The ep performance of certain S-benzylisoformamidinothiocarbamides in the four-ball test

Load carrying capacities of certain 1-formamidino-2-S-benzyliso-3-arylthiocarbamides were assessed using a four-ball extreme-pressure (ep) lubricant testing machine. All the compounds tested were found to be effective at high loads. 1-formamidino-2-S-benzyliso-3-phenylthiocarbamide was potentially useful at high loads; m-chlorophenyl- and p-tolyl derivatives were effective at low loads as well. For a comparative study a reference additive was used. Scanning electron microscopy was used to study the tribological properties.     

Critical points of transition in boundary lubrication with solid additives

The determination of the critical points of transition at which the failure of lubricants takes place is of scientific interest, and is necessary for establishing the limits of their applications. This paper defines the critical transition lines for a lubricant oil with several non-lamellar solid ep additives, as a function of load, velocity and temperature. Also the role of these lubricants in the non-scuffing zone is discussed, taking into account the influence of velocity, load, and temperature in wear and friction.     

永磁同步电动机的开环步进驱动器的研究

步进电机是增量运动控制系统的主要执行机构。如果采用合适的驱动方式,永磁同步电机(Permanent Magnet Synchronous Motor,PMSM)和步进电机(Stepping Motor)都可以工作在步进模式。主要研究永磁同步电机的开环步进驱动器的理论和方法。通过对永磁同步电机的驱动方式的深入研究发现,在其驱动器中引入一种新型开环脉冲宽度调制(Pulse Width Modulated,PWM)死区时间补偿方法,就可以改善永磁同步电机绕组电流的控制精度,从而也进一步提高了永磁同步电机在步进驱动模式下步距的控制精度。     

小直径深孔珩磨头的研制

小直径深孔的精加工，在单件小批量生产或维修过程中，其尺寸精度和表面精度比较难以控制。通过对内燃机气门导管的加工方法研究，采用小直径的深孔珩磨头进行深孔的珩磨，能够保证深孔加工的尺寸精度与表面精度要求，加工质量达到了良好效果。     

基于傅里叶相位差的抗噪声位移估计算法

提出了一种利用连续图像相位谱的差估计运动目标位移的抗噪声算法。根据傅里叶相移特性,用连续两幅图像相位谱差的周期性变化或剖面的斜率计算图像中运动物体的位移。向量滤波的应用在去除噪声的同时,有效保留了周期性信号在一个周期结束点的跳变性质。分段拟合是从周期性信号中计算斜率的合理方法。本算法在频域估计运动位移,能够克服背景光照变化的影响,克服10％的高斯白噪声,分辨率达到一个像素。     

A re-examination of the four-ball test

The four ball test is widely used to assess the ep properties of lubricants. The full test procedure involves the measurement of wear scars on three of the test balls at 20 separate load stages in order to calculate the mean Hertz load (MHL). This paper presents an analysis of the procedure used to calculate MHL and describes a method to determine MHL from only one measurement of wear combined with the normal determination of weld load (WL) and initial seizure load (ISL) using the friction curve. The time taken for the test is cut in this way from 10 h to less than 2 h: no loss of accuracy is incurred     

A novel tri-pin-on-disc tribometer designed to retain lubricants

This paper describes a novel tri-pin-on-disc tribometer designed and built to evaluate the friction and wear behaviour of test materials lubricated by a small quantity of fluid which is retained on the stationary disc up to high pin sliding speeds. Results are presented which illustrate the use of a stepwise loading (graphical) method for the determination of the dynamic coefficient of friction μ given by a with sliding speed is explained in terms of the different modes of lubrication, which at high speeds may include lubricant ep additive action     

浅析压力容器不开罐检验检测技术

本文主要介绍压力容器不开罐检验检测技术,此次检验针对设备结构和使用特点,结合现有检验手段,重点检出内外表面裂纹、腐蚀状况、材质劣化。通过对100台压力容器的检验,发现存在危险性缺陷的有32台,让用户充分认识到该类压力容器的安全状态,也为下一步检验提供了切实可行的检验方案。     

二次正交连杆与齿轮齿条机构的手动加压装置

介绍了一种过临界点自锁的二次正交连杆增力机构和齿轮齿条机构组成的加压装置.分析了其工作原理和技术特性,并给出了力学计算公式.该机构不仅利用了过临界点连杆增力机构的力放大与自锁功能,而且通过二次正交连杆机构进行二次力放大,增力效果远大于常规的力放大机构.     

基于相对步宽的两足步行结构的机械能耗研究

在对高邮鸭、珍珠鸡、人的观测和对非洲鸵鸟、仙鹤、皇企鹅的生物学调研基础上,分析不同的两足步行机构的几何特点与其步宽大小的关系,发现特定动物的步宽与腿长的比值是一个常数,不随速度而发生变化,据此定义相对步宽。从步宽与腿长的综合角度出发,建立动力学模型,计算出机械能损耗与相对步宽之间的关系,不同动物步行的实际能耗数据证明该结论正确。该结论为步行机器人下肢的结构设计和步态规划提供了重要的理论依据和设计思想。     

Observation and sliding mode observer for nonlinear fractional-order system with unknown input

The main purpose of this paper is twofold. First, the observability and the left invertibility properties and the observable canonical form for nonlinear fractional-order systems are introduced. By using a transformation, we show that these properties can be deduced from an equivalent nonlinear integer-order system. Second, a step by step sliding mode observer for fault detection and estimation in nonlinear fractional-order systems is proposed. Starting with a chained fractional-order integrators form, a step by step first-order sliding mode observer is designed. The finite time convergence of the observer is established by using Lyapunov stability theory. A numerical example is given to illustrate the performance of the proposed approach.     

WEL-TEN610CF钢应力腐蚀行为及防腐研究

通过对WEL-TEN610CF钢母材和焊缝材料在不同H2S浓度环境中的应力腐蚀敏感性试验和分析，提出了只有H2S含量小于20ppm才能不发生应力腐蚀开裂的论点。浓度升高敏感性增加，小于50ppm母材不敏感。未经热处理的焊缝及热影响区裂纹扩展平台速率4倍于热处理的，并对防止应力腐蚀开裂及高强钢订货提供了意见。     

基于IEC 61850标准的变压器保护装置的建模

以变压器微机保护装置为例,阐述了如何利用IEC 61850标准提供的面向对象的统一建模方法,建立智能电子设备(intelligent electronic deviceI,ED)的信息模型,以实现不同厂家生产的不同IED之间的互操作性。首先具体分析变压器微机保护IED应具备的功能以及功能分解,接着按照标准一步步建立该IED的功能模型,最后以两个逻辑节点为例介绍如何依据标准建立装置的数据模型。     

大型船用螺旋桨桨毂粗加工刀具路径规划研究

针对大型船用螺旋桨毛坯余量较大,相邻桨叶间存在重叠区,现有加工方法吊装复杂、需要二次装夹且叶根桨毂加工周期长等问题,提出了一种多轴对称加工叶根桨毂方案,并依据加工方案,应用定轴加工方法研究桨毂粗加工刀具路径规划.根据桨毂曲面特征,计算走刀行距与步长;基于定向包围盒(Oriented Bounding Box,OBB)干...     

Large-area Co-silicide nanodot arrays produced by colloidal nanosphere lithography and thermal annealing

We report here the successful fabrication of large-area size-tunable periodic arrays of cobalt and Co-silicide nanodots on silicon substrates by employing the colloidal nanosphere lithography (NSL) technique and heat treatments. The growth of low-resistivity epitaxial CoSi(2) was found to be more favorable for the samples with smaller Co nanodot sizes. The sizes of the epitaxial CoSi(2) nanodots can be tuned from 50 to 100nm by varying the diameter of the colloidal spheres and annealing temperatures. The epitaxial CoSi(2) nanodots were found to grow with an epitaxial orientation with respect to the (001)Si substrates: [001]CoSi(2)//[001]Si and (200)CoSi(2)//(400)Si. From the results of planview HRTEM, XTEM, and SAED analysis, the epitaxial CoSi(2) nanodots were identified to be inverse pyramids in shape, and the average sizes of the faceted silicide nanodots were measured to decrease with annealing temperature. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to facilitate the growth of a variety of well-ordered silicide nanodots with selected shape, size, and periodicity.     

高温构件蠕变损伤的概率计算及概率损伤图

由于材料性质以及操作条件的随机性 ,高温构件的蠕变损伤也同样具有随机性。文中根据概率计算的基本原理和高温构件蠕变损伤确定性解 ,得到蠕变损伤的概率方程。探讨各参数的分布规律 ,利用K S检验方法 ,对高温材料数据进行全面的检验 ,包括高温材料的蠕变系数和指数、损伤系数和指数 ;同时 ,对操作温度以及高温构件的蠕变损伤进行检验 ,认为这些参数分别符合正态或对数正态分布。在全面考虑各参数的随机性和相关性基础上 ,最终获得高温构件的概率蠕变损伤解。为了表达它们之间的关系 ,以期最终达到高温构件寿命预测和可靠性评估的目的 ,考虑两个参数 ,确定性时间t和随机性的炉管损伤值D。将它们之间的关系表述成为t—D—f(D)图 ,形成高温构件的概率损伤图 ,清晰地勾画出不同时间D值的概率分布关系 ,为高温构件的可靠性分析和概率寿命预测提供基础     

六分量力传感器及其校准系统

对当前国内外多分量测力传感器进行了分析,从理论上探讨了六分量力传感器的数学模型。在传统的牛顿迭代算法中引入了遗传算法的思想,创造了随机牛顿算法;对逐步回归算法进行了研究与相应的改进,并进行了大量的结果对比分析;设计开发了六分量力传感器及其校准系统,从而使六分量力传感器的精度得到可靠的保证。     

Ultrasonic beam propagation in highly anisotropic materials simulated by multi-Gaussian beams

The necessity of nondestructively inspecting fiber-reinforced composites, austenitic steels, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface play a key role in the beam models based on the paraxial approximation. In this paper, we apply a modular muiti-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal (qL) beam propagates in the symmetry plane of a transversely isotropic gr/ep composite. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.     

Recrystallization and ice-crystal growth in a biological specimen,as shown by a simple freeze substitution method

The sensory hairs of the silkmoth, Bombyx mori, are suitable test objects to check for recrystallization and secondary freezing damage in a biological object, because cryofixation by immersion into propane (90 K) routinely yields well-preserved specimens without noticeable freezing damage. After rewarming the frozen specimens for 10 min to 230 K (boiling propane), the tissue preservation has not deteriorated, and even after 45 min at 230 K, ice-crystal ghosts rarely exceed 50 nm. Two minutes at 250 K (in deep freezer) produced moderate freezing damage with ice-crystal ghosts of 30–75 nm, whereas 90 min at 250 K resulted in severe damage with ice-crystal ghosts well over 100 nm. Secondary freezing damage by ice-crystal growth upon rewarming well-frozen biological specimens, therefore, is a relatively slow process, depending not only on the temperature, but also on the exposure time. Moreover, with some biological specimens, secondary ice-crystal growth starts at much higher temperatures than previously guessed, and with short exposure times rarely should become a hazard in fine structure work.     

考虑蠕变特性的橡胶微凸体与金属表面接触特性分析

金属-橡胶接触广泛存在于密封结构中,密封接触表面上微凸体间的相互作用会直接影响整个密封界面的接触特性,进而影响其密封性能。基于粗糙密封界面的单个微凸体,考虑橡胶的蠕变特性,采用理论分析和仿真研究相结合的方式研究橡胶微凸体与金属表面的接触特性。通过橡胶蠕变特性的实验结果,构建橡胶蠕变计算模型;构建半球微凸体与金属平板间的有限元模型,进行考虑蠕变特性的仿真,分析其接触特性,并与Hertz接触理论的计算值进行对比。结果表明：在蠕变阶段,接触半径、法向变形量和最大等效蠕变应变均随蠕变时间的增加而增大,最大接触压力随蠕变时间增大而减小,这均可能导致密封性能的下降;随压力载荷的增大,接触半径、法向变形量、最大接触压力和最大等效蠕变应变均增大,但增大的趋势逐渐减小;橡胶微凸体与金属表面间的等效模量随蠕变时间的增加而减小,随压力载荷增大而增大。