Modeling elasto-plastic behavior of polycrystalline grain structure of steels at mesoscopic level

Abstract

The multiscale model is proposed to explicitly account for the inhomogeneous structure of polycrystalline materials. Grains and grain boundaries are modeled explicitly using Voronoi tessellation. The constitutive model of crystal grains utilizes anisotropic elasticity and crystal plasticity. Commercially available finite element code is applied to solve the boundary value problem defined at the macroscopic scale. No assumption regarding the distribution of the mesoscopic strain and stress fields is used, apart the finite element discretization. The proposed model is then used to estimate the minimum size of polycrystalline aggregate of selected reactor pressure vessel steel (22 NiMoCr 3 7), above which it can be considered macroscopically homogeneous. Elastic and rate independent plastic deformation modes are considered. The results are validated by the experimental and simulation results from the literature. KEY WORDSPolycrystalline material, elasto-plastic material behavior, mesoscale, Voronoi tessellation, finite elements, crystal plasticity

A crystal plasticity study of cyclic constitutive behaviour, crack-tip deformation and crack-growth path for a polycrystalline nickel-based superalloy

“…However, at a low strain level (up to 1%), deformation bands are highly localized within individual grains, as shown in Fig.18, which is also true for the von Mises equivalent strain. FE analyses were carried out for the RVE cyclically loaded at a high strain level, up to 10% at a strain rate of 0.005%/s and strain ratio of −1, and the grey-scale contour plot of the von Mises equivalent strain at the maximum strain level of the 2 nd cycle (Fig.19) clearly shows the cyclic deformation bands inclined at 45 or 135 degree with respect to the loading direction, similar to that observed in Kovač et al [15] for monotonic loading condition. This is also the case for the contour plot of the accumulated inelastic strain in ε .…”

“…A review of literature shows that the physically-based crystal plasticity theory has been generally used to describe the mechanical behaviour of materials at grain level. With the assistance of the finite element (FE) method, the theory is able to predict the global and local stress-strain response [10][11][12][13][14][15], the evolution of crystallographic grain texture [10,16] and micro-structural crack nucleation [17][18][19] in polycrystalline materials under monotonic, creep and fatigue loading conditions. Recently, application of the theory has also been extended to polycrystalline nickel superalloy, where material microstructure was considered as one of the major factors influencing the fatigue and creep properties of the material.…”

Crystal plasticity modeling of cyclic deformation for a polycrystalline nickel-based superalloy at high temperature

“…The physically-based crystal plasticity theory has been successful for description of anisotropic deformation of single crystals and polycrystals, including body-centered-cubic [1,2], face-centered-cubic [3,4] and highly-closed-packed [5,6] lattice structures. With the assistance of finite element method, the theory is able to predict the global and local stress-strain response [1][2][3][5][6][7], the evolution of crystallographic grain texture [1,4] and micro-structural crack nucleation [8][9][10] in polycrystalline materials under monotonic, creep and fatigue loading conditions. The essence of the crystal plasticity is to resolve the macroscopic stresses onto each slip system following the Schmid's law, where the shear strain rate can be expressed as a function of the resolved shear stress [11].…”

Crack tip displacements of microstructurally small cracks in 316L steel and their dependence on crystallographic orientations of grains

“…The number of grains included in the model is not sufficient to result in a size‐independent macroscopic response of the aggregate (representative volume element). However, the experience with similar simulations shows that the error caused by this omission is limited to about 5 % 32 …”