Published on 21 January 2013
A fracture test developed by TWI has helped an Industrial Member solve a toughness measuring problem.
The member wished to determine the tolerance of a single V MMA butt weld to long surface cracks in the TIG welded root.
However, the standard BS 7448 deep notched fracture toughness test (a/W > 0.45) is unable to measure fracture toughness associated with shallow surface cracks. Conventional tests can result in gross over- or under-estimates of toughness with potentially severe consequences.
By using TWI's shallow crack fracture mechanics toughness test method, suitable data were obtained. The toughness results, combined with a fracture mechanics fitness-for-purpose assessment of the structure, showed that the TIG weld would tolerate long surface cracks to the full depth of the root. This increased confidence in the use of NDT methods for detecting significant flaws from the fill-in side (outside) of the weld.
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