电接触可靠性研究中的几个热点问题分析

根据电接触理论的发展过程，并结合煤矿生产现状对目前国内外电接触可靠性研究中的几个热点问题进行了分析。     

Electrical resistivity and point contact studies on Al-Pd-Mn icosahedral quasicrystals

We report measurement of the electrical resistivityρ(T) and point contact differential conductance (dI/dV) for icosahedral Al₇₀Pd_{30 −x} (x=7,9 and 11) at low temperatures. Below 10 K, forx=11,ρ(T) follows a logT dependence. All the three compositions show a sharp minimum in the differential conductance near zero bias. Magnitude of the dip in the point contact conductance increases as the Mn concentration increases. The dip near zero bias also follows a logV dependence forV < 30 mV.     

Standing contact fatigue with a cylindrical indenter

A hardened steel cylinder was repeatedly pressed against a flat case‐hardened steel specimen that was equally wide as the cylinder was long. Some contact end effects were noted as a result of limited plastic deformation. A strain gauge on the contact surface, just outside the contact and oriented perpendicular to the cylinder detected a surface strain when the cylinder was loaded. The non‐zero surface strain was the result of boundary effects of the finite specimen. Four different types of contact fatigue cracks developed in and below the specimen contact surface. The cracks were named lateral, median, contact end and edge cracks. Changes in the measured surface strain values could be used to determine when the lateral and edge cracks developed. The order in which all four crack types typically developed was determined from optical crack observation at test termination, strain measurements and stress computations. Numerical computations using finite‐element (FE) analyses were used to verify the surface strain behaviour due to loading and cracking; to verify contact end effects; crack locations and crack orientation by aid of the Findley multi‐axial fatigue criterion.     

Optimum shapes of tire‐treads for avoiding lateral slippage between tires and roads

Optimum design of tire‐tread sections is an important practical issue. However, useful study of the problem that can suggest a reliable guideline for determining the optimum tread sections had hardly been made in the past. The present paper describes a new analysis of the state of stresses in tire‐tread sections in contact with the road surface, taking special care of the boundary conditions. Based on the analysis, a method is proposed to determine the optimum tread shapes for avoiding lateral slippage between tires and roads. The displacement potential function formulation, an ideal mathematical model for the practical stress problems, has been used in conjunction with finite‐difference method of solution. For the present analysis, lateral slipping in absence of frictional resistance as well as the no‐slip conditions of the tire‐tread contact surface have been considered along with a large number of tread aspect ratios. The present computational approach proves to be a powerful tool for determining the optimum tread shapes for avoiding the lateral slippage of tire‐treads. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrotribological behavior of Cu−Ag−Zr contact wire against copper-base strip

Cu−Ag−Zr alloy has an excellent combination of mechanical strength and electrical conductivity, and is a promising contact wire material for high-speed electrified railways. An investigation of the electritrobological behavior of Cu−Ag−Zr wire is presented here. Wear tests are conducted under laboratory conditions with a specified sliding wear tester that simulated train motion under an electrical current applied across the sliding interface. The Cu−Ag−Zr alloy wire is slid against a copper-based powder metallurgy strip used in railway systems under unlubricated conditions. Worn surfaces of the Cu−Ag−Zr alloy wire are analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). Within the studied range of electrical current, normal pressure, and sliding speed, the wear rate increases with increasing electrical current and sliding distance. Adhesive wear, abrasive wear, and electrical erosion are the dominant mechanisms during the electrical sliding processes. Compared with a Cu−Ag contact wire under the same test conditions, the Cu−Ag−Zr alloy wire has much better wear resistance.     

静态时间继电器延时接点瞬动检测方法的探讨

介绍了SSJ-11A型静态时间继电器的应用及构造原理,探讨了时间继电器延时接点瞬动的可能原因,举例说明了SSJ-11A型时间继电器延时接点瞬动的检测方法.     

浅谈电气化铁路分段绝缘器的安装

论述了电气化铁路牵引供电系统接触网施工中安装分段绝缘器存在的问题，并提出了相应的解决措施。     

The mechanisms of cracks formation of silver-based contact materials under arc and making pressure

The arc erosion experiments on five kinds of silver-based contact materials,AgZnO (10), AgSnO2 (8.5) In2O3 (4), AgCdO (12), AgNi(10), AgWC(12)C(3) were carried out according to different breaking times, breaking currents, and making pressures. Then based on the theoretical analysis and the photographs taken by scanning electronic microscope with EDAX analyzer, the crack morphology was studied scientifically. Three types of cracks, which are cavity cracks, grain boundaries (or phase boundaries) slipping cracks, and thermal stress cracks, were put forward under arc and making pressure through establishing their physical models and discussing their formation mechanisms.     

Cu-Cr触头材料的制备方法及进展

简要介绍了Cu-Cr合金触头材料的结构特点及其优良性能．叙述了Cu—Cr合金制备技术的进展，重点介绍了触头材料的几种制备工艺，并比较了各种制备工艺的优缺点及其应用范围，最后展望了触头材料的发展趋势．     

卧式铣床外置内联系传动链装置的设计与应用

铣床的主轴与传动机构之间没有传动联系,因而不能在铣床上用展成法加工零件,通过方案设计,误差分析,结构设计,介绍了一种外置、内联系的传动链装置;使用该装置,可以在卧式铣床上用展成法加工齿轮类零件。