Development of an Optical System for Simultaneous Ultrasonic Wave Propagation Imaging at Multi-points

Abstract

This paper introduces the development of an optical system for simultaneous ultrasonic propagation imaging at multi-points. For the system, fiber acoustic wave grating sensors (FAWGSs) and a Q-switched pulsed laser (QPL) mirror scanner are utilized for simultaneous multipoint sensing and remote scanning ultrasonic generation, respectively. The structural strain-free FAWGS based on a fiber Bragg grating allows simultaneous multipoint acoustic emission (AE) sensing. A structure in which the FAWGSs are deployed can sense external ultrasonic stimulus. Consequently, the structure with the integrated FAWGSs cannot only detect damage event under the passive AE technique, but can also evaluate the damage under the active scheme of ultrasonic transmission and reception. The feasibility of the simultaneous multipoint ultrasonic sensing system based on the FAWGSs as built-in sensors is studied with ultrasound transmitted by a piezoelectric transducer and a QPL. Then the QPL ultrasonic generator is modified into a QPL mirror scanner for laser beam scanning and finally an optical UPI system is integrated. The ultrasonic wave propagation movie (UWPM) obtained by the optical UPI system visualizes impact damage on a carbon-fiber reinforced composite.