Browsing by Author "Shinohara, T"

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    Bragg-edge elastic strain tomography
    (Engineers Australia, 2017-11-27) Wensrich, CM; Gregg, AWT; Hendriks, JN; Aggarwal, R; Tremsin, AS; Shinohara, T; Luzin, V; Meylan, MH; Kisi, EH; Kirstein, O
    Time-of-flight neutron imaging has now progressed to the point where high-resolution energy-resolved imaging is possible. Among many other applications, this technology allows the imaging of elastic strain fields within polycrystalline solids using a geometry identical to a traditional radiograph. 3D strain tomography from measurements such as these has been a current topic of research over the past decade. The authors recently solved this tomography problem and provided a reconstruction algorithm for the set of all systems subject to external loads in the absence of residual or eigenstrain. In this paper we provide an overview of the recent experiment carried out at the J-PARC pulsed neutron source in Japan focused on demonstrating this algorithm. This now represents the first-ever practical demonstration of Bragg-edge neutron transmission strain tomography in a non-axisymmetric system. The results of the experiment are presented along with the validation of the reconstructed field through Digital Image Correlation and traditional constant wavelength neutron strain scanning within the Australian Centre for Neutron Scattering at ANSTO. An outlook on potential strategies for reconstruction in the general case is also provided. © 2017 Engineers Australia
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    Bragg-edge neutron strain imaging and tomography
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-18) Wensrich, C; Gregg, AWT; Hendriks, JN; Luzin, V; Shinohara, T; Kirstein, O; Meylan, MH; Kisi, EH
    For more than 10 years, time-of-flight detectors at pulsed neutron sources have been capable of providing high-resolution images of strain fields through Bragg-edge analysis [1]. With a geometry akin to a traditional radiograph, these images represent a projection of the full 3D tensor strain distribution to a scalar field. This poses a rich tomography problem based on a generalised version of the Radon transform known as the Longitudinal Ray Transform (LRT). The solution to this Bragg-edge strain tomography problem promises a new approach by which the full triaxial elastic strain (and hence stress) distribution could be observed within crystalline solids over the scale of centimetres. This presentation will provide an overview of Bragg-edge imaging and strain measurement before outlining recent work by the Authors focused on solving the associated tomography problem. The central issue that rendered the problem ill-posed will be discussed before introducing a range of approaches based on equilibrium constraints. A two dimensional experimental demonstration based on data from the RADEN energy-resolved imaging instrument (at J-PARC in Japan) will be presented with comparisons to detailed constant wavelength strain scans from the KOWARI diffractometer (ANSTO). The generalisation of this approach to three-dimensions will also be discussed. [1] Tremsin et al. “High-resolution strain mapping through time-of-flight neutron transmission diffraction with a microchannel plate neutron counting detector”, Strain, v48 pp296-305, 2012. © The Authors
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    Investigation of microstructure within metal welds by energy resolved neutron imaging
    (IOP Publishing, 2016-01-01) Tremsin, AS; Kockelmann, W; Paradowska, AM; Zhang, SY; Korsunsky, AM; Shinohara, T; Feller, WB; Lehmann, EH
    The recent development of bright pulsed neutron sources and high resolution neutron counting detectors enables simultaneous acquisition of a neutron transmission spectrum for each pixel of the image. These spectra can be used to reconstruct microstructure parameters within welds, such as strain, texture and phase composition through Bragg edge analysis, and in some cases elemental composition through resonance absorption analysis. In this paper we demonstrate the potential of energy-resolved neutron imaging to study the microstructures of two steel welds, where the spatial distribution of residual strain within the welds, as well as some information on the texture, are obtained with sub-mm spatial resolution. A friction stir weld of two steel plates and a conventional weld of two steel pipes were studied at pulsed neutron facilities, where a Δλ/λ resolution as low as 0.2% can be attained over a wide range of neutron wavelengths ranging from 0.5 Å to 8 Å. Creative Commons Attribution 3.0 licence © Copyright 2021 IOP Publishing