PSI - Issue 71

Nikhil Andraskar et al. / Procedia Structural Integrity 71 (2025) 158–163

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The JH-2 material model Johnson et al. (1994) comprises of three models, strength, damage and fracture. The strength model predicts the behavior of the material to the applied load. This model describes elastic deformation, plastic deformation, and the effect of strain rate on the yield strength of the material. The damage model describes the degradation in the material at elevated loading conditions. This helps quantify the accumulated damage in the material, the strength reduction in the material as damage increases, and the threshold point where damage starts to occur in the material. The fracture model describes fracture initiation, propagation and energy required for crack propagation. The detailed equations for all models are mentioned in Johnson et al. (1994). 2.2 Johnson-Cook material model (JC) The JC material model is employed to characterize the nature of metals under high strain rate loading. It incorporates aspects of strain hardening, sensitivity to strain rate, and criteria for failure. The equations for this model have been used in many literatures. Johnson et al. (1983) The material parameters for fragment-simulating projectile are taken from Khan et al. (2020). 3. Numerical modelling Finite element simulations were performed on ANSYS/LS-DYNA explicit code. The fragment-simulating projectile was modeled using 8-noded hexahedral elements using the element size of 0.25 mm. The size of this element was established according to the mesh convergence criteria, resulting in a total of 12,625 elements. The meshing and the dimensions of the fragment-simulating projectile is mentioned in Fig. 1. For the alumina plate, 8-noded hexahedral elements were used with a mesh size of 0.25 mm and 960000 total elements. The alumina plate had a thickness of 6 mm and dimensions of 50 mm × 50 mm as shown in Fig. 2. The alumina plate was supported using two simple rigid supports during the impact with a projectile. The whole arrangement is as shown in the Fig. 3. An eroding surface-to surface contact was implemented between the projectile and the target surface. The coefficient of friction value was taken as 0.1. The alumina plate and rigid support have automatic surface-to-surface contact and frictionless contact is assumed. The movement of rigid supports is restricted in all directions. The projectile is given velocity using the velocity generation card and velocities of 100 to 800 m/s were used.

Fig. 1. Meshing and dimension of fragment simulating projectile

Fig. 2. Meshing and dimension of alumina plate

Fig. 3. FEM model setup of projectile and target