The Finite Element Method And Study Of Experiment For The Hybrid Segmental-blank-holder Method Of Square Box In Deep Drawing

Wrinkling and fracture are common defects in deep drawing.The holding forces are different in each position of the flange area because the thickness is different in forming process.The wrinkling tendency increase when the BHF(blank holding force)become small while the fracture risk increase and the forming limit decrease when the blank holding force become large.The blank holding method and the controlling methods of BHF are always hot for study and important in techniques investigation.Firstly,the hybrid segmental-blank-holder method in which the straight edge area and the circular area are pressed with the circumferential segmental-blank-holder method and the fillet corner area is pressed with the radial segmental-blank-holder method is more accessible in forming process.What's more,the radial segmental-blank-holder method for the straight edge area is also investigated,in which the blank holder in the straight edge area is divided into to components.The best ratio of blank holding forces in the straight edge area and the fillet corner area is 0.8:1 while the best ratio of blank holding forces of the inner and the outer blank holders is 1.5:1.The influence factors including the radius of the convex punch and the concave die,friction and the shape of blank are analysed using FE(finite element)method.Afterwards,the square box formed in modules including the integral blank holder method,the integral blank-holder-method with the conical convex punch,the integral blank-holder-method with the side-wall blank holder,the hybrid segmental-blank-holder method with the side-wall blank holder are analysed using FE method.Through the comparison of the surface quality,the largest forming height,the thickness distribution and the largest tensile stress,the hybrid segmental-blank-holder method with the side-wall blank holder is confirmed to be the best scheme to produce a square box part.The segmentation method and position are determined based on the thickness distribution gradient law,in which the fillet corner area of the flange is pressed by the integral blank holder and the straight edge area was held using the radial segmental-blank-holder method.Finally,the experiments system for forming square box parts is produced including the experiments mould,the hydraulic system and the controlling system.Results show that the experiments system can realize the hybrid segmental-blank-holder method and finish the forming process.Exchange the punch with different straight edge and blank materials based the experiments system,the conclusion can be drew that it is necessary to divided the blank holder in the radial direction based on the segmentation in the circumferential direction.The forming limit can increase nearly 50% with pellicle lubrication than the oil when the other conditions are the same.