装药结构对破片初速影响特性

为了满足低附带战斗部的毁伤效果,将炸药与破片混合形成新型混合装药模式。在混合装药模式中,为了研究不同装药结构对破片初速的影响特性,设计了3种不同装药结构并进行数值模拟和试验;对比发现,数值模拟与试验结果规律吻合,破片的初速与装药结构有一定的关系。根据试验数据拟合了3种不同装药结构中破片最大速度曲线对比图,通过分析得出:不同装药结构中,炸药与破片分层越多,爆轰瞬间,相邻炸药所产生爆轰效果会发生叠加,爆轰波对破片的驱动效果会增强,则破片的初速也就越大。     

爆轰波斜冲击作用下破片飞散特性研究

为研究非对称结构战斗部的破片飞散特性,利用斜激波理论对爆轰波作用于壳体表面的过程进行研究,并利用自由面速度倍增定律对波在自由面反射后质点速度的计算进行简化,得到了破片飞散角的计算模型。利用D型战斗部试验数据对计算模型进行验证,结果表明,斜激波理论计算得到的破片飞散与试验结果吻合很好;当入射角较小时,壳体飞散角与入射角成线性关系。     

钨合金(碳化钨)柱形预制破片战斗部对均质钢甲的毁伤效能分析

针对现代战争的需要,特别是对战场轻型装甲的攻击需要,基于预制破片技术,以柱形杆(钨合金)预制破片为对象建立物理模型,对其破片尺寸、装药形式及尺寸的相互关系进行分析,进而通过引入TBM战斗部设计的关系式对所建模型的破片进行速度预报,依照该速度按照侵彻理论推算其对均质钢甲的毁伤效能。结合分析结果指出了柱形杆(钨合金)预制破片战斗部在攻击均制钢甲方面的优点。     

装备战场损伤试验布局设计仿真研究

装备战场损伤试验存在实施难度大,试验效率低的问题。为提高试验效能,采用AUTODYN,建立预制破片战斗部有限元仿真模型,模拟了战斗部爆炸及预制破片飞散的过程,仿真结果同实弹试验所采集数据基本吻合,验证了所用模拟方法的有效性。通过分析破片侵彻靶板的损伤规律,建立了球形破片撞击靶板损伤相图,结合破片飞散规律,建立了试验布局参考相图。研究结果表明:预制破片战斗部的爆炸及对装备的打击过程,能够通过数值仿真方式准确的进行模拟,从而大大减少试验费用;所建立的试验布局参考相图,能够为试验布局的设计和优化提供一定的参考。     

活性破片飞散特性及毁伤效应研究

为了掌握活性破片的空间飞散特性及毁伤效能,采用数值仿真与试验相结合的方法研究了某预制活性破片战斗部在爆炸作用下的飞散特性,得到了活性破片的空间分布和初始速度分布参数的有关数据,分析了活性破片对靶板的毁伤规律.结果表明:活性破片战斗部在起爆300 μs后,70％的活性破片速度分布在1 500～2 000 m/s;50％的...     

轴向和环向双聚焦破片战斗部壳体形状设计

破片定向聚焦是战斗部实现高效毁伤的重要途径。基于Shapiro公式和壳体微元分析方法,提出一种轴向和环向双聚焦破片战斗部壳体形状设计方法,可根据需要的聚焦程度设计对应的壳体形状,利用LS-DYNA中ALE算法对设计的壳体飞散过程进行数值模拟,并考察了壳体形状对破片分布的影响。结果表明:设计的壳体可实现破片在轴向和环向2个方向聚焦飞散,从而获得较大的破片密度增益。     

杀伤战斗部破片定向飞散特性研究

研究了钢预制破片壳体在四种装药爆轰驱动下的飞散特性。求得了使破片飞行路径呈平行型的预制破片壳体的临界半径及相应的破片初始速度。     

双球破片冲击柱壳装药的临界起爆条件

为了研究导弹战斗部(柱壳装药)在破片场中的累积毁伤问题,在现有单破片起爆平板装药的Jacobs-Roslund经验准则的基础上,分别建立了考虑破片尺寸、破片撞击角度、柱壳装药的装药半径和壳体厚度的单球破片、双球破片冲击柱壳装药临界起爆条件的工程分析模型.该模型计算结果与数值模拟结果和现有试验结果相吻,证明利用该模型能较...     

随动定向战斗部破片飞散特性研究

针对防空导弹常规破片式杀伤战斗部使用中存在能量利用率低的缺陷,提出采用随动定向战斗部的观点。建立随动定向战斗部的破片动态飞散区和飞散速度的计算模型,采用数值解析方法,解决在复杂弹目交会条件下破片的飞散区域与打击速度的计算问题．并用MATLAB软件对建立的模型进行验证,得出仿真结果与实际结果一致,这表明模型是合理、正确的。     

可变形定向破片战斗部模型试验和数值模拟研究

基于可变形定向破片战斗部的作用原理,设计了试验结构模型,并对其进行了静爆试验研究。根据试验结果,建立了有限元分析模型,利用LS-DYNA程序对可变形定向战斗部变形过程以及破片的飞散过程进行了数值模拟。结果表明,在目标方向破片密度和速度都有较大幅度增益,数值模拟与试验结果比较吻合。     

Effect of the end cap on the fragment velocity distribution of a cylindrical cased charge

The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been con-ducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang's formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.     

Deformation,fragmentation and acceleration of a controlled fragmentation charge casing

Two different finite element software, LS-DYNA and Impetus, have been evaluated to test their ability to predict the deformation, fragmentation and acceleration of a controlled fragmentation charge casing. The general-purpose program LS-DYNA was used with a multi-material ALE formulation and a mass-preserving erosion criterion coupled to a Johnson-Cook fracture criterion. In the Impetus simulations, a third order Lagrangian element formulation was used for the casing and a node-splitting element erosion treatment coupled to a Cockcroft-Latham failure criterion was used to describe casing fracture. The high-explosive gases were described by a discrete particle formalism.In order to acquire data to validate our computational tools and constitutive models, a series of experiments have been performed using a laboratory charge with an internal grooved casing. In the test series, the charge geometry was fixed except that the groove depth were varied from very shallow to very deep resulting in different deformation patterns, fracture modes and terminal velocities. Various diagnostic tools captured the different stages of the expansion and fragmentation of the casing. A high-speed framing camera depicted the deformation pattern before fragmentation and was used to determine the moment when the casing failed. Three different complementary techniques were used to follow the acceleration of the fragments; a Photon Doppler velocimetry to determine the initial acceleration of the casing, double exposed radiographs to estimate the fragment velocity after break-up and a high-speed video to determine the terminal velocity of the fragment after leaving the fireball. In addition, the fragments were soft recovered in a set of sawdust pit tests and their final shape and weight were measured. A SEM was used to characterise the fracture surfaces and to determine the modus of fracture (tensile or shear failure).Comparisons to experiments show that both software can predict the change in deformation behaviour when the groove depth increases, from tangential necking for shallow grooves to radial punching for deep groves. Both software could also reasonable well predict the acceleration of the fragments, though both overestimates the terminal velocity for the charge with the deepest grooves.     

利用MSC/DYTRAN程序仿真分析导弹战斗部立方体破片的侵彻威力

对反辐射导弹的破片杀伤战斗部中较为常见的立方体破片的 3种典型姿态侵彻 (尖端、棱边及正面侵彻 ) 4mm厚 94 5钢的侵彻过程进行仿真数值计算 .通过仿真计算 ,结合实验结果比较 ,得出结论 :不同初始侵彻姿态的立方体破片在侵彻过程中 ,由于旋转角速度的作用及稳定性的要求 ,破片的侵彻姿态将趋于正面侵彻 .不同姿态的侵彻 ,侵彻威力相差不大     

Experimental studies of explosion energy output with different igniter mass

For study the energy output law of cylindrical charge with shell induced by different input energies, four different black powder masses were selected to ignite the main charge. Fragmentation degree of the shell was qualitatively analyzed by the area of holes on the witness plate and the recovered fragments mass. Through theoretical analysis, established the functional relationship between the average mass of fragments and the relative energy output of warhead, obtained how the relative energy output of charge changed with different initial energy input. The results showed that the change of input energy could lead to obvious variation in fragment characteristics, and could also control the output of charge. When the igniter mass increases from 1.55 g to 5.00 g, the relative energy output of the charge increases by 26.28%. Excessive initial input energy will destroy the shell confine in advance, resulting in a decrease in the relative energy output of charge.     

Effect of tongue clearance on hydraulic performance of double support vortex pump

In order to study influence of tongue clearance on the hydraulic performance of double support vortex pump, three dimensional flow model with symmetric variable size tongue clearance was established by changing section parameter of tongue clearance, and applied to numerically simulate the steady inner flow in a vortex pump based on fixed working conditions and impeller through ANSYS FLUENT. The numerical results show the influence of tongue channel with two sections (non-uniform and uniform sections) on flow field characteristics in vortex pump. Firstly, the variation of tongue channel section changes the vortex structure distribution in circumferential flow channel. Specifically the spiral forward vortex structure in the circumferential direction shifts to large radius side with increasing tongue width. Secondly, the circumferential velocity gradient and axial pressure gradient both diminish with the increase of the tongue section, and the inlet/outlet pressure difference and velocity distribution also reduce with increasing tongue channel section. Finally, for vortex pump with non-uniform section of tongue channel, the head diminishes and the efficiency remains constant approximately with the increase of the tongue width, while the head and the efficiency both diminish for uniform section of tongue channel.     

Real-time calculation of fragment velocity for cylindrical warheads

To simulate explosion fragments, it is necessary to predict many variables such as fragment velocity, size distribution and projection angle. For active protection systems these predictions need to be made very quickly, before the weapon hits the target. Fast predictions also need to be made in real time simulations when the impact of many different computer models need to be assessed. The research presented in this paper focuses on creating a fast and accurate estimate of one of these variables - the initial fragment velocity. The Gurney equation was the first equation to calculate initial fragment velocity. This equation, sometimes with modifications, is still used today where finite element analysis or complex mathematical approaches are considered too computationally expensive. This paper enhances and improves Breech’s two-dimensional Gurney equation using available empirical data and the principals of conservation of momentum and energy. The results are computationally quick, providing improved accuracy for estimating initial fragment velocity. This will allow the developed model to be available for real-time simulation and fast computation, with improved accuracy when compared to existing approaches.     

Simulation of natural fragmentation of rings cut from warheads

Natural fragmentation of warheads that detonates causes the casing of the warhead to split into various sized fragments through shear or radial fractures depending on the toughness,density,and grain size of the material.The best known formula for the prediction of the size distribution is the Mott formulae,which is further examined by Grady and Kipp by investigating more carefully the statistical most random way of portioning a given area into a number of entities.We examine the fragmentation behavior of radially expanding steel rings cut from a 25 mm warhead by using an in house smooth particle hydrodynamic(SPH) simulation code called REGULUS.Experimental results were compared with numerical results applying varying particle size and stochastic fracture strain.The numerically obtained number of fragments was consistent with experimental results.Increasing expansion velocity of the rings increases the number of fragments.Statistical variation of the material parameters influences the fragment characteristics,especially for low expansion velocities.A least square regression fit to the cumulative number of fragments by applying a generalized Mott distribution shows that the shape parameter is around 4 for the rings,which is in contrast to the Mott distribution with a shape parameter of 1/2.For initially polar distributed particles,we see signs of a bimodal cumulative fragment distribution.Adding statistical variation in material parameters of the fracture model causes the velocity numerical solutions to become less sensitive to changes in resolution for Cartesian distributed particles.     

Theoretical and numerical investigations on the headspace of cartridge cases considering axial deformation and movement

The cartridge case headspace is the axial clearance between the cartridge and bolt of an automatic weapon, and influences the reliability and security of the weapon. Accordingly, theoretical and numerical studies were conducted to analyze the dynamic response of cartridge cases during internal impact considering the initial radial clearances between the cartridge case and chamber. A theoretical model was proposed to predict the cartridge case headspace considering both the deformation and movement of the cartridge case and confirmed by the results of nonlinear finite element simulations. The differences between the results of the conventional static model and the dynamic model were then comprehensively evaluated. The effects of the angle between the cartridge and chamber, the cartridge case material, and the internal impact pressure on the predicted headspace value were also analyzed. The dynamic response of the cartridge case predicted by the dynamic model was more accurate than that predicted by the conventional static model. The internal impact pressure, pressure change rate, and cartridge material were all found to affect the predicted headspace.     

Numerical investigation on free air blast loads generated from center-initiated cylindrical charges with varied aspect ratio in arbitrary orientation

In current guidelines, the free air blast loads (overpressure and impulse) are determined by spherical charges, although most of ordnance devices are more nearly cylindrical than spherical in geometry. This may result in a great underestimation of blast loads in the near field and lead to an unsafe design. However, there is still a lack of systematic quantitative analysis of the blast loads generated from cylindrical charges. In this study, a numerical model is developed by using the hydrocode AUTODYN to investigate the influences of aspect ratio and orientation on the free air blast loads generated from center-initiated cylindrical charges. This is done by examining the pressure contours, the peak overpressures and impulses for various aspect ratios ranged from 1 to 8 and arbitrary orientation monitored along every azimuth angle with an interval of 5°. To characterize the distribution patterns of blast loads, three regions, i.e., the axial region, the vertex region and the radial region are identified, and the propagation of blast waves in each region is analyzed in detail. The complexity of blast loads of cylindrical charges is found to result from the bridge wave and its interaction with primary waves. Several empirical formulas are presented based on curve-fitting the numerical data, including the orientation where the maximum peak overpressure emerges, the critical scaled distance beyond which the charge shape effect could be neglected and blast loads with varied aspect ratio in arbitrary orientation, all of which are useful for blast-resistant design.