The Study on Control of Bending Springback and Die-Face Compensation Technology of Tailor-Welded Blanks

With the advantages such as lowering manufacturing cost, vehicle weight reduction and safety improvement, etc, tailor-welded blanks(TWBs) are more and more adopted to form auto panels, and have brought out remarkable economic and social results. However, there are also some technical problems, such as cracking, wrinkling, weld-line movement and springback, etc, in punching. Researchers have done a great deal of works on cracking, wrinkling and weld-line movement, but little work has done on springback.Bending, with springback as its uppermost forming problem, is one of the commonest forming manner; and the U-channel is a typical part, so the study of springback of U-channel is representative and significative. In this thesis, the springback of TWBs was researched with the springcack of flangeless U-channel for example ,with the methods of arc bottoming and stretch bending trimming cut. The main contents are presented as follows:1. Theoretical analysis. The principle of bending springback of blank was analyzed theoretically. The springback formulas of TWBs were expounded. The forming character of U-channel bending and the principle of arc bottoming and stretch bending trimming cut were discussed. The methods that control the springback were summarized.2. The FEA simulation of U-channel of TWBs. The key factors that influence the springback simulation precision were analyzed; The numerical model for TWBs considering weld-line and geometrical central coincidence was created; The influences of correction angle, pad force, punch profile radius and die gaps of arc bottoming method, and constant blank holding forces (BHFs) and variable BHFs of stretch bending trimming cut technique upon TWBs U-channel were researched and compared with blanks, and orthogonal test were adopted. Results show that, right processing parameter in arc botoming and appropriate BHFs in stretch bending trimming cut ,especially the variable BHFs, could keep the springback of flangeless U-channel within the scope allowed. At last ,the results were validated by experiment, which proved the credibility of simulation.3. Tools shape design base on reserve springback compensation. For 0.8/1.2mm TWBs with longitudinal weld line, the reserve springback compensation technique was adopted to study the springback control problem. Through step-by-step iterative simulation, trimming cut, reserve springback compensation, the tools that could compensation the springback were designed, and the flangeless U-channel accorded with the precision was gained.Arc bottoming method and stretch bending trimming cut technique were effective measures to control the springback. The first method is easy, but the configuration of the tools is complicated; the latter has more technics that is the trimming cut than first method, but it could realized the diversification of BHFs, and the effects is very obviously Tools shape design base on reserve springback compensation could greatly reduce the cost and time.Every method has its’applied rangle and must be collected rationalization.