Effects of precracked specimen geometry on local cleavage fracture stress sigma_f of low alloy steel

摘要

An elastic-plastic finite element method (FEM) is used to analyze the stress distributions ahead of crack tips for three types of COD specimens with different precracked depth a/W and height W of a low alloy steel, and the tensile and COD tests are carried out at various temperatures. By accurately measuring the distances of the cleavage initiation sites from the blunted crack tips, the local cleavage fracture stresses are measured. With increasing precracked depth a/W, specimen height W and test temperatures in a certain range, it was found that the sigma_f essentially does not change. The sigma_f is a steady inherent parameter of the material whose value is independent of the precracked specimen geometry.