铝锂合金材料状态方程的研究

Equation of State for Al-Li Alloy

多数材料是应变率正敏感的 ,其屈服应力随着应变率的增加而提高 ;但是在应变率相关的动力学实验中 ,发现铝锂合金是应变率负敏感的 ,具有明显的冲击韧性特征。为了全面认识该种材料的动态力学行为 ,有必要进一步研究其在较高压力下的冲击压缩性能。通过轻气炮实验 ,测量了靶板自由面质点速度时程曲线等相关参量 ,得到了材料的D u型Hugoniot线。实验揭示了在突加载荷作用之下 ,在应变率负敏感的铝锂合金材料中可出现类似于弹塑性材料中的双波结构 ,从而证明了所提出的“极限应变率负敏感粘塑性材料”这一概念的合理性。最后 ,在弱激波假设的前提下 ,推导了材料Hugoniot方程与Murnagham状态方程之间的关系 。

The most materials have the positive strain-rate sensitivity, the yield stresses of which will increase with the strain-rate increasement. However, based on the dynamic experiments we found that the Al-Li alloy has the negative strain-rate sensitivity and the impact ductility. By means of the gas gun experiments, the free-surface velocity history and other related parameters are measured, and the D-u Hugoniot curve of Al-Li alloy is obtained. The experiments reveal that under the impact loading the double wave structure similar to that in elastoplastic materials will occur in this strain-rate sensitive material, which shows that our concept about the material of limited negative strain-rate sensitivity is reasonable. Finally, under the hypothesis of weak shocks, we deduced the relationship between the D-u Hugoniot curve and the Murnagham equation, and the parameters of Murnagham equation of Al-Li alloy are obtained based on the experimental data.