The Numerical Study Of Defects Of Material Effect On Hole Flanging Forming

With the rapid development of the automobile industry in our country, the product is more and more diversified and complicated, covering parts forming technology has also been pushing enhances unceasingly. Most of automobile covering parts need flanging process, and the flanging quality of parts has great influence on the quality of vehicle. In the process of practical production, blank with various initial defects is inevitable, the different defect type and degree has different impact on the result of the process. With the development of product diversification and complication of parts process, and high demand on the quality of products,The influence of initial defects on the forming quality of sheet metal is becoming more and more important, and it has become a hot research topic.At present, whether in the domestic or foreign research environment of the sheet metal forming, hole flanging forming process of less study relative to other processes. In the hole flanging process study, the calculation formula about the hole flanging height has certain theoretical flaw, but the previous few involved here, and took a direct use this formula to carry out the study. In order to make the hole flanging height formula of calculation is more tally with the concrete engineering practice, this paper makes a concrete analysis and correction of formula. The study of hole flanging process is mostly about the effects of process parameters on sheet metal forming quality, few involved in the important factors of initial blank defects. Therefore, study on the hole flanging process in sheet metal effect of initial defects on the forming quality is very necessary. In this paper, based on the above background, the following is the main content:(1) Which have analyzed the forming process of hole flanging and the forming characteristics on theoretical, At one time, have analyzed the factors of affecting forming.(2) The formation, growth and polymerization process of the initial defects in sheet materials are studied by theory and experiment, and introduced the BAMMAN_DAMAGE material model with initial void ratio defects.(3) Which have analyzed the defects of formula, which is used to calculate the hole flanging height, from the principle. Then used the plastic deformation before and after the material volume invariance principle, and according to the actual engineering practice,launched a new hole flanging height calculation formula, and verify the rationality.(4) In the hole flanging process based on using ANSYS_LS-DYNA finite element analysis software established two finite element model with defects to do analysis of CAE.Used the characteristics of two models, respectively studied the influence on forming limit byinitial defects of materials, and the influence on stress-strain distribution, and the influence on Material thinning rate and so on.