Effect of abrasives' characteristics on brake squeal noise generation

Abstract

Despite many studies on the subject, brake squeal remains a major concern for the automotive industry. Much progress was made toward understanding and preventing this issue, focusing on the dynamic behavior of the brake. However, the problem is far from fully understood. Among many friction material ingredients, abrasives are extensively used to regulate friction and wear and are recognized as the main contributors to brake noise. This work investigates the correlation between characteristics of abrasives and squeal noise occurrence determined through the SAE J2521 dynamometer test procedure, FESEM, EDS, nanoindentation, and roughness profiling analyses. The particle size, hardness, Young's modulus, and resistance to elastic deformation of 13 different grades of abrasives were measured. The correlation between these characteristics and squeal noise occurrence was determined through statistical analysis. Spearman's rank correlation coefficient (ρ) showed that squeal noise strongly correlated with hardness and resistance to elastic deformation (ρ = 0.61 and ρ = 0.56, respectively) of abrasive materials and exhibited a poor correlation with their particle size (ρ = −0.099). However, considering groups of samples of the abrasive type, particle size is a characteristic that should be regarded in analyzing squeal noise propensity. In the case of SiC, coarser particles (D90 = 196.70 μm) showed a significant reduction in squeal noise compared to finer particles (D90 = 6.30 μm). On the other hand, coarse particles markedly increased the mass loss of the brake pad and brake disk.