Deformation and Fracturing of Thick-Walled Steel Cylinders under Explosive Attack

Abstract

Tests have been conducted on annealed heavy-walled cylinders of low carbon (1020) steel internally loaded by explosive charges. The purpose of these tests was to obtain basic information on the manner and type of fracturing and plastic flow obtained by extremely high pressures acting for short durations. It was observed that all of the cylinders tended to fracture in long fragments in the same basic pattern, but with variations because of wall thickness and manner of loading. Experimental results indicate that the radial cleavage type of fracture is initiated within the cylinder wall and propagated to the surface, while the shear type fracture associated with the inner portion of the cylinder wall appears as an independent energy relieving process. Microstructure analysis of the cylinder fragments shows a definite relationship between the type of fracture and the amount of distortion of the grain boundary. Considerable shock twinning is present in the cylinder fragments, and the grain structure near the inner surface shows severe distortion and flow. Strain measurements indicate that considerable plastic strain occurs during the explosive loading and cleavage fractures were always observed to occur in association with considerable plastic deformation.