The stability of residual stress plays an important role in the fatigue
performance of materials. In this work, the stability of surface
residual stress in carburized alloy steel with different carburized
layers is studied by axial fatigue tests. Different stress amplitudes
are applied to the specimens over several cycles, and the resulting
residual stress on the surface is measured by X-ray diffraction. It is
found that residual stress relaxation occurs on the specimens when the
applied stress amplitude is large, and that the relaxation rate depends
on the magnitude of the stress amplitude. The stress relaxation is most
obvious in the first cycle, and changes slowly in the subsequent cycles.
A model of surface residual stress evolution is established which can
accurately describe the relaxation process. The residual stress on the
surface of the specimen is found to be in a stable state, if the stress
amplitude is less than 30% of the material yield strength.