Browsing by Author "Wensrich, CM"

Now showing 1 - 9 of 9
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    Application and validity of the Radon transform applied to axisymmetric neutron strain imaging
    (Elsevier B. V., 2019-12-15) Kirkwood, HJ; Wensrich, CM; Paradowska, AM; Abbey, B
    Next generation pulsed neutron sources and wavelength dispersive imaging detectors are creating new opportunities for strain analysis. One such technique is Bragg edge transmission analysis in which projected measurements of the crystallographic properties of bulk polycrystalline samples are recorded on a time-of-flight area detector. The ability to measure the elastic strain field poses the question of whether it is possible to reconstruct a three-dimensional map of the elastic strain tensor from a set of lower order projection data. Here we present a fundamental exploration of the validity of axisymmetric strain reconstruction algorithms available for inverting Bragg edge data. The results demonstrate that the compatibility of the elastic strain field under investigation is critical in determining which algorithm may be successfully applied. Finally, a more robust approach to Radon transform strain tomography is presented based on the condition of zero total strain. ©2019 Elsevier Ltd.
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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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    Energy-resolved neutron imaging options at a small angle neutron scattering instrument at the Australian Center for Neutron Scattering
    (AIP Publishing, 2019-03-26) Tremsin, AS; Sokolova, AV; Salvemini, F; Luzin, V; Paradowska, AM; Muránsky, O; Kirkwood, HJ; Abbey, B; Wensrich, CM; Kisi, EH
    Energy-resolved neutron imaging experiments conducted on the Small Angle Neutron Scattering (SANS) instrument, Bilby, demonstrate how the capabilities of this instrument can be enhanced by a relatively simple addition of a compact neutron counting detector. Together with possible SANS sample surveying and location of the region of interest, this instrument is attractive for many imaging applications. In particular, the combination of the cold spectrum of the neutron beam and its pulsed nature enables unique non-destructive studies of the internal structure for samples that are opaque to other more traditional techniques. In addition to conventional white beam neutron radiography, we conducted energy-resolved imaging experiments capable of resolving features related to microstructure in crystalline materials with a spatial resolution down to ∼0.1 mm. The optimized settings for the beamline configuration were determined for the imaging modality, where the compromise between the beam intensity and the achievable spatial resolution is of key concern. © 2020 AIP Publishing LLC
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    Force chains in monodisperse spherical particle assemblies: three-dimensional measurements using neutrons
    (American Physical Society, 2014-10-03) Wensrich, CM; Kisi, EH; Luzin, V; Garbe, U; Kirstein, O; Smith, AL; Zhang, JF
    The full triaxial stress state within individual particles in a monodisperse spherical granular assembly has been measured. This was made possible by neutron imaging and computed tomography combined with neutron diffraction strain measurement techniques and associated stress reconstruction. The assembly in question consists of 549 precision steel ball bearings under an applied axial load of 85 MPa in a cylindrical die. Clear evidence of force chains was observed in terms of both the shape of the probability distribution function for normal stresses and the network formed by highly loaded particles. An extensive analysis of the source and magnitude of uncertainty in these measurements is also presented.©2014 American Physical Society.
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    Measurement and analysis of the stress distribution during die compaction using neutron diffraction
    (Springer, 2012-11-01) Wensrich, CM; Kisi, EH; Zhang, JF; Kirstein, O
    The full axisymmetric stress state of a granular material undergoing compaction in a cylindrical die has been measured using a technique based on neutron powder diffraction. This technique allowed the detailed distribution of stress to be measured in situ, deep within a copper powder inside a solid die. Four components of normal strain were measured over a radial cross section. These components consisted of the axial, radial, hoop and an off-axis strain in the axial-radial direction. This allowed for the reconstruction of the full axisymmetric stress tensor as a distribution over the radial cross section. Many interesting features were observed in this distribution, such as exponential decay of the axial stress (described by Janssen in Zeitschrift des Vereines duetscher Ingenieure 39:1045, 1895), and highly localised regions of high shear stress. The potential of this type of data in the validation of numerical models is discussed. © 2012, Springer.
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    Neutron diffraction strain tomography: demonstration and proof-of-concept
    (AIP Publishing LLC., 2020-01-03) Gregg, AWT; Hendriks, JN; Wensrich, CM; Luzin, V; Willis, A
    Recently, 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.
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    Non-contact stress measurement in granular materials via neutron and x-ray diffraction: theoretical foundations
    (Springer, 2013-06-01) Wensrich, CM; Kisi, EH; Luzin, V
    Model validation remains a serious problem within the field of computational granular materials research. In all cases the rigor of the validation process is entirely dependent on the quality and depth of the experimental data that forms the point of comparison. Neutron and X-ray diffraction methods offer the only quantitative non-contact method for determining the spatially resolved triaxial stress field within granular materials under load. Measurements such as this can provide an unprecedented level of detail that will be invaluable in validating many models. In this paper the theoretical foundation underpinning diffraction-based strain measurements, their conversion to local stress in the particles and ultimately into the bulk stress field is developed. Effects such as elastic anisotropy within the particles of the granular material, particle plasticity and locally inhomogeneous stress distribution are shown to not offer any obstacles to the method and a detailed treatment of the calculation of the bulk stresses from the particle stresses is given. © 2013, Springer.
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    Samurai’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, F
    A 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.
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    Stress distribution in iron powder during die compaction
    (Trans Tech Publications Ltd, 2014-02) Kisi, EH; Wensrich, CM; Luzin, V; Kirstein, O
    The unique and unusual state of matter represented by granular materials has historically made it very difficult to develop models of stress distributions and was previously not able to be explored experimentally in the required detail. This paper reports the application of the neutron diffraction strain scanning method, originally developed for residual stress measurements within engineering components, to the problem of the stress distribution in granular Fe under a consolidating pressure. Strains were measured in axial, radial, circumferential and an oblique direction using the neutron strain scanning diffractometer KOWARI at ANSTO (Sydney). The full stress tensor as a function of position was able to be extracted for both straight walled, converging and stepped dies. © 2014, Trans Tech Publications.