A methodology for the experimental characterization of rubber isolators with frequency and preload dependency

In the context of dynamic substructuring applied to the automotive industry, a crucial factor for determining a vehicle's noise properties is evaluating the transfer behaviour of rubber elements connecting its various components. Conventional techniques to extract the frequency dependent dynamic stiffness of rubber components are valid only for low frequencies or very low (zero) preloads. In this paper, we develop a methodology that addresses these shortcomings by proposing a novel method for extracting the frequency-dependent dynamic stiffness of rubber components for higher frequency ranges and higher preloads than what usual techniques allow. Firstly, the general framework to characterize rubber mounts, based on virtual point transformation, is described. As a second step, to overcome the current challenges in literature, we extend the method by proposing a novel technique which allows for the application of uniaxial preloads by the use of tensile elastic components. In this framework, the elimination of the suspension influence can be guaranteed even for high preloads. The proposed framework is validated on an automotive bushing. We discuss the construction of a test bench and experimentally verify the free-free conditions at the boundaries of our experiments. To conclude, for our specific study case, we highlight the changes in the behaviour in terms of dynamic stiffness caused by the application of a preload.