Influence of stress corrosion crack merging on remaining life predictions. Final report
- Newcastle upon Tyne Univ. (United Kingdom). Dept. of Mechanical, Materials, and Mfg. Engineering
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.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); Newcastle upon Tyne Univ. (United Kingdom). Dept. of Mechanical, Materials, and Mfg. Engineering
- Sponsoring Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 10146524
- Report Number(s):
- EPRI-TR-100458; ON: UN92013834
- Resource Relation:
- Other Information: PBD: Apr 1992
- Country of Publication:
- United States
- Language:
- English
Similar Records
Chloride-Induced Stress Corrosion Cracking Characteristics of the Used Nuclear Fuel Canister Material
Development and Integration of Light Water Reactor (LWR) Materials Corrosion Degradation Codes into Grizzly
Related Subjects
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