Methods for improved spatial characterization of vibration isolators and structures

The primary goal of this work was to develop an improved method for quantifying the dynamic characteristics of structures, such as vibration isolators, in the mid-frequency region. Most analytical approaches are limited by the inherent use of lumped quantities to represent the critical variables, such as with lumped value four-pole parameters. Conventional approaches usually neglect the spatially varying responses across the contact region even though these responses are known to be more important as frequency increases. While discretization methods can often be used at these frequencies, even these techniques fail to provide meaningful insight when the response quantities of interest, such as the force, vary with position over the contact region. As a result, there is a need for meaningful characterization methods in the mid-frequency region where the structural wavelength is comparable to the size of the contact region. Moreover, as analysis techniques often have inherent limitations, it is imperative that one be able to experimentally acquire meaningful performance data at these higher frequencies. In order to provide a spatial characterization of dynamic structures at mid-frequencies, therefore, the initial part of the effort focused on the development of a fundamental technique, called the four-plane method, for characterizing the important spatial characteristics in structures. Of particular interest was the characterization of vibration isolators in terms of the contact regions between the isolator and the attached structures. In the primary approach that was considered in this research, the conventional lumped parameter model was extended so that spatial variations across these regions can be investigated through analytical studies. Then, to provide a means by which one can measure spatial response quantities, such as forces, conventional force reconstruction techniques were extended.