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Several precracking methods for crack-tip opening displacement (CTOD) testing of weldments were studied, including as local precompression, reverse bending, and high R-ratio fatigue. The precracking procedure could influence the validity of the precrack shape. However, it was found that an irregular precrack front had little effect on CTOD values of the heat-affected zone (HAZ). Results indicate that the current limitations on the fatigue precrack shape can be relaxed.
CTOD values comparable to those of the standard B × 2B specimen were obtained from the subsidiary B × B specimen with a through-thickness notch of a length-to-specimen-width ratio of 0.5. Hence, it can be possible to use B × B specimens instead of B × 2B specimens in the standard CTOD testing of weldments.
The CTOD test results for weld HAZ were strongly affected by the notch positioning in the welded joint. By analyzing the weld thermal history, HAZ microstructures were classified. Then, it was revealed that CTOD values were closely related to the maximum size of the local brittle zone (LBZ) at the crack tip.
weldments, crack-tip opening displacement, fracture toughness, welded joint, weld heat-affected zone, residual stress, testing standards, local brittle zone, fracture testing
Professor, University of Tokyo, Tokyo,
Associate professor, Nagoya University, Nagoya,
Associate professor, Kyushu University, Fukuoka,
Senior research engineer, R & D Laboratories, Nippon Steel Corp., Sagamihara,