chrome combination. Wear particles were isolated and characterized from the hip simulator lubricants. The wear particles were similar in size and morphology for both head materials. The particle isolation methodology used could not detect a statistically significant difference between the particles produced by the cobalt chrome and alumina ceramic femoral heads.

  12. Friction and wear of carbon-graphite materials for high energy brakes

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1975-01-01

    Caliper-type brakes simulation experiments were conducted on seven different carbon-graphite material formulations against a steel disk material and against a carbon-graphite disk material. The effects of binder level, boron carbide (B4C) additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level and additions of B4C each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. This transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur. The exposure of the fiber structure of the cloth constituent is believed to play a role in the shear film disruption.

  13. Friction and wear of carbon-graphite materials for high-energy brakes

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1978-01-01

    Caliper type brake simulation experiments were conducted on seven different carbon graphite materials formulations against a steel disk material and against a carbon graphite disk material. The effects of binder level, boron carbide (B4C) additions, SiC additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level, additions of B4C, and additions of SiC each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. The transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur.

  14. High vitamin E content, impact resistant UHMWPE blend without loss of wear resistance.

    PubMed

    Oral, Ebru; Neils, Andrew; Muratoglu, Orhun K

    2015-05-01

    Antioxidant stabilization of radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) has been introduced to improve the oxidative stability of total joint implant bearing surfaces. Blending of antioxidants (most commonly vitamin E) with UHMWPE resin powder followed by consolidation and uniform radiation cross-linking is currently available for use in both total hips and total knees. It was previously shown that the fatigue resistance of vitamin E-blended and irradiated UHMWPEs could be further improved by spatially manipulating the vitamin E concentration throughout the implant and limiting cross-linking to the surface of the implant where it is necessary for wear resistance. This was possible by designing a low concentration of vitamin E on the surface and higher concentration in the bulk of the implant because cross-linking is hindered in UHMWPE as a function of increasing vitamin E concentration. In this study, we hypothesized that such a surface cross-linked UHMWPE with low wear rate and high fatigue strength could be obtained by limiting the penetration of radiation into UHMWPE with uniform vitamin E concentration. Our hypothesis tested positive; we were able to obtain control of the surface cross-linked region by manipulating the energy of the irradiation, resulting in extremely low wear, and high impact strength. In addition, we discussed alternatives of improving the oxidation resistance of such a material by using additional vitamin E reservoirs. These results are significant because this material may allow increased use of antioxidant-stabilized, cross-linked UHMWPEs in high stress applications and in more active patients.

  15. Comparative wear tests of ultra-high molecular weight polyethylene and cross-linked polyethylene.

    PubMed

    Harsha, A P; Joyce, Tom J

    2013-05-01

    Wear particle-induced osteolysis is a major concern in hip implant failure. Therefore, recent research work has focussed on wear-resistant materials, one of the most important of which is cross-linked polyethylene. In view of this, the objective of this study was to compare the in vitro wear performance of cross-linked polyethylene to traditional ultra-high molecular weight polyethylene. In order to mimic appropriate in vivo conditions, a novel high-capacity wear tester called a circularly translating pin-on-disc was used. The results of this in vitro study demonstrated that the wear rate for cross-linked polyethylene was about 80% lower than that of conventional ultra-high molecular weight polyethylene. This difference closely matches in vivo results reported in the literature for total hip replacements that use the two biopolymers. The in vitro results were also verified against ASTM F732-00 (standard test method for wear testing of polymeric materials for use in total joint prostheses). The 50-station circularly translating pin-on-disc proved to be a reliable device for in vitro wear studies of orthopaedic biopolymers.

  16. Extended-wear of high oxygen-permeable quantum contact lenses.

    PubMed

    Kok, J H; Hilbrink, H J; Rosenbrand, R M; Visser, R

    1992-03-01

    This study was performed to investigate the effects of extended-wear of rigid aspherical high gas-permeable contact lenses on the cornea. In the study 32 subjects (62 eyes) were followed over a period of 3 to 24 months. A high gas-permeable contact lens (Dk 92), made of fluoro-silicone-acrylate copolymer, was used. Vision remained constant during the studied period. The corneal thickness decreased significantly (p less than 0.05) during the first six months. Significant changes (p less than 0.05) were found after three months in the corneal curvature, especially in the vertical meridian. No further topographical changes were noted in the period between three and six months of extended-wear. Complications, like acute red eye syndrome and bacterial infections, which may be encountered in soft lens extended-wear, were not noticed. At the end of the study 20 subjects (38 eyes, 61%) were still on extended-wear, 9 subjects (18 eyes, 29%) changed to daily wear and 3 subjects (six eyes, 10%) became unavailable for follow-up. Extended-wear of rigid aspherical high gas-permeable contact lenses may be considered as an acceptable alternative for soft lens extended-wear.

  17. Volatility and Wear Characteristics of a Variety of Liquid Lubricants for Space Applications

    NASA Technical Reports Server (NTRS)

    Nguyen, QuynhGiao N.; Jones, William R., Jr.

    2001-01-01

    The vapor pressures and wear characteristics are critical properties for liquid lubricants to assure long-term reliability and performance in space applications. Vapor pressures, obtained using a Knudsen cell technique, and wear properties, obtained using a vacuum four-ball apparatus, were measured for a series of unformulated liquid lubricants. These included two multiply alkylated cyclopentanes (MACs) (X-1000 and X2000), two linear perfluoropolyalkylethers (PFPAEs) (Z-25 and 815Z), and four silahydrocarbons (a tri, a tetra, and two pentas). Vapor pressures were measured at three elevated temperatures (423, 448, and 498 K) and extrapolated to room temperature 298 K. The lowest 298 K vapor pressure of 5.7 x 10(exp -14) Pa was obtained with the PFPAE fluid (815Z) and the highest value with the low molecular weight MAC (X-1000) at 3.6 x 10(exp -7) Pa. In addition, vacuum wear rates were determined for some of the lubricants. The lowest wear rates (approximately 3 x 10(exp -11) cubic mm/mm) were observed for three of the silahydrocarbons while the highest wear rates (approximately 2 x 10(exp -9) cubic mm/mm) were observed with the two PFPAE fluids (Z-25 and 815Z). The MAC (X-2000) yielded a wear rate of about 10(exp -10) cubic mm/mm. The results indicated that the silahydrocarbon class of liquid lubricants offers the better potential for space applications.

  18. High-temperature wear and deformation processes in metal matrix composites

    NASA Astrophysics Data System (ADS)

    Singh, J.; Alpas, A. T.

    1996-10-01

    Dry-sliding wear behaviors of a particulate-reinforced aluminum matrix composite 6061 Al-20 pet A12O3 and an unreinforced 6061 Al alloy were investigated in the temperature range 25 °C to 500 °C against a SAE 52100 bearing steel counterface. Experiments were carried out at a constant sliding speed of 0.2 m·s- at different test loads. The deformation behavior of the materials was studied by performing uniaxial compression tests in the same temperature range as the wear tests. Both alloys showed a mild-to-severe wear transition above a certain test temperature. In the mild wear regime, the wear rate and the coefficient of friction of the unreinforced 6061 Al decreased slightly with temperature, but the temperature had almost no effect on the wear rate and the coefficient of friction of the 6061 Al-20 pet Al2O3 in the same regime. Particulate reinforcement led to an increase in the transition temperature and a 50 to 70 pet improvement in the wear resistance in the severe wear regime. This was attributed to the formation of tribological layers consisting of comminuted A12O3 particles at the contact surface. High-temperature compression tests showed that the flow strength of 6061 Al-20 pet A12O3 and 6061 Al decreased monotonically with temperature and both alloys exhibited a work-softening behavior at temperatures higher than the inflection point on the flow stress vs temperature curves. The logarithmic maximum stress vs reciprocal temperature relationship was not linear, indicating that the deformation processes were too complicated to be characterized by a single activation energy over the whole temperature range. For the range of 250 °C to 450 °C, the activation energy for deformation was estimated to be 311 kJ·mol-1; for both the matrix alloy and the composite. Severe wear proceeded by thermally activated deformation processes involving dynamic recrystallization along a subsurface strain gradient. A power-Arrhenius type relationship was found to describe well

  19. The High performance of nanocrystalline CVD diamond coated hip joints in wear simulator test.

    PubMed

    Maru, M M; Amaral, M; Rodrigues, S P; Santos, R; Gouvea, C P; Archanjo, B S; Trommer, R M; Oliveira, F J; Silva, R F; Achete, C A

    2015-09-01

    The superior biotribological performance of nanocrystalline diamond (NCD) coatings grown by a chemical vapor deposition (CVD) method was already shown to demonstrate high wear resistance in ball on plate experiments under physiological liquid lubrication. However, tests with a close-to-real approach were missing and this constitutes the aim of the present work. Hip joint wear simulator tests were performed with cups and heads made of silicon nitride coated with NCD of ~10 μm in thickness. Five million testing cycles (Mc) were run, which represent nearly five years of hip joint implant activity in a patient. For the wear analysis, gravimetry, profilometry, scanning electron microscopy and Raman spectroscopy techniques were used. After 0.5 Mc of wear test, truncation of the protruded regions of the NCD film happened as a result of a fine-scale abrasive wear mechanism, evolving to extensive plateau regions and highly polished surface condition (Ra<10nm). Such surface modification took place without any catastrophic features as cracking, grain pullouts or delamination of the coatings. A steady state volumetric wear rate of 0.02 mm(3)/Mc, equivalent to a linear wear of 0.27 μm/Mc favorably compares with the best performance reported in the literature for the fourth generation alumina ceramic (0.05 mm(3)/Mc). Also, squeaking, quite common phenomenon in hard-on-hard systems, was absent in the present all-NCD system.

  20. Friction and wear evaluation of high-strength gel

    NASA Astrophysics Data System (ADS)

    Kameyama, Toshiki; Wada, Masato; Makino, Masato; Kawakami, Masaru; Furukawa, Hidemitsu

    2016-04-01

    In the last decade, several innovative polymer gel materials with enhanced mechanical proper ties have been invented by Japanese researches. In 2003, a most effective but simple way was proposed to synthesize double network gels, with compression fracture stress of about 30MPa, compared to several tens of kPa for common gels. In this study, we evaluate the wear of a double network gel, both with and without water lubrication. In the un-lubricated experiment, the gel surface is worn with a stainless steel ball. In the other experiment with water lubrication, the gel surface is worn by different counter surfaces because the stainless steel ball was too smooth to wear. It was found that frictional vibration of wear gel is transitioning to steady sliding in lubricated. As conventional reduction method of the friction by the contact between general solids, there are surface processing such as the texturing, attachment of lubrication materials. In the case of gel, the minute processing to the surface such as the texturing is difficult, because the gel is soft in comparison with the hard materials such as the metal. By proceeding with this study, the surface processing of low-frictional gels will be enabled.

  1. 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.

  2. A thermal, thermoelastic, and wear analysis of high-energy disk brakes

    NASA Technical Reports Server (NTRS)

    Kennedy, F. E., Jr.; Wu, J. J.; Ling, F. F.

    1974-01-01

    A thermomechanical investigation of the sliding contact problem encountered in high-energy disk brakes is described. The analysis includes a modelling, using the finite element method of the thermoelastic instabilities that cause transient changes in contact area to occur on the friction surface. In order to include the effect of wear at the contact surface, a wear criterion is proposed that results in the prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake assembly can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It also shows that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and, especially, the heat capacity of the brake components.

  3. Enhanced wear resistivity of a Zr-based bulk metallic glass processed by high-pressure torsion under reciprocating dry conditions

    NASA Astrophysics Data System (ADS)

    Joo, Soo-Hyun; Pi, Dong-Hai; Guo, Jing; Kato, Hidemi; Lee, Sunghak; Kim, Hyoung Seop

    2016-05-01

    Wear properties of bulk metallic glasses (BMGs) are important for industrial applications as much as strength and ductility. Free volume of BMGs is a significant factor which decides wear mechanism and resistance. Increased free volume of a Zr55Al10Ni5Cu30 BMG processed by high-pressure torsion (HPT) affected wear resistance under dry reciprocating conditions. Two- and three-body abrasive wear as well as the delamination of oxide layers simultaneously operated during the wear tests of both as-cast and HPT-processed BMG (HPT-BMG). However, the HPT- BMG had a larger area of the oxide layers on a worn surface compared to the as-cast BMG at the early stage of the wear tests. The increased free volume by the HPT process resulted in ductile plastic deformation, prohibited crack propagation, and delayed delamination of the oxide layers. Therefore, the HPT-BMG had thicker oxide layers, which acted as an adequate protection and increased wear properties of the Zr-based BMG.

  4. Abrasive wear of high velocity oxygen fuel (HVOF) superalloy coatings under vibration load

    NASA Astrophysics Data System (ADS)

    Kandeva, M.; Ivanova, B.; Karastoyanov, D.; Grozdanova, T.; Assenova, E.

    2017-02-01

    The present paper considers wear of coatings deposited by HVOF (High velocity oxy-fuel) technology, under conditions of dry friction against abrasive surface accompanied with the action of vibrations perpendicular to the sliding axis. Results are obtained with four type coatings: two types with Ni matrix of composition 602P – without preliminary heating of the basic surface (the substrate) and after substrate heating up to 650°C in a chamber; coating WC-12Co with tungsten matrix and coating obtained by 1:1 proportion powder mixture of both compositions 602P and WC-12Co. Results about the thickness, hardness and coating’ morphology are presented, as well as dependences of the wear and the relative wear resistance on vibration speeds in the interval 3.03 to 21.08 mm/s. New results are obtained about the nonlinear relationship between abrasive wear and vibration speed showing minimal wear for all specimens by 6.04 mm/s. It is found that lowest wear shows WC-12Co coating in the entire interval of vibration speed variation: 3.03 to 21.08 mm/s. The obtained results are new in the literature; they are not presented and published by the authors.

  5. Wear-resistant ball bearings for space applications. [coated with titanium carbide

    NASA Technical Reports Server (NTRS)

    Boving, H.; Hintermann, H. E.; Haenni, W.; Bondivenne, E.; Boeto, M.; Conde, M.

    1977-01-01

    Ball bearings for hostile environments were developed. They consist of normal ball bearing steel parts of which the rings are coated with hard, wear-resistant, chemical vapor deposited (C.V.D) TiC. Experiments in ultrahigh vacuum, using cages of various materials with self-lubricating properties, have shown that such bearings are suitable for space applications.

  6. Study on critical-sized ultra-high molecular weight polyethylene wear particles loaded with alendronate sodium: in vitro release and cell response.

    PubMed

    Liu, Yumei; Shi, Feng; Gong, Kemeng; Liu, Yang; Zhi, Wei; Weng, Jie; Qu, Shuxin

    2017-04-01

    The aim of this study was to investigate the in vitro release and the effect of RAW 264.7 macrophages of critical-sized wear particles of ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), one of the most effective drugs to treat osteoporosis in clinic. The critical-sized UHMWPE-ALN 0.5 wt.% wear particles were prepared by vacuum gradient filtration combined with Pluronic F-68. In vitro release of ALN from critical-sized UHMWPE-ALN wear particles was investigated in phosphate buffered saline (PBS) at 37 °C with a shaker. Cell morphology, proliferation, lactate dehydrogenase (LDH) leakage and secretions of cytokines were evaluated after co-cultured with critical-sized UHMWPE-ALN wear particles in vitro. Results showed that ALN released from critical-sized UHMWPE-ALN wear particles included burst release and slow release in vitro. Macrophages would be chemotaxis and aggregated around the critical-sized UHMWPE-ALN or UHMWPE wear particle, which was phagocytosed with time. The proliferation of macrophages co-cultured with critical-sized UHMWPE-ALN wear particles was significantly decreased compared with that of critical-sized UHMWPE group. Meanwhile, the critical-sized UHMWPE-ALN wear particles significantly induced the LDH leakage of macrophages, which indicated the cell death. The death of macrophages induced by ALN was one of pathways to inhibit their proliferation. The secretions of cytokines (interleukin-6 and tumor necrosis factor-alpha) in critical-sized UHMWPE-ALN group were significantly lower than those in critical-sized UHMWPE group due to the released ALN. The present results suggested that UHMWPE-ALN had the potential application in clinic to treat osteolysis induced by wear particles.

  7. A study of energy-size relationship and wear rate in a lab-scale high pressure grinding rolls unit

    NASA Astrophysics Data System (ADS)

    Rashidi Dashtbayaz, Samira

    This study is focused on two independent topics of energy-size relationship and wear-rate measurements on a lab-scale high pressure grinding rolls (HPGR). The first part of this study has been aimed to investigate the influence of the operating parameters and the feed characteristics on the particle-bed breakage using four different ore samples in a 200 mm x 100 mm lab-scale HPGR. Additionally, multistage grinding, scale-up from a lab-scale HPGR, and prediction of the particle size distributions have been studied in detail. The results obtained from energy-size relationship studies help with better understanding of the factors contributing to more energy-efficient grinding. It will be shown that the energy efficiency of the two configurations of locked-cycle and open multipass is completely dependent on the ore properties. A test procedure to produce the scale-up data is presented. The comparison of the scale-up factors between the data obtained on the University of Utah lab-scale HPGR and the industrial machine at the Newmont Boddington plant confirmed the applicability of lab-scale machines for trade-off studies. The population balance model for the simulation of product size distributions has shown to work well with the breakage function estimated through tests performed on the HPGR at high rotational speed. Selection function has been estimated by back calculation of population balance model with the help of the experimental data. This is considered to be a major step towards advancing current research on the simulation of particle size distribution by using the HPGR machine for determining the breakage function. Developing a technique/setup to measure the wear rate of the HPGR rolls' surface is the objective of the second topic of this dissertation. A mockup was initially designed to assess the application of the linear displacement sensors for measuring the rolls' weight loss. Upon the analysis of that technique and considering the corresponding sources of

  8. Cold atmospheric pressure gas plasma enhances the wear performance of ultra-high molecular weight polyethylene.

    PubMed

    Perni, Stefano; Kong, Michael G; Prokopovich, Polina

    2012-03-01

    Ultra-high molecular weight polyethylene (UHMWPE) is frequently employed in joint replacements because of its high biocompatibility; however, this material does not exhibit particularly strong wear performance, thus potentially reducing the longevity of such devices. Numerous techniques have been investigated to increase the resistance to wear of UHMWPE, but they are all based on expensive machinery and require a high level of safety precautions. Cold atmospheric pressure gas plasma treatment is an inexpensive process that has been used as a surface modification method and as a sterilization technique. We demonstrate for the first time that a helium/oxygen cold atmospheric pressure gas plasma can be used to enhance the wear performance of UHMWPE without affecting the cytocompatibility of the material. The exposure to a cold atmospheric pressure gas plasma results in a greater level of crosslinking of the polyethylene chains. As a consequence of the higher crosslinking, the material stiffness of the treated surface is increased.

  9. Lightweight materials for automotive applications/topic 2: Wear resistant aluminum alloy

    SciTech Connect

    Viswanathan, S.

    1997-01-31

    The replacement of cast iron by aluminum alloys in automotive engine blocks and heads represents a significant weight reduction in automobiles. The primary hurdle to the widespread use of aluminum alloy engine blocks in the North American automobile industry was high cost. The lack of wear resistance in most aluminum alloys added to manufacturing cost, since expensive procedures such as the incorporation of cast iron liners or special coatings were needed to achieve the required wear properties. The project targeted the development of a wear resistant aluminum alloy, as well as tools and the knowledge-base required to design the casting process, to allow it to be cast economically into engine blocks without the use of a cast iron liner or special coating, thereby providing benefits to both the material and manufacturing aspects of the process. The project combined the alloy development, wear and microstructural characterization, and casting modeling capabilities of the laboratory with the partners extensive alloy and casting process development and manufacturing experience to develop a suitable wear resistant aluminum alloy and casting process.

  10. Composition, microstructure, hardness, and wear properties of high-speed steel rolls

    SciTech Connect

    Park, J.W.; Lee, H.C.; Lee, S.

    1999-02-01

    The effects of alloying elements on the microstructural factors, hardness, and wear properties of four high-speed steel (HSS) rolls fabricated by centrifugal casting were investigated. A hot-rolling simulation test was carried out using a high-temperature wear tester capable of controlling speed, load, and temperature. The test results revealed that the HSS roll containing a larger amount of vanadium showed the best wear resistance because it contained a number of hard MC-type carbides. However, it showed a very rough roll surface because of cracking along cell boundaries, the preferential removal of the matrix, and the sticking of the rolled material onto the roll surface during the wear process, thereby leading to an increase in the friction coefficient and rolling force. In order to improve wear resistance with consideration to surface roughness, it is suggested that a reduction in the vanadium content, an increase in solid-solution hardening by adding alloying elements, an increase in secondary hardening by precipitation of fine carbides in the matrix, and formation of refined prior austenite grains by preaustenitization treatment be employed to strengthen the matrix, which can hold hard carbides in it.

  11. Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

    NASA Astrophysics Data System (ADS)

    Murray, J. W.; Ang, A. S. M.; Pala, Z.; Shaw, E. C.; Hussain, T.

    2016-12-01

    Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10-5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

  12. Comprehensive study of the abrasive wear and slurry erosion behavior of an expanded system of high chromium cast iron and microstructural modification for enhanced wear resistance

    NASA Astrophysics Data System (ADS)

    Chung, Reinaldo Javier

    High chromium cast irons (HCCIs) have been demonstrated to be an effective material for a wide range of applications in aggressive environments, where resistances to abrasion, erosion and erosion-corrosion are required. For instance, machinery and facilities used in mining and extraction in Alberta's oil sands suffer from erosion and erosion-corrosion caused by silica-containing slurries, which create challenges for the reliability and maintenance of slurry pumping systems as well as other processing and handling equipment. Considerable efforts have been made to determine and understand the relationship between microstructural features of the HCCIs and their wear performance, in order to guide the material selection and development for specific service conditions with optimal performance. The focus was previously put on a narrow group of compositions dictated by ASTM A532. However, with recent advances in casting technology, the HCCI compositional range can be significantly expanded, which potentially brings new alloys that can be superior to those which are currently employed. This work consists of three main aspects of study. The first one is the investigation of an expanded system of white irons with their composition ranging from 1 to 6 wt.% C and 5 to 45 wt.% Cr, covering 53 alloys. This work has generated wear and corrosion maps and established correlation between the performance and microstructural features for the alloys. The work was conducted in collaboration with the Materials Development Center of Weir Minerals in Australia, and the results have been collected in a database that is used by the company to guide materials selection for slurry pump components in Alberta oil sands and in other mining operations throughout the world. The second part consists of three case studies on effects of high chromium and high carbon, respectively, on the performance of the HCCIs. The third aspect is the development of an approach to enhance the wear resistance of

  13. "Severe" wear challenge to 36 mm mechanically enhanced highly crosslinked polyethylene hip liners.

    PubMed

    Bowsher, J G; Williams, P A; Clarke, I C; Green, D D; Donaldson, T K

    2008-07-01

    Our purpose was to compare the wear performance of mechanically enhanced 5Mrad highly crosslinked polyethylene (MEP, ArComXL) hip liners to (control) 3Mrad UHMWPE liners (ArCom) in 36 mm head size. As a more severe synergy of clinically relevant test models, we contrasted wear with custom roughened Co-Cr surfaces (Ra 500 nm) to the standard pristine Co-Cr heads (Ra < 20 nm) using a severe microseparation test mode in our hip simulator. We adopted a previously published model to estimate potential biological activity. On new Co-Cr heads, the MEP liners showed a 47% reduction in volumetric wear a 13% reduction in wear particle size and a 27% reduction in Functional Biological Activity (FBA) compared to our control. On rough Co-Cr heads, the MEP liners showed little advantage in terms of volumetric wear compared with the control. However, the MEP liners overall showed a 38% reduction in FBA compared to the control owing to a larger volume fraction of larger particles. Thus overall the MEP liners appeared to offer advantages in terms of reduced FBA indices.

  14. Reduction of total knee replacement wear with vitamin E blended highly cross-linked ultra-high molecular weight polyethylene.

    PubMed

    Vaidya, C; Alvarez, E; Vinciguerra, J; Bruce, D A; DesJardins, J D

    2011-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) is a common bearing component in total knee replacement (TKR) implants, and its susceptibility to wear continues to be the long-term limiting factor in the life of these implants. This study hypothesized that in TKR systems, a highly cross-linked (HXL) UHMWPE blended with vitamin E will result in reduced wear as compared to a direct compression-moulded (DCM) UHMWPE. A wear simulation study was conducted using an asymmetric lateral pivoting '3D Knee' design to compare the two inserts. The highly cross-linked UHMWPE was aged prior to the testing and force-controlled wear testing was carried out for 5 million cycles using a load-controlled ISO-14243 standard at a frequency of 1 Hz on both groups. Gravimetric measurements of DCM UHMWPE (4.4 +/- 3.0 mg/million cycles) and HXL UHMWPE with vitamin E (1.9 +/- 1.9 mg/million cycles) showed significant statistical differences (p < 0.01) between the wear rates. Wear modes and surface roughness for both groups revealed no significant dissimilarities.

  15. Wear and friction properties of experimental Ti-Si-Zr alloys for biomedical applications.

    PubMed

    Tkachenko, Serhii; Datskevich, Oleg; Kulak, Leonid; Jacobson, Staffan; Engqvist, Håkan; Persson, Cecilia

    2014-11-01

    Titanium alloys are widely used in biomedical applications due to their higher biocompatibility in comparison to other metallic biomaterials. However, they commonly contain aluminum and vanadium, whose ions may be detrimental to the nervous system. Furthermore, they suffer from poor wear resistance, which limits their applications. The aim of this study was to evaluate the tribological performance of experimental Ti-1.25Si-5Zr, Ti-2.5Si-5Zr, Ti-6Si-5Zr and Ti-2.5Si-5Zr-0.2Pd alloys as compared to that of control Ti-6Al-4V, CoCr F75 and CoCr F799 alloys. Friction and wear tests were performed using a standard ball-on-disc rig in serum solution at ambient temperature with Si3N4-balls as counterparts. The alloys microstructure and hardness were investigated using optical microscopy, XRD, scanning electron microscopy (SEM) and Vickers indentation. The coefficients of friction of the experimental Ti-Si-Zr alloys were generally lower than the commercial ones with Ti-6Si-5Zr presenting the lowest value (approx. 0.1). Their wear rates were found to be 2-7 times lower than that of the commercial Ti-6Al-4V alloy, but still higher than those of the CoCr alloys. SEM analysis of worn surfaces showed that abrasion was the predominant wear mechanism for all studied materials. Wear and friction were influenced by the formation and stability of transfer layers, and while commercial Ti-6Al-4V as well as the experimental Ti-Si-Zr alloys demonstrated extensive material transfer to the ceramic counterparts, the CoCr alloys did not show such material transfer.

  16. Predicting the Wear of High Speed Rocket Sleds

    DTIC Science & Technology

    2012-12-01

    25 2.5.1 SESAME tables...weighing the worn slider and comparing it to its initial state prior to the run. Some of his results are applicable to our studies, and are used as...for most situations, the vibrations are too small to notice. They exist in a static or quasistatic equilibrium. Application of forces can be described

  17. The application of counter immunoelectrophoresis (CIE) in ocular protein studies Part II: Kinin activity in the lens wearing eye.

    PubMed

    Mann, Aisling M; Tighe, Brian J

    2002-06-01

    The kinin family are a group of bioactive peptides that are closely involved in the modulation of vascular inflammation and local injury. We have demonstrated here, for the first time, a link between kinin activity and contact lens wear. Protein extracts from daily and extended wear etafilcon A, Group IV, Acuvue lenses (Vistakon), were analysed by counter immunoelectrophoresis. In this way, kinin activity associated with contact lens wear was detected. High molecular weight kininogen was used as the marker protein. In contrast, no kinin activity was detected in the non-lens wearing normal eye.

  18. Extended release of high molecular weight hydroxypropyl methylcellulose from molecularly imprinted, extended wear silicone hydrogel contact lenses.

    PubMed

    White, Charles J; McBride, Matthew K; Pate, Kayla M; Tieppo, Arianna; Byrne, Mark E

    2011-08-01

    Symptoms of contact lenses induced dry eye (CLIDE) are typically treated through application of macromolecular re-wetting agents via eye drops. Therapeutic soft contact lenses can be formulated to alleviate CLIDE symptoms by slowly releasing comfort agent from the lens. In this paper, we present an extended wear silicone hydrogel contact lens with extended, controllable release of 120 kDa hydroxypropyl methylcellulose (HPMC) using a molecular imprinting strategy. A commercial silicone hydrogel lens was tailored to release approximately 1000 μg of HPMC over a period of up to 60 days in a constant manner at a rate of 16 μg/day under physiological flowrates, releasing over the entire range of continuous wear. Release rates could be significantly varied by the imprinting effect and functional monomer to template ratio (M/T) with M/T values 0, 0.2, 2.8, 3.4 corresponding to HPMC release durations of 10, 13, 23, and 53 days, respectively. Lenses had high optical quality and adequate mechanical properties for contact lens use. This work highlights the potential of imprinting in the design and engineering of silicone hydrogel lenses to release macromolecules for the duration of wear, which may lead to decreased CLIDE symptoms and more comfortable contact lenses.

  19. Dry Sliding Wear Behaviours of Valve Seat Inserts Produced from High Chromium White Iron

    NASA Astrophysics Data System (ADS)

    Kalyon, Ali; Özyürek, Dursun; Günay, Mustafa; Aztekin, Hasan

    2015-11-01

    In this present study, wear behaviours of high chromium white iron valve seat inserts and tappets used in the automotive sector were investigated. Wear behaviours of three different rates of high chromium white cast irons (containing 10, 12 and 14% chromium) were examined under heavy service conditions. For that purpose, the produced valve seat inserts were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and hardness measurements. They were tested at a sliding speed of 1 ms-1, under 120 N load and for six different sliding distances (500, 1000, 1500, 2000, 2500, 3000 m) by using a standard wear apparatus (pin-on-disk type). The result showed that as the amount of Cr increased in the alloys, their hardness decreased. The decrease in the hardness were considered to be as the result of transformation of M7C3 carbides into M23C6 carbides in the structure. This decrease in hardness with increasing chromium content also increased the weight loss. Thus, it was determined that the white iron with 14% Cr (which had a greater amount of M23C6 carbides) was subjected to the highest wear.

  20. Microstructure and properties of laser-clad high-temperature wear-resistant alloys

    NASA Astrophysics Data System (ADS)

    Yang, Yongqiang

    1999-02-01

    A 2-kW CO 2 laser with a powder feeder was used to produce alloy coatings with high temperature-wear resistance on the surface of steel substrates. To analyze the microstructure and microchemical composition of the laser-clad layers, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microanalysis system was employed. X-ray diffraction techniques were applied to characterize the phases formed during the cladding process. The results show that the microstructure of the cladding alloy consists mainly of many dispersed particles (W 2C, (W,Ti)C 1- x, WC), a lamellar eutectic carbide M 12C, and an (f.c.c) matrix. Hardness tested at room and high temperature showed that the laser-clad zone has a moderate room temperature hardness and relatively higher elevated temperature hardness. The application of the laser-clad layer to a hot tool was very successful, and its operational life span was prolonged 1 to 4 times.

  1. Wear of materials - 1987

    SciTech Connect

    Ludema, K.C.

    1987-01-01

    This book presents the papers given at a conference on materials testing to determine wear resistance. Topics considered at the conference included the wear of metals in a magnetic field, ceramics in advanced heat engine applications, wear tests of silicon carbides, microstructure, hardfacing alloys, sliding friction, coated systems, abrasion, erosion, test methods, tribology, stacking fault energy, and adhesion.

  2. Volatility and Wear Characteristics of a Variety of Liquid Lubricants for Space Applications

    NASA Technical Reports Server (NTRS)

    Nguyen, Quynhgiao N.; Jones, William R., Jr.

    2001-01-01

    The vapor pressures and near characteristics are critical properties for liquid lubricants to assure long-term reliability and performance in space applications. Vapor pressures, obtained using a Knudsen cell technique, and near properties, obtained using a vacuum four-ball apparatus, were measured for a series of unformulated liquid lubricants. These include: two multiple alkylated cyclopentanes (MACs) (X-1000 and X-2000), two linear perfluoropolyalkylethers (PFPAEs) (Z-25 and 815Z), and four silahydrocarbons (a tri-, a tetra-, and two pentas). Vapor pressures were measured at three elevated temperatures (423, 448, and 498 K) and extrapolated to room temperature 298 K. The lowest 298 K vapor pressure of 5.7 x 10(exp -14) Pa, was obtained with the PFPAE fluid (815Z) and the highest value with the low molecular weight MAC (X-1000) at 3.6 x 10(exp -7) Pa. In addition, vacuum near rates were determined for some of the lubricants. The lowest wear rates (approximately 3 x 10(exp -11) cubic mm/mm) were observed for three of the silahydrocarbons while the highest wear rate (approximately 2 x 10(exp-9) cubic mm/mm) were observed with the two PFPAE fluids (Z-25 and 815Z). The MAC (X-2000) yielded a wear rate of about 10(exp -10) cubic mm/mm. The results indicated that the silahydrocarbon class of liquid lubricants offers the better potential for space applications.

  3. Wear resistance of highly cross-linked and remelted polyethylenes after ion implantation and accelerated ageing.

    PubMed

    Medel, F J; Puértolas, J A

    2008-08-01

    Ion implantation may provide medical polyethylenes with excellent mechanical and tribological properties, helping to lower the risk of long-term osteolysis. Highly crosslinked and remelted polyethylenes, materials currently used as soft components in artificial joints, were implanted with N+ and He+ ions at different ion fluences. The mechanical and tribological properties under distilled water lubrication at body temperature were assessed after ion implantation by means of microhardness and pin-on-disc tests respectively. Thus, the influences of the ionic species and implantation dose on surface hardness, friction coefficient, and wear factor were fully characterized. Furthermore, the tribological behaviour was evaluated after an accelerated ageing protocol (120 degrees C for 36h). Ion implantation increased the surface hardness, as well as friction coefficients, and decreased the wear factors especially at the highest doses. Also, even though all artificially aged materials showed a worse wear behaviour, polyethylenes implanted with either N+ or He+ at the highest doses maintained a relatively good wear factor in comparison with the aged non-implanted material. The origins of these modifications are discussed according to the effects of ion implantation on the microstructure of the polymer.

  4. High pressure slurry pump. Sand slurry test loop design and results. Wear parts lifetime analysis

    SciTech Connect

    Fongaro, S.; Severini, P.; Vinciguerra, G.

    2000-07-01

    This paper shows the experimental phase, following previous work presented at the Sixth International Conference on ``Multiphase Flow in Industrial Plants'', Milan, September 98. A Sand Water Slurry Test Loop has been tested using different sand percentages for a total power of 680 HP with a flow-rate of 35,000 [gpm] and pressure of 2300 [psig]. Its design considered, carefully, the particles build-up effect respecting flow velocity and dead space along the loop and into the hydraulics. The test pump is a TRIPLEX SINGLE ACTING that is one third of the COAL SLURRY SEPTUPLEX PUMP designed for a CHINA PROJECT. Wear rate on the main parts of an high pressure slurry pump have been analyzed running at 145 rpm (piston mean speed of 3.3 [ft/s]) with a net flow of 33,290 [gpm] and pressures between 1216 and 1575 [psig]. Tests gave indications of a damaging process on valves, piston seals and the relative weight on the overall damages. Design changes of piston-seal and its material have been done, results being a longer parts lifetime. The authors compared the results with literature on coal slurry and other sand tests. The pump speed, i.e., valve cycle, isn't the main wear factor, while the fluid speed under the valve is. Their goals are to improve the wear parts lifetime and define functions to relate the wear to operating parameters, design choice, and materials used.

  5. Does cyclic stress and accelerated ageing influence the wear behavior of highly crosslinked polyethylene?

    PubMed

    Affatato, Saverio; De Mattia, Jonathan Salvatore; Bracco, Pierangiola; Pavoni, Eleonora; Taddei, Paola

    2016-06-01

    First-generation (irradiated and remelted or annealed) and second-generation (irradiated and vitamin E blended or doped) highly crosslinked polyethylenes were introduced in the last decade to solve the problems of wear and osteolysis. In this study, the influence of the Vitamin-E addition on crosslinked polyethylene (XLPE_VE) was evaluated by comparing the in vitro wear behavior of crosslinked polyethylene (XLPE) versus Vitamin-E blended polyethylene XLPE and conventional ultra-high molecular weight polyethylene (STD_PE) acetabular cups, after accelerated ageing according to ASTM F2003-02 (70.0±0.1°C, pure oxygen at 5bar for 14 days). The test was performed using a hip joint simulator run for two millions cycles, under bovine calf serum as lubricant. Mass loss was found to decrease along the series XLPE_VE>STD_PE>XLPE, although no statistically significant differences were found between the mass losses of the three sets of cups. Micro-Raman spectroscopy was used to investigate at a molecular level the morphology changes induced by wear. The spectroscopic analyses showed that the accelerated ageing determined different wear mechanisms and molecular rearrangements during testing with regards to the changes in both the chain orientation and the distribution of the all-trans sequences within the orthorhombic, amorphous and third phases. The results of the present study showed that the addition of vitamin E was not effective to improve the gravimetric wear of PE after accelerated ageing. However, from a molecular point of view, the XLPE_VE acetabular cups tested after accelerated ageing appeared definitely less damaged than the STD_PE ones and comparable to XLPE samples.

  6. Wear Performance of Laser Processed Tantalum Coatings

    PubMed Central

    Dittrick, Stanley; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit

    2011-01-01

    This first generation investigation evaluates the in vitro tribological performance of laser-processed Ta coatings on Ti for load-bearing implant applications. Linear reciprocating wear tests in simulated body fluid showed one order of magnitude less wear rate, of the order of 10−4mm3(N.m)−1, for Ta coatings compared to Ti. Our results demonstrate that Ta coatings can potentially minimize the early-stage bone-implant interface micro-motion induced wear debris generation due to their excellent bioactivity comparable to that of hydroxyapatite (HA), high wear resistance and toughness compared to popular HA coatings. PMID:22058608

  7. Wear transition of solid-solution-strengthened Ti-29Nb-13Ta-4.6Zr alloys by interstitial oxygen for biomedical applications.

    PubMed

    Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken; Liu, Huihong

    2015-11-01

    In previous studies, it has been concluded that volume losses (V loss) of the Ti-29Nb-13Ta-4.6Zr (TNTZ) discs and balls are larger than those of the respective Ti-6Al-4V extra-low interstitial (Ti64) discs and balls, both in air and Ringer's solution. These results are related to severe subsurface deformation of TNTZ, which is caused by the lower resistance to plastic shearing of TNTZ than that of Ti64. Therefore, it is necessary to further increase the wear resistance of TNTZ to satisfy the requirements as a biomedical implant. From this viewpoint, interstitial oxygen was added to TNTZ to improve the plastic shear resistance via solid-solution strengthening. Thus, the wear behaviors of combinations comprised of a new titanium alloy, TNTZ with high oxygen content of 0.89 mass% (89O) and a conventional titanium alloy, Ti64 were investigated in air and Ringer's solution for biomedical implant applications. The worn surfaces, wear debris, and subsurface damage were analyzed using a scanning electron microscopy and an electron probe microanalysis. V loss of the 89O discs and balls are smaller than those of the respective TNTZ discs and balls in both air and Ringer's solution. It can be concluded that the solid-solution strengthening by oxygen effectively improves the wear resistance for TNTZ materials. However, the 89O disc/ball combination still exhibits higher V loss than the Ti64 disc/ball combination in both air and Ringer's solution. Moreover, V loss of the disc for the 89O disc/Ti64 ball combination significantly decreases in Ringer's solution compared to that in air. This decrease for the 89O disc/Ti64 ball combination in Ringer's solution can be explained by the transition in the wear mechanism from severe delamination wear to abrasive wear.

  8. Optical Emission Characterization of High-Power Hall Thruster Wear

    NASA Technical Reports Server (NTRS)

    WIlliams, George J.; Kamhawi, Hani

    2013-01-01

    Optical emission spectroscopy is employed to correlate BN insulator erosion with high-power operation of the NASA 300M Hall-effect thruster. Actinometry leveraging excited xenon states is used to normalize the emission spectra of ground state boron as a function of thruster operating condition. Trends in the strength of the boron signal are correlated with thruster power, discharge voltage, discharge current and magnetic field strength. The boron signals are shown to trend with discharge current and show weak dependence on discharge voltage. The trends are consistent with data previously collected on the NASA 300M and NASA 457M thrusters but are different from conventional wisdom.

  9. Short term wear of high Dk soft contact lenses does not alter corneal epithelial cell size or viability

    PubMed Central

    Stapleton, F.; Kasses, S.; Bolis, S.; Keay, L.

    2001-01-01

    BACKGROUND/AIMS—Current contact lenses (CLs) when worn on an extended wear basis cause corneal epithelial alterations. The aim of this study was to evaluate changes in corneal epithelial cell morphology and physiology following short term (3 months) wear of highly oxygen permeable CLs and to compare this with disposable CLs.
METHODS—Subjects were wearers of highly oxygen permeable CLs (n=11, wearing CLs on a 30 night schedule), disposable CL users (n=6, wearing CLs on a 6 night schedule), and non-CL wearers (n=20). Mean CL wear experience was 3 months. Epithelial cells were harvested using corneal cytology and were stained using acridine orange and ethidium bromide. Epithelial cell size and viability were determined.
RESULTS—The majority of epithelial cells recovered were non-viable (71%), and the mean longest cell diameter was 38 (SD 8) µm. Disposable CLs caused an increase in cell size (42 (7) µm) compared with both non-wear (39 (7) µm, p=0.01) and wear of highly oxygen permeable CLs (37 (10) µm, p=0.0049). There was no difference in cell viability between groups.
CONCLUSIONS—Extended wear of disposable CLs caused an 8% increase in cell diameter in harvested corneal epithelial cells following 3 months of CL wear. Cells harvested following 3 months' wear of highly oxygen permeable CLs were indistinguishable from those recovered from non-CL wearers.

 PMID:11159475

  10. Simple colorimetric methods for determination of sub-milligram amounts of ultra-high molecular weight polyethylene wear particles.

    PubMed

    Vesely, F; Zolotarevova, E; Spundova, M; Kaftan, F; Slouf, M; Entlicher, G

    2012-05-01

    New colorimetric methods are described for determination of sub-milligram amounts of ultra-high molecular weight polyethylene (UHMWPE) wear particles. These methods are based on the irreversible binding of the fluorescein-conjugated bovine serum albumin or the hydrophobic dye Oil Red O to wear particles. UHMWPE particles bind both substances from their solutions and thus decrease the absorbance of these solutions. The decrease is linearly dependent on the amount of added wear particles in the sub-milligram range suitable for practical use. The newly developed method offers improved accuracy and precision compared to Fourier transformed infrared spectroscopy (Slouf M, et al. Quantification of UHMWPE wear in periprosthetic tissues of hip arthoplasty: description of a new method based on IR and comparison with radiographic appearance. Wear 2008;265:674-684.).

  11. Study on mild and severe wear of 7075 aluminum alloys by high-speed wire electrical discharge machining

    NASA Astrophysics Data System (ADS)

    Xu, Jinkai; Qiu, Rongxian; Xia, Kui; Wang, Zhichao; Xu, Lining; Yu, Huadong

    2017-01-01

    The recast and the carbon layers were fabricated on 7075Al alloys surface by the high-speed wire electrical discharge machining (HS-WEDM) technologyunder various working parameters. The mechanical properties and friction behaviors of the layers were investigated by UMT. 7075 Al alloys were used to do dry sliding wear tests on a pin-ondisk wear tester at room temperature under various contact pressures. 7075 Al alloys had almost the same wear regularity as a function of sliding velocity and rated frequency. The hardness of recast layer was improved. And this method can enhance durability of 7075 Al alloy effectively.The transition to severe wear occurred at a higher load (12N) for asmachined samples, compared with 7075 matrix (9N), the as-machined samples exhibited lower wear rates within the tested loading range.

  12. Wear characteristics of bonded solid film lubricant under high load condition

    NASA Technical Reports Server (NTRS)

    Hiraoka, Naofumi; Sasaki, Akira; Kawashima, Noritsugu; Honda, Toshio

    1991-01-01

    Wear properties of phenolic resin bonded molybdenum disulfide film lubricant were studied. In-vacuo journal bearing tests were performed to evaluate the wear-life of this film lubricant. The wear-life depends on substrate materials and on sliding velocity. Pretreated substrate surfaces were examined to reveal the reasons for these results. Additionally, investigations on film wear mechanisms were made.

  13. Wear of ultra-high molecular weight polyethylene against damaged and undamaged stainless steel and diamond-like carbon-coated counterfaces.

    PubMed

    Firkins, P; Hailey, J L; Fisher, J; Lettington, A H; Butter, R

    1998-10-01

    The wear of ultra-high molecular weight polyethylene (UHMWPE) in artificial joints and the resulting wear debris-induced osteolysis remains a major clinical concern in the orthopaedic sector. Third-body damage of metallic femoral heads is often cited as a cause of accelerated polyethylene wear, and the use of ceramic femoral heads in the hip is gaining increasing favour. In the knee prostheses and for smaller diameter femoral heads, the application of hard surface coatings, such as diamond-like carbon, is receiving considerable attention. However, to date, there has been little or no investigation of the tribology of these coatings in simulated biological environments. In this study, diamond-like carbon (DLC) has been compared to stainless steel in its undamaged form and following simulated third-body damage. The wear of UHMWPE was found to be similar when sliding against undamaged DLC and stainless steel counterfaces. DLC was found to be much more damage resistant than DLC. Under test conditions that simulate third-body damage to the femoral head, the wear of UHMWPE was seven times lower against DLC than against stainless steel (P < 0.05). The study shows DLC has considerable potential as a femoral bearing surface in artificial joints.

  14. Nanoscale wear and kinetic friction between atomically smooth surfaces sliding at high speeds

    SciTech Connect

    Rajauria, Sukumar Canchi, Sripathi V. Schreck, Erhard; Marchon, Bruno

    2015-02-23

    The kinetic friction and wear at high sliding speeds is investigated using the head-disk interface of hard disk drives, wherein the head and the disk are less than 10 nm apart and move at sliding speeds of 5–10 m/s relative to each other. While the spacing between the sliding surfaces is of the same order of magnitude as various AFM based fundamental studies on friction, the sliding speed is nearly six orders of magnitude larger, allowing a unique set-up for a systematic study of nanoscale wear at high sliding speeds. In a hard disk drive, the physical contact between the head and the disk leads to friction, wear, and degradation of the head overcoat material (typically diamond like carbon). In this work, strain gauge based friction measurements are performed; the friction coefficient as well as the adhering shear strength at the head-disk interface is extracted; and an experimental set-up for studying friction between high speed sliding surfaces is exemplified.

  15. Understanding Friction and Wear Mechanisms of High-Purity Titanium against Steel in Liquid Nitrogen Temperature

    NASA Astrophysics Data System (ADS)

    Basu, Bikramjit; Sarkar, J.; Mishra, Ravi

    2009-02-01

    Although the friction and wear properties of several metallic alloys in unlubricated conditions are widely investigated, such understanding for high-purity metals in cryogenic environment is rather limited. This article reports the tribological properties of high-purity α-titanium ( α-Ti), prepared by cold rolling and recrystallization annealing, under liquid nitrogen (LN2) and room temperature (RT) environments against steel (bearing grade: SAE 52100) at varying loads (up to 15 N) and sliding speeds (0.6 to 4.19 m/s). It has been found that the steady-state coefficient of friction (COF) of titanium under LN2 environment (˜0.27 to 0.33) is lower than that at RT COF (˜0.33 to 0.58) irrespective of sliding speed. For cryogenic sliding conditions, the COF decreased steadily with sliding speed to a mean value of about 0.28 and no appreciable variation in COF is noticed for sliding speed of more than 1.5 m/s. The wear rate under both environment conditions was of the order of 10-3 mm3 N-1 m-1 irrespective of variation in operating parameters, but the RT wear rate was found to be higher compared to the LN2 case. Overall, the experimental results demonstrate improved tribological properties of high-purity titanium at LN2 temperature compared to the RT. Flow localization at tribological interfaces because of the large strain rate and subsequent damage accumulation at the titanium test piece are some of the attributes of the wear of Ti at LN2 temperature. In addition, the galling of titanium was also observed to occur under large contact stress and sliding speed conditions.

  16. Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

    2016-05-01

    Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

  17. Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings

    NASA Technical Reports Server (NTRS)

    Dufrane, K. F.; Merriman, T. L.; Kannel, J. W.; Stockwell, R. D.; Hauser, D.; Vanecho, J. A.

    1984-01-01

    The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication.

  18. Cryogenic Treatment of Production Components in High-Wear Rate Wells

    SciTech Connect

    Milliken, M.

    2002-04-29

    Deep Cryogenic Tempering (DCT) is a specialized process whereby the molecular structure of a material is ''re-trained'' through cooling to -300 F and then heating to +175-1100 F. Cryocon, Inc. (hereafter referred to as Cryocon) and RMOTC entered an agreement to test the process on oilfield production components, including rod pumps, rods, couplings, and tubing. Three Shannon Formation wells were selected (TD about 500 ft) based on their proclivity for high component wear rates. Phase 1 of the test involved operation for a nominal 120 calendar day period with standard, non-treated components. In Phase 2, treated components were installed and operated for another nominal 120 calendar day period. Different cryogenic treatment profiles were used for components in each well. Rod pumps (two treated and one untreated) were not changed between test phases. One well was operated in pumped-off condition, resulting in abnormal wear and disqualification from the test. Testing shows that cryogenic treatment reduced wear of rods, couplers, and pump barrels. Testing of production tubing produced mixed results.

  19. Voltage assisted asymmetric nanoscale wear on ultra-smooth diamond like carbon thin films at high sliding speeds.

    PubMed

    Rajauria, Sukumar; Schreck, Erhard; Marchon, Bruno

    2016-05-06

    The understanding of tribo- and electro-chemical phenomenons on the molecular level at a sliding interface is a field of growing interest. Fundamental chemical and physical insights of sliding surfaces are crucial for understanding wear at an interface, particularly for nano or micro scale devices operating at high sliding speeds. A complete investigation of the electrochemical effects on high sliding speed interfaces requires a precise monitoring of both the associated wear and surface chemical reactions at the interface. Here, we demonstrate that head-disk interface inside a commercial magnetic storage hard disk drive provides a unique system for such studies. The results obtained shows that the voltage assisted electrochemical wear lead to asymmetric wear on either side of sliding interface.

  20. Voltage assisted asymmetric nanoscale wear on ultra-smooth diamond like carbon thin films at high sliding speeds

    NASA Astrophysics Data System (ADS)

    Rajauria, Sukumar; Schreck, Erhard; Marchon, Bruno

    2016-05-01

    The understanding of tribo- and electro-chemical phenomenons on the molecular level at a sliding interface is a field of growing interest. Fundamental chemical and physical insights of sliding surfaces are crucial for understanding wear at an interface, particularly for nano or micro scale devices operating at high sliding speeds. A complete investigation of the electrochemical effects on high sliding speed interfaces requires a precise monitoring of both the associated wear and surface chemical reactions at the interface. Here, we demonstrate that head-disk interface inside a commercial magnetic storage hard disk drive provides a unique system for such studies. The results obtained shows that the voltage assisted electrochemical wear lead to asymmetric wear on either side of sliding interface.

  1. Friction and oxidative wear of 440C ball bearing steels under high load and extreme bulk temperatures

    NASA Technical Reports Server (NTRS)

    Chaudhuri, Dilip K.; Slifka, Andrew J.; Siegwarth, James D.

    1993-01-01

    Unlubricated sliding friction and wear of 440C steels in an oxygen environment have been studied under a variety of load, speed, and temperature ranging from approximately -185 to 675 deg C. A specially designed test apparatus with a ball-on-flat geometry has been used for this purpose. The observed dependencies of the initial coefficient of friction, the average dynamic coefficient of friction, and the wear rate on load, speed, and test temperatures have been examined from the standpoint of existing theories of friction and wear. High contact temperatures are generated during the sliding friction, causing rapid oxidation and localized surface melting. A combination of fatigue, delamination, and loss of hardness due to tempering of the martensitic structure is responsible for the high wear rate observed and the coefficient of friction.

  2. Voltage assisted asymmetric nanoscale wear on ultra-smooth diamond like carbon thin films at high sliding speeds

    PubMed Central

    Rajauria, Sukumar; Schreck, Erhard; Marchon, Bruno

    2016-01-01

    The understanding of tribo- and electro-chemical phenomenons on the molecular level at a sliding interface is a field of growing interest. Fundamental chemical and physical insights of sliding surfaces are crucial for understanding wear at an interface, particularly for nano or micro scale devices operating at high sliding speeds. A complete investigation of the electrochemical effects on high sliding speed interfaces requires a precise monitoring of both the associated wear and surface chemical reactions at the interface. Here, we demonstrate that head-disk interface inside a commercial magnetic storage hard disk drive provides a unique system for such studies. The results obtained shows that the voltage assisted electrochemical wear lead to asymmetric wear on either side of sliding interface. PMID:27150446

  3. Polymer wear and its control

    SciTech Connect

    Lee, L.H.

    1985-01-01

    Recent advances in polymer (P) tribology are discussed in reviews and reports based on contributions to a symposium held by the Division of Polymeric Materials Science and Engineering of the Americal Chemical Society in St. Louis in spring 1984. Topics examined are mechanisms of P wear, controls of P wear, the tribological behavior of Ps, wear of biomaterials and P composites, characterization and measurements of P wear, and degradation and wear of polymeric films and filaments. Consideration is given to the fracture and surface energetics of P wear, fatigue-abrasive mechanisms of P wear, plasma modification of P surfaces, the wear characteristics of articular cartilage, the role of fillers in the wear of high-density polyethylene, the tribology of fiber-reinforced polyimides sliding against steel and Si3N4, laboratory and in-service wear tests of Ps, and the effect of degree of crystallinity on wear of poly(ethylene terephthalate).

  4. Brush Seals for Cryogenic Applications: Performance, Stage Effects, and Preliminary Wear Results in LN2 and LH2

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Walker, James F.; Perkins, H. Douglas; Hoopes, Joan F.; Williamson, G. Scott

    1996-01-01

    Brush seals are compliant contacting seals and have significantly lower leakage than labyrinth seals in gas turbine applications. Their long life and low leakage make them candidates for use in rocket engine turbopumps. Brush seals, 50.8 mm (2 in.) in diameter with a nominal 127-micron (0.005-in.) radial interference, were tested in liquid nitrogen (LN2) and liquid hydrogen (LH2) at shaft speeds up to 35,000 and 65,000 rpm, respectively, and at pressure drops up to 1.21 MPa (175 psid) per brush. A labyrinth seal was also tested in liquid nitrogen to provide a baseline. The LN2 leakage rate of a single brush seal with an initial radial shaft interference of 127 micron (0.005 in.) measured one-half to one-third the leakage rate of a 12-tooth labyrinth seal with a radial clearance of 127 micron (0.005 in.). Two brushes spaced 7.21 micron (0.248 in.) apart leaked about one-half as much as a single brush, and two brushes tightly packed together leaked about three-fourths as much as a single brush. The maximum measured groove depth on the Inconel 718 rotor with a surface finish of 0.81 micron (32 microinch) was 25 micron (0.0010 in.) after 4.3 hr of shaft rotation in liquid nitrogen. The Haynes-25 bristles wore approximately 25 to 76 micron (0.001 to 0.003 in.) under the same conditions. Wear results in liquid hydrogen were significantly different. In liquid hydrogen the rotor did not wear, but the bristle material transferred onto the rotor and the initial 127 micron (0.005 in.) radial interference was consumed. Relatively high leakage rates were measured in liquid hydrogen. More testing is required to verify the leakage performance, to validate and calibrate analysis techniques, and to determine the wear mechanisms. Performance, staging effects, and preliminary wear results are presented.

  5. A rolling-gliding wear simulator for the investigation of tribological material pairings for application in total knee arthroplasty

    PubMed Central

    2010-01-01

    Background Material wear testing is an important technique in the development and evaluation of materials for use in implant for total knee arthroplasty. Since a knee joint induces a complex rolling-gliding movement, standardised material wear testing devices such as Pin-on-Disc or Ring-on-Disc testers are suitable to only a limited extent because they generate pure gliding motion only. Methods A rolling-gliding wear simulator was thus designed, constructed and implemented, which simulates and reproduces the rolling-gliding movement and loading of the knee joint on specimens of simplified geometry. The technical concept was to run a base-plate, representing the tibia plateau, against a pivoted cylindrical counter-body, representing one femur condyle under an axial load. A rolling movement occurs as a result of the friction and pure gliding is induced by limiting the rotation of the cylindrical counter-body. The set up also enables simplified specimens handling and removal for gravimetrical wear measurements. Long-term wear tests and gravimetrical wear measurements were carried out on the well known material pairings: cobalt chrome-polyethylene, ceramic-polyethylene and ceramic-ceramic, over three million motion cycles to allow material comparisons to be made. Results The observed differences in wear rates between cobalt-chrome on polyethylene and ceramic on polyethylene pairings were similar to the differences of published data for existing material-pairings. Test results on ceramic-ceramic pairings of different frontal-plane geometry and surface roughness displayed low wear rates and no fracture failures. Conclusions The presented set up is able to simulate the rolling-gliding movement of the knee joint, is easy to use, and requires a minimum of user intervention or monitoring. It is suitable for long-term testing, and therefore a useful tool for the investigation of new and promising materials which are of interest for application in knee joint replacement

  6. Microstructure and its effect on toughness and wear resistance of laser surface melted and post heat treated high speed steel

    NASA Astrophysics Data System (ADS)

    Åhman, Leif

    1984-10-01

    High speed steel hacksaw blade blanks were laser surface melted and rapidly solidified along one edge. The laser melting resulted in complete carbide dissolution. By subsequent machining and heat treatments saw teeth were manufactured with a refined internal structure of the edges and corners. The structure was fully martensitic with a uniform and dense dispersion of small primary carbides. Sawing tests in quenched and tempered steel showed that blade life was somewhat improved, as compared to conventionally heat treated blades. The increased wear resistance is believed to be due to improved toughness along with high hardness caused by the refined carbide structure. Sawing tests in austenitic stainless steel did not give any significant improvement in performance. The effect of the altered microstructure on performance is likely to be more or less pronounced depending on application, tool and work material.

  7. Wear of Spur Gears Having a Dithering Motion and Lubricated with a Perfluorinated Polyether Grease

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy; Oswald, Fred; Handschuh, Robert

    2007-01-01

    Gear contact surface wear is one of the important failure modes for gear systems. Dedicated experiments are required to enable precise evaluations of gear wear for a particular application. The application of interest for this study required evaluation of wear of gears lubricated with a grade 2 perfluorinated polyether grease and having a dithering (rotation reversal) motion. Experiments were conducted using spur gears made from AISI 9310 steel. Wear was measured using a profilometer at test intervals encompassing 10,000 to 80,000 cycles of dithering motion. The test load level was 1.1 GPa maximum Hertz contact stress at the pitch-line. The trend of total wear as a function of test cycles was linear, and the wear depth rate was approximately 1.2 nm maximum wear depth per gear dithering cycle. The observed wear rate was about 600 times greater than the wear rate for the same gears operated at high speed and lubricated with oil.

  8. Characterization of the resistance of pyrolytic carbon to abrasive wear.

    PubMed

    Vitale, E; Giusti, P

    1995-12-01

    Si-alloyed pyrolitic carbon (PyC) is currently employed in many biomedical devices, due to its fairly good biological compatibility and non biodegradeability. For prosthetic heart valve applications, required to operate safely for many years, the resistance to abrasive wear is one of the limiting factors which must be accurately evaluated. The present study reports on abrasive wear testing of Ti/PyC and PyC/PyC sliding couples. For both couples it was found that the wear behaviour can be shifted from a low wear regime, characterised by very small wear rates and reduced scatter, to a high wear regime, characterised by high wear rates and high scatter, due to the presence of particle contamination coming from the environment and/or from the specimen polishing process. Actual biomedical devices, particularly heart valves, should not experience the high wear regime, due to the absence of any hard particle contamination source. The wear observed in these items is in fact minimal and may depend on mechanisms other than abrasive wear. In these conditions the experimental evaluation of the wear behaviour should definetely be performed by tests on actual devices.

  9. Effects of Alloying Elements on Microstructure, Hardness, Wear Resistance, and Surface Roughness of Centrifugally Cast High-Speed Steel Rolls

    NASA Astrophysics Data System (ADS)

    Ha, Dae Jin; Sung, Hyo Kyung; Park, Joon Wook; Lee, Sunghak

    2009-11-01

    A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up to 25 vol pct) of carbides, such as MC, M2C, and M7C3 carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous. The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent, and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively.

  10. Microstructure and Wear Behavior of High-Cr WCI Matrix Surface Composite Reinforced with Cemented Carbide Rods

    NASA Astrophysics Data System (ADS)

    Hou, Shuzeng; Bao, Chonggao; Zhang, Zhiyun; Bai, Yaping

    2013-07-01

    The present article reports a new superior wear resistance surface composite prepared by a vacuum evaporative pattern casting-in process. This surface composite was constructed with reinforcing cemented carbide rod (CCR) array within high-Cr white cast iron (WCI) matrix. Three reaction zones that formed around the CCRs were characterized and established the good metallurgical bonding between CCRs and matrix. In addition, some compound carbide containing Fe, Cr, W, and Co elements were formed in the reaction zones, owing to the partial dissolution of the CCRs and the resulting interdiffusion of elements such as W, Co, C, Fe, and Cr. The wear behavior of the composite was evaluated and compared with unreinforced high-Cr WCI by means of a three-body abrasive wear tester. The results showed that the wear resistance of the composite was significantly higher than that of the unreinforced high-Cr WCI. The exciting wear resistance can be ascribed to protective effect introduced by the CCRs during wear process and the good metallurgical bonding between CCRs and matrix.

  11. Perspectives from the Wearable Electronics and Applications Research (WEAR) Lab, NASA Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Moses, Haifa R.

    2017-01-01

    As NASA moves beyond exploring low earth orbit and into deep space exploration, increased communication delays between astronauts and earth drive a need for crew to become more autonomous (earth-independent). Currently crew on board the International Space Station (ISS) have limited insight into specific vehicle system performance because of the dependency on monitoring and real-time communication with Mission Control. Wearable technology provides a method to bridge the gap between the human (astronaut) and the system (spacecraft) by providing mutual monitoring between the two. For example, vehicle or environmental information can be delivered to astronauts through on-body devices and in return wearables provide data to the spacecraft regarding crew health, location, etc. The Wearable Electronics and Applications Research (WEAR) Lab at the NASA Johnson Space Center utilizes a collaborative approach between engineering and human factors to investigate the use of wearables for spaceflight. Zero and partial gravity environments present unique challenges to wearables that require collaborative, user-centered, and iterative approaches to the problems. Examples of the WEAR Lab's recent wearable projects for spaceflight will be discussed.

  12. Wear behaviour of epoxy resin filled with hard powders

    NASA Astrophysics Data System (ADS)

    Formisano, A.; Boccarusso, L.; Minutolo, F. Capece; Carrino, L.; Durante, M.; Langella, A.

    2016-10-01

    The development of high performance materials based on epoxy resin finds a growing number of applications in which high wear resistance is required. One major drawback in many of these applications is the relatively poor wear resistance of the epoxy resin. Therefore, in order to investigate on the possibility of increasing wear resistance of thermoset polymers filled with hard powders, sliding tests are carried out by means of a pin on disc apparatus. In particular, composite resins, constituted by an epoxy resin filled with different contents and sizes of Silicon Carbide powder, are analyzed; the wear resistance, in terms of volume loss, is measured for different abrasive counterfaces and loads.

  13. Wear in conventional and highly cross-linked polyethylene cups: a 5-year follow-up study.

    PubMed

    Olyslaegers, Christophe; Defoort, Koen; Simon, Jean-Pierre; Vandenberghe, Luc

    2008-06-01

    Highly cross-linked polyethylene (XLPE) has been introduced in total hip arthroplasty in an effort to reduce polyethylene wear and the associated periprosthetic osteolysis. Our aim was to demonstrate these reduced wear rates in a 2-dimensional head penetration model and to perform a clinical comparison of both groups using the Harris Hip Score (and SF-36 questionnaire). Sixty hips with a Trilogy XLPE liner (Zimmer) were matched and compared to a control group of 20 conventional Trilogy PE liners (Zimmer). No differences in clinical outcome were seen, but a statistically significant reduction in linear wear was observed in the XLPEgroup, after 5 years. It is clear that, because of the reduction and stabilization of free radicals in polyethylene, a reduction in annual wear can be achieved.

  14. Friction and wear behavior of ultra-high molecular weight polyethylene as a function of polymer crystallinity.

    PubMed

    Kanaga Karuppiah, K S; Bruck, Angela L; Sundararajan, Sriram; Wang, Jun; Lin, Zhiqun; Xu, Zhi-Hui; Li, Xiaodong

    2008-09-01

    In this study the friction, wear and surface mechanical behavior of medical-grade ultra-high molecular weight polyethylene (UHMWPE) (GUR 1050 resin) were evaluated as a function of polymer crystallinity. Crystallinity was controlled by heating UHMWPE to a temperature above its melting point and varying the hold time and cooling rates. The degree of crystallinity of the samples was evaluated using differential scanning calorimetry (DSC). A higher degree of crystallinity in the UHMWPE resulted in lower friction force and an increase in scratch resistance at the micro- and nanoscales. On the nanoscale, the lamellar structure appeared to affect the observed wear resistance. Reciprocating-wear tests performed using a microtribometer showed that an increase in crystallinity also resulted in lower wear depth and width. Nanoindentation experiments also showed an increase in hardness values with an increase in sample crystallinity.

  15. Predominant factor determining wear properties of β-type and (α+β)-type titanium alloys in metal-to-metal contact for biomedical applications.

    PubMed

    Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken

    2015-01-01

    The predominant factor determining the wear properties of a new titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) and a conventional titanium alloy, Ti-6Al-4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate.

  16. The creep and wear of highly cross-linked polyethylene: a three-year randomised, controlled trial using radiostereometric analysis.

    PubMed

    Glyn-Jones, S; McLardy-Smith, P; Gill, H S; Murray, D W

    2008-05-01

    The creep and wear behaviour of highly cross-linked polyethylene and standard polyethylene liners were examined in a prospective, double-blind randomised, controlled trial using radiostereometric analysis. We randomised 54 patients to receive hip replacements with either highly cross-linked polyethylene or standard liners and determined the three-dimensional penetration of the liners over three years. After three years the mean total penetration was 0.35 mm (SD 0.14) for the highly cross-linked polyethylene group and 0.45 mm (SD 0.19) for the standard group. The difference was statistically significant (p = 0.0184). From the pattern of penetration it was possible to discriminate creep from wear. Most (95%) of the creep occurred within six months of implantation and nearly all within the first year. There was no difference in the mean degree of creep between the two types of polyethylene (highly cross-linked polyethylene 0.26 mm, SD 0.17; standard 0.27 mm, SD 0.2; p = 0.83). There was, however, a significant difference (p = 0.012) in the mean wear rate (highly cross-linked polyethylene 0.03 mm/yr, SD 0.06; standard 0.07 mm/yr, SD 0.05). Creep and wear occurred in significantly different directions (p = 0.01); creep was predominantly proximal whereas wear was anterior, proximal and medial. We conclude that penetration in the first six months is creep-dominated, but after one year virtually all penetration is due to wear. Highly cross-linked polyethylene has a 60% lower rate of wear than standard polyethylene and therefore will probably perform better in the long term.

  17. High Wear Resistance of White Cast Iron Treated by Novel Process: Principle and Mechanism

    NASA Astrophysics Data System (ADS)

    Jia, Xiaoshuai; Zuo, Xunwei; Liu, Yu; Chen, Nailu; Rong, Yonghua

    2015-12-01

    Based on microstructure desired, a novel process is proposed to treat Fe-2.4C-12.0Cr (mass pct) white cast iron balls, that is, destabilizing heat treatment following multicycle quenching and sub-critical treatment (De-MQ-Sct) process, and such a complex process is simply performed by alternate water quenching and air cooling. For comparison, the white cast iron balls also were treated by conventional normalization (NOR) process and Oil-quenching process, respectively. The partitioning of carbon from martensite to retained austenite during De-MQ-Sct process promotes the interaction between carbide precipitation and martensitic transformation, while this interaction is a unique effect only produced by multicycle quenching linking destabilizing and sub-critical treatments, which leads to more and finer secondary carbides and more carbon-enriched austenite in De-MQ-Sct sample than those in NOR or Oil-quenching sample. The average hardness of 60 HRC and impact toughness of 12.6 J/cm2 are obtained in De-MQ-Sct white cast iron balls, which are much higher than those in NOR and Oil-quenching ones. The wear behaviours measured by pin-on-disk wear tests indicate that the weight loss of De-MQ-Sct sample is only about one third of the NOR sample and one half of the Oil-quenching sample. Microstructural characterization reveals that high wear resistance related to hardness and toughness of the De-MQ-Sct balls are mainly attributed to the considerable fine secondary carbides and stable carbon-enriched retained austenite.

  18. Erosive Wear Behavior of High-Alloy Cast Iron and Duplex Stainless Steel under Mining Conditions

    NASA Astrophysics Data System (ADS)

    Yoganandh, J.; Natarajan, S.; Kumaresh Babu, S. P.

    2015-09-01

    Centrifugal pumps used in the lignite mines encounter erosive wear problems, leading to a disastrous failure of the pump casings. This paper attempts to evaluate the erosive wear resistance of Ni-Hard 4, high-chromium iron, and Cast CD4MCu duplex stainless steel (DSS), for mining conditions. The prepared test coupons were subjected to an erosion test by varying the impingement velocity and the angle of impingement, under two different pH conditions of 3 and 7, which pertained to the mining conditions. XRD analysis was carried out to confirm the phases present in the alloy. The eroded surface was subjected to SEM analysis to identify the erosion mechanisms. The surface degradation of Ni-Hard 4 and high-chromium iron came from a low-angle abrasion with a grooving and plowing mechanism at a low angle of impingement. At normal impingement, deep indentations resulted in lips and crater formations, leading to degradation of the surface in a brittle manner. A combined extrusion-forging mechanism is observed in the CD4MCu DSS surface at all the impingement angles.

  19. Role of hard second phases in the mild oxidational wear mechanism of high-speed steel-based materials

    NASA Astrophysics Data System (ADS)

    Vardavoulias, M.

    1994-04-01

    In the case of dry unlubricated wear of metals, an oxidational wear mechanism can be established under certain conditions, with oxide films being developed on the sliding surface which markedly influence the friction and wear behaviour. For high-speed steel-based materials containing various hard second phases, an a-Fe2O3 film is formed during pin-on-disc testing (under mild conditions of load and sliding speed), which reaches a critical thickness of 1-2 microns before breaking up in loose wear debris. The role of the second phases in the oxidational wear mechanism was studied in this investigation. The size of the hard second phase particles appears to be the most important parameter determining the possibility for the particles to provide protection against oxidational wear of the matrix. Particles of a size less than or equal to the critical thickness are carried away when the oxide breaks up, while particles larger than the critical oxide thickness remain in place. In this case, their ability to protect the metallic matrix from the loads imposed by the counterbody depends on their mechanical resistance to these loads, as well as the strength of their cohesion with the metallic matrix.

  20. Microstructures and friction-wear behaviors of cathodic arc ion plated CrC coating at high temperatures

    NASA Astrophysics Data System (ADS)

    Dejun, Kong; Shouyu, Zhu

    2016-11-01

    A CrC coating was deposited on YT14 cemented carbide cutting tools by a CAIP (cathodic arc ion plating). The surface and interface morphologies, chemical composition, and phases of the obtained coating were analyzed with a field emission scanning electronic microscope (FESEM), energy dispersive spectroscope (EDS), and x-ray diffraction (XRD), respectively. The COFs (coefficient of frictions) and worn morphologies of the CrC coating at 300 °C, 400 °C, and 500 °C were investigated by using a high temperature tribometer, the effects of wear temperatures on the friction-wear properties of the CrC coating were discussed. The results show that the CrC coating exhibits fine dense structure, and the lattice constants of CrC coatings are dependent on processing parameters. The C and Cr elements in the coating are mutually diffused with the W, Co, and Ti in the substrate. The average COF of the coating at 300 °C, 400 °C, and 500 °C is 0.64, 0.63, and 0.40, respectively. The Cr2O3 layer formed on the CrC coating at 500 °C has excellent oxidation resistance, which improves lubrication and wear performance, the wear mechanism is abrasive wear and oxidation wear.

  1. The comparison of manual lymph drainage and ultrasound therapy on the leg swelling caused by wearing high heels.

    PubMed

    Lee, Dong-Yeop; Han, Ji-Su; Jang, Eun-Ji; Seo, Dong-Kwon; Hong, Ji-Heon; Lee, Sang-Sook; Lee, Dong-Geol; Yu Lee, Jae-Ho

    2014-01-01

    One of the major symptoms when women are wearing high heels for a long time is leg swelling. The purpose of this study was to compare the effect of manual lymph drainage with ultrasound therapy. The forty-five healthy women of twenties were participated in this study and divided randomly into three groups; manual lymph drainage group (n=15), ultrasound therapy group (n=15) and control group (n=15). Swelling was measured before wearing the high heels (10 cm-height), after one-hour of wearing the high heels, wearing the high heels of one-hour after the intervention of 15 minutes. Also swelling was calculated by using a tape measure, volumeter and body composition analyzer. Statistical analysis of the comparison between the three groups was performed by one-way ANOVA. Also comparison to the mean value in swelling according to the time was performed by repeated measure ANOVA. As the result of this study, a significant changes have emerged within each of manual lymph drainage, ultrasound therapy and control group (p< 0.05). However, there were no significant differences between each group (p> 0.05). But the mean value of manual lymph drainage group showed the tendency of fast recovering before causing swelling. Therefore, we consider that the clinical treatment of manual lymph drainage and ongoing studies will be made since manual lymph drainage is very effective in releasing the leg swelling caused by wearing high heels and standing for a long time at work.

  2. Solid Lubrication Fundamentals and Applications. Properties of Clean Surfaces: Adhesion, Friction, and Wear

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    This chapter presents the adhesion, friction, and wear behaviors of smooth, atomically clean surfaces of solid-solid couples, such as metal-ceramic couples, in a clean environment. Surface and bulk properties, which determine the adhesion, friction, and wear behaviors of solid-solid couples, are described. The primary emphasis is on the nature and character of the metal, especially its surface energy and ductility. Also, the mechanisms of friction and wear for clean, smooth surfaces are stated.

  3. Damage tolerant functionally graded materials for advanced wear and friction applications

    NASA Astrophysics Data System (ADS)

    Prchlik, Lubos

    The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to

  4. Effect of high-intensity ultrasonic treatment on microstructure, hardness and wear behaviour of the hypereutectic Mg-5Si alloy

    NASA Astrophysics Data System (ADS)

    Moussa, M. E.; Waly, M. A.; El-Sheikh, A. M.

    2016-07-01

    The effect of high-intensity ultrasonic treatment (HIUST) on microstructure, hardness and wear behavior in Mg-5wt.%Si hypereutectic alloy has been investigated. The results showed clearly that without HIUST, most of primary Mg2Si appeared as coarse dendritic morphology with average size of about 200 µm. With HIUST, the average size of primary Mg2Si decreased significantly to about 33 µm and their morphologies changed to polyhedral shape. The modification mechanism is mainly attributed conjugation of two mechanisms: cavitation-enhanced heterogeneous nucleation and cavitation-induced dendrite fragmentation. The alloy treated with HIUST has higher hardness and wear resistance than that untreated with HIUST. The wear mechanism of investigated alloys at low applied load (10 N) and low sliding speed (0.3 m/s) is a mild abrasive oxidative wear with little adhesion. However, the wear mechanism due to the applied high loads (30, 50 N) at low sliding speed (0.3 m/s) and/or to the applied high sliding speeds (0.6, 0.9 m/s) under low load (10 N), could be described as delamination mechanism. The microstructures of the specimens were analyzed by optical microscope (OM) (model OPTIKA M-790, Italy). Energy dispersion spectrum (EDS) affiliated to field emission scanning electron microscopy (FESEM) (model Quanta FEG, The Netherlands) were performed to reveal the concentration of alloying elements in selected areas of the microstructure.

  5. Wear Testing of Moderate Activities of Daily Living Using In Vivo Measured Knee Joint Loading

    PubMed Central

    Reinders, Jörn; Sonntag, Robert; Vot, Leo; Gibney, Christian; Nowack, Moritz; Kretzer, Jan Philippe

    2015-01-01

    Resumption of daily living activities is a basic expectation for patients provided with total knee replacements. However, there is a lack of knowledge regarding the impact of different activities on the wear performance. In this study the wear performance under application of different daily activities has been analyzed. In vivo load data for walking, walking downstairs/upstairs, sitting down/standing up, and cycling (50 W & 120 W) has been standardized for wear testing. Wear testing of each activity was carried out on a knee wear simulator. Additionally, ISO walking was tested for reasons of comparison. Wear was assessed gravimetrically and wear particles were analyzed. In vivo walking produced the highest overall wear rates, which were determined to be three times higher than ISO walking. Moderate wear rates were determined for walking upstairs and downstairs. Low wear rates were determined for standing up/sitting down and cycling at power levels of 50 W and 120 W. The largest wear particles were observed for cycling. Walking based on in vivo data has been shown to be the most wear-relevant activity. Highly demanding activities (stair climbing) produced considerably less wear. Taking into account the expected number of loads, low-impact activities like cycling may have a greater impact on articular wear than highly demanding activities. PMID:25811996

  6. Communication research between working capacity of hard- alloy cutting tools and fractal dimension of their wear

    NASA Astrophysics Data System (ADS)

    Arefiev, K.; Nesterenko, V.; Daneykina, N.

    2016-06-01

    The results of communication research between the wear resistance of the K applicability hard-alloy cutting tools and the fractal dimension of the wear surface, which is formed on a back side of the cutting edge when processing the materials showing high adhesive activity are presented in the paper. It has been established that the wear resistance of tested cutting tools samples increases according to a fractal dimension increase of their wear surface.

  7. Development of a gear vibration indicator and its application in gear wear monitoring

    NASA Astrophysics Data System (ADS)

    Hu, Chongqing; Smith, Wade A.; Randall, Robert B.; Peng, Zhongxiao

    2016-08-01

    Gear tooth wear is an inevitable phenomenon and has a significant influence on gear dynamic features. Although vibration analysis has been widely used to diagnose localised gear tooth faults, its techniques for gear wear monitoring have not been well-established. This paper aims at developing a vibration indicator to evaluate the effects of wear on gear performance. For this purpose, a gear state vector is extracted from time synchronous averaged gear signals to describe the gear state. This gear state vector consists of the sideband ratios obtained from a number of tooth meshing harmonics and their sidebands. Then, two averaged logarithmic ratios, ALR and mALR, are defined with fixed and moving references, respectively, to provide complementary information for gear wear monitoring. Since a fixed reference is utilised in the definition of ALR, it reflects the cumulated wear effects on the gear state. An increase in the ALR value indicates that the gear state deviates further from its reference condition. With the use of a moving reference, the indicator mALR shows changes in the gear state within short time intervals, making it suitable for wear process monitoring. The efficiency of these vibration indicators is demonstrated using experimental results from two sets of tests, in which the gears experienced different wear processes. In addition to gear wear monitoring, the proposed indicators can be used as general parameters to detect the occurrence of other faults, such as a tooth crack or shaft misalignment, because these faults would also change the gear vibrations.

  8. Fabrication of wear-resistant silicon microprobe tips for high-speed surface roughness scanning devices

    NASA Astrophysics Data System (ADS)

    Wasisto, Hutomo Suryo; Yu, Feng; Doering, Lutz; Völlmeke, Stefan; Brand, Uwe; Bakin, Andrey; Waag, Andreas; Peiner, Erwin

    2015-05-01

    Silicon microprobe tips are fabricated and integrated with piezoresistive cantilever sensors for high-speed surface roughness scanning systems. The fabrication steps of the high-aspect-ratio silicon microprobe tips were started with photolithography and wet etching of potassium hydroxide (KOH) resulting in crystal-dependent micropyramids. Subsequently, thin conformal wear-resistant layer coating of aluminum oxide (Al2O3) was demonstrated on the backside of the piezoresistive cantilever free end using atomic layer deposition (ALD) method in a binary reaction sequence with a low thermal process and precursors of trimethyl aluminum and water. The deposited Al2O3 layer had a thickness of 14 nm. The captured atomic force microscopy (AFM) image exhibits a root mean square deviation of 0.65 nm confirming the deposited Al2O3 surface quality. Furthermore, vacuum-evaporated 30-nm/200-nm-thick Au/Cr layers were patterned by lift-off and served as an etch mask for Al2O3 wet etching and in ICP cryogenic dry etching. By using SF6/O2 plasma during inductively coupled plasma (ICP) cryogenic dry etching, micropillar tips were obtained. From the preliminary friction and wear data, the developed silicon cantilever sensor has been successfully used in 100 fast measurements of 5- mm-long standard artifact surface with a speed of 15 mm/s and forces of 60-100 μN. Moreover, the results yielded by the fabricated silicon cantilever sensor are in very good agreement with those of calibrated profilometer. These tactile sensors are targeted for use in high-aspect-ratio microform metrology.

  9. The Effects of Austenitizing Conditions on the Microstructure and Wear Resistance of a Centrifugally Cast High-Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Kang, Minwoo; Lee, Young-Kook

    2016-07-01

    The influences of austenitizing conditions on the microstructure and wear resistance of a centrifugally cast high-speed steel roll were investigated through thermodynamic calculation, microstructural analysis, and high-temperature wear tests. When the austenitizing temperature was between 1323 K and 1423 K (1050 °C and 1150 °C), coarse eutectic M2C plates were decomposed into a mixture of MC and M6C particles. However, at 1473 K (1200 °C), the M2C plates were first replaced by both new austenite grains and MC particles without M6C particles, and then remaining M2C particles were dissolved during the growth of MC particles. The wear resistance of the HSS roll was improved with increasing austenitizing temperature up to 1473 K (1200 °C) because the coarse eutectic M2C plates, which are vulnerable to crack propagation, changed to disconnected hard M6C and MC particles.

  10. The influence of scratches to metallic counterfaces on the wear of ultra-high molecular weight polyethylene.

    PubMed

    Fisher, J; Firkins, P; Reeves, E A; Hailey, J L; Isaac, G H

    1995-01-01

    A number of studies of explanted metallic femoral heads have shown scratches or damage caused by bone cement, bone or metallic particles. This damage has been cited as a cause of increased wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups. In this laboratory study, small scratches 2 mu m deep were made on smooth stainless steel surfaces at a spacing of 10 mm. These individual scratches were found to increase the wear rate of UHMWPE by a factor of 30 in unidirectional sliding and a factor of 70 in reciprocating motion. It is of particular concern that a single small scratch, which is not detected by the average surface roughness measurement Ra can cause such a dramatic increase in the wear of ultra-high molecular weight polyethylene.

  11. Poly(2-methacryloyloxyethyl phosphorylcholine) grafting and vitamin E blending for high wear resistance and oxidative stability of orthopedic bearings.

    PubMed

    Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Watanabe, Kenichi; Hashimoto, Masami; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko

    2014-08-01

    The ultimate goal in manipulating the surface and substrate of a cross-linked polyethylene (CLPE) liner is to obtain not only high wear resistance but also high oxidative stability and high-mechanical properties for life-long orthopedic bearings. We have demonstrated the fabrication of highly hydrophilic and lubricious poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) grafting layer onto the antioxidant vitamin E-blended CLPE (HD-CLPE(VE)) surface. The PMPC grafting layer with a thickness of 100 nm was successfully fabricated on the vitamin E-blended CLPE surface by using photoinduced-radical graft polymerization. Since PMPC has a highly hydrophilic nature, the water wettability and lubricity of the PMPC-grafted CLPE and HD-CLPE(VE) surfaces were greater than that of the untreated CLPE surface. The PMPC grafting contributed significantly to wear reduction in a hip-joint simulator wear test. Despite high-dose gamma-ray irradiation for cross-linking and further UV irradiation for PMPC grafting, the substrate modified by vitamin E blending maintained high-oxidative stability because vitamin E is an extremely efficient radical scavenger. Furthermore, the mechanical properties of the substrate remained almost unchanged even after PMPC grafting or vitamin E blending, or both PMPC grafting and vitamin E blending. In conclusion, the PMPC-grafted HD-CLPE(VE) provided simultaneously high-wear resistance, oxidative stability, and mechanical properties.

  12. Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies.

    PubMed

    Liu, Aiqin; Ingham, Eileen; Fisher, John; Tipper, Joanne L

    2014-04-01

    It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies.

  13. Effect of slide track shape on the wear of ultra-high molecular weight polyethylene in a pin-on-disk wear simulation of total hip prosthesis.

    PubMed

    Saikko, Vesa; Calonius, Olof; Keränen, Jaakko

    2004-05-15

    Prosthetic joints appear to show a strong relationship between the type of relative motion and wear, requiring careful consideration in the design of wear simulators. This relationship was studied with a 12-station pin-on-disk device, specifically adapted for the wear simulation of prosthetic hip joints. Each station had a unique motion, characterized by the so-called slide track, the track of the pin on the disk. The slide track shapes included 10 ellipses, their aspect ratio (AR) varying from 1.1 to 11.0, and a circle and a straight line as extreme cases. Hence for the first time in hip wear simulation, the motion was systematically varied over a wide range. Conventional UHMWPE pins were tested against polished CoCr disks in diluted calf serum three times for 3 million cycles. Below the AR value of 5.5, the polyethylene wear factor and wear mechanisms agreed with clinical observations. Above this value, the wear factor decreased to unrealistically low values, and the wear surface topography differed from that of retrieved acetabular cups. The wear particles, however, were similar to those isolated from periprosthetic tissues, irrespective of the AR value. In conclusion, it is recommended that the AR value be kept well below the critical point of 5.5.

  14. Design of High-speed Wear Lifetime Tester of the Instrument Ball Bearings

    NASA Astrophysics Data System (ADS)

    Liu, C. H.; Gu, J. M.; Sun, Y.; Chen, X. Y.

    2006-10-01

    The instrument ball bearings are the key components of movable components for various kinds of measuring and control instruments; they often operate in the environmental condition of high-speed and light preload. In general, the non metal, disposable oilimpregnated retainer material has been used for these kinds of high precision miniature bearing. The engineering practice shows that the common failure mode of them is the wear which appears under the condition of insufficient lubrication condition. As the results, the vibration and noise will be enlarged, so does the frictional torque, which makes the ball bearings to lose its original working accuracy. It is the lifetime test of bearings that can enable the designers and manufacturers to chose the material of the bearing properly, optimize the product structure, mend the manufacturing technique process, and to enhance the technical level of the bearing products significantly. In this paper, the wear lifetime tester has been designed according to the requirements of the life test for the instrument ball bearings, which consists of the main body of tester, electric system, drive unit and computer measure and control system, etc. The motor spindle has been selected to drive the device which is supported by the aerostatic bearing; frequency conversion speed adjustment mode, its scope of rotating speed is between 0 and 10,000 rpm. A pair of bearings can be tested under the pure axial preload condition, the maximum load is up to 50N, the control accuracy is ±2% the scope of temperature control is up to 200°C. The variation of frictional torque on the bearing couple will be measured by an online torque transducer. The variation of power dissipation can be monitored under arbitrary speed by use of an on-line high-precision power meter. The wear and quality situation of the contact surface of the bearings will be reflected on these two parameters. Meanwhile, the values of temperature and vibration will also be monitored

  15. Wear behaviour and microstructural characterization of worn surfaces and wear debris of a high purity aluminum and an aluminum-silicon alloy and an aluminum-silicon/silicon carbide composite sliding against an M2 steel

    NASA Astrophysics Data System (ADS)

    Li, Xianyao

    1999-11-01

    The present dissertation discusses wear behavior and microstructural characterization of the wear surface and wear debris of an Al-Si alloy (A356) and an Al-Si (A356) based composite reinforced with 20 vol.% SiC particulate as well as a high purity (99.99%) Al sliding against an M2 steel under unlubricated conditions using a block-on-ring sliding wear tester. It was observed that the wear resistance of the Al-Si/SiCp composite material was superior to that of the Al-Si alloy by one order of magnitude at a low sliding load. It was also observed that the wear resistance of the Al-Si/SiC composite could slightly be increased by approximately 10% due to the T6 beat treatment of the composite. The increase in the wear resistance, however, was not significant when compared to the increase in the hardness of the matrix due to the beat treatment. This can be partially attributed to the fact that in-situ precipitation occurred in the subsurface during the sliding wear of the as-cast Al composites. Microstructural characterization of the worn surfaces and weer debris was carried out by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) equipped with Energy Dispersive Spectroscopy (EDS), X-ray mapping and X-ray Diffraction (XRD). In particular, longitudinal cross-section TEM analyses of the worn surfaces and wear debris were successfully conducted in the present work. The results showed that the deformed structures in the worn surfaces of the Al-Si alloy and the composite contained a large number of cells and elongated subgrains with an aspect ratio of 5 to 10. It was also observed that mechanically mixed layers (MMLs) were formed during the sliding wear of the Al-Si/SiC composite and Al-Si alloy as well as the high purity (BP) Al against the steel. Characterization of the wear debris by means of the above mentioned techniques and Mossbauer spectroscopy revealed that the wear debris had features similar to those of the MMLs in the worn surfaces

  16. Wear resistance of the biocompatible phospholipid polymer-grafted highly cross-linked polyethylene liner against larger femoral head.

    PubMed

    Moro, Toru; Takatori, Yoshio; Kyomoto, Masayuki; Ishihara, Kazuhiko; Kawaguchi, Hiroshi; Hashimoto, Masami; Tanaka, Takeyuki; Oshima, Hirofumi; Tanaka, Sakae

    2015-07-01

    The use of larger femoral heads to prevent the dislocation of artificial hip joints has recently become more common. However, concerns about the subsequent use of thinner polyethylene liners and their effects on wear rate have arisen. Previously, we prepared and evaluated the biological and mechanical effects of a novel highly cross-linked polyethylene (CLPE) liner with a nanometer-scaled graft layer of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Our findings showed that the PMPC-grafted particles were biologically inert and caused no subsequent bone resorptive responses and that the PMPC-grafting markedly decreased wear in a hip joint simulator. However, the metal or ceramic femoral heads used in this previous study had a diameter of 26 mm. Here, we investigated the wear-resistance of the PMPC-grafted CLPE liner with a 40-mm femoral head during 10 × 10(6) cycles of loading in the hip joint simulator. The results provide preliminary evidence that the grafting markedly decreased gravimetric wear rate and the volume of wear particles, even when coupled with larger femoral heads. Thus, we believe the PMPC-grafting will prolong artificial hip joint longevity both by preventing aseptic loosening and by improving the stability of articular surface.

  17. Does ultra-mild wear play any role for dry friction applications, such as automotive braking?

    PubMed

    Osterle, Werner; Dmitriev, A I; Kloss, H

    2012-01-01

    Nanostructured third body films and/or storage of wear debris at the surfaces of the first bodies are deemed as prerequisites of sliding under ultra-mild wear conditions. Since such features have been observed experimentally on brake pads and discs, attempts were undertaken to study their sliding behaviour by modelling on the nanoscopic scale with an approach based on Movable Cellular Automata (MCA). The model rendered the possibility to study the influence of different nanostructures systematically and to assess the impact of different brake pad ingredients on the sliding behaviour, velocity accommodation and friction force stabilization at a sliding contact. Besides providing a review on previously published modelling results, some additional new graphs enabling better visualization of dynamic processes are presented. Although ultra-mild wear conditions were considered to be essential for achieving the desired tribological properties, transitions to mesoscopic and macroscopic wear mechanisms were studied as well. The final conclusion is that ultra-mild wear and corresponding smooth sliding behaviour play an important role during automotive braking, even though temporarily and locally events of severe wear may cause friction instabilities, surface damage and release of coarse wear particles.

  18. Wear simulation of ultra-high molecular weight polyethylene hip implants by incorporating the effects of cross-shear and contact pressure.

    PubMed

    Kang, L; Galvin, A L; Brown, T D; Fisher, J; Jin, Z-M

    2008-10-01

    The effect of multi-directional cross-shear (CS) motion and contact pressure on ultra-high molecular weight polyethylene (UHMWPE) wear was investigated in this study, based on an integrated experimental and computational approach. The wear factor as a function of CS was determined experimentally from a multi-directional pin-on-plate wear tester under a nominal contact pressure of 1 MPa. A computational wear model was developed which included the effects of CS as well as the load and sliding distance imposed on the hip joint employing a UHMWPE cup against a metallic femoral head under both gait and Leeds ProSim hip joint simulator conditions. The CS ratios were quantified over the articular surface of the UHMWPE cup and the CS-dependent wear factors derived from multi-directional pin-on-plate studies were applied in the computational wear model. Outputs from the computational wear model were validated independently against an experimental hip simulator study. Comparisons of linear and volumetric wear were made between the computational wear model and the hip simulator testing for a nominal conventional (0 MRad) UHMWPE cup of 28mm diameter and a highly cross-linked (10 MRad) UHMWPE cup. The difference between the computed and experimental volumetric wear was approximately 30 per cent for the 0 MRad UHMWPE, although the worn areas between the prediction and the measurement were similar. For the 10 MRad UHMWPE, the discrepancy was reduced to 16 per cent. In both cases, the computational model predicted a lower wear rate than the experimental simulator testing. The effect of using alternative wear factors under a different nominal contact pressure of 3MPa was also considered. The input wear factor to the computational model, derived from a constant loaded pin-on-plate test configuration, may underestimate the dynamic effect due to the variation in the load in the hip joint simulator.

  19. Surface modification of Monel K-500 as a means of reducing friction and wear in high-pressure oxygen

    NASA Technical Reports Server (NTRS)

    Gunaji, Mohan; Stoltzfus, Joel M.; Schoenman, Leonard; Kazaroff, John

    1989-01-01

    A study is conducted of the tribological characteristics of Monel K-500 during rubbing in a high pressure oxygen atmosphere, upon surface treatment by ion-implanted oxygen, chromium, lead, and silver, as well as electrolyzed chromium and an electroless nickel/SiC composite. The electrolyzed chromium dramatically increased total sample wear, while other surface treatments affected sample wear only moderately. Although the ion-implant treatments reduced the average coefficient of friction at low contact pressure, higher contact pressures eliminated this improvement.

  20. Improving Tribological Properties of Cast Al-Si Alloys through Application of Wear-Resistant Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Culliton, David; Betts, Anthony; Carvalho, Sandra; Kennedy, David

    2013-04-01

    Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity.

  1. Effects of duration of wearing high-heeled shoes on plantar pressure.

    PubMed

    Yin, Chun-Ming; Pan, Xiao-Hua; Sun, Yu-Xin; Chen, Zhi-Bin

    2016-10-01

    In the present study we investigated the effects of different durations of using high-heeled shoes on plantar pressure and gait. A questionnaire survey and dynamic plantar pressure measurements were performed in 20 control females and 117 females who had worn high-heeled shoes for a long time. According to the duration of using high-heeled shoes (as specified in the questionnaire), subjects were divided into a control group and five groups with different durations of use (i.e. <2years, 2-5years, 6-10years, 11-20years and >20years). Parameters, including peak pressure, impulse and pressure duration, in different plantar regions were measured with the Footscan pressure plate. The 2-5years group had smaller midfoot contact areas for both feet and higher subtalar joint mobility, while the 6-10years group had larger midfoot contact areas for both feet and prolonged foot flat phase during gait. The peak pressure and impulse under the second and fourth metatarsus were increased with the prolonged wearing of high-heeled shoes, and the pressure and impulse under the midfoot were substantially reduced in the 2-5years group. The findings suggest that long-term use of high-heeled shoes can induce changes in arch morphology: the longitudinal arch tends to be elevated within 2-5years; the longitudinal arch tends to be flattened within 6-10years; and the forefoot latitudinal arch tends to collapse in more than 20years.

  2. Wear Measurement System

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Lewis Research Center developed a tribometer for in-house wear tests. Implant Sciences Corporation (ISC), working on a NASA contract to develop coatings to enhance the wear capabilities of materials, adapted the tribometer for its own use and developed a commercial line of user-friendly systems. The ISC-200 is a pin-on-disk type of tribometer, functioning like a record player and creating a wear groove on the disk, with variables of speed and load. The system can measure the coefficient of friction, the wear behavior between materials, and the integrity of thin films or coatings. Applications include measuring wear on contact lenses and engine parts and testing disk drives.

  3. Applications of Electrostatic Sensor for Wear Debris Detecting in the Lubricating Oil

    NASA Astrophysics Data System (ADS)

    Wen, Z.; Yin, X.; Jiang, Z.

    2013-10-01

    In this study, an advanced monitoring technology has been presented based on the electrostatic induction principle to monitor timely wear fault on-line. The paper begins with the principle of the electrostatic monitoring technology, then we focus on the electrostatic sensor, the most important component in the electrostatic monitoring system, establish a measurement model for an electrostatic sensor with the given structure parameters. Based on the measurement model, we use the finite element method to analyze the characteristics of an electrostatic sensor for wear debris detecting in lubricating oil. Lastly we build an experiment platform to validate the feasibility of the electrostatic monitoring method. The experiment results show, to some extent, that the electrostatic signal can reflect the relative density of wear debris, and the sensor proposed can satisfy the primary demand of wear debris on-line monitoring.

  4. Clinical safety and wear resistance of the phospholipid polymer-grafted highly cross-linked polyethylene liner.

    PubMed

    Moro, Toru; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Oda, Hiromi; Kim, Yoon Taek; Umeyama, Takashige; Fukatani, Eisei; Ito, Hideya; Kyomoto, Masayuki; Oshima, Hirofumi; Tanaka, Takeyuki; Kawaguchi, Hiroshi; Nakamura, Kozo

    2016-11-03

    To reduce the production of wear particles and subsequent aseptic loosening, we created a human articular cartilage-mimicked surface for a highly cross-linked polyethylene liner, whose surface grafted layer consisted of a biocompatible phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine). Although our previous in vitro findings showed that poly(2-methacryloyloxyethyl phosphorylcholine)-grafted particles were biologically inert and caused no subsequent bone resorptive responses, and poly(2-methacryloyloxyethyl phosphorylcholine) grafting markedly decreased wear in hip joint simulator tests, the clinical safety, and in vivo wear resistance of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners remained open to question. Therefore, in the present study, we evaluated clinical and radiographic outcomes of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners 5 years subsequent to total hip replacement in 68 consecutive patients. No reoperation was required for any reason, and no adverse events were associated with the implanted liners. The average Harris Hip Score increased from 38.6 preoperatively to 96.5 5 years postoperatively, and health-related quality of life, as indicated by the Short Form 36 Health Survey, improved. Radiographic analyses showed no periprosthetic osteolysis or implant migration. Between 1 and 5 years postoperatively, the mean steady-state wear rate was 0.002 mm/year, which represented a marked reduction relative to other highly cross-linked polyethylene liners, and appeared to be unaffected by patient-related or surgical factors. Although longer follow up is required, poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners improved mid-term clinical outcomes. The clinical safety and wear-resistance results are encouraging with respect to the improvement of long-term clinical outcomes with poly(2

  5. A model for predicting wear rates in tooth enamel.

    PubMed

    Borrero-Lopez, Oscar; Pajares, Antonia; Constantino, Paul J; Lawn, Brian R

    2014-09-01

    It is hypothesized that wear of enamel is sensitive to the presence of sharp particulates in oral fluids and masticated foods. To this end, a generic model for predicting wear rates in brittle materials is developed, with specific application to tooth enamel. Wear is assumed to result from an accumulation of elastic-plastic micro-asperity events. Integration over all such events leads to a wear rate relation analogous to Archard׳s law, but with allowance for variation in asperity angle and compliance. The coefficient K in this relation quantifies the wear severity, with an arbitrary distinction between 'mild' wear (low K) and 'severe' wear (high K). Data from the literature and in-house wear-test experiments on enamel specimens in lubricant media (water, oil) with and without sharp third-body particulates (silica, diamond) are used to validate the model. Measured wear rates can vary over several orders of magnitude, depending on contact asperity conditions, accounting for the occurrence of severe enamel removal in some human patients (bruxing). Expressions for the depth removal rate and number of cycles to wear down occlusal enamel in the low-crowned tooth forms of some mammals are derived, with tooth size and enamel thickness as key variables. The role of 'hard' versus 'soft' food diets in determining evolutionary paths in different hominin species is briefly considered. A feature of the model is that it does not require recourse to specific material removal mechanisms, although processes involving microplastic extrusion and microcrack coalescence are indicated.

  6. Fret wear mediation of NIRCam filter wheel assembly

    NASA Astrophysics Data System (ADS)

    Privári, Béla I.

    2011-10-01

    We will discuss a fret wear solution developed for the James Webb Space Telescope NIRCam filter wheel assembly by implementation of a hard coating. With mechanisms and structures designed for space flight application, titanium is often selected as the choice material of construction. Titanium offers a low-density high strength material that is good for use with many optical instruments due to its' favorable thermal properties. An important factor to consider with titanium mechanisms and structures are component fits and the vibration environment that must be survived during launch. In many instances, small (slip) fits between titanium components can cause fret wear during launch induced vibration. Titanium is particularly susceptible to fret wear, although other materials also demonstrate the fret wear. Fretting is adhesive failure of a material that experiences impact and micro-slip with an adjacent part. The mechanism of fret wear involves small particles that are pulled from the surface of parts that turn into hard oxides that further accelerate the wear between the parts. To mitigate fret wear, the mechanism or structure can be designed to eliminate all slip fits altogether, lubricants may be added to the wear surfaces or hard coatings can be applied to the wear surfaces when the other approaches are not feasible. For the NIRCam filter wheel assembly, which must operate at 35K and remain optically clean, only hard coatings are feasible. A discussion of several coating alternatives and associated wear testing will be presented along with the selection of an optimal solution.

  7. Ti6Al4V Blade Wear Behavior During High-Speed Rubbing with NiAl-hBN Abradable Seal Coating

    NASA Astrophysics Data System (ADS)

    Xue, Weihai; Gao, Siyang; Duan, Deli; Zhang, Jiaping; Liu, Yang; Li, Shu

    2017-02-01

    The high-speed rubbing wear behavior between a Ti6Al4V blade and a NiAl-hBN seal coating was studied with a high-speed rub test rig. Blade wear behavior, which had not received enough attentions, was the key concern of this study. The rub tests conducted at different linear speeds and single-pass depths indicated that although wear distance was constant and rub forces decreased at high linear speed, blade wear increased with the increment of linear speed when single-pass depth was invariable. According to scanning electron microscopy, x-ray diffraction, electron probe microanalysis and microhardness analyses of the wear scars, different blade and coating wear mechanisms were observed when rubbed at different linear speeds. Remarkably, when rubbing was done at high linear speed, there was severe blade oxidation with the generation of oxidation layer full of cracks and high-hardness transfer layer in the coating wear scar, and these were identified as reasons of aggravated blade wear.

  8. Ti6Al4V Blade Wear Behavior During High-Speed Rubbing with NiAl-hBN Abradable Seal Coating

    NASA Astrophysics Data System (ADS)

    Xue, Weihai; Gao, Siyang; Duan, Deli; Zhang, Jiaping; Liu, Yang; Li, Shu

    2016-12-01

    The high-speed rubbing wear behavior between a Ti6Al4V blade and a NiAl-hBN seal coating was studied with a high-speed rub test rig. Blade wear behavior, which had not received enough attentions, was the key concern of this study. The rub tests conducted at different linear speeds and single-pass depths indicated that although wear distance was constant and rub forces decreased at high linear speed, blade wear increased with the increment of linear speed when single-pass depth was invariable. According to scanning electron microscopy, x-ray diffraction, electron probe microanalysis and microhardness analyses of the wear scars, different blade and coating wear mechanisms were observed when rubbed at different linear speeds. Remarkably, when rubbing was done at high linear speed, there was severe blade oxidation with the generation of oxidation layer full of cracks and high-hardness transfer layer in the coating wear scar, and these were identified as reasons of aggravated blade wear.

  9. Extremely high wear resistance and ultra-low friction behaviour of oxygen-plasma-treated nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Radhika, R.; Kumar, N.; Sankaran, K. J.; Dumpala, Ravikumar; Dash, S.; Ramachandra Rao, M. S.; Arivuoli, D.; Tyagi, A. K.; Tai, N. H.; Lin, I.-Nan

    2013-10-01

    The diamond nanowire (DNW) film was deposited by N2-enriched microwave plasma-enhanced chemical vapour deposition (MPECVD) process. As-deposited DNW film was treated in O2 plasma which resulted in chemical and microstructural modification. Sheath of the DNW film is chemically constituted by amorphous carbon (a-C)- and graphite (sp2C=C)-like bonding. However, nanowires transformed into ultra-small spherical grains after the O2-plasma treatments. In this condition, a-C and sp2C=C bonding significantly reduced due to plasma etching caused by oxygen atoms. After the O2-plasma treatment, formation of functional groups such as C=O, C-O-C, O-H, O-CH3 and H2O was observed on the surface and inside the wear track as evident from the micro FTIR analysis. H2O is hydrogen bonded to oxygen-containing groups such as -OH and -H. The O2-plasma-exposed DNW film exhibits surface charging and causes formation of dangling bonds and electron trapping centres. This results in significant decrease in contact angle, hence superhydrophilic behaviour. The friction coefficient of O2-plasma-treated film showed super low value ˜0.002 with high wear resistance 2 × 10-12 mm3 N-1 m-1. In the reciprocating ball-on-disc tribology test, only ˜80 nm wear loss was observed after the 1 km of sliding distance at 10 N loads. Such an advance in tribological properties is explained by passivation of covalent carbon bonding and transformation of sliding surfaces by weak van der Waals and hydrogen bondings. High surface energy and the consequent superhydrophilic behaviour of film is attributed to the formation of the above-mentioned functional groups on the surface. This protects against deformation of the wear track leading to extremely high wear resistance.

  10. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  11. The influence of irradiation dose on mechanical properties and wear resistance of molded and extruded ultra high molecular weight polyethylene.

    PubMed

    Xiong, Lei; Xiong, Dangsheng

    2012-05-01

    Ultra high molecular weight polyethylene (UHMWPE) is a type of biomedical material used in total joint replacement. In this study, molded and extruded UHMWPE was used to investigate the influence of irradiation dose on its mechanical properties and wear resistance. The results of tensile and compressive tests showed that tensile properties decreased as the irradiation dose increased. Compressive properties decreased significantly after irradiation, but then increased as the irradiation dose increased. Microhardness also had a similar variety tendency as compressive properties. It could be corresponding to the variety of crystallinity for UHMWPE. The fracture surfaces of tensile samples indicated that molded and extruded UHMWPE had a similar fracture mechanism, although the tensile properties were significantly different. The wear tests of knee joint moving simulator showed that the wear rate of molded and extruded UHMWPE decreased as the irradiation dose increased, and a significant reduction of wear rate was exhibited till the irradiation dose of 100 kGy under saline lubrication, and 150 kGy under calf serum lubrication. The IR results indicated that packaging and remelting in vacuum was an effective method to remove oxygen in UHMWPE blocks.

  12. Effects of high-temperature hydrogenation treatment on sliding friction and wear behavior of carbide-derived carbon films.

    SciTech Connect

    Erdemir, A.; Kovalchenko, A.; McNallan, M. J.; Welz, S.; Lee, A.; Gogotsi, Y.; Carroll, B.; Energy Technology; Univ. of Illinois; Drexel Univ.

    2004-01-01

    In this study, we investigated the effects of a high-temperature hydrogenation treatment on the sliding friction and wear behavior of nanostructured carbide-derived carbon (CDC) films in dry nitrogen and humid air environments. These films are produced on the surfaces of silicon carbide substrates by reacting the carbide phase with chlorine or chlorine-hydrogen gas mixtures at 1000 to 1100 C in a sealed tube furnace. The typical friction coefficients of CDC films in open air are in the range of 0.2 to 0.25, but in dry nitrogen, the friction coefficients are 0.15. In an effort to achieve lower friction on CDC films, we developed and used a special hydrogenation process that was proven to be very effective in lowering friction of CDC films produced on SiC substrates. Specifically, the films that were post-hydrogen-treated exhibited friction coefficients as low as 0.03 in dry nitrogen, while the friction coefficients in humid air were 0.2. The wear of Si{sub 3}N{sub 4} counterface balls was hard to measure after the tests, while shallow wear tracks had formed on CDC films on SiC disks. Detailed mechanical and structural characterizations of the CDC films and sliding contact surfaces were done using a series of analytical techniques and these findings were correlated with the friction and wear behaviors of as-produced and hydrogen-treated CDC films.

  13. Effect of niobium interlayer on high-temperature sliding friction and wear of silver films on alumina

    SciTech Connect

    Erdemir, A.; Erck, R.A.

    1994-03-01

    We investigated the effect of a thin Nb bond layer (15--20 mn thick) on the high-temperature sliding friction and wear of silver films ({approx}1.5 {mu}m thick) produced on {alpha}-alumina (Al{sub 2}O{sub 3}) substrates by ion-beam assisted deposition. The friction coefficients of test pairs without an Ag film fluctuated between 0.8 to 1.1, whereas the friction coefficients of pairs with an Ag film were 0.32 to 0.5. The wear of uncoated Al{sub 2}O{sub 3} balls sliding against the Ag-coated flats was reduced by factors of 25 to {approx}2000, depending on test temperature and the presence or absence of an Nb bond layer. The wear of silver-coated flats was virtually unmeasurable after tests at temperatures up to 400C. At much higher temperatures (e.g., 600C), Ag films without an Nb bond layer delaminated from the sliding surfaces and lost their effectiveness; however, Ag films with an Nb bond layer remained intact on the sliding surfaces of the Al{sub 2}O{sub 3} substrates even at 600C and continued to impart low friction and low wear.

  14. Improved resistance to wear and fatigue fracture in high pressure crystallized vitamin E-containing ultra-high molecular weight polyethylene

    PubMed Central

    Oral, Ebru; Beckos, Christine A. Godleski; Lozynsky, Andrew J.; Malhi, Arnaz S.; Muratoglu, Orhun K.

    2013-01-01

    Higher crystallinity and extended chain morphology are induced in ultra-high molecular weight polyethylene (UHMWPE) in the hexagonal phase at temperatures and pressures above the triple point, resulting in improved mechanical properties. In this study, we report the effects of the presence of a plasticizing agent, namely vitamin E (α-tocopherol), in UHMWPE during high pressure crystallization. We found that this new vitamin E-blended and high pressure crystallized UHMWPE (VEHPE) has improved fatigue strength and wear resistance compared to virgin high pressure crystallized (HP) UHMWPE. This suggested different mechanisms of wear reduction and fatigue crack propagation resistance in UHMWPE. PMID:19135247

  15. Improved resistance to wear and fatigue fracture in high pressure crystallized vitamin E-containing ultra-high molecular weight polyethylene.

    PubMed

    Oral, Ebru; Godleski Beckos, Christine A; Lozynsky, Andrew J; Malhi, Arnaz S; Muratoglu, Orhun K

    2009-04-01

    Higher crystallinity and extended chain morphology are induced in ultra-high molecular weight polyethylene (UHMWPE) in the hexagonal phase at temperatures and pressures above the triple point, resulting in improved mechanical properties. In this study, we report the effects of the presence of a plasticizing agent, namely vitamin E (alpha-tocopherol), in UHMWPE during high pressure crystallization. We found that this new vitamin E-blended and high pressure crystallized UHMWPE (VEHPE) has improved fatigue strength and wear resistance compared to virgin high pressure crystallized (HP) UHMWPE. This suggested different mechanisms of wear reduction and fatigue crack propagation resistance in UHMWPE.

  16. Effect of experimental parameters on the high-stress abrasive wear behavior of steels and a software package for its prediction

    SciTech Connect

    Dasgupta, R.; Roy, A.; Prasad, B.K.; Yegneswaran, A.H.

    1999-06-01

    The effect of different experimental factors on the high-stress abrasive wear properties of steels has been studied. A correlation among the factors has been established by linear regression analysis. A computer software in Microsoft Basic language utilizing linear regression analysis has been developed with the capability of predicting the wear response of steels from the experimental factors.

  17. A comparison of the wear and physical properties of silane cross-linked polyethylene and ultra-high molecular weight polyethylene.

    PubMed

    Sakoda, H; Voice, A M; McEwen, H M; Isaac, G H; Hardaker, C; Wroblewski, B M; Fisher, J

    2001-12-01

    Cross-linked polyethylenes are being introduced widely in acetabular cups in hip prostheses as a strategy to reduce the incidence of wear debris-induced osteolysis. It will be many years before substantial clinical data can be collected on the wear of these new materials. Silane cross-linked polyethylene (XLPE) was introduced into clinical practice in a limited series of acetabular cups in 1986 articulating against 22.225-mm alumina ceramic femoral heads and showed reduced wear rates compared with conventionally sterilized (gamma irradiation in air) ultra-high molecular weight polyethylene (UHMWPE). We compared the wear of XLPE manufactured in 1986 with the wear of UHMWPE manufactured in 1986 in nonirradiated and irradiated forms. In the nonirradiated forms, the wear of XLPE was 3 times less than UHWMPE when articulating against smooth counterfaces. The nonirradiated materials did not show signs of oxidation. In the irradiated forms, only UHMWPE showed high levels of oxidation, and this caused a substantial increase in wear. Antioxidants added to XLPE during processing gave resistance to oxidative degradation. When sliding against scratched counterfaces, the wear of UHMWPE increased by a factor of 2 to 3 times. Against the same scratched counterfaces, the wear of XLPE increased dramatically by 30 to 200 times. This difference may be attributed to the reduction in toughness of XLPE. Clinically, XLPE has been articulated against damage-resistant ceramic heads, and this probably has been an important factor in contributing to reduced wear. New cross-linked polyethylenes differ considerably from XLPE. This study indicates that it is prudent to examine the wear of new polyethylenes under a range of conditions that may occur in vivo.

  18. Wearing gloves in the hospital

    MedlinePlus

    Infection control - wearing gloves; Patient safety - wearing gloves; Personal protective equipment - wearing gloves; PPE - wearing gloves; Nosocomial infection - wearing gloves; Hospital acquired infection - wearing gloves

  19. Facile and scalable preparation of highly wear-resistance superhydrophobic surface on wood substrates using silica nanoparticles modified by VTES

    NASA Astrophysics Data System (ADS)

    Jia, Shanshan; Liu, Ming; Wu, Yiqiang; Luo, Sha; Qing, Yan; Chen, Haibo

    2016-11-01

    In this study, an efficient, facile method has been developed for fabricating superhydrophobic surfaces on wood substrates using silica nanoparticles modified by VTES. The as-prepared superhydrophobic wood surface had a water contact angle of 154° and water slide angle close to 0°. Simultaneously, this superhydrophobic wood showed highly durable and robust wear resistance when having undergone a long period of sandpaper abrasion or being scratched by a knife. Even under extreme conditions of boiling water, the superhydrophobicity of the as-prepared wood composite was preserved. Characterizations by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy showed that a typical and tough hierarchical micro/nanostructure was created on the wood substrate and vinyltriethoxysilane contributed to preventing the agglomeration of silica nanoparticles and serving as low-surface-free-energy substances. This superhydrophobic wood was easy to fabricate, mechanically resistant and exhibited long-term stability. Therefore, it is considered to be of significant importance in the industrial production of functional wood, especially for outdoor applications.

  20. Ceramic-on-metal for total hip replacement: mixing and matching can lead to high wear.

    PubMed

    Affatato, Saverio; Spinelli, Michele; Zavalloni, Mara; Traina, Francesco; Carmignato, Simone; Toni, Aldo

    2010-04-01

    Ceramic-on-ceramic and metal-on-metal bearing surfaces are often employed for total hip replacement because of their resistance to wear. However, they have some limits: brittleness is a major concern for ceramic, and ion release is a drawback for metal. To reduce the effect of these limitations, a hybrid coupling of ceramic-on-metal has been proposed. The theoretical advantage of this new coupling might lead orthopedic surgeons to use it indiscriminately. We asked whether the wear rate of this innovative solution was comparable with that of ceramic-on-ceramic, which is considered to be the gold standard for wear resistance. In a hip simulator study, we tested the wear pattern of a hybrid ceramic-on-metal coupling supplied by the same distributor; in particular, three different configurations were tested for 5 million cycles: 36-mm ceramic-on-ceramic, 32-mm and 36-mm ceramic-on-metal. These combinations were gravimetrically and geometrically evaluated. After 5 million cycles, the volumetric loss for the metal acetabular cups (Phi 36-mm) was 20-fold greater than that of the ceramic cups of the same size (Phi 36-mm); a volumetric loss of 4.35 mm(3) and 0.26 mm(3) was observed, respectively, for ceramic-on-metal and ceramic-on-ceramic combinations. Significant statistical differences were observed between all 36-mm different combinations (P < 0.0001). The increased diameter of the 36-mm ceramic-on-metal configuration resulted in a lower volumetric loss compared with that of the 32-mm ceramic-on-metal configuration. Our findings showed an increase in wear for the proposed hybrid specimens with respect to that of the ceramic-on-ceramic ones. This confirms that even in the case of ceramic-on-metal bearings, mixing and matching could not prove effective wear behavior, not even comparable with that of the ceramic-on-ceramic gold standard.

  1. Low wear partially fluorinated polyimides

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Hady, W. F.

    1984-01-01

    Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid (BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes.

  2. Effect of cryogenic treatment on wear resistance of Ti-6Al-4V alloy for biomedical applications.

    PubMed

    Gu, Kaixuan; Wang, Junjie; Zhou, Yuan

    2014-02-01

    The effect of cryogenic treatment on wear resistance of Ti-6Al-4V alloy for biomedical applications was experimentally investigated in this paper. Cryogenic treatments with the same soaking time of 24h at different temperatures of -80°C, -140°C and -196°C were conducted and the treatments at the same temperature of -196°C were then further given different soaking time of 3h, 48h and 72h to be investigated. After cryogenic treatment, the Vickers hardness of specimens was measured. Wear resistance of Ti-6Al-4V alloy was measured by pin-on-disk wear test under dry sliding condition. The results demonstrated that the Vickers hardness increased slightly with the reduction of temperature while it increased obviously with the elongation of soaking time at -196°C. The friction coefficients of specimens cryo-treated at -196°C were lower than those of untreated and of cryo-treated at -80°C and -140°C. And the longer the soaking time is during the cryogenic treatment, the higher the friction coefficient reduction can be achieved. The obvious reduction of mass loss can be obtained at -196°C with 72h soaking. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to detect the microstructure and worn surface of specimens. By cryogenic treatment, the plowing in the worn surface was smoothed and shallowed, and the degree of plastic deformation in the subsurface was decreased. There was no obvious phase transformation which can be detected in the microstructure after cryogenic treatment. However, the tendency of refinement in grain size can be detected by XRD which improved the wear resistance of Ti-6Al-4V alloy.

  3. Prediction of plastic strains in ultra-high molecular weight polyethylene due to microscopic asperity interactions during sliding wear.

    PubMed

    McNie, C; Barton, D C; Stone, M H; Fisher, J

    1998-01-01

    Studies of explanted femoral heads have shown that scratches caused by bone cement, bone or metallic particles are present on the rubbing surface. This damage has been cited as a cause of increased wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups and it is known that the particulate wear debris produced leads to osteolysis. A series of explanted Charnley femoral heads have been surface characterized using a Talysurf 6 profilometer and found to have scratches with lip heights in the size range 0.1-3.25 microns with an average height of 1 micron giving an average aspect ratio (defined as height/half-width) of 0.1. These geometries were incorporated into a finite element model of a stainless steel asperity sliding over UHMWPE under conditions similar to those in an artificial hip system. It was found that as the aspect ratio of the asperity lip increased, the plastic strains both on and below the surface of the UHMWPE increased non-linearly, but that the magnitude of the strain was independent of the asperity height. The asperity aspect ratio was also found to affect the position of the maximum sub-surface strain, as the asperity aspect ratio was increased the maximum strain rose to the surface. The high plastic strains predicted offer an explanation for the highly elevated wear rates in scratched counterface tests and the aspect ratio of scratch lips is therefore a critical determinant of plastic strain.

  4. Wear resistant performance of highly cross-linked and annealed ultra-high molecular weight polyethylene against ceramic heads in total hip arthroplasty.

    PubMed

    Sato, Taishi; Nakashima, Yasuharu; Akiyama, Mio; Yamamoto, Takuaki; Mawatari, Taro; Itokawa, Takashi; Ohishi, Masanobu; Motomura, Goro; Hirata, Masanobu; Iwamoto, Yukihide

    2012-12-01

    The purpose of this study was to examine the effects of ceramic femoral head material, size, and implantation periods on the wear of annealed, cross-linked ultra-high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non-cross-linked conventional UHMWPE (CPE). XLPE was fabricated by cross-linking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics and cobalt-chrome (CoCr) of 22 or 26 mm diameter were used. In this retrospective cohort study, the femoral head penetration into the cup was measured digitally on radiographs of 367 hips with XLPE and 64 hips with CPE. The average follow-up periods were 6.3 and 11.9 years, respectively. Both XLPE creep and wear rates were significantly lower than those of CPE (0.19 mm vs. 0.44 mm, 0.0001 mm/year vs. 0.09 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0008, 0.00007, and -0.009 mm/year for zirconia, alumina, and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period, and patient demographics. Further follow-up is required to determine the long-term clinical performance of the annealed XLPE.

  5. Processing, Characterization and Fretting Wear of Zinc Oxide and Silver Nanoparticles Reinforced Ultra High Molecular Weight Polyethylene Biopolymer Nanocomposite

    NASA Astrophysics Data System (ADS)

    Alam, Fahad; Kumar, Anil; Patel, Anup Kumar; Sharma, Rajeev K.; Balani, Kantesh

    2015-04-01

    Ultra-high molecular weight polyethylene (UHMWPE) is the most widely used biopolymer for articulating surfaces, such as an acetabular cup liner interfacing with a metal/ceramic femoral head. However, the formation of wear debris leads to the aseptic loosening of implants. Thus, in order to improve the life span via enhancing the fretting wear resistance, UHMWPE is reinforced with ZnO/Ag nanoparticles. It is envisaged that the ZnO/Ag addition will also exhibit antibacterial properties. In the current study, the synergetic effect of the reinforcement of ZnO/Ag nanoparticles (0-3 wt.% combinations) on the fretting wear behavior of a UHMWPE matrix is assessed. The phase characterization of compression- molded UHMWPE-Ag-ZnO biopolymer nanocomposites has elicited the retention of starting phases. All samples were processed at >98% density using compression molding. Silver and ZnO reinforcement showed enhanced hardness ~20.4% for U3A and 42.0% for U3Z. Fretting wear performance was evaluated at varying loads (5-15 N), keeping in mind the weight at different joints, with constant frequency (5 Hz) as well as amplitude of oscillation (100 µm). Laser surface profilometry showed change of wear volume from 8.6 × 10-5 mm3 for neat polymer to 5.8 × 10-5 mm3 with 1 wt.% Ag + 1 wt.% ZnO reinforcement (at 15 N load). Consequently, the mechanics of resistance offered by Ag and ZnO is delineated in the UHMWPE matrix. Further, S. aureus viability reduction is ~28.7% in cases with 1 wt.% Ag addition, ~42.5% with 1 wt.% ZnO addition, but synergistically increase to ~58.6% and 47.1% when each of Ag and ZnO is added with 1 wt.% and 3 wt.%, respectively (when compared to that of the UHMWPE control sample). Increased wear resistance and superior bioactivity and enhanced anti-bacterial properties of 1 wt.% Ag + 1 wt.% ZnO and 3 wt.% Ag + 3 wt.% ZnO shows the potential use of ZnO-Ag-UHMWPE biopolymer composites as an articulating surface.

  6. Fabrication and Wear Behavior Analysis on AlCrFeNi High Entropy Alloy Coating Under Dry Sliding and Oil Lubrication Test Conditions

    NASA Astrophysics Data System (ADS)

    Tang, Yipin; Wang, Shouren; Sun, Bin; Wang, Yan; Qiao, Yang

    2016-03-01

    In this paper, AlCrFeNi high entropy alloy coating was fabricated on the surface of Q235 steel using hot pressing sintering process. The coating has the controlled thickness size and excellent mechanical properties. Scanning electron microscopy (SEM), XRD and hardness testing method were used to study the morphology, phase structure and hardness of high entropy alloys coating. The lattice distortion plays a significant role in increasing the hardness. Coating formation mechanism caused by the element diffusion under the hot pressing effect is also discussed in the paper. Simultaneously, the dry sliding and oil lubrication wear tests, wear morphology observation and wear mechanism discussion were completed. As the result shows, AlCrFeNi high entropy alloys coating exhibits superior wear resistance either at dry sliding or oil lubrication tests owing to its hard high entropy solid solution structure.

  7. Influence of microscopic surface asperities on the wear of ultra-high molecular weight polyethylene in a knee prosthesis.

    PubMed

    Cho, C-H; Murakami, T; Sawae, Y

    2010-01-01

    The wear of ultra-high molecular weight polyethylene (UHMWPE) in knee and hip prostheses is one of the major factors restricting the longevity of these implants. A number of microscopic scratches caused by various factors were observed on the metallic femoral components of the retrieved knee prostheses with an anatomical design. It appears that microscopic surface asperities caused by this surface damage contribute to increasing and/or accelerating the wear of the UHMWPE tibial insert. In this study, in the first step, microscopic observations and surface roughness measurements of several retrieved metallic femoral components were performed in order to produce simplified two-dimensional (2D) finite-element method (FEM) models of a microscopic surface asperity using roughness parameters. Next, a three-dimensional (3D) microscopic surface profile measurement of the damaged surface of a retrieved metallic femoral component and the reproduction of the femoral component surface were performed in order to produce 3D FEM models of a microscopic surface asperity based on actual measurement data. 2D and 3D elastoplastic contact analyses between a metallic microscopic surface asperity and UHMWPE were also performed in order to investigate the mechanical state and microscopic wear of UHMWPE caused by a metallic microscopic surface asperity. The analytical findings of this study suggest that the aspect ratio, shape ratio, and indentation depth of the microscopic surface asperity have significant influence on increasing and/or accelerating the wear of UHMWPE. Higher aspect ratios, shape ratios, and indentation depths cause higher contact stresses and plastic strains in UHMWPE.

  8. Wear Resistant Amorphous and Nanocomposite Coatings

    SciTech Connect

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  9. Unveiling Ultra-High Temperature Wear and Indentation Damage Mechanisms of Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Bumgardner, Clifton; Li, Xiaodong

    2015-12-01

    Thermal barrier coatings are necessary to protect turbine blades within jet engines from extreme environments that the substrate material may not be capable of withstanding. Therefore, failure of the coating due to wear during its operational lifecycle is a critical event. In order to understand the failure mechanisms of the coating layers, a zirconia-based coating on a nickel alloy substrate was subjected to wear testing to simulate pressure and temperature conditions within a jet engine. Using a Hertzian contact model, the maximum shear and its depth were determined and analyzed in conjunction with the coating material properties and scanning electron microscopy and energy dispersive x-ray spectrometry images. The coupled imaging and contact model analyses made possible the identification of the location and time of delamination and its underlying causes. Our findings provide key insights for the development of more resilient thermal barrier coatings.

  10. Comparison of Periprosthetic Tissue Digestion Methods for Ultra-High Molecular Weight Polyethylene Wear Debris Extraction

    PubMed Central

    Baxter, R.M.; Steinbeck, M.J.; Tipper, J.L.; Parvizi, J.; Marcolongo, M.; Kurtz, S.M.

    2009-01-01

    There is considerable interest in characterization of wear debris from polyethylene (UHMWPE) bearing components used in total joint replacement. To isolate UHMWPE wear debris, tissue samples must be excised from regions adjacent to revised UHMWPE implant components, followed by exposure to one of many available tissue digestion methods. Numerous studies demonstrate successful digestion, but the relative efficiency of each method is not clear. The purpose of this study was to evaluate a variety of conditions for tissue digestion to provide a quantitative comparison of methods. Porcine and human hip tissues were exposed for 24 hr to basic, acidic or enzymatic agents, filtered and digestion efficiency calculated based on the percentage of initial to final tissue weight. Of the conditions tested, 5M NaOH, 5M KOH, 15M KOH or 15.8M HNO3 yielded the most complete porcine hip tissue digestion (<1% residual tissue weight; p<0.05). Proteinase K and Liberase Blendzyme 3 did not effectively digest tissue in a 24 hour period. Similar to results from the porcine dataset, human tissues digestion was most efficient using 5M NaOH, 5M KOH or 15.8M HNO3 (<1% residual tissue weight; p<0.05). To verify that particle surface modifications did not occur after prolonged reagent exposure, GUR415 and Ceridust 3715 particles were immersed in each solution for 24 hours. Overall, this study provides a framework for thorough and efficient digestive methods for UHMWPE wear debris extraction. PMID:19507139

  11. Ultralow wear of gallium nitride

    NASA Astrophysics Data System (ADS)

    Zeng, Guosong; Tan, Chee-Keong; Tansu, Nelson; Krick, Brandon A.

    2016-08-01

    Here, we reveal a remarkable (and surprising) physical property of GaN: it is extremely wear resistant. In fact, we measured the wear rate of GaN is approaching wear rates reported for diamond. Not only does GaN have an ultralow wear rate but also there are quite a few experimental factors that control the magnitude of its wear rate, further contributing to the rich and complex physics of wear of GaN. Here, we discovered several primary controlling factors that will affect the wear rate of III-Nitride materials: crystallographic orientation, sliding environment, and coating composition (GaN, InN and InGaN). Sliding in the ⟨ 1 2 ¯ 10 ⟩ is significantly lower wear than ⟨ 1 1 ¯ 00 ⟩ . Wear increases by 2 orders of magnitude with increasing humidity (from ˜0% to 50% RH). III-Nitride coatings are promising as multifunctional material systems for device design and sliding wear applications.

  12. High frequency circular translation pin-on-disk method for accelerated wear testing of ultrahigh molecular weight polyethylene as a bearing material in total hip arthroplasty.

    PubMed

    Saikko, Vesa

    2015-01-21

    The temporal change of the direction of sliding relative to the ultrahigh molecular weight polyethylene (UHMWPE) component of prosthetic joints is known to be of crucial importance with respect to wear. One complete revolution of the resultant friction vector is commonly called a wear cycle. It was hypothesized that in order to accelerate the wear test, the cycle frequency may be substantially increased if the circumference of the slide track is reduced in proportion, and still the wear mechanisms remain realistic and no overheating takes place. This requires an additional slow motion mechanism with which the lubrication of the contact is maintained and wear particles are conveyed away from the contact. A three-station, dual motion high frequency circular translation pin-on-disk (HF-CTPOD) device with a relative cycle frequency of 25.3 Hz and an average sliding velocity of 27.4 mm/s was designed. The pins circularly translated at high frequency (1.0 mm per cycle, 24.8 Hz, clockwise), and the disks at low frequency (31.4mm per cycle, 0.5 Hz, counter-clockwise). In a 22 million cycle (10 day) test, the wear rate of conventional gamma-sterilized UHMWPE pins against polished CoCr disks in diluted serum was 1.8 mg per 24 h, which was six times higher than that in the established 1 Hz CTPOD device. The wear mechanisms were similar. Burnishing of the pin was the predominant feature. No overheating took place. With the dual motion HF-CTPOD method, the wear testing of UHMWPE as a bearing material in total hip arthroplasty can be substantially accelerated without concerns of the validity of the wear simulation.

  13. Refractory lining system for high wear area of high temperature reaction vessel

    DOEpatents

    Hubble, David H.; Ulrich, Klaus H.

    1998-01-01

    A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag.

  14. Refractory lining system for high wear area of high temperature reaction vessel

    DOEpatents

    Hubble, D.H.; Ulrich, K.H.

    1998-09-22

    A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag. 10 figs.

  15. Refractory lining system for high wear area of high temperature reaction vessel

    DOEpatents

    Hubble, D.H.; Ulrich, K.H.

    1998-04-21

    A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag. 10 figs.

  16. Fractal characterization of wear-erosion surfaces

    SciTech Connect

    Rawers, J.; Tylczak, J.

    1999-12-01

    Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate. In this study stainless steel was evaluated as a function of wear erosion conditions.

  17. In vivo wear performance of highly cross-linked polyethylene vs. yttria stabilized zirconia and alumina stabilized zirconia at a mean seven-year follow-up

    PubMed Central

    2013-01-01

    Background Zirconia was introduced as an alternative to alumina for use in the femoral head. The yttria stabilized zirconia material was improved by adding alumina. We evaluated highly cross-linked polyethylene wear performance of zirconia in total hip arthroplasty. The hypothesis was that alumina stabilized zirconia could decrease highly cross-linked polyethylene wear. Methods Highly cross-linked polyethylene wear was measured with a computerized method (PolyWare) in 91 hips. The steady-state wear rates were measured based on the radiographs from the first year postoperatively to the final follow-up and were compared between hips with yttria stabilized zirconia and alumina stabilized zirconia. Results The steady-state wear rate of highly cross-linked polyethylene against zirconia was 0.02 mm/year at a mean follow-up of 7 years. No significant difference was observed between groups with yttria stabilized zirconia and alumina stabilized zirconia. Conclusions Addition of alumina to the zirconia material failed to show further reduction of highly cross-linked polyethylene wear and our hypothesis was not verified. PMID:23634809

  18. Microstructure and Wear Behavior of Atmospheric Plasma-Sprayed AlCoCrFeNiTi High-Entropy Alloy Coating

    NASA Astrophysics Data System (ADS)

    Tian, Li-Hui; Xiong, Wei; Liu, Chuan; Lu, Sheng; Fu, Ming

    2016-12-01

    Due to the advantages such as high strength, high hardness and good wear resistance, high-entropy alloys (HEAs) attracted more and more attentions in recent decades. However, most reports on HEAs were limited to bulk materials. Although a few of studies on atmospheric plasma-sprayed (APS) HEA coatings were carried out, the wear behavior, especially the high-temperature wear behavior of those coatings has not been investigated till now. Therefore, in this study, APS was employed to deposit AlCoCrFeNiTi high-entropy alloy coating using mechanically alloyed AlCoCrFeNiTi powder as the feedstock. The phase structure of the initial powder, the feedstock powder and the as-sprayed coating was examined by an x-ray diffractometer. The surface morphology of the feedstock powder and the microstructure of the as-sprayed coating were analyzed by field emission scanning electron microscopy and energy-dispersive spectroscopy. The bonding strength and the microhardness of the as-sprayed coating were tested. The wear behavior of the coating at 25, 500, 700 and 900 °C was investigated by analysis of the wear surface morphology and measurements of the volume wear rate and the coefficient of friction.

  19. The gigapixel image concept for graphic SEM documentation. Applications in archeological use-wear studies.

    PubMed

    Vergès, Josep M; Morales, Juan I

    2014-10-01

    In this paper, we propose a specific procedure to create gigapixel-like images from SEM (scanning electron microscope) micrographs. This methodology allows intensive SEM observations to be made for those disciplines that require of large surfaces to be analyzed at different scales once the SEM sessions have been completed (e.g., stone tools use-wear studies). This is also a very useful resource for academic purposes or as a support for collaborative studies, thus reducing the number of live observation sessions and the associated expense.

  20. 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.

  1. Wear of ultra-high molecular weight polyethylene (UHMWPE) in total knee prostheses: a review of key influences.

    PubMed

    McGloughlin, T M; Kavanagh, A G

    2000-01-01

    The formation and development of wear is now widely accepted as one of the major concerns in the long-term survivorship of contemporary knee prostheses in vivo. This review examines the role of surface topography, third-body debris, load, contact mechanics and material quality in the wear process. Some of the kinematic and physiological issues that need to be modelled in the development of wear testing regimes for evaluation of material combinations and geometrical combinations in total knee implant designs are considered. Wear testing procedures and some of the results from wear tests are discussed and the need to consider the impact of rolling and sliding in the study of wear in total knee components is highlighted. The dominant wear mechanisms that occur in vivo are identified and the role of these mechanisms is currently being examined experimentally at the University of Limerick wear testing machine.

  2. The wear of ultra-high molecular weight polyethylene sliding on metallic and ceramic counterfaces representative of current femoral surfaces in joint replacement.

    PubMed

    Lancaster, J G; Dowson, D; Isaac, G H; Fisher, J

    1997-01-01

    A number of studies have investigated the influence of surface roughness on the wear of ultra-high molecular weight polyethylene (UHMWPE) in total joint replacement. The results of these studies have shown that the wear factor is proportional to the counterface roughness raised to a power greater than one. In this laboratory study, the effect of surface finish of several biomaterials on the wear of UHMWPE was studied. The study was conducted using reciprocating pin-on-plate wear tests with bovine serum as a lubricant. The biomaterials investigated as the counterface material included stainless steel, cast cobalt chrome (CoCr), CoCr (ASTM F799), alumina ceramic and zirconia ceramic. The counterface topographies of the wear plates were produced using techniques representative of current manufacturing methods. The surface roughness of the wear plates was varied in the range Ra = 0.005-0.04 micron; this was representative of femoral heads and femoral knee components currently used clinically. Metals and ceramics with a similar surface roughness produced a similar wear rate of UHMWPE. For the limited range of smooth counterfaces used in this study only a moderate correlation was found between the surface roughness and the wear factors. For a change in counterface roughness Ra of 0.005 to 0.04 micron, the wear factor increased from 7.4 +/- 1.6 to 16.5 +/- 2.4 x 10(-9) mm3/N m (mean +/- standard error). This variation in counterface roughness had much less effect in wear than previously reported for rougher counterfaces. For an extended range of counterface roughness, a stronger correlation was found using an exponential function for the regression fit. The exponential function shows the benefits of decreased wear with decreased surface roughness. Although the wear rate decreased less rapidly with decreased counterface roughness for Ra values below 0.05 micron, there were significant advantages to be gained from improved femoral head roughness to below 0.01 micron Ra.

  3. Establishing a role for vancomycin powder application for prosthetic joint infection prevention-results of a wear simulation study.

    PubMed

    Qadir, Rabah; Ochsner, J Lockwood; Chimento, George F; Meyer, Mark S; Waddell, Bradford; Zavatsky, Joseph M

    2014-07-01

    Topical vancomycin powder (VP) has shown efficacy and safety in decreasing post-operative spine infections. VP use in arthroplasty has not been established. Concerns remain for third-body wear with the addition of crystalline substrate at the implant interface. The study's purpose was to compare wear behavior of CoCr on UHMWPE to identical wear couples with VP. A six-station wear simulator was utilized and cyclic articulations were run for 10 million cycles (Mc). UHMWPE wear was measured using photography, stereomicroscopy, and gravimetric measurement. There were no differences in wear mark length (P = 0.43), width (P = 0.49), or gravimetric wear at 10 Mc (P = 0.98). VP and control groups lost 0.32 and 0.33 mg, respectively. VP may have a role in PJI prevention. A well-designed clinical study is needed.

  4. Low-temperature growth of low friction wear-resistant amorphous carbon nitride thin films by mid-frequency, high power impulse, and direct current magnetron sputtering

    SciTech Connect

    Bakoglidis, Konstantinos D. Schmidt, Susann; Garbrecht, Magnus; Ivanov, Ivan G.; Jensen, Jens; Greczynski, Grzegorz; Hultman, Lars

    2015-09-15

    GPa. Nanoindentation showed a significant increase in film hardness and reduced elastic modulus with increasing V{sub s} for all techniques. The harder films were produced by MFMS with hardness as high as 25 GPa. Low friction coefficients, between 0.05 and 0.06, were recorded for all films. Furthermore, CN{sub x} films produced by MFMS and DCMS at V{sub s} = 100 and 120 V presented a high wear resistance with wear coefficients of k ≤ 2.3 × 10{sup −5} mm{sup 3}/Nm. While all CN{sub x} films exhibit low friction, wear depends strongly on the structural and mechanical characteristics of the films. The MFMS mode is best suited for the production of hard CN{sub x} films, although high compressive stresses challenge the application on steel substrates. Films grown in HiPIMS mode provide adequate adhesion due to low residual stress values, at the expense of lower film hardness. Thus, a relatively wide mechanical property envelope is presented for CN{sub x} films, which is relevant for the optimization of CN{sub x} film properties intended to be applied as low friction and wear resistant coatings.

  5. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  6. Effects of heat treatment on wear resistance and fracture toughness of duo-cast materials composed of high-chromium white cast iron and low-chromium steel

    NASA Astrophysics Data System (ADS)

    Kim, Chang Kyu; Lee, Sunghak; Jung, Jae-Young

    2006-03-01

    The objective of this study is to investigate effects of heat treatment on wear resistance and fracture toughness in duo-cast materials composed of a high-chromium white cast iron and a low-chromium steel as a wear-resistant part and a ductile part, respectively. Different size, volume fraction, and distribution of M7C3 carbides were employed in the wear-resistant part by changing the amount of chromium, and the volume fraction of martensite in the austenitic matrix was varied by the heat treatment. In the alloys containing a small amount of chromium, an interdendritic structure of eutectic M7C3 carbides was formed, and led to the improvement of wear resistance and fracture toughness. After the heat treatment, the selective wear of the matrix and the cracking or spalled-off carbides were considerably reduced since the hardness difference between carbides and matrix decreased by the increase in the matrix hardness, thereby leading to the improvement of the wear resistance. However, the fracture toughness of the heat-treated alloys was lower than that of the as-cast alloys because the matrix containing a considerable amount of martensite did not effectively prevent the crack propagation.

  7. Hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications

    SciTech Connect

    Seals, Roland D.

    2015-08-18

    The present disclosure relates generally to hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications. More specifically, the present disclosure relates to hardface coatings that include a network of titanium monoboride (TiB) needles or whiskers in a matrix, which are formed from titanium (Ti) and titanium diboride (TiB.sub.2) precursors by reactions enabled by the inherent energy provided by the process heat associated with coating deposition and, optionally, coating post-heat treatment. These hardface coatings are pyrophoric, thereby generating further reaction energy internally, and may be applied in a functionally graded manner. The hardface coatings may be deposited in the presence of a number of fluxing agents, beta stabilizers, densification aids, diffusional aids, and multimode particle size distributions to further enhance their performance characteristics.

  8. Fractal characterization of wear-erosion surfaces

    SciTech Connect

    Rawers, James C.; Tylczak, Joseph H.

    1999-12-01

    Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate.

  9. Friction and wear behaviour of self lubricating bearing liners

    NASA Astrophysics Data System (ADS)

    Gay, Russell

    The thesis describes a numerical model for evaluating the variation of friction and wear of a self lubricating bearing liner over its useful wear life. Self-lubricating bearings have been in widespread use since the mid-1950s, particularly in the aerospace industry where they have the advantage of being low maintenance components. They are commonly used in relatively low speed, reciprocating applications such as control surface actuators, and usually consist of a spherical bearing with the inner and outer elements separated by a composite textile resin-bonded liner. A finite element model has been developed to predict the local stiffness of a particular liner at different states of wear. Results obtained using the model were used to predict the overall friction coefficient as it evolves due to wear, which is a novel approach. Experimental testing was performed on a bespoke flat-on-flat wear test rig with a reciprocating motion to validate the results of the friction model.. These tests were carried out on a commercially-available bearing liner, predominantly at a high contact pressure and an average sliding speed of 0.2 ms-1. Good agreement between predicted and experimentally measured wear was obtained when appropriate coefficients of friction were used in the friction model, and when the reciprocating sliding distance was above a critical value. A numerical wear model was also developed to predict the trend of backlash development in real bearing geometries using a novel approach. Results from the wear model were validated against full-scale bearing tests carried out elsewhere by the sponsoring company. Good agreement was obtained between the model predictions and the experimental results for the first 80% of the bearing wear life, and explanations for the discrepancy during the last 20% of the wear life have been proposed..

  10. Effect of load on the friction-wear behavior of magnetron sputtered DLC film at high temperature

    NASA Astrophysics Data System (ADS)

    Ze, Sun; Dejun, Kong

    2017-01-01

    A DLC (diamond-like carbon) film was deposited on a YT14 cemented carbide cutting tool by using magnetron sputtering. The surface-interfacial morphologies, chemical composition, and phases of the obtained DLC film were analyzed by using scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction, respectively. The friction and wear characteristics of the DLC film were investigated under different loads, the distribution of the chemical elements on the worn tracks were analyzed by using a plane scan analysis, and the wear mechanism of the DLC film was also examined. The results showed that the DLC particles were uniformly covered on the substrate with a thickness of about 600 nm, and the diamond peaks at the crystal face of (1 1 1), and (2 2 0) appear at diffraction angles of 44.40, and 75.52°, respectively. The average coefficients of friction of the DLC film under loads of 2, 4, and 6 N were 0.65, 0.65, and 0.49, respectively, and the corresponding wear rates were 0.33  ×  10‑9, 0.26  ×  10‑9, and 0.25  ×  10‑9 mm3 N‑1 s‑1, respectively. Therefore, the film represents outstanding reducing friction and wear resistance. With the increasing wear loads, the atomic fraction of C decreased, while that of O increased; the oxidation reaction occurred in the wear test. The wear mechanisms under a load of 2 N were abrasive wear, adhesive wear and oxidation wear, while that under a load of 4 N were adhesive wear and oxidation wear, and that under the load of 6 N were only oxidation wear.

  11. Optimization of the EMS process parameters in compocasting of high-wear-resistant Al-nano-TiC composites

    NASA Astrophysics Data System (ADS)

    Shamsipour, Majid; Pahlevani, Zahra; Shabani, Mohsen Ostad; Mazahery, Ali

    2016-04-01

    Understanding of the electromagnetic stirrer (EMS) process parameters-wear relation in nanocomposite is required for further creation of tailored modifications of process in accordance with the demands for various applications. This study depicts the performance of hybrid algorithm for optimization of the parameters in EMS compocasting of nano-TiC-reinforced Al-Si alloys. Adaptive neuro-fuzzy inference system (ANFIS) coupled with particle swarm optimization (PSO) was applied to find the optimum combination of the inputs including mold temperature, mix time, impeller speed, powder temperature, cast temperature and average particle size. The optimized condition was obtained in minimization of objective function. The objective function is calculated by ANFIS and then minimized by PSO. The optimized parameters were used to produce semisolid cast aluminum matrix composites reinforced with nano-TiC particles. The optimized nanocomposites were then studied for their tribological properties.

  12. Ultra-high molecular weight polyethylene wear debris generated in vivo and in laboratory tests; the influence of counterface roughness.

    PubMed

    Hailey, J L; Ingham, E; Stone, M; Wroblewski, B M; Fisher, J

    1996-01-01

    The objective of this study was to investigate the effect of counterface roughness and lubricant on the morphology of ultra-high molecular weight polyethylene (UHMWPE) wear debris generated in laboratory wear tests, and to compare this with debris isolated from explanted tissue. Laboratory tests used UHMWPE pins sliding against stainless steel counterfaces. Both water and serum lubricants were used in conjunction with rough and smooth counterfaces. The lubricants and tissue from revision hip surgery were processed to digest the proteins and permit filtration. This involved denaturing the proteins with potassium hydroxide (KOH), sedimentation of any remaining proteins, and further digestion of these proteins with chromic acid. All fractions were then passed through a 0.2 micron membrane, and the debris examined using scanning electron microscopy. The laboratory studies showed that the major variable influencing debris morphology was counterface roughness. The rougher counterfaces produced larger numbers of smaller particles, with a size range extending below 1 micron. For smooth counterfaces there were fewer of these small particles, and evidence of larger platelets, greater than 10 microns in diameter. Analysis of the debris from explanted tissues showed a wide variation in the particle size distribution, ranging from below 1 micron up to several millimetres in size. Of major clinical significance in relation to osteolysis and loosening is roughening of the femoral components, which may lead to greater numbers of the sub-micron-sized particles.

  13. The rates of wear of X3 highly cross-linked polyethylene at five years when coupled with a 36 mm diameter ceramic femoral head in young patients.

    PubMed

    Selvarajah, E; Hooper, G; Grabowski, K; Frampton, C; Woodfield, T B F; Inglis, G

    2015-11-01

    Polyethylene wear debris can cause osteolysis and the failure of total hip arthroplasty. We present the five-year wear rates of a highly cross-linked polyethylene (X3) bearing surface when used in conjunction with a 36 mm ceramic femoral head. This was a prospective study of a cohort of 100 THAs in 93 patients. Pain and activity scores were measured pre- and post-operatively. Femoral head penetration was measured at two months, one year, two years and at five years using validated edge-detecting software (PolyWare Auto). At a mean of 5.08 years (3.93 to 6.01), 85 hips in 78 patients were available for study. The mean age of these patients was 59.08 years (42 to 73, the mean age of males (n = 34) was 59.15 years, and females (n = 44) was 59.02 years). All patients had significant improvement in their functional scores (p < 0.001). The steady state two-dimensional linear wear rate was 0.109 mm/year. The steady state volumetric wear rate was 29.61 mm(3)/year. No significant correlation was found between rate of wear and age (p = 0.34), acetabular component size (p = 0.12) or clinical score (p = 0.74). Our study shows low steady state wear rates at five years in X3 highly cross-linked polyethylene in conjunction with a 36 mm ceramic femoral head. The linear wear rate was almost identical to the osteolysis threshold of 0.1 mm/year recommended in the literature.

  14. Quantification of the effect of cross-shear and applied nominal contact pressure on the wear of moderately cross-linked polyethylene.

    PubMed

    Abdelgaied, Abdellatif; Brockett, Claire L; Liu, Feng; Jennings, Louise M; Fisher, John; Jin, Zhongmin

    2013-01-01

    Polyethylene wear is a great concern in total joint replacement. It is now considered a major limiting factor to the long life of such prostheses. Cross-linking has been introduced to reduce the wear of ultra-high-molecular-weight polyethylene (UHMWPE). Computational models have been used extensively for wear prediction and optimization of artificial knee designs. However, in order to be independent and have general applicability and predictability, computational wear models should be based on inputs from independent experimentally determined wear parameters (wear factors or wear coefficients). The objective of this study was to investigate moderately cross-linked UHMWPE, using a multidirectional pin-on-plate wear test machine, under a wide range of applied nominal contact pressure (from 1 to 11 MPa) and under five different kinematic inputs, varying from a purely linear track to a maximum rotation of +/- 55 degrees. A computational model, based on a direct simulation of the multidirectional pin-on-plate wear tester, was developed to quantify the degree of cross-shear (CS) of the polyethylene pins articulating against the metallic plates. The moderately cross-linked UHMWPE showed wear factors less than half of that reported in the literature for, the conventional UHMWPE, under the same loading and kinematic inputs. In addition, under high applied nominal contact stress, the moderately crosslinked UHMWPE wear showed lower dependence on the degree of CS compared to that under low applied nominal contact stress. The calculated wear coefficients were found to be independent of the applied nominal contact stress, in contrast to the wear factors that were shown to be highly pressure dependent. This study provided independent wear data for inputs into computational models for moderately cross-linked polyethylene and supported the application of wear coefficient-based computational wear models.

  15. The influence of bone and bone cement debris on counterface roughness in sliding wear tests of ultra-high molecular weight polyethylene on stainless steel.

    PubMed

    Caravia, L; Dowson, D; Fisher, J; Jobbins, B

    1990-01-01

    Studies of explanted hip prostheses have shown high wear rates of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups and roughening of the surface of the metallic femoral head. Bone and bone cement particles have also been found in the articulating surfaces of some joints. It has been proposed that bone or bone cement particles may cause scratching and deterioration in the surface finish of metallic femoral heads, thus producing increased wear rates and excessive amounts of wear debris. Sliding wear tests of UHMWPE pins on stainless steel have been performed with particles of different types of bone and bone cement added. Damage to the stainless steel counterface and the motion of particles through the interface have been studied. Particles of bone cement with zirconium and barium sulphate additives and particles of cortical bone scratched the stainless steel counterface. The cement particles with zirconium additive produced significantly greater surface damage. The number of particles entering the contact and embedding in the UHMWPE pin was dependent on particle size and geometry, surface roughness and contact stress. Particles are likely to cause surface roughening and increased wear rates in artificial joints.

  16. Application of high-rate cutting tools

    NASA Astrophysics Data System (ADS)

    Moriarty, John L., Jr.

    1989-03-01

    Widespread application of the newest high-rate cutting tools to the most appropriate jobs is slowed by the sheer magnitude of developments in tool types, materials, workpiece applications, and by the rapid pace of change. Therefore, a study of finishing and roughing sizes of coated carbide inserts having a variety of geometries for single point turning was completed. The cutting tools were tested for tool life, chip quality, and workpiece surface finish at various cutting conditions with medium alloy steel. An empirical wear-life data base was established, and a computer program was developed to facilitate technology transfer, assist selection of carbide insert grades, and provide machine operating parameters. A follow-on test program was implemented suitable for next generation coated carbides, rotary cutting tools, cutting fluids, and ceramic tool materials.

  17. Wear particle analysis from grease lubricated bearings

    SciTech Connect

    Rosenlieb, W.; Maciejewski, A.S.

    1980-11-01

    Ferrographic analysis has been shown to be useful in evaluating the wear/state condition of grease lubricated components. The major achievement was the successful application of dissolving the grease utilizing a solvent mixture and making ferrograms of equal quality as to that found in oil analysis. The types of wear particles found in used grease samples are comparative to those found in oil lubricated systems. Work is presently being performed on grease lubricated taper roller bearings, similar to the test conditions utilized in this study. The analysis of the grease samples was qualitative vs quantitative. Due to the uneven distribution of wear particulate in the grease and the relatively small amount of grease used in making the ferrograms. The primary emphasis was placed upon size distribution, morphology and elemental composition. The results of the ferrogram analysis showed a good correlation to those of the SKF personnel in terms of monitoring the wear state/condition of the bearings throughout their life. However, the on-condition monitoring of grease lubricated components in the field, is complicated by the physical location of the components and inaccessibility by maintenance personnel to remove grease samples. Where accessibility is no problem, this technique is highly recommended. As it appears presently, this analysis technique seems best suited to the examination of grease obtained from dismantled grease lubricated components or in design applications.

  18. Adverse events in allergy sufferers wearing contact lenses

    PubMed Central

    Urgacz, Agnieszka; Mrukwa, Ewa

    2015-01-01

    Allergy is the fifth leading chronic condition in industrialized countries among all ages, and the third most common chronic disease among children under 18 years old. Many of allergic patients also have problems with vision and want to improve their quality of life by wearing contact lenses. They are most frequently young and active individuals, for whom contact lenses provide greater convenience and more satisfying vision correction than spectacles. However, application of high quality and immunologically neutral products do not protect from allergic side reactions. Nowadays, eye-related allergy and contact lens wear concern larger and larger populations worldwide. The purpose of this review is to summarize the studies on ocular complications associated with wearing contact lenses. The article presents indications for allergic patients especially on the care system and wear schedule. PMID:26161062

  19. Patients presenting with miliaria while wearing flame resistant clothing in high ambient temperatures: a case series

    PubMed Central

    2011-01-01

    Introduction Clothing can be a cause of occupational dermatitis. Frequent causes of clothing-related dermatological problems can be the fabric itself and/or chemical additives used in the laundering process, friction from certain fabrics excessively rubbing the skin, or heat retention from perspiration-soaked clothing in hot working environments. To the best of our knowledge, these are the first reported cases of miliaria rubra associated with prolonged use of flame resistant clothing in the medical literature. Case presentation We report 18 cases (14 men and 4 women, with an age range of 19 to 37 years) of moderate to severe skin irritation associated with wearing flame resistant clothing in hot arid environments (temperature range: 39 to 50°C, 5% to 25% relative humidity). We describe the medical history in detail of a 23-year-old Caucasian woman and a 31-year-old African-American man. A summary of the other 16 patients is also provided. Conclusions These cases illustrate the potential serious nature of miliaria with superimposed Staphylococcus infections. All 18 patients fully recovered with topical skin treatment and modifications to their dress ensemble. Clothing, in particular blend fabrics, must be thoroughly laundered to adequately remove detergent residue. While in hot environments, individuals with sensitive skin should take the necessary precautions such as regular changing of clothing and good personal hygiene to ensure that their skin remains as dry and clean as possible. It is also important that they report to their health care provider as soon as skin irritation or rash appears to initiate any necessary medical procedures. Miliaria rubra can take a week or longer to clear, so removal of exposure to certain fabric types may be necessary. PMID:21939537

  20. Synthesis of High-Temperature Self-lubricating Wear Resistant Composite Coating on Ti6Al4V Alloy by Laser Deposition

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Liu, Xiu-Bo; Xiang, Zhan-Feng; Shi, Shi-Hong; Chen, Yao; Shi, Gao-Lian; Wu, Shao-Hua; Wu, Yu-Nan

    2015-05-01

    Laser deposition was adopted to prepare novel Ni-based solid solution (γ-NiCrAlTi)/ TiC/α-Ti/CaF2 high-temperature self-lubricating wear resistant composite coating on Ti6Al4V alloy. Microstructure, micro-hardness, wear behavior, and counter-body effect of the coating were investigated systematically. It can be seen that the coating mainly consists of γ-NiCrAlTi, TiC, α-Ti, and small fine CaF2 particles. Average micro-hardness of the coating is 1023 HV0.3, which is about three-factor higher than that of Ti6Al4V substrate (380 HV0.3). The friction coefficient and wear rate of the coating decrease at all test temperatures to different extents with respect to the substrate. The improvement in wear resistance is believed to be the combined effects of the γ-NiCrAlTi solid solution, the dominating anti-wear capabilities of the reinforced TiC carbides, and the self-lubricating property of CaF2.

  1. The effects of peroxide content on the wear behavior, microstructure and mechanical properties of peroxide crosslinked ultra-high molecular weight polyethylene used in total hip replacement.

    PubMed

    Gul, Rizwan M

    2008-06-01

    The wear of the ultra-high molecular weight polyethylene (UHMWPE) acetabular components and wear debris induced osteolysis are the major causes of failure in total hip replacements. Crosslinking has been shown to improve the wear resistance of UHMWPE by producing a network structure, resisting the plastic deformation of the surface layer. In this study organic peroxides were used to crosslink two different types of UHMWPE resins, using hot isostatic pressing as the processing method. The effects of peroxide content on the different properties were investigated, along with the effect of the crosslink density on the wear behavior. An increase in peroxide content decreases the melting point and the degree of crystallinity, which results in a decrease in the yield strength. The ultimate tensile strength remains essentially unchanged. The molecular weight between crosslinks decreases with an increase in the peroxide content and reaches a saturation limit at around 0.3-0.5 weight percent peroxide, its value at the saturation limit is a function of the virgin resin used for processing. The wear rate decreases linearly with the increase in crosslink density.

  2. Comparison of 10-year clinical wear of annealed and remelted highly cross-linked polyethylene: A propensity-matched cohort study.

    PubMed

    Hamai, Satoshi; Nakashima, Yasuharu; Mashima, Naohiko; Yamamoto, Takuaki; Kamada, Tomomi; Motomura, Goro; Imai, Hiroshi; Fukushi, Jun-Ichi; Miura, Hiromasa; Iwamoto, Yukihide

    2016-06-01

    No previous studies comparing the clinical wear rates of the two different kinds of cross-linked ultra-high-molecular-weight polyethylene (XLPE), annealed and remelted, are available. We compared the creep and steady wear rates of 36 matched pairs (72 hips in total) adjusting for baseline characteristics with propensity score matching techniques. Zirconia femoral heads with 26-mm diameter were used in all cases. The femoral-head cup penetration was measured digitally on radiographs. Significantly greater creep (p=0.006) was detected in the remelted (0.234mm) than annealed (0.159mm) XLPE. However, no significant difference (p=0.19) was found between the steady wear rates (0.003 and 0.008mm/year, respectively) of the annealed and remelted XLPE. Multiple regression analyses showed that remelted XLPE is significant independent variable (p<0.001) that is positively associated with creep. However, the patient age and body weight, cup size, the liner thickness, cup inclination, follow-up periods, and postoperative Merle d'Aubigné hip score had no significant effects (p>0.05) on the steady wear rates. No patients exhibited above the osteolysis threshold of 0.1mm/year, progressive radiolucencies, osteolysis, or polyethylene fracture. This propensity-matched cohort study document no significant difference in wear resistant performances of annealed and remelted XLPE over an average period of 10 years.

  3. Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

    SciTech Connect

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

    2011-01-17

    The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

  4. High-temperature frictional wear behavior of MCrAlY-based coatings deposited by atmosphere plasma spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Song, Xiu

    2017-02-01

    Al2O3-Cr2O3/NiCoCrAlYTa coatings were prepared via atmosphere plasma spraying (APS). The microstructure and phase composition of the coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser confocal scanning microscopy (LSCM), and transmission electron microscopy (TEM). The dry frictional wear behavior of the coatings at 500°C in static air was investigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approximately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhesive wear.

  5. Needs and challenges in precision wear measurement

    SciTech Connect

    Blau, P.J.

    1996-01-10

    Accurate, precise wear measurements are a key element in solving both current wear problems and in basic wear research. Applications range from assessing durability of micro-scale components to accurate screening of surface treatments and thin solid films. Need to distinguish small differences in wear tate presents formidable problems to those who are developing new materials and surface treatments. Methods for measuring wear in ASTM standard test methods are discussed. Errors in using alterate methods of wear measurement on the same test specimen are also described. Human judgemental factors are a concern in common methods for wear measurement, and an experiment involving measurement of a wear scar by ten different people is described. Precision in wear measurement is limited both by the capabilities of the measuring instruments and by the nonuniformity of the wear process. A method of measuring wear using nano-scale indentations is discussed. Current and future prospects for incorporating advanced, higher-precision wear measurement methods into standards are considered.

  6. Active wear and failure mechanisms of TiN-coated high speed steel and TiN-coated cemented carbide tools when machining powder metallurgically made stainless steels

    SciTech Connect

    Jiang, L.; Haenninen, H.; Paro, J.; Kauppinen, V.

    1996-09-01

    In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

  7. Active wear and failure mechanisms of TiN-Coated high speed steel and tin-coated cemented carbide tools when machining powder metallurgically made stainless steels

    NASA Astrophysics Data System (ADS)

    Jiang, Laizhu; Hänninen, Hannu; Paro, Jukka; Kauppinen, Veijo

    1996-09-01

    In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

  8. Is the wear factor in total joint replacements dependent on the nominal contact stress in ultra-high molecular weight polyethylene contacts?

    PubMed

    Vassiliou, K; Unsworth, A

    2004-01-01

    The exact dependence of wear factor on contact stress, load and apparent contact area is much disputed in the literature. This study attempts to solve this dispute. Pin-on-plate studies of ultra high molecular weight polyethylene against stainless steel were conducted under different combinations of load (33-250 N), nominal stress (0.56-12.73 MPa) and face diameter, as well as two tests where both stress and load were kept constant, while the diameter was changed. For these tests the centre of the pin face was bored out to create four different average pin diameters with similar face areas. Diameter and load were found to have no significant effect on the wear factor, while the wear factor decreased with increasing contact stress according to the relation K = 2 x 10(-6) sigma(-0.84).

  9. 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.

  10. The Changes of COP and Foot Pressure after One Hour's Walking Wearing High-heeled and Flat Shoes.

    PubMed

    Ko, Dong Yeol; Lee, Han Suk

    2013-10-01

    [Purpose] This study aimed to determine the most appropriate height for shoe heels by measuring the displacement of the COP (center of pressure) and changes in the distribution of foot pressure after walking in flat (0.5 cm), middle-heeled (4 cm), and high-heeled (9 cm) shoes for 1 hour. [Methods] A single-subject design was used, with 15 healthy women wearing shoes with heels of each height in a random order. The foot pressure and displacement of COP before and after walking in an ordinary environment for 1 hour were measured using an FDM-S (zebris Medical GmbH, Germany). [Results] The distribution of foot pressure did not change significantly after walking in middle-heeled (4 cm) shoes but did change significantly after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. Similarly, the COP was not significantly displaced after walking in middle-heeled (4 cm) shoes but was significantly displaced after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. [Conclusion] Both flat and high-heeled shoes had adverse effects on the body. Middle-heeled (4 cm) shoes are preferable to both flat (0.5 cm) and high-heeled (9 cm) shoes for the health and comfort of the feet.

  11. The Changes of COP and Foot Pressure after One Hour's Walking Wearing High-heeled and Flat Shoes

    PubMed Central

    Ko, Dong Yeol; Lee, Han Suk

    2013-01-01

    [Purpose] This study aimed to determine the most appropriate height for shoe heels by measuring the displacement of the COP (center of pressure) and changes in the distribution of foot pressure after walking in flat (0.5 cm), middle-heeled (4 cm), and high-heeled (9 cm) shoes for 1 hour. [Methods] A single-subject design was used, with 15 healthy women wearing shoes with heels of each height in a random order. The foot pressure and displacement of COP before and after walking in an ordinary environment for 1 hour were measured using an FDM-S (zebris Medical GmbH, Germany). [Results] The distribution of foot pressure did not change significantly after walking in middle-heeled (4 cm) shoes but did change significantly after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. Similarly, the COP was not significantly displaced after walking in middle-heeled (4 cm) shoes but was significantly displaced after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. [Conclusion] Both flat and high-heeled shoes had adverse effects on the body. Middle-heeled (4 cm) shoes are preferable to both flat (0.5 cm) and high-heeled (9 cm) shoes for the health and comfort of the feet. PMID:24259782

  12. Wear Resistant Carbide-based Thermal Sprayed Coatings: Process, Properties, Mechanical Degradation and Wear

    NASA Astrophysics Data System (ADS)

    Ghabchi, Arash

    Thermally sprayed ceramic-metallic composite (CerMet) materials consist of ceramic particles mainly in form of carbides reinforced by metallic binder exhibit unique microstructural and mechanical characteristics. Such structure brings in a novel combination of hardness and toughness enabling application of this class of material in wear resistant surfaces. Final deposit microstructure that defines the mechanical properties and wear performance of material depends on process parameters and starting material characteristics. Complex interaction of in-flight particles with supersonic flame, formation of complex defective deposit structure comprising of pores, cracks and splat boundaries make comprehending of interrelation of process, microstructure, properties and performance a difficult task. Additional challenge is development of systematic understanding on mechanical degradation, damage and wear mechanisms of cermet coatings due to their complex structure. This dissertation attempts to address these issues first by taking a systematic step by step approach, process map, to establish a correlation between process, particle state, microstructure and properties. Different strategies were proposed and examined to control the high velocity thermal spray process. This strategy assessment enabled a better control over in-flight particles state in high velocity thermal spray process and provided better understanding on interaction of in-flight particles with the flame. Further, possible advantages of reducing the carbide particle size from micron to nano in terms of mechanical properties and different wear performance were explored. It was suggested that poor wear performance of nano-structured coating is due to presence of brittle phases and less available binder promotes the excessive stress detrimental to load carrying capability of material. Material damage and wear mechanisms of coating under different tribological conditions were examined. The results suggest a

  13. Wear performance of neat and vitamin E blended highly cross-linked PE under severe conditions: The combined effect of accelerated ageing and third body particles during wear test.

    PubMed

    Affatato, Saverio; De Mattia, Jonathan Salvatore; Bracco, Pierangiola; Pavoni, Eleonora; Taddei, Paola

    2016-12-01

    The objective of this study is to evaluate the effects of third-body particles on the in vitro wear behaviour of three different sets of polyethylene acetabular cups after prolonged testing in a hip simulator and accelerated ageing. Vitamin E-blended, cross-linked polyethylene (XLPE_VE), cross-linked polyethylene (XLPE) and conventional polyethylene (STD_PE) acetabular cups were simulator tested for two million cycles under severe conditions (i.e. by adding third-body particles to the bovine calf serum lubricant). Micro-Fourier Transform Infrared and micro-Raman spectroscopic analyses, differential scanning calorimetry, and crosslink density measurements were used to characterize the samples at a molecular level. The STD_PE cups had twice mass loss than the XLPE_VE components and four times than the XLPE samples; statistically significant differences were found between the mass losses of the three sets of cups. The observed wear trend was justified on the basis of the differences in cross-link density among the samples (XLPE>XLPE_VE>STD_PE). FTIR crystallinity profiles, bulk DSC crystallinity and surface micro-Raman crystallinity seemed to have a similar behaviour upon testing: all of them (as well as the all-trans and ortho-trans contents) revealed the most significant changes in XLPE and XLPE_VE samples. The more severe third-body wear testing conditions determined more noticeable changes in all spectroscopic markers with respect to previous tests. Unexpectedly, traces of bulk oxidation were found in both STD_PE (unirradiated) and XLPE (remelting-stabilized), which were expected to be stable to oxidation; on the contrary, XLPE_VE demonstrated a high oxidative stability in the present, highly demanding conditions.

  14. Low-wear partially fluorinated polyimides

    SciTech Connect

    Fusaro, R.L.; Hady, W.F.

    1985-10-01

    Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)pgenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid(BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes. 28 references.

  15. Low-wear partially fluorinated polyimides

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Hady, W. F.

    1985-01-01

    Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)pgenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid (BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes.

  16. Thermal and Melt Wear Characterization of Materials in Sliding Contact at High Speed

    DTIC Science & Technology

    2014-03-01

    at high speeds . The high speed air flow will have a convective heating effect on the slipper. If the slipper were in constant contact with the rail...resulting from the high speed air flow also occurs on the top and front faces of the slipper. The cumulative effects of conductive frictional and...observe the effects of 11 convective heating in uniformly defined regions over the course of a modeled run. The speed of the air in the gap is assumed to

  17. New Mechanisms of rock-bit wear in geothermal wells

    SciTech Connect

    Macini, Paolo

    1996-01-24

    This paper presents recent results of an investigation on failure mode and wear of rock-bits used to drill geothermal wells located in the area of Larderello (Italy). A new wear mechanism, conceived from drilling records and dull bit evaluation analysis, has been identified and a particular configuration of rock-bit has been developed and tested in order to reduce drilling costs. The role of high Bottom Hole Temperature (BHT) on rock-bit performances seems not yet very well understood: so far, only drillability and formation abrasiveness are generally considered to account for poor drilling performances. In this paper, the detrimental effects of high BHT on sealing and reservoir system of Friction Bearing Rock-bits (FBR) have been investigated, and a new bearing wear pattern for FBR's run in high BHT holes has been identified and further verified via laboratory inspections on dull bits. A novel interpretation of flat worn cutting structure has been derived from the above wear pattern, suggesting the design of a particular bit configuration. Test bits, designed in the light of the above criteria, have been prepared and field tested successfully. The paper reports the results of these tests, which yielded a new rock-bit application, today considered as a standad practice in Italian geothermal fields. This application suggests that the correct evaluation of rock-bit wear can help to improve the overall drilling performances and to minimize drilling problems through a better interpretation of the relationships amongst rock-bits, formation properties and downhole temperature.

  18. Friction and Wear

    NASA Technical Reports Server (NTRS)

    Pomey, Jacques

    1952-01-01

    From the practical point of view, this analysis shows that each problem of friction or wear requires its particular solution. There is no universal solution; one or other of the factors predominates and defines the choice of the solution. In certain cases, copper alloys of great thermal conductivity are preferred; in others, plastics abundantly supplied with water. Sometimes, soft antifriction metals are desirable to distribute the load; at other times, hard metals with high resistance to abrasion or heat.

  19. Polymer Wear Modes.

    DTIC Science & Technology

    1977-10-01

    first was the rubbing of Nylon 6—6, Nylon 11, Delrin 500, Delrin AF, and ultra—high molecular weight polyethylene ( UHMWPE ) against 440C stainless steel...strength at* T T Measured Time to Temperature ofPolymer . room temp. _~~ _i ~2!~ U severe wear counterface substrate UHMWP E 24.1 MPa 140°C 400°C -1.47 rn/s

  20. 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.

  1. Graphitic polymer nanocomposites: Wear performance and wear debris analysis

    NASA Astrophysics Data System (ADS)

    Liu, Tian

    With the addition of appropriate nanofillers, nanocomposites have been shown to be an effective avenue to achieve a multitude of enhanced properties, even extending to multi-functionalities not normally considered possible for conventional polymer materials. However, the structure and properties of polymeric nanocomposites can be influenced by some environmental factors in practical use, such as wear and temperature, due to the nature of viscoelasticity of polymer matrix. The large interfacial areas exist between matrix and nanofillers are also susceptible to the wear/temperature-related changes. In this work, I was devoted to developing high wear and/or thermal performance graphitic nanofiller reinforced high density polyethylene (HDPE) composites. Two critical issues, including appropriate filler-matrix interactions and proper dispersion of the nano-reinforcement, were addressed through the effective nanofiller surface modification. Wear, thermal and mechanical properties of the resultant nanocomposites were systematically investigated. Meanwhile, the wear debris generated on the sliding surface of composite materials was analyzed morphologically and quantitatively. In particular, the research regarding the possibility of determining the effects of wear and thermal processes on the nanocomposites by detecting dielectric signals over the lifetime of polymeric materials was conducted. Correlations that exist between effects of wear or thermal processes and dielectric properties of the nanocomposites were then explored. Based on the studies of HDPE nanocomposites, high quality ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite reinforced by graphitic nanofillers was finally extended in this thesis. UHMWPE is an extremely viscous polymer and thus cannot be processed conventionally, typically resulting in dispersion issues far worse than that of other composite systems. The research presented aims at solving the issue by using ultrasonication-assisted melt

  2. Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

    NASA Astrophysics Data System (ADS)

    Zhao, Hang; Li, Jian-jun; Zheng, Zhi-zhen; Wang, Ai-hua; Huang, Qi-wen; Zeng, Da-wen

    2015-12-01

    In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350-400 µm thickness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti-Fe alloy powder. Microhardness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the samples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstructure and to the presence of TiC particles.

  3. Tribological characteristics of polyethylene glycol (PEG) as a lubricant for wear resistance of ultra-high-molecular-weight polyethylene (UHMWPE ) in artificial knee join.

    PubMed

    Kobayashi, Masanori; Koide, Takayuki; Hyon, Suong-Hyu

    2014-10-01

    For the longevity of total knee joint prostheses, we have developed an artificial lubricant using polyethylene glycol (PEG) for the prevention of wear of ultra-high-molecular-weight polyethylene (UHMWPE). In the present study, the lubricative function of this PEG lubricant was evaluated by a wear test using Co-Cr alloy and UHMWPE counter surface samples. As a result, human synovial fluid including the PEG lubricant showed good result regarding the wear volume and a worn surface of UHMWPE. Considering its lubrication mechanism, it is suspected that interaction between the PEG molecules and the proteins in synovial fluid was involved. Since PE molecules are also organic compounds having a hydroxyl group at one or both ends, the albumin and PEG molecule complex would have bound more strongly to the metal oxide surface and UHMWPE surfaces might enhance and stabilize the lubricating film between the contact surfaces under the boundary lubrication. This study suggests that PEG lubricant as an intra-articular viscous supplement has the potential to prevent wear of UHMWPE by mixing with synovial fluid and to contribute to the longevity of knee joint prostheses.

  4. The Use of Various Failure Criteria as Applied to High Speed Wear

    DTIC Science & Technology

    2011-12-01

    to the analytical model developed in this thesis. This conversion method and application of Wolfson’s data is described in greater detail in Section...Grüneisen EOS, and the tabular Sesame EOS. Vanderhyde’s [34] research provides insight to the two EOS models internal to CTH. Much of the infor- mation...2.20) Γ = 3Kvα Cv (2.21) 2.8.2.2 Sesame EOS. CTH also provides the Sesame equation of state. The Sesame EOS is a set of tabular data collected

  5. 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.

  6. Wear of engineering materials

    SciTech Connect

    Hawk, J.A.

    1998-12-31

    Nearly 60 papers discuss fundamental and applied research in the areas of wear, erosion and wear-corrosion of materials. Focus is on ceramics, ceramic and polymer-matrix composites, and coatings; the effect of sliding wear and wear-corrosion of materials in manufacturing processes, automobiles and bearings; and wear and erosion of materials used in fossil-fuel power plants, minerals processing and heavy manufacturing.

  7. Intelligent Detection of Drill Wear

    NASA Astrophysics Data System (ADS)

    Liu, T. I.; Chen, W. Y.; Anatharaman, K. S.

    1998-11-01

    Backpropagation neural networks (BPNs) were used for on-line detection of drill wear. The neural network consisted of three layers: input, hidden, and output. The input vector comprised drill size, feed rate, spindle speed, and eight features obtained by processing the thrust and torque signals. The output was the drill wear state which either usable or failure. Drilling experiments with various drill sizes, feed rates and spindle speeds were carried out. The learning process was performed effectively by utilising backpropagation with smoothing and an activation function slope. The on-line detection of drill wear states using BPNs achieved 100% reliability even when the drill size, feed rate and spindle speed were changed. In other words, the developed on-line drill wear detection systems have very high robustness and hence can be used in very complex production environments, such as flexible manufacturing systems.

  8. Real-time measurement of camshaft wear in an automotive engine-a radiometric method

    SciTech Connect

    Schneider, E.W.; Blossfeld, D.H.

    1990-01-01

    A radiometric method has been developed for the determination of camshaft wear during engine operation. After a radioactive tracer is induced at the tips of one or more cam lobes by the technique of surface layer activation, calibration procedures are performed to determine the amount of radioactive material remaining versus the depth worn. The decrease in {gamma}-ray intensity measured external to the engine is then directly related to cam lobe wear. By incorporating a high-resolution detector and an internal radioactive standard, measurement accuracy better than {plus}{equals}0.2 {mu}m at 95% confidence has been achieved. Without the requirement of engine disassembly, this method has provided unique measurements of break-in wear and wear as a function of operating conditions. Because this approach requires only low levels of radiation, it has significant potential applications in wear control.

  9. Morphological characteristics of total joint arthroplasty-derived ultra-high molecular weight polyethylene (UHMWPE) wear debris that provoke inflammation in a murine model of inflammation.

    PubMed

    Sieving, Allison; Wu, Bin; Mayton, Lois; Nasser, Sam; Wooley, Paul H

    2003-03-01

    It is recognized that the chronic inflammation in peri-prosthetic tissue that contributes to implant failure frequently is provoked by the presence of wear debris. Some wear debris is inevitable because of the nature of the prosthesis, but not all patients develop severe inflammatory responses. The precise factors that mediate the severity of tissue inflammation to wear debris has yet to be fully defined. Because wear debris retrieved from peri-prosthetic tissue consists of a heterogeneous mixture of materials with various sizes and shapes, this study evaluated the influence of two major physical aspects of ultra-high molecular weight polyethylene (UHMWPE) wear debris (shape and surface texture) using a model of tissue inflammation. UHMWPE debris particulates recovered from 50 peri-prosthetic tissue samples were examined by scanning electron microscopy and categorized into four groups based upon aspect ratio and surface texture of the material. The four groups were defined as: 1) smooth and globular, 2) smooth and fibular, 3) rough and globular, and 4) rough and fibular. Histological analysis and ELISA assays were conducted to evaluate variations in cellular responses and cytokine production between the groups. The strongest expression of tumor necrosis factor alpha and interleukin-1 beta was found in tissues exposed to UHMWPE debris with both a rough surface texture and fibular shape, and this response was significantly elevated over debris particles with a smooth surface texture and globular shape. The data suggest that both shape and texture influence the severity of specific inflammatory responses and that rough debris surface texture exerts a marked effect on adverse tissue responses when combined with particles that have a sharp, elongated shape.

  10. Optical Diagnostic Characterization of High-Power Hall Thruster Wear and Operation

    NASA Technical Reports Server (NTRS)

    Williams, George J., Jr.; Soulas, George C.; Kamhawi, Hani

    2012-01-01

    Optical emission spectroscopy is employed to correlate BN insulator erosion with high-power Hall thruster operation. Specifically, actinometry leveraging excited xenon states is used to normalize the emission spectra of ground state boron as a function of thruster operating condition. Trends in the strength of the boron signal are correlated with thruster power, discharge voltage, and discharge current. In addition, the technique is demonstrated on metallic coupons embedded in the walls of the HiVHAc EM thruster. The OES technique captured the overall trend in the erosion of the coupons which boosts credibility in the method since there are no data to which to calibrate the erosion rates of high-power Hall thrusters. The boron signals are shown to trend linearly with discharge voltage for a fixed discharge current as expected. However, the boron signals of the higher-power NASA 300M and NASA 457Mv2 trend with discharge current and show an unexpectedly weak to inverse dependence on discharge voltage. Electron temperatures measured optically in the near-field plume of the thruster agree well with Langmuir probe data. However, the optical technique used to determine Te showed unacceptable sensitivity to the emission intensities. Near-field, single-frequency imaging of the xenon neutrals is also presented as a function of operating condition for the NASA 457 Mv2.

  11. Erosive wear of ductile metals by a particle-laden high velocity liquid jet

    SciTech Connect

    Ka-Keung Li, Simon; Humphrey, Joseph A. C.; Levy, Alan V.

    1981-11-30

    In this paper, a liquid-solid particle jet impingement flow apparatus is described and experimental measurements are reported for the accelerated erosion of copper, aluminum and mild steel sheet metal by coal suspensions in kerosene and Al2O3 and SiC suspensions in water. Slurry velocities of up to 130 ft s-1 (40 m s-1) and impingement angles of 15°–90° were investigated. The maximum particle concentration used was 40 wt.%. For high velocity the results of this work show two erosion maxima; these are found at impingement angles of 90° and 40°. However, in corresponding gas-solid particle investigations maximum erosion occurs at approximately 20°. In this work both particle concentration and composition were varied. Finally, a polynomial regression technique was used to calculate empirical and semitheoretical correlation constants.

  12. Features of erosion-corrosion wear in low-pressure evaporators of combined-cycle plant heat-recovery boilers at high void factor values

    NASA Astrophysics Data System (ADS)

    Galetsky, N. S.; Schwarz, A. L.

    2013-12-01

    The features of erosion-corrosion wear (ECW) in a low-pressure evaporator (LPE) combinedcycle plant (CCP) at high void factor values in the heat carrier are considered. It is shown that if the medium pressure in the evaporator is less than 1 MPa and steam quality x ≈ 0.5, the void fraction β is close to 1, at the outlet of the evaporator almost dry saturated steam moves, and the formation of liquid films is excluded. Under these conditions, the wear of the evaporator coil sections has an erosive nature, caused by high velocity steam, carrying the dense particles of corrosion products and large drops of water, previously plucked from the surface of the liquid films.

  13. Wear tests of polymer composite compressor seal materials in hydrogen environments

    SciTech Connect

    Yu, K.; Bayliss, R.; Hillman, B.

    1999-07-01

    A high-speed reciprocating wear test rig with moisture control facilities has been further developed for undertaking wear tests in hydrogen environments with moisture content of 1--1,OOO ppmV to evaluate the wear performance of four commercial compressor seal materials. The test results are presented and compared to those obtained in nitrogen environment, where available. It was found that the wear rate and the friction coefficient of sample A increased significantly as moisture content decreased below {approximately}150 ppmV, whilst the other three samples showed much less or no dependence of the wear rates and the friction coefficients upon moisture content. Moreover, at moisture content below {approximately}150 ppmV, significant differences in the wear rate as well as friction coefficients were observed for Sample B in hydrogen and in nitrogen. The tests showed that, for a material for compressor applications, it is vitally important to undertake wear tests in the gas to be compressed and at the appropriate moisture levels to obtain a realistic evaluation of wear performance of the material.

  14. Effects of simulated oxidation on the in vitro wear and mechanical properties of irradiated and melted highly crosslinked UHMWPE.

    PubMed

    Oral, Ebru; Neils, Andrew L; Doshi, Brinda N; Fu, Jun; Muratoglu, Orhun K

    2016-02-01

    Radiation crosslinked ultrahigh molecular weight polyethylene (UHMWPE) have reduced the wear rate of the bearing surface in total joint arthroplasty and the incidence of peri-prosthetic bone loss due to wear particles. The oxidation potential afforded to the material by the trapped residual free radicals after irradiation was addressed in first generation crosslinked UHMWPEs by using thermal treatments such as annealing or melting after irradiation. Postirradiation melted crosslinked UHMWPE did not contain detectable free radicals at the time of implantation and was expected to be resistant against oxidation for the lifetime of the implants. Recent analyses of long-term retrievals showed it was possible for irradiated and melted UHMWPEs to oxidize in vivo but studies on the effects of oxidation on these materials have been limited. In this study, we determined the effects of in vitro aging on the wear and mechanical properties of irradiated and melted UHMWPE as a function of radiation dose and found that even small amount of oxidation (oxidation index of 0.1) can have detrimental effects on its mechanical properties. There was a gradual increase in the wear rate below an oxidation index of 1 and a drastic increase thereafter. Therefore, it was shown in a simulated environment that oxidation can have detrimental effects to the clinically relevant properties of irradiated and melted UHMWPEs.

  15. Friction, wear, transfer, and wear surface morphology of ultrahigh-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1985-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  16. Investigations of mechanical and wear properties of alumina/titania/fire-clay reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Patel, Vinay Kumar; Chauhan, Shivani; Sharma, Aarushi

    2016-05-01

    In this work, the effect of various particulates (alumina, titania, fire clay) reinforcements on mechanical and wear properties of epoxy composites have been studied with a prime motive of replacing the costly alumina and titania by much economical fire clay for high mechanical strength and/or wear resistant materials. Fire clay based epoxy composites delivered better mechanical (both tensile and impact) properties than the alumina filled or neat epoxy composites and slightly lower than titania reinforced composites, which qualified the fire clay a very suitable cost effective alternatives of both alumina and titania for high mechanical strength based applications. However, the poor wear behavior of fire clay reinforced composites revealed its poor candidacy for wear and tear applications.

  17. Influence of third-body particles originating from bone void fillers on the wear of ultra-high-molecular-weight polyethylene.

    PubMed

    Cowie, Raelene M; Carbone, Silvia; Aiken, Sean; Cooper, John J; Jennings, Louise M

    2016-08-01

    Calcium sulfate bone void fillers are increasingly being used for dead space management in infected arthroplasty revision surgery. The presence of these materials as loose beads close to the bearing surfaces of joint replacements gives the potential for them to enter the joint becoming trapped between the articulating surfaces; the resulting damage to cobalt chrome counterfaces and the subsequent wear of ultra-high-molecular-weight polyethylene is unknown. In this study, third-body damage to cobalt chrome counterfaces was simulated using particles of the calcium sulfate bone void fillers Stimulan(®) (Biocomposites Ltd., Keele, UK) and Osteoset(®) (Wright Medical Technology, TN, USA) using a bespoke rig. Scratches on the cobalt chrome plates were quantified in terms of their density and mean lip height, and the damage caused by the bone void fillers was compared to that caused by particles of SmartSet GMV PMMA bone cement (DePuy Synthes, IN, USA). The surface damage from Stimulan(®) was below the resolution of the analysis technique used; SmartSet GMV caused 0.19 scratches/mm with a mean lip height of 0.03 µm; Osteoset(®) led to a significantly higher number (1.62 scratches/mm) of scratches with a higher mean lip height (0.04 µm). Wear tests of ultra-high-molecular-weight polyethylene were carried out in a six-station multi-axial pin on plate reciprocating rig against the damaged plates and compared to negative (highly polished) and positive control plates damaged with a diamond stylus (2 µm lip height). The wear of ultra-high-molecular-weight polyethylene was shown to be similar against the negative control plates and those damaged with third-body particles; there was a significantly higher (p < 0.001) rate of ultra-high-molecular-weight polyethylene wear against the positive control plates. This study showed that bone void fillers of similar composition can cause varying damage to cobalt chrome counterfaces. However, the lip heights of the

  18. Influence of third-body particles originating from bone void fillers on the wear of ultra-high-molecular-weight polyethylene

    PubMed Central

    Cowie, Raelene M; Carbone, Silvia; Aiken, Sean; Cooper, John J; Jennings, Louise M

    2016-01-01

    Calcium sulfate bone void fillers are increasingly being used for dead space management in infected arthroplasty revision surgery. The presence of these materials as loose beads close to the bearing surfaces of joint replacements gives the potential for them to enter the joint becoming trapped between the articulating surfaces; the resulting damage to cobalt chrome counterfaces and the subsequent wear of ultra-high-molecular-weight polyethylene is unknown. In this study, third-body damage to cobalt chrome counterfaces was simulated using particles of the calcium sulfate bone void fillers Stimulan® (Biocomposites Ltd., Keele, UK) and Osteoset® (Wright Medical Technology, TN, USA) using a bespoke rig. Scratches on the cobalt chrome plates were quantified in terms of their density and mean lip height, and the damage caused by the bone void fillers was compared to that caused by particles of SmartSet GMV PMMA bone cement (DePuy Synthes, IN, USA). The surface damage from Stimulan® was below the resolution of the analysis technique used; SmartSet GMV caused 0.19 scratches/mm with a mean lip height of 0.03 µm; Osteoset® led to a significantly higher number (1.62 scratches/mm) of scratches with a higher mean lip height (0.04 µm). Wear tests of ultra-high-molecular-weight polyethylene were carried out in a six-station multi-axial pin on plate reciprocating rig against the damaged plates and compared to negative (highly polished) and positive control plates damaged with a diamond stylus (2 µm lip height). The wear of ultra-high-molecular-weight polyethylene was shown to be similar against the negative control plates and those damaged with third-body particles; there was a significantly higher (p < 0.001) rate of ultra-high-molecular-weight polyethylene wear against the positive control plates. This study showed that bone void fillers of similar composition can cause varying damage to cobalt chrome counterfaces. However, the lip heights of the scratches

  19. Microstructural Characterization and Wear Behavior of Nano-Boride Dispersed Coating on AISI 304 Stainless Steel by Hybrid High Velocity Oxy-Fuel Spraying Laser Surface Melting

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

    The current study concerns the detailed microstructural characterization and investigation of wear behavior of nano-boride dispersed coating developed on AISI 304 stainless steel by high velocity oxy-fuel spray deposition of nickel-based alloy and subsequent laser melting. There is a significant refinement and homogenization of microstructure with improvement in microhardness due to laser surface melting (1200 VHN as compared to 945 VHN of as-sprayed and 250 VHN of as-received substrate). The high temperature phase stability of the as-coated and laser melted surface has been studied by differential scanning calorimeter followed by detailed phase analysis at room and elevated temperature. There is a significant improvement in wear resistance of laser melted surface as compared to as-sprayed and the as-received one due to increased hardness and reduced coefficient of friction. The mechanism of wear has been investigated in details. Corrosion resistance of the coating in a 3.56 wt pct NaCl solution is significantly improved (4.43 E-2 mm/year as compared to 5 E-1 mm/year of as-sprayed and 1.66 mm/year of as-received substrate) due to laser surface melting as compared to as-sprayed surface.

  20. Conjoint corrosion and wear in titanium alloys.

    PubMed

    Khan, M A; Williams, R L; Williams, D F

    1999-04-01

    When considering titanium alloys for orthopaedic applications it is important to examine the conjoint action of corrosion and wear. In this study we investigate the corrosion and wear behaviour of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr in phosphate buffered saline (PBS), bovine albumin solutions in PBS and 10% foetal calf serum solutions in PBS. The tests were performed under four different conditions to evaluate the influence of wear on the corrosion and corrosion on the wear behaviour as follows: corrosion without wear, wear-accelerated corrosion, wear in a non-corrosive environment and wear in a corrosive environment. The corrosion behaviour was investigated using cyclic polarisation studies to measure the ability of the surface to repassivate following breakdown of the passive layer. The properties of the repassivated layer were evaluated by measuring changes in the surface hardness of the alloys. The amount of wear that had occurred was assessed from weight changes and measurement of the depth of the wear scar. It was found that in the presence of wear without corrosion the wear behaviour of Ti-13Nb-13Zr was greater than that of Ti-6Al-7Nb or Ti-6Al-4V and that in the presence of proteins the wear of all three alloys is reduced. In the presence of corrosion without wear Ti-13Nb-13Zr was more corrosion resistant than Ti-6Al-7Nb which was more corrosion resistant than Ti-6Al-4V without proteins whereas in the presence of protein the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb was reduced and that of Ti-6Al-4V increased. In the presence of corrosion and wear the corrosion resistance of Ti-13Nb-13Zr is higher than that of Ti-6Al-7Nb or Ti-6Al-4V in PBS but in the presence of proteins the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb are very similar but higher than that of Ti-6Al-4V. The wear of Ti-13Nb-13Zr is lower than that of Ti-6Al-7Nb and Ti-6Al-4V with or without the presence of proteins in a corrosive environment. Therefore the overall

  1. Wear mechanism and wear prevention in coal-fueled diesel engines. Task 3, Traditional approaches to wear prevention

    SciTech Connect

    Schwalb, J.A.

    1991-06-01

    Contamination of the lube-oil with hard abrasive particles leads to a three-body abrasive wear mechanism that highly accelerates piston ring/cylinder liner wear in coal-fueled diesel engines. One approach to reducing that wear is to modify the size and orientation of surface asperities on the cylinder to enhance the formation of a hydrodynamic film, and to provide avenues of escape for particles that would otherwise be trapped in the wear zone. Another approach is to introduce additives into the contaminated lube-oil that further enhance hydrodynamic film formation, form chemical films on the wearing surfaces, or form films on the contaminant particles. This work focuses on defining the effects of cylinder liner surface finish, various configurations of slots in the cylinder liner surface, and various additives in the contaminated lube-oil on the wear process. Wear tests were initiated in a bench apparatus using coal-ash contaminated lube-oil to test the various wear configurations. The results of these tests indicate that the formation of a hydrodynamic film between the ring and cylinder specimens is enhanced by increasing surface roughness, and by orienting the surface asperities normal to the direction of ring travel but modifications to the cylinder liner surface did not greatly reduce the wear rate. Additives to the lubricant seemed to have a much more significant effect on wear, with a dispersant additive highly accelerating the wear, while a detergent additive was able to reduce the wear almost to the rate achieved where there was no contaminant.

  2. Friction and Wear Behavior of Silicon Under Conditions of Sliding.

    NASA Astrophysics Data System (ADS)

    Nadimpalli, Chandrasekhar Venkata

    Silicon is gaining importance as a material in micromechanical applications such as micromotors and microactuators. Friction and wear can affect the performance of these devices and hence it is important to study the friction and wear behavior of silicon. The deformation behavior of n-type silicon is fundamentally different from p-type. On deformation, n -type silicon may convert to p-type, but p-type silicon does not convert to n-type on deformation. This is related to the effect of dislocations interacting with the electrical charge carriers. Friction and wear behavior of n and p-type silicon was studied under conditions of sliding wear. Sliding was selected because the stress system associated with sliding introduces large plastic strains at the surface. The friction and wear behavior of n and p-type silicon is expected to be different due to the differences in their deformation behavior. Also, the n to p transition may show up in the friction and wear behavior. The samples were tested in air and in vacuum. Diamond was used as the slider. The wear tracks showed evidence of plastic flow. The morphology of this material was similar to that seen in more ductile materials. The coefficient of friction was also high. Other researchers have reported that DC Silicon transforms to a more ductile phase when sufficient pressure is applied. When shear stresses are present, as in sliding wear, the pressure for phase transformation has been reported to be about 8 GPa. The maximum pressure under the slider in the present set of experiments was estimated to be 8.2 GPa. Therefore, it is possible that transformed material extruded during sliding to produce the flow-like features observed at the wear track. The work involved in this phase transformation, as well as the work in deforming DC Silicon and/or the ductile product phase would contribute to the frictional energy. The debris from the air tests was DC silicon (as determined by XRD and TEM). No significant differences were

  3. Wear of materials 1985

    SciTech Connect

    Ludema, K.C.

    1985-01-01

    This book presents the papers given at a conference on wear resistance. Topics considered at the conference included erosion in aluminium oxides, abrasive wear tests, x-ray diffraction, transmission electron microscopy, wear tests of low-cobalt alloys for hardfacing nuclear components, microstructure, the elevated temperature erosion of steels, and steels under cyclic operation in corrosive liquids.

  4. Wear-mechanism modelling

    SciTech Connect

    Ashby, M.F. . Dept. of Engineering)

    1993-03-01

    Goals of the program are to calculate the surface temperatures in dry sliding, develop a soft wear tester for ceramics, survey the wear mechanisms in brittle solids, and couple the temperature calculations with models to give wear maps for brittle solids. (DLC)

  5. Wear resistance of ductile irons

    NASA Astrophysics Data System (ADS)

    Lerner, Y. S.

    1994-06-01

    This study was undertaken to evaluate the wear resistance of different grades of ductile iron as alterna-tives to high- tensile- strength alloyed and inoculated gray irons and bronzes for machine- tool and high-pressure hydraulic components. Special test methods were employed to simulate typical conditions of reciprocating sliding wear with and without abrasive- contaminated lubricant for machine and press guideways. Quantitative relationships were established among wear rate, microstructure and micro-hardness of structural constituents, and nodule size of ductile iron. The frictional wear resistance of duc-tile iron as a bearing material was tested with hardened steel shafts using standard test techniques under continuous rotating movement with lubricant. Lubricated sliding wear tests on specimens and compo-nents for hydraulic equipment and apparatus were carried out on a special rig with reciprocating motion, simulating the working conditions in a piston/cylinder unit in a pressure range from 5 to 32 MPa. Rig and field tests on machine- tool components and units and on hydraulic parts have confirmed the test data.

  6. Erosive Wear Behavior of Nickel-Based High Alloy White Cast Iron Under Mining Conditions Using Orthogonal Array

    NASA Astrophysics Data System (ADS)

    Yoganandh, J.; Natarajan, S.; Babu, S. P. Kumaresh

    2013-09-01

    Nihard Grade-4, a nickel-bearing cast iron widely used in slurry pumps and hydrodynamic components, is evaluated for its erosive wear response under mining conditions using a statistical approach. Experiments were conducted by varying the factors namely velocity, slurry concentration, angle of impingement, and pH in three levels, using L9 orthogonal array. Analysis of variance was used to rank the factors influencing erosive wear. The results indicate that velocity is the most influencing factor followed by the angle of impingement, slurry concentration, and pH. Interaction effects of velocity, slurry concentration, angle of impingement, and pH on erosion rate have been discussed. Wear morphology was also studied using SEM characterization technique. At lower angle (30°) of impingement, the erosion of material is by micro fracture and shallow ploughing with the plastic deformation of the ductile austenitic matrix. At the normal angle (90°) of impingement, the material loss from the surface is found because of deep indentation, forming protruded lips which are removed by means of repeated impact of the erodent.

  7. Third-body abrasive wear challenge of 32 mm conventional and 44 mm highly crosslinked polyethylene liners in a hip simulator model.

    PubMed

    Sorimachi, T; Clarke, I C; Williams, P A; Gustafson, A; Yamamoto, K

    2009-07-01

    Hip simulator studies have shown that wear in the polyethylene liners used for total hip replacements increased with the larger-diameter femoral balls and could also be exacerbated by third-body abrasion. However, they also indicated that the more highly cross-linked polyethylene (HXPE) bearings were more wear resistant than conventional polyethylene (CXPE) bearings. Unfortunately the HXPE bearings appeared to be particularly sensitive to adverse wear conditions. One simulator study in particular indicated that poly(methyl methacrylate) (PMMA) debris increased wear sixfold by means of two-body abrasive interactions rather than the supposed third-body abrasion or roughening effects of the Co-Cr surfaces. There has been no confirmation of such novel theories. Therefore the goal of this study was to investigate the sensitivity of large-diameter HXPE bearings to the third-body PMMA wear challenge in a hip simulator model. An orbital hip simulator was used in standard test mode with a physiological load profile. The 32 mm control liners were machined from moulded GUR1050 and gamma irradiated to 35 kGy under nitrogen (CXPE). The 44 mm liners were also from moulded blanks, gamma irradiated to 75 kGy, machined to shape, given a proprietary heat treatment, and sterilized by gas plasma (HXPE). As in the published simulator model, the study was conducted in three phases. In phase 1, all cups were run in standard ('clean') lubricant for 1.5 x 10(6) cycles duration. In phase 2, three CXPE cups and six HXPE cups were run for 2 x 10(6) cycles with a slurry of PMMA particles added to the lubricant. In phase 3, the implants were again run in 'clean' lubricant for 2 x 10(6) cycles duration. In addition, three HXPE cups were run as wear controls for 5.5 x 10(6) cycles duration in clean lubricant. In phase-1, the HXPE liners demonstrated twelvefold reduced wear compared with the CXPE controls. The 32 mm and 44 mm Co-Cr balls were judged of comparable roughnesses. However, the surface

  8. Wear Behavior Characterization for the Screening of Magnesium-based Alloys

    NASA Astrophysics Data System (ADS)

    McGhee, Paul R.

    This research is focused on the development of a systematic approach to evaluate the selection of materials for Mg-based alloys under wear conditions for biomedical applications. A pilot study was carried out in order to establish an accurate and reliable wear testing technique for magnesium and its alloys. This pilot study was conducted on aluminum (Al) and pure Mg, and showed that aluminum has a lower wear rate compared to Mg. The technique displayed good repeatability and high precision. For the main study, an ERC Mg-based alloy was to be compared with pure Mg. The same technique, when applied to pure Mg from a different vendor, produced up to 90% scatter in the data. Microstructure was studied to see if it had any correlation with the scatter. It was discovered that Mg ingot from the second vendor had outsized grains that contributed to the disproportional scatter in the wear data. Increasing the stroke length during wear testing was required so that the wear data would be averaged over multiple grains and reduces the variation in computed wear rates. In the main study, wear behavior and friction properties were analyzed using microtribometery, mechanical stylus profilometry, and microindentation. Surface morphology and microstructure were characterized using optical microscopy, scanning electron microscopy, and optical profilometry. For the main study, pure Mg and the ERC alloy as-cast and extruded conditions were compared. Pure Mg and MZCR alloys were extruded at 350°C and 400°C, respectively. Mg and MZCR alloy were cast at 350°C and heat treated at 510°C. The extruded specimens were divided into two sections, cross-section and longitudinal section. Wear tests were carried out under the applied normal load 0.5 N - 2.5 N in 0.5 N increments sliding at a rate of 0.2 Hz for 240 passes. The results show that the alloying and extrusion processes increase the hardness of the MZCR alloy significantly up to 80%. The as-cast MZCR has a lower resistance to wear

  9. The hardness, adhesion, and wear resistance of coatings developed for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.; Wilson, W.L.

    2000-05-01

    One potential approach for reducing the level of nuclear plant radiation exposure that results from activated cobalt wear debris is the use of a wear resistant coating. However, large differences in stiffness between a coating/substrate can result in high interfacial stresses that produce coating de-adhesion when a coated substrate is subjected to high stress wear contact. Scratch adhesion and indentation tests have been used to identify four promising coating processes [1,2]: (1) the use of a thin Cr-nitride coating with a hard and less-stiff interlayer, (2) the use of a thick, multilayered Cr-nitride coating with graded layers, (3) use of the duplex approach, or nitriding to harden the material subsurface followed by application of a multilayered Cr-nitride coating, and (4) application of nitriding alone. The processing, characterization, and adhesion of these coating systems are discussed. The wear resistance and performance has been evaluated using laboratory pin-on-disc, 4-ball, and high stress rolling contact tests. Based on the results of these tests, the best coating candidate from the high-stress rolling contact wear test was the thin duplex coating, which consists of ion nitriding followed deposition of a thin Cr-nitride coating, while the thin Cr-nitride coating exhibited the best results in the 4-ball wear test.

  10. Wear mechanism and wear prevention in coal-fueled diesel engines

    SciTech Connect

    Schwalb, J.A.; Ryan, T.W.

    1991-10-01

    Coal fueled diesel engines present unique wear problems in the piston ring/cylinder liner area because of their tendency to contaminate the lube-oil with high concentrations of highly abrasive particles. This program involved a series of bench-scale wear tests and engine tests designed to investigate various aspects of the ring/liner wear problem and to make specific recommendations to engine manufacturers as to how to alleviate these problems. The program was organized into tasks, designed to accomplish the following objectives: (1) define the predominant wear mechanisms causing accelerated wear in the ring/liner area; (2) investigate the effectiveness of traditional approaches to wear prevention to prevent wear in coal-fueled engines; (3) further refine information on the most promising approaches to wear prevention; (4) present detailed information and recommendations to engine manufacturers on the most promising approach to wear prevention; (5) present a final report covering the entire program; (6)complete engine tests with a coal-derived liquid fuel, and investigate the effects of the fuel on engine wear and emissions.

  11. Wear mechanism and wear prevention in coal-fueled diesel engines. Final report

    SciTech Connect

    Schwalb, J.A.; Ryan, T.W.

    1991-10-01

    Coal fueled diesel engines present unique wear problems in the piston ring/cylinder liner area because of their tendency to contaminate the lube-oil with high concentrations of highly abrasive particles. This program involved a series of bench-scale wear tests and engine tests designed to investigate various aspects of the ring/liner wear problem and to make specific recommendations to engine manufacturers as to how to alleviate these problems. The program was organized into tasks, designed to accomplish the following objectives: (1) define the predominant wear mechanisms causing accelerated wear in the ring/liner area; (2) investigate the effectiveness of traditional approaches to wear prevention to prevent wear in coal-fueled engines; (3) further refine information on the most promising approaches to wear prevention; (4) present detailed information and recommendations to engine manufacturers on the most promising approach to wear prevention; (5) present a final report covering the entire program; (6)complete engine tests with a coal-derived liquid fuel, and investigate the effects of the fuel on engine wear and emissions.

  12. IMPROVEMENT OF WEAR COMPONENT'S PERFORMANCE BY UTILIZING ADVANCED MATERIALS AND NEW MANUFACTURING TECHNOLOGIES: CASTCON PROCESS FOR MINING APPLICATIONS

    SciTech Connect

    Xiaodi Huang; Richard Gertsch

    2003-02-27

    The project was highlighted by continued fabrication of drill bit inserts and testing them: (1) The inserts were subjected to hammer tests to determine brittleness. Selected inserts experienced multiple blows from a 16 pound sledge hammer. The resulting damage was minimal. (2) Three inserts were placed on three different 16.5 inch diameter rotary drill bits, and the bits drilled taconite rock until the entire bit failed. (3) The inserts had somewhat less wear resistance than current art, and exhibited no brittle failures. (4) More work is needed to produce the inserts at near net shape. The test inserts required too much machining. The project next turned to manufacturing 6.5 inch diameter disc cutters. The cutters will feature a core of tungsten carbide (TC) in a disc body composed of H13 tool steel. The TC inserts are in manufacture and the dies for the disc are being designed. The plan for next quarter: (1) Investigate materials and manufacturing changes for the fibrous monolith drill bit inserts that will increase their wear life. (2) Begin manufacturing disc cutters.

  13. The Effect of Long-Time Austenization on the Wear Resistance and Thermal Fatigue Properties of a High-Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodan; Liu, Wei; Godfrey, Andrew; Liu, Qing

    2009-09-01

    The effects of a long-time austenization treatment on a high-speed steel (HSS) roll have been investigated. Several interesting phenomena were observed, including the decomposition of the primary bulky M3C carbides on grain boundaries and the precipitation of a large number of MC carbides of size comparable to the primary MC carbides in the grains. As a consequence of these changes, the overall carbide size decreased and the homogeneity of the carbide distribution increased. The wear resistance and thermal fatigue properties of the HSS roll were also investigated, and it was found that the long-time austenization treatment resulted in improvements to both properties.

  14. Development of Modified Pag (Polyalkylene Glycol) High VI High Fuel Efficient Lubricant for LDV Applications

    SciTech Connect

    Gangopadhyay, Arup; McWatt, D. G.; Zdrodowski, R. J.; Liu, Zak; Elie, Larry; Simko, S. J.; Erdemir, Ali; Ramirez, Giovanni; Cuthbert, J.; Hock, E. D.

    2015-09-30

    Engine oils play a critical role in friction reduction. Improvements in engine oil technology steadily improved fuel economy as the industry moved through ILSAC GF-1 to GF-5 specifications. These improvements were influenced by changes in base oil chemistry, development of new friction modifiers and their treat levels, and the total additive package consisting of various other components. However, the improvements are incremental and further fuel consumption reduction opportunities are becoming more challenging. Polyalkylene glycol (PAG) based engine oils are being explored as a step forward for significant fuel consumption reduction. Although PAG fluids are used in many industrial applications, its application as an engine oil has been explored in a limited way. The objective of this project is to deep dive in exploring the applicability of PAG technology in engine oil, understanding the benefits, and limitations, elucidating the mechanism(s) for friction benefits, if any, and finally recommending how to address any limitations. The project was designed in four steps, starting with selection of lubricant technology, followed by friction and wear evaluations in laboratory bench tests which are relatively simple and inexpensive and also served as a screener for further evaluation. Selected formulations were chosen for more complex engine component level tests i.e., motored valvetrain friction and wear, piston ring friction using a motored single cylinder, and motored engine tests. A couple of formulations were further selected based on component level tests for engine dyno tests i.e., Sequence VID (ASTM D6709) for fuel economy, Sequence IVA (ASTM D6891) for valvetrain wear, and Sequence VG (ASTM D6593) for sludge and varnish protection. These are some of the industry standard tests required for qualifying engine oils. Out of these tests, a single PAG oil was selected for chassis roll dynamometer tests for fuel economy and emission measurements using FTP (Federal

  15. Advanced Wear-resistant Nanocomposites for Increased Energy Efficiency

    SciTech Connect

    Cook, B. A.; Harringa, J. L.; Russel, A. M.

    2012-12-01

    This report summarizes the work performed by an Ames-led project team under a 4-year DOE-ITP sponsored project titled, 'Advanced Wear-resistant Nanocomposites for Increased Energy Efficiency.' The Report serves as the project deliverable for the CPS agreement number 15015. The purpose of this project was to develop and commercialize a family of lightweight, bulk composite materials that are highly resistant to degradation by erosive and abrasive wear. These materials, based on AlMgB{sub 14}, are projected to save over 30 TBtu of energy per year when fully implemented in industrial applications, with the associated environmental benefits of eliminating the burning of 1.5 M tons/yr of coal and averting the release of 4.2 M tons/yr of CO{sub 2} into the air. This program targeted applications in the mining, drilling, machining, and dry erosion applications as key platforms for initial commercialization, which includes some of the most severe wear conditions in industry. Production-scale manufacturing of this technology has begun through a start-up company, NewTech Ceramics (NTC). This project included providing technical support to NTC in order to facilitate cost-effective mass production of the wear-resistant boride components. Resolution of issues related to processing scale-up, reduction in energy intensity during processing, and improving the quality and performance of the composites, without adding to the cost of processing were among the primary technical focus areas of this program. Compositional refinements were also investigated in order to achieve the maximum wear resistance. In addition, synthesis of large-scale, single-phase AlMgB{sub 14} powder was conducted for use as PVD sputtering targets for nanocoating applications.

  16. The Impact of Weather on Women’s Tendency to Wear Red or Pink when at High Risk for Conception

    PubMed Central

    Tracy, Jessica L.; Beall, Alec T.

    2014-01-01

    Women are particularly motivated to enhance their sexual attractiveness during their most fertile period, and men perceive shades of red, when associated with women, as sexually attractive. Building on this research, we recently found that women are more likely to wear reddish clothing when at peak fertility (Beall & Tracy, 2013), presumably as a way of increasing their attractiveness. Here, we first report results from a methodological replication, conducted during warmer weather, which produced a null effect. Investigating this discrepancy, we considered the impact of a potentially relevant contextual difference between previous research and the replication: current weather. If the red-dress effect is driven by a desire to increase one’s sexual appeal, then it should emerge most reliably when peak-fertility women have few alternative options for accomplishing this goal (e.g., wearing minimal clothing). Results from re-analyses of our previously collected data and a new experiment support this account, by demonstrating that the link between fertility and red/pink dress emerges robustly in cold, but not warm, weather. Together, these findings suggest that the previously documented red-dress effect is moderated by current climate concerns, and provide further evidence that under certain circumstances red/pink dress is reliably associated with female fertility. PMID:24586414

  17. The impact of weather on women's tendency to wear red or pink when at high risk for conception.

    PubMed

    Tracy, Jessica L; Beall, Alec T

    2014-01-01

    Women are particularly motivated to enhance their sexual attractiveness during their most fertile period, and men perceive shades of red, when associated with women, as sexually attractive. Building on this research, we recently found that women are more likely to wear reddish clothing when at peak fertility (Beall & Tracy, 2013), presumably as a way of increasing their attractiveness. Here, we first report results from a methodological replication, conducted during warmer weather, which produced a null effect. Investigating this discrepancy, we considered the impact of a potentially relevant contextual difference between previous research and the replication: current weather. If the red-dress effect is driven by a desire to increase one's sexual appeal, then it should emerge most reliably when peak-fertility women have few alternative options for accomplishing this goal (e.g., wearing minimal clothing). Results from re-analyses of our previously collected data and a new experiment support this account, by demonstrating that the link between fertility and red/pink dress emerges robustly in cold, but not warm, weather. Together, these findings suggest that the previously documented red-dress effect is moderated by current climate concerns, and provide further evidence that under certain circumstances red/pink dress is reliably associated with female fertility.

  18. 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

  19. Analysis of the application of the generalized monod kinetics model to describe the human corneal oxygen-consumption rate during soft contact lens wear.

    PubMed

    Compañ, V; Aguilella-Arzo, M; Del Castillo, L F; Hernández, S I; Gonzalez-Meijome, J M

    2016-07-26

    This work is an analysis of the application of the generalized Monod kinetics model describing human corneal oxygen consumption during soft contact lens wear to models previously used by Chhabra et al. (J Biomed Mater Res B Appl Biomater, 2009a;90:202-209, Optom Vis Sci 2009b;86:454-466) and Larrea and Büchler (Invest Ophthalmol Vis Sci 2009;50:1076-1080). We use oxygen tension from in vivo estimations provided by Bonanno [Bonanno et al., Invest Ophthalmol Vis Sci 2002;43:371-376, and Bonanno et al 2009]. We consider four hydrogel and six silicone hydrogel lenses. The cornea is considered a single homogeneous layer, with constant oxygen permeability regardless of the type of lens worn. Our calculations yield different values for the maximum oxygen consumption rate Qc,max , whith differents oxygen tensions (high and low pc ) at the cornea-tears interface. Surprisingly, for both models, we observe an increase in oxygen consumption near an oxygen tension of 105 mmHg until a maximum is reached, then decreasing for higher levels of oxygen pressure. That is, when lowering the pressure of oxygen, the parameter Qc,max initially increases depending on the intensity of the change in pressure. Which, it could be related with the variation of the pH. Furthermore, it is also noted that to greater reductions in pressure, this parameter decreases, possibly due to changes in the concentration of glucose related to the anaerobic respiration. The averaged in vivo human corneal oxygen consumption rate of 1.47 × 10(-4) cm(3) of O2 /cm(3) tissue s, with Monod kinetics model, considering all the lenses studied, is smaller than the average oxygen consumption rate value obtained using the Larrea and Büchler model. The impact that these calculations have on the oxygen partial pressure available at different depths in the corneal tissue is presented and discussed, taking into consideration previous models used in this study. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl

  20. 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.

  1. Wear mechanism and wear prevention in coal-fueled diesel engines

    SciTech Connect

    Schwalb, J.A.

    1991-06-01

    Contamination of the lube-oil with hard abrasive particles leads to a three-body abrasive wear mechanism that highly accelerates piston ring/cylinder liner wear in coal-fueled diesel engines. One approach to reducing that wear is to modify the size and orientation of surface asperities on the cylinder to enhance the formation of a hydrodynamic film, and to provide avenues of escape for particles that would otherwise be trapped in the wear zone. Another approach is to introduce additives into the contaminated lube-oil that further enhance hydrodynamic film formation, form chemical films on the wearing surfaces, or form films on the contaminant particles. This work focuses on defining the effects of cylinder liner surface finish, various configurations of slots in the cylinder liner surface, and various additives in the contaminated lube-oil on the wear process. Wear tests were initiated in a bench apparatus using coal-ash contaminated lube-oil to test the various wear configurations. The results of these tests indicate that the formation of a hydrodynamic film between the ring and cylinder specimens is enhanced by increasing surface roughness, and by orienting the surface asperities normal to the direction of ring travel but modifications to the cylinder liner surface did not greatly reduce the wear rate. Additives to the lubricant seemed to have a much more significant effect on wear, with a dispersant additive highly accelerating the wear, while a detergent additive was able to reduce the wear almost to the rate achieved where there was no contaminant.

  2. Wear studies on the likely performance of CFR-PEEK/CoCrMo for use as artificial joint bearing materials.

    PubMed

    Scholes, S C; Unsworth, A

    2009-01-01

    It is well known that a reduction in the volume of wear produced by articulating surfaces in artificial joints is likely to result in a lower incidence of failure due to wear particle induced osteolysis. Therefore, new materials have been introduced in an effort to produce bearing surfaces with lower, more biologically acceptable wear. Polyetheretherketone (PEEK-OPTIMA) has been successfully used in a number of implant applications due to its combination of mechanical strength and biocompatibility. Pin-on-plate wear tests were performed on various combinations of PEEK-OPTIMA and carbon fibre reinforced PEEK-OPTIMA (CFR-PEEK) against various CoCrMo alloys to assess the potential of this material combination for use in orthopaedic implants. The PEEK/low carbon CoCrMo produced the highest wear. CFR-PEEK against high carbon or low carbon CoCrMo provided low wear factors. Pin-on-plate tests performed on ultra-high molecular weight polyethylene (UHMWPE) against CoCrMo (using comparable test conditions) have shown similar or higher wear than that found for CFR-PEEK/CoCrMo. This study gives confidence in the likelihood of this material combination performing well in orthopaedic applications.

  3. Tribopolymerization as an anti-wear mechanism. Quarterly progress report

    SciTech Connect

    Furey, M.J.

    1996-04-01

    The primary objective of this activity is to obtain the necessary data which would enhance, promote, and encourage the introduction of advanced lubrication technology into the marketplace. This includes (a) defining specific but different applications, (b) establishing the limits or ranges of applied loads, speeds, and temperatures over which the concept of tribopolymerization would work in reducing wear and/or friction, (c) continuing in efforts to understand the film-forming process (this rates to (b) above), using this knowledge to develop new and even more effective additives, and (d) exploring possible connections with private and investment companies for the licensing and marketing of products which will reduce friction and wear in a variety of applications. Progress was made in several different but connected areas. These included (a) establishing of load/velocity limits of selected monomers for ceramic lubrication, (b) the discovery of new and effective monomers designed for higher temperature anti-wear applications, (c) improvements and modifications of the high load/high speed pin-on-disk machine, (d) the initiation of related or spin-off projects designed to get their advanced technology into the marketplace, (e) the filing of three new patent applications, and (f) collaborative research with Dr. Kajdas--the co-inventor with Dr. Furey--on tribopolymerization as a novel and effective approach to the boundary lubrication of ceramics and steel. These and other elements of progress made during the first Quarter of 1996 are discussed briefly.

  4. Wear of ultra-high molecular weight polyethylene acetabular cups in a physiological hip joint simulator in the anatomical position using bovine serum as a lubricant.

    PubMed

    Bigsby, R J; Hardaker, C S; Fisher, J

    1997-01-01

    The Leeds physiological anatomical (PA) hip joint simulator was developed to apply three axes of loading and a complex three-dimensional motion so that the forces and motions can reproduce exactly the walking cycles defined by Paul. This paper presents the results of a study using the Leeds PA hip joint simulator to determine the wear of 32 mm ultra-high molecular weight polyethylene (UHMWPE) acetabular cups against stainless steel and zirconia ceramic heads, using bovine serum as lubricant. These results have been compared with the results of a previous study that used water as the lubricant, which led to UHMWPE transfer film being formed on the stainless steel head. Comparisons are also made with clinical results and results from other simulators. The study indicates that it is preferable to use bovine serum in simulator studies. In addition, the results indicate that if the surface roughness of the metallic and femoral heads are similar, and they remain undamaged during the tests, the wear rates of the UHMWPE cups are likely to be similar.

  5. The application of high-speed camera for analysis of chip creation process during the steel turning

    NASA Astrophysics Data System (ADS)

    Struzikiewicz, Grzegorz

    2016-09-01

    The paper presents the results of application of the high-speed camera Phantom v5.2 and Tracker program for the analysis of chip forming in the case of the AMS6265 steel turning. The experimental research was carried for two cutting speeds and different wear of cutting inserts.

  6. Wear of moderately cross-linked polyethylene in fixed-bearing total knee replacements.

    PubMed

    Brockett, Claire L; Jennings, Louise M; Hardaker, Catherine; Fisher, John

    2012-07-01

    Cross-linked polyethylene has been introduced into total joint replacement to improve wear resistance. Although the performance of highly cross-linked polyethylene is well documented clinically and experimentally for total hip replacements, the reduction in mechanical properties with increasing irradiation is of concern for application to total knee replacement. The aim of this study was to investigate the wear performance of a moderately cross-linked polyethylene material in a fixed-bearing total knee replacement. The study was conducted using two femoral geometries, a conventional cruciate-retaining femoral and a high-flexion femoral geometry. The femoral geometry appeared to have no effect on the wear of the knee replacement under standard gait conditions. A significant reduction in wear volume was measured with the moderately cross-linked polyethylene compared with the conventional polyethylene over a six-million-cycle wear study. This study indicates the use of a moderately cross-linked polyethylene in a fixed-bearing total knee replacement may provide a low wearing option for total knee replacement.

  7. Research on the effect of wear-ring clearances to the axial and radial force of a centrifugal pump

    NASA Astrophysics Data System (ADS)

    Zhao, W. G.; Y He, M.; Qi, C. X.; Li, Y. B.

    2013-12-01

    Varying of the wear-ring clearance not only has a distinct effect on the volumetric loss of the centrifugal pump, but also on the performance of the centrifugal pump including the axial and radial forces. Comparing with the experimental studies, numerical simulation methods have some special advantages, such as the low cost, fast and high efficiency, and convenient to get the detailed structure of the internal flow characteristics, so it has been widely used in the fluid machinery study in recent years. In order to study the effect of wear-ring clearance on the force performance of the centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump with three variable styles of the wear-rings was simulated: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Comparing with the experiment, numerical results show a good agreement. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the axial force of the centrifugal pump, while has tiny effect on the radial force for all the conditions.

  8. Characterization of Wear Mechanisms in Distorted Conical Picks After Coal Cutting

    NASA Astrophysics Data System (ADS)

    Dewangan, Saurabh; Chattopadhyaya, Somnath

    2016-01-01

    The interest in understanding the wear mechanisms of cemented carbide (CC) is not a new development. For a long time, there have been studies on different wear mechanisms under different coal/rock cutting conditions. These studies have helped improving the quality of CC, thereby preventing such wearing of tools. Due to highly unpredictable character of coal/rock, the wearing phenomena cannot be attributed to one single domain of conditions. However, one conclusion that can be drawn in this context is that, under similar working conditions, similar types of CC undergo similar nature of wearing process. An optimum combination of high wear resistance, strength and hardness has facilitated widespread application of CC in the field of mining engineering. The abrasive parts of the mining tools are made of CC materials. The current study is focussed on a detailed characterization of the wear mechanisms of conical picks, which are used for coal mining. Conical picks consist of a steel body with an inserted cone-shaped CC tip. After being used for a certain period of time, both, the CC tip and the steel body get distorted. In this study, selection of appropriate samples was followed by critical observation of them through field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS). In the previous study, we explained the distortion process of both, the tip as well as the body, using the SEM images. For the present study, two samples were taken from our previous investigation for further analysis. Three other samples were also included in the present study. Seven different types of wear mechanisms, such as, cracking and crushing, cavity formation, coal intermixing, chemical degradation along with abrasion, long and deep cracks, heating effect and body deformation were observed in the five tool samples.

  9. Effect of radiation cross-linking on the abrasive wear behaviour of polyethylenes

    NASA Astrophysics Data System (ADS)

    Gul, Rizwan M.; Khan, Tahir I.

    2014-06-01

    This study explores the differences in the dry abrasive wear behavior of different polyethylenes, and compares the effect of radiation cross-linking on the wear behavior. Four different types of polyethylenes: LDPE, LLDPE, HDPE and UHMWPE were studied. Cross-linking was carried out by high energy electron beam with radiation dose of 200 kGy. The results show that in unirradiated state UHMWPE has excellent wear resistance, with HDPE showing comparable wear properties; both LDPE and LLDPE exhibit high wear rate. Cross-linking improves wear rate of LDPE and UHMWPE, however, the wear rate of HDPE and LLDPE increases with cross-linking.

  10. Nanoscale thermomechanics of wear-resilient polymeric bilayer systems.

    PubMed

    Kaule, Tassilo; Zhang, Yi; Emmerling, Sebastian; Pihan, Sascha; Foerch, Renate; Gutmann, Jochen; Butt, Hans-Jürgen; Berger, Rüdiger; Duerig, Urs; Knoll, Armin W

    2013-01-22

    We explore the effect of an ultrathin elastic coating to optimize the mechanical stability of an underlying polymer film for nanoscale applications. The coating consists of a several nanometer thin plasma-polymerized norbornene layer. Scanning probes are used to characterize the system in terms of shear-force-induced wear and thermally assisted indentation. The layer transforms a weakly performing polystyrene film into a highly wear-resistive system, ideal for high-density and low-power data storage applications. The result can be understood from the indentation characteristics with a hot and sharp indenter tip. The latter gives rise to a deformation mode in the fully plastic regime, enabling a simple interpretation of the results. The softening transition and the yield stress of the system on a microsecond time scale and a nanometer size scale were obtained. We show that the plastic deformation is governed by yielding in the polystyrene sublayer, which renders the overall system soft for plastic deformation. The ultrathin protection layer contributes as an elastic skin, which shields part of the temperature and pressure and enables the high wear resistance against lateral forces. Moreover, the method of probing polymers at microsecond and nanometer size scales opens up new opportunities for studying polymer physics in a largely unexplored regime. Thus, we find softening temperatures of more than 100 °C above the polystyrene glass transition, which implies that for the short interaction time scales the glassy state of the polymer is preserved up to this temperature.

  11. Structures and Properties of Polymers Important to Their Wear Behavior

    NASA Technical Reports Server (NTRS)

    Tanaka, K.

    1984-01-01

    The wear and transfer of various semicrystalline polymers sliding against smooth steel or glass surfaces were examined. The effects of structures, and properties of polymers on their wear behavior are discussed. It is found that the high wear characteristics of PTFE is due to the easy destruction of the banded structure of PTFE. The size of spherulites and the molecular profile are closely related to the magnitude of wear rates of typical semicrystalline polymers. The effects of these factors on the wear rate on the basis of the destruction or melting of spherulites at the frictional surface are discussed. Although the fatigue theory of wear indicates that some mechanical properties are important to wear behavior, it is shown that the theory does not always explain the experimental result obtained on a smooth surface.

  12. Study of Wear-Preventive Properties of Macrocyclic Compounds for High Temperature Application

    DTIC Science & Technology

    1990-01-01

    phosphoric acid esters, silicones and fluorinated esters. In addition, compounds such as the phthalocyanines (i.e., metal-free- and metal chelate... phthalocyanine (ii) Copper (II) - phthalocyanine (iii) Nickel (II) - phthalocyanine (iv) Nickel (II) - phthalocyanine (Tetra-sulfonic acid - Na -salt) (v...Porphyrins 21 Contract No. N62269-88-R-0234 Report No. NADC-91049-60 N N N N N\\ -/ N N .. 05 NICKEL PHTH-ALOCYANINE TETRASULFONIC ACID TETRA SODIUM SALT

  13. A hip joint simulator study using simplified loading and motion cycles generating physiological wear paths and rates.

    PubMed

    Barbour, P S; Stone, M H; Fisher, J

    1999-01-01

    In some designs of hip joint simulator the cost of building a highly complex machine has been offset with the requirement for a large number of test stations. The application of the wear results generated by these machines depends on their ability to reproduce physiological wear rates and processes. In this study a hip joint simulator has been shown to reproduce physiological wear using only one load vector and two degrees of motion with simplified input cycles. The actual path of points on the femoral head relative to the acetabular cup were calculated and compared for physiological and simplified input cycles. The in vitro wear rates were found to be highly dependent on the shape of these paths and similarities could be drawn between the shape of the physiological paths and the simplified elliptical paths.

  14. Wear Resistant Amorphous and Nanocomposite Steel Coatings

    SciTech Connect

    Branagan, Daniel James; Swank, William David; Haggard, Delon C; Fincke, James Russell; Sordelet, D.

    2001-10-01

    In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (?104 K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568°C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.

  15. Anti-oxidation treatment of ultra high molecular weight polyethylene components to decrease periprosthetic osteolysis: evaluation of osteolytic and osteogenic properties of wear debris particles in a murine calvaria model.

    PubMed

    Green, Justin M; Hallab, Nadim J; Liao, Yen-Shuo; Narayan, Venkat; Schwarz, Edward M; Xie, Chao

    2013-05-01

    Wear debris-induced osteolysis remains the greatest limitation of long-term success for total joint replacements with ultra-high molecular weight polyethylene (UHMWPE) bearings. To address oxidative degradation post-gamma irradiation, manufacturers are investigating the incorporation of antioxidants into PE resins. Similarly, larger molecular weight monomers have been developed to increase crosslinking and decrease wear debris, and ultimately osteolysis. However, the effects of modifying monomer size, crosslink density, and antioxidant incorporation on UHMWPE particle-induced osteoclastic bone resorption and coupled osteoblastic bone formation have never been tested. Here, we review the field of antioxidant-containing UHMWPE, and present an illustrative pilot study evaluating the osteolytic and osteogenic potential of wear debris generated from three chemically distinct particles (MARATHON®, XLK, and AOX™) as determined by a novel 3D micro-CT algorithm designed for the murine calvaria model. The results demonstrate an approach by which the potential osteoprotective effects of antioxidants in UHMWPE can be evaluated.

  16. Submicron sized ultra-high molecular weight polyethylene wear particle analysis from revised SB Charité III total disc replacements.

    PubMed

    Punt, Ilona; Baxter, Ryan; van Ooij, André; Willems, Paul; van Rhijn, Lodewijk; Kurtz, Steven; Steinbeck, Marla

    2011-09-01

    Submicron sized particles are frequently observed in retrieved total hip and knee periprosthetic tissues and appear to be critical in the activation of the phagocytic inflammatory response. In this paper the concentration, size and shape of ultra-high molecular weight polyethylene (UHMWPE) wear particles between 0.05 and 2.00μm were determined after isolation from periprosthetic tissues from retrieved lumbar SB Charité III total disc replacements (TDR) using scanning electron microscopy (SEM). For comparison, UHMWPE wear particles were isolated from γ-radiation-air sterilized total hip arthroplasty (THA) revision tissues. The mean concentration of UHMWPE particles in TDR tissues was 1.6×10(9)g(-1)tissue (range 1.3-2.0), which was significantly lower than the concentration of 2.3×10(9)g(-1) THA revision tissue (range 1.8-3.2) (P=0.03). The mean particle size (equivalent circular diameter: TDR, 0.46μm; THA 0.53μm, P=0.60) and mean shape were comparable between TDR and THA (aspect ratio: TDR, 1.89; THA, 1.99, P=0.35; roundness: TDR, 0.58; THA, 0.56, P=0.35). However, the TDR particles tended to be smaller and more round. Although no correlations were found between visible damage to the UHMWPE core and the concentration or shape of the UHMWPE particles, a positive correlation was found between increasing particle size and increasing rim penetration of the TDR core (P=0.04). The presence of UHMWPE particles of similar size and shape in TDR tissue, albeit lower in concentration, might explain why, unlike THA, pain rather than osteolysis is the major reason for revision surgery.

  17. Long-wearing TFE/metal bearings

    NASA Technical Reports Server (NTRS)

    Brass, R. A.; Gillon, W. A., Jr.

    1980-01-01

    Method for making metal/polytetrafluoroethylene (TFE) bearing surfaces embeds long-wearing layer of TFE in microscopic pits in metal. Technique has potential applications in automotive gears, ball joints, and roller chain components. Other applications are in use of unlubricated bearings in chemical, pharmaceutical, and food-processing equipment.

  18. Nuclear fuel assembly wear sleeve

    SciTech Connect

    Cadwell, D.J.; Kmonk, S.

    1983-03-08

    An improved control rod guide tube for use in a fuel assembly in a nuclear reactor. The guide tube extends the complete length of the fuel assembly and has its upper end fastened in a cylindrical housing by swaging the guide tube material into grooves formed in the housing walls. To eliminate wear on the guide tube inner walls caused by hydraulic induced vibratory forces on a control rod adapted to move therein, a thin-walled chrome plated sleeve is threaded into the top end of the guide thimble and extends downwardly a distance sufficient to be engaged by the control rod during reactor operation. The sleeve serves as a highly resistant wear surface between the control rod and walls on the guide tube in the fuel assembly.

  19. Corneal epithelial permeability during extended wear of disposable contact lenses versus daily wear of soft contact lenses.

    PubMed Central

    Schurmans, L R; Boets, E P; van Best, J A

    1995-01-01

    AIMS--The corneal epithelial permeability during extended wear of disposable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeability value than the daily wear of soft contact lenses. A higher permeability makes the cornea more vulnerable for bacterial infections and thus could explain the higher incidence of bacterial keratitis found in extended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. METHOD--The corneal epithelial permeability was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. Thereafter the determination was repeated in each volunteer after extended wear of disposable contact lenses for 1 month. The permeability in 34 healthy non-contact lens wearing volunteers was determined as a control. The permeability value was calculated from the amount of fluorescein that passed into the cornea after application by means of an eyebath. RESULTS--The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not significantly different (Wilcoxon paired test p > 0.5). The mean permeability for the non-contact lens wearing controls was 0.042 nm/s. CONCLUSION--The results do not sustain the explanation that a difference in permeability value is the main cause of the increased incidence of keratitis during extended wear of disposable contact lenses in comparison with daily wear. PMID:7742282

  20. What Not to Wear and Other Stories: Addressing Religious Diversity in Schools

    ERIC Educational Resources Information Center

    Blair, Ann; Aps, Will

    2005-01-01

    This article considers the position of religion in schools in England and Wales in light of the recent decision in "The Queen on the application of SB v Headteacher and Governors of Denbigh High School". This held that the refusal to allow a pupil to wear the jilbab was a breach of her rights under the European Convention for the…

  1. Tempering-Induced Microstructural Changes in the Weld Heat-Affected Zone of 9 to 12 Pct Cr Steels and Their Influence on Sliding Wear

    NASA Astrophysics Data System (ADS)

    Velkavrh, Igor; Kafexhiu, Fevzi; Klien, Stefan; Diem, Alexander; Podgornik, Bojan

    2017-01-01

    Increasing amount of tribological applications is working under alternating high/low temperature conditions where the material is subjected to temperature fatigue mechanisms such as creep, softening due to annealing, and at the same time must withstand mechanical wear due to sliding contact with pairing bodies. Steam turbine valves, gate valves, valve heads, stems, seats and bushings, and contacting surfaces of the carrier elements are some examples of such applications. The purpose of the present study is to evaluate the potential of X20 and P91 steels as materials for applications operating under combined effect of mechanical wear and alternating high/low temperature conditions. It was focused on how the microstructural changes occurring in the weld zone affect the wear properties of the selected materials. Generally, with longer tempering time and higher tempering temperature, the number of carbide precipitates decreased, while their relative spacing increased. Before tempering, the morphology of the steel matrix (grain size, microstructure homogeneity) governed the wear resistance of both steels, while after tempering wear response was determined by the combination of the number and the size of carbide particles. After tempering, in X20 steel larger number of stable M23C6 carbides was observed as compared with P91 steel, resulting in lower wear rates. It was observed that for both steels, a similar combination of number density and size distribution of carbide particles provided the highest wear resistance.

  2. Are there biological markers of wear?

    PubMed

    Bauer, Thomas W; Shanbhag, Arun S

    2008-01-01

    Potential systemic markers of implant wear include products of the wear process (particles and ions) and mediators of the inflammatory reaction that can be induced by wear. Ions from polymers used in arthroplasty are not specific, but high metal ion levels may help identify patients with unexpectedly high wear of metal-on-metal implants. The kinetics of ion production, transport, and excretion are complex, however, so it is currently difficult to interpret the significance of mild elevations in metal ions. Indices of bone turnover (eg, collagen fragments) and mediators involved in the inflammatory reaction to particles (eg, osteoprotegerin, RANKL, interleukins) may be associated with osteolysis, but systemic disorders (eg, osteoarthritis) and the use of medications that influence bone remodeling limit the predictive value of these analytes with respect to the consequences of implant wear. Using genomic and proteomic methods to measure multiple analytes offers promise, but the challenge is to identify markers specifically associated with wear that are not elevated by other conditions that often coexist in this patient population.

  3. Study on the applicability of a precise, accurate method for rapid evaluation of engine and lubricant performance. [determination of wear metal in used lubricating oils

    NASA Technical Reports Server (NTRS)

    Kinard, J. T.

    1975-01-01

    The development of a procedure for obtaining data related to wear metal determinations in used lubricants is discussed. The procedure makes it possible to obtain rapid, simultaneous determinations of a number of wear metals at levels of parts per thousand to low parts per billion using a small amount of sample. The electrode assembly and instrumentation used in the process are described. Samples of data obtained from tests conducted under controlled conditions are tabulated.

  4. Ceramic-like wear behaviour of human dental enamel.

    PubMed

    Arsecularatne, J A; Hoffman, M

    2012-04-01

    This paper reports a transmission electron microscopy (TEM) analysis of subsurfaces of enamel specimens following in vitro reciprocating wear tests with an enamel cusp sliding on a flat enamel specimen under hydrated conditions. The obtained results show that crack formation occurred in the wear scar subsurface. The path followed by these cracks seems to be dictated either by the histological structure of enamel or by the contact stress field. Moreover, the analysis of a set of enamel wear results obtained from the literature and application of fracture-based models, originally developed for ceramics, correlate well, confirming the similar wear processes taking place in these materials. This analysis also reveals a marked influence of coefficient of friction on the enamel wear rate: for a higher coefficient of friction value, enamel wear can be severe even under forces generated during normal operation of teeth.

  5. Wear behavior of pressable lithium disilicate glass ceramic.

    PubMed

    Peng, Zhongxiao; Izzat Abdul Rahman, Muhammad; Zhang, Yu; Yin, Ling

    2016-07-01

    This article reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressable lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using three-dimensional laser scanning microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation, and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behavior of LDGC and will provide guidelines for better utilization and preparation of the material for long-term success in dental restorations. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 968-978, 2016.

  6. Wear Behaviour of Pressible Lithium Disilicate Glass Ceramic

    PubMed Central

    Peng, Zhongxiao; Rahman, Muhammad Izzat Abdul; Zhang, Yu; Yin, Ling

    2015-01-01

    This paper reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressible lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using 3D laser scanning microscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behaviour of LDGC and will provide guidelines for better utilisation and preparation of the material for long-term success in dental restorations. PMID:25980530

  7. Dynamic surface microstructural changes during tribological contact that determine the wear behaviour of hip prostheses: metals and ceramics.

    PubMed

    Rainforth, W Mark; Zeng, Peng; Ma, Le; Valdez, Akemi Nogiwa; Stewart, Todd

    2012-01-01

    It is often the dynamic microstructural changes induced by tribological contact that determine whether or not a material exhibits good wear resistance. It is well known that the mechanical properties of a surface are significantly different from the bulk, an effect amplified by wear induced plastic deformation and electrochemical effects. Despite the importance of these dynamic microstructural changes, there remains little quantitative understanding of how the surface microstructure changes during tribo-contact, and how this modifies the surface mechanical properties and chemical activity. This contribution will focus on key total hip arthroplasty materials, specifically CoCrMo alloys, third and fourth generation alumina/zirconia toughened alumina. High resolution techniques have been used to characterise the wear induced microstructural changes for both in vivo and in vitro samples, which has provided new insight into the wear mechanisms. The results are discussed in detail, in particular, how they inform future materials development for this important application.

  8. Development of Advanced Surface Enhancement Technology for Decreasing Wear and Corrosion of Equipment Used for Mineral Processing

    SciTech Connect

    Daniel Tao; Craig A. Blue

    2004-08-01

    Equipment wear is a major concern in the mineral processing industry, which dramatically increases the maintenance cost and adversely affects plant operation efficiency. In this research, wear problems of mineral processing equipment including screens, sieve bends, heavy media vessel, dewatering centrifuge, etc., were identified. A novel surface treatment technology, high density infrared (HDI) surface coating process was proposed for the surface enhancement of selected mineral processing equipment. Microstructural and mechanical properties of the coated samples were characterized. Laboratory-simulated wear tests were conducted to evaluate the tribological performance of the coated components. Test results indicate that the wear resistance of AISI 4140 and ASTM A36 steels can be increased 3 and 5 folds, respectively by the application of HDI coatings.

  9. Wear behavior of austenite containing plate steels

    NASA Astrophysics Data System (ADS)

    Hensley, Christina E.

    As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

  10. Casing wear caused by tooljoint hardfacing

    SciTech Connect

    Best, B.

    1986-02-01

    Casing wear caused by new tooljoint hardfacings, such as fine-mesh tungsten-carbide hardfacing and a hardfacing covered with a layer of relatively soft material, has been investigated in the laboratory. The tests were performed on a full-scale test facility with field conditions-forces, motions, and fluids-simulated as closely as possible. It was found that the major mechanisms responsible for casing wear by tooljoints are adhesive wear, abrasive wear, and ploughing. Wear mechanisms can be classified as mild, normal, and severe. A thorough understanding of these mechanisms could lead to measures for lessening casing wear. This can be achieved with (1) tooljoints that have a sufficiently large, smooth, round, and uniform surface and (2) an appropriate mud that has a sufficiently high content of soft solid particles, such as barites, to form a layer in the tooljoint/casing contact area so that metal-to-metal contact is avoided and small, hard mud particles are embedded.

  11. Optical wear monitoring

    SciTech Connect

    Kidane, Getnet S; Desilva, Upul P.; He, Chengli; Ulerich, Nancy H.

    2016-07-26

    A gas turbine includes first and second parts having outer surfaces located adjacent to each other to create an interface where wear occurs. A wear probe is provided for monitoring wear of the outer surface of the first part, and includes an optical guide having first and second ends, wherein the first end is configured to be located flush with the outer surface of the first part. A fiber bundle includes first and second ends, the first end being located proximate to the second end of the optical guide. The fiber bundle includes a transmit fiber bundle comprising a first plurality of optical fibers coupled to a light source, and a receive fiber bundle coupled to a light detector and configured to detect reflected light. A processor is configured to determine a length of the optical guide based on the detected reflected light.

  12. 3D finite element modeling of sliding wear

    NASA Astrophysics Data System (ADS)

    Buentello Hernandez, Rodolfo G.

    Wear is defined as "the removal of material volume through some mechanical process between two surfaces". There are many mechanical situations that can induce wear and each can involve many wear mechanisms. This research focuses on the mechanical wear due to dry sliding between two surfaces. Currently there is a need to identify and compare materials that would endure sliding wear under severe conditions such as high velocities. The high costs associated with the field experimentation of systems subject to high-speed sliding, has prevented the collection of the necessary data required to fully characterize this phenomena. Simulating wear through Finite Elements (FE) would enable its prediction under different scenarios and would reduce experimentation costs. In the aerospace, automotive and weapon industries such a model can aid in material selection, design and/or testing of systems subjected to wear in bearings, gears, brakes, gun barrels, slippers, locomotive wheels, or even rocket test tracks. The 3D wear model presented in this dissertation allows one to reasonably predict high-speed sliding mechanical wear between two materials. The model predictions are reasonable, when compared against those measured on a sled slipper traveling over the Holloman High Speed Tests Track. This slipper traveled a distance of 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s.

  13. 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.

  14. Effect of Polyethylene Crosslinking and Bearing Design on Wear of Unicompartmental Arthroplasty.

    PubMed

    Netter, Jonathan; Hermida, Juan C; D'Alessio, Jerry; Kester, Mark; D'Lima, Darryl D

    2015-08-01

    Wear and polyethylene damage continue to be important factors affecting outcomes of unicompartmental knee arthroplasty. We compared two design rationales for unicompartmental arthroplasty: fully congruent mobile bearings; or moderately conforming fixed bearings using experimental and computational wear simulation. Experimental wear rates were 3.89 (±0.12) mg/million cycles for the highly crosslinked Triathlon PKR fixed bearing compared to 18.35 (±0.19) mg/million cycles for the low crosslinked Oxford mobile bearing. Finite element analysis was used to calculate the effect of crosslinking and backside wear. Increase in polyethylene crosslinking reduced wear by 68% while backside wear comprised 46% of the total wear in the mobile bearing. Increasing conformity may not be the sole predictor of wear performance and highly crosslinked fixed-bearing polyethylene insert can also provide high wear performance.

  15. Wear and migration of highly cross-linked and conventional cemented polyethylene cups with cobalt chrome or Oxinium femoral heads: a randomized radiostereometric study of 150 patients.

    PubMed

    Kadar, Thomas; Hallan, Geir; Aamodt, Arild; Indrekvam, Kari; Badawy, Mona; Skredderstuen, Arne; Havelin, Leif Ivar; Stokke, Terje; Haugan, Kristin; Espehaug, Birgitte; Furnes, Ove

    2011-08-01

    This randomized study was performed to compare wear and migration of five different cemented total hip joint articulations in 150 patients. The patients received either a Charnley femoral stem with a 22.2 mm head or a Spectron EF femoral stem with a 28 mm head. The Charnley articulated with a γ-sterilized Charnley Ogee acetabular cup. The Spectron EF was used with either EtO-sterilized non-cross-linked polyethylene (Reflection All-Poly) or highly cross-linked (Reflection All-Poly XLPE) cups, combined with either cobalt chrome (CoCr) or Oxinium femoral heads. The patients were followed with repeated RSA measurements for 2 years. After 2 years, the EtO-sterilized non-cross-linked Reflection All-Poly cups had more than four times higher proximal penetration than its highly cross-linked counterpart. Use of Oxinium femoral heads did not affect penetration at 2 years compared to heads made of CoCr. Further follow-up is needed to evaluate the benefits, if any, of Oxinium femoral heads in the clinical setting. The Charnley Ogee was not outperformed by the more recently introduced implants in our study. We conclude that this prostheses still represents a standard against which new implants can be measured.

  16. Wear behavior of the plasma and thermal oxidized Ti-15Mo and Ti-6Al-4V alloys

    NASA Astrophysics Data System (ADS)

    Hacisalioglu, I.; Yildiz, F.; Alsaran, A.; Purcek, G.

    2017-02-01

    Titanium and its alloys widely used in load bearing applications. Titanium alloys are capable of providing lower elastic modulus and better corrosion resistance with alloying processes. In spite of the modified mechanical properties, the surface degradation is still the main critical defect. Ti-15Mo alloy is one of the alpa+beta titanium alloys with acceptable mechanical and chemical superiority. Recent researches in literature show that the wear performance of base Ti-15Mo is relatively low as compared to Ti-6Al-4V, using in high performance applications. Plasma oxidized surfaces increase the tribological and chemical performance of titanium alloys. In this study the Ti-15Mo alloy and Ti-6Al-4V alloys were compared in terms of wear performance. To obtain alloys with similar microstructure they were solution treated at 800°C 1H and then air-cooled. The plasma and thermal oxidations were applied at 650°C for 1 hour. Wear performance of oxidized surfaces investigated in dry conditions. Oxidized surface characterized with XRD, SEM, 3D profilometer and hardness measurements. Wear volume calculated with 3D profilometer. Results show that oxidizing increased the surface roughness and improved the wear performance of Ti15Mo alloy. The plasma and thermal oxidized Ti-15Mo showed a remarkable increase in wear resistance.

  17. Wear analysis of disc cutters of full face rock tunnel boring machine

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaohuang; Meng, Liang; Sun, Fei

    2014-11-01

    Wear is a major factor of disc cutters' failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine(TBM) to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead(radius for installation); in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians' experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project(excavation length 173 m). The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project(excavation length of 5621 m). The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate(accuracy 16.12%) but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient(accuracy 41%, which is in agreement with the prediction of disc cutters' life in the field). This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.

  18. IMPROVEMENT OF WEAR COMPONENT'S PERFORMANCE BY UTILIZING ADVANCED MATERIALS AND NEW MANUFACTURING TECHNOLOGIES: CASTCON PROCESS FOR MINING APPLICATIONS

    SciTech Connect

    Xiaodi Huang; Richard Gertsch

    2001-10-30

    The fibrous monolith material was successfully consolidated in both the hot press and the hot isostatic press. Initial evaluations indicate the material will have a very high fracture toughness and be very hard. Tungsten carbide was successfully consolidated in an H13 tool steel with the incorporation of a Co-Cr layer between the WC and the steel.

  19. Hardfacing of high temperature alloys for ethylene pyrolysis applications

    SciTech Connect

    Agosta, P.; Levesque, C.; Kurlekar, A.

    1994-12-31

    Materials of construction in an ethylene pyrolysis furnace must withstand severe conditions including high temperatures, alternating oxidizing and carburizing atmospheres, impinging coke particles, and thermal cycling. The creep, high temperature corrosion, and erosion which are experienced by furnace components can be resisted by proper materials selection. Positioned directly in the process stream, thermowells are used to monitor process temperatures. Thermowell materials of construction must be selected with the extreme process conditions in mind. As always, safety is an underlying factor. Given the highly flammable ethylene stream, thermowell failures must be prevented at any cost. No single material was found to resist both creep and erosion under existing operating conditions. However, the combination of a creep resistant base material with a wear resistant coating was found to not only prevent failures, but also greatly extend thermowell life, reducing downtime and maintenance costs. Laboratory research and actual operations data have shown a nickel based superalloy with a ceramic hardfacing to be highly cost effective in thermowell applications in resisting the combination of creep and erosion found in ethylene pyrolysis applications.

  20. IMPROVEMENT OF WEAR COMPONENT'S PERFORMANCE BY UTILIZING ADVANCED MATERIALS AND NEW MANUFACTURING TECHNOLOGIES: CASTCON PROCESS FOR MINING APPLICATIONS

    SciTech Connect

    Xiaodi Huang; Richard Gertsch

    2004-03-22

    During this reporting period, the debinding and off-gassing furnace was switched from a vacuum furnace to a conventional kiln to solve the HIP can expansion problem during high temperature off-gassing, which caused disc distortion. Two 6.5 inch discs were produced. Both looked acceptable and one was machined. It was found that the disc hub section was little bit thin and micro cracks were seen along the disc radial directions.

  1. Employees Wearing Religious Attire

    ERIC Educational Resources Information Center

    Zirkel, Perry

    2004-01-01

    While adherents to many religions can be identified by distinctive clothing or accessories, the wearing of such garb by teachers is not necessarily related to evangelism in the classroom. The following case and the accompanying question-and-answer discussion illustrate the problem of the principal caught between the rock of First Amendment…

  2. Wear resistant valve

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1980-01-01

    A valve which is resistant to wear caused by particles trapped between the valve seat and the valve member or poppet when the valve closes, including an outlet for directing washing fluid at the valve seat and/or sealing face of the poppet and means for supplying pressured fluid to the outlet at the time when the valve is closing.

  3. Wear characteristics of severely deformed aluminum sheets by accumulative roll bonding (ARB) process

    SciTech Connect

    Talachi, A. Kazemi; Eizadjou, M. Manesh, H. Danesh; Janghorban, K.

    2011-01-15

    Wear behavior of severely deformed aluminum sheets by accumulative roll bonding (ARB) process was characterized using a pin on disc wear machine at different conditions. The sheets were processed up to eight ARB cycles in order to induce a high strain ({approx} 6.4) to the samples. EBSD results showed that after eight cycles of ARB, sheets were found to contain ultrafine grains with high fraction of high angle grain boundaries. Wear experiments were conducted under different loading and operating conditions, including dry and immersion lubrication, and rotation speeds. Wear was continuously monitored by measuring the wear rates and morphologies of worn surfaces by scanning electron microscope (SEM). Contrary to expectation, the wear resistance of the ARBed Al sheets was less than the non-processed sheets. Wear rates of the ARBed Al sheets increased by increasing wear load and rotation speed, while, immersion lubrication decreased the wear rate significantly. Based on the observation and results, a model for the wear of the ARBed Al was proposed. - Research Highlights: {yields}The wear rate of the ARBed Al was higher than that of the non-processed alloy. {yields}This unexpected behavior was related to the low strain hardening capability and evolution of the ARB subsurface microstructure during the wear process. {yields}Sliding wear of the ARBed Al proceeded by surface deformation, and progressed by delamination of the deformed surface layer. {yields}The wear rate of ARBed Al increased by increasing applied load and sliding speed.

  4. Low Temperature Unbalanced Magnetron Deposition of Hard, Wear-Resistant Coatings for Liquid-Film Bearing Applications

    NASA Technical Reports Server (NTRS)

    Sproul, William D.

    1996-01-01

    The original program for evaluating the tribological properties several different hard coatings for liquid film bearing applications was curtailed when the time for the program was reduced from 3 years to 1. Of the several different coatings originally planned for evaluation, we decided to concentrate on one coating, carbon nitride. At BIRL, we have been instrumental in the development of reactively sputtered carbon nitride coatings, and we have found that it is a very interesting new material with very good tribological properties. In this program, we found that the reactively sputtered carbon nitride does not bond well directly to hardened 440C stainless steel; but if an interlayer of titanium nitride is added between the carbon nitride and the 440C, the adhesion of the dual coating combination is very good. Statistically designed experiments were run with the dual layer combination, and 3 variables were chosen for the Box-Benken design, which were the titanium nitride interlayer thickness, the nitrogen partial pressure during the reactive sputtering of the carbon nitride, and the carbon nitride substrate bias voltage. Two responses were studied from these three variables; the adhesion of the dual coating combination to the 440C substrate and the friction coefficient of the carbon nitride in dry sliding contact with 52100 steel in air. The best adhesion came with the thickness interlayer thickness studied, which was 4 micrometers, and the lowest coefficient of friction was 0.1, which was achieved when the bias voltage was in the range of -80 to - 120 V and the nitrogen partial pressure was 3 mTorr.

  5. Magnetic Fluid Friction and Wear Behavior

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.

    1998-01-01

    The friction and wear properties of two groups of magnetic fluids, one developed at NASA Lewis Research Center and a commercial fluid, were evaluated for boundary lubrication. Friction and wear measurements were made using a pin-on-disk apparatus. Three different ball materials were evaluated, (1) 440C, (2) Al2O3, and (3) Si3N4 against 440C disks. The first class of magnetic fluids have a low vapor pressure hydrocarbon base oil and are suitable for space application. Four variations of this fluid were evaluated: (1) the base oil, (2) base oil with anti-wear additives, (3) a 100 Gauss strength magnetic fluid, and (4) a 400 gauss magnetic fluid. The commercial fluid base oil and four different magnetic particle concentration levels have been evaluated. A space qualified fluorinated lubricant was tested for base line comparison. Hardness, optical microscopy, surface profilometry, and surface analysis were used to characterize the test specimens. Friction was unaffected by the concentration of magnetic particles. Wear rates for magnetic fluids were slightly higher than the base oil. The low vapor pressure magnetic fluid has better wear characteristics than the space qualified fluorinated lubricant.

  6. Effect of processing, sterilization and crosslinking on UHMWPE fatigue fracture and fatigue wear mechanisms in joint arthroplasty.

    PubMed

    Ansari, Farzana; Ries, Michael D; Pruitt, Lisa

    2016-01-01

    Ultra high molecular weight polyethylene (UHMWPE) has been used as a bearing surface in total joint replacements (TJR) for nearly five decades. This semi-crystalline polymer has extraordinary energetic toughness owing to its high molecular weight and entanglement density. However, it is challenged by a need to offer a combined resistance to fatigue, wear and oxidation in vivo. The processing, sterilization treatment, and microstructural tailoring of UHMWPE has evolved considerably in the past 50 years but an optimized microstructure remains elusive. This review seeks to provide an overview of this processing history to address two primary questions: First, how does microstructure affect fatigue fracture and fatigue wear mechanisms in UHMWPE? And second, can microstructure be optimized to provide resistance to fatigue, oxidation and wear in vivo? Previous literature demonstrates that while crosslinking improves resistance to adhesive/abrasive wear, it also reduces resistance to fatigue crack propagation and fatigue wear by restricting molecular mobility and rendering the polymer more brittle. Crystallinity improves fatigue resistance but generally increases elastic modulus and concomitant contact stresses in vivo. The presence of fusion defects or oxidation reduces further fatigue resistance and enhances fatigue wear. Thus, UHMWPE microstructural evolution comes with trade-offs. Currently there is no singular formulation of UHMWPE that is ideal for all TJR applications.

  7. Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

    PubMed

    Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

    2015-01-13

    Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

  8. Hardfacing and wear plates battle abrasion

    SciTech Connect

    Miller, R.F.

    1983-06-01

    This article examines abrasion-resistant steels and hardfacing as two effective weapons at the disposal of material handlers. It points out that abrasion is probably the single most destructive form of wear in the mixing and processing of coal. Particulate matter such as quartz sand and other minerals including coal curtail in-service life of dragline buckets, chute, crusher rolls, gates and valves, exhauster fan blades, target plates, truck beds, hoppers, vibrating pans, grinding mills, piping elbows, etc. The advantages of abrasion-resistant steels and hardfacing can be obtained in the form of a composite wear plate-hardfacing on a carbon steel backup plate. It concludes that the composite wear plate represents a major innovation since its advantages include ease of handling, low cost and easy installation, minimum on-site welding time and versatility. Its use is limited only to the consumer's creativity in application.

  9. Thermal Oxidation of Ti6Al4V Alloy with Enhanced Wear and Corrosion Resistance for Oil and Gas Application: Effect of Temperature

    NASA Astrophysics Data System (ADS)

    Lin, Naiming; Zhou, Peng; Wang, Yating; Zou, Jiaojuan; Ma, Yong; Wang, Zhenxia; Tian, Wei; Yao, Xiaofei; Tang, Bin

    2015-03-01

    Thermal oxidation (TO) treatments were performed at 873 K, 898 K, 923 K, 948 K, 973 K, 998 K and 1023 K for 10 h in air to improve the wear and corrosion resistance of Ti6Al4V alloy. The effect of TO temperature on microstructural characterizations and surface properties of the obtained TO layers were investigated. The results showed that TO layers with various thickness values were formed on Ti6Al4V alloy under different temperatures. The thickness of the TO layers increased with the increasing of TO temperature. TO layer that was obtained at 973 K suggested the highest surface hardness and the best wear resistance. TO layer that was realized at 948 K exhibited superior corrosion resistance to other TO layers. TO treatment could be considered as an effective method for preventing wear and corrosion of Ti6Al4V alloy.

  10. Effect of Different Forefoot and Heel Support Surfaces on the Activities of the RF and HAM Muscles during the Sit-to-stand Task while Wearing High-heel Shoes.

    PubMed

    Yoo, Won-Gyu

    2014-10-01

    [Purpose] The purpose of this study was to show the effect of different forefoot and heel support surfaces on the activities of the rectus femoris and medial hamstring muscles during the sit-to-stand task while wearing high-heel shoes. [Subjects] Fifteen female subjects were recruited. [Methods] The muscle activities of the rectus femoris and hamstring muscles were recorded using an MP150 system during the sit-to-stand task while wearing various high-heeled shoes. [Results] The activities of the rectus femoris and medial hamstring muscles significantly decreased when subjects wore condition 1 shoes compared with when they wore condition 2, 3 or 4 high-heeled shoes. The activities of the rectus femoris and medial hamstring muscles significantly decreased when subjects wore condition 2 high-heeled shoes compared with condition 3 or 4 high-heeled shoes. [Conclusion] The results can be interpreted as indicating that the size of the forefoot supporting surface can influence the lower extremity muscles of women wearing high-heeled shoes more than the size of the heel supporting surface.

  11. Continued force wear and part correction experiments

    SciTech Connect

    Hannah, P.R.; Day, R.D.; Hatch, D.J.

    1995-12-31

    This abstract reports the near completion of the first phase of this program. It is the aim of this program to provide the operator of a N/C diamond turning machine or N/C grinding machine (jig grinder) with the wear characteristics necessary to achieve uniform material removal. The second phase of this program addresses a different problem, although solving this problem is highly dependent on the results of the first phase. Diamond turned, or any lathe turned surface, exhibits regular tool marks due to the tool passing over the surface being cut. Changes in depth of cut, feed rate and work rpm will change the character of these groves, but will not eliminate them. Optical surfaces produced by this process exhibit increased scattering as the light wavelength decreases limiting their use; at least for optical purposes, to IR and some visible applications. Utilizing wear information gathered in the first part of this program we will attempt to reduce these residual tool marks by polishing. The polishing of diamond turned surfaces is not new. Diamond turned metal surfaces, especially in electroless nickel and high phosphorus nickel electroplate have been polished to improve their scatter characteristics. What we believe is unique is the use of a spherical wheel, rotating on axis and being moved over the part in a prescribed manner by numerical control. Over the past year we have made some major changes in our polishing methods and procedures. We have listed below these changes, as a refresher for the reader as to our previous procedures.

  12. Wear testing of materials and surfaces for total knee replacement.

    PubMed

    Walker, P S; Blunn, G W; Lilley, P A

    1996-01-01

    A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements.

  13. Wear mechanism and tribological characteristics of porous NiTi shape memory alloy for bone scaffold.

    PubMed

    Wu, Shuilin; Liu, Xiangmei; Wu, Guosong; Yeung, Kelvin W K; Zheng, Dong; Chung, C Y; Xu, Z S; Chu, Paul K

    2013-09-01

    The abraded debris might cause osteocytic osteolysis on the interface between implants and bone tissues, thus inducing the subsequent mobilization of implants gradually and finally resulting in the failure of bone implants, which imposes restrictions on the applications of porous NiTi shape memory alloys (SMAs) scaffolds for bone tissue engineering. In this work, the effects of the annealing temperature, applied load, and porosity on the tribological behavior and wear resistance of three-dimensional porous NiTi SMA are investigated systematically. The porous structure and phase transformation during the exothermic process affect the tribological properties and wear mechanism significantly. In general, a larger porosity leads to better tribological resistance but sometimes, SMAs with small porosity possess better wear resistance than ones with higher porosity during the initial sliding stage. It can be ascribed to the better superelasticity of the former at the test temperature. The porous NiTi phase during the exothermic reaction also plays an important role in the wear resistance. Generally, porous NiTi has smaller friction coefficients under high loads due to stress-induced superelasticity. The wear mechanism is discussed based on plastic deformation and microcrack propagation.

  14. Wear and Life Characteristics of Microwave-Sintered Copper-Graphite Composite

    NASA Astrophysics Data System (ADS)

    Rajkumar, K.; Aravindan, S.; Kulkarni, M. S.

    2012-11-01

    Copper-graphite composite is an important tribological material used in electrical sliding contact applications like electrical brushes in motors and generators. The electrical sliding contact experiences multiple stresses such as mechanical pressure and temperature. Traditional life tests under normal operating condition would be a time-consuming process due to the longer expected life of the composite. Accelerated wear testing was carried out to evaluate the life characteristics of the composite. This work focuses on evaluation of tribological performance of microwave-sintered copper-graphite composite using accelerated wear testing methodology using high temperature pin-on-disc tribometer. Microstructural studies of worn out surfaces were carried out using SEM with EDAX. Reliability and analysis on life characteristics were performed on the time-to-failure data using temperature-nonthermal-accelerated life-stress model. The obtained times-to-failure data from the accelerated wear testing was extrapolated to normal usage condition. Temperature and pressure are significantly affecting the wear performance. Self-lubricating action of graphite and improvement in wear resistance is helpful in extending the life of copper graphite composite. The life of the composite obtained through testing at mean and 99% reliability are 18,725 and 16,950 h, respectively.

  15. In Situ Wear Test on Thermal Spray Coatings in a Large Chamber Scanning Electron Microscope

    NASA Astrophysics Data System (ADS)

    Luo, Weifeng; Tillmann, Wolfgang; Selvadurai, Ursula

    2015-01-01

    Currently, the determination of the mass loss is usually used for a quantitative evaluation of wear tests, while the analysis of wear tracks is utilized for a qualitative evaluation of wear. Both evaluation methods can only be used after the wear testing process and their results only present the final outcome of the wear test. However, the changes during the wear test and the time-dependent wear mechanisms are of great interest as well. A running wear test in a large chamber scanning electron microscope (SEM) offers the first opportunity to observe the wear process in situ. Different wear mechanisms, such as the adhesive, abrasive wear, surface fatigue and tribochemical reaction, can be recorded with high magnification. Within this research, a special pin-on-disk testing device is designed for a vacuum environment. Using this device, arc-sprayed NiCrBSi coatings and high-velocity-oxygen-fuel-sprayed WC-12Co coatings were tested in a large chamber SEM with Al2O3 ceramic balls as wear counterparts. During the wear testing, different wear mechanisms were determined and the processes were recorded in short video streams.

  16. Wear Modalities and Mechanisms of the Mining Non-asbestos Composite Brake Material

    NASA Astrophysics Data System (ADS)

    Bao, Jiusheng; Yin, Yan; Zhu, Zhencai; Tong, Minming; Lu, Yuhao; Peng, Yuxing

    2013-08-01

    The mining brake material is generally made of composite materials and its wear has important influences on the braking performance of disc brakes. In order to improve the braking reliability of mine hoisters, this paper did some tribological investigations on the mining brake material to reveal its wear modalities and mechanisms. The mining non-asbestos brake shoe and 16Mn steel were selected as braking pairs and tested on a pad-on-disc friction tester. And a SEM was used to observe the worn surface of the brake shoe. It is shown that the non-asbestos brake material has mainly five wear modalities: adhesive wear, abrasive wear, cutting wear, fatigue wear and high heat wear. At the front period of a single braking the wear modality is mainly composed of some light mechanical wear such as abrasive, cutting and point adhesive. With the temperature rising at the back period it transforms to some heavy mechanical wear such as piece adhesive and fatigue. While in several repeated brakings once the surface temperature rises beyond the thermal-decomposition point of the bonding material, the strong destructive high heat wear takes leading roles on the surface. And a phenomenon called friction catastrophe (FC) occurs easily, which as a result causes a braking failure. It is considered that the friction heat has important influences on the wear modalities of the brake material. And the reduction of friction heat must be an effective technical method for decreasing wear and avoiding braking failures.

  17. Wear Resistance and Wear Mechanism of a Hot Dip Aluminized Steel in Sliding Wear Test

    NASA Astrophysics Data System (ADS)

    Xue, Zhiyong; Hao, Xiaoyang; Huang, Yao; Gu, Lingyun; Ren, Yu; Zheng, Ruipeng

    2016-12-01

    Sliding wear experiments were conducted on a hot dip aluminized steel to investigate its wear resistance and wear mechanism. The wear tests were also carried out on a hot dip galvanized steel and the base material (steel Q345) as a comparison. Results show that the wear resistance and hardness of the hot dip aluminized steel are significantly higher than that of the hot dip galvanized steel and the steel Q345 at room temperature. The better wear resistance of the hot dip aluminized steel attributes mainly to the formation of a transition layer containing abundant Fe-Al intermetallic compounds and the transformation of wear-resisting oxides during the friction process. The main phase in the transition layer is Fe2Al5. The thickness of the transition layer is about 90-120 μm. When the wear load increases from 3 N to 19 N, the wear type of the aluminized layer transform from adhesive wear (3 N) into abrasive wear (7 N) and finally into slight wear mixed with oxidation (higher than 11 N).

  18. Reciprocating seals: Lubrication and wear resistance. (Latest citations from Fluidex (Fluid Engineering Abstracts) database). Published Search

    SciTech Connect

    Not Available

    1993-10-01

    The bibliography contains citations concerning theoretical and practical analyses of reciprocating seal wear and lubrication. Topics include behavior, friction coefficient, cylinder wear, lubrication film thickness, friction forces, design innovations, lubricating oil viscosity, and wear modeling relative to reciprocating seal frictional wear and lifetime optimization. Applications in piston ring lubrication, internal combustion engines, and vehicle suspension systems are considered. (Contains 250 citations and includes a subject term index and title list.)

  19. Friction and wear of TPS fibers: A study of the adhesion and friction of high modulus fibers

    NASA Technical Reports Server (NTRS)

    Bascom, Willard D.; Lee, Ilzoo

    1990-01-01

    The adhesional and frictional forces between filaments in a woven fabric or felt, strongly influenced the processability of the fiber and the mechanical durability of the final product. Even though the contact loads between fibers are low, the area of contact is extremely small giving rise to very high stresses; principally shear stresses. One consequence of these strong adhesional and frictional forces is the resistance of fibers to slide past each other during weaving or when processed into nonwoven mats or felts. Furthermore, the interfiber frictional forces may cause surface damage and thereby reduce the fiber strength. Once formed into fabrics, flexural handling and manipulation of the material again causes individual filaments to rub against each other resulting in modulus, brittle fibers such as those used in thermal protection systems (TPS). The adhesion and friction of organic fibers, notably polyethylene terephthalate (PET) fibers, have been extensively studied, but there has been very little work reported on high modulus inorganic fibers. An extensive study was made of the adhesion and friction of flame drawn silica fibers in order to develop experimental techniques and a scientific basis for data interpretation. Subsequently, these methods were applied to fibers of interest in TPS materials.

  20. High-temperature wear and oxidation behaviors of TiNi/Ti2Ni matrix composite coatings with TaC addition prepared on Ti6Al4V by laser cladding

    NASA Astrophysics Data System (ADS)

    Lv, Y. H.; Li, J.; Tao, Y. F.; Hu, L. F.

    2017-04-01

    TiNi/Ti2Ni matrix composite coatings were produced on Ti6Al4V surfaces by laser cladding the mixed powders of Ni-based alloy and different contents of TaC (0, 5, 10, 15, 20, 30 and 40 wt.%). Microstructures of the coatings were investigated. High-temperature wear tests of the substrate and the coatings were carried out at 600 °C in air for 30 min. High-temperature oxidation tests of the substrate and the coatings were performed at 1000 °C in air for 50 h. Wear and oxidation mechanisms were revealed in detail. The results showed that TiNi/Ti2Ni as the matrix and TiC/TiB2/TiB as the reinforcements are the main phases of the coatings. The friction coefficients of the substrate and the coatings with different contents of TaC were 0.431 (the substrate), 0.554 (0 wt.%), 0.486 (5 wt.%), 0.457 (10 wt.%), 0.458 (15 wt.%), 0.507 (20 wt.%), 0.462 (30 wt.%) and 0.488 (40 wt.%). The wear rates of the coatings were decreased by almost 83%-98% than that of the substrate and presented a decreasing tendency with increasing TaC content. The wear mechanism of the substrate was a combination of serious oxidation, micro-cutting and brittle debonding. For the coatings, oxidation and slight scratching were predominant during wear, accompanied by slight brittle debonding in partial zones. With the increase in content of TaC, the oxidation film better shielded the coatings from destruction due to the effective friction-reducing role of Ta2O5. The oxidation rates of the substrate and the coatings with different contents of TaC at 1000 °C were 12.170 (the substrate), 5.886 (0 wt.%), 4.937 (5 wt.%), 4.517 (10 wt.%), 4.394 (15 wt.%), 3.951 (20 wt.%), 4.239 (30 wt.%) and 3.530 (40 wt.%) mg2 cm-4 h-1, respectively. The oxidation film formed outside the coating without adding TaC was composed of TiO2, NiO, Cr2O3, Al2O3 and SiO2. When TaC was added, Ta2O5 and TaC were also detected, which effectively improved the oxidation resistance of the coatings. The addition of TaC contributed to the

  1. Corrosive wear principles

    SciTech Connect

    Schumacher, W.J.

    1993-12-31

    The dual effects of corrosion and wear operate together in such industries as paper and pulp, coal handling, mining, and sugar beet extraction. There is a synergistic effect that causes far greater wastage to carbon steels, alloy steels, and even much more abrasion resistant cast irons. Several laboratory and in situ studies have been conducted to better understand the contributions of corrosion and wear to the wastage process. The environmental conditions are usually set by the process. However, there are a few instances where inhibitors as sodium nitrite, sodium chromate, and sodium metasilicate have been successfully used to reduce metal wastage of carbon steels. Hardness has been found to be an unreliable guide to performance under wet sliding conditions. Heat treated alloy steels and cast irons are inferior to stainless steels. Even distilled water is too severe a corrodent for steels. While the austenitic stainlesses perform the best, cold rolling to increase hardness does not further improve their performance. The surface roughness of stainless steels gets smoother during corrosive wear testing while it gets rougher for the alloy steels. This observation substantiated the reputation of improved slideability for stainless alloys over alloy steels.

  2. Transparent, superhydrophobic, and wear-resistant coatings on glass and polymer substrates using SiO2, ZnO, and ITO nanoparticles.

    PubMed

    Ebert, Daniel; Bhushan, Bharat

    2012-08-07

    It is of significant interest to create surfaces that simultaneously exhibit high water contact angle, low contact angle hysteresis, and high transmission of visible light, as well as mechanical wear resistance for industrial applications. The fabrication of such surfaces has often involved complex or expensive processes, required techniques that were not suitable for a variety of substrates and particles, required surface post-treatment, or lacked wear resistance. A systematic study has been performed in which transparent superhydrophobic surfaces were created on glass, polycarbonate, and poly(methyl methacrylate) (PMMA) substrates using surface-functionalized SiO(2), ZnO, and indium tin oxide (ITO) nanoparticles. The contact angle, contact angle hysteresis, and optical transmittance were measured for samples using all particle-substrate combinations. To examine wear resistance, multiscale wear experiments were performed using an atomic force microscope (AFM) and a water jet apparatus.

  3. Wear and Tear - Mechanical

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore

    2008-01-01

    The focus of this chapter is on the long term wear and tear, or aging, of the mechanical subsystem of a spacecraft. The mechanical subsystem is herein considered to be the primary support structure (as in a skeleton or exoskeleton) upon which all other spacecraft systems rest, and the associated mechanisms. Mechanisms are devices which have some component that moves at least once, in response to some type of passive or active control system. For the structure, aging may proceed as a gradual degradation of mechanical properties and/or function, possibly leading to complete structural failure over an extended period of time. However, over the 50 years of the Space Age such failures appear to be unusual. In contrast, failures for mechanisms are much more frequent and may have a very serious effect on mission performance. Just as on Earth, all moving devices are subject to normal (and possibly accelerated) degradation from mechanical wear due to loss or breakdown of lubricant, misalignment, temperature cycling effects, improper design/selection of materials, fatigue, and a variety of other effects. In space, such environmental factors as severe temperature swings (possibly 100's of degrees C while going in and out of direct solar exposure), hard vacuum, micrometeoroids, wear from operation in a dusty or contaminated environment, and materials degradation from radiation can be much worse. In addition, there are some ground handling issues such as humidity, long term storage, and ground transport which may be of concern. This chapter addresses the elements of the mechanical subsystem subject to wear, and identifies possible causes. The potential impact of such degradation is addressed, albeit with the recognition that the impact of such wear often depends on when it occurs and on what specific components. Most structural elements of the mechanical system typically are conservatively designed (often to a safety factor of greater than approximately 1.25 on yield for

  4. c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus)

    PubMed Central

    Fu, Jimin; He, Chong; Xia, Biao; Li, Yan; Feng, Qiong; Yin, Qifang; Shi, Xinghua; Feng, Xue; Wang, Hongtao; Yao, Haimin

    2016-01-01

    Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance. PMID:27001150

  5. Effects of a Destabilization Heat Treatment on the Microstructure and Abrasive Wear Behavior of High-Chromium White Cast Iron Investigated Using Different Characterization Techniques

    NASA Astrophysics Data System (ADS)

    Gasan, Hakan; Erturk, Fatih

    2013-11-01

    The hypoeutectic white cast iron was subjected to various destabilization heat treatment temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C) for 2 hours. The as-cast and destabilized specimens were characterized by optical metallography, classical direct comparison, and the Rietveld method. The volume fractions of carbides were measured by optical metallography. Moreover, the volume fractions of retained austenite and martensite were measured by the classical direct comparison method. Despite the limitations of optical metallography and the classical direct comparison method, the Rietveld method was successively and accurately applied to determine the volume fractions of all phases. In addition, the Rietveld analysis yielded certain results, such as the crystallographic properties of the phases that can be used to explain the relationship between the microstructural parameters and the wear behavior. Abrasive wear tests with different sliding speeds were carried out on the as-cast and destabilized alloys to identify the effect of microstructural parameters on the wear behavior. The results indicated that the morphologies of secondary carbides, the crystallographic properties of the phases, and the proper combination of the amount of martensite, retained austenite, and carbides were the principle parameters that affect the hardness and wear behavior of the alloy.

  6. c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus)

    NASA Astrophysics Data System (ADS)

    Fu, Jimin; He, Chong; Xia, Biao; Li, Yan; Feng, Qiong; Yin, Qifang; Shi, Xinghua; Feng, Xue; Wang, Hongtao; Yao, Haimin

    2016-03-01

    Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance.

  7. 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

  8. Development of ball bearings with solid film for high-vacuum, high-temperature, high-speed application

    NASA Astrophysics Data System (ADS)

    Ogawa, Takashi; Konishi, Kazuaki; Aihara, Satoru; Sawamoto, Takeshi

    1993-04-01

    This paper describes the experimental results of long-life solid lubricated ball bearings tested under high-vacuum of 10 exp -4 Pa, high-temperature of 300 C, and high-speed (9000 rpm) conditions. For full ball-type bearings, the thin soft metals, either Ag or Pb, which were coated on the races and balls, appeared to have good torque properties. However, the durability of such bearings was less than 300 hours. The transfer films from the lamellar solid MoS2 and metal composite retainers improved the torque and wear properties. For ceramic, i.e., silicon nitride, balls used with steel rings, wear occurred on the inner rings. All ceramic bearings with composite retainers showed improved torque and wear properties.

  9. A lightweight, high strength dexterous manipulator for commercial applications

    NASA Technical Reports Server (NTRS)

    Marzwell, Neville I.; Schena, Bruce M.; Cohan, Steve M.

    1991-01-01

    The concept, design, and features are described of a lightweight, high strength, modular robot manipulator being developed for space and commercial applications. The manipulator has seven fully active degrees of freedom and is fully operational in 1 G. Each of the seven joints incorporates a unique drivetrain design which provides zero backlash operation, is insensitive to wear, and is single fault tolerant to motor or servo amplifier failure. Feedback sensors provide position, velocity, torque, and motor winding temperature information at each joint. This sensing system is also designed to be single fault tolerant. The manipulator consists of five modules (not including gripper). These modules join via simple quick-disconnect couplings and self-mating connectors which allow rapid assembly and/or disassembly for reconfiguration, transport, or servicing. The manipulator is a completely enclosed assembly, with no exposed components or wires. Although the initial prototype will not be space qualified, the design is well suited to meeting space requirements. The control system provides dexterous motion by controlling the endpoint location and arm pose simultaneously. Potential applications are discussed.

  10. Fault-Wear Under Constant Slip-Velocity: Experimental Observations

    NASA Astrophysics Data System (ADS)

    Boneh, Y.; Chang, J. C.; Lockner, D. A.; Reches, Z.

    2010-12-01

    Fault wear, which is a natural result of frictional slip, is a complex process that depends on rock properties (e.g., roughness, brittleness, hardness, strength, composition), and loading conditions (e.g., normal stress, slip velocity, slip history, temperature). Fault wear is indicated in the field primarily by the occurrence of gouge zones and slickenside striations. Analyses of natural faults suggest that gouge-thickness is proportional to fault-displacement over 6-8 orders of magnitude (Scholz, 1987). Experimental studies of fault-wear, which were mostly conducted under low-velocity and for short slip distances, indicate strong dependency of the wear-rate on normal stress. Our experimental study of fault-wear was conducted with a rotary shear apparatus that includes continuous monitoring of wear, friction, and temperature at slip velocities of 0.001-1 m/s and large displacements. Samples of Sierra white granite, approximately 7 cm-diameter, were sheared against each other at normal stress ranging between 0.48 and 6.9 MPa and at slip-velocities up to 0.5 m/s. The wear-rate was calculated from the continuously measured closure across the fault blocks, and presented here by the unit W= [(micron of surface wear) / (meter of slip distance)]. We observed three types of experiments: (1) experiments with transient stage of positive wear-rate (closure across the fault); (2) experiments with transient stage of negative wear-rate (dilation across the fault); and (3) experiments with quasi-constant wear-rate with no transient stage. The initial transient stages were followed by a steady-state wear-rate with low intensity of W=0.5-20 μ/m. The positive transient stage of type (1) corresponds to the well-known "running-in" stage of smoothening the initial roughness and high asperities (Wang and Scholz, 1984). The running-in stage in our experiments is characterize with high wear-rate intesntisy (W = 80-250 μ/m) that decays to the low steady-state values. The dilating

  11. Friction and wear performance of boron doped, undoped microcrystalline and fine grained composite diamond films

    NASA Astrophysics Data System (ADS)

    Wang, Xinchang; Wang, Liang; Shen, Bin; Sun, Fanghong

    2015-01-01

    Chemical vapor deposition (CVD) diamond films have attracted more attentions due to their excellent mechanical properties. Whereas as-fabricated traditional diamond films in the previous studies don't have enough adhesion or surface smoothness, which seriously impact their friction and wear performance, and thus limit their applications under extremely harsh conditions. A boron doped, undoped microcrystalline and fine grained composite diamond (BD-UM-FGCD) film is fabricated by a three-step method adopting hot filament CVD (HFCVD) method in the present study, presenting outstanding comprehensive performance, including the good adhesion between the substrate and the underlying boron doped diamond (BDD) layer, the extremely high hardness of the middle undoped microcrystalline diamond (UMCD) layer, as well as the low surface roughness and favorable polished convenience of the surface fine grained diamond (FGD) layer. The friction and wear behavior of this composite film sliding against low-carbon steel and silicon nitride balls are studied on a ball-on-plate rotational friction tester. Besides, its wear rate is further evaluated under a severer condition using an inner-hole polishing apparatus, with low-carbon steel wire as the counterpart. The test results show that the BD-UM-FGCD film performs very small friction coefficient and great friction behavior owing to its high surface smoothness, and meanwhile it also has excellent wear resistance because of the relatively high hardness of the surface FGD film and the extremely high hardness of the middle UMCD film. Moreover, under the industrial conditions for producing low-carbon steel wires, this composite film can sufficiently prolong the working lifetime of the drawing dies and improve their application effects. This research develops a novel composite diamond films owning great comprehensive properties, which have great potentials as protecting coatings on working surfaces of the wear-resistant and anti

  12. In vitro wear of flowable resin composite for posterior restorations.

    PubMed

    Shinkai, Koichi; Taira, Yoshihisa; Suzuki, Shiro; Suzuki, Masaya

    2016-01-01

    The purpose of this study was to examine three- and two-body wear values of flowable resin composites for posterior restorations, using a mechanical loading device. The cavities prepared on flattened extracted molars were restored with flowable resin composites (Clearfil Majesty LV: MLV, Estelite Flow Quick: EFQ, Beautifil Flow Plus F00: BFP, and MI Fill: MIF) using accompanying adhesive systems. A universal resin composite (Clearfil Majesty) was used as a control. The specimens were subjected to in vitro three- and two-body wear testing. MLV showed high wear value (three-body: 14.69 µm, two-body: 0.268 mm(3)) compared with other materials tested in both three- and two-body wear tests. BFP showed high three-body wear value (5.78 µm), whereas low two-body wear value (0.008 mm(3)). MIF and EFQ showed equivalent wear values (MIF, three-body: 0.42 µm, two-body: 0.026 mm(3); EFQ, three-body: 1.15 µm, two-body: 0.14 mm(3)) to that of the control in both wear tests.

  13. Application of a stereometric structural analysis for an evaluation of surface and for a forecast of the wear of endoprothesis acetabular cups

    SciTech Connect

    Cybo, Jerzy; Maszybrocka, Joanna . E-mail: jmaszybr@us.edu.pl; Cwajna, Jan

    2006-06-15

    To improve the resistance to wear and permanent deformation of polyethylene operating in a polymer/metal friction couple, initial plastic deformation of the polyethylene and its electron irradiation was applied. This contributed to a change of the polymer structure, visible already while machining when the sample surfaces were being prepared for a tribological test. The study shows that the interactions that shape the structure of polyethylene, at the same time cause adequate changes to the stereometric structure of its surface. The parameters of surface microgeometry characterize the future tribological behavior of polyethylene during its operation in a friction couple. It has been shown that an analysis of stereometric parameters may constitute the first projection of polymer wear resistance.

  14. Degradation of experimental composite materials and in vitro wear simulation

    NASA Astrophysics Data System (ADS)

    Givan, Daniel Allen

    2001-12-01

    The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects

  15. How to qualify and validate wear simulation devices and methods.

    PubMed

    Heintze, S D

    2006-08-01

    The clinical significance of increased wear can mainly be attributed to impaired aesthetic appearance and/or functional restrictions. Little is known about the systemic effects of swallowed or inhaled worn particles that derive from restorations. As wear measurements in vivo are complicated and time-consuming, wear simulation devices and methods had been developed without, however, systematically looking at the factors that influence important wear parameters. Wear simulation devices shall simulate processes that occur in the oral cavity during mastication, namely force, force profile, contact time, sliding movement, clearance of worn material, etc. Different devices that use different force actuator principles are available. Those with the highest citation frequency in the literature are - in descending order - the Alabama, ACTA, OHSU, Zurich and MTS wear simulators. When following the FDA guidelines on good laboratory practice (GLP) only the expensive MTS wear simulator is a qualified machine to test wear in vitro; the force exerted by the hydraulic actuator is controlled and regulated during all movements of the stylus. All the other simulators lack control and regulation of force development during dynamic loading of the flat specimens. This may be an explanation for the high coefficient of variation of the results in some wear simulators (28-40%) and the poor reproducibility of wear results if dental databases are searched for wear results of specific dental materials (difference of 22-72% for the same material). As most of the machines are not qualifiable, wear methods applying the machine may have a sound concept but cannot be validated. Only with the MTS method have wear parameters and influencing factors been documented and verified. A good compromise with regard to costs, practicability and robustness is the Willytec chewing simulator, which uses weights as force actuator and step motors for vertical and lateral movements. The Ivoclar wear method run on

  16. Wearing someone else's shoes.

    PubMed

    Rae, Kym

    2010-06-01

    This paper recounts a journey of discovery by a scientist who inadvertently takes on coordination of an ArtsHealth programme. The dynamics of role change are explored showcasing the vulnerabilities and fears that often accompany these career adjustments. The associated ArtsHealth programme (Gomeroi gaaynggal) works with Aboriginal and Torres Strait Islander women in Australia throughout their pregnancy to improve understanding of issues that impact the health of themselves and their developing baby. By wearing someone else shoes, the scientist is immersed in the project and must confront issues including skill mix, learning and cultural diversity.

  17. Modulation of bone ingrowth and tissue differentiation by local infusion of interleukin-10 in the presence of ultra-high molecular weight polyethylene (UHMWPE) wear particles.

    PubMed

    Goodman, Stuart; Trindade, Michael; Ma, Ting; Lee, Mel; Wang, Neal; Ikenou, Takashi; Matsuura, Ippe; Miyanishi, Keita; Fox, Nora; Regula, Donald; Genovese, Mark; Klein, John; Bloch, Dan; Smith, R Lane

    2003-04-01

    Interleukin-10 (IL-10) is a cytokine that plays a major role in suppressing the inflammatory response, particularly cell-mediated immunity that is characteristic of the TH1 response. The purpose of this study was to determine whether local infusion of IL-10 could mitigate the suppression of bone ingrowth associated with polyethylene wear particles. Drug test chambers were implanted in the proximal tibia of 20 mature New Zealand White rabbits. The DTC provided a continuous 1 x 1 x 5-mm canal for tissue ingrowth. After a 6-week period for osseointegration, the DTC was then connected to an osmotic diffusion pump. IL-10 at doses of 0.1-100 ng/mL (0.25 microL/h) was infused with or without ultra-high molecular weight polyethylene particles (0.5 +/- 0.2 microm diameter, 10(12) particles/mL) present in the chamber for a 3- or 6-week period. The tissue in the chamber was harvested after each treatment; sections were stained with hematoxylin and eosin for morphometric analysis. Osteoclast-like cells were identified by immunohistochemical staining using a monoclonal antibody directed against the alpha chain of the vitronectin receptor, CD51. Osteoblasts were identified using alkaline phosphatase staining. In dose-response studies, infusion of 1 ng/mL IL-10 yielded the greatest bone ingrowth in the presence of particles. The addition of polyethylene particles evoked a marked foreign body reaction and fibrosis; bone ingrowth was significantly suppressed (p = 0.0003). Bone ingrowth was increased by over 48% with infusion of IL-10 for the final 3 weeks of a 6-week ultra-high molecular weight polyethylene particle exposure compared with particles alone (p = 0.027). IL-10 is a cytokine that plays a major role in suppressing the inflammatory response, especially cell-mediated immunity that is characteristic of the TH1 response. Local infusion of immune-modulating cytokines such as IL-10 may prove to be useful in abating particle-induced periprosthetic osteolysis.

  18. Antioxidant Impregnated Ultra-High Molecular Weight Polyethylene Wear Debris Particles Display Increased Bone Remodeling and a Superior Osteogenic:Osteolytic Profile vs. Conventional UHMWPE Particles in a Murine Calvaria Model

    PubMed Central

    Chen, Yu; Hallab, Nadim J.; Liao, Yen-Shuo; Narayan, Venkat; Schwarz, Edward M.; Xie, Chao

    2015-01-01

    Periprosthetic osteolysis remains a major limitation of long-term successful total hip replacements with ultra-high molecular weight polyethylene (UHMWPE) bearings. As intra and extracellular reactive oxygen species are know to contribute to wear debris-induced osteoclastic bone resorption and decreased osteoblastic bone formation, antioxidant doped UHMWPE has emerged as an approach to reduce the osteolytic potential of wear debris and maintain coupled bone remodeling. To test this hypothesis in vivo, we evaluated the effects of crosslinked UHMWPE wear debris particles (AltrX™), versus similar wear particles made from COVERNOX™ containing UHMWPE (AOX™), in an established murine calvaria model. Eight-week-old female C57B/6 mice (n=10/Group) received a pre-op micro-CT scan prior to surgical implantation of the UHMWPE particles (2mg), or surgery without particles (sham). Dynamic labeling was performed by intraperitoneal injection of calcein on day 7 and alizarin on day 9, and the calvaria were harvested for micro-CT and histology on day 10. Surprisingly, we found that AOX particles induced significantly more bone resorption (1.72-fold) and osteoclast numbers (1.99-fold) vs. AltrX (p<0.001). However, AOX also significantly induced 1.64-fold more new bone formation vs. AltrX (p<0.01). Moreover, while the osteolytic:osteogenic ratio of both particles was very close to 1.0, which is indicative of coupled remodeling, AOX was more osteogenic (Slope=1.13±0.10 vs. 0.97±0.10). Histomorphometry of the metabolically labeled undecalcified calvaria revealed a consistent trend of greater MAR in AOX vs. AltrX. Collectively, these results demonstrate that anti-oxidant impregnated UHMWPE particles have decreased osteolytic potential due to their increased osteogenic properties that support coupled bone remodeling. PMID:26495749

  19. Wear resistance of TiAlSiN thin coatings.

    PubMed

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions.

  20. Elucidation of wear mechanisms by ferrographic analysis

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1981-01-01

    The use of ferrographic analysis in conjunction with light and scanning electron microscopy is described for the elucidation of wear mechanisms taking place in operating equipment. Example of adhesive wear, abrasive wear, corrosive wear, rolling element fatigue, lubricant breakdown, and other wear modes are illustrated. In addition, the use of magnetic solutions to precipitate nonmagnetic debris from aqueous and nonaqueous fluids is described.

  1. 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.

  2. Wear detection by means of wavelet-based acoustic emission analysis

    NASA Astrophysics Data System (ADS)

    Baccar, D.; Söffker, D.

    2015-08-01

    Wear detection and monitoring during operation are complex and difficult tasks especially for materials under sliding conditions. Due to the permanent contact and repetitive motion, the material surface remains during tests non-accessible for optical inspection so that attrition of the contact partners cannot be easily detected. This paper introduces the relevant scientific components of reliable and efficient condition monitoring system for online detection and automated classification of wear phenomena by means of acoustic emission (AE) and advanced signal processing approaches. The related experiments were performed using a tribological system consisting of two martensitic plates, sliding against each other. High sensitive piezoelectric transducer was used to provide the continuous measurement of AE signals. The recorded AE signals were analyzed mainly by time-frequency analysis. A feature extraction module using a novel combination of Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) were used for the first time. A detailed correlation analysis between complex signal characteristics and the surface damage resulting from contact fatigue was investigated. Three wear process stages were detected and could be distinguished. To obtain quantitative and detailed information about different wear phases, the AE energy was calculated using STFT and decomposed into a suitable number of frequency levels. The individual energy distribution and the cumulative AE energy of each frequency components were analyzed using CWT. Results show that the behavior of individual frequency component changes when the wear state changes. Here, specific frequency ranges are attributed to the different wear states. The study reveals that the application of the STFT-/CWT-based AE analysis is an appropriate approach to distinguish and to interpret the different damage states occurred during sliding contact. Based on this results a new generation of condition monitoring

  3. Ultrahigh molecular weight polyethylene/graphene oxide nanocomposites: wear characterization and biological response to wear particles.

    PubMed

    Suñer, S; Gowland, N; Craven, R; Joffe, R; Emami, N; Tipper, J L

    2016-12-09

    In the field of total joint replacements, polymer nanocomposites are being investigated as alternatives to ultrahigh molecular weight polyethylene (UHMWPE) for acetabular cup bearings. The objective of this study was to investigate the wear performance and biocompatibility of UHMWPE/graphene oxide (GO) nanocomposites. This study revealed that low concentrations of GO nanoparticles (0.5 wt %) do not significantly alter the wear performance of UHMWPE. In contrast, the addition of higher concentrations (2 wt %) led to a significant reduction in wear. In terms of biocompatibility, UHMWPE/GO wear particles did not show any adverse effects on L929 fibroblast and PBMNC viability at any of the concentrations tested over time. Moreover, the addition of GO to a UHMWPE matrix did not significantly affect the inflammatory response to wear particles. Further work is required to optimize the manufacturing processes to improve the mechanical properties of the nanocomposites and additional biocompatibility testing should be performed to understand the potential clinical application of these materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  4. Wear Behavior of Newly Developed Bainitic Wheel Steels

    NASA Astrophysics Data System (ADS)

    Sharma, S.; Sangal, S.; Mondal, K.

    2015-02-01

    The present work concentrates on the analysis of wear behavior of bainitic steels made by austempering from a microalloyed steel MAS2, meant for making railway wheel, and comparison with that of a conventional railway wheel steel, wheel-R19. Austempering of the MAS2 steel samples has been performed at different times and temperatures to obtain different morphologies of bainite. Linearly reciprocating dry sliding wear tests of these samples have been carried out at laboratory scale using five different loads. The wear behavior of the bainitic steels has been compared with that of the ferritic-pearlitic steel, wheel-R19. Mechanical properties of the bainitic MAS2 steels are found to be more than that of the wheel-R19 steel. Considerable enhancement in wear resistance of the bainitic steels is attributed to high hardness and strength of the steels. The wear mechanism has been critically analyzed by examining wear track morphology. The wear data gathered have been graphically presented in the form of wear mechanism map to understand the material behavior under different sliding conditions and subsequent morphological variations.

  5. Influence of Ni Content on Dry Sliding Wear Behavior of Sintered and Carburized Steels

    NASA Astrophysics Data System (ADS)

    Metinoz, Ibrahim; Cristofolini, Ilaria; Molinari, Alberto

    2014-10-01

    The dry sliding wear behavior of two sintered and carburized steels with different Ni amounts has been investigated. The microstructure of the two steels comprises martensite, bainite, and the Ni-rich austenite. Under the sliding conditions investigated, wear is either oxidative or adhesive. In both cases, the lower amount of the soft Ni-rich austenite results in a better wear resistance. A design procedure for parts subject to dry sliding wear applications is proposed, based on the maximum acceptable wear depth, in order to evaluate the practical significance of the differences between the two materials.

  6. Friction and Wear Properties of Selected Solid Lubricating Films

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Iwaki, Masanori; Gotoh, Kenichi; Obara, Shingo; Imagawa, Kichiro

    1999-01-01

    To evaluate commercially developed solid film lubricants for aerospace bearing applications, we investigated the friction and wear behavior of bonded molybdenum disulfide (MoS2), magnetron-sputtered MoS2 and ion-plated silver films in sliding contact with 6-mm-diameter American Iron and Steel Institute (AISI) 440 C stainless steel balls. Unidirectional sliding friction experiments were conducted with a load of 5.9 N (600 g), a mean Herizian contact pressure of 0.79 GPa maximum 1.19 GPa), and a sliding velocity of 0.2 m/s at room temperature in three environments: ultrahigh vacuum (7x10 (exp -7Pa)), humid air (approx. 20 percent humidity), and dry nitrogen (less than 1 percent humidity). The resultant films were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and surface profilometry. Marked differences in friction and wear resulted front the environmental conditions and the film materials. The main criteria for judging the performance were coefficient of friction and wear rate, which had to be less than 0.3 and on the order of 10 (exp -6mm exp 3/Nm or less), respectively. The bonded MoS2 and magnetron-sputtered MoS2 films met the criteria in all three environments. Also, the wear rates of the counterpart AISI 440 C stainless steel balls met that criterion in all three environments. The ion-plated silver films met the criteria only in ultrahigh vacuum. In ultrahigh vacuum the bonded MoS2 films were superior. In humid air the bonded MoS2 films had higher coefficient of friction and shorter wear life than did the magnetron-sputtered MoS2 films. The ion-plated silver films had a high coefficient of friction in humid air but relatively low coefficients of friction in the nonoxidative environments. Adhesion and plastic deformation played important roles in all three environments. All sliding involved adhesive transfer of materials.

  7. The function of prehistoric lithic tools: a combined study of use-wear analysis and FTIR microspectroscopy.

    PubMed

    Nunziante Cesaro, Stella; Lemorini, Cristina

    2012-02-01

    The application of combined use-wear analysis and FTIR micro spectroscopy for the investigation of the flint and obsidian tools from the archaeological sites of Masseria Candelaro (Foggia, Italy) and Sant'Anna di Oria (Brindisi, Italy) aiming to clarify their functional use is described. The tools excavated in the former site showed in a very high percentage spectroscopically detectable residues on their working edges. The identification of micro deposits is based on comparison with a great number of replicas studied in the same experimental conditions. FTIR data confirmed in almost all cases the use-wear analysis suggestions and added details about the material processed and about the working procedures.

  8. Prevalence and Indicators of Tooth Wear among Chinese Adults

    PubMed Central

    Wei, Zhao; Du, Yangge; Zhang, Jing; Tai, Baojun

    2016-01-01

    Numerous epidemiological studies have focused on the prevalence and related indicators of tooth wear. However, no sufficient studies have been conducted with Chinese adults. The purpose of this study was to assess the prevalence of tooth wear and identify related indicators among adults aged 36 to 74 years in Wuhan City, P.R. China. A cross-sectional and analytic study was conducted with 720 participants, aged 35–49 yrs and 50–74 yrs, in 2014. Each age group included 360 participants, of which 50% were males and 50% were females. All participants completed a questionnaire before examination. Tooth wear was assessed using the modified Basic Erosive Wear Examination (BEWE) index. The data were analyzed using the chi-square test and binary logistic regression analysis. The prevalence of tooth wear was 67.5% and 100% in the 35–49 and 50–74 age groups, respectively. The prevalence of dentin exposure was 64.7% and 98.3%, respectively. A significantly higher prevalence of tooth wear and dentin exposure was found in the 50–74 yr group than in the 35–49 yr group (p < 0.05). Critical indicators of tooth wear and dentin exposure included high frequency of acidic drinks and foods consumption, low socio-economic status, and unilateral chewing. The frequency of changing toothbrushes and the habit of drinking water during meals were associated with tooth wear. In addition, the usage of hard-bristle toothbrushes and consuming vitamin C and aspirin were found to be linked with dentin exposure. In conclusion, the prevalence of tooth wear and dentin exposure observed in Chinese adults was high, and the results revealed an association between tooth wear and socio-behavioral risk indicators. PMID:27583435

  9. Development of wear-resistant ceramic coatings for diesel engine components

    SciTech Connect

    Naylor, M.G.S. )

    1992-06-01

    The tribological properties of a variety of advanced coating materials have been evaluated under conditions which simulate the piston ring -- cylinder liner environment near top ring reversal in a heavy duty diesel engine. Coated ring'' samples were tested against a conventional pearlitic grey cast iron liner material using a high temperature reciprocating wear test rig. Tests were run with a fresh CE/SF 15W40lubricant at 200 and 350{degrees}C, with a high-soot, engine-tested oil at 200{degrees}C and with no lubrication at 200{degrees}C. For lowest wear under boundary lubricated conditions, the most promising candidates to emerge from this study were high velocity oxy-fuel (HVOF) Cr{sub 3} C{sub 2} - 20% NiCr and WC - 12% Co cermets, low temperature arc vapor deposited (LTAVD) CrN and plasma sprayed chromium oxides. Also,plasma sprayed Cr{sub 2}O{sub 3} and A1{sub 2}O{sub 3}-ZrO{sub 2} materials were found to give excellent wear resistance in unlubricated tests and at extremely high temperatures (450{degrees}C) with a syntheticoil. All of these materials would offer substantial wear reductions compared to the conventional electroplated hard chromium ring facing and thermally sprayed metallic coatings, especially at high temperatures and with high-soot oils subjected to degradation in diesel environments. The LTAVD CrN coating provided the lowest lubricated wear rates of all the materials evaluated, but may be too thin (4 {mu}m) for use as a top ring facing. Most of the coatings evaluated showed higher wear rates with high-soot, engine-tested oil than with fresh oil, with increases of more than a factor of ten in some cases. Generally, metallic materials were found to be much more sensitive to soot/oil degradation than ceramic and cermet coatings. Thus, decreased soot sensitivity'' is a significant driving force for utilizing ceramic or cermet coatings in diesel engine wear applications.

  10. Wear Resistance Improvement of Small Dimension Invar Massive Molds for CFRP Components

    NASA Astrophysics Data System (ADS)

    Giolli, C.; Turbil, M.; Rizzi, G.; Rosso, M.; Scrivani, A.

    2009-12-01

    Invar alloy (Fe-36%Ni) is used in industrial applications that require high dimensional stability because of its exceptionally low thermal expansion coefficient. The purpose of this work is to improve the wear resistance of the molds in the production of carbon-fiber reinforced plastic (CFRP) components applying thermal spray coatings. Four different kinds of commercial powders were coated on an Invar substrate: ZrO2-8Y2O3, Al2O3-13TiO2, and Cr2O3 by air plasma spray (APS) and WC-CoCr by high-velocity oxygen fuel (HVOF). Metallographic microscopy observation and scanning electron microscopic analysis were carried out, microhardness and fracture toughness were evaluated using the microindentation method. Friction behavior and wear resistance were evaluated with pin-on-disk apparatus. Tungsten carbide coating had the lowest average coefficient of friction. Cermet and alumina-titania coatings showed the lowest wear mass loss. Among the APS ceramic coatings, alumina-titania exhibited the best wear behavior and the HVOF cermet coating exhibited the best behavior among all the coatings.

  11. Structure characterization and wear performance of NiTi thermal sprayed coatings

    NASA Astrophysics Data System (ADS)

    Cinca, N.; Isalgué, A.; Fernández, J.; Guilemany, J. M.

    2010-08-01

    NiTi shape memory alloy (SMA) has been studied for many years for its shape memory and pseudoelastic properties, as well as its biocompatibility, which make it suitable for many biomedical applications. However, SMA NiTi is also interesting for relevant wear resistance near the transition temperature which, along with its high oxidation and corrosion resistance, suggests its use as a coating to increase the lifetime of some components. Also, whereas bulk material properties have been characterized in respect of the nominal composition, manufacturing methods and thermo-mechanical treatments, NiTi overlays have been investigated much less. Most existent works in this field specifically deal with magnetron sputtering technology for thin films and its use in micro-devices (micro-electro-mechanical systems, MEMS), just some works refer to vacuum plasma spraying (VPS) for thicker coatings. The present paper explores and compares the microstructure and wear-related properties of coatings obtained from atomized NiTi powders, by VPS as well as by atmospheric plasma spraying (APS) and high velocity oxygen fuel (HVOF) techniques. In the present case, the wear behaviour of the NiTi deposits has been studied by rubber-wheel equipment and ball-on-disk tests. The results obtained at room temperature show that the APS-quenched coatings exhibit a preferential dry sliding wear mechanism, while the VPS and HVOF coatings show an abrasive mechanism.

  12. Wear of cross-linked polyethylene against itself: a material suitable for surface replacement of the finger joint.

    PubMed

    Sibly, T F; Unsworth, A

    1991-05-01

    Cross-linking of polyethylene (XLPE) has dramatically improved its properties in industrial applications, and it may also have some application in the field of human joint replacement. Additionally it has the advantage of permitting a lower molecular weight base material to be used, so that components may be injection moulded rather than machined. This study therefore investigates the wear resistance of medical grade cross-linked polyethylene (XLPE), cross-linked by a silane-grafting process, with a molecular weight between cross links of 5430 g mol(-1). This first report investigates the wear resistance of XLPE against itself, because for certain joints, such as the metacarpo-phalangeal joint, the material may have a high enough wear resistance to allow both bearing surfaces to be made from it. Tests were carried out both on a reciprocating pin and plate machine with pins loaded at 10 and 40 N and also on a new finger joint simulator, which simulates the loads applied to and the movements of, the metacarpo-phalangeal joint. An average wear rate of 1.8 x 10(-6) mm3 N-1 m-1 was found (range 0.9-2.75 x 10(-6) mm3 N-1 m-1). This is about six times greater than the wear rate of non-cross-linked ultra high molecular weight polyethylene (UHMWPE) against stainless steel, but for applications with low loading, such as the metacarpo-phalangeal joint, this material is shown to have adequate wear resistance. The coefficient of friction was 0.1, which is similar to that of UHMWPE on stainless steel.

  13. Tribology: The science of combatting wear. Part IX

    SciTech Connect

    Glaeser, W.A.; Erickson, R.C.; Dufrane, K.F.; Kannel, J.W.

    1994-10-01

    Boundary lubrication (BL)is defined as a condition of lubrication of metals in which the friction and wear between two surfaces in relative motion are determined by the properties of the surfaces and by the properties of the lubricant other than viscosity. This paper describes the industrial significance, devices requiring BL, solid surface films, chemical properties of the base oils and additives, chemical properties of the metal surfaces, surface temperatures, and application of BL for wear control.

  14. Risk Assessment for Tooth Wear.

    PubMed

    Kontaxopoulou, Isavella; Alam, Sonia

    2015-08-01

    Tooth wear has an increasing prevalence in the UK population. The aetiology is commonly multifactorial, and the aetiopathology is through a combination of erosion, attrition, abrasion and abfraction. Erosion is associated with intrinsic or extrinsic acids, and therefore subjects with reflux disease and eating disorders are at increased risk. Fruit juice, fruits and carbonated drink consumption, frequency of consumption and specific habits are also risk factors. Attrition is more prevalent in bruxists. Other habits need to be considered when defining the risk of tooth wear. Abrasion is usually associated with toothbrushing and toothpastes, especially in an already acidic environment. Patients with extensive lesions that affect dentin may be at higher risk, as well as those presenting with unstained lesions. Monitoring of the progress of tooth wear is recommended to identify those with active tooth wear. Indices for tooth wear are a helpful aid.

  15. Wear-Out Sensitivity Analysis Project Abstract

    NASA Technical Reports Server (NTRS)

    Harris, Adam

    2015-01-01

    During the course of the Summer 2015 internship session, I worked in the Reliability and Maintainability group of the ISS Safety and Mission Assurance department. My project was a statistical analysis of how sensitive ORU's (Orbital Replacement Units) are to a reliability parameter called the wear-out characteristic. The intended goal of this was to determine a worst case scenario of how many spares would be needed if multiple systems started exhibiting wear-out characteristics simultaneously. The goal was also to determine which parts would be most likely to do so. In order to do this, my duties were to take historical data of operational times and failure times of these ORU's and use them to build predictive models of failure using probability distribution functions, mainly the Weibull distribution. Then, I ran Monte Carlo Simulations to see how an entire population of these components would perform. From here, my final duty was to vary the wear-out characteristic from the intrinsic value, to extremely high wear-out values and determine how much the probability of sufficiency of the population would shift. This was done for around 30 different ORU populations on board the ISS.

  16. The Prevalence of Tooth Wear in the Dutch Adult Population

    PubMed Central

    Wetselaar, Peter; Vermaire, Jan H.; Visscher, Corine M.; Lobbezoo, Frank; Schuller, Annemarie A.

    2016-01-01

    This study aimed to assess the prevalence of tooth wear in different age groups of the Dutch adult population and to determine this tooth wear distribution by gender, socioeconomic class, and type of teeth. Results were compared with the outcomes of a previous study in a comparable population. As part of a comprehensive investigation of the oral health of the general Dutch adult population in 2013, tooth wear was assessed among 1,125 subjects in the city of ‘s-Hertogenbosch. The data collected were subjected to stratified analysis by 5 age groups (25-34, 35-44, 45-54, 55-64, and 65-74 years), gender, socioeconomic class, and type of teeth. Tooth wear was assessed using a 5-point ordinal occlusal/incisal grading scale. The number of teeth affected was higher in older age groups. Men showed more tooth wear than women, and subjects with low socioeconomic status (low SES) showed on average higher scores than those with high SES. Tooth wear prevalence found in this study was higher in all age groups than in the previous study. The present study found prevalences of 13% for mild tooth wear and 80% for moderate tooth wear, leading to the conclusion that these are common conditions in the Dutch adult population. Severe tooth wear (prevalence 6%) may however be characterized as rare. A tendency was found for there to be more tooth wear in older age groups, in men as compared with women, in persons with lower SES, and in the present survey as compared with the previous one. PMID:27694757

  17. Design and wear testing of a temporomandibular joint prosthesis articulation.

    PubMed

    van Loon, J P; Verkerke, G J; de Vries, M P; de Bont, L G

    2000-02-01

    As part of the development of a total temporomandibular joint prosthesis, a prosthesis articulation was designed. The articulation consists of a spherical head (ball) of the mandibular part, rotating against an enveloping ultra-high-molecular-weight polyethylene (UHMWPE) disc with a flat cranial side, which slides along the opposing skull part. The aim of this study was to determine the in vitro wear rate of the articulation, and to predict the in vivo wear rate from the results. Based on a disc thickness of 5 mm and a ball diameter of 8 mm, the stresses within the disc were calculated by means of a finite element computer model. The wear rate of the ball-disc articulation was determined by in vitro wear tests, with a stainless-steel ball rotating against a UHMWPE disc in a serum-based lubricant. Eight discs were tested for seven million cycles each. The in vitro wear rate of the disc-skull part articulation was calculated from the test results of the ball-disc articulation. The maximum Von Mises' stress was less than the yield strength of UHMWPE and, therefore, was sufficiently low. The in vitro wear rate of the ball-disc articulation was 0.47 mm3 per million cycles. The in vivo expected total wear rate is 0.65 mm3 per year, corresponding with a yearly decrease of disc thickness of 0.0094 mm. Although it is difficult to judge whether this wear rate is sufficiently low, because the influence of UHMWPE wear particles in the TMJ region is unknown, both the expected wear rate and the decrease of thickness appear to be acceptable.

  18. Low friction wear resistant graphene films

    DOEpatents

    Sumant, Anirudha V.; Berman, Diana; Erdemir, Ali

    2017-02-07

    A low friction wear surface with a coefficient of friction in the superlubric regime including graphene and nanoparticles on the wear surface is provided, and methods of producing the low friction wear surface are also provided. A long lifetime wear resistant surface including graphene exposed to hydrogen is provided, including methods of increasing the lifetime of graphene containing wear surfaces by providing hydrogen to the wear surface.

  19. Wear Analysis of Thermal Spray Coatings on 3D Surfaces

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Luo, W.; Selvadurai, U.

    2014-01-01

    Even though the application of thermal spray coatings on complex geometries gained a greater interest in the last decade, the effect of different geometrical features on the wear behavior is still ill-defined. In this study, the wear resistance of FTC-FeCSiMn coated 3D surfaces was investigated. The wear test was carried out by means of two innovative testing procedures. The first test is a Pin-on-Tubes test where the rotating motion is realized by a lathe chuck. The specimens in the second test were fixed on the table and a robot arm operated the pin. This wear test was applied on specimens with concave or convex surfaces. The residual stresses, which were determined by means of an incremental hole-drilling method, show a dependency on the substrate geometry. The obtained stresses were put in relation to the different radii. After the wear test, a 3D-profilometer determined the wear volume and the sections of the coatings were characterized by a scanning electron microscope. The results indicate that the wear resistance is strongly influenced by the geometry of the substrate.

  20. Switch wear leveling

    DOEpatents

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  1. Wear resistance and wear mechanisms in polymer + metal composites.

    PubMed

    Olea-Mejia, Oscar; Brostow, Witold; Buchman, Eli

    2010-12-01

    We have investigated composites containing metallic micro-size and nano-sized particles as the 10 wt% dispersed phase. Branched low density polyethylene (LDPE) was the matrix. Microsized metals were Al, Ag and Ni; nanosized metals were Al and Ag. Several mechanisms of wear are observed in function of the kind and size of metal used: deformation, delamination, abrasion, adhesion and rolls formation. The presence of Ag particles increases the wear rate as compared to neat LDPE. The presence of Al particles lowers the wear of LDPE significantly; nanoparticles are more effective than microparticles.

  2. Friction and wear behaviors of compacted graphite iron with different biomimetic units fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Sun, Na; Shan, Hongyu; Zhou, Hong; Chen, Darong; Li, Xiaoyan; Xia, Wen; Ren, Luquan

    2012-07-01

    Mimicking the biological characters on the cuticles of pangolin scales, biomimetic units were fabricated on the surfaces of compacted graphite cast iron (CGI) with different unit materials using laser cladding process. The influences of various unit materials including TiC, WC, B4C and Al2O3 powders on the friction and wear behaviors of CGI were investigated. The wear resistance mechanism of biomimetic specimens was discussed. The results indicated that the wear resistance of biomimetic specimens cladding TiC was the best; the specimens cladding WC or B4C were in the middle; and the specimens cladding Al2O3 was the worst. The sequence of friction coefficient values of biomimetic specimens cladding different ceramic powders from high to low was B4C, TiC, WC and Al2O3. The wear mechanism of untreated specimen was mainly adhesion wear, abrasive wear as well as the oxidation wear, whereas the adhesive wear and abrasive wear was the main wear mechanism of the regions of substrate in biomimetic specimens and slight adhesion, abrasive wear and fatigue wear on the regions of biomimetic units.

  3. 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.

  4. Applications of bulk high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Hull, J. R.

    The development of high-temperature superconductors (HTS's) can be broadly generalized into thin-film electronics, wire applications, and bulk applications. We consider bulk HTS's to include sintered or crystallized forms that do not take the geometry of filaments or tapes, and we discuss major applications for these materials. For the most part applications may be realized with the HTS's cooled to 77 K, and the properties of the bulk HTS's are often already sufficient for commercial use. A non-exhaustive list of applications for bulk HTS's includes trapped field magnets, hysteresis motors, magnetic shielding, current leads, and magnetic bearings. These applications are briefly discussed in this paper.

  5. Automated visual inspection of brake shoe wear

    NASA Astrophysics Data System (ADS)

    Lu, Shengfang; Liu, Zhen; Nan, Guo; Zhang, Guangjun

    2015-10-01

    With the rapid development of high-speed railway, the automated fault inspection is necessary to ensure train's operation safety. Visual technology is paid more attention in trouble detection and maintenance. For a linear CCD camera, Image alignment is the first step in fault detection. To increase the speed of image processing, an improved scale invariant feature transform (SIFT) method is presented. The image is divided into multiple levels of different resolution. Then, we do not stop to extract the feature from the lowest resolution to the highest level until we get sufficient SIFT key points. At that level, the image is registered and aligned quickly. In the stage of inspection, we devote our efforts to finding the trouble of brake shoe, which is one of the key components in brake system on electrical multiple units train (EMU). Its pre-warning on wear limitation is very important in fault detection. In this paper, we propose an automatic inspection approach to detect the fault of brake shoe. Firstly, we use multi-resolution pyramid template matching technology to fast locate the brake shoe. Then, we employ Hough transform to detect the circles of bolts in brake region. Due to the rigid characteristic of structure, we can identify whether the brake shoe has a fault. The experiments demonstrate that the way we propose has a good performance, and can meet the need of practical applications.

  6. Effect of low temperature annealing on the wear properties of NITINOL

    NASA Astrophysics Data System (ADS)

    Mukunda, Sriram; Nath. S, Narendra; Herbert, Mervin A.; Mukunda, P. G.

    2016-02-01

    NiTi shape memory alloy is a wonder material that is a solution looking for problems. The material finds wide biomedical applications like endodontic files for root canal treatment and cardiovascular stents. This material has rendered the surgical procedure simple compared to that with the existing Stainless Steel (SS) or titanium ones. NiTi as an endodontic file would cause less discomfort to the patients in comparison to that with far stiffer SS or titanium ones. Here nearly equi-atomic 50:50 commercial NiTi rods were subjected to low temperature aging at 300 to 450°C. The wear resistance of the as-received and the heat-treated samples was studied using adhesive wear tests on hardened steel counter face. Abrasive wear tests were run against Alumina disc to simulate the working of endodontic drills and files against dental hard and soft tissues. The abrasive wear resistance is expected to be proportional to the Vickers Hardness of the material and is high for the 450°C heat-treated sample. A correlation between the mechanical properties and microstructures of this material is attempted

  7. Knee simulator wear of vitamin E stabilized irradiated ultrahigh molecular weight polyethylene.

    PubMed

    Micheli, Brad R; Wannomae, Keith K; Lozynsky, Andrew J; Christensen, Steven D; Muratoglu, Orhun K

    2012-01-01

    Wear and damage of ultrahigh molecular weight polyethylene (UHMWPE) tibial inserts used in total knee arthroplasty are accelerated by oxidation. Radiation crosslinking reduces wear but produces residual free radicals adversely affecting stability. One alternative to stabilize radiation-crosslinked UHMWPE is to infuse the material with vitamin E (vit E). We investigated the properties of 100-kGy e-beam-irradiated UHMWPE that was subsequently doped with vitamin E in comparison with conventional UHMWPE. Both polymers were sterilized with gamma irradiation in vacuum packaging. Vitamin E-doped UHMWPE showed lower wear before and after aging (2.4 ± 0.5 and 2.5 ± 0.8 mg/million cycle, respectively, vs 26.9 ± 3.5 and 40.8 ± 3.0 mg/million cycle for conventional UHMWPE). Conventional UHMWPE showed oxidation after accelerated aging, and its mechanical properties were adversely affected, whereas vit E-doped UHMWPE showed no oxidation or changes in its mechanical properties. Vitamin E stabilization of radiation-crosslinked UHMWPE resulted in low wear and high oxidation resistance; it is an alternative load-bearing material for total knee applications.

  8. Surface folding in metals: a mechanism for delamination wear in sliding

    PubMed Central

    Mahato, Anirban; Guo, Yang; Sundaram, Narayan K.; Chandrasekar, Srinivasan

    2014-01-01

    Using high-resolution, in situ imaging of a hard, wedge-shaped model asperity sliding against a metal surface, we demonstrate a new mechanism for particle formation and delamination wear. Damage to the residual surface is caused by the occurrence of folds on the free surface of the prow-shaped region ahead of the wedge. This damage manifests itself as shallow crack-like features and surface tears, which are inclined at very acute angles to the surface. The transformation of folds into cracks, tears and particles is directly captured. Notably, a single sliding pass is sufficient to damage the surface, and subsequent passes result in the generation of platelet-like wear particles. Tracking the folding process at every stage from surface bumps to folds to cracks/tears/particles ensures that there is no ambiguity in capturing the mechanism of wear. Because fold formation and consequent delamination are quite general, our findings have broad applicability beyond wear itself, including implications for design of surface generation and conditioning processes. PMID:25197251

  9. Wear and Durability Variation Compared with Thickness of Cutting Inserts Coated with AlTiN Thin Films

    NASA Astrophysics Data System (ADS)

    Bădănac, A.; Lupescu, O.; Manole, V.; Ungureanu, C.; Popa, M.

    2016-08-01

    During the use of cutting tools in the cutting process, they lose their exploitation indices after a certain range of working, due to the occurrence of wear phenomenon. Wear occurs due to the parameters variation of the working regimes, fact that involves in order to not overcoming the limits of the maximum allowable wear, application of methods, to increase their durability. In order to increase the cutting tools durability are known various methods of surface coating with materials with better properties than the material of the cutting tool. In the case of cutting inserts, are known many researches concerning their coating by vacuum deposition of thin layers of metal, methods as: physical vapour deposition and chemical vapour deposition. The coatings realized by vacuum deposition have gained special attention because of their unique physical and chemical properties for example excellent resistance to oxidation at high temperatures. The main characteristics which are checked in the deposition process of thin layers are: thickness and the wear resistance. In this study the authors carried out researches regarding the coatings of AlTiN in thin layers, on surface of some cutting inserts. It was measured the variation of the wear and durability compared with the thickness of AlTiN thin layers deposited on the cutting inserts.

  10. Tooth wear: prevalence and associated factors in general practice patients

    PubMed Central

    Cunha-Cruz, Joana; Pashova, Hristina; Packard, J.D.; Zhou, Lingmei; Hilton, Thomas J.

    2011-01-01

    Objectives To estimate the prevalence of tooth wear and to investigate factors associated with tooth wear in patients from general practices in the Northwest United States. Methods Data on the diagnosis and treatment of oral diseases during the previous year were collected in a survey with a systematic random sample of patients (n = 1530) visiting general dentists from the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry (PRECEDENT) (n = 80). Prevalence ratios (PRs) of moderate to severe occlusal and incisal tooth wear by patient characteristics were estimated using cluster-adjusted multiple binomial regression for adults (18+ years) and children/adolescents (3–17 years). Results For adults, the mean number of teeth with wear facets was 5.4 [95% confidence interval (CI) = 4.6–6.2] and 51% of the adults had four or more teeth with wear. Participants 45–64 and 65+ years old were 1.3 (95% CI = 1.1–1.6) and 1.4 (95% CI = 1.1–1.8) times as likely to have 4+ teeth with moderate to severe wear facets as participants 18–44 years old. Adult males had a 20% (PR = 1.2; 95% CI = 1.1–1.4) higher prevalence of wear than adult females. Adults who were using, or had ever used occlusal splints had higher prevalence of tooth wear compared to those who never used such appliances (PR = 1.3; 95% CI = 1.0–1.5). Adults with any periodontal bone loss also had a 20% higher prevalence of wear than adults without periodontal disease (PR = 1.2; 95% CI = 1.0–1.4). For children/adolescents, the mean number of teeth with moderate to severe wear facets was 1.6 (95% CI = 0.9–2.6) and 31% of the children had one or more teeth with wear facets. The adjusted prevalence ratio of tooth wear (1+ teeth with wear facets) for boys was 1.6 times as high (95% CI = 1.1–2.4) as compared with girls. The prevalence of wear for children 12+ years old was 50% (PR = 0.5; 95% CI = 0.3–0.8) lower than that of children <12 years old. Angle’s class II was associated

  11. Dynamic superlubricity and the elimination of wear on the nanoscale.

    PubMed

    Lantz, Mark A; Wiesmann, Dorothea; Gotsmann, Bernd

    2009-09-01

    One approach to ultrahigh-density data storage involves the use of arrays of atomic force microscope probes to read and write data on a thin polymer film, but damage to the ultrasharp silicon probe tips caused by mechanical wear has proved problematic. Here, we demonstrate the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 m by modulating the force acting on the tip-sample contact. Friction measurements as a function of modulation frequency and amplitude indicate that a reduction of friction is responsible for the reduction in wear to below our detection limit. In addition to its relevance to data storage, this approach could also reduce wear in micro- and nanoelectromechanical systems and other applications of scanning probe microscopes.

  12. Dynamic superlubricity and the elimination of wear on the nanoscale

    NASA Astrophysics Data System (ADS)

    Lantz, Mark A.; Wiesmann, Dorothea; Gotsmann, Bernd

    2009-09-01

    One approach to ultrahigh-density data storage involves the use of arrays of atomic force microscope probes to read and write data on a thin polymer film, but damage to the ultrasharp silicon probe tips caused by mechanical wear has proved problematic. Here, we demonstrate the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 m by modulating the force acting on the tip-sample contact. Friction measurements as a function of modulation frequency and amplitude indicate that a reduction of friction is responsible for the reduction in wear to below our detection limit. In addition to its relevance to data storage, this approach could also reduce wear in micro- and nanoelectromechanical systems and other applications of scanning probe microscopes.

  13. Friction and wear of nickel in sulfuric acid

    NASA Technical Reports Server (NTRS)

    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1984-01-01

    Experiments were conducted with elemental nickel sliding on aluminum oxide in aerated sulfuric acid in concentrations ranging from very dilute (10 -4 N, i.e., 5 ppm) to very concentrated (96 percent) acid. Load and reciprocating sliding speeds were kept constant. With the most dilute concentration (10 -4 N) no observable corrosion occurred in or outside the wear area. This was used as the base condition to determine the high contribution of corrosion to total wear loss at acid concentrations between 0.5 percent (0.1 N) and 75 percent. Corrosion reached a maximum rate of 100 millimeters per year at 30 percent acid. At the same time, general corrosion outside the wear area was very low, in agreement with published information. It is clear that friction and wear greatly accelerated corrosion in the wear area. At dilute concentrations of 0.001 and 0.01 N, corrosion in the wear area was low, and general corrosion outside was also low, but local outside regions in the direction of the wear motion experienced some enhanced corrosion, apparently due to fluid motion of the acid.

  14. Interaction of sulfuric acid corrosion and mechanical wear of iron

    NASA Technical Reports Server (NTRS)

    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1984-01-01

    Friction and wear experiments were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

  15. Interaction of sulfuric acid corrosion and mechanical wear of iron

    NASA Technical Reports Server (NTRS)

    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1986-01-01

    Friction and wear experiment were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

  16. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  17. Digital photogrammetry for quantitative wear analysis of retrieved TKA components.

    PubMed

    Grochowsky, J C; Alaways, L W; Siskey, R; Most, E; Kurtz, S M

    2006-11-01

    The use of new materials in knee arthroplasty demands a way in which to accurately quantify wear in retrieved components. Methods such as damage scoring, coordinate measurement, and in vivo wear analysis have been used in the past. The limitations in these methods illustrate a need for a different methodology that can accurately quantify wear, which is relatively easy to perform and uses a minimal amount of expensive equipment. Off-the-shelf digital photogrammetry represents a potentially quick and easy alternative to what is readily available. Eighty tibial inserts were visually examined for front and backside wear and digitally photographed in the presence of two calibrated reference fields. All images were segmented (via manual and automated algorithms) using Adobe Photoshop and National Institute of Health ImageJ. Finally, wear was determined using ImageJ and Rhinoceros software. The absolute accuracy of the method and repeatability/reproducibility by different observers were measured in order to determine the uncertainty of wear measurements. To determine if variation in wear measurements was due to implant design, 35 implants of the three most prevalent designs were subjected to retrieval analysis. The overall accuracy of area measurements was 97.8%. The error in automated segmentation was found to be significantly lower than that of manual segmentation. The photogrammetry method was found to be reasonably accurate and repeatable in measuring 2-D areas and applicable to determining wear. There was no significant variation in uncertainty detected among different implant designs. Photogrammetry has a broad range of applicability since it is size- and design-independent. A minimal amount of off-the-shelf equipment is needed for the procedure and no proprietary knowledge of the implant is needed.

  18. RAID Disk Arrays for High Bandwidth Applications

    NASA Technical Reports Server (NTRS)

    Moren, Bill

    1996-01-01

    High bandwidth applications require large amounts of data transferred to/from storage devices at extremely high data rates. Further, these applications often are 'real time' in which access to the storage device must take place on the schedule of the data source, not the storage. A good example is a satellite downlink - the volume of data is quite large and the data rates quite high (dozens of MB/sec). Further, a telemetry downlink must take place while the satellite is overhead. A storage technology which is ideally suited to these types of applications is redundant arrays of independent discs (RAID). Raid storage technology, while offering differing methodologies for a variety of applications, supports the performance and redundancy required in real-time applications. Of the various RAID levels, RAID-3 is the only one which provides high data transfer rates under all operating conditions, including after a drive failure.

  19. Analysis of wear track and debris of stir cast LM13/Zr composite at elevated temperatures

    SciTech Connect

    Panwar, Ranvir Singh Pandey, O.P.

    2013-01-15

    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 using 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.

  20. Joining of ceramics for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vilpas, Martti

    1987-01-01

    Summarized is a literature survey of the methods for joining ceramics to ceramics or ceramics to metals for high temperature applications. Also mechanical properties and potential applications of the joints are considered. The joining of ceramics is usually carried out by brazing or diffusion bonding. Especially the latter has been found useful, increasing the application of bonded ceramics. The possibility of using electron beam and laser beam welding for joining ceramics has also recently been investigated. The bonding of ceramics has found numerous applications typical for high operating temperatures, i.e., sensors and thermocouples.

  1. They shall wear fringes.

    PubMed

    Sugar, M

    1999-01-01

    The multiple functions of clothes include utility, protection, rivalry, disguise, camouflage, display for seduction purposes, aggression, totemism, and status. Here the focus is on a decorative and distinctive hierarchical aspect of ancient dress, the tsitsit or fringes, whose original function is long absent, but that has endured for 3,500 years in Judaism. The beginning of their use beyond the totemic appears related to issues of changing identity from slavery to liberty, endowing noble status, exhibitionism, a symbol of identity, identification with the aggressor, a talisman, and potency. It is conceptualized that they became a symbol, or a specifier, that helped promote group cohesion in ex-slaves who were frightened, dependent, anxious, and not hopeful about their future. The tsitsit aided the development of a new identity and made all Israelites equal and noble to the observer. The durability of this symbol to the present is evident in its daily wear, as an accompaniment to daily prayers, as well as in its use as a burial shroud for males. It appears that the tsitsit have additional multiple functions. These are the promise of oral and genital satisfaction, and the pleasure of the after-life, superego warnings and control of sexual impulses, protection, survival value, and affirmation. Since they offer sublimation with acceptable gratification of instincts, the tsitsit have become ritualized and endure.

  2. Assessments of Hollow Cathode Wear in the Xenon Ion Propulsion System (XIPs(c)) by Numerical Analyses and Wear Tests

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.

    2008-01-01

    The standard approach presently followed by NASA to qualify electric propulsion for the required mission throughput has been based largely on life tests, which can be costly and time consuming. Revised electric propulsion lifequalification approaches are being formulated that combine analytical and/or computational methods with (shorter-duration) wear tests. As a model case, a wear test is being performed at JPL to assess the lifetime of the discharge hollow cathode in the Xenon Ion Propulsion System (XIPS(c)), a 25-cm ion engine developed by L-3 Communications Electron Technologies, Inc. for commercial applications. Wear and plasma data accumulated throughout this life-assessment program are being used to validate the existing 2-D hollow cathode code OrCa2D. We find that the OrCa2D steady-state solution predicts very well the time-averaged plasma data and the keeper voltage after 5500 hrs of operation in high-power mode. When the wave motion that occurs naturally in these devices is accounted for, based on an estimate of the maximum wave amplitude, the molybdenum-keeper erosion profile observed in the XIPS(c) discharge cathode is also reproduced within a factor of two of the observation. When the same model is applied to predict the erosion of a tantalum keeper we find that erosion is reduced by more than two orders of magnitude compared to the molybdenum keeper due the significantly lower sputtering yield of tantalum. A tantalum keeper would therefore allow keeper lifetimes that greatly exceed the present requirements for deep-space robotic missions considered by NASA. Moreover, such large reduction of the erosion renders the largest uncertainties in the models, which are associated with the wave amplitude estimates and the electron transport model, negligible.

  3. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    PubMed

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified.

  4. The wear of two orthopaedic biopolymers against each other.

    PubMed

    Joyce, T J

    2005-01-01

    The potential for all-polymer prostheses has not been widely investigated. It might be expected that the wear of such biomaterial combinations would be excessive, but an in vivo study of all polymer knee prostheses reported that there were no failures due to wear, even after ten years of clinical use. This design of knee prosthesis used polyacetal and ultra high molecular weight polyethylene (UHMWPE) as the biopolymers. Similarly, an earlier in vitro study of polyacetal and UHMWPE hip prostheses indicated lower wear than for a cobalt chrome and UHMWPE combination. Therefore this study set out to test the poly-acetal and UHMWPE combination in a wear screening rig which had previously been validated against clinical data for artificial hip joints. Two different motion conditions were applied to the test samples and each biopolymer was tested as both pin and plate. Interestingly it was found that, whatever the contribution from pin or plate, the total mean wear factors were 1.5 10 -6 mm 3/Nm under reciprocation-only, and 4.1 10 -6 mm 3 /Nm under multi-directional motion. These wear factors were greater than those found when a conventional metal-on-UHMWPE couple was tested under the same loading, motion and lu-bricant conditions. A comparison was also undertaken with the wear of other orthopaedic biopolymer combinations, namely cross-linked polyethylene (XLPE) against itself, and UHMWPE against itself. The XLPE pairing showed somewhat lower wear than the polyacetal and UHMWPE couple, while the UHMWPE pairing showed the highest wear of all, approximately an or-der of magnitude greater than the polyacetal and UHMWPE combination.

  5. Motor for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Roopnarine (Inventor)

    2013-01-01

    A high temperature motor has a stator with poles formed by wire windings, and a rotor with magnetic poles on a rotor shaft positioned coaxially within the stator. The stator and rotor are built up from stacks of magnetic-alloy laminations. The stator windings are made of high temperature magnet wire insulated with a vitreous enamel film, and the wire windings are bonded together with ceramic binder. A thin-walled cylinder is positioned coaxially between the rotor and the stator to prevent debris from the stator windings from reaching the rotor. The stator windings are wound on wire spools made of ceramic, thereby avoiding need for mica insulation and epoxy/adhesive. The stator and rotor are encased in a stator housing with rear and front end caps, and rear and front bearings for the rotor shaft are mounted on external sides of the end caps to keep debris from the motor migrating into the bearings' races.

  6. Applications of High Speed Networks

    DTIC Science & Technology

    1991-09-01

    extended computer interconnections are the charactenstic properties of ligh speed networks, low error rates, high bandwidth, low latency, full...implementation and designi of ligh speed networks, the need for gigabit per second services for an end user will be justified. A. FIBER OPTICS 1. Brief...conferencing muc& more useful. 5. Full motion video - HDTV The distribution of entertainment and news, based on broadcast signals, has been an activity

  7. Aeronautical applications of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Turney, George E.; Luidens, Roger W.; Uherka, Kenneth; Hull, John

    1989-01-01

    The successful development of high-temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. A preliminary examination of the potential application of HTS for aeronautics indicates that significant benefits may be realized through the development and implementation of these newly discovered materials. Applications of high-temperature superconductors (currently substantiated at 95 k) were envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft, and solar, microwave and laser powered aircraft. Introduced and described are the particular applications and potential benefits of high-temperature superconductors as related to aeronautics and/or aeronautical systems.

  8. Aeronautical applications of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Turney, George E.; Luidens, Roger W.; Uherka, Kenneth; Hull, John

    1989-01-01

    The successful development of high-temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. A preliminary examination of the potential application of HTS for aeronautics indicates that significant benefits may be realized through the development and implementation of these newly discovered materials. Applications of high-temperature superconductors (currently substantiated at 95 K) were envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft, and solar, microwave and laser powered aircraft. Introduced and described are the particular applications and potential benefits of high-temperature superconductors as related to aeronautics and/or aeronautical systems.

  9. High-Level Application Framework for LCLS

    SciTech Connect

    Chu, P; Chevtsov, S.; Fairley, D.; Larrieu, C.; Rock, J.; Rogind, D.; White, G.; Zalazny, M.; /SLAC

    2008-04-22

    A framework for high level accelerator application software is being developed for the Linac Coherent Light Source (LCLS). The framework is based on plug-in technology developed by an open source project, Eclipse. Many existing functionalities provided by Eclipse are available to high-level applications written within this framework. The framework also contains static data storage configuration and dynamic data connectivity. Because the framework is Eclipse-based, it is highly compatible with any other Eclipse plug-ins. The entire infrastructure of the software framework will be presented. Planned applications and plug-ins based on the framework are also presented.

  10. Towards In Situ-Process Control in Tribological or Tool Applications: A Material Concept for the Design of Smart Thin Film Wear Sensors

    NASA Astrophysics Data System (ADS)

    Ulrich, Sven; Klever, C.; Leiste, H.; Seemann, K.; Stüber, M.

    The optimization of processes for tribological or machining applications requires the development of (i) high performance substrate materials, especially ultra fine grain cemented carbides for cutting tools, (ii) complex tool geometries and (iii) innovative, nano-scaled hard and tough multi-functional protective coatings. Very important is also the in-situ process control which can be realized with (i) sensors which are embedded in the protective coating using microsystem technology or (ii) if possible, by using tailored coating designs which show itself both protective and sensor functionality.

  11. Tool wear mechanisms in the machining of Nickel based super-alloys: A review

    NASA Astrophysics Data System (ADS)

    Akhtar, Waseem; Sun, Jianfei; Sun, Pengfei; Chen, Wuyi; Saleem, Zawar

    2014-06-01

    Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the tool wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

  12. Influence of material characteristics on the abrasive wear response of some hardfacing alloys

    SciTech Connect

    Jha, A.K.; Prasad, B.K.; Dasgupta, R.; Modi, O.P.

    1999-04-01

    This study examines the abrasive wear behavior of two iron-base hardfacing materials with different combinations of carbon and chromium after deposition on a steel substrate. Effects of applied load and sliding distance on the wear behavior of the specimens were studied. Operating material removal mechanisms also were analyzed through the scanning electron microscopy (SEM) examination of typical wear surfaces, subsurface regions, and debris particles. The results suggest a significant improvement in the wear resistance of the hardfaced layers over that of the substrate. Further, the specimens overlaid with the material with low carbon and high chromium contents attained better wear resistance than the one consisting of more carbon but less chromium. The former specimens also attained superior hardness. Smoother abrasion grooves on the wear surfaces and finer debris formation during the abrasion of the hardfaced samples were consistent with wear resistance superior to that of the substrate.

  13. A Software Architecture for High Level Applications

    SciTech Connect

    Shen,G.

    2009-05-04

    A modular software platform for high level applications is under development at the National Synchrotron Light Source II project. This platform is based on client-server architecture, and the components of high level applications on this platform will be modular and distributed, and therefore reusable. An online model server is indispensable for model based control. Different accelerator facilities have different requirements for the online simulation. To supply various accelerator simulators, a set of narrow and general application programming interfaces is developed based on Tracy-3 and Elegant. This paper describes the system architecture for the modular high level applications, the design of narrow and general application programming interface for an online model server, and the prototype of online model server.

  14. Antioxidant impregnated ultra-high molecular weight polyethylene wear debris particles display increased bone remodeling and a superior osteogenic:osteolytic profile vs. conventional UHMWPE particles in a murine calvaria model.

    PubMed

    Chen, Yu; Hallab, Nadim J; Liao, Yen-Shuo; Narayan, Venkat; Schwarz, Edward M; Xie, Chao

    2016-05-01

    Periprosthetic osteolysis remains a major limitation of long-term successful total hip replacements with ultra-high molecular weight polyethylene (UHMWPE) bearings. As intra and extracellular reactive oxygen species are know to contribute to wear debris-induced osteoclastic bone resorption and decreased osteoblastic bone formation, antioxidant doped UHMWPE has emerged as an approach to reduce the osteolytic potential of wear debris and maintain coupled bone remodeling. To test this hypothesis in vivo, we evaluated the effects of crosslinked UHMWPE wear debris particles (AltrX(™) ), versus similar wear particles made from COVERNOX(™) containing UHMWPE (AOX(™) ), in an established murine calvaria model. Eight-week-old female C57B/6 mice (n = 10/Group) received a pre-op micro-CT scan prior to surgical implantation of the UHMWPE particles (2mg), or surgery without particles (sham). Dynamic labeling was performed by intraperitoneal injection of calcein on day 7 and alizarin on day 9, and the calvaria were harvested for micro-CT and histology on day 10. Surprisingly, we found that AOX particles induced significantly more bone resorption (1.72-fold) and osteoclast numbers (1.99-fold) vs. AltrX (p < 0.001). However, AOX also significantly induced 1.64-fold more new bone formation vs. AltrX (p < 0.01). Moreover, while the osteolytic:osteogenic ratio of both particles was very close to 1.0, which is indicative of coupled remodeling, AOX was more osteogenic (Slope = 1.13 ± 0.10 vs. 0.97 ± 0.10). Histomorphometry of the metabolically labeled undecalcified calvaria revealed a consistent trend of greater MAR in AOX vs. AltrX. Collectively, these results demonstrate that anti-oxidant impregnated UHMWPE particles have decreased osteolytic potential due to their increased osteogenic properties that support coupled bone remodeling. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:845-851, 2016.

  15. Wear analysis and finishing of bioceramic implant surfaces.

    PubMed

    Denkena, Berend; Reichstein, Martin; van der Meer, Marijke; Ostermeier, Sven; Hurschler, Christof

    2008-01-01

    A primary cause for revision operations of joint replacements is the implant loosening, due to immune reactions resulting from the agglomeration of polyethylene wear debris. Motivated by the successful application of bioceramic materials in hip joint prostheses, a trend towards the development of hard implant materials has occurred. Nonetheless in the area of total knee arthroplasty (TKA), modern efforts have still utilized polyethylene as the tibial-inlay joint component. The use of bioceramic hard-hard-pairings for total knee arthroplasty has been prevented by the complex kinematics and geometries required. Ceramics cannot cope with non-uniform loads, which suggests the need for new designs appropriate to the material. Furthermore, biomechanical requirements should be considered. A rolling-gliding wear simulator, which reproduces the movements and stresses of the knee joint on specimens of simplified geometry, has therefore been developed. High-precision machining processes for free formed bioceramic surfaces, with suitable grinding and polishing tools which adjust to constantly changing contact conditions, are essential. The goal is to put automated finishing in one clamping with five simultaneous controlled axes into practice. The developed manufacturing technologies will allow the advantageous bioceramic materials to be applied and accepted for more complex joint replacements such as knee prostheses.

  16. Space applications of high temperature superconductivity technology

    NASA Technical Reports Server (NTRS)

    Connolly, D. J.; Aron, P. R.; Leonard, R. F.; Wintucky, E. G.

    1991-01-01

    A review is presented of the present status of high temperature superconductivity (HTS) technology and related areas of potential space application. Attention is given to areas of application that include microwave communications, cryogenic systems, remote sensing, and space propulsion and power. Consideration is given to HTS phase shifters, miniaturization of microwave filters, far-IR bolometers, and magnetic refrigeration using flux compression.

  17. A review of the use of wear-resistant coatings in the cutting-tool industry

    NASA Technical Reports Server (NTRS)

    Salik, J.

    1983-01-01

    The main mechanisms involved in the wear of cutting tools are reviewed. Evaluation of the different coating properties required for the reduction of the different kinds of wear was also reviewed. The types of coatings and their ranges of applicability are presented and discussed in view of their properties. Various coating processes as well as their advantages and shortcomings are described. Potential future developments in the field of wear-resistant coatings are discussed.

  18. Computational analysis of polyethylene wear in anatomical and reverse shoulder prostheses.

    PubMed

    Quental, C; Folgado, J; Fernandes, P R; Monteiro, J

    2015-02-01

    The wear of ultra-high molecular weight polyethylene, UHMWPE, components has been associated with the failure of joint prostheses in the hip, knee, and shoulder. Considering that in vitro experiments are generally too expensive and time-consuming, computational models are an attractive alternative to study the wear behavior of UHMWPE components. The objective of the present study was to develop a computational wear model to evaluate the wear resistance of anatomical and reverse shoulder prostheses. The effects of the wear law and the updating of the UHMWPE surface on the prediction of wear were also considered. Apart from Archard's law, a new wear law, so-called second generation law, which includes the concept of cross-shear and a pressure-independent wear factor, was considered. The wear analyses were performed considering three shoulder joint motions. The muscle and joint reaction forces applied were estimated by an inverse biomechanical model of the upper limb. The results show that abrasive wear is as important for the reverse components as it is for the anatomical. Nevertheless, the volumetric wears estimated over 1 year are within the range considered clinically desirable to reduce the risk of osteolysis. For the anatomical components, the predictions from Archard's law compare better, than those of the second generation law, to the experimental and clinical data available in the literature. Yet, the opposite result is obtained for the reverse components. From the numerical point of view, an updating procedure for the UHMWPE surface is mandatory to improve the numerical predictions.

  19. Use of GPR technique in surveying gravel road wearing course

    NASA Astrophysics Data System (ADS)

    Saarenketo, Timo; Vesa, Heikki

    2000-04-01

    antenna surface reflection method, represents well the suction properties of the wearing course. High dielectric values reflect the water sensitive and frost susceptible wearing course materials where as low values reveal the lack of binder. A quality rating of the wearing course by its dielectrics and layer thickness is also suggested. In the measuring results analysis and presentations, GIS-maps proved to be invaluable.

  20. Adhesion, friction and wear on the nanoscale of MWNT tips and SWNT and MWNT arrays.

    PubMed

    Bhushan, Bharat; Galasso, Barbara; Bignardi, Cristina; Nguyen, Cattien V; Dai, Liming; Qu, Liangti

    2008-03-26

    The nanotribological characterization of carbon nanotubes is fundamental for the exploration of new sliding applications. In this study, a comprehensive investigation of adhesion, friction and wear of a multiwalled nanotube (MWNT) tip, and SWNT (single-walled nanotube) and MWNT arrays has been carried out. A nonlinear response of the MWNT tip is observed when the tip is brought into and out of contact with various surfaces. A nonlinear response occurs due to the buckling of the nanotube and its subsequent sliding on the surface. In addition to the role of surface chemistry, it can also explain the relatively high value of the coefficient of friction obtained on different surfaces, as compared to that of Si and Si(3)N(4) tips. The adhesion and friction studies carried out on SWNT and MWNT arrays using Si tips show that SWNT arrays, compared to MWNT arrays, exhibit lower values, possibly due to lower van der Waals forces as a result of lower packing density and higher flexibility. The wear tests conducted with the MWNT tip and a Si tip on a gold film, at two normal loads, show less damage of the surface when the MWNT tip is used because of the MWNT acting as a compliant spring, absorbing part of the load. Wear tests conducted with a Si tip on SWNT and MWNT arrays show that the arrays do not wear. The tip wear and the friction force in the SWNT array are lower, because of lower adhesion and higher flexibility of the SWNTs, which causes less opposition to the motion of the tip.

  1. 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.

  2. Hardfacing fights wear in oil sands operation

    SciTech Connect

    Llewellyn, R.; Tuite, C.

    1995-03-01

    Wear attack is responsible for high production losses and over $40 million per year in equipment repairs and replacement costs at Syncrude`s synthetic crude oil plant near Fort McMurray in Northern Alberta. Most of this damage is caused by the fine quartz particle constituents which predominate in oil sands. It occurs in a multiplicity of forms which can be classified into three primary mechanisms: Sliding abrasive wear and sporadic impact, which affects mainly mining equipment; Slurry abrasion and erosion, which occur in bitumen extraction, separation plants, and in tailings lines; and High-temperature erosion, which is often augmented by corrosion in bitumen upgrading operations. Process streams in this area also contain fine coke particles and catalyst debris. The paper gives an overview of Syncrude`s operations in mining, extraction, and upgrading, then describes the following: wear materials and protection systems, surface engineering systems, weld deposited hardfacing, benefits, surface modification system experience, thermal spray coating experience, disk centrifuge bowls, investigation of plasma arc spraying, and combating pump erosion.

  3. 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

  4. Wear of Cast Chromium Steels With TiC Reinforcement

    SciTech Connect

    Dogan,O.N.; Hawk, J.A.; Tylczak, J.H.

    2001-10-01

    Wear resistance of a series of new titanium carbide reinforced cast chromium steels was investigated under various wear conditions. The steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Microstructure of these materials was characterized using scanning electron microscopy, light optical microscopy, and X-ray diffraction. Microstructure of steels consisted of TiC phase dispersed in a martensitic matrix. High-stress and low-stress abrasion tests, and an erosion test, were utilized to understand the wear behavior of these materials under different environments. The steels were tested in as-cast and heat treated conditions. Wear rates of the cast Cr/TiC steels were compared to those of an AISI type 440C steel and P/M composites reinforced with TiC.

  5. Wear Behavior of Thermal Spray Coatings on Rotavator Blades

    NASA Astrophysics Data System (ADS)

    Kang, Amardeep Singh; Grewal, Jasmaninder Singh; Jain, Deepak; Kang, Shivani

    2012-03-01

    A rotavator is a motorized cultivator, popularly used to decrease the total time and human efforts in soil preparation. However, under dynamic loading, rotavator blades are subjected to extreme abrasive wear. The objective of this study was to enhance the working life of the rotavator blade in order to decrease the idle time required to reinstate the blade periodically during cultivation. The objective was carried out by means of thermal spray coatings, where the effect of the coatings on the extent of wear and the wear characteristics of the rotavator blades were examined. Three different detonation gun sprayed coatings, namely WC-Co-Cr, Cr3C2NiCr and Stellite-21 were compared in this study on high tensile steel rotavator blades. The wear rates of Cr3C2NiCr and Stellite-21 coated blades showed significant superiority over the uncoated blade, but not as much as shown by WC-Co-Cr coated blade.

  6. 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.

  7. Wear and friction behavior of metal impregnated microporous carbon composites

    SciTech Connect

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

    1996-11-01

    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.

  8. Abrasive wear of alumina fibre-reinforced aluminium

    NASA Astrophysics Data System (ADS)

    Axen, N.; Alahelisten, A.; Jacobson, S.

    1994-04-01

    The friction and abrasive wear behaviour of an Al-Si1MgMn aluminium alloy reinforced with 10, 15 and 30 vol.% of alumina fibers has been evaluated. The influence of fiber content, matrix hardness, applied load as well as the hardness and size of the abrasive grits was investigated. The tests were performed with a pin-on-drum two-body abrasion apparatus. The wear mechanisms were studied using scanning electron microscopy. It is shown that fiber reinforcement increases the wear resistance in milder abrasive situations, i.e. small and soft abrasives and low loads. However, in tougher abrasive situations, meaning coarse and hard abrasives and high loads, the wear resistance of the composites is equal to or, in some cases, even lower than that of the unreinforced material. It is also shown that the coefficient of friction decreases with increasing fiber content and matrix hardness of the composites.

  9. Aerospace applications of high temperature superconductivity

    NASA Technical Reports Server (NTRS)

    Heinen, V. O.; Connolly, D. J.

    1991-01-01

    Space application of high temperature superconducting (HTS) materials may occur before most terrestrial applications because of the passive cooling possibilities in space and because of the economic feasibility of introducing an expensive new technology which has a significant system benefit in space. NASA Lewis Research Center has an ongoing program to develop space technology capitalizing on the potential benefit of HTS materials. The applications being pursued include space communications, power and propulsion systems, and magnetic bearings. In addition, NASA Lewis is pursuing materials research to improve the performance of HTS materials for space applications.

  10. Service Oriented Architecture for High Level Applications

    SciTech Connect

    Chu, Chungming; Chevtsov, Sergei; Wu, Juhao; Shen, Guobao; /Brookhaven

    2012-06-28

    Standalone high level applications often suffer from poor performance and reliability due to lengthy initialization, heavy computation and rapid graphical update. Service-oriented architecture (SOA) is trying to separate the initialization and computation from applications and to distribute such work to various service providers. Heavy computation such as beam tracking will be done periodically on a dedicated server and data will be available to client applications at all time. Industrial standard service architecture can help to improve the performance, reliability and maintainability of the service. Robustness will also be improved by reducing the complexity of individual client applications.

  11. Microstructure Evolution and Wear Behavior of the Laser Cladded CoFeNi2V0.5Nb0.75 and CoFeNi2V0.5Nb High-Entropy Alloy Coatings

    NASA Astrophysics Data System (ADS)

    Jiang, Li; Wu, Wei; Cao, Zhiqiang; Deng, Dewei; Li, Tingju

    2016-04-01

    The high-entropy alloy (HEA) coatings have received considerable attentions owing to their unique structures and properties caused by the quick solidification. In this work, the CoFeNi2V0.5Nb0.75 and CoFeNi2V0.5Nb HEAs which show fully eutectic and hypereutectic microstructures in their casting samples were laser cladded on 304 stainless steel substrate with laser power of 1400, 1600, and 1800 W. Results show that the HEA coatings are composed of the FCC solid solution phase and the Fe2Nb-type Laves phase. The cladding zones of the CoFeNi2V0.5Nb0.75 and CoFeNi2V0.5Nb coatings show cellular dendritic crystals, while the bonding zones show directional columnar crystals. Compared to the 304 stainless steel substrate, the HEA coatings show better wear resistance because of the combination of the hard Fe2Nb-type Laves phase and the ductile FCC solid solution matrix. Moreover, the HEA coatings with power of 1600 W show the best wear resistance attributing to the maximum volume fraction of the hard Fe2Nb-type Laves phase.

  12. The friction and wear of carbon-carbon composites for aircraft brakes

    NASA Astrophysics Data System (ADS)

    Hutton, Toby

    Many carbon-carbon composite aircraft brakes encounter high wear rates during low energy braking operations. The work presented in this thesis addresses this issue, but it also elucidates the microstructural changes and wear mechanisms that take place in these materials during all braking conditions encountered by aircraft brakes. A variety of investigations were conducted using friction and wear testing, as well as examination of wear surfaces and wear debris using OM, SEM, X-RD, TGA and Density Gradient Separation (DOS). Friction and wear tests were conducted on a PAN fibre/CVI matrix carbon-carbon composite (Dunlop) and a pitch fibre/Resin-CVI matrix carbon-carbon composite (Bendix). Extensive testing was undertaken on the Dunlop composites to asses the effects of composite architecture, fibre orientation and heat treatment temperatures on friction and wear. Other friction and wear tests, conducted on the base Dunlop composite, were used to investigate the relative influences of temperature and sliding speed. It was found that the effect of temperature was dominant over composite architecture, fibre orientation and sliding speed in governing the friction and wear performance of the Dunlop composites. The development of bulk temperatures in excess of 110 C by frictional heating resulted in smooth friction and a low wear rate. Reducing heat treatment temperature also reduced the thermal conductivity producing high interface temperatures, low smooth friction coefficients and low wear rates under low energy braking conditions. However, this was at the expense of high oxidative wear rates under higher energy braking conditions. The Bendix composites had lower thermal conductivities than the fully heat treated Dunlop composite and exhibited similar friction and wear behaviour to Dunlop composites heat treated to lower temperatures. Examination of the wear surfaces using OM and SEM revealed particulate or Type I surface debris on wear surfaces tested under low energy

  13. Aerospace applications of high temperature superconductivity

    NASA Technical Reports Server (NTRS)

    Connolly, D. J.; Heinen, V. O.; Aron, P. R.; Lazar, J.; Romanofsky, Robert R.

    1990-01-01

    A review is presented of all the applications that are part of the NASA program to develop space technology capitalizing on the potential benefit of high temperature superconducting materials. The applications in three major areas are being pursued: sensors and cryogenic systems, space communications, and propulsion and power systems. This review places emphasis on space communications applications and the propulsion and power applications. It is concluded that the power and propulsion applications will eventually be limited by structural considerations rather than by the availability of suitable superconductors. A cursory examination of structural limitations implied by the virial theorem suggested that there is an upper limit to the size of high field magnetic systems that are feasible in space.

  14. Students Wearing Police Uniforms Exhibit Biased Attention toward Individuals Wearing Hoodies

    PubMed Central

    Civile, Ciro; Obhi, Sukhvinder S.

    2017-01-01

    Police provide an essential public service and they often operate in difficult circumstances, requiring high-speed cognition. Recent incidents involving apparent profiling and aggressive behavior have led to accusations that the police are sometimes biased. Given that previous research has shown a link between clothing and cognition, we investigated the question of whether the police uniform itself might induce a bias in social attention. To address this question, and using a Canadian university student sample, we assessed whether wearing a police uniform biases attention toward black faces compared to white faces, and low-status individuals compared to high-status individuals. In Experiment 1 (n = 28), participants wore either a police-style uniform or mechanic overalls, and performed a shape categorization task in the presence of a distractor that could be either: a black face, a white face, a person wearing a hoodie (whom we propose will be associated with low SES), or a person wearing a suit (whom we propose will be associated with high SES). Participants wearing the police-style uniform exhibited biased attention, indexed by slower reaction times (RTs), in the presence of low-SES images. In Experiment 2 (n = 28), we confirmed this bias using a modified Dot-Probe task – an alternate measure of attentional bias in which we observed faster RTs to a dot probe that was spatially aligned with a low SES image. Experiment 3 (n = 56) demonstrated that attentional bias toward low-SES targets appears only when participants wear the police-style uniform, and not when they are simply exposed to it – by having it placed on the desk in front of them. Our results demonstrate that wearing a police-style uniform biases attention toward low-SES targets. Thus, wearing a police-style uniform may induce a kind of “status-profiling” in which individuals from low-status groups become salient and capture attention. We note that our results are limited to university students

  15. Microstructural effects in abrasive wear. Quarterly progress report, September 15-December 15, 1979

    SciTech Connect

    Fiore, N F; Kosel, T H; Channigiri, M; Desai, V; Fulcher, J

    1980-01-15

    This is the 11th quarterly report describing research aimed at establishing quantitative relations between microstructure and wear resistance of highly alloyed materials, including high-Cr white irons and experimental Co-base and Ni-base powder metallurgy (PM) alloys. The specific types of wear under study are low-stress abrasion and gouging wear encountered in mining, coal conversion and transfer applications. The white irons range in carbide volume fracton (v/sub f/) from 10 to 45%. They are of carefully balanced composition to produce maximum carbide hardness, v/sub f/ and matrix hardenability at minimum alloy content. Effort has been devoted to metallographic characterization of these alloys and to low-stress abrasion testing against dry SiO/sub 2/. Low-stress abrasion resistance passes through a maximum at intermediate v/sub f/, a finding which corroborates wet-sand, low-stress test results from another laboratory. Low- and high-matrix alloy content Co-base alloys are also under investigation. Both types of alloys have been processed by powder metallurgy (PM) to display a uniform array of fine, medium or coarse carbides in a FCC matrix. Extensive effort has been expended to develop metallographic procedures for characterizing the microstructures of the alloys. Of particular significance is the development of a one-step electrolytic etching-staining procedure which reveals matrix, matrix grain boundaries and carbides simultaneously in high contrast.

  16. Wear of sequentially enhanced 9-Mrad polyethylene in 10 million cycle knee simulation study.

    PubMed

    Tsukamoto, Riichiro; Williams, Paul Allen; Shoji, Hiromu; Hirakawa, Kazuo; Yamamoto, Kengo; Tsukamoto, Mikiko; Clarke, Ian C

    2008-07-01

    Highly crosslinked polyethylene (HXPE) has been shown to be effective in reducing wear in total hip replacements. HXPE has not found widespread use in TKR, because the crosslinking inevitably leads to reductions in critical properties such as toughness and fatigue strength. Sequentially enhanced crosslinking (SXPE) have been suggested for improved wear resistance for tibial inserts with maintenance of mechanical properties and anticipated high oxidation resistance superior to conventional polyethylene (XLPE). We compared the wear of SXPE (9Mrad) to XLPE inserts (3Mrad) to 10 million cycles. Triathlon femoral condyles were identical in both. This is the first wear study of SXPE inserts. According to the power law relating irradiation dose to wear of XLPE inserts, wear of 9 Mrad inserts should be reduced by 70% compared to 3Mrad controls. The wear rates of the SXPE inserts were reduced by 86% at 10 million cycles duration, somewhat greater than predicted. The one prior investigation by the manufacturer reported a 79% wear reduction for SXPE compared to controls in a 5 million cycle simulator study in knee design and test parameters. There were important differences between the two studies. Nevertheless there clearly appeared to be a major benefit for sequentially enhanced polyethylene in tibial inserts. This combined wear reduction of 80-85% with improved oxidation resistance and retention of mechanical properties may prove beneficial for active patients who may otherwise risk high wear rates over many years of use.

  17. Wear of hot rolling mill rolls: An overview

    NASA Astrophysics Data System (ADS)

    Spuzic, S.; Strafford, K. N.; Subramanian, C.; Savage, G.

    1994-08-01

    Rolling is today one of the most important industrial processes because a greater volume of material is worked by rolling than by any other technique. Roll wear is a multiplex process where mechanical and thermal fatigue combines with impact, abrasion, adhesion and corrosion, which all depend on system interactions rather than material characteristics only. The situation is more complicated in section rolling because of the intricacy of roll geometry. Wear variables and modes are reviewed along with published methods and models used in the study and testing of roll wear. This paper reviews key aspects of roll wear control - roll material properties, roll pass design, and system factors such as temperature, loads and sliding velocity. An overview of roll materials is given including adamites, high Cr materials, high speed tool steels and compound rolls. Non-uniform wear, recognized as the most detrimental phenomenon in section rolling, can be controlled by roll pass design. This can be achieved by computer-aided graphical and statistical analyses of various pass series. Preliminary results obtained from pilot tests conducted using a two-disc hot wear rig and a scratch tester are discussed.

  18. Wear Assessment of Conical Pick used in Coal Cutting Operation

    NASA Astrophysics Data System (ADS)

    Dewangan, Saurabh; Chattopadhyaya, Somnath; Hloch, Sergej

    2015-09-01

    Conical pick is a widely used tool for cutting coal in mines. It has a cemented carbide tip inserted in a steel body. Cemented carbide has been in use for many years for coal/rock cutting because it has the optimum combination of hardness, toughness and resistance against abrasive wear. As coal/rock is a heterogeneous substance, the cutting tool has to undergo various obstructions at the time of excavation that cause the tool to wear out. The cracks and fractures developing in the cemented carbide limit the life of the tool. For a long time, different wear mechanisms have been studied to develop improved grades of cemented carbide with high wear resistance properties. The research is still continuing. Moreover, due to the highly unpredictable nature of coal/rock, it is not easy to understand the wear mechanisms. In the present work, an attempt has been made to understand the wear mechanisms in four conical picks, which were used in a continuous miner machine for underground mining of coal. The wearing pattern of the conical pick indicates damage in its cemented carbide tip as well as the steel body. The worn out parts of the tools have been critically examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) point analysis. Mainly four types of wear mechanisms, namely, coal/rock intermixing, plastic deformation, rock channel formation and crushing and cracking, have been detected. The presence of coal/rock material and their respective concentrations in the selected area of worn out surface were observed using the spectra generated by EDX analysis.

  19. Wear resistant alloys for coal handling equipment. Final technical report, October 1, 1977-March 31, 1981

    SciTech Connect

    Garrison, W.M.; Parker, E.R.; Misra, A.; Finnie, I.

    1981-01-01

    In the progress report for 1977-1979, an extensive literature survey was completed in the areas of abrasive wear mechanisms, wear testing and microstructural effects on abrasive wear. Definitions of the various abrasive wear processes were clarified. A laboratory wear tester capable of simulating high stress two-body abrasive wear and low stress three-body wear was designed, constructed and calibrated. Experiments were run on some standard metals and alloys in the annealed, work hardened, and heat treated conditions under both two-body and three-body wear. In the 1979 to 1980 period, a detailed analysis of the abrasive size effect was performed based on the observations made on two- and three-body abrasion and erosion. It was concluded that the size effect was due to a shallow surface layer exhibiting higher flow stress than the bulk material when the material is abraded or eroded. The effect of certain variables on the wear resistance of different pure metals was compared for two-body abrasion, three-body abrasion and erosion. The variables studied are annealed hardness of the worn metal, the increase in hardness of the worn metal before the wear process due to work hardening and heat treatment, applied load, distance travelled, the abrasive particle size and abrasive hardness. The effect of most of these variables is similar for the three different wear processes. The existing low-stress, open three-body abrasive wear tester was modified and calibrated for testing abrasive wear up to 600/sup 0/C. Some standard materials were tested and in the case of pure aluminum it was found that the wear rate decreased with increase in temperature.

  20. Microstructure and wear characteristics of si particulate reinforced al matrix composites

    NASA Astrophysics Data System (ADS)

    Song, Suk-Jin; Kim, Do-Hyang; Kim, Jun-Su

    1997-08-01

    In order to obtain a homogeneous distribution of fine Si particles in aluminium matrix and thus to improve the adaptability of Al-Si alloy for aerospace and automobile applications, Si particulate reinforced aluminium matrix composites have been processed by using powder metallurgy method. The Si pariticulates with 20-40 μm size and Al alloy powders were mixed, degassed and extruded at 350°C or 400°C depending on the composition of the matrix alloy. The microstructural characteristics of the composites such as interfacial stability at high temperatures have been investigated by various experimental techniques. Wear properties of the composites were investigated by using a pin-on-disk type wear tester. The results were compared with these obtained from the conventionally cast hypereutectic Al-Si alloys and discussed in terms of the observed microstructural characteristics and physical properties such as hardness and tensile properties.

  1. A Study on 3-Body Abrasive Wear Behaviour of Aluminium 8011 / Graphite Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Latha Shankar, B.; Anil, K. C.; Patil, Rahul

    2016-09-01

    Metals and alloys have found their vital role in many applications like structural, corrosive, tribological, etc., in engineering environment. The alloys/composites having high strength to low weight ratio have gained attention of many researchers recently. In this work, graphite reinforced Aluminium 8011 metal matrix composite was prepared by conventional stir casting route, by varying the weight % of reinforcement. Uniform distribution of Graphite in matrix alloy was confirmed by optical micrographs. Prepared composite specimens were subjected to 3-body abrasive testing by varying applied load and time, the silica particles of 400 grit size were used as abrasive particles. It was observed that with the increase of weight% of Graphite the wear resistance of composite was also increasing and on comparison it was found that reinforced composite gives good wear resistance than base alloy.

  2. Functionally gradient hard carbon composites for improved adhesion and wear

    NASA Astrophysics Data System (ADS)

    Narayan, Roger Jagdish

    A new approach is proposed for fabricating biomedical devices that last longer and are more biocompatible than those presently available. In this approach, a bulk material is chosen that has desirable mechanical properties (low modulus, high strength, high ductility and high fatigue strength). This material is coated with corrosion-resistant, wear-resistant, hard, and biocompatible hard carbon films. One of the many forms of carbon, tetrahedral amorphous carbon, consists mainly of sp3-bonded atoms. Tetrahedral amorphous carbon possesses properties close to diamond in terms of hardness, atomic smoothness, and inertness. Tetrahedral amorphous carbon and diamond films usually contain large amounts of compressive and sometimes tensile stresses; adhesive failure from these stresses has limited widespread use of these materials. This research involves processing, characterization and modeling of functionally gradient tetrahedral amorphous carbon and diamond composite films on metals (cobalt-chromium and titanium alloys) and polymers (polymethylmethacrylate and polyethylene) used in biomedical applications. Multilayer discontinuous thin films of titanium carbide, titanium nitride, aluminum nitride, and tungsten carbide have been developed to control stresses and graphitization in diamond films. A morphology of randomly interconnected micron sized diamond crystallites provides increased toughness and stress reduction. Internal stresses in tetrahedral amorphous carbon were reduced via incorporation of carbide forming elements (silicon and titanium) and noncarbide forming elements (copper, platinum, and silver). These materials were produced using a novel target design during pulsed laser deposition. These alloying atoms reduce hardness and sp3-bonded carbon content, but increase adhesion and wear resistance. Silver and platinum provide the films with antimicrobial properties, and silicon provides bioactivity and aids bone formation. Bilayer coatings were created that couple

  3. GEANT4: Applications in High Energy Physics

    SciTech Connect

    Mahmood, Tariq; Zafar, Abrar Ahmed; Hussain, Talib; Rashid, Haris

    2007-02-14

    GEANT4 is a detector simulation toolkit aimed at studying, mainly experimental high energy physics. In this paper we will give an overview of this software with special reference to its applications in high energy physics experiments. A brief of process methods is given. Object-oriented nature of the simulation toolkit is highlighted.

  4. Cannon Wear and Erosion Science and Technology Objective Program (STO) 155-mm Projectile Rotating Band/Obturation for Extended Range

    DTIC Science & Technology

    2015-06-01

    use of alternate rotating band materials with high melting temperatures and improved wear characteristics. One dimensional finite element wear...past for nickel and stainless steel, ArrowTech Associates interpolated a wear function by comparing the melt temperatures of iron, stainless steel...dimensional (1-D) model that estimates temperature distributions and wear in rotating bands taking into account parameters such as axial acceleration-time

  5. Structurally Integrated Coatings for Wear and Corrosion

    SciTech Connect

    Beardsley, M. Brad; Sebright, Jason L.

    2008-11-18

    Wear and corrosion of structures cuts across industries and continues to challenge materials scientists and engineers to develop cost effective solutions. Industries typically seek mature technologies that can be implemented for production with rapid or minimal development and have little appetite for the longer-term materials research and development required to solve complex problems. The collaborative work performed in this project addressed the complexity of this problem in a multi-year program that industries would be reluctant to undertake without government partnership. This effort built upon the prior development of Advanced Abrasion Resistant Materials conduct by Caterpillar Inc. under DOE Cooperative Agreement No. DE-FC26-01NT41054. In this referenced work, coatings were developed that exhibited significant wear life improvements over standard carburized heat treated steel in abrasive wear applications. The technology used in this referenced work, arc lamp fusing of thermal spray coatings, was one of the primary technical paths in this work effort. In addition to extending the capability of the coating technology to address corrosion issues, additional competitive coating technologies were evaluated to insure that the best technology was developed to meet the goals of the program. From this, plasma transferred arc (PTA) welding was selected as the second primary technology that was investigated. Specifically, this project developed improved, cost effective surfacing materials and processes for wear and corrosion resistance in both sliding and abrasive wear applications. Materials with wear and corrosion performance improvements that are 4 to 5 times greater than heat treated steels were developed. The materials developed were based on low cost material systems utilizing ferrous substrates and stainless steel type matrix with hard particulates formed from borides and carbides. Affordability was assessed against other competing hard surfacing or coating

  6. Tribological Performance of PM300 Solid Lubricant Bushings for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Striebing, Donald R.; Stanford, Malcolm K.; DellaCorte, Christopher; Rossi, Anne M.

    2007-01-01

    PM300 is a high temperature solid lubricant material produced through conventional powder metallurgy processing. PM300 is a combination of metal binder (NiCr), hardener (Cr2O3) and lubricant (Ag and BaF2/CaF2) phases and is in commercial use in high temperature furnace conveyors. In this paper, the tribological characteristics of PM300 are evaluated using a newly developed bushing test rig in which PM300 bushings are loaded against rotating steel shafts at temperatures from 25 to 650 C. The data shows that friction and wear are low to moderate and that the lubrication performance (friction) improves with increasing temperature. Several alternative PM300 compositions are evaluated which do not contain silver and are targeted at aircraft gas turbine applications in which environmental compatibility of silver is a concern. It is expected that the data resulting from this research will further the commercialization of this technology.

  7. Raman tensor analysis of ultra-high molecular weight polyethylene and its application to study retrieved hip joint components.

    PubMed

    Takahashi, Yasuhito; Puppulin, Leonardo; Zhu, Wenliang; Pezzotti, Giuseppe

    2010-09-01

    The angular dependences of the polarized Raman intensity of A(g), B(1g), B(2g), and B(3g) modes have been preliminary investigated on a model fiber sample of ultra-high molecular weight polyethylene (UHMWPE) in order to retrieve the Raman tensor elements, i.e. the intrinsic parameters governing the vibrational behavior of the orthorhombic structure of polyethylene. Based on this Raman analysis, a method is proposed for determining unknown crystallographic orientation patterns in UHMWPE biomedical components concurrently with the orientation distribution functions for orthorhombic lamellae. An application of the method is shown, in which we quantitatively examined the molecular orientation patterns developed on the surface of four in vivo exposed UHMWPE acetabular cups vs. an unused cup. Interesting findings were: (i) a clear bimodal distribution of orientation angles was observed on worn surfaces; and (ii) a definite and systematic increase in both molecular orientation and crystallinity in main wear zones vs. non-wear zones was found in all retrieved acetabular cups. The present crystallographic analysis is an extension of our previous Raman studies of UHMWPE acetabular cups related to assessments of oxidation and residual strain and suggests a viable path to track back wear-history information from the surface of UHMWPE, thus unfolding the in vivo kinematics of the bearing surfaces in hip joints on the microscopic scale.

  8. Computer modeling of wear in extrusion and forging of automotive exhaust valves

    NASA Astrophysics Data System (ADS)

    Tulsyan, R.; Shivpuri, R.

    1995-04-01

    In an automotive engine valve forging process, the billet is cold sheared, induction heated, and fed to a mechanical press for a two-stage forging operation with the first stage being extrusion. The main limiting factor in this operation is the wear of the dies during the first stage, extrusion. In this study. abrasive wear was identified as the primary mode of wear, and computer simulation was used to investigate the effect of process variables, such as press speed, initial billet temperature, and die preheat temperature upon abrasive wear. The result generated by this study should be applicable to other part geometry and not limited just to exhaust valves.

  9. Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates.

    PubMed

    Ebert, Daniel; Bhushan, Bharat

    2016-11-01

    Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM).

  10. Industrial Applications of High Power Ultrasonics

    NASA Astrophysics Data System (ADS)

    Patist, Alex; Bates, Darren

    Since the change of the millennium, high-power ultrasound has become an alternative food processing technology applicable to large-scale commercial applications such as emulsification, homogenization, extraction, crystallization, dewatering, low-temperature pasteurization, degassing, defoaming, activation and inactivation of enzymes, particle size reduction, extrusion, and viscosity alteration. This new focus can be attributed to significant improvements in equipment design and efficiency during the late 1990 s. Like most innovative food processing technologies, high-power ultrasonics is not an off-the-shelf technology, and thus requires careful development and scale-up for each and every application. The objective of this chapter is to present examples of ultrasonic applications that have been successful at the commercialization stage, advantages, and limitations, as well as key learnings from scaling up an innovative food technology in general.

  11. High temperature superconductors for magnetic suspension applications

    NASA Technical Reports Server (NTRS)

    Mcmichael, C. K.; Cooley, R. S.; Chen, Q. Y.; Ma, K. B.; Lamb, M. A.; Meng, R. L.; Chu, C. W.; Chu, W. K.

    1994-01-01

    High temperature superconductors (HTS) hold the promise for applications in magnetic levitation bearings, vibration damping, and torque coupling. Traditional magnetic suspension systems require active feedback and vibration controls in which power consumption and low frequency vibration are among the major engineering concerns. HTS materials have been demonstrated to be an enabling approach towards such problems due to their flux trapping properties. In our laboratory at TCSUH, we have been conducting a series of experiments to explore various mechanical applications using HTS. We have constructed a 30 lb. model flywheel levitated by a hybrid superconducting magnetic bearing (HSMB). We are also developing a levitated and vibration-dampled platform for high precision instrumentation. These applications would be ideal for space usages where ambient temperature is adequate for HTS to operate properly under greatly reduced cryogenic requirements. We will give a general overview of these potential applications and discuss the operating principles of the HTS devices we have developed.

  12. Wear-related fatigue in a wire rope failure

    SciTech Connect

    Schrems, K.K. . Albany Research Center)

    1994-09-01

    The fatigue failure of a nonrotating wire rope used on a skip hoist in an underground mine has been studied as part of the ongoing research by the US Bureau of Mines into haulage and materials handling hazards in mines. Correlation of individual wire failures within two segments of the failed rope were used to gain an understanding of the progression of degradation leading to rope failure. Wire failures occurred predominantly at locations of wear between adjacent strands. These interstrand wear site are identifiable by a large reduction in diameter; however, reduction in area is not responsible for the location of failure. Fractography revealed crack initiation sites to be located opposite the characteristic wear site or at other less noticeable wear sites. The primary failure mechanism of individual wires within the rope is believed t be a function of contact stress at the interstrand wear sites. Axially loading and unloading the rope produces high compressive stresses at the contact sites, which in turn produce large alternating tensile stresses on the opposite side of the wire. This mechanism has been termed contact stress-accelerated fatigue. This mechanism and the affiliated wear pattern both are consequences of interstrand contact.

  13. Friction and wear of iron in sulfuric acid

    NASA Technical Reports Server (NTRS)

    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Elemental iron sliding on aluminum oxide in aerated sulfuric acid concentrations ranging from very dilute (0.000007 N; i.e., 4 ppm) to very concentrated (96 percent acid) was studied. Load and reciprocating sliding speeds were kept constant. With the most dilute acid of 0.7 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent, the high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid, and decreased somewhat at 50 percent in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It is apparent that the normal passivating film was being worn away and a galvanic cell established which rapidly attached to the wear area.

  14. Computational prediction and experimental validation of revolute joint clearance wear in the low-velocity planar mechanism

    NASA Astrophysics Data System (ADS)

    Lai, Xiongming; He, Huang; Lai, Qinfang; Wang, Cheng; Yang, Jianhong; Zhang, Yong; Fang, Huaiying; Liao, Shuirong

    2017-02-01

    Within the multibody dynamics framework, the paper proposed an efficient procedure to calculate revolute joint wear of planar mechanism with low velocity. Firstly, based on the wear test data, a method to calculate the wear coefficient that corresponds to the actual working condition of the mechanism is proposed. Then, an efficient iterative prediction method for joint clearance wear evolving in the multibody dynamic system in is proposed based on the Archard's wear model. Meanwhile, the wear tests of the typical mechanism have verified the method proposed in this paper. The research shows that when the increments of the wear depth of revolute joints are not big, the method can provide high prediction accuracy; however, as the predicted wear depth increases, the prediction error increases as well.

  15. The development of a bearing spectral analyzer and algorithms to detect turbopump bearing wear from deflectometer and strain gage data

    NASA Astrophysics Data System (ADS)

    Martinez, Carol L.

    1992-07-01

    Over the last several years, Rocketdyne has actively developed condition and health monitoring techniques and their elements for rocket engine components, specifically high pressure turbopumps. Of key interest is the development of bearing signature analysis systems for real-time monitoring of the cryogen-cooled turbopump shaft bearings, which spin at speeds up to 36,000 RPM. These system elements include advanced bearing vibration sensors, signal processing techniques, wear mode algorithms, and integrated control software. Results of development efforts in the areas of signal processing and wear mode identification and quantification algorithms based on strain gage and deflectometer data are presented. Wear modes investigated include: inner race wear, cage pocket wear, outer race wear, differential ball wear, cracked inner race, and nominal wear.

  16. Reciprocating sliding wear of in-situ reinforced silicon nitride

    SciTech Connect

    Yust, C.S.

    1995-10-01

    The reciprocating sliding wear response of two in-situ reinforced-silicon nitride compositions provided by AlliedSignal have been evaluated. The materials were prepared by AlliedSignal-Ceramic Components Division and were tested at conditions of interest to the Bendix Engine Controls Division (South Bend, IN) and AlliedSignal Research and Technology (Des Plaines, IL). The materials are being considered for a variety of new applications, and the current tests provide critical friction and wear values under anticipated operating conditions. Both pin and disk specimens of GS-44 and GN-10 in-situ reinforced silicon nitride of specified dimensions for wear testing were provided by the AlliedSignal participants. An initial series of tests examined the unlubricated behavior of these materials at elevated temperature (up to 900 C) in an inert atmosphere. The results revealed excessive levels of both friction and wear in the unlubricated condition. The test conditions were modified to include the use of jet fuel as a lubricant because of an intended application in that medium. The introduction of the lubricant resulted in very limited wear of both the pin and disk specimens.

  17. GEM Applications Outside High Energy Physics

    NASA Astrophysics Data System (ADS)

    Pinto, Serge Duarte

    2013-04-01

    From its invention in 1997, the Gas Electron Multiplier (GEM) has been applied in nuclear and high energy physics experiments. Over time however, other applications have also exploited the favorable properties of GEMs. The use of GEMs in these applications will be explained in principle and practice. This paper reviews applications in research, beam instrumentation and homeland security. The detectors described measure neutral radiations such as photons, x-rays, gamma rays and neutrons, as well as all kinds of charged radiation. This paper provides an overview of the still expanding range of possibilities of this versatile detector concept.

  18. Synthesis of Bulk Nanostructured Al Alloys with Ultra-High Strength and Wear Resistance for Army Applications

    DTIC Science & Technology

    2007-11-02

    A185Ni10La5is estimated to be only -2.9 g/cma. In addition, effect of swaging , annealing or HIP’ing on the mechanical properties of the as-extruded...A185Ni10La5 sample particles has a compressive strength larger than 100OMPa, but has limited ductility. (c) Swaging could increase the ductility of the 10...Al85Ni10La5 particles and matrix. The influence of annealing, HIP’ing and swaging on the ductility was studied. Results show that the fracture strength

  19. Microstructure and elevated temperature wear behavior of induction melted Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Hu, Ge; Meng, Huimin; Liu, Junyou

    2014-10-01

    Fe-based composite coating prepared onto the component of guide wheel using ultrasonic frequency inductive cladding (UFIC) technique has been investigated in terms of microstructure, phase constitutions, microhardness and elevated temperature wear behavior by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Vickers microhardness tester and ball-on-disc wear tester. The results indicated that the primary phase in the coating contained austenite γ-Fe, eutectic γ-Fe/(Cr,Fe)2B, boride (Cr,Fe)2B and precipitation enriched in Mo. The average microhardness of the coating was 760 ± 10 HV0.2, which was three times higher than that of the substrate. With increasing temperature, the friction coefficients of the coating and high-chromium cast iron decreased gradually while the wear rates increased during dry sliding wear condition. The relative wear resistance of the coating was 1.63 times higher than that of the high-chromium cast iron at 500 °C, which was ascribed to the hard borides with high thermal stability uniformly embedded in the coating and the formation of dense transfer layer formed onto the worn surface. The high temperature wear mechanism of the coating was dominated by mild abrasive wear. The study revealed that Fe-based composite coating had excellent high temperature wear resistance under dry sliding wear condition.

  20. Wear Test Results of Candidate Materials for the OK-542 Towed Array Handling Machine Level Winder

    DTIC Science & Technology

    1994-12-29

    were being considered. Unfortunately, these other options, which included thermal spraying , carbide inserts and wear coatings required long lead...applications. these include various wear-resistant coatings, thermal spraying , and the use of special inserts. 4 TM941159 Based on the testing and

  1. High Performance Fortran for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Mehrotra, Piyush; Zima, Hans; Bushnell, Dennis M. (Technical Monitor)

    2000-01-01

    This paper focuses on the use of High Performance Fortran (HPF) for important classes of algorithms employed in aerospace applications. HPF is a set of Fortran extensions designed to provide users with a high-level interface for programming data parallel scientific applications, while delegating to the compiler/runtime system the task of generating explicitly parallel message-passing programs. We begin by providing a short overview of the HPF language. This is followed by a detailed discussion of the efficient use of HPF for applications involving multiple structured grids such as multiblock and adaptive mesh refinement (AMR) codes as well as unstructured grid codes. We focus on the data structures and computational structures used in these codes and on the high-level strategies that can be expressed in HPF to optimally exploit the parallelism in these algorithms.

  2. 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

    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.

  3. 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

  4. Alloys developed for high temperature applications

    NASA Astrophysics Data System (ADS)

    Basuki, Eddy Agus; Prajitno, Djoko Hadi; Muhammad, Fadhli

    2017-01-01

    Alloys used for high temperatures applications require combinations of mechanical strength, microstructural stability and corrosion/oxidation resistance. Nickel base superalloys have been traditionally the prime materials utilized for hot section components of aircraft turbine engines. Nevertheless, due to their limited melting temperatures, alloys based on intermetallic compounds, such as TiAl base alloys, have emerged as high temperature materials and intensively developed with the main aim to replace nickel based superalloys. For applications in steam power plants operated at lower temperatures, ferritic high temperature alloys still attract high attention, and therefore, development of these alloys is in progress. This paper highlights the important metallurgical parameters of high temperature alloys and describes few efforts in the development of Fe-Ni-Al based alloys containing B2-(Fe,Ni)Al precipitates, oxide dispersion strengthening (ODS) ferritic steels and titanium aluminide based alloys include important protection system of aluminide coatings.

  5. Clinical measurement of tooth wear: Tooth wear indices

    PubMed Central

    López-Frías, Francisco J.; Castellanos-Cosano, Lizett; Martín-González, Jenifer; Llamas-Carreras, José M.

    2012-01-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, the interpretation and comparison of clinical and epidemiological studies, it is increasingly difficult because of differences in terminology and the large number of indicators/indices that have been developed for the diagnosis, classification and monitoring of the loss of dental hard tissue. These indices have been designed to identify increasing severity and are usually numerical, none have universal acceptance, complicating the evaluation of the true increase in prevalence reported. This article considers the ideal requirements for an erosion index. A literature review is conducted with the aim of analyzing the evolution of the indices used today and discuss whether they meet the clinical needs and research in dentistry. Key words:Tooth wear, tooth wear indices, attrition, erosion, abrasion, abfraction. PMID:24558525

  6. Clinical measurement of tooth wear: Tooth wear indices.

    PubMed

    López-Frías, Francisco J; Castellanos-Cosano, Lizett; Martín-González, Jenifer; Llamas-Carreras, José M; Segura-Egea, Juan J

    2012-02-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, the interpretation and comparison of clinical and epidemiological studies, it is increasingly difficult because of differences in terminology and the large number of indicators/indices that have been developed for the diagnosis, classification and monitoring of the loss of dental hard tissue. These indices have been designed to identify increasing severity and are usually numerical, none have universal acceptance, complicating the evaluation of the true increase in prevalence reported. This article considers the ideal requirements for an erosion index. A literature review is conducted with the aim of analyzing the evolution of the indices used today and discuss whether they meet the clinical needs and research in dentistry. Key words:Tooth wear, tooth wear indices, attrition, erosion, abrasion, abfraction.

  7. Synthesis and characterization of Ni60-hBN high temperature self-lubricating anti-wear composite coatings on Ti6Al4V alloy by laser cladding

    NASA Astrophysics Data System (ADS)

    Lu, Xiao-Long; Liu, Xiu-Bo; Yu, Peng-Cheng; Qiao, Shi-Jie; Zhai, Yong-Jie; Wang, Ming-Di; Chen, Yao; Xu, Dong

    2016-04-01

    Ni60-hBN composite coatings with varying hBN content were prepared on Ti6Al4V substrates by laser cladding. The composite coatings with no cracks and few pores are bonded metallurgically with the substrates. The phase composition and microstructure of the composite coatings were investigated. The tribological properties of the composite coatings were evaluated under dry sliding wear test conditions at 20 °C, 300 °C and 600 °C, respectively. The microhardness gradually increased from the bottom to the top of the coating and increased with increasing of hBN content. The laser clad Ni60-10%hBN coating exhibits excellent tribological behavior at high temperatures (300 °C and 600 °C).

  8. The influence of nominal stress on wear factors of carbon fibre-reinforced polyetheretherketone (PEEK-OPTIMA® Wear Performance) against zirconia toughened alumina (Biolox® delta ceramic).

    PubMed

    Evans, Andrew; Horton, Henrietta; Unsworth, Anthony; Briscoe, Adam

    2014-06-01

    Carbon fibre-reinforced polyetheretherketone is an attractive alternative to ultra-high-molecular-weight polyethylene in artificial joints, but little has been published on the influence of stress on the wear factor. We know that in ultra-high-molecular-weight polyethylene, the wear factor reduces as the normal stress increases, which is counter-intuitive but very helpful in the case of non-conforming contacts. In this study, carbon fibre-reinforced polyetheretherketone (PEEK-OPTIMA(®) Wear Performance) has been investigated in a pin-on-plate machine under steady loads and under stresses typical of hip and knee joints. At stresses below about 6 MPa, wear factors are between 10 and a 100 times lower than for ultra-high-molecular-weight polyethylene but at higher stresses the wear factors increase substantially.

  9. Research on the effect of wear-ring clearances to the performance of centrifugal pump

    NASA Astrophysics Data System (ADS)

    Zhao, W. G.; Li, Y. B.; Wang, X. Y.; Sun, J. P.; Wu, G. X.

    2012-11-01

    In order to study the effect of wear-ring clearance on the performance of centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump was simulated with three variable styles of the wear-rings: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Numerical results agree well with the experimental results. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the performance of centrifugal pump. The existence of wear-ring not only has an effect on the volumetric loss of the centrifugal pump, but also on the performance of the centrifugal pump. Relative to the experimental studies, numerical simulation methods have some advantages, such as low cost, fast and efficient, and easy to get the detailed structure of the internal flow characteristics, so it has been widely used in the fluid machinery study. In order to study the effect of wear-ring clearance on the performance of centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump was simulated with three variable styles of the wear-rings: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Numerical results agree well with the experimental results. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the performance of centrifugal pump.

  10. Wear Resistance of Friction Pair of Metal Composite/Copper under Electric Current

    NASA Astrophysics Data System (ADS)

    Aleutdinova, M. I.; Fadin, V. V.; Rubtsov, V. Ye; Aleutdinov, K. A.

    2016-11-01

    Sliding of metal composites against copper counterbody under severe conditions (i.e. at the contact current density higher 50 A/cm2 and at high roughness of counterbody) is carried out. It is shown that the composite of composition of Cu-30% of graphite shows low wear resistance in these conditions. Higher wear resistance is inherent in the composites containing lead and bearing steel. Impregnation of these composites by industrial oil hasn't led to noticeable increase in wear resistance.

  11. 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.

  12. Fretting Wear Mechanisms in A216 Plain Carbon Steel

    NASA Astrophysics Data System (ADS)

    Maich, Alyssa Anne

    The subsurface and surface microstructures during pin-on-disk fretting wear of A216 steel disks under various loading conditions and times are investigated. The corresponding pins are fabricated from 410 stainless steel to simulate in-service conditions found in such engineering components as the Siemens W501FD engine row-2 diaphragm of a Siemens turbine engine, which is known to be prone to failure by fretting wear. Loading conditions range from 2N to 15N and times from 1 hour to a maximum of 69 hours, when steady state is confirmed. Wear track depth is quantitatively determined by optical profilometry, and found to range from 3 to 11 microns dependent upon load. Wear depth increases from 2N to 10N load, but decreases when increased to 15N load, due to heavier transfer of pin material to disk, as can be seen by EDS images of chromium transfer on A216 disk. Microstructures are evaluated by transmission electron microscopy of samples prepared by focused ion beam machining to pinpoint wear tracks and expose them in cross-section. EDS is used, in conjunction with TEM, to elucidate primary wear mechanisms at each stage of fretting wear. Microstructures in the subsurface of wear tracks are found to be heavily dislocated and layered, features that vary with both applied load and time. The microstructure eventually evolves into stable dislocation cells with cell walls aligned parallel to the surface. Penetration depth of the damaged layers increases with applied load, associated with a non-uniform maximum shear stress distribution that varies with depth. Primary oxide appears to evolve from Fe2O3 to Fe3O4, with increasing fretting time, leading to a uniform oxide on the surface of the A216 disk. Oxidation rate may be increased with the evolution of this subsurface dislocation cell structure. It is concluded that fretting wear failure is likely associated with a synergy between oxidative wear and crack initiation and propagation along dislocation cell walls under high

  13. Space applications of superconductivity - High field magnets

    NASA Technical Reports Server (NTRS)

    Fickett, F. R.

    1979-01-01

    The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

  14. Critical length scale controls adhesive wear mechanisms

    PubMed Central

    Aghababaei, Ramin; Warner, Derek H.; Molinari, Jean-Francois

    2016-01-01

    The adhesive wear process remains one of the least understood areas of mechanics. While it has long been established that adhesive wear is a direct result of contacting surface asperities, an agreed upon understanding of how contacting asperities lead to wear debris particle has remained elusive. This has restricted adhesive wear prediction to empirical models with limited transferability. Here we show that discrepant observations and predictions of two distinct adhesive wear mechanisms can be reconciled into a unified framework. Using atomistic simulations with model interatomic potentials, we reveal a transition in the asperity wear mechanism when contact junctions fall below a critical length scale. A simple analytic model is formulated to predict the transition in both the simulation results and experiments. This new understanding may help expand use of computer modelling to explore adhesive wear processes and to advance physics-based wear laws without empirical coefficients. PMID:27264270

  15. Silver based batteries for high power applications

    NASA Astrophysics Data System (ADS)

    Karpinski, A. P.; Russell, S. J.; Serenyi, J. R.; Murphy, J. P.

    The present status of silver oxide-zinc technology and applications has been described by Karpinski et al. [A.P. Karpinski, B. Makovetski, S.J. Russell, J.R. Serenyi, D.C. Williams, Silver-Zinc: status of technology and applications, Journal of Power Sources, 80 (1999) 53-60], where the silver-zinc couple is still the preferred choice where high specific energy/energy density, coupled with high specific power/power density are important for high-rate, weight or size/configuration sensitive applications. Perhaps the silver oxide cathode can be considered one of the most versatile electrode materials. When coupled with other anodes and corresponding electrolyte management system, the silver electrode provides for a wide array of electrochemical systems that can be tailored to meet the most demanding, high power requirements. Besides zinc, the most notable include cadmium, iron, metal hydride, and hydrogen electrode for secondary systems, while primary systems include lithium and aluminum. Alloys including silver are also available, such as silver chloride, which when coupled with magnesium or aluminum are primarily used in many seawater applications. The selection and use of these couples is normally the result of a trade-off of many factors. These include performance, safety, risk, reliability, and cost. When high power is required, silver oxide-zinc, silver oxide-aluminum, and silver oxide-lithium are the most energetic. For moderate performance (i.e., lower power), silver oxide-zinc or silver-cadmium would be the system of choice. This paper summarizes the suitability of the silver-based couples, with an emphasis on the silver-zinc system, as primary or rechargeable power sources for high energy/power applications.

  16. High temperature superconductor materials and applications

    NASA Technical Reports Server (NTRS)

    Doane, George B., III.; Banks, Curtis; Golben, John

    1990-01-01

    Research on processing methods leading to a significant enhancement in the critical current densities (Jc) and the critical temperature (Tc) of high temperature superconducting in thin bulk and thin film forms. The fabrication of important devices for NASA unique applications (sensors) is investigated.

  17. Should School Nurses Wear Uniforms?

    ERIC Educational Resources Information Center

    Journal of School Health, 2001

    2001-01-01

    This 1958 paper questions whether school nurses should wear uniforms (specifically, white uniforms). It concludes that white uniforms are often associated with the treatment of ill people, and since many people have a fear reaction to them, they are not necessary and are even undesirable. Since school nurses are school staff members, they should…

  18. Rigid gas permeable extended wear.

    PubMed

    Maehara, J R; Kastl, P R

    1994-04-01

    We have reviewed the pertinent literature on rigid gas permeable (RGP) extended wear contact lenses, and we discuss the benefits and adverse reactions of this contact lens modality, drawing conclusions from reviewed studies. We suggest parameters for success with these lenses and guidelines for the prevention of adverse reactions.

  19. Fissure sealant materials: Wear resistance of flowable composite resins

    PubMed Central

    Asefi, Sohrab; Eskandarion, Solmaz; Hamidiaval, Shadi

    2016-01-01

    Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow), Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists). A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm2 and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm2of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics. PMID:27651887

  20. Fissure sealant materials: Wear resistance of flowable composite resins.

    PubMed

    Asefi, Sohrab; Eskandarion, Solmaz; Hamidiaval, Shadi

    2016-01-01

    Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow), Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists). A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm(2) and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm(2)of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics.

  1. Porous alumina based ordered nanocomposite coating for wear resistance

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Muthukumar, M.; Bobji, M. S.

    2016-08-01

    Uniformly dispersed nanocomposite coating of aligned metallic nanowires in a matrix of amorphous alumina is fabricated by pulsed electrodeposition of copper into the pores of porous anodic alumina. Uniform deposition is obtained by controlling the geometry of the dendritic structure at the bottom of pores through stepwise voltage reduction followed by mild etching. The tribological behaviour of this nanocomposite coating is evaluated using a ball on flat reciprocating tribometer under the dry contact conditions. The nanocomposite coating has higher wear resistance compared to corresponding porous alumina coating. Wear resistant nanocomposite coating has wide applications especially in protecting the internal surfaces of aluminium internal combustion engines.

  2. Influence of Cycle Temperature on the Wear Resistance of Vermicular Iron Derivatized with Bionic Surfaces

    NASA Astrophysics Data System (ADS)

    Sui, Qi; Zhang, Peng; Zhou, Hong; Liu, Yan; Ren, Luquan

    2016-11-01

    Depending on their applications, such as in brake discs, camshafts, etc., the wear behavior of vermicular iron is influenced by the thermal cycling regime. The failure of a working part during its service life is a consequence of both thermal fatigue and wear. Previously, the wear and thermal fatigue resistance properties of vermicular iron were separately investigated by researchers, rather than a study combining these two factors. In the present work, the effect of cycle temperature on the wear resistance of specimens with bionic units processed by laser has been investigated experimentally. The wear behavior pre- and post-thermal cycling has also been investigated, and the influence of different cycle temperatures on the wear resistance is discussed. The results indicate that the thermal cycling regime brought about negative influences with varying degrees, on the material properties, such as the microstructures, micro-hardness, cracks, and oxidation resistance properties. All these factors synergistically reduced the wear resistance of vermicular iron. In particular, the negative influence apparently increased with an increase in cycle temperature. Nevertheless, the post-thermal-cycle wear resistance of the specimens with bionic units was superior to those without bionic units. Hence, the laser bionic process is an effective way to improve the performance of vermicular iron in combined thermal cycling and wear service conditions.

  3. [Research on monitoring mechanical wear state based on oil spectrum multi-dimensional time series model].

    PubMed

    Xu, Chao; Zhang, Pei-lin; Ren, Guo-quan; Li, Bing; Yang, Ning

    2010-11-01

    A new method using oil atomic spectrometric analysis technology to monitor the mechanical wear state was proposed. Multi-dimensional time series model of oil atomic spectrometric data of running-in period was treated as the standard model. Residues remained after new data were processed by the standard model. The residues variance matrix was selected as the features of the corresponding wear state. Then, high dimensional feature vectors were reduced through the principal component analysis and the first three principal components were extracted to represent the wear state. Euclidean distance was computed for feature vectors to classify the testing samples. Thus, the mechanical wear state was identified correctly. The wear state of a specified track vehicle engine was effectively identified, which verified the validity of the proposed method. Experimental results showed that introducing the multi-dimensional time series model to oil spectrometric analysis can fuse the spectrum data and improve the accuracy of monitoring mechanical wear state.

  4. Fretting wear of iron, nickel, and titanium under varied environmental conditions

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1978-01-01

    Fretting wear experiments were conducted on high purity iron, nickel and titanium in air under conditions of varied humidity and temperature, and in nitrogen. For iron and titanium, maximum fretting occurred at 10 and 30 percent relative humidity respectively. Nickel showed a minimum in fretting wear at about 10 percent relative humidity. With increasing temperature, all three metals initially showed reduced fretting wear, with increasing wear observed as temperatures increased beyond 200-300 C. For titanium, dramatically reduced fretting wear was observed at temperatures above 500 C, relatable to a change in oxidation kinetics. All three metals showed much less fretting wear in N2 with the presence of moisture in N2 having a proportionally stronger effect than in air.

  5. Testing of a Fiber Optic Wear, Erosion and Regression Sensor

    NASA Technical Reports Server (NTRS)

    Korman, Valentin; Polzin, Kurt A.

    2011-01-01

    The nature of the physical processes and harsh environments associated with erosion and wear in propulsion environments makes their measurement and real-time rate quantification difficult. A fiber optic sensor capable of determining the wear (regression, erosion, ablation) associated with these environments has been developed and tested in a number of different applications to validate the technique. The sensor consists of two fiber optics that have differing attenuation coefficients and transmit light to detectors. The ratio of the two measured intensities can be correlated to the lengths of the fiber optic lines, and if the fibers and the host parent material in which they are embedded wear at the same rate the remaining length of fiber provides a real-time measure of the wear process. Testing in several disparate situations has been performed, with the data exhibiting excellent qualitative agreement with the theoretical description of the process and when a separate calibrated regression measurement is available good quantitative agreement is obtained as well. The light collected by the fibers can also be used to optically obtain the spectra and measure the internal temperature of the wear layer.

  6. Wear particle analysis using the ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1983-01-01

    The use of the Ferrograph in analyzing wear particles from a variety of different sources is reported. Examples of wear particles from gas turbine engines, bearing tests, friction and wear tests, hydraulic systems, and human joints are illustrated. In addition, the separation of bacteria and human cells is described.

  7. Wear and impact resistance of HVOF sprayedceramic matrix composites coating

    NASA Astrophysics Data System (ADS)

    Prawara, B.; Martides, E.; Priyono, B.; Ardy, H.; Rikardo, N.

    2016-02-01

    Ceramic coating has the mechanical properties of high hardness and it is well known for application on wear resistance, but on the other hand the resistance to impact load is low. Therefore its use is limited to applications that have no impact loading. The aim of this research was to obtain ceramic-metallic composite coating which has improved impact resistance compared to conventional ceramic coating. The high impact resistance of ceramic-metallic composite coating is obtained from dispersed metallic alloy phase in ceramic matrix. Ceramic Matrix Composites (CMC) powder with chrome carbide (Cr3C2) base and ceramic-metal NiAl-Al2O3 with various particle sizes as reinforced particle was deposited on mild steel substrate with High Velocity Oxygen Fuel (HVOF) thermal spray coating. Repeated impact test showed that reinforced metallic phase size influenced impact resistance of CMC coating. The ability of CMC coating to absorb impact energy has improved eight times and ten times compared with original Cr3C2 and hard chrome plating respectively. On the other hand the high temperature corrosion resistance of CMC coating showed up to 31 cycles of heating at 800°C and water quenching cooling.

  8. A wear simulation study of nanostructured CVD diamond-on-diamond articulation involving concave/convex mating surfaces

    PubMed Central

    Baker, Paul A.; Thompson, Raymond G.; Catledge, Shane A.

    2015-01-01

    Using microwave-plasma Chemical Vapor Deposition (CVD), a 3-micron thick nanostructured-diamond (NSD) layer was deposited onto polished, convex and concave components that were machined from Ti-6Al-4V alloy. These components had the same radius of curvature, 25.4mm. Wear testing of the surfaces was performed by rotating articulation of the diamond-deposited surfaces (diamond-on-diamond) with a load of 225N for a total of 5 million cycles in bovine serum resulting in polishing of the diamond surface and formation of very shallow, linear wear grooves of less than 50nm depth. The two diamond surfaces remained adhered to the components and polished each other to an average surface roughness that was reduced by as much as a factor of 80 for the most polished region located at the center of the condyle. Imaging of the surfaces showed that the initial wearing-in phase of diamond was only beginning at the end of the 5 million cycles. Atomic force microscopy, scanning electron microscopy, Raman spectroscopy, and surface profilometry were used to characterize the surfaces and verify that the diamond remained intact and uniform over the surface, thereby protecting the underlying metal. These wear simulation results show that diamond deposition on Ti alloy has potential application for joint replacement devices with improved longevity over existing devices made of cobalt chrome and ultra-high molecular weight polyethylene (UHMWPE). PMID:26989457

  9. Numerical controlled polishing, continued force wear and part correction experiments

    SciTech Connect

    Hannah, P.R.; Day, R.D.; Hatch, D.J.; McClure, E.R.

    1994-09-01

    This abstract reports the near completion of the first phase of this program. It is the aim of this program to provide the operator of a N/C diamond turning machine or N/C grinding machine (jig grinder) with the wear characteristics necessary to achieve uniform material removal. The second phase of this program addresses a different problem, although solving this problem is highly dependent on the results of the first phase. Diamond turned, or any lathe turned surface, exhibits regular tool marks due to the tool passing over the surface being cut. Changes in depth of cut, feed rate and work rpm will change the character of these groves, but will not eliminate them. Optical surfaces produced by this process exhibit increased scattering as the light wavelength decreases limiting their use; at least for optical purposes, to IR and some visible applications. Utilizing wear information gathered in the first part of this program we will attempt to reduce these residual tool marks by polishing. The polishing of diamond turned surfaces is not new. Diamond turned metal surfaces, especially in electroless nickel and high phosphorus nickel electroplate have been polished to improve their scatter characteristics. What we believe is unique is the use of a spherical wheel, rotating on axis and being moved over the part in a prescribed manner by numerical control. Over the past year we have made some major changes in our polishing methods and procedures. We have listed below these changes, as a refresher for the reader as to our previous procedures. These changes will be addressed in the body of the text.

  10. Mechanical Properties of High Entropy Alloy Al0.1CoCrFeNi for Peripheral Vascular Stent Application.

    PubMed

    Alagarsamy, Karthik; Fortier, Aleksandra; Komarasamy, Mageshwari; Kumar, Nilesh; Mohammad, Atif; Banerjee, Subhash; Han, Hai-Chao; Mishra, Rajiv S

    2016-12-01

    High entropy alloys (HEAs) are new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion, and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community. However, their applications are yet to be explored. This paper discusses the mechanical behavior and microstructure of Al0.1CoCrFeNi HEA subjected to thermo-mechanical processing, and its potential application in peripheral vascular stent implants that are prone to high failure rates. Results show that Al0.1CoCrFeNi alloy possesses characteristics that compare well against currently used stent materials and it can potentially find use in peripheral vascular stent implants and extend their life-cycle.

  11. Assessment of Abrasive Wear of Nanostructured WC-Co and Fe-Based Coatings Applied by HP-HVOF, Flame, and Wire Arc Spray

    NASA Astrophysics Data System (ADS)

    Lima, C. R. C.; Libardi, R.; Camargo, F.; Fals, H. C.; Ferraresi, V. A.

    2014-10-01

    Thermal spray processes have been widely used to minimize losses caused by wear mechanisms. Sprayed deposits using conventional wire and powder materials have been long solving tribological problems in engineering equipment. More recently, the option for new different technologies and consumables like nanostructured powder materials and nanocomposite cored wires have expanded the possibilities for technical solutions. Cored wire technology allows the use of compositions that cannot be drawn into wire form like carbides in metallic matrix and high-temperature materials, thus, intensifying the use of spraying processes with low operating cost to demanding wear and corrosion applications. The objective of this work was to study the mechanical characteristics and wear performance of coatings obtained by Flame, Wire Arc, and HVOF spraying using selected nanostructured WC10Co4Cr, WC12Co, and Fe-based 140 MXC powder and wire materials. Abrasive wear performance of the coatings was determinate following the ASTM G-65 standard. Based on the results, a higher abrasive wear resistance was found for the HVOF-sprayed WC10Co4Cr nanostructured coating.

  12. Risk Factors for Contact Lens Bacterial Contamination During Continuous Wear

    PubMed Central

    Szczotka-Flynn, Loretta B.; Bajaksouzian, Saralee; Jacobs, Michael R.; Rimm, Alfred

    2009-01-01

    Purpose Microbial contamination of contact lenses is associated with corneal infection and inflammation. This study determined which microbiological, clinical and demographic factors are associated with bacterial contamination of a silicone hydrogel contact lens when worn for continuous wear. Methods Two hundred five normal subjects were enrolled in the Longitudinal Analysis of Silicone Hydrogel (LASH) Contact Lens Study and were fitted with lotrafilcon A lenses for monthly continuous wear and followed for 1 year. Lenses were aseptically removed after 1 week and 4 months of wear and cultured using an agar sandwich technique. Lids and conjunctiva were routinely cultured at baseline, and after 1 week and 4 months of continuous wear. Lenses and ocular sites were considered to have substantial microbial bioburden when they harbored pathogenic organisms or high levels of commensal organisms. Univariate and multivariate logistic regression analyses were conducted to examine whether substantial conjunctival or lid bioburden, subject demographics, lens wearing history, symptoms, and biomicroscopic signs were associated with lens bioburden. Results About one-third (32.4%) of subjects had substantial bacterial bioburden in either eye across multiple visits. Over half (53.2%) and about one-tenth (11.7%) of subjects had substantial lid and conjunctival bioburden, respectively, and 11.2% discontinued due to discomfort. The adjusted odds ratios (and 95% confidence intervals) for presence of substantial lens bioburden were 2.49 (1.17–5.30), 4.24 (1.45–12.40), and 4.11 (1.17–14.46) for substantial lid bioburden, substantial conjunctival bioburden, and lens discomfort, respectively. Conclusions Bacterial contamination of silicone hydrogel contact lenses is common during continuous wear. Substantial lens bioburden is associated with discomfort precluding successful continuous wear. The presence of substantial lid and conjunctival bioburden are associated with a 2.5 fold and

  13. Friction and Wear Characteristics of a Modified Composite Solid Lubricant Plasma Spray Coating

    NASA Technical Reports Server (NTRS)

    Stanford, M. K.; DellaCorte, C.

    2004-01-01

    LCR304 is a solid lubricant coating composed of Ni-10Cr, Cr2O3, BaF2-CaF2 and Ag and developed for dimensional stability in high temperature air. This coating is a modification of PS304, which differs in that the Ni-Cr constituent contains 20wt% Cr. The tribological characteristics of LCR304 were evaluated by pin-on-disk and foil air bearing rig testing from 25 to 650 C and compared to previous test results with PS304. For both tests, the friction coefficient decreased as temperature increased from 25 to 650 C. Wear generally decreased with increasing temperature for all pin-on-disk tests. LCR304 coated components produced the least wear of Inconel X-750 counterface materials at 427 and 650 C. These results indicate that the LCR304 coating has potential as a replacement for PS304 in, for example, low cycle (minimum wear) applications where dimensional stability is imperative.

  14. 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.

  15. Atmospheric applications of high-energy lasers

    NASA Astrophysics Data System (ADS)

    Cook, Joung R.

    2005-03-01

    It has been over forty years since the invention of the laser, which has inspired the imagination of scientists and science fiction writers alike. Many ideas have been realized, many still remain as dreams, and new ones are still being conceived. The High Energy Laser (HEL) has been associated with weapon applications during the past three decades. Much of the same technology can be directly applied to power beaming, laser propulsion, and other potential remote energy and power transfer applications. Economically, these application areas are becoming increasingly more viable. This paper reviews the evolutionarey history of the HEL device technologies. It points out the basic system components and layouts with associated key technologies that drive the effectiveness and efficiency of the system level performance. It describes the fundamental properties and wavelength dependencies of atmospheric propagation that in turn have become the prescription for wavelength properties that are desired from the device.

  16. Strain sensing technology for high temperature applications

    NASA Technical Reports Server (NTRS)

    Williams, W. Dan

    1993-01-01

    This review discusses the status of strain sensing technology for high temperature applications. Technologies covered are those supported by NASA such as required for applications in hypersonic vehicles and engines, advanced subsonic engines, as well as material and structure development. The applications may be at temperatures of 540 C (1000 F) to temperatures in excess of 1400 C (2500 F). The most promising technologies at present are the resistance strain gage and remote sensing schemes. Resistance strain gages discussed include the BCL gage, the LaRC compensated gage, and the PdCr gage. Remote sensing schemes such as laser based speckle strain measurement, phase-shifling interferometry, and x-ray extensometry are discussed. Present status and limitations of these technologies are presented.

  17. High Absorptance Coatings for THz Applications

    NASA Technical Reports Server (NTRS)

    Wollack, Edward J.

    2012-01-01

    High absorptance materials find application throughout the electromagnetic spectrum as radiation terminations, calibration standards, and glint reduction coatings. Successful use of materials at millimeter through submillimeter wavelengths requires an accurate knowledge and control over their thermal, mechanical, and electromagnetic properties in order to achieve the desired response while minimizing mass and volume. In practice, the achieved blackness is intimately linked to the material properties and geometry. Here, we summarize the characteristics of a variety of tunable artificial dielectric mixtures appropriate for THz applications at room and cryogenic temperatures. Theoretical guidelines for their application will be provided in the context of the effective-medium mean-field-approximation. The performance of these coatings as elements of reflectance standards, radiometric flux calibrators, passive thermal radiators, and stray light suppression baffles for imaging systems will be reviewed.

  18. Processing, wear, and mechanical properties of polyethylene composites prepared with pristine and organosilane-treated carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Wood, Weston

    Polymers and nanocomposites have been increasingly used for tribological applications over the last few decades. In particular, ultrahigh molecular weight polyethylene (UHMWPE) is a high performance polymer with excellent strength, toughness, and wear resistance. Because of these properties, UHMWPE is an ideal material for a variety of applications including body armor, components of sporting goods such as skies and snowboards, and liners in total joint replacement. Though the toughness and wear resistance far exceed that of most other polymeric materials, there is a high demand for improving the tribological and mechanical properties of UHMWPE for many applications. The approach used in this work for improving such properties is through nanocomposite technology, specifically via the incorporation of carbon nanofibers. In order to obtain the full potential of nanocomposite technology, two critical issues need to be addressed: appropriate interactions between the filler and matrix and proper dispersion of the nano-reinforcement. These critical issues are particularly important for UHMWPE nanocomposites in that UHMWPE is an extremely viscous polymer and thus cannot be processed conventionally, typically resulting in dispersion issues far worse than that of other composite systems. Furthermore, UHMWPE is non-polar, so interactions between filler and matrix will be limited to Van der Waals forces for untreated nanofillers. Therefore, the research presented aims at solving these issues by using a paraffin-assisted processing method and applying appropriate surface treatment to the carbon nanofibers. Under optimized processing conditions, wear and mechanical properties of UHMWPE composites can be substantially improved.

  19. Corrosive Wear in Wet Ore Grinding Systems

    NASA Astrophysics Data System (ADS)

    Jones, Denny A.

    1985-06-01

    Wear processes in ball and rod mills have recently received increased attention in order to increase efficiency and conserve grinding media. Direct removal of metal from the grinding media surface by abrasive wear occurs in both dry and wet grinding. Additional corrosive wear is apparent during wet grinding, in which less resistant corrosion product films are abraded away. Inhibitors and higher pH solutions, in which corrosion product films are more tenacious, improve wear resistance during wet grinding. Softer surfaces are less resistant to corrosive wear, suggesting that film formation and subsequent film abrasion on newly furrowed surfaces must be a factor.

  20. Dry Sliding Wear Behavior of Fly Ash Cenosphere/AZ91D Mg Alloy Composites

    NASA Astrophysics Data System (ADS)

    Yu, S. R.; Huang, Z. Q.

    2014-10-01

    Fly ash cenosphere/AZ91D Mg alloy (FAC/AZ91D) composites were prepared using stir casting method. The effects of the applied load, the wearing time, and the diameter and the content of fly ash cenosphere on the wear behavior of the composites were investigated under dry sliding condition. The results showed the wear resistance of FAC/AZ91D composites is generally better than that of AZ91D Mg alloy. The mass fraction and diameter of FAC have important effects on the wear resistance of the composites, and the wear resistance of the composites is excellent when the mass fraction and diameter of FAC are moderate. When the mass fraction and diameter of FAC are more than the critical values, the wear resistance of the composites lowers again. The wear resistance of the composites decreases with the increase in the applied load. The relationship between the worn mass loss and the applied load is nonlinear. When the applied load is smaller, the worn mass loss of the composites increases rapidly with the increase of the applied load. These research results show that the composites have broad application prospects under dry sliding wear condition, and they can provide guidance for the selection of the raw materials, the structure design, and the application conditions of the composites.

  1. Assessment of microelectronics packaging for high temperature, high reliability applications

    SciTech Connect

    Uribe, F.

    1997-04-01

    This report details characterization and development activities in electronic packaging for high temperature applications. This project was conducted through a Department of Energy sponsored Cooperative Research and Development Agreement between Sandia National Laboratories and General Motors. Even though the target application of this collaborative effort is an automotive electronic throttle control system which would be located in the engine compartment, results of this work are directly applicable to Sandia`s national security mission. The component count associated with the throttle control dictates the use of high density packaging not offered by conventional surface mount. An enabling packaging technology was selected and thermal models defined which characterized the thermal and mechanical response of the throttle control module. These models were used to optimize thick film multichip module design, characterize the thermal signatures of the electronic components inside the module, and to determine the temperature field and resulting thermal stresses under conditions that may be encountered during the operational life of the throttle control module. Because the need to use unpackaged devices limits the level of testing that can be performed either at the wafer level or as individual dice, an approach to assure a high level of reliability of the unpackaged components was formulated. Component assembly and interconnect technologies were also evaluated and characterized for high temperature applications. Electrical, mechanical and chemical characterizations of enabling die and component attach technologies were performed. Additionally, studies were conducted to assess the performance and reliability of gold and aluminum wire bonding to thick film conductor inks. Kinetic models were developed and validated to estimate wire bond reliability.

  2. Anisotropic mechanical amorphization drives wear in diamond

    NASA Astrophysics Data System (ADS)

    Pastewka, Lars; Moser, Stefan; Gumbsch, Peter; Moseler, Michael

    2011-01-01

    Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond’s widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp3-sp2 order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.

  3. Anisotropic mechanical amorphization drives wear in diamond.

    PubMed

    Pastewka, Lars; Moser, Stefan; Gumbsch, Peter; Moseler, Michael

    2011-01-01

    Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond's widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp(3)-sp(2) order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.

  4. High Performance Databases For Scientific Applications

    NASA Technical Reports Server (NTRS)

    French, James C.; Grimshaw, Andrew S.

    1997-01-01

    The goal for this task is to develop an Extensible File System (ELFS). ELFS attacks the problem of the following: 1. Providing high bandwidth performance architectures; 2. Reducing the cognitive burden faced by applications programmers when they attempt to optimize; and 3. Seamlessly managing the proliferation of data formats and architectural differences. The approach for ELFS solution consists of language and run-time system support that permits the specification on a hierarchy of file classes.

  5. Wear mechanisms in a nonrotating wire rope

    SciTech Connect

    Schrems, K.K.; Dogan, C.P.; Hawk, J.A.

    1995-04-01

    A nonrotating wire rope used in main hoist operations is being examined by the US Bureau of Mines to determine operative wear mechanisms. Typically, bending and loading the ropes during service cause small, localized movements at interwire contacts, leading to material loss through wear.The cumulative effect of both material loss by wear and wire breakage by fatigue failure accelerates rope retirement. If the macroscopic mechanics of wire rope failure are to be understood, microscopic deformation and degradation processes must be identified and quantified. As a first step in this study, interwire wear and deformation were studied using a combination of scanning electron microscopy and hardness measurements. Both fretting and abrasive wear were identified as wear mechanisms. Preferential sites for fretting and abrasive wear were identified and are discussed regarding rope construction and geometry and the tribo-system.

  6. Backside Wear Analysis of Retrieved Acetabular Liners with a Press-Fit Locking Mechanism in Comparison to Wear Simulation In Vitro.

    PubMed

    Puente Reyna, Ana Laura; Jäger, Marcus; Floerkemeier, Thilo; Frecher, Sven; Delank, Karl-Stefan; Schilling, Christoph; Grupp, Thomas M

    2016-01-01

    Backside wear due to micromotion and poor conformity between the liner and its titanium alloy shell may contribute to the high rates of retroacetabular osteolysis and consequent aseptic loosening. The purpose of our study was to understand the wear process on the backside of polyethylene liners from two acetabular cup systems, whose locking mechanism is based on a press-fit cone in combination with a rough titanium conical inner surface on the fixation area. A direct comparison between in vitro wear simulator tests (equivalent to 3 years of use) and retrieved liners (average 13.1 months in situ) was done in order to evaluate the backside wear characteristics and behavior of these systems. Similar wear scores between in vitro tested and retrieved liners were observed. The results showed that this locking mechanism did not significantly produce wear marks at the backside of the polyethylene liners due to micromotion. In all the analyzed liners, the most common wear modes observed were small scratches at the cranial fixation zone directly below the rough titanium inner surface of the shell. It was concluded that most of the wear marks were produced during the insertion and removal of the liner, rather than during its time in situ.

  7. Backside Wear Analysis of Retrieved Acetabular Liners with a Press-Fit Locking Mechanism in Comparison to Wear Simulation In Vitro

    PubMed Central

    Jäger, Marcus; Floerkemeier, Thilo; Frecher, Sven; Delank, Karl-Stefan

    2016-01-01

    Backside wear due to micromotion and poor conformity between the liner and its titanium alloy shell may contribute to the high rates of retroacetabular osteolysis and consequent aseptic loosening. The purpose of our study was to understand the wear process on the backside of polyethylene liners from two acetabular cup systems, whose locking mechanism is based on a press-fit cone in combination with a rough titanium conical inner surface on the fixation area. A direct comparison between in vitro wear simulator tests (equivalent to 3 years of use) and retrieved liners (average 13.1 months in situ) was done in order to evaluate the backside wear characteristics and behavior of these systems. Similar wear scores between in vitro tested and retrieved liners were observed. The results showed that this locking mechanism did not significantly produce wear marks at the backside of the polyethylene liners due to micromotion. In all the analyzed liners, the most common wear modes observed were small scratches at the cranial fixation zone directly below the rough titanium inner surface of the shell. It was concluded that most of the wear marks were produced during the insertion and removal of the liner, rather than during its time in situ. PMID:27722174

  8. Solar Selective Coatings for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Shumway, Dean A.

    2003-01-01

    Solar selective coatings are envisioned for use on minisatellites, for applications where solar energy is to be used to power heat engines or to provide thermal energy for remote regions in the interior of the spacecraft. These coatings are designed to have the combined properties of high solar absorptance and low infrared emittance. The coatings must be durable at elevated temperatures. For thermal bus applications, the temperature during operation is likely to be near 100 C. For heat engine applications. the temperature is expected to be much greater. The objective of this work was to screen candidate solar selective coatings for their high temperature durability. Candidate solar selective coatings were composed of molecular mixtures of metal and dielectric, including: nickel and aluminum oxide, titanium and aluminum oxide, and platinum and aluminum oxide. To identify high temperature durability, the solar absorptance and infrared emittance of the candidate coatings were evaluated initially, and after heating to temperatures in the range of 400 C to 700 C. The titanium and aluminum oxide molecular mixture was found to be the most durable.

  9. Wear testing of crosslinked polyethylene: wear rate variability and microbial contamination.

    PubMed

    Brandt, J-M; Vecherya, A; Guenther, L E; Koval, S F; Petrak, M J; Bohm, E R; Wyss, U P

    2014-06-01

    The wear performance of two types of crosslinked polyethylene (Marathon™ and XLK™, DePuy Synthes Inc., Warsaw, IN) was evaluated in a pin-on-disc wear tester, a hip wear simulator, and a knee wear simulator. Sodium azide was used as the microbial inhibitor in the calf serum-based lubricant. In the pin-on-disc wear tester, the Marathon wear rate of 5.33±0.54mm(3)/Mc was significantly lower (p=0.002) than the wear rate of 6.43±0.60mm(3)/Mc for XLK. Inversely, the Marathon wear rate of 15.07±1.03mm(3)/Mc from the hip wear simulator was 2.2-times greater than the XLK wear rate of 6.71±1.03mm(3)/Mc from the knee wear simulator. Differences in implant design, conformity, GUR type, and kinematic test conditions were suggested to account for the difference between the wear rates generated in the different types of wear testing apparati. In all wear tests, sodium azide was ineffective at inhibiting microbial growth in the lubricant. Eight different organisms were identified in the lubricant samples from the wear tests, which suggested the necessity of using an alternative, more effective microbial inhibitor. Careful sample preparation and thorough cleaning has shown to improve the consistency of the wear results. The wear rates generated in the hip and knee wear simulators closely reflected the wear behaviour of Marathon and XLK reported in published data that were tested under similar conditions.

  10. Effect of Deformation Mode on the Wear Behavior of NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2016-06-01

    Owing to good biocompatibility, good fatigue resistance, and excellent superelasticity, various types of bio-medical devices based on NiTi shape memory alloy (SMA) have been developed. Due to the complexity in deformation mode in service, for example NiTi implants, accurate assessment/prediction of the surface wear process is difficult. This study aims at providing a further insight into the effect of deformation mode on the wear behavior of NiTi SMA. In the present study, two types of wear testing modes were used, namely sliding wear mode and reciprocating wear mode, to investigate the effect of deformation mode on the wear behavior of NiTi SMA in both martensitic and austenitic states. It was found that, when in martensitic state and under high applied loads, sliding wear mode resulted in more surface damage as compared to that under reciprocating wear mode. When in austenitic state, although similar trends in the coefficient of friction were observed, the coefficient of friction and surface damage in general is less under reciprocating mode than under sliding mode. These observations were further discussed in terms of different deformation mechanisms involved in the wear tests, in particular, the reversibility of martensite variant reorientation and stress-induced phase transformation, respectively.

  11. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    NASA Technical Reports Server (NTRS)

    Chase, T. J.; Mccarty, J. P.

    1993-01-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given.

  12. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    NASA Astrophysics Data System (ADS)

    Chase, T. J.; McCarty, J. P.

    1993-12-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated