Abstract: Based on assumption of rigid-plastic isotropic rough couple surfaces and random size of the third body to be rigid-solid, relations among the distance between the surface 1 and surface 2, plastic deformation amount of surface 1 and surface 2 and profile height probability distribution density function of the surface 1 and surface 2 before and after contact, load, the probability distribution density function of the third-body are given. In the computing example, there existed a roughness of surface 1 and surface 2 which made their plastic deformation least.

Key words: Plastic deformation Probability distribution function, Three-body contact Rough surface