Algorithm to estimate notch root strain in bending using numerical analysis

Fatigue life assessment of notched components, requires an evaluation of nonlinear stress and strain behavior at the notch root. Neuber's rule (Neuber, 1961) [1] and the Glinka equivalent strain energy density (ESED) (Molski and Glinka, 1981) [2] method are two well-known approaches for elastic-plastic notch analysis. The success of Neuber's rule has been shown to depend on the material constitutive relation and the mode of loading, and the Glinka SED approach has been shown to be limited to situations where the plastic zone size ahead of notch root is small, surrounded with predominantly elastic deformation (Kilambi and Tipton, 2013) [3]. An empirical model was presented to estimate notch root strains for notches in tension (Kilambi and Tipton, 2015). This paper extends this approach to notches in bending. The approach stems from the empirical observation that a normalized stress concentration factor is a function of maximum permanent strain. Results from the algorithm are demonstrated to estimate notch root strains to within 15% when maximum notch root strain is within 2-3% and much more closely for lower maximum strains.