A computational analysis to assess the influence of specimen geometry on cleavage fracture toughness of metallic materials

The fracture response of mild steel in the domain of brittle behavior, i.e., the cleavage range, has been carefully evaluated using a weakest link statistical model, assuming the existence of a distribution of cracked carbide particles in the microstructures. Experiments have provided an evidence of both scatter in test results and the existence of constraints. Statisticalbased model to include micromechanics were developed in an attempt to study and analyze the problem. The Weibull stress micro-mechanical model was used in this study to quantify the constraint effects. This was done numerically using a constraint function (g(M)) derived from the Weibull stress model. The non-dimensional function (g(M)) describes the evolution of the effects of constraint loss on fracture toughness relative to the reference condition, i.e., plane-strain, small scale yielding (SSY) (T-stress = 0). Single-edge SE(B) notched bending specimens having different crack lengths, different cross-sections and side-grooves were modeled and the constraint function (g(M)) was calculated. In this paper, we compare the loss in constraint for both the deep notch and shallow notch specimens for a given cross-section of the single-edge notched bend specimen (SE(B)).