Numerical and experimental methods for determining the parameters of generalized models of damaged visco-plastic media in predicting durability

In this work, the processes of strain hardening and fracture are based on the combination of physically nonlinear stress-strain states at the mesolevel with models of phase field fracture. The combination of these models allows for the description of the degradation of the material's mechanical properties and its progression to critical states. Unlike classical approaches based on Rabotnov-Kachanov type models, phase field models allow predicting durability not only at the stage of defect initialization but also at the stage of crack growth. The physically nonlinear environment includes combined isotropic and kinematic hardening with the viscous response of the material. Isotropic hardening is described by the Voce exponential function, while kinematic hardening is described by the Chaboche model. The viscous response of the material (creep) is described by the Norton power law. The effects of local multi-axial stress-strain states and their influence on fracture resistance parameters are described by the models proposed by Bai and Wierzbicki. The application of the described approach significantly simplifies the applicability of methods for predicting the durability of real structural elements and provides satisfactory prediction accuracy. The complex methodology for determining parameters proposed in this work allows u to obtain the parameters of individual models included in the final system of equations without reference to a specific combination of constitutional equations. The methods for determining parameters considered in this paper will also remain valid when changing the set of constitutional equations. Particular emphasis in this work is placed on the limitations of the proposed approach for predicting the durability of real structural elements.