Page 147 - Failure Analysis Case Studies II

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Fig. 18. Fracture surface of ground bar butt weld in sample 1 in single-sided region, close to inboard edge of
bulb bar. Note smooth, featureless region in root of weld x 4

Fig. 19. Fracture surface of ground bar butt weld in sample 1 in single-sided region, close to outboard edge
of ground bar. Note smoother fracture surface in weld root, from which some chevron patterns (arrowed)
emerge. x4.

(b) evidence from chevron patterns showed that the crack ran through the bilge bar to shell plate
weld into the shell bilge plate;
(c) the notch acuity of the defect was lower in these areas due to the absence of a fatigue crack.
The directions of propagation from the initiation sites in the port sample are believed to have been
as shown in Fig. 20.