基于闪光光谱的侵彻过程光学观察窗口分析

Optical Observation Window Analysis of Penetration Process Based on Flash Spectrum

可见光高速摄影是研究弹丸侵彻过程的重要方式,然而弹丸侵彻过程中发出的强烈闪光会导致高速摄影丢失诸如着靶、侵入等时刻的关键画面。因此,分析侵彻光谱发生机理、选取合适的侵彻过程光学观察窗口尤为重要。针对400 mm直径高强度钢卵形弹以804 m·s^(-1)侵彻20 cm厚度45^(#)钢靶的实验,设计了光谱瞄准采集设备。利用多模光纤耦合物镜在距离靶板25 m处采集了侵彻全过程积分光谱,采集区覆盖靶板直径431 mm。对侵彻靶板破片中可能存留的弹头熔融物质以及弹托其他样品进行LIBS(laser induced breakdown spectroscopy)分析,并与侵彻积分光谱成分对比分析。研究表明,侵彻光谱与高速碰撞闪光光谱发生机理相同,均包含连续光谱与线光谱。615~700 nm区间内的平稳积分连续光谱由两部分组成:(a)弹靶少量金属元素和OⅠ、OⅡ发射光谱的展宽积分;(b)少量热辐射光谱积分。侵彻热辐射主要源于剪切应变做功和摩擦做功,然而侵彻光谱中的热辐射强度明显低于高速碰撞光谱,这是弹丸在剪切冲塞、侵彻后大部分动能得以保留造成的;侵彻过程可见光光谱具有明显原子发射谱线,主要来自于金属原子及其一级电离的发射光谱。干扰最强的可见光成分来源于588.88~589.53和766.41~766.43 nm的FeⅠ等离子体线光谱,且由于斯塔克展宽效应,线光谱呈洛伦兹线型,其FWHM(full width at half maximum)可达27 nm。因此,在野外环境侵彻实验中,当Fe为弹靶主要成分时,380~450 nm为可见光高速摄影的最佳观察窗口,可以避免侵彻发光干扰,实现对侵彻全过程拍摄。考虑到大气对该波段的散射影响,应保证高速摄影设备的光通量。

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 OⅠand OⅡemission 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.