Cyclic Nanoindentation for Local High Cycle Fatigue Investigations: A Methodological Approach Accounting for Thermal Drift

Cyclic nanoindentation allows characterizing the influence of single phases and their interactions on fatigue mechanisms. Herein, a method for high cycle fatigue testing by nanoindentation is presented. By combining high- and low-frequency indentation modes, high cycle numbers are achieved while obtaining sufficient data points to reconstruct force–displacement hysteresis loops. A challenge is the stochastic course of thermal drift which is addressed by measuring drift rate in regular low-force holding segments. Drift rates are used to correct the displacement values, yielding reproducible cyclic deformation data as it is shown for two very different materials, a ductile metal and a brittle ceramic.     

平面旋涡(中心型奇点)水力特性的探讨

本文讨论了平面旋涡(中心型奇点)的水力特性.说明了这种旋涡的中心被封闭的流线所包围，中心点的流速为零，封闭流线为椭圆曲线；给出了旋涡内流速与压强，旋涡的环量、涡量以及角动量的表达式；建立了旋涡水力参数和主流水力参数的连接条件，包括两个运动连接条件和两个动力连接条件；将得到的理论结果应用于侧墙突扩或跌坎流，得到的旋涡中心压强表明，在一般明渠条件下，主流流速大于20m/s时旋涡区有可能出现空蚀；应用于水跃时发现，跃长与跃高之比和突扩流旋涡的长宽比基本相同，估计了水跃旋滚区的紊流运动粘滞系数；应用于交岔渠道的旋涡时，指出了旋涡宽度与渠宽之比必须小于0.160，给出了一个数例     

High-Throughput Nanoindentation for Statistical and Spatial Property Determination

Standard nanoindentation tests are “high throughput” compared to nearly all other mechanical tests, such as tension or compression. However, the typical rates of tens of tests per hour can be significantly improved. These higher testing rates enable otherwise impractical studies requiring several thousands of indents, such as high-resolution property mapping and detailed statistical studies. However, care must be taken to avoid systematic errors in the measurement, including choosing of the indentation depth/spacing to avoid overlap of plastic zones, pileup, and influence of neighboring microstructural features in the material being tested. Furthermore, since fast loading rates are required, the strain rate sensitivity must also be considered. A review of these effects is given, with the emphasis placed on making complimentary standard nanoindentation measurements to address these issues. Experimental applications of the technique, including mapping of welds, microstructures, and composites with varying length scales, along with studying the effect of surface roughness on nominally homogeneous specimens, will be presented.     

凹槽中的旋涡及初生空化数的估算

本文阐述了凹槽中旋涡形成的力学机制；利用文献［1］中的结果建立了凹槽中旋涡的涡量平衡、能量平衡近似关系式；给出了旋涡初生空化数的表达式，它不仅和凹槽的宽深比有关，还和参数K1有关(K1为流道宽和槽深之比)；对不同的深宽比和K1值计算了凹槽中的旋涡参数和初生空化数，把计算的初生空化数和已有的实测凹槽旋涡初生空化数进行了对比，两者的值和变化趋势基本一致。     

Nanotribologie: Messung von mechanischen Eigenschaften im Sub-Mikrometer-Bereich

Hardness of a material describes the resistance of a material under indentation by a solid body. The vickers hardness [1] is determined by loading a diamond pyramid with a known force that is in contact with a specimen. The length of the diagonal of the remaining indent is used to calculate the contact area. The ratio of force and contact area is the vickers hardness. The abilities of modern technique of measurement replace the optical analysis of each indent by calculating the hardness from force and displacement recorded during the indent. Nano-hardness measurements now can be used to determine the mechanical properties of thin films and structures in the range from less than 10 nm to 1μm. Hardness can be measured with very small indentations, which could not be analyzed according to vickers. Time dependent properties as creep and viscose flux of material can be checked on sub-micron scale. The technique of nano-hardness measurements is comparable to the universal hardness test [2] for metals, whose minimum indentation depth of h = 0.2 μm still is too big for many applications. Combined with an atomic force microscope (AFM) the presented technique is capable image the area of interest before and after testing. Mechanical properties like friction-constants and wear can be measured quantitatively. The indenter can be used as a micro-machining tool with high precision as well.     

急流冲击波简化式

本文在Ｉｐｐｅｎ冲击波理论的基础上推导得到新的冲击波简化式，在ＶｏｎＫａｒｍａｎ积分基础上建立了缓冲击波简化积分式．这两个简化式形式简单，适用范围广，便于应用．     

Kinematic CT of the patellofemoral joint

The relationship between time structure and procrastination was investigated among 115 Irish undergraduate students. Significant negative zero-order correlations were found among scores for all five subscales of time structure and procrastination. A follow-up stepwise multiple regression indicated a significant multiple correlation (R = .61) between all five time structure subscale scores and procrastination. Significant predictors of procrastination were scores on the Time Structure subscales of Effective Organization followed by Sense of Purpose. These results suggest that strategies focusing on time management in conjunction with existential approaches of psychotherapy may be an effective intervention for reducing procrastination.     

溴化锂制冷机的应用与节能效果

往复式氨压机是常用的制冷设备,但它的能耗较高,与此相比,本文介绍的吸收式溴化锂制冷机则具有热效率高,低能耗等特点。     

泄水建筑物过流壁面不平整体初生空化与空蚀研究述评

泄水建筑物过流壁面不平整体初生空化与空蚀的研究进展，本文作了扼要的综述与评论。内容包括不平整度的定义及其初生空化与空蚀的理论分析、试验研究、比尺效应和理论预测，以及尚存在的问题。文中也包括了作者在上述工作中所作的研究和相应的看法。     

地震时坝面散粒体跃移距离的估计

本文讨论了当地材料坝在强震作用下的两种损伤形态和斜面上散粒体的起始滑动加速度,证实了颗粒在坝面上跃移时所受的阻力基本上为0-2阻力,说明了估计地震时坝面颗粒总跃移量的方法和步骤。