The titanium tailor-welded blanks (Ti-TWBs) are being developed in different industries such as automobile and aerospace, combining the advantages of both tailor-welded blanks technology and titanium alloys. In recent decades, computer simulation of sheet metal forming processes has been employed increasingly over conventional production test and adjustment methodology to achieve the optimum and cost-effective operation procedures. Recently, certain amounts of theoretical analysis for the sheet metal forming process have been developed. However, these analyses could not be applied directly to the material under multi-stage forming process. Thus, some researchers have developed a damage-based model to predict the instability and failure of sheet metals, particularly for the above Ti-TWBs, with consideration of material damage under discontinuous or proportional loading strain paths. So far this model has been used and proved to be successful to predict formability of selected sheets of steel and aluminium alloy. However, the application of the damage-coupled model has yet to be extended to the Ti-TWBs under thermal multi-stage forming operation.The main objective of this paper is to investigate numerically the formability of Ti-TWBs under multi-stage forming process with experimental verification. Titanium alloy sheets (Ti-6Al-4V) in thickness of 0.7mm and 1.0mm were selected and laser-welded the specimen of Ti-TWBs. The model based on the damage mechanics is introduced to predict the thermal formability of Ti-TWBs with change of strain paths. In this study, the anisotropic damage model incorporate with the finite element codes and user-define material subroutine were developed to predict the formability of Ti-TWBs with change of strain paths. The mechanical properties and damage parameters of Ti-TWBs for the simulation were measured experimentally. The simulation of Ti-TWB under multi-stage forming process were then conducted and validated experimentally at similar forming conditions. The predicted results have been found to agree well with those obtained from the experiments. This analysis can be applied readily to design and manufacture TWB components or structures so as to satisfy the need of such market demands.
Non associated-anisotropic plasticity model fully coupled with isotropic ductile damage for sheet metal forming applications
