Title: Determination of engine motion for analysis of the automobile exhaust system using a simple equivalent matrix

Authors: B.K. Koh, G.J. Park

Addresses: Research Associate, Mechanical Engineering and Technology Research Institute, Hanyang University, Korea. ' Associate Professor, Department of Mechanical Design and Production Engineering, College of Engineering, Hanyang University, 17 Haengdang-Dong, Sungdong-Gu, Seoul, Korea

Abstract: In the numerical analysis of an automobile exhaust system, the external forces from the engine motion must be identified to evaluate the vibrational behaviour. The forces can be obtained from experiments. However, the experiments are not precise due to the harsh conditions around the engine. Therefore, the forces are usually calculated indirectly. A method has been developed and verified to determine the engine motion using the linear characteristics. The automobile exhaust system is modelled by beam and shell elements for finite element analysis. A reduced matrix is defined to have 6 by 6 dimension. The matrix represents the overall behaviour of the system. Since the system has linear characteristics, the coefficients of the matrix are numerically determined by the linear modal analysis and harmonic response analyses. After the matrix is defined, displacements are measured in a few places where the measurement can be easily conducted. The engine motion of six DOFs is calculated from the relation between the matrix and experiments. Since any artificial assumption is not utilised, the method gives quite accurate results. The suggested method can be generalised for any linear structural system with unknown external forces.

Keywords: automobile exhaust system: bellows; conical frustum shell element shape; optimisation method; top-down approach; design methodology; vibration; engine motion; FEA; finite element analysis; linear modal analysis; harmonic response analysis.

DOI: 10.1504/IJVD.2000.005188

International Journal of Vehicle Design, 2000 Vol.24 No.2/3, pp.287 - 297

Published online: 09 Sep 2004 *

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