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National Advisory Committee for Aeronautics, Technical Notes - An Investigation of the Characteristics of Steel Diaphragms for Automatic Fuel Injection Valves

This research on steel diaphragms was undertaken at the
Langley'Hemorial Aeronautical Laboratory, as a part of a gen:
Bral investigation of fuel injection engines for aircraft.

The work determined the loadedeflection, loadrdeformation and
hysteresis characteristics for single diaphragms having thick»
nesses fran 0.002 inch to 0-012 inch, and for similar dia—
phragms tested in multiple having total thicknesses from 0.012
I inch to 0.180 inch. The elastic lhnit loads and deflections,
and rupture points of single diaphragms were also determined.
Some work was done on diaphragms having central orifices in or-
der_to determine the.effeot of orifice diameter upon the load—
deflection characteristics.

All diaphragms were firmly clamped at their_edges in'an ml_
injection valve and loaded by hydraulic pressure. The deflec—
tions were measured with a dial test indicator. The diameters
of the unsupported area and of the whole diaphragm were 0.4

The results of these tests show that the deflections of
single diaphragms vary with the square root of the unit load
multiplied by a constant and inversely as a variable function
of the diaphragm thickness which, for very small deflections,
is the cube of the thickness but which decreases rapidly to
approximately the 0.8 power of the thickness at a deflection
of 0.010 inch. The elastic limit deflections were found to
vary from approximately 0.016 inch to 0.011 inch for diaphragm
thicknesses ranging from Oa002 inch to 0.012 inch. The rupture
point deflections ranged from 0.027 inch t5 0.038 inch.

The load Capacities of diaphragms used in multiple ins
creased almost directly with multiple thickness and for equal
multiple thicknesses, with a variable function of the indi—
vidual diaphragm thickness. The load capacities of diaphragms
with orifices increased rapidly with increase in the orifice
size.