Evaluation of hydrogen content in metallic samples by neutron computed tomography

Zanarini, M.; Chirco, P.; Rossi, M.; Baldazzi, G.; Guidi, G.; Querzola, E.; Scannavini, M.G.; Casali, Franco; Garagnani, A.; Festinesi, A.

doi:10.1109/23.467910

Cited by 14 publications

(6 citation statements)

References 3 publications

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“…Techniques involving neutron scattering are among the most suitable tools for obtaining information on H distribution because neutrons have the advantage of a high sensitivity to light elements like hydrogen. Neutron scattering techniques are appropriate for measuring microstructures in the scale range from sub-angstrom (neutron diffraction) [17] to millimetre level (neutron radiography) [18,19]. In particular, small angle neutron scattering (SANS) is an appropriate technique for detecting H interactions with nanoscale microstructural features.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen trapping by VC precipitates and structural defects in a high strength Fe–Mn–C steel studied by small-angle neutron scattering

Malard

Rémy

Scott

et al. 2012

Materials Science and Engineering: A

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 8740To link to this article : Keywords:Small-angle neutron scattering Hydrogen embrittlement Hydrogen trapped by nanoprecipitates a b s t r a c t The trapping of hydrogen by VC precipitates and structural defects in high strength Fe-Mn-C steel was studied by small angle neutron scattering. No interaction between H and V in solid solution has been detected but a significant interaction between H and structural defects introduced by plastic deformation has been measured. This last effect was reversible upon outgassing of the H. Moreover a significant interaction between H and VC precipitates has been measured; 5 ppm wt. of H could be trapped in the precipitates. This is consistent with the homogeneous trapping of H within the precipitates rather than at the precipitate/matrix interface.

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Section: Introductionmentioning

confidence: 99%

Hydrogen trapping by VC precipitates and structural defects in a high strength Fe–Mn–C steel studied by small-angle neutron scattering

Malard

Rémy

Scott

et al. 2012

Materials Science and Engineering: A

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“…and sof = f(1 + 8 /8n) (7) Inthese equations the Sare the signals normalized by the actual beam intensity, I,,, so & is 'J'b, Sn is J,/4, and 4 is 'J'b…”

Section: Preprocessing Of Images To Correct Systematic Noise Errorsmentioning

confidence: 99%

Advanced neutron tomography

2000

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A neutron tomography system has been developed as a nondestructive technique for quantitative assessment of impurity concentrations in metal castings. Neutrons maximize the sensitivity for certain isotope while tomography provides the threedimensional density information. A specific application is the detection ofhydrogen down to 200 ppm weight in aircraft engine compressor blades. A number ofpreprocessing corrections have been implemented for the projection images in order to achieve the detection requirements at a testing rate ofthree blades per hour. Among the procedures are corrections for neutron scattering and beam hardening. Post processing ofthe reconstructions consists of aligning test object images with standard object images. With these procedures the artifacts in tomographic reconstructions are shown to be less than the signal for 100 ppm hydrogen in titanium alloy samples.

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Section: Introductionmentioning

confidence: 99%

“…The associate editor coordinating the review of this manuscript and approving it for publication was Yi Zhang . up for the inadequacy of conventional X/γ CT is an efficient nondestructive testing method [1]- [3]. Neutron CT (NCT) has the advantages of no internal structure information overlap as compared with neutron radiography [1]. NCT has two steps under prerequisites of neutron radiography: (1) rotating the scanned object to obtain multiple neutron radiography with equal spacing angles; (2) and then, reaping reasonably reconstruction images by using reconstruction algorithms (e.g., filtered back projection (FBP) algorithms or maximum likelihood-expectation maximization algorithm (MLEM) to deal with the obtained radiography.…”

Section: Introductionmentioning

confidence: 99%

A MLEM-TV-MRP Algorithm for Fast Neutron Computed Tomography Reconstruction of High Statistical Noise and Sparse Sampling

Dong

Gan

et al. 2020

IEEE Access

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Fast neutron computed tomography (FNCT) generally needs a longer measurement time because of low source strength and low detection efficiency. In order to reduce measurement time, methods of reducing single measurement time and the numbers of projection are employed, but, the two reductions lead to high statistics noise projections and sparse sampling. A good reconstruction algorithm can reduce the influence of these problems for reconstructed images. In this study, the maximum likelihood-expectation maximization algorithm (MLEM) based on the total variation algorithm (TV) and median root prior algorithm (MRP), named MLEM-TV-MRP has been proposed. The proposal incorporates the assumption of the Poisson distribution of projection noises, gradient image sparseness, and locally monotonous. The use of MLEM in the proposal was for reducing the influence of high statistics noise by considering the statistical characteristics of projection noise; the TV algorithm was employed to decrease the influence of sparse sampling by considering gradient image sparseness. Also, the MRP was introduced to remove artifacts and noise by considering the locally monotonous. In addition, a consistency-controlled steepest descent (CCSD) method and TV change method were respectively employed to adaptively adjust the iteration step-size of TV iteration and adaptively stop TV iteration in the proposed algorithm. A classical noise-free phantom was used to initially test the performance of the proposed algorithm− the results showed high-quality reconstruction. To further illustrate its performance in FNCT, a lead-polyethylene (Pb-CH2) sample with 25 high statistics noise projections was employed. SNR value of MLEM-TV-MRP showed an increase of about 62%, 40.7%, 36.7%, and 12.6% respectively as compared to the single-use of MLEM, MLEM-MRP, TV-POCS (projection on convex sets) and MLEM-TV. Also, the profile of the MLEM-TV-MRP algorithm is found to be closest to that of a reference image. In addition, the MLEM-TV-MRP has good convergence performance especlially in convergence value. The results have demonstrated that the proposed algorithm can greatly reduce the influences of few high statistical noise projections on reconstruction in FNCT.INDEX TERMS Fast neutron computed tomography, maximum likelihood-expectation maximization, total variation, median root prior.

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Evaluation of hydrogen content in metallic samples by neutron computed tomography

Cited by 14 publications

References 3 publications

Hydrogen trapping by VC precipitates and structural defects in a high strength Fe–Mn–C steel studied by small-angle neutron scattering

Hydrogen trapping by VC precipitates and structural defects in a high strength Fe–Mn–C steel studied by small-angle neutron scattering

Advanced neutron tomography

A MLEM-TV-MRP Algorithm for Fast Neutron Computed Tomography Reconstruction of High Statistical Noise and Sparse Sampling

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