A Novel Noninvasive Microwave Sensor for Quantitative Assessment of Degree of Sensitization in Marine Aluminum Alloys

In phase I, we have proven the feasibility of using the microwave cavity perturbation technique to detect and quantify DoS in marine aluminum alloys. We implemented an alpha version sensor prototype, characterized and validated its performance using ASTM G67 method. We also identified methods to further enhance the sensor sensitivity, so that DoS in the low (a few mg/cm2) to moderate range can be accurately measured. Phase II will be focusing on the optimization of the sensor system to improve its performance in terms of sensitivity and dynamic range, and the implementation of a handheld, inexpensive and field testable prototype. Additionally, we will develop models to predict the IGSCC crack growth and the remaining service time of a sensitized marine aluminum alloy structure. Our approach to achieve these goals include: a) Enhance the sensor sensitivity with amplitude and phase measurements of the cavity resonance at higher microwave frequencies, b) High throughput mapping of sensitization levels across a large sample using a frequency hopping technique, c) Develop a coupling environment model to predict the IGSCC crack growth in sensitized marine aluminum alloys, and d) Implement data acquisition and signal processing function with a microcontroller to obtain a low cost handheld sensor.