| ID | 121 |
| Title | Evaluation of the applicability of microwave nondestructive testing to detection of cracking on the inner surface of a pipe |
| Author | Yijun Guo, Noritaka Yusa, Hidetoshi Hashizume |
| Published in | International Journal of Applied Electromagnetics and Mechanics 71 (2023), S107-115. |
| Keywords | circumferential and axial cracks, microwave mode, crack size, pipe wall penetration |
| Abstract | This study explores the applicability of microwave nondestructive testing to detecting a metal pipe’s inner crack. Three-dimensional finite element simulations were conducted to study the inspectability of cracks using microwaves in different modes and the dependency of the reflection characteristics of microwaves on crack size. The simulation results showed that microwaves in the TM01 and TE01 modes can detect circumferential and axial cracks, respectively. The positive relationship between crack size and intensity corresponding to the reflected microwaves was obtained in simulations and then verified by experiments. In both simulations and experiments, the axial crack length showed a small influence on the results, especially for shallow crack detection. In the experiments, circumferential and axial cracks with a width of 0.3 mm were detected using microwaves. The experimental results revealed that signal amplitudes decreased when a slit penetrated a pipe wall, probably due to a microwave leakage. |
| ID | 122 |
| Title | Applicability of simulation-assisted probability of detection analysis considering multiple signal features to eddy current testing of weld |
| Author | Takuma Tomizawa, Yijun Guo, Noritaka Yusa |
| Published in | International Journal of Applied Electromagnetics and Mechanics 71 (2023), S75-83. |
| Keywords | multi-parameter, POD, slit, butt weld, detection capability, uniform eddy current, stainless steel |
| Abstract | In this study, a simulation-assisted probability of detection (POD) analysis that considers multiple flaw parameters and signal features is presented, including an evaluation of its applicability to eddy current testing for weld inspection. In the proposed method, both the real and imaginary parts of eddy current signals were considered, unlike conventional methods that only consider signal amplitude. Type 304 stainless steel plates were joined by butt welding, and slits were fabricated on the weld path. The eddy current inspection was conducted using a uniform eddy current probe. Numerical simulations were also performed using the finite element method, with the model imitating the experimental situation. The POD contours were calculated using the proposed method, and they exhibited a reasonable tendency. In addition, the 95% lower confidence intervals of the proposed and conventional PODs were compared and were almost equal with respect to the decision threshold, indicating the applicability of the proposed method. |
| ID | 123 |
| Title | High frequency ultrasonic inspection of the bonded interface between a divertor monoblock and a cooling pipe |
| Author | Noritaka Yusa, Mohammadjavad Faridafshin, Ryouji Suzuki, Takashi Furukawa, Masayuki Tokitani |
| Published in | Fusion Engineering and Design 187 (2023), 113367 |
| Keywords | This study evaluated the applicability of a high-frequency ultrasonic test to the inspection of the bonded interfaces between a divertor monoblock and a cooling pipe. This study prepared a tungsten block bonded with 1 mm of oxygen-free copper and 1.5 mm-thick CuCrZr plates, which simplifies one of the fundamental designs of a divertor: a tungsten monoblock bonded with a cooling pipe with a copper interlayer. The samples were fabricated using a high-temperature vacuum furnace for diffusion bonding. A high-frequency ultrasonic immersion test using a 30 MHz probe was performed from the CuCrZr surface to simulate inspecting the interface from inside the pipe. Ultrasonic images obtained by the test were consistent with the actual bonding condition revealed by sectioning the samples; whether a flaw exists on the interface between CuCrZr and the oxygen-free copper or that between the oxygen-free copper and tungsten was clearly distinguished. The results of this study also suggested the possibility of detecting the growth of crystal grains caused by improper bonding such as too high bonding temperature. |
| Abstract | non-destructive inspection, interlayer, divertor, imaging, delamination |
| ID | 124 |
| Title | Receiver operating characteristic analysis for evaluating a proper experimental condition of eddy current tests under a low signal-to-noise ratio |
| Author | Fanwei Yu, Takuma Tomizawa, Haicheng Song, Noritaka Yusa |
| Published in | International Journal of Applied Electromagnetics and Mechanics 71 (2023), S171-189. |
| Keywords | weld inspection, pitting corrosion, detection reliability evaluation, non-destructive testing, probability of detection, probability of false alarm |
| Abstract | This study proposed a method to evaluate proper experimental conditions of eddy current tests under a low signal-to-noise ratio. This method was applied to quantify the detection reliability of the eddy current test to detect corrosion pits on the surface of austenitic stainless-steel weld cladding from the perspectives of probability of detection and probability of false alarm. The fluctuations of flaw signal and noise were described using truncated bivariate normal distributions of a two-dimensional vector composed of the real and imaginary components of a signal. The probabilities of detection and false alarms were formalized as cumulative distributions of the estimated distributions of the maximum flaw signal and the noise exceeding a decision threshold. The receiver operating characteristic curves were created by coupling the probabilities of detection and false alarms at various thresholds. The area under the curve was used to quantify the detection reliability, simultaneously considering the probabilities of detection and false alarms. The results obtained in this study support the applicability of this method in quantitatively evaluating the detection reliability of a non-destructive inspection under a low signal-to-noise ratio. |
| ID | 125 |
| Title | A probability of detection model for a sensor-based monitoring method against local wall thinning |
| Author | Haicheng Song, Noritaka Yusa |
| Published in | International Journal of Applied Electromagnetics and Mechanics 71 (2023), S29-S37. |
| Keywords | electromagnetic non-destructive evaluation, probability of detection, sensor network |
| Abstract | In this study, a multivariable probability of detection (POD) model is developed to quantify the detection capability of a low frequency electromagnetic (LFEM) testing method with permanently installed sensors to monitor the thinning of pipe walls. Numerical simulations are utilized to predict the signal response by modeling LFEM testing against local wall thinning with different profiles. By probabilistically calibrating the simulated signal response with a limited number of experimental samples, signal response distributions due to various flaw profiles are inferred. Subsequently, a model is developed using Monte Carlo simulation to determine the distribution of the signal response affected by sensor placement and to calculate the POD. The resultant POD contours reflect the effect of multiple flaw parameters and sensor placement on the detection capability of the LFEM testing method. |
| ID | 126 |
| Title | 電磁超音波共鳴法による腐食減肉試験片の肉厚計測精度向上のための信号処理法の検討 |
| Author | 廣瀬悠一，岩田大輝，武田翔，遊佐訓孝，内一哲哉 |
| Published in | 日本機械学会論文集 89 (2023), p.22-00283. |
| Keywords | EMAT, EMAR, Pipe wall thinning, Thickness measurement, Signal processing |
| Abstract | Electromagnetic acoustic resonance method (EMAR) is promising for online monitoring of pipes wall thinning with corrosion during operation. However, the improvement of measurement accuracy is one of issues to be solved, although some signal processing methods such as superposition of nth compression method (SNC) have been proposed in order to improve the accuracy of wall thickness estimation. In this study, for the purpose of highly accurate evaluation of the wall thickness, the thickness of 51 corrosion specimens was measured and compared with the true thickness obtained by 3D laser scanner. The fundamental resonance frequency of EMAR signal spectrum was evaluated by discrete Fourier transform method (DFT) and SNC method, and the wall thickness was calculated. As a result, evaluated thickness by EMAR almost corresponded to the average of true thickness. The accuracy of the evaluated thickness by the SNC method depends on the method to set the postulated thickness for determining the number of compressions. It was found that using the evaluated thickness by the DFT method for determining the number of compressions improved the estimation accuracy of the evaluated thickness by the SNC method. In addition, it was confirmed the estimation accuracy of this evaluated thickness was higher than that of the evaluated thickness by the DFT method. |
| ID | 127 |
| Title | The applicability of remote field eddy current testing to outer flaws on cooling tubes in the blanket of a fusion DEMO reactor |
| Author | Mizuki Kako, Takuma Tomizawa, Jiuhao Ge, Xiaoyong Ruan, Takashi Nozawa, Noritaka Yusa |
| Published in | Fusion Engineering and Design 194 (2023), 113709. |
| Keywords | F82H, Blanket, Prototype reactor, Cooling pipe, Wall thinning, Fretting wear |
| Abstract | This study investigated the applicability of remote field eddy current testing (RFECT) to the non-destructive inspection of cooling tubes in the blanket of a fusion DEMO reactor. Pipes made of F82H steel with inner and outer diameters of 9.0 and 11.0 mm, respectively, were prepared, and artificial grooves were machined on the outer surface of the pipes. The pipes were inspected using an RFECT probe consisting of one exciter and one detector. The results confirmed that RFECT was capable of detecting a groove with a depth of 0.5 mm if the axial length of the groove was 5 mm or more. Subsequently, stress analysis was performed using the three-dimensional finite element method to evaluate the stress caused by the presence of a groove. The calculated stress was compared with the strength of the F82H steel. The stress caused by undetectable flaws was smaller than the strength. |
| ID | 128 |
| Title | Design of a simple side-incident TE11 mode microwave probe for nondestructive pipe inspection |
| Author | Yijun Guo, Ryo Yoshikawa, Noritaka Yusa, Hidetoshi Hashizume |
| Published in | Measurement Science and Technology 34 (2023), 085104. |
| Keywords | |
| Abstract | This study proposed a simple side-incident TE11 mode microwave probe for the rapid and long-range inspection of cracks in metallic pipes. The probe feeds the microwaves to a metallic pipe, which works as a waveguide; the reflection signal provoked by a defect is measured for detection and localization. The probe enables the detection of both circumferentially and axially oriented cracks, unlike those reported in earlier studies. To achieve better performance, numerical simulations were conducted to evaluate the conversion efficiency and optimize the insertion length of the coaxial cable and the exposed length of the cable core wire. The simulation results suggest that the optimized probe configuration is feasible for pipes with various diameters by proportionally changing the current probe configuration. Although injected microwaves propagated in two directions, the ratio of microwaves to one direction could be controlled by adjusting the inclination angle and the exposed length of the cable core wire. Subsequently, three TE11 probes fabricated according to the simulation results were used to detect circumferential and axial slits in a brass pipe. The results showed that circumferential slits in the vertical positions (parallel to the nontilted coaxial cable) and axial slits in the horizontal positions (perpendicular to the nontilted coaxial cable) caused large reflections, consistent with the electromagnetic field distribution of the TE11 mode microwaves in a circular waveguide. Further experiments verified the feasibility of the designed probe for pipes with different diameters and for directional pipe inspection. |
| ID | 129 |
| Title | The effect of the grain size of divertor’s cooling pipe on the capability of high-frequency ultrasonic tests to evaluate the quality of the bond between divertor’s cooling pipe and armor |
| Author | Mohammadjavad Faridafshin, Noritaka Yusa, Ryouji Suzuki, Takashi Furukawa, Masayuki Tokitani, Suguru Masuzaki |
| Published in | Plasma and Fusion Research 18 (2023), 2405068. |
| Keywords | nuclear fusion reactor, non-destructive inspection, bonded
interface, diffusion bonding, heat treatment |
| Abstract | This study evaluated the effect of the grain size of the divertor’s cooling pipe on the capability of high-frequency ultrasonic tests to evaluate the quality of the bonded interface between the divertor’s cooling pipe and armor. First, simple oxygen-free copper and copper-chromium-zirconium block samples with different grain sizes were prepared and measured by an ultrasonic microscope with a 35 MHz probe. The results of the measurements confirmed that the non-uniformity of backwall echoes increased with the grain size of the samples. Samples with large grains provided distinctive signals that can be clearly confirmed on the ultrasonic C-scan images. Subsequently, two bonded samples consisting of 2.5 mm oxygen-free copper bonded with a block of pure tungsten that meets the material specifications of tungsten for ITER components which mimicked the basic design of a divertor’s cooling pipe and a monoblock, were measured to evaluate their bonded interfaces. One of the bonded samples bonded at a high temperature provided distinctive signals due to the enlargement of the grain of the oxygen-free copper. Results confirmed that the grain enlargement is the reason for reduced defect detection capability of the high-frequency ultrasonic tests as was suggested previously. This study also revealed that the enlargement of grain caused by improper manufacturing would be non-destructively detectable by high-frequency ultrasonic tests. |
| ID | 130 |
| Title | Board Game Design to Understand the National Power Mix |
| Author | Noritaka Yusa, Ryoju Hamada |
| Published in | Education Sciences 13 (2023), 793. |
| Keywords | best mix of power sources; public acceptance; energy policy;
electricity supply; simulation and gaming; game-based learning |
| Abstract | This study reports a board game design that would be an effective tool for teaching and learning the best mix of national power sources in a class concerning energy and sustainability in higher education courses. A board game was developed to understand the characteristics of power sources from a Japanese viewpoint based on an earlier study of the authors. The purpose of the game is to satisfy electricity demands by choosing power sources and procuring the resources necessary for power generation to help develop a country. A total of 50 undergraduate and graduate students were asked to assess the game. The results of the questionnaire-based survey conducted after the game con-firmed the students’ evaluation that the game was highly enjoyable and could serve as an effective tool for energy and environmental education in high schools or universities. In addition, the average of “the ratio of the power sources proper to win the game” given by the students was similar to Japanese power mix before the Fukushima disaster, although the game significantly simplified, and even excluded, various factors affecting the national policy of power sources. |
| ID | 131 |
| Title | Bayesian data fusion of eddy current testing for flaw characterization with uncertainty evaluation |
| Author | Takuma Tomizawa, Noritaka Yusa |
| Published in | NDT&E International 141 (2024), 102996. |
| Keywords | ECT, Sizing, Inverse problem, Stainless-steel, Bayesian estimation |
| Abstract | This study proposed a data fusion method based on Bayesian estimation for flaw characterization using eddy current signals and evaluated its applicability using measured signals. The proposed method can fuse several measured data to define the likelihood function as multiplication of probabilistic distributions of eddy current signals and calculate posterior distribution based on the assumption that all signals are independent. Rectangular slits on austenitic stainless-steel plates were measured by plus-point and uniform eddy current probes with three frequencies: 50 kHz, 200 kHz, and 400 kHz. All combinations of probes and frequencies were utilized to estimate flaw size distribution. The results indicate that the proposed method can accurately evaluate the flaw size from the eddy current signals and probabilistically evaluate the error. Furthermore, variations in the importance of each data were found in the comparison of all combinations of probes and frequencies; therefore, the probabilistic sizing method could be used to determine the proper measurement conditions from the viewpoints of uncertainty of the evaluation. |
| ID | 132 |
| Title | Comparison between the results of three surveys in Japan about the attitudes towards energy and power sources conducted in 2020, 2022, and 2023 |
| Author | Noritaka Yusa |
| Published in | Maintenology 23 (2024), 95-102. |
| Keywords | Public acceptance, Questionnaire survey, Power sources, Attitudes towards energy and electricity |
| Abstract | This study compared three surveys about the public attitudes towards energy and seven power sources, including nuclear power, conducted in 2020, 2022, and 2023 in Japan. The surveys were performed in the same manner using a crowd-sourcing service to evaluate the change in the attitudes especially between 2020 and 2022. Analyzing the answers from 1457 respondents revealed that the change in the attitudes toward nuclear power was largest among seven power sources: oil, coal, gas, hydro, solar, wind, and nuclear powers. Whereas elder generations tended to be negative against nuclear power, attitudes toward nuclear power improved regardless of the attributes of the respondents. However, the ratio that female respondents chose nuclear power as a major power source 30 years later remained almost unchanged, unlike male respondents. |
| ID | 133 |
| Title | Signal-distribution-based crack detection for divertor monoblock inspection using eddy current testing, Fusion Engineering and Design (accepted for publication) |
| Author | Fanwei Yu, Takuma Tomizawa, Noritaka Yusa, Masayoshi Tokitani |
| Published in | Fusion Engineering and Design 203 (2024), 114404. |
| Keywords | divertor monoblock, cracking, eddy current testing, detection evaluation |
| Abstract | This study evaluated the applicability of eddy current testing to the surface inspection of a divertor plasma-facing unit in a Tokamak fusion reactor. Artificial slits were introduced on the surfaces of some samples. The eddy current testing was performed to detect these slits. A quantitative detection evaluation method based on evaluating the distribution differences is proposed. The results reveal that the signals of slits near the edge are easily buried by the edge signals and difficult to detect directly from the signal amplitude image. With the aid of the proposed method, not only the slit in the middle of the sample surface but also the slits near the sample edges were successfully detected by eddy current testing. |
| ID | 134 |
| Title | Hiroki Shishido, Noritaka Yusa, Hidetoshi Hashizume, Yoshiki Ishii, Norikazu Ohtori, |
| Author | Numerical prediction of heat transfer properties of molten salt flinabe for a coolant in a nuclear system |
| Published in | Annals of Nuclear Energy 206 (2024), 110631. |
| Keywords | flinabe, physical properties, molecular dynamics, fusion reactor, liquid blanket |
| Abstract | This study evaluated the dependence of heat transfer properties of the molten salt mixture LiF?NaF?BeF2 (Flinabe) on the composition ratio to determine its applicability as a coolant in a nuclear system. Specifically, we evaluated the density, specific heat, viscosity, and thermal conductivity using molecular dynamics simulation and calculated the Prandtl number and figure of merit as heat transfer metrics. The calculated density, specific heat, and viscosity differed from the experimental values by up to approximately 20%. Although the calculated thermal conductivity of Flinabe was not directly comparable due to the lack of accurate experimental measurements, it showed a temperature dependence consistent with that of highly accurate experimental reports for other salts. Overall, the findings of the present study revealed that the lighter LiF-rich molten salts have favorable heat transfer characteristics. The ternary system LiF?NaF?BeF2 = 33?29?38 mol% has a relatively lower Prandtl number and figure of merit compared to the binary system LiF?BeF2, while the melting point is 25 K lower than the binary salt. This study concluded that LiF?NaF?BeF2 = 33?29?38 mol% is the optimal composition for the heat transfer medium in nuclear power systems. |
| ID | 135 |
| Title | The applicability of high-frequency ultrasonic testing for the inspection of the bonded interface between a divertor’s mono-block and screw pipe |
| Author | Mohammadjavad Faridafshin, Noritaka Yusa, Weixi Chen |
| Published in | Fusion Engineering and Design 205 (2024), 114535. |
| Keywords | screw pipe, divertor, bonded interface, non-destructive testing, high-frequency ultrasonic testing |
| Abstract | This study investigated the applicability of high-frequency ultrasonic testing to inspect the tungsten-copper bonded interface between a divertor’s mono-block and a cooling pipe called the “screw pipe.” Mock-up samples simulating the interface were fabricated by diffusion bonding of a 2.5 mm thick oxygen-free copper plate to a 12 mm thick tungsten block that satisfied the ITER material specifications. After making the bond, grooves were machined on the oxygen-free copper side of the samples. High-frequency ultrasonic tests were performed before and after machining the grooves using an ultrasonic scanner with a 30 MHz probe in the immersion pulse-echo setting. The testing results showed that the original screw pipe has a low capability for inspection with high-frequency ultrasonic testing. The visibility of a defect at the interface decreased because of the reflection of ultrasonic waves from the slope of the grooves and interference by the echoes from the interface and the grooves’ surfaces. These issues were addressed by proposing geometrical modifications for the grooves and testing with high-frequency ultrasonic testing. The proposed modifications considerably increased the visibility of a defect at the interface and improved detectability by high-frequency ultrasonic tests. |
| ID | 136 |
| Title | Experimental investigation of low-frequency and pulsed eddy current testing in thickness measurement |
| Author | Jiuhao Ge, Fei Xu, Noritaka Yusa |
| Published in | Nondestructive Testing and Evaluation (accepted for publication) |
| Keywords | Redundant frequency, phase, linearity, SNR |
| Abstract | This paper experimentally compares low-frequency and pulsed eddy current testing techniques in their performance of measuring plate thickness. The experimental setups for both low-frequency and pulsed eddy current testing were built using general commercial devices. A single polarity rectangular wave with a 10 Hz pulse repetition frequency and 50% duty was utilised as the excitation wave in pulsed eddy current testing. Ferromagnetic steel and nonferromagnetic aluminium alloy plates of 1-, 3-, 5-, and 10-mm thicknesses were tested at various liftoff distances to discuss the capabilities and characteristics of both methods. Using peak amplitude, valley amplitude, time to attenuate, logarithmic slope, and reciprocal square root of the logarithmic slope as features, pulsed eddy current testing could effectively evaluate the steel plates thicker than 3 mm and all the aluminium alloy plates. However, the selection of threshold values in the time domain determining the features significantly affects the performance of pulsed eddy current testing. In contrast, low-frequency eddy current testing using a 10 Hz excitation frequency could evaluate both steel and aluminium plates using signal phase. This indicates that redundant frequency components may impair the effectiveness of pulsed eddy current testing. Moreover, low signal-to-noise ratio and simple signal processing methods struggle to detect minor signal variations. Signal-to-noise ratios should be considered in pulsed eddy current testing. Additionally, the linearity of phase versus thickness for steel is better than for an aluminium alloy, potentially indicating that ferromagnetic materials enhance the coupling between the coil and the plate. |
| ID | 137 |
| Title | Development of a Non-digital Educational Game for Understanding the Characteristics of Power Sources and the Scale of Power Demand and Generation |
| Author | Noritaka Yusa, Shinya Nakayama |
| Published in | Journal of Energy and Environmental Education (accepted for publication) |
| Keywords | |
| Abstract | 発電設備の特徴と電力需給の規模感を実感することを目的とし て開発しているゲーム型教材「電力王になろう！！」の最新版概要及びその評価結果 を報告する．当該ゲームはカード，チップ，コマなどを用いて3〜5人で行うアナログゲームであり，各プレイヤーは電力会社の社長となり，自社の発 電所を建設し，多くの人・都市に電力を供給することを目的する．ゲームには実在する国内外の発電所をモデルとした石炭火力，ガス火力，原子 力，水 力，太陽光，風力の6種類の発電設備があり，電力の供給先も，鎌倉市や宮城県，東京都などの実在のものをモデルとしている．教育学を専攻する学部 及び大学院学生14名による評価により，当該ゲームはゲームとして楽しめつつも，電源特性の理解及び都市の電力需要の規 模感の実感に繋がるということが確認された． |
| ID | 138 |
| Title | Pipe Failure Prediction Model based on Periodic Pipe Wall Thickness Measurement using Electromagnetic Acoustic Resonance |
| Author | Noritaka Yusa, Sho Takeda, Tetsuya Uchimoto, Masahiko Endo, Yasuhiro Saito |
| Published in | International Journal of Applied Electromagnetics and Mechanics (accepted for publication) |
| Keywords | nondestructive testing and evaluation, electromagnetic acoustic
transducer, flow assisted corrosion, pipe wall thinning management,
wall thinning |
| Abstract | This study proposes a numerical model to predict pipe failure based on periodic non-destructive inspections using electromagnetic acoustic resonance (EMAR). A total of 149 artificially corroded samples that simulated flow-assisted corrosion were prepared; 27 of them were plates, and others were from pipes of various dimensions. The samples were measured using EMAR, and the thicknesses of the samples were evaluated based on the fundamental resonance frequency. The results of the evaluations were compared with the actual thicknesses measured by a caliper gauge to quantify the uncertainty in pipe wall thickness evaluation. Numerical evaluations were performed to predict pipe failure probability in the future based on the results of periodic EMAR measurements. Three scenarios of pipe thickness reduction were considered, and each scenario assumed that pipe thickness measurements by EMAR were performed every five years. The actual pipe wall thickness, which is not necessarily the same as the EMAR evaluations, is estimated as a probability density function using the Bayesian approach proposed in an earlier study by the authors. Whereas this study considers only pipe rupture, the results of numerical simulations support the validity of the model especially when the corrosion rate is not constant. |
| ID | 139 |
| Title | Evaluation of local wall thinning severity in a metal pipe using guided microwaves |
| Author | Yijun Guo, Haitao Huang, Noritaka Yusa, Hidetoshi Hashizume |
| Published in | Nondestructive Testing and Evaluation (accepted for publication) |
| Keywords | resonant frequency, high-order mode, 1D CNN, classification |
| Abstract | This study explores the applicability of guided microwave testing to assess the severity of partial circumferential pipe wall thinning (PWT). Numerical simulations revealed that the resonant frequency of reflected TM01 mode microwaves exhibited a negative correlation with the circumferential angle, depth, and length of PWT. Notably, high-order modes activated in the defect region produced frequency outliers, with corresponding frequencies decreasing as PWT depth or length increased. Experiments conducted using a 15 m long pipe yielded a frequency spectrum of the processed signals with a similar waveform to that of the simulation results, suggesting the feasibility of using simulation data to train the evaluation model. A one-dimensional convolutional neural network (1D CNN), built to automatically extract information from the frequency spectrum, achieved remarkable accuracy exceeding 96.7% in classifying the partial circumferential PWT severity in both simulated and experimental scenarios. Comparative analysis revealed that both 1D CNN and k-Nearest Neighbor classifiers, utilizing full waveform information, outperformed traditional back-propagation neural networks relying on handcrafted frequency points. These findings highlight the critical importance of waveform information in PWT evaluation and present a novel approach for PWT severity assessment using guided microwave testing for long pipe inspection. |
| ID | 140 |
| Title | Probabilistic detection capability evaluation of eddy current testing to detect cracks on the divertor monoblock surface |
| Author | Fanwei Yu, Noritaka Yusa, Masayuki Tokitani |
| Published in | Fusion Engineering and Design (accepted for publication) |
| Keywords | divertor monoblock, cracking, eddy current testing, detection evaluation, probability of detection |
| Abstract | This study proposed a multi-parameter probability of detection (POD) model to probabilistically assess the capability of eddy current testing (ECT) for the inspection of divertor monoblock surfaces. The model assumes that a signal caused by the presence of a crack follows a probability density function with the depth, length, and position of the crack as variables. The parameters of the model are estimated by the combinational use of measured and experimental signals, and the probability that the signal exceeds a certain threshold is regarded as the probability of detection as the conventional â-a POD analysis. To demonstrate the model, sixty-three tungsten samples with an artificial slit were prepared to simulate the thermal fatigue cracking of the monoblock plasma-facing surface. The samples were measured using a differential plus-point ECT probe with a 1 mm lift-off and 500 kHz frequency. Correspondingly, numerical simulations of an eddy current simulator based on the A-ϕ formulation were performed. The difference between the normalized slit signals and a flawless signal, which is obtained with the aid of image processing, was considered as the signal response to mitigate the influence of large noise caused at the edges of monoblocks. The results show that the proposed model can evaluate POD much more reasonably than conventional models that represent a flaw using one or two parameters. |