Response of Circular Plates Subjected to Shock Waves Propagating in Air and Water: A Comparative Study

• Mode I deformation in plates regardless of stiffness & shock propagating media • For same peak pressure, air shock response was around 50% higher than static load • Same deflection in underwater shock & static pressure (post cavitation peak pressure) • Air shock response was greater than underwater shock due to higher load rapidity • Stiff plate oscillations in air medium, not observed in water for the added mass This study compares the dynamic response of clamped circular plates exposed to air and underwater shocks. Shock loads of varying intensities were applied to the plates with same areal mass density, but different structural compliances. A conventional gas shock tube and a water-filled underwater shock simulator were used to generate lab-scale shock wave. Loading pressure and corresponding plate deformation were recorded using dynamic pressure sensors and high-speed imaging coupled with the stereo digital image correlation technique. Experimental results showed that plates exhibited Mode 1 dominant deformation under both air and underwater shock loading. For same loading pressure, the maximum deformation as well as velocity of the plate specimens under air shock loading was greater than that measured for the underwater shock loading. Flexural waves in polyurea plates travelled faster in air shock than underwater shock loading. In underwater shock loading, peak deflection occurred in the post-cavitation secondary loading phase. Furthermore, the circular plates exhibited an oscillatory response under air shock loading, which was not resolvable in underwater shock response. However, the higher vibration modes of plates reflected as high frequency fluctuations in secondary loading pressure in underwater shocks. While dynamic deflections during air shock loading were 50% to 60% greater than the static deflections, they were absent in underwater shock loading. The maximum deflection during underwater shock loading was comparable to their static deflection at pressure magnitudes measured during secondary loading phase.