Durability Methods Development. Volume 7. Phase 2. Documentation
Final rept. Jun 1979-Jan 1984
GENERAL DYNAMICS FORT WORTH TX FORT WORTH DIV
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A statistically-based durability analysis methodology is evaluated, refined and demonstrated in this report for advanced metallic airframes. This methodology can be used to 1 analytically assure the U.S. Air Forces durability design requirements, 2 evaluate durability design tradeoffs, and 3 evaluate structural maintenance requirements and user options affecting life-cycle costs. The methodology accounts for initial fatigue quality, crack growth accumulation in a population of structural details, load spectra and structural properties. Analytical procedures and guidelines are developed and described for quantifying the extent of damage due to fatigue cracking in structural details as a function of service time and design variables. An initial fatigue quality model is described and discussed. This model is based on the time-to-crack-initiation TTCI and the equivalent initial flaw size EIFS concepts and a deterministic crack growth power law. An experimental test program and the resulting fractographic data for cracks in clearance-fit fastener holes are described and discussed.