PSI - Issue 37

Theodosios Stergiou et al. / Procedia Structural Integrity 37 (2022) 250–256 T. Stergiou et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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2012). As a result of the highly non-linear region in the true stress-true strain relationship in the vicinity of the yield strength, a modified JC constitutive relation was selected with four additional parameters characterising the dependency of the flow stress on the plastic strain. Fig. 1 illustrates the true stress-strain profile of the AlMg6 target and the proposed model capabilities in describing the constitutive behaviour.

Fig. 1: Results of uniaxial tensile experiments (solid lines) and numerical simulations (dashed lines) for target material.

2.2. Projectile information A 50 g projectile can be described as having a plate-like, non-axisymmetric geometry, with a central vertex of varying sharpness at its impacting region (Fig. 2a). The width and thickness of the projectile were kept constant at 46 mm and 5 mm, respectively, while its length varied to ensure the constant projectile ’s volume. The projectile ’s half angle ( ̂) varied from 15° to 90°, with the lower limit representing the minimum half-angle possible for this configuration (having a zero-shank length) and the higher one corresponding to the blunt-impact configuration. The projectile was made of Ti-6Al-4V, and its condition after impact, as extracted from experimental observations, suggested that it experienced no visible permanent deformation during its interaction with the target. Therefore, to simplify the numerical analysis, the projectile was assumed as a rigid body.

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Fig. 2: (a) Projectile geometry showing some critical parameters. (b) Footage from experimental testing that presents the target failure by transverse tearing mechanism.

2.3. Numerical modelling An explicit scheme was used to solve the system of dynamic equations of motion, with deformations calculated at