Dissertation Defence: Towards Microwave Sensor-integrated Smart Coatings for Real-time Erosive Wear Monitoring
April 17 at 9:00 am - 1:00 pm
Vishal Balasubramanian, supervised by Dr. Mohammad H. Zarifi, will defend their dissertation titled “Towards Microwave Sensor-integrated Smart Coatings for Real-time Erosive Wear Monitoring” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering.
An abstract for Vishal Balasubramanian’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Please email mohammad.zarifi@ubc.ca to receive the Zoom link for this exam.
ABSTRACT
The degradation of protective coatings due to erosion, delamination, and corrosion compromises the structural integrity of critical assets in aviation, marine, and infrastructure industries. Existing non-destructive testing (NDT) methods lack real-time monitoring capabilities, suffer from environmental interference, and exhibit poor spatial localization, limiting their effectiveness in detecting early-stage coating damage. This thesis presents the design, development, and experimental validation of microwave-based coating health monitoring systems, focusing on enhancing detection accuracy, spatial localization, and environmental robustness through differential and multi-resonant sensor architectures.
Firstly, a wired differential split-ring resonator (SRR) sensor was developed and validated for coating wear detection in homogeneous mono-layered, and heterogeneous multi-layered protective coatings with a sensitivity in the order of 10s of μm. The system demonstrated a 4 MHz increase in resonant frequency per ~25 μm of wear for coating thicknesses less than 1 mm. Additionally, in multi-layered protective coatings, the system accurately distinguished wear depth and layer-specific erosion while self-compensating for environmental fluctuations. Subsequently, the developed microwave sensor was expanded for simultaneous coating wear detection and localization. A wired multi-resonant SRR sensor was developed, employing three resonators operating at distinct frequencies (1.992 GHz, 1.628 GHz, 1.268 GHz), alongside a shielded reference SRR at 2.428 GHz. This system achieved an average sensitivity of 35 MHz per 125 μm of coating wear, effectively localizing wear regions while mitigating environmental noise. Additionally, a passive frequency-selective surface (FSS)-based wireless sensor was developed for wear detection over large surfaces, while being integrated with artificial intelligence methods for coating damage localization and augmented reality technology to visualize the damaged region. Finally, a passive FSS system was designed, operating at ~2.5 GHz, with a shielded reference FSS at ~5 GHz to minimize environmental fluctuations. The system maintained minimal hysteresis (~10 MHz for temperature variations and ~2 MHz for humidity changes) while detecting coating wear in real time. The developed FSS sensor was capable of detecting coating delamination, in addition to integration with a multi-resonant FSS system for damage localization without the need for post-processing techniques.
This thesis advances the body of knowledge in microwave-based non-destructive testing by integrating for the first time a differential microwave sensor, a multi-resonant architecture, AI-driven wear localization, and augmented reality visualization for real-time, passive, and environmentally robust coating health monitoring, thus promising its application in aerospace, marine, and civil infrastructure industries.
