Polyurethane (PU) foams are widely used as acoustic package materials to eliminate vehicle interior noise. Therefore, it is important to improve the acoustic performances of PU foams. In this paper, the grey relational analysis (GRA) method and multi-objective particle swarm optimization (MOPSO) algorithm are applied to improve the acoustic performances of PU foam composites. The average sound absorption coefficient and average transmission loss are set as optimization objectives. The hardness and content of Ethylene Propylene Diene Monomer (EPDM) and the content of deionized water and modified isocyanate (MDI) are selected as design variables. The optimization process of GRA method is based on the orthogonal arrays L9(34), and the MOPSO algorithm is based on the Response Surface (RS) surrogate model. The results show that the acoustic performances of PU foam composites can be improved by optimizing the synthetic formula. Meanwhile, the results that were obtained by GRA method show the degree of influence of the four design variables on the optimization objectives, and the results obtained by MOPSO algorithm show the specific effects of the four design variables on the optimization objectives. Moreover, according to the confirmation experiment, the optimal synthetic formula is obtained by MOPSO algorithm when the weight coefficient of the two objectives set as 0.5.

Based on the meshing principle of silent chain and the structure of an automobile engine, timing silent chain system including involute tooth sprocket, guide plate, tension plate, and silent chain is designed in this paper. Dynamics analysis model is built, and vibration of the chain system is studied. The link tensile force and the contact force between link and other components, and the transmission error of crankshaft sprocket and exhaust camshaft sprocket are analyzed. The design and analysis method of the timing silent chain system is proposed. The wear elongation of the timing silent chain system is studied through the road test. The wear morphology of the link plate and pin working surface are observed. Analysis results show that the design method of the timing silent chain system is feasible. The major wear mechanism of the pin is fatigue wear, and the major wear mechanism of the link plate is fatigue wear and abrasive wear. The results of the dynamic simulation and the experimental research show that the design and analysis method of timing silent chain system is scientific and feasible, and wear resistant of the timing silent chain system is high.

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Polyurethane foam is commonly used in the automobile industry due to its favorable acoustic performances. In this study, a new tung oil-based polyurethane composite foam (TOPUF) was prepared by a one-step method. Different forms and contents of miscanthus lutarioriparius (ML) were used in TOPUF for improving acoustic performance. Polyurethane foams were characterized by means of Fourier transform infrared and SEM. The acoustic properties and mechanical properties of TOPUF, obtained with ML, were determined and compared with pure petroleum-based polyurethane foam. The results illustrate that the modification of TOPUF with the ML has a positive effect on the acoustic and mechanical properties in comparison to the unmodified foam. TOPUF obtained with ML powders has better acoustic performance than that obtained with ML strips. The optimum acoustic performance is achieved at the filler content of 0.3 wt%. The average sound absorption coefficient and transmission loss can reach 0.518, and 19.05 dB, respectively.

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