药型罩切分方式对射流形成影响的数值模拟

为了研究药型罩切分方式对其形成射流性能的影响,利用数值模拟软件ANSYS/LS-DYNA对横向切分和纵向切分的药型罩以及未切分药型罩在爆轰波作用下形成射流的过程以及对45号板的侵彻能力进行了数值模拟,比较了不同切分方式的药型罩在爆轰波作用下形成射流的形状、头尾部速度、拉伸长度和抗拉伸性能及其对45号钢板的侵彻能力。结果表明,在相同装药条件下,横向切分药型罩相比纵向切分药型罩的头部速度提高约220m/s,且抗拉伸性能更好,对45号钢板的侵彻深度提高约3.26cm;横向切分药型罩相比未切分药型罩的头部速度提高约360m/s,对45号钢板的侵彻能力提高约5.62cm。     

一种新型M形顶部结构药型罩的设计及形成射流的侵彻能力分析

在锥角药型罩结构基础上通过改变其顶部结构设计了一种新型M形顶部结构药型罩,并分析了其射流头部的形成机理;采用有限元软件ANSYS/LS-dyna对在爆轰波作用下M形顶部结构药型罩射流的形成过程,以及对45号钢板的侵彻过程进行了数值模拟,并与锥角药型罩、平顶药型罩形成射流的头尾部速度、拉伸长度、杵体大小以及对45号钢板的侵彻能力进行了对比。结果表明,M形顶部结构药型罩的M形顶部结构在爆轰波作用下经二次汇聚形成了射流头部,相同装药条件下,其形成射流的头部速度相比锥角药型罩形成射流的头部速度提高约9.10%,比平顶药型罩形成的射流头部速度提高约5.56%;其侵彻深度比锥角药型罩提高约10.4%,比平顶药型罩提高约7.28%。     

一种喇叭-锥角结合药型罩形成射流的数值模拟

为了提高锥角药型罩装药结构的侵彻能力,通过改变其顶部锥角为喇叭形研发了一种新型喇叭-锥角结合药型罩。采用模拟软件ANSYS/LS-DYNA对喇叭-锥角结合药型罩、平顶药型罩、锥角药型罩在爆轰波作用下射流的形成以及对45号钢板的侵彻过程进行数值模拟,并对3种药型罩形成的射流参数如头部速度、射流断裂时间等以及对45号钢板的侵彻性能进行了对比。结果表明,在装药口径为80mm、装药高度为100mm的圆柱和圆锥结合型装药结构的条件下,喇叭-锥角结合药型罩形成的射流头部速度为7 690m/s,比锥角药型罩形成的射流提高约9.54%,对45号钢板的侵彻深度提高约19.82%;比平顶药型罩形成的射流头部速度提高约6.36%,对45号钢板的侵彻深度提高约12.25%。     

钨铜粉末药型罩形成聚能射流的数值模拟

利用LS-DYNA3D软件对钨铜粉末药型罩聚能射流的形成过程进行了数值模拟,采用多物质ALE算法,模拟了钨铜聚能射流的形成过程,并与实验结果进行了对比。结果表明,随着药型罩密度的增加,射流直径变细,头部速度降低,数值模拟结果与实验结果较一致。     

贴隔板法形成尾翼型EFP的试验研究及数值模拟

通过合理设计隔板的几何尺寸和炸药的装药量,对在药型罩凸面粘附隔板的方法形成尾翼型爆炸成型弹丸(EFP)进行试验研究.同时利用LS-DYAN对新方法形成的尾翼进行数值模拟,通过数值计算得到了药型罩微元上的压跨速度和压力曲线,从药型罩微元压跨速度变化和药型罩表面爆轰压力变化的角度出发,分析了新方法形成尾翼的可行性.试验与数值模拟结果表明,贴隔板法可以形成尾翼型EFP.     

变壁厚双层药型罩壁厚匹配的数值计算与实验验证

参考变壁厚药型罩和双层药型罩的结构优点,根据能量利用的观点提出了一种新型变壁厚双层药型罩,采用正交实验及AUTODYN有限元软件对药型罩的结构参数进行优化并通过试验进行了验证。数值计算结果表明,在同等装药量下,由变壁厚双层药型罩形成的侵彻体的性能要优于由变壁厚药型罩或双层药型罩形成的侵彻体的性能。与常用的等壁厚单层药型罩相比,射流头部速度增大559m/s,射流质量基本不变,铜的利用率提高了19.1%。由变壁厚双层药型罩形成的侵彻体可以提高战斗部的侵彻能力,同时也有利于节约昂贵的金属材料。     

线性聚能装药切割岩石的数值模拟

运用改进的MOCL程序,数值模拟了线性聚能装药金属射流的形成以及射流侵彻岩石的全过程,得到了锥角为60°的聚能装药结构爆轰产物膨胀、药型罩变形、射流形成过程及锥角为60°和90°时的射流速度梯变分布。不同时刻射流的分布显示,在拉伸过程中,锥角为60°的聚能射流速度变小,速度梯度较大,头部速度为4500m·s-1;锥角为90°的聚能射流,头部速度为3500m·s-1速度梯度较小,与实际物理过程相一致。结果表明,模拟结果基本符合聚能射流的物理现象和规律,说明采用的物理模型和数值算法是合理的。     

变壁厚石油射孔弹聚能射流形成的影响因素分析

为研究药型罩锥角、壁厚等对石油射孔弹聚能装药引爆形成的聚能射流影响,利用有限元分析软件ANSYS/LS-DYNA,采用ALE方法对变壁厚石油射孔弹聚能射流的形成过程进行了模拟分析,得出型罩结构与射流头部速度的关系。研究结果表明,药型罩锥角越大,射流速度越小,形成的杵体长度相比于射流的长度也越小;同锥角药型罩壁厚越小,聚能射流的形态发育得越好,药型罩壁厚越大,射流速度越低。     

基于修正SPH方法的爆轰波绕射传播的数值模拟

为研究内置金属球体的球壳装药在一点起爆情况下的非理想爆轰波的传播行为,基于修正的光滑粒子流体动力学(SPH)方法进行绕射爆轰波传播的数值模拟,并应用一种工程上简便的近似计算方法对该球壳装药模型的爆轰波传播时间进行计算.结果表明,数值模拟的特征爆轰时间与理论计算结果非常吻合,验证了修正SPH方法在爆炸数值模拟领域的可行性.     

局部变壁厚球缺型药型罩侵彻威力性能的数值模拟及试验验证

为了提高聚能杆式射流的侵彻威力性能,设计了3种药型罩罩口边缘局部变壁厚球缺型药型罩,并采用LS-DYNA软件对3种不同结构球缺型药型罩的成型过程进行数值模拟,研究了不同结构药型罩的杆式射流对侵彻靶板威力性能的影响,并通过试验对模拟结果进行验证。数值模拟结果表明,与等壁厚球缺型药型罩相比,罩口端外壁采用局部凸弧、平弧、凹弧结构时,杆式射流穿孔深度分别增加8.4%、10.9%、19.5%,且平均开孔孔径分别增加2.4%、7.2%、5.5%;其中,采用凹弧结构时侵彻深度最大,采用平弧结构时平均开孔孔径最大。试验结果表明,相对于等壁厚球缺型药型罩,采用局部平弧球缺型药型罩可在提高战斗部穿孔深度的同时兼顾开孔威力要求。试验结果与数值模拟结果具有较好的一致性。     

Initiation of an explosion of a single bubble and bubble detonation

Interaction of a single chemically active bubble in water with acoustic waves is numerically studied within the framework of the model of a two-dimensional unsteady flow of an ideal compressible medium. The boundaries between the phases are explicitly identified. It is demonstrated that bubble explosion initiation can be determined by the character of bubble deformation. Nonsphericity of deformation and jet formation lead to an explosion even if the bubble does not collapse. The possibility of the bubble explosion in an expansion wave, transfer of detonation from one bubble to another, and, thus, emergence of bubble detonation is demonstrated.     

Studies of shaped charges with built-in asymmetries. Part II: Modelling

A well-characterized shaped charge was used to study the influence of asymmetrical initiation on the jet. An experimental study yielded flash radiographs of the jets from charges fired with the initiation point offset 2, 4, 6, 8 and 10 mm, respectively, from the central axis. The axial and lateral velocities of the jet particles were determined from the sets of radiographs. In a previous paper it was hypothesized that a simple relationship might exist between the departure vectors of the jet particles and the geometry of the impingement of the detonation front on the liner. Any part of the jet from an asymmetrically initiated shaped charge departs at an angle determined by the difference between the current angle between the actual detonation wave where it contacts the liner, and that which would have arisen had the initiation been perfectly axial. We set up a simple computer code which evaluates, for any given initiation offset distance, the instantaneous angles between the detonation front and the successive elements of the liner which are encountered as the wave sweeps along it. Since it is possible to map particle velocities in the jet on to those regions of the liner where they originated, simulated sets of axial and lateral jet velocities were readily generated. Agreement between theory and experiment is sufficiently close to suggest that our approximation is useful and can assist in understanding the jet dynamics of asymmetrically initiated shaped charges.     

Initiation of detonation of fuel-air mixtures in a flow-type annular combustor

Initiation of detonation in a fuel-air mixture flow formed in an annular cylindrical combustor 306 mm in diameter is studied. The source of detonation initiation is the detonation wave entering the annular channel from a plane-radial vortex chamber, a jet of products, or a low-power heat pulse. It is demonstrated that continuous spin detonation (CSD) can be ensured by all these methods. Its formation is accompanied by a transitional process with a duration up to 10 ms, which is associated with violation of injection of the species (initiation by the detonation wave) or with the time of evolution of tangential instability in CSD (jet or spark initiation). Transfer of detonation to a flow of fuel-air mixtures with low chemical activity (propane-air, methane-air, kerosene-air, and gasoline-air mixtures) by the initiating detonation wave formed within fractions of a millisecond by a low-energy pulse or as a result of self-ignition of the hydrogen-air mixture in the plane-radial vortex chamber is realized. It is found that organization of CSD in these mixtures requires combustors with greater (than 306 mm) diameters. A possibility of CSD in kerosene-air and gasoline-air mixtures with low chemical activity by means of air enrichment by oxygen ahead of the combustor entrance is demonstrated.     

Studies on jet formation and penetration for a double-layer shaped charge

An analysis for liner collapsing and jet/slug formation of a double-layer shaped charge (DLSC) is presented. Variations of the collapse angle, collapse velocity, and jet velocity of the DLSC are discussed. Numerical simulations based on the Lee-Tarver model are performed to have an insight into the jet formation. Ballistic tests are conducted using a conical (60°) metal liner 56 mm in diameter to have a contrast with an ordinary shaped charge jet. It is shown that the collapse angle and velocity are both increased by the convergent detonation wave in the DLSC. The jet velocity, kinetic energy, and ballistic capability are significantly increased by using the DLSC, and the DLSC is an efficient way to improve shaped charge performance.     

Methodology for simulation of the jet formation process in an elongated shaped charge

The performance of linear shaped charges depends on several different parameters. The density, the detonation velocity of the explosive, the shape of the detonation wave, the shape and wall thickness of the liner, and the distance of the shaped charge from the target are among the parameters that can be optimized by using computer simulation methods. In this paper, the jet formation process in a linear shaped charge and its action on an obstacle are simulated by using the LS-DYNA software. The results obtained are compared with experimental data.     

Numerical simulation of the influence of an axially asymmetric charge on the impact initiation capability of a rod-like jet

With the aim to improve the impact initiation capability of a rod-like jet, this paper presents the influence of an axially asymmetric shaped charge on the jet studied by means of numerical simulations. According to Held’s initiation criterion, the impact initiation capability of the jet is affected by the jet tip velocity and diameter. The detonation radius over the longitudinal axis, restricted by the charge radius over the same axis, affects the detonation wave in the charge, the force acting on the liner, and, therefore, the jet velocity and shape. Based on these laws, the structure of the axially asymmetric charge is optimized. Compared with axisymmetric jets, axially asymmetric rod-like jets possess a higher impact initiation capability.     

Generation of Hypervelocity Particle Flows by Explosive Compression of Ceramic Tubes

The compression of ceramic (corundum) tubes by the detonation products of explosives have been studied experimentally and numerically. The formation of the shaped-charge jet of ceramic particles and its effect on steel witnesses targets has been investigated. The tubes were produced by detonation spraying. Ceramic particles were deposited on copper tubes, which were then dissolved in a solution of ferric chloride. In the experiments, a considerable penetration of the flow of ceramic particles was observed. During the interaction of the flow with the target, the target material was partially evaporated, as shown by metallographic analysis. Numerical analysis of the formation of the discrete shaped-charge jet showed that the maximum velocity of the jet head was about 23 km/s, and the velocity of the main part of the jet was about 14 km/s.     

Detonation synthesis of nanoscale silicon carbide from elemental silicon

Direct reaction of precursors with the products of detonation remains an underexplored area in the ever-growing body of detonation synthesis literature. This study demonstrated the synthesis of silicon carbide during detonation by reaction of elemental silicon with carbon products formed from detonation of RDX/TNT mixtures. Continuum scale simulation of the detonation showed that energy transfer by the detonation wave was completed within 2–9 μs depending on location of measurement within the detonating explosive charge. The simulated environment in the detonation product flow beyond the Chapman-Jouguet condition where pressure approaches 27 GPa and temperatures reach 3300 K was thermodynamically suitable for cubic silicon carbide formation. Carbon and added elemental silicon in the detonation products remained chemically reactive up to 500 ns after the detonation wave passage, which indicated that the carbon-containing products of detonation could participate in silicon carbide synthesis provided sufficient carbon-silicon interaction. Controlled detonation of an RDX/TNT charge loaded with 3.2 wt% elemental silicon conducted in argon environment lead to formation of ～3.1 wt% β-SiC in the condensed detonation products. Other condensed detonation products included primarily amorphous silica and carbon in addition to residual silicon. These results show that the energized detonation products of conventional high explosives can be used as precursors in detonation synthesis of ceramic nanomaterials.