中间隔震层位置变化对混合被动控制体系控制效果影响的试验研究

提出了一种分段隔震结构与相邻结构连接耗能的新型混合被动控制体系。与单一的减隔震体系相比,这种新体系将隔震与阻尼器耗能结合在一起,对不同频域地震动具有较强的鲁棒性。通过振动台试验输入不同频域的地震动,研究了分段隔震结构中间隔震层位置变化对隔震效果的影响。最后将有限元数值模拟与试验结果进行了对比。研究表明：长周期地震波对隔震结构的位移、加速度的影响相较于其他频域地震动更为显著,会使隔震支座超限的可能性增大;中间隔震层位于结构竖向靠中部位置时结构整体动力响应最小;混合被动控制体系可以有效解决高层减隔震结构目前所存在的位移超限、结构整体倾覆等问题,对不同频域地震波激励下的结构响应均有更为优越的控制效果。     

Experimental investigation on the effect of melt delivery tube position on liquid metal atomization

Metal powders are often made by gas atomization of liquid metal. During the process, liquid metal which flows from a melt delivery tube (MDT) is atomized by high speed gas discharging from a gas nozzle. In this work, the effect of the melt delivery tube position on atomization outcomes such as the yield, mass median diameter, and spread of the particle size distribution, is studied experimentally. A melt atomization setup (pilot-scale) is used to produce tin powder by gas-atomization. Three MDT positions, namely, intruded, extruded and flush with respect to the gas nozzle, are chosen for this study. Three pressure regimes (atmospheric, aspiration and pressurization) are established by varying the relative distance between the MDT and the gas nozzle exit for the three positions. Experimental investigations revealed that the intruded position produces powder with lower mean particle sizes and lower spread than the extruded configuration. The intruded position also gives a significantly higher yield compared to the extruded and flush positions at low gas flow rates, and hence appears to be the most suited for metal atomization using a free-fall configuration.     

Experimental investigation on the piezo-composite actuator with piezoelectric single-crystal layer

Studies on muscle mimicking actuators have increased in the last two decades due to the possibility of various applications for compact lightweight actuators including small unmanned aircrafts, missile, and biomimetic robots. Piezoelectric materials have been used in a variety of applications ranging from shape control of structure and active vibration control of structure to noise suppression due to compact size and good frequency response. Conventional polycrystal piezoelectric ceramic materials, however, have limited actuating strains and displacement, hindering their use in actuators for small aerospace vehicles. In this study, the design and fabrication method of an actuator with a piezoelectric single-crystal layer were investigated to increase the actuation strain and displacement. From a comparison of the performance of the LIPCA-C2 and LIPCA-S prototypes, it was found that the new LIPCA-S2, which has much higher coefficient of the unimorph actuator, can generate an actuating displacement more than twice that of LIPCA-C2.     

双电层对水润滑特性影响的实验研究

双电层是固液界面处普遍存在的自然现象,双电层现象使得固液界面处的液体一方中存在过剩电荷,液体流动产生流动电流,液体中同时产生方向相反的传导电流,使带电离子反向流动,阻碍液体的流动,使得液体的等效粘度增加,产生电粘度效应．近年来,双电层效应对润滑的影响逐渐受到人们的重视．理论研究表明,薄膜润滑时双电层效应对摩擦系数和润滑膜厚有明显影响．     

空气层对RDX水下爆炸性能影响的实验研究

为了探究空气层对RDX爆炸性能的影响,采用水下爆炸实验测出含不同体积空气层的RDX水下爆炸参数,结果表明,空气层对水下爆炸参数的衰减作用显著。在相同不耦合系数K下,R_1和R_2处的比气泡能大小近似相等,分析认为比气泡能仅与炸药产生的爆生气体有关,与冲击波传播的距离无关。在R_1=0.8 m处,不耦合系数K为1～7时,峰值压力显著降低,通过实验结果拟合得到RDX的峰值压力经验公式;当K为7时,对RDX药柱冲量的影响较小,相反地,峰值压力、比冲击波能、比气泡能、水下爆炸总能量分别降低了46.62%、42.98%、37.26%、40.03%。同时,对空气层衰减RDX水下爆炸性能机理进行了分析,总结并提出一种全新的水下冲击波调节方法。     

Experimental investigation of salt fog effect on the CFRP laminates

To investigate the effect of an ocean environmental condition to Carbon Fiber Reinforced Plastics (CFRP) specimen, salt fog tests were conducted on long immersion hours. After salt fog tests, tensile test was performed to examine the durability of specimens under salt fog condition. Fabric types, fiber orientations, and different manufacturing methods were also investigated to look into effects of salt fog and tensile strength. Diverse fabric types, resin types, and manufacturing methods exhibited different experimental results. Finally, the experimental results showed the salt fog reduced the tensile strength of CFRP laminates.     

Experimental investigation of the influence of flow of viscous liquid on transport processes

The authors have made an experimental examination and verification of the molecular separation effect in binary mixtures under the influence of viscous momentum transfer.     

Experimental investigation of the effect of high-energy protons on charge-coupled devices

The effect of 1000-MeV protons on CCD matrix based image sensors, which are widely used in various equipment on-board space vehicles, have been studied in order to determine how the local structural damage of crystalline lattice caused by high-energy nuclear particles influences the parameters of CCD matrices. The dependence of the dark current of CCD matrices on the proton irradiation has been studied in a range of fluences up to 2 × 10¹¹ cm⁻².     

An investigation into the effect of water quality on froth stability

Froth stability plays a major role in determining the mineral grade and recovery in flotation operations, and it depends on the type and amount of both frother and suspended particles. Furthermore, there are other parameters such as quality of the process water which may affect the froth stability. In plant practice, the recycling of process water instead of using fresh water is increasingly being common. However, using recycled water normally leads to building up salts and surfactants in solution. Therefore, the effect of the process water chemistry on froth stability and metallurgical performance is important. In this study, the effect of water quality, including pH, and type and concentration of salts (CaCl₂, AlCl₃ and NaCl) on froth stability and its relationship with mineral particles zeta potential and slurry viscosity was studied. It was found that the forth stability is higher in the presence of multivalent metal ions. Addition of CaCl₂ and AlCl₃ considerably increased both froth stability and pulp viscosity. This may be due to bridging effect of polyvalent metal ions between the ore particles.     

Experimental investigation of pulsation motion in a free-convection boundary layer

Singularities of measurement of pulsation characteristics in nonisothermal flows with a high degree of turbulence are discussed. A modification of the hot-wire anemometer method of velocity measurement for similar flows is suggested. The results are given of measurements of different characteristics of pulsation motion in the free-convection boundary layer forming along a heated vertical surface.     

机载喷雾冷却换热特性关键影响因素实验研究

为详细研究喷雾冷却系统在大热沉表面积和无沸腾区下的换热特性,并为喷雾冷却系统的机载应用提供技术基础,搭建以水为冷却介质的开放式喷雾冷却实验台。基于实验数据从特征参数和无量纲数两方面研究加热功率、喷雾入口压力对换热性能的影响;并根据飞行工况考查重力角度的影响。得到实验结果:在加热功率500~1 400 W及入口压力0.45~0.85 MPa的条件下,热沉表面温度均能控制在80℃以下。加热功率一定时,系统表面传热系数随入口压力的增加而增加,且增加速率随着功率的增加而增加;热沉表面温度随入口压力增加而减小,且减小速率随着功率增加而增加;表面传热系数随Re和We的增加而增加,增加速率随功率增加主要是由于蒸发强度的增加。此外,与重力方向夹角为30°或120°时,喷雾冷却性能最好。结果表明各工况下喷雾冷却换热效果良好,表面参数均处于合理范围,为该技术在机载领域的应用提供技术参考。     

航空相机的像移计算及其补偿分析

航空相机拍照时难免会产生像移,要提高成像质量和相机分辨力必须进行像移补偿。推导出前向像移、飞行器俯仰、滚动和偏航产生的像移及其误差计算公式,以美国 KS-146 航空侦察相机为例,计算出前向像移的大小数量级在 10-3,而其它像移量大小则为 10-4数量级,提出在航空垂直拍照时前向像移占主导地位,应作为像移补偿的主要方向,同时提出在航空相机设计中通过缩短曝光时间和提高快门精度等途径来减小像移、增强航摄图像的清晰度。     

节流元件对空调Cd系数影响的试验研究

试验研究热力膨胀阀和节流阀芯对空调Cd系数的影响，测试数据表明，与采用节流阀芯的空调系统相比，采用热力膨胀阀的空调系统Cd系数降低47．5％～63．4％，整机SEER提高0．5左右。建议SE—ER值高于15的定速空调系统采用热力膨胀阀进行节流。     

潜艇指挥台位置对水动力的影响研究

对6条指挥台处于不同相对位置的潜艇若干水动力特性分别进行建模计算，经分析、比较，得到一种水动力性能优良、尾部流场较均匀的方案，为探讨指挥台的最佳水动力位置奠定了基础．     

热复合磁脉冲粉末压坯致密度的试验研究

对加热Cu粉末进行磁脉冲致密试验研究,探索提高压坯致密度且不使粉末颗粒产生明显长大的致密方法.通过压坯平均致密度和微观金相形貌分析,揭示了加热温度、放电参数和粉末体高径比等工艺参数对Cu粉末热复合磁脉冲致密压坯致密度的影响规律.研究表明:压坯致密度不随温度升高而线性增加,200℃时的致密度最高;在给定放电能量和200℃下,压坯的致密度随电压和电容量增加而提高,随粉末质量增加而降低;3次放电显著改善压坯致密效果,致密度达98.75%,再增加次数的影响甚微.     

Experimental investigation of the influence of modes of nitriding on the damping ability of 45 steel

By using numerical methods, for specimens of 45 steel subjected to various modes of nitriding in a hydrogen-free atmosphere, we determine the parameters of the process of nitriding guaranteeing the maximum possible level of their damping ability. The results of testing control specimens of 45 steel subjected to the optimal procedure of nitriding revealed practically complete coincidence between the numerical and experimental values of the decrement of vibrations whose level was higher than for nonnitrided specimens by a factor of 3.4.     

Experimental investigation of the influence of modes of nitriding on the damping ability of 45 steel

By using numerical methods, for specimens of 45 steel subjected to various modes of nitriding in a hydrogen-free atmosphere, we determine the parameters of the process of nitriding guaranteeing the maximum possible level of their damping ability. The results of testing control specimens of 45 steel subjected to the optimal procedure of nitriding revealed practically complete coincidence between the numerical and experimental values of the decrement of vibrations whose level was higher than for nonnitrided specimens by a factor of 3.4. Translated from Problemy Prochnosti, No. 5, pp. 95–97, September–October, 1997.     

Experimental and theoretical investigation of the effect of kinematic hardening on spherical indentation

When investigating material properties, the indentation test is often used in spite of the fact that very complicated nonhomogeneous processes are involved. In order to understand this test in more detail, an analysis was given by Huber and Tsakmakis using Finite Element calculations. It was shown that there exists an analogy between uniaxial homogeneous tensile experiments and spherical indentation for cyclic loading conditions. In fact, in both cases, existence, e.g., of kinematic hardening can be identified by the existence of hysteresis loops in the strain–stress diagram and the depth–load plot, respectively. The present paper deals with an experimental verification of the existence of such hysteresis loops for the case of depth-sensing indentation tests. Further, two measures are considered in order to quantify the size of hysteresis loops. The first one is the area enclosed by the hysteresis loop while the second one is a suitable defined middle opening of the hysteresis loop. Using various Finite Element calculations, it is shown that both measures can be regarded to be correlated. These theoretical relationships are proved to be in agreement with experimental results as well. Finally, the effect of kinematic hardening on the hysteresis loops is discussed experimentally by studying the opening of the hysteresis loop as a function of the depth.