Fiber optic acoustic emission distributed crack sensor for large structures

Preliminary experiments leading to the development of an optical fiber acoustic emission sensor is described. The objective was to develop a single sensor for simultaneous detection of acoustic emission events, from many locations within a large structure. The optical fiber sensor can be adhered to the surface of structural materials, i.e. steel or concrete. There are no individual sensor arrays or components built into the fiber. This characteristic provides simplicity and renders the system practical for applications in bridge structures. Alternatively, the optical fiber could be embedded in new concrete construction. Acoustic emissions from micro‐cracks or defects from various locations in the structure create stress wave perturbations in the optical fiber that are detected by a portable interferometer. Time‐domain measurements are instantaneous, in real‐time, and the entire structure is interrogated through a one‐time operation. The time domain signal acquired from the optical fiber discerns the number and locations of damage zones i.e., weld cracks, bolt‐hole cracks, corrosion activity, or brittle fracture of fibers in composite materials.