Research Papers

Modal Methodology for the Simulation and Optimization of the Free-Layer Damping Treatment of a Car Body

[+] Author and Article Information
Marco Danti

Vehicle Engineering NVH, Centro Ricerche FIAT, Strada Torino 50, 10043 Orbassano (TO), Italymarco.danti@crf.it

Davide Vigè

Vehicle Engineering NVH, Centro Ricerche FIAT, Strada Torino 50, 10043 Orbassano (TO), Italy

Guido Vincent Nierop

Engineering and Design Virtual Analysis-NVH, Fiat Auto, Corso Settembrini 40, 10135 Torino, Italy

J. Vib. Acoust 132(2), 021001 (Mar 15, 2010) (8 pages) doi:10.1115/1.4000844 History: Received October 06, 2006; Revised October 26, 2009; Published March 15, 2010; Online March 15, 2010

The cost and weight reduction requirements in automotive applications are very important targets in the design of a new car. For this reason, all the components of the vehicle have to be optimized and the design of the damping material layout has to be deeply analyzed in order to have a good noise, vibration, and harshness (NVH) performance with minimum mass and cost. A tool for the optimization of the damping material layout has been implemented and tested; the need to explore the entire design space with a big number of variables suggested the use of a genetic multi-objective algorithm for the optimization. These algorithms require a large number of calculations and the solution of the complete NVH model would be too expensive in terms of computation time. For this reason, a new software tool has been developed based on the simulation of the damping material treatments by means of an auxiliary mass and stiffness matrix, which was added to the baseline modal base; using this procedure, the required time for the simulation of each damping material layout configuration is reduced to a few minutes, allowing to exploit the genetic algorithm capability to efficiently explore the design space. As a result, some configurations with an important mass reduction or a much better acoustic performance have been found. This method has been verified on a simple Aluminum box in order to verify all the assumptions and to test the effectiveness in predicting the vibration levels of plates with free layer damping added to it.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

FE trimmed model of a passenger car

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Figure 2

Internal cavity FE model

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Figure 3

A unit force acting on the structure excites the pressure inside passenger compartment by means of fluid structure interaction

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Figure 4

Sketch of the system

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Figure 5

Frequency variation in the equivalent damping coefficient while varying the thickness ratio between damping layer and metal sheet

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Figure 6

Aluminum box with a damped panel

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Figure 7

Structural transfer function from the front strut to the damped panel (experimental—solid, NASTRAN—dash, new approach—dash-dot)

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Figure 8

Acoustic transfer function from the front strut toward the microphone inside the cavity (experimental—solid, NASTRAN—dash, new approach—dash-dot)

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Figure 9

Layout of the reference configuration of the damping patches on the fastback vehicle

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Figure 10

Thirty-four variables considered for the second optimization run

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Figure 11

Distribution of the optimized configuration—dark patches are the most effective ones

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Figure 12

A Pareto frontier has been found as final result of the optimization procedure

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Figure 13

Example of improved acoustic transfer function (dash-dot)

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Figure 14

Results of the second optimized configuration—dark patches are the most effective ones



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