Broadband Performance of a Magnetostrictive Shaker

Abstract

Performance data from a magnetostrictive broadband (100 Hz-10 kHz) vibration source is presented. An original design for a magnetostrictive transducer was built and tested. The transducer used a rod of ETREMA Terfenol-DTM (EDGE Technologies, Ames, Iowa) as the motion source (rod dimensions: 51 mm long x 6.35 mm diameter). This communication will convey the characteristics of magnetostrictive transducer behavior. The shaker is considered to be a single input (electric current) single output (force) system. For low signal operation it behaves in a linear fashion; output force is proportional to input electric current and harmonic content is low. Comparisons with a commercially available permanent magnet shaker show that the magnetostrictive shaker's linear region extends to high enough forces (or displacements) to be of use as a vibration excitation source. Higher input currents eventually lead to degradation of the magnetostrictive shaker's linear behavior; output harmonics become appreciable, force levels increase disproportionately and, of course, linear systems analysis techniques become inappropriate. The magnetostrictive shaker discussed is capable of producing peak acceleration amplitudes in excess of 1960 m/s² (200 g's, at frequencies greater than 4 kHz with a 24 gram load using sinusoidal excitation). Experimental results are presented for: 1) output force as a function of frequency, load, and current amplitude (30 Hz-10 kHz with sinusoidal excitation); 2) typical electrical impedance as a function of frequency; 3) frequency response functions as Newtons per ampere, Newtons per volt, and meter per ampere; and 4) performance comparisons made with a commercially available permanent magnet shaker. Experimental results 2, 3, and 4 are for operation of the magnetostrictive shaker in its linear range (linear in a least squares sense).