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Brake squeal noise is a top warranty concernsmplaints for virtually all automotive companies. How to identify squeal frequencies and mode shapes is typically very challenging. The identification of potential squeal problems still rely heavily on experimental methods using inertia and chassis dynamometers or on-road tests, but these require hardware to run. Good numerical methods have advantages of evaluating up-front designs before the cutting tools ever hit any metal. But for brake squeal, there are still many challenges to overcome to correctly model a complete brake system due to the nature of the complexity of the frictional excitation. In this paper, a disc brake system model was established to simulate brake squeal using nonlinear transient analysis methods provided through LS-DYNA. The model includes rotor, pads, linings, caliper and pistons. From the example analyzed, the squeal frequency is identified using frequency domain analysis of the numerical time-domain output.

The effect of suspension system parameters on NVH performance is presented using the results of a design of experiments analysis of a quarter-car model with elastomeric elements. The elastomeric elements are modeled using Maxwell elements with stiffness increasing with frequency. Fourteen design parameters are considered. The force spectrum acting on the sprung mass is partitioned into frequency bands. The amplitude in each frequency band as well as location and amplitudes of resonance peaks in the force spectrum are used as response variables. Major factors that effect each response variable are quantified using sensitivity coefficients. Constrained optimization studies were run to identify the minimum and maximum responses that can be expected. Suspension and bushing designers can use this work to estimate the behavior of design alternatives early in the design process.

Improved formulas are developed for the optimum tuning of damped vibration absorbers whose motion may or may not be in-line with the motion axis of the main mass. J. Ormondroyd and J. P. Den Hartog (1928), studied a class of dynamic vibration absorbers whose motion is in-line with that of the main mass and reported the existence of optimum tuning and damping values for the absorber mass along with supporting numerical results. An asymptotic solution for the optimum damping of J. Ormondroyd's and J. P. Den Hartog's absorber was presented by J. E. Brock (1946); however, his solution breaks down as the mass ratio increases. In this paper, an exact solution for the optimum damping of J. Ormondroyd's and J.P. Den Hartog's absorber is given along with an analysis of vibration absorbers whose motion is not in-line with the motion axis of the main mass. This work was made possible by the use of a symbolic algebra program which was not available to the earlier investigators.