Residual Normal and Shear Stresses on Different Machining-Finished Surfaces of Martensitic Ultrahigh Strength Steel

Abstract

Machining induced residual stresses are known to have influenced mechanical properties of high strength metallic alloys. In this paper, we have compared the surface residual stresses of an ultrahigh strength martensitic/bainitic steel grade 56NiCrMoV7 induced by two different machining processes, namely turning and milling. Using the established d~sin2ψ method, x-ray diffraction technique was employed to measure the residual stresses on both the axial and hoop directions of cylindrical samples. The results reveal that, turning finish led to tensile residual stress in the axial direction and compressive residual stress in the hoop direction. On the other hand, milling finish led to compressive residual stresses in both the axial and hoop directions. In addition, large splitting in the d~sin2ψ linear regressions has been interpreted by the presence of residual shear stresses.