Influence on strain-rate history effects on the development of necking instabilities under dynamic loading conditions

[Display omitted] •Neck formation in materials exhibiting strain-rate history effects is investigated.•The effects of the instantaneous and work-hardening rate sensitivities are analysed.•Only the instantaneous strain-rate sensitivity leads to neck retardation.•The critical impact velocity is unaffected by strain-rate history effects. The present paper is devoted to the analysis of strain-rate history effects on neck formation under dynamic loading. For materials presenting strain-rate history effects, two different strain-rate sensitivities should be distinguished: the instantaneous strain-rate sensitivity and the work-hardening strain-rate sensitivity. We have analysed the relative contributions of these two kinds of strain-rate sensitivities to neck retardation for two different configurations: a bar under impact tension and a dynamically expanding ring. For this purpose, we have developed finite element models and, for the second configuration, an analytical model based on the linear stability analysis. The obtained results show that strain-rate history effects have a significant influence on the onset and development of necking. The reason of this phenomenon is that, contrary to the instantaneous strain-rate sensitivity, the work-hardening strain-rate sensitivity does not contribute to delay the neck formation.