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Surface-breaking fatigue cracks are common defects in metal components
subjected to cyclic loads. Such cracks tend to propagate in stress
fields that are below the critical stress level for static loading. An
important part of a damage tolerant design philosophy is the requirement
that surface-breaking cracks should be detectable before they reach a
critical depth. In this paper, we consider a surface-breaking crack in a
two-dimensional geometry, whose original depth is defined by a
probability density function. The increase of the crack depth with
number of cycles is governed by Paris law, and the detectability depends
on a probability of crack detection (POD). Based on this information we
determine the probability that the crack depth will have exceeded a
prescribed critical value at a specified number of cycles. |
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