WAVELET PACKET ANALYSIS OF TIME-FREQUENCY CHARACTERISTIC OF CABIN SHOCK RESPONSE DUE TO UNDERWATER EXPLOSION

A blast-resistant cabin structure with double bottoms was designed where the power equipment is mounted resiliently. Underwater explosion experiments were carried out with the blast-resistant cabin structure. Through wavelet packet analysis, the time-frequency distribution of the underwater pressure in the explosion was studied, and the cabin’s shock response was derived. The relationship between the time-frequency characteristic of the cabin’s shock response and the underwater shock environment was obtained. Results from the investigation show that the pressure in the underwater explosion contains abundant frequency components. The main frequency components of the shock wave are higher than 1 kHz which may cause the damage of the local underwater structure. The main frequency components of the after-flow are between 10 Hz and 1 kHz which is the important energy source of the shock and vibration of the ship. The frequency components of the second pressure pulse are generally less than 100 Hz which may cause a great displacement in the vibration isolation system for the power equipment. The blast-resistant cabin structure with double bottoms can markedly enhance the shock-resistant properties of the naval vessel with the resilient mounting system.