The Effect of Broken Stringers on the Stress Intensity Factor for a Uniformly Stiffened Sheet Containing a Crack.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER
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A linear elastic stress analysis was made of a centrally cracked sheet stiffened by riveted, uniformly spaced and sized stringers. The stress intensity factor for the sheet and the load concentration factor for the most highly loaded stringer were determined for various numbers of broken stringers. A broken stringer causes the stress intensity factor to be very high when the crack the crack tip extends beyond several intact stringers. A broken stringer also causes an increase in the load concentration factor of the adjacent stringers. The calculated residual strengths and fatigue-crack growth lives of a stiffened aluminum sheet with a broken stringer were only slightly less than a sheet with all intact stringers and were still much higher than those of an unstiffened sheet. The strengthens and lives with a broken stringer were also higher for stiffer and more closely spaced stringers and rivets -- much as when all stringers are intact.
- Properties of Metals and Alloys