板材粘性介质压力成形粘性附着力影响因素试验研究

针对粘性介质压力成形过程是粘性介质与板材耦合的变形过程,不易确定板材在粘着应力作用下变形行为的情况,自行设计了粘性附着力拉伸试验装置,将粘着应力作为板材拉伸力,直接测量粘着应力对板材变形的作用。采用聚甲基乙烯基聚合物作为成形传力介质,初步研究了粘性附着力拉伸过程板材受到的粘性介质粘性附着力对板材变形的影响以及粘性附着力的影响因素。试验结果表明,增大板材表面压力差、提高粘性介质流动速度及提高粘性介质压力有利于提高粘性附着力的作用。研究结果可为合理利用粘性附着应力作用,提高板材成形性提供理论基础。     

7075铝合金板预拉伸工艺研究

采用直接热力耦合的方法,引入7075铝合金高温下的流变应力特征曲线,对不同厚度的7075铝合金板材在实际淬火工艺下的淬火过程进行数值模拟,揭示铝合金板材淬火残余应力分布规律;考虑铝合金板材拉伸过程中的实际夹持方式,对不同厚度7075铝合金板材实际拉伸过程进行数值模拟,分析对比拉伸后残余应力分布规律,并对拉伸工艺进行优化,确定最佳拉伸率和锯切量,揭示厚度变化对淬火残余应力、拉伸后残余应力以及锯切量的影响规律.利用钻孔法对实际拉伸的7075铝合金板材进行拉伸后残余应力的试验测试,数值模拟结果与试验测试结果相吻合.研究结果表明,随着厚度的增加,淬火残余应力、最佳拉伸率以及锯切量都相应增大,锯切量中过渡区长度为板材厚度的60％～70％.     

AZ31镁合金板材成形极限及温热成形应变速度研究

AZ31镁合金板材的伸长率随着温度和高温下应变速度的变化而改变，所以在研究AZ31镁合金板材的温成形性能时，必须考虑温度和变形速度对其的影响。在本文中，在不同成形条件下，对板材进行半球形凸模的拉伸试验和强度测试试验，并结合有限元模型，分析了温度和应变速度对AZ31板材的温成形性的影响。     

6000t拉伸矫直机电控系统

6000t拉伸矫直机将由铝板轧机轧制后的板材沿长度方向上拉伸，消除板材在轧制矫直后的残余应力，提高了板材性能，本文简述了电控系统。     

模具粗糙度对板材拉延件摩擦特性的影响

金属板材拉延是一个复杂的塑性变形过程,广泛应用在各种大型汽车覆盖件等零件生产中。介绍了金属带料弯曲拉伸试验机的工作原理和试验方法。该试验机能很好地模拟凹模圆角区的摩擦场变化规律;通过选用不同的模具表面粗糙度,改变带料拉伸力、变形速度和成形头平均面压,测出摩擦因数的变化规律,用以研究模具表面粗糙度等对板材拉延件摩擦特性的影响。研究表明,适当降低模具表面粗糙度,有利于发展边界润滑,减少摩擦热的产生和作用。该研究方法把拉延过程中的摩擦、磨损和润滑有机地结合起来,为优化拉延件加工的摩擦条件奠定了理论基础。     

"H"形钛合金拉深件的成形工艺研究

针对钛合金板材拉伸过程中存在的变形范围小、回弹大和成品率低等缺点，分析了钛合金板材成形的工艺性能和造成废品的原因，采取了相应的成形工艺措施，有效地解决了生产中遇到的问题。     

条形金属板材拉伸机的设计与应用

条形金属板材拉伸机主要应用于挠度弯曲大、宽长比系数小的薄型板材。笔者提出条形金属板材拉伸机总体设计方案,采用液压系统控制,根据液压拉伸力、变形量、楔形摩擦角等主要参数分析完成拉伸机的总体设计。通过金属板材拉伸机的应用,对存在的隔板变形规律性较小,人工矫直效果不稳定,难以保证装配精度,严重影响机组运转的平稳性等问题进行了探究,在一定程度上解决了预热器在安装过程中隔板变形大的难题,并提高了装配精度,满足结构可靠,节约了成本,缩短了制造周期。     

杯拉深承载极限研究

应用塑性流动理论和拉伸塑性失稳准则,导出基于三种常用材料硬化曲线的拉深临界失稳载荷通解,反映了板材厚向异性、加工硬化和凸模几何尺寸的影响。四种板材的拉深试验表明,理论解与试验结果的相对误差在5%以内。分析了对应不同硬化曲线的特解适合的板材种类。指出忽略板材的厚向异性或用不匹配的方程拟合试验硬化曲线会对解的精度产生明显影响。提出的通解适用于绝大部分板材的拉深性分析。     

金属板件等离子体弧柔性成形热过程计算与分析

建立了金属板件等离子体弧柔性成形的热过程数学模型，计算并分析了成形过程中板材的热物理参数、几何尺寸、等离子体弧扫描速度、冷却条件等因素对成形零件的温度场分布的影响规律。研究发现：在一定的成形条件下，可实现成形的板材厚度存在极限值；在保证板材表面温度足够高的前提下，采用较高的扫描速度仍可以获得较好的成形效果，而引入冷源，可更好地控制板件最终形状。     

基于应变梯度塑性理论的微塑性成形力学性能

不同厚度的T2紫铜试样的单向拉伸、微硬度和微弯曲试验表明,材料的力学行为与内禀的材料特征参数相关：厚度为30μm的板材,其拉伸强度比厚度为150μm的板材提高了28%,平均晶粒尺寸D为50μm的细晶,其拉伸强度比平均晶粒尺寸D为120μm的粗晶拉伸强度提高了33%,拉伸时呈现出“越小越强”的特征;当压痕深度与板材厚度的比值大于0.2时,压入深度越大,压痕硬度越大,呈现出“越大越硬”的现象;回弹角随板料厚度的减小而增大,当材料厚度小于一定值（0.06mm）时,材料的应变梯度硬化效应使得回弹角随板料厚度的变化更为剧烈,这种变化与采用应变梯度塑性理论预测的结果基本一致。     

二维零件DXF数据的获取与数控加工

通过对新版DXF文件结构及2维零件几何结构特征的分析，研究了从DXF文件的获取2维零件图形数据的方法；采用封闭环及树形线性表，提出了一种存储复杂2维零件几何特征的数据结构，可从复杂的DXF文件中识别分离2维机构特征；依据2维板材切割加工的工艺特点，给出了2维结构件切割下料的数控前后置处理与实现方法。本文方法对于各种类型的切割下料及其辅助工艺有参考价值。     

Workpiece Compatibility of Ceramic Cutting Tools

It is now well known that certain types of cemented carbides give excellent results when used to cut cast irons but poor results when used to cut steels and vice versa. This relative ability of a given tool material to perform well when cutting a given workpiece material is referred to here as compatibility.

Ceramic metal cutting tools have been in use in machining metals such a short time that it is not yet generally known on which materials these tools can be used to best advantage. In this report the performance of ceramic and cemented carbide tools is compared when machining a wide variety of metals. It is found that there are certain metals for which either the surface chemical or thermal characteristics of ceramic tools are particularly advantageous.

The report is concluded by a table which lists a large number of ferrous and nonferrous metals in order of decreasing compatibility with aluminum oxide tools.     

The tribology of ion implanted metal surfaces

Friction and wear experiments with ion implanted metals are described and mechanisms are outlined to account for the large changes observed in friction coefficient and wear parameter. It is concluded that the effects are due to a combination of the complex effects on the contact stress field introduced by a surface compressive stress resulting from ion implantation, as well as alterations in the oxidative properties of the surfaces brought about by the injection of chemically active species.     

Low load multiple scratch tests of ceramics and hard metals

Abrasion is caused by the repeated scratching of materials by individual particles in an abrasive, often under fairly light loads. This process has been simulated by carrying out scratch tests on a range of ceramics and hard metals. An array of different scratches was carried out on each sample with a different number of repeats along the same track for each scratch. The magnitude of the damage was measured by the width of the scratches. The frictional force between the indenter and test sample was also measured.

Although the width of single pass scratches in some of the harder materials was smaller than in softer materials, in multiple pass scratches, the final widths of scratches in some of the harder materials were greater than in the softer materials. This was due to differences in the contribution of fracture in the development of damage in multiple pass scratches.

It was found that fracture was a predominant form of damage to both hard metals and ceramics. In the case of the hard metals the fracture was on a fine scale, but with the ceramics fracture occurred on a larger scale, often removing large fragments of material.

These results, and the results of the friction measurements are correlated with the results of a microstructural examination of the mechanisms that occurred. They are also compared with a microstructural assessment of the early stages of wear in the abrasion of these materials.     

从废弃镍基电池中回收有价金属的研究进展

随着电子产业迅猛发展,废弃电池已成为重要的污染源,在废弃的二次充电电池中,镍基电池约占60％～80%,这些电池中含有大量镍、钴、铁、不锈钢等有用成分,而且某些金属成分在自然界中还是稀有资源,对废旧镍基电池回收利用的研究是非常有价值的,本文介绍了从废弃镍基电池中回收利用有价金属的研究进展,着重介绍了火法冶金技术、湿法冶金技术及其他新技术从废旧镍镉电池、废旧镍氢电池中回收利用有价金属的研究,最后对现有的废弃电池回收体系提出了建议。     

Thermo-oxidative behaviour of perfluoropolyalkylethers

For high-temperature aircraft turbine engines in the next century, new, extremely stable lubricants will be required. The chemical class known as perfluoropolyalkylethers is well known for its good and wide range of temperature behaviour. This paper reports on investigations into the thermo-oxidative stability of these fluids at high temperatures. The work includes the influence of metals on the stability, and corrosion tests, of selected PFPAE oils. The results show the large influence of the chemical structure and of certain metals.     

A new mechanism of plastic flow

When ductile materials are tested in simple shear, with moderate amounts of compressive stress on the shear plane, what appears to be negative strain hardening occurs at relatively large strains. These results are in apparent contradiction to the commonly held views that metals strain harden without saturation to the highest values of strain and that compressive stress on the shear plane does not influence flow stress.A new mechanism of plastic flow is presented that involves the formation and rewelding or microcracks of limited extent on shear surfaces. Possible applications of the new theory to metal cutting and geological events are briefly discussed.     

Application of laser joining process for elimination of stair steps in steel laminate tooling

Laminate tooling is a relatively fast and simple method of making large metal tools directly for various moulding processes in the rapid prototyping and manufacturing field. Metal sheets are usually cut, stacked, aligned and joined. In most cases, lasers are used only for the cutting of steel sheets in laminate tooling, but in this study, the use of the laser was expanded for improved laminate tooling. First, the laser was applied to eliminate the stair steps of steel laminates by filling them with molten filler metals. Then application of hard particles to molten filler metals for improved surface hardness of laminate tools was investigated. To achieve this goal, a CO₂ laser system composed of a CO₂ laser, a five-axis CNC table, an automatic feeding equipment of filler metal and flux and a personal computer was developed. Various experiments on filling stair steps and hardening were performed and the results were verified and estimated.     

Wear prediction for metals

In spite of the large number of wear models found in the literature, no model can predict metal wear a priori based only on materials property data and contact information. The complexity of wear and the large number of parameters affecting the outcome are the primary reasons for this situation. This paper summarizes the current understanding of wear modelling for metals. Several recent approaches such as wear mapping and wear transition diagrams have suggested some future possible directions for improvement. Some success has been achieved in describing severe wear of steels under unlubricated conditions using thermomechanical approaches. However, modelling of mild wear remains problematic, especially under lubricated conditions. In mild wear, asperity contact events dominate the wear processes. A single asperity collision simulation apparatus has been used to study asperity-asperity contact phenomena. Shear strain and strain accumulation were found to be the dominant underlying causes for wear. It is proposed that future research in wear prediction for metals incorporate the following aspects: wear mapping, temperature, shear strain response, boundary lubricating film strength, and surface roughness.     

Boundary element analysis of stress singularity in dissimilar metals by friction welding

Friction-welded dissimilar metals are widely applied in automobiles, rolling stocks, machine tools, and various engineering fields. Dissimilar metals have several advantages over homogeneous metals, including high strength, material property, fatigue endurance, impact absorption, high reliability, and vibration reduction. Due to the increased use of these metals, understanding their behavior under stress conditions is necessary, especially the analysis of stress singularity on the interface of friction-welded dissimilar metals. To establish a strength evaluation method and a fracture criterion, it is necessary to analyze stress singularity on the interface of dissimilar metals with welded flashes by friction welding under various loads and temperature conditions. In this paper, a method analyzing stress singularity for the specimens with and without flashes set in friction-welded dissimilar metals is introduced using the boundary element method. The stress singularity index (??) and the stress singularity factor (??) at the interface edge are computed from the stress analysis results. The shape and flash thickness, interface length, residual stress, and load are considered in the computation. Based on these results, the variations of interface length (c) and the ratio of flash thickness (t ₂/t ₁) greatly influence the stress singularity factors at the interface edge of friction-welded dissimilar metals. The stress singularity factors will be a useful fracture parameter that considers stress singularity on the interface of dissimilar metals.