Research On Springback Prediction And Control Method Of Complex Cross-sectional Ultra High Strength Steel In Cold Roll Forming

In recent years,automotive lightweighting become a new kind of inevitable trend for affordability and cost,fuel efficiency and environment.Advanced High-Strength Steels(AHSS)and Ultra High-Strength steels(UHSS)is increasingly used in automotive industry to reduce weight and improve consumers’ safety.Compared with the stamping,cold roll forming is an economical and efficient method for the production of constant-section parts with high measurement accuracy without changing the material thickness.One major defect in AHSS and UHSS roll forming process is their high tendency to springback,which often results in undesired product shapes to hinder their wider application in the automotive industry.However,control springback in cold roll forming is one of the crucial problems to be solved for ensuring dimensional tolerance.With the support of the Ministry of Science and Teachnolog’s Innovative Methods Work(2016IM010300)and to meet lightweight structure service requirements,the present work aims to explore the main factors that influence the UHSS sheet springback in cold roll forming by the combination of the basic experiment,theoretical analytical modeling,finite element numerical simulation,industrial test and application method.Integration of Springback Control mothod is general to compensate the UHSS springback in cold roll forming to meet automobile lightweight user requirements by studing of the UHSS material properties and the process of complex cross-sectional in cold roll forming.The main work in this paper is as follows.(1)This paper present one model which discrible the Young’s modulus variation,the anisotropic yield,kinematic hardening.One 3D finite element analysis(FEA)model have been built to investigate the cold roll forming complex cross-sectional UHSS process.The springback prediction was significantly improved by the model.Uniaxial and loading-unloading-loading cycle tests are introduced to determine the Young’s modulus variation.Three different yield criteria,Hill-48,Barlat-89,and Yld2000-2d are evaluated in the present investigation for accurate springback prediction in cold roll forming complex cross-sectional UHSS.It was show that the Young’s modulus variation,Yld-2000-2d yield criteria and kinematic hardening model was significantly improved the springback prediction in cold roll forming complex cross-sectional UHSS.It was found that implicit computation method and solid-shell element type can improve the springback prediction accuracy effectively in cold roll forming.Furemore,the use of solid-shell elements and the appropriate integration points led to a significant reduction in CPU time and can accurate springback prediction in cold roll forming complex cross-sectional UHSS.The springback prediction values were in good agreement with experimental in cold roll forming complex cross-sectional UHSS.It is provided an efficient method in cold roll forming complex cross-sectional UHSS research.(2)Based on experiment and FEA numerical simulation,the UDT(USTB-Durable T)forming model was built.The major reasons for the development of springback in a cold roll forming part are presented.The effect of forming strategy,process parameters and geometric parameters is discussed.Compared to namaste strategy and platform strategy,the UDT strategy have been reduced the springback angle in cold roll forming complex cross-sectional steel UHSS steel.Combined with the direction of the wind rose diagram method,a nonlinear regression method was applied to evaluate its effect on the UHSS material springback by using Minitab software.Results indicate that the forming angle increment,loading pattern,bending radius and bottom line strategy have the greatest impacts on springback and transverse strains in the bending regions.The results also showed that compared with other factors,lubrication conditionand forming speed have the least effects on springback in cold roll forming.(3)Based on the small radius compensation method,the reverse bending compensation method and over bending of UHSS strip compensation method,one new UDI method(USTB-Durable Integration of Springback Control)was established for providing one basis theory to control springback of complex cross-sectional UHSS in cold roll forming.It show that the UDI method effectively solve the UHSS springback problem in cold roll forming.The findings were applied to eliminate anticollision beam and side impact beams.The products steel with high quality is produced.