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National Advisory Committee for Aeronautics, Technical Memorandum - The Behavior Under Shearing Stress of Duralumin Strip with Round, Flanged Holes

This report presents the results of an investigation
to determine the behavior of duralumin strip with flanged
holes in the center when.subjected to shear stresses.
They buckle under a certain load just as a flat sheet.
There is one Optimum hole spacing a0 (equation 4) and
one corresponding buckling load in shear PRO (equation
7) for each sheet width, sheet thickness, and flange form.
Comparison with nonflanged sheets revealed a marked in~
crease of buckling load in shear due to the flanging and
a slightly greater diSplacement. The stiffening effect of
flanging showed itself in a considerably higher buckling'
load for thin, wide strip than for the unweakened sheet.
Lastly, the displacement 8, under a l kg/mm (55.99 lb./
in.) load (equation 8) was determined. It is considerably
higher for the flanged sheet than for the unweakened sheet,
and slightly higher than for the unflanged sheet. Sheets
may not be stressed beyond buckling load unless special
cross stiffeners are available to take up the load compo—
nent K perpendicular to the direction of shear. The
shear—displacement diagram (fig. 6) is substantially a ten—
sile stress~strain diagram above the buckling load. The
formulas develOped for ac, Pko’ and 5 are the results of
pure experimentation and may therefore become quite faulty
outside of the analyzed range.
The location of the- -forces- relative to the elastic
axis of the system- is essential for- the type of stress.‘
The.forces'lying on acplane"withcthis axis simply set up
tension, compressioni or bending in.the elastic structure,
whereas all others effect ansadditiveztorsion. This
ostresses,.apart from specific-cases; the individual sheets
innshearrt When the.forces are at.great distance from the
elastic'axis, the shear may become so great as to make the
other stresses negligible; that~is,umake it a case of sim~
ple shearing stress.