In English

Characterisation of the Acoustical Response of External Gearshift System Methods

Romain Demory
Göteborg : Chalmers tekniska högskola, 2004. 62 s.
[Examensarbete på avancerad nivå]

The purpose of this thesis work was to develop methods to characterise the acoustical response of an external gearshift system. First there was a study of what is already done nowadays in terms of processing of recorded noise and testing of the system in a car. Interviewing persons that use the test in their work gave an overview of the situation. A research of existing models (especially for the cables) was done. A general summary of what former methods were developed and what should be in the field of study has been done. The type of model and associated calculations were chosen after these summary. It has been decided to build up a finite element model of the external gearshift system (approximately 5000 elements) using CATIA. This shell and beam mesh will be processed in the NASTRAN computation software in order to obtain the modal response of the system. I-DEAS may be used as a post processor to visualise modal shapes. The goal is to find a way to obtain a empty spectrum between 0 and 300Hz. The excitations coming from the engine are indeed included in this frequency range, the eigen frequencies below 300Hz have then been processed in order to be risen. Simulations were made on the reference system. The results were then compared to values from physical testing and a former study. It appeared that the values were similar and the model was thus validated. Calculations were ran for different physical properties and thermal conditions configurations. The simulations results matched the theory results, and the influence of the exhaust pipe tunnel dynamic stiffness and the temperature were evaluated. Calculations were made on different geometry of external gearshift systems either to improve an existing EGS or to understand the link between the geometry of some regions and the modal response. General conclusions were drawn from those simulations as well as possible improvements. A methodology covering different modes origins has been written. It explains how to improve the response (rise the eigen frequencies) with respect to the mode origin.

Nyckelord: External gearshift system, vibration, noise, acoustical, FEM, shift, gear stick, modes, eigen frequencies.



Publikationen registrerades 2006-09-25. Den ändrades senast 2013-04-04

CPL ID: 11350

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