Study on High-Pressure Compression Waves in Powdered or Porous Material

我们构建了一种高压气枪，用于在包括多孔材料在内的凝聚态介质中产生精确可复制和可控的平面激波。采用高压气枪，可以利用各种光学技术对冲击波现象进行精确测量。它有一个直径20毫米的膛，一个1米长的发射管，和一个320升的观察室。高压室容积约16升。首先，我们尝试开发一个弹丸速度测量系统。氦氖激光束通过一个窗口进入观察室，穿过发射器延伸管的三个小通孔，引导到外面的光电二极管。通过放大器的输出用于速度测量，输入用于触发脉冲发生器。通过改变气压（3 - 30atm）、弹丸质量（4.5 - 10.7 g）等参数进行了初步运行。在30…大气压、4.5 g弹质量的条件下，测得的速度为360m /s。在其他参数相同的情况下，弹丸速度与气体压力的对数大致成正比。弹丸速度在不同参数下的重现性很好。研制了一种新型光学针，具有探测弹性波的可能性。两根塑料光纤以超过45度的角度融合在一起。入射到光纤一端表面的光束应在熔接表面被完全反射并从另一端输出。然而，我们发现光波到达时光强的下降并不剧烈，这可能是因为在我们实验中产生的几千巴的压力水平下，光纤表面的破坏不是瞬间的。引脚系统仍然是有用的测量传播速度。采用引脚法和电磁计法研究了孔隙率为0.6的氧化铝粉末的压缩波传播特性。当弹丸速度为272 m/s时，冲击波速度为571 m/s，前压力为0.185 GPa，压缩密度为2.4 g/cm^3。在我们实验的压力范围内，达到的密度没有达到晶体密度，因此压实是不完全的。少

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 … More 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