Magnetic disks are metal discs that are coated with special material to store data.
Galileo Azul,P. Non-destructive techniques are used widely in the metal industry in order to control the quality of materials.
Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor.
This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems.
Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.
Introduction Non-destructive techniques are used in the metal industry and science in order to evaluate the properties of a wide variety of materials without causing damage. Some of the most common non-destructive techniques are electromagnetic, ultrasonic and liquid penetrant testing.
One of the conventional electromagnetic methods utilized for the inspection of conductive materials such as copper, aluminum or steel is eddy current non-destructive testing [ 1 ].
Electromagnetic methods such as eddy current, magnetic particle or radiographic and ultrasonic methods all introduce electromagnetic or sound waves into the inspected material in order to extract its properties. Penetrant liquid techniques can detect cracks in the test material by using either fluorescent or non-fluorescent dyes.
In addition to these methods, scientists such as Shujuan et al. The principle of the eddy current technique is based on the interaction between a magnetic field source and the test material. This interaction induces eddy currents in the test piece [ 1 ].
Scientists can detect the presence of very small cracks by monitoring changes in the eddy current flow [ 5 ]. Eddy current testing is especially fast at automatically inspecting semi-finished products such as wires, bars, tubes or profiles in production lines.
The results of eddy current testing are practically instantaneous, whereas other techniques such as liquid penetrant testing or optical inspection require time-consuming procedures that make it impossible [ 8 ], even if desired, to inspect all production.
Eddy current testing permits crack detection in a large variety of conductive materials, either ferromagnetic or non-ferromagnetic, whereas other non-destructive techniques such as the magnetic particle method are limited to ferromagnetic metals.
Another advantage of the eddy current method over other techniques is that inspection can be implemented without any direct physical contact between the sensor and the inspected piece.
In addition, a wide variety of inspections and measurements may be performed with the eddy current methods that are beyond the scope of other techniques. Measurements of non-conductive coating thickness [ 9 ] and conductivity can be done. Conductivity is related to the composition and heat treatment of the test material.
Therefore, the eddy current method can also be used to distinguish between pure materials and alloy compositions and to determine the hardness of test pieces after heat treatments [ 8 ]. Since the s the role of eddy current testing has developed increasingly in the testing of materials, especially in the aircraft [ 10 ] and nuclear industries [ 11 ].
The extensive research and development in highly sensitive eddy current sensors and instruments over the last sixty years indicates that eddy current testing is currently a widely used inspection technique.
This paper presents the basis of non-destructive eddy current testing and provides an overview of the research conducted by many authors who continue to develop this technique. The fundamentals of eddy current inspection and the main variables of this technique are presented in Sections 2 and 3.
Section 4 reviews the state-of-the-art sensors and research.
Section 5 reviews the state of modern equipment, and Section 6 presents the applications and research trends of eddy current inspection. Finally, Section 7 presents a discussion of eddy current testing.
Principles of Operation of Eddy Current Testing The objective of this section is to describe the principles of eddy current testing. A transformer model is presented to demonstrate the fundamentals of eddy current induction and the impedance changes that occur in coil sensors.
After presenting operating principles, we present a block diagram of the constituent parts of eddy current testing equipment.Differences Between Magnetic Tape & Magnetic Disk. March 31, By: John Papiewski. Share; Share on Facebook; Magnetic tape and disk have evolved together since the s, filling different data storage needs for computer users.
Tape drives store and archive large amounts of data economically. Disk drives access the data with . Magnetic tapes are polymers that are coated with special material to store data.
Magnetic tapes and magnetic disks are widely used in fields such [ ] yunusemremert.com Compare and Discern the Clear Difference Between Any Similar Things. Home» Difference Between Magnetic Tape and Magnetic Disk.
Bear with gaps in development but generally — Magnetic media started with wire that was magnetized and played audio. With the advent of plastics — magnetic particles were embedded in the plastic and an electromagnetic head would magnetize portions of the tape and it passed over the head.
The basic difference between magnetic tape and magnetic disk is that magnetic tape is used for backups whereas, magnetic disk are used as secondary yunusemremert.com us discuss some more differences between magnetic tape and magnetic disk with the help of comparison chart shown below.
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Difference between Magnetic and Optical Storage By Aakar Anil November 12, If you are unable to see the yunusemremert.com, copy it and paste it into microsoft word. Magnetic tape etc.
a) Stores data optically & used laser to read/write. b) It is not affected by magnetic field. c) It has less storage than hard disk.