Abstract: The paper proposes an incremental relaxation plasticity (IRP) model forpredicting possible instabilities and overall behavior of flow curves underdynamic loads. Compared to its original non-incremental version, the IRP modelallows one to predict the behavior of stress-strain curves over a longer timeafter the start of yielding and to more accurately describe their instabilitiessuch as sharp yield points (yield drops) and further nonmonotonic or oscillatoryeffects. The efficiency of the IRP model is demonstrated by comparing itspredictions with those of the original non-incremental version and of the widelyknown Johnson–Cook model on the example of experimental flow curves fordual-phase high-strength steel DP800 and aluminum alloy 2519A. The major featureof the proposed IRP model is that its parameters are invariant with the loadinghistory and strain rate of a material and are related only to the evolution ofits defect structure on the micro- and mesoscales. With such a set of IRP modelparameters, one can obtain a variety of flow curves of the same material atwidely varied strain rates.