微装配技术的发展现状

微器件的装配并不是一个新兴的领域 ,但随着微加工技术、显微技术和集成电路技术的发展 ,微装配概念发生了根本性的变化 ,产品的范围和应用领域被拓宽 ,出现了许多新的技术 ,它的发展是与微机电系统 (MEMS)、纳米技术 (Nanotechnology)密切相关的。本文对微装配技术的发展现状进行了综述 ,介绍了微装配的特点和使用的许多新技术     

铝合金液冷冷板窄台阶搭接搅拌摩擦焊工艺研究

文中研究了铝合金液冷冷板窄台阶搭接搅拌摩擦焊工艺。冷板基底材料为6063 铝合金,盖板材料为3A21 铝合金。设计了窄搭接搅拌头,减小了轴肩宽度和焊接压力,增加了接头焊接时材料的流动性,针对不同焊深窄台阶冷板进行了窄搭接焊接工艺试验。研究表明,通过优化搅拌头形貌尺寸和工艺参数能够实现4-2（焊缝深度–台阶宽度,mm）、6-4 和9-6 的窄搭接搅拌摩擦焊焊接,焊接过程中进行定位预焊能有效避免产生焊缝S 型曲线,前进侧为6063 或3A21 时均能形成良好的焊缝。     

Stability of the friction stir welding process in presence of workpiece mating variations

This paper explores common process variations encountered in friction stir welding (FSW) and the limits to which acceptable joint strength is maintained while welding with a robotic FSW system. Part fit-up and mating variations are common in manufacturing, yet the limits to which a friction stir welding process can weld without major process adjustment are unclear. The effects on joint strength and mechanical properties of several of the most common mating variations (i.e., faying surface gap, misalignment, mismatch, etc.) are experimentally determined as individual effects as well as among common welding parameters. Experimental results on 5-mm-thick aluminum alloy 5083-H111 show that ultimate tensile strength, yield strength, and elongation begin to decrease from nominal weld conditions when either the tool offset distance from weld centerline or gap in abutted plates exceeds 25% of the average pin diameter (6?mm). In addition, vertical plate mismatch and lack of penetration can be tolerated up to 2.5% and 10%, respectively, before adverse effects on mechanical properties are observed. The work also indicates that of all the mating variations tested in this study, tool misalignment, followed by travel angle, has the most significant effect on the measured joint strength. Process stability testing has shown that the FSW process is able to endure part fit-up and mating variations within a defined tolerance, giving the practitioner an awareness of how well stock workpiece tolerances must be controlled before joint strength is adversely effected.     

Precise Micro-Assembly Through an Integration of Micro-EDM and Nd-YAG

Micro-EDM (micro electro-discharge machining) integrated with Nd-YAG laser as a novel process for precise micro-assembly is presented in the paper. In the integrated system the individual micro-parts assembled can be machined using micro-EDM, and accurately moved to the desired position using ultra-precision motion control, and fuse bonded with a laser beam. This process is demonstrated through two cases of a precise endless diamond wire saw defined as a pin-to-pin and a pin-to-plate micro-mould using the novel integrated system. As a result of this on-line assembly process, the pin–plate positioning accuracy and perpendicularity can be maintained, and a smooth pin–pin joint can also be obtained.     

Intelligent control of microassembly process based on in-process monitoring of pressing force

To realize an automated and intelligent microassembly process, a method has been developed to monitor the position of the shaft in the plate of the high-precision spindle motor to reduce the shaft high and the shaft low problems. The shaft low occurs when the shaft is stuck in the plate lower than the setting tolerance due to the large tolerance of the shaft and the small tolerance of the plate. While the shaft high appears, the shaft is pressed through the plate over the setting tolerance due to the small tolerance of the shaft and the large tolerance of the plate. The plate is expanded to reduce the shaft low before microassembly by preheating technique at the experimentally simulated temperature. The force sensor is utilized to monitor the pressing force. A method proposed to reduce the shaft high introduces the reference voltage as the threshold value, which is obtained by taking the differentiation of the in-process pressing force. A slope detector is developed to calculate the output voltage and the motor driver of machine is controlled when the obtained output voltage is larger than the reference voltage. It is proved that the shaft high and the shaft low are well controlled and reduced regardless of the geometries of the shaft and the plate.     

2A14厚板铝合金SSFSW角焊缝接头组织及性能

采用自主研制搅拌针长度为8.5mm的静止轴肩搅拌工具和2A14-T4厚板铝合金进行150°角焊缝接头静止轴肩搅拌摩擦焊工艺试验,探讨焊接工艺参数对接头组织和力学性能的影响规律。结果表明:在500~700r/min主轴转速与40~100mm/min焊接速度范围内均可获得表面光滑无内部缺陷的角焊缝接头,其外观尺寸可精确控制基本无残余焊接角变形。焊缝区主要由焊核(Stir zone,SZ)组成,SZ形状类似搅拌针圆锥台状或椭圆状、其宽度沿厚度方向分布比较均匀;热力影响区(Thermal mechanical affected zone,TMAZ)及热影响区(Heat affected zone,HAZ)宽度明显较小。焊缝区硬度分布具有明显不均匀特征,最薄弱区位于TMAZ与HAZ的交界处。主轴转速变化对焊缝区平均硬度影响较小,但随着焊接速度增加其平均硬度明显增大。角焊缝前进侧等效拉伸强度大于后退侧,等效拉伸强度随转速增加而减小,焊速的增大而增大。在500r/min-100mm/min焊接工艺下所得到的接头等效拉伸强度最高,可达到母材的79.24%。在拉-剪复合承载模式下,角焊缝拉伸试样宏观塑性变形很小呈现脆性断裂特征。     

铝合金/钢异种材料熔钎焊接工艺及其研究现状*

铝合金/钢复合结构以具有重量轻、综合性能高等优势在汽车、航空航天、石油石化、电力、船舶等行业具有广泛的应用前景。但二者之间巨大的理化性能差异,使铝合金/钢板异种金属的焊接仍然存在诸多问题。熔钎焊接工艺是基于母材之间存在的熔点差异,通过精确控制焊接热输入,在确保高熔点母材不熔化的前提下,让低熔点母材和填充金属熔化形成熔焊接头,并与未熔化的高熔点母材形成钎焊连接接头,是适合铝合金/钢复合结构优质高效制备的合适焊接工艺。通过对国内外对铝合金/钢熔钎焊接工艺、接头组织性能调控等方面研究现状的综合评述,讨论了铝合金/钢熔钎焊接技术存在的问题,并对铝合金/钢熔钎焊接技术工程化应用所采取的措施进行阐述。     

紫铜搅拌摩擦焊接工艺研究及接头组织分析

试验研究了板厚为 2 m m和 12 mm的紫铜板的搅拌摩擦焊工艺 ,分析了焊接接头组织及性能。结果表明 ,板厚为 2 mm的紫铜 ,在一较宽的规范范围内 ,可得到组织致密、无孔洞、无裂纹的焊接接头 ,接头强度可达到母材的90 %。板厚为 12 m m时 ,采用双面焊 ,仅中部有未融合的缺陷 ,但缺陷在板厚方向的尺寸小于 1%的板厚 ,大大小于钨极氩弧焊时所容许的缺陷率。焊缝的显微组织为典型的再结晶组织 ,晶粒细小 ,焊缝两侧热影响区的组织不对称。     

Effects of welding speed on microstructures and mechanical properties of AA2219-T6 welded by the reverse dual-rotation friction stir welding

Reverse dual-rotation friction stir welding (RDR-FSW) is a novel FSW technology in which the tool pin and the assisted shoulder rotates reversely, thus it has the capability to obtain appropriate welding conditions through adjusting the rotating tool pin and surrounding assisted shoulder independently. In the present study, a RDR-FSW tool system was designed and successfully applied to weld high strength aluminum alloy 2219-T6, and the effects of welding speed on microstructures and mechanical properties were investigated in detail. At a constant rotation speed of 800 rpm for both the rotating tool pin and the reversely rotating assisted shoulder, defect-free joints were obtained at welding speeds ranging from 50 to 150 mm/min, while a cavity defect appeared at the three-phase confluction on the advancing side when the welding speed increased to 200 mm/min. With increasing of the welding speed, the width of the softened region decreased, but the minimum microhardness value increased gradually. When compared with the joints welded by the conventional FSW, there is only a minor variation of the Vickers hardness across the stirring zone in the joint welded by the RDR-FSW. The maximum tensile strength 328 MPa (73.7 % of the base material) was obtained at the welding speed of 150 mm/min, while the elongation reached its maximum 7.0 % (60.9 % of the base material) at the welding speed of 100 mm/min. All defect-free joints were fractured at the weakest region with the minimum Vickers hardness, while for the joint with cavity defects the fracture occurred at the defect location. The tensile fracture was in the ductile fracture mode.     

某雷达冷板双轴肩搅拌摩擦焊接工艺试验

文中介绍了某雷达MB8镁合金冷板的双轴肩搅拌摩擦焊接试验。双轴肩搅拌摩擦焊接技术对夹具设计以及应用环境的要求较常规搅拌摩擦焊接低。本试验中搅拌头转速设计为1000～1600 r／min,焊接速度设计为100～160 mm／min。通过测量冷板焊接接头处的拉伸强度和硬度,分析了焊接工艺参数对接头力学性能影响的机制。试验结果表明,MB8镁合金冷板双轴肩搅拌摩擦焊接接头处没有出现未焊透、气孔和夹杂等镁合金熔焊常见的缺陷,接头处的拉伸强度为199～211 MPa,平均拉伸强度达到母材强度的91％,接头处布氏硬度为30～39 HBS ,相比母材略有下降。试验结果说明双轴肩搅拌摩擦焊接技术非常适合用于冷板以及其他结构件的焊接。     

铝合金搅拌摩擦焊技术研究

论述了搅拌摩擦焊的焊接方法、工艺过程和基本原理；通过大量的工艺参数优化，解决了焊缝中的孔洞问题，使ＬＦ６板材搅拌摩擦焊的焊缝达到与母材等强，ＬＹ１２焊后未经热处理，连接强度接近母材的８０（。由金相分析可以看出，搅拌摩擦焊属于固相连接，焊缝晶粒细小，无气孔、夹杂、裂纹等焊接缺陷。初步应力测试发现，搅拌摩擦焊焊缝比熔焊焊缝的残余应力低。试验研究结果表明，搅拌摩擦焊焊接过程稳定可靠，焊接接头性能良好，具有广泛的应用前景。     

UV-LIGA和微细电火花加工技术组合制作三维金属微结构的研究

研究了UV-LIGA和微细电火花加工技术组合制作三维金属微结构的工艺方法。首先通过UV-LIGA制作二维金属微结构,再对该微结构进行微细电火花加工得到三维金属微结构。该方法具有加工精度高、可实现自由曲面三维金属微结构制作的优点。制作出了局部为梯形凸台和锥形凹槽三维微结构的镍模具。分析了微细电火花加工中放电参数对表面粗糙度的影响,通过减小放电电压和电容的方法降低了表面粗糙度。     

Manufacturing of complex-shaped ceramic components by micropowder injection molding

The micropowder injection molding process (microPIM) offers a large-scale fabrication technology for metal/ceramic microstructures. Current R + D efforts focus on increasing the degree of complexity of the 3D microparts molded rendering it necessary to implement novel tools and demolding methods. The increase in the degree of complexity was demonstrated by a dispenser screw. Progress included the adaptation of the untwisting technique known from plastic injection molding to PIM green compacts. This allowed for a burr-free demolding in spite of the backcuts of the screw design.     

BONDING OF MINIATURE PARTS WITH ADHESIVES AND VISION BASED PROCEDURE INSPECTION

Bonding with adhesives is an important technique for building up hybrid microsystems.Some adhesives are tested with capillary dispensing system for microassembly, and volume of dropletsless than 10 nl with good repeatability can be acquired. 1-part UV curing adhesive hardens rapidly andis suitable for bonding of transparent microparts. Light-activated adhesive starts the curing process inan adjustable short period of time after the radiation of visible light, and thus suits bonding ofnon-transoarent microparts. A method is proposed for bonding the guides of a miniature linear motorbeing developed by collaborate research center 516 (SFB516) in Germany.With the method high as-sembly accuracy in the vedical direction can be guaranteed. By making small grooves on the stator forcontaining adhesive, the deterioration of the accuracy due to the thickness of adhesive layer can beavoided. The criteria on deciding the size of the groove are given and analyzed. Vision based inspec-tion method is introduced for aut     

焊后热处理对高氮奥氏体不锈钢搅拌摩擦焊接头组织及性能的影响

对高氮奥氏体不锈钢进行搅拌摩擦焊接。焊接过程中没有出现氮元素的损失及其他相的生成。对焊接接头进行焊后热处理,以得到具有不同组织差异性的搅拌摩擦焊接头。微观组织分析表明：在焊态的接头中,焊核区晶粒细化且含有大量的小角度晶界,母材区与焊核之间存在明显的组织差异;热处理态接头中,焊核区的晶粒尺寸略小于母材,各种特征晶界的比例分数都与母材基本相当,接头内组织差异性减小。力学性能分析表明：大的组织差异使焊接接头呈现出典型的高匹配特征,屈服强度、抗拉强度明显升高,伸长率有所降低。较小组织差异的接头匹配模式发生变化,进而导致力学性能发生明显改变,屈服强度、抗拉强度降低,伸长率恢复到母材水平。     

高强铝合金厚板窄间隙激光焊接新工艺

针对铝合金厚板激光焊接存在的问题,提出采用窄间隙激光焊接的工艺技术路线,在分析了这种工艺方法的难点后,采用3.5 kW高光束质量扩散冷却slab CO2激光器,通过工艺方案的优化,首次成功实现了20 mm厚铝合金的窄间隙激光焊接.     

UV-LIGA和微细电火花加工技术组合制作三维金属微结构

为了制作三维金属微结构,研究了UV-LIGA和微细电火花加工技术组合的工艺方法。使用UV-LIGA技术制作了准三维金属微结构,然后,对该微结构进行微细电火花加工制作三维金属微结构。使用提出的方法制作出了局部为梯形凸台和锥形凹槽三维微结构的镍模具,给出了梯形凸台和锥形凹槽的尺寸。分析了微细电火花加工中放电参数对表面粗糙度的影响,在工作电压为65V,标称电容为100pF时得到了Ra为0.08μm的微细电火花加工表面。研究结果表明,使用该方法可实现三维金属微结构的制作;通过减小工作电压和标称电容的方法可降低微细电火花加工的表面粗糙度。     

双相不锈钢制冷凝器SAF2507换热管与316L管板的焊接工艺

塔顶冷凝冷却系统是炼油厂腐蚀最严重的部位，寻求新材料代替碳钢、高合金钢等腐蚀比较严重的材料，是工程应用的需求。文章介绍了双相不锈钢焊接的特点，提出了双相不锈钢制冷凝器SAF2507换热管与316L板焊接工艺，采用不同接头形式、不同的焊接保护气体进行了焊接试验，并通过对焊缝及热影响区组织的金相分析，找出了合理的焊接工艺。     

活性激光电弧复合焊接法研究

为了进一步提高激光电弧复合焊接的熔深,提出活性激光电弧复合焊接法。在氧气的保护下,用小功率光纤激光在待焊焊件表面进行预熔处理,使表面熔化生成一层氧化层,然后用激光电弧复合焊接覆盖氧化层,达到增加熔深的目的。结果表明,激光预熔后进行激光电弧复合焊接,电弧明显收缩,熔深增加1.5倍左右,表面成形良好。激光预熔后,焊缝含氧量增加,熔池表面张力温度系数由负变正,使得复合焊接熔深增加。研究工艺参数对焊缝熔深和熔宽的影响,随着激光预熔功率的增加,熔深增加熔宽减小;随着电流的增加,熔深熔宽都增加,但激光预熔后的焊道增加更快。随着复合焊接速度的增加,熔深和熔宽都减小。随着复合焊接中激光功率的增加,熔深增加,对熔宽的影响较小。利用活性激光电弧复合焊接法,可以得到较为细小的焊缝组织,提高焊接接头的抗拉强度,能达到母材抗拉强度的95%,且面弯和背弯180°后未出现裂纹,表明接头具有良好的韧性。     

A hybrid approach for cam shape design and profile machining of general plate cam mechanisms

Plate cam mechanism can easily produce the positive and functional motions in contact of cam and follower. Generally cam mechanism is used in many fields of mechanical control, automation, and industrial machinery. To obtain the accurate motion of follower, the profile of cam must be designed and machined precisely. This paper proposes an instant velocity center method for the profile design and a biarc fitting method for the profile machining to 4 different types of plate cam mechanisms with reciprocating or oscillating motion and roller or flat-faced followers. The key of this paper is the introduction of a hybrid system combined the design procedures and the manufacturing procedures. The main idea is that the minimum machining data are built by the accurate biarc curves fitted directly from the design parameters. The radial direction angles toward biarc centers for the accurate biarc curve fitting can be defined directly by the contact angle of cam and follower given in the design procedures. An application of the proposed approach is verified the accurate profiles of a designed cam and a machining cam using the minimum NC data within a given machining tolerance.