High-speed photographic investigation of underwater shock wave due to electric pulse power

Abstract

In recent years, researches of high energy emitted in a short time are performed actively. The high energy is used for manufacturing and forming. The propagation velocity of the reaction in a high energy explosive may reach the maximum about 10 km/s, and may be accompanied by the shock wave. Many products using the high pressure r the shock wave produced by explosion of explosives are put in practical use. However, a legal restriction to use explosives is severe and needs many efforst for qualification acquisition for handling, maintenance, and security. It is simple to generate shock wave by electric pulse power, instead. In this study, when the shock large current was discharged for electrode, the underwater shock wave generated from electrode was investigated. Furthermore, when attaching metal wires with electrode, the shock large current was passed through metal wires and electrode. We compared the underwater shock wave generated from electrode and electrode with metal wire. The shadowgraph system and a high-speed camera (IMACON468 of HADLAND PHOTONICS, interframe times 10ns to 1ms in 10ns steps independently variable, number of channels framing:4 streak:1) were used to observe the underwater shockwave. The recorded a framing photograph and also by a streak photograph. The shadowgraph method is to observe and project the shadow of the light by density change on a screen or the film of a camera, and is also called direct projective technique. Firstly, we evaluated the explosion power of metal wire. When the shock large current was passed through a metal wire, we investigated underwater shock wave generated from metal wire using high-speed camera. The shock wave velocity and the peak pressure were obtained by using a streak photograph. It seems taht a strong shcok wave is obtained, if the bold wire using a mass condenser bank is exploded. Secondly, we observed underwater shock wave generated by discharge from electrode. When optical observation of the underwater shock wave was performed about the equipment which crushes a structure and a rock by sparking the shock large current, having generated the underwater shock wave near the sound velocity of water continuously at intervals of about 5 μs was checked. Since a continuous wave generated, it is possible that the action time rise for a structure and a rock. Although a peak pressure value was not so high, it is possible that impulse to a structure can improve and it can crush a structure by the impulse rise.