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Title: Influence of stress corrosion crack merging on remaining life predictions. Final report

Abstract

This work has been concerned with the influences of stress corrosion crack coalescence on crack growth kinetics and hence upon remaining life predictions for cracked structures or components. Two systems of relevance to the electric utility industry were chosen for the study, one involving a Mn-Cr generator retaining ring steel exposed to water or humid air and the other a Ni-Cr-Mo-V turbine disc steel exposed to a concentrated sodium hydroxide solution. The approach used was to expose cyclically loaded specimens for various times and to interrupt the tests to measure the sizes and distributions of cracks. It is shown that the coalescence or merging of adjacent stress corrosion cracks can occur in both systems when the lengths and distances of separation of the cracks fall within reasonably defined domains. A computer program has been developed that allows crack nucleation, growth and coalescence to be recognized as important constituents of the overall process. It uses a Monte Carlo approach to randomly distribute crack nucleation sites and to decide whether or nor a given crack is in an active, i.e. growth phase. The rate of nucleation is governed by a power law relationship. The variable rates of crack growth obey a Weibullmore » distribution, as determined from experimental measurements, which were the basis also of the conditions for crack coalescence. The simulation runs for both systems give results that are in reasonable agreement with failure times determined in laboratory experiments. The results indicate that crack coalescence needs to be taken into account in estimating the remaining lifetimes of some cracked structures or components. The incorporation of crack coalescence processes into crack growth kinetics requires relevant data to be collected.« less

Authors:
 [1]
  1. Newcastle upon Tyne Univ. (United Kingdom). Dept. of Mechanical, Materials, and Mfg. Engineering
Publication Date:
Research Org.:
Electric Power Research Inst., Palo Alto, CA (United States); Newcastle upon Tyne Univ. (United Kingdom). Dept. of Mechanical, Materials, and Mfg. Engineering
Sponsoring Org.:
Electric Power Research Inst., Palo Alto, CA (United States)
OSTI Identifier:
10146524
Report Number(s):
EPRI-TR-100458
ON: UN92013834
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Apr 1992
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 22 GENERAL STUDIES OF NUCLEAR REACTORS; 20 FOSSIL-FUELED POWER PLANTS; STEELS; STRESS CORROSION; CRACK PROPAGATION; MANGANESE ALLOYS; CHROMIUM ALLOYS; NICKEL ALLOYS; MOLYBDENUM ALLOYS; COMPUTERIZED SIMULATION; SODIUM HYDROXIDES; SERVICE LIFE; TURBINES; 360105; 220200; 200104; CORROSION AND EROSION; COMPONENTS AND ACCESSORIES; COMPONENTS

Citation Formats

Parkins, R N. Influence of stress corrosion crack merging on remaining life predictions. Final report. United States: N. p., 1992. Web.
Parkins, R N. Influence of stress corrosion crack merging on remaining life predictions. Final report. United States.
Parkins, R N. Wed . "Influence of stress corrosion crack merging on remaining life predictions. Final report". United States.
@article{osti_10146524,
title = {Influence of stress corrosion crack merging on remaining life predictions. Final report},
author = {Parkins, R N},
abstractNote = {This work has been concerned with the influences of stress corrosion crack coalescence on crack growth kinetics and hence upon remaining life predictions for cracked structures or components. Two systems of relevance to the electric utility industry were chosen for the study, one involving a Mn-Cr generator retaining ring steel exposed to water or humid air and the other a Ni-Cr-Mo-V turbine disc steel exposed to a concentrated sodium hydroxide solution. The approach used was to expose cyclically loaded specimens for various times and to interrupt the tests to measure the sizes and distributions of cracks. It is shown that the coalescence or merging of adjacent stress corrosion cracks can occur in both systems when the lengths and distances of separation of the cracks fall within reasonably defined domains. A computer program has been developed that allows crack nucleation, growth and coalescence to be recognized as important constituents of the overall process. It uses a Monte Carlo approach to randomly distribute crack nucleation sites and to decide whether or nor a given crack is in an active, i.e. growth phase. The rate of nucleation is governed by a power law relationship. The variable rates of crack growth obey a Weibull distribution, as determined from experimental measurements, which were the basis also of the conditions for crack coalescence. The simulation runs for both systems give results that are in reasonable agreement with failure times determined in laboratory experiments. The results indicate that crack coalescence needs to be taken into account in estimating the remaining lifetimes of some cracked structures or components. The incorporation of crack coalescence processes into crack growth kinetics requires relevant data to be collected.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {4}
}

Technical Report:
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