Efficiency and electromechanical resonance in magnetostrictive transducers

Abstract

Analysis of the transduction phenomenon of a Tonpilz Terfenol-D magnetostrictive transducer is presented. Transducer efficiency is discussed from electroacoustic and scalar energy perspectives. Equations are presented for identifying the frequency of most efficient transducer operation based on electroacoustic theory [F. V. Hunt, in Electroacoustics: The Analysis of Transduction, and Its Historical Background (Acoustical Society of America, New York, 1982)]. Experimental results are presented that show this analysis to be accurate. However, two nonintuitive results are observed: most efficient transducer operation occurs at a frequency above mechanical resonance; and changes in operating conditions which result in an increase in transducer efficiency cause the frequency of highest efficiency to increase even further above the frequency of mechanical resonance. This motivated a comparison with a scalar energy analysis for development of a better, or at least more intuitive, understanding of the mechanisms which might explain this result. Energy analysis aids in recognizing the distinction between the transducer’s mechanical and electromechanical resonances and that the magnitude of achievable efficiency will be enhanced by separation of electromechanical and mechanical resonances. Coupling the energy and electroacoustic analyses, one arrives at persuasive arguments for explaining the experimental observations regarding magnetostrictive transducer efficiency.