Brake Impedance Test Machine - Modal Testing of Brake Pads under Pressurized Condition using 3D SLDV and Scalable Automatic Modal Hammer

Paper #:
  • 2017-01-2485

  • 2017-09-17
Brake squeal is an NVH issue experienced by brake systems and vehicle manufacturers for decades. This leads to customer dissatisfaction and the questioning of quality of the brake system. Advanced testing tools, design modification, dynamometer testing, vehicle validation etc., are performed to study, analyze and eliminate this problem. But, still it continues to exist. One of the most important reasons is the complexity of the brake pad which leads to its non-linear properties. Therefore, it is imperative to understand the behavior of the brake pad, in terms of its dynamic properties (eigenfrequencies, damping and mode shapes), under varying boundary conditions. Experimental Modal Analysis (EMA) is used to study the dynamic properties of any structure and is generally performed under free-free boundary conditions. An approach to study brake pads under pressure condition is a step towards reality, as brake pads squeal only during braking events. Therefore, the Brake Impedance Test machine (BIT) was developed to study the behavior of brake pads under pressure. This work describes the development of the BIT to study brake pads under different piston compression loads, analyzing their results and proposing an approach to standardize the testing procedure. The brake pads are excited by a Scalable Automatic Modal hammer (SAM), with a precise controllable force level. The vibration response is measured contactless using a 3D Scanning Laser Doppler Vibrometer (3D SLDV). This research, under these conditions and advanced techniques, results in dynamic characteristics of brake pads closer to those in a real braking event. These results are correlated with dynamometric data for further validation. The conclusions of these upcoming studies will lead to effective brake pad parameters for a robust brake against squeal research.
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