Abstract
As a part of a study on material- and size-dependence of notch effect in metal fatigue, the two elastic-mechanical parameters, which are based on the Mises effective stress distribution on a notch root cross-section of a notched element under tension, are defined and formulated. The one is the ratio of cross-sectional average of the Mises effective stress to nominal axial stress and it is symbolized as p-value. The other is the ratio of the Mises effective stress at the notch root to the cross-sectional average of the Mises effective stress and it is symbolized as Ktef. FEM analyses are carried out for the plane stress and strain conditions of a double edge-notched plate and for axisymmetric condition of circumferential notched round bar. Notch shape is semi-elliptical, and the depth t/D is selected from 0.025 to 0.35 (6 cases) for the gross-sectional width/diameter D=200 mm and the root-radius ρ/D is varied from 1 to 0.005 (10 cases). Ktef and p-value were supplied as base data for formulation in addition to the axial stress concentration factor Kt usually used. It is found that the relation of Ktef = 1 + (Kt - 1)/p is composed among Kt , Ktef and p-value. The p-value is formulated as a step function of tan-1 {log(ρ/D)} with t/D an auxiliary variable, and absolute error of the equation is smaller than about ±0.05 for the p-value changing from 0.43 to 1. The elastic-mechanical parameters of Ktef and p-value are applied to formulation of a yield zone growth curve of an elastic-completely plastic body.
