Prediction Of Forming Limit For Square-cup Parts Of High Strength Steel TRB In Hot Stamping

With the requirement of lightweight,safety and anti-collision performance of automobile become more and more advanced,the hot stamping technology of high strength steel has been used in automobile structural parts manufacturing,the stamping part was designed with different thickness distribution baesd on its carrying capacity demands,and it realizes the lightweight of automobile from structure and material.However,with the changing of the thickness in TRB,the defects such as the rupture and wrinkle of the parts during the hot stamping process will be more prominent,therefore,it is necessary to make an intensive study of the forming limit of the high-strength steel TRB in hot stamping process.The square-parts as a typical non axisymmetric component in the engineering field,to study its forming limit has a general significance in the studying of the forming property of other automobile panel.According to the stress-strain curve of B1500 HS which obtain by the hot tensile test,a constitutive relation model of B1500 HS TRB which relative to temperature,strain rate and sheet thickness was established in this paper.The Lemaitre and Rice-Tracey ductile fracture criterion of high strength steel TRB in hot forming process was established based on the continuous damage mechanics and mesoscopic damage mechanics,and the numerical simulations and tests are carried out to acquire the material parameters of Ductile Fracture Criterion(DFC).The ABAQUS finite element simulate software was used to study the hot stamping process of high strength steel TRB square-parts which in different blank holder force,different ratio of plate thickness difference and different length of transition zone.And a secondary development of ABAQUS was made based on DFC,and the DFC was put into the results file of simulation to get the forming limit of TRB box hot stamping in different stamping conditions.A high-strength steel TRB square-shaped hot stamping mold and blank holding control system were designed,and the test of the hot stamping limit was carried out based on the mold.The influence of different technological parameters and sheet metal structure on the hot stamping forming limit of high strength steel TRB box parts was studied based on the test.Through numerical simulation and experimental verification,it is concluded that the Lemaitre ductile fracture criterion can predict the fracture accurately of high strength steel TRB in hot stamping and the forecast error of Forming limit is about 6.35%.The reasonable technological parameters of hot stamping forming of high strength steel TRB box parts were obtained by studying the influence of different process parameters on the hot stamping forming limit of high strength steel TRB box parts.