Optical measurement and scaling of blasts from gram-range explosive charges

Laboratory-scale experiments with gram-range explosive charges are presented. Optical shadowgraphy and high-speed digital imaging are used to measure the explosive-driven shock-wave position as a function of time. From this, shock Mach number-versus-distance from the explosion center can be found. These data then yield the peak overpressure and duration, which are the key parameters in determining the potential damage from an explosion as well as the TNT equivalent of the explosive. Piezoelectric pressure gage measurements of overpressure duration at various distances from the explosive charges compare well with theoretical calculations. A scaling analysis yields an approach to relate the gram-range blast to a large-scale blast from the same or different explosives. This approach is particularly suited to determining the properties and behavior of exotic explosives like triacetone triperoxide (TATP). Results agree with previous observations that the concept of a single TNT equivalence value is inadequate to fully describe an explosive yield, rather TNT equivalence factor and overpressure duration should be presented as functions of radius.      

FAE爆炸场超压与威力的实验研究

利用现场测试系统动态灵敏度标定技术,分别等精度测试了FAE和TNT爆炸场峰值超压。在此基础上获得了各自的爆炸波峰值超压随传播距离的拟合曲线和TNT当量比。结果表明:FAE爆炸场超压分布规律与TNT有显著区别,前者属于大体积云雾爆炸,爆炸场可划分为云雾爆轰区、云雾边缘区和冲击波作用区;在云雾爆轰区,超压平均值在2.6MPa左右,在小于2/3云雾半径的范围内比同质量的TNT低,在大于2/3的云雾半径范围则显著大于TNT;在冲击波作用区,环氧丙烷燃料的FAE爆炸超压约是TNT爆炸效果的5倍,超压均呈衰减趋势,但FAE衰减比TNT缓慢许多。     

Secondary shock features for large surface explosions: results from the Sayarim Military Range,Israel and other experiments

A series of surface explosions was designed and conducted by the Geophysical Institute of Israel at the Sayarim Military Range in the Negev desert, including two large-scale explosions: approx. 82 tons of high explosives in 2009, and approx. 100 tons of low-grade ANFO explosives in 2011. The main goal of the explosions was to provide large controlled sources for calibration of global infrasound stations designated for monitoring nuclear tests; however, the geophysical experiment also provided valuable observations for shock wave research. High-pressure gauges were deployed at distances between 100 and 600 m to record air blast properties and to provide reliable estimation of the true charge yield compared to the design value. Secondary shock phenomena were clearly observed at all near-source gauges as characteristic shock wave shapes. Secondary shocks were also observed at numerous seismic and acoustic sensors deployed in the range 0.3–20 km as acoustic phases. Empirical relationships for standard air blast parameters (peak pressure and impulse) and for a new parameter called secondary shock time delay, as a function of distance, were established and analyzed. The standard parameters, scaled by the cubic root of the estimated TNT yield, were found to be consistent for all analyzed explosions. However, the scaled secondary shock delays were clearly separated for the 2009 and 2011 explosions, thus demonstrating dependence on the explosive type. Additionally, air blast records from other experiments were used to extend the charge and distance ranges for the secondary shock observation, and showed consistency with the Sayarim data. Analysis and interpretation of observed features of the secondary shock phenomenon are proposed and a new empirical relationship of scaled secondary shock delay versus scaled distance is established. The results suggest that the secondary shock delay can be used as a new additional waveform feature for simple and cost-effective explosive yield estimation.     

钢筋混凝土排架结构的抗爆破坏等级

为了研究钢筋混凝土排架结构在大当量爆炸冲击波下的破坏规律,依据最大TNT当量为3 t的爆炸试验,对排架主体结构的抗爆破坏等级进行数值模拟研究。通过量纲分析得到1/2缩比模型的荷载参数和结构尺寸。基于Abaqus有限元软件,利用CONWEP方法实现爆炸加载,分别计算装药0.5 t爆距33 m和装药3 t爆距33 m两种工况下排架结构的破坏形态,并与试验结果进行对比。进一步通过控制药量和距离,计算不同超压和冲量下缩比模型的破坏形态。研究结果表明,排架的关键破坏特征为中间承重柱的倾覆转动;数值计算与试验破坏形态吻合较好,特征位移和特征转角的最大相对误差分别为5.6%和4.6%。以承重柱的倾覆角作为划分依据,将计算结果分为3种破坏等级,拟合得到的超压-冲量曲线和药量-距离曲线可用于厂房安全距离和仓库容量设计以及意外爆炸下的破坏程度预估。     

新型发射药爆炸TNT当量系数的实验研究

TNT当量系数是危险品工程抗爆设计和安全距离确定的重要依据。为确定H1和H2两种新型高能发射药的TNT当量系数,分别开展了10 kg TNT和新型发射药的空气自由场静爆实验。基于修正的当量系数计算方法和测量得到的不同爆心距离处冲击波超压时程曲线,确定了不同比例距离处两种高能发射药的超压和比冲量TNT当量系数。研究结果表明,发射药爆炸产生的冲击波传播规律与TNT炸药爆炸产生的冲击波传播规律相同,符合爆炸相似律,相同质量发射药爆炸产生的冲击波超压和比冲量都显著高于TNT的。随着比例距离的增大,H1的超压当量系数先增大后减小,最大值为1.34;H2的超压当量系数逐渐减小,最大值为1.26。两种新型发射药的比冲量TNT当量系数均随比例距离的增大先减小后增大,H2的比冲量TNT当量系数大于H1的,最大值为1.38。本文中修正的计算方法能更准确计算被试样品的TNT当量系数,实验结果可为提高抗爆结构安全性设计提供参考。     

Analysis of reflected blast wave pressure profiles in a confined room

To understand the blast effects of confined explosions, it is necessary to study the characteristic parameters of the blast wave in terms of overpressure, impulse and arrival time. In a previous study, experiments were performed using two different scales of a pyrotechnic workshop. The main purpose of these experiments was to compare the TNT equivalent for solid and gaseous explosives in terms of mass to define a TNT equivalent in a reflection field and to validate the similitude between real and small scales. To study the interactions and propagations of the reflected shock waves, the present study was conducted by progressively building a confined volume around the charge. In this way, the influence of each wall and the origins of the reflected shock waves can be determined. The purpose of this paper is to report the blast wave interactions that resulted from the detonation of a stoichiometric propane-oxygen mixture in a confined room.     

Investigating ground effects on mixing and afterburning during a TNT explosion

In this paper, the unconfined and semi-confined condensed phase explosions of TNT will be studied using large eddy simulations based on the unsteady, compressible, reacting, multi-species Navier–Stokes equations to gain further understanding of the physical processes involved in a condensed phase explosion and the effect of confinement on the physical processes involved. The analysis of the mixing and afterburning of TNT explosions in free air (unconfined) and near the ground (semi-confined) indicates that the combustion region of detonation products and air is determined by the vorticity patterns, which are induced by the Richtmeyer–Meshkov instabilities that arise during the explosion. When the explosive is detonated in the vicinity of a surface, the surface affects the shock propagation by creating complex shock systems, thereby changing the orientation of the vorticity, giving the afterburning a mushroom shape, and increasing performance of an explosive charge by prolonging the existence of the mixing layer and thereby the afterburning.     

TNT药柱水中爆炸近场压力轴向衰减规律

通过TNT药柱水中爆炸实验,建立了利用高速相机测量水中爆炸近场冲击波的实验方法,得到了药柱轴向的扫描图像,并对图像进行了数字化分析;利用Rankine-Hugoniot关系从冲击波的扫描轨迹求得冲击波阵面压力,并外推至冲击波的初始压力;用LS-DYNA计算了柱形装药近场压力沿轴向的衰减曲线;用锰铜压力传感器测量了冲击波的初始压力。研究结果表明,测试结果与计算结果比较符合,TNT药柱的近场轴向压力遵循指数衰减规律。     

固态燃料小型FAE装置空中爆炸场效应分析

通过一次引爆固态复合粉尘燃料小型FAE装置与等质量TNT在自由空间的爆炸对比实验,获得了不同距离的峰值超压值,并运用粉尘爆炸下极限浓度对云雾爆轰区半径进行了估算。结果表明,固态燃料小型FAE装置空爆峰值超压分布规律不同于TNT,云雾爆轰区内的峰值超压不呈现单调减的特征,而是在有限范围内呈现波动趋势;云雾爆轰区外的峰值超压随距离增大迅速衰减,但固态燃料小型FAE装置的峰值超压大于相同距离处等质量的TNT。高速摄影观测结果显示,固态燃料小型FAE装置爆炸的化学反应持续时间大于等质量TNT。     

近距离爆炸比例爆距的界定标准及荷载模型

如何准确界定“近距离爆炸（close-in explosion）”一直是防护工程研究领域的热点。本文中基于已被充分验证的精细化有限元模型,研究了TNT球形装药自由场爆炸冲击波传播与爆轰产物高速膨胀共同作用的特点和规律,发现在比例爆距小于0.80 m/kg1/3的范围内,爆轰产物对刚性壁面的爆炸荷载影响显著,提出球形装药近距离爆炸的比例爆距界定标准为0.30～0.80 m/kg1/3。研究发现,在近距离爆炸下,爆炸波在入射角为0°～5°范围内的刚性壁面反射荷载峰值会出现急剧下降的现象,这是由爆轰产物喷射的不均匀性和随机性导致的;近距离爆炸下,刚性壁面反射超压出现了两个峰值的现象,这是由冲击波和爆轰产物分别与刚性壁面相互作用导致的。提出了近距离爆炸情况下两个荷载峰值的计算公式,以及适合工程结构响应计算的简化荷载模型;揭示了近距离爆炸下刚性壁面反射超压的分布规律。     

复合装药空气中爆炸冲击波传播特性

为了研究复合装药超压爆轰时的径向能量输出特性,选择典型的TNT、JO-8、海萨尔等理想、非理想高能炸药,进行了单一装药、内外层复合装药冲击波超压测试实验。采用自由场压电传感器测量了距爆心2、3、4 m处的冲击波压力,通过Origin软件对实验数据进行去除“零漂”和积分处理,获得了冲击波超压、冲量随距离的变化规律,分析了装药结构、装药类型对实验结果的影响。研究结果表明:与同体积单一装药相比,内外层复合装药对提高径向冲击波超压无优势,但对径向冲击波冲量增益显著,且冲量随传播距离的增加而增大;装药类型对内外层复合装药径向冲击波冲量增益影响较大,非理想/理想复合装药在4 m处的冲量增益大于20%,比理想/理想复合装药更有利于提高战斗部的径向输出威力。     

Application of background oriented schlieren for quantitative measurements of shock waves from explosions

This paper describes application of a background oriented schlieren technique in order to obtain quantitative measurements of shock waves from explosions by processing high speed digital video recordings. The technique is illustrated by an analysis of two explosions, a high explosive test and a hydrogen gas explosion test. The visualization of the shock front is utilized to calculate the shock Mach number, leading to a predicted shock front pressure. For high explosives the method agreed quite well with a standard curve for side-on shock pressures. In the case of the gas explosion test we can also show that the shock front is non-spherical. It should be possible to develop this technique to investigate external blast waves and external explosions from vented gas explosions in more details. This paper is based on work that was presented at the 21th International Colloquium on the Dynamics of Explosions and Reactive Systems, Poitiers, France, July 23–27, 2007.     

Height of burst explosions: a comparative study of numerical and experimental results

In the current work, we use the Constant Volume model and the numerical method, Regularized Smoothed Particle Hydrodynamics (RSPH) to study propagation and reflection of blast waves from detonations of the high explosives C-4 and TNT. The results from simulations of free-field TNT explosions are compared to previously published data, and good agreement is found. Measurements from height of burst tests performed by the Norwegian Defence Estates Agency are used to compare against numerical simulations. The results for shock time of arrival and the pressure levels are well represented by the numerical results. The results are also found to be in good agreement with results from a commercially available code. The effect of allowing different ratios of specific heat capacities in the explosive products are studied. We also evaluate the effect of changing the charge shape and height of burst on the triple point trajectory.      

Blast wave propagation in air from a gaseous charge

In the point explosion problem it is assumed that an instantaneous release of finite energy causing shock wave propagation in the ambient gas occurs at a space point. The results of the solution of the problem of such blasts are contained in [1–4]. This point model is applied for the determination of shock wave parameters when the initial pressure in a sphere of finite radius exceeds the ambient air pressure by 2–3 orders of magnitude. The possibility of such a flow simulation at a certain distance from the charge is shown in papers [4, 5] as applied to the blast of a charge of condensed explosive and in [6, 8] as applied to the expansion of a finite volume of strongly compressed hot gas. In certain practical problems the initial pressure in a volume of finite dimensions exceeds atmospheric pressure by a factor 10–15 only. Such cases arise, for example, in the detonation of gaseous fuel-air mixtures. The present paper considers the problem of shock wave propagation in air, caused by explosion of gaseous charge of spherical or cylindrical shape. A numerical solution is obtained in a range of values of the specific energy of the charge characteristic for fuel-air detonation mixtures by means of the method of characteristics without secondary shock wave separation. The influence of the initial conditions of the gas charge explosion (specific energy, nature of initiation, and others) is investigated and compared with the point case with respect to the pressure difference across the shock wave and the positive overpressure pulse.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 110–118, May–June, 1986.     

温压炸药在野外近地空爆中的冲击波规律

为了研究温压炸药在敞开空间爆炸中冲击波的规律,选取典型温压炸药制成不同量级的裸药柱进行野外近地空爆实验,同时用TNT进行对比实验,获取温压炸药与TNT的冲击波参数并拟合得到相似律公式。结果表明,温压炸药的冲击波超压峰值在中远场略高于TNT;在相同对比距离处,温压炸药的比冲量明显高于TNT,在对比距离小于2 m/kg1/3的近场,温压炸药的比冲量达到TNT的2倍。引入超压-比冲量曲线描述冲击波特征,表明当超压峰值相同时,温压炸药比冲量更大, 超压峰值在20~50 kPa的中度以下毁伤范围时,温压炸药的比冲量比TNT高40%~60%,可产生更严重的毁伤效应。冲量是爆炸冲击波的重要毁伤元素,应建立与冲量有关的方法评价温压炸药的威力。     

Experimental and numerical studies of underwater shock wave attenuation

The attenuation of an underwater shock wave by a thin porous layer is studied both experimentally and numerically. The shock waves are generated by exploding 10 mg silver azide pellets and the pressures at different distances from the explosion center are measured. Measurements are also carried out with a gauze layer placed between the explosion source and the pressure gauge. The results with and without the gauze layer are compared evaluating the shock wave attenuation. Numerical simulations of the phenomenon are also carried out for a simple wave attenuation model. The results are compared with the experimental data. Despite the simple mathematical model of wave attenuation, the agreement between the experimental and numerical results is reasonable.Received: 22 October 2002, Accepted: 17 June 2003, Published online: 5 August 2003PACS: 47.11.+j, 47.40.Nm, 47.55.Mh     

岩石中化学爆炸气体渗漏行为的实验研究

通过小药量化爆模拟实验,研究了岩石中满足缩比关系的不同药量化学爆炸一氧化碳渗漏时间、渗漏份额与药量的关系。研究结果表明:相同介质中缩比爆炸实验气体渗漏时间大致与药量的三分之二次方成正比,渗漏停止时间也大致与药量的三分之二次方成正比;封闭空间内化学爆炸在爆室内产生的高温能够使爆室内一些物质分解产生非冷凝气体;对于不同药量的缩比实验,小药量实验的气体渗漏份额不小于大药量实验的气体渗漏份额。根据此研究结果,可以用小药量地下爆炸气体渗漏行为的监测结果预估大药量实验的气体渗漏行为。     

接触爆炸荷载对钢筋混凝土梁的局部毁伤效应

为得到接触爆炸下钢筋混凝土（reinforced concrete,RC）梁的局部破坏模式和毁伤效应,对同一尺寸的RC梁进行了不同装药量的接触爆炸试验研究。试验中采用框架结构中典型工程尺度RC原型梁为研究对象,通过4次爆炸试验,观测了RC梁在不同装药量下的局部破坏模式和破坏特征,分析了装药量对局部毁伤效应的影响。研究结果表明:接触爆炸荷载作用下,RC梁将发生正面成坑、侧面崩落、背面震塌和截面冲切等局部破坏模式,爆坑深度、震塌厚度、表面毁伤面积以及受压区纵筋变形均与装药量立方根近似呈线性增加关系。在试验数据基础上,将RC梁局部毁伤程度划分为轻度毁伤、中度毁伤、重度毁伤和严重毁伤4个等级,采用比例装药量判据进行评估。研究成果可为抗爆结构设计和结构毁伤评估提供理论依据。     

大断面隧道钻爆冲击波的衰减规律

隧道开挖爆破产生的空气冲击波的破坏效应,将会对人员、机具设备与周围环境造成危害。隧道钻孔爆破冲击波的影响因素比裸露药包爆炸更多、更复杂,研究其衰减规律对采取合适的防护措施意义重大。本文中开展了时速350 km双线铁路大断面隧道钻孔爆破空气冲击波的现场测试,分析了不同工况下冲击波传播规律及影响因素。结果表明:钻爆冲击波超压时程曲线存在多个不同幅值的超压波峰,波峰之间具有明显微差延时的短间隔性,传播至远场未形成稳定的单一平面波,与单一药包爆炸冲击波的传播规律存在差异;钻爆冲击波超压信号由多段与微差延时相对应的子信号叠加而成,子信号数量与毫秒延期雷管段数相同,呈现出典型的时域特征;相同爆破条件下,大断面隧道钻爆时的乳化炸药冲击波转化因数小于小断面巷道工况下的;相较于总药量及最大段药量,按掏槽药量计算的超压峰值与实测超压峰值之间的相关性最强,钻爆冲击波最大超压峰值宜按掏槽段炸药TNT当量确定;隧道内大型机械设备等障碍物改变了钻爆冲击波流场的传播规律,呈现较明显的叠加放大效应。     

基于爆能等效原理大型模爆器燃气爆炸冲击加载的数值模拟

运用非线性显式动力有限元程序LS-DYNA,基于多物质Euler算法,对TNT炸药和乙炔-空气混合气体两种爆炸源在自由大气场中爆炸产生的冲击波荷载特征参数进行数值模拟,比较两种爆源产生的冲击波压力传播规律。基于爆能等效原理,按超压相等的原则给出了气体爆炸名义比例距离计算公式。结果表明,基于Euler算法可以较好地描述乙炔-空气混合气体爆炸空气冲击波传播规律,爆炸压力随着距爆源距离的增大而迅速衰减,且两种爆源产生的冲击波超压峰值误差随着冲击波传播距离的增大而逐渐减小。采用名义比例距离公式修正后,气体爆炸与炸药爆炸冲击波计算误差可以得到有效控制。当爆炸冲击波超压小于0.5MPa时,可以采用乙炔-空气混合气体代替化学炸药进行模爆器内爆炸实验加载。