Drum brake squeal noise has been under investigation by automotive companies for decades due to consistent customer complaints and high warranty costs. Unstable natural frequencies of a brake system are closely linked with brake squeal noise. Complex eigenvalues are widely used to predict unstable frequencies of brake systems. Unstable frequencies are very sensitive to various system parameters such as vehicle speed, coefficient of friction, contact pressure distribution at the liner-drum interface, brake pressure, etc.
In this paper, the author has focused on the brake pad wear effects on pressure distribution and eventually on the squeal noise propensity of a commercial vehicle drum-brake system. Wear at brake pads interface is simulated using simplified wear rate formula followed by complex eigenvalue analysis. Predicted unstable frequencies considering the effect of pad wear are found closer to the frequencies of measured noise in physical testing.
After successful prediction of unstable frequencies, another challenge in understanding and solving brake squeal issues is to be able to generate insights into this complex phenomenon. Analytical techniques like component contribution factor (CCF) and component mode contribution factor (CMCF) are very useful in this task.
In this paper, the effect of brake-liner wear on the prediction accuracy of squeal noise is discussed with the help of a live case. Subsequently how to make effective use of techniques like CCF and CMCF to identify the root cause of the problem is also discussed.
