Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1983-03-22
1987-02-03
Karlsen, Ernest F.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
324262, G01N 2772, G01R 3312
Patent
active
046410937
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to methods of nondestructive testing of materials and articles, and more specifically is concerned with a magnetic inspection of a moving elongated ferromagnetic test piece for determining mechanical properties thereof and a device for carrying out the same.
BACKGROUND ART
It is a common knowledge that magnetic and mechanical properties of ferromagnetic materials, for instance steel, depend on their chemical composition and structure obtained during their manufacture. Therefore, manufacturing a steel possessing desirable melchanical properties, such as hardness, ultimate strength, yield strength, and elongation, may be ensured by maintaining the chemical composition constant and the manufacturing process stable. Since one and the same departure (within tolerance limits) from a chemical composition and the manufacturing process employed cause changes both in mechanical and magnetic properties, there exists a correlation dependence between these properties, which allow determining mechanical properties by measuring magnetic properties. The best magnetic properties for the above purpose are a coercive force and a remanent induction (or magnetization).
In a known in the art method entitled as "Method for measuring remanent magnetization" (cf. Japan accepted patent specification No. 53-29109, Int. Cl. G 01n 27/68) the test piece (plate) is passed between two electromagnets disposed in opposing relationship at the both sides of said plate, one at the top side and the other one at the underside. The electromagnets provides formation of a magnetic track in the test material, which magnetic track extends in the direction of movement of said test material. Located some distance from said electromagnets are transducers mounted for movement along a path crossing said magnetic track. The signal from the transducer is used to determine the quantity of remanent magnetization in the test plate. The inspection results in this method are influenced by displacement of the test material due to vibration, which affects the accuracy of measurement.
Furthermore, the presence of moving parts makes carrying out this method more difficult and impairs the reliability thereof.
In another known in the art method entitled as "Method and apparatus for detecting the presence of magnetic anomalies in ferromagnetic and non-ferromagnetic materials" (cf. U.K. Pat. No. 1,498,218, Int. Cl. G 01n 27/86) the test material is passed through a ring magnet so that said test material is magnetized by the magnet field. The parameters of the test material are determined by the magnitude of signals formed in the sensing coils under the action of the magnetic dipoles set up in the test material. The amplitudes of the thus produced signals representative of the properties of the test material are proportional to the magnitude of the magnetic dipoles and velocity of the test material.
The above-mentioned dependence of the output signal on the velocity of the test material affect the accuracy of the method.
There is also known a method for magnetic inspection of moving ferromagnetic articles of round section (cf. USSR Author's Certificate No. 696,369, 5.11.79) which comprises a pulse generator adapted to generate magnetizing pulses with a variable frequency of pulse repetition. The magnetizing means are made in the form of solenoids placed in antiparallel relationship in the circuit of the pulse generator. Inside one of the solenoids are mounted reading devices symmetric about the axis of said solenoid. As reading devices use is made of a convential ferroprobe-gradiometers which are placed in a circuit so that their output signals are summed. Field coils of the ferroprobes are connected through power amplifiers to an exciting circuit, and measuring coils are connected to the input of a selective amplifier tuned to the second harmonic.
Magnetic testing of the material for mechanical properties with the use of the above method is carried out as follows.
The test piece is passed inside the magnetizing solenoids and be
REFERENCES:
patent: 3586963 (1969-04-01), Arrott et al.
patent: 3940690 (1976-04-01), Suhr et al.
patent: 4044302 (1977-08-01), Mayberry
Melgui Mikhail A.
Sandomirsky Sergei G.
Institut Prikladnoi Fiziki Akademii Nauk Belorusskoi SSR
Karlsen Ernest F.
Snow Walter E.
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