Research On Influencing Factors And Control Methods Of Forming Quality Of Tailor-welded Blanks

As an important way to realize lightweight products,TWBs forming has been widely recognized worldwide.However,due to its lower forming performance than the base metal,quality problems are more likely to occur in the forming process.Therefore,the related research on the forming of TWBs has been continued until now.The important factors affecting the forming quality of TWBs include the structure parameters of die,the material properties of base material and the technological parameters in the forming process.Many influencing parameters and various influencing rules,especially the welding seam caused the change of the performance of the sheet metal on both sides compared with the base metal,which caused the whole sheet metal performance to be complicated.The forming process of TWBs becomes complicated.Therefore,it is of great significance to analyze the law and reason of the influence of these parameters on the forming of TWBs and to study the method of improving the forming quality of TWBs by controlling these parameters.By analyzing the forming process of the U-shaped part of the TWBs,a numerical model of the welding seam movement of the U-shaped part of the TWBs is established,and its accuracy is verified by finite element simulation and experiment.Based on the analysis of the forming characteristics of TWBs,the stress distribution in the forming of TWBs is researched by using the stress approximation theory of TWBs,and the welding seam movement of TWBs under the condition of bidirectional drawing is analyzed.In this paper,the parameters affect the forming quality of TWBs box are studied,such as the die structure,process and sheet metal and so on.In this paper,the influence rules of convex and concave die fillet,blank holder force,sheet shape,sheet thickness ratio,friction coefficient and material performance on the maximum drawing depth and bottom seam movement of sheet are studied.The results show that blank holder force,sheet metal thickness ratio,friction coefficient and material property are the main factors affecting the forming quality of TWBs box.In this article,the problems of weld seam movement,wrinkle and thinning in the forming of TWBs box are analyzed by means of simulation.The results show that reducing the weld movement is the key to solve the problem.A method to improve the forming quality of TWBs box by changing the structure of the blank holder and matching the proper blank holder force and friction coefficient is proposed.At the position of flange weld corresponding to the blank holder,a four-block blank holder structure formed by elliptical conical deep drawing rib formed by rotation of an elliptic line is arranged.Through the proper ratio of blank holder force and friction coefficient,this blank holder structure can control the wrinkling,and significantly reduce the amount of welding seam movement and the maximum rate of thinning.The design of the experimental mould,the sheet processing and the establishment of the experimental platform were carried out.The tensile test of the sheet sample was completed.The strain strengthening coefficient and hardening index of the sheet were analyzed.The influence of different blank holder structure,blank holder force,lubrication condition and other parameters on the forming quality of the welded blank box is completed.The results show that the forming quality of the welded blank can be improved effectively by the structure of four blank holder with drawing rib,the proper blank holder force and the reduction of friction coefficient of the strong plate.