Blast Damage Simulation With the Discontinuous Galerkin Finite Element Method of Bond⁃Based Peridynamics北大核心CSCD

近场动力学是一种积分型非局部的连续介质力学理论,已广泛应用于固体材料和结构的非连续变形与破坏分析中,其数值求解方法主要采用无网格粒子类的显式动力学方法.近年来,弱形式近场动力学方程的非连续Galerkin有限元法得到发展,该方法不仅可以描述考察体的非局部作用效应和非连续变形特性,还可以充分利用有限单元法高效求解的特点,并继承了有限元法能直接施加局部边界条件的优点,可有效避免近场动力学的表面效应问题.该文阐述了键型近场动力学的非连续Galerkin有限元法的基本原理,导出了计算列式,给出了具体算法流程和细节,计算模拟了脆性玻璃板动态开裂分叉问题,并对爆炸冲击荷载作用下混凝土板的毁伤过程进行了计算分析.研究结果表明,该方法能够再现爆炸冲击荷载作用下结构的复杂破裂模式和毁伤破坏过程,且具有较高的计算效率,是模拟结构爆炸冲击毁伤效应的一种有效方法.     

乙醇液滴撞击高温壁面蒸发过程的模拟预测研究北大核心CSCD

采用CLSVOF方法,引入描述壁面润湿特性的动态接触角,建立了乙醇液滴撞击高温壁面的数值模型,对乙醇液滴撞击高温壁面后的沸腾蒸发过程展开了研究,并与实验数据进行了对比验证.研究表明:在相同液滴温度下,壁面温度越高,亲水性越强,乙醇液滴的撞击速度越快,液滴的沸腾时间越早,蒸发完成所用时间也越短.在此研究基础上,基于机器学习算法,建立了液滴蒸发预测模型,对乙醇液滴撞击高温壁面后蒸发剩余量随时间的变化进行了预测研究,并通过将不同机器学习算法的预测结果与模拟结果对比,选出最优预测模型.     

爆炸焊接驻点近区应变率分布规律计算

为了认识爆炸焊接驻点近区材料的力学和热学行为 ,分析波状界面和绝热剪切带生成 ,采用理想流体对称碰撞模型沿流线研究了驻点近区的应变率分布规律 ,并推导出了驻点应变率的理论计算公式。通过数值与理论计算对爆炸焊接碰撞角、界面距离等因素对应变率的影响进行了讨论。计算结果表明 ,爆炸焊接中强烈变形集中在驻点附近区域 ,其应变率高达 10 6～ 10 7s-1,拉压应变率的绝对值在驻点处达到最大 ;而剪应变在焊接界面上为零 ,其最大值出现在驻点的前方 ,为拉压应变率的约二倍。     

JOB-9003和JB-9014炸药平面爆轰驱动飞片的对比研究

采用双灵敏度激光速度干涉仪(VISAR)测量了JOB-9003和JB-9014两种炸药平面一维爆轰驱动飞片的速度历史,比较了二者的做功能力;并用DYNA2D程序进行了数值模拟。在有JO-9159炸药的条件下,实验和计算结果表明,JB-9014炸药的做功能力可以达到JOB-9003炸药的75.0%;无JO-9159炸药条件下的计算结果表明,JB-9014炸药的做功能力约为JOB-9003炸药的71.2%     

可调控靶中应力波形的吉帕压力范围平面爆炸加载技术

分析了应力波通过不同介质的交界面时,应力波所具有的动量在界面两边的重新分配与影响动量在边界上转移的因素。讨论了靶中应力波幅度和宽度的调控方法、冲击器的飞行速度与厚度的相关性、靶中应力波的平面范围。给出了可调控靶中应力波形的平面低压化爆加载装置的应用实例。     

Development of ambient sampling chemi/chemical ion source with dielectric barrier discharge

The development of a new configuration of chemical ionization (CI)‐based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub‐ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high‐voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non‐volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non‐proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of a hyperbranched hydrogen bond acidic carbosilane sorbent polymer

Sorbent polymers can be designed to target molecular interactions with a variety of hazardous chemicals including explosives, chemical agents, narcotics, and toxic industrial chemicals. Applications of functionalized sorbent polymers include preconcentrator devices, SPME fibers, membrane introduction systems, chromatographic stationary phases and coatings for chemical sensors. One common feature of a wide range of hazardous chemicals is their hydrogen bond (h‐b) basicity. In this work, we report on the synthesis and characterization of a h‐b acidic hyperbranched carbosilane fluoroalcohol based sorbent polymer (poly(methyldi(1,1,1‐trifluoro‐2‐trifluoromethyl‐2‐hydroxypent‐4‐enyl)silane; HCSFA2), which is suitable for sorbing these hazardous h‐b basic analytes. Multiple batches of HCSFA2 were characterized with routine composition, spectroscopic, thermal analysis, and inverse gas chromatography (iGC) to evaluate polymer physicochemical properties. In comparison with previously developed h‐b acidic polymers (e.g., FPOL and SXFA), HCSFA2 exhibits a sorption improvement of 10–15 fold for h‐b basic analytes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3000–3009, 2010     

Theory and refined theory of elasticity for transversely isotropic plates and a new theory for tnick plates

A theory of elasticity for the bending of transversely isotropic plates has been developed from the basic equations of elasticity in terms of displacements for transversely isotropic bodies, which takes into account the loads distributed over the surfaces of the plates. Based on this theory, a refined theory of plates which can satisfy three boundary conditions along each edge of the plates and a new theory of thick plates are established. The solution of the refined theory for simply supported polygonal plates has been obtained; and its numerical result is very close to the exact solution of the three-dimensional theory of elasticity. A systematic comparison with the former theories of thick plates shows that the present theory of thick plates is closest to the result of the theory of elasticity.     

高电感和高能量放大系数的MFCG的理论分析

 根据爆炸磁通量压缩发生器(MFCG)的基本理论,计算MFCG的非对称多分支螺线管的电感、电阻和电流,并讨论大电感螺线管和小电感负载的运行性能。通过增加MFCG的初始电感以增加其初始电感对负载电感的比值,是获得高能量放大系数的一个有效方法。增加螺线管段数和导线并联分支数,可得到一个比较好的电压平台。