Efficient modelling of the elastoplastic anisotropy of additively manufactured Ti-6Al-4V

The expanded design freedom offered by Additive Manufacture (AM) technologies is stimulating innovation in new directions, but it is also introducing new challenges in material characterisation. The inherent anisotropic behaviour observed in AM materials, like Ti-6Al-4V alloy, is of critical importance to safe and reliable implementation in structurally significant roles. To fully leverage the design freedom offered by AM, an accurate modelling capability is required to characterise this material behaviour. Building on the limited research efforts to date, this paper proposes a model that combines the Hill48 anisotropic yield function with the nonlinear multicomponent Armstrong-Frederick kinematic hardening rule. This model permits the accurate simulation of the anisotropic behaviour of these materials both under monotonic tensile and cyclic elastic-plastic loading. The performance of the model was evaluated by comparing the results of simulation with previously published stepped symmetric strain-controlled experimental data for Ti-6Al-4V fabricated via SLM in the three primary build orientations. An efficient process to establishing the model parameters from limited tests is also presented. The results of the simulations are in good agreement with the experimental data, thus demonstrating the proposed model's capacity to simulate efficiently the difference in cyclic stress-strain evolution between different build orientations.