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Wear Mechanisms (wear + mechanism)
Selected AbstractsWear Mechanisms of TiB2 and TiB2,TiSi2 at Fretting Contacts with Steel and WC,6 wt% CoINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Golla Brahma Raju Unlubricated fretting wear tests on TiB2 and TiB2,5 wt% TiSi2 ceramics against two different mating materials (bearing grade steel and WC,6 wt% Co balls) were performed with a view to understand the counterbody-dependent difference in friction and wear properties. The fretting experiments were conducted systematically by varying load (2,10 N) at an oscillating frequency of 4 Hz and 100 ,m linear stroke, for a duration of 100,000 cycles. Adhesion, abrasion, and three-body wear have been observed as mechanisms of material damage for both the TiB2/steel and TiB2/WC,Co tribosystems. The third body is predominantly characterized as tribochemical layer for TiB2/steel and loose wear debris particles for TiB2/WC,Co tribocouple. An explanation on differences in tribological properties has been provided in reference to the counterbody material as well as microstructure and mechanical properties of flat materials. [source] Influence of fiber orientation on high stress wear behavior of sisal fiber-reinforced epoxy compositesPOLYMER COMPOSITES, Issue 4 2007Navin Chand Sisal fiber-reinforced epoxy composites having three different fiber orientations, namely LL, LT, TT mentioned in the text were prepared and tested for their high stress abrasive wear behavior. Effect of fiber orientation, sliding distance, and load on abrasive wear of sisal,epoxy composites have been determined. Wear data of composites have been compared with the pure epoxy. Incorporation of fibers decreases the wear rate of epoxy resin, which varies with the fiber orientation. Wear rate in case of TT composite is found minimum as compared to other two composites. Wear rate follows the following trend, WTT < WLT < WLL. Owing to minimum exposed area of fiber to the sliding asperities, lowest wear rate occurs in the case of TT composite. Increase of load and sliding distance increases the wear volume in all the composites, because of the progressive loss of material. Wear mechanism has been discussed by using SEM micrographs of the worn surfaces. POLYM. COMPOS., 28:437,441, 2007. © 2007 Society of Plastics Engineers. [source] Preparation and tribological properties of polyetheretherketone compositesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010Dangsheng Xiong Abstract Polyetheretherketone (PEEK) is a thermoplastic engineering plastic with excellent mechanical properties. In this article, PEEK and its composites filled with ultrahigh-molecular-weight polyethylene (UHMWPE) were prepared by vacuum hot-pressing method. Tribological properties of these materials were investigated by block-on-ring friction and wear rig. An alloy (CoCrMo) ring and a ceramic (Si3N4) ring were used as friction pairs. The experiments were conducted under deionized water lubrication (DWL), saline lubrication (SL), and calf serum solution lubrication (CSSL). Worn surfaces morphology was observed and analyzed by metallographic microscope. The results indicated that friction coefficients of PEEK/UHMWPE composites were effectively reduced when compared with pure PEEK. When the materials slid against the alloy (CoCrMo) ring, wear rates of PEEK/UHMWPE were also effectively reduced when compared with pure PEEK. Wear mechanisms of PEEK were mainly ploughing and slight scratches under CSSL condition, whereas the quantity of the ploughing and scratches for PEEK/20%UHMWPE were significantly reduced. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] Wear mechanisms in metal-on-metal bearings: The importance of tribochemical reaction layersJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2010Markus A. Wimmer Abstract Metal-on-metal (MoM) bearings are at the forefront in hip resurfacing arthroplasty. Because of their good wear characteristics and design flexibility, MoM bearings are gaining wider acceptance with market share reaching nearly 10% worldwide. However, concerns remain regarding potential detrimental effects of metal particulates and ion release. Growing evidence is emerging that the local cell response is related to the amount of debris generated by these bearing couples. Thus, an urgent clinical need exists to delineate the mechanisms of debris generation to further reduce wear and its adverse effects. In this study, we investigated the microstructural and chemical composition of the tribochemical reaction layers forming at the contacting surfaces of metallic bearings during sliding motion. Using X-ray photoelectron spectroscopy and transmission electron microscopy with coupled energy dispersive X-ray and electron energy loss spectroscopy, we found that the tribolayers are nanocrystalline in structure, and that they incorporate organic material stemming from the synovial fluid. This process, which has been termed "mechanical mixing," changes the bearing surface of the uppermost 50 to 200 nm from pure metallic to an organic composite material. It hinders direct metal contact (thus preventing adhesion) and limits wear. This novel finding of a mechanically mixed zone of nanocrystalline metal and organic constituents provides the basis for understanding particle release and may help in identifying new strategies to reduce MoM wear. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:436,443, 2010 [source] Verschleißmechanismen bei moderater und extremer GrenzreibungMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 10-11 2004M. Scherge wear mechanisms; continuous wear measurement; surface analysis Abstract Mit einem Stift-Scheibe-Tribometer wurden für das System Stahlstift/Stahlscheibe Versuche durchgeführt, die drastisch unterschiedliche Verschleißraten zur Folge hatten. Durch Wahl der Normalkraft wurde die Energiedissipation so eingestellt, dass im ersten Versuch Verschleißraten in der Größenordnung von Nanometern pro Stunde erreicht wurden, während im zweiten Versuch Mikrometer pro Stunde erzielt wurden. Die Proben wurden nach dem Experiment hinsichtlich Struktur und chemischer Zusammensetzung analysiert. Im Bereich der kleinen Verschleißraten dominierten plastisches Fließen und mechanische Vermischung während die hohen Verschleißraten mit starker Topographieänderung und Oxidation einher gingen. Wear mechanisms at moderate and extreme friction conditions Using a pin-on-disk tribometer drastically different wear rates were obtained in experiments running a steel pin against a steel disk. By tuning the normal force the energy dissipation was varied resulting in either mild wear in the range of nanometers per hour or severe wear with a wear rate of micrometers per hour. After the tribological tests the samples were analyzed with respect to structure and chemical composition. Whereas small wear rates are accompanied by plastic flow and mechanical intermixing, severe wear results in significant topography changes and oxidation. [source] Mechanical Behavior and Failure Analysis of Prosthetic Retaining Screws after Long-term Use In Vivo.JOURNAL OF PROSTHODONTICS, Issue 3 2008Part 1: Characterization of Adhesive Wear, Structure of Retaining Screws Abstract Purpose: The general aim of this study and those presented in Parts 2,4 of this series was to characterize the structure, properties, wear, and fracture of prosthetic retaining screws in fixed detachable hybrid prostheses after long-term use in vivo. This part of the overall investigation addresses whether there are differences in thread wear between the screws closest to the fulcrum and those that are farthest from the fulcrum in fixed detachable hybrid prostheses. Materials and Methods: The total number of prosthetic retaining screws used in this study was 100 (10 new and 90 used). New screws (controls) from Nobel Biocare (NB) were divided into Group 1 (slotted) and Group 2 (hexed). Ninety used screws (in service 18,120 months) were retrieved from fixed detachable hybrid prostheses in 18 patients (5 screws from each patient, 60 from NB and 30 from Sterngold). The used screws were divided into 18 groups. Additionally, each group was subdivided into A and B categories. Category A contained the middle three prosthetic screws, which were considered the farthest screws from the fulcrum line. Category B contained the most posterior two screws, which were considered the screws closest to the fulcrum line. All 100 screws were subjected to thorough, nondestructive testing. Results: Light and scanning electron microscopic examination of all used screws for each group revealed surface deterioration of the active profile of the screw threads consistent with adhesive wear. The observed thread profile deterioration ranged from mild to severe. The wear was aggressive enough to cause galling, which led to thinning of the threads and, in severe cases, to knife-edges at thread crests. In ten groups, the most anterior three screws exhibited more wear than the most posterior two screws. In addition to thread wear, severe plastic deformation was detected on the bottom part of each screw for three groups, and a long external longitudinal crack was detected in one screw of Group 2. Conclusions: The findings of this study and those presented in Parts 2,4 demonstrate that different retaining screws from the same manufacturer and/or from different manufacturers have different geometrical design, microstructures, major alloy constituents, and microhardness, and that these differences influence their preload and fractured load values. In this part of the overall investigation, the occurrence of galling as a result of wear involving prosthetic retaining screws appears to be an inevitable and unavoidable consequence of long-term use in vivo in fixed detachable hybrid prostheses regardless of the intended/original preload value. The galling rate is greater on the middle three screws compared to the most posterior two screws in fixed detachable hybrid prostheses. The wear pattern is consistent with an adhesive wear mechanism; however, this study does not provide enough data to support a definitive analysis. [source] Mechanical Behavior and Failure Analysis of Prosthetic Retaining Screws after Long-Term Use In Vivo.JOURNAL OF PROSTHODONTICS, Issue 3 2008Microhardness Analysis, Part 2: Metallurgical Abstract Purpose: This study involved testing and analyzing multiple retrieved prosthetic retaining screws after long-term use in vivo to: (1) detect manufacturing defects that could affect in-service behavior; (2) characterize the microstructure and alloy composition; and (3) further characterize the wear mechanism of the screw threads. Materials and Methods: Two new (control) screws from Nobel Biocare (NB) and 18 used (in service 18,120 months) retaining screws [12 from NB and 6 from Sterngold (SG)] were: (1) metallographically examined by light microscopy and scanning electron microscopy (SEM) to determine the microstructure; (2) analyzed by energy dispersive X-ray (EDX) microanalysis to determine the qualitative and semiquantitative average alloy and individual phase compositions; and (3) tested for Vickers microhardness. Results: Examination of polished longitudinal sections of the screws using light microscopy revealed a significant defect in only one Group 4 screw. No significant defects in any other screws were observed. The defect was considered a "seam" originating as a "hot tear" during original casting solidification of the alloy. Additionally, the examination of longitudinal sections of the screws revealed a uniform homogeneous microstructure in some groups, while in other groups the sections exhibited rows of second phase particles. The screws for some groups demonstrated severe deformation of the lower threads and the bottom part of the screw leading to the formation of crevices and grooves. Some NB screws were comprised of Au-based alloy with Pt, Cu, and Ag as alloy elements, while others (Groups 4 and 19) were Pd-based with Ga, Cu, and Au alloy elements. The microstructure was homogeneous with fine or equiaxed grains for all groups except Group 4, which appeared inhomogeneous with anomalous grains. SG screws demonstrated a typical dendritic structure and were Au-based alloy with Cu and Ag alloy elements. There were differences in the microhardness of gold alloy screws from NB and SG as well as palladium alloy screws from NB. Conclusions: Significant differences within NB retaining screws and between NB and SG screws were found for microstructure, major alloy constituents, and microhardness. [source] Abrasive wear mechanisms of VPS- and HVOF-sprayed TiC-Ni based nanocrystalline coatingsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 10-11 2004X. Qi Verschleißmechanismen; nanokristalline Schichten; TiC-Ni; thermisches Spritzen Abstract Nanocrystalline coatings have a high potential for various engineering applications, e.g. against wear of rolls in the paper fabrication and as corrosion protection. Using vacuum plasma spray (VPS) and high velocity oxy-fuel (HVOF) spray techniques, coating materials are exposed to high flame temperatures only for less than a millisecond. Therefore, high-energy milled powders can be used as feedstock material without losing its nanocrystalline microstructure during the thermal spray process. In this way, homogeneous, dense nanocrystalline coatings can be produced, which show enhanced hardness, thus obtaining promising superior wear resistance. In the present study, (Ti,Mo)(C,N)-45vol.%NiCo nanocrystalline coatings were prepared by VPS- and HVOF-spraying of high-energy milled powders. Abrasive wear tests JIS H 8615 with varying number of strokes and scratch tests with a Vickers indenter were applied to produce wear traces on the polished surfaces of the nanocrystalline coatings. Abrasive wear behaviour was analyzed by investigating the surface morphologies with optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental results indicate that the VPS-coating has higher abrasive wear resistance than the HVOF-coating according to the JIS H8615 test. The abrasive wear mechanism of VPS-sprayed nanocrystalline coatings can be delineated as cutting plus ploughing. For HVOF-sprayed nanocrystalline coatings the abrasive wear mechanism can be described as cutting plus material delamination. Abrasive Verschleißmechanismen von VPS- und HVOF-gespritzten nanokristallinen TiC-Ni-Schichten Nanokristalline Schichten haben ein hohes technisches Anwendungspotenzial, z.,B. für Papierwalzen zum Schutz gegen Verschleiß und Korrosion. Während des thermischen Spritzens mit der Vakuumplasmaspritz (VPS)- und der hochgeschwindigkeits-Flammspritz (HVOF)-Technik werden die Beschichtungsmaterialien nur für weniger als eine Millisekunde den hohen Temperaturen ausgesetzt. Daher können hochenenergiegemahlene Pulver als Beschichtungswerkstoff genutzt werden, ohne dass diese während des Spritzprozesses ihre nanokristalline Mikrostruktur verlieren. Dadurch können homogene, dichte nanokristalline Schichten produziert werden, die hohe Härte aufweisen und damit auch eine hohe Verschleißfestigkeit zeigen sollten. In der vorliegenden Arbeit werden nanokristalline Schichten auf der Basis von (Ti, Mo)(C, N)-45Vol.%NiCo durch die VPS- und HVOF-Technik hergestellt. Verschleißtests nach JIS H 8615 mit unterschiedlicher Hubzahl und Ritztests mit dem Vickers-Indenter werden durchgeführt, um Verschleißspuren auf den polierten Oberflächen der nanokristallinen Schichten zu erzeugen. Die Verschleißmechanismen werden aufgrund der Oberflächenmorphologien von verschleißbeanspruchten Schichten durch optische Mikroskopie (OM), Raster-Elektronenmikroskopie (REM) und Rasterkraftmikroskopie (AFM) analysiert. Die experimentellen Ergebnisse zeigen, dass die VPS-gespritzte Schicht eine höhere Verschleißfestigkeit aufweist als die HVOF-gespritzte Schicht. Der Verschleißmechanismus der VPS-gespritzten nanokristallinen Schicht kann als Kombination von Spanen und Pflügen charakterisiert werden. Für HVOF-gespritzte nanokristalline Schichten stellt sich der Verschleißmechanismus dagegen als Spanen mit partiellen Schichtablösungen dar. [source] Unlubricated Wear Behavior of Ce-TZP/ Al2O3 Nanocomposites Against Bearing Steel,ADVANCED ENGINEERING MATERIALS, Issue 3 2005G. Yang Unlubricated friction and wear tests of Ce-TZP/Al2O3 nanocomposites against bearing steel were performed. In order to elucidate the wear mecahnism, the morphological investigation and phase structural analysis of worn surfaces were carried out by X-ray diffractometer and scanning electron microscope. Additionally, three kinds of wear mechanisms such as plastic deformation, adhesive wear and brittle fracture have been revealed. [source] Modeling UHMWPE wear debris generationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007H. Baudriller Abstract It is widely recognized that polyethylene wear debris is one of the main causes of long-term prosthesis loosening. The noxious bioreactivity associated with this debris is determined by its size, shape, and quantity. The aim of this study was to develop a numerical tool that can be used to investigate the primary polyethylene wear mechanisms involved. This model illustrates the formation of varying flow of polyethylene debris with various shapes and sizes caused by elementary mechanical processes. Instead of using the classical continuum mechanics formulation for this purpose, we used a divided materials approach to simulate debris production and release. This approach involves complex nonlinear bulk behaviors, frictional adhesive contact, and characterizes material damage as a loss of adhesion. All the associated models were validated with various benchmark tests. The examples given show the ability of the numerical model to generate debris of various shapes and sizes such as those observed in implant retrieval studies. Most of wear mechanisms such as abrasion, adhesion, and the shearing off of micro-asperities can be described using this approach. Furthermore, it could be applied to study the effects of friction couples, macroscopic geometries, and material processing (e.g. irradiation) on wear. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] Development of Nanocrystalline Wear-Resistant Y-TZP CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2004Bikramjit Basu The present contribution reports some interesting and new results obtained while developing yttria-stabilized tetragonal zirconia (Y-TZP) using spark plasma sintering (SPS). The experimental results clearly showed that ZrO2 -nanoceramics with high hardness(,14.5 GPa) can be processed at a lower sintering temperature of 1200°C in a short time (5 min). Another important result is that the newly developed Y-TZP nanoceramics, compared with the conventional sintered TZP, exhibit better fretting wear resistance against bearing steel. The intergranular fracture and the grain pullout were observed as the major wear mechanisms of the zirconia nanoceramics. [source] Reciprocative sliding friction and wear properties of electrical discharge machined ZrO2 -based compositesLUBRICATION SCIENCE, Issue 9 2009Koenraad Bonny Abstract Hot-pressed, laboratory-made, ZrO2 -based composites with 40 vol. % WC, TiCN or TiN were surface finished by electrical discharge machining in order to compare their reciprocating sliding friction and wear response against WC,6wt%Co cemented carbide in unlubricated conditions. Sliding experiments were performed using a Plint TE77 pin-on-flat wear test rig, revealing a strong impact of the secondary phase on the tribological behaviour of the ZrO2 -based composites. The worn surfaces and wear debris were characterised by scanning electron microscopy, energy dispersive X-ray analysis and surface topography scanning, pointing out abrasion, polishing and adhesion as main wear mechanisms. The most favourable friction and wear characteristics were encountered with ZrO2,WC composites compared to the other grades with equal amount of volumetric secondary phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of Temperature and Relative Humidity on the Friction and Wear of Unlubricated Reciprocating Sliding Steel/ Steel CouplesLUBRICATION SCIENCE, Issue 4 2004D. Klaffke Abstract Many tribosystems are subjected to different conditions with respect to temperature and humidity. Reciprocating sliding tests with steel/steel couples were performed using a laboratory test rig in air with varying relative humidity and temperature. During each test the friction force, the total linear wear, the electrical contact resistance, and the acoustic emission were recorded. Tests with self-mated couples of bearing steel (100r6) and of stainless steel (X10CrNiMoNb18-10/X5CrNi18-9) in a ball-on-disc arrangement revealed small effects of temperature and humidity on friction, but a strong effect of the water vapour content on the wear rate of the system. Attempts were made to correlate changes of wear behaviour with different wear mechanisms. [source] Verschleißmechanismen bei moderater und extremer GrenzreibungMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 10-11 2004M. Scherge wear mechanisms; continuous wear measurement; surface analysis Abstract Mit einem Stift-Scheibe-Tribometer wurden für das System Stahlstift/Stahlscheibe Versuche durchgeführt, die drastisch unterschiedliche Verschleißraten zur Folge hatten. Durch Wahl der Normalkraft wurde die Energiedissipation so eingestellt, dass im ersten Versuch Verschleißraten in der Größenordnung von Nanometern pro Stunde erreicht wurden, während im zweiten Versuch Mikrometer pro Stunde erzielt wurden. Die Proben wurden nach dem Experiment hinsichtlich Struktur und chemischer Zusammensetzung analysiert. Im Bereich der kleinen Verschleißraten dominierten plastisches Fließen und mechanische Vermischung während die hohen Verschleißraten mit starker Topographieänderung und Oxidation einher gingen. Wear mechanisms at moderate and extreme friction conditions Using a pin-on-disk tribometer drastically different wear rates were obtained in experiments running a steel pin against a steel disk. By tuning the normal force the energy dissipation was varied resulting in either mild wear in the range of nanometers per hour or severe wear with a wear rate of micrometers per hour. After the tribological tests the samples were analyzed with respect to structure and chemical composition. Whereas small wear rates are accompanied by plastic flow and mechanical intermixing, severe wear results in significant topography changes and oxidation. [source] Abrasive wear mechanisms of VPS- and HVOF-sprayed TiC-Ni based nanocrystalline coatingsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 10-11 2004X. Qi Verschleißmechanismen; nanokristalline Schichten; TiC-Ni; thermisches Spritzen Abstract Nanocrystalline coatings have a high potential for various engineering applications, e.g. against wear of rolls in the paper fabrication and as corrosion protection. Using vacuum plasma spray (VPS) and high velocity oxy-fuel (HVOF) spray techniques, coating materials are exposed to high flame temperatures only for less than a millisecond. Therefore, high-energy milled powders can be used as feedstock material without losing its nanocrystalline microstructure during the thermal spray process. In this way, homogeneous, dense nanocrystalline coatings can be produced, which show enhanced hardness, thus obtaining promising superior wear resistance. In the present study, (Ti,Mo)(C,N)-45vol.%NiCo nanocrystalline coatings were prepared by VPS- and HVOF-spraying of high-energy milled powders. Abrasive wear tests JIS H 8615 with varying number of strokes and scratch tests with a Vickers indenter were applied to produce wear traces on the polished surfaces of the nanocrystalline coatings. Abrasive wear behaviour was analyzed by investigating the surface morphologies with optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental results indicate that the VPS-coating has higher abrasive wear resistance than the HVOF-coating according to the JIS H8615 test. The abrasive wear mechanism of VPS-sprayed nanocrystalline coatings can be delineated as cutting plus ploughing. For HVOF-sprayed nanocrystalline coatings the abrasive wear mechanism can be described as cutting plus material delamination. Abrasive Verschleißmechanismen von VPS- und HVOF-gespritzten nanokristallinen TiC-Ni-Schichten Nanokristalline Schichten haben ein hohes technisches Anwendungspotenzial, z.,B. für Papierwalzen zum Schutz gegen Verschleiß und Korrosion. Während des thermischen Spritzens mit der Vakuumplasmaspritz (VPS)- und der hochgeschwindigkeits-Flammspritz (HVOF)-Technik werden die Beschichtungsmaterialien nur für weniger als eine Millisekunde den hohen Temperaturen ausgesetzt. Daher können hochenenergiegemahlene Pulver als Beschichtungswerkstoff genutzt werden, ohne dass diese während des Spritzprozesses ihre nanokristalline Mikrostruktur verlieren. Dadurch können homogene, dichte nanokristalline Schichten produziert werden, die hohe Härte aufweisen und damit auch eine hohe Verschleißfestigkeit zeigen sollten. In der vorliegenden Arbeit werden nanokristalline Schichten auf der Basis von (Ti, Mo)(C, N)-45Vol.%NiCo durch die VPS- und HVOF-Technik hergestellt. Verschleißtests nach JIS H 8615 mit unterschiedlicher Hubzahl und Ritztests mit dem Vickers-Indenter werden durchgeführt, um Verschleißspuren auf den polierten Oberflächen der nanokristallinen Schichten zu erzeugen. Die Verschleißmechanismen werden aufgrund der Oberflächenmorphologien von verschleißbeanspruchten Schichten durch optische Mikroskopie (OM), Raster-Elektronenmikroskopie (REM) und Rasterkraftmikroskopie (AFM) analysiert. Die experimentellen Ergebnisse zeigen, dass die VPS-gespritzte Schicht eine höhere Verschleißfestigkeit aufweist als die HVOF-gespritzte Schicht. Der Verschleißmechanismus der VPS-gespritzten nanokristallinen Schicht kann als Kombination von Spanen und Pflügen charakterisiert werden. Für HVOF-gespritzte nanokristalline Schichten stellt sich der Verschleißmechanismus dagegen als Spanen mit partiellen Schichtablösungen dar. [source] | ||||||||||||||||||||||