<DOC>
<DOCNO>
829
</DOCNO>
<TITLE>
stability of thin-walled tubes under torsion .
</TITLE>
<AUTHOR>
donnel,l.h.
</AUTHOR>
<BIBLIO>
naca r.479, 1933, 12.
</BIBLIO>
<TEXT>
  in this paper a theoretical solution is developed for the
torsion on a round thin-walled tube for which the walls
become unstable .  the results of this theory are given by
a few simple formulas and curves which cover all cases .
the differential equations of equilibrium are derived in a
simpler form than previously found, it being shown that
many items can be neglected .  the solution obtained is
length ratio is zero and infinite, and is a good approximation
for intermediate cases .  the theory is compared
with all available experiments, including about 50 tests
made by the author .  the experimental-failure torque is
always smaller than the theoretical-buckling torque, averaging
about 75 percent of it, with a minimum of 60 percent
.  as the form of the deflection checks closely with
that predicted by theory and the experiments cover a great
range of shapes and materials, this discrepancy can reasonably
be ascribed largely to initial eccentricities in
actual tubes .
</TEXT>
</DOC>
