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Sample records for 2000-hour wear test

  1. Computational Modeling of NEXT 2000-Hour Wear Test Results

    NASA Technical Reports Server (NTRS)

    Malone, Shane P.

    2004-01-01

    Ion optics computational models are invaluable tools for the design of ion optics systems. In this study, a new computational model developed by an outside vendor for NASA Glenn Research Center (GRC) is presented. This model is a gun code which has been modified to model the plasma sheaths both upstream and downstream of the ion optics. The model handles multiple species (e.g. singly and doubly-charged ions) and includes a charge-exchange model for erosion estimates. The model uses commercially available solid design and meshing software, allowing high flexibility in ion optics geometric configurations. This computational model is compared to experimental results from the NASA Evolutionary Xenon Thruster (NEXT) 2000-hour wear test, including over-focusing along the edge apertures, pit-and-groove erosion due to charge exchange, and beamlet distortion at the edge of the hole pattern.

  2. Computational Modeling of NEXT 2000-hour Wear Test Results

    NASA Astrophysics Data System (ADS)

    Malone, Shane; Soulas, George

    2004-11-01

    Ion optics computational models are invaluable tools for the design of ion optics systems. In this study, a new computational model developed by an outside vendor for NASA Glenn Research Center (GRC) is presented. This model is a gun code which has been modified to model the plasma sheaths both upstream and downstream of the ion optics. The model handles multiple species (e.g. singly and doubly-charged ions) and includes a charge-exchange model for erosion estimates. The model uses commercially available solid design and meshing software, allowing high flexibility in ion optics geometric configurations. This computational model is compared to experimental results from the NASA Evolutionary Xenon Thruster (NEXT) 2000-hour wear test, including over-focusing along the edge apertures, pit-and-groove erosion due to charge exchange, and beamlet distortion at the edge of the hole pattern.

  3. NEXT Ion Engine 2000 Hour Wear Test Results

    NASA Technical Reports Server (NTRS)

    Soulas, George C.; Kamhawi, Hani; Patterson, Michael J.; Britton, Melissa A.; Frandina, Michael M.

    2004-01-01

    The results of the NEXT 2000 h wear test are presented. This test was conducted with a 40 cm engineering model ion engine, designated EM1, at a 3.52 A beam current and 1800 V beam power supply voltage. Performance tests, which were conducted over a throttling range of 1.1 to 6.9 kW throughout the wear test, demonstrated that EM1 satisfied all thruster performance requirements. The ion engine accumulated 2038 h of operation at a thruster input power of 6.9 kW, processing 43 kg of xenon. Overall ion engine performance, which includes thrust, thruster input power, specific impulse, and thrust efficiency, was steady with no indications of performance degradation. The ion engine was also inspected following the test. This paper presents these findings.

  4. Results of a 2000 hour wear test of the NEXIS ion engine

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Goebel, Dan M.; Polk, James E.; Schneider, Analyn C; Sengupta, Anita

    2005-01-01

    The Nuclear Electric Xenon Ion System (NEXIS) ion thruster was developed for potential outer planet robotic missions under NASA's Prometheus program. This engine was designed to operate at power levels ranging from 16 to over 20 kWe at specific impulses of 6000 to 7500 s for burn times of up to 10 years, satisfying the requirements of nuclear electric propulsion systems such as that on the proposed Prometheus 1 mission to explore the icy moons of Jupiter. State-of-the-art performance and life assessment tools were used to design the thruster. Following the successful performance validation of a Laboratory Model thruster, Development Model hardware was fabricated and subjected to vibration and wear testing. The results of a 2000-hour wear test are reported herein. Thruster performance achieved the target requirements and was steady for the duration of the test. Ion optics performance was similarly stable. Discharge loss increases of 6 eV/ion were observed in the first 500 hours of the test and were attributed to primary electron energy decreases due to cathode insert conditioning. Relatively high recycle rates were observed and were identified to be high-voltage-to-ground arcs in the back of the thruster caused by wire insulation outgassing and electron penetration through the plasma screen. Field emission of electrons between the accelerator and screen grids was observed and attributed to evolution of field emitter sites at accelerator grid aperture edges caused by ion bombardment. Preliminary modeling and analysis indicates that the NEXIS engine can meet mission performance requirements over the required lifetime. Finally, successful validation of the NEXIS design methodology, design tools, and technologies with the results of the wear test and companion performance and vibration tests presents significant applicability of the NEXIS development effort to missions of near-term as well as long-term interest for NASA.

  5. Results of a 2000 Hour Wear Tof the NEXIS Ion Engine

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Goebel, Dan M.; Polk, James E.; Schneider, Analyn C; Sengupta, Anita

    2005-01-01

    The Nuclear Electric Xenon Ion System (NEXIS) ion thruster was developed for potential outer planet robotic missions under NASA's Prometheus program. This engine was designed to operate at power levels ranging from 16 to over 20 kWe at specific impulses of 6000 to 7500 s for burn times of up to 10 years, satisfying the requirements of nuclear electric propulsion systems such as that on the proposed Prometheus 1 mission to explore the icy moons of Jupiter. State-of-the-art performance and life assessment tools were used to design the thruster. Following the successful performance validation of a Laboratory Model thruster, Development Model hardware was fabricated and subjected to vibration and wear testing. The results of a 2000-hour wear test are reported herein. Thruster performance achieved the target requirements and was steady for the duration of the test. Ion optics performance was similarly stable. Discharge loss increases of 6 eV/ion were observed in the first 500 hours of the test and were attributed to primary electron energy decreases due to cathode insert conditioning. Relatively high recycle rates were observed and were identified to be high-voltage-to-ground arcs in the back of the thruster caused by wire insulation outgassing and electron penetration through the plasma screen. Field emission of electrons between the accelerator and screen grids was observed and attributed to evolution of field emitter sites at accelerator grid aperture edges caused by ion bombardment. Preliminary modeling and analysis indicates that the NEXIS engine can meet mission performance requirements over the required lifetime. Finally, successful validation of the NEXIS design methodology, design tools, and technologies with the results of the wear test and companion performance and vibration tests presents significant applicability of the NEXIS development effort to missions of near-term as well as long-term interest for NASA.

  6. A 2000-Hour Durability Test of a 5-Centimeter Diameter Mercury Bombardment Ion Thruster

    NASA Technical Reports Server (NTRS)

    Nakanishi, S.; Finke, R. G.

    1972-01-01

    A 2000-hour durability test of a modified Hughes SIT-5 (Structurally Integrated Thruster, 5 cm) was conducted at the Lewis Research Center. The thruster operated with a translating screen thrust vector grid locked in position for 10 deg beam deflection. The test was essentially continuous except for seven stoppages of beam current. The neutralizer keeper voltage and thruster floating potential increased slightly with time. Performance profiles and maps of thruster characteristics were obtained at 453 and 2023 hours into the test. Overall efficiency was nearly constant at 31 - 32 percent, and operating characteristics were similar at both points in the test. A post-shutdown inspection showed negligible erosion damage to the accelerator and cathode baffle. Some erosion was found in the aperture of the neutralizer cathode.

  7. Multiple Hollow Cathode Wear Testing

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    1994-01-01

    A hollow cathode-based plasma contactor has been baselined for use on the Space Station to reduce station charging. The plasma contactor provides a low impedance connection to space plasma via a plasma produced by an arc discharge. The hollow cathode of the plasma contactor is a refractory metal tube, through which xenon gas flows, which has a disk-shaped plate with a centered orifice at the downstream end of the tube. Within the cathode, arc attachment occurs primarily on a Type S low work function insert that is next to the orifice plate. This low work function insert is used to reduce cathode operating temperatures and energy requirements and, therefore, achieve increased efficiency and longevity. The operating characteristics and lifetime capabilities of this hollow cathode, however, are greatly reduced by oxygen bearing contaminants in the xenon gas. Furthermore, an optimized activation process, where the cathode is heated prior to ignition by an external heater to drive contaminants such as oxygen and moisture from the insert absorbed during exposure to ambient air, is necessary both for cathode longevity and a simplified power processor. In order to achieve the two year (approximately 17,500 hours) continuous operating lifetime requirement for the plasma contactor, a test program was initiated at NASA Lewis Research Center to demonstrate the extended lifetime capabilities of the hollow cathode. To date, xenon hollow cathodes have demonstrated extended lifetimes with one test having operated in excess of 8000 hours in an ongoing test utilizing contamination control protocols developed by Sarver-Verhey. The objectives of this study were to verify the transportability of the contamination control protocols developed by Sarver-Verhey and to evaluate cathode contamination control procedures, activation processes, and cathode-to-cathode dispersions in operating characteristics with time. These were accomplished by conducting a 2000 hour wear test of four hollow

  8. Status of the NEXT Ion Engine Wear Test

    NASA Technical Reports Server (NTRS)

    Soulas, George C.; Domonkos, Matthew T.; Kamhawi, Hani; Patterson, Michael J.; Gardner, Michael M.

    2003-01-01

    The status of the NEXT 2000 hour wear test is presented. This test is being conducted with a 40 cm engineering model ion engine, designated EM1, at a beam current higher than listed on the NEXT throttle table. Pretest performance assessments demonstrated that EM1 satisfies all thruster performance requirements. As of 7/3/03, the ion engine has accumulated 406 hours of operation at a thruster input power of 6.9 kW. Overall ion engine performance, which includes thrust, thruster input power, specific impulse, and thrust efficiency, has been steady to date with no indications of performance degradation. Images of the downstream discharge cathode, neutralizer, and accelerator aperture surfaces have exhibited no significant erosion to date.

  9. Oscillatory wear tests of dental composites.

    PubMed

    Pilliar, R M; Smith, D C; Maric, B

    1984-09-01

    The wear behavior of 12 commercial restorative composites (conventional and microfilled) and an unfilled restorative material was evaluated using an in vitro wear test referred to as an oscillatory wear test. The effect of varying test conditions was evaluated in a series of preliminary experiments in order to define test conditions for material evaluation. The materials were tested after being aged in water at 37 degrees C for periods of from seven days to one year. The results indicated consistently lower wear rates for the microfilled materials as compared with those of the conventional composites. Aging did not result in significant differences in wear rates measured by this method. Scanning electron micrography of worn surfaces suggested a possible effect of filler particle shape and bonding to the matrix to explain this difference. Although the relevance of the results to clinical behavior is not yet known, the study indicated the importance of material variables on wear.

  10. The 2.3 kW Ion Thruster Wear Test

    NASA Technical Reports Server (NTRS)

    Parkes, James; Rawlin, Vincent K.; Sovey, James S.; Kussmaul, Michael J.; Patterson, Michael J.

    1995-01-01

    A 30-cm diameter xenon ion thruster is under development at NASA to provide an ion propulsion option for auxiliary and primary propulsion on missions of national interest. Specific efforts include thruster design optimizations, component life testing and validation, and performance characterizations. Under this program, the ion thruster will be brought to engineering model development status. This paper describes the results of a 2.3-kW 2000-hour wear test performed to identify life limiting phenomena, measure the performance and characterize the operation of the thruster, and obtain wear, erosion, and surface contamination data. These data are being using as a data base for proceeding with additional life validation tests, and to provide input to flight thruster design requirements.

  11. Assessment of variations in wear test methodology.

    PubMed

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

    2010-01-01

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

  12. Multiple Hollow Cathode Wear Testing for the Space Station Plasma Contactor

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    1994-01-01

    A wear test of four hollow cathodes was conducted to resolve issues associated with the Space Station plasma contactor. The objectives of this test were to evaluate unit-to-unit dispersions, verify the transportability of contamination control protocols developed by the project, and to evaluate cathode contamination control and activation procedures to enable simplification of the gas feed system and heater power processor. These objectives were achieved by wear testing four cathodes concurrently to 2000 hours. Test results showed maximum unit-to-unit deviations for discharge voltages and cathode tip temperatures to be +/-3 percent and +/-2 percent, respectively, of the nominal values. Cathodes utilizing contamination control procedures known to increase cathode lifetime showed no trends in their monitored parameters that would indicate a possible failure, demonstrating that contamination control procedures had been successfully transferred. Comparisons of cathodes utilizing and not utilizing a purifier or simplified activation procedure showed similar behavior during wear testing and pre- and post-test performance characterizations. This behavior indicates that use of simplified cathode systems and procedures is consistent with long cathode lifetimes.

  13. Wear Test Of A Preselected Diamond Tool

    NASA Astrophysics Data System (ADS)

    Hurt, H. H.; Showman, G. A.

    1987-02-01

    An investigation was conducted to develop a set of criteria that would allow the typical user to preselect a diamond-turning tool for the most critical optical finishing operations. A wide variety of tools used in this study had their edge quality evaluated by Nomarski and scanning electron microscopy methods, and the diamond crystal orientation and quality were determined by Laue x-ray methods. One of the tools was subjected to a long-term machining test to evaluate the tool wear process and to correlate the wear observed with changes in the scattering properties of the surface.

  14. Wear testing of total hip replacements under severe conditions.

    PubMed

    Zietz, Carmen; Fabry, Christian; Reinders, Joern; Dammer, Rebecca; Kretzer, Jan Philippe; Bader, Rainer; Sonntag, Robert

    2015-07-01

    Controlled wear testing of total hip replacements in hip joint simulators is a well-established and powerful method, giving an extensive prediction of the long-term clinical performance. To understand the wear behavior of a bearing and its limits under in vivo conditions, testing scenarios should be designed as physiologically as possible. Currently, the ISO standard protocol 14242 is the most common preclinical testing procedure for total hip replacements, based on a simplified gait cycle for normal walking conditions. However, in recent years, wear patterns have increasingly been observed on retrievals that cannot be replicated by the current standard. The purpose of this study is to review the severe testing conditions that enable the generation of clinically relevant wear rates and phenomena. These conditions include changes in loading and activity, third-body wear, surface topography, edge wear and the role of aging of the bearing materials. PMID:26048088

  15. Geometry of wear in the sliding four-ball wear test

    NASA Astrophysics Data System (ADS)

    Strunks, Gregory A.; Toth, Douglas K.; Saba, Costandy S.

    1992-10-01

    The geometry of the four-ball test configuration was examined to develop a method to calculate the wear volume of noncircular scars. It was found that the length of the scar normal to the direction of sliding is related to the relative displacement between the upper and lower balls. The width of the scar parallel to the direction of sliding is dependent upon the curvature of the scar normal to the sliding direction. This curvature is a function of upper ball wear, and it is the upper ball wear that causes noncircularity of the lower ball scars. A model was developed to calculate wear volumes for the upper and lower balls using the length and width of the scars on the lower balls to generate a dimensionless profile parameter, alpha. For an inhibited polyphenyl ether-based lubricant, the wear volume of the upper ball is consistently greater than the total wear volume of the three lower balls. In addition to wear volume calculations, this model can also be used to predict the scar shape for given lengths and widths of the lower ball wear scar.

  16. Cryogenically treated gin saw wear test-Second season

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This is the second year of comparative testing of crygenically treated gin saws versus standard gin saws. Paired sets of standard and experimental saws were installed in Lummus saw gin stands that were operated side by side during the 2015/2016 ginning season. Test criteria will include saw wear e...

  17. 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.

  18. Rig for testing the relative wear resistance of materials

    SciTech Connect

    Berdikov, V.F.; Diulin, A.I.; Efimchuk, V.P.; Pushkarev, O.I.; Finogenov, G.P.

    1987-01-01

    The authors have developed a simple and compact rig for studying the relative wear resistance of materials subjected to mechanical abrasion and friction. The rig has an electronic control system. It was used to test the relative wear resistance of a wide range of superhard and brittle materials under mechanical abrasion against a counterbody. The counterbody was made of modified iron and the test medium was a diamond suspension in oil. The results showed that specimen wear exhibits a linear relationship with abrasion time (in the range of 0.5-20 min.) at unit pressure from 0.01 to 0.10 MPa. That a standard wear pattern exists within a wide range of parameters indicates that abrasive conditions are highly stable and makes it possible to control conditions. The rig was used to establish the relative wear resistance of several abrasives, minerals, and refractory compounds. The very large difference (15.2 times) between the most and least-resistant materials (tungsten carbide and fluoride) illustrates the sensitivity of the methodology.

  19. Wear mechanism and wear prevention in coal-fueled diesel engines. Task 7, Extended wear testing

    SciTech Connect

    Wakenell, J.F.; Fritz, S.G.; Schwalb, J.A.

    1991-07-01

    Over the past several years, interest has arisen in the development of coal-fired diesel engines for the purpose of efficiently utilizing the extensive coal reserves in the United States, and therefore reducing dependence on foreign oil. One process, which is being considered for use in producing clean coal fuel products involves mild gasification. This process produces by-products which can be further refined and, when blended with neat diesel fuel, used as an engine fuel. The purpose of this task was to test a blend of this coal liquid and diesel fuel (referred to as coal-lite) in an engine, and determine if any detrimental results were observed. This was done by performing a back-to-back performance and emission test of neat diesel fuel and the coal-lite fuel, followed by a 500-hour test of the coal-lite fuel, and completed by a back-to-back performance and emission test of the coal-lite fuel and neat diesel fuel.

  20. 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.

  1. Experimental testing of total knee replacements with UHMW-PE inserts: impact of severe wear test conditions.

    PubMed

    Zietz, Carmen; Reinders, Joern; Schwiesau, Jens; Paulus, Alexander; Kretzer, Jan Philippe; Grupp, Thomas; Utzschneider, Sandra; Bader, Rainer

    2015-03-01

    Aseptic implant loosening due to inflammatory reactions to wear debris is the main reason for the revision of total knee replacements (TKR). Hence, the decrease in polyethylene wear particle generation from the articulating surfaces is aimed at improving implant design and material. For preclinical testing of new TKR systems standardized wear tests are required. However, these wear tests do not reproduce the entire in vivo situation, since the pattern and amount of wear and subsequent implant failure are underestimated. Therefore, daily activity, kinematics, implant aging and position, third-body-wear and surface properties have to be considered to estimate the wear of implant components in vivo. Hence, severe test conditions are in demand for a better reproduction of the in vivo situation of TKR. In the present article an overview of different experimental wear test scenarios considering clinically relevant polyethylene wear situations using severe test conditions is presented. PMID:25716024

  2. Wear testing of moderate activities of daily living using in vivo measured knee joint loading.

    PubMed

    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.

  3. 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

  4. Friction and wear in surface micromachined tribological test devices

    SciTech Connect

    Senft, D.C.; Dugger, M.T.

    1997-08-01

    We report on the design, construction, and initial testing of surface micromachined devices for measuring friction and wear. The devices measure friction coefficients on both horizontal deposited polysilicon surfaces and vertical etched polysilicon surfaces. The contact geometry of the rubbing surfaces is well-defined, and a method is presented for the determination of the normal and frictional forces. Initial observations on test devices which have been dried with supercritical CO{sub 2} and devices coated with octadecyltrichlorosilane suggest that the coatings increase the lifetime of the devices and the repeatability of the results.

  5. In vitro tests of substitute lubricants for wear testing orthopaedic biomaterials.

    PubMed

    Scholes, Susan C; Joyce, Thomas J

    2013-06-01

    Bovine serum is the lubricant recommended by several international standards for the wear testing of orthopaedic biomaterials; however, there are issues over its use due to batch variation, degradation, cost and safety. For these reasons, alternative lubricants were investigated. A 50-station Super-CTPOD (circularly translating pin-on-disc) wear test rig was used, which applied multidirectional motion to ultra-high-molecular-weight polyethylene test pins rubbing against cobalt chromium discs. Thirteen possible alternative lubricants were tested. The use of soy protein as a lubricant gave statistically higher wear, while soya oil, olive oil, Channel Island milk, whole milk, whey, wheatgerm oil, 11 mg/mL egg white, albumin/globulin mix and albumin/globulin/chondroitin sulphate mix all gave statistically lower wear than bovine serum. The lubricants giving the closest wear results to bovine serum were 20 and 40 mg/mL egg white solutions. A light absorbance assay found that these egg white solutions suffered from a high degradation rate that increased with increasing protein content. While egg white solutions offer the best alternative lubricant to bovine serum due to the wear volumes produced, cost-effectiveness and safety of handling, protein degradation will still occur, leading to the need for regular lubricant replacement. Of the lubricants tested in this study, none were found to be superior to bovine serum.

  6. Synovial fluid replication in knee wear testing: an investigation of the fluid volume.

    PubMed

    Reinders, Jörn; Sonntag, Robert; Kretzer, Jan Philippe

    2015-01-01

    Wear testing cannot replicate the variations in wear rates and wear mechanisms seen in vivo, which may be related to differences between in vivo and in vitro conditions. A considerable difference exists between the in vivo synovial fluid volume (few milliliter) and the in vitro substituted bovine serum volume (several hundred milliliter). The aim of this study was to analyze the effects of a reduced fluid volume on the wear behavior in a knee wear simulator study. Four wear tests with decreasing fluid volumes (250, 150, 75, and 45 ml) were carried out. Using a large fluid volume of 250 ml for wear testing resulted in a wear rate of 9.7±1.2 mm3/10(6)  cycles. Decreasing the fluid volume consecutively reduced the wear rate to down to 8.8±1.4 mm3/10(6) for 150 ml (p=1.00), 5.6±1.2 mm3/10(6) for 75 ml (p=0.01), and 1.0±0.2 mm3/10(6) cycles for 45 ml fluid volume (p≤0.01). Additionally, higher serum degradation and larger wear particles were observed with smaller fluid volumes used for testing. This study demonstrates the high relevance of the protein-based lubricant on the wear behavior and the technical limitation to replicate the synovial fluid in simulator tests. Wear testing should be carried out using larger fluid volumes (e.g., 250 ml) to generate physiological relevant wear masses.

  7. Fluid composition impacts standardized testing protocols in ultrahigh molecular weight polyethylene knee wear testing.

    PubMed

    Schwenke, T; Kaddick, C; Schneider, E; Wimmer, M A

    2005-11-01

    Wear of total knee replacements is determined gravimetrically in simulator studies. A mix of bovine serum, distilled water, and additives is intended to replicate the lubrication conditions in vivo. Weight gain due to fluid absorption during testing is corrected using a load soak station. In this study, three sets of ultrahigh molecular weight polyethylene tibial plateau were tested against highly polished titanium condyles. Test 1 was performed in two different institutions on the same simulator according to the standard ISO 14243-1, using two testing lubricants. Test 2 and test 3 repeated both previous test sections. The wear and load soak rates changed significantly with the lubricant. The wear rate decreased from 16.9 to 7.9 mg weight loss per million cycles when switching from fluid A to fluid B. The weight gain of the load soak specimen submersed in fluid A was 6.1 mg after 5 x 10(6) cycles, compared with 31.6 mg for the implant in fluid B after the same time period. Both lubricants were mixed in accordance with ISO 14243 (Implants for surgery - wear of total knee-joint prostheses), suggesting that calf serum should be diluted to 25 +/- 2 per cent with deionized water and a protein mass concentration of not less than 17 g/l. The main differences were the type and amount of additives that chemically stabilize the lubricant throughout the test. The results suggest that wear rates can only be compared if exactly the same testing conditions are applied. An agreement on detailed lubricant specifications is desirable.

  8. A study of coal particle shape and three-body wear: Part 1, Design and development of a new three-body wear testing machine: Part 2, Particle shape and three-body wear

    SciTech Connect

    Clark, N.N.; Means, K.H.; James, R.; Thompson, T.

    1991-01-01

    Three-body wear involves two surfaces and an intermediate particle trapped between the two surfaces. A machine has been constructed to measure normal and frictional forces due to three-body wear. This machine accurately positions specimens a predetermined distance apart from each other and introduces particles to the interface between the specimens. Different types of specimen combinations have been tested to give a variety of data. Loads that result from the wear test are sampled and stored. Wear coefficients and rates of wear have been calculated for all specimens. (VC)

  9. Advanced Petroleum-Based Fuels - Diesel Emissions Project (APBF-DEC): 2,000-Hour Performance of a NOx Adsorber Catalyst and Diesel Particle Filter System for a Medium-Duty, Pick-Up Diesel Engine Platform; Final Report

    SciTech Connect

    Not Available

    2007-03-01

    Presents the results of a 2,000-hour test of an emissions control system consisting of a nitrogen oxides adsorber catalyst in combination with a diesel particle filter, advanced fuels, and advanced engine controls in an SUV/pick-up truck vehicle platform.

  10. Polyurethane unicondylar knee prostheses: simulator wear tests and lubrication studies.

    PubMed

    Scholes, S C; Unsworth, A; Jones, E

    2007-01-01

    Many materials are used as artificial joint bearing surfaces; these include conventional stainless steel or CoCrMo-on-ultra-high molecular weight polyethylene (UHMWPE), CoCrMo on itself and alumina-on-alumina. However, these joints have a limited lifespan resulting in failure of the prosthesis and the need for revision surgery. A number of materials have been introduced recently in an attempt to overcome these problems. Polycarbonate urethane (PU) is a compliant material that can be used as an artificial joint bearing surface which has been developed to mimic the natural synovial joint more accurately by promoting fluid film lubrication. Tribological tests were performed on CoCrMo-on-PU unicondylar knee prostheses to assess their performance in vitro. The wear produced by these components was considerably lower than that found for conventional joints. They also exhibited low friction and operated close to full-fluid film lubrication with viscosities of lubricant similar to those found in patients with arthritis. These tests gave encouraging results for the tribological performance of this material couple for use as an alternative bearing combination.

  11. Abrasive Wear Resistance of Tool Steels Evaluated by the Pin-on-Disc Testing

    NASA Astrophysics Data System (ADS)

    Bressan, José Divo; Schopf, Roberto Alexandre

    2011-05-01

    Present work examines tool steels abrasion wear resistance and the abrasion mechanisms which are one main contributor to failure of tooling in metal forming industry. Tooling used in cutting and metal forming processes without lubrication fails due to this type of wear. In the workshop and engineering practice, it is common to relate wear resistance as function of material hardness only. However, there are others parameters which influences wear such as: fracture toughness, type of crystalline structure and the occurrence of hard precipitate in the metallic matrix and also its nature. In the present investigation, the wear mechanisms acting in tool steels were analyzed and, by normalized tests, wear resistance performance of nine different types of tool steels were evaluated by pin-on-disc testing. Conventional tool steels commonly used in tooling such as AISI H13 and AISI A2 were compared in relation to tool steels fabricated by sintering process such as Crucible CPM 3V, CPM 9V and M4 steels. Friction and wear testing were carried out in a pin-on-disc automated equipment which pin was tool steel and the counter-face was a abrasive disc of silicon carbide. Normal load of 5 N, sliding velocity of 0.45 m/s, total sliding distance of 3000 m and room temperature were employed. The wear rate was calculated by the Archard's equation and from the plotted graphs of pin cumulated volume loss versus sliding distance. Specimens were appropriately heat treated by quenching and three tempering cycles. Percentage of alloying elements, metallographic analyses of microstructure and Vickers microhardness of specimens were performed, analyzed and correlated with wear rate. The work is concluded by the presentation of a rank of tool steel wear rate, comparing the different tool steel abrasion wear resistance: the best tool steel wear resistance evaluated was the Crucible CPM 9V steel.

  12. 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.

  13. The wear of oriented UHMWPE under isotropically rough and scratched counterface test conditions.

    PubMed

    Dharmastiti, R; Barton, D C; Fisher, J; Edidin, A; Kurtz, S

    2001-01-01

    Unidirectional wear tests of UHMWPE against smooth counterfaces show that molecular chains at the surface of virgin material become oriented parallel to the sliding direction giving low wear rate. It is postulated that under more abrasive conditions and predominantly unidirectional motion as in knee prostheses, it may proof beneficial to provide molecular orientation of the bulk material. Therefore strips of UHMWPE were oriented by die drawing at elevated temperature and the resulting anisotropic material subjected to tensile tests, small punch tests and also unidirectional wear tests both parallel and perpendicular to the draw direction. The tensile tests showed that, in the parallel direction, the oriented UHMWPE became stiffer and less ductile compared to the virgin UHMWPE. In the perpendicular direction, there were reductions in yield stress, 5% proof stress and energy to failure compared to the virgin material. The small punch test showed that the oriented UHMWPE exhibited apparent hardening when tested in both parallel and perpendicular directions but the mechanical behaviour in the perpendicular direction was comparable to the virgin UHMWPE. The wear tests demonstrated that the oriented UHMWPE did not show any significant improvement of wear resistance for sliding against either isotropically rough or scratched counterfaces. There was no clear dependency between the mechanical properties and wear factors of the oriented UHMWPE. PMID:11564907

  14. 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.

  15. Comparative in vitro wear testing of PEEK and UHMWPE capped metacarpophalangeal prostheses.

    PubMed

    Joyce, T J; Rieker, C; Unsworth, A

    2006-01-01

    Six metacarpophalangeal prostheses were each wear tested to five million cycles. Each prosthesis consisted of a metacarpal component with an approximately hemispherical shell on a titanium body, articulating against a titanium phalangeal component. Four prostheses had a shell made from ultra-high molecular weight polyethylene (UHMWPE) and two had a shell made from polyether ether ketone (PEEK). The tests were undertaken using a finger wear simulator. Despite pre-soaking and the use of control components, lubricant uptake by the metacarpal components was significant. Gravimetrically, the UHMWPE test components showed a greater weight gain than the UHMWPE control components. Therefore there was no apparent wear of any of the UHMWPE test metacarpal components. The original concentric machining marks of the UHMWPE components could still be seen after five million cycles of testing. For the metacarpal components with PEEK shells, gravimetric wear could be measured. Gravimetrically, all of the titanium phalangeal components showed little or no wear. Light scratches in the direction of sliding appeared on the articulating faces of all metacarpal and phalangeal test components, indicating slight abrasive wear. PMID:16410639

  16. 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.

  17. Characterization of wear debris generated in accelerated rolling-element fatigue tests

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Parker, R. J.

    1978-01-01

    A ferrographic analysis was used to determine the types and quantities of wear debris generated during accelerated rolling contact fatigue tests. The five-ball rolling contact fatigue tester was used. Ball specimens were made of a corrosion resistant, high-temperature bearing steel. The lubricant was a superrefined naphthenic mineral oil. Conditions included a maximum Hertz stress of 5.52 10 to the 9th power Pa and a shaft speed of 10,000 rpm. Four types of wear debris were observed: (1) normal rubbing wear particles, (2) fatigue microspall particles, (3) spheres, and (4) friction polymer deposits. The characterization of wear debris as a function of time was of limited use in predicting fatigue failures in these accelerated tests.

  18. Computational Wear Simulation of Patellofemoral Articular Cartilage during In Vitro Testing

    PubMed Central

    Li, Lingmin; Patil, Shantanu; Steklov, Nick; Bae, Won; Temple-Wong, Michele; D'Lima, Darryl D.; Sah, Robert L.; Fregly, Benjamin J.

    2011-01-01

    Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament injury) contribute to the development of knee osteoarthritis, the precise mechanism by which these changes induce osteoarthritis remains unknown. As a first step toward identifying this mechanism, this study evaluates computational wear simulations of a patellofemoral joint specimen wear tested on a knee simulator machine. A multi-body dynamic model of the specimen mounted in the simulator machine was constructed in commercial computer-aided engineering software. A custom elastic foundation contact model was used to calculate contact pressures and wear on the femoral and patellar articular surfaces using geometry created from laser scan and MR data. Two different wear simulation approaches were investigated – one that wore the surface geometries gradually over a sequence of 10 one-cycle dynamic simulations (termed the “progressive” approach), and one that wore the surface geometries abruptly using results from a single one-cycle dynamic simulation (termed the “non-progressive” approach). The progressive approach with laser scan geometry reproduced the experimentally measured wear depths and areas for both the femur and patella. The less costly non-progressive approach predicted deeper wear depths, especially on the patella, but had little influence on predicted wear areas. Use of MR data for creating the articular and subchondral bone geometry altered wear depth and area predictions by at most 13%. These results suggest that MR-derived geometry may be sufficient for simulating articular cartilage wear in vivo and that a progressive simulation approach may be needed for the patella and tibia since both remain in continuous contact with the femur. PMID:21453922

  19. How have wear testing and joint simulator studies helped to discriminate among materials and designs?

    PubMed

    McKellop, Harry A; D'Lima, Darryl

    2008-01-01

    Historically, hip joint simulators most often have been used to model wear of a bearing surface against a bearing surface. These simulators have provided highly accurate predictions of the in vivo wear of a broad spectrum of bearing materials, including cross-linked polyethylenes, metal-on-metal, ceramic-on-ceramic, and others in development. In recent years, more severe conditions have been successfully modeled, including jogging, stair climbing, ball-cup micro separation, third-body abrasion, and neck-socket impingement. These tests have served to identify improved materials and to eliminate some with inadequate wear resistance prior to their clinical use. Simulation of the knee joint is inherently more complex than it is for the hip. It is more difficult to compare the results of laboratory tests with actual clinical performance, due to the lack of accurate in vivo measures of wear. Nevertheless, knee simulators, based on force control or motion control, have successfully reproduced the type of surface damage that occurs in vivo (eg, burnishing, scratching, pitting) as well as the size and shapes of the resultant wear particles. Knee simulators have been used to compare molded versus machined polyethylene components, highly cross-linked polyethylenes, fixed versus mobile bearings, and oxidized zirconia and other materials, under optimal conditions as well as more severe wear modes, such as malalignment, higher loading and activity levels, and third-body roughening. PMID:18612005

  20. Increased force simulator wear testing of a zirconium oxide total knee arthroplasty.

    PubMed

    Lee, Joshua K L; Maruthainar, Kunalan; Wardle, Nic; Haddad, Fares; Blunn, Gordon W

    2009-08-01

    Total knee replacements provide cost effective treatment for debilitating conditions such as osteoarthritis. Their long term performance is governed by ultra-high molecular weight polyethylene (UHMWPE) wear which produces wear debris leading to osteolysis and aseptic loosening of the implant. An oxidised zirconium alternative to cobalt chrome is being used to reduce wear debris formation in the younger patients. Two TKRs of cobalt chrome and two of zirconium oxide coated zirconium were tested in a six degrees of freedom of motion, Stanmore-Instron force controlled knee wear simulator over 4 million increased force cycles. Oxidised zirconium was demonstrated to be more scratch resistant than CoCr. Increases in Ra (mean average roughness) of 12-fold compared to 1.9 fold rise for ZrO. The differences in roughness were accompanied by a 78%, statistically significant, reduction in wear of UHMWPE with the ZrO femoral components compared to the CoCr (p=0.037). Long term clinical results from the use of oxidised zirconium femoral components are awaited. However, it shows potential to reduce the wear rate.

  1. Analysis of wear debris from full-scale bearing fatigue tests using the Ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Loewenthal, S. H.

    1980-01-01

    The Ferrograph was used to determine the types of quantities of wear particles generated during full-scale bearing fatigue tests. Deep-groove ball bearings made from AISI 52100 steel were used. A MIL-L-23699 tetraester lubricant was used in a recirculating lubrication system containing a 49-micron absolute filter. Test conditions included a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the Ferrograph was more sensitive (up to 23 h) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis (SOAP). Four particle types were observed: normal rubbing wear particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  2. Analysis of wear-debris from full-scale bearing fatigue tests using the ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Loewenthal, S. H.

    1980-01-01

    The ferrograph was used to determine the types and quantities of wear particles generated during full-scale bearing fatigue tests. Deep-groove ball bearings made from AISI 52100 steel were used. A MIL-L-23699 tetraester lubricant was used in a recirculating lubrication system containing a 49 mm absolute filter. Test conditions included a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm, and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the ferrograph was more sensitive (up to 23 hr) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis. Four particle types were observed: normal rubbing wear particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  3. Airborne brake wear debris: size distributions, composition, and a comparison of dynamometer and vehicle tests.

    PubMed

    Sanders, Paul G; Xu, Ning; Dalka, Tom M; Maricq, M Matti

    2003-09-15

    Particle size distributions of light-duty vehicle brake wear debris are reported with careful attention paid to avoid sampling biases. Electrical low-pressure impactor and micro-orifice uniform deposit impactor measurements yield consistent size distributions, and the net particulate matter mass from each method is in good agreement with gravimetric filter measurements. The mass mean diameter of wear debris from braking events representative of urban driving is 6 microm, and the number-weighted mean is 1-2 microm for three currently used classes of lining materials: low metallic, semimetallic, and non-asbestos organic (NAO). In contrast, the wear rates are very material dependent, both in number and mass of particles, with 3-4 times higher emissions observed from the low metallic linings as compared to the semimetallic and NAO linings. Wind tunnel and test track measurements demonstrate the appearance of micron size particles that correlate with braking events, with approximately 50% of the wear debris being airborne for the test vehicle in this study. Elemental analysis of the wear debris reveals a consistent presence of the elements Fe, Cu, and Ba in both dynamometer and test track samples. PMID:14524436

  4. Aggressive wear testing of a cross-linked polyethylene in total knee arthroplasty.

    PubMed

    Muratoglu, Orhun K; Bragdon, Charles R; O'Connor, Daniel O; Perinchief, Rebecca S; Jasty, Murali; Harris, William H

    2002-11-01

    Recently, highly cross-linked polyethylenes with high wear and oxidation resistance have been developed. These materials may improve the in vivo performance of polyethylene components used in total knee arthroplasty. To date, the in vitro knee wear testing of these new polyethylenes has been done under conditions of normal gait. However, their critical assessment also must include aggressive in vitro fatigue and wear testing. In the current study, an aggressive in vitro knee wear and device fatigue model simulating a tight posterior cruciate ligament balance during stair climbing was developed and used to assess the performance of one type of highly cross-linked polyethylene tibial knee insert in comparison with conventional polyethylene. The highly cross-linked inserts and one group of conventional inserts were tested after sterilization. One additional group of conventional inserts was subjected to accelerated aging before testing. The articular surfaces of the inserts were inspected visually for surface delamination, cracking, and pitting at regular intervals during the test. The aged conventional polyethylene inserts showed extensive delamination and cracking as early as 50,000 cycles. In contrast, the unaged conventional and highly cross-linked polyethylene inserts did not show any subsurface cracking or delamination at 0.5 million cycles. The appearance and location of delamination that occurred in the aged conventional inserts tested with the current model previously have been observed in vivo with posterior cruciate-sparing design knee arthroplasties with a tight posterior cruciate ligament.

  5. 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.

  6. Laboratory testing of airborne brake wear particle emissions using a dynamometer system under urban city driving cycles

    NASA Astrophysics Data System (ADS)

    Hagino, Hiroyuki; Oyama, Motoaki; Sasaki, Sousuke

    2016-04-01

    To measure driving-distance-based mass emission factors for airborne brake wear particulate matter (PM; i.e., brake wear particles) related to the non-asbestos organic friction of brake assembly materials (pads and lining), and to characterize the components of brake wear particles, a brake wear dynamometer with a constant-volume sampling system was developed. Only a limited number of studies have investigated brake emissions under urban city driving cycles that correspond to the tailpipe emission test (i.e., JC08 or JE05 mode of Japanese tailpipe emission test cycles). The tests were performed using two passenger cars and one middle-class truck. The observed airborne brake wear particle emissions ranged from 0.04 to 1.4 mg/km/vehicle for PM10 (particles up to 10 μm (in size), and from 0.04 to 1.2 mg/km/vehicle for PM2.5. The proportion of brake wear debris emitted as airborne brake wear particles was 2-21% of the mass of wear. Oxygenated carbonaceous components were included in the airborne PM but not in the original friction material, which indicates that changes in carbon composition occurred during the abrasion process. Furthermore, this study identified the key tracers of brake wear particles (e.g., Fe, Cu, Ba, and Sb) at emission levels comparable to traffic-related atmospheric environments.

  7. In vitro wear testing of a contemporary design of reverse shoulder prosthesis.

    PubMed

    Smith, S L; Li, B L; Buniya, A; Lin, S Ho; Scholes, S C; Johnson, G; Joyce, T J

    2015-09-18

    Reverse shoulder arthroplasty is an increasingly common surgical intervention. However there are concerns and known limitations in relation to such joint replacement, while novel designs of reverse shoulder prostheses continue to appear on the market. Many claim to offer improvements over older designs but such assertions are difficult to validate when there is no consensus as to how such implants should be tested in vitro or even if such testing is necessary. In order to permit appropriate in vitro testing of reverse shoulder prostheses a unique, multi-station test rig was designed which was capable of applying motion in three axes to test prostheses. The shoulder simulator can apply up to 110° of motion in the flexion-extension and abduction-adduction axes and up to 90° in the internal-external rotation axis. Dynamic loading of up to 1500 N can be provided. The simulator is computer controlled so that the motions and loading associated with particular activities of daily living can be applied. A 4.5 million cycle wear test of commercially available reverse shoulder prostheses was undertaken using a 'mug to mouth' activity of daily living. Gravimetric analysis was used to characterise wear. After 4.5 million cycles of 'mug to mouth', the average wear rate of the test components was 14.3mm(3)/million cycles. Polyethylene test components showed a reduction in roughness and the median wear particle diameter was 167 nm. A three axis shoulder simulator has been designed and used to successfully test multiple samples of a commercially available reverse shoulder prosthesis.

  8. Development of the ASTM sequence IIIE engine oil oxidation and wear test

    SciTech Connect

    Smolenski, D.J.; Bergin, S.P

    1988-01-01

    The ASTM Sequence IIID engine-dynamometer test has been used to evaluate the high-temperature protection provided by engine oils with respect to valve train wear, viscosity increase (oil thickening), deposits, and oil consumption. The obsolescence of the engine used in this test along with the need to define even higher levels of performance associated with a new oil category (SG) prompted efforts at developing a replacement test. This paper describes the hardware and procedure development of this replacement test, the ASTM Sequence IIIE test. Test precision and correlation with field and Sequence IIID results on a series of reference oils is also discussed.

  9. Ferrographic analysis of wear debris from full-scale bearing fatigue tests

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Loewenthal, S. H.

    1979-01-01

    The Ferrograph was used to determine the types and quantities of wear particles generated during full scale bearing fatigue tests. Deep-groove ball bearings made from steel were used. A tetraester lubricant was used in a recirculating lubricant system containing a 49 micrometers absolute filter. Test conditions include a maximum Hertz stress of 2.4 GPa, a shaft speed of 15,000 rpm, and a lubricant supply temperature of 74 C (165 F). Four fatigue failures were detected by accelerometers in this test set. In general, the Ferrograph was more sensitive (up to 23 hr) in detecting spall initiation than either accelerometers or the normal spectrographic oil analysis. Four particle types were observed: normal rubbing weather particles, spheres, nonferrous particles, and severe wear (spall) fragments.

  10. a Development of Multi Purpose Testing Machine for Friction, Wear and Rolling Contact Fatigue

    NASA Astrophysics Data System (ADS)

    Choi, Gab-Su; Pyun, Young-Sik; Kim, Jun-Hyoung; Kim, Hak-Doo; Tominaga, Yasutoshi; Darisuren, Shirmendagwa

    In this paper, the newly developed tribometer was introduced. Ball-on-disk, pin-on-disk, small-sized journal and thrust bearings tests on friction and wear were carried out using a newly developed tribometer which is built up according to the ASTM G99. Those friction and wear test results were compared with the friction results which were approved by Korean (KOLAS) and CSM Instruments. The comparison revealed that friction characteristics and trends of three different tribometers were similar to each other. The objective of this paper is to demonstrate the capability of the newly developed tribometer. As a result, the newly developed tribometer is capable of performing friction tests using pin-on-disk, disk-on-disk, journal and thrust bearings configurations.

  11. Interpretation of friction and wear in DLC film: role of surface chemistry and test environment

    NASA Astrophysics Data System (ADS)

    Polaki, S. R.; Kumar, N.; Madapu, K.; Ganesan, K.; Krishna, N. G.; Srivastava, S. K.; Abhaya, S.; Kamruddin, M.; Dash, S.; Tyagi, A. K.

    2016-11-01

    In spite of the large amount of tribological work carried out to explain the friction and wear mechanism in diamond-like carbon (DLC) films, some of the core issues relating to the evolution of reactive species across sliding interfaces and their role on the friction and wear mechanism remain unclear. The phase composition, film density and hydrogen content present in a DLC film can be tailored by substrate biasing during film deposition to achieve a nearly vanishing friction coefficient. Furthermore, nitrogen doping in DLC films significantly improves wear resistance, and sliding occurs in a nearly wearless regime. Undoped and nitrogen-doped DLC films exhibit a nearly frictionless value with ultra-low wear behavior when tests are performed in argon, nitrogen and methane atmospheres. The antifriction and antiwear properties of the DLC films were improved with the reduction of adsorbed oxygen impurities on the film surface. This behavior was understood by correlating the oxygen impurities present at the surface/subsurface region of the DLC film while using x-ray photoelectron spectroscopy and depth-resolved Auger electron spectroscopy.

  12. End-of-test Performance and Wear Characterization of NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test

    NASA Technical Reports Server (NTRS)

    Shastry, Rohit; Herman, Daniel Andrew; Soulas, George C.; Patterson, Michael J.

    2014-01-01

    This presentation describes results from the end-of-test performance characterization of NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test (LDT). Sub-component performance as well as overall thruster performance is presented and compared to results over the course of the test. Overall wear of critical thruster components is also described, and an update on the first failure mode of the thruster is provided.

  13. Fabrication and wear test of a continuous fiber/particulate composite total surface hip replacement

    NASA Technical Reports Server (NTRS)

    Roberts, J. C.; Ling, F. F.; Jones, W. R., Jr.

    1981-01-01

    Continuous fiber woven E-glass composite femoral shells having the ame elastic properties as bone were fabricated. The shells were then encrusted with filled epoxy wear resistant coatings and run dry against ultrahigh molecular weight polyethylene acetabular cups in 42,000 and 250,000 cycle were tests on a total hip simulator. The tribological characteristics of these shells atriculating with the acetabular cups are comparable to a vitallium bal articulating with an ultrahigh molecular weight polyethylene cup.

  14. Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

    DOE PAGES

    Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; Schultz, Bradley M.; Unocic, Raymond R.; Kennedy, Marian S.

    2016-01-13

    In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

  15. Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

    NASA Astrophysics Data System (ADS)

    Economy, D. Ross; Mara, N. A.; Schoeppner, R. L.; Schultz, B. M.; Unocic, R. R.; Kennedy, M. S.

    2016-03-01

    In complex loading conditions ( e.g., sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed regions (as-deposited). Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 µm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally, the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022, respectively) were less than that determined for 100 nm systems ( n ≈ 0.041). These results suggest that single-dislocation-based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.

  16. Determining pump wear and remaining life from electric submersible pump test curves. [Wear and service life estimation of oil well pumps

    SciTech Connect

    Divine, D.L.; Lannom, R.W.; Johnson, R.A. )

    1993-08-01

    The remaining useful life of an electric submersible pump (ESP) is an important economic consideration in deciding whether the used pump should be returned to service without repair. This paper presents quantitative and qualitative techniques to determine the type and amount of wear that a pump has experienced from analysis of pump test data. This paper discusses methods of categorizing used pumps, depending on the wear and associated performance deterioration. This work also describes failure modes, pump reliability, and the concept of pump (product) infant mortality. The authors show that a used pump can be more reliable and have a longer run life than a new or rebuilt pump. They use test data, tear-down analysis, and a case history to develop these concepts.

  17. A new test machine for measuring friction and wear in controlled atmospheres to 1200 C

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1989-01-01

    This paper describes a new high temperature friction and wear test apparatus (tribometer) at NASA Lewis Research Center, Cleveland, Ohio. The tribometer can be used as a pin-on-disk or pin-on-ring configuration and is specially designed to measure the tribological properties of ceramics and high temperature metallic alloys from room temperature to 1200 C. Sliding mode can be selected to be either unidirectional at velocities up to 22 m/sec or oscillating at frequencies up 4.5 Hz and amplitudes up to + or - 60 deg. The test atmosphere is established by a controlled flow rate of a purge gas. All components within the test chamber are compatible with oxidizing, inert, or reducing gases.

  18. A new test machine for measuring friction and wear in controlled atmospheres to 1200 C

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1991-01-01

    This paper describes a new high-temperature friction and wear test apparatus (tribometer). The tribometer can be used as a pin-on-disk or pin-on-ring configuration and is specially designed to measure the tribological properties of ceramics and high temperature metallic alloys from room temperature to 1200 C. Sliding mode can be selected to be either unidirectional at velocities up to 22 m/sec or oscillating at frequencies up to 4.6 Hz and amplitudes up to + or - 60 deg. The test atmosphere is established by a controlled flow rate of a purge gas. All components within the test chamber are compatible with oxidizing, inert or reducing gases.

  19. CR TKA UHMWPE wear tested after artificial aging of the vitamin E treated gliding component by simulating daily patient activities.

    PubMed

    Schwiesau, Jens; Fritz, Bernhard; Kutzner, Ines; Bergmann, Georg; Grupp, Thomas M

    2014-01-01

    The wear behaviour of total knee arthroplasty (TKA) is dominated by two wear mechanisms: the abrasive wear and the delamination of the gliding components, where the second is strongly linked to aging processes and stress concentration in the material. The addition of vitamin E to the bulk material is a potential way to reduce the aging processes. This study evaluates the wear behaviour and delamination susceptibility of the gliding components of a vitamin E blended, ultra-high molecular weight polyethylene (UHMWPE) cruciate retaining (CR) total knee arthroplasty. Daily activities such as level walking, ascending and descending stairs, bending of the knee, and sitting and rising from a chair were simulated with a data set received from an instrumented knee prosthesis. After 5 million test cycles no structural failure of the gliding components was observed. The wear rate was with 5.62 ± 0.53 mg/million cycles falling within the limit of previous reports for established wear test methods.

  20. Tribological Properties of CrAlN and TiN Coatings Tested in Nano- and Micro-scale Laboratory Wear Tests

    NASA Astrophysics Data System (ADS)

    Hong, Ling; Bian, Guangdong; Hu, Shugen; Wang, Linlin; Dacosta, Herbert

    2015-07-01

    We investigated the tribological properties of CrAlN and TiN coatings produced by electron beam plasma-assisted physical vapor deposition by nano- and micro-scale wear tests. For comparison, we also conducted nano-indentation, nano-scanning wear tests, and pin-on-disk tribotests on uncoated M2 steel. The results indicate that, after nano-scale sliding tests against diamond indenter and pin-on-disk tests against ceramic alumina counterface pins, the CrAlN coating presents superior abrasive wear resistance compared to the TiN-coated and uncoated M2 steel samples. Against aluminum counterface, aluminum is more prone to attach on the CrAlN coating surface compared to TiN coating, but no apparent adhesive wear was observed, which has occurred on the TiN coating.

  1. Wear products that form during tribological tests of aluminum-matrix composite materials

    NASA Astrophysics Data System (ADS)

    Kalashnikov, I. E.; Bolotova, L. K.; Kobeleva, L. I.; Bykov, P. A.; Kolmakov, A. G.

    2015-04-01

    The wear products and the friction surfaces of the composite materials fabricated by reactive casting after the addition of commercial-purity aluminum AD1, titanium and nickel powders, and nanosized modifiers to a matrix melt are studied. The dispersity and the chemical composition of the wear products that form an intermediate layer between the contacting surfaces are analyzed, and the dominating wear mechanisms under experimental tribological loading conditions are determined. It is shown that the formation of such a disperse intermediate layer during lubricant-free friction of the synthesized composite materials decreases the temperature in the tribological contact and ensures a transition from weak to intense wear at higher critical loads.

  2. Wear Scar Similarities between Retrieved and Simulator-Tested Polyethylene TKR Components: An Artificial Neural Network Approach.

    PubMed

    Orozco Villaseñor, Diego A; Wimmer, Markus A

    2016-01-01

    The aim of this study was to determine how representative wear scars of simulator-tested polyethylene (PE) inserts compare with retrieved PE inserts from total knee replacement (TKR). By means of a nonparametric self-organizing feature map (SOFM), wear scar images of 21 postmortem- and 54 revision-retrieved components were compared with six simulator-tested components that were tested either in displacement or in load control according to ISO protocols. The SOFM network was then trained with the wear scar images of postmortem-retrieved components since those are considered well-functioning at the time of retrieval. Based on this training process, eleven clusters were established, suggesting considerable variability among wear scars despite an uncomplicated loading history inside their hosts. The remaining components (revision-retrieved and simulator-tested) were then assigned to these established clusters. Six out of five simulator components were clustered together, suggesting that the network was able to identify similarities in loading history. However, the simulator-tested components ended up in a cluster at the fringe of the map containing only 10.8% of retrieved components. This may suggest that current ISO testing protocols were not fully representative of this TKR population, and protocols that better resemble patients' gait after TKR containing activities other than walking may be warranted. PMID:27597955

  3. Wear Scar Similarities between Retrieved and Simulator-Tested Polyethylene TKR Components: An Artificial Neural Network Approach

    PubMed Central

    2016-01-01

    The aim of this study was to determine how representative wear scars of simulator-tested polyethylene (PE) inserts compare with retrieved PE inserts from total knee replacement (TKR). By means of a nonparametric self-organizing feature map (SOFM), wear scar images of 21 postmortem- and 54 revision-retrieved components were compared with six simulator-tested components that were tested either in displacement or in load control according to ISO protocols. The SOFM network was then trained with the wear scar images of postmortem-retrieved components since those are considered well-functioning at the time of retrieval. Based on this training process, eleven clusters were established, suggesting considerable variability among wear scars despite an uncomplicated loading history inside their hosts. The remaining components (revision-retrieved and simulator-tested) were then assigned to these established clusters. Six out of five simulator components were clustered together, suggesting that the network was able to identify similarities in loading history. However, the simulator-tested components ended up in a cluster at the fringe of the map containing only 10.8% of retrieved components. This may suggest that current ISO testing protocols were not fully representative of this TKR population, and protocols that better resemble patients' gait after TKR containing activities other than walking may be warranted.

  4. Wear Scar Similarities between Retrieved and Simulator-Tested Polyethylene TKR Components: An Artificial Neural Network Approach

    PubMed Central

    2016-01-01

    The aim of this study was to determine how representative wear scars of simulator-tested polyethylene (PE) inserts compare with retrieved PE inserts from total knee replacement (TKR). By means of a nonparametric self-organizing feature map (SOFM), wear scar images of 21 postmortem- and 54 revision-retrieved components were compared with six simulator-tested components that were tested either in displacement or in load control according to ISO protocols. The SOFM network was then trained with the wear scar images of postmortem-retrieved components since those are considered well-functioning at the time of retrieval. Based on this training process, eleven clusters were established, suggesting considerable variability among wear scars despite an uncomplicated loading history inside their hosts. The remaining components (revision-retrieved and simulator-tested) were then assigned to these established clusters. Six out of five simulator components were clustered together, suggesting that the network was able to identify similarities in loading history. However, the simulator-tested components ended up in a cluster at the fringe of the map containing only 10.8% of retrieved components. This may suggest that current ISO testing protocols were not fully representative of this TKR population, and protocols that better resemble patients' gait after TKR containing activities other than walking may be warranted. PMID:27597955

  5. Definition and evaluation of testing scenarios for knee wear simulation under conditions of highly demanding daily activities.

    PubMed

    Schwiesau, Jens; Schilling, Carolin; Kaddick, Christian; Utzschneider, Sandra; Jansson, Volkmar; Fritz, Bernhard; Blömer, Wilhelm; Grupp, Thomas M

    2013-05-01

    The objective of our study was the definition of testing scenarios for knee wear simulation under various highly demanding daily activities of patients after total knee arthroplasty. This was mainly based on a review of published data on knee kinematics and kinetics followed by the evaluation of the accuracy and precision of a new experimental setup. We combined tibio-femoral load and kinematic data reported in the literature to develop deep squatting loading profiles for simulator input. A servo-hydraulic knee wear simulator was customised with a capability of a maximum flexion of 120°, a tibio-femoral load of 5000N, an anterior-posterior (AP) shear force of ±1000N and an internal-external (IE) rotational torque of ±50Nm to simulate highly demanding patient activities. During the evaluation of the newly configurated simulator the ability of the test machine to apply the required load and torque profiles and the flexion kinematics in a precise manner was examined by nominal-actual profile comparisons monitored periodically during subsequent knee wear simulation. For the flexion kinematics under displacement control a delayed actuator response of approximately 0.05s was inevitable due to the inertia of masses in movement of the coupled knee wear stations 1-3 during all applied activities. The axial load and IE torque is applied in an effective manner without substantial deviations between nominal and actual load and torque profiles. During the first third of the motion cycle a marked deviation between nominal and actual AP shear load profiles has to be noticed but without any expected measurable effect on the latter wear simulation due to the fact that the load values are well within the peak magnitude of the nominal load amplitude. In conclusion the described testing method will be an important tool to have more realistic knee wear simulations based on load conditions of the knee joint during activities of daily living. PMID:22922096

  6. Test devices for investigation of piston-ring/cylinder-liner wear on coal-fueled diesel engines: Review and evaluation

    SciTech Connect

    Stodolsky, F.; Sekar, R.; Aronov, V.

    1987-05-01

    Literature on existing devices has been searched to determine their appropriateness for coal/water-slurry (CWS) diesel wear investigations. Parameters involved in the piston-ring/cylinder-liner tribological system are identified, as are materials that could potentially mitigate the wear problem. Many devices exist for materials screening, but none specifically addresses the dynamic interaction at high cyclical pressures and temperatures of the piston ring/cylinder liner with an abrasive containment in the interface. Simulation of these dynamic processes is a necessary step in solving the wear problem, although the first step must be to screen candidate materials using a device that would simply reciprocate flat specimens. Elimination of wear (other than by fuel modification) is found to depend on achieving adequate film thickness to prevent particulate contaminants from contacting the surfaces, as well as on developing surfaces substantially harder than the contaminants. A candidate wear-test device (based on a commercially available single-cylinder research engine) that would allow investigation of materials and lubrication schemes under representative engine conditions is recommended for further consideration. The device can be motored and pressurized to combustion conditions with nitrogen or ash introduced with the lubricant, or it can be motored with coal contaminants introduced into the cylinder by employing an external, low-pressure coal combustor. A similarity condition on lubricant film thickness is used to extrapolate the results to engines of different bore sizes.

  7. Effects of Microstructural Features and Test Parameters on the Abrasive Wear Response of an Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Gupta, A. K.; Prasad, B. K.

    2013-07-01

    This article discusses some observations pertaining to the abrasive wear response of an Al-Si alloy as influenced by microstructural features and test parameters (applied load and traversal distance). The wear performance has also been correlated with corresponding changes in mechanical properties (hardness, UTS, and elongation) and morphology (length, diameter, and length/diameter ratio) of microconstituents like Si. Microstructural/morphological alterations in the alloy were brought about through T6 heat treatment involving solutionizing followed by artificial aging for different durations. Heat treatment brought about significant alterations in the morphology (length, diameter, and length/diameter ratio) of Si particles, as was also reflected in terms of microstructural changes. The length of the Si particles decreased while their diameter increased leading to a reduction in the aspect (length/diameter) ratio of the phase in the case of the heat-treated samples compared to the as cast alloy. Decreasing length, rising diameter, and reduction in the aspect (length/diameter) ratio indicates a higher degree of spheroidization of the phase as a result of heat treatment. Increasing aging duration caused the aspect ratio to decrease further. The study suggests increasing wear loss with a rise in the applied load and traversal distance. The heat-treated samples attained improved mechanical and reduced wear loss over the as-cast samples in general, an exception being the elongation wherein the property became comparable to that of the as-cast alloy at aging durations beyond 7 h. Also, aging for 3 h seems to be sufficient to realize the benefit of heat treatment in terms of improvement in the wear behavior and mechanical properties since it leads to the highest hardness, UTS and elongation properties. Aging durations longer than 3 h led to deterioration in the UTS and elongation properties, while hardness and wear loss attained steady-state condition. The wear

  8. Testing and Analysis of NEXT Ion Engine Discharge Cathode Assembly Wear

    NASA Technical Reports Server (NTRS)

    Domonkos, Matthew T.; Foster, John E.; Soulas, George C.; Nakles, Michael

    2003-01-01

    Experimental and analytical investigations were conducted to predict the wear of the discharge cathode keeper in the NASA Evolutionary Xenon Thruster. The ion current to the keeper was found to be highly dependent upon the beam current, and the average beam current density was nearly identical to that of the NSTAR thruster for comparable beam current density. The ion current distribution was highly peaked toward the keeper orifice. A deterministic wear assessment predicted keeper orifice erosion to the same diameter as the cathode tube after processing 375 kg of xenon. A rough estimate of discharge cathode assembly life limit due to sputtering indicated that the current design exceeds the qualification goal of 405 kg. Probabilistic wear analysis showed that the plasma potential and the sputter yield contributed most to the uncertainty in the wear assessment. It was recommended that fundamental experimental and modeling efforts focus on accurately describing the plasma potential and the sputtering yield.

  9. Validation of the SenseWear Pro3 Armband using an incremental exercise test.

    PubMed

    van Hoye, Karen; Mortelmans, Patricia; Lefevre, Johan

    2014-10-01

    The purpose of this study is to assess the accuracy of a multisensor activity monitor in measuring energy expenditure (EE) using an incremental exercise test. The SenseWear Pro3 Armband (SWA) has been shown a valid and practical tool in measuring the EE of daily living activities but shows significant errors in estimating EE of activities of vigorous and very vigorous intensity. Recently, a new algorithm was developed for SWA (SWA v5.2). The aim of this study was to validate the new SWA algorithm in assessing EE using an incremental exercise test. Data were obtained from 44 students (age, 21.1 ± 1.4 years). During an incremental running test, EE estimates of the SWA were compared with the indirect calorimetry (IC). A paired t-test, Bland and Altman plots, and correlation coefficients were used as statistical techniques. Compared with the IC, the SWA showed no significant difference when walking at 1.5 m·s (p = 0.901) but significantly underestimated EE at higher speeds starting from a jogging speed of 1.67 m·s for men and from a running speed of 2 m·s for women. The underestimation increased significantly with increasing intensity in both male and female participants. The accurate measurement of EE at moderate intensity makes the monitor a valid tool in estimating daily life activities. However, our study results question the applicability of the monitor for individuals willing to monitor their EE during vigorous or very vigorous exercise intensities because a significant underestimation of the new algorithm is still present. In future, the EE algorithm needs to be further adjusted to give an accurate estimate of EE for high-intensity exercises.

  10. End-of-Test Performance and Wear Characterization of NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test

    NASA Technical Reports Server (NTRS)

    Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

    2014-01-01

    The NASA's Evolutionary Xenon Thruster (NEXT) program is developing the next-generation solar electric ion propulsion system with significant enhancements beyond the state-of-the-art NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) ion propulsion system to provide future NASA science missions with enhanced capabilities. A Long-Duration Test (LDT) was initiated in June 2005 to validate the thruster service life modeling and to quantify the thruster propellant throughput capability. Testing was recently completed in February 2014, with the thruster accumulating 51,184 hours of operation, processing 918 kg of xenon propellant, and delivering 35.5 MN-s of total impulse.As part of the test termination procedure, a comprehensive performance characterization was performed across the entire NEXT throttle table. This was performed prior to planned repairs of numerous diagnostics that had become inoperable over the course of the test. After completion of these diagnostic repairs in November 2013, a comprehensive end-of-test performance and wear characterization was performed on the test article prior to exposure to atmosphere. These data have confirmed steady thruster performance with minimal degradation as well as mitigation of numerous life limiting mechanisms encountered in the NSTAR design. Component erosion rates compare favorably to pretest predictions based on semi-empirical models used for the thruster service life assessment. Additional data relating to ion beam density profiles, facility backsputter rates, facility backpressure effects on thruster telemetry, and modulation of the neutralizer keeper current are presented as part of the end-of-test characterization. Presently the test article for the NEXT LDT has been exposed to atmosphere and placed within a clean room environment, with post-test disassembly and inspection underway.

  11. In vitro wear testing of the PyroCarbon proximal interphalangeal joint replacement: Five million cycles of flexion and extension.

    PubMed

    Naylor, Andrew; Bone, Martin C; Unsworth, Anthony; Talwalkar, Sumedh C; Trail, Ian A; Joyce, Thomas J

    2015-05-01

    Clinical results of the PyroCarbon proximal interphalangeal joint replacement are inconsistent with various complications reported. To address this, in vitro testing was conducted using finger joint simulators. Two PyroCarbon proximal interphalangeal prostheses were tested in a lubricant of dilute bovine serum to 5 × 10(6) cycles of flexion-extension (90°-30°) with dynamic forces of 10 N applied. At intervals of 3000 cycles testing ceased and a static load of 100 N was applied to simulate gripping. In addition, two 'control' prostheses were immersed alongside the test prostheses to account for lubricant absorption. Wear and roughness averages (Ra) were measured every 1 × 10(6) cycles. Minimal wear for all of the components was measured with a negligible increase in Ra for most of the components. One condyle of one component increased in Ra over the 5 × 10(6) cycles with a value above the recommended 50 nm. Unidirectional marks were visible on the condyle from micrographs, consistent with an abrasive wear mode.

  12. Prospects for Adapting Current ASTM Wear and Erosion Tests for Bulk Materials to Thin Films, Coatings, and Surface Treatments

    SciTech Connect

    Blau, Peter Julian

    2007-01-01

    Most of ASTM Committee G2's erosion, wear, and friction test standards were developed for use with bulk materials, yet there is a growing need to evaluate the tribological behavior of films, coatings, and surface treatments (FCSTs), some that affect layers only tens of nanometers to a few micrometers thick. Tribotesting standards for bulk materials can sometimes be modified for use on FCSTs, but the conditions and methods developed for bulk materials may sometimes be too severe or inapplicable. An internet search and literature review indicated that a number of G2 Committee standards are currently being used for FCSTs. Of these, ASTM G99 and G65 seem to be the most popular. When attempting to apply an existing wear standard for bulk materials to FCSTs, two key issues must be addressed: (1) whether changes are needed in the magnitudes of the applied conditions, and (2) whether more precise methods are needed to measure the magnitude of surface damage. Straightforward calculations underscore the limitations for wear measurement of thin layers when evaluated using block-on-ring and pin-on-disk tests. Finally, suggestions are given for modifying selected ASTM G2 standards to enable their use on films, coatings, and surface treatments.

  13. A simple surrogate test method to rank the wear performance of prospective ceramic materials under hip prosthesis edge-loading conditions.

    PubMed

    Sanders, Anthony P; Brannon, Rebecca M

    2014-02-01

    This research has developed a novel test method for evaluating the wear resistance of ceramic materials under severe contact stresses simulating edge loading in prosthetic hip bearings. Simply shaped test specimens - a cylinder and a spheroid - were designed as surrogates for an edge-loaded, head/liner implant pair. Equivalency of the simpler specimens was assured in the sense that their theoretical contact dimensions and pressures were identical, according to Hertzian contact theory, to those of the head/liner pair. The surrogates were fabricated in three ceramic materials: Al2 O3 , zirconia-toughened alumina (ZTA), and ZrO2 . They were mated in three different material pairs and reciprocated under a 200 N normal contact force for 1000-2000 cycles, which created small (<1 mm(2) ) wear scars. The three material pairs were ranked by their wear resistance, quantified by the volume of abraded material measured using an interferometer. Similar tests were performed on edge-loaded hip implants in the same material pairs. The surrogates replicated the wear rankings of their full-scale implant counterparts and mimicked their friction force trends. The results show that a proxy test using simple test specimens can validly rank the wear performance of ceramic materials under severe, edge-loading contact stresses, while replicating the beginning stage of edge-loading wear. This simple wear test is therefore potentially useful for screening and ranking new, prospective materials early in their development, to produce optimized candidates for more complicated full-scale hip simulator wear tests. PMID:23996812

  14. 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.

  15. 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.

  16. 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.

  17. Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis.

    PubMed

    Watanabe, Kenichi; Kyomoto, Masayuki; Saiga, Kenichi; Taketomi, Shuji; Inui, Hiroshi; Kadono, Yuho; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Moro, Toru

    2015-01-01

    The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

  18. Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis

    PubMed Central

    Watanabe, Kenichi; Kyomoto, Masayuki; Saiga, Kenichi; Taketomi, Shuji; Inui, Hiroshi; Kadono, Yuho; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Moro, Toru

    2015-01-01

    The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances. PMID:26583106

  19. NASA's Evolutionary Xenon Thruster (NEXT) Prototype Model 1R (PM1R) Ion Thruster and Propellant Management System Wear Test Results

    NASA Technical Reports Server (NTRS)

    VanNoord, Jonathan L.; Soulas, George C.; Sovey, James S.

    2010-01-01

    The results of the NEXT wear test are presented. This test was conducted with a 36-cm ion engine (designated PM1R) and an engineering model propellant management system. The thruster operated with beam extraction for a total of 1680 hr and processed 30.5 kg of xenon during the wear test, which included performance testing and some operation with an engineering model power processing unit. A total of 1312 hr was accumulated at full power, 277 hr at low power, and the remainder was at intermediate throttle levels. Overall ion engine performance, which includes thrust, thruster input power, specific impulse, and thrust efficiency, was steady with no indications of performance degradation. The propellant management system performed without incident during the wear test. The ion engine and propellant management system were also inspected following the test with no indication of anomalous hardware degradation from operation.

  20. Wear Characterization of Carbon Nanotubes Reinforced Acetal Spur, Helical, Bevel and Worm Gears Using a TS Universal Test Rig

    NASA Astrophysics Data System (ADS)

    Yousef, Samy; Osman, T. A.; Abdalla, Abdelrahman H.; Zohdy, Gamal A.

    2015-12-01

    Although the applications of nanotechnologies are increasing, there remains a significant barrier between nanotechnology and machine element applications. This work aims to remove this barrier by blending carbon nanotubes (CNT) with common types of acetal polymer gears (spur, helical, bevel and worm). This was done by using adhesive oil (paraffin) during injection molding to synthesize a flange and short bars containing 0.02% CNT by weight. The flanges and short bars were machined using hobbing and milling machines to produce nanocomposite polymer gears. Some defects that surfaced in previous work, such as the appearance of bubbles and unmelted pellets during the injection process, were avoided to produce an excellent dispersion of CNT in the acetal. The wear resistances of the gears were measured by using a TS universal test rig using constant parameters for all of the gears that were fabricated. The tests were run at a speed of 1420 rpm and a torque of 4 Nm. The results showed that the wear resistances of the CNT/acetal gears were increased due to the addition of CNT, especially the helical, bevel and worm gears.

  1. Can pin-on-disk testing be used to assess the wear performance of retrieved UHMWPE components for total joint arthroplasty?

    PubMed

    Kurtz, Steven M; MacDonald, Daniel W; Kocagöz, Sevi; Tohfafarosh, Mariya; Baykal, Doruk

    2014-01-01

    The objective of this study was to assess the suitability of using multidirectional pin-on-disk (POD) testing to characterize wear behavior of retrieved ultrahigh molecular weight polyethylene (UHMWPE). The POD wear behavior of 25 UHMWPE components, retrieved after 10 years in vivo, was compared with 25 that were shelf aged for 10-15 years in their original packaging. Components were gamma sterilized (25-40 kGy) in an air or reduced oxygen (inert) package. 9 mm diameter pins were fabricated from each component and evaluated against CoCr disks using a super-CTPOD with 100 stations under physiologically relevant, multidirectional loading conditions. Bovine serum (20 g/L protein concentration) was used as lubricant. Volumetric wear rates were found to vary based on the aging environment, as well as sterilization environment. Volumetric wear rates were the lowest for the pins in the gamma inert, shelf aged cohort. These results support the utility of using modern, multidirectional POD testing with a physiologic lubricant as a novel method for evaluating wear properties of retrieved UHMWPE components. The data also supported the hypothesis that wear rates of gamma-inert liners were lower than gamma-air liners for both retrieved and shelf aging conditions. However, this difference was not statistically significant for the retrieved condition.

  2. 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

  3. Wear properties of polyethylene-metal and polyethylene-ceramic bearings for hip joint replacements: The effect of temperature and protein precipitation in hip simulator tests

    NASA Astrophysics Data System (ADS)

    Liao, Yen-Shuo

    Ultra-high-molecular weight polyethylene (PE) cups bearing against metal or ceramic balls are the most commonly used combinations of materials for human hip joint replacements. The wear properties of these materials are typically evaluated in the laboratory using hip joint wear simulators, while lubricated with bovine serum. A previous test evaluating the PE cups against cobalt-chrome (CoCr), zirconia (Zr) and alumina balls demonstrated the sensitivity of serum proteins to elevated temperature; especially for Zr/PE, which showed the highest protein precipitation and bulk lubricant temperature but the lowest cup wear. In the present investigation, a temperature control system was used on a hip simulator to systematically evaluate the relationship between temperature and denaturation of the serum proteins which, in turn, affects the friction and wear properties of the prosthetic materials being tested. In order to control protein precipitation, the interface was temperature reduced by circulating coolant at 4°C through the center of the CoCr or Zr balls during a wear test. With cooling, protein assay of the serum showed 66% and 50% reductions in protein precipitation with the CoCr and Zr balls, respectively. The wear rate of the PE cups against the CoCr balls decreased by an average of 44%, whereas two of the three PE cups running against Zr balls exhibited slight increases in their wear rates, and the third showed a two fold increase. Under scanning electron microscopy, there were marked differences in the worn surfaces of the cups for the various conditions, and differences in the morphology of the PE wear debris recovered from the serum. For example, granular particles predominated without cooling, whereas fibrous particles predominated with cooling. Since particles generated in vivo (i.e., retrieved from periprosthetic tissues) typically show approximately equal proportions of granules and fibrils, the use of an intermediate coolant temperature might provide

  4. Amplitude Dependence of the Lateral-Vibration Wear Test for Perpendicular Recording Magnetic Disks Treated by Heat Curing

    NASA Astrophysics Data System (ADS)

    Miyake, Shojiro; Wakatsuki, Yukihiko; Wang, Mei; Matsunuma, Satoshi

    2005-05-01

    The tribological characteristics of perfluoropolyether (PFPE) and heat-treated PFPE lubricant films deposited on magnetic thin diamond-like carbon (DLC) film-coated disks by dip coating were studied using lateral modulation frictional force microscopy (LM-FFM). The topography and microstructural properties of the DLC film disk before PFPE lubricant dip coating were investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) in the dynamic force modulation (DFM) and frictional force modulation (FFM) modes. The TEM and AFM images show valleys and fine spaces formed between grain boundaries. It is possible that free lubricants reserved in these valleys and spaces during dip coating replenished the surface as a result of tip sliding. In wear tests, the friction properties of the PFPE-DLC disk without heat curing were improved due to the supply of lubricant.

  5. Effect of acetabular cup abduction angle on wear of ultrahigh-molecular-weight polyethylene in hip simulator testing.

    PubMed

    Korduba, Laryssa A; Essner, Aaron; Pivec, Robert; Lancin, Perry; Mont, Michael A; Wang, Aiguo; Delanois, Ronald E

    2014-10-01

    The effect of acetabular component positioning on the wear rates of metal-on-polyethylene articulations has not been extensively studied. Placement of acetabular cups at abduction angles of more than 40° has been noted as a possible reason for early failure caused by increased wear. We conducted a study to evaluate the effects of different acetabular cup abduction angles on polyethylene wear rate, wear area, contact pressure, and contact area. Our in vitro study used a hip joint simulator and finite element analysis to assess the effects of cup orientation at 4 angles (0°, 40°, 50°, 70°) on wear and contact properties. Polyethylene bearings with 28-mm cobalt-chrome femoral heads were cycled in an environment mimicking in vivo joint fluid to determine the volumetric wear rate after 10 million cycles. Contact pressure and contact area for each cup abduction angle were assessed using finite element analysis. Results were correlated with cup abduction angles to determine if there were any differences among the 4 groups. The inverse relationship between volumetric wear rate and acetabular cup inclination angle demonstrated less wear with steeper cup angles. The largest abduction angle (70°) had the lowest contact area, largest contact pressure, and smallest head coverage. Conversely, the smallest abduction angle (0°) had the most wear and most head coverage. Polyethylene wear after total hip arthroplasty is a major cause of osteolysis and aseptic loosening, which may lead to premature implant failure. Several studies have found that high wear rates for cups oriented at steep angles contributed to their failure. Our data demonstrated that larger cup abduction angles were associated with lower, not higher, wear. However, this potentially "protective" effect is likely counteracted by other complications of steep cup angles, including impingement, instability, and edge loading. These factors may be more relevant in explaining why implants fail at a higher rate if

  6. Effect of acetabular cup abduction angle on wear of ultrahigh-molecular-weight polyethylene in hip simulator testing.

    PubMed

    Korduba, Laryssa A; Essner, Aaron; Pivec, Robert; Lancin, Perry; Mont, Michael A; Wang, Aiguo; Delanois, Ronald E

    2014-10-01

    The effect of acetabular component positioning on the wear rates of metal-on-polyethylene articulations has not been extensively studied. Placement of acetabular cups at abduction angles of more than 40° has been noted as a possible reason for early failure caused by increased wear. We conducted a study to evaluate the effects of different acetabular cup abduction angles on polyethylene wear rate, wear area, contact pressure, and contact area. Our in vitro study used a hip joint simulator and finite element analysis to assess the effects of cup orientation at 4 angles (0°, 40°, 50°, 70°) on wear and contact properties. Polyethylene bearings with 28-mm cobalt-chrome femoral heads were cycled in an environment mimicking in vivo joint fluid to determine the volumetric wear rate after 10 million cycles. Contact pressure and contact area for each cup abduction angle were assessed using finite element analysis. Results were correlated with cup abduction angles to determine if there were any differences among the 4 groups. The inverse relationship between volumetric wear rate and acetabular cup inclination angle demonstrated less wear with steeper cup angles. The largest abduction angle (70°) had the lowest contact area, largest contact pressure, and smallest head coverage. Conversely, the smallest abduction angle (0°) had the most wear and most head coverage. Polyethylene wear after total hip arthroplasty is a major cause of osteolysis and aseptic loosening, which may lead to premature implant failure. Several studies have found that high wear rates for cups oriented at steep angles contributed to their failure. Our data demonstrated that larger cup abduction angles were associated with lower, not higher, wear. However, this potentially "protective" effect is likely counteracted by other complications of steep cup angles, including impingement, instability, and edge loading. These factors may be more relevant in explaining why implants fail at a higher rate if

  7. 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.

  8. Refractory Wear Mechanisms in the Nonferrous Metal Industry: Testing and Modeling Results

    NASA Astrophysics Data System (ADS)

    Gregurek, D.; Ressler, A.; Reiter, V.; Franzkowiak, A.; Spanring, A.; Prietl, T.

    2013-11-01

    Nonferrous pyrometallurgical processes today operate at a high intensity requiring the best standards for the furnace refractory systems. From one plant to another, there is a range of process conditions such as temperature, slag chemistry, and feed types, and each of these parameters can influence refractory life. It is generally understood that process changes at plants can impact refractory life. The ability to test and understand refractory responses to a wide range of furnace operating conditions is therefore important. The RHI Technology Centre in Leoben, Austria is well equipped with laboratory and pilot plant facilities to evaluate refractory suitability over the range of conditions encountered in modern nonferrous pyrometallurgical systems. This article describes refractory testing at the RHI Technology Centre of the impact of two metallurgical slags on a number of different RHI test bricks. The slags were a fayalite slag and a calcium ferrite slag supplied by two smelter plants. High-temperature corrosion tests were carried out in a 250-mm-diameter induction furnace and a 165-mm-diameter short rotary kiln; each unit was lined with a number of refractory bricks and tested against attack by the particular slag. After testing, the refractory bricks were subjected to several laboratory tests to determine the extent of corrosion. Optimal refractory choices for the customers' plants were developed based on the test results.

  9. Development of wear-resistant ceramic coatings for diesel engine components. Volume 1, Coating development and tribological testing: Final report: DOE/ORNL Ceramic Technology Project

    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 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.

  11. Development of a synovial fluid analogue with bio-relevant rheology for wear testing of orthopaedic implants.

    PubMed

    Smith, Alan M; Fleming, Leigh; Wudebwe, Uchena; Bowen, James; Grover, Liam M

    2014-04-01

    The rheological properties of synovial fluid (SF) are crucial to the performance of joint prostheses. During the development of joint prostheses, wear tests are performed, which simulate joint movements in diluted solutions (usually between 25 and 33% v/v) of bovine serum which has very different rheological properties compared with native SF, where rheology is maintained by hyaluronan. Consequently, there is a need to develop a more suitable artificial SF. In this study, we used rheological techniques to understand SF flow properties which provided an insight into the mechanical behaviour required of a practical SF analogue. Steady-shear viscosity measurements were performed to reveal changes as a function of shear rate. To analyse the viscoelastic properties small deformation oscillatory measurements of storage modulus (G') loss modulus (G″) and complex viscosity (η(⁎)) were made. The rheological properties of the SF where compared with those of the polysaccharides sodium alginate, gellan gum and mixtures of both polymers. Initial results revealed classic shear thinning behaviour for the SF with a small Newtonian plateau at low shear rates with a gradual reduction in viscosity with increasing shear rate. Viscoelasticity measurements also showed that at low frequencies of oscillation there was a viscous response with G″ greater than G' and at higher frequencies there was an elastic response. Rheological properties were found to be similar to that of a 50:50 mix of 2% w/v high molecular weight alginate and 0.75% w/v gellan gum. Importantly, the lubricating behaviour of the serum differed significantly from the biopolymer blend over a full range of sliding velocities. The biopolymer blend was shown to lubricate the opposing surfaces more effectively. This difference was attributed to the more rapid alignment of the polysaccharide during shear when compared with the bovine albumin (the most abundant protein in serum), which typically exhibits a globular

  12. In vitro response of the natural cadaver knee to the loading profiles specified in a standard for knee implant wear testing.

    PubMed

    Sutton, Levi G; Werner, Frederick W; Haider, Hani; Hamblin, Tracy; Clabeaux, Jonathan J

    2010-08-10

    The purpose of this study was to examine how a natural knee responds to the inputs of a total knee replacement testing standard developed by the International Organization for Standardization (ISO). This load control standard prescribes forces to be used for wear testing of knee replacements independent of implant size or design. A parallel ISO standard provides wear testing inputs that are displacement based instead of force based. Eight fresh frozen cadaveric knees were potted and tested in a 6 degree of freedom knee simulator using the load-control standard. The resulting displacements during load-control testing were compared to the prescribed displacements of the ISO displacement standard. At half the tibial torque prescribed by the load standard there was three times more average internal tibial rotation (20.3 degrees) than is prescribed by the displacement standard (5.7 degrees). The AP motion resulting from load testing was much different than is specified by the displacement standard. All eight knees had anterior tibial translation with respect to the femur during swing phase while the displacement standard specifies posterior tibial displacement. The variation in these motions among knees and their difference from the ISO displacement standard may be one factor that explains why wear results of total knee replacements based on ISO load or displacement testing frequently do not agree with each other or with clinical retrievals.

  13. Computational wear prediction of artificial knee joints based on a new wear law and formulation.

    PubMed

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

    2011-04-01

    Laboratory joint wear simulator testing has become the standard means for preclinical evaluation of wear resistance of artificial knee joints. Recent simulator designs have been advanced and become successful at reproducing the wear patterns observed in clinical retrievals. However, a single simulator test can be very expensive and take a long time to run. On the other hand computational wear modelling is an alternative attractive solution to these limitations. Computational models have been used extensively for wear prediction and optimisation of artificial knee designs. However, all these models have adopted the classical Archard's wear law, which was developed for metallic materials, and have selected wear factors arbitrarily. It is known that such an approach is not generally true for polymeric bearing materials and is difficult to implement due to the high dependence of the wear factor on the contact pressure. Therefore, these studies are generally not independent and lack general predictability. The objective of the present study was to develop a new computational wear model for the knee implants, based on the contact area and an independent experimentally determined non-dimensional wear coefficient. The effects of cross-shear and creep on wear predictions were also considered. The predicted wear volume was compared with the laboratory simulation measurements. The model was run under two different kinematic inputs and two different insert designs with curved and custom designed flat bearing surfaces. The new wear model was shown to be capable of predicting the difference of the wear volume and wear pattern between the two kinematic inputs and the two tibial insert designs. Conversely, the wear factor based approach did not predict such differences. The good agreement found between the computational and experimental results, on both the wear scar areas and volumetric wear rates, suggests that the computational wear modelling based on the new wear law and the

  14. The John Deere E diesel Test & Research Project

    SciTech Connect

    Fields, Nathan; Mitchell, William E.

    2008-09-23

    Three non-road Tier II emissions compliant diesel engines manufactured by John Deere were placed on a durability test plan of 2000 hours each at full load, rated speed (FLRS). The fuel was a blend of 10% fuel ethanol and 90% low sulfur #2 diesel fuel. Seven operational failures involving twenty seven fuel system components occurred prior to completion of the intended test plan. Regulated emissions measured prior to component failure indicated compliance to Tier II certification goals for the observed test experience. The program plan included operating three non-road Tier II diesel engines for 2000 hours each monitoring the regulated emissions at 500 hour intervals for changes/deterioration. The program was stopped prematurely due to number and frequency of injection system failures. The failures and weaknesses observed involved injector seat and valve wear, control solenoid material incompatibility, injector valve deposits and injector high pressure seal cavitation erosion. Future work should target an E diesel fuel standard that emphasizes minimum water content, stability, lubricity, cetane neutrality and oxidation resistance. Standards for fuel ethanol need to require water content no greater than the base diesel fuel standard. Lubricity bench test standards may need new development for E diesel.

  15. Gin saw wear test

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most current gin saw manufacturers use a 1074 steel or similar as a basis to manufacture their saw blades. The saw teeth are individually punched on the edges of the blades and then the blade goes through a heat treating process prior to use. There are indications from other industries with similar ...

  16. 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.

  17. Rub tolerance evaluation of two sintered NiCrAl gas path seal materials. [wear tests of gas turbine engine seals

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1978-01-01

    Two strength level variations of sintered NiCrAl (about 40 percent dense), candidate high pressure turbine seal materials, were subject to rub tolerance testing against AM 355 steel blade tips. The high strength material (17 N/sq mm tensile strength) showed frictional and radial loads that were 20 to 50 percent higher than those measured for the low strength material (15.5 N/ sq mm tensile strength). Measured wear to the AM 355 blade tips was not significantly different for the two sintered NiCrAl seal materials. Wear of the sintered NiCrAl was characterized by material removal to a depth greater than the depth to which blade tips were driven into the seal, indicating self-erosion effects.

  18. Wear study under plastic deformation conditions

    NASA Astrophysics Data System (ADS)

    Shukla, B. M.; Singhal, S.; Singh, D. V.

    1994-03-01

    Lubrication in metalworking processes is characterized by plastic deformation conditions resulting in generation of a large amount of virgin surface and of heat of deformation. The study of wear under these conditions is important from the point of view of product quality and tool/die wear. A laboratory study of wear under simulated plastic deformation conditions using pairs of mild steel and EN31 discs on an Amsler friction and wear testing machine was carried out. The worn surfaces and wear particles were examined by scanning electron microscopy. It was observed that wear with a mineral oil was greater than that with a vegetable oil. This paper analyzes the phenomenon through an examination of the surfaces and the wear particles.

  19. Multiple pollutant removal using the condensing heat exchanger: Phase 1 final report, November 1995--June 1997. Addendum 2: Task 3 topical report -- Long term wear test

    SciTech Connect

    Kudlac, G.A.

    1998-06-01

    Long-term operation of a condensing heat exchanger under typical coal-fired flue gas conditions was investigated in Phase 1, Task 3 of the Multiple Pollutant Removal Using the Condensing Heat Exchanger test program. The specific goal of this task was to determine the amount of wear, if any, on the Teflon{reg_sign}-covered heat transfer tubes in a condensing heat exchanger. A pilot-scale single-stage condensing heat exchanger (CHX{reg_sign}) was operated under typical coal-fired flue gas conditions on a continuous basis for a period of approximately 10 months. Operating conditions and particulate loadings for the test unit were monitored, Teflon{reg_sign} film thickness measurements were conducted, and surface replications (which duplicate the surface finish at the microscopic level) were taken at various times during the test. Data from the test indicate that virtually no decrease in Teflon{reg_sign} thickness was observed for the coating on the first two rows of heat exchanger tubes, even at high inlet particulate loadings (400 mg/dscm [0.35 lb/10{sup 6} Btu]). Evidence of wear was present only at the microscopic level, and even then was very minor in severity. Operation at high inlet particulate loadings resulted in accumulated ash deposits within the heat exchanger. Installation of a modified (higher flow rate) wash nozzle manifold substantially reduced subsequent deposit formation.

  20. Low stress abrasive wear behavior of a hardfaced steel

    NASA Astrophysics Data System (ADS)

    Dasgupta, R.; Prasad, B. K.; Jha, A. K.; Modi, O. P.; Das, S.; Yegneswaran, A. H.

    1998-04-01

    A plain carbon steel was overlayed with a wear-resistant hardfacing alloy by manual arc welding. Low stress abrasive wear tests were conducted with an ASTM rubber wheel abrasion tester using crushed silica and as the abrasive medium. The wear rate decreased with sliding distance, and there was an overall improvement in the abrasive wear resistance as a result of overlaying. The wear behavior of the samples has been discussed in terms of microstructural features while the examination of wear surface and subsurface regions provides insight into the wear mechanisms.

  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. A Review of Sub-Scale Test Methods to Evaluate the Friction and Wear of Ring and Liner Materials for Spark- and Compression Ignition Engines

    SciTech Connect

    Blau, P.J.

    2002-01-22

    A review was conducted of past laboratory-scale test methods and to assess their validity for ranking materials and lubricants for use as piston and liner materials in compression-ignition (CI) and spark-ignition (SI) engines. Most of the previous work was aimed at simulating SI engine environments. This report begins with a discussion of the numerous factors that can affect the validity of an approach to simulating engine conditions in a laboratory. These include not only mechanical, chemical and thermal factors, but also human factors as regards how the vehicle is operated and maintained. The next section provides an annotated review of open literature publications that address the issues of laboratory simulation of engine components. A comparison of these studies indicates a lack of sufficient standardization in procedures to enable a systematic comparison of one publication to another. There were just a few studies that compared several laboratory test methods to engine test results, and these indicated that some test methods correlate, at least qualitatively, better than others. The last section provides a series of recommendations for improving the accuracy and validity of laboratory-scale simulations of engine behavior. It became clear that much of the engine wear damage occurs during start-up when the engine is cold, and this calls into the question the usefulness of test methods that attempt to simulate steady-state running conditions. It is recommended that a new standard test method, perhaps developed with the help of the ASTM wear and erosion committee, be developed. It would use cold start-up conditions in the presence of degraded oil, or simulated degraded oil.

  3. 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.

  4. Understanding wear in dentistry.

    PubMed

    Mair, L H

    1999-01-01

    Tooth wear is an increasing problem in dentistry. Traditionally, it has been divided into three categories: abrasion, attrition, and erosion. However, most clinical cases of tooth wear involve more than one of these processes. It is often easier to make a diagnosis by looking for the signs of the fundamental wear processes rather than trying to categorize the individual case. Wear can be caused by direct surface-to-surface wear, an intervening slurry, or a corrosive environment. Wear occurs during mastication, but also at other times, often at night. Although it may be possible to institute a preventive regimen, this will not always help the patient if his or her prime concern is esthetics. The same processes that cause tooth wear will cause wear to restorative materials. To diagnose and prevent wear, its processes must be understood.

  5. NEXT Long-Duration Test Plume and Wear Characteristics after 16,550 h of Operation and 337 kg of Xenon Processed

    NASA Technical Reports Server (NTRS)

    Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

    2009-01-01

    The NASA s Evolutionary Xenon Thruster (NEXT) program is developing the next-generation ion propulsion system with significant enhancements beyond the state-of-the-art. The NEXT ion propulsion system provides improved mission capabilities for future NASA science missions to enhance and enable Discovery, New Frontiers, and Flagship-type NASA missions. As part of a comprehensive thruster service life assessment utilizing both testing and analyses, a Long-Duration Test (LDT) was initiated to validate and qualify the NEXT propellant throughput capability to a qualification-level of 450 kg, 1.5 times the mission-derived throughput requirement of 300 kg. This wear test is being conducted with a modified, flight-representative NEXT engineering model ion thruster, designated EM3. As of June 25, 2008, the thruster has accumulated 16,550 h of operation: the first 13,042 h at the thruster full-input-power of 6.9 kW with 3.52 A beam current and 1800 V beam power supply voltage. Operation since 13,042 h, i.e., the most recent 3,508 h, has been at an input power of 4.7 kW with 3.52 A beam current and 1180 V beam power supply voltage. The thruster has processed 337 kg of xenon (Xe) surpassing the NSTAR propellant throughput demonstrated during the extended life testing of the Deep Space 1 flight spare. The NEXT LDT has demonstrated a total impulse of 13.3 106 N s; the highest total impulse ever demonstrated by an ion thruster. Thruster plume diagnostics and erosion measurements are obtained periodically over the entire NEXT throttle table with input power ranging 0.5 to 6.9 kW. Observed thruster component erosion rates are consistent with predictions and the thruster service life assessment. There have not been any observed anomalous erosion and all erosion estimates indicate a thruster throughput capability that exceeds 750 kg of Xe, an equivalent of 36,500 h of continuous operation at the full-power operating condition. This paper presents the erosion measurements and plume

  6. 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

  7. 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

  8. Predicting and preventing casing wear while drilling

    SciTech Connect

    Perdue, J.M.

    1998-06-01

    Drillpipe rotating inside a well`s intermediate string of casing has long been recognized as the principal cause of internal casing wear. Because today`s wells are longer and deeper than ever, prolonged contact can cause sufficient wear to either breach the casing or weaken it to the extent that it will rupture when the casing is pressure tested, delaying the project while an unplanned tieback casing string is installed. Based on more than 300 casing wear experiments, a computer program was developed to calculate the potential for casing wear during drilling operations. Taking proper precautions can save operators more than $1 million per well.

  9. A new methodology for predictive tool wear

    NASA Astrophysics Data System (ADS)

    Kim, Won-Sik

    An empirical approach to tool wear, which requires a series of machining tests for each combination of insert and work material, has been a standard practice for industries since early part of the twentieth century. With many varieties of inserts and work materials available for machining, the empirical approach is too experiment-intensive that the demand for the development of a model-based approach is increasing. With a model-based approach, the developed wear equation can be extended without additional machining experiments. The main idea is that the temperatures on the primary wear areas are increasing such that the physical properties of the tool material degrade substantially and consequently tool wear increases. Dissolution and abrasion are identified to be the main mechanisms for tool wear. Flank wear is predominantly a phenomenon of abrasion as evident by the presence of a scoring mark on the flank surface. Based on this statement, it is reasonable to expect that the flank-wear rate would increase with the content of hard inclusions. However, experimental flank wear results did not necessary correspond to the content of cementite phase present in the steels. Hence, other phenomena are believed to significantly affect wear behavior under certain conditions. When the cutting temperature in the flank interface is subjected to high enough temperatures, pearlitic structure austenizes. During the formation of a new austenitic phase, the existing carbon is dissolved into the ferrite matrix, which will reduce the abrasive action. To verify the austenitic transformation, turning tests were conducted with plain carbon steels. The machined surface areas are imaged using X-ray diffraction the Scanning Electron Microscope (SEM) and the Transmission Electron Microscope (TEM). On the other hand, crater wear occurs as a result of dissolution wear and abrasive wear. To verify the wear mechanisms of crater wear, various coating inserts as well as uncoated inserts were

  10. 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.

  11. 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.

  12. Volumetric wear of various orthotic appliance materials.

    PubMed

    Issar-Grill, Noana; Roberts, Howard W; Wright, Edward F; Dixon, Sara A; Vandewalle, Kraig S

    2013-10-01

    The purpose of this study was to compare the resistance to wear of six commonly used orthotic appliance materials. These materials were: SR Ivocap (Ivoclar Vivadent, Inc., Amherst, NY), Eclipse (Dentsply International, York, PA), ProBase (Ivoclar Vivadent), Valplast (Valplast International Corp., Oceanside, NY), Impak (CMP Industries LLC, Albany, NY), and Clearsplint (Astron Dental Corp., Lake Zurich, IL). Twelve cylindrical specimens of each material were fabricated per manufacturer instructions. Occlusal wear was simulated in a custom-made wear simulator with each specimen receiving four wear scars in a two-body wear simulation using a 1.5 mm tungsten-carbide tipped stylus at 40 newtons for 2500 cycles at 1 Hz, while immersed in 37 degrees C distilled water (n = 48). The specimens were evaluated before and after wear testing using a three-dimensional (3D) noncontact profilometer (Proscan 2000, Scantron Corp., Eagan, MN). A mean change in volume was determined for each orthotic material. Results found that Clearsplint material displayed the greatest amount of volume loss/wear, while SR Ivocap, Eclipse, and ProBase materials had the least amount of wear. Valplast and Impak performed more moderately. Based upon this wear knowledge, practitioners are able to more reliably choose the appliance material necessary for their various patients. PMID:24308100

  13. Engine wear and lubricating oil contamination from plant oil fuels

    SciTech Connect

    Darcey, C.L.; LePori, W.A.; Yarbrough, C.M.

    1982-12-01

    Engine disassembly with wear measurements, and lubricating oil analysis were used to determine wear rates on a one cylinder diesel engine. Results are reported from short duration tests on the wear rates of various levels of processed sunflower oil, a 25% blend with diesel fuel, and processed cottonseed oil.

  14. 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.

  15. Adhesive Wear of Rollers in Vacuum

    NASA Technical Reports Server (NTRS)

    Shaeef, Iqbal; Krantz, Timothy L.

    2012-01-01

    This work was done to support NASA's James Webb Space Telescope that is equipped with a Near Infrared Camera and Spectrograph and Micro Shutter Assembly (MSA). A MSA mechanism's qualification test in cryogenic vacuum at 30deg K for 96K cycles resulted in roller wear and formation of some debris. Lab tests in vacuum were conducted at NASA Glenn Research Center (GRC) to understand the wear of Ti6Al4V mated with 440F steel rollers. Misalignment angle was found to have the most significant effect on debris formation. At misalignment angle of 1.4deg, significant amount of wear debris were formed within 50,000 cycles. Very few wear particles were found for a zero misalignment angle, and the total wear was small even after 367,000 cycles. The mode of wear in all the tests was attributed to adhesion, which was clearly evident from video records as well as the plate-like amalgamated debris material from both rollers. The adhesive wear rate was found to be approximately proportional to the misalignment angle. The wear is a two-way phenomenon, and the mixing of both roller materials in wear debris was confirmed by x-ray fluorescence (XRF) and EDX spectra. While there was a net loss of mass from the steel rollers, XRF and energy dispersive x-ray (EDX) spectra showed peaks of Ti on steel rollers, and peaks of Fe on Ti rollers. These results are useful for designers in terms of maintaining appropriate tolerances to avoid misalignment of rolling elements and the resulting severe wear

  16. Wear testing under high load conditionsThe effect of ``anti-scuff'' additions to AISI 3135, 52100 and 9310 steels introduced by ion implantation and ion beam mixing

    NASA Astrophysics Data System (ADS)

    Hartley, N. E. W.; Hirvonen, J. K.

    1983-05-01

    There is a need to eliminate the sudden onset of severe adhesive wear ("scuffing") in high performance hardened steels (e.g. AISI 9310) under arduous load conditions. We have investigated the friction and wear behavior of three ion implanted and ion beam mixed steels under simulated scuffing conditions using a Falex friction and wear tester. This machine enabled tests to be carried out at a load of 700 lb (318 kg), corresponding to a mean contact pressure of approximately 20 000 psi (i.e., 1×10 8 N/m 2) which was sufficient to induce scuffing. A series of lower load tests at 200 lb (91 kg) load (5.2 × 10 7 N/m 2) enabled the longer term wear performance of various ion/substrate combinations to be measured. The frictional force experienced during wear testing was used to assess the degree of scuffing, and the amount of material worn away was measured on the Falex tester or by subsequent weight loss determinations, depending on the type of test. The following ions were implanted: C +, N +, P +, Ti +, Cr +, Mo +, and Ta +, chosen in order to evaluate the effects of intermetallic additions (C, N, P), alloys elements (Ti, Cr), and anti-scuff elements (Mo, Ta). In addition some thin ( ˜1000 Å) vacuum evaporated layers of Si, V, Ni, Nb, Sn, Mo, Ta and W were prepared, and in some cases intermixed with N + ions at a fluence of typically 2×10 17/cm 2, to compare with the effects of ion implantation. Under the low load conditions the wear rate of AISI 3135 steel (1.5% Ni, 0.65% Cr alloy tool steel) was found to be reduced by a factor 3 as a result of N + implantation under low load, in agreement with previous work reported elsewhere, whereas other ions gave inconclusive results. The 52100 steel (a through-hardened martensitic bearing steel) showed marked improvements after Ti + implantation, revealing a sensitivity to fluence which correlated with known dry sliding behaviour of this steel modified by titanium implantations. Ta + and Mo + implantations into 9310 steel (a

  17. 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.

  18. 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

  19. Wear characterization of abrasive waterjet nozzles and nozzle materials

    NASA Astrophysics Data System (ADS)

    Nanduri, Madhusarathi

    Parameters that influence nozzle wear in the abrasive water jet (AWJ) environment were identified and classified into nozzle geometric, AWJ system, and nozzle material categories. Regular and accelerated wear test procedures were developed to study nozzle wear under actual and simulated conditions, respectively. Long term tests, using garnet abrasive, were conducted to validate the accelerated test procedure. In addition to exit diameter growth, two new measures of wear, nozzle weight loss and nozzle bore profiles were shown to be invaluable in characterizing and explaining the phenomena of nozzle wear. By conducting nozzle wear tests, the effects of nozzle geometric, and AWJ system parameters on nozzle wear were systematically investigated. An empirical model was developed for nozzle weight loss rate. To understand the response of nozzle materials under varying AWJ system conditions, erosion tests were conducted on samples of typical nozzle materials. The effect of factors such as jet impingement angle, abrasive type, abrasive size, abrasive flow rate, water pressure, traverse speed, and target material was evaluated. Scanning electron microscopy was performed on eroded samples as well as worn nozzles to understand the wear mechanisms. The dominant wear mechanism observed was grain pullout. Erosion models were reviewed and along the lines of classical erosion theories a semi-empirical model, suitable for erosion of nozzle materials under AWJ impact, was developed. The erosion data correlated very well with the developed model. Finally, the cutting efficiency of AWJ nozzles was investigated in conjunction with nozzle wear. The cutting efficiency of a nozzle deteriorates as it wears. There is a direct correlation between nozzle wear and cutting efficiency. The operating conditions that produce the most efficient jets also cause the most wear in the nozzle.

  20. Brush seal shaft wear resistant coatings

    NASA Astrophysics Data System (ADS)

    Howe, Harold

    1995-03-01

    Brush seals suffer from high wear, which reduces their effectiveness. This work sought to reduce brush seal wear by identifying and testing several industry standard coatings. One of the coatings was developed for this work. It was a co-sprayed PSZ with boron-nitride added for a high temperature dry lubricant. Other coatings tested were a PSZ, chrome carbide and a bare rotor. Testing of these coatings included thermal shocking, tensile testing and wear/coefficient of friction testing. Wear testing consisted of applying a coating to a rotor and then running a sample tuft of SiC ceramic fiber against the coating. Surface speeds at point of contact were slightly over 1000 ft/sec. Rotor wear was noted, as well as coefficient of friction data. Results from the testing indicates that the oxide ceramic coatings cannot withstand the given set of conditions. Carbide coatings will not work because of the need for a metallic binder, which oxidizes in the high heat produced by friction. All work indicated a need for a coating that has a lubricant contained within itself and the coating must be resistant to an oxidizing environment.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  3. Wear Modeling: Evaluation and Categorization of Wear Models

    NASA Astrophysics Data System (ADS)

    Meng, Hsien-Chung

    The objective of this study was to evaluate progress in wear modeling and propose guidelines for future work. Such guidelines can help wear modelers to make appropriate decisions and ascertain information relevant to wear modeling. Over 5,000 papers in the literature were surveyed. 182 erosion wear and sliding wear equations proposed between 1957 and 1992 were found and studied. Two approaches were taken to analyze the surveyed models. The first approach focuses on common features and variations in each of five wear modeling steps. The second approach identifies characteristics of the overall development of wear modeling. The conclusions and recommendations of this study: (1) No single universal equation or extensively accepted theory fully explains the many types of wear behavior. (2) Wear mechanisms as typically described in research literature are not fundamental processes of material loss. Mechanical, chemical, physical and metallurgical action are the four fundamental processes: future wear models should include consideration of these four simultaneously, together with their interactions. (3) Wear models based on a single academic discipline cannot fully explain a wearing process even if for a single wear mechanism. An interdisciplinary approach should be applied to build wear models. (4) Two characteristics in past development of wear modeling are positive and should be carried into future work: (a) progressively more and more local information about the variations of working conditions has been considered in wear modeling, and (b) the approaches of different disciplines has been more frequently and extensively applied together to build wear models which explain progressively more wear phenomena in a wearing system. (5) Wear modelers should derive wear equations to concisely present research results and to complete wear modeling. Out of the 5000 papers considered in this study, only 182 presented equations as well as word descriptions to describe erosion and

  4. 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.

  5. Sliding wear and friction behaviour of zircaloy-4 in water

    NASA Astrophysics Data System (ADS)

    Sharma, Garima; Limaye, P. K.; Jadhav, D. T.

    2009-11-01

    In water cooled nuclear reactors, the sliding of fuel bundles in fuel channel handling system can lead to severe wear and it is an important topic to study. In the present study, sliding wear behaviour of zircaloy-4 was investigated in water (pH ˜ 10.5) using ball-on-plate sliding wear tester. Sliding wear resistance zircaloy-4 against SS 316 was examined at room temperature. Sliding wear tests were carried out at different load and sliding frequencies. The coefficient of friction of zircaloy-4 was also measured during each tests and it was found to decrease slightly with the increase in applied load. The micro-mechanisms responsible for wear in zircaloy-4 were identified to be microcutting, micropitting and microcracking of deformed subsurface zones in water.

  6. Drill wear monitoring in cortical bone drilling.

    PubMed

    Staroveski, Tomislav; Brezak, Danko; Udiljak, Toma

    2015-06-01

    Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities.

  7. Drill wear monitoring in cortical bone drilling.

    PubMed

    Staroveski, Tomislav; Brezak, Danko; Udiljak, Toma

    2015-06-01

    Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities. PMID:25922212

  8. 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

  9. 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.

  10. Wear characteristics of ultrahigh molecular weight polyethylene (UHMWPE)

    NASA Astrophysics Data System (ADS)

    El-Domiaty, A.; El-Fadaly, M.; Nassef, A. Es.

    2002-10-01

    The wear of ultrahigh molecular weight polyethylene (UHMWPE) bearing against 316 stainless steel or cobalt chromium (Co-Cr) alloy was measured using a 12-channel wear tester especially developed for the evaluation of candidate materials for prosthetic joints. The coefficient of friction and wear rate were determined as a function of lubricant, contact stress, and metallic surface roughness in tests lasting 2 3 million cycles, the equivalent of several years use of a prosthesis. Wear was determined by the weight loss of the polyethylene (PE) specimens corrected for the effect of fluid absorption. The friction and wear processes in blood serum differed markedly from those in saline solution or distilled water. Only serum lubrication produced wear surfaces resembling those observed on removed prostheses. The experimental methods provided accurate reproducible measurement of PE wear. The long-term wear rates were proportional to load and sliding distance. Although the PE wear rate increased with increasing surface roughness, wear was not severe except with very coarse metal surfaces. The data obtained in these studies formed a comparison basis for the subsequent evaluation of potentially superior materials for prosthetic joints.

  11. 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.

  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. A physically-based abrasive wear model for composite materials

    SciTech Connect

    Lee, Gun Y.; Dharan, C.K.H.; Ritchie, Robert O.

    2001-05-01

    A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the matrix material. The size of this non-contributing portion of the reinforcement is estimated by modeling the three primary wear mechanisms, specifically plowing, interfacial cracking and particle removal. Critical variables describing the role of the reinforcement, such as its relative size and the nature of the matrix/reinforcement interface, are characterized by a single contribution coefficient, C. Predictions are compared with the results of experimental two-body (pin-on drum) abrasive wear tests performed on a model aluminum particulate-reinforced epoxy matrix composite material.

  14. Effect of filler size on wear resistance of resin cement.

    PubMed

    Shinkai, K; Suzuki, S; Katoh, Y

    2001-11-01

    The purpose of this study was to evaluate the effect of filler size on the wear of resin cements. Materials tested included four experimental dual-cure resin cements (Kuraray) consisting of different-sized filler particles. A rectangular box cavity was prepared on the flattened occlusal surface of extracted human molars. Ceramic inlays for the cavities were fabricated using the Cerec 2 system. The Cerec inlays were cemented with the respective cements and adhesive systems according to the manufacturer's directions. The restored surface was finished by wet-grinding with an 800-grit silicon carbide paper. Six specimens were prepared for each resin cement. Half of the specimens were subjected to a three-body wear test for 200,000 cycles, and the others were subjected to a toothbrush abrasion test for 30,000 cycles. The worn surface of each restoration was scanned by a profilometer (Surfcom 475 A) at eight different points for each restoration. The wear value was determined by measuring the vertical gap depth on the profilometric tracings. The data were statistically analyzed by one-way analysis of variance (ANOVA) and Scheffe's test. The results showed that, with increase of filler size, the wear value decreased in the toothbrush test and increased in the three-body wear test. The cement with 0.04-microm filler exhibited the lowest wear value among the materials in the three-body wear test, and the same wear value as the cement with 0.97-microm filler in the toothbrush test. Based upon the results of this study, it is concluded that the wear of resin cements was affected by the filler size as well as the mode of wear test.

  15. 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.

  16. 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.

  17. Incisor wear and age in Yellowstone bison

    USGS Publications Warehouse

    Christianson, D.A.; Gogan, P.J.P.; Podruzny, K.M.; Olexa, E.M.

    2005-01-01

    Biologists commonly use tooth eruption and wear patterns or cementum annuli techniques to estimate age of ungulates. However, in some situations the accuracy or sampling procedures of either approach are undesirable. We investigated the progression of several quantitative measures of wear with age, using permanent first incisors from Yellowstone bison (Bison bison), and tested for differences between sexes and herds. We further investigated the relationship of wear and age to explore an age-estimation method. Labial-lingual width (LLW) correlated best with assigned age (r2=0.66, males; r2=0.76 females). Labial-lingual width differed between sexes, with females showing ∼0.2 mm more wear than males. Additionally, differences in rate of wear existed between bison of the northern and central Yellowstone herds (1.2 and 0.9 mm/year, respectively). We developed a regression formula to test the power of LLW as an estimator of Yellowstone bison age. Our method provided estimated ages within 1 year of the assigned age 73% and 82% of the time for female and male bison, respectively.

  18. Development of wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    1999-10-22

    The level of nuclear plant radiation exposure due to activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. Laboratory pin-on-disc and rolling contact wear tests were used to evaluate the wear performance of several coatings. Based on the results of these tests, multilayer Cr-nitride coatings and ion nitriding are the most promising approaches.

  19. 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…

  20. 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

  1. Tribological bench and engine dynamometer tests of a low viscosity SAE 0W-16 engine oil using a combination of ionic liquid and ZDDP as anti-wear additives

    SciTech Connect

    Barnhill, William C.; Gao, Hong; Kheireddin, Bassem; Papke, Brian L.; Luo, Huimin; West, Brian H.; Qu, Jun

    2015-09-29

    We have previously reported an oil-miscible phosphonium-organophosphate ionic liquid (IL) with an effective anti-wear (AW) functionality when added to a base oil by itself or combined with a conventional zinc dialkyldithiophosphate (ZDDP) for a synergistic effect. In this research, we investigated whether this synergy manifests in formulated engine oils. An experimental SAE 0W-16 engine oil was generated containing a combination of IL and ZDDP with equal phosphorus contribution. The prototype engine oil was first evaluated using tribological bench tests: AW performance in boundary lubrication (BL) and friction behavior (Stribeck curves) in elastohydrodynamic, mixed, and BL. In addition, the forthcoming standard Sequence VIE engine dynamometer test was then conducted to demonstrate improved fuel economy. Results were benchmarked against those of another experimental engine oil with almost the same formulation except using ZDDP only without the IL (similar total phosphorus content). The IL-ZDDP formulation consistently outperforms the ZDDP-only formulation in friction reduction and wear protection, and results from the bench and engine tests are well correlated.

  2. Tribological bench and engine dynamometer tests of a low viscosity SAE 0W-16 engine oil using a combination of ionic liquid and ZDDP as anti-wear additives

    DOE PAGES

    Barnhill, William C.; Gao, Hong; Kheireddin, Bassem; Papke, Brian L.; Luo, Huimin; West, Brian H.; Qu, Jun

    2015-09-29

    We have previously reported an oil-miscible phosphonium-organophosphate ionic liquid (IL) with an effective anti-wear (AW) functionality when added to a base oil by itself or combined with a conventional zinc dialkyldithiophosphate (ZDDP) for a synergistic effect. In this research, we investigated whether this synergy manifests in formulated engine oils. An experimental SAE 0W-16 engine oil was generated containing a combination of IL and ZDDP with equal phosphorus contribution. The prototype engine oil was first evaluated using tribological bench tests: AW performance in boundary lubrication (BL) and friction behavior (Stribeck curves) in elastohydrodynamic, mixed, and BL. In addition, the forthcoming standardmore » Sequence VIE engine dynamometer test was then conducted to demonstrate improved fuel economy. Results were benchmarked against those of another experimental engine oil with almost the same formulation except using ZDDP only without the IL (similar total phosphorus content). The IL-ZDDP formulation consistently outperforms the ZDDP-only formulation in friction reduction and wear protection, and results from the bench and engine tests are well correlated.« less

  3. Wear Mechanisms in a Reliability Methodology

    NASA Astrophysics Data System (ADS)

    Tanner, Danelle M.; Dugger, Michael T.

    2003-01-01

    The main thrust in any reliability work is identifying failure modes and mechanisms. This is especially true for the new technology of MicroElectroMechanical Systems (MEMS). The methods are sometimes just as important as the results achieved. This paper will review some of the methods developed specifically for MEMS. Our methodology uses statistical characterization and testing of complex MEMS devices to help us identify dominant failure modes. We strive to determine the root cause of each failure mode and to gain a fundamental understanding of that mechanism. Test structures designed to be sensitive to a particular failure mechanism are typically used to gain understanding. The development of predictive models follows from this basic understanding. This paper will focus on the failure mechanism of wear and how our methodology was exercised to provide a predictive model. The MEMS device stressed in these studies was a Sandia-developed microengine with orthogonal electrostatic linear actuators connected to a gear on a hub. The dominant failure mechanism was wear in the sliding/contacting regions. A sliding beam-on-post test structure was also used to measure friction coefficients and wear morphology for different surface coatings and environments. Results show that a predictive model of failure-time as a function of drive frequency based on wear fits the functional form of the reliability data quite well, and demonstrates the benefit of a fundamental understanding of wear. The results also show that while debris of similar chemistry and morphology was created in the two types of devices, the dependence of debris generation on the operating environment was entirely different. The differences are discussed in terms of wear maps for ceramics, and the mechanical and thermal contact conditions in each device.

  4. 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.

  5. 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.

  6. High Temperature Wear of Advanced Ceramics

    NASA Technical Reports Server (NTRS)

    DellaCorte, C.

    2005-01-01

    It was initially hypothesized that advanced ceramics would exhibit favorable high te- friction and wear properties because of their high hot hardness and low achievable surface roughness welding observed in metals does not occur in ceramics. More recent tribological studies of many nitride, carbide, oxide and composite ceramics, however, have revealed that ceramics often exhibit high friction and wear in non-lubricated, high temperature sliding contacts. A summary is given to measure friction and wear factor coefficients for a variety of ceramics from self mated ceramic pin-on-disk tests at temperatures from 25 to up to 1200 C. Observed steady state friction coefficients range from about 0.5 to 1.0 or above. Wear factor coefficients are also very high and range from about to 10(exp -5) to 10(exp -2) cubic millimeters per N-m. By comparison, oil lubricated steel sliding results in friction coefficients of 0.1 or less and wear factors less than 10(exp -9) cubic millimeters per N-m.

  7. Wear evaluation of high interstitial stainless steel

    SciTech Connect

    Rawers, J.C.; Tylczak, J.H.

    2008-07-01

    A new series of high nitrogen-carbon manganese stainless steel alloys are studied for their wear resistance. High nitrogen and carbon concentrations were obtained by melting elemental iron-chromium-manganese (several with minor alloy additions of nickel, silicon, and molybdenum) in a nitrogen atmosphere and adding elemental graphite. The improvement in material properties (hardness and strength) with increasing nitrogen and carbon interstitial concentration was consistent with previously reported improvements in similar material properties alloyed with nitrogen only. Wear tests included: scratch, pin-on-disk, sand-rubber-wheel, impeller, and jet erosion. Additions of interstitial nitrogen and carbon as well as interstitial nitrogen and carbide precipitates were found to greatly improve material properties. In general, with increasing nitrogen and carbon concentrations, strength, hardness, and wear resistance increased.

  8. 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.

  9. Structural transformations, strengthening, and wear resistance of titanium nickelide upon abrasive and adhesive wear

    NASA Astrophysics Data System (ADS)

    Korshunov, L. G.; Pushin, V. G.; Chernenko, N. L.; Makarov, V. V.

    2010-07-01

    Wear resistance and structural transformations upon abrasive and adhesive wear of titanium nickelide Ti49.4Ni50.6 in microcrystalline (MC) and submicrocrystalline (SMC) states have been investigated. It has been shown that the abrasive wear resistance of this alloy exceeds that of the steel 12Kh18N9 by a factor of about 2, that of the steel 110G13 (Hadfield steel), by a factor of 1.3, and is close to that of the steel 95Kh18. Upon adhesive wear in a testing-temperature range from -50 to +300°C, the Ti49.4Ni50.6 alloy, as compared to the steel 12Kh18N9, is characterized by the wear rate that is tens of times smaller and by a reduced (1.5-2.0 times) friction coefficient. The enhanced wear resistance of the Ti49.4Ni50.6 alloy is due to the development of intense strain hardening in it and to a high fracture toughness, which is a consequence of effective relaxation of high contact stresses arising in the surface layer of the alloy. The SMC state produced in the alloy with the help of equal-channel angular pressing (ECAP) has no effect on the abrasive wear resistance of the alloy. The favorable effect of ECAP on the wear resistance of the Ti49.4Ni50.6 alloy takes place under conditions of its adhesive wear at temperatures from -25 to +70°C. The electron-microscopic investigation showed that under conditions of wear at negative and room temperatures in the surface layer (1-5 μm thick) of titanium nickelide there arises a mixed structure consisting of an amorphous phase and nanocrystals of supposedly austenite and martensite. Upon friction at 200-300°C, a nanocrystalline structure of the B2 phase arises near the alloy surface, which, as is the case with the amorphous-nanocrystalline structure, is characterized by significant effective strength and wear resistance.

  10. 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.

  11. Wear simulation strategies for reverse shoulder arthroplasty implants.

    PubMed

    Langohr, G Daniel G; Athwal, George S; Johnson, James A; Medley, John B

    2016-05-01

    Reverse total shoulder arthroplasty is a clinically accepted surgical procedure; however, its long-term wear performance is not known. The purpose of this work is to review wear simulator testing of reverse total shoulder arthroplasty, to develop a wear simulator protocol for reverse total shoulder arthroplasty, and to test it by performing a pilot study. The review of wear simulator testing in the literature revealed considerable variation in protocols. A combination of our own cadaveric testing and those of other research groups helped in determining the magnitude and direction of joint loading for the development of the present protocol. A MATCO orbital-bearing simulator was adapted using custom fixtures to simulate a circumduction motion of the shoulder under mildly adverse conditions, and a pilot study gave wear rates within the wide range found in the literature. Arguments were presented in support of the currently developed protocol, but it was also suggested that, rather than rely on one protocol, a series of simulator wear protocols should be developed to fully test the implant wear performance in reverse total shoulder arthroplasty.

  12. Wear simulation strategies for reverse shoulder arthroplasty implants.

    PubMed

    Langohr, G Daniel G; Athwal, George S; Johnson, James A; Medley, John B

    2016-05-01

    Reverse total shoulder arthroplasty is a clinically accepted surgical procedure; however, its long-term wear performance is not known. The purpose of this work is to review wear simulator testing of reverse total shoulder arthroplasty, to develop a wear simulator protocol for reverse total shoulder arthroplasty, and to test it by performing a pilot study. The review of wear simulator testing in the literature revealed considerable variation in protocols. A combination of our own cadaveric testing and those of other research groups helped in determining the magnitude and direction of joint loading for the development of the present protocol. A MATCO orbital-bearing simulator was adapted using custom fixtures to simulate a circumduction motion of the shoulder under mildly adverse conditions, and a pilot study gave wear rates within the wide range found in the literature. Arguments were presented in support of the currently developed protocol, but it was also suggested that, rather than rely on one protocol, a series of simulator wear protocols should be developed to fully test the implant wear performance in reverse total shoulder arthroplasty. PMID:27160563

  13. 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.

  14. 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.

  15. 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.

  16. Friction and wear behavior of in-situ reinforced silicon nitride. Final report

    SciTech Connect

    Yust, C.S.

    1995-10-01

    Specimens of in-situ-reinforced silicon nitride (ISRSH) have been wear tested in lubricated, reciprocating, sliding motion against a silicon nitride counterface. Only mild wear of the ISRSN was observed at contact pressures up to 4.8 GPa at an average sliding velocity of 0.3 m/s. At 0.6 m/s, a wear mode transition was observed in ISRSN at 4.2 - 4.4 GPa. In comparison, the wear mode transition in silicon carbide whisker reinforced silicon nitride at both velocities was evident at about 2.2 - 2.4 GPa. Scanning electron microscopy of the ISRSN wear surfaces revealed the presence of a 40 pm thick debris layer on the mild wear tracks. The ISRSN wear mode transition response indicated a potential for an improved wear resistance in this material as compared to whisker reinforced silicon nitride.

  17. 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.

  18. Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains

    PubMed Central

    Min, Jie; Zhang, Qianqian; Qiu, Xiaoli; Zhu, Minhao; Yu, Haiyang; Gao, Shanshan

    2015-01-01

    Objectives The primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains. Methods Five kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated. Results The friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes. Significance Wear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings. PMID:26368532

  19. Wear mechanism based on adhesion

    NASA Technical Reports Server (NTRS)

    Yamamoto, T.; Buckley, D. H.

    1982-01-01

    Various concepts concerning wear mechanisms and deformation behavior observed in the sliding wear track are surveyed. The mechanisms for wear fragment formation is discussed on the basis of adhesion. The wear process under unlubricated sliding conditions is explained in relation to the concept of adhesion at the interface during the sliding process. The mechanism for tearing away the surface layer from the contact area and forming the sliding track contour is explained by assuming the simplified process of material removal based on the adhesion theory.

  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. Friction measurement in a hip wear simulator.

    PubMed

    Saikko, Vesa

    2016-05-01

    A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated.

  2. Effect of contact pressure on wear and friction of ultra-high molecular weight polyethylene in multidirectional sliding.

    PubMed

    Saikko, V

    2006-10-01

    Computational wear models need input data from valid tribological tests. For the wear model of a total hip prosthesis, the contact pressure dependence of wear and friction of ultra-high molecular weight polyethylene (UHMWPE) against polished CoCr in diluted calf serum lubricant was studied, and useful input data produced. Two test devices were designed and built: a heavy load circularly translating pin-on-disc (HL-CTPOD) wear test device and an HL-CTPOD friction measurement device. Both can be used with a wide range of loads. The wear surface diameter of the test pin was kept constant at 9 mm, whereas the load was varied so that the nominal contact pressure ranged from 0.1 to 20 MPa. The wear factor decreased with increasing contact pressure, whereas the coefficient of friction first increased with increasing contact pressure with low pressure values and then decreased. Up to the pressure of 2.0 MPa, the wear mechanisms and wear factors were in good agreement with clinical findings. In the critical range of 2.0-3.5 MPa, the wear mechanisms and wear factors started to differ from clinical ones, and the decrease of the wear factor steepened. The discrepancy became more and more evident as the pressure was gradually increased beyond 3.5 MPa. It appears that the pressure value of 2.0 MPa should not be exceeded in pin-on-disc wear tests that are to reproduce the clinical wear of UHMWPE acetabular cups.

  3. 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

  4. Prevalence and Indicators of Tooth Wear among Chinese Adults.

    PubMed

    Wei, Zhao; Du, Yangge; Zhang, Jing; Tai, Baojun; Du, Minquan; Jiang, Han

    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

  5. Evaluation of hardness and wear resistance of interim restorative materials

    PubMed Central

    Savabi, Omid; Nejatidanesh, Farahnaz; Fathi, Mohamad Hossein; Navabi, Amir Arsalan; Savabi, Ghazal

    2013-01-01

    Background: The interim restorative materials should have certain mechanical properties to withstand in oral cavity. The aim of this study was to evaluate the hardness and wear resistance of interim restorative materials. Materials and Methods: Fifteen identical rectangular shape specimens with dimensions of 2 mm × 10 mm × 30 mm were made from 7 interim materials (TempSpan, Protemp 3 Garant, Revotek, Unifast LC, Tempron, Duralay, and Acropars). The Vickers hardness and abrasive wear of specimens were tested in dry conditions and after 1 week storage in artificial saliva. The depth of wear was measured using surface roughness inspection device. Data were subjected to Kruskal–Wallis and Mann–Whitney tests. The Pearson correlation coefficient was used to determine the relationship between hardness and wear (α =0.05). Results: TempSpan had the highest hardness. The wear resistance of TempSpan (in dry condition) and Revotek (after conditioning in artificial saliva) was significantly higher (P < 0.05). There was no statistically significant correlation between degree of wear and hardness of the materials (P = 0.281, r = −0.31). Conclusion: Hardness and wear resistance of interim resins are material related rather than category specified. PMID:23946734

  6. Experimental, numerical and analytical studies of abrasive wear: correlation between wear mechanisms and friction coefficient

    NASA Astrophysics Data System (ADS)

    Mezlini, Salah; Zidi, M.; Arfa, H.; Ben Tkaya, Mohamed; Kapsa, Philippe

    2005-11-01

    The transport of granular material often generates severe damage. Understanding the correlation between the friction coefficient, particle geometry and wear mechanisms is of primary importance for materials undergoing abrasive wear. The aim of this study is to investigate the effect of particle geometry on wear mechanisms and the friction coefficient. Numerical and analytical simulations and experimental results have been compared. The process to be studied is the scratch made by a rigid cone with different attack angles on a 5xxx aluminium alloy (Al-Mg) flat surface. A scratch test was used and the wear mechanisms were observed for different attack angles. A numerical study with a finite element code was made in order to understand the effect of attack angle on the friction coefficient. The contact surface and the friction coefficient were also studied, and the results compared to the Bowden and Tabor model. The superposition of the numerical, analytical and experimental results showed a better correlation between the wear mechanisms and the friction coefficient. It also showed the importance of the model hypothesis used to simulate the scratch phenomenon. To cite this article: S. Mezlini et al., C. R. Mecanique 333 (2005).

  7. Wear of metal fiber brushes

    NASA Astrophysics Data System (ADS)

    Brown, Lloyd Perryman, Jr.

    The goal of this dissertation was determining the wear mechanism of metal fiber brushes on commutators and slip rings with the goal of achieving the lowest possible wear rate. To this end, metal fiber brushes were operated, while conducting direct current, on gold-plated copper rotors with and without unfilled gaps to simulate slip rings and commutators, respectively. Wear rates on unfilled-groove commutators were found to be only modestly higher than on slip ring style rotors. Three possible causes for enhanced metal fiber brush wear on commutators were considered: (i) accelerated "adhesive" wear controlled by contact spots, (ii) fatigue induced wear and (iii) "fiber chopping". Similarly, SEM analysis of fiber tips and wear particles produced scant, if any, evidence of fiber chopping, which would occur as, again, fiber tips extend elastically into the commutator grooves and small slices of them would be "chopped" off by oncoming edges of commutator bars. Finally considered was "modified chopping", wherein fiber tips would be dragged over groove edges, resulting in tensile fracture and chopping. Only a single fiber fragment showed damage that might be compatible with that mechanism. Moreover, the fact that it was exemplified by a single tenuous case, rules it out as significant. The same conclusion also follows from comparing commutator wear rates with that on slip rings. These show good correlation in terms of effective brush pressure, which on commutators is increased because only bars conduct current and gaps do not support load. (Abstract shortened by UMI.)

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

    NASA Astrophysics Data System (ADS)

    Que, Like

    Wear is one of the major causes of artificial total knee arthroplasty (TKA) failure. Wear debris can cause adverse reactions to the surrounding tissue which can ultimately lead to loosening of the prosthesis. The wear behavior of UHMWPE tibial components have been studied extensively, but relatively little attention has been paid to the CoCrMo femoral component. The goal of the present study was to investigate the wear mechanisms of CoCrMo femoral components, to study the effect of CoCrMo alloy surface roughness on the wear of UHMWPE, and to determine the effect of heat treatments on the wear resistance of the CoCrMo implant alloys. The surface roughness of twenty-seven retrieved CoCrMo femoral components was analyzed. A multiple station wear testing machine and a wear fixture attached to an MTS 858 bionix system were built and used for in vitro wear studies of the CoCrMo/UHMWPE bearing couple. Solution and aging treatments were applied to the CoCrMo alloys. A white light interference surface profilometer (WLISP) and a scanning electron microscope (SEM) were used to measure the surface roughness and to study wear mechanisms of CoCrMo alloy. An optical microscope was used for alloy microstructure study. X-ray diffraction tests were performed to identify alloy phase transformation after aging. The micro-structure, hardness, and wear resistance of the alloys were studied. Surface roughness was used to quantify alloy wear, and the minimum number of surface roughness measurements required to obtain a reliable and repeatable characterization of surface roughness for a worn alloy surface was determined. The surfaces of the retrieved CoCrMo femoral components appeared to be damaged by metal particles embedded in the UHMWPE tibial component and metal-on-metal wear due to UHMWPE tibial component through-wear. Surface roughness of the femoral components was not correlated with patient age, weight, sex, or length of implantation. In vitro wear tests showed that when the Co

  9. 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. PMID:26556515

  10. 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.

  11. Predicted wear resistances of binary carbide coatings

    SciTech Connect

    Kramer, B.M.

    1986-11-01

    A mechanistic model of the tool wear process has been presented (B. M. Kramer and P. K. Judd, J. Vac. Sci. Technol. A 3, 2439 (1985)) that includes the effects of both the abrasion of the tool material by inclusions within the workpiece and the chemical dissolution of the tool material into the matrix of the workpiece. Machining tests have been run on steel with titanium carbide coated tooling and the resulting test data have been employed to produce a rough calibration of the proposed model. This model has been used to predict the wear resistances of the other group IV B carbides and of the (Ti,Hf)C system in the machining of steel.

  12. Switch wear leveling

    SciTech Connect

    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.

  13. Friction and Wear Behavior of Selected Dental Ceramics

    NASA Astrophysics Data System (ADS)

    Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah

    The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm × 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).

  14. Effect of the microhardness difference between base metal and bionic coupling unit on wear resistance of gray cast iron

    NASA Astrophysics Data System (ADS)

    Pang, Zuobo; Zhou, Hong; Chang, Fang; Zhang, Peng; Cong, Dalong; Meng, Chao; Wang, Chuanwei; Ren, Luquan

    2015-12-01

    In order to improve the wear resistance of gray cast iron guide rail, the samples with different microhardness difference between bionic coupling units and base metal were manufactured by laser surface remelting. Wear behavior of gray cast iron with bionic coupling units has been studied under dry sliding condition at room temperature using a homemade liner reciprocating wear testing machine. The wear resistance was evaluated by means of weight loss measurement and wear morphology. The results indicated that when the microhardness difference is 561 HV0.2, the wear resistance of sample is the best.

  15. Assessment of polyethylene wear in total hip replacement.

    PubMed

    Devane, P A; Horne, J G

    1999-12-01

    The three-dimensional technique is a method for the measurement of polyethylene wear in patients with total hip joint replacement. Application of image processing technology allows automation of point selection from digital images of radiographs scanned into the computer. Validation of image processing modifications reveals a three-fold increase in accuracy and a 40-fold increase in reproducibility compared with manual input of points from a digitizer during bench testing. A review of three-dimensional technique application to clinical patients gives information on the factors that influence polyethylene wear. Increasing age, activity level, femoral head size, decreasing polyethylene thickness, and insertion of total hip prostheses without cement all increase polyethylene wear. Restoration of femoral offset during total hip replacement seems to decreases polyethylene wear. No apparent difference in polyethylene wear rate could be found between two groups of patients, one group had a stainless steel-polyethylene articulation and the other had a ceramic-polyethylene articulation. Measurement of the serial polyethylene wear of individual patients reveals a high rate of femoral head penetration during the first 2 years after total hip replacement using metal-backed acetabular components inserted without cement. Interpretation of this femoral head penetration as true polyethylene wear may be erroneous, however, because creep of the polyethylene and acetabular liner movement within its metal shell cannot be measured. PMID:10611861

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Ullah Khan, Muhammad Zafar

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

  19. Steam generator fretting-wear damage: A summary of recent findings

    SciTech Connect

    Guerout, F.M.; Fisher, N.J.

    1999-08-01

    Flow-induced vibration of steam generator (SG) tubes may sometimes result in fretting-wear damage at the tube-to-support locations. Fretting-wear damage predictions are largely based on experimental data obtained at representative test conditions. Fretting-wear of SG materials has been studied at the Chalk River Laboratories for two decades. Tests are conducted in fretting-wear test machines that simulate SG environmental conditions and tube-to-support dynamic interactions. A new high-temperature force and displacement measuring system was developed to monitor tube-to-support interaction (i.e., work-rate) at operating conditions. This improvement in experimental fretting-wear technology was used to perform a comprehensive study of the effect of various environment and design parameters on SG tube wear damage. This paper summarizes the results of tests performed over the past 4 yr to study the effect of temperature, water chemistry, support geometry, and tube material on fretting-wear. The results show a significant effect of temperature on tube wear damage. Therefore, fretting-wear tests must be performed at operating temperatures in order to be relevant. No significant effect of the type of water treatment on tube wear damage was observed. For predominantly impacting motion, the wear of SG tubes in contact with 410 stainless steel is similar regardless of whether Alloy 690 or Alloy 800 is used as tubing material or whether lattice bars or broached hole supports are used. Based on results presented in this paper, an average wear coefficient value is recommended that is used for the prediction of SG tube wear depth versus time.

  20. 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.

  1. Friction and wear behavior of aluminum and composite airplane skins

    NASA Technical Reports Server (NTRS)

    Jackson, K. E.

    1984-01-01

    Friction and wear behavior was determined for small skin specimens under abrasive loading conditions typical of those occurring on the underside of a transport airplane during emergency belly landing. A test apparatus consisting of a standard belt sander provided the sliding surface. Small test specimens constructed of aluminum, standard graphite-epoxy composite, aramid-epoxy composite, and toughened-resin composites were tested undar a range of pressures, belt velocities, and belt-surface textures. The effects of these test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. The effect of fiber orientation in the composite materials on wear rate was also investigated. In addition, tests were performed in which thermocouples were imbedded into the various test specimens to obtain temperature-time histories during abrasion.

  2. 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.

  3. Evaluation Of Saltstone Mixer Paddle Configuration For Improved Wear Resistance

    SciTech Connect

    Reigel, M. M.; Fowley, M. D.; Pickenheim, B. R.

    2012-09-27

    A soft metal with low wear resistance (6000 series aluminum), was used to minimize run time while maximizing wear rate. Two paddle configurations were tested, with the first four paddles after the augers replaced by the wear paddles. The first configuration was all flat paddles, with the first paddle not aligned with the augers and is consistent with present SPF mixer. The second configuration had helical paddles for the first three stages after the augers and a flat paddle at the fourth stage. The first helical paddle was aligned with the auger flight for the second configuration. The all flat paddle configuration wear rate was approximately double the wear rate of the helical paddles for the first two sets of paddles after the augers. For both configurations, there was little or no wear on the third and fourth paddle sets based on mass change, indicating that the fully wetted premix materials are much less abrasive than the un-wetted or partially wetted premix. Additionally, inspection of the wear surface of the paddles at higher magnification showed the flat paddles were worn much more than the helical and is consistent with the wear rates. Aligning the auger discharge flight with the first set of helical paddles was effective in reducing the wear rate as compared to the flat paddle configuration. Changing the paddle configuration from flat to helical resulted in a slight increase in rheological properties. Although, both tests produced grout-like material that is within the processing rage of the SPF, it should be noted that cement is not included in the premix and water was used rather than salt solution, which does affect the rheology of the fresh grout. The higher rheological properties from the helical wear test are most likely due to the reduced number of shearing paddles in the mixer. In addition, there is variation in the rheological data for each wear test. This is most likely due to the way that the dry feeds enter the mixer from the dry feeder. The

  4. Wear aspects of internal combustion engine valves

    NASA Astrophysics Data System (ADS)

    Panţuru, M.; Chicet, D.; Paulin, C.; Alexandru, A.; Munteanu, C.

    2016-08-01

    Because the surface engineering is becoming an increasingly viable alternative to the constructive changes made to improve the efficiency of internal combustion engines, have been proposed and tested various types of coatings of some organs of internal combustion engines. One vital organ is the engine valves, which is subjected during operation to combined thermal, mechanical, corrosion and wear solicitations, which are leading to severe corrosion and complete breakdown. In this paper were analyzed aspects of valves wear and the active surfaces were coated using the atmospheric plasma spraying method (APS) with two commercial powders: Ni-Al and YSZ. Microstructural analyzes were made on these layers and also observations regarding the possibility of using them as thermal barrier and anti-oxidant coatings.

  5. Wear Behavior and Mechanism of H13 Steel in Different Environmental Media

    NASA Astrophysics Data System (ADS)

    Li, Xinxing; Zhou, Yin; Cao, Huan; Li, Yixian; Wang, Lan; Wang, Shuqi

    2016-10-01

    Sliding wear tests were performed for H13 steel in atmosphere, distilled water, 3.5% NaCl, and 5% NaOH water solutions under various loads on a pin-on-disk wear tester. The results showed that for different environmental media, the wear rate of H13 steel in atmosphere was the maximum and that in 3.5% NaCl solution was the minimum. The maximum wear rate in atmosphere was caused by a larger quantity of heat produced in the friction process. In this case, the adhesive wear prevailed. In three wet environments, the mild wear prevailed due to the good lubrication and cooling capacity of media as well as corrosion product film on worn surface. In distilled water, the wear mechanism was a typical fatigue wear. On the other hand, in 3.5% NaCl and 5% NaOH solutions, corrosive wear prevailed. The minimum wear rate in 3.5% NaCl solution was attributed to the protective function of corrosion product film. On the contrary, noncompact corrosion product film in 5% NaOH solution resulted in higher wear rate.

  6. Wear Behavior and Mechanism of H13 Steel in Different Environmental Media

    NASA Astrophysics Data System (ADS)

    Li, Xinxing; Zhou, Yin; Cao, Huan; Li, Yixian; Wang, Lan; Wang, Shuqi

    2016-08-01

    Sliding wear tests were performed for H13 steel in atmosphere, distilled water, 3.5% NaCl, and 5% NaOH water solutions under various loads on a pin-on-disk wear tester. The results showed that for different environmental media, the wear rate of H13 steel in atmosphere was the maximum and that in 3.5% NaCl solution was the minimum. The maximum wear rate in atmosphere was caused by a larger quantity of heat produced in the friction process. In this case, the adhesive wear prevailed. In three wet environments, the mild wear prevailed due to the good lubrication and cooling capacity of media as well as corrosion product film on worn surface. In distilled water, the wear mechanism was a typical fatigue wear. On the other hand, in 3.5% NaCl and 5% NaOH solutions, corrosive wear prevailed. The minimum wear rate in 3.5% NaCl solution was attributed to the protective function of corrosion product film. On the contrary, noncompact corrosion product film in 5% NaOH solution resulted in higher wear rate.

  7. 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

  8. Refining the parameters of Archard's wear model for calculating wear of wheels applied for 25 t per axle freight wagons on Russian railways

    NASA Astrophysics Data System (ADS)

    Saidova, Alina; Orlova, Anna

    2014-05-01

    The aim of the research is for a reasonable choice of wear coefficients for severe and mild phases in Archard's abrasive wear theory and friction coefficients for wheel flange and tread that correspond to conditions of Russian track for wheel profile wear modelling using dynamic models of wagons. This paper considers the gondola wagon on bogies model 18-9855 that are of the three-piece Barber S-2-R design. The wagon running test results on Experimental Loop Track in Scherbinka, the results of hardness measurements of wheel flange/tread and of wheel profile wear modelling are presented in this paper. In conclusion, a comparison of wheels wear of two freight wagons' bogies (with friction and elastic-friction links of wheel sets with side frames) on the basis of specified wear model was carried out.

  9. New wear resistant composite material

    SciTech Connect

    Angers, R.; Champagne, B.; Fiset, M.; Chollet, P.

    1983-01-01

    A composite material consisting of WC-Co particles in a steel matrix was fabricated by sintering mixtures of WC-Co particles and a steel powder and infiltrating the sintered pieces with a copper alloy. Its wear resistance and mechanical properties were studied as a function of the content in WC-Co particles and other characteristics of the composite material microstructure. Infiltration provided a simple means to obtain a strong cohesion between WC-Co particles and the steel matrix. An effective matrix protection against wear is obtained with relatively low additions of particles especially with a silica abrasive which is soft with respect to cemented carbide. The experimental results show that this material has good mechanical properties and wear resistance. Depending upon abrasion resistance, wear losses are reduced up to 10 times by a 30 vol% addition of cemented carbide particles.

  10. 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.

  11. Wear of Steel and Ti6Al4V Rollers in Vacuum

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.; Shareef, Iqbal

    2012-01-01

    This investigation was prompted by results of a qualification test of a mechanism to be used for the James Webb Space Telescope. Post-test inspections of the qualification test article revealed some loose wear debris and wear of the steel rollers and the mating Ti6Al4V surfaces. An engineering assessment of the design and observations from the tested qualification unit suggested that roller misalignment was a controlling factor. The wear phenomena were investigated using dedicated laboratory experiments. Tests were done using a vacuum roller rig for a range of roller misalignment angles. The wear in these tests was mainly adhesive wear. The measured wear rates were highly correlated to the misalignment angle. For all tests with some roller misalignment, the steel rollers lost mass while the titanium rollers gained mass indicating strong adhesion of the steel with the titanium alloy. Inspection of the rollers revealed that the adhesive wear was a two-way process as titanium alloy was found on the steel rollers and vice versa. The qualification test unit made use of 440F steel rollers in the annealed condition. Both annealed 440F steel rollers and hardened 440C rollers were tested in the vacuum roller rig to investigate possibility to reduce wear rates and the risk of loose debris formation. The 440F and 440C rollers had differing wear behaviors with significantly lesser wear rates for the 440C. For the test condition of zero roller misalignment, the adhesive wear rates were very low, but still some loose debris was formed

  12. Targeted computational probabilistic corroboration of experimental knee wear simulator: the importance of accounting for variability.

    PubMed

    Strickland, M A; Dressler, M R; Render, T; Browne, M; Taylor, M

    2011-04-01

    Experimental testing is widely used to predict wear of total knee replacement (TKR) devices. Computational models cannot replace this essential in vitro testing, but they do have complementary strengths and capabilities, which make in silico models a valuable support tool for experimental wear investigations. For effective exploitation, these two separate domains should be closely corroborated together; this requires extensive data-sharing and cross-checking at every stage of simulation and testing. However, isolated deterministic corroborations provide only a partial perspective; in vitro testing is inherently variable, and relatively small changes in the environmental and kinematic conditions at the articulating interface can account for considerable variation in the reported wear rates. Understanding these variations will be key to managing uncertainty in the tests, resulting in a 'cleaner' investigation environment for further refining current theories of wear. This study demonstrates the value of probabilistic in silico methods by describing a specific, targeted corroboration of the AMTI knee wear simulator, using rigid body dynamics software models. A deterministic model of the simulator under displacement-control was created for investigation. Firstly, a large sample of experimental data (N>100) was collated, and a probabilistic computational study (N>1000 trials) was used to compare the kinetic performance envelopes for in vitro and in silico models, to more fully corroborate the mechanical model. Secondly, corresponding theoretical wear-rate predictions were compared to the experimentally reported wear data, to assess the robustness of current wear theories to uncertainty (as distinct from the mechanical variability). The results reveal a good corroboration for the physical mechanics of the wear test rig; however they demonstrate that the distributions for wear are not currently well-predicted. The probabilistic domain is found to be far more sensitive at

  13. Polyethylene Wear in Knee Arthroplasty.

    PubMed

    Chakravarty, Rajit; Elmallah, Randa D K; Cherian, Jeffrey Jai; Kurtz, Steven M; Mont, Michael A

    2015-10-01

    Polyethylene (PE) wear and osteolysis are common causes for late revisions of knee arthroplasties. Several implant and surgical factors have been implicated in contributing to the development of wear, such as type of bearing surface used, inaccurate articular geometry, and poor knee kinematics. In addition, patient-related factors, such as younger age and higher activity levels, may also contribute to wear. Our purpose was to evaluate and compare the effect of these variables on wear rates following knee arthroplasty. Recently, technological advancements have been aimed at reducing the incidence of wear by improving the PE manufacturing process, creating implants that minimize contact stresses, and refining our surgical techniques. Furthermore, the development of newer highly cross-linked PEs (HXLPEs) and the introduction of additives, such as vitamin E, to the PEs may improve overall implant survivorship. As a result, with the advent of newer implant and PE designs, wear is no longer the most common cause of early failure, though it remains an important factor in limiting long-term implant survivorship. However, there are a few clinical studies evaluating the long-term outcomes of newer HXLPEs and implant designs, with further evaluations necessary to determine the best implant-PE combination for improved knee arthroplasty survivorship. PMID:26030263

  14. Two-body wear of dental porcelain and substructure oxide ceramics.

    PubMed

    Rosentritt, Martin; Preis, Verena; Behr, Michael; Hahnel, Sebastian; Handel, Gerhard; Kolbeck, Carola

    2012-06-01

    The aim of this in vitro study was to investigate the two-body wear of different ceramics. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists, respectively. Specimens were loaded in a pin-on-block design with a vertical load of 50 N for 1.2 × 10(5) cycles; (f = 1.6 Hz; lateral movement, 1 mm; mouth opening: 2 mm). Human enamel was used as a reference. Three zirconia ceramics, three veneering porcelains, two glass-infiltrated and one lithium disilicate ceramic were investigated. Veneering and lithium disilicate ceramics were glazed before testing. Surface roughness Ra (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D scanner (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures of the worn specimens and antagonists were made for evaluating wear performance. Veneering porcelain provided wear traces between 71.2 and 124.1 μm (enamel antagonist) and 117.4 and 274.1 μm (steatite). Wear of the steatite antagonists varied between 0.618 and 2.85 mm². No wear was found for zirconia and glass-infiltrated substructure ceramics. Also, no wear was found for the corresponding antagonists. Wear of specimens and antagonists was strongly material dependent. No visible wear was found on zirconia and glass-infiltrated ceramics. Porcelain and lithium disilicate ceramic showed a comparable or lower wear than the enamel reference. Antagonist wear was found to be lower when specimens were made of substructure oxide ceramics instead of veneering porcelain. From the point of wear testing, zirconia may be used for the fabrication of fixed dental prosthesis without veneering.

  15. 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.

  16. Effect of EGR contamination of diesel engine oil on wear.

    SciTech Connect

    Ajayi, O. O.; Erdemir, A.; Fenske, G. R.; Aldajah, S.; Goldblatt, I. L.; Energy Systems; United Arab Emirates Univ.; BP-Global Lubricants Technology

    2007-09-01

    Exhaust gas recirculation (EGR) is one of the effective means to reduce the NO{sub X} emission from diesel engines. Returning exhaust product to the diesel engine combustion chamber accelerated the degradation of the lubricant engine oil, primarily by increasing the total acid number (TAN) as well as the soot content and, consequently, the viscosity. These oil degradation mechanisms were observed in engine oil exposed to EGR during a standard Cummins M-l 1 diesel engine test. Four-ball wear tests with M-50 balls showed that, although the used oils slightly decrease the friction coefficients, they increased the ball wear by two orders of magnitude when compared to tests with clean oil. Wear occurred primarily by an abrasive mechanism, but in oil with the highest soot loading of 12%, scuffing and soot particle embedment were also observed. Laboratory wear tests showed a linear correlation with the TAN, while the crosshead wear during the engine test was proportional to the soot content.

  17. Quantitative wear and wear damage analysis of composite resins in vitro.

    PubMed

    Koottathape, Natthavoot; Takahashi, Hidekazu; Iwasaki, Naohiko; Kanehira, Masafumi; Finger, Werner J

    2014-01-01

    The aim of this study was to investigate volume loss and worn surfaces' morphologies of eight composite resins: Durafill VS (DUR), Clearfil AP-X (APX), Filtek Z250 (Z250), Filtek Supreme XT (FIL), Kalore (KAL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP). Disc-shaped specimens were fabricated and mounted in a ball-on-disc wear testing machine and abraded in water or with the third-body media, poppy seed slurry and polymethyl methacrylate (PMMA) slurry. Volume loss (n=5) was determined after 50k sliding cycles, and analyzed using two-way ANOVA (α=0.05). The worn surfaces were examined with SEM. Two-way ANOVA suggested significant interaction between composite and wear condition. DUR, KAL and MFL showed low wear in water. DUR, Z250 and FIL showed moderate wear with PMMA slurry, whereas APX, KAL and MFL were deeper abraded. Under the action of poppy seed slurry DUR proved high volume loss. SEM showed that Z250, FIL and MFL were uniformly abraded in water. KAL and MFL with poppy seed were heavily destructed, whereas VED and VEP appeared very smooth. KAL and MFL abraded with PMMA slurry showed many cracks, but VEP remained crack-free and smooth. Volume loss and worn surfaces' morphologies varied with type of composite and third-body media used. PMID:24219861

  18. Effect of axle misalignments on rolling resistance and wheel wear

    SciTech Connect

    Leary, J.F.; Wilson, N.G.

    1985-01-01

    High energy costs impacting the railroad industry and the use of rail lubrication to lower energy consumption have led to investigation of axle misalignment as a cause of train resistance and wear. This paper brings together the results of field and laboratory misalignment tests designed to measure the effects of axle misalignment on roller resistance and wheel wear of standard trucks run on curved and tangent track. These tests employed the Transportation Test Center's Roll Dynamics Unit for the lab tests, an instrumented coupler for field testing, and a modified version of the AAR Curving Model to validate the RDU results and correlate them to field data. All testing was conducted at the Transportation Test Center near Pueblo, Colorado, under the sponsorship of the Association of American Railroads (RDU Test) and the Federal Railroad Administration (Track Test). During testing, deliberate misalignments were introduced in test wheelsets, and measurements were taken in field and laboratory settings. The train resistance and wheel wear data correlated well with the curving model, showing that reasonably accurate results are achievable by modeling within a common range of known conditions. The undesirable effects of axle misalignment on train resistance and wear were confirmed.

  19. 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.

  20. Total hip wear assessment: a comparison between computational and in vitro wear assessment techniques using ISO 14242 loading and kinematics.

    PubMed

    Matsoukas, George; Willing, Ryan; Kim, Il Yong

    2009-04-01

    In the present study a direct comparison was made between in vitro total hip wear testing and a computational analysis considering the effects of time and a nonlinear stress-strain relationship for ultrahigh molecular weight polyethylene (UHMWPE) at 37 degrees C. The computational simulation was made correct through calibration to experimental volumetric wear results, and the predicted damage layout on the acetabular liner surface was compared with results estimated from laser scanning of the actual worn specimens. The wear rates for the testing specimens were found to be 17.14+/-1.23 mg/10(6) cycles and 19.39+/-0.79 mg/10(6) cycles, and the cumulative volumetric wear values after 3x10(6) cycles were 63.70 mm(3) and 64.02 mm(3) for specimens 1 and 2, respectively. The value of the calibrated wear coefficient was found to be 5.32(10(-10)) mm(3)/N mm for both specimens. The major difference between the computational and experimental wear results was the existence of two damage vectors in the experimental case. The actual location of damage was virtually the same in both cases, and the maximum damage depth of the computational model agreed well with the experiment. The existence of multiple wear vectors may indicate the need for computational approaches to account for multidirectional sliding or strain hardening of UHMWPE. Despite the limitation in terms of describing the overall damage layout, the present computational model shows that simulation can mimic some of the behavior of in vitro wear. PMID:19275440

  1. Total hip wear assessment: a comparison between computational and in vitro wear assessment techniques using ISO 14242 loading and kinematics.

    PubMed

    Matsoukas, George; Willing, Ryan; Kim, Il Yong

    2009-04-01

    In the present study a direct comparison was made between in vitro total hip wear testing and a computational analysis considering the effects of time and a nonlinear stress-strain relationship for ultrahigh molecular weight polyethylene (UHMWPE) at 37 degrees C. The computational simulation was made correct through calibration to experimental volumetric wear results, and the predicted damage layout on the acetabular liner surface was compared with results estimated from laser scanning of the actual worn specimens. The wear rates for the testing specimens were found to be 17.14+/-1.23 mg/10(6) cycles and 19.39+/-0.79 mg/10(6) cycles, and the cumulative volumetric wear values after 3x10(6) cycles were 63.70 mm(3) and 64.02 mm(3) for specimens 1 and 2, respectively. The value of the calibrated wear coefficient was found to be 5.32(10(-10)) mm(3)/N mm for both specimens. The major difference between the computational and experimental wear results was the existence of two damage vectors in the experimental case. The actual location of damage was virtually the same in both cases, and the maximum damage depth of the computational model agreed well with the experiment. The existence of multiple wear vectors may indicate the need for computational approaches to account for multidirectional sliding or strain hardening of UHMWPE. Despite the limitation in terms of describing the overall damage layout, the present computational model shows that simulation can mimic some of the behavior of in vitro wear.

  2. Wear reduction systems liquid piston ring

    SciTech Connect

    Raymond, R.J.; Chen, T.N.; DiNanno, L.

    1990-09-01

    The overall objective of the program was to demonstrate the technical feasibility of achieving an acceptable wear rate for the cylinder liner, piston, and piston rings in a coal/water-slurry-fueled engine that utilized the concept of a liquid piston ring above the conventional piston rings and to identify technical barriers and required research and development. The study included analytical modeling of the system, a bench study of the fluid motion in the liquid piston ring, and a single-cylinder test rig for wear comparison. A system analysis made on the different variations of the liquid supply system showed the desirability of the once-through version from the standpoint of system simplicity. The dynamics of the liquid ring were modeled to determine the important design parameters that influence the pressure fluctuation in the liquid ring during a complete engine cycle and the integrity of the liquid ring. This analysis indicated the importance of controlling heat transfer to the liquid ring through piston and liner to avoid boiling the liquid. A conceptual piston design for minimizing heat transfer is presented in this report. Results showed that the liquid piston ring effectively reduced the solid particles on the wall by scrubbing, especially in the case where a surfactant was added to the water. The wear rates were reduced by a factor of 2 with the liquid ring. However, leakage of the contaminated liquid ring material past the top ring limited the effectiveness of the liquid ring concept. 8 refs., 33 figs., 1 tab.

  3. The microstructural dependence of wear resistance in austenite containing plate steels

    NASA Astrophysics Data System (ADS)

    Wolfram, Preston Charles

    The purpose of this project was to examine the microstructural dependence of wear resistance of various plate steels, with interests in exploring the influence of retained austenite (RA). Materials resistant to abrasive wear are desirable in the industrial areas of agriculture, earth moving, excavation, mining, mineral processing, and transportation. Abrasive wear contributes to significant financial cost associated with wear to the industry. The motivation for the current study was to determine whether it would be beneficial from a wear resistance perspective to produce plate steels with increased amounts of retained austenite. This thesis investigates this motivation through a material matrix containing AR400F, Abrasive (0.21 wt pct C, 1.26 wt pct Mn, 0.21 wt pct Si, 0.15 wt pct Ni, 0.18 wt pct Mo), Armor (0.46 wt pct C, 0.54 wt pct Mn, 0.36 wt pct Si, 1.74 wt pct Ni, 0.31 wt pct Mo), 9260, 301SS, Hadfield, and SAE 4325 steels. The Abrasive, Armor and 9260 steels were heat treated using different methods such as quench and temper, isothermal bainitic hold, and quench and partitioning (Q&P). These heat treatments yielded various microstructures and the test matrix allowed for investigation of steels with similar hardness and varying levels of RA. The wear test methods used consisted of dry sand rubber wheel (DSRW), impeller-tumbler impact-abrasion (impeller), and Bond abrasion wear testing. DSRW and impeller wear resistance was found to increase with hardness and retained austenite levels at certain hardness levels. Some Q&P samples exhibited similar or less wear than the Hadfield steels in DSRW and impeller tests. Scanning electron microscopy investigation of wear surfaces revealed different wear mechanisms for the different wear test methods ranging from micro-plowing, to micro-cutting and to fragmentation.

  4. Correlation between the wear resistance of Cu-Ni alloy and its electron work function

    NASA Astrophysics Data System (ADS)

    Huang, X. C.; Lu, H.; He, H. B.; Yan, X. G.; Li, D. Y.

    2015-12-01

    This article reports our studies on the performance of isomorphous Cu-Ni alloy during sliding and erosive wear processes with attempt to correlate its wear behaviour with the electron work function (EWF). EWF, mechanical behaviour and wear resistance of the Cu-Ni alloy with respect to the concentration of Ni were measured using ultraviolet photoelectron spectroscopy, micro-indenter, pin-on-disc and air-jet testers, respectively. It was demonstrated that EWF, hardness and Young's modulus of the alloy increased as the concentration of Ni increased. During solid-particle erosion tests, the wear resistance of the alloy was enhanced with an increase in the Ni concentration, corresponding to an increase in EWF. However, an opposite trend was observed during sliding wear tests, which was ascribed to the formation of oxide scale that affected the sliding wear resistance.

  5. Mechanical and wear properties of aluminum coating prepared by cold spraying

    SciTech Connect

    Yusof, Siti Nurul Akmal Manap, Abreeza Afandi, Nurfanizan Mohd; Salim, Musdalilah; Misran, Halina

    2015-07-22

    In this study, aluminum (Al) powders were deposited onto Al substrates using cold spray to form a coating. The main objective is to investigate and compare the microstructure, mechanical and wear properties of Al coating to that of the Al substrate. The microstructure of the coating and substrate were observed using Scanning Electron Microscope (SEM). Hardness was evaluated using the Vickers Hardness test and wear properties were investigated using a pin-on-disk wear test machine. The elemental composition of the coating and substrate was determined using Energy-dispersive X-ray spectroscopy (EDX). Results showed that the friction coefficient and specific wear rate decreased while wear rate increased linearly with increasing load. It was found that the coating exhibit slightly better mechanical and wear properties compared to the substrate.

  6. Mechanical and wear properties of aluminum coating prepared by cold spraying

    NASA Astrophysics Data System (ADS)

    Yusof, Siti Nurul Akmal; Manap, Abreeza; Afandi, Nurfanizan Mohd; Salim, Musdalilah; Misran, Halina

    2015-07-01

    In this study, aluminum (Al) powders were deposited onto Al substrates using cold spray to form a coating. The main objective is to investigate and compare the microstructure, mechanical and wear properties of Al coating to that of the Al substrate. The microstructure of the coating and substrate were observed using Scanning Electron Microscope (SEM). Hardness was evaluated using the Vickers Hardness test and wear properties were investigated using a pin-on-disk wear test machine. The elemental composition of the coating and substrate was determined using Energy-dispersive X-ray spectroscopy (EDX). Results showed that the friction coefficient and specific wear rate decreased while wear rate increased linearly with increasing load. It was found that the coating exhibit slightly better mechanical and wear properties compared to the substrate.

  7. Ceramic versus cobalt-chrome femoral components; wear of polyethylene insert in total knee prosthesis.

    PubMed

    Oonishi, Hironobu; Ueno, Masaru; Kim, Sok Chol; Oonishi, Hiroyuki; Iwamoto, Mikio; Kyomoto, Masayuki

    2009-04-01

    The present study aimed to determine the effect of femoral component materials and sterilization methods on wear properties of total knee prostheses by using a knee simulator test and retrieval analysis. The simulator test revealed that ultrahigh molecular weight polyethylene (UHMWPE) inserts had remarkably lower wear against the ceramic femoral component than against the Co-Cr femoral component. However, the retrieval study revealed no significant difference in the linear wear between the former and the latter. The alumina ceramic/UHMWPE insert combination showed a mild wear. However, whether cross-linking by gamma-ray sterilization reduces wear remained unconfirmed. In contrast, oxidative degradation and/or delamination was confirmed. Thus, we conclude that alumina ceramic/ethylene oxide gas-sterilized UHMWPE insert in a total knee prosthesis might exhibit a good wear resistance. PMID:18524533

  8. Wear and corrosion performance of metallurgical coatings in sodium

    SciTech Connect

    Johnson, R.N.; Farwick, D.G.

    1980-04-24

    The friction, wear, and corrosion performance of several metallurgical coatings in 200 to 650/sup 0/C sodium are reviewed. Emphasis is placed on those coatings which have successfully passed the qualification tests necessary for acceptance in breeder reactor environments. Tests include friction, wear, corrosion, thermal cycling, self-welding, and irradiation exposure under as-prototypic-as-possible service conditions. Materials tested were coatings of various refractory metal carbides in metallic binders, nickel-base and cobalt-base alloys and intermetallic compounds such as the aluminides and borides. Coating processes evaluated included plasma spray, detonation gun, sputtering, spark-deposition, and solid-state diffusion.

  9. Wear Performance of Cu-Alloyed Austempered Ductile Iron

    NASA Astrophysics Data System (ADS)

    Batra, Uma; Batra, Nimish; Sharma, J. D.

    2013-04-01

    An investigation was carried out to examine the influence of structural and mechanical properties on wear behavior of austempered ductile iron (ADI). Ductile iron (DI) samples were austenitized at 900 °C for 60 min and subsequently austempered for 60 min at three temperatures: 270, 330, and 380 °C. Microstructures of the as-cast DI and ADIs were characterized using optical and scanning microscopy, respectively. The structural parameters, volume fraction of austenite, carbon content of austenite, and ferrite particle size were determined using x-ray diffraction technique. Mechanical properties including Vicker's hardness, 0.2% proof strength, ultimate tensile strength, ductility, and strain hardening coefficient were determined. Wear tests were carried out under dry sliding conditions using pin-on-disk machine with a linear speed of 2.4 m/s. Normal load and sliding distance were 45 N and 1.7 × 104 m, respectively. ADI developed at higher austempering temperature has large amounts of austenite, which contribute toward improvement in the wear resistance through stress-induced martensitic transformation, and strain hardening of austenite. Wear rate was found to depend on 0.2% proof strength, ductility, austenite content, and its carbon content. Study of worn surfaces and nature of wear debris revealed that the fine ausferrite structure in ADIs undergoes oxidational wear, but the coarse ausferrite structure undergoes adhesion, delamination, and mild abrasion too.

  10. Investigation on the Surface Integrity and Tool Wear in Cryogenic Machining

    SciTech Connect

    Dutra Xavier, Sandro E.; Delijaicov, Sergio; Farias, Adalto de; Stipkovic Filho, Marco; Ferreira Batalha, Gilmar

    2011-01-17

    This work aimed to study the influences of cryogenic cooling on tool wear, comparing it to dry machining during on the surface integrity of test circular steel SAE 52100 hardened to 62 HRC, during the turning of the face, with the use of special PcBN, using liquid nitrogen with cooler. The surface integrity parameters analyzed were: surface roughness and white layer and tool wear. The results of the present work indicated reduction in tool wear, which enhance the tool life.

  11. Wear, friction, and temperature characteristics of an aircraft tire undergoing braking and cornering

    NASA Technical Reports Server (NTRS)

    Mccarty, J. L.; Yager, T. J.; Riccitiello, S. R.

    1979-01-01

    An investigation to evaluate the wear, friction, and temperature characteristics of aircraft tire treads fabricated from different elastomers is presented. The braking and cornering tests performed on aircraft tires retreaded with currently employed and experimental elastomers are described. The tread wear rate is discussed in relation to the slip ratio during braking and yaw angle during cornering. The extent of wear in either operational mode is examined in relation to the runway surface.

  12. Surface roughness and wear of resin cements after toothbrush abrasion.

    PubMed

    Ishikiriama, Sérgio Kiyoshi; Ordoñéz-Aguilera, Juan Fernando; Maenosono, Rafael Massunari; Volú, Fernanda Lessa Amaral; Mondelli, Rafael Francisco Lia

    2015-01-01

    Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm) were fabricated according to manufacturer instructions for each group (n = 10): Nexus 3, Kerr (NX3); RelyX ARC, 3M ESPE (ARC); RelyX U100, 3M ESPE (U100); and Variolink II, Ivoclar/Vivadent (VL2). Initial roughness (Ra, µm) was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles), and further evaluation was conducted for final roughness. Vertical wear (µm) was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey's test (p < 0.05). The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05). The mean values of initial/final roughness (Ra, µm)/wear (µm) were as follows: NX3 (0.078/0.127/23.175); ARC (0.086/0.246/20.263); U100 (0.296/0.589/16.952); and VL2 (0.313/0.512/22.876). Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations.

  13. Impact of Advertising on Tampon Wear-time Practices

    PubMed Central

    Woeller, Kara E.; Miller, Kenneth W.; Robertson-Smith, Amy L.; Bohman, Lisa C.

    2015-01-01

    OBJECTIVES (1) To determine whether advertising nighttime tampon use for up to eight hours was understood to be consistent with label recommendations and (2) to determine whether television and print advertising with this message affected tampon wear times in adults and teens. METHODS (1) A comprehension study (online advertising and follow-up questionnaire) among women aged 14–49 years (300 per group) who viewed either the test or a control advertising message; (2) Diary-based surveys of tampon wear times performed prior to (n = 292 adults, 18–49 years, 74 teens, 12–17 years) and after (n = 287 adults, 104 teens) the launch of national advertising. RESULTS Significantly more test message viewers than controls stated tampons should be worn less than or equal to eight hours (93.6% vs. 88.6%, respectively, P = 0.049). A directionally higher percentage of test message viewers said they would use a pad if sleeping longer than eight hours (52% vs. 42% of controls). Among the women who used tampons longer than eight hours when sleeping, 52% reported they would wake up and change compared with 45% of controls. No significant difference between baseline and follow-up diary surveys was found among teens or adults in various measures of tampon wear time (mean wear times; usage intervals from less than two hours to more than 10 hours; percentage of tampons used for more than or equal to eight hours; frequency of wearing at least one tampon more than eight hours). CONCLUSIONS Advertising nighttime tampon wear for up to eight hours effectively communicated label recommendations but did not alter tampon wear times. The informational intervention had limited impact on established habits. PMID:26688668

  14. Surface roughness and wear of resin cements after toothbrush abrasion.

    PubMed

    Ishikiriama, Sérgio Kiyoshi; Ordoñéz-Aguilera, Juan Fernando; Maenosono, Rafael Massunari; Volú, Fernanda Lessa Amaral; Mondelli, Rafael Francisco Lia

    2015-01-01

    Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm) were fabricated according to manufacturer instructions for each group (n = 10): Nexus 3, Kerr (NX3); RelyX ARC, 3M ESPE (ARC); RelyX U100, 3M ESPE (U100); and Variolink II, Ivoclar/Vivadent (VL2). Initial roughness (Ra, µm) was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles), and further evaluation was conducted for final roughness. Vertical wear (µm) was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey's test (p < 0.05). The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05). The mean values of initial/final roughness (Ra, µm)/wear (µm) were as follows: NX3 (0.078/0.127/23.175); ARC (0.086/0.246/20.263); U100 (0.296/0.589/16.952); and VL2 (0.313/0.512/22.876). Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations. PMID:25466330

  15. 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.

  16. Alternate paddle configuration for improved wear resistance in the saltstone mixer

    SciTech Connect

    Reigel, M.; Fowley, M.

    2013-09-23

    The Saltstone Production Facility has a 10-inch Readco-Kurimoto continuous mixer that mixes the premix dry feeds and low-level waste salt solution to make fresh (uncured) saltstone. Inspection of the mixer in January 2013 showed significant wear on the third, fourth and fifth paddle pairs after the conveying augers. A 2-inch Readco-Kurimoto continuous mixer was used to test alternate paddle configurations for use in the 10-inch mixer to decrease the wear rate on the paddles. Two wear tests were conducted to investigate a method of reducing wear on the mixer paddles. The first test (wear test 2a) had a paddle configuration similar to the currently installed 10-inch mixer in the SPF. This test established baseline wear. The second test (wear test 2b) had a reconfigured paddle arrangement that replaced the flat paddles with helical paddles for paddle pairs 2 - 6 and aligned paddle pair 1 with the augers. The intent of the reconfiguration was to more effectively convey the partially wetted dry feeds through the transition region and into the liquid feed where paddle wear is reduced due to dry feeds and salt solution being mixed at the intended water to premix ratio. The design of the helical paddles provides conveyance through the transition region to the liquid feed inlet. The alignment with the auger is aimed to provide a smoother transition (minimizing the discontinuity between the auger and paddle pair 1) into the downstream paddles. A soft metal with low wear resistance (6000 series aluminum) was used for the wear testing paddles to determine wear patterns while minimizing run time and maximizing wear rate. For the two paddle configurations tested using the scaled 2-inch Readco-Kurimoto continuous mixer, with the first six paddles after the augers replaced by the wear paddles and the remaining paddles were stainless steel. Since the 10-inch SPF mixer is designed with the liquid inlet centered over paddle pairs 5 and 6, the scaled 2-inch mixer was configured the

  17. RPP-WPT Slurry Wear Evaluation: Literature Review

    SciTech Connect

    Duignan, M.R.

    2001-06-12

    Tests are planned to measure the wear rates in scaled flow loops that represent full-scale systems in Pretreatment sections of the Waste Treatment Plant to be built as part of the Department of Energy (DOE) River Protection Project. Those tests are to be done in the Experimental Thermal Fluids Laboratory of the Savannah River Technology Center at the DOE Savannah River Site.

  18. Wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    2000-04-01

    High interfacial stresses and coating failure are expected when a hard coating protects a more-compliant substrate in applications involving high-stress wear contact. Assuming that small differences in stiffness (or modulus) between the coating and substrate are required for a wear-resistant coating in such applications, four approaches have been taken to develop such coatings for cobalt-base alloys. Hardness, scratch adhesion, and nano-indentation testing identified the most promising candidates for cobalt-base alloys: A thin coating with hard Cr{sub 2}N and less-stiff Cr-N(ss) layers; a thick, four-layered coating with a 4{mu}m inner layer of Cr-N(ss)/ 1 {mu}m layer of Cr{sub 2}N/4 {micro}m layer of Cr-N(ss)/1 {micro} outer layer of Cr{sub 2}N; a duplex approach of ion nitriding to harden the subsurface,followed by application of a dual-layered Cr{sub 2}N/Cr-N(ss) coating; and ion nitriding alone. The low scratch adhesion values and high modulus/hardness values indicate that ZrN, TiN, and plasma carburized coatings represent less beneficial approaches. Two different cobalt-base alloys were studied in this work: Haynes 25 and Stellite 3 (Stoody Deloro Stellite). Based on weight change, profilometry measurements, and metallographic and SEM examinations after four-ball wear testing, the thin Cr{sub 2}N/CrN(ss) coated coupons exhibited a significantly lower wear rate than the uncoated Haynes 25 coupons. Of greater importance, the thin Cr{sub 2}N/Cr-N(ss) coatings were adherent on the Stellite 3 intermediate balls and Haynes 25 cups, and prevented the wear of the cobalt-base substrate. based on these results, the thin Cr{sub 2}N/Cr-N(ss) coating was the best coating candidate, and this coating could result in a reduced wear rate and less cobalt wear debris. The ion nitrided coupons exhibited slightly higher wear than the thin Cr{sub 2}N/Cr-N(ss) coated coupons, while the wear of the thin duplex coated coupons was the highest. However, the nitride layer was adherent

  19. Structurally Integrated Coatings for Wear and Corrosion

    SciTech Connect

    Beardsley, M. Brad; Sebright, Jason L.

    2008-11-18

    techniques, balanced with overall materials performance. State-of-the-art design and simulation capabilities were used to guide materials and process refinement. Caterpillar was the lead of the multi-partner collaborative project. Specific tasks were performed by the partners base on their unique capabilities. The project team was selected to include leaders in the field of material development, processing, modeling, and material characterization. Specifically, industrial members include the suppliers Deloro Stellite and Powder Alloy Corporation., who provided the experimental alloys and who aided in the development of the costs for the alloys, the Missouri University of Science and Technology and Iowa State University, who provided help in the alloy development and material characterization, QuesTek Innovations, a small company specializing the microstructural modeling of materials, and the DOE laboratories, Oak Ridge National Laboratory and National Energy Technology Laboratory (Albany), who provided unique coating process capability and wear characterization testing. The technologies developed in this program are expected to yield energy savings of about 50% over existing technologies, or 110 trillion BTUs per year by 2020 when fully implemented. Primary applications by Caterpillar are to replace the surface of machine components which are currently carburized and heat treated with new cladding materials with double the wear life. The new cladding technologies will consume less energy than carburizing. Thus, nearly 50% energy savings can be expected as a result from elimination of the heat treat process and the reduce wear of the materials. Additionally, when technologies from this project are applied on titanium or other non-ferrous substrates to make lighter weight, more wear resistant, and more efficient structures, significant fuel savings can be realized. With the anticipated drastic reduction in cost for refining titanium-containing ores, the usage of titanium

  20. Wear and hardness of different core build-up materials.

    PubMed

    Schmage, Petra; Nergiz, Ibrahim; Sito, Fekry; Platzer, Ursula; Rosentritt, Martin

    2009-10-01

    Before crown preparation, teeth with extensive coronal destructions are built up with core materials. Sometimes, these build ups are exposed to the oral environment without the protection of crowns. Therefore, this in vitro investigation was aimed at evaluating the wear, surface roughness, Vickers hardness, and surface structure of 10 core composites, two glass ionomer cements (GICs), and four posterior restoration composites. The three-body wear was tested after water storage and 2,00,000 cycles. We measured both surface roughness and Vickers hardness (DIN 50133) and evaluated the surface structures by scanning electron microscopy. Results were statistically analyzed by use of the Mann-Whitney U test (alpha = 0.05). Lowest wear was found for the restorative composites (20 microm Grandio; others about 40 microm). A comparison of the composites Build-It, Chroma Core, Rebilda LC, and Rebilda DC to Quixfil showed similar wear values for each material (43-50 microm). Wear values of GICs and all others core composites ranged between 58 and 75 microm. Only Ti-Core showed significantly higher wear than all other materials (p < 0.05). All core materials except Ti-Core (35 HV) showed Vickers hardness values between 42 and 61 HV. Most core composites, particularly Build-It, Multicore Flow, Rebilda LC, Ecusit, and Tetric Evo Ceram, showed more homogenous surface structures compared to GICs and restorative composites. Therefore, wear values of core build-up materials not only differed widely but were higher than those of conventional restorative materials; yet, core build-up materials showed advantageous surface structures.

  1. Wear studies of materials for tubes and anti-vibration bars in nuclear steam generators

    SciTech Connect

    Ko, P.L.; Taponat, M.C.; Zbinden, M.

    1995-12-01

    Wear occurs as a result of relative motion at the interface of two contacting bodies. In nuclear power steam generators, high flow rates can induce vibration of the tubes resulting in wear damage due to impact and sliding contacts between the tubes and their supports. A research project aiming to gain better understanding of the mechanisms and mechanics involved in vibratory wear and to develop a more versatile predictive wear model was carried out. Combinations of Inconel tubes against flat anti-vibration bars of 403 s.s. and electrolytic chrome plated Inconel 600 were tested under conditions of reciprocating sliding and impacting in water at room temperature and at 250 C. The results show that depending on the material combinations and the loading conditions distinctively different wear mechanisms and often drastically different wear rates can occur.

  2. Effects of Temperature on the Hardness and Wear Resistance of High-Tungsten Stellite Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Rong; Wu, X. J.; Kapoor, Samit; Yao, M. X.; Collier, Rachel

    2015-02-01

    In this research, two new Stellite alloys containing high tungsten are developed for wear resistance application owing to the distinct beneficial effects of tungsten in Stellite alloys. The microstructures of these alloys are analyzed using a scanning electron microscope (SEM) with an EDAX energy dispersive X-ray (EDX) spectroscopy system and X-ray diffraction spectrum. The micro-hardness and wear resistance of the alloys at room temperature and at elevated temperatures are investigated utilizing a Microhardness Tester Unit, with a Hot Stage, and a Hot Pin-on-Disk Tribometer, respectively. The wear test results of these alloys are compared with those of commercial wear-resistant Stellite 3 and Stellite 12. The worn surfaces of the specimens are analyzed using SEM/EDX to explore the wear mechanisms of these alloys with temperature change. The variations of hardness and wear resistance of these alloys with temperature are studied and discussed.

  3. An Experimental Investigation of the Influence of the Lubricant Viscosity and Additives on Gear Wear

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.; Kahraman, Ahmet

    2005-01-01

    The influence of lubricant viscosity and additives on the average wear rate of spur gear pairs was investigated experimentally. The gear specimens of a comprehensive gear durability test program that made use of seven lubricants covering a range of viscosities were examined to measure gear tooth wear. The measured wear was related to the as-manufactured surface roughness, the elastohydrodynamic film thickness, and the experimentally determined contact fatigue lives of the same specimens. In general, the wear rate was found to be inversely proportional to the viscosity of the lubricant and to the lambda ratio (also sometimes called the specific film thickness). The data also show an exponential trend between the average wear rates and the surface fatigue lives. Lubricants with similar viscosities but differing additives and compositions had somewhat differing gear surface fatigue lives and wear rates.

  4. Wear studies of materials for tubes and antivibration bars in nuclear steam generators

    SciTech Connect

    Ko, P.L.; Taponat, M.C.; Zbinden, M.

    1996-08-01

    Wear occurs as a result of relative motion at the interface of two contacting bodies. In nuclear power steam generators, high flow rates can induce vibration of the tubes resulting in wear damage due to impact and sliding contacts between the tubes and their supports. A research project aiming to gain better understanding of the mechanisms and mechanics involved in vibratory wear and to develop a more versatile predictive wear model was carried out. Combinations of Inconel tubes against flat antivibration bars of 403 SS and electrolytic-chrome plated Inconel 600 were tested under conditions of reciprocating sliding and impacting in water at room temperature and at 250 C. The results show that, depending on the material combinations and the loading conditions, distinctively different wear mechanisms and often drastically different wear rates can occur.

  5. REDUCED ENGINE FRICTION AND WEAR

    SciTech Connect

    Ron Matthews

    2005-05-01

    This Final Technical Report discusses the progress was made on the experimental and numerical tasks over the duration of this project regarding a new technique for decreasing engine friction and wear via liner rotation. The experimental subtasks involved quantifying the reduction in engine friction for a prototype rotating liner engine relative to a comparable baseline engine. Both engine were single cylinder conversions of nominally identical production four-cylinder engines. Hot motoring tests were conducted initially and revealed that liner rotation decreased engine friction by 20% under motoring conditions. A well-established model was used to estimate that liner rotation should decrease the friction of a four-cylinder engine by 40% under hot motoring conditions. Hot motoring tear-down tests revealed that the crankshaft and valve train frictional losses were essentially the same for the two engines, as expected. However, the rotating liner engine had much lower (>70%) piston assembly friction compared to the conventional engine. Finally, we used the Instantaneous IMEP method to compare the crank-angle resolved piston assembly friction for the two engines. Under hot motoring conditions, these measurements revealed a significant reduction in piston assembly friction, especially in the vicinity of compression TDC when the lubrication regime transitions from hydrodynamic through mixed and into boundary friction. We have some remaining problems with these measurements that we expect to solve during the next few weeks. We will then perform these measurements under firing conditions. We also proposed to improve the state-of-the-art of numerical modeling of piston assembly friction for conventional engines and then to extend this model to rotating liner engines. Our research team first modeled a single ring in the Purdue ring-liner test rig. Our model showed good agreement with the test rig data for a range of speeds and loads. We then modeled a complete piston

  6. Abrasive wear by coal-fueled diesel engine and related particles

    SciTech Connect

    Ives, L.K. )

    1992-09-01

    The development of commercially viable diesel engines that operate directly on pulverized coal-fuels will require solution to the problem of severe abrasive wear. The purpose of the work described in this report was to investigate the nature of the abrasive wear problem. Analytical studies were carried out to determine the characteristics of the coal-fuel and associated combustion particles responsible for abrasion. Laboratory pinon-disk wear tests were conducted on oil-particle mixtures to determine the relationship between wear rate and a number of different particle characteristics, contact parameters, specimen materials properties, and other relevant variables.

  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. 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

  9. Comparative gravimetric wear analysis in mobile versus fixed-bearing posterior stabilized total knee prostheses.

    PubMed

    Delport, Hendrik P; Sloten, Jos Vander; Bellemans, Johan

    2010-06-01

    Polyethylene (PE) wear is the limiting factor for the longevity of a conventional total knee arthroplasty (TKA). Excessive wear leads to loosening and eventual implant failure. The aim of our in vitro study was to investigate wear of a PE tibial insert on a rotating platform as compared to the same insert fixed to the tibial baseplate and articulating with a similar femoral component. All tests were performed at Endolab Laboratories, Rosenheim, Germany using a knee joint simulator following ISO 14243-1. Three specific configurations were tested and compared to a loaded soak control: (1) the rotating platform using machined polyethylene (PE), (2) fixed bearing using machined PE, (3) fixed bearing using compression-moulded PE. Calf serum with a high protein concentration of 30 g/l was chosen as test lubricant. PE wear was measured gravimetrically using the ISO 14243-2 protocol. The total wear rates found for all systems tested were low. The mean wear rate was 1.40 mg per million cycles for the moulded fixed bearing, 4.07 mg per million cycles for the machined fixed bearing type and 0.82 mg per million cycles for the machined rotating platform bearing type. We conclude that the TKA system we tested (Performance, Biomet, Warsaw, IND, USA) demonstrated very low gravimetric wear. The wear rate of the same implant in the fixed mode compared to the rotating platform mode was four times higher.

  10. Anti-wear properties of Cr C and Ni Co alloy coatings as substitutes for conventional nanocrystalline Cr coatings

    NASA Astrophysics Data System (ADS)

    Zeng, Zhixiang; Zhang, Junyan

    2008-09-01

    Nanocrystalline Ni-Co, amorphous Cr-C alloy and nanocrystalline Cr-C coatings were electrodeposited from 'environmentally acceptable' electrolytes as potential substitutes for conventional nanocrystalline Cr coatings electrodeposited from noxious hexavalent chromium. The structure, morphology and hardness of coatings are investigated using a transmission electron microscope, a scanning electronic microscope and a Vickers hardness tester, respectively. Anti-wear properties are tested on a pin-on-plate vibrant wear tester. The correlation between the wear resistance, hardness, brittleness and the lubricated state is investigated. The results show that the wear behaviour of specimens significantly depends on their lubricated state, hardness and brittleness. Under the lubricated sliding condition, abrasive wear is the primary wear mechanism for all specimens. With respect to the abrasive wear mechanism, both the elastic and plastic deformations play important roles during the lubricated sliding process. Thus, the amorphous and nanocrystalline Cr-C alloy coatings, with both high brittleness and high hardness, exhibit a lower wear rate than the conventional Cr and Ni-Co coatings. On the other hand, under the dry sliding condition, the annealed Ni-Co coating, with an excellent compromise between high hardness and toughness, exhibits an abrasive wear mechanism and a relatively low wear rate; in contrast, the brittle Cr-matrix coatings exhibit a severe fatigue/delamination wear mechanism and high wear rate.

  11. 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.

  12. Sliding Wear Response of Beryl Reinforced Aluminum Composite - A Factorial Design Approach

    NASA Astrophysics Data System (ADS)

    Bharat, V.; Durga Prasad, B.; Prabhakar, M. Bhovi; Venkateswarlu, K.

    2016-02-01

    Al-Beryl MMCs were successfully fabricated using powder metallurgy route. Processing conditions such as beryl content and particle size were varied and its influence on dry sliding wear response was studied. Effect of test parameters like applied load and sliding distance on wear performance of Al-Beryl MMCs were discussed detail. Sliding wear tests were conducted using a pin on disc machine based on the 24 (4 factors at 2 levels) factorial design. Analysis of variance (ANOVA) was performed to obtain the contribution of control parameters on wear rate. The present study shows that wear resistance of Al-beryl MMCs not only depends on the beryl content but also influenced by normal load, sliding distance and particle size. The results show that most significant variables affecting wear rate of Al - beryl MMCs are size of the beryl particles (22%), beryl content (19.60%), sliding distance (18.47%), and normal load (10.30%). The interaction effects of these parameters are less significant in influencing wear rate compared to the individual parameters. The correlation between sliding wear and its parameters was obtained by multiple regression analysis. Regression model developed in the present study can be successfully implemented to predict the wear response of Al-Beryl MMCs.

  13. A comparative wear study on Al-Li and Al-Li/SiC composite

    SciTech Connect

    Okumus, S. Cem Karslioglu, Ramazan Akbulut, Hatem

    2013-12-16

    Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al{sub 2}O{sub 3} ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms{sup −1} and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

  14. A comparative wear study on Al-Li and Al-Li/SiC composite

    NASA Astrophysics Data System (ADS)

    Okumus, S. Cem; Karslioglu, Ramazan; Akbulut, Hatem

    2013-12-01

    Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al2O3 ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms-1 and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

  15. Study on quantitative relation between characteristics of striature bionic coupling unit and wear resistance of gray cast iron

    NASA Astrophysics Data System (ADS)

    Pang, Zuobo; Zhou, Hong; Zhang, Peng; Cong, Dalong; Meng, Chao; Wang, Chuanwei; Ren, Luquan

    2015-03-01

    In order to improve the wear resistance of gray cast iron guide rail, striature bionic coupling units of different characteristics were manufactured by laser surface remelting. Wear behavior of gray cast iron with striature bionic coupling units has been studied under dry sliding condition at room temperature using a homemade linear reciprocating wear testing machine. The wear resistance was evaluated by means of weight loss measurement and wear morphology. The results indicated that there is a relationship between weight loss and the area of striature bionic coupling units and α: Δm = Δm0 - 0.0212S × cos α - 0.0241S × sin α.

  16. 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.

  17. Wear of tillage tools coated by thermoplastic coatings

    NASA Astrophysics Data System (ADS)

    Ali, Waheed Y.; Ezzat, Fawzy M. H.

    1994-04-01

    Experiments were carried out to investigate the abrasive wear of tillage tools caused by soil. Low-carbon steel and hardened steel specimens as well as specimens coated by thermoplastic composites were tested. Silicon oxide (SiO2), aluminium oxide (Al2O3), iron, copper and glass fibre were used as filling materials in polyamide (PA6) and polyethylene (PE) coatings. Low-carbon steel was used as substrate. An abrasive wear tester was constructed to simulate the operation of real tillage tools. The relative motion between the test specimens and soil was controlled. PA6 showed promising results, especially if both the concentration and grain size of the additives were carefully selected. The addition of iron and Al2O3 powders to PA6 showed a considerable mitigation in the wear process if their concentrations were controlled to a certain limit.

  18. Wear resistance of experimental titanium alloys for dental applications.

    PubMed

    Faria, Adriana Cláudia Lapria; Rodrigues, Renata Cristina Silveira; Claro, Ana Paula Rosifini Alves; da Gloria Chiarello de Mattos, Maria; Ribeiro, Ricardo Faria

    2011-11-01

    The present study evaluated microstructure, microhardness and wear resistance of experimental titanium alloys containing zirconium and tantalum. Alloys were melted in arc melting furnace according to the following compositions: Ti-5Zr, Ti-5Ta and Ti-5Ta-5Zr (%wt). Hemispheres and disks were obtained from wax patterns that were invested and cast by plasma. Microstructures were evaluated using optical microscopy and X-ray diffraction (XRD) analysis and also Vickers microhardness was measured. Hemispherical samples and disks were used for 2-body wear tests, performed by repeated grinding of the samples. Wear resistance was assessed as height loss after 40,000 cycles. The data were compared using ANOVA and post-hoc Tukey test. Ti-5Zr presented a Widmanstätten structure and the identified phases were α and α' while Ti-5Ta and Ti-5Ta-5Zr presented α, β, α' and α" phases, but the former presented a lamellar structure, and the other, acicular. The microhardness of Ti-5Zr was significantly greater than other materials and cp Ti presented wear resistance significantly lower than experimental alloys. It was concluded that wear resistance was improved when adding Ta and Zr to titanium and Zr increased microhardness of Ti-5Zr alloy.

  19. Wear of nanofilled dental composites at varying filler concentrations.

    PubMed

    Lawson, Nathaniel C; Burgess, John O

    2015-02-01

    The aim of this study is to examine the effects of nanofiller concentration on the mechanisms of wear of a dental composite. Nanofilled composites were fabricated with a bisphenol A glycidyl methacrylate polymer and 40 nm SiO2 filler particles at three filler loads (25, 50, and 65 wt %). The elastic modulus, flexural strength, and hardness of the composites and the unfilled resin were measured. The materials (n = 8) were tested in the modified wear testing device at 50,000, 100,000, and 200,000 cycles with 20N force at 1 Hz. A 33% glycerine lubricant and stainless steel antagonist were used. The worn composite and antagonist surfaces were analyzed with noncontact profilometry and SEM. The volumetric wear data indicated that there are significant differences between filler concentrations and cycles (p < 0.05). A trend was noted that increasing filler content beyond 25% decreased the wear resistance of the composites. Increasing filler content increased hardness and modulus and increased flexural strength up to 50% fill. SEM evaluation of the worn specimens indicated that the resin and 25% filled materials exhibited cracking and failed by fatigue and the 50 and 65% filled materials exhibited microcutting and failed by abrasive wear. Based on the results of this study, composite manufacturers are recommended to use a filler concentration between 25 and 50% when using nanosized filler particles.

  20. Investigation of the time-dependent wear behavior of veneering ceramic in porcelain fused to metal crowns during chewing simulations.

    PubMed

    Guo, Jiawen; Tian, Beimin; Wei, Ran; Wang, Weiguo; Zhang, Hongyun; Wu, Xiaohong; He, Lin; Zhang, Shaofeng

    2014-12-01

    The excessive abrasion of occlusal surfaces in ceramic crowns limits the service life of restorations and their clinical results. However, little is known about the time-dependent wear behavior of ceramic restorations during the chewing process. The aim of this in vitro study was to investigate the dynamic evolution of the wear behavior of veneering porcelain in PFM crowns as wear progressed, as tested in a chewing simulator. Twenty anatomical metal-ceramic crowns were prepared using Ceramco III as the veneering porcelain. Stainless steel balls served as antagonists. The specimens were dynamically loaded in a chewing simulator with 350N up to 2.4×10(6) loading cycles, with additional thermal cycling between 5 and 55°C. During the testing, several checkpoints were applied to measure the substance loss of the crowns' occlusal surfaces and to evaluate the microstructure of the worn areas. After 2.4×10(6) cycles, the entire wear process of the veneering porcelain in the PFM crowns revealed three wear stages (running-in, steady and severe wear stages). The occlusal surfaces showed traces of intensive wear on the worn areas during the running-in wear stage, and they exhibited the propagation of cracks in the subsurface during steady wear stage. When the severe wear stage was reached, the cracks penetrated the ceramic layer, causing the separation of porcelain pieces. It also exhibited a good correlation among the microstructure, the wear loss and the wear rate of worn ceramic restorations. The results suggest that under the conditions of simulated masticatory movement, the wear performance of the veneering porcelain in PFM crowns indicates the apparent similarity of the tribological characteristics of the traditional mechanical system. Additionally, the evaluation of the wear behavior of ceramic restorations should be based on these three wear stages. PMID:25194522

  1. Investigation of the time-dependent wear behavior of veneering ceramic in porcelain fused to metal crowns during chewing simulations.

    PubMed

    Guo, Jiawen; Tian, Beimin; Wei, Ran; Wang, Weiguo; Zhang, Hongyun; Wu, Xiaohong; He, Lin; Zhang, Shaofeng

    2014-12-01

    The excessive abrasion of occlusal surfaces in ceramic crowns limits the service life of restorations and their clinical results. However, little is known about the time-dependent wear behavior of ceramic restorations during the chewing process. The aim of this in vitro study was to investigate the dynamic evolution of the wear behavior of veneering porcelain in PFM crowns as wear progressed, as tested in a chewing simulator. Twenty anatomical metal-ceramic crowns were prepared using Ceramco III as the veneering porcelain. Stainless steel balls served as antagonists. The specimens were dynamically loaded in a chewing simulator with 350N up to 2.4×10(6) loading cycles, with additional thermal cycling between 5 and 55°C. During the testing, several checkpoints were applied to measure the substance loss of the crowns' occlusal surfaces and to evaluate the microstructure of the worn areas. After 2.4×10(6) cycles, the entire wear process of the veneering porcelain in the PFM crowns revealed three wear stages (running-in, steady and severe wear stages). The occlusal surfaces showed traces of intensive wear on the worn areas during the running-in wear stage, and they exhibited the propagation of cracks in the subsurface during steady wear stage. When the severe wear stage was reached, the cracks penetrated the ceramic layer, causing the separation of porcelain pieces. It also exhibited a good correlation among the microstructure, the wear loss and the wear rate of worn ceramic restorations. The results suggest that under the conditions of simulated masticatory movement, the wear performance of the veneering porcelain in PFM crowns indicates the apparent similarity of the tribological characteristics of the traditional mechanical system. Additionally, the evaluation of the wear behavior of ceramic restorations should be based on these three wear stages.

  2. Critical length scale controls adhesive wear mechanisms.

    PubMed

    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

  3. 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

  4. Critical length scale controls adhesive wear mechanisms

    NASA Astrophysics Data System (ADS)

    Aghababaei, Ramin; Warner, Derek H.; Molinari, Jean-Francois

    2016-06-01

    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.

  5. Investigation of machining damage and tool wear resulting from drilling powder metal aluminum alloy

    SciTech Connect

    Fell, H.A.

    1997-05-01

    This report documents the cutting of aluminum powder metallurgy (PM) parts for the North Carolina Manufacturing Extension Partnership. The parts, an aluminum powder metal formulation, were supplied by Sinter Metals Inc., of Conover, North Carolina. The intended use of the alloy is for automotive components. Machining tests were conducted at Y-12 in the machine shop of the Skills Demonstration Center in Building 9737. Testing was done on June 2 and June 3, 1997. The powder metal alloy tested is very abrasive and tends to wear craters and produce erosion effects on the chip washed face of the drills used. It also resulted in huge amounts of flank wear and degraded performance on the part of most drills. Anti-wear coatings on drills seemed to have an effect. Drills with the coating showed less wear for the same amount of cutting. The usefulness of coolants and lubricants in reducing tool wear and chipping/breakout was not investigated.

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

    SciTech Connect

    Mickalonis, J.; Torres, R.

    2012-08-15

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

  7. Abrasive wear behavior of heat-treated ABC-silicon carbide

    SciTech Connect

    Zhang, Xiao Feng; Lee, Gun Y.; Chen, Da; Ritchie, Robert O.; De Jonghe, Lutgard C.

    2002-06-17

    Hot-pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC-SiC), was subjected to three-body and two-body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC-SiC, with suitable heat treatment, was superior to that of commercial SiC.

  8. Profiling the third-body wear damage produced in CoCr surfaces by bone cement, CoCr, and Ti6Al4V debris: a 10-cycle metal-on-metal simulator test.

    PubMed

    Halim, Thomas; Burgett, Michelle; Donaldson, Thomas K; Savisaar, Christina; Bowsher, John; Clarke, Ian C

    2014-07-01

    Particles of bone cement (polymethyl methacrylate), CoCr and Ti6Al4V were compared for their abrasion potential against CoCr substrates. This appears to be the first study utilizing CoCr and Ti6Al4V particulates to abrade CoCr bearings and the first study profiling the morphology of third-body abrasive wear scratches in a hip simulator. The 5 mg debris allotments (median size range 140-300 µm) were added to cups mounted both inverted and anatomically with metal-on-metal (MOM) bearings in a 10-cycle, hip simulator test. Surface abrasion was characterized by roughness indices and scratch profiles. Compared to third-body abrasion with metal debris, polymethyl methacrylate debris had minimal effect on the CoCr surfaces. In all, 10 cycles of abrasion with metal debris demonstrated that roughness indices (Ra, PV) increased approximately 20-fold from the unworn condition. The scratch profiles ranged 20-108 µm wide and 0.5-2.8 µm deep. The scratch aspect ratio (W/PV) averaged 0.03, and this very low ratio indicated that the 140 µm CoCr beads had plastically deformed to create wide but shallow scratches. There was no evidence of transfer of CoCr beads to CoCr bearings. The Ti64 particles produced similar scratch morphology with the same aspect ratio as the CoCr particulates. However, the titanium particulates also showed a unique ability to flatten and adhere to the CoCr, forming smears and islands of contaminating metal on the CoCr bearings. The morphology of scratches and metal transfer produced by these large metal particulates in the simulator appeared identical to those reported on retrieved metal-on-metal bearings.

  9. Ignition of a Combustible Atmosphere by Incandescent Carbon Wear Particles

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.; Swikert, Max A.; Johnson, Robert L.

    1960-01-01

    A study was made to determine whether carbon wear particles from carbon elements in sliding contact with a metal surface were sufficiently hot to cause ignition of a combustible atmosphere. In some machinery, electric potential differences and currents may appear at the carbon-metal interface. For this reason the effect of these voltages and currents on the ability of carbon wear particles to cause ignition was evaluated. The test specimens used in the investigation were carbon vanes taken from a fuel pump and flat 21-inch-diameter 2 metal disks (440-C stainless steel) representing the pump housing. During each experiment a vane was loaded against a disk with a 0.5-pound force, and the disk was rotated to give a surface speed of 3140 feet per minute. The chamber of the apparatus that housed the vane and the disk was filled with a combustible mixture of air and propane. Various voltages and amperages were applied across the vane-disk interface. Experiments were conducted at temperatures of 75, 350, 400, and 450 F. Fires were produced by incandescent carbon wear particles obtained at conditions of electric potential as low as 106 volts and 0.3 ampere at 400 F. Ignitions were obtained only with carbon wear particles produced with an electric potential across the carbon-vane-disk interface. No ignitions were obtained with carbon wear particles produced in the absence of this potential; also, the potential difference produced no ignitions in the absence of carbon wear particles. A film supplement showing ignition by incandescent wear particles is available.

  10. 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.

  11. 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

  12. 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. PMID:27651887

  13. 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.

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

    NASA Astrophysics Data System (ADS)

    Paniogue, Tanille J.

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

  15. Erosive Tooth Wear and Related Risk Factors in 8- and 14-Year-Old Greek Children.

    PubMed

    Provatenou, Efthymia; Kaklamanos, Eleftherios G; Kevrekidou, Aikaterini; Kosma, Ismini; Kotsanos, Nikolaos

    2016-01-01

    The aim of the present study was to investigate the erosive tooth wear of primary and permanent teeth and its association with related risk factors. Two groups of Greek children aged 8 (n = 329) and 14 years (n = 263) were examined in the classroom using the Basic Erosive Wear Examination (BEWE) index. Data concerning risk factors were collected using questionnaires. Dental caries (DMFS/dmfs) was also recorded. The data were analyzed using the t test, one-way ANOVA, multiple regression analysis, Fisher's exact test, and the χ2 test. In the 8-year-olds, the primary teeth showed a predominantly medium level of wear and the permanent teeth no wear. A majority of the 14-year-olds exhibited low risk levels of wear. The most frequently affected dental surface in both age groups was the occlusal surface of the mandibular posterior teeth. In the 8-year-olds, BEWE scores and the prevalence of wear in the primary teeth was influenced by gender (p = 0.020). In their permanent teeth, soft drink consumption (p < 0.0001) and preference for lemon/vinegar (p = 0.041) significantly affected wear prevalence and BEWE scores, while habitually retaining soft drinks in the mouth influenced wear prevalence (p = 0.008), risk (p = 0.004), and BEWE scores (p = 0.022). In the 14-year-olds, wear prevalence was significantly affected by the consumption of lemon-flavored candies (p = 0.016) and soft drinks (p = 0.050). BEWE scores were significantly affected by gender (p = 0.022) and soft drink consumption (p = 0.030). Gender influenced tooth wear risk in both age groups (p = 0.010 and p = 0.021, respectively). The results of this study indicate that erosive tooth wear differed between primary and permanent teeth and was influenced by gender and dietary factors. PMID:27286713

  16. Wear patterns of, and wear volume formulae for, cylindrically elongated acetabular cup liners.

    PubMed

    Wu, James Shih-Shyn; Hsu, Shu-Ling; Chen, Jian-Horng

    2010-07-01

    This study analyzed the wear patterns of, and wear volume formulae for, cylindrically elongated acetabular cup liners. The geometric patterns of the wear surface were first classified, then wear volume formulae were derived by integral calculus. SolidWorks((R)) software or published formulae were used to verify the accuracy of the proposed formulae. The analytical results showed that the wear shape of the liner can be categorized into seven wear patterns, including the special case of wear at 90 degrees , and the seven corresponding wear formulae were derived. In addition, wear of the cylindrical elongation might add considerably to the volume loss of the liner, depending on the height and shape of the elongation and the depth and direction of the linear penetration, being maximally 21% in the investigated model. The proposed wear formulae and patterns will be useful for more accurate performance evaluation of existing hip components implanted in patients and for the designing of new hip components.

  17. 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.

  18. Metal nitride coatings by physical vapor deposition (PVD) for a wear resistant aluminum extrusion die.

    PubMed

    Lee, Su Young; Kim, Sang Ho

    2014-12-01

    The purpose of this study is to investigate the friction and wear behaviors of CrN, TiN, CrAlN, and TiAIN coated onto SKD61 for application to Al 7000 series extrusion dies. On the wear test, the experimental parameters are the load and the counter material's temperature. The results showed that the friction coefficient increased with load but decreased with the counter material's temperature, and the friction coefficients of CrN and CrAIN were lower than the friction coefficients of TiAIN and TIN, especially at a higher temperature. The wear track with different coatings identified different wear behaviors; the wear behavior of CrAIN was found to be abrasive, but the wear behavior of TiN, CrN, and TiAIN was adhesive. Therefore, CrAIN showed the least wear loss with a lower friction coefficient and less adhesion with counter materials at the highest range of wear load and temperature. This resulted in the easy formation of aluminum oxide in the wear track and less Al adhesion; moreover during the hard second phase, AIN dispersed in the film during deposition.

  19. Agave Chewing and Dental Wear: Evidence from Quids

    PubMed Central

    Hammerl, Emily E.; Baier, Melissa A.; Reinhard, Karl J.

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present. PMID:26230855

  20. Wear and related characteristics of an aircraft tire during braking

    NASA Technical Reports Server (NTRS)

    Mccarty, J. L.

    1972-01-01

    Wear and related characteristics of friction and temperature developed during braking of size 22 x 5.5, type aircraft tires are studied. The testing technique involved gearing the tire to a driving wheel of a ground vehicle to provide operations at constant slip ratios on asphalt, concrete, and slurry-seal surfaces. Data were obtained over the range of slip ratios generally attributed to an aircraft braking system during dry runway operations. The results show that the cumulative tire wear varies linearly with distance traveled and the wear rate increases with increasing slip ratio and is influenced by the runway-surface character. Differences in the wear rates associated with the various surfaces suggest that runways can be rated on the basis of tire wear. The results also show that the friction coefficients developed during fixed-slip-ratio operations are in good agreement with those obtained by other investigators during cyclic braking, in that the dry friction is insensitive to the tire tread temperature is shown to increase with increasing slip ratio and, at the higher ratios, to be greater during braking on asphalt and slurry seal than on concrete.

  1. Agave Chewing and Dental Wear: Evidence from Quids.

    PubMed

    Hammerl, Emily E; Baier, Melissa A; Reinhard, Karl J

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present. PMID:26230855

  2. Agave Chewing and Dental Wear: Evidence from Quids.

    PubMed

    Hammerl, Emily E; Baier, Melissa A; Reinhard, Karl J

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present.

  3. Modeling and Tool Wear in Routing of CFRP

    SciTech Connect

    Iliescu, D.; Fernandez, A.; Gutierrez-Orrantia, M. E.; Lopez de Lacalle, L. N.

    2011-01-17

    This paper presents the prediction and evaluation of feed force in routing of carbon composite material. In order to extend tool life and improve quality of the machined surface, a better understanding of uncoated and coated tool behaviors is required. This work describes (1) the optimization of the geometry of multiple teeth tools minimizing the tool wear and the feed force, (2) the optimization of tool coating and (3) the development of a phenomenological model between the feed force, the routing parameters and the tool wear. The experimental results indicate that the feed rate, the cutting speed and the tool wear are the most significant factors affecting the feed force. In the case of multiple teeth tools, a particular geometry with 14 teeth right helix right cut and 11 teeth left helix right cut gives the best results. A thick AlTiN coating or a diamond coating can dramatically improve the tool life while minimizing the axial force, roughness and delamination. A wear model has then been developed based on an abrasive behavior of the tool. The model links the feed rate to the tool geometry parameters (tool diameter), to the process parameters (feed rate, cutting speed and depth of cut) and to the wear. The model presented has been verified by experimental tests.

  4. Influence of low temperatures of friction and wear

    NASA Technical Reports Server (NTRS)

    Udovenko, V. F.; Presnyakova, G. N.

    1974-01-01

    A brief review of studies on low-temperature friction are briefly reviewed. A facility and technique for studying friction both in air and in vacuum at temperatures of +20 and -190 C is described. Results of a wear study of structural steels operating together with chromium steel are presented. It is shown that reduction of the test temperature in vacuum leads in certain cases to marked increase of the wear magnitude and friction coefficient. This is associated not only with the general change of the mechanical properties of the materials but also with the influence of temperature reduction on the hardening and structural formation taking place in the surface layers during friction.

  5. Wear and friction behavior of Zr implanted D3 steel

    SciTech Connect

    Akbas, N.; Saklakoglu, I.E.; Monteiro, O.R.; Brown, I.G.

    2001-08-23

    Multicharged, pure, high current and pulsed ion beams of Zr have been extracted from a metal vapor vacuum arc (MEVVA) source and implanted into AISI D3 (C: 2-2,35%, Mn: 0,60%, Si: 0,60%, Cr: 11-13,50%, Ni: 0,30%, W: 1%, V: 1%) tool steel samples at the 3,6.1016, 5.1016 and 1.1017 ions/cm2 doses. The wear resistance and friction coefficient have been estimated using pin-on-disc wear tests. Implantation of Zr decreased the wear loss and friction coefficient. RBS, AES and SEM Microprobe analyses were used as a guide for explanation of implantation's effects.

  6. Wear resistance of a metal surface modified with minerals

    NASA Astrophysics Data System (ADS)

    Kislov, S. V.; Kislov, V. G.; Balasch, P. V.; Skazochkin, A. V.; Bondarenko, G. G.; Tikhonov, A. N.

    2016-02-01

    The article describes the advantages of the new technology of mineral coating of metal products for the friction pair of mechanical systems. It presents the research results of the wear rate of the samples made of 12X13 steel (X12Cr13) with mineral layers, in the experiments with a piston ring sliding inside a cylinder liner with grease. The wear rate of the samples with mineral layers is lower almost by two factors than that of the samples made of grey foundry iron and untreated samples. As the result of slip/rolling abrasion tests of parts with mineral layers under conditions of high contact pressure, a suggestion was made concerning probable mechanics of surface wear.

  7. Temperature effect of friction and wear characteristics for solid lubricating graphite

    NASA Astrophysics Data System (ADS)

    Kim, Yeonwook; Kim, Jaehoon

    2015-03-01

    Graphite is one of the effective lubricant additives due to its excellent high-temperature endurance and self-lubricating properties. In this study, wear behavior of graphite used as sealing materials to cut off hot gas is evaluated at room and elevated temperature. Wear occurs on graphite seal due to the friction of driving shaft and graphite. Thus, a reciprocating wear test to evaluate the wear generated for the graphite by means of the relative motion between a shaft material and a graphite seal was carried out. The friction coefficient and specific wear rate for the changes of applied load and sliding speed were compared under different temperature conditions considering the actual operating environment. Through SEM observation of the worn surface, the lubricating film was observed and compared with test conditions.

  8. Hip prothesis: an in vitro wear protocol based on a comparison between gravimetric and profilometric analysis.

    PubMed

    Affatato, S; Tagliati, M; Toni, A

    1999-01-01

    Ultra high molecular weight polyethylene acetabular cups were analysed by means of a shadowgraph method (using a profile projector) to measure linear wear. The results were compared with those of previous wear tests performed on a hip joint simulator. Twelve polyethylene acetabular cups were analysed. The specimens were evaluated visually for evidence of polyethylene wear. Examination of the polyethylene inner surface did not reveal evidence of surface failure such as delamination, fatigue cracks or scratches. Volumetric wear was calculated using a formula based on dimensional change due to the penetration of the femoral head in the acetabular cup. It was found to be of the same order of magnitude as the wear obtained in in vitro experimental tests.

  9. Tribological investigations of the wear couple alumina-CFRP for total hip replacement.

    PubMed

    Früh, H J; Willmann, G

    1998-07-01

    Wear debris is the main reason for aseptic loosening in total hip. Most troublesome is the wear of polyethylene cups. Ceramic femoral heads were introduced about 20 years ago. The combination ceramic-on-polyethylene reduces the wear rate and the loosening rate. But cups of polyethylene are still the weakest link in a hip prosthesis. Carbon fibre reinforced plastic (CFRP) was proposed as an alternative for polyethylene. Various test were performed to study the combination metal-on-CFRP, zirconia-on-CFRP, and alumina-on-CFRP. The simulator tests showed that the wear rate of alumina-on-CFRP is in the order of 1-3 microm per year. Based on investigation of retrieved implants the wear rate is 6.3 microm per year. Based on these results the combination alumina femoral heads (Biolox-forte) and CFRP cups (Caproman) could be approved for total hip replacement.

  10. In vitro wear resistance, hardness and elastic modulus of artificial denture teeth.

    PubMed

    Suwannaroop, Pii; Chaijareenont, Pisaisit; Koottathape, Natthavoot; Takahashi, Hidekazu; Arksornnukit, Mansuang

    2011-01-01

    In this study, the wear resistance, hardness, elastic modulus, and the correlations between them of artificial denture teeth at the sub-enamel layer were examined. Four types of tested artificial denture teeth consisted of 3 conventional acrylic resin teeth (Cosmo HXL, Major Dent, and Yamahachi FX), 1 high cross-linked acrylic resin teeth (Trubyte Bioform IPN), 2 composite resin teeth (SR Orthosit PE, and Yamahachi PX), and 1 porcelain teeth (ACE Teeth). The two-body wear test was performed using a custom made pin on disc apparatus. Volume and weight loss were measured. Hardness and elastic modulus were also assessed by using a nanoindentation system. The results suggested wear resistance varied among the denture tooth materials. Wear resistance of high cross-linked acrylic resin teeth was the lowest. A definite relation between wear resistance and mechanical properties of materials could not be found in this study. PMID:21778606

  11. Does tooth wear influence ageing? A comparative study across large herbivores.

    PubMed

    Gaillard, Jean-Michel; Berger, Vérane; Tidière, Morgane; Duncan, Patrick; Lemaître, Jean-François

    2015-11-01

    We test whether the intensity of tooth wear influences the strength of actuarial senescence across species of large herbivores. We collected from the literature data on tooth wear in the wild (measured as the slope of the regression of log-transformed M1 crown height on age), longevity (measured as the age at which 90% of individuals are dead) and two metrics of actuarial senescence in captive populations (rate of senescence between 6 and 12 years of age and Gompertz rate of senescence). Between-species differences and variation in tooth height accounted for most of the observed variation in tooth wear among large herbivores: tooth height and tooth wear were positively correlated. In contrast, tooth wear was little influenced by sex, body mass, or taxonomy. No marked between-sex differences in longevity occurred. Males senesced faster than females when tooth wear was low (for both senescence metrics), while between-sex differences in actuarial senescence when tooth wear was high depended on the metric used to measure actuarial senescence. While longevity was mostly independent of the intensity of tooth wear, we found general support for a positive relationship between both measures of actuarial senescence and tooth wear. These patterns were consistent whether hypsodonty was controlled for or not. Although varying according to sex and to the metric used for assessing actuarial senescence, our findings suggest overall that tooth wear could be positively associated with actuarial senescence among large herbivores. Further longitudinal studies focusing on changes within individuals will be required to test whether a mechanistic link between tooth wear and actuarial senescence occurs in large herbivores.

  12. PMMA Third-Body Wear after Unicondylar Knee Arthroplasty Decuples the UHMWPE Wear Particle Generation In Vitro

    PubMed Central

    Paulus, Alexander Christoph; Franke, Manja; Kraxenberger, Michael; Schröder, Christian; Jansson, Volkmar

    2015-01-01

    Introduction. Overlooked polymethylmethacrylate after unicondylar knee arthroplasty can be a potential problem, since this might influence the generated wear particle size and morphology. The aim of this study was the analysis of polyethylene wear in a knee wear simulator for changes in size, morphology, and particle number after the addition of third-bodies. Material and Methods. Fixed bearing unicondylar knee prostheses (UKA) were tested in a knee simulator for 5.0 million cycles. Following bone particles were added for 1.5 million cycles, followed by 1.5 million cycles with PMMA particles. A particle analysis by scanning electron microscopy of the lubricant after the cycles was performed. Size and morphology of the generated wear were characterized. Further, the number of particles per 1 million cycles was calculated for each group. Results. The particles of all groups were similar in size and shape. The number of particles in the PMMA group showed 10-fold higher values than in the bone and control group (PMMA: 10.251 × 1012; bone: 1.145 × 1012; control: 1.804 × 1012). Conclusion. The addition of bone or PMMA particles in terms of a third-body wear results in no change of particle size and morphology. PMMA third-bodies generated tenfold elevated particle numbers. This could favor an early aseptic loosening. PMID:25866795

  13. Development of a self-lubricating plasma sprayed coating for rolling/sliding contact wear

    NASA Astrophysics Data System (ADS)

    Niebuhr, David Vernon

    The friction and wear that occurs between wheel and rail exacts millions of dollars out of maintenance budgets each year. Standard lubrication practices have been found to be unreliable in effectively lubricating curved track sections. Consequently, a method of reducing cost and increasing rail life is of significance to the railroad industry. Through the use of self-lubricating materials and thermal spray technology a composite surface coating was developed. A 1080 steel coating provided a wear-resistant matrix, in which to incorporate solid lubricants. The 1080 steel coating was found to provide increased wear resistance and some friction reduction (mu = 0.46 vs. mu = 0.5-0.7 for uncoated rail). The reduced wear stems from the coatings resistance to degenerate into severe wear modes. The wear rate of uncoated rail steel can be an order of magnitude greater than that of a 1080 steel coating. Three solid lubricant/steel coating systems were investigated; graphite incorporated into 1080 steel, copper incorporated into 1080 steel, and various polymers deposited over a 1080 steel coating. The structure of the coatings were evaluated by metallography and wear performance. Metallographic analysis included optical, SEM, and FIB. Polymer film analysis was performed with FTIR. Wear testing and friction measurement were accomplished with the Amsler twin disk wear testing machine. Coatings were tested against class C wheel steel at 5% and 35% slide/roll ratios, with contact pressures ranging from 700 to 1315 N/mmsp2. The work identified unique wear mechanisms for each coating system. The friction reduction and durability of the graphite/steel coatings was good at low slide/roll ratios. The copper/steel coatings were unable to control friction and had limited life. The polymer/steel coatings, particularly nylon/steel, had excellent performance at a wide range of slide/roll ratios and contact pressures. The nylon/1080 steel coatings were applied to rail sections for large

  14. 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.

  15. Coatings for wear and lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1978-01-01

    Recent advances in the tribological uses of rf-sputtered and ion plated films of solid film lubricants (laminar solids, soft metals, organic polymers) and wear resistant refractory compounds (carbides, nitrides, silicides) are reviewed. The sputtering and ion plating potentials and the corresponding coatings formed were evaluated relative to the friction coefficient, wear endurance life and mechanical properties. The tribological and mechanical properties for each kind of film are discussed in terms of film adherence, coherence, density, grain size, morphology, internal stresses, thickness, and substrate conditions such as temperature, topography, chemistry and dc-biasing. The ion plated metallic films in addition to improved tribological properties also have better mechanical properties such as tensile strength and fatigue life.

  16. 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.

  17. Impact wear behavior of human tooth enamel under simulated chewing conditions.

    PubMed

    Zheng, Jing; Zeng, Yangyang; Wen, Jian; Zheng, Liang; Zhou, Zhongrong

    2016-09-01

    Previous studies mostly focused on the sliding wear behavior of human teeth, and little effort has been made so far to study the impact wear of human teeth. The objective of this study was to investigate the impact wear process and mechanism of human tooth enamel and the influence of water content within enamel. In this paper, the impact wear behaviors of fresh and dried human tooth enamel against SiC ceramic have been investigated using a specially designed impact test machine. Tests lasting up to 5×10(3), 5×10(4), 2.5×10(5), 5.5×10(5), 8×10(5) and 1×10(6) cycles were conducted, respectively. Results showed that for the fresh enamel, the surface damage was dominated by plastic deformation at the early stage of impact wear. Iridescent rings appeared around the impact mark as a result of the accumulation and spread of plastic deformation. As the impact wear progressed, delamination occurred on the surface of enamel, and thus the iridescent rings gradually disappeared. Wear loss increased rapidly with the increase of impact cycles. When a wear particle layer was formed on the enamel surface, the wear rate decreased. It was found that the surface hardness of enamel increased with the impact cycles, and no cracks appeared on the cross section of wear scar. Compared with the fresh enamel, the fracture toughness of dried enamel decreased, and thus there were microcracks appearing on the cross section of wear scar. More obvious delamination occurred on the worn surface of dried enamel, and no iridescent rings were observed. The wear loss of dried enamel was higher than that of fresh enamel. In summary, the impact wear behavior of sound human tooth enamel was metal-like to some degree, and no subsurface cracking occurred. The water content within enamel could increase its fracture toughness and protect the surface from impact wear. The wear mechanism of human tooth enamel is determined by its microstructure. PMID:27183431

  18. Exposure and risks from wearing asbestos mitts

    PubMed Central

    Cherrie, John W; Tindall, Matthew; Cowie, Hilary

    2005-01-01

    Background Very high fibre inhalation exposure has been measured while people were wearing personal protective equipment manufactured from chrysotile asbestos. However, there is little data that relates specifically to wearing asbestos gloves or mitts, particularly when used in hot environments such as those found in glass manufacturing. The aim of this study was to assess the likely personal exposure to asbestos fibres when asbestos mitts were used. Results Three types of work activity were simulated in a small test room with unused mitts and artificially aged mitts. Neither pair of mitts were treated to suppress the dust emission. The measured respirable fibre exposure levels ranged from <0.06 to 0.55 fibres/ml, with no significant difference in fibre exposure between aged and unused mitts. The use of high localised ventilation to simulate convective airflows from a furnace reduced exposure levels by about a factor of five. Differences between tasks were statistically significant, with simulated "rowing" of molten glass lowest and replacement of side seals on the furnace highest. Estimated lifetime cancer risk from 20 years exposure at the upper end of the exposure range measured during the study is less than 22 per 100,000. Conclusion People who wore asbestos mitts were likely to have been exposed to relatively low levels of airborne chrysotile asbestos fibres, certainly much lower than the standards that were accepted in the 1960's and 70's. The cancer risks from this type of use are likely to be very low. PMID:16202137

  19. Wear of steel by rubber

    NASA Technical Reports Server (NTRS)

    Gent, A. N.; Pulford, C. T. R.

    1978-01-01

    Wear of a steel blade used as a scraper to abrade rubber surfaces has been found to take place much more rapidly on a cis-polyisoprene (natural rubber) surface than on a cis-polybutadiene surface, and much more rapidly in an inert atmosphere than in air. These observations are attributed to the direct attack upon steel of free-radical species generated by mechanical rupture of elastomer molecules during abrasion.

  20. Enhancing the wear resistance of case carburized steel (En 353) by cryogenic treatment

    NASA Astrophysics Data System (ADS)

    Bensely, A.; Prabhakaran, A.; Mohan Lal, D.; Nagarajan, G.

    2005-12-01

    All mechanical components that undergo sliding or rolling contact are subject to some degree of wear. So wear is an important tribological phenomenon while studying the failure of components. The observed frequent failure of crown and pinion due to wear and fatigue lead to this study on effect of cryogenic treatment on the wear resistance of case carburized steel (En 353). This paper deals with the pin on disk wear test without lubrication as per ASTM standard, designation: G 99-95A. The test was carried out for three different load conditions and seven sliding speeds for the samples, which has undergone three different treatment conditions namely conventional heat treatment (CHT), shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT). It has been found that the wear resistance has been considerably increased due to shallow cryogenic treatment and deep cryogenic treatment includes much more improvement in wear resistance when compared to conventional heat treatment. Also it is concluded that for better wear resistance, it is advisable to go for deep cryogenic treatment. The results are consistent with the previous studies reported in the literature on cryogenic treatments for other materials.

  1. Preliminary study on the effect of wear process on drug release of ALN-loaded UHMWPE

    NASA Astrophysics Data System (ADS)

    Yang, Dan; Qu, Shuxin; Lin, Sunzhong; Huang, Jie; Fu, Rong; Zhou, Zhongrong

    2012-12-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) for anti-osteolysis was developed in our previous study. As a potential material of artificial joints, ALN-loaded UHMWPE is subjected to friction and wear which probably affect the ALN release in vivo. This study aims to explore the influence of friction and wear on the ALN release rate. For comparison, the specimens of control group, immersed motionlessly in distilled water, were not applied any friction. The morphological change of worn surface of ALN-loaded UHMWPE was observed through an independent wear test and was compared with that of control UHMWPE. The ALN release rate in the friction and wear process was higher than that of non-friction test. The cumulative mass of ALN increased slowly at the onset of wear process and then speeded up. The fibrils-like wear debris accumulated on the worn surface of ALN-loaded UHMWPE but did not appear on that of UHMWPE. The micro-pores formed during wear process, were probably favorable of the dissolution of ALN. It indicated that the ALN release of ALN-loaded UHMWPE was affected by the friction and wear. The frictional factors should be taken into account in predicting the ALN release rate of ALN-loaded UHMWPE.

  2. Wear evaluation of a cross-linked medical grade polyethylene by ultra thin layer activation compared to gravimetry

    NASA Astrophysics Data System (ADS)

    Stroosnijder, Marinus F.; Hoffmann, Michael; Sauvage, Thierry; Blondiaux, Gilbert; Vincent, Laetitia

    2005-01-01

    Most of today's artificial joints rely on an articulating couple consisting of a CoCrMo alloy and a medical grade polyethylene. The wear of the polyethylene component is the major cause for long-term failure of these prostheses since the wear debris leads to adverse biological reactions. The polyethylene wear is usually measured by gravimetric methods, which are limited due to a low sensitivity and accuracy. To demonstrate the reliability of ultra thin layer activation (UTLA) as an alternative technique, wear tests on a cross-linked ultra-high-molecular weight polyethylene (XLPE) sliding against CoCrMo were performed on a wear tester featuring multi-directional sliding motion. The amount of polyethylene wear was evaluated by both UTLA and gravimetry. The particular TLA method used in this work employed the implantation of 7Be radioactive recoils into the polyethylene surface by means of a light mass particle beam. The results indicate that apart from its relatively high sensitivity, UTLA also offers the possibility for on-line measurements of polyethylene wear. This makes it a viable and complementary technique in wear test studies for medical implant purposes especially for those involving wear resistant materials and for rapid wear screening.

  3. 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

  4. Humidity Dependence of Tribochemical Wear of Monocrystalline Silicon.

    PubMed

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

    2015-07-15

    The nanowear tests of monocrystalline silicon against a SiO2 microsphere were performed using an atomic force microscope in air as a function of relative humidity (RH=0%-90%) and in liquid water at a contact pressure of about 1.20 GPa. The experimental results indicated that RH played an important role in the nanowear of the Si/SiO2 interface. In dry air, a hillock-like wear scar with a height of ∼0.4 nm was formed on the silicon surface. However, with the increase of RH, the wear depth on the silicon surface first increased to a maximum value of ∼14 nm at 50% RH and then decreased below the detection limit at RH above 85% or in water. The transmission electron microscopy analysis showed that the serious wear on the silicon surface at low and medium RHs occurred without subsurface damage, indicating that the wear was due to tribochemical reactions between the Si substrate and the SiO2 counter surface, rather than mechanical damages. The RH dependence of the tribochemical wear could be explained with a model involving the formation of "Si-O-Si" chemical bonds (bridges) between two solid surfaces. The suppression of tribochemical wear at high RHs or in liquid water might be attributed to the fact that the thickness of the interfacial water layer is thick enough to prevent the solid surfaces from making chemical bridges. The results may help us understand the nanowear mechanism of silicon that is an important material for dynamic microelectromechanical systems. PMID:26098989

  5. Wear characteristics of trimethylolpropane trimethacrylate filler-containing resins for the full crown restoration of primary molars.

    PubMed

    Wada, Kanae; Ikeda, Eri; Wada, Junichiro; Inoue, Go; Miyasaka, Munenaga; Miyashin, Michiyo

    2016-01-01

    Although the demand for aesthetic restoration of primary molars has increased, the full-crown restorations using resin and the details of the wear characteristics of trimethylolpropane trimethacrylate (TMPT) filler containing resins for primary molars are not well understood. This study was conducted to determine whether new light-cured composite resin (Fantasista) and 4-META/MMATBB resin (Bondfill SB) are appropriate for full crown restoration of primary molars by evaluating their wear characteristics. Both resins products contain TMPT filler. The properties of the resins were evaluated through in vitro impacting-sliding wear tests; the wear properties of the opposing enamel specimens used in the tests were also studied. The properties of the resins were compared with those of Litefill, MetafilC, and Clearfil FII, which had been evaluated previously. Fantasista exhibited simple shape of wear that was suggestive of a higher wear resistance than that of Litefill. Fantasista caused the least damage to the antagonistic primary enamel.

  6. Modeling of complex wear behavior associated with grid-to-rod fretting in light water nuclear reactors

    DOE PAGES

    Blau, P. J.; Qu, J.; Lu, R.

    2016-09-21

    One significant concern in the operation of light water nuclear reactors is the fretting wear damage to fuel cladding from flow-induced vibrations. For years, research on the grid-to-rod fretting (GTRF) phenomena has been underway in countries where nuclear power production is a significant industry. Under the auspices of the U.S. Department of Energy Consortium for Advanced Simulation of Light Water Reactors, an effort has been underway to develop and test an engineering wear model for zirconium alloy fuel rod cladding against a supporting grid. Furthermore, the multi-stage model accounts for oxide layers and wear rate transitions. Our paper describes themore » basis for a GTRF engineering wear model, the physical significance of the wear factor it contains, and recent progress toward model validation based on a fretting wear testing apparatus that accounts for coolant temperature, pressure, and the presence of periodic impacts (gaps) in grid/rod contact.« less

  7. Modeling of Complex Wear Behavior Associated with Grid-to-Rod Fretting in Light Water Nuclear Reactors

    NASA Astrophysics Data System (ADS)

    Blau, P. J.; Qu, J.; Lu, R.

    2016-09-01

    Fretting wear damage to fuel cladding from flow-induced vibrations can be a significant concern in the operation of light water nuclear reactors. For years, research on the grid-to-rod fretting (GTRF) phenomena has been underway in countries where nuclear power production is a significant industry. Under the auspices of the U.S. Department of Energy Consortium for Advanced Simulation of Light Water Reactors, an effort has been underway to develop and test an engineering wear model for zirconium alloy fuel rod cladding against a supporting grid. The multi-stage model accounts for oxide layers and wear rate transitions. This paper describes the basis for a GTRF engineering wear model, the physical significance of the wear factor it contains, and recent progress toward model validation based on a fretting wear testing apparatus that accounts for coolant temperature, pressure, and the presence of periodic impacts (gaps) in grid/rod contact.

  8. Friction and wear of Si3N4 ceramic/stainless steel sliding contacts in dry and lubricated conditions

    NASA Astrophysics Data System (ADS)

    Zhao, X. Z.; Liu, J. J.; Zhu, B. L.; Miao, H. Z.; Luo, Z. B.

    1997-04-01

    Austenitic stainless steel AISI 321 is one of the most difficult-to-cut materials. In order to investigate the wear behavior of Si3N4 ceramic when cutting the stainless steel, wear tests are carried out on a pin-ondisk tribometer, which could simulate a realistic cutting process. Test results show that the wear of Si3N4 ceramic is mainly caused by adhesion between the rubbing surfaces and that the wear increases with load and speed. When oil is used for lubrication, the friction coefficient of the sliding pairs and the wear rate of the ceramic are reduced. A scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), and an energy dispersive x-ray analyzer (EDXA) are used to examine the worn surfaces. The wear mechanisms of Si3N4 ceramic sliding against the stainless steel are discussed in detail.

  9. Effect of microseparation and third-body particles on dual-mobility crosslinked hip liner wear.

    PubMed

    Netter, Jonathan D; Hermida, Juan C; Chen, Peter C; Nevelos, James E; D'Lima, Darryl D

    2014-09-01

    Large heads have been recommended to reduce the risk of dislocation after total hip arthroplasty. One of the issues with larger heads is the risk of increased wear and damage in thin polyethylene liners. Dual-mobility liners have been proposed as an alternative to large heads. We tested the wear performance of highly crosslinked dual-mobility liners under adverse conditions simulating microseparation and third-body wear. No measurable increase in polyethylene wear rate was found in the presence of third-body particles. Microseparation induced a small increase in wear rate (2.9mm(3)/million cycles). A finite element model simulating microseparation in dual-mobility liners was validated using these experimental results. The results of our study indicate that highly crosslinked dual-mobility liners have high tolerance for third-body particles and microseparation.

  10. Sliding wear behaviors of steam generator tube materials in high temperature water environment

    NASA Astrophysics Data System (ADS)

    Park, Gi Sung; Kim, Gyung Guk; Kim, Seon Jin

    2006-06-01

    Wear damage of steam generator tubes for nuclear power plants can cause the leakage of radioactive substances. Therefore, the evaluation of the tube integrity is very important in the view point of nuclear safety. In the present study, to investigate the effects of the applied normal load and sliding distance on wear volume in 575 K water environment, sliding wear tests were performed with Inconel 600 and 690 steam generator tube materials mated with 409 stainless steel commonly used as support plate. Based on the accumulated data, the newly modified Archard equation was proposed and then the wear coefficients of tube materials were estimated with both Archard equation and the modified Archard equation. The reliabilities, which are parameters to assess how well a model fits a set of data, for prediction of wear behaviors of Inconel 600 and 690 improved from 20.5% to 65.5% and from 38.5 to 65.3%, respectively.

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

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.

    1977-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  13. Wear resistance of diffusion coatings on the working parts of impact-rebound crushers

    SciTech Connect

    Nedzel'skii, M.D.; Katkov, Y.K.

    1984-01-01

    Impact-rebound crushers used in the chemical industry suffer intensive wear of the crusher blades when crushing materials like quartz sand, corundum, and diabase. A special impact-rebound crushers has been made for testing the wear resistance of hardened prototype blades, andi it is described in detail in this paper. Tests were done to determine the most effective methods of surface hardening for the replaceable inserts made of readily available steel and it is found that the carbonitriding of steel gives a hardened layer to increase the wear resistance of the crusher body and rotor surfaces.

  14. Shape classification of wear particles by image boundary analysis using machine learning algorithms

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Chin, K. S.; Hua, Meng; Dong, Guangneng; Wang, Chunhui

    2016-05-01

    The shape features of wear particles generated from wear track usually contain plenty of information about the wear states of a machinery operational condition. Techniques to quickly identify types of wear particles quickly to respond to the machine operation and prolong the machine's life appear to be lacking and are yet to be established. To bridge rapid off-line feature recognition with on-line wear mode identification, this paper presents a new radial concave deviation (RCD) method that mainly involves the use of the particle boundary signal to analyze wear particle features. Signal output from the RCDs subsequently facilitates the determination of several other feature parameters, typically relevant to the shape and size of the wear particle. Debris feature and type are identified through the use of various classification methods, such as linear discriminant analysis, quadratic discriminant analysis, naïve Bayesian method, and classification and regression tree method (CART). The average errors of the training and test via ten-fold cross validation suggest CART is a highly suitable approach for classifying and analyzing particle features. Furthermore, the results of the wear debris analysis enable the maintenance team to diagnose faults appropriately.

  15. Gravimetric wear analysis and particulate characterization of bilateral facet-augmentation system--PercuDyn™.

    PubMed

    Bhattacharya, Sanghita; Nayak, Aniruddh; Goel, Vijay K; Warren, Chris; Schlaegle, Steve; Ferrara, Lisa

    2010-01-01

    Dynamic stabilization systems are emerging as an alternative to fusion instrumentation. However, cyclic loading and micro-motion at various interfaces may produce wear debris leading to adverse tissue reactions such as osteolysis. Ten million cycles of wear test was performed for PercuDyn™ in axial rotation and the wear profile and the wear rate was mapped. A validation study was undertaken to assess the efficiency of wear debris collection which accounted for experimental errors. The mean wear debris measured at the end of 10 million cycles was 4.01 mg, based on the worst-case recovery rate of 68.2%. Approximately 40% of the particulates were less than 5 μm; 92% less than 10 μm. About 43% of particulates were spherical in shape, 27% particulates were ellipsoidal and the remaining particles were of irregular shapes. The PercuDyn™ exhibited an average polymeric wear rate of 0.4 mg/million cycles; substantially less than the literature derived studies for other motion preservation devices like the Bryan disc and Charité disc. Wear debris size and shape were also similar to these devices.

  16. Study of sapphire probe tip wear when scanning on different materials

    NASA Astrophysics Data System (ADS)

    Nicolet, Anaïs; Küng, Alain; Meli, Felix

    2012-09-01

    The accuracy of today's coordinate measuring machines (CMM) has reached a level at which exact knowledge of each component is required. The role of the probe tip is particularly crucial as it is in contact with the sample surface. Understanding how the probe tip wears off will help to narrow the measurement errors. In this work, wear of a sapphire sphere was studied for different scanning conditions and with different sample materials. Wear depth on the probe was investigated using an automated process in situ on the METAS micro-CMM and completed by measurements with an atomic force microscope. We often found a linear dependence between the wear depth and the scan length ranging from 0.5 to 9 nm m-1, due to variations in scan speed, contact force or sample material. In the case of steel, the wear rate is proportional to the scan speed, while for aluminum several processes seem to interact. A large amount of debris was visible after the tests. Except for aluminum, wear was visible only on the sphere and not on the sample. Sapphire/steel is the worst combination in terms of wear, whereas the combination sapphire/ceramic exhibits almost no wear.

  17. 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.

  18. Orbital transfer rocket engine technology program: Soft wear ring seal technology

    NASA Technical Reports Server (NTRS)

    Lariviere, Brian W.

    1992-01-01

    Liquid oxygen (LOX) compatibility tests, including autogenous ignition, promoted ignition, LOX impact tests, and friction and wear tests on different PV products were conducted for several polymer materials as verification for the implementation of soft wear ring seals in advanced rocket engine turbopumps. Thermoplastics, polyimide based materials, and polyimide-imide base materials were compared for oxygen compatibility, specific wear coefficient, wear debris production, and heat dissipation mechanisms. A thermal model was generated that simulated the frictional heating input and calculated the surface temperature and temperature distribution within the seal. The predictions were compared against measured values. Heat loads in the model were varied to better match the test data and determine the difference between the measured and the calculated coefficients of friction.

  19. Wear of liquid nitrogen-cooled 440C bearing steels in an oxygen environment

    NASA Technical Reports Server (NTRS)

    Chaudhuri, Dilip K.; Verma, Ravi

    1988-01-01

    This paper presents up-to-date findings of the research being conducted to understand the mechanism of sliding wear in unlubricated 440C bearing steels under oxidative conditions. A sliding wear test rig has been designed and built with a cylinder-on-flat geometry. The equipment is capable of testing specimens under high axial loads and sliding speeds in a simulated LOX environment. Samples of 440C steel, quenched and tempered to a hardness of Rc 56, were tested under a load of 890 N and a sliding speed of 2.05 m/sec for total sliding distances of up to 5.54 km. Flash temperatures during these tests were measured with an IR camera and a fast digital recorder. Microstructural and microanalytical data from the worn surfaces and the debris particles are analyzed extensively, along with wear rates, flash temperatures, surface profiles, hardnesses, and residual stresses, in the context of oxidation and wear theories.

  20. The effect of insert conformity and material on total knee replacement wear

    PubMed Central

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

    2014-01-01

    The mean average life is increasing; therefore, there is a need to increase the lifetime of the prostheses. To fulfil this requirement, new prosthetic designs and materials are being introduced. Two of the design parameters that may affect wear of total knee replacements, and hence the expected lifetime, are the insert conformity and material. Computational models have been used extensively for wear prediction and optimisation of artificial knee designs. The objective of the present study was to use a previously validated non-dimensional wear coefficient-based computational wear model to investigate the effect of insert conformity and material on the predicted wear in total knee replacements. Four different inserts (curved, lipped, partial flat and custom flat), with different conformity levels, were tested against the same femoral and under two different kinematic inputs (intermediate and high), with different levels of cross-shear. The insert bearing materials were either conventional or moderately cross-linked ultra-high molecular weight polyethylene (UHMWPE). Wear predictions were validated against the experimental data from Leeds knee simulation tests. The predicted wear rates for the curved insert (most conformed) were more than three times those for the flat insert (least conformed). In addition, the computationally predicted average volumetric wear rates for moderately cross-linked UHMWPE bearings were less than half of their corresponding conventional UHMWPE bearings. Moreover, the wear of the moderately cross-linked UHMWPE was shown to be less dependent on the degree of cross-shear, compared to conventional UHMWPE. These results along with supporting experimental studies provide insight into the design variables, which may reduce wear in knee replacements. PMID:24297773

  1. The effect of insert conformity and material on total knee replacement wear.

    PubMed

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

    2014-01-01

    The mean average life is increasing; therefore, there is a need to increase the lifetime of the prostheses. To fulfil this requirement, new prosthetic designs and materials are being introduced. Two of the design parameters that may affect wear of total knee replacements, and hence the expected lifetime, are the insert conformity and material. Computational models have been used extensively for wear prediction and optimisation of artificial knee designs. The objective of the present study was to use a previously validated non-dimensional wear coefficient-based computational wear model to investigate the effect of insert conformity and material on the predicted wear in total knee replacements. Four different inserts (curved, lipped, partial flat and custom flat), with different conformity levels, were tested against the same femoral and under two different kinematic inputs (intermediate and high), with different levels of cross-shear. The insert bearing materials were either conventional or moderately cross-linked ultra-high molecular weight polyethylene (UHMWPE). Wear predictions were validated against the experimental data from Leeds knee simulation tests. The predicted wear rates for the curved insert (most conformed) were more than three times those for the flat insert (least conformed). In addition, the computationally predicted average volumetric wear rates for moderately cross-linked UHMWPE bearings were less than half of their corresponding conventional UHMWPE bearings. Moreover, the wear of the moderately cross-linked UHMWPE was shown to be less dependent on the degree of cross-shear, compared to conventional UHMWPE. These results along with supporting experimental studies provide insight into the design variables, which may reduce wear in knee replacements.

  2. Investigation of wear phenomena by microscopy

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1982-01-01

    The various wear mechanisms involved in the loss of material from metallic and nonmetallic surfaces are discussed. The results presented indicate how various microscopy techniques used in conjunction with other analytical tools can assist in the elucidation of a wear mechanism. Without question, microscopy is the single most important tool for the study of the wear of surfaces, to assess and address inherent mechanisms of the material removal process.

  3. Surface Wear Measurement Using Optical Correlation Technique

    NASA Astrophysics Data System (ADS)

    Acinger, Kresimir

    1983-12-01

    The coherent optical correlation technique was applied for measuring the surface wear of a tappet (part of car engine), worn by friction with the camshaft. It was found that maximum correlation intensity decays exponentially with the number of wear cycles (i.e. camshaft revolutions). Tappets of the same make have an identical rate of correlation decay. Tappets of different makes have different rates of correlation decay which are in agreement with observed long term wear.

  4. Dry sliding wear behavior of epoxy composite reinforced with short palmyra fibers

    NASA Astrophysics Data System (ADS)

    Biswal, Somen; Satapathy, Alok

    2016-02-01

    The present work explores the possibility of using palmyra fiber as a replacement for synthetic fiber in conventional polymer composites for application against wear. An attempt has been made in this work to improve the sliding wear resistance of neat epoxy by reinforcing it with short palmyra fibers (SPF). Epoxy composites with different proportions (0, 4, 8 and 12 wt. %) of SPF are fabricated by conventional hand lay-up technique. Dry sliding wear tests are performed on the composite samples using a pin-on-disc test rig as per ASTM G 99-05 standards under various operating parameters. Design of experiment approach based on Taguchi's L16 Orthogonal Arrays is used for the analysis of the wear. This parametric analysis reveals that the SPF content is the most significant factor affecting the wear process followed by the sliding velocity. The sliding wear behavior of these composites under an extensive range of test conditions is predicted by a model based on the artificial neural network (ANN). A well trained ANN has been used to predict the sliding wear response of epoxy based composites over a wide range.

  5. An analysis of the physiologic parameters of intraoral wear: a review

    NASA Astrophysics Data System (ADS)

    Lawson, Nathaniel C.; Janyavula, Sridhar; Cakir, Deniz; Burgess, John O.

    2013-10-01

    This paper reviews the conditions of in vivo mastication and describes a novel method of measuring in vitro wear. Methods: parameters of intraoral wear are reviewed in this analysis, including chewing force, tooth sliding distance, food abrasivity, saliva lubrication, and antagonist properties. Results: clinical measurement of mastication forces indicates a range of normal forces between 20 and 140 N for a single molar. During the sliding phase of mastication, horizontal movement has been measured between 0.9 and 2.86 mm. In vivo wear occurs by three-body abrasion when food particles are interposed between teeth and by two-body abrasion after food clearance. Analysis of food particles used in wear testing reveals that food particles are softer than enamel and large enough to separate enamel and restoration surfaces and act as a solid lubricant. In two-body wear, saliva acts as a boundary lubricant with a viscosity of 3 cP. Enamel is the most relevant antagonist material for wear testing. The shape of a palatal cusp has been estimated as a 0.6 mm diameter ball and the hardest region of a tooth is its enamel surface. pH values and temperatures have been shown to range between 2-7 and 5-55 °C in intraoral fluids, respectively. These intraoral parameters have been used to modify the Alabama wear testing method.

  6. Macro- to nanoscale wear prevention via molecular adsorption.

    PubMed

    Asay, David B; Dugger, Michael T; Ohlhausen, James A; Kim, Seong H

    2008-01-01

    As the size of mechanical systems shrinks from macro- to nanoscales, surface phenomena such as adhesion, friction, and wear become increasingly significant. This paper demonstrates the use of alcohol adsorption as a means of continuously replenishing the lubricating layer on the working device surfaces and elucidates the tribochemical reaction products formed in the sliding contact region. Friction and wear of native silicon oxide were studied over a wide range of length scales from macro- to nanoscales using a ball-on-flat tribometer (millimeter scale), sidewall microelectromechanical system (MEMS) tribometer (micrometer scale), and atomic force microscopy (nanometer scale). In all cases, the alcohol vapor adsorption successfully lubricated and prevented wear. Imaging time-of-flight secondary ion mass spectrometry analysis of the sliding contact region revealed that high molecular weight oligomeric species were formed via tribochemical reactions of the adsorbed linear alcohol molecules. These tribochemical products seemed to enhance the lubrication and wear prevention. In the case of sidewall MEMS tests, the lifetime of the MEMS device was radically increased via vapor-phase lubrication with alcohol.

  7. Macro- to nanoscale wear prevention via molecular adsorption.

    SciTech Connect

    Kim, Seong H.; Asay, David B.; Dugger, Michael Thomas; Ohlhausen, James Anthony

    2007-04-01

    As the size of mechanical systems shrinks from macro- to nanoscales, surface phenomena such as adhesion, friction, and wear become increasingly significant. This paper demonstrates the use of alcohol adsorption as a means of continuously replenishing the lubricating layer on the working device surfaces and elucidates the tribochemical reaction products formed in the sliding contact region. Friction and wear of native silicon oxide were studied over a wide range of length scales from macro- to nanoscales using a ball-on-flat tribometer (millimeter scale), sidewall microelectromechanical system (MEMS) tribometer (micrometer scale), and atomic force microscopy (nanometer scale). In all cases, the alcohol vapor adsorption successfully lubricated and prevented wear. Imaging time-of-flight secondary ion mass spectrometry analysis of the sliding contact region revealed that high molecular weight oligomeric species were formed via tribochemical reactions of the adsorbed linear alcohol molecules. These tribochemical products seemed to enhance the lubrication and wear prevention. In the case of sidewall MEMS tests, the lifetime of the MEMS device was radically increased via vapor-phase lubrication with alcohol.

  8. Factors influencing PM 10 emissions from road pavement wear

    NASA Astrophysics Data System (ADS)

    Gustafsson, Mats; Blomqvist, Göran; Gudmundsson, Anders; Dahl, Andreas; Jonsson, Per; Swietlicki, Erik

    Accelerated pavement wear is one of the major environmental disadvantages of studded tyres in northern regions and results in increased levels of PM 10. Measurements of PM 10 in a road simulator hall have been used to study the influence of pavement properties, tyre type and vehicle speed on pavement wear. The test set-up included three different pavements (one granite and two quartzite with different aggregate sizes), three different tyre types (studded, non-studded, and summer tyres) and different speeds (30-70 km h -1). The results show that the granite pavement was more prone to PM 10 production compared to the quartzite pavements. Studded winter tyres yield tens of times higher PM 10 concentrations compared to non-studded winter tyres. Wear from summer tyres was negligible in comparison. It was also shown that wear is strongly dependent on speed; every 10 km h -1 increase yielded an increase of the PM 10 concentration of 680 μg m -3 in one of the simulator experiments.

  9. Impact of tool wear on joint strength in friction stir spot welding of DP 980 steel

    SciTech Connect

    Miles, Michael; Ridges, Chris; Hovanski, Yuri; Peterson, Jeremy; Santella, M. L.; Steel, Russel

    2011-09-14

    Friction stir spot welding has been shown to be a viable method of joining ultra high strength steel (UHSS), both in terms of joint strength and process cycle time. However, the cost of tooling must be reasonable in order for this method to be adopted as an industrial process. Recently a new tool alloy has been developed, using a blend of PCBN and tungsten rhenium (W-Re) in order to improve the toughness of the tool. Wear testing results are presented for two of these alloys: one with a composition of 60% PCBN and 40% W-Re, and one with 70% PCBN and 30% W-Re. The sheet material used for all wear testing was 1.4 mm DP 980. Lap shear testing was used to show the relationship between tool wear and joint strength. The Q70 tool provided the best combination of wear resistance and joint strength.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  11. Fault Wear and Friction Evolution: Experimental Analysis

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Wear is an inevitable product of frictional sliding of brittle rocks as evidenced by the ubiquitous occurrence of fault gouge and slickenside striations. We present here experimental observations designed to demonstrate the relationship between wear and friction and their governing mechanisms. The experiments were conducted with a rotary shear apparatus on solid, ring-shaped rock samples that slipped for displacements up to tens of meters. Stresses, wear and temperature were continuously monitored. We analyzed 86 experiments of Kasota dolomite, Sierra White granite, Pennsylvania quartzite, Karoo gabbro, and Tennessee sandstone at slip velocities ranging from 0.002 to 0.97 m/s, and normal stress from 0.25 to 6.9 MPa. We conducted two types of runs: short slip experiments (slip distance < 25 mm) primarily on fresh, surface-ground samples, designed to analyze initial wear mechanisms; and long slip experiments (slip distance > 3 m) designed to achieve mature wear conditions and to observe the evolution of wear and friction as the fault surfaces evolved. The experiments reveal three wear stages: initial, running-in, and steady-state. The initial stage is characterized by (1) discrete damage striations, the length of which is comparable to total slip , and local pits or plow features; (2) timing and magnitude of fault-normal dilation corresponds to transient changes of normal and shear stresses; and (3) surface roughness increasing with the applied normal stress. We interpret these observations as wear mechanisms of (a) plowing into the fresh rock surfaces; (b) asperity breakage; and (c) asperity climb. The running-in stage is characterized by (1) intense wear-rate over a critical wear distance of Rd = 0.3-2 m; (2) drop of friction coefficient over a weakening distance of Dc = 0.2-4 m; (3) Rd and Dc display positive, quasi-linear relation with each other. We interpret these observations as indicating the organizing of newly-created wear particles into a 'three

  12. 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

  13. Enamel wear caused by monolithic zirconia crowns after 6 months of clinical use.

    PubMed

    Stober, T; Bermejo, J L; Rammelsberg, P; Schmitter, M

    2014-04-01

    The purpose of this study was to evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For measurement of wear, impressions of both jaws were made at baseline after crown cementation and at 6-month follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists and of the two contralateral natural antagonists were measured by the use of plaster replicas and 3D laser scanning methods. Wear differences were investigated by the use of two-sided paired Student's t-tests and by linear regression analysis. Mean vertical loss (maximum vertical loss in parentheses) was 10 (43) μm for the zirconia crowns, 33 (112) μm for the opposing enamel, 10 (58) μm for the contralateral teeth and 10 (46) μm for the contralateral antagonists. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral antagonists. Gender and activity of the masseter muscle at night (bruxism) were identified as possible confounders which significantly affected wear. Under clinical conditions, monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth. With regard to wear behaviour, clinical application of monolithic zirconia crowns is justifiable because the amount of antagonistic enamel wear after 6 months is comparable with, or even lower than, that caused by other ceramic materials in previous studies.

  14. Microtomography evaluation of dental tissue wear surface induced by in vitro simulated chewing cycles on human and composite teeth.

    PubMed

    Bedini, Rossella; Pecci, Raffaella; Notarangelo, Gianluca; Zuppante, Francesca; Persico, Salvatore; Di Carlo, Fabio

    2012-01-01

    In this study a 3D microtomography display of tooth surfaces after in vitro dental wear tests has been obtained. Natural teeth have been compared with prosthetic teeth, manufactured by three different polyceramic composite materials. The prosthetic dental element samples, similar to molars, have been placed in opposition to human teeth extracted by paradontology diseases. After microtomography analysis, samples have been subjected to in vitro fatigue test cycles by servo-hydraulic mechanical testing machine. After the fatigue test, each sample has been subjected again to microtomography analysis to obtain volumetric value changes and dental wear surface images. Wear surface images were obtained by 3D reconstruction software and volumetric value changes were measured by CT analyser software. The aim of this work has been to show the potential of microtomography technique to display very clear and reliable wear surface images. Microtomography analysis methods to evaluate volumetric value changes have been used to quantify dental tissue and composite material wear. PMID:22456018

  15. Microtomography evaluation of dental tissue wear surface induced by in vitro simulated chewing cycles on human and composite teeth.

    PubMed

    Bedini, Rossella; Pecci, Raffaella; Notarangelo, Gianluca; Zuppante, Francesca; Persico, Salvatore; Di Carlo, Fabio

    2012-01-01

    In this study a 3D microtomography display of tooth surfaces after in vitro dental wear tests has been obtained. Natural teeth have been compared with prosthetic teeth, manufactured by three different polyceramic composite materials. The prosthetic dental element samples, similar to molars, have been placed in opposition to human teeth extracted by paradontology diseases. After microtomography analysis, samples have been subjected to in vitro fatigue test cycles by servo-hydraulic mechanical testing machine. After the fatigue test, each sample has been subjected again to microtomography analysis to obtain volumetric value changes and dental wear surface images. Wear surface images were obtained by 3D reconstruction software and volumetric value changes were measured by CT analyser software. The aim of this work has been to show the potential of microtomography technique to display very clear and reliable wear surface images. Microtomography analysis methods to evaluate volumetric value changes have been used to quantify dental tissue and composite material wear.

  16. Fretting wear behaviors of a dual-cooled nuclear fuel rod under a simulated rod vibration

    SciTech Connect

    Lee, Young-Ho; Kim, Hyung-Kyu; Kang, Heung-Seok; Yoon, Kyung-Ho; Kim, Jae-Yong; Lee, Kang-Hee

    2012-06-06

    Recently, a dual-cooled fuel (i.e., annular fuel) that is compatible with current operating PWR plants has been proposed in order to realize both a considerable amount of power uprating and an increase of safety margins. As the design concept should be compatible with current operating PWR plants, however, it shows a narrow gap between the fuel rods when compared with current solid nuclear fuel arrays and needs to modify the spacer grid shapes and their positions. In this study, fretting wear tests have been performed to evaluate the wear resistance of a dual-cooled fuel by using a proposed spring and dimple of spacer grids that have a cantilever type and hemispherical shape, respectively. As a result, the wear volume of the spring specimen gradually increases as the contact condition is changed from a certain gap, just contact to positive force. However, in the dimple specimen, just contact condition shows a large wear volume. In addition, a circular rod motion at upper region of contact surface is gradually increased and its diametric size depends on the wear depth increase. Based on the test results, the fretting wear resistance of the proposed spring and dimple is analyzed by comparing the wear measurement results and rod motion in detail.

  17. Fretting wear behaviors of a dual-cooled nuclear fuel rod under a simulated rod vibration

    NASA Astrophysics Data System (ADS)

    Lee, Young-Ho; Kim, Hyung-Kyu; Kang, Heung-Seok; Yoon, Kyung-Ho; Kim, Jae-Yong; Lee, Kang-Hee

    2012-06-01

    Recently, a dual-cooled fuel (i.e., annular fuel) that is compatible with current operating PWR plants has been proposed in order to realize both a considerable amount of power uprating and an increase of safety margins. As the design concept should be compatible with current operating PWR plants, however, it shows a narrow gap between the fuel rods when compared with current solid nuclear fuel arrays and needs to modify the spacer grid shapes and their positions. In this study, fretting wear tests have been performed to evaluate the wear resistance of a dual-cooled fuel by using a proposed spring and dimple of spacer grids that have a cantilever type and hemispherical shape, respectively. As a result, the wear volume of the spring specimen gradually increases as the contact condition is changed from a certain gap, just contact to positive force. However, in the dimple specimen, just contact condition shows a large wear volume. In addition, a circular rod motion at upper region of contact surface is gradually increased and its diametric size depends on the wear depth increase. Based on the test results, the fretting wear resistance of the proposed spring and dimple is analyzed by comparing the wear measurement results and rod motion in detail.

  18. Effect of periwinkles shell particle size on the wear behavior of asbestos free brake pad

    NASA Astrophysics Data System (ADS)

    Amaren, S. G.; Yawas, D. S.; Aku, S. Y.

    The effect of periwinkle shell particle size on the wear behavior of asbestos free brake pad has been investigated. The asbestos free brake pad produced by varying the periwinkle shell particles was from +125 to +710 μm with phenolic resin as the binder. The wear test was performed using pin on disk machine by varying the sliding speed, applied load, temperatures and periwinkle shell particle size. Full factorial design of four factor-two levels and analysis of variance were used in the study of the wear test. The results shown that wear rate increases with increasing the sliding speed, load, temperatures and periwinkle particle size. The co-efficient of friction obtained is within the recommended standard for automobile brake pad. The +125 μm particles of periwinkles gave the best wear resistance. Factorial design of the experiment can be successfully employed to describe the wear behavior of the samples and developed linear equation for predicting wear rate within selected experimental conditions. The results of this research indicate that periwinkle shell particles can be effectively used as a replacement for asbestos in brake pad manufacture.

  19. 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.

  20. Friction and wear in hot forging of steels

    SciTech Connect

    Daouben, E.; Dubar, L.; Dubar, M.; Deltombe, R.; Dubois, A.; Truong-Dinh, N.; Lazzarotto, L.

    2007-04-07

    In the field of hot forging of steels, the mastering of wear phenomena enables to save cost production, especially concerning tools. Surfaces of tools are protected thanks to graphite. The existing lubrication processes are not very well known: amount and quality of lubricant, lubrication techniques have to be strongly optimized to delay wear phenomena occurrence. This optimization is linked with hot forging processes, the lubricant layers must be tested according to representative friction conditions. This paper presents the first part of a global study focused on wear phenomena encountered in hot forging of steels. The goal is the identification of reliable parameters, in order to bring knowledge and models of wear. A prototype testing stand developed in the authors' laboratory is involved in this experimental analysis. This test is called Warm and Hot Upsetting Sliding Test (WHUST). The stand is composed of a heating induction system and a servo-hydraulic system. Workpieces taken from production can be heated until 1200 deg. C. A nitrided contactor representing the tool is heated at 200 deg. C. The contactor is then coated with graphite and rubs against the workpiece, leaving a residual track on it. Friction coefficient and surface parameters on the contactor and the workpiece are the most representative test results. The surface parameters are mainly the sliding length before defects occurrence, and the amplitude of surface profile of the contactor. The developed methodology will be first presented followed by the different parts of the experimental prototype. The results of experiment show clearly different levels of performance according to different lubricants.

  1. Astronaut James Buchli wearing extravehicular mobility unit

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Astronaut James F. Buchli, wearing an extravehicular mobility unit (EMU), is about to be submerged in the weightless environment training facility (WETF) to simulate a contingency extravehicular activity (EVA) for STS 61-A. In this portrait view, Buchli is wearing a communications carrier assembly (CCA).

  2. Friction, wear, and lubrication in vacuum

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1971-01-01

    A review of studies and observations on the friction, wear, and lubrication behavior of materials in a vacuum environment is presented. The factors that determine and influence friction and wear are discussed. They include topographical, physical, mechanical, and the chemical nature of the surface. The effects of bulk properties such as deformation characteristics, fracture behavior, and structure are included.

  3. Characterization of Wear Particles Generated from CoCrMo Alloy under Sliding Wear Conditions

    PubMed Central

    Pourzal, R.; Catelas, I.; Theissmann, R.; Kaddick, C.; Fischer, A.

    2011-01-01

    Biological effects of wear products (particles and metal ions) generated by metal-on-metal (MoM) hip replacements made of CoCrMo alloy remain a major cause of concern. Periprosthetic osteolysis, potential hypersensitivity response and pseudotumour formation are possible reactions that can lead to early revisions. To accurately analyse the biological response to wear particles from MoM implants, the exact nature of these particles needs to be characterized. Most previous studies used energy-dispersive X-ray spectroscopy (EDS) analysis for characterization. The present study used energy filtered transmission electron microscopy (TEM) and electron diffraction pattern analysis to allow for a more precise determination of the chemical composition and to gain knowledge of the crystalline structure of the wear particles. Particles were retrieved from two different test rigs: a reciprocating sliding wear tribometer (CoCrMo cylinder vs. bar) and a hip simulator according to ISO 14242-1 (CoCrMo head vs. CoCrMo cup). All tests were conducted in bovine serum. Particles were retrieved from the test medium using a previously published enzymatic digestion protocol. Particles isolated from tribometer samples had a size of 100 – 500 nm. Diffraction pattern analysis clearly revealed the lattice structure of strain induced hcp ε-martensite. Hip simulator samples revealed numerous particles of 15 – 30 nm and 30 – 80 nm size. Most of the larger particles appeared to be only partially oxidized and exhibited cobalt locally. The smallest particles were Cr2O3 with no trace of cobalt. It optically appeared that these Cr2O3 particles were flaking off the surface of larger particles that depicted a very high intensity of oxygen, as well as chromium, and only background noise of cobalt. The particle size difference between the two test rigs is likely related to the conditions of the two tribosystems, in particular the difference in the sample geometry and in the type of sliding

  4. Wear mechanisms of partially stabilized zirconia

    SciTech Connect

    Aronov, V.

    1987-01-01

    This paper is devoted to an investigation of the wear mechanisms of magnesia and yttria partially-stabilized zirconia in ceramic/ceramic and ceramic/metal sliding-contact tribological systems at high temperature. It was found that the wear of ceramics rubbed against ceramics at room temperature may be attributed to intensive plastic deformation of surfaces resulting in low cycle fatigue. The wear mechanism of ceramics rubbed against metals was by polishing and surface fracture, while that of metals was adhesive transfer of material on to ceramic surfaces. Investigation of the wear behavior of magnesia partially-stabilized zirconia rubbed against itself showed that up to three orders of magnitude increase in wear resistance can be achieved in a particular temperature range, depending on both sliding speed and the ambient temperature. XRD analysis revealed that a thermally-induced phase transformation takes place on the frictional interface.

  5. Modeling wear of cast Ti alloys

    PubMed Central

    Chan, Kwai S.; Koike, Marie; Okabe, Toru

    2007-01-01

    The wear behavior of Ti-based alloys was analyzed by considering the elastic–plastic fracture of individual alloys in response to the relevant contact stress field. Using the contact stresses as the process driving force, wear was computed as the wear rate or volume loss as a function of hardness and tensile ductility for Ti-based cast alloys containing an α, α+β or β microstructure with or without the intermetallic precipitates. Model predictions indicated that wear of Ti alloys increases with increasing hardness but with decreasing fracture toughness or tensile ductility. The theoretical results are compared with experimental data to elucidate the roles of microstructure in wear and contrasted against those in grindability. PMID:17224314

  6. Wear simulation effects on overdenture stud attachments.

    PubMed

    Rutkunas, Vygandas; Mizutani, Hiroshi; Takahashi, Hidekazu; Iwasaki, Naohiko

    2011-01-01

    The aim of this study was to evaluate wear effects on overdenture resilient attachments. Six commercially available attachments were investigated: ERA orange and white (EO and EW), Locator pink, white and blue (LRP, LRW and LRB) and OP anchor (OP). Five specimens were used for wear simulation while other two specimens served as controls. Fifteen thousands insertion-removal cycles were simulated. Dimensional changes and surface characteristics were evaluated using light microscopy and SEM, respectively. Sudden decrease of retentive force was characteristic for EO and EW attachments. Retentive force of Locator attachments fluctuated throughout the wear simulation period. Dimensional changes and surface wear was more expressed on plastic cores than on plastic rings of attachment males. Based on SEM analysis, some of the specimens obtained smoother surface after wear simulation. Mechanism of retention loss of resilient overdenture attachments can be only partially explained by dimensional changes and surface alterations.

  7. 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

  8. 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.

  9. 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.

  10. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  11. Corrosion and wear resistance of tungsten carbide-cobalt and tungsten carbide-cobalt-chromium thermal spray coatings

    SciTech Connect

    Quets, J.; Alford, J.R.

    1999-07-01

    Tungsten carbide thermal spray coatings provide wear surfaces to new and overhauled components for various industries. Their wear resistance is obtained by incorporating small tungsten carbide particles into a metal matrix. This presentation will show what parameters influence their corrosion resistance in the ASTM B-117 Salt Spray Corrosion Test,

  12. Influence of the microstructure of ceramic materials on their wear behavior in mechanical seals

    SciTech Connect

    Wallis, R.

    1994-10-01

    Ceramic materials such as aluminium oxide and silicon carbide are regularly used as one of the counterfaces to oppose carbon graphite in a mechanical seal. Under nominally identical test conditions, the same carbon graphite face can show high wear rates against a material from one supplier but a significantly lower wear rate on a similar material from another. The general descriptions of aluminium oxide and silicon carbide can cover significant differences in properties between materials from various suppliers. Ceramic counterfaces from several manufacturers have been examined, after testing under similar conditions, in order to understand the microstructural factors that influence the wear of the carbon graphite and hence the lift of the mechanical seal. There is evidence to suggest that the wear resistance of the system depends on the grain size distribution, the integrity of the grain bonding and the presence of additional phases. 13 refs., 15 figs., 1 tab.

  13. 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.

  14. 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.

  15. High Cup Angle and Microseparation Increase the Wear of Hip Surface Replacements

    PubMed Central

    Williams, Sophie; Isaac, Graham; Ingham, Eileen; Fisher, John

    2009-01-01

    High wear rates and high patient ion levels have been associated with high (> 55°) cup inclination angles for metal-on-metal surface replacements. Wear rates and patterns have been simulated for ceramic-on-ceramic bearings by applying microseparation to replicate head offset deficiency. We tested 39-mm metal-on-metal surface replacements (n = 5) in a hip simulator with (A) an increased cup inclination angle of 60° and (B) an increased cup inclination angle and microseparation over 2 million cycles. (A) resulted in a ninefold increase in wear rate and (B) resulted in a 17-fold increase in wear rate compared to a standard gait condition study. Wear particles produced under microseparation conditions were larger than those produced under standard conditions but of similar shape (round to oval). The data suggest both head and cup position influence the wear of surface replacements; we believe it likely bearings with high wear either have a high cup inclination angle, an offset deficient head, or a combination of both. PMID:19363640

  16. Wear behavior of light-cured dental composites filled with porous glass-ceramic particles.

    PubMed

    Tan, Yanni; Liu, Yong; Grover, Liam M; Huang, Baiyun

    2010-01-01

    Wear resistance is still perceived to be one of the most important limiting factors in the long-term performance of dental restorations. Consequently, a range of different materials have been used as filler particles to reduce the rate of wear, particularly in posterior restorations. In this study, novel bioactive glass-ceramic powders exhibiting different nominal calcium-mica to fluorapatite ratios were used as fillers for light-cured dental composites. Wear tests on the resulting samples were undertaken using a micro-tribometer with a linear reciprocating ball-on-flat geometry using lubrication from artificial saliva. The surfaces of the worn composites were then evaluated using optical microscopy. In order to enhance matrix bonding, the surfaces of the different particulates were treated using hydrofluoric acid to provide a porous surface and the resulting surface morphology was evaluated using scanning electron microscopy. Although in the case of the samples containing low fluorapatite contents (20 wt%; A2), surface etching enhanced the wear resistance of the composite, etching reduced the wear resistance of materials containing 50 wt% fluorapatite (A5). The reduction in wear resistance was attributed to the friability of the A5 particles following surface treatment. This suggests that in order to optimize wear resistance, it is important to find a critical balance between surface roughness and porosity and the strength of individual particles.

  17. The Dry Sliding Wear Behavior of HVOF-Sprayed WC: Metal Composite Coatings

    NASA Astrophysics Data System (ADS)

    Ward, Liam P.; Pilkington, Antony

    2014-09-01

    WC-based cermet coatings containing various metallic binders such as Ni, Co, and Cr are known for their superior tribological properties, particularly abrasion resistance and enhanced surface hardness. Consequently, these systems are considered as replacements for traditional hard chrome coatings in critical aircraft components such as landing gear. The purpose of this investigation was to conduct a comparative study on the dry sliding wear behavior of three WC-based cermet coatings (WC-12Ni, WC-20Cr2C3-7Ni, and WC-10Co-4Cr), when deposited on carbon steel substrates. Ball on disk wear tests were performed on the coatings using a CSEM Tribometer (pin-on-disk) with a 6-mm ruby ball at 20 N applied load, 0.2 m/s sliding velocity, and sliding distances up to 2000 m. Analysis of both the coating wear track and worn ruby ball was performed using optical microscopy and an Alphastep-250 profilometer. The results of the study revealed both wear of the ruby ball and coated disks allowed for a comparison of both the ball wear and coating wear for the systems considered. Generally, the use of Co and Cr as a binder significantly improved the sliding wear resistance of the coating compared to Ni and/or Cr2C3.

  18. Wing wear reduces bumblebee flight performance in a dynamic obstacle course.

    PubMed

    Mountcastle, Andrew M; Alexander, Teressa M; Switzer, Callin M; Combes, Stacey A

    2016-06-01

    Previous work has shown that wing wear increases mortality in bumblebees. Although a proximate mechanism for this phenomenon has remained elusive, a leading hypothesis is that wing wear increases predation risk by reducing flight manoeuvrability. We tested the effects of simulated wing wear on flight manoeuvrability in Bombus impatiens bumblebees using a dynamic obstacle course designed to push bees towards their performance limits. We found that removing 22% wing area from the tips of both forewings (symmetric wear) caused a 9% reduction in peak acceleration during manoeuvring flight, while performing the same manipulation on only one wing (asymmetric wear) did not significantly reduce maximum acceleration. The rate at which bees collided with obstacles was correlated with body length across all treatments, but wing wear did not increase collision rate, possibly because shorter wingspans allow more room for bees to manoeuvre. This study presents a novel method for exploring extreme flight manoeuvres in flying insects, eliciting peak accelerations that exceed those measured during flight through a stationary obstacle course. If escape from aerial predation is constrained by acceleration capacity, then our results offer a potential explanation for the observed increase in bumblebee mortality with wing wear.

  19. Application of grey-taguchi method for optimization of dry sliding wear properties of aluminum MMCs

    NASA Astrophysics Data System (ADS)

    Siriyala, Rajesh; Alluru, Gopala Krishna; Penmetsa, Rama Murthy Raju; Duraiselvam, Muthukannan

    2012-09-01

    Through a pin-on-disc type wear setup, the dry sliding wear behavior of SiC-reinforced aluminum composites produced using the molten metal mixing method was investigated in this paper. Dry sliding wear tests were carried on SiC-reinforced metal matrix composites (MMCs) and its matrix alloy sliding against a steel counter face. Different contact stresses, reinforcement percentages, sliding distances, and sliding velocities were selected as the control variables, and the responses were selected as the wear volume loss (WVL) and coefficient of friction (COF) to evaluate the dry sliding performance. An L25 orthogonal array was employed for the experimental design. Initially, the optimization of the dry sliding performance of the SiC-reinforced MMCs was performed using grey relational analysis (GRA). Based on the GRA, the optimum level parameters for overall grey relational grade in terms of WVL and COF were identified. Analysis of variance was performed to determine the effect of individual factors on the overall grey relational grade. The results indicated that the sliding velocity was the most effective factor among the control parameters on dry sliding wear, followed by the reinforcement percentage, sliding distance, and contact stress. Finally, the wear surface morphology and wear mechanism of the composites were investigated through scanning electron microscopy.

  20. Wear behavior of light-cured dental composites filled with porous glass-ceramic particles.

    PubMed

    Tan, Yanni; Liu, Yong; Grover, Liam M; Huang, Baiyun

    2010-01-01

    Wear resistance is still perceived to be one of the most important limiting factors in the long-term performance of dental restorations. Consequently, a range of different materials have been used as filler particles to reduce the rate of wear, particularly in posterior restorations. In this study, novel bioactive glass-ceramic powders exhibiting different nominal calcium-mica to fluorapatite ratios were used as fillers for light-cured dental composites. Wear tests on the resulting samples were undertaken using a micro-tribometer with a linear reciprocating ball-on-flat geometry using lubrication from artificial saliva. The surfaces of the worn composites were then evaluated using optical microscopy. In order to enhance matrix bonding, the surfaces of the different particulates were treated using hydrofluoric acid to provide a porous surface and the resulting surface morphology was evaluated using scanning electron microscopy. Although in the case of the samples containing low fluorapatite contents (20 wt%; A2), surface etching enhanced the wear resistance of the composite, etching reduced the wear resistance of materials containing 50 wt% fluorapatite (A5). The reduction in wear resistance was attributed to the friability of the A5 particles following surface treatment. This suggests that in order to optimize wear resistance, it is important to find a critical balance between surface roughness and porosity and the strength of individual particles. PMID:19878904

  1. Effect of Experimental Variables of Abrasive Wear on 3D Surface Roughness and Wear Rate of Al-4.5 % Cu Alloy

    NASA Astrophysics Data System (ADS)

    Ghosh, Debashis; Mallik, Manab; Mandal, Nilrudra; Dutta, Samik; Roy, Himadri; Lohar, Aditya Kumar

    2016-05-01

    This investigation was primarily carried out to examine the abrasive wear behavior of as cast Al-4.5 % Cu alloy. Wear tests have been carried out using an abrasive wear machine with emery paper embedded with SiC particles acting as abrasive medium. The experiments were planned using central composite design, with, load, cycle and grit size as input variables, whereas wear rate and 3D roughness were considered as output variable. Analysis of variance was applied to check the adequacy of the mathematical model and their respective parameters. Microstructural investigations of the worn surfaces have been carried out to explain the observed results and to understand the wear micro-mechanisms as per the planned experiments. Desirability function optimization technique was finally employed to optimize the controlling factors. The observed results revealed that, grit size plays a significant role in the variation of wear rate and 3D roughness as compared to load and cycles. Based on the significance of interactions, the regression equations were derived and verified further with a number of confirmation runs to assess the adequacy of the model. A close agreement (±10 %) between the predicted and experimentally measured results was obtained from this investigation.

  2. A Multidirectional Tribo-System: Wear of UHMWPE under Sliding, Rolling, and Rotation

    NASA Astrophysics Data System (ADS)

    Patten, Elias Wolfgang

    Total knee replacements (TKR) have become a successful surgical procedure for addressing end-stage osteoarthritis, with ultra-high molecular weight polyethylene and cobalt chrome alloy (UHMWPE/Co-Cr) serving as the bearing materials of choice for decades. However, more than 10% of TKRs fail and require revision surgery. The predominant challenge with UHMWPE is the particulate debris generated through wear-mediated processes; wear debris from the UHMWPE tibial bearing surface leading to loosening is still the main cause for post-fifth-year revisions. UHMWPE wear in hip arthroplasty has been linked to microstructural evolution at the surface from multidirectional sliding in the hip joint but little is known about how the microstructure responds to clinically relevant sliding conditions in the knee. This is likely because wear tests are typically performed under basic motion parameters with simplified geometry (pin-on-disk tests) while the knee has more complex kinematics: it is neither a ball-and-socket joint nor a simple hinge joint, but has 2D sliding, rolling/slip motion, and rotation. There is also disagreement over how to best quantify cross-shear and how to model how much wear it will cause. A custom multidirectional tribo-system was used to investigate the individual and combined effects of the different motions in TKR: 2D sliding, rolling, and rotation, for a total of eight separate kinematic conditions. The trends in wear rates and wear factors for these different motions were compared with many different definitions for magnitudes and ratios of cross-shear. Additionally, the wear surfaces were examined for wear mechanism and the microstructural changes in lamellae orientation for the different motions were analyzed. To mimic the tribological conditions of a condyle in a TKR, polished Co-Cr spheres were articulated against flat, smooth UHMWPE disks with physiologically relevant loading, speed, and lubrication conditions. The motion parameters were selected

  3. Effect of SiC and Graphite Particulates Addition on Wear Behaviour of Al2219 Alloy Hybrid Composites

    NASA Astrophysics Data System (ADS)

    Nagaral, Madeva; Shivananda, B. K.; Jayachandran; Auradi, V.; Kori, S. A.

    2016-09-01

    In this investigation wear behaviour of A12219 alloy reinforced with SiC and graphite particulates were studied. The percentage of silicon carbide and graphite as reinforcements were varied from 2 wt.% to 4 wt.% in steps of 2. Energy dispersive spectroscopy and scanning electron microphotographs were used to confirm the presence of SiC and graphite particulates and its uniform distribution over the aluminum matrix. Wear behaviour of aluminum alloy Al2219 reinforced with silicon carbide and graphite fabricated by stir casting process was investigated. The wear properties of the metal matrix composites were studied by performing dry sliding wear test using a pin-on-disc wear tester. The experiments were conducted at a constant sliding velocity of 1.73m/s over a load of 2kg. The results showed that the wear resistance of Al2219-2%SiC-2% graphite and Al2219-4%SiC-4% graphite composites were better than the unreinforced alloy. The wear in terms of weight loss and wear rate was found to decrease with the increasing the weigh percentages of SiC and graphite. To study the dominant sliding wear mechanism worn surfaces were analyzed using scanning electron microscopy.

  4. FIBROUS MONOLITH WEAR RESISTANT COMPONENTS FOR THE MINING INDUSTRY

    SciTech Connect

    Mike L. Fulcher; Kenneth L. Knittel

    2004-06-08

    The work performed on this program was to develop wear resistant, tough FM composite materials with efforts focused on WC-Co based FM systems. The materials were developed for use in mining industry wear applications. Components of interest were drill bit inserts for drilling blast holes. Other component applications investigated included wear plates for a variety of equipment such as pit shovels, wear surfaces for conveyors, milling media for ball milling operations, hydrocyclone cones, grader blades and dozer teeth. Cross-cutting technologies investigated included hot metal extrusion dies, drill bits for circuit board fabrication, cutting tools for cast iron and aluminum machining. An important part of the work was identification of the standard materials used in drilling applications. A materials trade study to determine those metals and ceramics used for mining applications provided guidance for the most important materials to be investigated. WC-Co and diamond combinations were shown to have the most desirable properties. Other considerations such as fabrication technique and the ability to consolidate shifted the focus away from diamond materials and toward WC-Co. Cooperating partners such as Kennametal and Kyocera assisted with supplies, evaluations of material systems, fabricated parts and suggestions for cross-cutting technology applications for FM architectures. Kennametal provided the raw materials (WC-Co and Al-TiCN powders) for the extent of the material evaluations. Kyocera shared their research into various FM systems and provided laboratory testing of fabricated materials. Field testing provided by partners Superior Rock Bit and Brady Mining and Construction provided insight into the performance of the fabricated materials under actual operational conditions. Additional field testing of cross-cutting technology, the extrusion of hot metals, at Extruded Metals showed the potential for additional market development.

  5. Wear of two pit and fissure sealants in contact with primary teeth

    PubMed Central

    Galo, Rodrigo; Contente, Marta Maria Martins Giamatei; Borsatto, Maria Cristina

    2014-01-01

    Objectives: Wear simulations may provide an indication of the clinical performance of pit-and-fissure sealants when associated with primary teeth as counterbody, restricting the involved variables. The aim of this study was to evaluate wear of dental materials used as pit-and-fissure sealants in contact with primary teeth. Materials and Methods: A resinous sealant (Fluroshield®) and a resin-modified glass ionomer cement (Vitremer®) were selected in a post-plate design, using as counterbody primary tooth pins (4 × 4 × 2 mm) at 3 and 10 N vertical load, 1 Hz frequency, 900 wear cycles in artificial saliva (n = 15). Attrition coefficient values were obtained and the material and primary tooth volumes were analyzed. Data were analyzed statistically by ANOVA and Duncan's test (P < 0.05). Results: Fluroshield® presented the highest attrition coefficient values for the 3 N but these values decreased significantly for the 10 N load. The means for volume loss (3 mm) of the different samples after the wear test were not statistically different for the materials. The volume loss values for the primary teeth were statistically different and there was an increase in volume loss with the increase of the load applied in the wear tests. Conclusions: Differences were also observed with regard to the surface deformation characteristics. The wear rates of primary tooth enamel vary according to the type of material and the load applied during mastication. PMID:24966777

  6. Molecular dynamics simulations of wear processes

    NASA Astrophysics Data System (ADS)

    Yu, Hualiang

    Wear has been recognized as a vital problem in many industries. It results in a loss of durability, reliability, and efficiency and costs tens of billions of dollars annually. Significant effort has been devoted in both experimental and theoretical studies. However, the mechanisms of wear are still poorly understood and therefore wear control is far behind its demand. One way to study wear process is via computer simulation, which has become more powerful with the rapid development in computer facilities and efficient algorithms. It allows observation of atomic scale deformation and therefore it is a very good tool to study wear mechanisms at the nano-scale. This study presents a series of molecular dynamic simulation of some nano-scale wear processes, such as indentation and plowing, with the goal of exploring the factors that affect wear and predicting wear for different conditions. Molecular Dynamics simulations were carried out on a system that includes an aluminum substrate and a hard tip. Embedded atom method (EAM) and Lennard-Jones potentials were used to describe interactions between atoms. For nano-indentation simulations, both constant indent force and constant loading speed were applied to study the wear mechanisms as well as material properties. Some phenomenon, such as jump-to-contact, local melting, and dislocation nucleation were observed. More importantly, the effects of system temperature, indent force, substrate orientation, tip-substrate bond, indenter shape, boundary condition, and defect concentrations of the substrate were systematically investigated during indentation. The results are in qualitative agreement with limited experimental data. Similar simulations were carried out for plowing. The effects of plowing force, substrate orientation, the tip-substrate bond, and alloy elements are discussed based on the simulation results. In addition, a simple analytic model of plowing behavior is provided. The model reveals two parameters, static

  7. Wear of polyethylene cups in total hip arthroplasty: a parametric mathematical model.

    PubMed

    Pietrabissa, R; Raimondi, M; Di Martino, E

    1998-04-01

    This paper presents a parametric mathematical model of the head-cup wear coupling in total hip arthroplasty (THA). The model evaluates the dependence of acetabular volumetric wear upon the characteristic parameters of patient and hip prosthesis. Archard's law is assumed to calculate the wear coupling behaviour. The wear factor is taken from pin-on-disc wear tests as a function of materials and finishing of the articular joint. The forces acting on the hip joint are taken from experimental data found in the literature whilst the load distribution is calculated under the hypotheses of perfectly rigid ideal wear coupling. The sliding distance is obtained by combining the three elementary displacements -- due to rotations around the three axes -- at the generic bearing surface location. The simulations show that the polymeric wear volume per step cycle decreases ranging from fast walking speeds to low running speeds, it increases linearly with patient body weight and with femoral head diameter, it decreases slightly for positive variations of the socket inclination angle and it increases exponentially with femoral head roughness. The volumetric wear rate per year calculated for a standard reference patient is 5.8 mm3. The relevant iso-wear maps show a marginal pattern with the maximum located near the cup superior borderline. At the instant of peak load, the iso-stress maps show a paracentral pattern with the maximum superior to the cup polar point, and the iso-sliding distance maps show a marginal pattern with two maxima located near the cup's superior and inferior borderlines. PMID:9690490

  8. The influence of material and design on total knee replacement wear.

    PubMed

    Essner, Aaron; Herrera, Lizeth; Hughes, Phillip; Kester, Mark

    2011-03-01

    It is difficult for surgeons to make the decision on which design or material to use given the different options available. Marketing claims and direct-to-consumer advertising certainly complicate this further. One company may claim a higher percentage of wear reduction with their bearing surfaces compared with those of another manufacturer. If the percentage of wear reduction is lower, it is unclear as to whether this creates a more effective technology for reducing wear in the clinical situation. The relative contribution and relationship of design and materials to wear performance must be considered before making that important judgment. To examine the overall influence of implant design on wear reduction, a knee simulator study was undertaken. This simulator study compared the Oxinium Genesis II system with the Triathlon Conventional and Triathlon X3 knee systems under physiologic stair-climb loading and motion profiles. This allows a similar comparison of material effect within one design but also a global comparison across designs. Test results show the Triathlon Conventional and Triathlon X3 knee systems have superior wear resistance compared with that of the Genesis II Oxinium system under stair-climbing simulation. This finding indicates that implant design plays a more significant role in knee wear reduction than material. Although material technology may improve a given knee system's ability to wear, design geometry has a first-order effect and should be addressed before materials. This study represents an effort to differentiate design effect from two different approaches to material enhancement. The results of this study support the predominance of design in knee replacement wear performance. Ultimately, only clinical evidence such as published studies or outcomes reported in the available joint registries will establish whether any material or design can achieve a 30-year outcome. PMID:21618933

  9. Integrated friction measurements in hip wear simulations: short-term results.

    PubMed

    Spinelli, M; Affatato, S; Tiberi, L; Carmignato, S; Viceconti, M

    2010-01-01

    Hip joint wear simulators are used extensively to simulate the dynamic behaviour of the human hip joint and, through the wear rate, gain a concrete indicator about the overall wear performance of different coupled bearings. Present knowledge of the dynamic behaviour of important concurrent indicators, such as the coefficient of friction, could prove helpful for the continuing improvement in applied biomaterials. A limited number of commercial or custom-made simulators have been designed specifically for friction studies but always separately from wear tests; thus, analysis of these two important parameters has remained unconnected. As a result, a new friction sensor has been designed, built, and integrated in a commercial biaxial rocking motion hip simulator. The aim of this study is to verify the feasibility of an experimental set-up in which the dynamic measurement of the friction factor could effectively be implemented in a standard wear test without compromising its general accuracy and repeatability. A short wear test was run with the new set-up for 1 x 10(6) cycles. In particular, three soft-bearings (metal-on-polyethylene, phi = 28 mm) were tested; during the whole test, axial load and frictional torque about the vertical loading axis were synchronously recorded in order to calculate the friction factor. Additional analyses were performed on the specimens, before and after the test, in order to verify the accuracy of the wear test. The average friction factor was 0.110 +/- 0.025. The friction sensors showed good accuracy and repeatability throughout. This innovative set-up was able to reproduce stable and reliable measurements. The results obtained encourage further investigations of this set-up for long-term assessment and using different combinations of materials.

  10. Wear of Selected Oxide Ceramics and Coatings

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Sayir, A.; Farmer, S. C.

    2005-01-01

    The use of oxide ceramics and coatings for moving mechanical components operating in high-temperature, oxidizing environments creates a need to define the tribological performance and durability of these materials. Results of research focusing on the wear behavior and properties of Al2O3/ZrO2 (Y2O3) eutectics and coatings under dry sliding conditions are discussed. The importance of microstructure and composition on wear properties of directionally solidified oxide eutectics is illustrated. Wear data of selected oxide-, nitride-, and carbide-based ceramics and coatings are given for temperatures up to 973K in air.

  11. Wear mechanism of diamond coated cutting tools

    SciTech Connect

    Leyendecker, T.; Lemmer, O.; Esser, S.

    1995-12-31

    Since Diamond Coatings were introduced into the market in 1989, five years experience in industrial applications of diamond coated cutting tools enables to present an overview of tool life and wear behavior of diamond coated cutting tools due to different cutting conditions and workpiece-materials. Machining reinforced plastics, presintered ceramic compacts, aluminum alloys, metal-matrix composites and graphite, different wear behavior occurs at the cutting edges of diamond coated tools. Having a good adhesion fatigue and chemical wear of Diamond coatings determines life time of the tools. By a profound pretreatment procedure CVD Diamond coated tools can compete with conventional PCD-tools.

  12. Microstructural influence on abrasive wear resistance of high-strength, high-toughness medium-carbon steels

    SciTech Connect

    Kwok, C.K.; Thomas, G.

    1982-09-01

    A systematic study of abrasive wear resistance of Fe/Cr/Mn experimental steels has been carried out in two-body pin-on-disc abrasion tests. Silicon carbide, alumina, and quartz were used as abrasives. The relationships between microstructures, mechanical properties, and abrasive wear resistance for these experimental steels were studied. In addition, several commercial alloys were tested to provide a basis for comparison. Results show that dislocated lath martensite with continuous interlath film of retained austenite appears to be a desirable microstructure for good wear resistance. Grain refinement by double heat treatment was found to improve the toughness in the experimental steels but have little effect on the abrasive wear resistance. In general, superior tensile properties and wear resistance, without sacrifice in toughness, can be achieved by a lath martensitic microstructure. 8 figures.

  13. Adhesive Wear Behavior of Heat Treated Spheroidal Graphite Cast Iron

    NASA Astrophysics Data System (ADS)

    Salim, M.; Shama, S.; Mozumder, Y. H.; Behera, R. K.; P, Sindhoora L.; Pattanaik, A.; Mishra, S. C.; Sen, S.

    2015-02-01

    Spheroidal graphite cast iron is one of the most favorable materials in cast iron family due to its wide range of mechanical and tribological properties. In the current research priority is given towards the investigation of wear system response of spheroidal graphite cast iron subjected to various heat treatment conditions. Pearlitic/ferritic and upper bainitic matrix was obtained through normalizing and austempering treatment for an austenitizing temperature of 1000°C. Dry sliding wear test was performed at 10N, 20N, 30N for a sliding distance of 7.54m. With increase in load weight loss was observed for as-cast specimen whereas normalized specimen showed very less weight loss with increasing load. On the other hand the austempered specimen observed to lose weight when operated at 10N, whereas at 20N and 30N drastic gain in weight was observed.

  14. Evaluating lubricant performance by 3D profilometry of wear scars

    NASA Astrophysics Data System (ADS)

    Georgescu, C.; Deleanu, L.; Pirvu, C.

    2016-08-01

    Due to improvement in analysing surface texture and optical instruments for investigating the texture surface, the authors propose to evaluate the lubricant performance by analysing the change in several 3D parameters in comparison to an analysis on 2D profile. All the surface of the wear scar generated on the four ball machine is investigated and the conclusion is that from the tribological point of view, the 3D parameters reflect better the surface quality evolution after testing. Investigation was done on the wear scars generated on the three fixed balls, for five lubricants: a non-additivated transmission mineral oil (T90), two grades of rapeseed oil (coarse degummed and refined) and two grades of soybean oil (coarse and degummed).

  15. Characterization of cathode keeper wear by surface layer activation

    NASA Technical Reports Server (NTRS)

    Polk, James E.

    2003-01-01

    In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

  16. Simultaneous measurement of friction and wear in hip simulators.

    PubMed

    Haider, Hani; Weisenburger, Joel N; Garvin, Kevin L

    2016-05-01

    We propose and have evaluated a method to measure hip friction during wear testing on a popular multi-station hip simulator. A 6-degree-of-freedom load cell underneath the specimen sensed forces and torques during implant wear testing of simulated walking. This included internal-external and adduction-abduction rotations which are often neglected during friction testing on pendulum-type machines. Robust mathematical analysis and data processing provided friction estimates in three simultaneous orthogonal rotations, over extended multi-million cycle wear tests. We tested various bearing couples including metal-on-plastic, ceramic-on-plastic, and metal-on-metal material couples. In one test series, new and intentionally scratched CoCrMo 40-mm-diameter femoral heads were tested against conventional ultrahigh-molecular-weight polyethylene, highly cross-linked, and highly cross-linked with vitamin E versions. The scratching significantly increased friction and doubled the wear of all groups. Before scratching, friction levels for the aforementioned plastic groups were 0.056 ± 0.0060, 0.062 ± 0.0080, and 0.070 ± 0.0045, respectively, but after scratching increased to 0.088 ± 0.018, 0.076 ± 0.0066, and 0.082 ± 0.0049, respectively, all statistically significant increases (p = 0.00059, 0.00005, 0.0115, respectively). In another test series of 44-mm femoral head diameter hips, metal-on-plastic hips with conventional ultrahigh-molecular-weight polyethylene showed the lowest friction at 0.045 ± 0.0085, followed by highly cross-linked with 0.046 ± 0.0035 (not significantly different). In a ceramic-on-plastic design with conventional ultrahigh-molecular-weight polyethylene, higher friction 0.079 ± 0.0070 was measured likely due to that ceramic surface being rougher than usual. Metal-on-metal hips were compared without and with a TiN coating, resulting in 0.049 ± 0.014 and 0.097 ± 0.020 friction factors, respectively

  17. Simultaneous measurement of friction and wear in hip simulators.

    PubMed

    Haider, Hani; Weisenburger, Joel N; Garvin, Kevin L

    2016-05-01

    We propose and have evaluated a method to measure hip friction during wear testing on a popular multi-station hip simulator. A 6-degree-of-freedom load cell underneath the specimen sensed forces and torques during implant wear testing of simulated walking. This included internal-external and adduction-abduction rotations which are often neglected during friction testing on pendulum-type machines. Robust mathematical analysis and data processing provided friction estimates in three simultaneous orthogonal rotations, over extended multi-million cycle wear tests. We tested various bearing couples including metal-on-plastic, ceramic-on-plastic, and metal-on-metal material couples. In one test series, new and intentionally scratched CoCrMo 40-mm-diameter femoral heads were tested against conventional ultrahigh-molecular-weight polyethylene, highly cross-linked, and highly cross-linked with vitamin E versions. The scratching significantly increased friction and doubled the wear of all groups. Before scratching, friction levels for the aforementioned plastic groups were 0.056 ± 0.0060, 0.062 ± 0.0080, and 0.070 ± 0.0045, respectively, but after scratching increased to 0.088 ± 0.018, 0.076 ± 0.0066, and 0.082 ± 0.0049, respectively, all statistically significant increases (p = 0.00059, 0.00005, 0.0115, respectively). In another test series of 44-mm femoral head diameter hips, metal-on-plastic hips with conventional ultrahigh-molecular-weight polyethylene showed the lowest friction at 0.045 ± 0.0085, followed by highly cross-linked with 0.046 ± 0.0035 (not significantly different). In a ceramic-on-plastic design with conventional ultrahigh-molecular-weight polyethylene, higher friction 0.079 ± 0.0070 was measured likely due to that ceramic surface being rougher than usual. Metal-on-metal hips were compared without and with a TiN coating, resulting in 0.049 ± 0.014 and 0.097 ± 0.020 friction factors, respectively

  18. Wear and friction of oxidation-resistant mechanical carbon graphites at 650 C in air

    NASA Technical Reports Server (NTRS)

    Allen, G. P.; Wisnader, D. W.

    1975-01-01

    Studies were conducted to determine the friction and wear properties of experimental carbon-graphites. Hemispherically tipped carbon-graphite rider specimens were tested in sliding contact with rotating Inconel X-750 disks in air. A surface speed of 1.33 m/sec, a load of 500 g, and a specimen temperature of 650 C were used. Results indicate: (1) hardness is not a major factor in determining friction and wear under the conditions of these studies. (2) Friction and wear as low as or lower than those observed for a good commercial seal material were attained with some of the experimental materials studied. (3) The inclusion of boron carbide (as an oxidation inhibitor) has a strong influence on wear rate. (4) Phosphate treatment reduces the friction coefficient when boron carbide is not present in the base material.

  19. Optimization of Wear Behavior of Magnesium Alloy AZ91 Hybrid Composites Using Taguchi Experimental Design

    NASA Astrophysics Data System (ADS)

    Girish, B. M.; Satish, B. M.; Sarapure, Sadanand; Basawaraj

    2016-06-01

    In the present paper, the statistical investigation on wear behavior of magnesium alloy (AZ91) hybrid metal matrix composites using Taguchi technique has been reported. The composites were reinforced with SiC and graphite particles of average size 37 μm. The specimens were processed by stir casting route. Dry sliding wear of the hybrid composites were tested on a pin-on-disk tribometer under dry conditions at different normal loads (20, 40, and 60 N), sliding speeds (1.047, 1.57, and 2.09 m/s), and composition (1, 2, and 3 wt pct of each of SiC and graphite). The design of experiments approach using Taguchi technique was employed to statistically analyze the wear behavior of hybrid composites. Signal-to-noise ratio and analysis of variance were used to investigate the influence of the parameters on the wear rate.

  20. Lightweight TiC/Ti alloy wear resistant coatings for lightweight materials in aerospace applications

    SciTech Connect

    Smith, R.W.; Mohanty, M.

    1994-12-31

    Plasma spray deposition of titanium and up to 80 vol% titanium carbide (TiC)/titanium matrix composite materials have been investigated for their applicability as wear resistant coatings for protecting light weight substrate materials, such as aluminum. Studies of the air and low pressure plasma sprayed TiC/Ti coatings were completed and are reported. The coatings were characterized and the influence of processing methods on structure and the subsequent wear behavior of the coatings is reported. The investigation includes the effects of spraying in air, controlled atmosphere and in shrouded spray systems. Coating hardness values are reported and wear rates and friction behavior on aluminum substrates in ASTM C99-93 Pin-on-Disk (P.O.D.) wear testing are characterized.

  1. 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

  2. Interactions among friction wear, and system stiffness. Part 3. Wear model

    SciTech Connect

    Aronov, V.; D'Souza, A.F.; Kalpakjian, S.; Shareef, I.

    1983-01-01

    It is shown that wear is an increasing function of system stiffness. The increase in the frequency of the applied load oscillations in normal direction causes increase of number of loading cycles per unit time that, in turn, causes increased rate of wear particles formation due to fatigue. A wear model has been developed which accounts for slider oscillation in the normal direction. Experimental data correlate very well with the theoretical analysis. 11 references, 7 figures, 3 tables.

  3. Reducing Wear of Steel Rolling Against Ti6Al4V Operating in Vacuum

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.

    2014-01-01

    This work was motivated by a qualification test of a mechanism for a space telescope. During the test undesired wear debris was formed. In this project alterative materials and coatings were tested with intent to reduce wear and debris when steel has a misaligned rolling contact against Ti6Al4V. Testing was done using a vacuum roller rig mimicking the mechanism's contact conditions. Ten configurations were tested. Most configurations resulted in significant debris. A sputtered 1-micrometer-thick nan-ocomposite molybdenum disulfide (MoS2) film provided the best wear protection. The best configuration made use of the MoS2 coating on both materials, and in preparing for sputtering the anodized Ti6Al4V working surface was smoothed using an ultrasonic process.

  4. Effect of active screen plasma nitriding pretreatment on wear behavior of TiN coating deposited by PACVD technique

    NASA Astrophysics Data System (ADS)

    Raoufi, M.; Mirdamadi, Sh.; Mahboubi, F.; Ahangarani, Sh.; Mahdipoor, M. S.; Elmkhah, H.

    2012-08-01

    Titanium based alloys are used extensively for improving wear properties of different parts due to their high hardness contents. Titanium nitride (TiN) is among these coatings which can be deposited on surface using various techniques such as CVD, PVD and PACVD. Their weak interface with substrate is one major drawback which can increase the total wear in spite of favorite wear behavior of TiN. Disc shaped samples from AISI H13 (DIN 1.2344) steel were prepared in this study. Single TiN coating was deposited on some of them while others have experienced a TiN deposition by active screen plasma nitriding (ASPN). Hardness at the surface and depth of samples was measured through Vickers micro hardness test which revealed 1810 Hv hardness as the maximum values for a dual-layered ASPN-TiN. Pin-on-disc wear test was done in order to study the wear mechanism. In this regard, the wear behavior of samples was investigated against pins from 100Cr6 (Din 1.3505) bearing steel and tungsten carbide-cobalt (WC-Co) steel. It was evidenced that the dual-layer ASPN-TiN coating has shown the least weight loss with the best wearing behavior because of its high hardness values, stable interface and acceptable resistance against peeling during wearing period.

  5. Sliding wear studies using acoustic emission

    NASA Astrophysics Data System (ADS)

    Lingard, S.; Yu, C. W.; Yau, C. F.

    1993-04-01

    Deformation processes in solids, such as dislocation movements under plastic flow, crack propagation and void crushing, produce stress waves at ultrasonic frequencies, usually described as acoustic emission (AE), which can be detected by sensitive instruments and which are related to the severity and nature of the deformations. The paper discusses the characteristics of the stress waves and their variation with wear rates, wear regimes, and friction forces, as determined during laboratory experiments on metallic specimens in relative sliding motion, both unlubricated and with elastohydrodynamic lubrication. It is shown that there are systematic relationships between the acoustic emissions, the wear rates, the frictional work inputs and established tribological contact variables. The predominant frequencies of the emissions are also evaluated and considered in relation to the materials and wear conditions.

  6. The Wearing Out of Genre Materials

    ERIC Educational Resources Information Center

    Russ, Joanna

    1971-01-01

    Scenes and plots wear out in three distinct stages: Innocence, Plausibility, and Decadence. Examines westerns, spy stories, nurse novels, detective stories, science fiction, pornography, avant-garde fiction, etc. (Author/RB)

  7. 19 CFR 10.35 - Models of women's wearing apparel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Models of women's wearing apparel. 10.35 Section... Temporary Importations Under Bond § 10.35 Models of women's wearing apparel. (a) Models of women's wearing... the importer or his employees. (b) Invoices covering models of women's wearing apparel entered...

  8. 19 CFR 10.35 - Models of women's wearing apparel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Models of women's wearing apparel. 10.35 Section... Temporary Importations Under Bond § 10.35 Models of women's wearing apparel. (a) Models of women's wearing... the importer or his employees. (b) Invoices covering models of women's wearing apparel entered...

  9. 19 CFR 10.35 - Models of women's wearing apparel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Models of women's wearing apparel. 10.35 Section... Temporary Importations Under Bond § 10.35 Models of women's wearing apparel. (a) Models of women's wearing... the importer or his employees. (b) Invoices covering models of women's wearing apparel entered...

  10. 19 CFR 10.35 - Models of women's wearing apparel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Models of women's wearing apparel. 10.35 Section... Temporary Importations Under Bond § 10.35 Models of women's wearing apparel. (a) Models of women's wearing... the importer or his employees. (b) Invoices covering models of women's wearing apparel entered...

  11. 19 CFR 10.35 - Models of women's wearing apparel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Models of women's wearing apparel. 10.35 Section... Temporary Importations Under Bond § 10.35 Models of women's wearing apparel. (a) Models of women's wearing... the importer or his employees. (b) Invoices covering models of women's wearing apparel entered...

  12. Studies of friction and wear characteristics of various wires for wire-brush skids

    NASA Technical Reports Server (NTRS)

    Dreher, R. C.

    1977-01-01

    The friction and wear characteristics of 22 types and sizes of wires for potential use in wire-brush skids were studied. These characteristics were determined by placing brushes made from candidate wires on a belt sander whose moving belt simulated landing roll-out distance. At the same time, the drag force and wear behavior were monitored. Data were obtained over distances up to 3048 m (10,000 ft) at preselected bearing pressures of 172 to 1034 kPa (25 to 150 psi). In general, the friction coefficient developed by the candidate wires was found to be independent of bearing pressure and ranged between 0.4 and 0.6 under the test conditions of this investigation. The friction coefficient was not degraded when the surface was wetted and appears to be independent of wire diameter except perhaps when wire size is relatively large compared with the surface asperities. Generally, the high friction demonstrated by the soft materials was accompanied by high wear rates; conversely, the hard materials provided greater wear resistance but offered lower friction. For all test wires, the wear was shown to increase with increasing bearing pressure, in general, for the same bearing pressure, wear increased with increasing wire diameter and decreased when the surface was wetted.

  13. Epoxy matrix composites filled with micro-sized LD sludge: wear characterization and analysis

    NASA Astrophysics Data System (ADS)

    Purohit, Abhilash; Satapathy, Alok

    2016-02-01

    Owing to the very high cost of conventional filler materials in polymer composites, exploring the possibility of using low cost minerals and industrial wastes for this purpose has become the need of the hour. In view of this, the present work includes the development and the wear performance evaluation of a new class of composites consisting of epoxy and microsized LD sludge. LD sludge or the Linz-Donawitz Sludge (LDS) are the fine solid particles recovered after wet cleaning of the gas emerging from LD convertors during steel making. Epoxy composites filled with different proportions (0, 5, 10, 15 and 20 wt %) of LDS are fabricated by conventional hand lay-up technique. Dry sliding wear trials are performed on the composite specimens under different test conditions as per ASTM G 99 following a design of experiment approach based on Taguchi's orthogonal arrays. The Taguchi approach leads to the recognition of most powerful variables that predominantly control the wear rate. This parametric analysis reveals that LDS content and sliding velocity affects the specific wear rate more significantly than normal load and sliding distance. Furthermore with increase in LDS content specific wear rate of the composite decreases for a constant sliding velocity. The sliding wear behavior of these composites under an extended range of test conditions is predicted by a model based on the artificial neural network (ANN).

  14. In vitro wear of four ceramic materials and human enamel on enamel antagonist.

    PubMed

    Nakashima, Jun; Taira, Yohsuke; Sawase, Takashi

    2016-06-01

    The purpose of the present study was to evaluate the wear of four different ceramics and human enamel. The ceramics used were lithium disilicate glass (e.max Press), leucite-reinforced glass (GN-Ceram), yttria-stabilized zirconia (Aadva Zr), and feldspathic porcelain (Porcelain AAA). Hemispherical styli were fabricated with these ceramics and with tooth enamel. Flattened enamel was used for antagonistic specimens. After 100,000 wear cycles of a two-body wear test, the height and volume losses of the styli and enamel antagonists were determined. The mean and standard deviation for eight specimens were calculated and statistically analyzed using a non-parametric (Steel-Dwass) test (α = 0.05). GN-Ceram exhibited greater stylus height and volume losses than did Porcelain AAA. E.max Press, Porcelain AAA, and enamel styli showed no significant differences, and Aadva Zr exhibited the smallest stylus height and volume losses. The wear of the enamel antagonist was not significantly different among GN-Ceram, e.max Press, Porcelain AAA, and enamel styli. Aadva Zr resulted in significantly lower wear values of the enamel antagonist than did GN-Ceram, Porcelain AAA, and enamel styli. In conclusion, leucite-reinforced glass, lithium disilicate glass, and feldspathic porcelain showed wear values closer to those for human enamel than did yttria-stabilized zirconia. PMID:27059093

  15. Effects of long-term corset wearing on chronic low back pain.

    PubMed

    Sato, Naoto; Sekiguchi, Miho; Kikuchi, Shinichi; Shishido, Hiroaki; Sato, Katsuhiko; Konno, Shinichi

    2012-01-01

    There are few studies of the therapeutic effects of long-term corset wearing in patients with chronic low back pain. The aim of this study was to evaluate the effects of long-term corset wearing on chronic low back pain and to examine the myoelectrical activities of the paravertebral muscles. Forty subjects with chronic low back pain were enrolled and randomly divided into two groups: a group wearing corsets for 6 months (CW) group and a group not wearing corsets (NW). The treatment effects were measured using the Japanese Orthopaedic Association (JOA) score. Muscle endurance was evaluated during the Biering-Sorensen test (S-test), and the degree of muscle fatigue was evaluated by the change in percent mean power frequency (%MPF) of the paravertebral muscles. Corset treatment for chronic low back pain improved low back pain and increased muscle endurance for a short period of time. Paravertebral muscle fatigue was not increased by long-term corset wearing for chronic low back pain, and weakening of the paravertebral muscles was not observed up to 6 months after the start of corset wearing.

  16. The use of analytical surface tools in the fundamental study of wear. [atomic nature of wear

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1977-01-01

    Various techniques and surface tools available for the study of the atomic nature of the wear of materials are reviewed These include chemical etching, x-ray diffraction, electron diffraction, scanning electron microscopy, low-energy electron diffraction, Auger emission spectroscopy analysis, electron spectroscopy for chemical analysis, field ion microscopy, and the atom probe. Properties of the surface and wear surface regions which affect wear, such as surface energy, crystal structure, crystallographic orientation, mode of dislocation behavior, and cohesive binding, are discussed. A number of mechanisms involved in the generation of wear particles are identified with the aid of the aforementioned tools.

  17. Characterization and measurement of polymer wear

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Aron, P. R.

    1984-01-01

    Analytical tools which characterize the polymer wear process are discussed. The devices discussed include: visual observation of polymer wear with SEM, the quantification with surface profilometry and ellipsometry, to study the chemistry with AES, XPS and SIMS, to establish interfacial polymer orientation and accordingly bonding with QUARTIR, polymer state with Raman spectroscopy and stresses that develop in polymer films using a X-ray double crystal camera technique.

  18. 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.

  19. Meibomian therapy in problematic contact lens wear.

    PubMed

    Paugh, J R; Knapp, L L; Martinson, J R; Hom, M M

    1990-11-01

    Utilizing the principal diagnostic criterion of an absent or cloudy Meibomian gland secretion upon repeated expression, patients with Meibomian gland dysfunction (MGD) were selected to participate in a study of the efficacy of lid scrubs and massage in the treatment of MGD. Twenty-one patients with contact lens intolerance unrelated to lens, care system, or health factors were randomly assigned to treatment of one eye with common clinical therapy for MGD. After 2 weeks of treatment, gland expression, biomicroscopy, staining, comfort, and fluorescein breakup time were assessed in a masked manner. Analyzed using a paired-data t-test, the results indicated a significant increase in mean tear film breakup time (BUT) in the treated eye at follow-up compared to baseline (mean increase = 4.0 s, p = 0.0001). The control eye demonstrated no significant change (mean increase = 0.2 s, p = 0.5955). These objective results were corroborated by reports of improved subjective comfort with contact lens wear after therapy.

  20. Effect of wear of bearing surfaces on elastohydrodynamic lubrication of metal-on-metal hip implants.

    PubMed

    Liu, F; Jin, Z M; Hirt, F; Rieker, C; Roberts, P; Grigoris, P

    2005-09-01

    The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 microm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul bearing to achieve a fluid film lubrication regime during this period, and this was

  1. Brief communication: Comparative patterns of enamel thickness topography and oblique molar wear in two Early Neolithic and medieval population samples.

    PubMed

    Le Luyer, Mona; Rottier, Stéphane; Bayle, Priscilla

    2014-09-01

    Enamel thickness has been linked to functional aspects of masticatory biomechanics and has been demonstrated to be an evolutionary plastic trait, selectively responsive to dietary changes, wear and tooth fracture. European Late Paleolithic and Mesolithic hunter-gatherers mainly show a flat wear pattern, while oblique molar wear has been reported as characteristic of Neolithic agriculturalists. We investigate the relationships between enamel thickness distribution and molar wear pattern in two Neolithic and medieval populations. Under the assumption that dietary and/or non-dietary constraints result in directional selective pressure leading to variations in enamel thickness, we test the hypothesis that these two populations will exhibit significant differences in wear and enamel thickness patterns. Occlusal wear patterns were scored in upper permanent second molars (UM2) of 64 Neolithic and 311 medieval subadult and adult individuals. Enamel thickness was evaluated by microtomography in subsamples of 17 Neolithic and 25 medieval individuals. Eight variables describing enamel thickness were assessed. The results show that oblique molar wear is dominant in the Neolithic sample (87%), while oblique wear affects only a minority (42%) of the medieval sample. Moreover, in the Neolithic molars, where buccolingually directed oblique wear is dominant and greatest enamel lost occurs in the distolingual quadrant, thickest enamel is found where occlusal stresses are the most important-on the distolingual cusp. These results reveal a correlation between molar wear pattern and enamel thickness that has been associated to dietary changes. In particular, relatively thicker molar enamel may have evolved as a plastic response to resist wear.

  2. Characterization of coating wear phenomena in nitride and carbide coated tool inserts

    SciTech Connect

    Fenske, G.R.; Kaufherr, N.; Lee, R.H.; Kramer, B.M.; Bunshah, R.F.; Sproul, W.D.

    1988-01-01

    Hard nitride- and carbide- coatings of Ti, Zr, and Hf were deposited on T-15 cutting tool inserts using high-rate reactive sputtering (HRRS) and activated reactive evaporation (ARE) processes. The coated inserts were subjected to a series of metal cutting tests to evaluate their performance and to compare their relative ranking with wear model predictions. The cutting tests indicated the coated inserts outperformed uncoated inserts by a factor of 2- to 10 depending on the coating process and composition; however their ranking based on measured lifetime (to reach a 0.003 in. crater depth) did not agree with predicted wear model predictions. Subsequently, a series of short-term cutting tests were initiated to study the wear behavior of the coatings during the early stages of the wear process when the coating was still intact. Post-test examination of the inserts suggest that the predominant wear mechanism was not due to abrasion or thermochemical dissolution as predicted by the model, but was a result of substrate softening followed by microfracture of the coating. The substrate softening is attributed to the severe cutting conditions (325 sfpm under dry cutting conditions) used in the cutting tests. 12 refs., 5 figs., 1 tab.

  3. Association between friction and wear in diarthrodial joints lacking lubricin

    PubMed Central

    Jay, Gregory D; Torres, Jahn R; Rhee, David K; Helminen, Heikki J; Hytinnen, Mika M; Cha, Chung-Ja; Elsaid, Khaled; Kim, Kyung-Suk; Cui, Yajun; Warman, Matthew L

    2007-01-01

    Objective The glycoprotein lubricin (encoded by the gene Prg4) is secreted by surface chondrocytes and synovial cells, and has been shown to reduce friction in vitro. In contrast to man-made bearings, mammalian diarthrodial joints must endogenously produce friction-reducing agents. This study was undertaken to investigate whether friction is associated with wear. Methods The lubricating ability of synovial fluid (SF) samples from humans with genetic lubricin deficiency was tested in vitro. The coefficient of friction in the knee joints of normal and lubricin-null mice was measured ex vivo; these joints were also studied by light and electron microscopy. Atomic force microscopy was used to image and measure how lubricin reduces friction in vitro. Results SF lacking lubricin failed to reduce friction in the boundary mode. Joints of lubricin-null mice showed early wear and higher friction than joints from their wild-type counterparts. Lubricin self-organized and reduced the work of adhesion between apposing asperities. Conclusion These data show that friction is coupled with wear at the cartilage surface in vivo. They imply that acquired lubricin degradation occurring in inflammatory joint diseases predisposes the cartilage to damage. Lastly, they suggest that lubricin, or similar biomolecules, will have applications in man-made devices in which reducing friction is essential. PMID:17968947

  4. Wear mechanisms in thermally-sprayed Mo-based coatings

    NASA Astrophysics Data System (ADS)

    Wayne, S. F.; Sampath, S.; Anand, V.

    1994-07-01

    The successful development of advanced diesel engines relies heavily on piston ring coating materials which can withstand elevated temperatures and reduce friction. Traditional hard chrome plating and flame-sprayed Mo-wire materials have reached their potential in the diesel engine environment, and alternatives are needed. Thermally-sprayed Mo-based alloys and composites are being evaluated for applications as next-generation ring-face coatings. The alloy development task of producing complex Mo-based alloy powders for use as thermally-sprayed coating materials requires an understanding of their wear resistance under contact stress conditions. In this paper, the wear behavior of Mo and Mo + NiCrBSi thermally sprayed coatings is exmined by pin-on-disc and single-point scratch-test methods. Microstructural analysis beneath worn regions have revealed that fracture of splats and their decohesion constitute the mode of failure. Improved wear resistance and stability of low friction coefficient was obtained by prealloying Mo with NiCrBSi prior to thermal spraying.

  5. Dynamic evolution of interface roughness during friction and wear processes.

    PubMed

    Kubiak, K J; Bigerelle, M; Mathia, T G; Dubois, A; Dubar, L

    2014-01-01

    Dynamic evolution of surface roughness and influence of initial roughness (S(a) = 0.282-6.73 µm) during friction and wear processes has been analyzed experimentally. The mirror polished and rough surfaces (28 samples in total) have been prepared by surface polishing on Ti-6Al-4V and AISI 1045 samples. Friction and wear have been tested in classical sphere/plane configuration using linear reciprocating tribometer with very small displacement from 130 to 200 µm. After an initial period of rapid degradation, dynamic evolution of surface roughness converges to certain level specific to a given tribosystem. However, roughness at such dynamic interface is still increasing and analysis of initial roughness influence revealed that to certain extent, a rheology effect of interface can be observed and dynamic evolution of roughness will depend on initial condition and history of interface roughness evolution. Multiscale analysis shows that morphology created in wear process is composed from nano, micro, and macro scale roughness. Therefore, mechanical parts working under very severe contact conditions, like rotor/blade contact, screws, clutch, etc. with poor initial surface finishing are susceptible to have much shorter lifetime than a quality finished parts. PMID:23440686

  6. Characterization of wear in composite material orthopaedic implants. Part II: The implant/bone interface.

    PubMed

    Albert, K; Schledjewski, R; Harbaugh, M; Bleser, S; Jamison, R; Friedrich, K

    1994-01-01

    Carbon fiber/PEEK polymer (C/PEEK) composite materials are being developed for use as orthopaedic implant materials. Wear is an issue of increasing importance in orthopaedic implants; particulate debris generated by the wearing of biomaterials may be a causal factor leading to osteolysis and implant loosening. Therefore, numerical and experimental studies were completed to characterize the wear of C/PEEK composite materials in comparison to current orthopaedic implant materials. Finite element analyses (FEA) of a composite material hip stem implanted in a femur and loaded at 890 N determined that peak contact stresses will occur at the proximal-medial and distal regions of the implant. These contact stresses were found to be below 1.0 MPa over most of the implant surface; however the peak stress in the proximal-medial region was 1.8 MPa and higher still at the distal portion of the stem. In vivo forces result in contact stress values up to 9.0 MPa. The composite implant exhibited 10-40% lower contact stresses in the distal region compared to a titanium-alloy implant of identical design. Composite material wear samples were slid against porous hydroxylapatite (HA) to simulate the stem/bone interface. An identical series of experiments was run for comparison to a current orthopaedic implant material--Ti6A14V titanium alloy. Two domains of motion were studied; a composite ring-on-HA disc large amplitude sliding wear test; and a composite pin-on-HA disc small amplitude fretting regimen. Nominal contact pressures during testing were 1.4 MPa and 7.6 MPa for sliding and fretting tests, respectively. Fretting and sliding abrasive wear tests resulted in the composite material exhibiting a lower wear rate than the titanium-alloy. The magnitude of the difference was greatly dependent on the contact pressures, sliding amplitudes, and counterface material properties.

  7. Enhanced computational prediction of polyethylene wear in hip joints by incorporating cross-shear and contact pressure in additional to load and sliding distance: effect of head diameter.

    PubMed

    Kang, Lu; Galvin, Alison L; Fisher, John; Jin, Zhongmin

    2009-05-11

    A new definition of the experimental wear factor was established and reported as a function of cross-shear motion and contact pressure using a multi-directional pin-on-plate wear testing machine for conventional polyethylene in the present study. An independent computational wear model was developed by incorporating the cross-shear motion and contact pressure-dependent wear factor into the Archard's law, in additional to load and sliding distance. The computational prediction of wear volume was directly compared with a simulator testing of a polyethylene hip joint with a 28 mm diameter. The effect of increasing the femoral head size was subsequently considered and was shown to increase wear, as a result of increased sliding distance and reduced contact pressure. PMID:19261286

  8. Friction and wear of Si{sub 3}N{sub 4} ceramic/stainless steel sliding contacts in dry and lubricated conditions

    SciTech Connect

    Zhao, X.Z.; Liu, J.J.; Zhu, B.L.; Miao, H.Z.; Luo, Z.B.

    1997-04-01

    Austenitic stainless steel AISI 321 is one of the most difficult-to-cut materials. In order to investigate the wear behavior of Si{sub 2}N{sub 4} ceramic when cutting the stainless steel, wear tests are carried out on a pin-on-disk tribometer, which could simulate a realistic cutting process. Test results show that the wear of Si{sub 3}N{sub 4} ceramic is mainly caused by adhesion between the rubbing surfaces and that the wear increases with load and speed. When oil is used for lubrication, the friction coefficient of the sliding pairs and the wear rate of the ceramic are reduced. A scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), and an energy dispersive x-ray analyzer (EDXA) are used to examine the worn surfaces. The wear mechanisms of Si{sub 3}N{sub 4} ceramic sliding against the stainless steel are discussed in detail.

  9. Simulation of enamel wear for reconstruction of diet and feeding behavior in fossil animals: A micromechanics approach.

    PubMed

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

    2016-01-01

    The deformation and wear events that underlie microwear and macrowear signals commonly used for dietary reconstruction in fossil animals can be replicated and quantified by controlled laboratory tests on extracted tooth specimens in conjunction with fundamental micromechanics analysis. Key variables governing wear relations include angularity, stiffness (modulus), and size of the contacting particle, along with material properties of enamel. Both axial and sliding contacts can result in the removal of tooth enamel. The degree of removal, characterized by a "wear coefficient," varies strongly with particle content at the occlusal interface. Conditions leading to a transition from mild to severe wear are discussed. Measurements of wear traces can provide information about contact force and particle shape. The potential utility of the micromechanics methodology as an adjunct for investigating tooth durability and reconstructing diet is explored.

  10. Influence of carbon nanotube addition on sliding wear behaviour of pulse electrodeposited cobalt (Co)-phosphorus (P) coatings

    NASA Astrophysics Data System (ADS)

    Edward Anand, E.; Natarajan, S.

    2015-09-01

    This work examines the sliding wear behaviour of nanostructured cobalt-phosphorus (Co-P) alloy electrodeposits reinforced with multiwalled carbon nanotubes (MWCNTs). Nanocrystalline cobalt-phosphorus alloy coatings reinforced with carbon nanotubes were produced by pulse electrodeposition from an aqueous bath. Tribological properties of the coatings with and without MWCNT addition were characterized. Anisotropic tribological behaviour was observed for the coatings reinforced with MWCNTs when slided against hard steel counterparts. The nanocrystalline Co-P-CNT coatings display better wear resistance and friction reduction compared with the nanocrystalline Co-P coating. The friction coefficients and wear rates of the nanocrystalline Co-P-CNT coating are influenced by the test conditions including the applied load, sliding speed and more importantly the alignment of MWCNTs in the deposits. The wear mechanisms of the nanocrystalline Co-P and Co-P-CNT alloy coatings involved in different sliding conditions are explained related to their friction and wear properties.

  11. Simulation of enamel wear for reconstruction of diet and feeding behavior in fossil animals: A micromechanics approach.

    PubMed

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

    2016-01-01

    The deformation and wear events that underlie microwear and macrowear signals commonly used for dietary reconstruction in fossil animals can be replicated and quantified by controlled laboratory tests on extracted tooth specimens in conjunction with fundamental micromechanics analysis. Key variables governing wear relations include angularity, stiffness (modulus), and size of the contacting particle, along with material properties of enamel. Both axial and sliding contacts can result in the removal of tooth enamel. The degree of removal, characterized by a "wear coefficient," varies strongly with particle content at the occlusal interface. Conditions leading to a transition from mild to severe wear are discussed. Measurements of wear traces can provide information about contact force and particle shape. The potential utility of the micromechanics methodology as an adjunct for investigating tooth durability and reconstructing diet is explored. PMID:26643447

  12. A WEAR MODEL FOR DIESEL ENGINE EXHAUST VALVES

    SciTech Connect

    Blau, Peter Julian

    2009-11-01

    The work summarized here comprises the concluding effort of a multi-year project, funded by the U.S. Department of Energy, Office of Vehicle Technologies. It supports the development of a better understanding of advanced diesel engine designs in which enhanced power density, energy efficiency, and emissions control place increasing demands upon the durability of engine materials. Many kinds of metallic alloys are used in engines depending on the operating stresses, temperatures, and chemical environments. Exhaust valves, for example, are subjected to high temperatures and repetitive surface contacts that place demands on durability and frictional characteristics of the materials. Valves must continue to seal the combustion chamber properly for thousands of hours of cyclic engine operation and under varying operating conditions. It was the focus of this effort to understand the wear processes in the valve-seat area and to develop a model for the surface deformation and wear of that important interface. An annotated bibliography is provided to illustrate efforts to understand valve wear and to investigate the factors of engine operation that affect its severity and physical manifestation. The project for which this modeling effort was the final task, involved construction of a high-temperature repetitive impact test system as well as basic tribology studies of the combined processes of mechanical wear plus oxidation at elevated temperatures. Several publications resulted from this work, and are cited in this report. The materials selected for the experimental work were high-performance alloys based on nickel and cobalt. In some cases, engine-tested exhaust valves were made available for wear analysis and to ensure that the modes of surface damage produced in experiments were simulative of service. New, production-grade exhaust valves were also used to prepare test specimens for experimental work along with the other alloy samples. Wear analysis of valves and seats

  13. Atomic-scale wear of amorphous hydrogenated carbon during intermittent contact: a combined study using experiment, simulation, and theory.

    PubMed

    Vahdat, Vahid; Ryan, Kathleen E; Keating, Pamela L; Jiang, Yijie; Adiga, Shashishekar P; Schall, J David; Turner, Kevin T; Harrison, Judith A; Carpick, Robert W

    2014-07-22

    In this study, we explore the wear behavior of amplitude modulation atomic force microscopy (AM-AFM, an intermittent-contact AFM mode) tips coated with a common type of diamond-like carbon, amorphous hydrogenated carbon (a-C:H), when scanned against an ultra-nanocrystalline diamond (UNCD) sample both experimentally and through molecular dynamics (MD) simulations. Finite element analysis is utilized in a unique way to create a representative geometry of the tip to be simulated in MD. To conduct consistent and quantitative experiments, we apply a protocol that involves determining the tip-sample interaction geometry, calculating the tip-sample force and normal contact stress over the course of the wear test, and precisely quantifying the wear volume using high-resolution transmission electron microscopy imaging. The results reveal gradual wear of a-C:H with no sign of fracture or plastic deformation. The wear rate of a-C:H is consistent with a reaction-rate-based wear theory, which predicts an exponential dependence of the rate of atom removal on the average normal contact stress. From this, kinetic parameters governing the wear process are estimated. MD simulations of an a-C:H tip, whose radius is comparable to the tip radii used in experiments, making contact with a UNCD sample multiple times exhibit an atomic-level removal process. The atomistic wear events observed in the simulations are correlated with under-coordinated atomic species at the contacting surfaces.

  14. In-vitro corrosion and wear of titanium alloys in the biological environment.

    PubMed

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

    1996-11-01

    Cyclic anodic polarization studies were undertaken for several titanium alloys of varying composition and phase structures. All materials were exposed to an accelerated corrosion test using a potentiostat and their electrochemical behaviour was analysed within a potential range of 0 to 5000 mV. The electrolyte used was a phosphate buffered saline (PBS) solution at pH = 5, 7.4 and 9. The polarization curves obtained represented both the passive and active regions of the materials and these curves were used to compare the resistance to pitting corrosion of each material. The sliding-wear of these materials was studied in both non-corrosive and corrosive environments. A simple pin-on-disc type wear apparatus was designed and built to simulate the co-joint action of corrosion and sliding-wear. Using this apparatus, it was also possible to evaluate the effect of wear-accelerated corrosion, which was also evaluated by wearing the surface of the specimens prior to corrosion. It was evident that the mixed phase alpha-beta alloys (Ti-6AI-4V and Ti-6AI-7Nb) possessed the best combination of both corrosion and wear resistance, although commercially pure titanium and the near-beta (Ti-13Nb-13Zr) and beta (Ti-15Mo) alloys displayed the best corrosion resistant properties.

  15. Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

    PubMed Central

    Maharaj, Dave

    2012-01-01

    Summary Nano-object additives are used in tribological applications as well as in various applications in liquids requiring controlled manipulation and targeting. On the macroscale, nanoparticles in solids and liquids have been shown to reduce friction and wear. On the nanoscale, atomic force microscopy (AFM) studies have been performed in single- and multiple-nanoparticle contact, in dry environments, to characterize friction forces and wear. However, limited studies in submerged liquid environments have been performed and further studies are needed. In this paper, spherical Au nanoparticles were studied for their effect on friction and wear under dry conditions and submerged in water. In single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the nanoscale with AFM as well as on the macroscale by using a ball-on-flat tribometer to relate friction and wear reduction on the nanoscale and macroscale. Results indicate that the addition of Au nanoparticles reduces friction and wear. PMID:23213639

  16. Effect of gamma irradiation on the friction and wear of ultrahigh molecular weight polyethylene

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Hady, W. F.; Crugnola, A.

    1981-01-01

    The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against stainless steel 316L in dry air at 23 C is investigated, the results to be used in the development of artificial joints which are to surgically replace diseased human joints. A pin-on-disk sliding friction apparatus is used, a constant sliding speed in the range 0.061-0.27 m/s is maintained, a normal load of 1 kgf is applied with dead weight, and the irradiation dose levels are: 0, 2.5, and 5.0 Mrad. Wear and friction data and conditions for each of the ten tests are summarized, and include: (1) wear volume as a function of the sliding distance for the irradiation levels, (2) incremental wear rate, and (3) coefficient of friction as a function of the sliding distance. It is shown that (1) the friction and wear properties of UHMWPE are not significantly changed by the irradiation doses of 2.5 and 5.0 Mrad, (2) the irradiation increases the amount of insoluble gel as well as the amount of low molecular weight material, and (3) after run-in the wear rate is either steady or gradually decreases as a function of the sliding distance.

  17. Dry sliding wear behaviour of magnesium oxide and zirconium oxide plasma electrolytic oxidation coated magnesium alloy

    NASA Astrophysics Data System (ADS)

    Bala Srinivasan, P.; Liang, J.; Blawert, C.; Dietzel, W.

    2010-03-01

    Two types of PEO coatings, one consisting of magnesium oxide (MgO) and the other comprising zirconium oxide (ZrO 2) as the main phase composition were produced on AM50 magnesium alloy from alkaline and acidic electrolytes, respectively. The ZrO 2 coating was found to be spongy and thicker with a higher roughness, whilst the relatively more compact MgO coating was having contrasting features. In the dry sliding oscillating wear tests under two different loads viz., 2 N and 5 N, the ZrO 2 coating exhibited a very poor wear resistance. The MgO coating showed an excellent resistance to sliding wear under 2 N load; however, the load bearing capacity of the coating was found to be insufficient to resist the wear damage under 5 N load. The higher specific wear rates of the MgO coating under 5 N load and that of the ZrO 2 coating under 2 N and 5 N loads were attributed to the poor load bearing capacity and a three-body-abrasive wear mechanism.

  18. Evaluation of boundary lubricants using steady-state wear and friction

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  19. Neural network analysis for erosion wear of nickel-aluminide coatings on steel by plasma spraying

    NASA Astrophysics Data System (ADS)

    Mishra, S. C.; Chaithanya, M.; Satapathy, Alok; Ananthapadmanabhan, P. V.; Sreekumar, K. P.

    2010-02-01

    In the present investigation plasma spray inter metallic coating of Nickel-aluminide was deposited on mild steel substrates. The response of plasma sprayed nickel-aluminide coatings to the impingement of such solid particles has been presented in this work. Nickel pre-mixed with alumina powder is deposited on mild steel substances by atmospheric plasma spraying at various operating power level. The coatings are subjected to erosion wear test. An erosion test setup developed in our laboratory is used to simulate real time erosive situations. Dry silica sand of average particle size 400 micron is used as the erodent. The erosion rate is calculated on the basis of 'coating mass losses. The erosion studies are made and different velocities and impingement angles. A computational technique (ANN analysis) is used to predict the rate of erosion wear under various operational conditions. This technique involves database training to predict property parameter evolutions in process having large number of interdependent variables. This paper presents the database construction, implementation protocol and also the set of predicted results related to the erosion wear rate of nickel-aluminide coating. It is shown that the erosion wear is strongly influenced by the angle of impact. The test is conducted at room temperature i.e.27°C and 60% RH. Ni3Al coatings deposited at different power levels (10, 12, 16, 20, 24 kW) are found to exhibit different wear rate under similar test conditions.

  20. Plantar loading during jumping while wearing a rigid carbon graphite footplate.

    PubMed

    Queen, Robin M; Verma, Ravi; Abbey, Alicia N; Nunley, James A; Butler, Robert J

    2014-02-01

    Fifth metatarsal stress fractures are common in sports and often result in delayed and non-union. The purpose of this study was to examine the effect of a rigid carbon graphite footplate (CGF) on plantar loading during take-off and landing from a jump. Nineteen recreational male athletes with no history of lower extremity injury in the past 6 months and no foot or ankle surgery in the past 3 years participated in this study. Subjects completed 7 jumping tasks while wearing a standard running shoe and then the shoe plus the CGF while plantar loading data was recorded. A series of paired t-tests were used to examine differences between the two footwear conditions independently for both takeoff and landing (a = 0.05). The contact area in the medial midfoot (p < .001) and forefoot (p = .010) statistically decreased when wearing the CGFP. The force–time integral was significantly greater when wearing the CGFP in the middle (p < .001) and lateral forefoot (p = .019). Maximum force was significantly greater beneath the middle (p < .001) and lateral forefoot (p < .001) when wearing the CGFP, while it was decreased beneath the medial midfoot (p < .001). During landing, the contact area beneath the medial (p = .017) and lateral midfoot (p = .004) were significantly decreased when wearing the CGFP. The force– time integral was significantly decrease beneath the medial midfoot (p < .001) when wearing the CGFP. The maximum force was significantly greater beneath the medial (p = .047) and middle forefoot (p = .001) when the subject was wearing the CGFP. The maximum force beneath the medial midfoot (p < .001) was significantly reduced when wearing the carbon graphite footplate. The results of the study indicate that the CGF is ineffective at reducing plantar loading during jumping and landing.

  1. Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

    NASA Technical Reports Server (NTRS)

    Jarmon, David C.; Ojard, Greg; Brewer, David N.

    2013-01-01

    As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

  2. Biotribological evaluation of artificial disc arthroplasty devices: influence of loading and kinematic patterns during in vitro wear simulation

    PubMed Central

    Yue, James J.; Garcia, Rolando; Basson, Janet; Schwiesau, Jens; Fritz, Bernhard; Blömer, Wilhelm

    2008-01-01

    Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). In vitro wear simulation was performed with six activ® L lumbar artificial disc devices (Aesculap Tuttlingen, Germany). The applied kinematic pattern of movement was multidirectional for ISO (elliptic track) and unidirectional with a curvilinear shape for ASTM. Testing was done for 10 million cycles in the ISO loading mode and afterwards with the same specimens for 5 million cycles according to the ASTM protocol with a customized six-station servohydraulic spinal wear simulator (EndoLab Thansau, Germany). Gravimetrical and geometrical wear assessment, a slide track analysis correlated to an optical surface characterization, and an estimation of particle size and morphology were performed. The gravimetric wear rate for the first 10 million cycles was ISOinitial = 2.7 ± 0.3 mg/million cycles. During the ASTM test period (10–15 million cycles) a gravimetric wear rate of 0.14 ± 0.06 mg/million cycles was estimated. The wear rates between the ISO and ASTM driven simulations differ substantially (approximately 20-fold) and statistical analysis demonstrates a significant difference (p < 0.001) between the test groups. The main explanation of divergency between ISO and ASTM driven wear simulations is the multidirectional pattern of movement described in the ISO document resulting in a cross-shear stress on the polyethylene material. Due to previous retrieval observations, it seems to be very unlikely that a lumbar

  3. High temperature friction and wear characteristics of superalloys X-750 and 188 for use in low heat rejection engines

    SciTech Connect

    Erdemir, A.; Fenske, G.R.

    1988-01-01

    Engineering materials for use in low heat rejection engines are required to function under stringent tribological conditions. Severe wear damage and high friction between the components of the tribosystem limit the number of potential materials suitable for such application conditions. The superalloys X-750 and 188 are composed of alloying elements that not only promote a high mechanical and chemical stability but may also result in a reduced wear rate and friction coefficient at elevated temperatures. As a part of the DOE-ECUT Tribology program at Argonne, the present study was undertaken to evaluate the tribological characteristics of these alloys that will also be utilized as the substrates for ion beam deposited lubricous coatings. A wear test rig that crudely simulated the sliding conditions between a piston ring and a cylinder liner in an operating engine was utilized for friction and wear studies. The test results indicated that the wear and friction properties of these alloys were very sensitive to the test temperature. At lower temperatures, the friction coefficients and the wear rates were high. Whereas, at high temperatures (i.e., 600 oC), the coefficients of friction and the wear rates were relatively low and the oxidation of rubbing surfaces was rather severe. 10 refs., 5 figs., 3 tabs.

  4. The effects of three different food acids on the attrition-corrosion wear of human dental enamel

    NASA Astrophysics Data System (ADS)

    Zhang, Yichi; Arsecularatne, Joseph A.; Hoffman, Mark

    2015-07-01

    With increased consumption of acidic drinks and foods, the wear of human teeth due to attrition in acidic environments is an increasingly important issue. Accordingly, the present paper investigates in vitro the wear of human enamel in three different acidic environments. Reciprocating wear tests in which an enamel cusp slides on an enamel flat surface were carried out using acetic, citric and lactic acid lubricants (at pH 3-3.5). Distilled water was also included as a lubricant for comparison. Focused ion beam milling and scanning electron microscopy imaging were then used to investigate the enamel subsurfaces following wear tests. Nanoindentation was used to ascertain the changes in enamel mechanical properties. The study reveals crack generation along the rod boundaries due to the exposure of enamel to the acidic environments. The wear mechanism changes from brittle fracture in distilled water to ploughing or shaving of the softened layer in acidic environments, generating a smooth surface with the progression of wear. Moreover, nanoindentation results of enamel samples which were exposed to the above acids up to a duration of the wear tests show decreasing hardness and Young’s modulus with exposure time.

  5. Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Singh, Harpreet; Singh, Balraj; Singh, Bhupinder

    2010-01-01

    Two metallic powders namely Ni-20Cr and Ni3Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni3Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni3Al phase for the Ni3Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni3Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni3Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.

  6. A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes

    SciTech Connect

    Sundararajan, G.; Rao, D.S.; Prasad, K.U.M.; Joshi, S.V.

    1998-06-01

    In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, Al{sub 2}O{sub 3}, and Cr{sub 3}C{sub 2}-NiCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. Among all the coating materials studied, D-gun sprayed WC-12% Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al{sub 2}O{sub 3} shows least wear resistance to every wear mode.

  7. Abrasive Wear Performance of Aluminium Modified Epoxy-Glass Fiber Composites

    NASA Astrophysics Data System (ADS)

    Kamble, Vikram G.; Mishra, Punyapriya; Al Dabbas, Hassan A.; Panda, H. S.; Fernandez, Johnathan Bruce

    2015-07-01

    For a long time, Aluminum filled epoxies molds have been used in rapid tooling process. These molds are very economical when applied in manufacturing of low volume of plastic parts. To improve the thermal conductivity of the material, the metallic filler material is added to it and the glass fiber improves the wear resistance of the material. These two important parameters establish the life of composites. The present work reports on abrasive wear behavior of Aluminum modified epoxy and glass fiber composite with 5 wt.% and 10 wt.% of aluminum particles. Through pin on disc wear testing machine, we studied the wear behaviors of composites, and all these samples were fabricated by using hand layup process. Epoxy resin was used as matrix material which was reinforced with Glass fiber and Aluminum as filler. The composite with 5 wt.% and 10 wt.% of Al was cast with dimensions 100 × 100 × 6 mm. The specimens were machined to a size of 6 × 6 × 4 mm for abrasive testing. Abrasive tests were carried out for different grit paper sizes, i.e., 150, 320, 600 at different sliding distance, i.e., 20, 40, 60 m at different loads of 5, 10 and 15 N and at constant speed. The weight loss due to wear was calculated along with coefficient of friction. Hardness was found using Rockwell hardness machine. The SEM morphology of the worn out surface wear was analyzed to understand the wear mechanism. Results showed that the addition of Aluminum particles was beneficial for low abrasive conditions.

  8. Wear simulation of sucker rod couplings

    SciTech Connect

    Schumacher, W.J. )

    1991-09-01

    This paper reports that sucker rod strings are devices used to actuate pumps located at the bottom of oil wells. The individual rods are connected together by threaded couplings. Since the couplings have a larger diameter than the rods, they sometimes contact the inside diameter of the tubing during the up and down pumping cycle. Usually, this is not problem unless buckling occurs in the downstroke; however, this can lead to accelerated wear of the coupling and tubing. In nonvertical wells (offset, deviated, or slanted), the contact is more severe and rapid wear takes place. Couplings are more easily replaced during shutdowns; it is very important to minimize wear to tubing since it is virtually impossible to replace. TRIBONIC 20, an iron-based alloy containing approximately 13% Mn, 5% Si, 5.5% Cr, and 5% Ni, was laboratory evaluated to determine whether or not it could solve the sucker rod coupling-production tubing wear problem. The alloy demonstrated outstanding wear resistance both to itself and in protecting type 1019 steel.

  9. Dental Wear: A Scanning Electron Microscope Study

    PubMed Central

    Levrini, Luca; Di Benedetto, Giulia

    2014-01-01

    Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction. PMID:25548769

  10. Tooth wear: diet analysis and advice.

    PubMed

    Young, William George

    2005-04-01

    Diet analysis and advice for patients with tooth wear is potentially the most logical intervention to arrest attrition, erosion and abrasion. It is saliva that protects the teeth against corrosion by the acids which soften enamel and make it susceptible to wear. Thus the lifestyles and diet of patients at risk need to be analysed for sources of acid and reasons for lost salivary protection. Medical conditions which put patients at risk of tooth wear are principally: asthma, bulimia nervosa, caffeine addiction, diabetes mellitus, exercise dehydration, functional depression, gastroesophageal reflux in alcoholism, hypertension and syndromes with salivary hypofunction. The sources of acid are various, but loss of salivary protection is the common theme. In healthy young Australians, soft drinks are the main source of acid, and exercise dehydration the main reason for loss of salivary protection. In the medically compromised, diet acids and gastroesophageal reflux are the sources, but medications are the main reasons for lost salivary protection. Diet advice for patients with tooth wear must: promote a healthy lifestyle and diet strategy that conserves the teeth by natural means of salivary stimulation; and address the specific needs of the patients' oral and medical conditions. Individualised, patient-empowering erosion WATCH strategies; on Water, Acid, Taste, Calcium and Health, are urgently required to combat the emerging epidemic of tooth wear currently being experienced in westernised societies.

  11. Clinical Biomechanics of Wear in Total Hip Arthroplasty

    PubMed Central

    Callaghan, John J; Pedersen, Douglas R; Johnston, Richard C; Brown, Thomas D

    2003-01-01

    Complementary clinical and laboratory studies were performed to identify variables associated with polyethylene wear following total hip replacement, and to elucidate the mechanisms responsible for accelerated wear in the total hip arthroplasty construct. Observational cohort studies were performed using a prospective clinical database of more than 4000 consecutive primary total hip arthroplasties performed by a single surgeon, to identify wear-related variables. These variables included head size, acetabular/femoral component impingement, and third body debris. Novel digital edge detection techniques were developed and employed to accurately measure wear, and to determine the relationships of head size and third body debris to acceleration of wear. A novel slidingdistance-coupled finite element model was formulated and employed to examine the mechanisms responsible for wear. The long-term cohort studies demonstrated smaller head sizes to be associated with less wear. Third body debris generated from cable fretting was associated with an increase in wear, osteolysis, and acetabular loosening, especially with larger head sizes. The sliding-distance-coupled finite element model replicated the wear rates occurring in vitro and in vivo, demonstrating the importance of sliding distance on polyethylene wear following total hip arthroplasty. It also demonstrated substantial increases in wear associated with femoral head scratching from third body debris. Further extension of the finite element formulation demonstrated the potential for acetabular component rim damage from impingement wear, and the enhanced potential for third body ingress to the bearing surface with larger head sizes. Edge detection wear measurement techniques demonstrated that early wear rates were predictive of long-term wear rates. These complementary clinical and laboratory investigations have provided insight into 1) the significance of sliding distance and physiologic loci of motion as contributing

  12. Improved wear properties of high energy ion-implanted polycarbonate

    SciTech Connect

    Rao, G.R.; Lee, E.H. ); Bhattacharya, R.; McCormick, A.W. )

    1995-01-01

    Polycarbonate (Lexan[sup TM]) (PC) was implanted with 2 MeV B[sup +] and O[sup +] ions separately to fluences of 5[times]10[sup 17], 1[times]10[sup 18], and 5[times]10[sup 18] ions/m[sup 2], and characterized for changes in surface hardness and tribological properties. Results of tests showed that hardness values of all implanted specimens increased over those of the unirradiated material, and the O[sup +] implantation was more effective in improving hardness for a given fluence than the B[sup +] implantation. Reciprocating sliding wear tests using a nylon ball counterface yielded significant improvements for all implanted specimens except for the 5[times]10[sup 17] ions/m[sup 2] B[sup +]-implanted PC. Wear tests conducted with a 52100 steel ball yielded significant improvements for the highest fluence of 5[times]10[sup 18] ions/m[sup 2] for both ions, but not for the two lower fluences. The improvements in properties were related to Linear Energy Transfer (LET) mechanisms, where it was shown that the O[sup +] implantation caused greater ionization, thereby greater cross-linking at the surface corresponding to much better improvements in properties. The results were also compared with a previous study on PC using 200 keV B[sup +] ions. The present study indicates that high energy ion irradiation produces thicker, more cross-linked, harder, and more wear-resistant surfaces on polymers and thereby improves properties to a greater extent and more efficiently than lower energy ion implantation.

  13. Some wear studies on aircraft brake systems

    NASA Technical Reports Server (NTRS)

    Ho, T. L.

    1975-01-01

    An initial investigation of worn surfaces in friction pads and steel rotors used in current aircraft brakes was carried out using electron microprobe and X-ray diffraction analysis. It consists of the topographical study and the analysis of chemical element distribution. Based upon this initial examination, two approaches, microscopic and macroscopic have been conducted to interpret and formulate the wear mechanism of the aircraft brake materials. Microscopically, the wear particles were examined. The initiation and growth of surface cracks and the oxidation were emphasized in this investigation. Macroscopically, it has been found that, for the current copper based brake material sliding against 17-22 AS steel in a caliper brake, the surface temperature raised due to frictional heat is nonlinearly proportional to the load applied and slide time with speed at 1750 rpm. The wear of brake materials is then proportional to this temperature and is also a function of the melting temperature for copper.

  14. Adhesion and wear resistance of materials

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1986-01-01

    Recent studies into the nature of bonding at the interface between two solids in contact or a solid and deposited film have provided a better understanding of those properties important to the adhesive wear resistance of materials. Analytical and experimental progress are reviewed. For simple metal systems the adhesive bond forces are related to electronic wave function overlap. With metals in contact with nonmetals, molecular-orbital energy, and density of states, respectively can provide insight into adhesion and wear. Experimental results are presented which correlate adhesive forces measured between solids and the electronic surface structures. Orientation, surface reconstruction, surface segregation, adsorption are all shown to influence adhesive interfacial strength. The interrelationship between adhesion and the wear of the various materials as well as the life of coatings applied to substrates are discussed. Metallic systems addressed include simple metals and alloys and these materials in contact with themselves, both oxide and nonoxide ceramics, diamond, polymers, and inorganic coating compounds, h as diamondlike carbon.

  15. A novel cross-shear metric for application in computer simulation of ultra-high molecular weight polyethylene wear.

    PubMed

    Petrella, Anthony J; Armstrong, Jeffrey R; Laz, Peter J; Rullkoetter, Paul J

    2012-01-01

    Wear testing of polyethylene in total joint replacements is common and required for any new device. Computational wear modelling has obvious utility in this context as it can be conducted with much greater economy than physical testing. Archard's law has become the accepted standard for wear simulation in total joints but it does not account for cross-shear, which is known to increase wear significantly relative to unidirectional sliding. The purpose of this study was to develop a robust cross-shear model applicable to any interface geometry under any kinematic conditions. The proposed metric, x (*), is distinguished from existing cross-shear models by the fact that it measures cross-path motion incrementally throughout a motion cycle and quantifies cross-shear based on incremental changes in sliding direction. Validation showed strong support for the predictive capability of x (*) when applied to pin-on-disc test data. PMID:22136186

  16. The effect of lubrication on the friction and wear of Biolox®delta.

    PubMed

    Ma, L; Rainforth, W M

    2012-07-01

    The performance of total hip-joint replacements depends strongly on the state of lubrication in vivo. In order to test candidate prosthetic materials, in vitro wear testing requires a lubricant that behaves in the same manner as synovial fluid. The current study investigated three lubricants and looked in detail at the lubrication conditions and the consequent effect on ball-on-flat reciprocating wear mechanisms of Biolox®delta against alumina. Biolox®delta, the latest commercial material for artificial hip-joint replacements, is an alumina-matrix composite with improved mechanical properties through the addition of zirconia and other mixed oxides. Three commonly used laboratory lubricants, ultra pure water, 25 vol.% new-born calf serum solution and 1 wt.% carboxymethyl cellulose sodium salt (CMC-Na) solution, were used for the investigation. The lubrication regimes were defined by constructing Stribeck curves. Full fluid-film lubrication was observed for the serum solution whereas full fluid-film and mixed lubrications were observed in both water and the CMC-Na solution. The wear rates in the CMC-Na and new-born calf serum were similar, but were an order of magnitude higher in water. The worn surfaces all exhibited pitting, which is consistent with the transition from mild wear to severe or "stripe" wear. The extent of pitting was greatest in the serum solution, but least in the water. On all worn surfaces, the zirconia appeared to have fully transformed from tetragonal to monoclinic symmetry. However, there was no evidence of microcracking associated with the transformed zirconia. Nevertheless, AFM indicated that zirconia was lost preferentially to the alumina grains during sliding. Thus, the current study has shown conclusively that the wear mechanisms for Biolox®delta clearly depend on the lubricant used, even where wear rates were similar.

  17. Wear Behaviour of Al-6061/SiC Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Mishra, Ashok Kumar; Srivastava, Rajesh Kumar

    2016-06-01

    Aluminium Al-6061 base composites, reinforced with SiC particles having mesh size of 150 and 600, which is fabricated by stir casting method and their wear resistance and coefficient of friction has been investigated in the present study as a function of applied load and weight fraction of SiC varying from 5, 10, 15, 20, 25, 30, 35 and 40 %. The dry sliding wear properties of composites were investigated by using Pin-on-disk testing machine at sliding velocity of 2 m/s and sliding distance of 2000 m over a various loads of 10, 20 and 30 N. The result shows that the reinforcement of the metal matrix with SiC particulates up to weight percentage of 35 % reduces the wear rate. The result also show that the wear of the test specimens increases with the increasing load and sliding distance. The coefficient of friction slightly decreases with increasing weight percentage of reinforcements. The wear surfaces are examined by optical microscopy which shows that the large grooved regions and cavities with ceramic particles are found on the worn surface of the composite alloy. This indicates an abrasive wear mechanism, which is essentially a result of hard ceramic particles exposed on the worn surfaces. Further, it was found from the experimentation that the wear rate decreases linearly with increasing weight fraction of SiC and average coefficient of friction decreases linearly with increasing applied load, weight fraction of SiC and mesh size of SiC. The best result has been obtained at 35 % weight fraction and 600 mesh size of SiC.

  18. Surface Damage Characteristics and Specific Wear Rates of a New Continuous Carbon Fiber (CF) / Polyetheretherketone (PEEK) Composite under Sliding and Rolling Contact Conditions

    NASA Astrophysics Data System (ADS)

    Almajid, Abdulhakim; Friedrich, Klaus; Floeck, Joachim; Burkhart, Thomas

    2011-06-01

    The surface damage characteristics of a continuous carbon fiber reinforced composite, having a polyetheretherketone (PEEK) matrix, were investigated under sliding and rolling contact. The corresponding mechanisms were studied by the use of scanning electron microscopy (SEM) in three different fiber orientations, namely: Paralllel direction to the fibers, AntiParallel direction to the fibers, and Normal direction to the fibers. All wear tests were conducted against smooth steel surfaces for both contact conditions. Mechanical properties under tension, compression, and shear were investigated for the material at two different temperature levels, i.e. room temperature and 150 °C. The composite material under normal fiber orientation has the lowest specific wear rate in case of rolling wear while the parallel orientation has the lowest specific wear rate under sliding wear conditions. Both results were compared to wear data of the neat PEEK matrix.

  19. Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings

    PubMed Central

    Ali, Murat; Al-Hajjar, Mazen; Partridge, Susan; Williams, Sophie; Fisher, John; Jennings, Louise M

    2016-01-01

    Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing. PMID:27160559

  20. Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings.

    PubMed

    Ali, Murat; Al-Hajjar, Mazen; Partridge, Susan; Williams, Sophie; Fisher, John; Jennings, Louise M

    2016-05-01

    Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing. PMID:27160559

  1. Diamond wheel wear sensing with acoustic emission --wheel wear mechanisms and the effects of process variables

    SciTech Connect

    Tang, Jianshe; Dornfeld, D.; Syoji, Katsuo

    1996-12-31

    The wear of diamond wheels has significant influence on the surface finish of ground ceramics and the resulting subsurface fracture damage. For optimization and control of the grinding process it is necessary to monitor the wear states of the grinding wheels. A project on diamond wheel wear sensing with acoustic emission was started recently in the Laboratory of Manufacturing Automation at the University of California at Berkeley. The main aims of the project are: (a) to identify the possible wheel wear patterns at different combinations of bond materials, grits, and grinding conditions; (b) to develop suitable AE signal processing methods to extract the AE features to represent the wheel wear characteristics, and establish a strategy for using AE for in-process monitoring of diamond wheel wear in grinding of ceramics. This paper presents the results of part of the project. It mainly focuses on the diamond wheel wear mechanisms, the effects of process variables including basic wheel elements and grinding parameters, and the relationship with AErms and AE frequency content.

  2. Wear Analysis of Wind Turbine Gearbox Bearings

    SciTech Connect

    Blau, Peter Julian; Walker, Larry R; Xu, Hanbing; Parten, Randy J; Qu, Jun; Geer, Tom

    2010-04-01

    The objective of this effort was to investigate and characterize the nature of surface damage and wear to wind turbine gearbox bearings returned from service in the field. Bearings were supplied for examination by S. Butterfield and J. Johnson of the National Wind Technology Center (NREL), Boulder, Colorado. Studies consisted of visual examination, optical and electron microscopy, dimensional measurements of wear-induced macro-scale and micro-scale features, measurements of macro- and micro-scale hardness, 3D imaging of surface damage, studies of elemental distributions on fracture surfaces, and examinations of polished cross-sections of surfaces under various etched and non-etched conditions.

  3. Tooth Wear Prevalence and Sample Size Determination : A Pilot Study

    PubMed Central

    Abd. Karim, Nama Bibi Saerah; Ismail, Noorliza Mastura; Naing, Lin; Ismail, Abdul Rashid

    2008-01-01

    Tooth wear is the non-carious loss of tooth tissue, which results from three processes namely attrition, erosion and abrasion. These can occur in isolation or simultaneously. Very mild tooth wear is a physiological effect of aging. This study aims to estimate the prevalence of tooth wear among 16-year old Malay school children and determine a feasible sample size for further study. Fifty-five subjects were examined clinically, followed by the completion of self-administered questionnaires. Questionnaires consisted of socio-demographic and associated variables for tooth wear obtained from the literature. The Smith and Knight tooth wear index was used to chart tooth wear. Other oral findings were recorded using the WHO criteria. A software programme was used to determine pathological tooth wear. About equal ratio of male to female were involved. It was found that 18.2% of subjects have no tooth wear, 63.6% had very mild tooth wear, 10.9% mild tooth wear, 5.5% moderate tooth wear and 1.8 % severe tooth wear. In conclusion 18.2% of subjects were deemed to have pathological tooth wear (mild, moderate & severe). Exploration with all associated variables gave a sample size ranging from 560 – 1715. The final sample size for further study greatly depends on available time and resources. PMID:22589636

  4. The wear of titanium, titanium alloy, and UHMW polyethylene caused by LTI carbon and Stellite 21.

    PubMed

    Shim, H S

    1977-08-01

    The comparative wear resistance of a commercially pure titanium (A-70), a titanium alloy (Beta III), and a UHMW polyethylene (Lennite) has been evaluated by employing a test procedure described previously. Either an LTI carbon or a Stellite 21 was the disk material. All material combinations exhibited a low volume wear rate ranging from about 1.2 x 10(-6) to 1.6 x 10(-6) mm3/km. The wear behavior of pure titanium seems to be related not only to its mechanical properties but also to its chemical reactivity with the test environment. A comparison of the current results with earlier data for LTI carbons suggests that LTI carbons may be used as a component material for many artificial joints. PMID:615881

  5. Effect of Heat Treatment on Wear Resistance of Nickel Aluminide Coatings Deposited by HVOF and PTA

    NASA Astrophysics Data System (ADS)

    Benegra, M.; Santana, A. L. B.; Maranho, O.; Pintaude, G.

    2015-08-01

    This study aims to compare the wear resistance of nickel aluminide coatings deposited using plasma transferred arc (PTA) and high-velocity oxygen fuel (HVOF) processes. Wear resistance was measured in rubber wheel abrasion tests. In both deposition processes, the same raw material (nickel aluminide powder) was atomized and deposited on a 316L steel plate substrate. After deposition, specimens were subjected to thermal cycling, aiming solubilization and precipitation. Coatings deposited using PTA developed different microstructures as a result of the incorporation of substrate elements. However, despite the presence of these microstructures, they performed better than coatings processed using HVOF before the heat treatment. After thermal cycling, the superficial hardness after the wear tests for both processes was similar, resulting in similar mass losses.

  6. Effect of fullerene containing lubricants on wear resistance of machine components in boundary lubrication

    NASA Astrophysics Data System (ADS)

    Titov, Andriy

    Fullerenes, a new form of carbon nanomaterials, possess unique physical and mechanical properties that make their use as additives to liquid lubricants potentially beneficial. The goal of this study was to investigate the effect of fullerene containing lubricants on wear resistance of steel-bronze couples operating under boundary lubrication conditions. A mathematical model of deformed asperity contact was built to calculate real contact area and real contact pressure. Computer controlled wear friction testing methodology and equipment were designed, developed and implemented for obtaining reliable and objective experimental data. In addition, optical and scanning electron microscopy and standard surface texture analysis were employed. Heavy duty motor oil SAE 10 was modified by admixing fullerenes C60, a fullerene mixture of C60 and C70, fullerene containing soot, and graphite powder. The experiments showed that all of the selected fullerene additives dissolved in liquid lubricants reduce wear of the tested materials. In addition, it was found that despite improvements in wear resistance, the selected modified lubricants did not significantly change friction characteristics. Improvement of wear resistance of contact surfaces operating with fullerene modified lubricants can be explained by the presence of fullerenes in real contact while the liquid lubricant is squeezed out. Fullerenes are considered to function as minute hard particles that do not break down under applied normal force, and tend to separate direct contact of functional surfaces of selected materials.

  7. Wear rate quantifying in real-time using the charged particle surface activation

    NASA Astrophysics Data System (ADS)

    Alexandreanu, B.; Popa-Simil, L.; Voiculescu, D.; Racolta, P. M.

    1997-02-01

    Surface activation, commonly known as Thin Layer Activation (TLA), is currently employed in over 30 accelerator laboratories around the world for wear and/or corrosion monitoring in industrial plants [1-6]. TLA was primarily designed and developed to meet requirements of potential industrial partners, in order to transfer this technique from research to industry. The method consists of accelerated ion bombardment of a surface of interest, e.g., a machine part subjected to wear. Loss of material owing to wear, erosive corrosion or abrasion is characterized by monitoring the resultant changes in radioactivity. In principle, depending upon the case at hand, one may choose to measure either the remnant activity of the component of interest or to monitor the activity of the debris. For applications of the second type, especially when a lubricating agent is involved, dedicated installations have been constructed and adapted to an engine or a tribological testing stand in order to assure oil circulation around an externally placed detection gauge. This way, the wear particles suspended in the lubricant can be detected and the material loss rates quantified in real time. Moreover, in specific cases, such as the one presented in this paper, remnant activity measurements prove to be useful tools for complementary results. This paper provides a detailed presentation of such a case: in situ resistance-to-wear testing of two types of piston rings.

  8. Preparation and wear resistance of Ti-Zr-Ni quasicrystal and polyamide composite materials

    NASA Astrophysics Data System (ADS)

    Wang, Xinlu; Li, Xuesong; Zhang, Zhenjiang; Zhang, Shanshan; Liu, Wanqiang; Wang, Limin

    2011-07-01

    Ti-Zr-Ni icosahedral quasicrystal powders (Ti-QC), prepared by mechanical alloying and then annealing in a vacuum furnace, were used as a novel filler material in polyamide 12 (PA12). The melt processability of the composite was studied using a Haake torque rheometer. This indicates that PA12/Ti-QC composites can be melt-processed into a wear-resistant material. Further, these composites, fabricated by compression molding, were tested in sliding wear against a polished bearing steel counterface. The results from wear testing show that the addition of Ti-QC filler to PA12 enhances wear resistance and reduces volume loss by half compared with neat PA12. Furthermore, it is found that the hardness of the composite increases with increasing content of Ti-QC filler. In addition, PA12/Ti-QC composites exhibit a slightly higher crystallization temperature and better thermal stability than PA12. These combined results demonstrate that Ti-QC filler may be a desirable alternative when attempting to increase the wear resistance of PA12.

  9. Effect of swing phase load on metal-on-metal hip lubrication, friction and wear.

    PubMed

    Williams, Sophie; Jalali-Vahid, Davood; Brockett, Claire; Jin, Zhongmin; Stone, Martin H; Ingham, Eileen; Fisher, John

    2006-01-01

    There is renewed interest in metal-on-metal (MOM) total hip replacements (THRs), however, variable wear rates have been observed clinically. It is hypothesised that changes in soft tissue tensioning during surgery may alter loading of THRs during the swing phase of gait leading to changes in fluid film lubrication, friction and wear. This study aimed to assess the effect of swing phase load on the lubrication, friction and wear of MOM hip replacements. Theoretical lubrication modelling was carried out using elastohydrodynamic theory. All the governing equations were solved numerically for the lubricant film thickness between the articulating surfaces under the transient dynamic conditions with low and high swing phase loads. Friction testing was completed using a single axis pendulum simulator, simplified loading cycles were applied with low and high swing phase loads. MOM hip replacements were tested in a hip simulator, modified to provide different swing phase loading regimes; a low (100 N) and a high load (as per ISO 14242-1; 280 N). Results demonstrated that the performance of MOM bearings is highly dependent on swing phase load. Hence, changes in the tension of the tissues at surgery and variations in muscle forces may increase swing phase load, reduce lubrication, increase friction and accelerate wear. This may explain some of the variations that have been observed with clinical wear rates.

  10. Wear characteristics of polished and glazed lithium disilicate ceramics opposed to three ceramic materials.

    PubMed

    Saiki, Osamu; Koizumi, Hiroyasu; Akazawa, Nobutaka; Kodaira, Akihisa; Okamura, Kentaro; Matsumura, Hideo

    2016-01-01

    This study compared the wear characteristics of a heat-pressed lithium disilicate ceramic material opposed to feldspathic porcelain, a lithium disilicate glass ceramic, and zirconia materials. Ceramic plate specimens were prepared from feldspathic porcelain (EX-3 nA1B), lithium disilicate glass ceramics (e.max CAD MO1/C14), and zirconia (Katana KT 10) and then ground or polished. Rounded rod specimens were fabricated from heat-pressed lithium disilicate glass ceramic (e.max press LT A3) and then glazed or polished. A sliding wear testing apparatus was used for wear testing. Wear of glazed rods was greater than that of polished rods when they were abraded with ground zirconia, ground porcelain, polished porcelain, or polished lithium disilicate ceramics. For both glazed and polished rods, wear was greater when the rods were abraded with ground plates. The findings indicate that application of a polished surface rather than a glazed surface is recommended for single restorations made of heat-pressed lithium disilicate material. In addition, care must be taken when polishing opposing materials, especially those used in occlusal contact areas. (J Oral Sci 58, 117-123, 2016). PMID:27021548

  11. Wear characteristics of polished and glazed lithium disilicate ceramics opposed to three ceramic materials.

    PubMed

    Saiki, Osamu; Koizumi, Hiroyasu; Akazawa, Nobutaka; Kodaira, Akihisa; Okamura, Kentaro; Matsumura, Hideo

    2016-01-01

    This study compared the wear characteristics of a heat-pressed lithium disilicate ceramic material opposed to feldspathic porcelain, a lithium disilicate glass ceramic, and zirconia materials. Ceramic plate specimens were prepared from feldspathic porcelain (EX-3 nA1B), lithium disilicate glass ceramics (e.max CAD MO1/C14), and zirconia (Katana KT 10) and then ground or polished. Rounded rod specimens were fabricated from heat-pressed lithium disilicate glass ceramic (e.max press LT A3) and then glazed or polished. A sliding wear testing apparatus was used for wear testing. Wear of glazed rods was greater than that of polished rods when they were abraded with ground zirconia, ground porcelain, polished porcelain, or polished lithium disilicate ceramics. For both glazed and polished rods, wear was greater when the rods were abraded with ground plates. The findings indicate that application of a polished surface rather than a glazed surface is recommended for single restorations made of heat-pressed lithium disilicate material. In addition, care must be taken when polishing opposing materials, especially those used in occlusal contact areas. (J Oral Sci 58, 117-123, 2016).

  12. "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.

  13. Tantalum-based thin film coatings for wear resistant arthroprostheses.

    PubMed

    Balagna, C; Faga, M G; Spriano, S

    2011-10-01

    Cobalt-chromium-molybdenum alloys with high carbon content (HC-CoCrMo) are widely used as materials for arthroprosthesis, in particular in metal-on-metal (MoM) hip joints. In spite of their good wear and corrosion resistance, production of metallic wear particles and metal ion release will occur on a large time-scale. An enhancement of the metal ion level in the patient's blood and urine is often reported in clinical data. Hypersensitivity, inflammatory response and cell necrosis can occur as consequence. So implants on young patients and women on childbearing age are not so widespread. The aim of this research is the realization of a thin film coating in order to improve the biocompatibility of Co-based alloys and to reduce debris production, ion release and citotoxicity. The innovative process consists of a thermal treatment in molten salts, in order to obtain a tantalum enriched thin film coating. Tantalum is chosen because it is considered a biocompatible metal with high corrosion resistance and low ion release. Three HC-CoCrMo alloys, produced by different manufacturing processes, are tested as substrates. The coating is a thin film of TaC or it can be composed by a multilayer of two tantalum carbides and metallic tantalum, depending on the temperature of the treatment and on the carbon content of the substrate. The thin films as well the substrates are characterized from the structural, chemical and morphological point of view. Moreover mechanical behaviour of treated and untreated materials is analyzed by means of nanohardness, scratch and ball-on-disc wear tests. The coating increases the mechanical and tribological properties of HC-CoCrMo.

  14. Abrasive wear by diesel engine coal-fuel and related particles

    SciTech Connect

    Ives, L.K.

    1994-09-01

    The purpose of the work summarized in this report was to obtain a basic understanding of the factors which are responsible for wear of the piston ring and cylinder wall surfaces in diesel engines utilizing coal-fuel. The approach included analytical studies using scanning electron microscopy and energy dispersive x-ray analyses to characterize coal-fuel and various combustion particles, and two different wear tests. The wear tests were a modified pin-on-disk test and a block-on-ring test capable of either unidirectional or reciprocating-rotational sliding. The wear tests in general were conducted with mixtures of the particles and lubricating oil. The particles studied included coal-fuel, particles resulting from the combustion of coal fuel, mineral matter extracted during the processing of coal, and several other common abrasive particle types among which quartz was the most extensively examined. The variables studied included those associated with the particles, such as particle type, size, and hardness; variables related to contact conditions and the surrounding environment; and variables related to the type and properties of the test specimen materials.

  15. 22 CFR 1203.735-212 - Wearing of uniforms.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... RESPONSIBILITIES AND CONDUCT Ethical and Other Conduct and Responsibilities of Employees § 1203.735-212 Wearing of... States to wear a uniform, care shall be taken that the uniform is worn only at authorized times and...

  16. 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.

  17. The effect of contact load on CoCrMo wear and the formation and retention of tribofilms

    PubMed Central

    Wimmer, M.A.; Laurent, M.P.; Mathew, M.T.; Nagelli, C.; Liao, Y.; Marks, L.D.; Jacobs, J.J.; Fischer, A.

    2015-01-01

    Tribochemical reactions in a protein lubricated metal-on-metal (MoM) sliding contact may play a significant role for its wear performance. Such reactions lead to the formation of a carbonaceous ‘tribofilm’, which can act as a protective layer against corrosion and wear. The purpose of this study was to determine the effect of contact load on wear and the formation and retention of tribofilms. Wear tests were performed in a custom-made ball-on-flat testing apparatus that incorporated an electrochemical cell. A ceramic ball was used to articulate against low-carbon wrought CoCrMo alloy pins in bovine serum. Using a range of contact loads at a single potentiostatic condition (close to free potential), weight loss and changes in surface properties were evaluated. We determined that wear was influenced by the loading condition. As expected, wear increased with load, but the association between applied load and measured weight loss was not linear. In the intermediate load region, in the range of 32–48 N (~58–80 MPa), there was more than an order of magnitude drop in the wear per unit load, and the wear versus load data suggested an inflexion point at 49 N. Regression analyses yielded a cubic model (R2=0.991; p=0.0002), where the cubic term, which represents the inflexion, was highly significant (p=0.0021). This model is supported by the observations that the minimum in the friction versus load curve is at 52 N and the highest relative increase in polarization resistance occurred at 49 N. Scanning electron microscopy and Raman spectroscopy indicated the absence of a tribofilm for the low and within the contact area of the high load cases. Synergistic interactions of wear and corrosion seem to play an important role. PMID:26085697

  18. Sliding wear of self-mated Al2O3-SiC whisker reinforced composites at 23-1200 C

    NASA Technical Reports Server (NTRS)

    Farmer, Serene C.; Book, Patricia O.; Dellacorte, Christopher

    1991-01-01

    Microstructural changes occurring during sliding wear of self-mated Al2O3-SiC whisker reinforced composites were studied using optical, scanning electron microscopy, and transmission electron microscopy. Pin-on-disk specimens were slid in air at 2.7 m/sec sliding velocity under a 26.5 N load for 1 hr. Wear tests were conducted at 23, 600, 800, and 1200 C. Mild wear with a wear factor of 2.4 times 10(exp -7) to 1.5 times 10(exp -6) cu mm/Nm was experienced at all test temperatures. The composite shows evidence of wear by fatigue mechanisms at 800 C and below. Tribochemical reaction (SiC oxidation and reaction of SiO2 and Al2O3) leads to intergranular failure at 1200 C. Distinct microstructural differences existing at each test temperature are reported.

  19. 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.

  20. Tribology: Friction, lubrication, and wear technology

    NASA Technical Reports Server (NTRS)

    Blau, Peter J.

    1993-01-01

    The topics are presented in viewgraph form and include the following: introduction and definitions of terms; friction concepts; lubrication technology concepts; wear technology concepts; and tribological transitions. This document is designed for educators who seek to teach these concepts to their students.

  1. Lubrication And Wear Of Hot Ceramics

    NASA Technical Reports Server (NTRS)

    Sliney, H. E.; Jacobson, T. P.; Deadmore, D.; Miyoshi, K.

    1988-01-01

    Report presents results of experiments on tribological properties of ceramics. Describes friction and wear characteristics of some ceramics under consideration for use in gas turbines, diesel engines, and Stirling engines. Discusses formulation of composite plasma-sprayed ceramics containing solid lubricant additives, and data for carbide- and oxide-based composite coatings for use at temperatures up to at least 900 degree C.

  2. 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.

  3. Measuring Bearing Wear Via Weight Loss

    NASA Technical Reports Server (NTRS)

    Keba, John E.; Moore, Richard S.

    1989-01-01

    Wear in critical parts of bearings measured via amounts of weight lost during use. Technique applicable in general to bearings made of nonporous materials. Weight-loss measurements easier, faster, more precise, and less likely to damage measured parts. Weight-loss measurements performed in clean rooms and under constraint of extreme cleanliness for compatability with liquid oxygen.

  4. Friction and wear of human hair fibres

    NASA Astrophysics Data System (ADS)

    Bowen, James; Johnson, Simon A.; Avery, Andrew R.; Adams, Michael J.

    2016-06-01

    An experimental study of the tribological properties of hair fibres is reported, and the effect of surface treatment on the evolution of friction and wear during sliding. Specifically, orthogonally crossed fibre/fibre contacts under a compressive normal load over a series of 10 000 cycle studies are investigated. Reciprocating sliding at a velocity of 0.4 mm s‑1, over a track length of 0.8 mm, was performed at 18 °C and 40%–50% relative humidity. Hair fibres retaining their natural sebum were studied, as well as those stripped of their sebum via hexane cleaning, and hair fibres conditioned using a commercially available product. Surface topography modifications resulting from wear were imaged using scanning electron microscopy and quantified using white light interferometry. Hair fibres that presented sebum or conditioned product at the fibre/fibre junction exhibited initial coefficients of friction at least 25% lower than those that were cleaned with hexane. Coefficients of friction were observed to depend on the directionality of sliding for hexane cleaned hair fibres after sufficient wear cycles that cuticle lifting was present, typically on the order 1000 cycles. Cuticle flattening was observed for fibre/fibre junctions exposed to 10 mN compressive normal loads, whereas loads of 100 mN introduced substantial cuticle wear and fibre damage.

  5. Friction and wear of human hair fibres

    NASA Astrophysics Data System (ADS)

    Bowen, James; Johnson, Simon A.; Avery, Andrew R.; Adams, Michael J.

    2016-06-01

    An experimental study of the tribological properties of hair fibres is reported, and the effect of surface treatment on the evolution of friction and wear during sliding. Specifically, orthogonally crossed fibre/fibre contacts under a compressive normal load over a series of 10 000 cycle studies are investigated. Reciprocating sliding at a velocity of 0.4 mm s-1, over a track length of 0.8 mm, was performed at 18 °C and 40%-50% relative humidity. Hair fibres retaining their natural sebum were studied, as well as those stripped of their sebum via hexane cleaning, and hair fibres conditioned using a commercially available product. Surface topography modifications resulting from wear were imaged using scanning electron microscopy and quantified using white light interferometry. Hair fibres that presented sebum or conditioned product at the fibre/fibre junction exhibited initial coefficients of friction at least 25% lower than those that were cleaned with hexane. Coefficients of friction were observed to depend on the directionality of sliding for hexane cleaned hair fibres after sufficient wear cycles that cuticle lifting was present, typically on the order 1000 cycles. Cuticle flattening was observed for fibre/fibre junctions exposed to 10 mN compressive normal loads, whereas loads of 100 mN introduced substantial cuticle wear and fibre damage.

  6. Evaluation of wear rates and mechanisms of titanium diboride-graphite composite materials proposed for use as cathodes in Hall-Heroult cells

    SciTech Connect

    Pool, K.H.; Brimhall, J.L.; Raney, P.J.; Hart, P.E.

    1987-01-01

    Purpose of this study was to measure the initial wear rates of TiB/sub 2/ carbon-containing cathode materials (TiB/sub 2/-G) under electrolytic conditions. Parameters evaluated included bath ratio, current density, and aluminum pad thickness. In order to measure initial wear rates, the tests were limited to 8 h.

  7. Importance of Properties of Solids to Friction and Wear Behaviour

    NASA Technical Reports Server (NTRS)

    Czichos, H.

    1984-01-01

    The main properties of solids which influence friction and wear are discussed and published rules which relate material properties to friction and wear are considered. In addition, recent experimental results on the tribological behaviour of metals and polymers illustrating the effect of some important interaction characteristics on friction and wear are presented. Finally, a framework for the systematic compilation and documentation of relevant tribological parameters in experimental friction and wear investigations is given.

  8. A panorama of tooth wear during the medieval period.

    PubMed

    Esclassan, Rémi; Hadjouis, Djillali; Donat, Richard; Passarrius, Olivier; Maret, Delphine; Vaysse, Frédéric; Crubézy, Eric

    2015-01-01

    Tooth wear is a natural phenomenon and a universal occurrence that has existed from the origin of humankind and depends on the way of life, especially diet. Tooth wear was very serious in ancient populations up to the medieval period. The aim of this paper is to present a global view of tooth wear in medieval times in Europe through different parameters: scoring systems, quantity and direction of wear, gender, differences between maxilla and mandible, relations with diet, caries, tooth malpositions and age.

  9. Temperature-dependent wear mechanisms for magnetron-sputtered AlTiTaN hard coatings.

    PubMed

    Khetan, Vishal; Valle, Nathalie; Duday, David; Michotte, Claude; Mitterer, Christian; Delplancke-Ogletree, Marie-Paule; Choquet, Patrick

    2014-09-10

    AlTiTaN coatings have been demonstrated to have high thermal stability at temperatures up to 900 °C. It has been speculated that the high oxidation resistance promotes an improved wear resistance, specifically for dry machining applications. This work reports on the influence of temperature up to 900 °C on the wear mechanisms of AlTiTaN hard coatings. DC magnetron-sputtered coatings were obtained from an Al(46)Ti(42)Ta(12) target, keeping the substrate bias at -100 V and the substrate temperature at 265 °C. The coatings exhibited a single-phase face-centered cubic AlTiTaN structure. The dry sliding tests revealed predominant abrasion and tribo-oxidation as wear mechanisms, depending on the wear debris formed. At room temperature, abrasion leading to surface polishing was observed. At 700 and 800 °C, slow tribo-oxidation and an amorphous oxide formed reduced the wear rate of the coating compared to room temperature. Further, an increase in temperature to 900 °C increased the wear rate significantly due to fast tribo-oxidation accompanied by grooving. The friction coefficient was found to decrease with temperature increasing from 700 to 900 °C due to the formation of oxide scales, which reduce adhesion of asperity contacts. A relationship between the oxidation and wear mechanisms was established using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, surface profilometry, confocal microscopy, and dynamic secondary ion mass spectrometry.

  10. Adhesive Wear Performance of CFRP Multilayered Polyester Composites Under Dry/wet Contact Conditions

    NASA Astrophysics Data System (ADS)

    Danaelan, D.; Yousif, B. F.

    The tribo-performance of a new engineering composite material based on coconut fibers was investigated. In this work, coconut fibers reinforced polyester (CFRP) composites were developed. The tribo-experiments were conducted by using pin-on-disc machine under dry and wet sliding contact condition against smooth stainless steel counterface. Worn surfaces were observed using optical microscope. Friction coefficient and specific wear rate were presented as a function of sliding distance (0-0.6 km) at different sliding velocities (0.1-0.28 m/s). The effect of applied load and sliding velocity was evaluated. The results showed that all test parameters have significant influence on friction and wear characteristics of the composites. Moreover, friction coefficient increased as the normal load and speed increased, the values were about 0.7-0.9 under dry contact condition. Meanwhile, under wet contact condition, there was a great reduction in the friction coefficient, i.e. the values were about 0.1-0.2. Furthermore, the specific wear rates were found to be around 2-4 (10-3) mm3/Nm under dry contact condition and highly reduced under wet condition. In other words, the presence of water as cleaner and polisher assisted to enhance the adhesive wear performance of CFRP by about 10%. The images from optical microscope showed evidence of adhesive wear mode with transition to abrasive wear mode at higher sliding velocities due to third body abrasion. On the other hand, optical images for wet condition showed less adhesive wear and smooth surfaces.

  11. Mechanics of interaction and atomic-scale wear of amplitude modulation atomic force microscopy probes.

    PubMed

    Vahdat, Vahid; Grierson, David S; Turner, Kevin T; Carpick, Robert W

    2013-04-23

    Wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM), including for the widely used amplitude modulation (AM-AFM) mode. Unfortunately, a comprehensive scientific understanding of nanoscale wear is lacking. We have developed a protocol for conducting consistent and quantitative AM-AFM wear experiments. The protocol involves controlling the tip-sample interaction regime during AM-AFM scanning, determining the tip-sample contact geometry, calculating the peak repulsive force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging. The peak repulsive tip-sample interaction force is estimated from a closed-form equation accompanied by an effective tip radius measurement procedure, which combines transmission electron microscopy and blind tip reconstruction. The contact stress is estimated by applying Derjaguin-Müller-Toporov contact mechanics model and also numerically solving a general contact mechanics model recently developed for the adhesive contact of arbitrary axisymmetric punch shapes. We discuss the important role that the assumed tip shape geometry plays in calculating both the interaction forces and the contact stresses. Contact stresses are significantly affected by the tip geometry while the peak repulsive force is mainly determined by experimentally controlled parameters, specifically, the free oscillation amplitude and amplitude ratio. The applicability of this protocol is demonstrated experimentally by assessing the performance of diamond-like carbon-coated and silicon-nitride-coated silicon probes scanned over ultrananocrystalline diamond substrates in repulsive mode AM-AFM. There is no sign of fracture or plastic deformation in the case of diamond-like carbon; wear could be characterized as a gradual atom-by-atom process. In contrast, silicon nitride wears through removal of the cluster of atoms and plastic

  12. Improved hardness and wear properties of B-ion implanted polycarbonate

    SciTech Connect

    Lee, E.H.; Rao, G.R.; Mansur, L.K. )

    1992-07-01

    Polycarbonate (Lexan) was implanted with 100 and 200 keV B{sup +} ions to doses of 0.26, 0.78, and 2.6{times}10{sup 15} ions/cm{sup 2} at room temperature ({lt}100 {degree}C). Mechanical characterization of implanted materials was carried out by nanoindentation and sliding wear tests. The results showed that the hardness of implanted polycarbonate increased with increasing ion energy and dose, attaining hardness up to 3.2 GPa at a dose of 2.6{times}10{sup 15} ions/cm{sup 2} for 200 keV ions, which is more than 10 times that of the unimplanted polymer. Wear properties were characterized using a reciprocating tribometer with nylon, brass, and SAE 52100 Cr-steel balls with 0.5 and 1 N normal forces for 10 000 cycles. The wear mode varied widely as a function of ion energy, dose, wear ball type, and normal load. For given ion energy, load, and ball type conditions, there was an optimum dose that produced the greatest wear resistance and lowest friction coefficient. For polycarbonate implanted with 0.78{times}10{sup 15} ions/cm{sup 2}, the nylon ball produced no wear after 10 000 cycles. Moreover, the overall friction coefficient was reduced by over 40% by implantation. The results suggest that the potential of ion-beam technology for improving polycarbonate is significant, and that surface-sensitive mechanical properties can be tailored to meet the requirements for applications demanding hardness, wear, and abrasion resistance.

  13. 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.

  14. Friction and wear studies of graphite and a carbon-carbon composite in air and in helium

    SciTech Connect

    Li, C.C.; Sheehan, J.E.

    1980-10-01

    Sliding friction and wear tests were conducted on a commercial isotropic graphite and a carbon-carbon composite in air, purified helium, and a helium environment containing controlled amounts of impurities simulating the primary coolant chemistry of a high-temperature gas-cooled reactor (HTGR). The friction and wear characteristics of the materials investigated were stable and were found to be very sensitive to the testing temperature. In general, friction and wear decreased with increasing temperature in the range from ambient to 950/sup 0/C. This temperature dependence is concluded to be due to chemisorption of impurities to form lubricating films and oxidation at higher temperatures, which reduce friction and wear. Graphite and carbon-carbon composites are concluded to be favorable candidate materials for high-temperature sliding service in helium-cooled reactors.

  15. 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

  16. Friction and wear characteristics of carbon steels in vacuum

    NASA Technical Reports Server (NTRS)

    Verkin, B. I.; Lyubarskiy, I. M.; Udovenko, V. F.; Guslyakov, A. A.

    1974-01-01

    The nature of carbon steel friction and wear under vacuum conditions is described within the framework of general friction and wear theory. Friction is considered a dynamic process and wear is considered to be the result of a continuous sequence of transitions of the friction surface material from one state into another.

  17. 32 CFR 507.12 - Possession and wearing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Possession and wearing. 507.12 Section 507.12... Possession and wearing. (a) The wearing of any decoration, service medal, badge, service ribbon, lapel button... possession by a person of any of the articles prescribed in § 507.8 of this part is authorized provided...

  18. Increasing Wearing of Prescription Glasses in Individuals with Mental Retardation

    ERIC Educational Resources Information Center

    DeLeon, Iser G.; Hagopian, Louis P.; Rodriguez-Catter, Vanessa; Bowman, Lynn G.; Long, Ethan S.; Boelter, Eric W.

    2008-01-01

    This study evaluated an intervention for promoting wearing of prescription glasses in 4 individuals with mental retardation who had refused to wear their glasses previously. Distraction through noncontingent reinforcement (NCR) increased independent glasses wearing for 1 of the 4 participants. An intervention consisting of NCR, response cost, and…

  19. Contact damage failure analyses of fretting wear behavior of the metal stem titanium alloy-bone cement interface.

    PubMed

    Zhang, Lanfeng; Ge, Shirong; Liu, Hongtao; Wang, Qingliang; Wang, Liping; Xian, Cory J

    2015-11-01

    Although cemented titanium alloy is not favored currently in the Western world for its poor clinical and radiography outcomes, its lower modulus of elasticity and good biocompatibility are instrumental for its ability supporting and transforming physical load, and it is more suitable for usage in Chinese and Japanese populations due to their lower body weights and unique femoral characteristics. Through various friction tests of different cycles, loads and conditions and by examining fretting hysteresis loops, fatigue process curves and wear surfaces, the current study investigated fretting wear characteristics and wear mechanism of titanium alloy stem-bone cement interface. It was found that the combination of loads and displacement affected the wear quantity. Friction coefficient, which was in an inverse relationship to load under the same amplitude, was proportional to amplitudes under the same load. Additionally, calf serum was found to both lubricate and erode the wear interface. Moreover, cement fatigue contact areas appeared black/oxidative in dry and gruel in 25% calf serum. Fatigue scratches were detected within contact areas, and wear scars were found on cement and titanium surfaces, which were concave-shaped and ring concave/ convex-shaped, respectively. The coupling of thermoplastic effect and minimal torque damage has been proposed to be the major reason of contact damage. These data will be important for further studies analyzing metal-cement interface failure performance and solving interface friction and wear debris production issues. PMID:26241891

  20. Influence of the electrical sliding speed on friction and wear processes in an electrical contact copper stainless steel

    NASA Astrophysics Data System (ADS)

    Bouchoucha, A.; Chekroud, S.; Paulmier, D.

    2004-02-01

    Among the various parameters that influence the friction and wear behaviour of a copper-stainless steel couple crossed by an electrical current and in a dry contact is the sliding speed. The tests were carried out under ambient environment and the sliding speed was in the range of 0.2-8 ms -1. The electrical current intensity was varied from 0 to 40 A and held constant during each experiment. The normal load was maintained constant corresponding to an average Hertzian stress of 10 7 Pa. It appears that the friction coefficient and the wear rate increase at first with the speed, reach their maximums, then slowly decrease and tend to constant values. Over the entire range of sliding speeds two types of wear are observed. These latters are essentially mild wear as long as hard debris do not appear at the interface and severe wear when debris consisting of oxides or oxide metal mixture become big enough, they are removed from the surface and have abrasive effect. The results are discussed in terms of observations of wear debris size and composition, wear track study, metallographic study of worn surfaces and friction and electrical contact resistance records.

  1. Wear of aluminum and hypoeutectic aluminum-silicon alloys in boundary-lubricated pin-on disk sliding

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Brainard, W. A.

    1979-01-01

    The friction and wear of pure aluminum and a number of hypoeutectic aluminum-silicon alloys (with 3 to 12 wt %Si) were studied with a pin-on-disk apparatus. The contacts were lubricated with mineral oil and sliding was in the boundary-lubrication regime at 2.6 cm/sec. Surfaces were analyzed with photomicrographs, scanning electron microscopy, X-ray dispersive analysis, and diamond pyramid hardness measurements. There were two wear regimes for the alloys - high and low - whereas pure aluminum exhibited a high wear rate throughout the test period. Wear rate decreased and the transition stress from high to low wear increased with increasing hardness. There was no correlation between friction coefficient and hardness. A least squares curve fit indicated a wear-rate dependence greater than the inverse first power of hardness. The lower wear rates of the alloys may be due to the composites of silicon platelets in aluminum resulting in increased hardness and thus impairing the shear of the aluminum.

  2. Validation of the Basic Erosive Wear Examination.

    PubMed

    Olley, R C; Wilson, R; Bartlett, D; Moazzez, R

    2014-01-01

    The Basic Erosive Wear Examination (BEWE) is a practical index for screening tooth wear, using a 4-point ordinal scale (0-3). The highest score is recorded in each sextant and a total score (or BEWE sextant cumulative) is calculated per subject. This study aims to investigate if the BEWE sextant cumulative score compares to one comprising a percentage score from all tooth surfaces and as a highest BEWE per subject. The aim is to assess the validity of this score. A total of 350 subjects were recruited from hospital and general practice in south-east England. Buccal, occlusal and lingual/palatal BEWE scores were collected and percentages calculated based on scores 1, 1 and above, 2 and above and 3. BEWE sextant cumulative scores and highest BEWE scores were also recorded per subject. Spearman's correlation coefficients (p values) assessed the relationship between BEWE sextant cumulative scores, BEWE percentages and BEWE highest score per subject. The BEWE sextant cumulative score correlates significantly to a BEWE score taken as a percentage score from all tooth surfaces (Spearman's r > 0.5, p < 0.001) and especially to BEWE surface scores of 1 and above and 2 and above (r > 0.8, p < 0.001) and as a highest surface score per subject (r > 0.8, p < 0.001). BEWE sextant score provides a representation of tooth wear on all tooth surfaces. This study validates a tooth wear index, which provides clinicians with risk indicators of a patient's level of tooth wear and may help to guide clinical management. PMID:24217059

  3. Comparison between PEEK and Ti6Al4V concerning micro-scale abrasion wear on dental applications.

    PubMed

    Sampaio, M; Buciumeanu, M; Henriques, B; Silva, F S; Souza, J C M; Gomes, J R

    2016-07-01

    In the oral cavity, abrasive wear is predictable at exposed tooth or restorative surfaces, during mastication and tooth brushing. Also, wear can occur at contacting surfaces between the Ti-based prosthetic structures and implants in presence of abrasive compounds from food or toothpaste. Thus, the aim of this work was to compare the abrasive wear resistance of PEEK and Ti6Al4V on three-body abrasion related to different hydrated silica content and loads. Surfaces of Ti6Al4V or PEEK cylinders (8mm diameter and 4mm height) were wet ground on SiC papers and then polished with 1µm diamond paste. After that, surfaces were ultrasonically cleaned in propyl alcohol for 15min and then in distilled water for 10min. Micro-scale abrasion tests were performed at 60rpm and on different normal loads (0.4, 0.8 or 1.2N) after 600 ball revolutions using suspensions with different weight contents of hydrated silica. After abrasive tests, wear scars on flat samples were measured to quantify the wear volume and characterized by scanning electron microscope (SEM) to identify the dominant wear mechanisms. Results showed a higher volume loss rate on PEEK than that recorded on Ti6Al4V,, when subjected to three-body abrasion tests involving hydrated silica suspensions. An increase in volume loss was noted on both tested materials when the abrasive content or load was increased. PEEK was characterized by less wear resistance than that on Ti6Al4V after micro-scale abrasion wear in contact with hydrated silica particles, as commonly found in toothpastes. PMID:26849309

  4. Contact lens wear at altitude: subcontact lens bubble formation.

    PubMed

    Flynn, W J; Miller, R E; Tredici, T J; Block, M G; Kirby, E E; Provines, W F

    1987-11-01

    A concern in the past regarding contact lens wear in aviation has been the fear of subcontact lens bubble formation. Previous reports have documented the occurrence of bubbles with hard (PMMA) lenses. Reported here are the results of contact lens bubble studies with soft hydrophilic and rigid gas-permeable lenses. Testing was accomplished in hypobaric chambers and onboard USAF transport aircraft. Hypobaric chamber flights were of three types: high-altitude flights up to 7,620 m (25,000 ft); explosive rapid decompressions from 2,438.4 m (8,000 ft) to 7,620 m (25,000 ft); and 4-h flights at 3,048 m (10,000 ft). Flights aboard transport aircraft typically had cabin pressures equivalent to 1,524-2,438.4 m (5,000-8,000 ft), and ranged in duration from 3 to 10 h. For subjects wearing rigid gas-permeable lenses, central bubbles were detected in 2 of 10 eyes and occurred at altitudes greater than 6,096 m (20,000 ft). With soft contact lenses, bubble formation was detected in approximately 24% (22 of 92 eyes) of the eyes tested, sometimes occurring at altitudes as low as 1,828.8 m (6,000 ft). Soft lens bubbles were always located at the limbus and were without sequela to vision or corneal epithelial integrity. Bubbles under the rigid lenses were primarily central, with potential adverse effects on vision and the corneal epithelium.

  5. Modeling of cumulative tool wear in machining metal matrix composites

    SciTech Connect

    Hung, N.P.; Tan, V.K.; Oon, B.E.

    1995-12-31

    Metal matrix composites (MMCs) are notoriously known for their low machinability because of the abrasive and brittle reinforcement. Although a near-net-shape product could be produced, finish machining is still required for the final shape and dimension. The classical Taylor`s tool life equation that relates tool life and cutting conditions has been traditionally used to study machinability. The turning operation is commonly used to investigate the machinability of a material; tedious and costly milling experiments have to be performed separately; while a facing test is not applicable for the Taylor`s model since the facing speed varies as the tool moves radially. Collecting intensive machining data for MMCs is often difficult because of the constraints on size, cost of the material, and the availability of sophisticated machine tools. A more flexible model and machinability testing technique are, therefore, sought. This study presents and verifies new models for turning, facing, and milling operations. Different cutting conditions were utilized to assess the machinability of MMCs reinforced with silicon carbide or alumina particles. Experimental data show that tool wear does not depend on the order of different cutting speeds since abrasion is the main wear mechanism. Correlation between data for turning, milling, and facing is presented. It is more economical to rank machinability using data for facing and then to convert the data for turning and milling, if required. Subsurface damages such as work-hardened and cracked matrix alloy, and fractured and delaminated particles are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. Effects of surface grinding conditions on the reciprocating friction and wear behavior of silicon nitride

    SciTech Connect

    Blau, P.J.; Martin, R.L.; Zanoria, E.S.

    1997-12-31

    The relationship between two significantly different surface grinding conditions and the reciprocating ball-on-flat friction and wear behavior of a high-quality, structural silicon nitride material (GS-44) was investigated. The slider materials were silicon nitride NBD 200 and 440C stainless steel. Two machining conditions were selected based on extensive machining and flexural strength test data obtained under the auspices of an international, interlaboratory grinding study. The condition categorized as {open_quotes}low strength{close_quote} grinding used a coarse 80 grit wheel and produced low flexure strength due to machining-induced flaws in the surface. The other condition, regarded as {open_quotes}high strength grinding,{close_quotes} utilized a 320 grit wheel and produced a flexural strength nearly 70% greater. Grinding wheel surface speeds were 35 and 47 m/s. Reciprocating sliding tests were conducted following the procedure described in a newly-published ASTM standard (G- 133) for linearly-reciprocating wear. Tests were performed in directions both parallel and perpendicular to the grinding marks (lay) using a 25 N load, 5 Hz reciprocating frequency, 10 mm stroke length, and 100 m of sliding at room temperature. The effects of sliding direction relative to the lay were more pronounced for stainless steel than for silicon nitride sliders. The wear of stainless steel was less than the wear of the silicon nitride slider materials because of the formation of transfer particles which covered the sharp edges of the silicon nitride grinding grooves and reduced abrasive contact. The wear of the GS-44 material was much greater for the silicon nitride sliders than for the stainless steel sliders. The causes for the effects of surface-grinding severity and sliding direction on friction and wear of GS-44 and its counterface materials are explained.

  8. 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.

  9. Wear and microstructural integrity of ceramic plasma sprayed coatings

    NASA Astrophysics Data System (ADS)

    Erickson, Lynn C.

    1999-10-01

    In this work a series of ceramic plasma sprayed (PS) coatings, both alumina- and chromia-based, were sprayed according to a matrix of deposition parameters in order to produce a broad range of microstructures. To investigate the effect of splat size on the coating response, a series of mono-crystalline a -alumina powders with very narrow particle size ranges, nominally 5, 10 and 18 microns in diameter, was sprayed. The coatings were extensively characterized for a variety of microstructural features, including porosity, the angular distribution and density of microcracks as well as the lamellar, or splat, dimensions, using techniques of metallurgical analysis and electron microscopy. The coatings were then evaluated using a series of micromechanical techniques, including indentation, controlled scratch testing, abrasion and dry particle erosion, to investigate their response to different contact situations. It was found that the microstructural features with the most influence on the behaviour of ceramic PS coatings during contact, or wear, by hard particles include, in order of importance: (1) macro-porosity, (2) horizontal crack density, (3) degree of flattening of the splats and (4) volume of unmelted particles, which are all linked to the level and strength of interlamellar bonding in the coating. The major effect of the inter-lamellar bonding in ceramic PS coatings was seen in the wear mechanism transitions. As the level of inter-splat bonding in the coating decreases, the contact load at which the transition from plastic deformation to splat fracture and debonding occurs does as well. However, the load at which catastrophic brittle fracture and spalling occur is increased. All of the micromechanical and wear methods evaluated in the present work were sensitive to differences in the coating microstructures to varying degrees. The low load abrasion results showed the most sensitivity to the microstructural differences of the coatings, followed by controlled

  10. 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.

  11. Microstructure and Abrasive Wear Performance of Ni-Wc Composite Microwave Clad

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Zafar, Sunny; Sharma, Apurbba Kumar

    2015-10-01

    In the present work, Ni-WC powder was deposited on mild steel substrate to develop clads through microwave hybrid heating technique. The cladding trials were carried out in an industrial microwave applicator at 1.1 kW for 540 s. The Ni-WC composite clads were characterized for microstructure and abrasive wear performance through combination of x-ray diffraction, electron and optical microscopy, microhardness, and wear tests. Phase analysis of the Ni-WC clad indicated the presence of stable carbides such as WC, W2C, Ni2W4C, and Fe6W6C. The microstructure study of the clad layer revealed the presence of a uniformly distributed interlocked WC-based reinforcement embedded in the Ni-based matrix. The average Vicker's microhardness in the clad layer was observed to be 1028 ± 90 HV, which was approximately three times the microhardness of the substrate. Abrasive wear resistance of the microwave clads was superior to the MS substrate. Abrasion was the main wear mechanism in the Ni-WC clads and the substrate samples. However, the presence of WC-based reinforcement in the composite clads reduced microcutting, resulting in enhanced wear resistance.

  12. Effect of carbon nanotube addition on the wear behavior of basalt/epoxy woven composites.

    PubMed

    Kim, M T; Rhee, K Y; Lee, B H; Kim, C J

    2013-08-01

    The effect of acid-treated carbon nanotube (CNT) addition on the wear and dynamic mechanical thermal properties of basalt/epoxy woven composites was investigated in this study. Basalt/CNT/epoxy composites were fabricated by impregnating woven basalt fibers into epoxy resin mixed with 1 wt% CNTs which were acid-treated. Wear and DMA (dynamic mechanical analyzer) tests were performed on basalt/epoxy composites and basalt/CNT/epoxy composites. The results showed that the addition of the acid-treated CNTs improved the wear properties of basalt/epoxy woven composites. Specifically, the friction coefficient of the basalt/epoxy composite was stabilized in the range of 0.5-0.6 while it fell in the range of 0.3-0.4 for basalt/CNT/epoxy composites. The wear volume loss of the basalt/CNT/epoxy composites was approximately 68% lower than that of the basalt/epoxy composites. The results also showed that the glass transition temperature of basalt/CNT/epoxy composites was higher than that of basalt/epoxy composites. The improvement of wear properties of basalt/epoxy composites by the addition of acid-treated CNTs was caused by the homogeneous load transfer between basalt fibers and epoxy matrix due to the reinforcement of CNTs.

  13. 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.

    2016-10-01

    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.

  14. Age and Individual Foraging Behavior Predict Tooth Wear in Amboseli Baboons

    PubMed Central

    Galbany, Jordi; Altmann, Jeanne; Pérez-Pérez, Alejandro; Alberts, Susan C.

    2010-01-01

    Teeth represent an essential component of the foraging apparatus for any mammal, and tooth wear can have significant implications for survival and reproduction. This study focuses on tooth wear in wild baboons in Amboseli, southern Kenya. We obtained mandibular and maxillary tooth impressions from 95 baboons and analyzed digital images of replicas made from these impressions. We measured tooth wear as the percent dentine exposure (PDE, the percent of the occlusal surface on which dentine was exposed), and we examined the relationship of PDE to age, behavior, and life history variables. We found that PDE increased significantly with age for both sexes in all three molar types. In females, we also tested the hypotheses that long-term patterns of feeding behavior, social dominance rank, and one measure of maternal investment (the cumulative number of months that a female had dependent infants during her lifetime) would predict tooth wear when we controlled for age. The hypothesis that feeding behavior predicted tooth wear was supported. The percent of feeding time spent consuming grass corms predicted PDE when controlling for age. However, PDE was not associated with social dominance rank or maternal investment. Am J Phys Anthropol 000:000–000, 2010. PMID:20721946

  15. Nanostructured wear resistant coating for reversible cultivator shovels: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Dave, V.; Rao, G. P.; Tiwari, G. S.; Sanger, A.; Kumar, A.; Chandra, R.

    2016-04-01

    Cultivator, one of the agriculture farm tool, extensively suffers from the wear problem. In this paper, we report nanostructured chromium nitrite (CrN) coating for the cultivator shovels to mitigate wear problem. The (CrN) coating was developed using DC magnetron sputtering technique at 200 °C. The structural, morphological, hydrophobic and wear properties were investigated using X-ray diffractometer, scanning electron microscope, contact angle goniometer and custom designed soil bin assembly. The XRD reveals that the deposited coating was polycrystalline in nature with cubic structure. Also, The deposited coating was found to be anti wear resistant as well as hydrophobic in nature. The gravimetric wear for the coating developed at 200 °C coated was found out to be 8.15 gm and for non coated it was 14.48 gm tested for 100 hrs. The roughness of the coating plays an important role in determining the hydrophobicity of the coated film. Roughness and contact angle measured for 200 °C coated shovel was found out to be 11.17 nm and 105 ° respectively.

  16. 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.

  17. Preparation and Wear Resistance of Aluminum Composites Reinforced with In Situ Formed TiO/Al2O3

    NASA Astrophysics Data System (ADS)

    Qin, Q. D.; Huang, B. W.; Li, W.; Zeng, Z. Y.

    2016-05-01

    An in situ TiO/Al2O3-reinforced Al composite is successfully prepared using a powder metallurgy route by the reaction of Ti2CO and Al powder. The Ti2CO powder is produced by carrying out a carbothermic reduction of titanium dioxide at 1000 °C. XRD results show that the final product is composed of Al, TiO, Al2O3, and Al3Ti. Morphology examination of the composite reveals the presence of bigger blocks of TiO and fine particles of Al2O3 and the volume fraction of reinforcement is found to range between 18 and 55%. As the volume fraction of the reinforced materials approaches 50%, the particles start to agglomerate. Dry sliding wear tests conducted using a conventional pin-on-disk testing machine show that the wear resistance of the composite is higher than that of the pure aluminum ingot. The wear rate of the composite increases almost linearly with the increase in the wear distance. The sliding wear test shows that as the volume fraction of the reinforced phase increases, the coefficient of friction decreases. The wear mechanism is also discussed.

  18. REDUCED ENGINE FRICTION AND WEAR

    SciTech Connect

    Ron Matthews

    2003-07-08

    Progress was made on experimental and numerical subtasks during the second 6-month period of this project. One of the experimental subtasks scheduled for completion during the first 6 months was delayed due to a delay in receiving the prototype RLE face seal from the vendor. This component was acquired and testing was completed during the second 6 months. The test results indicate that this face seal fulfills the engineering objectives. The other experimental subtask scheduled for completion during the second 6-month period was final assembly of the prototype rotating liner engine. This subtask was completed on schedule. No results from this subtask were scheduled for this reporting period. One numerical subtask, development of the governing equations, was scheduled for completion during the first 6-month period but was completed during the second 6 months. However, we expect to re-explore these as we learn more throughout the course of the project. Two other numerical subtasks were scheduled to begin during the second 6 months: formulating the numerical equations governing piston assembly friction and coding/testing the resulting model. These subtasks were not scheduled for completion during this reporting period. Satisfactory progress was made.

  19. Wear mechanisms for polycrystalline-diamond compacts as utilized for drilling in geothermal environments. Final report

    SciTech Connect

    Hibbs, L.E. Jr.; Sogoian, G.C.

    1983-05-01

    The work, which was performed in the period from 12/6/79 to 9/30/81 included: (1) rock cutting experiments with single point polycrystalline sintered diamond compact (PDC) cutters to quantitatively determine cutter wear rates and identify wear modes, (2) PDC rock cutting experiments to measure temperatures developed and examine the effects of tool wear, cutting parameters and coolant flow rates on temperature generation, (3) assisting in performing full scale laboratory drilling experiments with PDC bits, using preheated air to simulate geothermal drilling conditions, and in analyzing and reporting the experimental results, and (4) acting in a consulting role with the purpose of establishing design specifications for geothermal hard matrix PDC bits to be procured by Sandia Laboratories for test purposes.

  20. Friction, wear, and thermal stability studies of some organotin and organosilicon compounds

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1973-01-01

    Thermal decomposition temperatures were determined for a number of organotin and organosilicon compounds. A ball-on-disk sliding friction apparatus was used to determine the friction and wear characteristics of two representative compounds, (1) 3-tri-n-butylstannyl (diphenyl) and (2) 3-tri-n-butylsilyl (diphenyl). Friction and wear test conditions included a 1-kg load, 25 to 225 C disk temperatures, and a dry air atmosphere. The tin and silicon compounds yielded friction and wear results either lower than or similar to those obtained with a polyphenyl ether and a C-ether. The maximum thermal decomposition temperatures obtained in the silicon and tin series were 358 and 297 C, respectively. Increasing the steric hindrance around the silicon or tin atoms increased the thermal stability. Future work with these compounds will emphasize their use as antiwear additives rather than base fluids.

  1. Influence on grip of knife handle surface characteristics and wearing protective gloves.

    PubMed

    Claudon, Laurent

    2006-11-01

    Ten subjects were asked to apply maximum torques on knife handles with either their bare hand or their hand wearing a Kevlar fibre protective glove. Four knife handles (2 roughnesses, 2 hardnesses) were tested. Surface electromyograms of 6 upper limb and shoulder muscles were recorded and subject opinions on both knife handle hardness and friction in the hand were also assessed. The results revealed the significant influence of wearing gloves (p<0.0001), knife type (p<0.0005) and handle hardness (p<0.005) on the applied torque. Wearing Kevlar fibre gloves greatly increased the torque independently of the other two parameters. Under the bare hand condition, a 90 degrees ShA slightly rough handle provided the greatest torque. Subject opinion agreed with the observed effects on recorded torque values except for the hardness factor, for which a preference for the 70 degrees ShA value over the 90 degrees ShA value emerged.

  2. Wear Behavior of Al-SiC Metal Matrix Composite under various Corrosive Environments

    NASA Astrophysics Data System (ADS)

    Pradhan, Smrutiranjan; Barman, Tapan Kumar; Sahoo, Prasanta; Sutradhar, Goutam

    2016-09-01

    This paper investigates the wear behavior under corrosive environments of LM6 based metal matrix composite reinforced with 5 wt% SiC prepared through the stir casting method. The experiments are carried out in a pin-on-disk tribotester varying five levels of normal load and sliding speed. The duration of each experiment is fixed for 30 minutes. Three environments viz. dry, deionised and dilute acid environments are considered to carry out the tribological tests. The composite exhibits slightly good wear resistance under low load and speed condition but weight loss increases as these parameters increases in all three environments. Maximum weight loss occurs in case of acid environment as it is more corrosive than dry and deionised environment. The wear surface of the composite is examined through the scanning electron microscopic (SEM) and energy dispersive x-ray analysis (EDX).

  3. Wear Behavior of Aluminium Metal Matrix Composite Prepared from Industrial Waste.

    PubMed

    Xavier, L Francis; Suresh, Paramasivam

    2016-01-01

    With an increase in the population and industrialization, a lot of valuable natural resources are depleted to prepare and manufacture products. However industrialization on the other hand has waste disposal issues, causing dust and environmental pollution. In this work, Aluminium Metal Matrix Composite is prepared by reinforcing 10 wt% and 20 wt% of wet grinder stone dust particles an industrial waste obtained during processing of quarry rocks which are available in nature. In the composite materials design wear is a very important criterion requiring consideration which ensures the materials reliability in applications where they come in contact with the environment and other surfaces. Dry sliding wear test was carried out using pin-on-disc apparatus on the prepared composites. The results reveal that increasing the reinforcement content from 10 wt% to 20 wt% increases the resistance to wear rate. PMID:26989764

  4. Wear and Corrosion Behavior of CoNiCrAlY Bond Coats

    NASA Astrophysics Data System (ADS)

    Rathod, W. S.; Khanna, A. S.; Rathod, R. C.; Sapate, S. G.

    2014-07-01

    The present study focusses on the wear and microstructural properties of CoNiCrAlY coatings fabricated on AISI 316L stainless steel substrate by using the (HVOF) and (CGDS) methods. A triobiological test was performed on the samples in order to understand the wear behaviour of thermally sprayed coatings. The microstructures of as-sprayed and worn out coatings were investigated by scanning electron microscopy. Coating hardness measurements were performed with nanoindentation. HVOF coating revealed lower hardness value in comparison with CGDS. Studies depicted better wear resistance of the CGDS sprayed with He, when compared to CGDS N2 and HVOF processing. Potentiodynamic polarization curves and tafel extrapolation experiments were carried at 7.5 pH value using 3.5 % NaCl as an electrolyte. Electrochemical studies depicted better corrosion resistance of the He processed coating when compared to N2 and HVOF processing.

  5. Receiving Wear-Resistance Coverings Additives of Nanoparticles of Refractory Metals at a Laser Cladding

    NASA Astrophysics Data System (ADS)

    Murzakov, M. A.; Petrovskiy, V. N.; Bykovskiy, D. P.; Andreev, A. O.; Birukov, V. P.; Markushov, Y. V.

    2016-02-01

    Laser cladding technology was used to conduct experiments on production of wear-resistant coatings with additive nanoparticles of refractory metals (WC, TaC). Mechanical testing of coating abrasion was made using Brinell-Howarth method. The obtained data was compared with wear- resistance of commercial powder containing WC. It was found that at a concentration 10-15% coating with nanopowder additives shows a dramatic increase in wear-resistance by 4-6 times as compared to carbon steel substrate. There were conducted metallurgical studies of coatings on inverse electron reflection. There was determined elemental composition of deposited coating and substrate, and microhardness measured. It was found that structure of deposited coating with nanoparticles is fine.

  6. Wear Behavior of Aluminium Metal Matrix Composite Prepared from Industrial Waste

    PubMed Central

    Xavier, L. Francis; Suresh, Paramasivam

    2016-01-01

    With an increase in the population and industrialization, a lot of valuable natural resources are depleted to prepare and manufacture products. However industrialization on the other hand has waste disposal issues, causing dust and environmental pollution. In this work, Aluminium Metal Matrix Composite is prepared by reinforcing 10 wt% and 20 wt% of wet grinder stone dust particles an industrial waste obtained during processing of quarry rocks which are available in nature. In the composite materials design wear is a very important criterion requiring consideration which ensures the materials reliability in applications where they come in contact with the environment and other surfaces. Dry sliding wear test was carried out using pin-on-disc apparatus on the prepared composites. The results reveal that increasing the reinforcement content from 10 wt% to 20 wt% increases the resistance to wear rate. PMID:26989764

  7. Wear behavior and microstructure of hypereutectic Al-Si alloys prepared by selective laser melting

    NASA Astrophysics Data System (ADS)

    Kang, Nan; Coddet, Pierre; Liao, Hanlin; Baur, Tiphaine; Coddet, Christian

    2016-08-01

    This work investigates the microstructure and wear behavior of hypereutectic Al-Si alloys, in-situ fabricated using selective laser melting of a mixture of eutectic Al-12Si (wt.%) and pure Si powders. The first observation was that the size and morphology of the Si phase are strongly influenced by the laser power. In addition, it was also observed that a high laser power causes serious evaporation of aluminum during the remelting process. Dry sliding wear test and Vickers microhardness measurements were employed to characterize the mechanical properties of the material. The lowest wear rate of about 7.0 × 10-4 mm3 N-1 m-1 was observed for samples having the highest value of relative density (96%) and microhardness (105 Hv0.3).

  8. Dynamic-scanning-electron-microscope study of friction and wear

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1974-01-01

    A friction and wear apparatus was built into a real time scanning electron microscope (SEM). The apparatus and SEM comprise a system which provides the capability of performing dynamic friction and wear experiments in situ. When the system is used in conjunction with dispersive X-ray analysis, a wide range of information on the wearing process can be obtained. The type of wear and variation with speed, load, and time can be investigated. The source, size, and distribution of wear particles can be determined and metallic transferal observed. Some typical results obtained with aluminum, copper, and iron specimens are given.

  9. Finger wear detection for production line battery tester

    SciTech Connect

    Depiante, Eduardo V.

    1997-01-01

    A method for detecting wear in a battery tester probe. The method includes providing a battery tester unit having at least one tester finger, generating a tester signal using the tester fingers and battery tester unit with the signal characteristic of the electrochemical condition of the battery and the tester finger, applying wavelet transformation to the tester signal including computing a mother wavelet to produce finger wear indicator signals, analyzing the signals to create a finger wear index, comparing the wear index for the tester finger with the index for a new tester finger and generating a tester finger signal change signal to indicate achieving a threshold wear change.

  10. Finger wear detection for production line battery tester

    DOEpatents

    Depiante, E.V.

    1997-11-18

    A method is described for detecting wear in a battery tester probe. The method includes providing a battery tester unit having at least one tester finger, generating a tester signal using the tester fingers and battery tester unit with the signal characteristic of the electrochemical condition of the battery and the tester finger, applying wavelet transformation to the tester signal including computing a mother wavelet to produce finger wear indicator signals, analyzing the signals to create a finger wear index, comparing the wear index for the tester finger with the index for a new tester finger and generating a tester finger signal change signal to indicate achieving a threshold wear change. 9 figs.

  11. Aluminum nanocomposites having wear resistance better than stainless steel

    SciTech Connect

    An, Linan; Qu, Jun; Luo, Jinsong; Fan, Yi; Zhang, Ligong; Liu, Jinling; Xu, Chengying; Blau, Peter Julian

    2011-01-01

    Tribological behavior of alumina-particle-reinforced aluminum composites made by powder metallurgy process has been investigated. The nanocomposite containing 15 vol% of Al2O3 nanoparticles exhibits excellent wear resistance by showing significantly low wear rate and abrasive wear mode. The wear rate of the nanocomposite is even lower than stainless steel. We have also demonstrated that such excellent wear resistance only occurred in the composite reinforced with the high volume fraction of nanosized reinforcing particles. The results were discussed in terms of the microstructure of the nanocomposite.

  12. The medical acceptability of soft contact lens wear by USAF tactical aircrews.

    PubMed

    Dennis, R J; Green, R P; Ketchum, N S

    1992-02-01

    Seventy-two Tactical Air Command (TAC) aircrew members completed one full year of soft contact lens (SCL) wear. A daily-wear regimen, using extended-wear lenses, was used to minimize corneal stress. Baseline measurements of visual acuity with SCLs and with spectacles after SCL removal and ocular indicator gradings were compared to measurements at 5-d, 10-d, 1-month, 3-month, 6-month, and 12-month examinations. Visual acuity did not decrease during the test. No aircrew member developed corneal ulcers or other serious complications requiring elimination from the test. Two aircrew members lost a total of 9 "duties not to include flying" (DNIF) days: one flyer was grounded for 1 d with a corneal abrasion and another for 8 d with epithelial microcysts. The TAC SCL Test, as designed, was generally successful. The conservative approach to SCL wear during the test and the meticulous follow-up care by United States Air Force eye care professionals most likely contributed to the low ocular complication rate.

  13. [The influence of irradiation into the wear behaviour of polyethylene (author's transl)].

    PubMed

    Ungethüm, M; Hinterberger, J

    1979-10-01

    Irradiated specimens of UHMW-PE have been tested by a "Pin-on-disc"-method against a metal pin. Increasing irradiation doses are leading to obviously increasing wear-rates. Irradiation in presence of nitrogen gives no advantage in comparison to normal air as an crosslinking agents, concerning tribological properties. PMID:549337

  14. A study on the in-vitro wear of the natural tooth structure by opposing zirconia or dental porcelain

    PubMed Central

    Jung, Yu-Seok; Lee, Jae-Whang; Choi, Yeon-Jo; Ahn, Jin-Soo; Shin, Sang-Wan

    2010-01-01

    PURPOSE This study was conducted to evaluate clinical validity of a zirconia full-coverage crown by comparing zirconia's wear capacity over antagonistic teeth with that of feldspathic dental porcelain. MATERIALS AND METHODS The subject groups were divided into three groups: the polished feldspathic dental porcelain group (Group 1), the polished zirconia group (Group 2), and the polished zirconia with glazing group (Group 3). Twenty specimens were prepared from each group. Each procedure such as plasticity, condensation, and glazing was conducted according to the manufacturer's manual. A wear test was conducted with 240,000 chewing cycles using a dual-axis chewing simulator. The degree of wear of the antagonistic teeth was calculated by measuring the volume loss using a three-dimensional profiling system and ANSUR 3D software. The statistical significance of the measured degree of wear was tested with a significant level of 5% using one-way ANOVA and the Tukey test. RESULTS The degrees of wear of the antagonistic teeth were 0.119 ± 0.059 mm3 in Group 1, 0.078 ± 0.063 mm3 in Group 3, and 0.031 ± 0.033 mm3 in Group 2. Statistical significance was found between Group 1 and Groups 2 and between Group 2 and 3, whereas no statistical significance was found between Group 1 and Group 3. CONCLUSION Despite the limitations of this study on the evaluation of antagonistic teeth wear, the degree of antagonistic tooth wear was less in zirconia than feldspathic dental porcelain, representing that the zirconia may be more beneficial in terms of antagonistic tooth wear. PMID:21165280

  15. Study of wear analysis with {sup 18}F

    SciTech Connect

    Schmidt, N.; Nolen, J.A.; Blumenthal, D.J.

    1995-08-01

    We are studying the possible use of low-energy radioactive beams for the wear analysis of various industrial components (e.g. engine parts and materials for orthopedic implants). Previous experiments with {sup 7}Be and {sup 22}Na studied components at implantation depths of several tens of micrometer. In a first series of experiments we implanted {sup 18}F ions into the surface layer, which opens the possibility to study wear in the critical first micrometer of various materials. {sup 18}F was produced via the p({sup 18}O, {sup 18}F)n reaction at E{sub 18}{sub O} = 110 MeV using a 1.22-mg/cm{sub 2} polypropylene foil as a hydrogen target. The {sup 18}F{sup 9+} ions were separated at {theta}=0{degrees} from the incident {sup 18}O{sup 8+} beam with the split-pole spectrograph. In order to allow for a rapid change of irradiation samples, the {sup 18}F ions penetrated a thin HAVAR foil and were implanted into the sample which was located outside the vacuum chamber behind the pressure window. The depth distribution of the {sup 18}F was tested by implantation into a series of 1.5-{mu} thick Mylar foils which were subsequently measured with respect to their {sup 18}F activity using a Si-surface barrier detector. The localization of the {sup 18}F ions was found to be better than 1.5 {mu}. The implantation depth could be varied in the range between 1.5 {mu} - 9 {mu} by choosing the appropriate distance between pressure window and implantation sample. The wear rate was determined by measuring the (decay-corrected) decrease of the activity remaining in the sample after it was polished with Emery paper. In a first experiment the wear of stainless steel could be measured by this technique with a sensitivity of better than 100 nm. A paper describing these results is under preparation.

  16. Wear Characteristics of Vitrified cBN Grinding Wheels

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masakazu; Ichida, Yoshio; Sato, Ryunosuke

    To clarify the wheel wear characteristics in grinding process using vitrified cBN wheels, we have investigated the change in wheel wear behavior when the load on the grain cutting edge is increased by increasing work speed. Wheel wear behavior in the grinding process may be classified into two main types, a) wheel wear process-type 1, that is consists of initial and steady-state wheel wear regions, and b) wheel wear process-type 2, that is consists of initial, steady-state and abnormal wheel wear regions. In the steady-state wear region of wheel wear process-type 1, lower wheel wear rate, lower stable grinding forces and good finished surface roughness are obtained, because self-sharpening due to micro fractures of the cutting edges takes place. In grinding with wheel wear process-type 2, it is very hard to obtain good finished surface and high grinding ratio, because of occurrences of fracture or releasing of cBN grains.

  17. NASA interdisciplinary collaboration in tribology. A review of oxidational wear

    NASA Technical Reports Server (NTRS)

    Quinn, T. F. J.

    1983-01-01

    An in-depth review of oxidational wear of metals is presented. Special emphasis is given to a description of the concept of oxidational wear and the formulation of an Oxidational Wear Theory. The parallelism between the formation of an oxide film for dry contact conditions and the formation of other surface films for a lubricated contact is discussed. The description of oxidational wear is prefaced with a unification of wear modes into two major classes of mild and severe wear including both lubricated and dry contacts. Oxidational wear of metals is a class of mild wear where protective oxide films are formed at real areas of contact and during the time of contact at temperataure T sub c. When the oxide reaches a critical thickness, frequently in the range of 1 to 3 microns, the oxide breaks up and eventually appears as a wear particle. These oxides are preferentially formed on plateaux which alternately carry the load as they reach their critical thickness and are removed. If the system is operated at elevated temperatures, thick oxides can form both out of contact and between the plateaux. Temperature is important in determining the structure of the oxide film present. Spinel oxide (Fe3O4) which forms above 300 C is more protective than the lower temperature rhomobohedral (alpha-Fe2O3) oxide which is abrasive. An Oxidational Wear Theory is derived using a modified Archard wear law expressed in terms of activation energy (Qp) and Arrhenius constant (Ap).

  18. Stiction, friction, and wear reduction in silicon microelectromechanical systems

    NASA Astrophysics Data System (ADS)

    Mantiziba, Fadziso Mabel

    Current reliability issues in silicon based microelectromechanical systems (MEMS) pose a challenge in the advancement of this pervasive technology. Silicon Microsystems are encumbered with adhesion induced catastrophic failures (stiction) during the final fabrication step where a wet chemical etch release is often conducted to produce functional, suspended microstructures. Irreversible adhesion of active device layer components to the substrate can drastically reduce yields of fully functional devices. Potential in-use problems of a tribological nature also limit the reliability and device lifetimes of these microstructures, particularly where intermittent or continuous contacting of surfaces occurs during a device's normal operation. Understanding the fundamental tribological properties such as friction coefficients and wear mechanisms that occur in the normal operation of these devices is a necessity in providing potential long term solutions to such reliability issues. A unique, simple, yet inexpensive solution to release related adhesion failures that utilizes a temporary physical barrier during the final rinsing stage of a typical silicon wet etch release process is presented. This temporary barrier is accomplished using polystyrene microspheres that prevent contact between the substrate and the components of the suspended device layer during drying. The microspheres are subsequently removed using a plasma etching process. Improvement of yields of stiction-free, functional devices >90% in comparison to <50% for air drying of water or isopropyl alcohol final rinse liquids have been demonstated using this process. To address tribological reliability issues for silicon MEMS, friction testing devices are utilized to measure the friction coefficients of silicon. Thin ceramic coatings of oxides of aluminum, zirconium, or titanium are applied to the silicon MEMS devices using the atomic layer deposition technique and tested for comparison to non-coated silicon

  19. Fullerence particles as an additive to liquid lubricants and greases for low friction and wear

    SciTech Connect

    Gupta, B.K.; Bhushan, B.

    1994-07-01

    Fullerene (C{sub 60}-rich) powder is tested as an additive to liquid lubricants and greases to improve their friction and wear characteristics. The coefficient of friction and wear of a 52100 steel ball sliding against a hardened M50 steel disk are measured at the contact in the presence of base petroleum oil with and without fullerene particles. For comparison, tests are also conducted in the presence of base oil with graphite and MoS{sub 2} powders (5 wt%). It was found that a 5 wt% addition of fullerene to base oil resulted in a reduction in width of the wear scar on the steel disk from 300-380 {mu}m to 120-130 {mu}m, and the diameter of the wear scar on the mating steel ball was reduced from approximately 200 {mu}m to 60 {mu}m. The coefficient of friction in the presence of oil with 5 wt% fullerene is observed to be approximately 20 percent lower than that of base oil with no additives. The improvements in friction and wear for fullerenes are comparable to those for graphite and MoS{sub 2} additives. Limited experiments conducted on diester grease with fullerene and solid lubricants demonstrate similar trends. The improvements in friction and wear are likely due to the formation of a transfer film at the contact region and the presence of C{sub 60} clusters which may act as tiny ball bearings which facilitate sliding. 19 refs., 4 figs., 3 tabs.

  20. 7-Be Implantation in Plastics for Prosthesis Wear Studies

    NASA Astrophysics Data System (ADS)

    Greife, Uwe; Erikson, L.; Patel, N.; Wimmer, M.; Dwiwedi, Y.; Laurent, M.; Chipps, K.; Blackmon, J.; Kozub, R.; Bardayan, D.; Gross, C.; Stracener, D.; Smith, M.; Nesaraya, C.; Rehm, E.; Ahmed, I.; Greene, J.

    2010-11-01

    The current generation of highly cross linked ultrahigh molecular weight polyethylenes (PE) for hip and knee joint replacement have achieved such low in vitro wear rates that efforts have been underway to develop more sensitive methods to measure polyethylene wear. The most widely used technique, the gravimetric method, suffers from the notable disadvantage that mass gain by fluid absorption can considerably exceed mass loss by wear, making the wear measurement inaccurate, sometimes even leading to negative ``wear'' values. The purpose of this experiment was to investigate the use of a radioactive tracer, beryllium-7 (7-Be), to circumvent the problem of fluid absorption and thereby achieve a much more sensitive and accurate wear measurement. This proof of principle study demonstrated the general feasibility of 7-Be implantation (performed at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory) for PE wear analysis.