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A stick-slip tangential contact model between rough surfaces was proposed in this paper. The Mindlin partial slip solution for elastic contact and the double linear formulation developed by Fujimoto for plastic contact in conjunction with the Coulomb dry friction law were used to derive tangential contact formulas. Pearson system of frequency curves was used to generate non-Gaussian random surfaces. Effects of skewness and kurtosis on normal and tangential contact responses were studied independently. The results showed that negative skewness predicted lower mean separation for a given normal force and greater tangential stiffness, while for positive skewness, there exist different trends from negative skewness. With the increase of kurtosis, the load capacity and tangential stiffness decreased. The practical significance of these findings is that it can help engineers to design proper surface textures based on their requirements. A comparison of initial tangential stiffness between predicted results and published experimental results was made. The results well agreed with the experimental results when the non-Gaussian surface effects were taken into consideration.

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This study proposed a physics-based heuristic modeling for the nonlinear constitutive relation of bolted joints based on the Iwan model accompanying with the rough surface contact theory. The approach led to an Iwan distribution function which possesses the tribology-related features of the contact interface. In particular, the break-free force distribution function of the Jenkins elements could be expressed in terms of height distribution of surface asperities. The model considered the contribution of elastically, elasto-plastically as well as plastically deformed asperities to the total tangential loads. Following this, constitutive relations for lap-type bolted joints and the corresponding backbone curves, hysteresis loops, and energy dissipation per cycle were obtained. A model application was implemented and the results were compared with the published experimental results. The proposed model agrees very well with the experimental results when the contact parameters met the actual contact situation. The obtained results indicated that the model can be used to study the tangential behaviors of rough surfaces.

Abstract:Wear is an important factor for failures of mechanical components. Current research on wear is mainly focused on experiments while the numerical simulation of wear is hardly used owing to the complexities of the wear process. Explaining the effect of friction on the wear process is important, as it will lead to a deeper understanding of the evolution of wear. This study proposed a numerical method to expound the wear process in the contact between an elastic cylinder and a half-space simulating the ring-block tester. There are two difficulties during the calculation; one is that the contact shapes vary with time, causing the pressure distribution to change simultaneously and the other is the integral equation for calculating the contact pressure under different worn shapes. In the present study, the wear rate was computed using Archard's law and the wear process was calculated step by step until the specified total sliding distance was achieved. During each step of the calculation, the contact topography was updated. The simulation intuitively reproduced the contact state of change from line to surface contact throughout the wear process. Reasonable agreements on the changes of the wear scar, achieved from experiments and numerical simulations, were obtained.