2.1.2. Models

The constitutive equation used to model material behavior in the FE model was the Johnson–Cook model equation shown in Equation (1), coupled with the Johnson–Cook damage model shown in Equation (2) [10],

where σ¯ is the equivalent stress, A is the yield stress initially, B is the hardening modulus, C is the strain rate factor, n is the work hardening exponent, m is the thermal softening coefficient, T_room is the room temperature and T_melt the melting temperature.

where Δ∈¯ is the increment in plastic strain, σm is the average of the 3 normal stresses and σ¯ is the von Mises equivalent stress, calculated from Equation (1). Fracture occurs and the element is removed from the computation when D reaches a value of 1.0 [11]. The Johnson–Cook material values A, B, C, n and m were set as 987.8 MPa, 761.5 MPa, 0.01516, 0.41433 and 1.516, respectively, while the damage model values D₁, D₂, D₃, D₄ and D₅ were set as −0.09, 0.25, −0.5, 0.014 and 3.87, respectively [1].