Research On Springback Characteristic And Prediction Accuracy Control Of Advanced High Strength Steel Automobile Beam Parts

Beam parts are the main structural components of automobile, also a large proportion of the automobile body panels. The stamping of automobile beam parts necessarily accompanies elastic deformation at the same time of plastic forming. Springback is the recovery of elastic deformation after external force unloading. The trimming parts after forming will also lead to springback, because of stress redistribution caused by shape change. It is inevitable during the forming process, can lead to size change which is a serious assembly problem, affects the stability and safety of automobile structure. The greater the yield strength of material the greater the springback, with the lightweight development process of automobile, the beam parts springback caused by high strength steel instead of traditional steel is more and more obvious.To accurately predict and effectively control springback, using the method of theory analysis and combination of numerical simulation with experiment, research has been done on the springback regularity and control of advanced high strength steel beam parts. Analyze the influence of unit type and size, integral point number in the direction of thickness, constraint condition, formula, time step and virtual drawing speed to springback accuracy in the numerical simulation process. Conclusion of research on the springback experiment and numerical simulation of U-shaped part is that the springback decreases with the increment of blank holder force and draw bead resistance, increases first and then decreases with the increment of sheet thickness, in a certain degree, it decreases with the increment of friction coefficient. Through numerical simulation of S-shaped beam springback, propose the method of measuring the section line angle in pretreatment. Adopt die profile compensation to inclined wall U-shaped beam, shape of the part after springback is similar to the standard shape, so the springback harm is eliminated.Take the behind beam for example, do some numerical simulation on these automobile beam parts which have complex profiles. Propose the method of dividing grids of tools according to the distinguish surfaces of deformation zone. Through analysis, the method of concrete calculating time step and single point constraint according to behind beam is obtained, and put forward the segmentation method of numerical simulation on springback. Predict the maximum displacement and position of unloading springback and trimming springback of the behind beam on the basis of controlling forming defects. Summarize the springback control scheme of matching blank holder force and draw bead resistance. Verified by test drawing, springback of the behind beam is decreased effectively with the optimized scheme.