Investigation of Off-axis Excitation due to Component Asymmetry with a Non-Resonant Dynamic Stiffness Test Method

Abstract

Elastomeric bushings are common components in automotive vehicle suspensions and steering systems. They influence the vehicle noise and vibration as well as the handling performance by providing compliance to accommodate for misalignments and structural isolation at the joints of various linkages and frames. Dynamic properties of bushings are often measured using an elastomer test machine, in which the bushing is mounted into a fixture that mates to a displacement actuator on an upper crosshead and a force sensor on a lower crosshead. Typical elastomer test machines only actuate and record displacements and forces along a single axis. Possible misalignments of the mounting fixture or asymmetrical geometry of the bushings can induce off-axis motions and forces. To help illustrate and analyze this problem, a reference component with well known properties is developed and tested using the elastomer test machine. An analytical model of the reference component is developed to understand its behavior and interaction with the test machine dynamics. Modifications to the fixture setup are also analytically and experimentally investigated. Using results from this preliminary investigation, a refined reference component is suggested.