Optical Observation Window Analysis of Penetration Process Based on Flash Spectrum
SI Yu1, LIU Ji1*, WU Jin-hui2, ZHAO Lei1, YAN Xiao-yan2
1. School of Information and Communication Engineering, North University of China, Taiyuan 030051, China
2. School of Instrument and Electronics, North University of China, Taiyuan 030051, China
Abstract：Visible high-speed photography is an important way to study projectile penetration. However, the intense flashes emitted during projectile penetration can cause high-speed photography to lose critical images of moments such as target impact and intrusion. Therefore, it is particularly important to analyze the mechanism of penetration spectroscopy and select a suitable optical observation window for the penetration process. For the experiment of a 400 mm diameter high-strength steel ovoid bullet penetrating a 20 cm thickness, 45# steel target at 804 m·s-1, a spectral targeting and acquisition device was designed. The integrated spectra of the whole process of target plate penetration were collected at 25 m from the target plate using a multimode fiber coupled with an objective lens, and the collection area could cover the 431 mm diameter of the target plate. The molten material of the payload and the other samples of the shells were analyzed by LIBS (Laser-Induced Breakdown Spectroscopy) and compared with the components of the intrusion integral spectrum. The smooth integral continuous spectrum in the interval of 615~700 nm consists of two parts: (a) the spreading integral of a small number of metal elements and O Ⅰ and O Ⅱ emission spectra of the bullet target (b) the integral of a small amount of thermal radiation spectrum; the thermal radiation of the intrusion mainly comes from shear strain work and friction work. However, the intensity of thermal radiation in the intrusion spectrum is significantly lower than that in the high-speed impact spectrum, which is caused by the retention of most of the kinetic energy of the projectile after the shear strain and intrusion into the target plate; the visible spectrum emitted during the intrusion process has obvious atomic emission spectra, mainly from the emission spectra of metal atoms and their primary ionization. The most disturbing visible light component comes from the Fe I. plasma line spectra of 588.88~589.53, 766.41~766.43 nm, and due to the Stark widening effect, the line spectrum is Lorentz linear, and it’s FWHM(Full Width at Half Maximum) can reach 27 nm. Therefore, in the experiments of the field environment where sunlight is the main light source when Fe is the main component of the target, the spectrum of 380~450 nm is the best observation window for visible high-speed photography, which can avoid the intrusion luminescence interference and achieve the whole intrusion process photography. The high-speed photography equipment should be ensured by sufficient luminous flux.
司 宇，刘 吉，武锦辉，赵 磊，闫晓燕. 基于闪光光谱的侵彻过程光学观察窗口分析[J]. 光谱学与光谱分析, 2023, 43(03): 718-723.
SI Yu, LIU Ji, WU Jin-hui, ZHAO Lei, YAN Xiao-yan. Optical Observation Window Analysis of Penetration Process Based on Flash Spectrum. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(03): 718-723.
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