A stiffness degradation model of bolted joint based on fourth polynomial pressure distribution

This paper proposed a new friction mechanical model based on the Coulomb friction law to describe the nonlinear stiffness degradation of bolted joints. Several different contact pressure distributions are analyzed, and the results show that the fourth polynomial distribution has a better effect on characterizing the contact pressure distribution of the bolted interface. Then, a new density function of friction shear stress is obtained through mathematical deduction. There is an interesting discovery that the new density function curve is similar to the truncated power-law spectrum curve. In addition, a method of parameter identification is proposed, and multiple sets of parameters are identified for the subsequent model verification. Finally, the correlation between the theoretical value and the experimental data under different pre-tightening forces is analyzed. The results show the accuracy improvement of the new model compared with the existing model. The new model has better mechanism rationality and can be applied to stiffness degradation analysis.