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INVESTIGATION OF CIRCULAR REINFORCEMENTS OF RECTANGULAR CROSS SECTION AROUND CENTRAL HOLES IN FLAT SHEETS UNDER BIAXIAL LOADS IN THE ELASTIC RANGE
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON D C
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A study was made of the stress concentrations around holes in flat sheets reinforced with rings of rectangular cross section symmetrically mounted ith respect to the sheets. The sheets were loaded in a biaxial loading machine, and stress-concentration factors for principal nominal stress ratios of 11, 1.51, 21, and 2.51 were determined. The sheet specimens were fabricated from plastic sheet and were instrumented with foil strain gages. The best reinforcements reduced the stress-concentration factors to below 1.1 for the range of stress-field ratios studied. For a given hub thickness, increasing the ring diameter results in shifting the point of maximum effective stress from the inner rim of the hub to the sheet. If the ring diameter is kept constant, an increase in the hub thickness will shift the location of maximum stress or will have a negligible reinforcing effect. In most cases, increasing the thickness will raise the stresses in the sheet slightly. Author
APPROVED FOR PUBLIC RELEASE