抄録
The equivalent cyclic stress ratio REQ followed by elastic-completely plastic yield zone partition type cross-section dimension dependence magnification factor, which is modified to fatigue strength criterion specification, is applied to estimation of plane bending fatigue strength of a smooth bar with rectangular, circular and rhombic cross-section, and rotating bending and torsion fatigue strength of a round smooth bar from an axial load fatigue strength diagram of a smooth specimen. This approach is expected to be effective in elucidating the size effect and its material dependence.
The main issues are as follows;
(1)REQ is calculated by using a plastic/elastic section modulus ratio (a shape factor) of elastic-completely plastic smooth specimen ZY/ZE in place of the stress concentration Kt.
(2)Cross-section dimension dependence magnification factor FS0 is derived as a yield strength criterion specification by means of the coordinate transformation of an equation of a yield zone growth curve, and the magnification factor FS0+- is modified to FS0kM as the fatigue strength criterion specification by using Schütz parameter M (a coefficient of a proportional term related to mean stress of a linear equation of fatigue strength).
(3)Rotating bending fatigue strength of a round bar specimen is simulated as completely reversed plane-bending fatigue strength of a smooth bar specimen with a cross-section of a pair of the isosceles triangles connected and fixed at the vertices.
