Design Parameter Study of a New Test Apparatus Developed for Quantitative Rating of Squeak Propensity of Materials

A novel, unique squeak test apparatus was developed to measure squeak propensity of a given pair of materials with a purpose to build a database for automotive engineers. The apparatus employs a sprag-slip mechanism to generate friction-induced, unstable sliding motion between the two materials that leads to a repeatable squeak noise to enable quantitative rating of the squeak propensity of a given pair of materials. An analytical model of the system was developed to study dynamic characteristics of the mechanism to gain insights to design the test apparatus. Stability analysis of the system identified unstable regions of the motion in parameter planes defined by the kinetic coefficient of friction and the attack angle. Furthermore, the effect of these system parameters on the amplitude of the limit cycle was investigated to obtain guidance to design the device. An automatic rating algorithm of squeak noises previously developed by authors was employed to calculate the squeak propensity of the material pairs. A practical engineering procedure is envisioned that can handle squeak problems in the design stage more effectively by taking advantage of such a squeak propensity database.