QUANTITATIVE PREDICTION OF ENVIRONMENTALLY ASSISTED CRACKING BASED ONA THEORETICAL-MODEL AND COMPUTER-SIMULATION

This paper describes a comparison between quantitative prediction of e nvironmentally assisted cracking by theoretical modelling and that by finite element method (FEM) computer simulation in terms of film ruptu re strain: at a crack tip. The crack growth rate was simulated on a 1T -CT (one inch-thick compact tension) specimen, which met I American So ciety for Testing and Materials (ASTM) E813, under the slow strain rat e test (SSRT) condition by an FEM simulation code, Finite Element Envi ronmentally Assisted Cracking Simulator (FEEACS) for him rupture strai n epsilon(f) = 10(-2), 10(-3), and 10(-4). As the theoretical model in cludes unknown parameters which cannot be determined theoretically, th ey were evaluated by chi-square fitting method so that the crack growt h rates of the theoretical model fit those of FEM computer simulation. In this method the film rupture strain epsilon(f) and the position r where crack tip strain is defined are evaluated. The calculation was c arried out for two cases. One is for irradiation-assisted stress corro sion cracking (IASCC), and the other is without irradiation. Parameter s for irradiated material are the yield strength sigma(y) = 980 MN/m(3 /2), the slope of the current decay m = 0.5, and the strain hardening exponent n = 3. In the irradiated case the crack growth rates obtained by the theory agree well with those obtained by FEM using the relatio n epsilon(f Theory) = 3.1 epsilon(f) (FEM), while they do not agree in the case without irradiation. (C) 1998 Elsevier Science B.V. All righ ts reserved.