Effects of plasticity and crack geometry on fracture

Two important aspects relating to crack extension in nuclear pressure vessels and piping are discussed in this paper. First, through the use of the finite element method, a procedure is given to estimate the extent of slow crack growth in a uniaxially loaded sheet with a through-crack. Comparisons between the theoretically predicted crack growth and the experimental values show very good correlation. The second aspect discussed in this paper is concerned with certain analytical considerations of the effect of crack profile and loading. From a linear elastic analysis of an arbitrarily oriented parabolic flaw embedded in a biaxially loaded infinite solid, certain limitations are presented of the existing empirical considerations of 'leak before burst' phenomenon in pressure vessels. Expressions are given for stress intensity factors and strain energy density for an arbitrarily oriented parabolic flaw. (orig.)