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Study on Macroscopic Aspects of Shock Compression Behavior of Polymer Materials

高分子材料冲击压缩行为的宏观研究

基本信息

批准号：
09450038
负责人：
NAGAYAMA Kunihito
金额：
$ 4.8万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Results of our study are as follows :We have first established Hugoniot measurement method for polymer shock waves. Continuous observation of free surface velocity or that of stress wave profile together with the shock Hugoniot parameters are realized by two different experimental methods. We measured two different polyethylene specimens with different crystallinity. Consequently, we found that Hugoniot curve for both specimens have a curvature around a point of the particle velocity of 150m/s, and a some scatter of the data around this region.To examine that the scatter might be due to the unsteadiness of the shock propagation velocity, we have then developed a novel technique of continuous observation of shock propagation velocity. PMMA specimen was first measured for comparison, which showed no appreciable unsteadiness. While for polyethylene specimens, shock decay was observed especially large in the vicinity of the curvature region of the Hugoniot. Higher stress region, shock velocity seemed almost constant. This result indicates an absorption of energy due to stress relaxation. This decay characteristics is found to depend on the polyethylene specimen. Unsteadiness of shock velocity suggests that shock Hugoniot is not regarded as a simple material compression curve, which could not be described by simple shock jump condition with shock velocity as a parameter. Furthermore, we have discussed the physics of the deflection of Hugoniot curve found for any polymer materials again in the region of 150 m/s particle velocity. Very large Gruneisen parameter of 3-4 was suggested at the lower stress region before the deflection point, while it decreases to a very small value of 0.1 after the deflection. Large Gruneisen parameter corresponds to that of intermolecular vibration modes, which is supposed to be excited selectively by the shock drive. Strong thermal nonequilibrium after shock front is then concluded from this discussion.

研究结果如下：首次建立了高分子冲击波的Hugoniot测量方法。用两种不同的实验方法实现了自由面速度或应力波剖面和冲击Hugoniot参数的连续观测。我们测量了两种不同的聚乙烯样品具有不同的结晶度。结果发现，两个试样的Hugoniot曲线在质点速度为150 m/s的点附近都有一个曲率，并且在这个区域附近的数据有一定的离散性，为了研究这种离散性可能是由于激波传播速度的不稳定性，我们发展了一种新的激波传播速度连续观测技术。首先对PMMA试样进行了测量比较，没有发现明显的不稳定性。而对于聚乙烯样本，在Hugoniot曲率区域附近观察到冲击衰减尤其大。在高应力区，激波速度几乎不变。该结果表明由于应力松弛引起的能量吸收。发现这种衰减特征取决于聚乙烯样本。冲击波速度的非定常性表明冲击Hugoniot不是一条简单的材料压缩曲线，不能用以冲击波速度为参数的简单冲击波跳跃条件来描述。此外，我们还讨论了在150 m/s粒子速度范围内，任何聚合物材料的Hugoniot曲线的偏转的物理现象。在变形点之前的低应力区，Gruneisen参数非常大，为3-4，而在变形点之后，Gruneisen参数减小到非常小的值0.1。大的Gruneisen参数对应于分子间振动模式，这应该是由冲击驱动选择性地激发。由此得出了激波后强热不平衡的结论。