Investigation into the effect of thickness on three- and four-point single edge notch bend specimens using two- and three-dimensional elastic-plastic stress analyses

ABSTRACT The effect of thickness in fracture behaviour has been investigated experimentally and through elastic-plastic finite element analyses on three and four-point Single Edge Notch Bend specimens. Special attention was paid to the constraint at the crack tip, the distribution of the J-integral and the Crack Tip Opening Displacement along the crack front. The results of experiments and of the stress analyses revealed there is an upper limit to the size of the transition zone, in which the stress state along the crack front develops from plane stress at the free surface to a triaxial stress state with high constraint deeper in the specimen. This upper limit appears to be 6 mm for the thicknesses above 30 mm for a Fe 510 Nb steel at −70 °C.