Contact analysis between rough surfaces considering the size-affected deformation behaviour of multi-scale asperities

Contact parameters such as the real contact area of rough surfaces depend on the interaction between asperities and the characteristic scale in which they remain. The high-stress deformation mechanism of the local contact spots exhibits size-dependent behaviour when the size of the asperities reaches a certain scale because of the scale effect. This causes deviations in the contact analysis, which can affect several tribological properties of the structural interface such as interface stiffness, fretting wear, and contact resistance. In this study, the deformation process affected by the scale effect is analysed using a finite element method that employs a conventional mechanism-based strain gradient plasticity (CMSGP) constitutive theory, whereas a full-scale elastoplastic contact model is developed for asperities at different size levels. Next, the contact analysis of rough surfaces is performed using the multi-scale contact theory proposed by Jackson and Streator (JS) considering this individual asperity model. The proposed model is validated using comparison with the refined finite element simulation analysis of rough surface contact that employs the CMSGP theory; further, the effect of morphology features on contact behaviour is discussed. The research results are conducive to the tribological design of small-size engineering interfaces.