| The tailor-welded-blank gained more and more attention in auto industry because of itsadvantages, such as improving the production efficiency, reducing the production cost, savingenergy to adapt to the environmental protection and increasing security. Stretch bendingforming is an important forming method of bending forming of profile. It has been widelyused in many fields with high accuracy, good film parts, and surface quality advantages. Withthe deepening research of tailor–welded-blank technique and the development of itstechnology in recent years, tailor–welded-blank have been used in automotive body structuralparts, such as frame structure, outer cover, inside cover, door pillar and door panels.Tailor–welded-blank structural part can get complicated welding structural components, andpromote the development of the body structural part of the integrated design andmanufacturing technology by bending forming.This paper mainly research on stretch bending forming of tailor-welded-blank structuralpart, the reasonable process plan of stretch bending technique was determined and optimized.Comparative analysis of the similarities and differences tailor–welded-blank structural partwith a single structural component forming quality laws, the main contents and conclusionsare as follows:Firstly, the tensile tests were done for base metal, tailor–welded-blank and welded joint,and it found that welded break was inward-arc shape for the―equal strain-unequal stressstate‖of welded joint. The crack sites of samples were all at the angle of45degrees ofspherical convex in the cupping test, though the specific sites were not identical. Thenmetallographic observation and hardness test was done for welding spot, and found that thehardness of welded joint is higher than base metal and it’s inverse for plasticity, because ofthat pearlite with coarse grain and high hardness was formed in the welded area for rapidthermal cycle of heating and cooling.Secondly, the3D and variable curvature structure feature of tailor-welded-blank partswas established after structural analysis, then the feeding way and layout was determined. Thespace shape, forming and location auxiliary planes were built in UGNX, then the stretchbending die-surface fixing to the structural part was obtained.Thirdly, the3D guide line of stretch bending part was projected into two plane guidelines and then modified. Then the modified plane guide lines were extruded into two surfacesand the intersection line of them was the modified guide line, so the stretch bendingdie-surface can be modified base on it. Fourthly, the orthogonal test of stretch bending forming for tailor–welded-blank showsthat the profile of outer line, reinforced surface and pocket surface are mainly affected by theextension force and the profile of inner and outer surface are mainly affected by the rotationangle, but the profile of inner line is almost unaffected.Fifthly, the multi-objective optimization was done with the grey relational degree andfinds that the second group of stretch bending forming process parameters is the best one, andthe parameters are the first rotation angle4°, the second rotation angle12°,the third rotationangle18°,the fourth rotation angle23°, the extension force38.5kN.Sixthly, the rules of forming quality between tailor–welded-blank and SPCD stretchbending parts were compared and analyzed. Then it discovered that the influences of eachprocess parameter were consistent in aspects of the profile of inner and outer line, the profileof reinforced surface, the profile of inner and outer surface, but different in the profile ofpocket surface for that the tailor–welded-blank parts are more stable. |
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