Page 145 - Failure Analysis Case Studies II

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Fig. 15. Ground bar butt weld in double-sided region. Note incomplete penetration. x 7

Fig. 16. Intermittent lap fillet weld in sample 1 between ground bar and bulb bar, seen from above

Although the lack of penetration defect of the starboard sample must have seen comparable
loading to that experienced by the detail which initiated in the port sample, this was not a critical
defect. The presence of a complete double-sided weld was obviously sufficient to reduce the overall
stress and local stress concentration effects experienced by this weld to levels below that at which
any significant fatigue crack propagation had occurred. Because of the lower overall stress and local
stress concentration levels, and the presence of a smaller and blunter defect in the starboard detail,
fracture initiation from this site was much less likely. As noted in [l], if the ground bar weld detail