A CONTINUOUS SMOOTH CONTACT STIFFNESS MODEL FOR JOINT SURFACE CONSIDERING SUBSTRATE DEFORMATION

The contact stiffness of the joint surface directly affects the static and dynamic mechanical properties of the machine tool and the level of accuracy retention. In the process of elastic, elastoplastic and fully plastic contact deformation, based on the idea that asperity contact state variables have continuous and smooth characteristics, a single asperity normal contact stiffness model is established through Hermite polynomial interpolation function. Considering the effect of substrate deformation, the elastic contact substrate deformation is introduced in the three deformation stages of asperity. A continuous smooth joint surface stiffness model considering substrate deformation is established by statistical methods. The differences between GW, ZMC, KE, and Brake models are compared with the proposed model, and the influence of surface roughness on contact stiffness is revealed. The research shows that the contact stiffness and contact load obtained by considering the substrate deformation are smaller than those of ignoring the substrate deformation. The influence of substrate deformation increases rapidly as the surface roughness decreases. In addition, the contact load and surface roughness are the two main factors that affect the contact stiffness of the joint surface. The contact stiffness increases with the increase of the load or the decrease of the surface roughness.