六棱钨柱冲击起爆带壳B炸药比动能阈值研究

为了研究钨合金六棱柱冲击起爆带壳B炸药比动能阈值,设计并实施了破片冲击带壳B炸药实验。基于实验数据,利用Autodyn-3D建立可信的仿真模型,计算得到了实验条件下的钨合金六棱柱冲击起爆比动能阈值。利用已验证的仿真模型,选取典型的六棱柱破片的外形尺寸,利用"升降法"求得破片的冲击起爆比动能阈值,绘制了相关曲线,并与同等情况下的速度阈值进行比较。结果表明,实验条件下的冲击起爆阈值为34.780 MJ/m2,在炸药及壳体一定的情况下,大长径比破片冲击起爆带壳B炸药的比动能阈值较大。     

甲烷-空气最小点火能与耦合系数的计算及应用

针对一种可以用于检测非金属制品在矿井下工作安全性的静电火花检测系统,研究了计算该系统中甲烷-空气引爆的最小点火能量的数学物理模型。并根据该检测系统的结构,提出了点火系统点火前后的电磁能量计算方法。通过计算系统点火前的电磁能量与最小点火能量,计算出检测样品被粉尘摩擦后的带电量,得出了点火能量耦合系数阈值与电荷阈值。结果表明,点火能量耦合系数阈值随电压升高而减小,随电极间距的增大而增大。以静电检测系统为例,当电极间距由1mm增大到5mm时,耦合阈值从0.416 3增加到0.769 1。同时,电荷阈值亦随电极间距增大而增大。研究结果可为进一步检测材料摩擦起电属性以及制定相关安全标准提供参考。     

破片对带铝壳炸药的冲击起爆数值模拟研究

 采用AUTODYN-2D数值模拟软件，应用冲击起爆Lee-Tarver模型，对钢破片撞击带铝壳Octol炸药的起爆问题进行了数值模拟，分析了冲击起爆机理及破片形状、着速、铝壳厚度等因素对炸药起爆特性的影响规律，利用“升-降”法得到了破片对Octol炸药的临界冲击起爆速度。研究结果对反导战斗部破片杀伤元素的设计具有指导意义。     

杆式钨合金弹超高速撞击薄靶的能量损耗

超高速撞击过程伴随着复杂的物理过程。为分析杆式圆柱形钨合金弹超高速撞击薄钢靶时的物理过程,采用AUTODYN/SPH数值仿真计算方法获得了撞击过程模型及每个光滑粒子流体动力学信息,并通过广度搜索破片识别程序识别每个破片所含粒子,利用MATLAB编程对破片粒子数据信息进行统计分析,获得弹靶撞击过程的变化特性、弹靶破片数量、相关能量随撞击时间的变化规律。通过分析发现:随着弹体撞击速度的增加,剩余弹体被严重侵蚀,且弹体能量损耗增加,弹体损失的能量主要转变为弹靶破片动能;计算得到了撞击20μs时的能量损耗直方图,同时分析了发生撞击时靶板的能量变化过程,并简要描述了该过程。     

钨珠在穿靶过程中破损问题的数值研究

 使用二维有限元法,研究了直径为6 mm和8.5 mm的预制破片（钨珠、钢珠）以不同速度在稠密气体中飞行时的破损问题,初步确定了珠子破损的阈值速度。研究表明,破损的程度与珠子的速度、材料、大小有密切关系。同时还研究了破损了的破片对6 mm厚钢靶的穿透能力。     

炸药枪击试验和数值模拟研究

HL-10炸药是一种以RDX为基的含铝炸药,为了研究该炸药在子弹或金属破片撞击作用下的安全性,利用12.7 mm机枪法对钢壳包覆的柱形HL-10装药进行了枪击试验,试验结果表明,炸药没有发生燃烧或爆轰现象,由此可定义该炸药的枪击感度试验反应等级为1级。建立了炸药枪击试验的计算模型和数值计算方法,对子弹撞击和穿透炸药过程进行了三维数值模拟计算,计算结果与试验结果相符,分析了子弹速度对HL-10炸药枪击感度的影响,其结果可为炸药安全性评价分析提供理论根据。为了进一步验证计算模型和方法,对美国的PBX-9404炸药的枪击作用过程进行了计算分析,结果表明,PBX-9404炸药在枪击作用下发生了完全爆轰反应,与Neff等人的试验结果相吻合。     

预制破片冲击起爆裸炸药的理论分析

为了研究球形、圆柱形和正多棱柱形预制破片冲击起爆裸炸药的规律,利用Mathcad软件,基于Held高能炸药冲击起爆u2 d判据进行了理论计算与分析,着重比较了破片的质量、密度、形状、长径比、棱数等对冲击起爆裸炸药特性的影响,并与AUTODYN的仿真结果进行了比较。结果表明:对于球形破片,直径一定时,破片密度增大,质量增加,起爆能力增强;相同材料和直径的球形破片与长径比为1的圆柱形破片相比,圆柱形破片的起爆能力优于球形破片。对于圆柱形和正棱柱形破片,密度和质量一定时,随着长径比的增加,破片的起爆能力下降;正棱柱破片的棱数增加时,起爆能力降低,当棱数趋于无穷时,效果趋近于相应的圆柱形破片。     

双液滴撞击平面液膜的流动与传热特性

采用耦合的水平集-体积分数法(CLSVOF)对双液滴连续撞击恒定壁温壁面上的热液膜的流动和换热特性进行了数值模拟及分析,得到了双液滴撞击热液膜后形态演变的过程.分析了液滴垂直间距、撞击速度、液膜厚度以及液滴直径对双液滴撞击液膜后的流动与传热特性的影响,结果显示,壁面平均热流密度随液滴撞击速度的增大而增大,液滴垂直间距、液膜厚度和液滴直径对平均热流密度的影响较小,但会对热流密度在撞击区域和交界区的分布产生重要影响.     

用组合式电磁粒子速度计研究一种活性材料的反应特性

针对一种密度为5.2g/cm~3的活性材料,用57mm口径火药炮发射飞片撞击活性材料产生平面冲击波的加载方式,首次采用组合式电磁粒子速度计测量了活性材料的粒子速度历程,同时获得了活性材料内部冲击波的传播轨迹。研究表明,在高速飞片撞击情况下活性材料可以发生反应,但是反应速率较慢,释能过程较长,反应无法自持。将活性材料与PBX 9502炸药以及惰性材料的粒子速度历程进行对比发现,活性材料的反应发展过程介于炸药与惰性材料之间。该研究方法可以用于研究其他活性材料反应特性,相应的研究结果可以为活性破片战斗部的活性材料选择以及活性破片设计提供参考。     

球形钨合金破片空气阻力系数实验研究

 实验研究了理想球形钨合金破片和经历爆轰驱动的球形钨合金破片长距离飞行时的速度衰减规律。实验结果表明：（1）对于理想球形钨合金破片，在同一初始速度条件下，衰减系数为常数，空气阻力系数与初始速度有关，两者成线性关系；（2）对于经历爆轰驱动的球形钨合金破片，由于有轻微的质量损失和变形，速度衰减规律与理想球形钨合金破片有明显的区别，空气阻力系数与飞行速度有关，两者成线性关系。     

Heat transfer from small tungsten spheres into an ambient H2 atmosphere

The transfer of heat from tungsten spheres into an ambient H₂ atmosphere was investigated. The spheres had a radius between 35 and 100 µm and were heated to 1400–2000 K by a laser beam. The H₂ pressure ranged from 35 to 1000 mbar. Heat transfer by convection is effective with large spheres and high H₂ pressures. With small spheres and low H₂ pressures, a pronounced temperature discontinuity at the interface between the tungsten sphere and the ambient gas was observed. The results are relevant to the modelling of gas-phase transport phenomena in laser processing.     

孔洞缺陷对B炸药性能影响的理论计算

为探究孔洞缺陷及其大小对B炸药性能的影响,建立了3种空位缺陷浓度一致但孔洞大小不同的B炸药缺陷模型.采用分子动力学方法,计算得到了不同B炸药模型与感度、结合能、爆轰性能和力学性能相关的参数并进行了比较.结果表明,缺陷模型的键连双原子作用能和内聚能密度下降了9.93～23.88 kJ·mol~(-1)和0.0082～0.0254 kJ·cm~(-3),表明孔洞缺陷的存在使B炸药更敏感,且孔洞越大,敏感程度越高.缺陷模型的结合能下降了368.43～391.46 kJ·mol~(-1),表明孔洞缺陷导致B炸药的稳定性下降,且孔洞越大,稳定性越差.孔洞缺陷对B炸药的爆轰性能影响比较微弱,受密度下降的影响,爆速和爆压轻微下降.孔洞缺陷导致B炸药的弹性模量、体积模量、剪切模量和柯西压分别下降0.21～1.24 GPa、0.23～1.46 GPa;0.08～0.48 GPa以及0.09～0.44 GPa,体积模量与剪切模量的比值几乎不变,表明孔洞缺陷导致B炸药的抗变形能力和延展性变差.     

Numerical Simulation of Random Close Packings in Particle Deformation from Spheres to Cubes

Variation of packing density in particle deforming from spheres to cubes is studied. A new model is presented to describe particle deformation between different particle shapes. Deformation is simulated by relative motion of component spheres in the sphere assembly model of a particle. Random close packings of particles in deformation form spheres to cubes are simulated with an improved relaxation algorithm. Packings in both 2D and 3D cases are simulated. With the simulations, we find that the packing density increases while the particle sphericity decreases in the deformation. Spheres and cubes give the minimum (0.6404) and maximum (0.7755) of packing density in the deformation respectively. In each deforming step, packings starting from a random configuration and from the final packing of last deforming step are both simulated. The packing density in the latter case is larger than the former in two dimensions, but is smaller in three dimensions. The deformation model can be applied to other particle shapes as well.     

钨/石墨烯/钨面向等离子体复合材料力学与热学及耐辐照性能衰减的第一性原理计算

通过第一性原理计算研究了钨/石墨烯/钨复合材料相比于纯钨金属在力学与热学性质方面的变化，并用氦原子-空位缔合缺陷模拟核聚变辐照损伤评估等离子体辐照条件下的性能。计算结果表明：钨/石墨烯/钨复合材料的体积弹性模量、杨氏模量与剪切模量呈现一定程度的下降，但是提升了钨基材料的延展性；钨/石墨烯/钨复合材料的热膨胀系数有所增加，但是具有较高的最小热导率。本文阐述了石墨烯界面层可以对基体杂质与缺陷进行吸附的独特机制，通过这种机制，钨/石墨烯/钨复合材料在力学、热膨胀系数以及最小热导率有更低程度的衰减，这显示了钨/石墨烯/钨复合材料在抗辐照性能方面具有较大的应用潜力。     

Single crystals of mesoporous tungstenosilicate W-MCM-48 molecular sieves for the conversion of methylcyclopentane (MCP)

Highly ordered W-MCM-48 mesoporous materials containing isolated W atoms in tetrahedral framework positions were successfully synthesized following the S⁺I⁻ pathway, up to a Si/W of 40. When tungsten content was increased up to a Si/W of 20, the ordered cubic structure was only partially maintained, and for a Si/W of 10 an amorphous phase was obtained. Highly isolated tetrahedral framework tungsten atoms in the W-MCM-48 with a Si/W of 40, have been identified by UV-vis band at 225 nm, IR-TF band at 970 cm⁻¹ and XRD. The W 4f XPS results suggest that the tungsten atoms exist in two oxidation states, W⁴⁺ and W⁵⁺. The morphology of the samples varies as a function of tungsten content. The W-MCM-48 samples with a Si/W ratio of 40 existed as crystals with a unique crystalline morphology consisting of cubes truncated rhombic dodecahedrons belonging to the cubic Ia3d space group, while the samples with a Si/W ratio of 20 exhibited a different morphology consisting of spheres and cubes truncated by rhombic dodecahedrons. A comparison of samples with Si/W of ∞, Si/W of 40 and Si/W of 20 was performed using the conversion of MCP carried out at 450 °C under H₂.     

Definition and properties of ideal amorphous solids

It is proposed that two ideal amorphous structures, type I and type II, based on maximally random jammed packing of spheres of equal size, form a distinct class of ideal amorphous solids. The ideal amorphous structures contain wide variations in local density, limited by the condition of solidity. Four distinct characteristics, based on statistical geometry and topology, are shown to define this class. Voronoi tessellations carried out on simulated cells of random packed spheres and amorphous polymers give a broad distribution of individual volumes, skewed, with a tail at the high volume end.     

Electrodeposition of CoWP film: V. Structural and morphological characterisations

CoWP films were electrochemically deposited on copper-coated silicon wafers from citrate electrolytes containing cobalt sulphate, sodium tungstate and sodium hypophosphite under various deposition conditions and characterisations of the films were carried out using various instrumental techniques. Composition analyses using XPS showed that the surfaces of the films contained large amounts of oxides and hydroxide of tungsten and cobalt, respectively. An AES depth-profile, however, revealed that the bulk of the films predominantly consisted of cobalt, tungsten and phosphorus. Microstructural analyses using XRD showed that, depending on the composition and/or deposition conditions, CoWP films could be amorphous, polycrystalline and crystalline with a strong preferred orientation. Amorphous films were obtained when deposited at higher applied potential and current density or the films contained high amount of phosphorus and/or tungsten, while films deposited by very low applied potential and current density were crystalline with a preferred orientation of [0 0 2] of hexagonal cobalt. SEM images showed that the films deposited from neutral or acidic baths at room temperature had typical spherical nodular structures, while the films deposited from basic solution or at elevated temperature had needle-like crystallites. The crystalline films were much rougher than the amorphous films.     

Electronic state calculations of spherical diamond nanocrystals

Electronic-state calculations of diamond nanocrystals simulated by ultrasmall quantum spheres of diamond passivated by hydrogen are performed by the extended Hückel-type nonorthogonal tight-binding method. Two kinds of surface configuration (ideal and dimerized ones) are studied. Special attention has been paid to surface as well as quantum-confinement effects. The calculated results have demonstrated that, while the HOMO (highest occupied molecular orbital) energies are independent of the surface configuration and depend clearly on the size of the diamond spheres, the LUMO (lowest unoccupied molecular orbital) energies of the diamond spheres with one or two dimers on the surface are rather insensitive to the size, in agreement with experiment. The latter is found to be ascribed to the occurrence of surfacelike states associated with the backbonds of the dimer. It is shown that calculated lifetimes across the energy gap are less than 100 microseconds, suggesting that the diamond nanocrystals are promising light-emitting materials.     

Investigation of interaction between methanol fed tandem porous spheres burning in a mixed convective environment

Flame interaction during the burning of two porous spheres in tandem arrangement fed with methanol and subjected to a mixed convective environment, has been studied experimentally and numerically. Porous sphere technique is employed for experimentally simulating the burning characteristics of methanol transpired spheres of different sizes, separated by fixed distances. The mass burning rates from both the spheres and visible flame stand-off distances from the sphere surfaces have been measured in the experiments. In the numerical simulations, transient, axisymmetric, mass, momentum, species and energy conservation equations are solved using a finite volume technique based on non-orthogonal semi-collocated grids. Features of the numerical model include finite rate chemistry and temperature and mixture composition dependent thermo-physical properties. Burning of tandem porous spheres in an air stream flowing vertically upwards, at atmospheric pressure has been simulated for different sphere sizes, separation distances and free stream velocities. The numerical predictions have been compared with experimental results. Results reveal that when two spheres burn one over the other, the transition from envelope to wake flame is delayed when compared with that of an isolated sphere. For two spheres of same diameter burning one over the other, depending on the separation distance, flame blows-off after the occurrence of transition from envelope to wake flame in the bottom sphere. For the case of larger sphere at the top, either the flame stabilises in the recirculation zone formed in between the spheres or the flame from the smaller sphere lifts off and stabilises near the front portion of the larger sphere, depending on the separation distance. At higher separation distances, around four times the diameter of the sphere, both the spheres burn independently. The burning rate undergoes complex variations with air stream velocity depending on the sphere sizes and separation distances.