Brake lining is a layer of hard material attached to a brake shoe or brake pad to increase friction against the drum or disc. It is a heat resistant padding, often of asbestos, attached to a brake shoe to produce friction.
It is a restraint provided when the brake linings are moved hydraulically against the brake drum to retard the wheel’s rotation. In simple words it is a protective covering that protects an inside surface.
Flaws in brake liners are produced in manufacturing(Curing and Post Curing stages). During these processes there may be chance of irregular distribution of pressure and temperature that may lead to defect in brake liner. Examples of flaws found in brake liners are: Delaminations; cracks; disbonds; voids; Impact or Barely Visible Impact Damage (BVID); porosity; inclusions; erosion; core splices; core disbonds; core crushing; environmental ingress; incorrect cure and incorrect volume fraction
The objective behind this research project was to find a simple and reliable method for detecting damage in brake lining. To find a cost effective inspection techqnique and automate the testing process. Predicting the quality of similar brake liners using the developed method.
The experimental process developed for this research consisted of three main stages. The first stage involved tapping the brake liner with an hammer and recording the acoustic sound signals captured by a microphone. The second stage consisted of taking the time based tap signals and reduce noise from it. Since the tapping is done in shop floor a lot of noise due to machines also records along with the tapping signal. The third stage is to employ signal processing technique on the refined signal. The objective of the signal processing stage is to identify characteristic patterns of each of the acoustic signals which describes the integrity of the structure. From this stage we were able to distinguish between good and brake liner by analyzing impact acoustic frequency spectrum.