A feasibility study was conducted on advancement of plant maintenance technology by noticing the integration of non destructive test, fracture mechanics, distributed netw ork, and human interface technologies. In fact, the study was conducted by dividing into the two area: Area A for the methods of non destructive testing and the simulatio n methods on fracture mechanics, while area B for human interface technologies for maintenance work support. During the course of the feasibility study, the developmenta...
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Feasibility Study on Advancement of Maintenance Quality for Nuclear Power Plants

Ferromagnetic materials have the interaction between mechanical and magnetic fields which is called magnetoelastic coupling. Also it is known that magnetic properties of ferromagnetic materials depend on plastic deformation. There are various kinds of Non-Destructive Testing (NDT) based on these phenomena for estimation of stress and plastic deformation. We propose a new analytical method of magnetic hysteresis curve, in which the saturation magnetic hyste resis curve is decomposed to neutral magnetization...
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Estimation of Stress and Plastic Deformation of SS400 SteelUsing Magnetic Properties

There are various inspection methods using Magnetic Flux Leakage Testing. In this paper, we attem pt to apply Thin-Film Flux Gate magnetic sensor to measure weak leakage flux density induced by s urface or back surface defects like cracks or notches. And it is shown that the measured magnetic flux density near the specimen surface indicates the pattern reflecting the shape of the defects....
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Non-destructive Evaluation Based on Measurement of Leaked Magnetic Flux by TFG sensor

There are few works using 2-dimensional measurement in Magnetic Flux Leakage testing. We attempt to estimate the flaw depth and distinguish front or back surface flaw by estimating horizontal component Bx and vertical componen t B, of the magnetic leakage flux density from magnetic structural material. We first calculate the distribution of magnetic flux density near a specimen surface by use of FEM analysis. The distribution is assumed to be approx imated by exponential function according to the dipole mo...
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Evaluation of Depth and Location of Defects Based on 2-Axis Sensing with Amorphous MI Sensors and Parameter Evaluation of Leakage Flux Density Function

Recently, more accurate and convenient Non-Destructive Evaluation techniques are required for flaw inspection of structural materials. Phased array ultrasonic transducers are expected as such a NDE technique but there are many subjects to be solved. Furthermore, commer cial phased array systems with conventional scanning and imaging techniques have not fulfilled their maximum potential. The purpose of this paper is to improve the phased array system to be applicable to the inhomogeneity evaluation of weldi...
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Non-Destructive Evaluation of Welding Part of Stainless Steels by Phased Array System

An Electromagnetic Acoustic Transducer (EMAT) consisting of magnets and a coil can transmit and receive ultrasonic waves wit hout contact to the object. So, it can be used for remote monitoring of metallic products and structures. In this paper, we c arried out numerical analysis for transmitting and receiving processes of EMAT with different frequencies of impressed curre nt. As a result, it is shown that eddy current and reflected echo decrease according as the transmitting frequency increases....
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Evaluation of Ultrasonic Characteristics generated from EMAT by Numerical Analysis - Frequency Dependence of Transmitting and Receiving Characteristics -

Austenitic stainless steel SUS304 is typically classified as a paramagnetic material, but it forms ferromagnetic martensite phase due to plastic deformation, stress or fatigue. This martensitic transformation can be applied to magnetic Non-Destructive Evaluation (NDE) technics. In this paper, we attempt to detect and estimate the artificially introduced notch, fatigue crack and fatigued part in SUS304 steel by measuring the Magnetic Flux Leakage (MFL) near the specimen surface. It is fo und that the notch ...
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Evaluation of Fatigue and Damage in SUS304 using Magnetic Flux Leakage

Magneto-Acoustic Emission (MAE) is stress pulses observed during dynamic magnetization process of ferromagnetic material, which is caused by abrupt and discontinuous motion of magnetic domain wall pinned by inclus ions, voids, dislocations, grain boundaries etc. The characteristics of MAE change with the applied stress, plastic deformation and fatigue since the stress, dislocation and residual stress influence the structure of the magnetic domains and the pinning effects. Therefore, MAE is potential techni...
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Fatigue Estimation of SUS304 Stainless Steel by Magneto-Acoustic Emission

Ferromagnetic materials have the interaction between mechanical and magnetic fields which is called the magnetomechanical coupling. Typical examples of such couplings are the magnetostriction and dependen ce of the stress strain relation on the magnetic field. The magnetoacoustic effect focused in this paper is also one of the magnetomechanical couplings. It has been shown that from the effect there exists the correlation of the plastic strain and the ultrasonic velocity change due to the magnetization. Th...
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Non-Destructive Evaluation of Plastic Deformation of Steelusing Magnetoelastic Coupling Effect

The Electro-Magnetic Acoustic Transducer (EMAT) consisting of magnets and coil can transmit and receive ultrasonic waves without contact to the specimen. So, it is expected to be used for remote testin g/monitoring of structures in severe condition. This paper discusses techniques of ultrasonic flaw detecting suitable for EMAT, e.g., waveform processing of the received signal and ultrasonic imaging t echnique. We next evaluate the characteristics of a self-produced Lorenz type EMAT such as the amplitude di...
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Visualization of Defects by Self-produced Electro-Magnetic Acoustic Transducer