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Modeling and Research of EMAT Based on Lorentz Mechanism

Author: LiZhiChao
Tutor: WangShuJuan
School: Harbin Institute of Technology
Course: Electrical Engineering
Keywords: Electromagnetic acoustic transducer Lorentz force mechanism SAW Body wave
CLC: TB552
Type: Master's thesis
Year: 2010
Downloads: 207
Quote: 4
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Abstract


The EMAT technology because no couplant produce many types of ultrasonic convenient , widely used in the field of ultrasonic nondestructive testing . In this paper, the Lorentz force mechanism - based electromagnetic acoustic transducer modeling and simulation analysis . The use of numerical and analytical combined to calculate the characteristics of electromagnetic ultrasonic transducer sound field , laid the basis of theoretical research design optimization for electromagnetic ultrasonic transducer . First, according to the electromagnetic field theory derivation of the Lorentz force generation mechanism . Analytical expression of the surface point force SAW displacement and horizontal and vertical displacement of the body wave analytical expression is derived by the kinetic theory of elasticity , provides a theoretical basis for the calculation of electromagnetic ultrasonic surface wave electromagnetic acoustic wave sound field . The three-dimensional finite element method of tortuous coil electromagnetic ultrasonic surface wave transducer modeling, simulation analysis of aluminum Lorentz force distribution and surface wave acoustic field distribution . Lorentz force consists of two components, a static magnetic field generated by the eddy currents and the outside world , and the other one is generated by the excited alternating magnetic field by the eddy currents and coil currents . Static magnetic field , the Lorentz force excitation of the surface wave amplitude and the excitation current is proportional to the size of the quadratic function , and the amplitude of the surface acoustic wave excited by an alternating magnetic field , Lorentz force is the energizing current size . When the excitation current is equal to 528.9 A , equal to the static magnetic field , the Lorentz force , and alternating magnetic field , the Lorentz force excitation of the surface wave amplitude . Excitation current is large , you can not ignore the influence of an alternating magnetic field , the Lorentz force . Helical coil electromagnetic acoustic body waves transducer modeling , simulation and analysis of its cross inside the aluminum plate , the longitudinal wave sound field distribution . Horizontal radial Lorentz force is mainly produced of shear wave propagation in the depth direction , the vertical direction , the Lorentz force is mainly generated along the depth direction of propagation of longitudinal waves . The spiral coil electromagnetic ultrasonic transducer, the transverse wave generated in the aluminum component is greater than the longitudinal wave component in the aluminum plate , the shear wave can propagate the distance from the longitudinal wave decay to zero quickly . To verify the correctness of the model using electromagnetic acoustic transducer probe with a mechanical device , SAW transducer excitation of electromagnetic ultrasonic surface wave acoustic field characteristics of experimental verification . Experimental test results and simulation results are consistent , to verify the correctness and validity of the model .

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CLC: > Industrial Technology > General industrial technology > Acoustic engineering > Ultrasonic Engineering > Ultrasonic transducer
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