Master curve analysis of ductile to brittle transition region fracture toughness round robin data

The "EURO" fracture toughness curve

Kim Wallin

Research output: Book/ReportReportProfessional

25 Citations (Scopus)

Abstract

Brittle fracture in the ductile to brittle transition regime is connected with specimen size effects and - more importantly- tremendous scatter of fracture toughness, which the technical community is currently becoming increasingly aware of. The size effects have the consequence that fracture toughness data obtained from small laboratory specimens do not directly describe the fracture behaviour of real flawed structures. Intensive research has been conducted in the last decade in order to overcome these problems. Different approaches have been developed and proposed, one of the most promising being the master curve method, developed at VTT Manufacturing Technology. For validation purposes, a large nuclear grade pressure vessel forging 22NiMoCr37 (A508 Cl.2) has been extensively characterised with fracture toughness testing. The tests have been performed on standard geometry CT-specimens having thickness 12.5 mm, 25 mm, 50 mm and 100 mm. The a/W-ratio is close to 0.6 for all specimens. One set of specimens had 20% side-grooves. The obtained data consists of a total of 757 results fulfilling the ESIS-P2 test method validity requirements with respect to pre-fatigue crack shape and the ASTM E-1921 pre-fatigue load. The master curve statistical analysis method is meticuously applied on the data, in order to verify the validity of the method. Based on the analysis it can be concluded that the validity of all the assumptions in the master curve method is confirmed for this material.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages58
ISBN (Electronic)951-38-5346-2
ISBN (Print)951-38-5345-4
Publication statusPublished - 1998
MoE publication typeD4 Published development or research report or study

Publication series

NameVTT Publications
PublisherVTT
No.367
ISSN (Print)1235-0621
ISSN (Electronic)1455-0849

Fingerprint

Fracture toughness
Brittle fracture
Forging
Pressure vessels
Statistical methods
Fatigue of materials
Geometry
Testing
Fatigue cracks

Keywords

  • fractures (materials)
  • steels
  • fracture strength
  • ductile brittle transition
  • brittleness
  • statistical analysis
  • master curve method

Cite this

Wallin, K. (1998). Master curve analysis of ductile to brittle transition region fracture toughness round robin data: The "EURO" fracture toughness curve. Espoo: VTT Technical Research Centre of Finland. VTT Publications, No. 367
Wallin, Kim. / Master curve analysis of ductile to brittle transition region fracture toughness round robin data : The "EURO" fracture toughness curve. Espoo : VTT Technical Research Centre of Finland, 1998. 58 p. (VTT Publications; No. 367).
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Wallin, K 1998, Master curve analysis of ductile to brittle transition region fracture toughness round robin data: The "EURO" fracture toughness curve. VTT Publications, no. 367, VTT Technical Research Centre of Finland, Espoo.

Master curve analysis of ductile to brittle transition region fracture toughness round robin data : The "EURO" fracture toughness curve. / Wallin, Kim.

Espoo : VTT Technical Research Centre of Finland, 1998. 58 p. (VTT Publications; No. 367).

Research output: Book/ReportReportProfessional

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AB - Brittle fracture in the ductile to brittle transition regime is connected with specimen size effects and - more importantly- tremendous scatter of fracture toughness, which the technical community is currently becoming increasingly aware of. The size effects have the consequence that fracture toughness data obtained from small laboratory specimens do not directly describe the fracture behaviour of real flawed structures. Intensive research has been conducted in the last decade in order to overcome these problems. Different approaches have been developed and proposed, one of the most promising being the master curve method, developed at VTT Manufacturing Technology. For validation purposes, a large nuclear grade pressure vessel forging 22NiMoCr37 (A508 Cl.2) has been extensively characterised with fracture toughness testing. The tests have been performed on standard geometry CT-specimens having thickness 12.5 mm, 25 mm, 50 mm and 100 mm. The a/W-ratio is close to 0.6 for all specimens. One set of specimens had 20% side-grooves. The obtained data consists of a total of 757 results fulfilling the ESIS-P2 test method validity requirements with respect to pre-fatigue crack shape and the ASTM E-1921 pre-fatigue load. The master curve statistical analysis method is meticuously applied on the data, in order to verify the validity of the method. Based on the analysis it can be concluded that the validity of all the assumptions in the master curve method is confirmed for this material.

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Wallin K. Master curve analysis of ductile to brittle transition region fracture toughness round robin data: The "EURO" fracture toughness curve. Espoo: VTT Technical Research Centre of Finland, 1998. 58 p. (VTT Publications; No. 367).