Browsing by Author "Kelleher, JF"

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    Effects of ausforming temperature on bainite transformation, microstructure and variant selection in nanobainite steel
    (Pergamon-Elsevier Science Ltd., 2013-06-01) Gong, W; Tomota, Y; Adachi, Y; Paradowska, AM; Kelleher, JF; Zhang, SY
    The bainite transformation behavior after plastic deformation of austenite, i.e., ausforming was studied by in situ neutron diffraction and ex situ experiments, and the effects of ausforming temperature was made clear. Ausforming, at a low temperature (573 K) was found to accelerate bainite transformation and produce a characteristic microstructure, whereas at a high temperature (873 K), ausforming had little influence. The reason for the different results stems from the dislocation structure introduced in austenite; planar dislocations remaining on the active slip planes are believed to assist bainite transformation, accompanied by strong variant selection. The variant selection rule that focuses on Shockley partial dislocation was verified from electron backscatter diffraction results. © 2013, Elsevier Ltd.
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    Energy-resolved neutron imaging for reconstruction of strain introduced by cold working
    (MDPI, 2018-02-28) Tremsin, AS; Kockelmann, W; Kelleher, JF; Paradowska, AM; Ramadhan, RS; Fitzpatrick, ME
    Energy-resolved neutron transmission imaging is used to reconstruct maps of residual strains in drilled and cold-expanded holes in 5-mm and 6.4-mm-thick aluminum plates. The possibility of measuring the positions of Bragg edges in the transmission spectrum in each 55 × 55 µm2 pixel is utilized in the reconstruction of the strain distribution within the entire imaged area of the sample, all from a single measurement. Although the reconstructed strain is averaged through the sample thickness, this technique reveals strain asymmetries within the sample and thus provides information complementary to other well-established non-destructive testing methods. © 1996-2021 MDPI
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    High-resolution strain mapping through time-of-flight neutron transmission diffraction
    (Trans Tech Publications, 2013-11-21) Tremsin, AS; McPhate, JB; Vallerga, JV; Siegmund, OHW; Kockelmann, W; Paradowska, AM; Zhang, SY; Kelleher, JF; Steuwer, A; Feller, WB
    The spatial resolution of time of flight neutron transmission diffraction was recently improved by the extension of photon/electron counting technology to imaging of thermal and cold neutrons. The development of novel neutron sensitive microchannel plates enables neutron counting with spatial resolution of ~55 um and time-of-flight accuracy of ~1 us, with efficiency as high as 70% for cold and ~40% for thermal neutrons. The combination of such a high resolution detector with a pulsed collimated neuron beam provides the opportunity to obtain a 2-dimensional map of neutron transmission spectra in one measurement. The results of our neuron transmission measurements demonstrate that maps of strains integrated along the beam propagation direction can be obtained with ~100 microstrain accuracy and spatial resolution of ~100 um providing there are sufficient neutron events collected. In this paper we describe the capabilities of the MCP neutron counting detectors and present the experimental results of 2-dimensional strain maps within austenitic steel compact tension (CT) crack samples measured at the ENGIN-X beamline of the ISIS pulsed neutron source. © 2014, Trans Tech Publications.
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    Modern and historical engineering components investigated by neutron diffractionon ENGIN-X
    (Japan Society of Mechanical Engineers, 2012-06-29) Paradowska, AM; Tremsin, A; Kelleher, JF; Zhang, SY; Paddea, S; Burca, G; James, JA; Ahmed, R; Faisal, NH; Festa, G; Andreani, C; Civita, F; Bouchard, PJ; Krockelman, W; Fitzpatrick, ME; Grazzi, F
    The ENGIN-X beamline is mainly used to determine residual strains/stresses deep within the interior of bulk engineering components. It is mainly used by scientists and engineers for the development of modern engineering processes and structural integrity investigations. ENGIN-X diffraction and transmission mode can be a very useful tool to measure strain, phase transitions, texture and material composition in spatial resolution in historical or archaeological artifacts and modern materials. The complexity of the shapes and sizes of the samples measured on ENGIN-X varies significantly between experiments, and this required the development of better planning, simulation and control software, SScanSS. In this paper an overview of recent developments in strain scanning on ENGIN-X and a highlight of current scientific research are presented. © 2012 The Japan Society of Mechanical Engineers