Comparison of methods for determining residual stresses in induction-hardened transmission shafts

This paper compares 3 methods for determining residual stresses in inductio n-hardened shafts, as function of the depth beneath the surface. The method s are X-ray diffraction, neutron diffraction and a simulation of the induct ion-hardening process. The simulation is performed with a finite-element pr ogram called SYSWELD. The residual stresses are needed to be able to calcul ate the fatigue life for the shafts. Fatigue tests have shown that cracks c an initiate in the core of the shaft. For both the Xray and the neutron dif fraction technique, it is necessary to do some machining of the shaft to be able to measure beneath the surface. Machining of specimens for the neutro n diffraction measurement means cutting the shaft into a plate and a disc. Hence, in this case, it is not possible to analytically calculate back to t he original stresses. Good agreement is found between simulation and X-ray diffraction measurement, while the conformity with neutron diffraction meas urements is not so good. Simulations of different hardening depth show a re latively large influence on the residual stress magnitude.