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Numerisk optimering av stötfångarsystem med hjälp av LS-OPT
2014 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Developing State of the Art CMS (Crash Management Systems) involves a lot of iterative work based on intuition, guesses and experience from the designers in order to achieve excellent performance in crashworthiness. This is due to the extremely non-linear nature of impacts resulting in plastic deformations. This master’s thesis was assign to investigate and evaluate if an optimization software could be utilized in order to improve the performance of the CMS subject to the Research Council for Automobile Repairs (RCAR) Structural Test. The test evaluates the repair cost of a low speed crash and is therefore an important factor of the insurance cost for the end-customer. The single most important part of the CMS with respect to the RCAR Structural test is the crashboxes. Each CMS contains two crashboxes which are located on each side of the crossmember connecting it to the siderails of the car. The object is to minimize the intrusion of the barrier without transmitting too high force to the siderails. This is done through initially creating a too stiff ‘box’ and then introducing weakening in the structure that triggers a more controlled behavior. The, size, position and shape of these geometrical weakening’s in the structure are very hard to predict and must therefore be designed with trial and error.By using computer-aided engineering (CAE) software’s LS-OPT and Hypermesh a metamodel based approach to find an optimized geometry of the crashboxes is obtained. A linear morphing method where node translations are stored in vectors to create the design variables directly on the mesh is used. The preprocessing of the optimization setup is performed using Hypermesh and a script customized for Hardtech’s development environment is created to minimize the setup-time. Four tests, based on real-case scenarios, were performed in order to examine the work method. It was found that the optimization routine is efficient enough to be directly adopted into the CMS development process. All four tests show that the optimization software was able to improve the performance subject to the RCAR Structural test. The design possibilities are however quite limited to linear scaling of predefined groups of node displacements.

Place, publisher, year, edition, pages
Keyword [en]
Keyword [sv]
Teknik, Optimering, LS-OPT, stötfångarsystem
URN: urn:nbn:se:ltu:diva-53349Local ID: a60715b9-ee22-4826-8e15-1063eff159f8OAI: diva2:1026723
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20140804 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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