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National Advisory Committee for Aeronautics, Report - Quasi Cylindrical Theory of Wing Body Interference at Supersonic Speeds and Comparison with Experiment

A method is presented for analyzing the stresses about cutouts
in circular semimonocoque cylinders with fleaible rings. The
method involves the use of so-called perturbation stress distrir
butions which are superposed on the stress distribution that
wmzldecistinthestrucmrewithnocutmdinsuchawayasto
givetheefi'ects ofacutout. Zhemethodcanbeusedfor_any
loading case for which the structure without the cutout can be
analyzed and is suficiently versatile to account for stringer
and shear reinforcement about the cutout.

An airplane fuselage usually has openings or cutouts for
entrance doors, cargo doors, windows, and manymther pur—
poses. The presence of such openings may result in a con-
siderable redistribution of stress in the structure. Some
knowledge of this stress redistribution is desirable in the
structural design of fuselages near cutouts.

A large portion of the structure of many fuselages can be
represented, approximately, by a circular semimonocoque
cylinder, that is, a thin-walled circular cylinder stiffened by
stringers (am'al stiffening members) and rings (circumferential
stiffening members). Some previous investigations relating
to the problem of stress analysis of cylindrical semimonocoque
shells with cutouts were reported in references 1 to 4. One
limitation common to all of these analyses is that the flexi-
bility of the rings or circumferential-stiffening members is
neglected. In reference 5, Cicala discussed this limitation
as well as certain other limitations in some of the previous
investigations and introduced the idea that the effect of a
cutout can be reproduced by superposing certain perturba-
tion stress states on the stresses which would occur in the
shell without a cutout.

The problem discussed by Cicala in reference 5 is that of a
cutout in a circular semimonocoque cylinder which is long in
comparison to the length of the cutout. The analysis of
reference 5 is somewhat limited because it can be used only
for loading conditions which produce stringer stresses longitu-
dinally antisymmetric about the center line of the cutout
(for example, torsion), and it cannot take into consideration
the effects of coaming stringer reinforcement.