Applications of Smart Materials to Diagnostics and Vibration Suppression
Gyuhae Park, Ph.D.
Center for Intelligent Material Systems and Structures
Virginia Polytechnic Institute and State University
Blackburg, VA 24061-0261
Sponsored by the Dept. of Engineering Mechanics
Date: Thursday, March 29, 2001
Time: 2:00 p.m.
Place: W128 Nebraska Hall
Smart material systems contain integrated sensors, actuators, and control algorithm that allow structures to respond or adaptively change as the result of external conditions. Such materials form transducers that are able to interchange electrical energy and mechanical motion or force. Examples of smart materials used for diagnostics and vibration reduction are presented.
This diagnostics method is referred to as the Impedance-based Health Monitoring Technique (IHMT), and it allows structures to monitor their own integrity continuously while in operation and throughout their lives, minimizing explicit preemptory maintenance and inspection tasks. The basic principle is to apply high frequency structural excitation (typically higher than 30 kHz) through surface-bonded piezoelectric transducers, and measure the impedance of the structure by monitoring the current and voltage applied to the transducers. Changes in impedance indicate changes in the structure, which in turn can indicate the presence of damage. Several case studies, including a quarter-scale bridge section, a pipeline structure, and a composite reinforced masonry wall, demonstrate how this technique can be used to detect damage in real-time.
Two current research applications of IHMT are the development of an ‘adaptive’ bolted joint and combining the hardware used for health monitoring and active vibration control. First, IHMT, along with a shape memory alloy actuator, has been used to actively monitor and control the preload in bolted joints. When damage occurs, the actuator will adjust the bolt tension in order to restore the lost torque and to allow continued operation. Secondly, analytical and experimental results indicate that the simultaneous health monitoring and vibration suppression using the same piezoceramic actuation is feasible, which reduces the number of system components while enhancing the performance of the structure. The presentation concludes with experimental examples to verify the proposed methodology.
