阳极氧化处理增强Al-Li合金胶接板剪切强度的机理

为揭示磷酸阳极氧化处理后Al-Li合金胶接接头剪切强度大幅度增强的机理,分别对其进行机械打磨和磷酸阳极化表面处理,并选用不同的分析仪器对表面处理后的Al-Li合金表面微观形貌、粗糙度、表面润湿性和表面自由能进行测试计算和分析。结果表明,机械打磨后仅在Al-Li合金表面留下纵横交错的沟槽,而磷酸阳极化处理后使得Al-Li合金表面产生了微观粗糙的多孔膜,增加了胶层与合金表面的接触面积,改善了胶质分布的均匀性;磷酸阳极化处理后Al-Li合金表面自由能明显提高,改善了粘接界面的润湿性能。两方面的共同作用,使得胶接界面的抗剪切能力大幅提高。     

AZ31镁合金的微弧氧化处理及其对粘接性能的影响

采用正交试验方法对镁合金硅酸盐体系的微弧氧化处理工艺进行优化,采用SEM、EDS、XPS和XRD对微弧氧化膜的微观成分与结构进行了表征,进而分析探讨了电解液成分及氧化参数对镁合金表面膜粘接性能的影响规律。研究结果表明,所研究的几种工艺参数对AZ31镁合金表面的粘接性能的影响程度从小到大排列为:KOH的浓度<频率相似文献   

Structural behavior of double-lap shear adhesive joints with metal substrates under humid conditions

Structural adhesive bonding is very often used joining method in aerospace and automotive industry, but in civil engineering, especially in façade applications, semi-flexible or semi-rigid adhesives are still rarely used. The article is focused on experimental analyses of structural adhesive joints intended for façade applications (e.g. bonding of façade cladding elements to the supporting substructure). The experimental study contains a comparison of the structural behavior of two different adhesives in joints with aluminum or zinc-electroplated steel substrates with various surface pre-treatments. The main goal of the study is a comparison of the mechanical properties of joints exposed and unexposed to laboratory ageing conditions; immersion on demineralized water according to ETAG 002 (Guideline for European Technical Approval for Structural Sealant Glazing Kits). Water content in adhesive layer can change significantly its mechanical properties and adhesion of glue to the substrate. Ageing resistance of joint can be improved by durability increasing of the substrate. For this reason, two different substrate materials with various surface treatments (mechanical roughening, smooth surface, anodizing) were tested. Different adhesive resistance against humid conditions was observed depending on the substrate material and pre-treatment. STP polymer joints showed strength reduction by 30% after immersion for almost all substrates, while acrylate adhesive proved 20% strength reduction for roughened aluminum substrate and 60% strength reduction for zinc-electroplated steel substrate with a roughened surface. The zinc-electroplated steel substrate showed problematic adhesion in case of the acrylate adhesive both reference set of specimens and specimens exposed to laboratory ageing. The positive effect of roughening on adhesion and ageing resistance was clearly observed in the specimens bonded by the acrylate adhesive.

     

超声强化氨基化多壁碳纳米管改性环氧黏接接头性能研究

目的 探究超声处理对氨基化多壁碳纳米管(MWCNTs–NH₂)改性环氧黏接接头黏接性能和热稳定性的影响,为强化MWCNTs–NH₂改性环氧胶黏剂与铝合金的黏接提供参考。方法 通过机械搅拌与声波破碎的方法将质量分数为0.75%的MWCNTs–NH₂添加到环氧胶黏剂基体中,使用MWCNTs–NH₂改性环氧胶黏剂制备铝合金黏接接头,基于超声辅助黏接工艺在铝合金黏接过程中进行超声处理。通过傅里叶变换红外光谱仪(FTIR)分析MWCNTs–NH₂改性环氧胶黏剂基体官能团的变化情况。采用单搭接剪切强度试验测定黏接接头的拉伸剪切强度。通过扫描电子显微镜(Scanning Electron Microscope,SEM)观察黏接接头拉伸失效断面以及铝合金与胶黏剂间的黏接界面。通过热失重分析仪(TGA)测试并记录胶黏剂试样质量随温度变化的曲线。结果 经超声处理后,MWCNTs–NH₂与树脂基体间的化学反应增强。与纯环氧黏接接头相比,超声处理后的MWCNTs–NH_2...     

铝合金裂纹板的阳极化处理与复合材料补片胶接修理效果

采用磷酸阳极化方法对胶接修理铝合金裂纹板的粘接表面进行了处理,并用单向碳纤维/环氧复合材料补片对铝合金进行了修补.测试了阳极化铝合金的粘接性能、修补结构的静态力学性能和疲劳性能,考察了粘接表面的阳极化处理对修补结构的静态力学性能和疲劳性能的影响.结果表明,磷酸阳极化在铝合金表面形成多孔膜,复合材料补片修补胶接时胶粘剂能渗透进入阳极化铝合金表面的多孔膜,在粘接界面上形成一层过渡层,该过渡层的形成能有效提高其与复合材料的粘接性能,其粘接副的拉剪强度提高了104%;铝合金裂纹板胶接修理前的粘接表面的阳极化处理能大幅度地提高修复结构的静态强度和疲劳寿命,当用单向碳纤维/环氧复合材料补片单面修补时,修补结构的破坏强度为418.13MPa,恢复到完好板的93.42%;修补结构的疲劳寿命相对裂纹板延长了1.42倍,比未阳极化的修补板的疲劳寿命增加了27.59%.修补前的阳极化处理也使修补结构在一定周次疲劳后的剩余强度有所提高.     

Friction stir spot welding of rare-earth containing ZEK100 magnesium alloy sheets

In this study, rare-earth containing ZEK100 magnesium alloy sheets were joined using friction stir spot welding. In order to determine the influence of welding parameters on lap-shear strength, overlap joints were created under various tool rotational rate and shoulder plunge depths. Relationships between the maximum lap-joint strength and key features of the weld including effective sheet thickness, interfacial hook width, and shoulder plunge depth were established. Based on the results of this study, welds with larger effective upper sheet thickness and small interfacial hook height generally exhibited the highest lap-shear strength. In addition, experiments indicated that overlap joints welded at 1500 rpm and 0.2 mm tool shoulder plunge depth exhibited the highest lap-shear strength.     

基于循环载荷的单搭胶接接头残余强度分析

为研究循环载荷下单搭胶接接头的残余强度及失效机理,以5052铝合金单搭胶接接头为研究对象,先后对其进行静强度测试、疲劳强度测试和残余强度测试,引入威布尔分布对试验数据进行分析,检验其有效性,并采用超声扫描显微镜和扫描电子显微镜对失效胶层进行失效机理分析。结果表明,在疲劳循环载荷作用下,接头刚度基本稳定,而残余强度随着疲劳循环载荷周次的增加,呈现出先增大后减小的变化趋势;疲劳裂纹从接头搭接端部的界面端点处开始萌生,并快速向中间扩展,当疲劳循环达到一定次数时,胶层瞬间断裂,裂纹萌生阶段几乎占据了其全部疲劳寿命,失效后的胶层会出现"凹台"状微观结构。     

钛合金胶接表面处理研究

钛合金表面处理方法是影响钛合金胶接耐久性的重要因素。本文介绍了各种钛合金胶接表面处理方法及其表面分析技术,评述了各种表面处理方法对胶接耐久性的贡献。以湿热耐久性为考核点的研究结果显示:电化学方法优于化学方法,化学方法优于机械方法。另外,处于研究阶段的等离子体、激光等物理方法因具有较好的耐久性和低污染特性,有望用于钛合金胶接的工业领域。     

Effect of anodizing on pulsed Nd:YAG laser joining of polyethylene terephthalate (PET) and aluminium alloy (A5052)

A series of laser joining experiments between polyethylene terephthalate (PET) and aluminium alloy (A5052) were conducted to investigate the effect of anodizing on A5052 surface on dissimilar materials used in joining. In this study, PET/A5052 joints with anodized A5052 surface exhibited greater shear strength compared to PET/A5052 joints without anodizing. The shear strength of the joints was increased with increasing of heat input and pulse duration. This indicates that the anodizing process could improve shear strength of the laser joining specimens. Significant molten pools were formed in both PET/A5052 (anodized) and PET/A5052 (as-received) joints except for PET/A5052 (as-received) sample joined at the lowest heat input and pulse duration. For the test results from laser joining under different pulse duration at the constant heat input, it was shown that joining behaviour was dominantly controlled by heat input and not by pulse duration.     

Ni–Cu alloy for diffusion bonding cermet/steel in air

Microstructural and mechanical evaluation for joints obtained by static and dynamic diffusion bonding of a 90MnCrV8 high strength steel coated with WC–Co, using a Ni–Cu alloy as interlayer, are shown in the present work. In all joints different reacted zones generated during the bonding process can be distinguished by means of scanning electron microscopy and dispersive X-ray spectrometry. The maximum tensile strength obtained using dynamic diffusion bonding process confirms a very promising technology for industrial applications.     

Adhesion improvement of copper/epoxy joints

Copper oxides have been formed to improve the adhesive strength of copper/epoxy joints. Initial adhesive strength and durability of copper/epoxy joints were compared depending upon the type of oxides, black or red oxide. Although the initial adhesive strength of black oxide treated joints was worse than that of red oxide treated joints, the durability in acidic environment was better. In order to improve the durability of red oxide treated joints, 5-amino-indazole was applied to inhibit the corrosion of oxide layer in acidic medium. With the treatment of 5-amino-indazole, initial adhesive strength was increased by 50%, and durability was improved. The loci of failure for oxide treated joints were investigated with scanning electron microscope and X-ray photoelectron spectroscopy.     

Adhesively-bonded joints in metallic alloys, polymers and composite materials: Mechanical and environmental durability performance

The factors affecting the mechanical and environmental durability (or stability), and performance of the adhesively bonded joints in various adherends including metallic alloys, polymers and composite materials are studied in detail. The primary function of a joint is to transfer load from one structural member to another. In most bonded joints the load transfer takes place through interfacial shear. At present, the use of adhesive bonded joints are largely applied to secondary non-critical structures. Whereas the use of adhesive bonding in primary structural applications has been somewhat limited because of the difficulty in defining and predicting joint strength, and designing the joint geometry to optimize strength and reliability. The determination of adhesive joint strength is complicated primarily by the nature of the polymeric material itself. Since these problems are mainly mechanical in nature, stress analysis is required to understand how the force loads are distributed along the adherends and adhesive layer. Most structural engineers consider the durability or stability of a joint to be fatigue related. This is only partly true for adhesive bonds as most durability issues are driven by environmental resistance rather than fatigue loads. The environmental resistance of an adhesive bond is determined by the chemical bonds formed during cure of the adhesive and the resistance of the chemical bonds to environmental degradation. Environmental resistance is fundamental to the durability of a bonded joint or repair. Most in-service failures are caused by environmental degradation of the interface between the bonding surface and the adhesive. Although the use of adhesive bonding is increasing rapidly, there are still important issues which need to be addressed in joint analysis, design, durability, and performance considerations. Therefore, the study of joints usually involves consideration of (a) joint geometries, (b) materials (i.e., adhesives and adherends), (c) loading conditions (i.e., static and dynamic loadings), (d) failure modes (i.e., cohesive, adhesive or mixed failure modes), and (e) temperature and moisture or environmental effects (humidity, solvents, corrosion, temperature extremes, thermal cyling etc.). Therefore, in the present paper the adhesive joints are critically assessed in terms of these factors which affect the durability and performance of them.There are two basic mathematical approaches for the analysis of adhesively bonded joints: (a) closed-form or analytical model and (b) numerical solutions (i.e., finite element analysis, FEA). In the closed-form approach, a set of differential equations and boundary conditions is formulated. The solutions of these equations are analytical expressions which give values of stresses at any point of joint. The analytical approach for the solution of complex stress distributions in the joints has been progressively refined until recent times. In the second approach, solutions of differential equations are obtained by numerical methods or the continuum is represented by a discrete model at the outset. The solution of these equations gives displacements at the determined points from which strains and stresses can be obtained for any point within the model. Among the numerical methods, finite element analysis (FEA) has been extensively used with success. The two- and three-dimensional finite element analyses approaches have been extensively applied by many workers to analyse the adhesive joints considering the linear and geometric nonlinearities.     

A Comparative Study of Friction Self-Piercing Riveting and Self-Piercing Riveting of Aluminum Alloy AA5182-O

In this paper, self-piercing riveting (SPR) and friction self-piercing riveting (F-SPR) processes were employed to join aluminum alloy AA5182-O sheets. Parallel studies were carried out to compare the two processes in terms of joint macrogeometry, tooling force, microhardness, quasi-static mechanical performance, and fatigue behavior. The results indicate that the F-SPR process formed both rivet–sheet interlocking and sheet–sheet solid-state bonding, whereas the SPR process only contained rivet–sheet interlocking. For the same rivet flaring, the F-SPR process required 63% less tooling force than the SPR process because of the softening effect of frictional heat and the lower rivet hardness of F-SPR. The decrease in the switch depth of the F-SPR resulted in more hardening of the aluminum alloy surrounding the rivet. The higher hardness of aluminum and formation of solid-state bonding enhanced the F-SPR joint stiffness under lap-shear loading, which contributed to the higher quasi-static lap-shear strength and longer fatigue life compared to those of the SPR joints.     

服役低温老化对铝合金-玄武岩纤维增强树脂复合材料粘接接头力学性能的影响及失效预测

为了给铝合金-玄武岩纤维增强树脂(BFRP)复合材料粘接结构在汽车工业中的应用提供参考和指导,加工了铝合金-BFRP复合材料粘接接头。结合汽车服役中的温度区间,选取?10℃和?40℃的低温老化环境,对接头进行0、10、20、30天的老化。对老化后的粘接接头进行准静态拉伸试验和剪切试验,得到不同老化时间下铝合金-BFRP粘接接头的准静态失效强度。结合DSC和FTIR分析低温老化对BFRP复合材料的影响,并对粘接接头的失效断面进行宏观分析和SEM分析。结果表明:在低温老化环境中,胶粘剂与BFRP复合材料的化学性质受低温老化作用影响不大,BFRP中的官能团与玻璃化转变温度(T_g)没有发生明显的变化,接头的失效强度和失效模式主要受胶粘剂与粘接基材的热应力影响。对于拉伸接头,随着低温老化时间的增加,BFRP复合材料纤维与树脂基体间的结合力降低,铝合金-BFRP复合材料接头的失效断面中纤维撕裂的比例逐渐减少,拉伸接头失效强度逐渐下降。老化后剪切接头仍为内聚失效,BFRP复合材料的低温老化对铝合金-BFRP复合材料剪切接头的失效强度几乎没有影响,剪切接头失效强度的下降主要是胶粘剂与粘接基材热膨胀系数不一致引起的热应力的影响。采用二次应力准则公式对?10℃和?40℃低温环境下,拉应力、剪应力值随老化时间的变化规律进行了拟合,在此失效准则的基础上,根据响应面原理,建立接头失效强度随老化时间变化的三维曲面,为粘接技术在车身结构中的工程应用提供参考。      

Investigation of an Optimum Concentration for Nano-Silica Used as an Adhesive Bonding Strength Enhancer

In this paper, the effect of silica nanoparticles (nano-silica) on the bonding strength of reinforced adhesive joints was experimentally studied in five concentrations. A two-part epoxy-based adhesive (Araldite 2015) was used to bond the adherends as well as silica nanoparticles for strengthening purposes. Nano-silica was added into the adhesive by 1, 1.5, 2, 2.5 and 3 wt.%. Some adhesive joints with and without nanoparticles were tested under uniaxial loading to obtain their bonding strength. The results showed that the change in the bonding strength is a function of nanoparticles concentration. Furthermore, it was concluded that the addition of silica nanoparticles has a suitable effect on the joint strength at an optimum point, in which the joint strength takes its maximum value, and a further increase in the nanoparticles weight fraction causes the joint strength to decrease.     

Innovative Leichtbau‐Fügetechnologien

Using examples from the adhesive bonding and ultrasonic welding technique shows how various methods of vacuum‐assisted analysis can contribute to explain joining mechanisms and derive optimization potentials for strength and durability of composites. Employing Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) to characterize epoxy‐adhesives, locally resolved and quantitative structural informa‐tions can be achieved. Multivariate data analysis methods prove to be very helpful here. Analytical investigations with high spatial resolution at the interface of ultrasonic welded aluminium joints provide structural and chemical data and allow the characterization of the bonding zone in detail. Thus the physical and chemical processes occurred during the welding process can be reconstruct. The increase of strength and longterm durability of ultrasonic‐ or induction welded hybrid joints (aluminium and carbon‐fibre reinforced thermoplastics) can be attributed to micromechanical interlocking of the CF‐matrixpolymer with Al‐oxide‐layer.     

铝合金表面特性对其胶接性能影响的研究进展

不同的表面处理方法会导致铝合金表面的表面理化特性发生改变,从而对铝合金板材与胶黏剂的界面结合强度以及胶接接头的耐腐蚀性能有很大的影响。本文从铝合金表面粗糙度、微观织构、表面氧化层和涂层化学特性等方面入手,对铝合金胶接接头的界面强度和耐腐蚀性能影响的研究现状进行了综述。探讨了铝合金胶接研究发展趋势,并认为铝合金表面理化特性的参数化表征以及表面特性与胶接性能的关系模型建立等方面是今后研究的重要方向。     

Environmental durability of phosphoric acid anodized aluminium adhesive joints protected with hydration inhibitors

An adsorbed monolayer of the organic inhibitor nitrilotris methylene phosphonic acid (NTMP) improves the bond durability of 2024 aluminium adherends prepared by phosphoric acid anodization (PAA). As had previously been determined for Forest Products Laboratories (FPL)-prepared adherends, maximum improvements occurred when a monolayer of NTMP was adsorbed onto the surface. Examination of the wedge test failure surfaces of PAA adherends treated in NTMP revealed that although crack propagation had initially involved oxide to hydroxide conversion of the original PAA oxide, the locus of failure transfers to the adhesive near the surface quite early in the test. This means that the failure of NTMP-treated PAA adherends was predominantly cohesive through the adhesive.     

Oxide morphology and adhesive bonding on titanium surfaces

Titanium metal was subjected to two surface treatments (alkaline peroxide etch and chromic acid anodization) and resulting oxide morphology examined by high-resolution scanning electron microscopy in a Jeol 100-CX STEM. The effects of treatment time in alkaline peroxide upon oxide morphology were followed and parallel mechanical measurements made on the strengths of adhesive bonds between the metal and an epoxy resin. These strengths were measured after a standard environmental exposure, namely 120 h in water at 80° C. As time-of-treatment increases, a micro-porous oxide layer is developed and adhesive strength rises to a maximum. Prolonged treatment with alkaline peroxide produces a drastic fall in adhesive strength accompanied by gross etching of the metal surface without changes in the oxide morphology. The loss of adhesive durability in this case is therefore attributable to surface chemistry effects rather than morphological changes.     

铝基超疏水表面的制备及其在包装方面的应用进展

在铝基体上构建具有特殊浸润性的超疏水表面,可以赋予其耐腐蚀、防覆冰、润滑减阻等功能,使其具有更大的应用价值和市场前景。制备铝基超疏水表面的方法主要有刻蚀法、阳极氧化法、沉积法、水热法等。化学刻蚀法、阳极氧化法和水热法等操作简单,应用范围广,但在制备过程中用到的强酸强碱等对环境和人体有害;激光刻蚀法等可以控制超疏水表面微观结构的形貌,但使用设备昂贵,难以大范围使用。为拓展超疏水表面的应用领域,开发简便方法制备多级微纳米粗糙结构、使用黏合层加固微观结构、构建自修复超疏水表面是未来的主要研究方向。