水下可移动多弹气动发射系统设计与仿真分析

针对水下可移动多弹气动发射的研究需求,对水下可移动多弹气动发射系统进行了整体设计,重点研究了弹丸的气动发射技术,建立了水下可移动多弹气动发射结构模型。通过对发射单元的有限元分析,发现发射筒与分割气室上下接触面的应变和变形量最大,但最大应变和变形量数值较小,3个发射筒往中心微偏,对发射过程没有影响。最后进行了试验研究,通过分析图片中弹丸的移动距离,绘制了水下弹丸发射的位移-时间曲线和速度-时间曲线,验证了多弹发射系统设计的可行性及可靠性,对水下发射过程中的空化现象、多弹干扰技术、水下弹道控制以及流场显示等方面的研究有重要的意义。     

On high explosive launching of projectiles for shock physics experiments

The hydrodynamic operation of the "Forest Flyer" type of explosive launching system for shock physics projectiles was investigated in detail using one and two dimensional continuum dynamics simulations. The simulations were numerically converged and insensitive to uncertainties in the material properties; they reproduced the speed of the projectile and the shape of its rear surface. The most commonly used variant, with an Al alloy case, was predicted to produce a slightly curved projectile, subjected to some shock heating and likely exhibiting some porosity from tensile damage. The curvature is caused by a shock reflected from the case; tensile damage is caused by the interaction of the Taylor wave pressure profile from the detonation wave with the free surface of the projectile. The simulations gave only an indication of tensile damage in the projectile, as damage is not understood well enough for predictions in this loading regime. The flatness can be improved by using a case of lower shock impedance, such as polymethyl methacrylate. High-impedance cases, including Al alloys but with denser materials improving the launching efficiency, can be used if designed according to the physics of oblique shock reflection, which indicates an appropriate case taper for any combination of explosive and case material. The tensile stress induced in the projectile depends on the relative thickness of the explosive, expansion gap, and projectile. The thinner the projectile with respect to the explosive, the smaller the tensile stress. Thus if the explosive is initiated with a plane wave lens, the tensile stress is lower than that for initiation with multiple detonators over a plane. The previous plane wave lens designs did, however, induce a tensile stress close to the spall strength of the projectile. The tensile stress can be reduced by changes in the component thicknesses. Experiments verifying the operation of explosively launched projectiles should attempt to measure porosity induced in the projectile: arrival time measurements are likely to be insensitive to porous regions caused by damaged or recollected material.     

不同结构弹体侵彻混凝土靶板数值模拟

针对用传统结构弹体进行侵彻数值模拟得到的加速度曲线与实测加速度曲线相差较大的问题,提出细化弹体结构进行数值模拟实验的方法。应用ANSYS／LS—DYNA对传统结构弹体和细化结构弹体侵彻8层混凝土靶板进行数值模拟,提取了两组加速度曲线;设计了打靶试验方案,获得实测加速度曲线。将两组仿真曲线与实测曲线比较后发现,细化结构弹体仿真加速度曲线更接近实测曲线。因此在数值模拟研究中,利用细化结构弹体得到的曲线更具有参考价值。     

易熔合金引信弹道安全的气动热力学建模仿真

为使易熔合金引信可靠延期解除保险以保证弹道安全,需要根据弹丸速度确定在安全时间和距离内引信易熔合金的熔点。以瑞士厄利空2ZLa/353式35 mm 双管自行高射炮爆破燃烧榴弹 KZVD 引信为例,从工程的角度出发,简化了外弹道,在初始弹速为1175 m/s 和误差范围为±15 m/s 的条件下,采用气动加热理论对榴弹外弹道起始阶段弹头驻点的温度进行了理论建模计算和仿真验证,通过分析相应弹速下的弹头驻点温度确定出满足安全距离要求的易熔合金熔点温度。仿真结果表明,理论计算与仿真试验确定出1160-1190 m/s 初始弹速范围内的易熔合金熔点温度的结果一致,因此可以利用该热力学模型并根据弹道安全要求来设计相应熔点的易熔合金引信,所用方法可以为高速飞行弹体的热力学研究提供参考。     

平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟

利用有限元软件ABAQUS建立模拟模型,开展38CrSi钢弹体撞击2A12-T4铝合金板数值模拟研究,分析撞击过程中弹体撞击角度对弹道姿态及靶体失效特性的影响。基于数值仿真和实验结果,分析靶体的失效特性,确立不同撞击条件下靶体主要失效模式的转变规律,以及由此对靶体抗撞击性能的影响。研究结果表明：弹体的弹道极限速度随其撞击角度的增大先减小后增大,弹道极限速度在撞击角度约为15°时达到最小值;弹体撞击角度对靶体失效模式存在很大影响,随着弹体撞击角度的增大,靶体主要失效模式由剪切破坏逐渐过渡到撕裂破坏,靶体的撕裂程度不断加剧;弹体初始撞击角度和速度对其在撞击过程中的弹道姿态存在影响,在弹道极限速度附近表现尤为显著。     

Research on intelligent launching control of dual clutch transmissions based on adaptive neural fuzzy inference system

Vehicle launching has an important influence on driving performance of the vehicle. For vehicles with dual clutch transmissions (DCT), the clutch torque control is the key to the launching control. Therefore, a data-driven control method for DCT launching process based on adaptive neural fuzzy inference system (ANFIS) is proposed. Firstly, the vehicle test data during launching process is collected and the optimal clutch torque is obtained based on multi-objective particle swarm optimization (MOPSO). Afterward, to learn the launching control rules from optimization results, the combination of neural network and fuzzy logic algorithm, referred to as an ANFIS, is established. The dataset of the optimized launching clutch torque is utilized to train the ANFIS controller. Finally, the simulation and test results show that the data-driven control can accurately learn the launching control rules from the optimality, thereby achieving the optimal control for different launching intentions.

     

A theoretical study for the design of a new ballistic range

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.     

Lamb wave propagation on a unidirectional CFRP plate: comparison of FEM simulations,experiments, and analytical calculations

Carbon fiber-reinforced plastics (CFRPs) are widely used in recreational products and industrial components. Ultrasound is a powerful tool to ensure the safety of CFRP structures, but the ultrasonic velocity on CFRP depends on the frequency and direction of propagation. Understanding ultrasonic propagation is the key to its proper application to CFRP structures. In the present work, experiments, 3D FEM simulations, and theoretical analyses were performed to investigate Lamb wave propagation on CFRP plates. The simulation and experimental results agreed well, proving that the FEM simulation results were reliable. On the basis of this reliability, further results were obtained for various fd values. The S0 mode’s group velocity was considerably affected by the propagation direction, but the A0 mode exhibited minimal dependence. In addition, unexpected waves were observed in the simulation and identified as the SH0 mode. A new approach for determining the theoretical group velocity was also presented.

     

Design optimization of clutch housing mold by fluid flow and solidification simulation

Aluminum die casting is so complex where flow momentum is critical matter in the mould filling process due the high velocity of the liquid metal. Actually, in complex parts the exact calculation of mould filling performance with using experimental knowledge is almost impossible. Aluminum die castings play a definitive role in the manufacturing of lightweight automobile bodies. Hence it is more essential today that these castings be produced with the high quality methods. In this condition the simulation is becoming more important in the designing procedure. This saves time and reduces the cost of the casting system design, which is an advantage of using simulation programs. Also, economical utilization of materials can be obtained when the quantity of test castings is decreased. This paper describes the advantages of the clutch housing die casting mold simulations to achieve better casting system design in High pressure die castings (HPDC). Filling analysis is used to determine the size and location of the gate as well as proper runner system design for ensuring a complete and balanced filling of the clutch housing part.

     

Single microparticle launching method using two-stage light-gas gun for simulating hypervelocity impacts of micrometeoroids and space debris

A single microparticle launching method is described to simulate the hypervelocity impacts of micrometeoroids and microdebris on space structures at the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. A microparticle placed in a sabot with slits is accelerated using a rifled two-stage light-gas gun. The centrifugal force provided by the rifling in the launch tube separates the sabot. The sabot-separation distance and the impact-point deviation are strongly affected by the combination of the sabot diameter and the bore diameter, and by the projectile diameter. Using this method, spherical projectiles of 1.0-0.1 mm diameter were launched at up to 7 km/s.     

无人机气液压弹射系统动摩擦力仿真与试验

介绍了基于蓄能器、液压马达驱动无人机(UAV)发射的气液压弹射系统,建立了系统各主要部分的数学模型。基于AMESim仿真软件搭建了弹射系统的仿真计算模型,评估了动摩擦力对无人机末端弹射速度的影响,拟合出末端弹射速度-动摩擦力曲线。在试验样机上对动摩擦力进行测试,得出设备的动摩擦力和动摩擦系数。研究表明,设备的动摩擦系数会因发射角度的增大而降低,影响无人机的最终发射速度,进而影响到弹射成功率。为后续弹射系统的仿真、试验和优化提供了参考。     

Instantaneous Frequency Estimation for Motion Echo Signal of Projectile in Bore Based on Polynomial Chirplet Transform

Microwave interferometer is one of the devices for measuring the movement travel–varying or time-varying velocity of projectile in bore. Microwave interferometer first obtains the Doppler echo signal including the motion information of the projectile in bore, then the velocity is measured based on instantaneous frequency estimation (IFE) of the processed and transformed signal. The parametric time-frequency analysis method can make spectral energy of nonlinear frequency modulation (FM) signal concentrate at some range in the new transform domain. As the motion echo signal of projectile in bore (MSPB) is a nonlinear FM signal, it could be described by polynomial chirplet, one of polynomial FM signal modes, which is used to construct transform kernel for the signal. In this paper, Polynomial chirplet transform (PCT) method is proposed to analyze the simulation and experiment echo signals of projectile in bore. The estimation error and Renyi entropy are used to measure quantify of the time-frequency distribution. Compared with short-time Fourier transform (STFT) method and Wigner-Ville distribution (WVD) method, our results show that the PCT method has most powerful anti-interference performance and highest accuracy of instantaneous frequency estimation for the simulation signal, and lowest Renyi entropy of the instantaneous frequency estimation for the experiment signal. In general, the PCT method has powerful anti-interference performance and high time-frequency concentration and accuracy of instantaneous frequency estimation for the motion echo signal of projectile in bore.     

新型细水雾灭火喷嘴的仿真及试验

为了解决细水雾喷头喷雾保护半径小的问题,研制了一种新颖的两级雾化高压细水雾灭火喷嘴。计算了索太尔雾滴直径DSM、喷嘴流速、流量和充分雾化距离。在CFD仿真中,将两级雾化喷嘴的速度场和水体积分数分布与单级雾化喷嘴的对应仿真结果分别进行对比,并优化了两级雾化喷嘴的结构参数。试验测量了DSM、喷雾速度、喷雾密度分布并和仿真结果进行对比验证。研究表明,优化设计后两级雾化喷嘴的喷雾保护半径为0.34 m,喷雾密度分布均匀;具有多喷嘴的两级雾化细水雾喷头的喷雾保护半径可以超过2 m,在消防领域具有实用价值。     

On the near-field aerodynamics of a projectile launched from a ballistic range

A computational fluid dynamics method has been applied to simulate the unsteady aerodynamics of the projectile launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was employed to investigate the unsteady flow with moving boundary. The coordinate system fixed to each moving domain was applied to the multi-domains, and the effect of virtual mass was added in the governing equations for each domain. The unsteady, axisymmetric Euler equation systems were numerically solved using the third order Chakravarthy-Osher total variation diminishing scheme, with MUSCL approach. The projectile mass and configuration effects on the unsteady aerodynamics were investigated based on the computational results. The present computations were validated with results of some other CFD works available. The computed results reasonably capture the major flow features, such as shock waves, blast waves, shear layers, vertical flows, etc. which are generated in launching a projectile up to a supersonic speed. The present computational method properly predicts the velocity, acceleration and drag histories of the projectile.     

某投掷式干扰机的结构设计

以炮弹为运载平台将干扰机投掷到目标区需完成炮射、空中开舱、落地、天线展开等系列动作,才能有效地开展后续工作。文中介绍了干扰弹的组成和工作流程,通过仿真分析、优化结构设计、结构设计创新、采用灌封工艺、静态和动态试验相结合等手段,进行工程化设计。试验结果表明,干扰机能可靠有效地工作,达到了设计要求。     

Dynamic response of aluminum honeycomb sandwich panels subjected to hypervelocity impact by porous volcanic rock projectile

The dynamic response and damage behavior of aluminum honeycomb sandwich panels (HC/SPs) subjected to hypervelocity impact by volcanic rock projectiles were investigated by hypervelocity impact tests and hydrocode simulations. The experiments were conducted using a two stage light gas gun and the results showed that the failure modes in HC/SPs subjected to hypervelocity impact by volcanic rock projectiles mainly took forms of front-face denting and circular perforation, honeycomb core collapsing and rapture, rear-face petal-ling and perforation etc. A 3D discrete configuration of the porous volcanic rock projectiles was set up. The hypervelocity impact behavior of the HC/SPs was investigated through hydrocode modeling, within a Lagrange-SPH coupling method in LS-DYNA solver. It was found that the dynamic response and failure modes in the HC/SPs were significantly influenced by the impact location and the impact velocity of the volcanic rock projectile.

     

Improvement and realization of linear travel-time interpolation ray tracing algorithm

The linear travel-time interpolation ray tracing algorithm has a drawback: rays can’t go round the low velocity area if the launching point, the receiving point and the low velocity area distribute on the same column (row). Aiming at the drawback, an improved algorithm is proposed on the basis of researching reconstruction theories. The given algorithm adopts a cross-scanning strategy to carry out forward processing and uses discrete points as the secondary sources to simplify backward processing. The numerical simulation experiments show that the rays can go round the low velocity areas located in the same column (row) of the launching points and the receiving points. Rays scan over the global region only once.     

Numerical analysis of the thermal characteristics of a gas-dynamic ignition system

As a multiple-start ignition method for liquid-fuel rocket engines, the gas-dynamic igniter has many advantages, such as a simple configuration, low weight and high structural strength. However, because of the complexity of the flow of the working fluid, the details of the thermal processes involved are not clearly understood. In this study, the thermal and flow characteristics of a gas-dynamic igniter are investigated through numerical simulations using the software OpenFOAM. The simulation results show that the pressure within the igniter undergoes oscillations. The axial flow velocity decreases across the pressure wave front so that the kinetic energy of the flow is converted to thermal energy. The temperature increase within the oscillation tube of the igniter is strongly correlated with the entry mass flow. Therefore, the tube inlet area should be designed according to the igniter nozzle flow to achieve the best performance from a gasdynamic igniter.

     

分瓣式气动弹射灭火弹发射强度分析与试验

根据实际参数计算灭火弹的受力情况,采用有限元分析软件对弹体的发射强度进行分析。结果表明:灭火弹最大应力位置位于弹头与分瓣弹身的边缘处,最大等效应力小于105 MPa;灭火弹最大塑性变形为0.010715 mm,总变形为0.9659 mm,均能够满足发射强度要求。进行发射试验结果表明:灭火弹工作正常,出膛后灭火弹未发生零部件破损,验证了结构设计的合理性。     

Wire electrical discharge machining of ASP30 tool steel

Wire electrical discharge machining is a non-traditional cutting process for machining of hard and high strength materials. This study analyzed the effects of the main input parameters of wire electrical discharge machining of ASP30 steel (high alloyed Powder metallurgical [PM] high speed steel) as the workpiece on the material removal rate and surface roughness. The input parameters included spraying pressure and electric conductivity coefficient of the dielectric fluid, linear velocity of the wire and wire tension. The machined surface quality was evaluated using SEM pictures. Results indicated that increasing the spraying pressure of dielectric fluid leads to a higher material removal rate and surface roughness and that increasing the wire tension, linear velocity of wire, and electric conductivity of the dielectric fluid decreases the material removal rate and surface roughness.