PNNL

Abstract

Military equipment is exposed to different types of mechanical stresses during various portions of their life cycles. Personnel handling, transportation, storage, and deployment can expose equipment to high levels of shock during inadvertent drops or collisions. Truck, airplane, and helicopter transport exposes equipment to moderate levels of vibration at many different resonant frequencies. Rapid temperature excursions can generate thermal stresses due to variations in material thermal expansion coefficients. Even though delicate components are usually placed in robust containers with shock damping features, most systems are susceptible to shock damage at some level. To address this vulnerability, engineers at the Pacific Northwest National Laboratory have developed a family of asset Health Monitors to determine when military assets have been exposed to environmental stress in excess of their design envelopes. The concept is embodied in a low cost, low power, battery powered Health Monitor mounted to the asset that is capable of measuring, recording, and analyzing mechanical shock and temperature excursions. By storing data along with a time stamp, the Health Monitor can be used to determine equipment readiness, flag potentially damaged equipment, and trace the root cause of equipment malfunction. The system concept includes a printed circuit board, temperature sensor, a tri-axial accelerometer, batteries, push buttons, and status indication lights. When a shock event is higher than a predefined threshold, an alarm light will be displayed when the health monitor status is evaluated. This paper will describe the overall system design, system components, energy conservation techniques, and concept of operations. Key Words: health monitoring, sensors, structural response, smart structures