Alternative approach to the concepts of special relativity Am.

The efforts described here are intended to provide a basis for the utilization of novel piezoelectric actuators in smart materials and structures. The actuator design developed in this study is a segmented, piezoelectric tube, with the individual segments driven in a d15 shear mode. The PZT-5A tubes were cut longitudinally into an even number of equal slender segments. These slender segments were poled individually along their length using a continuous poling technique developed at NRL. The polarization of the poled segments alternates in direction between adjacent segments. The segments were reassembled with a conductive epoxy so that it serves as both joint and electrode. The assembled actuator tubes were evaluated by applying electric field normal to the polarization direction ofthe segments, demonstrating proof of concept. These solid state prototype devices were driven to precise angular displacement and torque output. Reliability tests, including both fatigue and mechanical loading of the device, were conducted. In conjunction with this effort, numerical computation analyses were performed with respect to structural integrity versus segment joint thickness, and the relative effect of cylindrical versus polygonal configurations. These studies facilitated the successful production ofprototypes. Projected actuator outputs based on electromechanical test results are also discussed in terms of requirements for noise and vibration control of helicopter rotor blades.

Molybdenum nanocrystals (4 nm < particle size < 12 nm) were synthesized in the vapor by sputtering in a thermal gradient at argon pressures between 0.2 and 0.6 Torr. The gradient was achieved by cooling the substrate table with liquid nitrogen in order to enhance the deposition rate of the nanocrystals. The size of these nanocrystals depended on the sputtering argon gas pressure. Using appropriate deposition parameters, these nanocrystals were incorporated, either as a dispersed phase in a major phase produced by normal sputtering or as a layer in a layered structure to produce nanocomposite films. Results of Auger electron spectroscopy (AES) study of the Al/Mo layered nanocomposite films are presented. The Knoop microhardness of these films was increased by as much as a factor of four compared with the hardness of homogeneous Al films. A correlation of the microhardness to the microstructures as revealed by transmission electron microscopy (TEM) is discussed.

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