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Title: Experimental investigations of the fracture toughness enhancement associated with shallow flaws

Abstract

The Heavy Section Steel Technology Program (HSST) is investigating the influence of flaw depth on the fracture toughness of reactor pressure vessel (RPV) steel. Recently, it has been shown that shallow cracks tend to exhibit an elevated toughness as a result of a loss of constraint at the crack tip. The loss of constraint takes place when interaction occurs between the elastic-plastic crack-tip stress field and the specimen surface nearest the crack tip. An increased shadow-crack fracture toughness is of interest to the nuclear industry because probabilistic fracture-mechanics evaluations show that shallow flaws play a dominant role in the probability of vessel failure during postulated pressurized-thermal-shock (PTS) conditions. The HSST investigation is a joint analytical/experimental study combining the use of shallow-cracked laboratory specimens with RPV analysis. All tests have been performed on beam specimens loaded in 3-point bending using specimens about 100 mm deep. Primarily two crack depths have been considered: a = 50 and 9 mm (a/W = 0.5 and 0.1). Test results indicate a significant increase in the fracture toughness associated with the shallow flaw specimens in the lower transition region compared to the conventional fracture toughness. The testing has produced a limited database of fracture-toughness values asmore » a function of crack depth which can be used in probabilistic or deterministic fracture mechanics analyses of pressure vessel integrity. Final test results from the shallow-crack fracture toughness program will be included in this paper. Examination of previously tested thermal shock data reveals that no toughness elevation appears to be present even though the thermal shock cylinders were tested with shallow flaws.« less

Authors:
;  [1];  [2]
  1. Oak Ridge National Lab., TN (United States)
  2. University of Kansas, Lawrence, KS (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab., TN (United States)
Sponsoring Org.:
Nuclear Regulatory Commission, Washington, DC (United States)
OSTI Identifier:
10107147
Report Number(s):
CONF-9210209-2
ON: DE93003100
DOE Contract Number:  
AC05-84OR21400
Resource Type:
Conference
Resource Relation:
Conference: Organization for Economic Co-Operation Development/International Atomic Energy Agency/Commission of Safety Nuclear Installations (OECD/IAEA/CSNI) joint international specialists meeting on fracture mechanics verification by large scale testing,Knoxville, TN (United States),26-29 Oct 1992; Other Information: PBD: [1992]
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 36 MATERIALS SCIENCE; PRESSURE VESSELS; TESTING; FRACTURES; PWR TYPE REACTORS; REACTOR COMPONENTS; CRACKS; CRACK PROPAGATION; STRESSES; STEELS; 210200; 360103; POWER REACTORS, NONBREEDING, LIGHT-WATER MODERATED, NONBOILING WATER COOLED; MECHANICAL PROPERTIES

Citation Formats

Theiss, T J, Shum, D K.M., and Rolfe, S T. Experimental investigations of the fracture toughness enhancement associated with shallow flaws. United States: N. p., 1992. Web.
Theiss, T J, Shum, D K.M., & Rolfe, S T. Experimental investigations of the fracture toughness enhancement associated with shallow flaws. United States.
Theiss, T J, Shum, D K.M., and Rolfe, S T. Thu . "Experimental investigations of the fracture toughness enhancement associated with shallow flaws". United States.
@article{osti_10107147,
title = {Experimental investigations of the fracture toughness enhancement associated with shallow flaws},
author = {Theiss, T J and Shum, D K.M. and Rolfe, S T},
abstractNote = {The Heavy Section Steel Technology Program (HSST) is investigating the influence of flaw depth on the fracture toughness of reactor pressure vessel (RPV) steel. Recently, it has been shown that shallow cracks tend to exhibit an elevated toughness as a result of a loss of constraint at the crack tip. The loss of constraint takes place when interaction occurs between the elastic-plastic crack-tip stress field and the specimen surface nearest the crack tip. An increased shadow-crack fracture toughness is of interest to the nuclear industry because probabilistic fracture-mechanics evaluations show that shallow flaws play a dominant role in the probability of vessel failure during postulated pressurized-thermal-shock (PTS) conditions. The HSST investigation is a joint analytical/experimental study combining the use of shallow-cracked laboratory specimens with RPV analysis. All tests have been performed on beam specimens loaded in 3-point bending using specimens about 100 mm deep. Primarily two crack depths have been considered: a = 50 and 9 mm (a/W = 0.5 and 0.1). Test results indicate a significant increase in the fracture toughness associated with the shallow flaw specimens in the lower transition region compared to the conventional fracture toughness. The testing has produced a limited database of fracture-toughness values as a function of crack depth which can be used in probabilistic or deterministic fracture mechanics analyses of pressure vessel integrity. Final test results from the shallow-crack fracture toughness program will be included in this paper. Examination of previously tested thermal shock data reveals that no toughness elevation appears to be present even though the thermal shock cylinders were tested with shallow flaws.},
doi = {},
url = {https://www.osti.gov/biblio/10107147}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {12}
}

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