Research on high precision optical fiber acoustic emission system for weak damage location on concrete

Abstract

• Concrete weak AE location requires high detection accuracy of the system. • Random fiber laser enables the system to pick up weak AE waves on concrete. • Simulation and tests verify that the system can detect concrete AE wave reliably. • Random fiber laser and adaptive search strategy ensure a high location accuracy. • Accurate time difference of arrival can be used for a high precision AE location. A high precision optical fiber acoustic emission (AE) locating system with designed random fiber lasers (RFLs) and a proposed adaptive time of arrival extraction strategy for weak damage source location on concrete is proposed. The low frequency-noise and narrow linewidth of RFLs enable the system to obtain a high signal detection resolution of 8.32 × 10 −7 m/s within 500 kHz. Meanwhile, an adaptive threshold search strategy to optimize the onset time of the AE wave, thus maintaining small location errors from the perspective of improving the time difference of arrival (TDOA). Then, AE source localization is transformed into a genetic algorithm optimization process with TDOA as a parameter. The reliability of the RFL sensor in detecting weak pseudo-damage source signals from concrete is verified by simulation and experiment on a concrete slab with dimensions of 0.9 m × 0.9 m × 0.1 m. A total of 64 pseudo damage source location tests are performed at 16 random points on a concrete slab surface. The maximum axial location error of the system is 2.78%. The root mean square errors and standard deviations of the absolute errors are 2.8 cm and 9 mm, respectively. The accuracy and robustness of location are analyzed. Finally, the proposed system is used to locate the plane mapping points of concrete specimens cracked by crack water frost heaving, and the locating accuracy is 93.4%.