| As an important part of the vehicle, autobody is formed mainly by sheet metal withwelding spot. The number and layout of welding spot have an important influence on thestructure performance of autobody. Traditional welding spot layout design is mainly basedon experience, which will result in excessive welding spots in some areas, increasingmanufacturing cost; while in some areas small numbers of welding spots appear,influencing autobody structure performance.Because of welding defect, the quality of some welding spots can’t be guaranteed inwelding process. At the same time the use environment of commercial vehicle is bad, andsome welding spots may failure because of fatigue. Welding spot failure will not onlyinfluence the commercial vehicle structure performance, but also may threat driver’ssecurity. Therefore, optimizing the welding spot layout and analyzing the robustness ofwelding spot layout have great significance.Considering the influence of welding spot on first order modal frequency, stiffnessand strength under bending condition and torsion condition, the welding spot of cab isdivided based on first order modal strain energy density, torsion strain energy density andbending strain energy density. Then the welding spot layout of cab is optimized bytopology optimization method. The welding spot layout robustness before and afteroptimization is analyzed. The main research work is as follows:(1) The static stiffness and low modal frequency of cab body in white is analyzed, andthe first order modal strain energy density, torsion strain energy density and bending strainenergy density of welding spot can be gotten, which is the basis for welding spot layoutoptimization. (2)Based on the element strain energy density of welding spot, the welding spot layoutof cab is optimized. Setting all the welding spot of cab as design variable, welding spotvolume as constraint condition, maximizing the first order modal frequency and bendingstiffness as objective function respectively, welding spot layout of cab is optimized usingthe given search method, which is based on first order modal strain energy density andbending strain energy density of welding spot.(3)Topology optimization of welding spot layout of cab is conducted based on theelement strain energy density partition for the cab. Considering the first order modalfrequency, stiffness and strength under bending condition and torsion condition, thewelding spot of cab is divided into two areas of A and B based on element strain energydensity of welding spot. Set the welding spots with higher first order modal strain energydensity, torsion strain energy density and bending strain energy density as area A, and theother welding spots are set as area B. In order to strengthen welding spot connections inarea A, increase welding spot number in this area and set the increased welding spots asarea C. In order to ensure the structure performance of cab, at the same time increasing aproper number of welding spots in area A, topology optimization is conducted in area Band area C. Then a reasonable welding spot layout of cab is gotten.(4) The welding spot layout robustness of cab body in white is analyzed. Two kindsof method are used to select failure welding spots, and first order modal frequency andstatic stiffness is analyzed. Then the welding spot layout robustness of cab before and afteroptimization is analyzed based on first order modal frequency and static stiffness variation.The two selecting failure welding spot methods are: selecting welding spot with higher firstorder modal strain energy density, torsion strain energy density and bending strain energydensity to failure; ensuring welding spots with higher first order modal strain energydensity, torsion strain energy density and bending strain energy density not to failure,selecting welding spots with lower strain energy density to failure. Through comparison ofresults, welding spot layout robustness of cab after optimization is improved. |
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