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Most sub-compact vehicles with the rear multi-link system have road booming noise issues due to bending modes in the rear cross-member. Many engineers in the vehicle industry solve this problem by implementing a dynamic damper on the rear cross-member. However, the additional component of the rear cross-member increases cost and weight. This paper presents the methodology of the system-level optimization for rear cross-member structures to improve road booming noise. A feature extraction methodology is introduced. This method makes possible the application of topology optimization results to real design, rather than the results just being used as a concept suggestion.

An efficient method to determine optimal bushing stiffness for improving noise and vibration of passenger cars is developed. In general, a passenger vehicle includes various bushings to connect body and chassis systems. These bushings control forces transferred between the systems. Noise and vibration of a vehicle are mainly caused by the forces from powertrain (engine and transmission) and road excitation. If bushings transfer less force to the body, levels of noise and vibration will be decreased. In order to manage the forces, bushing stiffness plays an important role. Therefore, it is required to properly design bushing stiffness when developing passenger vehicles. In the development process of a vehicle, bushing stiffness is decided in the early stage (before the test of an actual vehicle) and it is not validated until the test is performed.