A process model for the initiation of stress-corrosion crack growth in BWR plant materials
- Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan). Research Inst.
The process of initiating the stress-corrosion crack growth comprises the following elementary processes: (A) the incubation period, (B) the process of nucleating the corrosion pits (or corrosion crevices), (C) the process of the growth of pits (or crevices), (D) the process of initiating microcracks, (E) the process of the propagation of microcracks, (F) the process of coalescing the microcracks. This paper deals with the last three by analyzing the stress-corrosion cracking behavior for each stage, and examines the models developed thereby to predict the initiation life of each. The following observations and conclusions have been made: (1) the critical pit depth to initiate the microcrack is approximately 20 {micro}m for the carbon steel, and the micro-cracks are non-propagative semicircular cracks of approximately 50 {micro}m in depth; (2) the processes B, D and F can all be represented to the Poissonian stochastic process; (3) inasmuch as the total crack-initiation life is determined by a stochastic process comprising these Poissonian processes concatenated in series, the probability distribution of the life leading to the onset of steady propagation of a main crack can be represented by the exponential distribution; (4) the applied stress exerts its influence mainly on the rate of proliferation of microcracks, but hardly on the propagation of microcrack, critical pit depth, and the probability of the pit`s generating microcracks; and (5) the distribution lower limit of the main-crack initiation life is in inverse proportion to the applied stress.
- OSTI ID:
- 548517
- Report Number(s):
- CONF-960588--; ISBN 0-8031-2408-2
- Country of Publication:
- United States
- Language:
- English
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