The application of local approach to assess the influence of in-plane constraint on cleavage fracture
- AEA Technology, Risley (United Kingdom)
- Nuclear Electric, Berkeley (United Kingdom)
- JAERI, Tokai, Ibaraki (Japan)
The assessment of real or postulated flaws within critical components is conventionally carried out using methods based on single parameter fracture mechanics. For low constraint configurations (e.g. shallow cracks) such methods can provide highly conservative assessments. Two-parameter (J-T, J-Q) fracture mechanics has been developed to quantify the influence of crack-tip constraint on fracture and this development has been incorporated into a modified R6 framework to reduce the conservatisms associated with the assessment of low constraint configurations. This framework requires that the constraint of the structure is quantified (with respect to T or Q) and that the materials fracture response to constraint is measured by testing a number of cracked specimens which sample a range of constraint levels. An alternative method of assessment, which may be used in situations where fracture data are unavailable over the full range of constraint, is the so-called local approach to fracture. In this Paper, the local approach has been used alongside the modified R6 framework to assess the cleavage fracture behavior of a well characterized mild steel plate at {minus}50 C. The local approach method predicts: (i) an upswing in cleavage fracture toughness as a function of decreasing crack-tip constraint which is conservative with respect to the actual materials response, (ii) an increase in the scatter of cleavage fracture toughness as a function of decreasing crack-tip constraint. This is a direct consequence of framing the local approach model within two-parameter Weibull statistics. Finally it is shown that the local approach may be used successfully alongside the modified R6 framework to assess low constraint geometries: resultant failure assessment curves reduce the conservatism of the conventional Option 1 curve.
- OSTI ID:
- 122636
- Report Number(s):
- CONF-950740--; ISBN 0-7918-1335-5
- Country of Publication:
- United States
- Language:
- English
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