Thixo-forging and simulation of complex parts of aluminum alloy AlSi7Mg

In order to investigate the formability of metal material in semisolid state,a series of experiments were carried out by thixo-forging the complex part of aluminum alloy AlSi7Mg.Through changing the upper punch,aluminum parts with different upper-cup dimensions can be successfully produced.The numerical simulation was conducted for investigating the forming limits of AlSi7Mg during thixo-forging.It is found that the simulation result is in good agreement with the experiment one.     

Fracture prediction in non-isothermal viscous pressure bulging of aluminum alloy sheet using ductile fracture criterion

The failure of AA3003 aluminum alloy sheet metal was predicted for non-isothermal viscous pressure bulging (VPB). Utilizing the coupled thermo-mechanical finite element method combined with ductile fracture criterion, the calculations were carried out for non-isotherm VPB at various temperatures and the influences of the initial temperature of viscous medium on failure mode of bulge specimens were investigated. The results show that the failure modes are different for the non-isothermal VPB with different initial temperatures of viscous medium. For the non-isothermal VPB of AA3003 aluminum alloy sheet with initial temperature of 250 ℃, when the initial temperature of viscous medium ranges from 150 to 180 ℃, the formability of sheet metal can be improved to a full extent. The validity of the predictions is examined by comparing with experimental results.     

Influence of process parameters on deep drawing of AA6111 aluminum alloy at elevated temperatures

To gain a deep insight into the hot drawing process of aluminum alloy sheet, simulations of cylindrical cup drawing at elevated temperatures were carried out with experimental validation. The influence of four important process parameters, namely,punch velocity, blank holder force(BHF), friction coefficient and initial forming temperature of blank on drawing characteristics(i.e.minimum thickness and thickness deviation) was investigated with the help of design of experiments(DOE), analysis of variance(ANOVA) and analysis of mean(ANOM). Based on the results of ANOVA, it is shown that the blank holder force has the greatest influence on minimum thickness. The importance of punch velocity for thickness deviation is 44.35% followed by BHF of 24.88%,friction coefficient of 15.77% and initial forming temperature of blank of 14.995%. After determining the significance of each factor on forming characteristics, how the individual parameter affects characteristics was further analyzed by ANOM.     

T4态Al-Mg-Si合金板材的预时效工艺研究

采用硬度和电导率测定结合TEM/EDS组织分析研究了预时效温度及预时效时间对T4态Al-1.3Si-1.2Mg-0.6Cu合金板材成形性能、室温停放稳定性及烤漆硬化性的影响.结果表明：能同时有效改善该合金T4态板材的成形性、室温停放过程中的组织性能稳定性及烤漆硬化性的最佳预时效工艺为190℃左右保温约8 min.当预时效温度高于190℃或预时效时间过长,将不利于合金板材成形性的改善;若预时效温度低于190℃或预时效时间过短,则不利于合金板材预时效处理后的室温停放稳定性及烤漆硬化性的发挥.     

静液压力下7075铝合金圆环压缩试验研究

在不同静液压力下对不同形状因子的圆环试件进行轴向压缩试验,得出了7075铝合金圆环压缩时静液压力对极限相对压缩量的影响规律.并进行了试件子午面剖分观察,利用流线变形分析了试件在不同静液压力条件下超过极限压缩量时的变形和断裂特征.实验结果表明,在测试的压力范围内,随着静液压力的增加,圆环的极限相对压缩量呈线性增大,从而证明施加静液压力能够显著提高7075铝合金的塑性变形能力.     

纤维金属层板成形极限测试的新试样设计

在拉深成形过程中,纤维金属层板常见的失效模式主要有起皱、纤维拉伸断裂以及界面分层.受金属拉深成形测试的启发,经研究,当纤维金属层板以纤维拉伸断裂与界面分层失效为主要的失效模式时,可以将纤维应变引入到成形极限图中.但是,由于用于拉深测试的传统金属条状试样形状会干扰纤维金属层板内纤维应变的计算,因此,本研究设计了一种新型切...     

汽车桥壳液压胀形工艺的研究及最新进展

介绍了半滑动式液压胀形的基本思想以及小型汽车桥壳的液压胀形工艺过程,在普通液压机上试制出模拟样件。提出了钢管胀压成形工艺,先将两端缩径的管坯进行液压胀形得到轴对称的预成形管坯,再对其内部充液（水）并用模具压制成形,并试制出胀压成形桥壳样件。与液压胀形样件比较表明：胀压成形样件轮廓清楚,桥包部分过渡小圆角贴模性好,壁厚减薄量小,成形液压力低。     

具有防皱功能的多点成形工艺数值模拟

介绍了一种无需压边圈的防皱多点成形方法,与目前常用的多点模具成形方法不同,在防皱多点成形方法中防皱单元与调形单元交错排列,离散的防皱单元在成形区内对板料进行挟持,且能够随板料的变形上下浮动。运用有限元方法对球形曲面在防皱多点成形方式中的成形过程进行了数值模拟,分析了板厚、防皱单元的压力对最大成形曲率的影响,并与多点模具成形进行了对比。研究发现,防皱多点成形方法能够很好地抑制板料在成形过程中的起皱现象。球形曲面采用防皱多点成形方式时能够获得明显大的变形量。板料越薄,防皱多点成形方法所能获得的效果越显著。增大防皱单元的压力能够提高防皱多点成形的防皱能力。     

高速率成形技术进展

高速率成形技术包括爆炸成形技术、液电成形技术和电磁成形技术。高速率成形技术成形力量大,成形时间短,成形装置简单,可在室温下对高强度难成形材料进行成形加工。综述了高速率成形技术的原理、特点和应用,重点就高速率成形目前的两项研究重点——成形效率和成形性能,分析了结合传统准静态液压预成形和高速率最终成形的混合成形加工工艺方面的研究进展,混合成形加工工艺有效提高了成形效率和成形性能,对高速率成形条件对材料成形性能的影响进行了归纳和讨论。     

低碳钢与铝合金异种金属搭接激光-滚轮焊接

为了提高低碳钢与铝合金异种金属的焊接性能,采用激光-滚轮焊接工艺对低碳钢和铝合金搭接接头的焊接性能进行了研究,通过试验确定最佳工艺参数.采用激光显微镜和拉伸试验机分别分析了焊接接头组织和拉伸剪切性能.结果表明,随着激光功率的减少或焊接速度的增加,金属间化合物层厚度和接合宽度随之减小.随着滚轮压力的增加,金属间化合物层厚度随之增加.当金属间化合物层厚度为4～6μm,热输入量范围为375～800 J/cm时,拉伸剪切试样断裂位置均位于低碳钢母材侧.     

板材多点成形过程中成形力的数值模拟

基于动力显式有限元格式,给出了多点成形中成形力的计算公式。对不同材料、不同厚度的圆柱面、球面及马鞍面三种典型形状的成形力进行了数值模拟,分析了成形力的变化过程及影响因素。结果表明:在成形过程中,随着基本体与板料接触数目的增多,成形力会越来越大。厚板成形、硬质材料成形时都将需要较大的成形力。由于变形的复杂性,成形双向曲率的目标面时所需的成形力明显高于单向曲率。这些结果对于选择多点成形设备、更好地控制板材多点成形过程以减少成形缺陷具有重要的指导作用。     

钛合金颅骨修复体的多点成形数值模拟

采用动态显式有限元软件,针对钛合金网板与压力机基本体直接接触、在基本体和钛合金网板之间放置聚氨酯弹性垫、在基本体和钛合金网板之间放置聚氨酯弹性垫和钢质垫板并使用压边圈3种不同的成形工艺进行数值模拟研究。模拟结果表明:采用前两种成形工艺得到的钛合金颅骨修复体表面出现压痕或起皱缺陷,采用在基本体和钛合金网板之间放置聚氨酯弹性垫和钢质垫板并使用压边圈这种成形工艺时,可以抑制压痕和起皱的产生,获得良好的成形效果。实验验证结果表明,应用多点成形技术,运用合理的成形工艺可以成形合格形状的钛合金颅骨修复体。     

铝合金板-混凝土界面粘结-滑移性能双面剪切试验研究

铝合金板具有强度高、耐蚀性及延性好等优点,可用于潮湿、高寒等复杂恶劣环境中混凝土结构的加固,但铝合金板-混凝土的界面性能是影响铝合金板加固混凝土结构效果的关键。进行48个铝合金板-混凝土试件的界面双剪试验,分析铝合金板厚度、铝合金板粘结长度及结构胶种类对界面破坏机理、剥离承载力、粘结剪应力及滑移演化规律的影响。结果表明：增加铝合金板厚度、铝合金板粘结长度以及采用低弹性模量的结构胶能有效提高界面的剥离承载力,但铝合金板粘结长度应控制在有效粘结长度范围内;试件的滑移量随着粘结长度的增加而增大,且铝合金板越厚,试件的滑移量越小。将双直线模型、双曲线模型、Nakaba模型计算结果与试验结果进行对比分析,Nakaba模型与铝合金板-混凝土粘结滑移曲线整体吻合较好。     

Influence of loading path on formability of 304 stainless steel tubes

The loading path affects the metal formability remarkably in tube hydroforming, and it is also one of the research focuses. Recently, some scholars abroad proposed a new fluctuant hydraulic loading method, which can improve the formability of tubes in hydroforming. Related studies have shown that this new loading method can improve the tube formability, the distribution of deformation is more uniform and this is useful for avoiding excessive local thinning. In this paper, tube hydroforming experiments without axial feeding were carried out; the influences of the loading methods on formability of stainless steel tubes were studied. Through the comparison of the experimental results under the condition of monotonous increase loading and fluctuation hydraulic loading, the outside diameter distribution, the thickness distribution and the crack expansion forms of deformation zone all fully prove that the uniformity of the distribution of tube deformation and formability have been increased significantly under the condition of fluctuation loading without axial feeding, the reasons should be distinguished from the fluctuation hydroforming with axial feeding. In order to study the forming mechanism, uniaxial tensile test of tubes similar to fluctuation loading deformation is designed in this paper, namely intermittent tensile test. It is found that intermittent uniaxial stretch can improve the tube elongation at fracture by about 40% and the deformation distribution is more uniform than that through uniaxial tensile test of the stainless steel tube. In the process of intermittent tensile tests, changes of metal microstructures brought by the loading and unloading processes are the main reasons that improve the formability of the tubes.     

Effect of P/M value on the preforms and microstructures of spray formed 70Si30Al alloy

A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.     

Numerical simulation on the rheo-diecasting of the semi-solid A356 aluminum alloy

The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow w...     

等离子体电解氧化陶瓷膜的工艺研究

利用等离子体电解氧化技术在铝合金6063表面生成了氧化物陶瓷膜．测试了氧化膜表面厚度和硬度，观察了膜层表面形貌，分析了氧化陶瓷膜的成分，探讨了不同电流密度对形成陶瓷膜厚度和硬度的影响．结果表明：铝合金6063表面陶瓷膜的厚度和硬度随电流密度的增大而提高，但有一极限值平均电流密度极限值为25A／dm^2；随氧化时间的延长而增厚增硬，但也有一极限值，氧化时间极限值为45min．     

正交试验法在前翼子板成形数值模拟中的应用

根据正交试验原理,应用板料成形软件PareStamp 2G对不同压边力、模具与板料间摩擦系数、凸凹模间隙和板料初始尺寸进行数值模拟,将数值模拟的厚度同实际成形件的厚度进行比较,得出上述因素对前翼子板成形结果的影响,并预测了前翼子板较优的理论成形条件。     

基于拉深孔成形技术的杯形件拉深数值模拟

分析了拉深孔成形时的力学机理,并以杯形件为研究对象,进行拉深孔成形有限元模拟,同时分析了拉深后拉深件的危险断面处厚度减薄率和成形极限图（FLD）。分析结果表明,拉深孔排列规律、密度和孔径变化对板料的极限拉深高度有很大影响。     

CBN-E306齿轮泵壳体的制造

介绍粉末冶金方法生产CBN-E306齿轮泵壳体的新工艺,并重点介绍了齿轮泵壳体型腔整形模具的设计以及壳体内连通孔隙的封堵方法。它是一个以廉价金属代替有色合金材料的典型案例,同时也是为解决低密度粉末冶金制品在高压容器领域中的应用提供了一些实践经验。