AN INFLUENCE OF ROLLER STRENGTHENING ON MULTCYCLIC FATIGUE OF SPECIMENS WITH CUTS OF VARIOUS DEPTH AND A PRESSURIZED HUB

The influence of roller strengthening on a residual stresses distribution and multicyclic fatigue of solid cylindrical specimens of 50 mm diameter made of steel 20 with cuts of various depths and a pressurized hub has been examined. As a result, an endurance limit of roller strengthened specimens diminishes. In order to preserve the effect of hardening with a cuts depth increase, its necessary to increase the thickness of a layer with compressive residual stresses. Surface hardening influence on an endurance limit of specimens has been estimated by two criteria: axial residual stresses on a concentrators surface and average integral residual stresses, calculated through the dangerous sections surface layer thickness that equal a critical depth of a non-propagating fatigue crack. Its been stated that its more reasonable to use the average integral residual stresses criterion for an evaluation of roller strengthening influence on an endurance limit of specimens with cuts of various depth and a pressurized hub.