Eddy Current Array Scan Example

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Register to read the introduction… This is Experiment No. 1 from the table; the specimen contains corrosion damage of 40mm X 20mm at four locations which was created by immersing the sample in electrolyte for one, two, three and four hours. The damages are imaged in order; extreme left representing the sample immersed in electrolyte for one hour and extreme right representing the sample immersed in electrolyte for four hours. Both the array coils were excited at a frequency of 15 kHz for a layer thickness of 1mm. On the right hand side shows the corrosion damage exposed for 4 hours by Ultrasonic phased array.

Fig. 9: Eddy current array result (left) and Ultrasonic phased array result (right) (Kathir & John 2005)

Figure 9 shows the Eddy current array scan result (left) for a specimen. This experiment is actually Experiment No. 3 from the table. The specimen contains corrosion damage which was created exclusively for this experiment by immersing the sample in the electrolyte for approximately 30 minutes and a circular notch of 0.2mm deep was made by electric discharge machining. Both the array coils were excited at a frequency of 15 kHz for a sample thickness of 1mm. On the right hand side is the corrosion damage of electric discharge machining notch by Ultrasonic phased
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Aluminum Oxide Trihydrate (Al (OH) 3): A white powder which is insoluble water but soluble in hydrochloric or sulfuric acid.
Aperture: In phased array testing, the width of the transducer element or group of elements pulsed simultaneously.
Chemical Etching: A process when acids, bases or other chemicals dissolve materials such as metals, semiconductor materials or glass.
Electrical Conductivity: Electrical conductivity is a measure of how well a material accommodates the movement of an electric charge. It is the ratio of the current density to the electric field strength.
Electric Discharge Machining: A machining method primarily used for removing hard metals by producing a rapid series of repetitive electrical discharges.
Electrolyte: Any substance containing free ions that make the substance electrically conductive.
Frequency: The number of complete cycles per second in alternating current direction.
Magnetic field: Defined by measuring the force the field exerts on a moving charged particle, such as an

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