A novel measurement method for specific impulse of underwater pressure pulse based on mass-spring

Abstract

Achieving the accurate evaluation of underwater explosion power is of great interest to the defense of warship. To address the limitations of traditional electrical sensors, a novel method for measuring the specific impulse of underwater pressure pulses using a mass-spring with constrained boundaries (MSCB) is proposed, wherein the specific impulse is estimated based on the mass of discharged water from MSCB. Experimental study using a modified split Hopkinson pressure bar (SHPB) is conducted to investigate the relationship between specific impulse and the mass of discharged water. Additionally, a verified finite element simulation is employed to predict the dynamic responses of MSCB considering the effects of pressure pulse properties and MSCB structural parameters. The findings reveal that, when subjected to pressure pulse loading, the mass block vibrates non-periodically within the constraint boundaries, with the water discharge mainly occurring during the first vibration cycle. The mass block tends to stay on the back constraint boundary as pressure amplitude and duration time increase. Furthermore, the mass of discharge water with respect to MSCB shows a linear correlation with the specific impulse of the pressure pulse, regardless of the rate at which pressure rise, demonstrating the feasibility of MSCB in measuring the specific impulse of underwater pressure pulse. An increase in either stiffness coefficient or weight of the mass block leads to a decrease in the sensitivity coefficient (ratio of discharge water mass to specific impulse) of MSCB. The proposed method for measuring specific impulse of underwater pressure pulses does not require a power supply and can serve as an important complement to electrical measurements, particularly for testing in extreme underwater explosion environments.