CRACK ARREST TOUGHNESS OF A HEAT AFFECTED ZONE CONTAINING LBZ

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Authors
  1. Malik, L.
  2. Pussegoda, L.N.
  3. Graville, B.A.
  4. Tyson, W.R.
Corporate Authors
Fleet Technology Ltd, Kanata ONT (CAN);Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
The awareness of the presence of local brittle zones (LBZs) in the heat affected zone (HAZ) of welds has led to the requirements for minimum initiation toughness for the HAZ for critical applications (API RP 2Z, CSA S473). Such an approach however is expensive to implement and limits the number of potential steel suppliers. A fracture control philosophy that is an attractive alternative to the prevention of initiation is the prevention of propagation. This is implemented via crack arrest requirements. In the Canadian offshore code (CSA S473), arrest requirements are imposed on base plate for ciritical applications. If it could be demonstrated that cracks initiated in LBZs will be arrested without causing catastrophic fracture, then requirements for initiation toughness could be relaxed. Unstable propagation of a crack initiating from an LBZ requires the rupture of tougher microstructural regions surrounding teh LBZ in the HAZ, and therefore the CTOD value reflecting the presence of the LBZ is unlikely to provide a true indication of the potential for fast fracture along the heat affected zone. One possible uncertainty realted to crack arrest is whether the presence of LBZs promotes propagation within the HAZ, i.e., whether a crack can run parallel to the weld within the HAZ causing fracture by avoiding arrest in the base plate. TRUNCATED
Report Number
DREA-NAMT-95-4-PAP-4 — CONTAINED IN 99-00779
Date of publication
30 May 1995
Number of Pages
20
DSTKIM No
99-00798
CANDIS No
510362
Format(s):
Hardcopy;Document Image stored on Optical Disk

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