ASME 1993 NADAI-LECTURE - ELASTOPLASTIC STRESS AND STRAIN CONCENTRATIONS

Elastic stress concentration factors are familiar and easily incorpora ted into the design of components or structures through charts or fini te element analysis. However when the material at the most concentrate d location no longer behaves elastically, computation of the local str esses and strains is not so easy. Local elastoplastic behavior is an e specially important consideration when the loading is cyclic. This pap er summarizes the predictive capability of the Neuber and the Glinka m odels that relate gross loading to the local stresses and strains. The author and his students have used a unique laser-based technique capa ble of measuring biaxial strains over very short gage lengths to evalu ate the two models. Their results, as well as those from earlier studi es by other researchers using foil gages, lead to the general conclusi on that the Neuber model works best when the local region is in a stat e of plane stress and the Glinka model is best for plane strain. There are intermediate levels of constraint that are neither plane stress n or plane strain. This paper presents a recommended practice for predic ting the local elastoplastic stresses and strains for any constraint. First, one computes or estimates the initial elastic strains. Then, ba sed on the amount of elastic constraint, one selects the appropriate m odel to compute the local elastoplastic stresses and strains.