平面一维应变电炮加载技术研究

 在分析电炮加载装置放电回路的基础上，探讨了电炮装置的设计原则。根据所提出的设计原则，设计和建立了一门储能14.4 kJ的电炮装置。实验测试结果表明，其性能参数诸如回路电感小于40 nH、放电周期7 μs、飞片平面度小于40 ns、初始电流上升陡度达750 GA/s。与国内外的同类型装置的参数相比较，该电炮装置达到了较高水平，具有较好的性能。在此基础上，提出了获得平面一维应变加载对电炮装置的一般要求。     

BIAXIAL LOADING OF NEO-CLASSICAL LIQUID CRYSTAL ELASTOMERS:CONSTITUTIVE RELATIONS AND SOFT BEHAVIOR

The thermo-order-mechanical behaviors of liquid crystal elastomers(LCEs) under biaxial loading are studied in this paper.Inverse method for nonlinear elastic problems is utilized by imposing biaxial stretching to thin rectangular samples.Neo-classical elastic energy is used together with the Landau-de Gennes nematic free energy.Under plane stress assumptions,the constitutive equations are derived.Due to the possible reorientations of the liquid crystal molecules induced by the imposed biaxial loading,the in-plane nonlinear stress-strain relations can have different expressions depending on which loading axis will have the largest effective principal strain.And the free energy is a multi-well non-convex potential function.As shown by some typical loading paths,the LCE samples will exhibit an anisotropic nonlinear elastic behavior,as long as the loading has not induced a reorientation of the liquid crystal molecules.When this did occur,jumps of stresses could take place for dead loadings due to the losing of stability.     

承重试验台同步加载系统设计计算及模糊PID耦合调平控制

针对试验台加载系统需具有高效率、快响应和高同步精度的特点,设计了一套液压油路系统,并开发了一种模糊PID交叉耦合同步调平四缸的控制算法。通过对理论模型输出位移的实时跟踪,实现了试验台的同步加载和精确调平控制。基于AMESim建立的同步加载系统的仿真结果,验证了主从式控制与模糊PID交叉耦合控制方案设计的合理性和可靠性。调平系统实验进一步表明,改变四液压油缸负载值使液压油缸负载不同步,可明显提高系统的高精度同步性能。     

Effect of passivation on higher order gradient plasticity models for non-proportional loading: energetic and dissipative gradient components

Abstract

In this work, a new class of thermodynamic-based higher order gradient plasticity theory is proposed and applied to the stretch-surface passivation problem for investigating the material behaviour under the non-proportional loading condition. This paper incorporates the thermal and mechanical responses of microsystems. It addresses phenomena such as size and boundary effects and in particular microscale heat transfer in fast-transient processes. The stored energy of cold work is considered in the development of the recoverable counterpart of the free energy. The main distinction in this formulation is the presence of the dissipative higher order microstress quantity that is known to give rise to the stress jump phenomenon, which causes a controversial dispute in the field of strain gradient plasticity theory with respect to whether it is physically acceptable or not. The finite element solution for the stretch-surface passivation problem is developed and validated by comparing with three sets of small-scale experiments. Based on the validated finite element solution, the stress jump phenomenon under the stretch-surface passivation condition is investigated with the effects of the various material parameters. The evolution of the free energy and dissipation potentials is investigated at elevated temperatures. The two-dimensional simulation is also given to examine the gradient and grain boundary effect, the mesh sensitivity of the two-dimensional model and the stress jump phenomenon. Finally, some significant conclusions are presented.     

Influence of boundary structure and near neighbor crystallographic orientation on the dynamic damage evolution during shock loading

The role of crystallographic orientation on damage evolution in ductile metals during shock loading has been investigated. By utilizing large-grained copper specimens, it has been shown that the development of intragranular damage, in the form of void growth and coalescence, is influenced by the grain orientation with respect to the applied load. Additionally, strain incompatibility and the inability to promote transmission or activation of secondary dislocation slip across a grain boundary, are proposed as the likely cause for intergranular failure. Finally, the free surface velocity profiles of each grain, specifically the decay of the oscillations after the pull-back, correlated well with the amount of damage measured within the respective grain.     

应用新型动光弹系统研究某设备受冲击载荷作用

结构受到冲击时,其应力分布与在静荷载作用下完全不同.本丈应用新型动光弹实验系统研究了某设备在冲击载荷作用下其内部动态应力分布情况.该系统由部分传统的动光弹实验装置、高速摄影系统和数字光弹图像处理系统组成,并且采用激光光源、落锤冲击载荷加载装置.加工制作了该设备模型的光弹性模型,应用到冲击载荷作用下的实验研究中,得到了该...     

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根据ITER运行的主要危险工况,设计了一个专用的三维加载测试平台,并对该测试平台进行了结构有限元分析。有限元分析结果表明,三维测试平台结构有足够的强度和刚度,能满足磁体支撑原型件的三维加载测试的精度要求,可以用该设计方案进行制造。为了确信三维加载测试的可靠,制定了专门的三维加载测试平台的验收方案并按此方案对测试平台进行了可靠性测试。     

Optically monitored high-pressure gas loading apparatus for diamond anvil cells

We describe a high-pressure system built to load rare gases (He, Ar, Ne) in various types of diamond anvil cells, at room temperature. These gases are used as pressure transmitting media to obtain the best hydrostatic compression conditions in high-pressure experiments. Optical windows allow control of the loading process. The loading success rate is close to 100% and the initial pressures in the diamond anvil cell are in between 0.2 and 1?GPa. This system can easily be adapted for loading of various gaseous samples, including gas mixtures, which generally cannot be loaded by cryogenic methods.     

钻孔雷达全向天线的设计与分析

根据钻孔雷达全向天线的设计要求,为减少天线的结构尺寸增加带宽,设计了一种新型电阻加载全向天线。通过理论分析和数值优化,选择了较优的结构尺寸,得到了较佳方向图和带宽。天线外径为65 mm,使用10 mm厚天线罩封装后外径为85 mm;天线的S11小于-10 dB频带为70~260 MHz,带宽约190 MHz。该天线的带宽超过100 MHz,中心频率处增益大于-3 dB,辐射电场脉冲波形拖尾小于主峰幅度1/5,方向图在H面为全向。基于矢量网络分析仪的天线特性测量结果与数值计算结果基本一致,结果表明设计的天线能够满足钻孔测井雷达系统小尺寸宽带的要求。