FJZ-1000型超高速转镜分幅相机及其应用

FJZ-1000型超高速转镜分幅相机最高摄影幅频为1107幅/s,画幅总数160幅,尺寸7.5 mm10 mm。光学系统中新加入场镜以使相机的所有画幅均完整成像,使相机摄影频率全面达到标称值的技术指标。配备了新型数字化微机控制台,使相机的操作更加方便,并且实现了两台气动相机的联合拍摄,与脉冲X光机也进行了联动实验。相机达到了设计技术性能指标,实验取得了满意的结果。     

WPG-30型微机控制铍转镜扫描相机及其应用

本文阐述了新研制的WPG-30型微机控制铍转镜扫描相机的主要技术性能、特点及其在爆炸力学实验中的初步应用情况。该机采用铍镜透平,扫描速度达15km/s,并保持相机的强光力,因而提高了它的时间分辨本领。使用微机控制台,提高了相机的自动控制程度和测速精度。通过爆轰实验表明,这种新相机对波形差的分辨能力和时间间隔的测量精度都有很大提高。     

APX-RS相机在高速摄影中的应用

通过分析APX-RS数字化相机的性能特点及主要技术指标,设计了针对高速运动中高速段、中速段及低速段的运动物体飞行姿态拍摄的动态实验,得到了飞行物体清晰的拍摄图像和准确的运动速度。结果表明,该相机能较好地记录4Ma以内的高速运动物体的飞行过程。     

APS—RS型高速相机在气相爆轰实验中的应用研究

基于气相燃烧转爆轰机理研究,探索利用APX-RS型高速数字相机测量氢氧混合气体在电火花点火后的火焰和前驱冲击波的变化历程,获得火焰加速以及冲击波的产生与成长过程的高速摄影图像;计算了不同位置的前驱冲击波参数和气体状态参数;分析了燃烧转爆轰机制。结果表明：APX—RS型高速相机可以成功地拍摄气相燃烧转爆轰过程,并获得氢氧混合气体燃烧转爆轰为局部爆炸机制。     

组合状态方程在数值计算上的应用及分析

利用建立在爆轰产物实验等熵线数据上的组合状态方程以及常用的Jones-Wilkins-Lee (JWL)和Becker-Kistiakowsky-Wilson (BKW)爆轰产物状态方程进行了爆炸数值分析。状态方程数值计算的压力波形与实验波形的对比表明:组合状态方程和JWL状态方程计算的波形的到时、峰值、形状能够与实验吻合;BKW状态方程等熵式计算的数值波形峰值基本能够与实验吻合,但形状吻合不佳。     

低冲击作用下JO-9159炸药的反应阈值

设计了改进的隔板实验装置,采用PVDF压力计测量受试炸药的入射压力,利用高速分幅相机得到炸药自由表面发展变化过程.通过分析计算得到入射压力与自由表面粒子速度之间的关系,并与未反应炸药计算的自由面粒子速度进行了比较,得到JO-9159炸药在低冲击作用下的化学反应阈值和点火阈值分别为1.13和1.98 GPa.     

岩石三轴力学教学实验装置研制及教学应用

随着构思—设计—实现—运作教学理念在国内高校的推广,实验教学对学生学习越来越重要,但传统的常规三轴力学实验装置造价高且实验过程具有一定的危险性。为了克服以上实验教学过程中的局限,设计了一种内置框架岩石三轴力学教学实验装置。该装置省去了传统装置中体积巨大的框架结构,具有刚度大、体积小、成本低、操作安全简单等特点,有利于在实验教学中激发学生的科研兴趣,培养学生的动手实践能力。

     

PVDF应力测量技术及在混凝土冲击实验中的应用

介绍了使用PVDF(polyvinylidene fluoride,聚偏二氟乙烯)应力计的应力直接测量技术。在SHPB装置上进行自制PVDF应力计动态压电系数的标定实验,分析了应力集中、横向泊松效应、摩擦效应对PVDF应力计信号及动态压电系数的影响。用PVDF应力计进行了混凝土的冲击压缩实验。利用混凝土前后端面PVDF应力计信号分析了实验过程中混凝土试样的应力均匀性。与应变计直测应变技术相结合得到了混凝土的动态应力-应变关系。     

电火工品桥丝与药剂升温模型及在可靠性设计中的应用

介绍了桥丝式电火工品的电容放电和直流输入方式的桥丝升温模型、药剂升温模型及其数值求解算法 ,提出了估算感度的能量平衡方程和用于输入可靠性设计的理论计算方法。给出了一个算例 ,并与实际产品作了比较 ,结果表明 ,将该模型用于可靠性设计的理论计算是可行的。     

银加载爆轰实验中生成的固体粒子表征

使用X射线衍射、扫描电子显微镜、X射线能谱、比表面和孔隙度等分析方法,对加载货币银爆轰 实验生成样品的成分含量、粒子形貌、形成物相、金属银的晶粒度、比表面及孔隙度进行了分析。结果表明,银 和铜在爆后的粒子中仍然为共熔体,相对金属银,晶格参数减小,生成银粒子的晶粒度为15.9~22.2nm;由 于高温高压和实验环境的影响,银粒子爆后和其他杂质粒子粘结在一起形成较大的颗粒,含有许多其他成分, 氧化亚铁来源于爆炸罐的罐体,大量无定形碳粉来源于缺氧环境下炸药的不完全燃烧,铝和硅来源于实验装 置。对生成样品的形貌分析证明了XRD对银晶粒度的分析结果。因为样品中含有较多量的碳粉,为了弄清 对气体的吸附作用,对样品进行了比表面、孔隙度以及孔径分析。     

Explosively driven particle fields imaged using a high speed framing camera and particle image velocimetry

A high speed framing camera and a particle image velocimetry instrument were used to determine the properties of explosively driven particle fields in early microsecond and later millisecond times. Test items were configured in a two inch long cylindrical shape with a half inch diameter core of organic explosive. The core was surrounded by a particle bed of aluminum or tungsten powder of a specific particle size distribution. Position data from the leading edge of the particle fronts for each charge was recorded with a high speed framing camera at early time and with a particle image velocimetry (PIV) instrument at later time to determine particle velocity. Using a PIV image, a velocity gradient along the length of the particle field was established by using the mean particle velocity value determined from three separate horizontal bands that transverse the particle field. The results showed slower particles at the beginning of the particle field closest to the source and faster ones at the end. Differences in particle dispersal, luminescence, and agglomeration were seen when changes in the initial particle size and material type were made. The aluminum powders showed extensive luminescence with agglomeration forming large particle structures while the tungsten powder showed little luminescence, agglomeration and no particle structures. Combining velocity data from the high speed framing camera and PIV, the average drag coefficient for each powder type was determined. The particle field velocities and drag coefficients at one meter showed good agreement with the numerical data produced from a computational fluid dynamics code that takes advantage of both Eulerian and Lagrangian solvers to track individual particles after a set post detonation time interval.     

DDGS high speed camera with some applications

DDGS high speed camera is an improved version of the multispark system. In this system the time delay and the frame interval can be set arbitrarily from 5 μs to 10 000 μs, and the intervals may be equal or not. The modified spark gaps can provide point flashes that are small enough in size and strong enough in light for both dynamic caustics and dynamic photo-elasticity. In addition, this system can be changed easily to observe the flow by schlieren method. Thus, this optical system is suitable to investigate many dynamic problems in the fields of solid and fluid mechanics.     

Three-dimensional channel flow of second grade fluid in rotating frame

An analysis is performed for the hydromagnetic second grade fluid flow between two horizontal plates in a rotating system in the presence of a magnetic field.The lower sheet is considered to be a stret...     

Independent continuous mapping for topological optimization of frame structures

Based on the Independent Continuous Mapping method (ICM), a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable stress and element stiffness, which transform the 0-1 type discrete topological variables into continuous topological variables between 0 and 1. Two methods for the filter functions are adopted to avoid the structural singularity and recover falsely deleted elements: the weak material element method and the tiny section element method. Three criteria (no structural singularity, no violated constraints and no change of structural weight) are introduced to judge iteration convergence. These criteria allow finding an appropriate threshold by adjusting a discount factor in the iteration procedure. To improve the efficiency, the original optimization model is transformed into a dual problem according to the dual theory and solved in its dual space. By using MSC/Nastran as the structural solver and MSC/Patran as the developing platform, a topological optimization software of frame structures is accomplished. Numerical examples show that the ICM method is very efficient for the topological optimization of frame structures.The project supported by the National Natural Science Foundation of China (10472003) and Beijing Natural Science Foundation (3042002) The English text was polished by Yunming Chen.     

含能材料药型罩的爆炸成型及毁伤作用

为了研究由含能材料制备的药型罩爆炸成型过程及其对目标靶的终点效应,设计了球缺形药型罩的装药结构,放置与药型罩曲率相同的缓冲垫在药型罩和主装药之间,运用高速摄影系统拍摄含能材料药型罩的成型过程。实验结果表明,含能材料药型罩在爆炸作用下能够形成弹丸,弹丸速度2km/s左右。含能弹丸穿透20mm厚的装甲钢靶后反应加剧,形成大量的气体。侵彻过程含动能和化学反应的综合作用,穿孔有明显的烧蚀现象,穿孔口径0.5 D,最大穿深1.4 D。利用含能材料制备成药型罩可以实现炸药的直接驱动,这可为含能材料战斗部的工程应用提供参考。

     

KKM technique and its applications

In this paper,the Knaster-Karatowski-Mazurkiewicz technique(KKM technique,in short)is presented.By using this technique a new alternative theorem and a new coincidence theorem are established.The results obtained in this paper unify and generalize the corresponding results in the recent works.     

A moving frame of reference algorithm for fluid/structure interaction of rotating and translating bodies

A mathematical and numerical formulation is derived for fluid/structure interaction problems involving arbitrary geometries relevant to the simulation of bridge deck instabilities due to cross winds. A translating and rotating moving frame of reference is attached to the body to utilize an efficient fixed mesh spectral/hp element solver. The formulation is validated against experiments with flow simulations of circular cylinders at Reynolds numbers of 100–400 undergoing free and forced motion in the transverse and in‐line directions. The well‐documented phenomena of vortex lock‐in is captured. The formulation is then applied a rectangular body at Re=250 under forced and free motion the latter of which demonstrates torsional galloping. Copyright © 2002 John Wiley & Sons, Ltd.