High-field Characterization of Piezoelectric and Magnetostrictive Actuators RADU POMIRLEANU AND VICTOR GIURGIUTIU* Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208 ABSTRACT: High-field theoretical and experimental analysis of piezoelectric and magneto- strictive actuators is presented. First, the analysis of a piezoelectric stack actuator (PiezoSystems Jena PAHL 120/20) is described. A theoretical model based on the linear theory of piezoelectricity is developed. Extensive experiments were conducted, aimed at low- frequency dynamic electro-mechanical behavior characterization. Curve fitting procedures are used to adjust the model coefficients for various load levels. Through comparison with experimental data, the model is adjusted to include nonlinear terms related to higher losses on the unloading cycle. Second, the impedance analysis of a magnetostrictive actuator (Etrema AA140J025) is described. Linear piezomagnetism is assumed, as an approximation to nonlinear magnetostrictive behavior about a bias point. Low-field and high-field impedance measurements were performed, revealing left shifting of the actuator resonance as the power is increased. Model tuning of the impedance model on the experimental data showed material parameters trends similar with those reported in the literature. Although the numerical values developed during this phenomenological study are particular for the actuators under consideration, the characterization approach can be extended to analysis of other actuators of this type. Key Words: Author please provide Keywords ??? INTRODUCTION A CTIVE-MATERIALS technology offers direct conver- sion of electrical energy to high-frequency linear motion. High-performance solid-state induced-strain actuators (piezoelectric, electrostrictive, or magneto- strictive) have large power densities relatively large forces at up to 0.1%. The opportunity for direct electrical-to-mechanical energy conversion is welcomed in a number of applications including vibration reduc- tion, active aeroelastic control, etc. Induced-strain actuators are basically of two types: . Electroactive, such that an induced strain is generated by the application of an electric field. Piezoelectric (e.g., PZT) and electrostrictive (e.g., PMN) ceramics are commonly used for electroactive high-power actuators . Magnetoactive, in which the induced strain is generated by the application of a magnetic field. Magnetostrictive alloys (e.g., Terfenol-D) are com- monly used in magnetoactive high-power actuators. These two active-material types have different but complementary characteristics. On one hand, the electroactive materials require high electric fields, which can be produced by applying relatively large voltages across very thin wafers. For this reason, practical electroactive material actuators are built in stacks, commonly known as piezostacks. Electroactive materials also have very large dielectric permittivity, and the resulting stacks have fairly large electric capacitance. When electroactive actuators are operated in dynamic regime, very large reactive powers are encountered, of the order of i!CV 2 . Under constant voltage operation, the reactive power of electroactive actuators increases linearly with frequency. On the other hand, the magnetoactive materials require high magnetic fields, which can be produced by applying relatively large currents through a multiturn coil. The resulting mag- netic field increases proportionally with both the current and the number of turns in the coil. When magnetoac- tive actuators are operated in dynamic regime, very large reactive powers are also encountered, of the order of V 2 =ði!LÞ. Under constant voltage operation, the reactive power of magnetostrictive actuators decreases with frequency as 1/!. Based on the reactive power requirements under constant voltage operation, it seems that piezoelectric devices are easier to use at low frequencies, while the magnetostrictive devices are easier to use at high frequencies. However, in several dynamic applications, the frequency is neither high frequency, nor low frequency. For these applications, *Author to whom correspondence should be addressed. E-mail: victorg@sc.edu JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES, Vol. 00—Month 200? 1 1045-389X/0?/00 0001–21 $10.00/0 DOI: 10.1177/104538902039133 ß 200? Sage Publications + [29.8.2003–9:59pm] [1–22] [Page No. 1] FIRST PROOFS {Sage}Jim/JIM-39133.3d (JIM) Paper: JIM-39133 Keyword Vol. 15, No. 3, March 2004,, pp. 161-180