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

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 -

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

This paper proposes a new flaw inspection technique by use of hysteresis heating and an infrared imaging device. If a periodical magnetic field is applied to a ferromagnetic material, it is heated by iron loss due to the m agnetic hysteresis as well as the Joule heat due to the eddy current. When the frequency of the magnetic field is not high and the magnetic permeability is large, the hysteresis heating is dominant, which enables us to uni formly heat a larger part of the specimen up to the deep region. ...
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Visualization of Surface Defects of Steel Using Iron Loss And Infrared Thermography

In order to detect back surface defects in a plate, the surface strain distribution is visualized by use of piezoelectric thin film. When the plate with a back surfa ce defect is deformed, the resultant strain distribution in the front surface reflects the defect. Such surface strain distribution can be obtained from the electric potential distribution on the piezoelectric film mounted on the front surface. The purpose of this paper is to detect the defects by measuring the electric potential distribution...
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Monitor of searching damage with polymer piezoelectric high-polymer film

This study attempt to detect cracks in austenitic stainless steel by Magnetic Flux Leakage Technique with a high sensitive magnetic sensor. If a specimen is subjected to the stress, the magnetic properties change or the martensite phase is formed due to the plastic deformation or the stress induced phase transformation.. When the generated phase is martensite, this local change of magnetic property can be detected by measuring the Magnetic Flux Leakage with a sensitiv e magnetic sensor. In order to verify ...
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Detection of Crack in Austenitic Stainless Steel with High Sensitive Magnetic Sensor