直流非转移弧等离子喷枪中电弧的工作特性研究

利用计算机数值模拟技术，采用有限容积方法，针对自制的低能耗、高效率内送粉等离子喷涂设备，对喷枪内部电弧长度及其对流体特性的影响进行了分析研究。结果表明，通过增加进气流量和减少电流的大小，均使得等离子电弧长度增加，阳极弧根位置逐渐向下游移动，但是产生这两种现象的机理以及对气流温度和速度的影响是不同的。     

Friction Stir Welding of Ceramic Particle Reinforced Aluminium Based Metal Matrix Composites

The mechanical and microstructural properties of 6061+20% Al₂O_3p and 7005+10% Al₂O_3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation.     

电子电气设备的熔断器、断路器保护

熔断器、断路器是电子电气设备最常用的保护电器,熔断器可以实现过载、短路保护,断路器除具上述功能外,还能实行失压保护.根据线路特点和所保护的设备,采取相应的保护设施,确保用电安全.     

Investigation of electrode and hydrogen induced crack in welded joint of dissimilar steel

The welded joint of dissimilar heat-resisting steels 20Crl2MoV(F12)and 12 Cr2MoWVTiB(102)generally works around 600°C.In this paperthree kinds of ferritic electrodes are used for testing.They are R817 high-strength electrode(CrllMoVNi),R347 low-strength electrode(Cr2MoVWB)and newly-developed R507MoNb medium-strength electrode.The study on theinfluence of those three different electrodes on carbon migration,HIC and hy-drogen diffusion shows that medium-strength electrodes can well control thecarbon migration,and that the tendency to HIC in the joint formed by R817 issmaller than that by R347 instead.Considering the effect of weld metal transfor-mation on the restraint stress and hydrogen concentration of a joint,the hydro-gen distribution in the heat-affected zone(HAZ)is calculated by using finite ele-ment method(FEM)with stress and strain changing,and so the effect of thetransformation behaviour on HIC is revealed.In addition,newly-developedR507MoNb electrodes,tested the elevated-temperature property,oxidation re-sistance and creep rupture strength,have fulfilled the technical standards con-cerned and passed the examination of on-the-spot operation.     

Analysis and optimization of weakly coupled thermoelastoplastic systems with applications to weldment design

A systematic approach for the design of weakly coupled thermoelastoplastic systems is presented. The Newton–Raphson iteration method is used in the solution process so that analytic design sensitivity formulations may be efficiently derived via the direct differentiation technique. The derived formulations are suitable for finite element implementations. Analysis and sensitivity analysis capabilities are combined with numerical optimization to form an optimum design algorithm. To demonstrate the algorithm, we optimally design a weldment with respect to manufacturing and service life aspects.     

一种椭圆弧长的作图求解法及其误差分析

本文给出了一种椭圆弧长的作图求解方法,即由作图求得椭圆弧长的近似值。通过对100个椭圆弧长的求解结果表明,由此方法求得的椭圆弧长的误差甚小,从而在相当高的精度范围内,提供了一种工程中适用并且简单易行的求解椭圆弧长的方法。     

Microstructural changes accompanying repair welding in 5xxx aluminium alloys and their effect on the mechanical properties

At the shipyards, the aluminium alloy 5083 is welded with a multi-pass sequence using the metal inert gas technique. If, while checking the weld integrity either after welding or during service, defects are detected in the vicinity of the weldment, repairs are usually employed to extend the service life.

The repair method involves removal of the upper passes, depending on the thickness and re-welding under the same conditions.

Purpose of this paper is to examine the microstructural changes accompanying repair welding, define their effect on properties of primary importance and set, if possible, an upper limit as far as the number of repairs is concerned.     

The Influence of Medium on Low-Voltage Circuit Breaker Arcs

This paper mainly focuses on the influence of three kinds of media： air, air-10%PA （Nylon） and air-10% POM （polyoxymethylene） on low-voltage circuit breaker arcs. A threedimensional （3-D） model of arc motioa under the effect of external magnetic field is built based on magnetohydrodynamics （MHD） equations. By adopting the commercial computational fluid dynamics （CFD） package based on the control-volume method, the above MHD equations are solved. For the media of air-10%PA and air-10%POM, the distributions of stationary temperature and electrical potential and the transient motion processes are compared with those of air arc. The research shows that both air-10%PA and air -10% POM can cool the arc plasma and the former is more effective. Both of them can increase the stationary voltage as well. Moreover, the presence of the two mixtures can accelerate the arc motion toward the quenching area and ensures the arc quenched in time.     

液氨装置工艺计算及改造总结

介绍我公司液氯装置由活塞式氨气压缩机氨-CaCl2盐水系统改为带经济器的螺杆式氯气液化机组的工艺计算,新建装置特点以及改造后的装置在我公司运行情况和使用效果。经改造后的液氯装置每年可节约电费73万余元,同时提高了装置的安全可靠性。     

焊补法带压堵漏技术与不停车带压堵漏技术的应用

介绍了传统的焊补法堵漏及目前常用的不停车带压堵漏技术的基本原理、操作步骤以及密封剂类型，并对两种方法进行了比较。