Structural Health Monitoring (SHM) is the science and technology of monitoring and can assess the condition of aerospace, civil, and mechanical infrastructures using a sensing system integrated into the structure. SHM is capable of detecting, locating, and quantifying various types of damage such as cracks, holes, corrosion, delamination, and loose joints, and can be applied to various kinds of infrastructures such as buildings, railroads, windmills, bridges, and aircraft. A major technical challenge for existing SHM systems is high power consumption, which severely limits the range of its applications. In this thesis, we investigated adoption of acoustic emission detection to reduce power dissipation of SHM systems employing the impedance and the Lamb wave methods. An acoustic emission sensor of the proposed system continuously monitors acoustic events, while the SHM system is in sleep mode. The SHM system is evoked to perform the SHM operation only when there is an acoustic event detected by the acoustic emission sensor. The proposed system avoids unnecessary operation of SHM operations, which saves power, and the system is effective for certain applications such as spacecraft and wind turbine blades. We developed prototype systems using a Texas Instruments TMS320F2812 DSP evaluation board for the Lamb wave method and an MSP430 evaluation board for the impedance method. / Master of Science

Structural Health Monitoring is a useful tool for reducing maintenance costs and improving the life and performance of engineering structures. Impedance-Based SHM utilizes the coupled electromechanical behavior of piezoelectric materials to detect adverse changes and material and mechanical failures of structures. Environmental variables such as temperature present a challenge to assessing the veracity of damage detected through statistical modeling of impedance signals. An effective frequency shift method was developed to compensate impedance measurements for changes resulting from environmental temperature fluctuations. This thesis investigates how the accuracy of this method can be improved and be applied to a 100oF range of temperatures. Building up the idea of eliminating temperature effects from impedance measurements, this thesis investigates the possibility of using statistical moments to create a temperature independent impedance baseline. / Master of Science