X. Teng

EFFECT OF FRACTURE CRITERIA ON HIGH VELOCITY PERFORATION OF THIN BEAMS

An adequate ductile fracture locus has to be developed to reasonably model crack initiation and propagation in high velocity impact. Most of the fracture loci in the literature were proposed on the basis of tensile tests while in high velocity impact cracks usually occur in the region where shear and compression are dominant. In this paper, perforation response of a thin beam struck by a rigid, blunt projectile moving at a high velocity is simulated using, respectively, uniform fracture strain, Johnson-Cooks, and Bao-Wierzbickis fracture locus for 2024-T351 aluminum alloy. The former two predict that materials in the impacted area of the beam beneath the rigid mass fail layer by layer, which is not consistent with experimental observations. By contrary, Bao-Wierzbickis fracture locus, which was developed from up-setting, shear and tensile tests, and covers the whole range of the stress triaxiality, is capable of capturing all of the features occurring in the whole failure process. Numerical results reveal that the beam would fail by shear plugging at a high impact velocity and by tensile tearing at a velocity near the ballistic limit.

Crush response of an inclined beam-column

Abstract Crush response of an inclined, inelastic clamped-sliding beam is investigated in this paper based on the assumption that the material elastic–plastic, nonlinear strain-hardening stress–strain relation is of a power-law form. Analytical expressions for crush resistance, deformation, bending moment, and energy are obtained in the form of definite integrals. A simple analytical model consisting of three fixed plastic hinges and two straight rigid bars is also developed showing rather good agreement with the exact solution. Comparison with finite element solutions verifies the accuracy of the present analytical solution. Finally, the analytical solution for a single beam is extended to the case of a Hybrid Stainless Steel Assembly (HSSA) sheet, which is idealized as a complex system of many inclined beams sandwiched between two face sheets. Based on the probability distribution of the inclination angle of the beam, the total crush resistance of the HSSA sheet is predicted.