A STUDY OF THE INFLUENCE OF GEOMETRY ON THE STRENGTH OF FATIGUE CRACKED PANELS
Final rept. Jun 1965-May 1966
NORTHROP CORP HAWTHORNE CA NORAIR DIV
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The objectives of the study program were to define and verify a synthesis of strength-limiting parameters for fatigue cracked panels which would be applicable to the wide range of conditions of interest in the engineering problem of strength analysis and to present this synthesis in a form that would lead to a better conceptual understanding of the interaction between parameters. The program consisted of an analytical study and a supporting experimental study. The analytical study, governed by the above objectives, considered fracture in the elastic range with buckling restraint provided, fracture combined with net section and gross section yielding, and fracture in the elastic range for unrestrained panels. The design problem involving appreciable amounts of slow tear was also considered. The experimental program provided supporting information on the behavior of fatigue cracks for bare 2024-T3 aluminum. Limited test data were also obtained for duplex annealed titanium 8Al-1Mo-1V. The aluminum alloy crack lengths ranged from .5 inch to over 10 inches. Panel widths were thirty, twenty, twelve and nine inches, and nominal panel thicknesses were .080 inch, .063 inch, and .032 inch. The titanium alloy panel widths were twelve and nine inches, and thicknesses were .045 inch and .020 inch. Buckling restraints were used for approximately half of the panels tested. Test information from other sources was used to illustrate specific points in theory and to show the generality of conclusions.