Coupled damage-viscoplasticity model for metals under cyclic loading conditions

The numerical simulations for the design of structures and components are a key aspect in order to prevent malfunctioning or the unpredicted material failure, and the consequent economic losses. In the recent decades, the developments in the field of continuum damage mechanics (CDM) led to the formulation of sophisticated constitutive models, which improved the technological limit and the service life of components and structures. A further complication is represented by the solid deformations under dynamic loading, either at low or high strain rate (i.e. explosions, earthquakes, cyclic loading overloads, etc.). In this scenario, it is fundamental to consider the rate-dependency of the irreversible deformations to account for a realistic description of the damaging phenomenon. The present work introduces a coupled viscoplastic and damage model based on an unconventional plasticity theory, the subloading surface theory. The neat distinction between an elastic and plastic domains is abolished, allowing the description of the viscoplastic strain accumulation even for stress states below the macroscopic yield stress. Moreover, the impact loading response can be modeled by introducing a material parameter which regulates the stress state for an infinite rate of deformation, correcting the pure elastic response obtained by other models. 2019 The Authors. Published by Elsevier B.V.