Analysis, design, and optimization of structures with integral compliant mechanisms for mid-frequency response

The vibration of lightweight structures in the 1 kHz to 10 kHz middle frequency region generates noise, which has adverse effects on human performance and perception of quality. Typical solutions, such as spring-mass absorbers, visco-elastic coatings, and active control, are effective across these frequencies. Nonetheless, they often lead to greater system complexity or weight. Accordingly, the objective of this research is to introduce a new technique for the reduction of middle frequency structural-borne noise.; In reducing mid-frequency response, a multi-scale technique based on amplification principles is explored to integrate small-scale compliant mechanisms into large-scale structures. Specifically, the principle of mechanical advantage is examined as a mechanism design tool to reduce energy transmission. An efficient spectral finite element computational approach is exploited for basic force-velocity and energy flow analyses of both two-dimensional and three-dimensional structures. A genetic algorithm is employed to optimize structure topology and size for greatest effectiveness in the frequency range of interest. The results of prototype testing using acoustic excitation and laser interferometry measurement techniques are presented to validate computational predictions of structural dynamic response. These investigations indicate that a significant decrease in structural vibration is achievable, and they suggest promising applications including the design of multi-functional structural-acoustic panels for broadband vehicle noise reduction.; In summary, there are three primary contributions of this research. First, the computational methods required for the analysis and design of structures with integral compliant mechanisms are synthesized. Second, a novel methodology is established as an integral part of the structural design process for the reduction of mid-frequency structural-borne noise. Third, the feasibility of this method is experimentally validated. Hence, the field of dynamic analysis is extended towards solving practical problems through the synthesis of several existing research fields including structural dynamics, compliant mechanism design, finite element computational analysis, and optimization via evolutionary algorithms.