Modeling loose joints in elastic structures - validation at higher excitation frequencies

Abstract

The bolted or riveted lap joint is a common fastening technology for structural members. When a joint becomes worn the joined members can move in a nonlinear fashion relative to each other as well as impact each other and the lap joint plates. For low frequency bending modes, the system can experience sticking or frictional sliding motion at a finite number of contact points in the joint. The work presented herein is the fifth paper in a series of papers used for the development and verification of a hybrid parameter modeling methodology applied to the analysis of damaged structures. By utilizing an experimental test bed suitable for providing excitations up to 60 Hz, this research further validates a low order frictional contact impact mathematical model of a typical loose bolted joint that was developed and partially validated the aforementioned companion papers published in this journal. For each of the different contact and motion regimes experienced by the jointed beam, experimental estimations of the damping and other parameters were determined. Contact patches, strain gauges, a force transducer, and accelerometers were used to measure the response of the experimental test bed model of a bolted joint cantilever beam. The simulation results were then compared to the experimental results using spectral and time domain techniques. Animations of the simulated joint motion were compared to a high-speed video of the experimental joint motion. The results indicate good correlation between the model and reality, thus the results presented in this paper provide supporting evidence of the efficacy of the underlying low order modeling techniques.