In situ observation of penetration process in silica aerogel: Deceleration mechanism of hard spherical projectiles
In situ observation of penetration process in silica aerogel: Deceleration mechanism of hard spherical projectiles
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DOI：
10.1016/j.icarus.2010.11.005
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发表时间：
2011-02
期刊：
影响因子：
3.2
通讯作者：
R. Niimi;T. Kadono;M. Arakawa;M. Yasui;K. Dohi;A. Nakamura;Y. Iida;A. Tsuchiyama
中科院分区：
文献类型：
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作者：
R. Niimi;T. Kadono;M. Arakawa;M. Yasui;K. Dohi;A. Nakamura;Y. Iida;A. Tsuchiyama
美国宇航局的星尘任务用低密度二氧化硅气凝胶捕获了大量的彗星尘埃颗粒。为了从撞击轨迹中正确推导出颗粒的原始特征，需要了解超高速颗粒在二氧化硅气凝胶中捕获机理的细节。然而，其机制尚未被完全理解。我们将几种不同材料的硬质球形弹丸射入密度为60mgcm−3的二氧化硅气凝胶中，并利用图像转换器或高速摄像机观察其穿透过程。为了清晰地观察弹丸的减速度，我们在两个速度范围内进行了撞击实验；∼4公里−1∼200 ms−1。从我们拍摄的电影中可以看出，在更快的穿透过程（~ 4km−1）中，弹丸受到与v2（v：弹丸速度）成正比的水动力减速，而在较慢的穿透过程（~ 200ms−1）中，它们仅仅克服了气凝胶的破碎强度。我们在整个捕获过程中应用这些减速机制来计算轨迹长度。我们的模型很好地解释了Burchell等人（Burchell, m.j., Creighton, j.a., Cole, m.j., Mann， J., Kearsley， A.T.[2001]）实验数据集中的轨迹长度。Meteorit。星球。科学36,209-221)。
A large number of cometary dust particles were captured with low-density silica aerogels by NASA’s Stardust Mission. Knowledge of the details of the capture mechanism of hypervelocity particles in silica aerogel is needed in order to correctly derive the original particle features from impact tracks. However, the mechanism has not been fully understood yet. We shot hard spherical projectiles of several different materials into silica aerogel of density 60mgcm−3and observed their penetration processes using an image converter or a high-speed video camera. In order to observe the deceleration of projectiles clearly, we carried out impact experiments at two velocity ranges; ∼4kms−1and ∼200ms−1. From the movies we took, it was indicated that the projectiles were decelerated by hydrodynamic force which was proportional to v2(v: projectile velocity) during the faster penetration process (∼4kms−1) and they were merely overcoming the aerogel crushing strength during the slower penetration process (∼200ms−1). We applied these deceleration mechanisms for whole capture process to calculate the track length. Our model well explains the track length in the experimental data set by Burchell et al. (Burchell, M.J., Creighton, J.A., Cole, M.J., Mann, J., Kearsley, A.T. [2001]. Meteorit. Planet. Sci. 36, 209–221).