Ductile fracture prediction of titanium foil based on shear-modified GTN damage model considering size effect

Uniaxial tensile of 0.1 mm TA1 foils with different grain size were conducted to analyze size effect on tensile behaviors. As the grain size increases, the true stress increases while the elongation and fraction of twins decrease, and the fracture mode changes from ductile to quasi-cleavage and ultimately to cleavage fracture. Thus this paper established a microscale damage model considering the size effect, and introduced the J-GTN damage model to adapt to the complex stress state, and the parameters were calibrated through tensile, shear and compression tests. VUMAT subroutine was written and embedded in Abaqus software to simulate the fracture process of the sample under various stress states. The simulation results of cracks agree well with the experimental ones. This model can accurately predict the crack initiation and the final failure, which indicates that it is feasibility and accuracy in the prediction of titanium foil microforming.