Highly loaded gears are usually casehardened to fulfill the high demands on
the load-carrying capacity. Several factors, such as material, heat treatment, or macro and micro geometry, can influence the load-carrying capacity. Furthermore, the residual stress condition also significantly
influences load-carrying capacity. The residual stress state results from heat treatment and can be further modified by manufacturing processes post heat treatment, e.g. grinding or shot peening.
I have heard that X-ray diffraction does not tell the whole story and that I should really run a fatigue test. I understand this may be the best way, but is there another method that gives a high degree of confidence in the residual stress measurement?