A hybrid explicit-implicit stress integration algorithm for elastoplastic models accounting for dynamic strain aging

Advanced constitutive models have greatly improved the characterization of thermomechanical behaviors of materials affected by dynamic strain aging (DSA). However, the inherent complexity of these mechanical responses usually poses significant challenges for the numerical implementation of these models. Thus, within a small-strain elastoplastic framework, this study developed a novel hybrid explicit-implicit integration algorithm (HEI-IA) to enhance the accuracy and reliability of stress updating for the constitutive models considering DSA. This algorithm follows the traditional return mapping framework but employs a hybrid strategy in the plastic correction phase. Specifically, it first attempts an implicit solution. If convergence difficulties arise due to DSA-induced anomalous material responses, it automatically switches to an explicit scheme to ensure calculation continuity. The performance of the proposed algorithm was compared with that of the conventional implicit and explicit algorithms by conducting three numerical tests, including single element tests, split Hopkinson pressure bar loading simulations, and steel tube impact tests. The results demonstrated that the proposed HEI-IA achieved good robustness and accuracy across all numerical tests, effectively resolving the convergence issues of implicit methods and the accuracy limitations of explicit methods. In addition, the computational efficiency and time step sensitivity of HEI-IA were also discussed.