Optimization of Bond Locations for Guided Waves Based SHM Using Coupled Optical Fibers

Guided waves (GW) allow fast inspection of a large area and hence have received great interest from the structural health monitoring (SHM) community. Fiber Bragg grating (FBG) sensors offer several advantages but their use has been limited for the GW sensing due to its limited sensitivity. FBG sensors in the edge-filtering configuration have overcome this issue with sensitivity and there is a renewed interest in their use. Unfortunately, the FBG sensors and the equipment needed for interrogation is quite expensive and their number is restricted. In the previous work by the authors the number and location of the actuators was optimized for developing a SHM system with single sensor and multiple actuators. But through the use of the phenomenon of acoustic coupling, multiple locations on the structure may be interrogated with a single FBG sensors. As a result, a sensor network with multiple sensing locations and few actuators is feasible and cost effective. Hence this paper develops the optimization problem for designing an SHM network for use with FBG sensors making use of acoustic coupling. The optimization problem is implemented on a simple aluminum plate. The directionality, bond efficiency and the factors influencing the acoustic coupling are taken into consideration for optimizing the sensor network. A multi-objective optimization problem is defined and solved using non-sorting genetic algorithm (NSGA). The results indicate that indeed a multi-objective optimization is necessary and has potential to improve the SHM system performance.