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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.

A competitive market and shrinking product development cycle have forced automotive companies to move from conventional testing methods to virtual simulation techniques. Virtual durability simulation of any component requires determination of loads acting on the structure when tested on the proving ground. In conventional method wheel force transducers are used to extract loads at wheel center. Extracted wheel center forces are used to derive component loads through multi-body simulation. Another conventional approach is to use force transducers mounted directly on the component joineries where load needs to be extracted. Both the methods are costly and time-consuming. Sometimes it is not feasible to place a load cell in the system to measure hard point loads because of its complexities. In that case, it would be advantageous to use structure itself as a load transducer by strain gauging the component and use those strain values to extract hard point loads in virtual simulation.

Stringent emission norms by government and higher fuel economy targets have urged automotive companies to look beyond conventional methods of optimization to achieve an optimal design with minimum mass, which also meets the desired level of performance targets at the system as well as at vehicle level. In conventional optimization method, experts from each domain work independently to improve the performance based on their domain knowledge which may not lead to optimum design considering the performance parameters of all domain. It is time consuming and tedious process as it is an iterative method. Also, it fails to highlight the conflicting design solutions. With an increase in computational power, automotive companies are now adopting Multi-Disciplinary Optimization (MDO) approach which is capable of handling heterogeneous domains in parallel. It facilitates to understand the limitations of performances of all domains to achieve good balance between them.