Development of a shock wave generation method through diaphragm laser rupture for high-precision control of shock wave generation time

Abstract

In this paper, we propose a shock wave generation method through laser rupture that can control the timing and condition with high accuracy using a simple mechanism. We also evaluate the response performance, structure, and propagation characteristics of the shock wave generated using this method. When laser-irradiated from the outside through the window, the laser hole in the film shock-tube diaphragm is opened momentarily. As a result, the diaphragm bursts, and a shock wave is generated. First, we investigated the best combination of laser rupture using various laser and diaphragm materials. For the combination of a continuous wave (CW) laser with a lower output but longer adjustable irradiation time and an oriented polypropylene (OPP) film with a high tensile strength and a low tear resistance, the shock wave was generated at almost the same time with the laser irradiation. Subsequently, by investigating the fracture response time using the OPP film and CW laser, it was found that the shock wave generation timing with an accuracy of 100 μs order can be controlled. Furthermore, when compared with a metal diaphragm through natural rupture, the initial opening rate of the OPP film through laser rupture was high, and it was believed to form an ideal shock front. In contrast, compared to the natural rupture of a cellophane film, which burst and spread over the entire separation surface of the diaphragm when over-pressurized, the laser rupture using the OPP film diaphragm formed a curved shock shape because a spherical shock wave was formed from the opening start point. However, Shock wave became flat with propagation and was propagated at almost the theoretical velocity.

Keywords

• shock wave
• shock tube
• shock generation
• laser rupture
• timing control
• diaphragm