Single Asperity Contact and Its Use for Fractal Surface Contact

This work first presents an elastic-plastic contact model of single hemisphere asperity with a rigid smooth flat based on the finite element method. The material of the deformable asperity was modeled as elastic-perfectly plastic, 9 kinds of materials were covered in this work to account for effects of material properties on the asperity deformation. Based on the results of finite element analysis, new empirical formulations with the consideration of material properties were proposed to predict the dependence of contact area, contact pressure and contact load on contact interference. Four regimes of asperity deformation as well as the transition points between them were also clearly reported. Then, the contact model of single hemisphere asperity was extended to three-dimensional rough surfaces to develop the elastic-plastic contact model of contacting surfaces using fractal theory. A new general contact stiffness model was also proposed to study the normal stiffness between rough surfaces. Numerical results of the presented models were validated by experimental data and those of other existing models. The effects of fractal dimension, roughness parameter and yield strength on contact behaviors of contacting surfaces were also be investigated.