The influence of the hardened layer thickness on the fatigue resistance under outstripping superficial plastic deforming

The influence of the hardened surface layer thickness under outstripping superficial plastic deforming on the endurance limit of hollow cylindrical specimens made of steel 20 of 25mm diameter with the 15 mm hole with circular cuts of semicircular profile of three radiuses: R=0,3 mm, R=0,5 mm, R=1,0 mm. Various thickness of the hardened surface layer was made by pneumoshot blasting and by rolling of two regimes. It is established that the residual stresses in the dangerous section of specimens decrease with the radius of cuts increase, therefore the endurance limit decreases. The thickness of part's hardened surface layer should be increased for the hardening effect conservation in the case of outstripping superficial plastic deforming under cut depth rising.