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• January 17, 2017 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - A Theoretical and Experimental Investigation of the Influence of Temperature Gradients on the Deformation and Burst Speeds of Rotating Disks

The purposes of this investigation were to evaluate the influence of
temperature gradients_and to test the validity of a recently developed
method of calculating plastic flow in disks by comparing calculated
results with experimental dbServations.

Short-time spin tests on paralle17sided, lO—inch—diameter disks
were conducted under conditions that subjected the disks to a range of
temperatures from 70° to 14400 F and to a range of temperature differences
between the rim and center from 00 to 12900 F. Measured plastic strains
and experimental burst speeds were compared with the strains and burst
speeds calculated from the short-time tensile properties of the disk
material.

The agreement between the theoretical and experimental results was
good over the wide range of temperature conditions investigated. Thermal
gradients produced little reduction in burst speed'of the disks which had
high ductility; however, these gradients had a strong influence on the
behavior of the disk during the early stages of plastic flow. The loss
in tensile properties of the material, caused by the temperature of the
material, had a greater effect in reducing the burst speed than the
stresses set up by the thermal gradient.

In turbojet and turbine-propeller engines, the turbine disk is one
of the heaviest components, and it is also one of the components which
uses-a large amount of strategic material. Accurate knowledge of the
factors that affect the strength of this part is needed to design turbine
disks which will utilize the material in the disk most efficiently. The
rim of an aircraft-gas-turbine wheel operates at higher temperatures

than the central portion of the disk. This condition may introduce
thermal stresses of considerable magnitude. Because stress distributions
in turbine disks are complex, many disks have been designed.using rather
large safety factors. If the stresses in the disk could be computed
more accurately and the significance of these stresses could be determined
experimentally, then disks could be designed less conservatively.