Discontinuous compliance nonlinearities in the hydraulic engine mount

In this article, we identify and quantify discontinuous compliance nonlinearities of hydraulic engine mounts. First, asymmetric nonlinearities are identified in transient step-up and step-down responses by using a quasi-linear mount model with parameters that are estimated from measured dynamic stiffness data. Second, an improved multistaged top chamber compliance model is developed which confirms the existence of highly nonlinear region(s) during the step transitions as well as during the decaying transients. Third, new semi-analytical solutions for both step-up and step-down responses have been successfully constructed by using a linear time-varying system formulation that incorporates time-varying compliance. Fourth, a mean displacement-dependent model is proposed for the bottom chamber compliance. It clearly explains the stiffening effect in measurements under higher mean loads. Finally, competing quasi-linear, linear time-varying and nonlinear formulations are comparatively evaluated for step and realistic excitations. Transient measurements confirm the validity of models, as well as their applicability and limitations.