Multidisciplinary optimization for spot welding locations
Examensarbete för masterexamen
Tangella, Sai Akshay
Automotive Body in white parts are joined using a method called spot welding. Previous studies have shown that the determined position of spot weld varies within ± 10mm from the nominal position . The variation in the location of spot welds influences three disciplines, such as geometrical assurance, strength, and residual stress. This thesis aims to choose the position of spot weld with minimized geometrical variations and still to satisfy the requirements for strength and residual stresses. A multidisciplinary optimization method that incorporates all these disciplines to find the optimal position of a spot weld is developed. This study was performed on an automotive test case model. This test case assembly consists of two parts, which are joined with seven spot welds. Individual modeling and simulation were performed on this assembly to study the effects of changing the positions of spot welds for all three disciplines. For this purpose, RD&T software was used to predict the geometrical variations, and Ansys workbench was used to analyze the strength and residual stresses for the test case model. Matlab programming tool was used to develop a search algorithm that is used as an optimization algorithm during MDO and also to establish a connection between different software. An MDO workflow, which evaluates the different positions of spot weld to minimize geometrical variations and still satisfy the strength and residual stress requirements has been developed. From the MDO results, it is seen that the position of spot welds has an effect on all three disciplines, and therefore it is necessary to consider it during the development stage. The suggested optimal position of spot weld from this thesis has shown a 25% improvement compared to the nominal weld position.