Crystal plasticity model of surface integrity effects on fatigue properties after Milling: An investigation on AISI 4140 steel

The surface integrity of AISI 4140 steel after milling at different feed rates (75–125 mm/min) was measured by performing laser scanning microscopy, X-ray diffraction, and electron backscatter diffraction. Subsequently, the fatigue responses under different maximum stress values (650–800 MPa) were analyzed. The results showed that the increase in the feed rate increases the residual stress and roughness, whereas the fatigue life at low stress is reduced. Moreover, the feed rate has a limited effect on the surface grain refinement layer, and fatigue life at high stress. The measured surface integrity models were used to predict the fatigue life based on the crystal plasticity theory, and these yielded results within the three times scatter bands from the corresponding experimental values.