A study of strain measurement in cylindrical shells subjected to underwater shock loading using FBG sensors

Abstract In the present study, we designed an underwater explosion experiment and applied a fiber Bragg grating (FBG) to observe the strain of underwater structures. First, we performed a four-point bending correction for FBG with a sensitivity of 1.4 pm/μe and average linearity of 99.92 %. In this experiment, we designed a cylindrical shell structure composed of aluminum alloy. The structure was placed at a fixed depth in a hydraulic test tank, and 1 g of trinitrotoluene (TNT) explosive was placed and detonated at depths of 30 cm, 15 cm, and 5 cm. Experimental results indicate that the strains measured by FBG were 2563 μe, 37,135 μe, and 32,923 μe for 30 cm, 15 cm, and 5 cm detonation depths, respectively. Notably, the results suggest that the FBG sensor system should be applied to the strain measurement of underwater shock to pay attention to the design of the mechanism to strengthen the shock wave. Additionally, FBG has a multi-point measurement function, high sensitivity, and electromagnetic immunity. As such, the development of strain measurement technology for underwater shock remains a worthwhile endeavor.