A New Contact Model of Joint Surfaces Accounting for Surface Waviness and Substrate Deformation

The joint surfaces in the computer numerically controlled (CNC) machines play a crucial role in transmitting load and energy in operations. In this paper, a new contact model between rough surfaces of a joint is proposed by considering the influence of surface waviness and substrate deformation. A contact model for a single asperity system is first established, in which the asperity and substrate deformations are calculated based on the Hertz theory. Then, it is extended to an entire rough surface by a statistical method, where the contact of rough surfaces is treated as the contact between a smooth waviness and a rough surface. The numerical results showed that when contact deformation is constant, the real contact area and the normal load of joint surfaces increase with increasing radius of the waviness peak while the normal load decreases with the increase of surface roughness. When a rough surface contains a coating layer or a surface film, the deformation of the joint surface has to consider both substrate deformation and asperity deformation. The substrate deformation will generate larger influence for a stiffer or harder coating. Compared with other models, the results obtained from the proposed model show better agreements with the experimental data.