Study On Twist Springback And Compensation In Stamping Forming Process Of High Strength Steel

High strength steel has been widely used in automobile body manufacturing due to its advantages of good lightweight ability and high safety performance.However,the high strength steel can easily generate a large springback after stamping forming,and there will be a serious twist springback for the stamping parts with complex structure,which has an important effect on the product quality and assembly accuracy.To improve the product quality and assembly accuracy,the double C rail of TRIP780 high strength steel is taken as the research object,the numerical analysis and experimental study of twist springback are carried out,and the structure design of die is optimized.The main work is as follows.TRIP780 steel has the characteristic of high strength and high plasticity,and retaines austenite will be transformed into martensite during cold forming,which enhances material plasticity and increases springback.Based on the twist springback characteristic of TRIP780 high strength steel,the die of double C rail with twist springback characteristic is designed,and the corresponding experiments are carried out by YJ32-100 A four-column hydraulic press and Micro575 three-coordinate measuring instrument.Based on ABAQUS software,the stamping forming and twist springback of TRIP780 high strength steel double C rail are simulated by explicit and implicit finite element method.An evaluation index for the twist springback is proposed,which is based on the angle between two lines in different planes.Based on three different hardening models,Ziegler hardening model,Johnson-Cook hardening model and Voce-Chaboche combined hardening model,the influence of different hardening models on the prediction accuracy of twist springback for double C rail is analyzed.In order to improve the precision of finite element model of double C rail and realize the accurate prediction of twsit springback,the parameters of Voce-Chaboche combined hardening model are inversed by response surface method and genetic algorithm based on the experimental data.The related factors affecting the twist springback are analyzed by the extreme difference analysis method based on the validated finite element model of double C rail,and the key factors affecting the twist springback are determined.It had provided a theoretical basis for the effective control of the twist springback.Based on finite element model,the twist springback compensation of double C rail is studied.According to the stress distribution and geometric characteristic of the double C rail after stamping,the structure optimization design of die and blank holder surface is carried out.The processive corner of die and macro-texture blank holder(longitudinal texture blank holder and transverse texture blank holder)are designed,and a comprehensive compensation study that combined the processive corner of die with the longitudinal texture blank holder is carried out.The results showed that,the springback angle based on the procressive corner of die is reduced by 23.8 percent.The springback angel based on the longitudinal texture blank holder is reduced by 27.9 percent,and the springback angle based on the transverse texture blank holder is reduced by 21.2 percent.The springback angle based on the processive corner of die and the longitudinal texture blank holder is reduced by 33.6 percent.In conclusion,the comprehensive compensation that combined the processive corner of die with the longitudinal texture blank holder can reduce the twist springback angel of TRIP780 high strength steel double C rail more effectively,and a new idear for the effective control of twist springback is presented.