Inclusion of measured frequency- and amplitude-dependent mount properties in vehicle or machinery models

This article proposes several new or refined analytical methods for vehicle or machinery system models that include measured dynamic stiffness of vibr ation isolators or mounts. Complications arising due to the spectrally vary ing and/or amplitude-dependent parameters are categorized, and the associat ed eigenvalue and frequency response problems are defined. First, the real and complex eigenvalue problems that include both viscous and visco-elastic damping models are critically examined and illustrated via examples. Secon d, a non-linear eigenvalue problem is formulated and the resulting eigensol utions are determined for a two-degree-of-freedom system with frequency-dep endent elastic and dissipative parameters. Several approximate methods, inc luding the modal expansion method, are also proposed to calculate the force d harmonic response, and their solution errors are assessed. Third, a quasi -linear method is applied to a 1/2 car model, using measured data of a typi cal hydraulic engine mount, to see the effect of excitation amplitude-depen dent dynamic stiffnesses. Finally, a refined non-linear, frequency domain s ynthesis method is proposed that includes local non-linearities in the form of measured dynamic stiffness data. The forced harmonic response of the ov erall system is obtained, and comparing to the corresponding time domain me thod for a specific 1/4 car vehicle model validates it. (C) 2001 Academic P ress.