In-situ measurement of stresses in carburized gears via neutron diffraction

R. A. LeMaster, B. L. Boggs, J. R. Bunn, J. V. Kolwyck, C. R. Hubbard, W. B. Bailey

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

The total stresses in a mating gear pairarise from two sources: (1) externally induced 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 of complex normal and shearing forces that develop during the meshing sequence. The total stress from these two sources contributes to the life of a gear. This paper presents the results of research directed at measuring the total stress in a pair of statically 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) of atoms in the crystal lattice using diffractometers that measure the position of a diffraction 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. Computation of strains using neutron diffraction methods requires that the lattice spacing in the strain-free condition (d 0) be known. The determination of d0 for a carburized material is not trivial due to carbon, phase and microstructure gradients that exist near the surface. These gradients require that a different value of do be known at each measurement location. The paper includes a summary of various methods that are used to determine d 0 and a discussion of their applicability to carburized gears. The possibility of determining d 0 using ψ-tilt methods is discussed and results are presented for d 0 variation through the carburized layer determined using the sin 2 ψ method.

Original languageEnglish
Title of host publicationAmerican Gear Manufacturers Association - American Gear Manufacturers Association Fall Technical Meeting 2008
Pages143-152
Number of pages10
StatePublished - 2008
EventAmerican Gear Manufacturers Association Fall Technical Meeting 2008 - San Antonio, TX, United States
Duration: Oct 12 2008Oct 14 2008

Publication series

NameAmerican Gear Manufacturers Association - American Gear Manufacturers Association Fall Technical Meeting 2008

Conference

ConferenceAmerican Gear Manufacturers Association Fall Technical Meeting 2008
Country/TerritoryUnited States
CitySan Antonio, TX
Period10/12/0810/14/08

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