Browsing by Author "Gregg, AWT"
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- ItemBragg-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, OTime-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
- ItemBragg-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, EHFor 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 . 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.  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
- ItemNeutron diffraction strain tomography: demonstration and proof-of-concept(AIP Publishing LLC., 2020-01-03) Gregg, AWT; Hendriks, JN; Wensrich, CM; Luzin, V; Willis, ARecently, a number of reconstruction algorithms have been presented for residual strain tomography from Bragg-edge neutron transmission measurements. In this paper, we examine whether strain tomography can also be achieved using diffraction instruments. We outline the proposed method and develop a suitable reconstruction algorithm. This technique is demonstrated in simulation, and a proof-of-concept experiment is carried out, where the strain field in an axisymmetric sample is reconstructed and validated using conventional diffraction strain scans. © 2020 AIP Publishing LLC.
- ItemSamurai’s swords, a non-invasive investigation by neutron techniques(Scientific.Net, 2020-03-01) Salvemini, F; Luzin, V; Avdeev, M; Tremsin, AS; Sokolova, AV; Gregg, AWT; Wensrich, CM; Gatenby, S; Kim, MJ; Grazzi, FA synergic combination of neutron techniques was applied to characterize non-invasively the laminated structure of a set of ancient katana, part of the East Asian Collection of the Museum of Applied Arts and Sciences (MAAS) in Sydney. Neutron tomography, diffraction, residual stress and Bragg-edge transmission analyses were undertaken on samples of well-known origin, time period and authorship to create a reference database on the main manufacturing methods developed by Japanese swordsmiths. In the attempt to attribute mumei (no-signature) blades basing on a scientific analytical method rather than a stylistic analysis, data from the reference samples were benchmarked against the results obtained from the unknown blade to identify differences and commonalities in the production process. © 2020 by Trans Tech Publications Ltd.