Research On Discrete Blank-holder Forming Process And Numerical Simulation For Deep Drawing Parts

Deep drawing is a large branch of sheet metal forming, having advantages of a stableproduct size, good-looking appearance, short processing time and high material utilization, etc.So it is playing a vital role in industrial production. Deep drawing often requires the use ofblank-holder device. Blank-Holder Force (BHF) for drawing parts has an important impact onforming quality. When forming simple parts, proper BHF can make blank maintain a steady statebefore entering the die. However, when forming complex parts, unreasonable BHF distribution isprone to wrinkling, cracking and other defects. With the curved shape of aluminum alloy, highstrength steel becoming increasingly complex and the widespread use of these poor formabilitymaterials, the traditional way of blank-holder forming has seriously hampered the developmentof deep drawing process.Through reference to flexible drawing forming process thoughts, discrete blank formingprocess is proposed combining multi-point forming and die forming technology. By usingcommon discrete blank blocks instead of the traditional deep drawing rigid blank-holder device,parts’ surface is formed with whole mold cavity surface. By adjusting the value of theindependent BHF to control material flow, restrain wrinkle, cracks and other defects, it has goodcontrollability.The main contents and conclusions are summarized as follows:1. The process of discrete black-holder forming and experimental research.Discrete blank-holder forming process has been systematically studied, including the designof equipment, the basic principles and technical characteristics of the process. The key parts ofblank block were designed. It was concluded that the use of multiple discrete blocks and thework-part die cavity can achieve the experiment by discrete blank-holder forming experiment forbox and irregular shape parts. The good quality parts proved that the technology was feasible.2. Build finite element model.Discuss the continuum mechanics equations, virtual work principle and materialsconstitutive relation. The finite element models of blank-holder and discrete blank-holder were established. The theoretical basis of numerical simulation for discrete blank-holder formingprocess was laid by introducing how to choose material model, define boundary conditions andmesh.3. The comparative analysis between blank-holder and discrete blank-holder formingprocess for spherical parts.The criteria of wrinkling and cracking were proposed. Blank-holder and discreteblank-holder forming process for spherical parts were analyzed, including stress curves,thickness variation curves and spring-back curves. The results showed that: the discrete way wasslightly better than the other way, but the difference was very little.4. The comparative analysis between blank-holder and discrete blank-holder formingprocess for box-shaped parts.Taking180×80mm box-shaped parts as the research object, discrete blank-holder formingprocess can reach the depth of70mm by numerical simulation. Blank-holder reaches the depth of40mm by adjusting independent BHF distribution. Discrete blank-holder forming processsignificantly improved the forming ability for the work-part. The results showed that: discreteblank-holder forming process was much better than the other way and could avoid wrinkling andcracking by adjusting independent BHF distribution. It verified that the discrete blank-holderway was feasible.5. The discrete blank-holder forming process for car fender.Taking the car fender as example, the effects of parameters for discrete blank-holder formingwere studied. Studies have shown that the force value, force distribution, thickness of flexibleblank-holder, friction coefficient, the blank block coverage and blank shapes of discreteblank-holder forming properties had a great influence on results. Based on the results of theprocess parameters, the optimal result was obtained by constantly adjusting various parameters.The results showed that: the discrete blank-holder forming process could achieve car fender partswithout using draw-beads, and forming results were good.