This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection\nbased on the principle of a Machââ?¬â??Zehnder interferometer. This sensor can be used to receive\nacoustic emission signals in the passive damage detection methods and other types of ultrasonic\nsignals propagating in the active damage detection methods, such as guided wave-based methods.\nThe sensitivity of an ultrasonic fiber sensor based on the Machââ?¬â??Zehnder interferometer mainly\ndepends on the length of the sensing optical fiber; therefore, the proposed sensor achieves the\nmaximum possible sensitivity by wrapping an optical fiber on a hollow cylinder with a base.\nThe deformation of the optical fiber is produced by the displacement field of guided waves in the\nhollow cylinder. The sensor was first analyzed using the finite element method, which demonstrated\nits basic sensing capacity, and the simulation signals have the same characteristics in the frequency\ndomain as the excitation signal. Subsequently, the primary investigations were conducted via a\nseries of experiments. The sensor was used to detect guided wave signals excited by a piezoelectric\nwafer in an aluminum plate, and subsequently it was tested on a reinforced concrete beam, which\nproduced acoustic emission signals via impact loading and crack extension when it was loaded to\nfailure. The signals obtained from a piezoelectric acoustic emission sensor were used for comparison,\nand the results indicated that the proposed 3D fiber optic sensor can detect ultrasonic signals in the\nspecific frequency response range.
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