J-integral evaluation for U- and V-blunt notches under Mode I loading and materials obeying a power hardening law

The paper deals with calculations of the J-integral for a plate weakened by U- and V-blunt notches under mode I loading in the case of a linear and nonlinear elastic material. The main aim of the study is to suggest simple equations suitable for rapid calculations of the J-integral. The semicircular arc of the notch, which is traction free, is assumed as integration path and the J-integral is given as a function of the strain energy over the notch edge. For a numerical investigation of the strain energy density distribution on the notch edge the equation W (theta) = W-max cos(delta) (theta) has been assumed, where 8 has been determined from finite element analyses. In particular, the following values of the notch acuity a/p and the opening angle 2 alpha have been analyzed: 4 <= a/p <= 400 and 0 <= 2 alpha <= 3 pi/4. Considering plates weakened by lateral and central notches under symmetric mode I loading, the approximate relationships for the strain energy density, which require the presence of a non zero notch radius for their application, and the J-integral are discussed firstly considering a linear elastic material and then a material obeying a power hardening law during the loading phase. The predicted results of the J-integral are consistent with those directly obtained from finite element analyses

Diffusion model of delayed hydride cracking in zirconium alloys

We develop a method for the evaluation of the rate of delayed hydride cracking in zirconium alloys. The model is based on the stationary solution of the phenomenological diffusion equation and the detailed analysis of the distribution of hydrostatic stresses in the plane of a sharp tensile crack. The rate of delayed hydride cracking in reactor tubes made of Zr-2.5 % Nb alloy is found both theoretically and experimentally. It is shown that the theoretical results are in good agreement with the experimental data