Experimental Studies on the Dynamic Quasi-Isentropic Compression of Oxygen Free-Copper
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摘要: 利用递变冲击阻抗材料叠合而成的组合飞片，在二级轻气炮上对无氧铜进行了准等熵压缩性测量，加载时间约达1 s。用激光速度干涉仪连续记录了不同厚度处无氧铜样品自由面速度随时间的变化过程，并通过拉格朗日波分析技术计算得到40 GPa下的准等熵的应力-应变曲线。结果表明：在低应力区，无氧铜的准等熵压缩线位于冲击绝热线之上；到32 GPa以上，准等熵压缩线才回落到冲击绝热线之下。这个现象与Barker、Chhabildas等对铝与钨的实测现象是一致的，它表明：在低应力区，材料的冲击强化效应与加载速率密切相关。Abstract: The experiments of quasi-isentropic compression of oxygen free-copper were performed in a two-stage light gas gun by means of the composite flyer, in which the shock impedance increased from the impact surface to the rear interface. The impact velocity was 2.51 km/s. The compression time attained was about 1 s. Using the Lagrangian analysis technique a quasi-isentropic stress-strain relation of oxygen free-copper was obtained from the laser interferometric measurements of the free surface velocity histories on the different thickness specimens. The preliminary results show that quasi-isentrope is located above the Hugoniot at stress lower than 32 GPa, which is contrary to the expectation, and falls back below the Hugoniot at the stress higher than 32 GPa. The phenomenon, which was similar to the results of aluminum and tungsten reported by Barker and Chhabildas et al., was attributed to the furth increasing of dynamic strength of the specimen with the lower strain rate, arising from the quasi-isentropic compressing process, at low stresses, comparing with the shock-loading condition.
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Key words:
- quasi-isentropic compression /
- composite flyer /
- two-stage light gas gun
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