Component Mode Synthesis of a Vehicle System Model Using the Fictitious Mass Method

[+] Author and Article Information
M. Karpel, B. Moulin, V. Feldgun

Faculty of Aerospace Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel

J. Vib. Acoust 129(1), 73-83 (Jan 08, 2006) (11 pages) doi:10.1115/1.2202156 History: Received September 27, 2004; Revised January 08, 2006

A new procedure for dynamic analysis of complex structures, based on the fictitious-mass component mode synthesis method, is presented. Normal modes of separate components are calculated by finite-element analysis with the interface coordinates loaded with fictitious masses that generate local boundary deformations in the low-frequency modes. The original fictitious-mass method is extended to include three types of component interconnections: displacement constraints, connection elements, and structural links. The connection elements allow the introduction of springs and dampers between the interface points without adding structural degrees of freedom. The structural links facilitate the inclusion the discrete finite-element representation of typically small components in the coupling equations. This allows a convenient treatment of loose elements and the introduction of nonlinear effects and parametric studies in subsequent analyses. The new procedure is demonstrated with the structural model of a typical vehicle with four major substructures and a relatively large number of interface coordinates. High accuracy is obtained in calculating the natural frequencies and modes of the assembled structure and the separate components with the fictitious masses removed. Dynamic response analysis of the vehicle travelling over a rough road, performed by modal coupling, is in excellent agreement with that performed for the full model.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 9

Time response of the right rear seat to hump excitation

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Figure 1

The vehicle finite element model, a general view

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Figure 2

Finite-element model of component A

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Figure 3

Finite-element model of component B

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Figure 4

Percentage errors of the elastic couple frequencies

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Figure 5

rms frequency errors of the first 11 coupled modes versus the fictitious masses at the interface points

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Figure 6

PSD of acceleration responses at the rear right wheel center in the X, Y, and Z directions

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Figure 7

PSD of acceleration responses at the driver’s seat in the X, Y, and Z directions

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Figure 8

Time response of the right shock absorber extension to hump excitation



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