轨道车辆用异种奥氏体不锈钢激光搭接焊接头的晶间腐蚀行为

采用高功率光纤激光焊接设备对0.8 mm厚SUS301L-DLT和2.0 mm厚EN1.4318+2G奥氏体不锈钢板进行了激光搭接焊工艺试验,并对接头分别进行了草酸腐蚀、硝酸腐蚀和电化学腐蚀试验,分析了接头及其母材在不同腐蚀条件下的晶间腐蚀行为。结果表明,焊接接头及母材经过草酸溶液浸蚀后,其晶界组织均为第一类阶梯组织,而在硝酸溶液热浸蚀时,接头的腐蚀率高于其母材金属。在硫酸溶液腐蚀介质中,焊接接头及其母材的双环电化学动电位再活化(DL-EPR)曲线上均出现再活化峰,其中接头的再活化率值较母材大,表明奥氏体不锈钢激光搭接焊接头的抗晶间腐蚀性能下降。     

6005A铝合金MIG焊接接头组织及性能研究

采用MIG焊接技术对6005A铝合金进行焊接,研究了搭接接头与对接接头的力学性能、拉伸断口形貌,接头不同位置的微观组织及焊缝合金成分。研究表明,对接接头的抗拉强度达到母材的68%,搭接接头抗拉剪切强度达到母材的50%以上;两种接头焊缝组织均为细小的树枝晶与等轴晶,熔合线附近组织为粗大的柱状晶,对接接头断裂位置为接头热影响区,搭接接头断裂在焊缝处,接头断口存在韧窝与准解离面,断裂机制为韧脆混合断裂。母材中的强化相为Mg_2Si,焊缝中存在的强化相为Mg_5Al_8与Mg_2Si。     

YAG脉冲激光焊接AZ61镁合金薄板对接接头的组织与性能

采用YAG脉冲激光焊方法对AZ61镁合金薄板进行焊接．利用光学显微镜、x射线能谱分析仪等手段分析焊接接头的宏观形貌、显微组织和化学成分,并对焊接接头的显微硬度和拉伸强度进行了测试．结果表明,焊缝正面有轻微塌陷,反面成形良好．焊缝表面圆滑、连续、鱼鳞纹细密均匀,接头成形良好．母材为粗大的等轴晶,焊缝区的晶粒比母材细小．焊缝区的显微硬度比母材区域明显提高,焊接接头的抗拉强度与母材相当,约为250MPa,焊接接头具有良好的力学性能;焊缝表面由于Mg元素的大量蒸发使铝的含量升高,而焊缝表面zn元素含量很低．     

几种铝钢异种金属熔钎焊工艺的对比与分析

采用脉冲旁路耦合电弧MIG焊、CMT及激光焊方法实现铝/镀锌钢板搭接焊,对焊缝界面微观组织、形貌及元素成分进行了观察分析,并测试了其力学性能.结果表明,三种焊接方法均可以实现铝/镀锌钢板异种金属的优质连接,获得成形良好的焊缝,搭接接头的抗拉剪强度均可以达到铝合金母材的80%以上,拉伸试样断裂在焊缝铝合金母材热影响区.当母材热输入及工艺合适时,三种方法下搭接接头界面处均形成一主要成分为Fe₂Al₅和FeAl₃,平均厚度约为8 μm的金属间化合物,而且控制金属间化合物的生成是获得铝/钢焊接优质接头的关键.     

铝合金搭接接头搅拌摩擦焊工艺研究

对LF2铝合金薄板，在摩擦搅拌焊焊机上进行了大量的搭接焊试验，通过对搭接接头成型时的特点及规律进行分析，总结了搭接焊过程中摩擦头转速、焊速等工艺参数对搭接焊缝质量的影响，确定了最佳焊接规范。结果表明，焊核区由平均尺寸6μm的晶粒组成，并且已无上下板的界面痕迹；因其晶粒度远小于母材，故拉伸断口均出现在接头的热影响区内；当摩擦头转速1100r／min，焊速在80～255mm／mm大范围内焊接时，接头质量均较高，焊速100mm／min时，接头剪切强度最大，可达到母材剪切强度的75％以上。     

添加层对6061铝合金激光搭接接头的影响

采用脉冲激光焊接方法对6061铝合金进行了搭接焊,研究了不同添加层对6061铝合金激光搭接接头的显微组织、剪切性能及腐蚀性能的影响。结果表明:当添加层为Zn粉、铝焊膏、Sn粉时Al板激光搭接焊容易产生缺陷,无法得到良好的焊接接头,当添加层为Ni粉时可以得到无明显缺陷的良好焊接接头。不同添加层焊接接头的剪切性能为Ni粉Zn粉铝焊膏Sn粉,Ni粉添加层焊接接头的剪切强度为27.7MPa,是Zn粉添加层焊接接头剪切强度的3.19倍。Ni粉添加层焊缝极化曲线的钝化区范围为322 mV,比母材极化曲线的钝化区大了172 mV, Ni粉添加层焊缝的耐腐蚀性能大于母材。     

不锈钢薄板大间隙接头激光-MIG电弧复合高速焊接工艺

采用填充ER316焊丝的光纤激光-MIG电弧复合焊方法,焊接间隙为0.5 mm、厚度为1 mm的SUS444铁素体不锈钢薄板对接接头和搭接接头,研究了获得成形良好的对接接头和搭接接头的工艺参数窗口和极限焊接速度,并对焊缝进行了着色渗透检验和拉伸试验. 结果表明,合理匹配焊接速度和焊接电流,是获得成形良好的大间隙接头的关键;当焊接速度过小或焊接电流过大时,较大的热输入导致焊缝过度熔透,焊缝成形不良;当焊接速度过大或焊接电流过小时,较小的热输入导致焊缝未熔透. 对接接头焊缝成形质量良好且熔透的极限焊接速度可达12 m/min,而搭接接头的极限焊接速度为5 m/min. 成形良好的焊缝均未发现表面裂纹. 拉伸试验表明,对接接头断裂在母材上;搭接接头绝大部分断裂在熔合线附近,极限焊接速度下获得的搭接接头的抗拉强度是母材的84.2%.     

镍基合金/不锈钢钨极惰性气体钎焊接头的特性

选用CuSi3焊丝对镍基合金／不锈钢进行钨极惰性气体（TIG）钎焊实验,运用OM、SEM和EDS分析接头微观组织,通过拉伸实验和硬度实验评定接头的力学性能。结果表明：TIG钎焊接头具有熔焊和钎焊的双重性质,不锈钢母材局部熔化,生成Fe基熔合区;在接头搭接区及镍基合金母材与焊缝金属之间存在界面反应层,反应层可分为熔化未混合区、Ni基树枝晶和晶间Cu基区;焊缝区为Cu基体上分布着颗粒状Fe基固溶体;CuSi3接头剪切强度达到195MPa,接头断裂于焊缝与不锈钢界面处,断口为微孔聚合机制引起的塑性断裂：在界面处硬度值发生突变,Ni基树枝晶硬度值达到HV433.3,不锈钢熔合区中的Fe基体硬度值达到HV453．4,近界面处焊缝区Cu基体硬度值为HV150。     

机械轻量化用轻合金的FSSW接头组织与性能

采用搅拌摩擦点焊进行了机械轻量化用Mg-8Al-1Zn-0.2Nd-0.1V新型轻合金的搭接焊试验,测试和分析接头的显微组织、物相组成、硬度分布和力学性能。结果表明,与母材相比,FSSW接头焊核区只发现α-Mg基体而未发现Mg17Al12相,FSSW接头焊核区硬度与母材相当,硬度最低值位于前进侧热影响区;接头系数达到90%。     

新型EH40船板钢大热输入量埋弧焊焊接接头组织性能研究

对EH40船板钢埋弧焊焊接接头的组织性能进行了试验分析。结果表明：以60kJ／cm的焊接热输入量焊接，接头的强度高于母材，热影响区（HAZ）没有出现焊接软化区。HAZ的低温冲击韧度低于母材。其中靠近熔合线的粗晶区冲击值（85．2J）最低，远离熔合线4mm处的冲击值（246．0J）已接近于母材。HAZ的组织状态对接头力学性能有较大影响，母材中Ti、Nb合金元素生成的碳、氮化合物在一定程度上改善了HAZ的韧性。     

基于激光表面微纳结构的胶接性能研究进展

胶接具有独特的性能而被广泛关注,但在实际应用中往往由于界面结合强度不足而导致接头在服役过程中过早失效。激光表面处理是一种能够有效提高胶接接头表面性能的方法,通过激光表面处理会使黏接材料表面形成不同的表面微纳结构,从而改善接头的性能。首先介绍了激光表面处理原理及激光器分类,对比了不同激光器的优缺点及加工质量特性,分析了激光加工参数对接头强度的影响。其次从激光加工不同表面微纳结构入手,阐述了不同表面微纳结构的加工方式,分析了不同表面微纳结构对不同材料接头强度的影响。此外,针对不同的表面微纳结构,其结构参数有所不同,导致接头表面化学成分和润湿性能也有所不同,使得接头强度有所差异,在此基础上分析了微纳结构参数对接头强度的影响及原因。同时,胶层间的作用机制与接头强度具有密不可分的联系,研究表明,不同的表面微纳结构对胶层的作用机制具有明显的不同,归纳总结发现,经激光表面处理形成表面微纳结构后接头表面粗糙度、化学性质、润湿性能及胶层间裂纹的扩展对接头强度的提升具有一定作用。最后,对激光表面处理微纳结构的研究进行了展望。     

Strength of spline joints assembled by forming

In this paper, a new assembling method of spline joints that enables tight fitting in a simple manner by allowing slight plastic deformation at the spline teeth was introduced. Experiments were carried out for the spline joints of medium carbon steel varying the overlap zone between the male and the female spline teeth. Axial joining strength was increased with increase in the overlap length due to the residual compressive stress by forming. The joint by the proposed method also showed higher torsional strength than the conventional joint. Improvement in the torsional strength was explained based on the deformation and hardness distribution around the spline teeth. With respect to the shape of overlap zone, better results were obtained when using the specimen having a uniform overlap length along the axial direction.     

Modelling of deformation and failure of crash toughened adhesive bonded lap shear joints

Abstract

With an increase in the use of advanced high strength steels in vehicle architectures, materials joining issues have become increasingly important. Among the various joining methods, adhesive bonding is increasingly used in automobile manufacturing. Successful implementation of adhesive bonding to improve structural crashworthiness and reduce vehicle weight requires the knowledge of issues related not only to processing but also to joint performance. In this study, a new anisotropic yield criterion which is determined from tensile and shear tests, is developed and incorporated into a finite element model to predict the static load displacement curves of various adhesive bonded steel joints. In the developed model, when the calculated plastic strain of bonded steel joint reaches the equivalent plastic strain of the adhesive the joint is regarded as failed. Modelling results have been validated by the experimental data. Since the model covers different steel grades, gages, and overlap distances, the model can be used to predict the static strengths of adhesive bonded assemblies. Finally, the model is employed to evaluate the effect dissimilar steel grades and sheet gages on the joint strength of lap shear bonded steel joints. The results show that for the joints made of dissimilar steel grade and sheet gage, the stiffness (i.e. strength and thickness) of the two adherends should be balanced to obtain the optimum joint strength.     

Influence of Multi-pass Friction Stir Processing on Microstructure and Mechanical Properties of Die Cast Al–7Si–3Cu Aluminum Alloy

The influence of overlap multi-pass friction stir processing on the microstructure and the mechanical properties, in particular, strength, ductility and hardness of die cast Al–7Si–3Cu aluminum alloy was investigated.It was observed that increase in the number of overlap passes friction stir processing resulted in significant refinement and redistribution of aluminum silicon eutectic phase and elimination of casting porosities. The microstructural refinement by the friction stir processing not only increases the ultimate tensile strength from 121 to273 MPa, but also increases the ductility as observed by the increase in fracture strain from 1.8% to 10%. Analysis of the fractured surface reveals that the microstructural refinement obtained by friction stir processing plays a vital role in transforming the fracture mode from completely mixed mode to the ductile mode of the fracture with increasing number of passes. The change in the size, shape, morphology and distribution of eutectic silicon particles and elimination of the porosities are the main reasons for the increases in tensile strength and ductility due to friction stir processing.     

基于有限元的搭接接头应力集中系数分析

针对双侧焊接的搭接接头进行有限元建模,计算不同搭接长度、焊缝宽度和焊趾过渡圆弧半径下焊根和焊趾处的应力集中系数,回归分析建立应力集中系数与各几何参数的关系方程.结果表明,搭接长度对应力集中系数的影响最显著,随着搭接长度增大,焊根和焊趾处应力集中系数都增大;随着焊缝宽度增大,焊根应力集中系数降低,焊趾应力集中系数升高;焊趾过渡半径较大时,随着焊趾过渡半径增大,焊根应力集中系数小幅增大,焊趾应力集中系数基本不变;应力集中系数关系方程与有限元计算结果吻合较好,焊根和焊趾应力集中系数的相对误差在5％和2％以内.     

异径接头热成形坯料形状数值模拟与实验研究

采用有限元成形分析软件DEFORM＿ 3D,对异径接头热成形在坯料形状选择上的数值模拟研究,并对模拟结果进行实验.总结出异径接头热成形坯料的最佳形状为锥形管.研究结果对异径接头的设计与制造有一定的指导作用.     

汽车车身钢-铝搭接连接技术的研究现状

目前汽车车身钢-铝搭接的连接方式有机械连接、焊接和粘铆复合连接三种方式。为适应汽车轻量化的趋势,单一的连接方法已经满足不了钢-铝搭接接头性能的要求,其连接技术亟待创新。突破传统的工艺局限,在钢-铝中添加夹层(或粘结剂),采用特制的搅拌头进行热致搅拌摩擦点焊或是激光点焊。钢-铝接头的连接机理、过程形成特征以及接头受力、力学响应特征是当前研究的主要发展趋势。论文概述了其搭接连接的研究现状及成果,并展望了前景。     

异种金属材料自冲铆接头位置对疲劳强度的影响

为了提高结构件的疲劳性能,基于大量实验研究了自冲铆接头位置布置对剪切结构件疲劳强度的影响。通过改变铆钉个数、搭接尺寸、最大循环载荷、铆钉到板长及板宽的边距等因素,对12种不同铆接位置的结构件进行了静力学实验,并在此基础上进行疲劳实验。实验结果表明:在搭接尺寸不变的情况下,铆钉到板长或板宽的距离过大或过小均会降低结构件的疲劳强度;结构件疲劳寿命随最大循环载荷的减小而增大;在一定范围内,结构件疲劳强度随搭接尺寸的增大而增大,随后呈降低趋势;二钉结构件的疲劳寿命显著高于单钉结构件的疲劳寿命,但并不随铆钉个数呈倍数的关系增长。     

飞机钛合金接头零件耳片槽加工方法研究

飞机钛合金接头类零件耳片槽加工一直困扰着航空制造企业。针对飞机钛合金接头零件耳片槽加工难点,深入分析导致耳片槽加工质量差的原因,并对钛合金接头零件耳片槽加工进行了多种加工验证,提出一种去应力式耳片槽常规加工方法,并设计一套用于接头零件加工的铣削装置,在实现钛合金耳片槽快速加工的同时,有效保障了接头零件耳片面表面质量,消除了接头零件耳片收口现象。     

Analysis of manufacturing parameters on the shear strength of aluminium adhesive single-lap joints

An experimental and numerical investigation into the shear strength behaviour of aluminium alloy adhesive lap joints was carried out in order to understand the effect of geometrical and manufacturing parameters on the strength of adhesive bonding joints, with the aim of optimizing shear strength. The adherend material used for the experimental tests was an aluminium alloy in the form of thin sheets, and the adhesive used was a high strength epoxy. Five surface treatments were studied. The surface treatments process using sodium dichromate–sulphuric acid etch (CSA) and abrasive polishing (AP) resulted in improved joint shear strength when compared to acetone cleaning (SW), caustic etch (CE), and Tucker's reagent etch (TR). The decrease in surface roughness was found to increase the shear strength of single-lap joints. An increase in adherend thickness and overlap length was found to increase shear strength which means that an increase in joint rigidity increases its strength. A numerical analysis was developed to explain the effect of the geometrical parameters on rotation angle, stress and strain fields, and failure load. An increase in adherend thickness and overlap length decreases the joint rotation angle, reducing the plastic strain peak and therefore increasing the failure load.