Dynamic shear rupture of steel plates

Abstract

Metallic sandwich panels with prismatic cores offer the potential for superior blast resistance relative to monolithic plates of equivalent areal density. However, under sufficiently high impulse, severe plastic strains can occur at the junctions of the face sheets and the core members shortly after arrival of the pressure wave but prior to significant deformation elsewhere. The potential consequence is localized shear rupture with minimal plastic dissipation. To characterize this failure mode, a combined experimentalnumerical protocol has been used to ascertain the plastic strain for dynamic shear rupture of ductile metals. The experimental component involves firing cylindrical projectiles through plates of the targeted materials and monitoring changes in projectile velocity during penetration. With appropriate combinations of plate thickness and projectile velocity, penetration occurs through propagation of an annular shear crack. In parallel, a numerical model of dynamic deformation and rupture has been employed to infer the critical strain through comparisons with projectile velocity change measurements. Experiments and analyses have been performed on both 304 stainless steel and superaustenitic AL6XN. Effects of mesh size on the resolution of the predicted strain distribution and the plastic dissipation associated with penetration are addressed.

Calibration procedures for a computational model of ductile fracture

“…Plastic loading has been assumed in writing both (17) and (18); if the increment is elastic, only the elastic moduli and compliances are used. The effective plastic strain-rate is defined in terms of the logarithmic strain rates in the usual way as…”

“…9 was designed to create a controlled test in which shear localization gives way to mode II fracture [17]. The corresponding load-displacement curve is used to infer the shear damage coefficient, k ω .…”

Numerical Investigation of Adhesive Wear and Static Friction Based on the Ductile Fracture of Junction

“…The size of those four-node square mesh elements is not greater than 2.5 /¿m, which was selected to be comparable to typical shear band widths (10-100 ;xm [33,34]). The finite element analysis with a fixed mesh fails to converge as a consequence of severe material deformation in the ruptured elements; thus, arbitrary Lagrangian Eulerian adaptive meshing [35] was employed in all of the calculations.…”

Dynamic failure of clamped circular plates subjected to an underwater shock

“…The mesh size w, coupled with the failure strain, dictates the amount of localized deformation that occurs on the fracture plane, and the displacement jump across the critical element is analogous to the critical displacement in a cohesive zone formulation. Thus, for an ideally plastic material with a yield strength σ Y , the intrinsic mode I crack tip toughness K I C is given as K I C ∼ Ewσ Y ε f (w being the element width), as discussed by Nahshon et al [2007]. Thus with w = 90 µm and σ Y = 220 MPa, this implies that the assumed fracture toughness K I C ≈ 22 MPa m 1/2 , which is consistent with a wide body of experimental data for copper.…”