Abstract
KEYWORDS – NVH, Experimental Modal Analysis, SLDV, compression, automatic modal hammer
ABSTRACT – Noise and vibrations during braking are challenges faced by automobile manufacturers. During decades, different methods have been developed to research on Noise, Vibration and Harshness (NVH) problems. A typical problem-solving approach is to test complete brake systems or individual components separately via Experimental Modal Analysis (EMA). Later, results are correlated with vibro-acoustic data from noise brake dynamometer and road test measurements. Improvements of noise/vibration and damping are made with respect to this correlation.
There is still a large gap between modal parameters obtained via EMA or Finite Elements Analysis and the reality. During a squealing brake event, pads are under compression. However, EMA is generally performed under free-free conditions. The aim of this paper is to investigate the dynamic characterisation and sensitivity analysis of a subsystem consisting of a brake pad/disc under operational pressure loads.
Automatic modal testing is conducted on a stand-alone pad/disc and piston/pad disc assemblies, under various compression loads to identify the modal parameters that affect the brake squeal. Brake pads and disc are first tested separately under free-free conditions for reference. Data is acquired using an automated excitation hammer and a Scanning Laser Doppler Vibrometer (SLDV) system. The observation on how brake pads behave under compression and how this fact impacts the resulting mode shapes is discussed in detail. The effect of the compression on the mode shapes is observed for the following clamping conditions: applied load, piston dimension/presence