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National Advisory Committee for Aeronautics, Technical Notes - Some Investigations of the General Instability of Stiffened Metal Cylinders - IV - Continuation of Tests of Sheet

This report is to deal primarily with the continua—
tion of tests of sheet—covered specimens and studies of
the buckling phenomena of unstiffened circular cylinders.
The earlier work on this investigation of the problem of
general instability of stiffened metal cylinders at C.I.T.
has been reported in references 1, 2. and 3. Tests have
been completed on the first series of sheet—covered spec—
imens.

The longitudinele and frames of the sheet—covered'
specimens were identical to those of the wire—braced spec-
imens discussed in reference 3. The sheet covering was
in all cases 0. 010— inch l7S—T aural. The longitudinal
spacing was varied from 2. 55 to 10.12 inches and the
frame spacing from 1 to 16 inches. An attempt has been
made to correlate the experimental data of the wire—braced
and sheet—covered specimens. A detailed discussion is
given in the discussion of the normal restraint coefficient
in this report. Ryder' s theoretical work has been applied
to three specimens.

In addition to the results on the sheet—covered spec~
imens, the results of an investigation on'axially loaded
thin-wall metal cylinders will be included in this report.
As the preliminary work of this investigation was dis-
cussed in reference 2. only results of the more recent
work are included. An important finding of this investi—
gation has been the determination of the initial wave form.
It has been found that the initial wave form does not agree
with the uniform sinusoidal type of wave which has been
previously assumed for the theoretical solution, but is
elliptical- in shape, scattered at random through the cyl-
inder, and changes to a diamond shape as the load is in—
creased.

As pointed out in reference 2, a number of sheet—
covered specimens were to be tested to determine whether
or not a correlation could be obtained between the fail—
ing bending moments of the wire-braced and the sheet—
covered specimens. The construction of the sheet—covered
and wire~braoed specimens was essentially similar, the
only difference being that the Wire bracing was replaced
by the sheet. Details of construction and test procedure
have been discussed in detail in reference 2 and will not
be repeated here.