Finite element evaluation of the J-integral in compact tension specimens with non-straight crack fronts

This report describes the FE analysis of the J-integral in a compact tension specimen, performed with the finite element code MARC. The shape of the crack front was the main variable in the analysis. The J-integral in specimens with a straight crack front was compared to the J-integral in specimens with curved, obliquely curved and sharp crack fronts. Both the average J-integral for the entire specimen and the J-integral along the crack front were compared. From the analysis it can be concluded that the actual shape of the crack front seems to have only a minor influence on the average J-integral for compact tension specimens. For the distribution of the J-integral along the crack front, differences were found between the straight and curved crack fronts. The analysis was limited to specimens with a non-growing crack, under growing load. As a result, the computed J-integral differed from experimentally determined J-integrals at higher load levels. (orig.)