The effect of the grinding wheel modification on the state of the workpiece surface layer after internal cylindrical grinding of steel C45

Internal cylindrical grinding is one of the most difficult grinding processes due to the very long zone of contact between the grinding wheel and the workpiece surface. Such conditions limit delivery of the grinding fluid into the grinding zone, as well as impeding the removal of chips from it. As a result, during the internal cylindrical grinding process, difficult thermal conditions occur in the machining zone which finally could lead to grinding defects. One of the most efficient and cost-effective ways of improving the grinding stability and repeatability is modifying the grinding wheel structure. As such, modifications usually do not require interfering with the construction of the grinding machine or its equipment, they are universal and, possibly, widely applicable. This article presents a modified grinding wheel with helical grooves shaped on its active surface. Such modification was developed to reduce the thermal load of the workpiece surface and the occurrence of thermal defects. The effectiveness of the proposed grinding wheel modification was examined experimentally in the reciprocal circumferential internal cylindrical grinding process of 45C steel. The goal of the described tests was to determine the influence of the suggested grinding wheel modification on the condition of the workpiece surface layer (the surface roughness and residual stresses). The test results obtained indicated that application of the modified grinding wheel has a positive influence on the residual stresses in the workpiece surface layer, resulting in better delivery of the grinding fluid into the area of contact between the wheel and the machined material. Moreover, a decrease of the Ra parameter value by approximately 7-19%, as compared to the results of the process carried out with the (unmodified) reference grinding wheel was indicated.