Numerical Simulation And Forming Process Research On Multi-point Forming For High Strengh Steel Sheet

With the development of modernization, the using of high strength steel in ships, cars,airplanes, etc. continues to increase. Traditional forming process of high-strength steel are lineheating technology and laser bending technology with the characteristic of low degree ofautomation, low productivity, poor woking environment etc, which can not achieveadvantageous position in the competition. In order to meet the needs of society and enhancemarket competitiveness, those companies need to optimize the production process of theirproducts constantly. Multi-point forming technology is a forming process with high degree ofautomation and high productivity, which changes the traditional mold forming method withbasic unit of a set of rules instead of the traditional whole mold，thus complex surfaces can beachieved by adjusting the height of the basic unit. As the workpiece in the ship, aircraft andother military product is relatively large, which makes the overall cost increase if we choose thetraditional mold forming process. The multi-point forming process can achieve large parts inthe small device, which reduces manufacturing costs.High strength steel with high yield strength is not easy to form in the forming process,because of the springback, wrinkle, low forming accuracy and other defects and formingaccuracy. In order to reduce defect, asymmetric multi-point forming process parameters andsegment-shaped transition zone selection parameters are simulated and optimized with themethod of finite element numerical simulation.(1) Introduce the theory of finite element analysis and multi-segmented and asymmetricmulti-die finite element model are established by combining with structural features ofmulti-point mold, elastic pad and high strength steel. At the same time exploring the unit,definition of boundary conditions and methods of load are explored. Analysising the demand oftransition zone in Multi-segment molding process and a reasonable transition zone areestablished by CAD/CAM.(2) The effect of elastic pad thickness and multi-steps on wrinkle was discussed byanalysising the model’s feature. Limit diagrams about the relationship between the thickness of elastic pad and parts’ radii are designed by numerical simulation. It will play guiding role inreducing wrinkle and selecting elastic pad. At the same time the method of asymmetric multimold is raised. Analysising the impact on forming different target parts and different materialsin asymmetric multi mold, and the stress-strain distribution in target parts are discussed.(3) The parts quality of sectional multi-point forming process become much more betterobvious by compare with the result of one-step forming and non-overlapping.As the yieldstrength of high strength steel is high，and the value of springback is more biger Compare thesimulation result of high strength steel with the result of08AL，the method of springbackcompensation is used to improve the quality of parts At the same time analysis the effect of thespring steel’s thickness.(4) Analysis the factors of high-strength steel segments forming process in detail andsimulates them to verify and get the conclusion: With the increase of the length of the transitionzone, the wrinkle of high-strength steel will reduce even disappear; With the increase of theslope of the end of the transition region, the wrinkle will gradually increase; The springbackwill be smaller when the shape of the end of the transition zone is a straight line than that ofcurve, which will reduce the forming error.