A simple physics-based constitutive model to describe strain hardening in a wide strain range

It is almost commonplace to say that physics-based constitutive models developed to characterize the mechanical behavior of materials are to be preferred over phenomenological models. However, the constitutive relations offered by physics-based approaches are oftentimes too involved to be handled in finite element (FE) simulations for practical applications. There is a demand for physics-based, yet robust and user-friendly models, and one such model will be highlighted in this article. A simple constitutive model developed recently by Bouaziz to extend the classical physics-based Kocks-Mecking model provides a viable tool for modelling a broad range of materials – beyond the single-phase coarse-grained materials it was initially devised for. The efficacy of the model was put to the test by investigating its applicability for different materials. A broad interval of the true stress vs. true strain curve was studied by the measurement-in-neck-section method in the uniaxial tensile mode for six types of metallic materials, and simulations using the finite element method emulating the experimental conditions were developed. In this way, the engineering stress-strain curves were obtained corresponding to the true stress-strain curves for these materials. A comparison of the numerical simulations of the tensile behaviour of all six materials with the experimental results for a broad range of strains showed that among the models trialled, the Bouaziz model was the best-performing one. The proposed model can be recommended for use in FE simulations of the mechanical behaviour of engineering structures as a viable alternative to complex physics-based or simplistic phenomenological constitutive models.