Experimental and theoretical studies on friction contact of bolted joint interfaces

This paper presents experimental and theoretical modeling studies on the tangential contact stiffness and friction hysteresis of bolted joint interfaces under transversal vibration. A new test rig was developed to measure the interface fretting response of bolted joints. This rig is based on a servo-hydraulic fatigue testing system in which the contact surfaces are arranged symmetrically to avoid bending of the specimen that could affect the friction measurement. Force-displacement curves were measured under different tangential loads and compared with those found in the literature. A multi-scale contact modeling method was proposed to calculate the tangential contact stiffness and reproduce the friction hysteresis of bolted joint interfaces. This method overcomes the complexity of identifying contact stiffness, which usually requires a model of the dynamic behavior of the joint and frequency responses measured with dedicated fretting test stands. Specifically, this method comprehensively considers the multi-scale features of randomly rough surfaces, the non-uniform contact pressure distribution, and the convenience of phenomenological contact models in simulating frictional hysteresis, relying on fractal contact theory and discretized Iwan model. The effectiveness of the proposed method was verified by comparing the simulation results with the experimental counterparts in different cases of tangential loading. The successful validation demonstrates the potential of the proposed modeling method for application to structures with bolted joint.