Study of Dynamic Characteristics of a Test Apparatus Developed to Build Squeak Propensity Database

摘要

Database that accurately ranks squeak propensity of material pairs will be very useful for NVH engineers and vehicle interior designers. The main challenge in developing such database is accurate quantitative rating of squeak propensity of given material pairs. A unique test apparatus that utilizes a sprag-slip mechanism was developed for this purpose by the authors. The device was designed to induce friction-induced, self-excited vibration of a pair of materials, which leads to squeak noise consistently and repeatedly. A simple analytic model was used in design of the apparatus to determine main design parameters. A finite element method model is developed and studied in this work to refine the design of the test apparatus and better understand underlying mechanism of squeak noise generation. The instability of the system is studied by the complex eigenvalue analysis of the model. It is shown that the system instability occurs by the coalescence of two modes that makes the effective damping of one of the coalesced modes negative. The instability condition identified from the complex eigenvalue analysis is confirmed by dynamic transient analysis in time domain. The instability condition identified from the analytical model shows good agreement with the results obtained from the FEM model.