UVM Theses and Dissertations
Format:
Online
Author:
Hurley, David A.
Dept./Program:
Mechanical Engineering
Year:
2012
Degree:
PhD
Abstract:
The topics of damage detection, assessment, and repair are addressed in three interrelated projects: coordinated self-healing, improved excitation for laser ultrasonic nondestructive evaluation, and monitoring ablative heat shield material degradation. Research and development of self-healing materials primarily focus on embedded systems for autonomous healing. The first project seeks to improve upon existing self-healing concepts by adding self-awareness through an integrated sensing network analogous to the nervous system. Enhanced damage detection and repair monitoring boost overall healing performance. The second project looks to improve nondestructive evaluation of large structures or complex geometries. Recent research in conventional ultrasonic testing has shown the benefits of matching excitation frequency to structural resonance for certain common inspection geometries.
Proof of concept experiments and analytical modeling show that these methods can be adapted to noncontact systems using lasers to excite and detect ultrasonic waves. Frequency-controlled noncontact ultrasonic excitation offers the potential for rapid, high-resolution scans of large areas. Harsh environments present additional, unique challenges for damage detection and assessment. The third project looks at the viability of acoustic emission testing for remotely monitoring the degradation of ablative heat shield materials. High frequency elastic waves produced by the thermal degradation of the test material are waveguided to sensors located in a less harsh environment. Post-processing the sensor data assesses the validity of the testing technique.
Proof of concept experiments and analytical modeling show that these methods can be adapted to noncontact systems using lasers to excite and detect ultrasonic waves. Frequency-controlled noncontact ultrasonic excitation offers the potential for rapid, high-resolution scans of large areas. Harsh environments present additional, unique challenges for damage detection and assessment. The third project looks at the viability of acoustic emission testing for remotely monitoring the degradation of ablative heat shield materials. High frequency elastic waves produced by the thermal degradation of the test material are waveguided to sensors located in a less harsh environment. Post-processing the sensor data assesses the validity of the testing technique.