Refined response axis decoupling axiom for a coupled vibrating system with spectrally-varying mount properties

Abstract

Real-life engine mounts inherently exhibit considerable frequency- and amplitude-dependent characteristics, and the base flexibility has a significant effect on engine vibration and forces transmitted to the vehicle body. A new analytical formulation is proposed that incorporates spectrally-varying stiffness and damping properties of multi-dimensional mounts in the presence of a compliant base (with many vibration modes over the applicable lower frequency regime). A refined analytical axiom for the response axis decoupling of coupled system is also mathematically formulated using spectral response axis decoupling indices. Two examples are chosen to prove the refined axiom. Firstly, a powertrain mounting system with two hydraulic mounts is redesigned in terms of their stiffness and damping properties, and mount locations for both powertrain and sub-frame systems used the refined axiom in torque roll axis (TRA) direction. Frequency and time domain results demonstrate that the TRA of the redesigned powertrain mounting system is indeed decoupled from other powertrain motions. The effects of parameter uncertainties on the response axis decoupling indices are also examined. Then, a laboratory experiment consisting of a powertrain, three powertrain mounts including two hydraulic mounts, a sub-frame, and four bushings is then used to mathematically validate the refined axiom in vertical axis direction. The quasi-linear system formulation of the coupled system is also verified by comparing the frequency responses with the results obtained by the direct (matrix) inversion method and measurements.