Showing papers by "Tetsuya Uchimoto published in 2012"
TL;DR: A very fast numerical solver is developed for simulation of PECT signal simulation of local wall thinning, and its validity is verified by comparing its numerical results with measured PECT signals and with those simulated using a conventional numerical code.
Abstract: A very fast numerical solver is developed for simulation of pulsed eddy current testing (PECT) signals caused by volumetric defects by introducing a database-type fast eddy current testing (ECT) simulation scheme for single frequency problems to the Fourier-series and interpolation-based PECT signal simulation code. First, the PECT signal simulation method based on a Fourier series scheme and an interpolation approach is briefly described. Then, a database-type fast numerical solver for single frequency ECT problems is introduced to the Fourier-series-based PECT simulation to enhance simulation efficiency. To cope with fast PECT signal simulation of 3D local wall thinning defects, a 2D shifting symmetry scheme is proposed for inspection targets of both plate and straight pipe geometries to reduce the computational burden required to establish databases of the unflawed field, which are necessary for fast ECT signal simulation. Using these strategies, a very fast numerical solver is developed for simulation of PECT signals of local wall thinning, and its validity is verified by comparing its numerical results with measured PECT signals and with those simulated using a conventional numerical code.
43 citations
TL;DR: In this paper, the correlation between plastic deformation and the deformation-induced magnetic field was investigated for the SUS304 austenitic stainless steel, and the experimental results showed that the amplitudes of the magnetic field have a clear and repeatable relationship with the maximum residual strains for all the specimens.
Abstract: In this paper, the correlation between plastic deformation and the deformation-induced magnetic field was exper- imentally investigated for the SUS304 austenitic stainless steel. Test-pieces with different shapes were fabricated to produce different strain distribution. Various plastic tensile loads were imposed into the specimens to introduce plastic deformations of different levels. The residual strain distributions at the surfaces of the specimens were measured by an optical 2D strain measurement system during loading process while the distributions of the deformation-induced magnetic fields above the specimens were measured by using a fluxgate magnetometer after each loading cycle. The experimental results show that the amplitudes of the magnetic field have a clear and repeatable relationship with the maximum residual strains for all the specimens, and the relationship is independent of the strain distribution. Based on the experimental results, the mechanism of the deformation-induced magnetic field was discussed, and a NonDestructive Evaluation (NDE) method was proposed for the quantitative evaluation of plastic deformation in the SUS304 stainless steel.
20 citations
TL;DR: In this article, an edge-element FEM code for carbon-fibre reinforced polymer composites (CFRP) was used to deal with eddy current testing simulation for CFRP.
Abstract: This paper deals with eddy current testing simulation for carbon-fibre reinforced polymer composites (CFRPs) using an edge - element FEM code. The FEM code is based on the A formulation and it uses the coupled analysis with external fields. The coil impedance variations due to the fibre orientation and cracks in CFRP plates with unidirectional plies are computed. The conductivity of CFRP is characterized as low value and high anisotropy, which cause the distinct difference between CFRP and isotropic metal ECT signals. The correlation of the fibre orientation with coil impedance variations is obtained, but the exact fibre arrangement in a composite plate can't be ascertained because of signal symmetry. Another method for determining the fibre orientation via the edge effect is presented in this study. According to the numerical results, the shape of cracks in a CFRP plate is not easily evaluated from the detection signal curves unless the fibre orientation is perpendicular to the crack path.
18 citations
TL;DR: In this article, a non-destructive method, called magnetic adaptive testing (MAGNET), was applied for detecting local wall thinning in ferromagnetic plates, based on the measurement of minor magnetic hysteresis loops.
Abstract: A recently developed nondestructive method, called magnetic adaptive testing, which is based on systematic measurement of minor magnetic hysteresis loops, was applied for detection of local wall thinning in ferromagnetic plates. It was shown that even a relatively small, local modification of the sample thickness could be detected with good signal/noise ratio from the other side of the specimen. The measurements gave good results also, if the investigated plate was covered by other plate(s).
17 citations
17 citations
TL;DR: In this paper, a partially-bonded region inside a material by bonding together surfaces that have grooves was used to simulate the characteristics of stress corrosion cracking, and six specimens made of type 316L austenitic stainless steel were fabricated on the basis of the results of the simulations.
10 citations
9 citations
TL;DR: In this paper, the authors discussed the electromagnetic modeling of fatigue cracks in plant environment to improve accuracy of depth sizing with eddy current testing, and evaluated the factors that influence eddy currents signals.
Abstract: This study discusses the electromagnetic modeling of fatigue cracks in plant environment to improve accuracy of depth sizing with eddy current testing. For the purpose, the factors that influence eddy current signals of fatigue cracks are evaluated. Here, martensitic layer and oxide fillings in fatigue cracks are focused on as influencing factors, and oxides are systematically filled in fatigue cracks by thermal treatment. The measured EC signals change depending on the presence and type of filling oxides. Numerical simulations are conducted to discuss the electromagnetic modeling of cracks with oxide fillings. The types of oxides in the cracks are identified by Raman spectroscopy, and the martensitic layers in vicinity of crack faces are observed by magnetic force microscopy. These results support for the electromagnetic model of environmental fatigue cracks developed in this study.
7 citations
TL;DR: Magnetic hysteresis curves were calculated using the Monte Carlo method to study the dependence of magnetic properties on the distribution of local magnetic sites on the grain boundaries of sensitized Alloy 600 as discussed by the authors.
Abstract: Magnetic hysteresis curves were calculated using the Monte Carlo method to study the dependence of magnetic properties on the distribution of local magnetic sites on the grain boundaries of sensitized Alloy 600. The simulated curves illustrate that the total number of the magnetic sites and the standard deviation of the site distribution on grain boundary influence strongly the magnetic remanence and coercivity. The magnetic system can, therefore, be regarded as a magnetic granular structure with a distribution, and the results suggest a possibility of new method to control magnetic hysteresis.
1 citations
TL;DR: In this article, the magnetic hysteresis curves were calculated using the Monte Carlo method to study the dependence of magnetic properties on the distribution of magnetic sites based on simple diffusion model and the simulated curves illustrate that the magnetic sites distributions influence strongly the magnetic remanence and coercivity depending on diffusion step.
Abstract: Magnetic hysteresis curves were calculated using the Monte Carlo method to study the dependence of magnetic properties on the distribution of magnetic sites based on simple diffusion model. The simulated curves illustrate that the magnetic sites distributions influence strongly the magnetic remanence and coercivity depending on diffusion step. Furthermore, the clusters are divided into “colonies”, which are defined as groups of magnetic sites linked by the nearest neighbors, to analyze effect for the hysteresis curves of local structures of magnetic sites in the clusters. These results support that the magnetic sites dispersion system included localized bias determines its magnetic properties depending on the diffusion step, and they would be a new point of view for control of magnetic properties.