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As an effort to solve high frequency brake squeals, increasing attentions have been placed on the relationship of the in-plane (IP) and the out-of-plane (OP) modes of a disc brake. However, there exists wide confusions between the frequency lineup and the mode coupling that largely hinders the efforts on correct solutions for brake squeals. This paper investigates the relationship between disc brake IP-OP modes interaction and brake squeal by both analytical and experimental approaches. It starts with a systematic discussion and categorization of the modal patterns of a typical disc brake rotor. Then, the relationship between IP-OP mode and high frequency squeal is evaluated by means of disc mode indicating function (DMIF) testing and dynamometer testing for three rotor designs. At last, comprehensive correlation study is performed for 19 different front and rear brake systems from the results of 60 dynamometer noise tests.

The perturbed boundary condition (PBC) model updating procedure has been developed to correct the finite element model [1]. The use of additional structural configurations adds more experimental information about the system and so better updating results can be expected. While it works well for simulated examples, practical limitations and additional requirements arise when it is used to update engineering structures. In this paper, the merits and the practical limitations of the techmques will be discussed in depth through the updating of a simulated system where the “measured” data is generated by computer and a real test structure where the experimentally measured data is noisy and distorted due to leakage. Useful suggestions and recommendations are drawn to guide the model updating of practical engineering structures.