Comparative Assessment of Multi-Axis Bushing Properties Using Resonant and Non-Resonant Methods

Abstract

Shaped elastomeric joints such as engine mounts or suspension bushings undergo broadband, multi-axis loading; however, in practice, the elastomeric joint properties are often measured at stepped single frequencies (non-resonant test method). This article helps provide insight into multi-axis properties with new benchmark experiments that are designed to permit direct comparison between system resonant and non-resonant identification methods of the dynamic stiffness matrices of elastomeric joints, including multi-axis (non-diagonal) terms. The joints are constructed with combinations of inclined elastomeric cylinders to control non-diagonal terms in the stiffness matrix. The resonant experiment consists of an elastic metal beam end-supported by elastomeric joints coupling the in-plane transverse and longitudinal beam motion. The dynamic stiffness and loss factors of the elastomeric cylinders are measured in a non-resonant commercial elastomer test machine in shear, compression, and inclined configurations and a coordinate transformation is used to estimate the kinematic non-diagonal stiffness terms. Strong agreement is found for both dynamic stiffness and loss factors between the resonant and non-resonant methods at small displacements.

Comparative Assessment of Frequency Dependent Joint Properties Using Direct and Inverse Identification Methods

“…Due to these characteristics common to direct measurements, the test can often be time consuming and only able to determine single stiffness terms in the joint stiffness matrix. Inverse methods have been developed as another approach to characterize joint stiffness properties [1,[5][6][7].…”

“…Other methods [5][6][7] incorporate the use of elastic beam theory in place of the rigid inertia elements and thus permit incorporating preload into the identification experiment. Hong and Lee [6] develop a method in which an unconstrained structure (base structure) and an experimental setup (base structure connected to joints) is used to identify joint properties.…”