金属的冲击波温度测量(Ⅳ)——“三层介质模型”及其应用

SHOCK TEMPERATURE MEASUREMENT FOR METALS(Ⅳ) —“Three Layer Model” and Its Applications

重点讨论了非理想界面对利用辐射法测量金属的冲击波温度的影响 ,建立并给出了“三层介质模型”的热传导方程的普适解析解 ,分别将该解析解应用于块状金属样品的冲击波温度测量、“热阻模型”以及利用对称夹心装置测量蓝宝石单晶的高压热传导问题 ;重点研究和讨论了利用块状样品进行金属材料冲击波温度测量的原理和可能性 ,以及在利用块状样品进行金属材料冲击波温度测量时实验装置设计应该满足的要求。“三层介质模型”的分析表明 :只要块状样品与透明窗口之间的间隙尺度小于 1 0 μm(最好小于 0 5μm) ,则“样品 /窗口”界面的温度在大约几十纳秒的时间内即可从尖峰温度衰减到与理想界面温度相当接近的值。根据“样品 /窗口”界面的这一热弛豫特性 ,可以直接利用块状金属样品测量冲击波温度而不必采用镀膜技术。给出了利用块状铁陨石样品和单晶蓝宝石 (Al2 O3 )窗口进行冲击波温度测量的初步实验结果 ,与三层介质模型的预期结果符合得很好。

Effects on shock temperature measurements of the gap between the bulk metal sample and the transparent window are specially discussed in detail.A “three layer model” corresponding to the “bulk metal sample/gap/transparent window” target sample assembly is proposed.A universal analytical solution of the heat conduction equation of this three layer model is obtained.The model is applied successfully to studies in radiometry shock temperature measurements,to the analyses of the “thermal resistance model” and of the heat conductivity measurement of the window materials at very high pressures.Special efforts are focused on the principle and the possibility of utilizing a bulk sample rather than a film in the radiometry shock temperature measurements for metals.Based on the three layer model,the sharp “peak” appearing at the beginning of the “sample/window” interface temperature profile will drop down at first rapidly in a few tens of nanoseconds.Then it will approach slowly to a level close to the equilibrium temperature predicted by the ideal interface model,if the width of the gap is less than 1 micron (0.5 micron less will be the better).It is therefore possible to use a lumpy sample(rather than )a film to conduct shock temperature measurement.We presented here some preliminary experimental records for the shock temperature measurement obtained by using the lumpy ironmeteorite samples,which demonstrated the feasibility of the technique. Also discussed here are the basic problems existing in the so called “thermal resistance model”,Applying the analytical solution of the three layer model according to the conditions specifed by the “thermal resistance model”,we obtained a result contradictory both to experimental observations and to the expectation of the thermal resistance model.An insight into the “thermal resistance model'reveals the paradox in the basic assumptions of the model itself.