Development and Evaluation of Methods of Plane Stress Fracture Analysis. Part 2. Volume I. A Technique for Predicting Residual Strength of Structure
Final rept. Jan 1973-Dec 1974 on phase 2
NORTHROP CORP HAWTHORNE CA AIRCRAFT DIV
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A procedure for residual strength analysis of complex structure has been outlined and tested in predicting failure stresses for several complex, riveted, bolted and adhesively bonded structural panels. This new method makes use of the material crack growth resistance curve incorporating both elasto- plastic and slow stable tear in the fracture criterion for skin critical structure. Comparisons were made with assumed Dugdale, Prandtl-Reuss, and elastic material behavior for both skin and stiffener critical structure using a J integral approach. The role of material slow tear has been examined for both linear elastic and elastic-plastic behavior and compared with the analysis which indicates the superiority of the elasto-plastic analysis to the point of stringer failure at ultimate strength. The importance of finite element modeling of attachment and stiffener has been determined and the use of a flexible fastener model for riveted and bolted structure verified. A shear spring model was demonstrated for use with adhesively bonded stringers with excellent correllation with measured panel failure stress.