Three-dimensional Numerical Analysis Of Transient Temperature/pressure/stress Field For Rough Surface Based On Fractal Theory

In mechanical engineering, the frictional heat will cause serious destruction to the important engineering surface, the two surfaces in sliding contact are rough,so it have an important theoretical meaning to analyzing the flash temperature and thermal-mechanical stress of micro-scale of the engineering rough surfaces. This paper research on the fractal characterization and contact model of rough surfaces, current situation and developing direction of the rough surface flash temperature. Based on three-dimensional fractal theory, the heat- conduction contact model of rough surfaces was set up and the law of heat transfer between the sliding surfaces was studied.Based on three-dimensional fractal theory, two engineering rough surfaces in contact that produce frictional heat were simplified into a smooth one and a rough one which has fractal characteristic. Thermal-elastic problem of the two frictional contact bodies was considered, and established a transient thermal and stress coupled FEM model using thermal-structure sequential coupling. Taking brake materials as the example, the course of the sliding with friction was simulated in ANSYS software using the nonlinear multiphysics field FEM, to calculate and analyze the temperature, contact pressure and stress field of the sliding contact surfaces with frictional heating. In the course of numerical calculation, the influence among asperities, the coupling problems of the variation of temperature and pressure on contact surfaces, the variation problems of the maximum temperature, maximum contact pressure, maximum stress were taken account into.In this paper, the regulation of distribution of temperature and contact pressure and thermal stress and the division of heat between the sliding surfaces were showed through the coupled analysis to the three-dimensional transient temperature, pressure and stress field of rough surface which has fractal characteristic. Considering the influence among asperities, the regulation of variation and the influence among maximum temperature, maximum contact pressure, maximum stress and real contact area were analyzed. The separate effect of the sampling section, sliding velocity, applied pressure, the natural convection changes hot coefficient, specific heat, thermal conductivity, volume temperature and ambient temperature on the flash temperature were discussed. The results of this paper are the basic for further research on the flash temperature, thermal-mechanical problems and the wear mechanisms of the rough surfaces, also helps to develop the excellent frictional material.