Section 18.104.22.168.10. Incremental Damage Growth Da
The remaining structure analysis of damage growth and residual
strength considers damage in the adjacent structure at the time of load path
failure which has grown an amount Da
from the time of manufacture (Figure 1.3.19).
Since the structure must met the single design lifetime requirement, it
becomes necessary to establish at what point during the lifetime the failure of
the load path is assumed to take place so that the proper amount of growth Da can be computed to represent growth during this
Figure 1.3.22 illustrates the
growth of the 0.005 inch manufacturing type damage from time zero for one
design lifetime. In this example, the
walk-around-visual inspection is used to detect the failure of the major load
path and the inspection interval is 10 flights. JSSG-2006 Table XXXIII requires a factor of 5 on this interval
and thus the damage growth life requirement is 50 flights. Therefore, the maximum amount of Da and the condition to be met would be growth for
one design lifetime minus 50 flights.
For any other in-service inspection interval the amount Da would be computed in a similar manner. For example, if the walk-around-visual
inspection was not conducted and fail safety was dependent upon discovery of
damage at the scheduled 10,000 hour depot level inspection, then the increment
of growth Da would be one design
lifetime minus 2x 10,000 hours, as in Figure 1.3.23.
Figure 1.3.22. Development of Increment of Growth Da2 for Walk-Around-Visual
Figure 1.3.23. Development of Increment of Growth Da2 for