SBIR-STTR Award

Los Gatos Research proposes to develop a multi-channel, distributed fiber optic sensor instrumentation, capable of monitoring acoustic emission (AE) for rapid detection of impact damage and cracks in structural components. Our novel sensor technology offers a number of advantages including sensor compactness and lightweight with multiplexing capability for load, temperature, and AE for monitoring, characterizing, and locating damages in metal structures and components. We achieve this by employing Bragg grating sensor arrays and using a novel interrogation technique combined with state-of-the-art AE method to detect AE events from growing cracks in the presence of quasi-static background strain field. In Phase I, we will demonstrate the sensor’s capability to monitor AE in a loaded (mechanical and thermal) aluminum panel using four FBG sensors and four piezoelectric sensors. The sensitivity of the system will be compared theoretically and experimentally to that of standard piezoelectric AE transducers. In Phase II, the grating sensors, interrogation system, and AE software will be integrated into a multi-channel, stand alone, dynamically reconfigurable, adaptive AE monitoring system with a small foot print.

Keywords:
Fiber Bragg Grating, Damage Detection, Acoustic Emission,

Los Gatos Research is developing light-weight, low-cost, real-time, compact, multi-channel fiber optic (FO) acoustic emission (AE) system for condition based maintenance applications. Using a novel laser-based optical fiber Bragg grating (FBG) sensor interrogation technique combined with state-of-the-art AE method, the instrument is capable of simultaneously measuring strain, temperature, and AE with high resolution and high sensitivity, and is scalable for integrated, multipoint sensing. The high detection sensitivity and accuracy are achieved by the inherently stable laser frequency tracking scheme which integrates the laser control electronics and photo-detector signals together in a dynamic feedback loop circuit to provide stable laser wavelength locking to the Bragg wavelength of the BG sensors. In Phase I, we have demonstrated the FO sensor’s capability to detect real AE sources from crack growth on an aluminum structure under loading. Pencil lead break (PLB) tests were performed, and the FO sensors demonstrated reasonably good AE signal detection sensitivity and reproducibility close to that of piezoelectric sensors. In Phase II, a field-programmable gate array (FPGA)-based multi-channel FO conditioning module, FBG sensors, and AE software and hardware will be integrated into a compact, stand alone, adaptive, dynamically reconfigurable system with AE detection sensitivity comparable to piezoelectric-based AE instrumentation.

Keywords:
Acoustic Emission, Acoustic Emission, Fiber Bragg Grating, Condition Based Monitoring