非相似圆筒内爆膨胀模型设计及试验验证

为了探索既能延长爆轰产物有效膨胀时间、又可避免大幅增加试验药量的圆筒试验方法,以满足释能时间较长的含铝炸药的试验需求,针对仅增加壁厚的非相似圆筒结构,分析其在内爆条件下的膨胀过程,优化了炸药格尼能计算模型,并通过3个不同壁厚且均装填TNT炸药的圆筒试样的内爆加载试验验证了试验可行性及计算模型的准确性。结果表明,内径Φ50mm、壁厚10mm、长度700mm的非相似圆筒结构,其破裂前的最大位移较Φ50mm标准圆筒未显著提升,但可使爆轰产物的有效膨胀时间提升42%,而装药量仅增加40%;且在经典格尼模型基础上增加爆轰产物沿圆筒轴向的运动、圆筒变形能两个因素后,该圆筒的爆轰能量数据与标准圆筒较为吻合,反映出优化后的分析模型可以准确地评估该非相似圆筒中的炸药驱动性能。     

压装工艺对CL-20基炸药性能及聚能破甲威力的影响

利用常温成型和热压成型两种工艺制备了典型的CL-20基混合炸药装药,测试了其装药密度、密度均匀性、力学性能、爆速,计算了格尼系数。对Φ50mm标准聚能装药进行了破甲试验。验证了不同压装工艺条件下装填CL-20基炸药装药聚能射流对45号钢靶的侵彻深度和穿孔直径效果。结果表明,与常温成型CL-20基装药相比,热压成型工艺条件时装药的密度提高不小于1.46%,密度均匀性、爆速和格尼系数和破甲能力试验数据均有不同程度的提高,且Φ50mm标准聚能射流对45号钢靶的平均穿深从310mm提高至343mm,平均穿孔直径由18.0mm增至23.5mm。     

DNTF基熔铸炸药的金属加速作功能力

用圆筒试验获得含铝和不含铝两种配方的DNTF基熔铸炸药的筒壁膨胀速度、比动能和格尼系数的变化规律,研究了其金属加速作功能力,并与Octol炸药进行了对比。结果表明,DNTF可显著提高混合炸药的金属加速作功能力;加入少量铝粉虽然会降低初始筒壁速度,但在圆筒膨胀后期,筒壁速度可超过不含铝配方,且提高了DNTF基熔铸炸药的持续金属加速作功能力;与Octol炸药相比,含铝DNTF基熔铸炸药的格尼系数提高了6.2%。     

DNTF基含铝炸药复合装药的驱动特性

设计了内外层分别由含铝质量分数为5%和20%的DNTF基炸药组成的复合装药。采用直径50mm圆筒试验测量了其爆速及圆筒壁的膨胀位移,研究了不同复合装药结构的能量释放特性,并与单一配方装药进行了对比。结果表明,内层为高爆速炸药时,爆速约为两种单一装药的平均值,后期驱动能力没有显著增强,格尼系数仅为2.86mm/μs;外层为高爆速炸药时,爆速略低于高爆速单一装药,爆轰波形具有明显的内聚特征,提高了内层低爆速炸药的能量释放速率,驱动能力持续增强,格尼系数为2.93mm/μs。     

金属柱壳约束对非理想炸药驱动效率的影响

通过分析金属柱壳在内部炸药滑移爆轰作用下的动力学响应,建立了爆轰产物压力与壳体径向膨胀位移、材料动态屈服强度之间的关系式。基于Taylor假定确定了壳体完全破裂时爆轰产物压力的阈值。以两种具有相近格尼系数的RDX基含铝炸药为例,对该模型的适用性进行了验证。结果表明,相同壳体下,与无硝酸酯的RDX基含铝炸药相比,含硝酸酯的RDX基含铝炸药的驱动能量利用率具有明显优势。当壳体材料动态屈服强度从0.2GPa增至0.8GPa时,其有效作功能的相对增量约从7.5%迅速增大至15.2%,符合战斗部实际应用中的趋势,表明该分析模型可用于非理想炸药驱动作功性能的综合评价。     

硝酸酯对RDX基含铝炸药驱动能力的影响

为了研究硝酸酯对RDX基含铝炸药驱动能力的影响,采用圆筒试验研究了含硝酸酯的RDX基含铝炸药加速圆筒壁膨胀速度和格尼能的变化过程,并与不含硝酸酯的RDX基含铝炸药进行了对比,分析了硝酸酯对炸药能量释放特性及金属驱动能力的影响。结果表明,硝酸酯可改善RDX基含铝炸药的铝氧比,改变其反应速率;在反应初期,含硝酸酯的RDX基炸药加速筒壁的速度低于不含硝酸酯的炸药,而在爆炸反应中后期,含硝酸酯的RDX基炸药加速筒壁的速度以及格尼能均高于不含硝酸酯的炸药;含硝酸酯的RDX基含铝炸药的能量释放特性使其适合用于破片战斗部中,可提高其金属驱动能力。     

炸药覆盖层厚度对爆炸焊接的影响

为提高爆炸焊接中炸药的能量利用率以及减噪降尘,采用水状胶体对炸药的上表面进行覆盖,以SUS304不锈钢板和Q235钢板分别作为复板和基板进行了爆炸焊接实验,通过实验测量和理论计算研究了不同的覆盖层厚度对复板碰撞速度的影响,并应用爆炸焊接窗口理论和光学显微镜分析了结合界面的微观形貌。结果表明,采用水状胶体作为炸药上端覆盖层可以显著提高炸药的能量利用率,相比于裸露装药,覆盖层厚度为15、30和45mm时,复板碰撞速度分别增加了38.9%、57.5%和71.9%。实验测得的炸药爆速和碰撞点移动速度一致性良好,格尼公式所预测的碰撞速度较实验值明显偏大,而考虑加速历史所获得的碰撞速度与实验碰撞速度吻合良好;金相分析表明,在焊接窗口以内,结合界面为没有孔洞、裂缝等缺陷的波形结合,并且复板的碰撞速度越大,界面波浪幅值越大,而在靠近和高于焊接窗口上限时,界面处产生孔洞、裂缝等缺陷。     

含铝典型炸药爆轰参数计算研究

用途不同,对炸药的爆速、爆压、爆热要求不一样。准确、快速计算炸药的爆轰参数对于设计指定性能新型炸药和炸药的应用研究具有十分重要的意义。本文用不同的方法对含铝炸药的爆轰参数进行了计算,采用含铝炸药经验公式计算含铝炸药的爆速、ω-Г公式方法计算的爆压、盖斯定律计算爆热,较其他计算方法计算结果相对误差小。     

低强度冲击下炸药点火的数值模拟

为了研究炸药在低强度冲击下的反应特性,根据标准的Steven试验建立了数值计算模型,采用热力耦合模型和Arrhenius方程描述炸药的热反应,对不同速度弹头撞击炸药过程进行了数值模拟计算,获得了炸药点火的弹头阈值速度,分析了弹头形状对炸药反应的影响。计算结果表明,在弹头阈值速度下,炸药点火存在一定的延迟时间,随着弹头速度的增大,延迟时间缩短;弹头形状会影响炸药受力过程,使炸药点火特性发生变化。     

LLM-105基PBX炸药的热分解反应动力学

通过布氏压力计法获得了普通的和纳米化的LLM-105基PBX炸药在不同温度条件下热分解放气量随时间的变化曲线。基于Arrhenius公式计算了两种PBX炸药分解深度为0.1%时的表观活化能。采用TG-DSC研究了两种LLM-105基PBX炸药的非等温热分解反应动力学。结果表明,由Arrhenius公式得到的普通和纳米化的LLM-105基PBX炸药在分解深度为0.1%时的表观活化能分别为74.67和138.09kJ/mol。利用Kissinger法计算获得两种LLM-105基PBX炸药在最大分解速率(分解深度约50%)下的表观活化能分别为389.26和215.73kJ/mol,与Ozawa法计算结果相吻合。升温速率趋于零时的特征分解峰值温度分别为606.94和586.48K,热爆炸临界温度分别为615.0和600.4K。相对于普通LLM-105基PBX炸药,纳米化LLM-105基PBX炸药热分解具有更高的反应活性,热感度也有所提高。     

Simplified and Extended Gurney Formulas for Imploding Cylinders and Spheres

The usefulness of the Gurney formulas in application to one-dimensional computer codes for shaped charge design has called for their extention to predict the asymptotic velocities of imploding cylinders. Two different approaches by Chou, Carleone, and Flis on 1981 and by Chanteret on 1983 have led to improvements which were shown to predict correctly two-dimensional code simulations for unconfined charges. Both works did not lead however to simple formulas which retain the conveniency of the original Gurney formulas. In the work presented, closed form analytical solutions for both the cylindrical as well as the spherical geometries are derived. The solution for each geometry is presented in a way in which the symmetry between the inner liner and the confinement is easily recognized. The relation of each solution to the Gurney formula for asymmetrical sandwich is also obvious. The presented solutions reduce to all the known Gurney formulas for the more simple geometries at the appropriate limits. The accuracy of the predictions by the obtained formulas is limited however when the assumptions of the Gurney model do not describe the real physical situation closely. This happens in general in extreme cases, e.g. when the liners are very light comparing to the explosive mass or when the ratio between the confinement radius and the inner liner radius is very large comparing to unity.     

On the inconsistency of the asymmetric-sandwich gurney formula when used to model thin plate propulsion

The asymmetric sandwich Gurney formula is used extensively worldwide during explosive reactive armor and shaped-charge war-head design, in either its original form^(1,2) or its extended form used to model implosion configurations^(3–5). It is therefore very important to realize that calculations may contradict physical observations when the formula is used to calculate the velocity of thin plates having mass which is smaller than half the explosive mass per unit area. This inconsistency between calculation and experimental results is explained as resulting from the failure of the assumption made in deriving all the Gurney formulas that the velocity distribution of the explosive products is a linear function of the expansion coordinate.     

Improved Gurney Formulas for Exploding Cylinders and Spheres using “Hard Core” Approximation

The final liner velocity predicted by the Gurney formulas for sandwich cylindrical and spherical configurations for very light liners (small M/C values) are (6E)^1/2, (4E)^1/2 and (10E/3)^1/2 respectively. The existance of these differences among the limiting velocity values contradicts the well known fact that the explosive products' escape velocity does not depend on the initial geometry of the explosive when no Mach waves are formed. An improvement to the Gurney formulas for exploding cylinders and spheres is suggested which corrects this basic inconsistancy. It is based on the observation that light liners are accelerated to their final velocity in a short time getting their kinetic energy mainly from that part of the explosive which is in contact with them. It is shown that by excluding from the explosive mass the inner volume and replacing it with an infinitely hard core the experimentally measured liner velocities for the cylindrical and spherical geometrics are more accurately reproduced. The core radius is found by maximizing the liner velocity, thus getting the fastest transformation of the gas potential energy to kinetic energy which is possible within the model assumptions. The improved formulas predict for the limit of very small M/C the same velocity, (6E)^1/2 for all the above mentioned geometries. The comparison of the improved formulas with available experimental data reveals how the accuracy of the Gurney model is limited at the large and the small values of M/C.     

Validation of the Gurney Model in Planar Geometry for a Conventional Explosive

The analytical model developed by Gurney is a seminal tool for analyzing the acceleration of metal flyers driven by detonating high explosives. Despite the continued relevance of this model, relatively few experimental validations over a wide range of flyer‐to‐charge mass ratios exist in the open literature. The current study presents experimental results for planar aluminum flyers propelled by a conventional explosive over a range of mass ratios varying from 4.65 to 0.03. Flyer velocity was measured via Heterodyne Laser Velocimetry (PDV), permitting a continuous measurement of the acceleration process. Measured flyer velocities are compared to terminal velocity estimations from the Gurney model. Experimental terminal velocities are compared to the open face and asymmetric sandwich Gurney models. Excellent agreement is observed for terminal velocity predictions considering the gasdynamic simplifications inherent in the model formulation.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Equivalence – I Ductile Casings

The initial velocity of casing fragments from bombs, shells etc. was first calculated by R. W. Gurney in 1943 [1]. Subsequent to this derivation by Gurney, which was based on a reasonable simplification of the case and gas dynamics, his wartime co‐worker, U. Fano [2], claimed to have calculated the proportion of kinetic energy remaining with the explosive gases following energy partition with the casing. This paper shows that both Fano’s equation for cased charge blast equivalence and a further derivation by Fisher in 1953 [3], based on Fano’s, are in fact inconsistent with Gurney’s reasonable physical model. Neither of these two reports has ever been the subject of independent peer‐review, despite having been extensively cited. This paper identifies the error made by Fano and copied by Fisher and draws attention to an alternate equation recently published by the author which gives similar predictions to that of Fisher, while being consistent with Gurney’s original derivation. Also, this paper establishes for the first time that the use of such equations for cased charge blast impulse equivalence is valid.     

Fragment Velocity Distribution of Cylindrical Rings Under Eccentric Point Initiation

A design mode, in which a casing is filled with a charge initiated off‐centre (eccentric point initiation), is common in the field of explosion and structural protection. The fragment velocity distribution along the circumference of the casing is distinctly non‐uniform due to the difference in blast loading around the circumference of the casing. To quantify the fragment velocity distribution, two kinds of cylindrical rings with different structural parameters were adopted. Static explosive experiments with three eccentric coefficients (0, 0.5, 1.0) were conducted with pulsed X‐ray diagnostics. Using coefficients derived from experimental data and calculating the effects of both the eccentricity of initiation and angle around the circumference, an angle‐dependent ratio β_θ of charge mass to casing mass has been derived as a mean to modify the fragment velocity formula of Gurney for this application. The derived formula was shown to correctly predict the fragment velocity distribution around the circumference of the cylindrical ring. The calculated velocity distributions show good agreement with the experimental results.     

Flyer Plate Motion by Thin Sheet of Explosive

Acceleration of a metal plate by explosive energy at low value of charge to metal mass ratio has been studied by employing a new theoretical model based on uniform pressure and density of detonation products behind the flyer plate. Theoretical velocities of flyer plates have been compared with those measured by radiographic technique and found in good agreement. Comparing the relations for plate velocity, obtained from the present model and earlier Gurney model at low C/M values, an analytical expression for Gurney energy has been obtained in terms of detonation velocity of the explosive and adiabatic exponent of the detonation products.     

装药结构参数对轴向预制破片抛掷速度的影响

为研究柱形装药长径比与装药壳体厚度等结构参数对轴向预制破片抛掷速度的影响规律,以Gurney公式的假设为基础,提出爆轰产物二维运动假设条件,推导并得到轴向预制破片抛掷速度与装药长径比和装药壳体厚度之间的关系式.模拟了柱形带壳装药结构对轴向驱动预制破片抛掷速度的影响,所得结果与文献值吻合.用数值模拟结果修正关系式,得到柱形带壳装药结构参数对轴向预制破片抛掷速度的影响规律,以及轴向预制破片抛掷速度沿径向的分布规律.     

颗粒物料临界速度和沉降速度的工程计算

在流化床干燥器(或冷却器)、气流干燥器、流化床吸收器、流化床反应器及气力输送等的工程设计中,颗粒物料的临界速度、沉降速度是主要的工艺参数,计算公式多,但这些公式的局限性较大.介绍了临界速度、沉降速度和操作速度的常用计算公式和计算实例,认为用普拉诺夫斯基修正式进行工程计算不需要进行区间判断,适用于床层孔隙率ε＝0.4～1.0的任何场合.