Examination of High Frequency Characterization Methods for Mounts

The knowledge of frequency-dependent dynamic stiffnesses of mounts, in axial and flexural motions, is needed to determine the behavior of many automotive sub-systems. Consequently, characterization and modeling of vibration isolators is increasingly becoming more important in mid and high frequency regimes where very few methods are known to exist. This paper critically examines some of the approximate identification methods that have been proposed in the literature. Then we present a new experimental identification method that yields frequency-dependent multi-dimensional dynamic stiffnesses of an isolator. The scope is however limited to a linear time-invariant system and our analysis is restricted to the frequency domain. The new characterization method uses two inertial elements at both ends of an isolator and free boundary conditions are maintained during testing. Multi-dimensional mobility synthesis formulation is also developed to predict the behavior of overall system, and the decomposed motilities of mount are extracted using synthesized mobilities. The proposed identification method is applied to one simulation example and one practical rubber isolator, and experimental results are successfully compared with data measured on commercial equipment for axial motions.