This paper deals with a recovery method of a crack shape for preventive maintenance of power plant. In order to detect a crack and recover of its shap e automatically, we develop a mobile robot with ECT (Eddy Current Testing) sensor composed of a transmitter-receiver coil probe. ECT is a major techn ique for detection of surface and subsurface cracks found out in structures of the power plant. The robot detects a crack by ECT sensor signals, local izes the crack and recover its shape by rough and fine insp...
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Development of Crack Shape Inspection System with ECT Sensor Robot

This paper is concerned with mechanism of ultrasonic test signals in magnetic materials using electromagnetic acoustic transducer(EMAT). The co upling mechanism between the electromagnetic fields and the applied excitation of ultrasonic testing are investigated. First, a nonlinear magnetic mod el in two dimensions is presented for the coupling mechanism. Secondly, the coupling mechanisms in ferromagnetic materials are studied analytically an d numerically. The final part of this monograph is devoted to num...
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Simulation on mechanism of ultrasonic test signals in magnetic materialsusing EMAT

Abstract This paper is concerned with transmit-receive mechanism of the electromagnetic ultrasonic tran sducer (EMAT) for the guided wave. First, the three-dimensional guided wave propagation simulator is de veloped. This simulator calculates the particle velocity from the force which are excited by EMATs with FDTD method. Second, configuration of EMATs is designed based on our study of the excitation mechanism of an EMAT, in order to transmit and receive the longitudinal mode (L-mode) or the torsional mod...
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Analysis of transmit-receive mechanism of EMAT for the guided wave

his paper is concerned with quantitative evaluation of corrosion shape on outer surface of Pipe by Electro agnetic Acoust ic Transducer (EMAT). The pipe wall thinning was modeled semi ellipse shape. And FAC s been considered more dangerous. Th e pipe wall thinning was able to be measured with precision. In neral, FAC had a smooth surface wall thinning. EMAT were a ble to measure the echo in the test piece with 11 thinning of smooth enough. The EMAT is able to use to test for the FAC....
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Measurement method of Pipe Wall Thinning Shape by EMAT

This paper is concerned with development of guided wave simulator on piping diagnostic system. First, a mathematical model of inspe ction procedures is described by a set of dynamical linear elastic equations in three spatial dimensions. Secondly, the numerical s cheme of the inspection model is given by using FDTD method. Finally, some numerical experiments are shown in order to assure the ap plicability of the proposed scheme to piping test. ...
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Development of Guided Wave Simulator using FDTD method and its Application toNondestructive Testing

The aim of this work presented here is to demonstrate the method for estimating the pipe wall thinning configuration: location, width, depth of pipe wall thinning in straight pipe based on velocity dispersions of longitudinal guided wave. First, group velocity dispersion curve is derived from frequency equation. Second, group velocity of longitudinal guided wave is analyzed using guided wave simulator for pipe with notch-shaped and ellipse-shaped circular pipe wall thinning. Finally, method for estimat...
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Estimation of the Pipe Wall Thinning Configuration Based on Velocity Dispersions of Longitudinal Guided Wave

This paper proposes a method of applying a reliability of inspection data to a calculation of hazard rate. First, the probability of detection (POD) is calculated from inspection data of thickness measurement of pipe wall by an ultrasonic thickness meter. The inspection data are collected from experiments by qualified or unqualified inspectors. The POD outputs probabilities of reliability assessment based on the inspection data. Second, the probabilities are used for a timing estimation of pipe hazard....
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Reliability assessment for thickness measurements of pipe wall using probability of detection and application to hazard rate

This study reports the development of automatic condition monitoring techniques and system. The techniques and the system have been developed to test industrial motors by their sound signals. In this study, several kinds of defects in motor can be detected using monitoring techniques. The programs make possible to compute diagnostic algorithm and to practice judgments correctly. This new condition monitoring method will be tested in some plant s and will be also applied to preventive maintenance for not on...
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Monitoring of Rotating Machine in Plants

A dynamic monitoring system for bearings has been developed. The defects of bearings in motors can be detected and classified into some groups from their vibration signals by an accelerometer screwed on the monitored bearings using the dynamic monitoring system. The abnormality of the bearings is judged from many factors such as the peak value, the root mean square value and the ratio of peak to root mean square value. And then, the grade of its abnormality is diagnosed how heavy the defect is, when t...
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Dynamic Monitoring for Bearings of Rotating Machines in Plant

The purpose of this report is to establish a predictive methodology for estimating rate of wall thinning in a piping system used in ag eing nuclear power plants. First, mechanism of flow accelerated corrosion caused by steam of flowing water is given by KWU-KR model. Se condly, a method for setting geometrical parameter based on pipe wall thickness measurements is considered. Thirdly, estimation method ology for wall thinning rate is formulated within the framework of Kalman filtering. Finally, some simula...
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Prediction of Wall Thinning by Flow Accelerated Corrosion using Kalman Filtering