Determination of carbon steel microhardness by the magnitude of temporary stresses in the deformation zone during reverse burnishing

The article presents the results of finite element modeling of the reverse burnishing process to determine the components of the temporary stress tensor and the intensity of temporary stresses depending on the main hardening parameters. Based on the results of experimental studies, the influence of reverse burnishing parameters on the microhardness value and the depth of the hardened layer was determined. A correlation has been established between the maximum value of temporary stress components and the depth of their occurrence with the maximum microhardness and depth of the strengthened layer. The results of regression analysis show that the value of the maximum microhardness during reverse burnishing most closely correlates with the maximum value of compressive tangential temporary stresses, the correlation between them is determined by the following equation: Hмах = (2E – 06)(σvrφmax)2 – 0.3025σvrφmax + 61.335 (approximation reliability coefficient R2 = 0.9874). And the depth of the strengthened layer is with the maximum value of radial temporary stresses, the correlation dependence between them is determined by the following equation: hmax = (2E – 06)(σvrφmax)2 + 0.0035σvrφmax + 2.3264 (approximation reliability coefficient R2 = 0.9874). Evaluating the presented equations based on the approximation reliability coefficients, we can say with confidence that there is a fairly close connection between the microhardness value and the depth of the hardened layer with the parameters of compressive temporary stresses and their depth. The obtained empirical equations make it possible, based on the results of determining the maximum value of the components of temporary compressive stresses and the depth of their occurrence, to determine the maximum microhardness and depth of the strengthened layer. Thus, based on the results of modeling the stress state in the deformation zone, it is possible to determine the main characteristics of the layer being strengthened without destroying the parts.