Influence of morphologic texture on stress analysis by X-ray and neutron diffraction in single-phase metallic materials

Abstract

International audienceIn this work, a study on the influence of morphologic texture on the residual stress determination by diffraction in metallic materials with cubic and hexagonal symmetry is proposed. To this end, elastic self-consistent model has been developed to properly take into account the morphologic texture. Extreme crystallites morphologies (sphere, disc and fiber) were studied, and coupled with the crystallographic texture to reflect the combined effect of morphologic and crystallographic texture in elasticity. In the case of morphologic texture, a stronger influence than the crystallographic texture on the estimated residual stresses (several tens of MPa difference) was observed. We propose a methodology through a scale transition model to take into account the influence of these different morphologies in the stress analysis by diffraction methods. The main purpose of this work is to make the best choice for lattice planes (hkl) used for residual or internal stress analysis, in elasticity, depending on the morphologic (and crystallographic) texture of the polycrystal, especially when the usual X-ray Elasticity Constants (XECs) are used instead of the stress factors

Stress measurement using area detectors: a theoretical and experimental comparison of different methods in ferritic steel using a portable X-ray apparatus

“…There are also variations in the experimental 2θ vs α profiles as can be seen in figure 5, which shows the 2θ position of the peaks as a function of α, along the Debye ring, for tests performed at ψ 0 = 35 • , 45 • . The measured profiles exhibit slight systematic undulations around the expected values: these 'undulations' are along the α angle and are not related to the well-known oscillations in sin 2 ψ [22][23][24][25][26], but are due to the (proprietary) pixel intensity-data analysis algorithm in this particular machine; these algorithms are inaccessible to the users. We also observed these undulations in data measured from the calibration powders (annealed ferrite powder with grain size around 1 µm) supplied by the system manufacturer [10].…”

Modeling contrary size effects of tensile- and torsion-loaded oligocrystalline gold microwires

“…Aggregates of grains with simplified shape and orientation distributions have been used in gradient plasticity simulations to model the mechanical response of oligocrystalline microwires. Considering that the (nondestructive) experimental 3D-characterization of grain morphologies has made significant progress during recent years (see, e.g., [47][48][49] and the review by [50]), it would be desirable to perform simulations using the actual morphology of all grains of the microwires, in order to have a representation of the microstructure in the simulations being closer to the experiment. For such an approach, the FE-meshes need to be substantially refined, for example, when modeling smaller grains of non-spheroidal or non-cuboid shape.…”