• Title/Summary/Keyword: neutron diffraction

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Residual stress measurements using neutron diffraction (중성자법에 의한 잔류응력 측정법)

  • Woo, Wanchuck;Kim, Dong-Kyu;An, Gyu-Baek
    • Journal of Welding and Joining
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    • v.33 no.1
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    • pp.30-34
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    • 2015
  • Residual stresses are inherently introduced into the engineering components during manufacturing including rolling, forging, bending and welding processes. Excessive residual stresses are known to be detrimental to the proper integrity and performance of components. Neutron diffraction has become a well-established technique for the determination of residual stresses in welds. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a powerful tool for the residual stress measurements through the thickness of the weld specimen. Furthermore, the unique volume-averaged bulk characteristic of the scattering beam and mapping capability in three dimensions is suitable for the engineering purpose. In this presentation, the neutron diffraction measurements of the residual stresses will be introduced and measurement results will highlighted in thick weld plates.

Residual Stress Measurement on Welded Specimen by Neutron Diffraction (중성자 회절을 이용한 용접부위의 잔류응력 측정)

  • 박만진;장동영;최희동
    • Journal of Welding and Joining
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    • v.20 no.2
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    • pp.50-58
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    • 2002
  • Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

Neutron Diffraction Study of Powders Prepared by Self-propagating High Temperature Synthesis

  • Park, Yong;Kim, Y S.;Y. D. Hahn;S. H. Shim;Lee, J. S.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.11-12
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    • 2000
  • Non-stoichiometric ceramics of $Ni_{x}ZnO_{1-x}Fe_{2}O_{4}$ were prepared by self-propagating high temperature synthesis reaction with various processing conditions and their stoichometric numbers were determined by neutron diffraction. The neutron diffraction patterns were measured at room temperature using monochromatic neutrons with a wave length of 0.18339 nm from a Ge(331) mocochromator at a 90 degree take off angle. The Rietveld refinement of each pattern converged to good agreement (x2=1.88-2.24). The neutron diffraction analysis revealed the final stoichiometries of the ferrites were $Ni_{0.38}Zn_{0.62}Fe_{2}O_{4}$ and $Ni_{0.33}Zn_{0.67}Fe_{2}O_{4]$, respectively. This supports that final stoichiometric number of the self-propagating high temperature synthesis product can be controlled by the processing parameters during the combustion reaction.

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Internal Stress/Strain Analysis during Fatigue Crack Growth Retardation Using Neutron Diffraction (피로 균열 성장 지연에 대한 중성자 회절 응력 분석)

  • Seo, Sukho;Huang, E-Wen;Woo, Wanchuck;Lee, Soo Yeol
    • Korean Journal of Materials Research
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    • v.28 no.7
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    • pp.398-404
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    • 2018
  • Fatigue crack growth retardation of 304 L stainless steel is studied using a neutron diffraction method. Three orthogonal strain components(crack growth, crack opening, and through-thickness direction) are measured in the vicinity of the crack tip along the crack propagation direction. The residual strain profiles (1) at the mid-thickness and (2) at the 1.5 mm away from the mid-thickness of the compact tension(CT) specimen are compared. Residual lattice strains at the 1.5 mm location are slightly higher than at the mid-thickness. The CT specimen is deformed in situ under applied loads, thereby providing evolution of the internal stress fields around the crack tip. A tensile overload results in an increased magnitude of the compressive residual stress field. In the crack growth retardation, it is found that the stresses are dispersed in the crack-wake region, where the highest compressive residual stresses are measured. Our neutron diffraction mapping results reveal that the dominant mechanism is by interrupting the transfer of stress concentration at the crack tip.

Phase Analysis of Immiscible V-Cu MA Powders by Neutron and X-ray Diffraction (비고용 V-Cu계 MA합금의 중성자 및 X선 회절에 의한 상분석)

  • Lee Chung-Hyo;Cho Jae-Moon;Lee Sang-Jin;Kim Ji-Soon
    • Korean Journal of Materials Research
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    • v.14 no.5
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    • pp.348-352
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    • 2004
  • The mechanical alloying (MA) effect in immiscible V-Cu system with positive heat of mixing was studied by not only the neutron and X-ray diffraction but also the analysis of DSC spectra. The total energy, ΔHt accumulated during MA for the mixture of $V_{50}$ $Cu_{50}$ / powders increased with milling time and approached the saturation value of 14 kJ/mol after 120 h of milling. It can be seen that the free energy difference between the amorphous phase and the pure V and Cu powders with an atomic ratio 5:5 is estimated to be 11 kJ/mol by Miedema et al. This is thermodynamically taken as one of the evidences for the amorphization. The structural changes of V-Cu MA powders were characterized by the X-ray diffraction and neutron diffraction. We take a full advantage of a negligibly small scattering length of the V atom in the neutron diffraction measurement. The neutron diffraction data definitely indicate that the amorphization proceeds gradually but incompletely even after 120 h of MA and bcc-Cu Bragg peaks appears after 60 h of MA.

Crystal Structure of $KD_2PO_4$: Neutron and X-ray Diffraction Studies ($KD_2PO_4$의 결정구조: 중성자와 X-선 회절에 의한 연구)

  • 김신애;심해섭;이창희
    • Korean Journal of Crystallography
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    • v.11 no.3
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    • pp.162-166
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    • 2000
  • KD₂PO₄ single crystals were grown from D₂O with reagent KH₂PO₄ and the crystal structure was determined by X-ray and neutron diffraction methods. The crystals are tetragonal at room temperature, I42d, with lattice parameters of a=7.4633(7), c=6.9785(5) Å and Z=4. Intensity data were collected on an Enraf-nonius CAD4 diffractometer with a graphite monochromated MoK/sub α/ radiation (λ=0.7107Å) and on the neutron four circle single crystal diffractometer with Ge(331) monochromated neutron beam (λ=0.997Å). The structure was refined by full-matrix least-square to final R and wR values of 0.030 and 0.072, respectively, for 204 observed reflections with I>2σ(I) by X-ray diffraction and to final R=0.041 and wR=0.096 for 144 observed relfecdtions by neutron diffraction. The O…O distance of 2.516(4)Å obtained by X-ray diffraction is the same as that of 2.515(4)Å by neutron diffraction. On the other hand, the O-D/H distance of 0.84(4)Å by X-ray diffraction is considerably shorter than 1.029(7) Åby neutron diffraction. Hydrogen and deuterium can be readily distinguished by neutrons. In this crystal 66% of H-positions were substituted by D and the rest 34% occupied by H. The phase transition temperature of DKDP obtained with deuteration levels is f193K. This value agrees fairly well with the result of DSC measurement. The nuclear density distribution by neutron diffraction provides an observation of the disordered state of D/H in KD₂PO₄ at room temperature.

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Flux Loss and Neutron Diffraction Measurement Ag-sheathed Bi-2223 Tapes in terms of Flux Creep

  • Jang Mi-Hye
    • KIEE International Transactions on Electrophysics and Applications
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    • v.5C no.5
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    • pp.204-210
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    • 2005
  • Alternating current (AC) losses of two Bi-2223 ([Bi, Pb]: Sr: Ca: Cu: O = 2:2:2:3) tapes [(Tape I, un-twist-pitch) and the other with a twist-pitch of 10 mm (Tape II)] were measured and compared. These samples, produced by the powder-in-(Ag) tube (PIT) method, are multi-filamentary. Also, it's produced by non-twist and different twist pitch (8, 10, 13, 30, 50 and 70 mm). The critical current measurement was carried out under the environment in liquid Nitrogen and in zero-field by 4-probe method. Susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O)

Crystallite Size Measurement of Uranium Oxide Fuel Powders by Neutron Diffraction (중성자 회절에 의한 산화우라늄 핵연료 분말의 결정크기 측정)

  • 류호진;강권호;문제선;송기찬;최용남
    • Journal of Korean Powder Metallurgy Institute
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    • v.10 no.5
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    • pp.318-324
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    • 2003
  • The nano-scale crystallite sizes of uranium oxide powders in simulated spent fuel were measured by the neutron diffraction line broadening method in order to analyze the sintering behavior of the dry process fuel. The mixed $UO_2$ and fission product powders were dry-milled in an attritor for 30, 60, and 120 min. The diffraction patterns of the powders were obtained by using the high resolution powder diffractometer in the HANARO research reactor. Diffraction line broadening due to crystallite size was measured using various techniques such as the Stokes' deconvolution, profile fitting methods using Cauchy function, Gaussian function, and Voigt function, and the Warren-Averbach method. The non-uniform strain, stacking fault and twin probability were measured using the information from the diffraction pattern. The realistic crystallite size could be obtained after separation of the contribution from the non-uniform strain, stacking fault and twin.

Residual Stress Measurement on Welded Specimen by Neutron Diffraction (중성자 회절을 이용한 용접부위의 잔류응력 측정)

  • ;;;;;;Vyacheslav T. Em
    • Proceedings of the KWS Conference
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    • pp.90-93
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    • 2000
  • Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways by using X-ray or neutron diffraction. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate(100$\times$100 $\textrm{mm}^2$)

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Residual Stress Measurement on Welded Stainless Steel Specimen by Neutron Diffraction

  • Park, M.J.;D.Y. Jang;Park, H.D.
    • International Journal of Korean Welding Society
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    • v.1 no.1
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    • pp.39-43
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    • 2001
  • In this paper, the neutron diffraction is applied to the residual stress measurement on the 20mm-thick welded stainless steel plate ($100^{\circ}$$\times$100$mm^2$). The High Resolution Powder Diffractormeter of the Korea Atomic Research Institute The power of nuclear reactor was 24 MWt and the measured reflection in the 220 plane (2$\theta$ is $95^{\circ}$and wavelength is 1.8340 ${\AA}$ . The Poisson ratio of 0.265 and elastic constant of 211 GPa are applied to the calculation of stresses and strains. Three directional components such as normal, transverse, and longitudinal stresses are measured and the results show that the most of longitudinal stress is tensile and decreases, changing to compressive depending on the distance away from the welded spot. However, transverse component is changing from tensile to compressive along the depth of the welded point.

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