Browsing by Author "Kockelmann, W"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    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
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
    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