Analysis of a New Squeak Test Apparatus developed for Objective Rating of Squeak Propensity and building a Database to Minimize Squeak Problems in Automotive Engineering

A test apparatus to rate squeak propensity of given materials pairs was designed utilizing a sprag-slip mechanism that can consistently induce unstable, self-exited sliding motion between the surfaces of the materials pair. A dynamics model of the system was developed and studied to guide the design of the apparatus. Stability analysis of the modified sprag-slip mechanism was conducted to identify the unstable region in terms of the kinetic coefficient of friction and angle of attack. Phase portraits were obtained numerically to further investigate dynamic characteristics of the system. To identify the natural frequencies of the system, modal analysis was performed using analytical model, FEM and experiment. To demonstrate the capability of the test apparatus, several materials pairs were tested and their motions and generated noises were measured. The measured data was processed using FFT and analytic wavelet transform to obtain frequency spectrum and time-frequency pattern. The automatic detection and rating algorithm of squeak and rattle noises, which was previously developed by the authors, was applied to rate squeak propensity of given material pairs. A systematic, overall procedure comprised of material pair testing, CAE, and component or system level test is proposed to handle squeak problems in the design stage.