Non-Destructive Structural Strength Monitoring using Micro- Electro Mechanical Systems (MEMS)

Abstract

Damage and Vibrations are a local phenomenon that appears in the structure (concrete/ mechanical) and needs to be captured in order to monitor structural health. The local phenomenon is captured by modes of higher frequency where as modes of lower frequency are employed for capturing global phenomenon material and geometry defects because of the reason that they are less sensitive to the local changes in the structure. Most researchers have presented ways and developed methods for low frequency devices where as the area of higher frequency devices for NDT is less explored which needs to be expedited for local phenomenon capturing occurring in the structures. The objective of the thesis is to design and simulate a MEMS Energy Harvester which is helpful for Non-Destructive Structural Strength Monitoring of high frequency vibration structures having an additional capability of Temperature measurement. In this work a Cantilevered based Single layer Piezoelectric Energy Harvester along with Temperature Measuring Bimorph is proposed that is capable of producing up to 2 Volts of voltage at a frequency of 17761Hz when subjected to vibrations. The proposed energy harvester consists of a suspended piezoelectric mass with dimensions of 280μm x 300 μm and thickness of 4μm made up of PZT 5A (Lead Zirconate Titanate) material. Two bimorphs are attached on each side of the mass that bend due to the changes in the ambient temperature because of different coefficient of thermal expansion. The bimorphs show a displacement of 0-3μm for the temperature range of 295K to 337K. It is shown through modeling and simulation (static and dynamic) that this device is viable option for use in structural health monitoring.