Abstract: The contact stiffness of the joint surface directly affects the static and dynamic properties and accuracy levels of the mechanical system. Based on the concept that the transitions from elastic, through elastoplastic, to fully plastic deformation of the asperity contact stiffness is continuous and smooth. The Hermite polynomial interpolation method is employed to correct the defect of discontinuity in the traditional asperity stiffness model, and a new stiffness model of a single asperity is proposed, which changes continuously and smoothly at transit points. Then, a normal contact stiffness model of the joint surface is developed based on statistical methods. Finally, the differences between the GW, ZMC, KE, BRAKE models and the proposed model are analyzed. The results show that the proposed model realizes the asperity contact stiffness changes continuously and smoothly between different deformation regimes. For smooth surface, the difference between different models is small, and the proposed model is close to the GW model. However, the difference between the GW model and other models becomes larger as the roughness increases, and the proposed model agrees well with the ZMC model that consider the multiple deformation regimes of the asperity. It is shown again that load and surface roughness are the two main influencing factors of contact stiffness, the contact stiffness increases with the increase of contact load or the decrease of surface roughness.

Key words: joint surface, Hermite polynomial interpolation function, elastoplastic regime, contact stiffness, contact load