Simulation of effect of counterface roughness on the friction transfer and wear of PTFE sliding against steel

Purpose This paper aims to simulate the effect of counterface roughness on the friction transfer and wear of the polymer material sliding against steel. Design/methodology/approach The dynamic process of friction transfer and wear of polytetrafluoroethylene (PTFE) sliding against steel 45 was simulated by the software of particle flow code in two dimensions and a discrete element method. The effect of the counterface roughness was considered in the simulation. The definitions of the transferred particle and worn particle were given. Findings The simulation results showed that a transferred particle layer was formed on the surface of steel 45 during friction. The wear rate of PTFE can be effectively reduced by the formation of the transferred particle layer. The formation and stability of this particle layer is certainly affected by the counterface roughness (Rz). In this paper, the transferred particle numbers increased with Rz increase. And so did the worn particle numbers. However, there was little effect of Rz on the wear rate of PTFE. Originality/value The dynamic process of the friction transfer and wear of the PTFE/ steel 45 friction pair was reproduced at the micro-level. Then, the transfer and wear were quantitatively exhibited. The relations between the transfer or wear and counterface roughness was simulated and discussed. It will be meaningful for the optimization and effective control of friction and wear of polymer/metal sliding system.

The Influence of Silicon Carbide Powders on the Enhancement of the Wear Resistance of Epoxy Resin

In order to improve wear properties of thermosetting resins, potential solutions are the reduction of the adhesion between the counterparts and the improvement of their hardness, stiffness and compressive strength. These goals can be achieved with success by using appropriate inorganic fillers. Concerning this, the present work shows the possibility to increase the abrasive wear resistance of an epoxy resin filled with hard powder. The filling is made by silicon carbide powders in different content and with different particle sizes. Abrasive tests, performed by means of a pin on disc apparatus, highlight that the wear of plain and reinforced resins increases both with the contact pressure between the counterparts and the counterface roughness. Moreover, the wear resistance of the filled resins increases with the increase of content and dimensions of the filling particles.

Influence of Compression Load and Counterface Roughness on Abrasive Wear Characteristic of UHMWPE

This paper studies the influence of work conditions, difference compression load and counterface roughness, on UHMWPE under abrasive wear test without lubrication according to GOST 426-77. It was found that the formation of deep and wide furrows on worn surface and abrasive intensity increased when the number of grit grade was decreased (average grit size increase). The behavior of abrasive wear can be classified as follows: the first characteristic volume loss quickly increases in the beginning of running time about 5-15 minutes, which is referred to as “run-in” wearing stage; the second characteristic volume loss regularly increases after running time about 15 minutes, which is approaching to “steady-state” wearing stage. In addition, the abrasive wear intensity increase with increasing compression load and/or decreasing number of grit grade (average grit size increase). The results of this research can be applied to abrasive applications in mechanical engineering.

Optimization on Abrasive Wear Performance of Pultruded Kenaf-Reinforced Polymer Composite Using Taguchi Method

This study examined the optimal abrasive wear performance of kenaf-reinforced polymer composite under different sliding conditions. Three different fiber loadings i.e. 43.05, 49.30 and 55.33 vol.% of kenaf fiber was reinforced into a polyester resin using the pultrusion technique. Optimal responses of wear rate and average coefficient of friction (COF) for kenaf fiber-reinforced polyester composites, based on different levels of control factors (fiber loading, applied load, counterface roughness and sliding speed) were determined by the Taguchi Design of experiment (DOE) with L9 (34) orthogonal array and Analysis of variance (ANOVA) methods. The wear behaviour of kenaf fiber-reinforced composites were investigated using DUCOM pin-on-disc tester with three levels of applied loads (10-30 N), sliding speeds (0.42-1.3 m/s) against different grit sizes of silicon carbide abrasive papers (average grain size~2.2-25.2 μm) under dry sliding condition. The optimization of S/N ratio and degree of significance of the control variables to minimize the wear rate and average COF of kenaf fiber-reinforced polyester composites was carry out. The results showed that the counterface roughness is the most significant factor in affecting the wear rate, followed by applied load, sliding speed, and fiber loading. For average COF, the fiber loading is the most significant factor followed by applied load, sliding speed and counterface roughness.

Effect of CoCr Counterface Roughness on the Wear of UHMWPE in the Noncyclic RandomPOD Simulation

With the random motion and load pin-on-disk (RandomPOD) wear test system, conventional and highly crosslinked ultrahigh molecular weight polyethylenes (UHMWPE) were run against CoCr counterfaces with different surface roughnesses. The unique 16-station, computer-controlled pin-on-disk device produced noncyclic motion and load. With appropriate specimen shapes, simulations of wear mechanisms of both hip and knee prostheses were performed. Against polished counterfaces, the crosslinked UHMWPE showed negligible wear. Its wear against severely roughened counterfaces was close to that of conventional UHMWPE against polished counterfaces. The reduction in wear with crosslinked versus conventional UHMWPE was 80–86% in the hip and 87–96% in the knee wear simulation. The wear particles were of clinically relevant size and shape which indicated realistic wear mechanisms.

Effect of counterface roughness on adhesion of mushroom-shaped microstructure

In this study, the effect of the substrate roughness on adhesion of mushroom-shaped microstructure was experimentally investigated. To do so, 12 substrates having different isotropic roughness were prepared from the same material by replicating topography of different surfaces. The pull-off forces generated by mushroom-shaped microstructure in contact with the tested substrates were measured and compared with the pull-off forces generated by a smooth reference. It was found that classical roughness parameters, such as average roughness ( R a ) and others, cannot be used to explain topography-related variation in pull-off force. This has led us to the development of an integrated roughness parameter capable of explaining results of pull-off measurements. Using this parameter, we have also found that there is a critical roughness, above which neither smooth nor microstructured surface could generate any attachment force, which may have important implications on design of both adhesive and anti-adhesive surfaces.

Friction and Wear Studies on Polyphenylene Sulfide Filled with a Complex Mixture

The tribological behavior of PPS filled with molybdenum-concentrate (MC) deposit from Armenia was studied. The deposit MC was a complex mixture of compounds such as MoS2, SO2, CuS, Al2O3, and others. Whereas MC as the filler in particulate form reduced the steady state wear rate of PPS, the optimum reduction in wear was found to occur with the addition of PTFE along with PPS. The behavior of PPS composites made with MC and PTFE sliding against a steel counterface was investigated as a function of the MC and PTFE proportions, sliding speed, and counterface roughness. Of all the above factors, the change in MC proportion, while PTFE was also present, had the greatest effect on the reduction in wear rate. The variation of the coefficient of friction was found to be in the narrow range of 0.27-0.33. The lowest wear rate was found in the case of PPS+ 17vol.%MC+10vol.%PTFE composite sliding at 1.5 m/s against a counterface roughness of 0.1 μm Ra.