Recycling of aluminum from fibre metal laminates

Recycling of aluminum alloy scrap obtained from delaminated fibre metal laminates (FMLs) was studied through high temperature refining in the presence of a salt flux. The aluminum alloy scrap contains approximately mass fraction w(Cu) = 4.4%, w(Mg) = 1.1% and w(Mn) = 0.6% (2024 aluminum alloy). The main objective of this research is to obtain a high metal yield, while maintaining its original alloy compositions. The work focuses on the metal yield and quality of recycled Al alloy under different refining conditions. The NaCl-KCl salt system was selected as the major components of flux in the Al alloy recycling. Two different flux compositions were employed at NaCl to KCl mass ratios of 44:56 and 70:30 respectively, based on either the eutectic composition, or the European preference. Different additives were introduced into the NaCl-KCl system to study the effect of flux component on recycling result. Although burning and oxidation loss of the alloying elements during re-melting and refining take place as the drawbacks of conventional refining process, the problems can be solved to a large extent by using an appropriate salt flux. Experimental results indicate that Mg in the alloy gets lost when adding cryolite in the NaCl-KCl salt system, though the metal yield can reach as high as 98%. However, by adding w(MgF₂) = 5% into the NaCl-KCl salt system (instead of using cryolite) all alloying elements were well controlled to its original composition with a metal yield of almost 98%.     

Analysis of through-the-thickness stress distribution in thick laminate multi-bolt joints using global-local method

The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain the stress state around the fastener hole in multi-bolt thick laminate joints, a global-local approach is introduced. In the method, the most seriously damaged zone is 3D modeled by taking the displacement field got from the 2D global model as boundary conditions. Through comparison and analysis there are the following findings: the global-local finite element method is a reliable and efficient way to solve the stress distribution problem; the stress distribution around the fastener hole is quite uneven in through-the-thickness direction, and the stresses of the elements close to the shearing plane are much higher than the stresses of the elements far away from the shearing plane; the out-of-plane stresses introduced by the single-lap joint cannot be ignored due to the delamination failure; the stress state is a useful criterion for further more complex studies involving failure analysis.     

高速动车组车轮踏面磨耗特征分析

为研究不同类型高速动车组车辆车轮踏面磨耗特征,探寻车轮发生磨耗后车辆运行性能的演变,以运行在武广客专上的CRH380A和CRH380B型动车组为研究对象,在线路数据统计的基础上,基于SIMPACK建立的高速动车组模型和编制的轮轨磨耗程序,对两类动车组车辆在一个镟修周期内的车轮磨耗特性及其对车辆运行性能的影响进行分析. 结果表明,该线路上运营的动车组车辆车轮磨耗特征主要表现为踏面凹槽磨耗,且CRH380A型动车组车轮踏面磨耗程度更为严重;在一个镟修周期内,由于车辆设计理念的差异,CRH380A型动车组车轮磨耗特征表现为磨耗范围较窄但磨耗深度较大,凹槽磨耗较为明显,而CRH380B型动车组则表现为磨耗范围较宽但磨耗深度较小,磨耗较为均匀;在运行2.5 × 105 km里程内,新轮状态下的CRH380A型动车组运行稳定性明显优于CRH380B型动车组,但在运营里程超过1.0 × 105 km后,由于受到车轮磨耗的影响,运行稳定性较CRH380B型动车组恶劣;同时,CRH380A型动车组车体最大振动加速度和平稳性指标分别为0.52 m/s2和2.26,均优于CRH380B型动车组的0.58 m/s2和2.38,但CRH380A型动车组脱轨系数和轮重减载率均为0.35,均大于CRH380B型动车组的0.14和0.28. 因此,在整个运行周期内,CRH380A型动车组车辆运行平稳性优于CRH380B型动车组,但运行安全性较CRH380B型动车组恶劣.      

热再生改性沥青SMA混合料配合比设计研究

通过对原材料进行试验分析,确定了新旧混合料、再生剂和新纤维的掺配比例及其相关技术参数,并对再生混合料进行了验证,为今后的热再生SMA配合比设计积累经验。     

聚丙烯纤维自密实混凝土工作性及强度性能研究

研究了不同体积掺量聚丙烯(PP)单丝纤维自密实混凝土的工作性、抗压强度和劈裂强度。研究表明:在不改变原有自密实混凝土配合比的情况下,PP纤维体积掺量不宜超过0.10%(体积份数);适当提高胶凝材料和高效减少剂的用量是改善纤维自密实工作性有效途径,并且可以提高纤维的掺量0.15%(体积份数);纤维对自密实混凝土的抗压强度影响较小,最优配合比下PP纤维自密实混凝土较普通自密实混凝土劈裂强度提高24%。     

单向短纤维复合材料中热残余应力研究

基于单向短纤维增强金属基复合材料的单纤维模型,利用轴对称弹塑性有限元分析方法,研究了该类复合材料中热残余应力的大小和分布情况以及各种微结构参数的变化对它的影响,同时还讨论了热残余应力的存在对基体与纤维之间应力传递的影响。研究表明,热应变的不匹配导致纤维受压、基体受拉,界面法向受压。热残余应力的存在降低了基体与纤维间的应力传递,不利于复合材料整体性能的提高。     

混杂纤维片材拉伸性能研究

参考标准GB/T3354-1999测试了由碳纤维、玻璃纤维和尼龙纤维等编织的不同混杂纤维布和增强环氧树脂复合板的拉伸强度、弹性模量和拉伸过程曲线等,分析了混杂比例对干纤维布和纤维增强环氧树脂板拉伸性能的影响。结果表明:与1C1G和2C1G纤维布相比,1C2G单向纤维布呈现出更为理想的分级破坏形式,应力传递更稳定;在碳、玻璃混杂纤维增强环氧树脂板体系中,1C2G复合板延性优越,最大延伸率达1.68%;与碳、玻璃混杂纤维增强环氧树脂板相比,含有尼龙纤维的混杂纤维树脂板在拉伸过程中具有下降段,延性效果改善良好,但抗拉强度偏低;环氧树脂在复合材料中进行应力传递和重分配,有效提高了复合材料的整体受力性能。     

Research on electron beam welding of in situ TiB<Subscript>2p</Subscript>/ZL101 composite

Electron beam welding of in situ TiB_2p reinforced aluminum composites was studied. The results show that no obvious pores or cracks is presented in the weld seam. The grains in the weld seam are remarkably refined and TiB₂ particles distribute much more homogeneously than that in base metal. The hardness values of fusion zone and heat affected zone (HAZ) are both increased in comparison with that of base metal. There are no interface reactions between TiB₂ particle and Al matrix. This results supply the evidence that the novel TiB_2p reinforced aluminum composites can be well joined with the electron beam welding.     

胶粘剂和CFRP吸湿对复合材料粘接接头失效的影响

对胶粘剂和复合材料的影响进行解耦;采用常温环境分别对胶粘剂、碳纤维增强树脂基复合材料(CFRP)和CFRP/铝合金粘接接头进行不同时间周期的浸泡,研究了不同应力状态对粘接接头失效的影响;以准静态失效测试的失效强度和失效模式分析为主,结合傅里叶变换红外光谱仪分析、差示扫描量热法分析和扫描电子显微镜分析,分别研究胶粘剂和CFRP吸湿后的失效机理,揭示了吸湿对复合材料粘接接头失效的影响机理。分析结果表明:胶粘剂在吸湿30 d后发生了水解,失效强度下降约53.7%,失效应变约为原来的3.2倍;CFRP吸湿后表面粘附性降低,容易引起界面失效,但打磨之后能够得到改善,CFRP吸湿后纤维/基体界面力学性能降低,在正应力状态下更容易造成纤维撕裂;CFRP/铝合金粘接接头的失效强度在吸湿30 d后下降了约23%,失效断面中胶粘剂出现了韧性断裂和界面失效;通过对胶粘剂、CFRP和CFRP/铝合金粘接接头吸湿后的失效分析,发现剪应力状态下的CFRP/铝合金粘接接头失效主要受胶粘剂吸湿后的性能下降影响,其次是界面失效的影响,而正应力状态下的CFRP/铝合金粘接接头失效还受CFRP性能下降造成的纤维撕裂影响。      

Structural intensity characterization of composite laminates subjected to impact load

Structural intensity (SI) characterization of composite laminates subjected to impact load was dis-cussed. The SI pattern of the laminates which have different fiber orientations and boundary conditions wasanalyzed. The resultant forces and velocities of the laminates were calculated, and the structural intensity wasevaluated. The SI streamlines of carbon fiber reinforced epoxy composite laminates and the steel plates werediscussed. The results show that the SI streamlines of the graphite/epoxy laminates are different from that ofthe steel plates, and the SI streamlines are influenced by the boundaries, the stacking sequence of the compositelaminates. The change of the historical central displacement of the graphite/epoxy laminates is fasten thanthat of the steel plates.     

DSC Analysis of LT-3 Aluminum Alloy Vacuum Brazing

Introduction Aluminumalloywasusedwidelyinmany waysinrecentyearsandtooktheplaceoftradi-tionalmaterialssuchascopperandstainlesssteel.Nowtheweldabilityresearchofaluminumwas mainlyinmetallurgy-abilityandmachiningtech-niques[1,2].Butthenucleationprocesswascared little,whichwasthekeyofbrazinglineformation.InthisresearchLT-3aluminumalloywasbra-zedbymeansofadvancedvacuumbrazing equipment,andthecortexmetalandthebasemet-alwereanalyzedbymeansofDSC.1Experiment LT-3aluminumalloyisakindofthree-layer com…     

复合材料在轨道交通车辆中的应用与展望

围绕玻璃纤维、碳纤维、铝基陶瓷等复合材料在轨道交通车辆中的应用展开了综述；介绍了针对上述复合材料开展的基础与应用研究历程及进展，分析了应用在大型复合材料构件的结构特点；针对头车/司机室、中间车车体、转向架、制动结构、其他结构，系统性地总结整理了复合材料种类、成型工艺、设计方法、优化方法等，全面阐述了复合材料在轨道交通车辆各个部件上的应用情况，并对目前应用存在的问题和未来应用发展方向进行了探讨。研究结果表明:复合材料的主要研究方法以理论研究为基础，在大型结构件中以有限元仿真研究为主，应用多尺度研究方法深入分析复合材料在微观、细观和宏观层面的性能；将复合材料应用到结构中时，在兼具刚度和轻量化的条件下，多采用三明治结构；复合材料之间、复合材料与金属材料的连接结构多采用胶接连接、螺栓连接、胶-螺混合连接等，其中混合连接结构强度大，稳定性高，在工程中应用最为广泛；复合材料已在轨道交通车辆中有一定的应用，纤维复合材料多用于头车/司机室、车体、转向架，而铝基陶瓷复合材料多用于制动结构；在未来应建立适用于轨道交通行业的复合材料相关标准与规范，研发新工艺，采用整体设计模式，扩大复合材料的使用范围，将更多高性能、低成本和轻质化的复合材料应用到轨道交通车辆中。      

服役温度对BFRP/铝合金粘接接头静态失效的影响

在车辆轻量化设计过程中, 为了预测BFRP/铝合金粘接接头在服役温度下的静态失效行为, 加工了处于拉应力、剪应力与拉剪组合应力状态的粘接接头, 根据车辆服役温度特点, 选取-40℃、-10℃、20℃、50℃、80℃五个温度测点, 通过准静态拉伸试验, 得到不同应力状态下接头失效强度随温度的变化规律, 分析了粘接接头失效形式和失效准则; 基于粘接接头在不同温度下的拉、剪应力, 建立了接头的二次应力失效准则方程, 对不同温度下的接头强度进行失效预测。分析结果表明: 粘接接头的失效强度受温度的影响明显, 随温度升高, 失效强度减小; 粘接接头中剪应力和拉应力的不同占比也会对接头失效强度造成一定的影响, 随着剪应力比例增大, 温度升高使接头失效强度下降更明显; 相比于低温-40℃, 高温80℃时的拉伸接头与剪切接头失效强度的下降幅度分别为47.77%与61.49%;随着温度升高, 粘接剂的失效应力和杨氏模量逐渐减小, 而失效应变逐渐增大, 说明温度很大程度上影响了粘接剂的力学性能; 粘接接头失效形式为内聚和纤维撕裂的混合失效, 拉应力作用下接头更容易发生纤维撕裂, 并且随温度升高, 纤维撕裂面积减小, 因此, 为了防止纤维撕裂, 需要避免粘接接头受拉应力作用; 粘接接头在不同温度下的二次应力失效准则曲线拟合精度均在0.957以上, 并绘制了失效准则响应曲面, 直观反映了粘接接头失效强度在车辆服役温度下的变化规律。      

Research on Electron Beam Welding of in situ TiB_(2p)/ZL101 Composite

AbstractElectron beam welding of in situ TiB2p reinforced aluminum composites was studied.The results show that no obvious pores or cracks is presented in the weld seam.The grains in the weld seam are remarkably refined and TiB2 particles distribute much more homogeneously than that in base metal.The hardness values of fusion zone and heat affected zone(HAZ)are both increased in comparison with that of base metal.There are no interface reactions between TiB2 particle and Al matrix.This results supply the evidence that the novel TiB2p reinforced aluminum composites can be well joined with the electron beam welding.     

炭纤维复合叠层铝板的制备工艺和实验研究

综合评论了从ＡＲＡＬＬ发展到新一代复合叠层铝合金板的进展。实验研究了新一代的叠层铝板－－炭纤维复合叠层铝板的制备工艺，并提供了所制备的炭纤维复合叠层铝板的性能。结果表明：这种铝板具有ＡＲＡＬＬ板的各种优点，能改进ＡＲＡＬＬ的一些缺点，它的各种性能指标皆优于铝合金板，因此可望取代高强度铝合金板而广泛应用于各类工程项目之中。     

立方形氢氧化铝粉体的制备及性能表征

采用水热合成方法,以硫酸铝为原料,乙醇水溶液为溶剂,合成了具有立方形貌的氢氧化铝粉体材料.利用SEM、XRD、TG、IR分别对氢氧化铝的形貌、物相结构、热分解行为及官能团结构进行了分析.研究结果表明,当水醇比为1∶1,反应时间24 h,反应温度为200℃时,可获得形貌规则、分散度良好的立方形貌的氢氧化铝粉体,并且在此条件下水热合成的粉体为薄水铝石相.经700℃和1 200℃焙烧后分别得到仍为立方形貌的γ-Al2O3和α-Al2O3粉体.     

铸造多孔铝的吸声性能与应用

多孔铝是一种新型的多用途金属材料,本文介绍了铸造多孔铝合金两种常用的制备方法,分析了孔径和孔隙率对吸声性能的影响及多孔铝合金在吸声、减震方面的应用。     

沥青路面温差发电系统设计分析与试验研究

针对沥青路面集热研究现状,设计了一种利用导热铝片取代水流管网作为载热体的沥青路面温差发电系统,通过构建沥青路面集热数学模型、导热铝片传热数学模型和半导体温差发电数学模型等动态仿真模型,对系统进行理论分析和试验研究,结果表明采用导热铝片作为载热体可以增强沥青混凝土内的热量转移,从而降低路面的温度梯度,减少路面的热应力,同时温差发电模块可将路面热量转化为电能输出,作为城市市政工程用电的补充.     

Modeling Nd<Superscript>3+</Superscript>-Yb<Superscript>3+</Superscript>-Tm<Superscript>3+</Superscript>-Er<Superscript>3+</Superscript> Codoped Telluride Glass Fiber for 0.4 to 2.0 μm Emission Spectra

The modeling of rare-earth-doped fiber amplifier is accomplished by utilizing the rate and propagation equations of distinct levels for a laser medium. A complex theoretical model for neodymium (Nd³⁺), erbium (Er³⁺), thulium (Tm³⁺) and ytterbium (Yb³⁺) codoped telluride glass fiber covering 0.4—2.0 μm emission spectra is presented. The emission spectra of Nd³⁺-Er³⁺-Tm³⁺-Yb³⁺ codoped telluride fiber are realized with the excitation of both 808 and 980 nm lasers pumped at 500mW. Numerical methods are used to calculate the emission spectra covering 0.4—2.0 μm. With the Nd³⁺, Tm³⁺ and Yb³⁺ ion concentrations fixed at 2 × 10²⁰ ion/m³, the Er³⁺ ion concentration optimized to 8 × 1020 ion/m3 and the fiber length spanning from 0.5 to 2 m, a peak amplified spontaneous emission (ASE) power of 19.8mW is attainable, and a minimum ASE power of 7.96mW can also be achieved. The analytical techniques and results indicate that when a telluride codoped fiber with suitable ion concentrations of Nd³⁺, Er³⁺, Tm³⁺ and Yb³⁺ is excited by both 980 and 808 nm pump lasers, 0.4—2.0 μm emission spectra are attainable for vast optical applications.     

Theoretical analysis of Er<Superscript>3+</Superscript>-doped telluride glass fiber amplifier for 2.700 μm laser amplification

The rate equations and power evolution equations of erbium-doped telluride glass fiber amplifier for both 1.530 and 2.700 μm lasers are solved numerically, the dependences of gain spectra on fiber length, dopant concentration and pump power are analyzed, and the gain of 2.700 μm laser is calculated and compared with the experimental result from reference. The numerical analysis shows that with 8 × 10²⁴ ion/m³ erbium ion concentration, 5m fiber length and 600mW pump power, the gains at 1.530 and 2.700 μm may achieve 23dB or so. With larger power pump and higher dopant concentration, a net gain of 17 dB is obtained from the Er³⁺-doped telluride glass fiber amplifier for 110mW input signal. This fiber amplifier is promising for both 1.530 μm signal amplification and 2.700 μm laser amplification.