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National Advisory Committee for Aeronautics, Technical Notes - Effect of Strength and Ductility on Burst Characteristics of Rotating Disks

An investigation was conducted to determine the influence of
strength and ductility on the room—temperature burst characteristics
of solid disks, disks with large-diameter central holes, and disks
with small—diameter central holes. Disks were machined from seven
materials, two of which were given various heat treatments.

For the solid disks and for the disks having stress concen-
trations consisting of large- and small—diameter central holes,
burst strength increased with increase in tensile strength. The
ratio of burst strength to tensile strength was relatively inde-
pendent of ductility. The strengths of solid disks were reduced
by the introduction of large-diameter central holes approximately
in proportion to the amount of material removed.' Small holes
reduced the strength by an amount greater than the amount of section
removed but not as much as would be predicted by calculating elastic
stresses.

The effect of ductility on the strength of rotating disks has
long been a serious concern of machine designers. Functional consid-
erations often require that disks be so designed that stress concen-
trations are set up in regions that are already highly stressed.

If small material defects are to be tolerated, they will also increase
the stresses. For disks that have stress concentrations, a material
having some ductility is usually selected in order that during
rotation small amounts of plastic deformation can redistribute the
stresses in a more satisfactory manner. The amount of ductility
considered necessary is often obtained at some sacrifice in tensile
strength. Because lack of ductility is considered to make a material
sensitive to stress concentrations, the designer is confronted with
a serious dilemma little information is available on which a
rational compromise between strength and ductility may be based.