Brake squeal has always been a major NVH problem to many car makers due to significant number of warranty claims. Brake squeal is a high frequency noise (above 1 kHz) emanating from car disc brakes that get excited due to one or more mechanisms such as mode coupling, stick-slip, hammering and sprag-slip. This paper attempts to investigate the effects of brake pad surface topography on squeal generation. Two pairs of a non-asbestos organic (NAO) brake pad will be tested on a brake dynamometer test rig. Surface topography of the brake pad will be analyzed through microscopic techniques using energy dispersive X-ray analysis (EDX), and optical microscope.
The open design and position of disc brake that is closed to road surfaces enable contaminants to enter the brake gap and caused noise and tribological disturbance at the brake interface. Contaminants such as dirt and soil can be present and are expected to influence the occurrence of brake squeal that produce an annoying sound during braking action. The objective of this study was to examine the effect of external hard particles at different disc sliding speed on generation of brake squeal using a brake dynamometer. Different rotational speed of disc brake was selected and the experiments squeal noise data was collected and analyzed using the Fast Fourier Transformation (FFT) analyzer. From the experiments, the presence of external particle and the rotation speed of disc brake promotes the generation of brake squeal phenomenon by changing the surface roughness and effective contact of brake interface. Results obtained from the experiment also showed that higher rotating disc generate higher sound level meter or squeal frequency and increase numbers of squeal noise generated.
Brake wear particles resulting from friction between the brake pad and disc are common in brake system. In this work brake wear particles were analyzed based on the size and shape to investigate the effects of speed and load applied to the generation of brake wear particles. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) was used to identify the size, shape and element compositions of these particles. Two types of brake pads were studied which are non-asbestos organic and semi metallic brake pads. Results showed that the size and shape of the particles generatedvary significantly depending on the applied brake load, and less significantly on brake disc speed. The wear particle becomes bigger with increasing applied brake pressure. The wear particle size varies from 300 nm to 600 µm, and contained elements such as carbon, oxygen, magnesium, aluminum, sulfur and iron.
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