电火花微能脉冲电源研究现状

微细电火花加工技术近年来发展非常迅速,使得它在精密加工领域获得了广泛的应用。综述了目前国内外微细电火花加工中使用的微能脉冲电源的研究现状,对制约微能脉冲电源发展的因素进行了分析。     

新型电火花混粉镜面加工液处理工艺流程及装置的设计

提出将磁力液力旋流器用于电火花加工工作液中加工渣的分离处理,分析了国内外普通电火花加工和混有导电性粉末物质的电火花加工分离处理过程的现状和存在问题,介绍了新型电火花加工工作液工艺流程及处理装置的特点和结构设计。     

电火花加工表面层残余应力的理论和实验研究

对电火花加工表面层残余应力的形成进行了分析,建立了物理模型,分别给出了单脉冲放电和重复脉冲放电情况下电火花加工电蚀区域拉应力区长度的计算方法;建立了电火花加工表面层热传导模型;并且对重复脉冲放电情况下电火花加工表面层残余拉应力区分布进行了理论计算和实测。对于电火花加工表面层残余应力分布提供了初步的计算方法。     

数控精密电火花与线切割加工在现代模具加工中的应用

分析了数控精密电火花线切割加工技术及电火花成型加工技术在冲模及型腔模加工中的应用,探讨了电火花与线切割在模具加工应用中的几种特殊加工方法,如电火花线切割、电火花成型以及电火花微细孔机的特殊加工方法。     

电火花数控仿铣加工研究现状与展望

介绍了电火花数控仿铣加工的原理、特点、应用前景和研究现状 ,并阐述了电火花数控仿铣加工研究的若干关键技术问题     

电火花数控仿铣加工研究现状与展望

介绍了电火花数控仿铣加工的原理、特点、应用前景和研究现状,并阐述了电火花数控仿铣加工研究的若干关键技术问题。     

磁力液力旋流器在电火花加工工作液处理装置中的应用研究

针对普通电火花加工和混粉电火花加工工作液分离处理过程的现状和存在问题，提出将磁力液力旋流器用于电火花加工工作液中加工渣的分离处理过程，从而提高电火花加工的精度和效率。     

电火花线切割技术研究现状及发展趋势

总结近年来电火花线切割技术的发展现状,就现阶段电火花线切割加工中所存在的问题进行分析,同时依据现有的研究成果分析电火花线切割加工的发展趋势。     

数控电火花线切割加工在塑料模加工中的应用

分析了数控电火花线切割加工在塑料模加工中的应用场合,探讨了数控电火花线切割加工在塑料模加工应用中的几种特殊方法.     

电极直接驱动的小型电火花加工装置的研究现状

概括了目前典型的电极直接驱动的小型电火花加工装置－椭圆动装置，冲击式驱动装置和蠕动装置的发展现状，介绍了这些装置的结构和工作原理，分析了其存在的不足，提出了改进措施。最后指出了电极直接驱动的小型电火花加工装置的发展趋势及其应用前景，并首镒提出了电火花加工机器人的新概念。     

Application of the local approach to the fatigue assessment for welded joints

The fatigue behavior of welded structures is currently determined by means of recommendations defined in terms of S-N curve corresponding to the detail classes of welded joints without taking account of the actual geometry of the weld. A new fatigue strength assessment method based on Dang Van multiaxial fatigue limit criterion was introduced, which is named the local approach and presented by lnstitut de Soudure recently. The local approach has advantages in taking welding residual stresses and the geometry of the weld toe and weld root into consideration. The application of the local approach to the fatigue strength assessment of low carbon steel Q235B welded joints was studied. The fatigue tests and finite element analysis results show that the local approach parameters recommended by lnstitut de Soudure were incorrectly for low carbon steel Q235B welded joints. With aluminum alloy welded joints being used widely, the parameters of the local approach used for aluminum alloy welded joints were obtained and verified on bases of the fatigue tests and finite element analysis.     

残余应力对W-Cu复合材料导热性能的影响

用熔渗法制备的W-Cu复合材料在小批量生产时，发现熔渗结束后样品的热导率数据分散不稳定，受熔渗时摆放位置的影响很大。将熔渗结束后的样品退火，采取不同的方式冷却。用X射线衍射法测量其残余应力，用热脉冲法测量其热导率，研究了残余应力对材料导热性能的影响。结果表明：随冷却速度的加快，残余应力值增大，热导率降低。钨和铜的热膨胀系数相差较大，从高温冷到室温时两相收缩程度不一样，冷却速度过快时，在界面处产生残余应力，使材料的热导率降低。分析了残余应力对材料导热性能的影响及机制。     

铝合金搅拌摩擦焊接头残余应力分布

采用小孔法对3 mm厚2024-T4铝合金板搅拌摩擦焊对接接头的残余应力分布规律进行研究.为了衡量钻孔引入应变对结果的影响,测量了退火2024铝合金板钻孔产生的应变,将其作为附加应变对焊接试件上测得的应变结果进行修正.结果表明,在试验条件下得到的焊接接头的残余应力以纵向应力为主,横向应力相对很小;纵向高应力区集中在轴肩作用区域,呈不对称分布,前进侧应力高于返回侧,在轴肩作用区域之外应力值迅速降低,在距焊缝中心较远的区域转变为压应力;纵向残余应力峰值为164.5 MPa.分析认为,机械搅拌和焊接温度场的叠加作用造成焊缝两侧纵向残余应力的不对称分布.     

The influence of some rolling parameters on the residual stresses after rolling

A 2D analysis of the deformation process in the rolling gap is presented. Flat strip rolling is considered for a low carbon steel at a temperature of 1000°C.

2D — Finite Element models with a rotating workroll have been installed using the Abaqus/Explicit-Code. The workroll is modelled as a rigid body. The main subject of the analysis is to show the influence of the phenomena taking place at the entrance to the rolling gap on the development of the stress and the strain fields in the rolled material. It can be shown that due to the shearing process the backward slip exists of the three zones A, B, C. The importance of these zones depends strongly on the shape coefficient Δ. The elastic — plastic modelling of the material behaviour allows the calculation of the residual stresses.     

缩短渗碳周期与强烈淬火相结合的节能热处理技术

在热处理行业,人们一直在探索降低生产成本、节约能源和减少环境污染的方法。汽车制造业在这方面将是大有作为的,其中包括：大幅度缩短渗碳时间,以节能和降低生产成本;开发新型淬火剂替代易燃、有毒的矿物油基淬火剂。采用非易燃的对环境友好的水基淬火剂进行强烈淬火（IQ）是达到这些目标的途径之一。此外,IQ还能使渗碳的扩散时间缩短50％或更多。本文论述了巴西圣保罗大学、巴西Combustol公司以及关国强烈淬火公司合作进行的采用一种强烈淬火工艺成功达到上述目标的研究成果。从长远看,这些成果对热处理工业将具有重要意义。     

Mechanical properties of hard AlCrN-based coated substrates

The present investigation has been conducted in order to study three commercially available hard AlCrN-based coated substrates by means of nano- and microindentation, aimed at determining the intrinsic hardness of the films. The results obtained are subsequently discussed taking into consideration the residual stresses and structure (grain size and texture) determined by X-ray diffraction and in the light of published data available in the literature. The study is first carried out with monolithic CrN and AlCrN coatings and it is further extended to the analysis of multilayer AlCrN/TiSiN coatings. Hardness obtained from nanoindentation at low depth and modelling the microindentation data match with values obtained at 22, 30 and 31 GPa for CrN, AlCrN and AlCrN/TiSiN coatings respectively. Residual stresses change from slightly tensile for CrN coating to highly compressive for AlCrN and AlCrN/TiSiN ones while the average grain sizes neglecting microstrains are similar for the three coatings (10-15 nm). AlCrN and AlCrN/TiSiN response similarities result from the low influence played by the stratification as compared to the nanostructure of the polycrystalline sublayers (nanometric grain size).     

Bond stress development at a surface coating-substrate interface due to the action of a nucleus of thermo-elastic strain

The class of problems dealing with surface reinforced elastic media is encountered in many areas of materials engineering, notably in connection with surface layers that are used to provide protection to an otherwise softer substrate. These problems are of particular importance to the assessment of the mechanical behaviour of thin films and other forms of industrial coatings. This paper examines the problem related to the flexure of a plate-like surface layer that is bonded to an elastic halfspace region, and where the flexure of the coating is induced by a nucleus of thermo-elastic strain acting within the halfspace region.     

Morphological characteristics of the oxidation of niobium II: The role of stresses on high-temperature morphologies

The oxidation of niobium at high temperature (900°C) leads to reaction products with exotic morphologies. Morphological and kinetics analysis have been undertaken with Nb platelets. A growth mechanism of the oxide at the edges of the platelet is proposed.     

CVD金刚石涂层中热应力的有限元模拟

在CVD涂层系统中,由于各种材料物理性能的差异,涂层在从沉积温度冷却到室温的过程中会产生热应力,影响膜基之间的附着力.为了考察各种因素对产生热应力的影响,利用热固耦合有限元方法分析了不同沉积条件下硬质合金基体上金刚石膜的热应力情况,还讨论了有不同过渡层的情况.对各情况下的轴向、径向和剪切应力做了比较分析.结果发现沉积温度和金刚石膜厚度对热应力影响较大,而过渡层厚度和物理性能对热应力影响不大.     

大型电机转子焊接残余应力的数值分析

利用轴对称模型研究了大型电机转子焊接残余应力分布规律 ,探讨了单层单道焊情况下两侧同时焊接、热套、预热等工艺以及三层四道焊情况下焊接顺序对焊接残余应力的影响。研究结果表明 ,磁轭圈与辐板焊接后在焊缝及其周围区域产生较大的三向残余拉应力 ;两侧同时焊接可大大降低径向残余应力 ;热套可降低三向残余拉应力 ,热套后直接焊与热套后先冷却后焊相比效果更佳 ;预热可以降低周向残余拉应力 ;多道焊时径向残余应力主要取决于最后一层 ,尤其是最后一道焊缝 ;两侧的最后一道焊缝同时焊接可显著降低径向残余应力 ,而前面的焊道同时焊接与否并不重要。研究结果为优化生产工艺 ,降低残余应力提供了理论依据