SUMMARYMultiscale mechanical behaviors of ferrite-pearlite steel were predicted using numerical material testing (NMT) based on the finite element method. The microstructure of ferrite-pearlite steel is regarded as a twocomponent aggregate of ferrite crystal grains and pearlite colonies. In NMT, the macroscopic stress-strain curve and the deformation state of the microstructure were examined by means of a two-scale finite element analysis method based on the framework of the mathematical homogenization theory. The microstructure of ferrite-pearlite steel was modeled with finite elements, and constitutive models for ferrite crystal grains and pearlite colonies were prepared to describe their anisotropic mechanical behavior at the microscale level. While the anisotropic linear elasticity and the single crystal plasticity based on representative characteristic length have been employed for the ferrite crystal grains, the constitutive model of a pearlite colony was newly developed in this study. For that reason, the constitutive behavior of the pearlite colony was investigated using NMT on a smaller scale than the scale of the ferrite-pearlite microstructure, with the microstructure of the pearlite colony modeled as a lamellar structure of ferrite and cementite phases with finite elements. On the basis of the numerical results, the anisotropic constitutive model of the pearlite colony was formulated based on the normal vector of the lamella. The components of the anisotropic elasticity were estimated with NMT based on the finite element method, where the elasticity of the cementite phase was numerically evaluated with a first-principles calculation. Also, an anisotropic plastic constitutive model for the pearlite colony was formulated with two-surface plasticity consisting of yield functions for the interlamellar shear mode and yielding of the overall lamellar structure. After addressing the microscopic modeling of ferrite-pearlite steel, NMT was performed with the finite element models of the ferrite-pearlite microstructure and with the microscopic constitutive models for each of the components. Finally, the results were compared with the corresponding experimental results on both the macroscopic response and the microscopic deformation state to ascertain the validity of the numerical modeling.

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