Section 4.1.1. Slow Crack Growth Structure
4.1.1 Slow Crack Growth Structure
In a slow crack growth structure,
the damage tolerance must be assured by the maintenance of a slow rate of crack
growth, a residual strength capacity, and the assurance that subcritical damage
will either be detected at the depot or will not reach unstable dimensions
within the design lifetime of the structure.
The residual strength curve for a structure which is inspected
periodically is schematically shown in Figure 4.1.4. As a result of the inspections, the
initially assumed cracks do not grow to a critical size and the structure is
restored to its original load carrying capability when an inspection capability
equal to that of the manufacturer’s is employed.
Figure 4.1.4. Strength Criteria for Periodically Inspected Damage Tolerant
Single-load-path “monolithic” structure must be qualified in
this category; the residual strength estimation procedure for this type of
structure is fairly straightforward.
Built-up (multiple-load-path) structure can be qualified either in this
category or in the fail-safe category.