Modeling and Vibration Analysis of Friction Joints

This paper presents a microslip model of friction joints, which may be viewed as a generalization of the simple model considered by Menq et al. (1986a). Laboratory experiments have shown that microslip of friction joints has important implications in the dynamic response of frictionally constrained structures in which the friction interface is subjected to high normal loads (Menq et al., 1986b). In the simple model, the friction interface is idealized as a bar pressed with a uniform normal pressure against a rigid support. The use of a rigid support in the model shows that a direct link between the model’s parameters and its physical counterparts is lacking. The model presented in this paper consists of two bars held together with uniform clamping normal pressure. In addition to these two bars, the third element, a shear layer, is added to account for the effects of the shear deformation of the two contact bodies. This generalization of the microslip model is to enhance the link between the model’s parameters and the physical configurations of the contacting surfaces of the friction joint. With a physical model like this, the objective is to determine the distribution of the friction force at the contact surface while quasi-steady axial loads applied to the ends of both bars increase gradually. In particular, it is of interest for the analysis of vibration problems to determine the force-displacement curve that describes the relationship, upon first loading, between the applied load and the resulting relative displacement between the two ends where the loads are applied. After the case of first loading, the cases of unloading and reloading of the joint will be examined; and then the hysteresis loop in the course of cyclic loading can be obtained.