Design of a generic subsystem fixture for physical squeak and rattle prediction

Examensarbete för masterexamen
Master Thesis
Yechouh, Markus
Kenaan, Khalil
Today Volvo Car Corporation uses parts of the body-in-white to build a fixture for the instrument panels. However, there is a need for a generic subsystem fixture that can be used instead of the cut-out parts of the body-in-white. The use of a fixture will lower the cost for future testing and decrease the manual work, since the generic fixture will replace a number of cut-out parts from the models. The structure of the generic fixture should thus have some flexibility in geometry, so that it fits a wide range of instrument panel models. This thesis focus on two vehicle models which will be called model A and B. A benchmark study is performed to get a better understanding of the body-in-whites an particularly in the region where the instrument panels are mounted in the cars. In that, a modal analysis is performed as well as stiffness analysis with the solver Nastran. A meshed solid block is used to allocate the design space of the fixture. The block with the connection parts placed inside are used to perform topology optimisation, where the solid block is the design space and the connection parts is the non-design space. Results from the topology optimisation give guidance on where to place beams and other material when designing the fixture. Using Catia V5 and having the platform drawing of the shaker rig, the design of the fixture was created. The main structural components of the fixture are plates, beams and AluflexTM components. In Ansa, the model of the fixture is meshed and a modal analysis is performed. Static and dynamic stiffness analysis are also performed, locally and globally, to investigate the stiffness with respect to the body-in-whites. The main structure of the proposed fixture was shown to have higher global stiffness compared to the body-in-whites. This gives a good foundation for future work. However, local stiffnesses in the connection points are much lower compared to the body-in-whites. This is based on the results from Aluflex, which gives the fixture its generic features. A conclusion from this is that other materials than aluminium profiles needs to be used for parts of the design. Future work could reveal the success of such design strategy. Although steel has a higher density, it can be used in a sophisticated way with other materials to create high rigidity and low weight. Keywords: generic, fixture, topology optimisation, static and dynamic stiffness, AluflexTM.
Teknisk mekanik, Transport, Applied Mechanics, Transport
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