Study on the effect of the crack length on the JIC value Original Research Article

The ductile fracture tests are carried out using compact type (CT) specimen, three point bend specimen and center cracked tension (CCT) specimens made of A533B steel and aluminum alloy with different crack lengths. The effect of the crack tip constraint on the microscopic fracture behavior is studied by the scanning electron microscope (SEM). It is shown that the apparent JIC value increases due to the decrease of the crack tip constraint. It is pointed out that the increase of the apparent JIC value is partly due to the error of the conventional equation to estimate the J value. Based on the FEM analyses, these apparent JIC values are corrected and are compared with the valid JIC values. The good co-relation between apparent JIC value and the Q factor, proposed by OʹDowd and Shih, is shown for all the specimens. The FEM analyses based on the Gursonʹs constitutive equation is also carried out. The effect of the constraint on the crack tip field is discussed.