OPTIMIZATION PRINCIPLE OF THE PROTECTIVE ATMOSPHERE FOR PINS IN HYDRODYNAMIC MEASUREMENTS

摘要

In order to study the protective effects of different gases on self-shortening pins, three typical gases (helium, argon and methane) were investigated. Our experiments indicated that both helium and methane could more effectively protect pins than argon. On the basis of theory of normal shock waves for argon and helium, and one-dimensional fluid dynamics theory with chemical reactive sources for methane and the state parameters were calculated when the velocities of flyers impacting these gases covering the range from 3km/s to 8km/s. By comparison of the parameters, the experimental phenomena were explained, and an optimization principle was suggested to select the protective atmosphere of pins.