Analysis of Multiple Site Damage with Implications for Nondestructive Evaluation
Multiple-Site Damage (MSD) in aging aircraft has motivated analysis of the fatigue life of a panel containing a row of cracked holes [1–3]. Given the initial MSD configuration and loading conditions, individual cracks are grown incrementally until link-up or the panel failes. First, stress intensity factors are calculated for all cracks. One crack tip is then assumed to advance a small amount, and the cycles for this increment of growth are calculated. The remaining cracks are then grown a distance corresponding to this cyclic interval by employing a fatigue crack growth model to relate the cyclic stress intensity factor and fatigue crack growth rate. After each incremental growth the current crack geometry is compared to one of several failure criteria  to determine whether the panel fails. For holes which are initially uncracked, cumulative damage is summed at these locations in conjunction with a Neuber notch analysis. When this strain-life analysis determines that “crack initiation” has occurred at a given hole, crack growth calculations continue at that location, and the routine is repeated until the failure criterion is satisfied.
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