Acoustic design optimization of structures subjected to random excitations is investigated in this paper. In this work, a Pseudo excitation method (PEM), an accurate and highly efficient algorithm series for structural stationary random response analysis, is extended to deal with random acoustic radiation problems. A boundary element method (BEM) and a finite element method (FEM) are combined with the PEM to calculate acoustic radiation from random excited structures. A design optimization model is presented, in which the pressure power spectral density (PSD), mass of the structure or eigenvalues of the structure is used as an objective function or constraint function. The thickness of the structure is used as a design variable. Based on acoustic radiation sensitivity analysis and structural sensitivity analysis, the design optimization model is solved with sequential linear programming. Numerical examples of sensitivity analysis and acoustic design optimization are given to demonstrate the effectiveness of the proposed method. © 2010 Institute of Noise Control Engineering.

With the help of the orthogonal experiment and the friction-wear mechanism by car as the research object of the clutch driven platen friction plate of Chongqing Changan CX20 auto power take-off installation, the optimization of clutch friction materials is studied.It was selected for the resin-base fiber materials of clutch driven platen to be commonly used in auto mechanical manufacture. It was analyzed for the abrasion mechanism of the clutch driven platen friction plate between the flywheel and the pressure plate,and discussed for the relationship of driven platen friction-plate heat recession-performance and the driven plate material at high temperature. The results show that the friction factor of the optimized driven platen lining materials do not change. In the process of the frequent friction heating to high temperature, the stability of the optimized driven platen lining materials is strong, the wear of those is reduced, and the optimized driven platen lining materials have good performance of high temperature-thermal recession.

A typical case of integral all-welded panel joints on Shanghai Minpu Second Bridge is discussed in this paper. The prediction of welding residual stresses at joints is achieved by thermal elasto finite element analysis, and the research reveals that a proper scheme of multi-layer welding craft will reduce welding distortions and residual stresses through mutual offset. The welding distortions at upper and lower chord joints (Type I) and those of the overall structural model are predicted with the distribution of residual stresses obtained. The research aims to provide a theoretical basis for the control of welding distortion, the optimization of welding craft and the constitution of optimal assembly welding craft.

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