Volumetric and Dynamic Performance Considerations of Elastomeric Components

Elastomeric joints such as mounts and suspension bushings undergo broadband excitation and are often characterized through a cross-point dynamic stiffness measurement; yet, at frequencies above 100 Hz for many elastomeric components, the cross- and driving-point dynamic stiffness results significantly deviate. An illustrative example is developed where two different sized mounts, constructed of the same material and are shaped to achieve the same static stiffness behavior, exhibit drastically different dynamic behavior. Physical insight is provided through the development of a reduced order single-degree-of-freedom model where an internal resonance is explained. Next, a method to extract the parameters for the reduced order model from a detailed finite element bushing model is provided. Further, a new benchmark experiment is used to validate the simulated behavior and provide insight into certain frequency dependent behavior where internal elastic modes of elastomeric component are present. Finally, the effect of the internal resonance is examined within the context of a hybrid vibro-acoustic vehicle system model. It is demonstrated that the internal mount resonance exhibits a significant influence on the sound pressure sensitivity that is dependent upon the size of the component.