Abstract
This paper investigates the problem of magnetostrictive generation of elastic waves in steel pipes. The elastic waves are generated by alternating current in a coil about the pipe in a static axial magnetic field. Electromagnetic theory is used to develop solutions for changing electromagnetic fields induced in the pipe, which are needed for coupling magnetostrictively to elastic waves. Elastic wave equations with magnetostrictive driving terms are then solved for the elastic wave solutions. The elastic wave solutions so generated correspond to the L(0,1) and L(0,2) modes for a cylinder, for the frequency range and cylinder geometry considered. Other cylindrical modes do not appear because of the axisymmetric way in which the waves are generated. Comparison with experimental data shows good agreement with the elastic wave dispersion found numerically from the theory. Predictions are made for the wave amplitudes at various frequencies, incorporating both radial and longitudinal displacements into the total amplitude.
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