A four-parameter model for nonlinear stiffness of a bolted joint with non-Gaussian surfaces

The nonlinear mechanics modeling is proposed to describe the nonlinear stiffness of the bolted joint interfaces induced by the stick-slip friction behaviors. By combining the microscale contact mechanics of the asperity interaction, the statistical analysis of the non-Gaussian surfaces is conducted to extract a four-parameter model to characterize the nonlinear softening stiffness and residual stiffness of the bolted joints. The Masing principle is then implemented to model the tangential hysteresis nonlinearity of the oscillatory loading process. Comparison with the experimental results of a lap-type bolted joint is performed to validate the proposed model and investigate the effects of the bolt preload. The results show that the proposed model can be used to simulate the nonlinear stick-slip behaviors of the bolted joint interfaces, and the prediction of the model parameters agrees well with the identification of the experimental results. Larger bolt preload will induce a larger critical stick-slip force, stronger nonlinearity, and better symmetry of the hysteresis nonlinearity, but hardly affect the residual stiffness.