In order to obtain the distribution of stress intensity factor (SIF) along thickness direction for the central through cracked finite thickness plates in tension, the paper proposes a new method to calculate SIF based on maximum crack opening displacement (MCOD). In this method, the expression of SIF describing thickness effect on stress field near the crack tip can be deduced, based on the triaxial stress constraint factor. Then, the concept of MCOD is introduced and the relationship between SIF and MCOD is established. In this way, the SIF at arbitrary crack tip can be estimated when MCOD is known.
Steel plates are widely used in ship hulls and marine engineering structures, which inevitably produce a variety of defects as well as crack damage in their life span. For a steel plate model with a central through crack, the thickness effect is usually neglected when 2-D fracture theory is employed to analyze the stress state near the crack tip. And indeed, the stress field of the local region around the crack tip is very complicated, and the distribution of SIF of the crack tip is related to 3-D stress constraint. The stress state can not be simply treated as plane strain or plane stress state, and also can not be accepted as interpolated results of two kinds of states. The stress distribution, in the region around crack tip, is discussed in a large number of literatures, and a simplified approach (Agrawal and Kishore, 2001; Kwon and Sun, 2000; Nakamura and Parks, 1988; Shivakumar and Raju, 1990; Su and Sun, 1996) is proposed, in which the free surface of plate is considered as the plane stress state and the other region as the plane strain state.