Study of 3-D stress development in parent and twin pairs of a hexagonal close-packed polycrystal: Part I – in-situ three-dimensional synchrotron X-ray diffraction measurement

Study of 3-D stress development in parent and twin pairs of a hexagonal close-packed polycrystal: Part II – crystal plasticity finite element modeling

“…Besides discussing some aspects of 3DXRD microscopy, the goal of this paper is to provide complementary information to support the interpretation of our experimental observations, given in [27], and to explain the local effects on twin and parent interaction. Obviously such a complex interaction cannot be fully explained in one paper; hence, we will focus here on stress development in twin and parent pairs.…”

“…The single crystal parameters that are used for simulations are given in Table 1 and are fitted against the continuous stress-strain curve using the M6S18 model. These parameters for Zircaloy-2 are reported in [29]; however they are slightly changed here to account for annealing and grain growth that occurred prior to the 3DXRD experiment [11,27]. Since each 3DXRD measurement step took more than 10 h under constant strain, a somewhat better agreement might be achieved by considering stress relaxation effects during the experiment; however, this is a second order effect [39] and is outside the scope of this study.…”

“…In the M6-model series, all elements are the same size cubes, yet by increasing the mesh densities, each integration point represents a smaller physical volume and hence a more accurate stress heterogeneity within each grain can be captured (see Table 2). About 10% and 42% of the measured grains reported in [27] are modeled in the M6 and M26 models, respectively. The reason why the number of the meshed grains for the same volume slightly changes in the M6 model series is that with using a smaller meshing step size, part of the grains that have their center-of-mass further outside the investigated volume will also be meshed.…”

“…In order to show how well grain shapes and neighbors can be captured using this method, the developed code is used for simulating grain shapes that were measured using electron backscatter diffraction (EBSD), as reported in the previous part of this research [27]. For construction of a 3D mesh that can be imported into ABAQUS, volumes with different sizes are picked so that different numbers of grains with different mesh densities could be modeled and the convergence of the FE simulation can be tested.…”

“…Results from a 3DXRD experiment carried out on Zircaloy-2 and explained in [27] are used for generating the input files for the ABAQUS solver. In this experiment, center-of-mass position, volume, orientation, elastic strain and stress for each grain in a 0.75 Â 0.75 Â 0.9 mm 3 volume of a Zircaloy-2 tensile specimen were measured at seven different loading steps.…”