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Two recently proposed elasto-visco-plastic self-consistent (EVPSC) models, based on solving for stress or stress increment, are discussed, and their results are compared with the ones of the visco-plastic self-consistent (VPSC) approach. The advantages and shortcomings of the models are demonstrated, with emphasis on how the grain responses are affected by the time increment and inclusion-medium interaction strength used. Experimental data obtained for an FCC stainless steel is used as the benchmark system for performing the simulations and assessing the reliability of the results. Predictions of stress-strain response of the aggregate, standard deviations in intergranular stress and strain rate, along with the evolution of internal lattice strain are presented and compared, with special focus on their dependence on the incremental approach chosen. We find that the chosen time increment may significantly affect predicted grain responses. To avoid such effect a method based on using two separate time increments is proposed, one for approximating the stress rate and another for actual integration of stress, strain, and state variables. The proposed method successfully eliminates the dependence of results on the time increment used, thus allowing more reliable computations while preserving the computational efficiency of the elasto-visco-plastic model.

The mechanical properties of an extruded Mg-10Gd sample, specifically designed for vascular stents, are crucial for predicting its behavior under service conditions. Achieving homogeneous stresses in the hoop direction, essential for characterizing vascular stents, poses challenges in experimental testing based on standard specimens featuring a reduced cross section. This study utilizes an elasto-visco-plastic self-consistent polycrystal model (ΔEVPSC) with the predominant twinning reorientation (PTR) scheme as a numerical tool, offering an alternative to mechanical testing. For verification, various mechanical experiments, such as uniaxial tension, compression, notched-bar tension, three-point bending, and C-ring compression tests, were conducted. The resulting force vs. displacement curves and textures were then compared with those based on the ΔEVPSC model. The computational model's significance is highlighted by simulation results demonstrating that the differential hardening along with a weak strength differential effect observed in the Mg-10Gd sample is a result of the interplay between micromechanical deformation mechanisms and deformation-induced texture evolution. Furthermore, the study highlights that incorporating the axisymmetric texture from the as-received material incorporating the measured texture gradient significantly improves predictive accuracy on the strength in the hoop direction. Ultimately, the findings suggest that the ΔEVPSC model can effectively predict the mechanical behavior resulting from loading scenarios that are impossible to realize experimentally, emphasizing its valuable contribution as a digital twin.

The mechanical behavior of a magnesium alloy E-form under bending was investigated using the elasto-visco-plastic polycrystal model (ΔEVPSC) and its finite element (FE) implementation (ΔEVPSC-FE) developed in Jeong et al. and Jeong and Tomé. The crystallographic orientation distribution (COD) obtained from X-ray diffraction was used to represent the initial texture, and the Voce hardening parameters were calibrated by fitting the uniaxial tension and the compression flow stress curves. A quasi-static FE analysis of a miniaturized V-bending operation was conducted using the ΔEVPSC-FE model. The bending induced an inhomogeneous stress response along the through-thickness and the lateral directions, which was well captured by the model. Moreover, the predictive capability of the model was validated by comparing with various experimental results such as (1) force vs. displacement curves; (2) the through-thickness variations in the twin volume fraction; and (3) the changes in crystallographic texture as a function of displacement. Additional bending simulation was performed using an isotropic texture, the result of which suggests that the potential improvement in bendability of the magnesium alloy is attainable by weakening the initial texture. Moreover, the simulation results imply that the crystallographic texture, which may affect the twin activation across the thickness direction, plays a significant role in the shifting direction of the neutral layer.

Abstract Titanium has a significant potential for the cryogenic industrial fields such as aerospace and liquefied gas storage and transportation due to its excellent low temperature properties. To develop and advance the technologies in cryogenic industries, it is required to fully understand the underlying deformation mechanisms of Ti under the extreme cryogenic environment. Here, we report a study of the lattice behaviour in grain families of Grade 2 CP-Ti during in-situ neutron diffraction test in tension at temperatures of 15–298 K. Combined with the neutron diffraction intensity analysis, EBSD measurements revealed that the twinning activity was more active at lower temperature, and the behaviour was complicated with decreasing temperature. The deviation of linearity in the lattice strains was caused by the load-redistribution between plastically soft and hard grain families, resulting in the three-stage hardening behaviour. The lattice strain behaviour further deviated from linearity with decreasing temperature, leading to the transition of plastically soft-to-hard or hard-to-soft characteristic of particular grain families at cryogenic temperature. The improvement of ductility can be attributed to the increased twinning activity and a significant change of lattice deformation behaviour at cryogenic temperature.