Elastic-Plastic Line-Spring Finite Elements for Surface-Cracked Plates and Shells

The elastic line-spring finite element of Parks, et al. [1], which was incorporated into the ABAQUS© finite element program, is extended to include elastic-plastic response for approximate evaluation of the J-integral in surface-cracked plates or shells. J-analysis of a long axial crack in a pressurized cylinder is performed both with the virtual crack extension method and with a single elastic-plastic line-spring element attached to a 180-deg ring of shell elements constrained to (axial) plane strain. Agreement of the two models is generally good, both in the elastic range (as was noted earlier by Buchalet and Bamford) and in the plastic range. An axially cracked, internally pressurized cylinder containing a semi-elliptical flaw of aspect ratio a/c = 1/3, and of varying maximum relative depths a/t has also been analyzed.