A three-dimensional analysis of fracture mechanics test pieces of different geometries - Part 1 Stress-state ahead of the crack tip

An extensive series of detailed three-dimensional elastic plastic finite element analyses has been carried Out to investigate the influence of fracture mechanics test specimen geometry on the near-tip stress fields. The specimens studied were pre-cracked plain-sided and side grooved bend specimens of Charpy specimen size, plain-sided and side-grooved compact tension specimens of thickness B = 25 mm and plain-sided compact tension specimens of thickness B = 100 mm. The standard ratio of the crack length to the specimen width a/W = 0.5 was employed in all the cases considered. Stress-strain curves of materials of different yield strength and strain hardening behaviour spanning the range of practical interest for typical structural steels were implemented into the finite element models. Variations of the local crack tip driving forces in terms of the J-integral and crack tip opening displacement (CTOD) over the crack front have been investigated. The near-tip stress fields in the fracture toughness specimens were analysed in detail with the emphasis on the opening mode stress. Further studies on the constraint parameter Q and hydrostatic and equivalent stress components are reported in a separate paper. Part 2 of this work. (C) 2012 Elsevier Ltd. All rights reserved.