The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform

Chungyue Wang - One of the best experts on this subject based on the ideXlab platform.

  • use of gamma rays in the inspection of steel wire ropes in suspension bridges
    Ndt & E International, 2015
    Co-Authors: Pengchi Peng, Chungyue Wang
    Abstract:

    Abstract Regularity visual inspections are performed on steel wire ropes of suspension bridges. However, because the steel wire ropes were coated with plastic materials, inspectors could not visually detect the deterioration conditions of the ropes. In this paper, radiation tests and Electromagnetic Testing were compared. The gamma rays used in the radiation tests were employed to develop two assessment techniques, namely the exposure time formula and sensitivity assessment of steel wire ropes. Actual tests showed that such techniques can be adopted to evaluate the defects of steel wire ropes and help engineers improve the safety of suspension bridges.

Pengchi Peng - One of the best experts on this subject based on the ideXlab platform.

  • use of gamma rays in the inspection of steel wire ropes in suspension bridges
    Ndt & E International, 2015
    Co-Authors: Pengchi Peng, Chungyue Wang
    Abstract:

    Abstract Regularity visual inspections are performed on steel wire ropes of suspension bridges. However, because the steel wire ropes were coated with plastic materials, inspectors could not visually detect the deterioration conditions of the ropes. In this paper, radiation tests and Electromagnetic Testing were compared. The gamma rays used in the radiation tests were employed to develop two assessment techniques, namely the exposure time formula and sensitivity assessment of steel wire ropes. Actual tests showed that such techniques can be adopted to evaluate the defects of steel wire ropes and help engineers improve the safety of suspension bridges.

V. P. Lunin - One of the best experts on this subject based on the ideXlab platform.

  • A neural-network classifier of flaws for multifrequency Eddy-current tests of heat-exchange pipes
    Russian Journal of Nondestructive Testing, 2007
    Co-Authors: V. P. Lunin, A. G. Zhdanov, D. Yu. Lazutkin
    Abstract:

    A neural-network classifier has been developed that evaluates the geometric characteristics of a detected flaw on the basis of the parameters of the corresponding multifrequency signals obtained via scheduled eddy-current tests conducted with a through-type probe. The classifier is intended for Testing heat-exchange pipes in steam generators of a nuclear power plant with a water-moderated water-cooled power reactor. The representative library of signals required for the design was formed on the basis of theoretical and experimental data. The theoretical data were obtained in a numerical physical and mathematical model of the Electromagnetic Testing procedure implemented with the MagNum3D program for finite-element analysis. The experimental data were obtained through measurement of multifrequency eddy-current signals from test specimens with artificial flaws.

  • A two-step algorithm for finite-element solution of Electromagnetic-Testing problems: Eddy-current Testing
    Russian Journal of Nondestructive Testing, 2006
    Co-Authors: V. P. Lunin
    Abstract:

    An algorithm for finite-element simulation of eddy-current Testing problems is described. This algorithm allows calculation of transducer signals from any 3D flaw in a metallic item. In practice, the studied flaws are often characterized by small dimensions. Therefore, the measured increment of the voltage induced in the transducer’s output winding owing to the presence of such a flaw is only several percent of the voltage’s average value. If a standard calculation scheme based on the finite-element method is applied, significant computational resources are needed to solve this problem. The two-step algorithm allows a significant reduction in the required resources. The essence of the algorithm is that the source of the field of a flaw’s effect is determined from the distribution of eddy currents in metal free of flaws. Such an approach allows the calculations of the “unperturbed field” to be simplified significantly through consideration of the geometric symmetry of the problem solved and thus, through reduction of its dimensionality. The efficiency of the two-step algorithm is demonstrated during the solution of a typical problem: the use of a through differential transducer for eddy-current Testing of a segment of a heat-exchange pipe in the steam generator of a nuclear power plant.

  • A two-step algorithm for finite-element solution of Electromagnetic-Testing problems: Electric-capacitance Testing
    Russian Journal of Nondestructive Testing, 2006
    Co-Authors: V. P. Lunin
    Abstract:

    A procedure for numerical solution of 3D Electromagnetic-Testing problems is described. This procedure is intended for problems where approximation of the systems of differential equations through standard finite-element schemes requires significant computer resources. Such a situation is mainly typical of the problems where effects of 3D flaws are not significant relative to the value of the main (usually 2D) field but nevertheless have to be calculated with a sufficiently high accuracy. At the first stage of the finite-element simulation algorithm, a 2D problem is numerically solved for a “flaw-free” field. At the second stage, the field of the flaw’s effect is calculated, the sources of this field being localized in the vicinity of the flaw. Owing to such an approach, the computer resources needed to solve the problems of this type may be significantly reduced so that the problems become solvable by means of PCs. The proposed procedure has been implemented in the MagNum3D package [1, 2] and the procedure’s efficiency has been confirmed via solution of a model problem of electric-capacitance Testing.

  • Phenomenological and algorithmic methods for the solution of inverse problems of Electromagnetic Testing
    Russian Journal of Nondestructive Testing, 2006
    Co-Authors: V. P. Lunin
    Abstract:

    Modern methods for the solution of inverse problems of nondestructive Testing are described. The discussion is mainly focused on the methods based on a mathematical model of the respective physical phenomenon (so-called phenomenological methods) and the methods based on the algorithms for the analysis of digital signals (so-called algorithmic methods). The phenomenological methods involving a mathematical model assume that the configuration of the flaws in a tested specimen is varied until the norm of the mismatch between the model solution and the experimentally obtained signal is minimized. A good result is only guaranteed if the physics of the phenomenon in the model is close to reality. In algorithmic methods, the inversion procedure applied to experimental data is considered as an image-recognition problem. In this case, the signal is identified as a representative of the classes associated with known types of flaws. The classification algorithms, which are most frequently used for Electromagnetic Testing, are developed through identification of diagnostic signatures. This approach assumes the use of an artificial neural network trained with the signals from a predefined database that corresponds to a broad variety of flaws.

L. J. Liu - One of the best experts on this subject based on the ideXlab platform.

Marc Bonnet - One of the best experts on this subject based on the ideXlab platform.

  • A Multi-Step Solution Algorithm for Maxwell Boundary Integral Equations Applied to Low-Frequency Electromagnetic Testing of Conductive Objects
    IEEE Transactions on Magnetics, 2016
    Co-Authors: Audrey Vigneron, Edouard Demaldent, Marc Bonnet
    Abstract:

    We consider the solution, using boundary elements (BEs), of the surface integral equation (SIE) system arising in Electromagnetic Testing of conducting bodies, with an emphasis on situations, such that $o(1) \leq ({\omega \varepsilon _{0}/\sigma })^{1/2} \leq O(1)$ and $L ({\omega \sigma \mu _{0}})^{1/2} = O(1)$ , which includes in particular the case of eddy current (EC) Testing and assuming $L\omega ({\varepsilon _{0} \mu _{0}})^{1/2} \leq 2\pi $ , i.e., low-frequency conditions ( $L$ : diameter of conducting body). Earlier approaches for dielectric objects at low frequencies are not applicable in the present context. After showing that a simple normalization of the BE system significantly improves its conditioning, we propose a multi-step solution method based on block-successive over-relaxation iterations, which facilitates the use of direct solvers and converges within a few iterations for the considered range of physical parameters. This new treatment, albeit simple, allows to perform EC-type analyses using standard Maxwell SIE formulations, avoiding the adverse consequences of ill-conditioning for low frequencies and high conductivities. Its performance and limitations are studied on three numerical examples involving low frequencies and high conductivities.

  • A multi-step solution algorithm for Maxwell boundary integral equations applied to low-frequency Electromagnetic Testing of conductive objects
    IEEE Transactions on Magnetics, 2016
    Co-Authors: Audrey Vigneron, Edouard Demaldent, Marc Bonnet
    Abstract:

    We consider the solution, using boundary elements (BE), of the surface integral equation system arising in Electromagnetic Testing of conducting bodies, with emphasis on situations such that $o(1) \leq \sqrt{\omega\varepsilon_{0}/\sigma} \leq O(1)$, $L \sqrt{\omega\sigma\mu_{0}} =O(1)$ which includes in particular the case of eddy current Testing) and assuming $L\omega\sqrt{\varepsilon_0 \mu_{0}}\leq 2\pi$, i.e. low-frequency conditions ($L$: diameter of conducting body). Earlier approaches for dielectric objects at low frequencies are not applicable in the present context. After showing that a simple normalization of the BE system significantly improves its conditioning, we propose a multi-step solution method based on block SOR iterations, which facilitates the use of direct solvers and converges within a few iterations for the considered range of physical parameters. This novel, albeit simple, treatment allows to perform eddy current-type analyses using standard Maxwell SIE formulations, avoiding the adverse consequences of ill-conditioning for low frequencies and high conductivities. Its performance and limitations are studied on three numerical examples involfing low frequencies and high conductivities.

  • Surface Integral Equations for Electromagnetic Testing: The Low-Frequency and High-Contrast Case
    IEEE Transactions on Magnetics, 2014
    Co-Authors: Audrey Vigneron, Edouard Demaldent, Marc Bonnet
    Abstract:

    This paper concerns boundary element methods applied to Electromagnetic Testing for a wide range of frequencies, conductivities and permeabilities. The eddy-current (EC) approximation cannot handle all configurations, while numerical instabilities at low-frequency or for highly contrasted media affect the Maxwell formulation. We examine on a test example how the performance of several Maxwell and EC formulations is affected by frequency, conductivity, and permeability. Among those tested, we propose a weighted loop-tree Maxwell formulation, which is found to be the only one yielding satisfactory results in all considered configurations.

  • Surface integral equations for Electromagnetic Testing: the low-frequency and high-contrast case
    IEEE Transactions on Magnetics, 2014
    Co-Authors: Audrey Vigneron, Edouard Demaldent, Marc Bonnet
    Abstract:

    This study concerns boundary element methods applied to Electromagnetic Testing, for a wide range of frequencies and conductivities. The eddy currents approximation cannot handle all configurations, while the common Maxwell formulation suffers from numerical instabilities at low frequency or in presence of highly contrasted media. We draw on studies that overcome these problems for dielectric configurations to treat conductive bodies, and show how to link them to eddy current formulations under suitable assumptions. This is intended as a first step towards a generic formulation that can be modified in each sub-domain according to the corresponding medium.