Me. Barkey et al., A YIELD SURFACE APPROACH TO THE ESTIMATION OF NOTCH STRAINS FOR PROPORTIONAL AND NONPROPORTIONAL CYCLIC LOADING, Journal of engineering materials and technology, 116(2), 1994, pp. 173-180
An analytical method is developed to estimate notch root strains in a
notched bar of elastic-plastic, isotropic material subjected to propor
tional and nonproportional multiaxial nominal loading. The method uses
anisotropic plasticity theory to define a structural yield surface in
nominal stress space that incorporates both the isotropic material pr
operties and the anisotropic geometry factors of the notch. Notch root
plastic strain increments and anisotropic work-hardening effects are
then related to this yield surface using standard methods of plasticit
y. Comparisons of the proposed method with previously published strain
estimates using the finite element method for a notched shaft under p
roportional nominal bending and torsion, and with strain gage measurem
ents of a circumferentially notched solid steel shaft subjected to a s
eries of box-shaped nonproportional loading paths in tension-torsion n
ominal stress space are presented. The strain calculations agree well
both qualitatively and quantitatively using an appropriate nominal loa
d-notch plastic strain relationship, and are suitable for strain-life
fatigue calculations.