A constitutive model for anisotropic tubes incorporating the variation of contractile strain ratio with deformation

The contractile strain ratio (CSR) is an important index measuring the anisotropy of tubes. The values of CSR vary non-linearly with the amount of plastic deformation. However, up to now, there are no constitutive models which are able to take this variation into account. In order to obtain the actual deformation characteristics and improve the prediction capability for plastic deformation processes of anisotropic tubes, this study developed an elasto-plastic constitutive model based on Hills 48 anisotropic yield function. In this constitutive model, the variation in CSR with plastic deformation was considered. A user material subroutine VUMAT incorporating the constitutive model was developed based on ABAQUS/Explicit platform. The comparisons between the finite element (FE) simulations and experiments for uniaxial tension, uniaxial compression and numerical control (NC) bending process of Ti-3Al-2.5 V titanium alloy anisotropic tube, show that this constitutive model is reliable. The simulation accuracy was improved and the plastic deformation characteristics could be better described for the anisotropic tubes by using this constitutive model.