Neuber's Rule Accuracy in Predicting Notch Stress-Strain Behavior for Several Geometries

Abstract

A numerical investigation has been undertaken to quantify the potential error in the use of Neuber’s rule in approximating stresses and strains for local stress concentration regions that undergo plastic deformation. A flat plate with an open hole, a round bar with a circumferential notch and a double-lap splice joint with three rows of pins were all modeled using finite element techniques, for two different material types. The local notch stress and strain values from the models were each compared to the notch strain values predicted using Neuber’s rule. The results show that Neuber’s approximation significantly overpredicts local strain when plasticity (0.8% to 2.0% strain) is encountered in the notch. The state of multiaxial stress in the notch region significantly affects the Neuber strain prediction error, but not in a consistent manner. Different material stress-strain curves also have an effect on the strain prediction error, but to a lesser extent. The results indicate that using finite element solutions in the place of Neuber’s rule to estimate notch strain behavior may significantly reduce the modeling error (epistemic uncertainty) of a probabilistic strain-life methodology.