Experimental Research On Radiation Behaviors And Temperatures Of Iron/Sapphire Interface Under Shock Compression

To obtain the shock temperature of metals, the radiance of the interface between metal plate and a transparent window is directly measured, and its radiation temperature is determined based on grey body model of Planck's radiation theory. It is according to the measured interface temperature that the release and shock temperature of metal sample are deduced respectively by a heat transfer model and by a model of equation of state. However, the feathers of radiation signal published by different groups of scientists were different from each other, because they adopted different target assembly and the procedure of preparing sample. The main problem is focused on the "peak"characteristic of the radiation from the interface, especially on the height and relaxation duration of the peak radiation signal and also on the various explanations.In this work, we use pure dense iron as samples and the sapphire plate as optical windows to measure the shock-induced radiation signals and temperature of the interface between iron/sapphire. The effects of the contact condition on the radiation feather are investigated. Some technique improvements and new knowledge are summarized as follows:(1)Obvious progresses in the surface polish technique for iron sample are made. We use UNIPOL810 polish machine, and find out an effective polish procedure for pure iron. Finally, the surface of pure iron, with good smoothness and flatness, is prepared to meet the demand of the experiments.(2)The method to press the target is improved, and the perfectly contacted interface without gap between iron and sapphire is obtained. The force is uniformly executed on the interface of iron and sapphire by multi-point press, which can reduce the gap to level of one fourth of visible light wavelength in the central area of 10mm. This is the most important step to measure the interface radiation with good repetition;(3)The pyrometer is in-situ calibrated during experiment, which reduces uncertainty from the change of geometry of fibers, and improves the reliability of measured result of radiance.(4)Under shock compressions, we obtain one shot of radiation signal without any "peak" radiation, and several shots of radiation signal with little peak radiation. These new data are meaningful to establish theoretical model.