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This paper presents a new FEA approach for brake squeal simulation, the energy flow analysis. It demonstrates that under certain conditions, two system normal modes with equal or close frequencies may start injecting vibration energy into each other, from dynamic friction mechanism. The vibrations, therefore, can “self-grow” (limited cycle), resulting in system instability, such as brake squeal and brake moan. The theoretical conditions for such positive energy flows to occur are discussed. Test examples and application case studies are presented, along with comparison with, and linkage to, complex eigenvalue analysis.

During vehicle development, NVH engineers often have a difficult time when faced with brake rattle issues. Resolving these issues becomes more challenging when vehicles are not available for evaluation, test schedules are short and subjective ratings are inconsistent. In part, the reason brake rattle issues are so difficult to resolve is the absence of a standard test and evaluation procedure. This paper will present an innovative technique to perform brake rattle screening on a laboratory shaker without the need of a vehicle corner or detailed road profile data. Additionally, an objective rating method will be discussed that will provide a more accurate and consistent method of grading results when comparing the rattle intensities of multiple test configurations and ultimately will allow the engineer to predict customer satisfaction levels. This objective rating technique is also applicable for identifying rattle patterns and quantifying intensity during vehicle evaluations.

The direct finite element analysis (FEA) approach for disc brake squeal prediction is presented in this paper. A linear model is developed to include the impact of negative μ-v slope on brake systems noise performance. The recently-developed iterative algorithm - ABLE, is used to solve the resulting large-scale complex eigenvalue problems on a PC. Efficiency and effectiveness of the algorithm are discussed. Good correlations are achieved between simulation and measurement, both in squeal frequencies and corresponding unstable modal shapes. Initial study has also validated the conventional wisdom that negative μ-v slope can cause more system instabilities.

This paper expands the oral presentation the authors made at 2000 Brake Colloquium [1], and publishes, for the first time, the key concept and procedures of applying an advanced component mode synthesis method, the MacNeal method, in brake squeal simulations. The effectiveness and the efficiency of the overall approach are demonstrated and verified by direct FEA. In addition to squeal propensities and the unstable complex mode shapes, this paper also investigates different mode participation factors (MPF) - Component MPF and System MPF, and component participation factors (CPF). The paper also introduces Acoustic Component Participation Factors (ACPF). Application case studies are presented to demonstrate the commonalities and differences of those factors.