Elastic-Plastic Fracture Mechanics Evaluations of Stainless Steel Tungsten/Inert-Gas Welds

Abstract In order to bound failure of austenitic stainless steel storage containers housing Ga-containing compounds, the liquid-metal embrittlement of Type 316L (UNS S31603) stainless steel (SS) by Ga was investigated. Type 316L SS compact tension specimens were exposed to liquid Ga using a depassivation technique to wet the specimen. Linear elastic and elastic-plastic fracture mechanics methods were used to compare the fatigue and fracture behavior. Mild liquid-metal embrittlement was observed, as indicated by increased fatigue crack growth rate, decreased number of fatigue cycles to failure, decreased crack initiation resistance, and increased crack growth rate. Stable cracking was observed for all test conditions. A small amount of intergranular cracking was observed following Ga exposure. No effect of test temperature on embrittlement was observed over the small temperature range examined (35°C to 75°C). Decreasing crosshead displacement rate promoted Ga embrittlement. Based on fractography, profilometry, and mechanics, it appears that both adsorption-induced decohesion and adsorption-enhanced plasticity mechanisms are operative in the Type 316L SS-Ga system.

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Elastic-Plastic Fracture Mechanics Analysis on Environmentally Accelerated Cracking of Stainless Steel in High Temperature Water

Journal of Engineering Materials and Technology ◽

10.1115/1.3225810 ◽

1985 ◽

Vol 107 (3) ◽

pp. 240-245 ◽

Cited By ~ 5

Author(s):

T. Kawakubo ◽

M. Hishida

Keyword(s):

Stainless Steel ◽

High Temperature ◽

Fracture Mechanics ◽

Stress Corrosion ◽

Crack Growth ◽

Mechanistic Model ◽

304 Stainless Steel ◽

Elastic Plastic ◽

Oxygenated Water ◽

Type 304

Stress corrosion crack growth during slow strain rate testing was investigated using elastic-plastic fracture mechanics. Thin compact and center-notched specimens of sensitized Type 304 stainless steel were examined at different extension rates in high temperature oxygenated water. The analytical results showed that the crack growth rate has a best correlation with a time differential of the J-integral, which is an estimate of a crack tip deformation rate. Based on the analysis, a new mechanistic model under both monotonic and cyclic loadings was suggested, where cracking was classified into three categories depending on the environmental acceleration, i.e., mechanical cracking, corrosion enhanced mechanical cracking, and stress corrosion cracking.

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Development of Load Multipliers (Z-Factors) in Elastic-Plastic Fracture Mechanics Evaluation in Rules on Fitness-for-Service for Nuclear Power Plants

Volume 1: Codes and Standards ◽

10.1115/pvp2012-78021 ◽

2012 ◽

Author(s):

Seiji Asada ◽

Masao Itatani ◽

Naoki Miura ◽

Hideo Machida

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Fracture Mechanics ◽

Ferritic Steel ◽

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Elastic Plastic ◽

Surface Flaws ◽

Steel Piping

Not only nonmandatory Appendix C, “Evaluation of Flaws in Piping,” in ASME Boiler & Pressure Vessel Code Section XI but also Appendix E-9, “Elastic-Plastic Fracture Mechanics Evaluation,” in the JSME Rules on Fitness-for-Service for Nuclear Power Plants use the load multiplier Z-factor that is applied to elastic-plastic fracture mechanics evaluation for a circumferential flaw of austenitic stainless steel piping and ferritic steel piping. The Z-factor is defined as the ratio of the limit load to the load at fracture load. Basically, the Z-factor equations were conservatively formulated by using the Z-factors for circumferential through-wall flaws. However, the Codes require flaw evaluation for circumferential surface flaws. Accordingly, Z-factors for circumferential surface flaws should be developed to have the consistency. Therefore Z-factor equations of austenitic stainless steel piping and ferritic steel piping have been developed for circumferential surface flaws.

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