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National Advisory Committee for Aeronautics, Technical Notes - Effect of Variation in Diameter and Pitch of Rivets on Compressive Strength of Panels with Z-Section Stiffeners

An experimental investigation is being conducted to determine the
effect of varying the rivet diameter and pitch on the compressive strength
of flat EhS-T aluminumralloy Z-stiffened panels of the type for which
design charts are available. The present part of the investigation is
concerned with panels which have various values of width-to-thickness
ratio of the webs of the stiffeners and have such length that failure is
by local buckling. The results show that for these panels, regardless
of their stiffener widths, the compressive strengths increased appreciably
with either an increase in the diameter of the rivets or a decrease in
the pitch of the rivets.

The design and analysis of sheet-stiffener panels for aircraft
structures have been the subject of extensive experimental and theoretical
investigations, but the determination of the size and pitch of rivets
for attaching sheet to stiffener is a problem that has not been adequately
solved. In reference 1 charts and procedures are presented for the
design of Z-stiffened panels to carry a given intensity of loading at
a given panel length. The test data on which these design charts were
based, however, were obtained for an arbitrary diameter and pitch of the
rivets. An investigation is therefore being conducted in the Langley
structures research laboratory of the National Advisory Committee for
Aeronautics to determine the effect of a variation in the rivet diameter-
and pitch on the strength of 2hS-T aluminum-alloy panels with longitudinal
Z-section stiffeners of the type for which the design charts of
reference 1 were prepared.

For allpparts of the investigation.- The specimens consisted
of 2hS—T aluminumralloy panels having longitudinal Z—section stiffeners
as shown in figure 1. The stiffeners were riveted to the sheet with
AlTS—T flat-head rivets (ANthAD)- In all cases the minimum rivet pitch
used was equal to three times the rivet diameter. The rivets were driven
, by the NACA flush-riveting process in which the rivet is inserted with
the head opposite the countersunk end of the hole, the shank of the rivet
is driven into the cavity formed by the countersink, and the excess
material is removed with a milling tool. A countersink angle of 60° was
used.