MODELING OF THERMAL CONTACT CONDUCTANCE

Nowadays a new science direction has arisen from decades of experimental work carried out in 20th century-micromechanics of contact processes (deformation, heat transfer, electric conduction). To determine contact area a dynamic elastic-plastic deformation problem is to be solved even in the simplest case butt contact of two rough surfaces under pressure. It is followed by the solution of spatial boundary heat transfer problem to obtain nonstationary temperature distribution for two bodies. In principal, this stage is not difficult to perform with finite element program ANSYS. Meanwhile the questions concerning deformation and conduction through oxide films of metals as well as directional effect remain. In the literature there are attempts to simulate thermal contact conductance numerically of such authors as M.K.Thompson, S.Lee et al, M. Ciavarella, M.M.Yovanovich and others. The disadvantages of existing spatial models are: - surfaces profiles has no random component; - only elastic or only plastic material behavior; - microroughncss is not considered. In the present work the roughness before contact of two rough surfaces of copper bodies was presented as spatial two-level (roughness and microroughness) model with the use of fractal Weierstrass-Mandelbrot function. In quasistatic approach the 3D deformation and heat transfer problems of contacting bodies under pressure were solved within elastic-plastic material behavior. Contact ANSYS elements were used. Copper compression diagram was replaced by multilinear model of isotropic hardening. From the cycle of calculations real contact areas, shapes of contact spots, temperature and stress distributions were determined for the range of pressures. Good agreement with experimental data took place only when microroughness is considered.