validation and case studies

FITNET FFS – MK7– Section 13plotted in Figure 13.30. The minimum thickness recorded was 45.5 mm at a position which corresponded to250 mm of growth from Crack Tip 1. The minimum thickness on the fracture surface of Crack Tip 2 was 59mm at between 100 and 175 mm out from the initial crack tip. These thicknesses are in comparison to a pretestvalue of 61.2 mm.The unloading chevrons appeared very clearly on the fracture surface, the most interesting being thatproduced by the first unloading at an applied load of 10.35 MN. It showed a degree of asymmetry whichreflected the asymmetrical nature of the weld preparation (Figure 13.31).The crack had propagated well intothe weld metal on each side, being deeper on the side with the thicker weld, but it had grown much less at thelocation near the middle of the plate where the welds from either side had met up. In fact the growth at thispoint was almost as little as that at the edge of the plate. However, by the second unloading, the crack fronthad assumed the usual chevron shape (Figure 13.31).The chevron marking due to the first unloading at a load of 10.35 MN was the only one available up to themaximum instability load of 10.83 MN. The crack growth data are therefore average values of the centre andthe surface of Crack Tips 1 and 2, and, the lowest value of initiation load which occurred at the centre of CrackTip 1 as evaluated by ACPD is taken.Summary of Analysis and Results: Analysis details are given in Table 13.11. Results are summarised inTable 13.12 and in Figure 13.32.13-38 © FITNET 2006 – All rights reserved