|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1990 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 1989 : ¥1,800,000 (Direct Cost : ¥1,800,000)
We have constructed a high-pressure gas gun to produce the precisely reproducible and controllable plane shock wave in condensed media including porous materials. By adopting the high-pressure gas powered gun, it is possible to measure the shock wave phenomena accurately by various optical techniques. It has a bore of 20 mm diameter, a launch tube of 1 m length, and an observation chamber of 320 liter. The volume of high-pressure chamber is about 16 liter.
First, we have tried to develop a projectile velocity measuring system. A He-Ne laser beam has been introduced into the observation chamber through one of the window, crossing three small through holes of the extension tube of the launcher, led to photodiodes outside. The outputs via amplifier have been used for the velocity measurement and the input for the trigger pulse generator.
Preliminary runs have been made by changing the parameters like gas pressure (3 - 30 atm), projectile mass (4.5 - 10.7 g), etc. Under the conditions of 30
atm gas pressure, and 4.5 g of projectile mass, the measured velocity is equal to 360 m/s. It is found that projectile velocity is roughly proportional to the logarithm of gas pressure with the same values of other parameters. Reproducibility of projectile velocity upon various parameters has been found to be very good.
A new optical pin has been developed, having possibility of detecting elastic waves. Two plastic optic fibers were fused together at an angle over 45 degrees. Light beam incident on one fiber end surface is supposed to be totally reflected at the fused surface to output from the other end. Light intensity decrease upon the wave arrival, however, has been found to be non-drastic, probably because the destruction of the fiber surface is not instantaneous at the pressure level of several kilobars generated in our experiments. The pin system is still useful to measure the propagation velocity.
This pin method and the electromagnetic gauge method have been used to investigate the compression wave propagation behavior of alumina powder of porosity 0.6. For the projectile velocity of 272 m/s, shock wave velocity, front pressure and the compressed density is estimated to be 571 m/s, 0.185 GPa and 2.4 g/cm^3, respectively. Within the range of pressure in our experiments, the attained density does not reach the crystal density, so that the compaction is incomplete. Less