Penetration failure behavior of ultra-high strength steel projectile/target

With the widespread application of ultra-high strength steel in warheads and protective structures, accurately characterizing its failure behavior under high-speed impact loading is crucial for projectile structural optimization and protection design. Firstly, three classical fracture criteria, Johnson-Cook (J-C), Bao-Wierzbicki (B-W) and Modified Mohr-Coulomb (MMC) were selected, and the effects of strain rate and temperature were introduced into the B-W and MMC fracture criteria. Besides, the J-C strength model was modified based on the Ludwik-Voce strain hardening law. Then, the constitutive model parameters of ultra-high strength steel were determined from the existing static and dynamic test data, and the constitutive model was implemented into Abaqus/Explicit program via a VUMAT user-defined subroutine. The reliability of the proposed fracture criteria and strength model parameters was validated by comparing the deformations and failure modes of specimens in Taylor bar impact tests. Finally, numerical simulations were conducted for typical projectile broken scenarios, including the ultra-high strength steel projectiles penetrating steel plates, armored steel composite structures, and corundum rubble concrete target. By comparing the projectile/target failure modes and the instantaneous contours of stress state parameters, the prediction accuracy of the above three fracture criteria was quantitatively evaluated, revealing the influence mechanisms of stress triaxiality and Lode angle parameters on the failure behavior of ultra-high strength steel projectile/target. The results show that the penetration failure behavior of projectile/target is affected by the coupled high strain rate, multiaxial stress state and local shear mechanism. The J-C criterion only depends on the stress triaxiality, which makes it difficult to characterize the shear-dominated failure mode. Although the B-W criterion accounts for the piecewise characteristics of stress triaxiality, it exhibits large prediction deviations under the tension/compression-shear coupling stress state. The MMC criterion accurately reproduces the failure characteristics of the projectile nose shear sharpening, shell fragmentation, target plate tearing failure and shear plugging during penetration by coupling the Lode angle parameter and the stress triaxiality.