Experimental investigation on variation of machined residual stresses by turning and grinding of hardened AISI 1053 steel

Residual stresses in machined surfaces are of great importance to the service life of a component under various loading conditions. In many cases, the material damage initiates from the weakest spot with the least compressive stress in the component surfaces. This situation leads to the consideration of residual stress moving beyond the traditional thinking of single or average values to the inclusion of variation of stress values on different measurement points. In this paper, we experimentally investigated the surface and in-depth residual stresses in hardened AISI 1053 steels machined using hard turning and surface grinding processes. Cubic boron nitride (CBN) cutting tools were used in both processes. The effects of depth of cut and number of passes were also studied. It was found that both processes produce a significant amount of compressive stress on the machined surfaces, as well as steep stress gradients underneath the surfaces. Compared with hard turning, surface grinding produces higher magnitudes of average compressive residual stresses, but it also generates up to 14 times higher scattering of residual stresses, indicated by the standard deviation of the residual stress measurements. As a result, the benefits of a highly compressive average residual stress will be offset by highly scattered individual measurements. The stochastic nature of abrasive grit distribution and orientations in grinding wheels is believed to be the contributing factor for the significant scattering. Meanwhile, for hard turning, the variation of surface and in-depth residual stresses greatly increases, up to 3.8 times, with a larger depth of cut and the use of multiple passes; however, this trend is less significant for surface grinding.