| The resistance spot welding is widely used in the connection of automobile body sheetparts, and the welding connection has an on important influence on the body structuralperformances, such as stiffness and strength and NVH etc. However, traditional welding spotlayout design is mainly depending on experience and test, which will result in the increasedmanufacture costing because of too much redundant welding spot in some areas, while thestructural performance may be influenced caused by insufficient number of welding spot inother areas. Hence the need is felt to optimize the welding spot layout without compromisingon the structural performance.Automobile body is composed of many sheet parts, the structure consists of two hatsection steel plates which represents simplified model of the joints used in the constructionof car bodies is selected as the research object in this paper. The welding spot layoutoptimization method based on the spot pitch parameterization is proposed underconsideration of the influence of welding spot on the stiffness, strength and the first ordermodal frequency. The method is used to optimize the welding spot layout of the researchobject and can be used in thickness and spot optimization simultaneously, thus realizing theoptimization of other performances as well as the welding spot layout at the same time. Acar B column is selected to verify the effectiveness of the proposed method. The mainresearch work is as follows:(1) The finite element model of both double cap shape thin-walled beam and the car Bcolumn is set up, which utilizing ACM unit to simulate spot. The corresponding staticperformance analysis and first order modal frequency is analyzed in order to the subsequentcomparative analysis.(2) The parameterized method of welding spot layout based on the spot pitch is proposed. Geometrical lines along the flanges referred here as weld lines is constructed. Thespot pitch in different areas is not the same with the spot distribution on each line isequidistant. The spot pitch on each line is regard as design variables, in order to realize localvariation in the spot weld density during the optimization iteration, the finite element modelneeds to be divided into two parts, namely FE model without spot and additional spotinformation. The creation of spot welds connection in FE model is achieved and can vary innumber between various optimization iterations. The simulation flow chart used to realizethe automatic cycle of welding spot optimization is constructed in isight.(3) The spot layout optimization of double cap shape thin-walled beams based on thespot pitch parameterization is conducted. The spot layout under bending condition andtorsion condition is optimized respectively using the proposed method and the correspondingperformances before and after optimization is analyzed. A more satisfactory optimizationscheme is obtained after comprehensive consideration of the two conditions.(4) The multi-objective optimization based on the spot pitch parameterization isconducted. The proposed method can be used to optimize the spot layout and thicknesssimultaneously. Setting all the welding spot pitch as design variable, stiffness and the firstorder modal frequency as constraint condition, minimizing the total number of welding spotand mass as objective function respectively, the multi-objective optimization using NSGAIIalgorithm under bending condition and torsion condition is conducted and the correspondingperformances before and after optimization are analyzed. A more satisfactory optimizationscheme is obtained after comprehensive consideration of the two conditions.(5) Instance application of vehicle body component. The spot layout of the car Bcolumn under bending condition is optimized utilizing the proposed method. The stiffnessreduction after optimization is in the5%range while the number of the welding spotdecreased significantly, which verifies the effectiveness of the proposed method again. |
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