(1): the best frequency of the various wall thickness of the tube (the highest wound injury) is different, adjust the frequency is changing the frequency of the tube (2): What is the difference between vertical polarization and horizontal polarization? (3): What is the reflector through the wave? Reflective value in the detection process? (4): I would also like to know the ultrasound (5): you use the electromagnetic sound related sources say something. Thank you enlighten me ... put away
Ask the professional to help, thank you.
Hertz also used a variety of experiments to prove that not only the nature of electromagnetic waves and the same light waves, and the propagation speed is the same, and can occur reflection, refraction, interference, diffraction and polarization phenomena. In other words, the electromagnetic wave obeys all the laws of the general wave.
5. According to Maxwell's theory of electromagnetic fields, the changing electromagnetic fields can be excited by each other, so that the electromagnetic field changes from the field source, from near and far to the surrounding space spread out to form electromagnetic radiation. This change in the electromagnetic field at a certain speed in the form of waves to spread around, it is called electromagnetic waves.
Theoretical Basis of Electromagnetic Ultrasonic Testing Technology
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1. Adjust the frequency without changing the refraction angle.
In 1888, Hertz used the principle of oscillating dipole and resonance absorption, and confirmed the existence of electromagnetic wave by experimental method, and verified that the electromagnetic wave and the light wave are the same in nature. At this point, Maxwell's theory of electromagnetic field was proved experimentally.
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The surface of the measured object is provided with a meandering coil, at some point, by loading a high-pressure narrow pulse or harmonic current source to generate an alternating electromagnetic field H, will be measured in the object to generate the induced current, that is, eddy current I The If a stable magnetic field is produced by the permanent magnet at the same time, it will interact with the internal eddy current of the metal to produce the Lorentz force. The particle of the measured object produces mechanical vibrations under the action of this force, resulting in ultrasonic waves propagating or traveling along the surface of the test object. This is the basic principle of electromagnetic ultrasonic excitation. Electromagnetic ultrasonic reception is the reverse process of excitation. When the surface of the measured object from the internal projection, the displacement of the particle, with a positive charge of the lattice under the action of the bias magnetic field, resulting in alternating current. This alternating current will cause the magnetic field of the alternating surface of the conductor to be measured. This alternating magnetic field leaks out the conductor and excludes the electromotive force in the coil above the conductor to be measured. This can be detected. In the electromagnetic ultrasonic non-destructive testing, the measured object as part of the turtle magnetic sensor, must be electrical or magnetic conductor. If the measured object is a ferromagnetic material, in addition to Lorentz force, but also by the role of magnetostrictive force.
