Development of a Test Apparatus That Consistently Generates Squeak to Rate Squeak Propensity of a Pair of Materials

Squeak is an undesirable noise generated by friction-induced self-excited vibration of two contacting surfaces. Due to the highly non-linear nature of the underlying mechanism, it is very difficult to develop a systematic procedure to address squeak noises in automotive engineering. Obviously it is impractical to eliminate all possible sliding contacts in automobiles, while good structural design will minimize occurrence of contacts. Therefore, the approach will have to be to identify potential contact areas in the design stage, and choose a material pair that has a minimum squeak propensity for such areas. A unique squeak test apparatus was built to enable rating squeak propensity of a given materials pair. The mechanism utilizes a sprag-slip mechanism to induce friction-induced unstable vibration for nearly all material pairs. An analytical model was developed to understand dynamic characteristics of the test apparatus and refine the design. Unstable motions and sounds generated by the apparatus were measured for several pairs of materials. Squeak detection and rating algorithms previously developed by the authors were applied to quantify squeak propensities of the pairs. The developed procedure will be able to build material database for NVH engineers to deal with squeak problems in the design stage.