Squeal Propensity of a Pad/Disk Brake System in a Reduced-Scale Dynamometer

Noise assessment of brake materials is typically conducted using a full-scale dynamometer or vehicle testing due to its complex and system-dependent nature. However, reduced-scale setups are of strong interest for their flexibility and cost-effectiveness. This study applied the SAE J2521 squeal procedure to a reduced-scale dynamometer using two specific configurations differing in damping and stiffness properties. The reference setup is a fully supported configuration, typical of pin-on-disk setups. In the second, we introduced a mechanical spacer between the disk and its support, where disk vibrations are less constrained, offering a closer representation of real application conditions. Both configurations exhibited squeal events at frequencies of 3.8–4 kHz, 11 kHz, and 12.4 kHz, whereas the spaced configuration showed additional frequencies at 7.0 kHz and 14.7 kHz, and exhibited higher squeal occurrence and amplitude. Experimental modal analysis revealed that the spaced setup exhibits, on average, about 25% lower modal damping than the reference setup. The differences between the two systems are discussed in relation to their dynamics obtained by experimental characterization using frequency response function (FRF) measurements. The study also investigates the influence of braking parameters, pressure, velocity, and temperature, on the squeal propensity.