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In situ determination of stresses from time‐of‐flight neutron transmission spectra
Author(s) -
Steuwer Axel,
Santisteban Javier Roberto,
Withers Philip J.,
Edwards Lyndon,
Fitzpatrick Mike E.
Publication year - 2003
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889803013748
Subject(s) - materials science , anisotropy , neutron diffraction , crystallite , isotropy , diffraction , neutron , lattice constant , spectral line , residual stress , ultimate tensile strength , optics , condensed matter physics , crystallography , composite material , physics , chemistry , metallurgy , nuclear physics , astronomy
The pulsed neutron transmission diffraction technique exploits the sharp steps in intensity (Bragg edges) appearing in the transmitted spectra of thermal neutrons through polycrystalline materials. In this paper the positions of these edges acquired by the time‐of‐flight (TOF) technique are used to measure accurately the interplanar lattice distances to a resolution of Δ d / d ≃ 10 −4 of specimens subjected to in situ uniaxial tensile loading. The sensitivity of the method is assessed for elastically isotropic (b.c.c. ferritic) and anisotropic (f.c.c. austenitic) polycrystalline specimens of negligible and moderately textured steels. For the more anisotropic austenitic steel, the elastic anisotropy is studied with regard to a Pawley refinement, and compared with previous results from conventional neutron diffraction experiments on the same material. It is shown that the method can be used to determine anisotropic strains, diffraction elastic constants, the residual and applied stress state as well as the unstrained lattice parameter by recording transmission spectra at different specimen inclinations, by complete analogy with the sin 2 ψ technique frequently used in X‐ray diffraction. The technique is shown to deliver reliable measures of strain even in the case of moderate texture and elastic anisotropy.