The light emission signatures generated following the impact of small cylindrical bulk Al, Ti, and Zr projectiles with an aluminum oxide target at supersonic speeds in the range of 0.4 – 1.1 km/s are investigated in air, argon, and vacuum using a suite of optical diagnostics, including a high-speed video camera, a three-colour optical pyrometer, a fast-response avalanche photodetector, and a low temporal resolution spectrometer. The history of the light emission in air may be divided into two distinct stages with different timescales. The first stage lasts up to 10 µs and is associated with the primary impact event. Within this stage the primary contribution to the light emission comes from projectile kinetic energy being converted into thermal energy. A second light emission stage, that lasts from hundreds of microseconds to a few milliseconds, is associated with the emission from the diffusion-limited combustion of metal fragments ignited upon impact. In contrast with the impact of Ti and Zr projectiles, for Al projectiles the second combustion stage was only observed above a threshold impact velocity of about 0.7 km/s. The low thermal conductivity, specific heat, and brittleness of Ti and Zr are believed to facilitate the formation of hot spots on the surface of fragments which contributes to ready fragment ignition.

在空气，氩气和真空环境中，使用一套套件，研究了在超声速为0.4 – 1.1 km / s的情况下，带有氧化铝靶的小的圆柱形散装Al，Ti和Zr弹丸撞击后产生的发光特征。光学诊断，包括高速摄像机，三色光学高温计，快速响应的雪崩光电探测器和低时间分辨率光谱仪。空气中发光的历史可以分为两个不同的阶段，它们具有不同的时标。第一阶段持续时间长达10 µs，并与主要冲击事件有关。在此阶段，对光发射的主要贡献来自于射弹动能转化为热能。第二个发光阶段持续数百微秒到几毫秒，与撞击时点燃的金属碎片的扩散限制燃烧所产生的排放有关。与Ti和Zr弹丸的影响相反，对于Al弹丸，仅在高于约0.7 km / s的阈值撞击速度时才观察到第二燃烧阶段。Ti和Zr的低热导率，比热和脆性被认为有利于在碎片表面上形成热点，这有助于随时点燃碎片。