The total stresses in amating gearpairarise from two sources: 1 ) externallyinduced stresses associated with
the transmission of power, and 2) residual stresses associated with the heat treatment and machining of the
tooth profiles. The stresses due to power transmission are the result ofcomplex normal and shearing forces
thatdevelop during the meshing sequence. The total stress from these two sources contributes to the life ofa
gear.
This paper presents the results ofresearch directed at measuring the total stress in a pair ofstatically loaded
and carburized spur gears. Measurements were made to examine the change in total stress as a function of
externally applied load and depth below the surface. The measurements were made using the new Neutron
Residual Stress Mapping Facility (NRSF2) instrument at Oak Ridge National Laboratory. A Static Load
Application Device (SLAD) was developed to load the gear pair while mounted on the NRSF2 instrument.
Neutron diffraction methods are non–destructive and involve measuring the inter–atomic spacing
(d–spacing) ofatoms in the crystal lattice using diffractometers thatmeasure the position ofadiffraction peak.
The measured position is converted to d–spacing using Bragg’s Law. The change in d–spacing between
stressed and unstressed states allows the determination of strains and consequently the stresses.

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