Modelling of mandrel rotary draw bending for accurate twist springback prediction of an asymmetric thin-walled tube

Of particular interest and complexity are twist springback of an asymmetric thin-walled tube in mandrel rotary draw bending (MRDB), which is a complex non-linear physical process with coupling multi-factor interactive effects. The aim of this paper is to explore the source of twist springback and develop a more effective numerical model. First, this paper analyses the torsion moment and twist angle relationship subjected to non-homogeneous loading. Second, non-quadratic anisotropic yield criterion (Yld2000-2d) integrated with mixed isotropic and kinematic hardening can be used to describe the material properties including anisotropy and Bauschinger effect. The corresponding mechanical tests are performed through uniaxial tension tests and monotonic and forward-reverse shear tests. Third, to improve the accuracy of the finite element model, the surface-based coupling HINGE constraint for flexible mandrel is developed and compared with the previous models. The frictions on various die-tube interfaces are identified by means of numerical inverse model. The validity of the FE model is assessed by comparing the predicted twist springback with the experimental one. The results show that the developed FE model with surface-based HINGE constraint has higher precision of twist springback prediction. The interfacial frictions have significant effects on twist springback of asymmetric thin-walled tube. (C) 2014 Elsevier B.V. All rights reserved.