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Numerical and experimental methods are applied effectively to reduce the interior noise of a mini-bus. In the frequency range where the booming noise occurs, acoustic forced response analysis is carried out, where experimentally measured vibrations of the floor by excitation test are used as boundary conditions. Through this analysis, the panels having positive effects to the interior noise are identified and confirmed through vehicle test. Then the coupling between the floor panels and the interior acoustic field is considered and the coupled acoustic field is analyzed by Boundary Element Method(BEM). As the result, the interior noise level of the bus is reduced effectively by structural modifications of the panels.

This paper discusses the flexible chassis effects on dynamic response of engine-mount systems using computer simulation techniques. Equations of motion for the engine-mount systems including flexible foundations are derived. The dynamic flexibility of the chassis is represented by modal information from finite element analysis or experimental modal tests. Solving the derived equations, natural frequencies and forced vibration response of an engine-mount system can be simulated accurately. It is shown that the flexibility of the engine-mount frame structure may have a significant impact on the idle shake vibration and mounting forces transmitted from the engine to the structure. The computational method developed is applied to an example engine-mount system and the results are compared to those of an associated experiment.

Production cost saving is the main subject of process control of all automobile industries. Recently introduced ADI is a suitable material for those issues, but usefulness is restricted because of its poor fracture toughness. In the study, the effect of casting and austempering conditions on the fracture toughness of ADI were determined in order to develop a suitable material which can replace forged alloy steel. For casting of DCI, sandwitch method was conducted as inoculation process involving spheroldizing treatment with calballoy. Austempering was carried out in a salt bath with a composition of 50% KNO3 and 50% NaNO3 and then cooled in air. Two main parameters, namely austempering temperature and time, were selected as variables and structural changes of ADI with initial casting conditions was monitored with them. According to the casting results, it was confirmed that the mechanical properties of ADI, especially fracture toughness, depends strongly on casting conditions of DCI.