Stress-driven solute diffusion under applied load in dynamic strain ageing

An experimental investigation of the stress dependence of the dynamic strain ageing process is performed and reveals a clear influence of the applied stress level on the evolution of the ageing response. In particular, both the characteristic time and the saturation limit are found to vary systematically with stress. Based on these observations, an enhanced constitutive modelling framework is proposed that reformulates the evolution of the ageing contribution in an incremental, rate-based form and couples it to the current stress state via an empirical, stress dependent scaling function. The resulting formulation retains the structure and predictive capabilities of the classical McCormick model while enabling a consistent representation of dynamic strain ageing under varying loading conditions in alignment with the experimental findings. Furthermore, it is shown that the proposed model reduces to the classical formulation as a special case. Finite element simulations of tensile loading scenarios demonstrate that the enhanced approach reproduces key features of Portevin-Le Chatelier behaviour, while exhibiting improved physical consistency over the classical modelling approach.