A Constitutive Model Of Large Strain And Its Application To Twist Springback Simulation

Sheet metal forming and springback numerical simulation is a strong geometric,material and boundary condition nonlinear problem. How to accurately predictspringback has been a important problem both in manufacturing industry and academeSome studies have suggested that the accuracy of the material constitutive model isone of the most important factors that influence the accuracy and reliability of thespringback analysis results. Specially, if the material undergoes inverse loading，modelling of Bauschinger effect and cyclic hardening characteristics of materials is ofvital importance for springback analysis. An accurate constitutive model mustconsider the above two points.Widely using of advance high strength steel in stamp forming process makes theproblem of springback more seriously. The springback between conventional steeland AHSS is different. Springback is one of the key factors influencing the shape andassemble quality of stamping parts. Angle change, curl and twist are three main formsof springback behavior, among which twist is the most difficult one to control andovercome.Around the issues of twist springback of AHSS，main research in this paperinclude the mechanism of twist springback, the prediction of twist springback andtwist springback compensation three aspects.1. Regarding to the diversity of deformation form of twist springback instamping, a generalization is made to summarize those geometry features which areprone to twist springback. Both theoretical and experimental work were done to studythe mechanism of twist springback.2. The Yoshida-Uemori two-surface model along with Von Mises yield functionwas implemented as a UMAT for ABAQUS-Standard using the return mappingalgorithm.3. In the FE simulations, the impacts on twist springback from multipleconstitutive model, including isotropic hardening constitutive model、 kinematichardening constitutive model and two surface constitutive model were analyzed. Atwist springback feature die and a measuring tool are designed.4. Springback compensation of AHSS has been studied based on displacementadjustment method.