Neutron diffraction study of stress field distribution in automotive gears

Automotive gears are mechanical components for which a hardening of the surface of the gear teeth is required to improve their wear behaviour. This is generally obtained by applying specific thermal or mechanical treatments to the specimen. However, these treatments usually produce also high residual stress fields, which in turn influence significantly the fatigue life of the gears. It is therefore particularly important to have a map of the residual stress fields in the component. In this work we report some results from neutron diffraction measurements of the triaxial stress field in two steel automotive gears. The strains were measured along the three principal directions at different depths from the surface of the throat between two adjacent teeth. The so obtained in depth results are compared to the very near surface stresses, determined by X-rays diffraction.