Portable impedance detecting transducer for marine structural damage detection

• Main Author: Tay, Zhong Han.
• Other Authors: Ling Shih Fu
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/16114
• Institution: Nanyang Technological University

This report studies the feasibility of incorporating the use of impedance for marine structural health monitoring. In earlier researches, it was successfully proven that the input electrical impedance of an actuator is a sensitive function of the mechanical impedance of a structure. Therefore, any changes to the structure’s mechanical properties could be detected by analysing the response of the actuator’s electrical impedance, enabling it to have a dual sensor-cum-actuator function. An initial evaluation of the transducer requirements had to be done to define the directions in which the upcoming prototypes should head into. Aspects such as the magnitude of dynamic forces required, targeted application, portability issues and power requirements are some points to be considered. Following that, various types of inertial actuators were being studied in order to determine the most suitable actuation type for our purpose. The Piezoelectric Inertial Actuator was chosen and conceptual designs were drafted. 3 prototypes were fabricated out of 2 different working principles. These prototypes were subjected to dynamic force testing and evaluation. The dynamic forces had to be of significant magnitudes in order to excite the steel structures sufficiently in order to result in any changes to the actuator’s input electrical impedance in the presence of a structural defect. Electrical impedance tests would follow if the prototypes were found to produce the required amount of dynamic forces. The mechanical properties of the steel plates used in these tests were altered in a bid to simulate structural defects. Changes in the electrical impedance response of the actuators were observed and these results were compared against one another to establish a relationship between changes in the electrical impedance and changes in the steel plates’ properties. Positive results were collected from these experiments and they proved that Piezo Inertial Actuators could successfully detect structural damages in steel plates. However, more developments to this project have to be done to enhance its detection capabilities for thicker steel plates, and for defect proximity and identification purposes.