Simulation of failure processes of as-cast Ti-5Al-5Nb-1Mo-1V-1Fe titanium alloy subjected to quasi-static uniaxial tensile testing

A three-dimensional (3D) microscopic structural finite element model reflecting the realistic pore distribution of as-cast Ti-5Al-5Nb-1Mo-1V-1Fe titanium alloy was built through micro-computed tomography (micro-CT). The model was then introduced into ANSYS LS-DYNA software to investigate the 3D spatial evolution process of damage and failure under quasi-static uniaxial tension. To validate the simulation results, we tested the uniaxial tensile responses of Ti-5Al-5Nb-1Mo-1V-1Fe and quantitatively characterized the tensile fracture morphology with a 3D profilometer. To reveal the underlying mechanism of damage and failure, we took the triaxiality of R_σ into consideration. Local principal stress concentration was found to exist around two micro-pores at the initial stage, thus inducing two crack sources; as the load increased, more crack sources were generated and steadily propagated through void growth and coalescence under the influence of multiaxial principal stress concentration, thus leading to the local tensile failure of the model. When cracks reached a critical size, the shear stress concentration became the dominant factor affecting failure, thus inducing severe effective plastic strain between cracks. The cracks rapidly connected through plastic slip and cleavage, thereby resulting in the final shear failure of the model. The simulation results were in good agreement with the observed experimental results.