A modified Bouc-Wen model to simulate asymmetric hysteresis loop and stochastic model updating in frictional contacts

In the Mechanical Systems and Control research area, the modeling and characterization of dominant mechanisms in contact interface restoring forces has recently attracted a significant attention of the researchers. The nonlinear phenomena such as micro-vibro-impacts and micro/macro-slip damping occur when the vibrational amplitudes increase in the frictional contact areas. This paper examines the nonlinear behavior of the frictional contact interfaces under variable contact preloads caused by the micro-vibro-impacts. The variation of the normal load on the frictional contacts affects on its tangential stiffness and yields an asymmetric hysteresis loop. The Bouc-Wen model may be used in modeling of the hysteric behavior of such systems. It assumes, however, that the contact preload is constant when the frictional interface properties and behaviors are modeled. Meanwhile, it does not take the micro-vibro-impacts at the interface into account. In this study, we investigate the effects of the variable preload on the contact interface as well as the resulting shear macro-slip and asymmetric hysteresis loops caused by the the micro-vibro-impacts. In order to model the potential consequential effects, the modified Bouc-Wen model has been developed and applied. The identification tests are conducted at various frequencies and amplitudes using a passive friction isolator made by passing a compressed polymer-rope through a helical spring. By using the genetic algorithm (GA) and stochastic model updating by the Bayesian approach based on the Markov Chain Monte Carlo (MCMC) methods, the unknown parameters in the modified Bouc-Wen model will be determined while validated with the experimental results obtained from the hysteresis loops. The simulated results indicate that the modified Bouc-Wen model describes the friction forces at the contact interfaces, accurately.