Constraint effects on fracture toughness


  1. Shen, G.
  2. Xu, S.
  3. Tyson, W.R.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Materials Technology Lab, Ottawa ONT (CAN)
Fracture resistance curves have been measured for a CSA 350WT ship plate using different a/W ratios, and stretch-zone-width (SZW) measurements have been made on the fracture surfaces. Associated calculations using finite element analysis (FEA) have have also been performed, with special attention paid to the crack tip blunting behaviour. It has been confirmed that the fracture resistance increases with decreasing constraint, i.e. with decreasing a/W. It has also been shown that the blunting line slope M Sigma Y depends on constraint as well as on material properties. FEA results indicate that M lies between the value recommended in ASTM standards (M=2) and that suggested by the European Structural Integrity Society (ESIS) (M=4 for this material), being closer to the ESIS value. The subjective nature of the measurement made it difficult to derive reproducible SZW values, and a recently developed ESIS procedure produced very conservative results. It is difficult to clearly distinguish between the stretch zone and the tearing regions, particularly when the resistance curve data is described using a power-law equation. This suggests that it would be preferable to define toughness by means of a value of J or CTOD at a specific amount of crack growth, e.g. 0.2 mm, without distinguishing between blunting and tearing contributions.

Il y a un résumé en français ici.

350WT steel;Stretch Zone Width;Crack blunting
Report Number
DREA-CR-2001-091 — Contractor Report
Date of publication
01 Jul 2001
Number of Pages
Hardcopy;Document Image stored on Optical Disk

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