A phase field model for high-speed impact based on the updated Lagrangian formulation

Abstract

High-speed impact problems usually undergo a form of highly localized plastic deformation under high strain rate with intense shock waves. In this paper, we present a coupled phase field model to simulate fracture in these situations. Our model considers the dynamic finite deformation with both strain hardening and strain rate hardening by the Johnson–Cook plasticity model. In particular, the formulation is posed in an updated Lagrangian framework and the constitutive update is realized with a return-mapping algorithm. Considering the tension–compression asymmetry, a new history variable is developed to enforce the irreversibility condition of crack propagation. The effectiveness of the proposed method is validated with a numerical example of 45 steel impact experiment along with two numerical simulations of split Hopkinson bar experiments on concrete and aluminum alloy specimens, where strong shock waves are generated. Besides, the effect of a few parameters is studied, namely, the regularization length parameter, the energy release rate, the initial impact velocity, and parameters of the Johnson–Cook model. These show the correct trend in terms of the time and extent of crack propagation.