Squeal measurement with 3D Scanning Laser Doppler Vibrometer: handling of the time varying system behavior and analysis improvement using FEM expansion

Abstract

In the presence of squeal, Operational Deflection Shapes (ODS) are classically performed to analyze behavior. A simple numeric example is used to show that two real shapes should dominate the response. This justifies an ad-hoc procedure to extract main shapes from the real brake time measurements. The presence of two shapes is confirmed despite variations with wheel position and reproducibility tests. To obtain a high spatial density measurement, 3D Scanning Laser Doppler Vibrometer is interesting but leads to iterative measurements on a time-varying system. An algorithm to merge sequential measurement and extract main shapes is detailed. Even with a high-density 3D SLDV measurement, shapes characterizing the squeal event are still only known on accessible surfaces. Minimum Dynamic Residual Expansion (MDRE) is thus finally used to estimate motion on a full FE mesh which eases interpretation and highlights areas where the test and the model contain errors.