ASME 1993 Nadai Lecture—Elastoplastic Stress and Strain Concentrations

Elastic stress concentration factors are familiar and easily incorporated into the design of components or structures through charts or finite element analysis. However when the material at the most concentrated location no longer behaves elastically, computation of the local stresses and strains is not so easy. Local elastoplastic behavior is an especially important consideration when the loading is cyclic. This paper summarizes the predictive capability of the Neuber and the Glinka models that relate gross loading to the local stresses and strains. The author and his students have used a unique laser-based technique capable of measuring biaxial strains over very short gage lengths to evaluate the two models. Their results, as well as those from earlier studies by other researchers using foil gages, lead to the general conclusion that the Neuber model works best when the local region is in a state of plane stress and the Glinka model is best for plane strain. There are intermediate levels of constraint that are neither plane stress nor plane strain. This paper presents a recommended practice for predicting the local elastoplastic stresses and strains for any constraint. First, one computes or estimates the initial elastic strains. Then, based on the amount of elastic constraint, one selects the appropriate model to compute the local elastoplastic stresses and strains.