Abstract: Accurately establishing a high-fidelity non-linear mechanical model of the bolt joint surface is the prerequisite and basis for the analysis of high-end equipment. A mechanical modelling method for modifying the Iwan model is proposed to address the hysteresis nonlinear mechanical problem of the bolt joint surface, making the physical meaning of the parameters of the traditional phenomenological Iwan model clearer. First, the normal contact model of the bolt joint surface, which has continuous smooth contact characteristics, is established based on the multi-scale theory and mathematical statistics. Then, by considering the difference between the dynamic and static friction coefficients and using the Coulomb friction law, the revised Iwan phenomenological model is connected with the specific normal contact model, and a new bolt joint surface tangential response model is proposed. Finally, based on Matlab simulation and existing experimental data, the correctness of the model is verified. The influence of loading conditions, plasticity index and dynamic and static friction coefficient ratio on the contact characteristics of the joint surface is explored. Research shows that the energy dissipation of a cycle of loading and unloading increases with the increase of the displacement amplitude. Compared with the plasticity index, the change of the dynamic and static friction coefficient ratio has a more significant effect on the tangential load of the joint surface, so it needs to be considered in the follow-up research. The critical slip force distribution of the asperity is affected by other factors, which is mainly reflected in the number of contact asperities, the position of the peak point and the change of the curve convergence speed.

Key words: bolt joint surface, hysteresis nonlinearity, Iwan model, dynamic and static friction coefficient, critical slip force distribution