The Research On Simulation And Optimization For Forming Of B-pillar Made Of Hsstwb

High strength steel tailor welded blank (HSSTWB) is an advanced processing technology, which based on laser welding technology and high strength steel technology. HSSTWBs are blanks of similar or dissimilar thickness, materials, coatings, etc. welded in a single plane before forming to meet the strength requirements of different area of the part. The main advantages of using a HSSTWB are as follows:(1) weight reduction, (2) energy-conserving and environment-protective, (3) improved safety performance, (4) reduced manufacturing costs due to fewer forming dies etc.. Now, auto parts such as cover parts, body frame parts, door inner panels, beams and so can be made of HSSTWBs. However, technical problems are often encountered in forming HSSTWB parts, including crack, wrinkle, weld-line movement and large springback, for the negative effect of heat affected zone, strength difference and thickness difference. These problems have become the practical difficulties in application of HSSTWB.In this paper, combination methods of numerical simulation and experimental study were used. Single factor experiment design, orthogonal design, artificial neural networks, genetic algorithms and technics experiment were applied to optimize the drawing process parameters, blank shapes and materials, drawbead, blank holder and other aspects of B-pillar. And the purpose of this paper is to obtain the technology law, to complete the drawing process optimization system for HSSTWB part and solve problems of application for HSSTWB in the domestic automobile industry.First, to discover the law between forming process parameters and quality, a single factor method was applied to study B- pillar based on numerical simulation. And the forming process of B-pillar was optimized using orthogonal design. Studies show that the B-pillar will get the best quality when punch speed is 3000 mm/s, die gap is 0.9t, friction coefficient is 0.105, blank holder force is 100 tons and die radius is 6mm. Second, the blank shape and material were optimized based on MSTEP. Studies show that blanking program A had better forming quality, and the selection of material B340/590 was reasonable. Third, the multi-objective optimization model of B-pillar between drawbead resistance value and forming properties were established, and the value of drawbead resistance was optimized to avoid defects and obtain good formability by genetic algorithm (GA). Forth, the blank holder was redesigned to accommodate the thickness difference of HSSTWB. Simulations demonstrated that the stepped binder can effectively improve weld-line movement, reduce material thinning and springback. Finally, dies were designed and manufactured according to the optimization results, and experiments were carried out to verify the optimization results.