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A method for estimating the actuation efficiency of a structurally integrated active material is presented. A background literature search revealed many different expressions for efficiency depending upon the application and discipline of interest. Following the review of the literature, an efficiency expression was developed for a piezoelectric actuator in the frequency domain. The actuation efficiency of the piezoceramic actuator was define as the ratio of total mechanical energy imparted to the structure to total electrical energy drawn by the piezoceramic from an electrical power source. The efficiency expression is a function of the piezo electromechanical coupling coefficient, the mechanical impedance ratio of the structural to the piezoceramic material, and the frequency of operation. The developed expression was then used to analytically predict the efficiency of a single degree-of- freedom system actuated by a piezoceramic actuator. Static and quasi-static efficiency results agree with analytical results found in the literature. Dynamic analysis of the efficiency expression, however, produced unexpected and interesting results. For the given definition of efficiency, there exists a combination of material parameters and drive frequency that yield efficiencies greater than one.Further analysis provided evidence that frequency domain formulation provides that while there are instances when relatively large quantities of mechanical energy in the system exist relative to the quantity of electrical energy being drawn by the actuator, total energy is always conserved. The important result of this work was the knowledge gained in the fundamental understanding of power, energy, and efficiency as it relates to dynamic actuation of an electromechanical system. The results shown here support the concept of actuation at or near a system resonance to increase efficiency. This work is on-going; the ultimate goal of which is to develop a tool for aiding active material actuation feasibility studies by using actuation efficiency as a performance metric.
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