Nano Si3N4 composites with improved tribological properties

Nano Si₃N₄ composites with tailored microstructure were developed using fine ß‐Si₃N₄ powders. Their wear behaviour was investigated. Whereas pure Si₃N₄ composites showed improved wear behaviour under dry rolling conditions with slip, TiN‐reinforced nano Si₃N₄ composites generate a self‐lubricating behaviour under dry sliding conditions. After chemical treatment with hydrogen sulphide, the friction coefficient and wear rate was found to be significantly decreased under dry sliding conditions. Additionally, the new composites possess higher fracture toughness than the pure nano Si₃N₄ materials. Copyright © 2009 John Wiley & Sons, Ltd.     

Actuator characterization of a man-portable precision maneuver concept

The US Army Research Laboratory is conducting research to explore technologies that may be suitable for maneuvering man-portable munitions. Current research is focused on the use of rotary actuators with spin-stabilized munitions. A rotary actuator holds the potential of providing a low-power solution for guidance of a spinning projectile. This is in contrast to a linear （reciprocating） actuator which would need to constantly change direction, resulting in large accelerations which in turn would require large forces, thereby driving up the actuator power. A rotational actuator would be operating at a fairly constant rotation rate once it is up to speed, resulting in much lower power requirements. Actuator experiments conducted over a variety of conditions validate the dynamic models of the actuator and supply the data necessary for model parameter estimation. Actuator performance metrics of spin rate response, friction, and power requirements were derived from the data. This study indicates that this class of maneuver concepts can be driven with these actuators. These results enable actuator design and multi- disciplinary simulation of refined maneuver concepts for a specific application.