Influence of diffusion time on property of steel—aluminum solid to liquid bonding

The bonding of solid steel to liquid aluminum was conducted using rapid solidification.The influence of diffusion time on interfacial shear strength was studied.The results show that when the temperature of aluminum liquid is 700℃and the preheat temperature of steel plate is 250℃,the relationship between diffusion time(t) and interfacial shear strength(σ)is σ=15.1 8.14t-0.37t 0.005t^3,and the maximum interfacial shear strength is 71.1MPa.     

航空铝合金高速铣削加工的有限元模拟

研究了铣削加工模拟所涉及的切削层的等效简化、工件材料的流动应力模型、刀屑接触面的摩擦模型和热传导控制方程等关键技术，并针对铣削加工的特点，建立了铣削加工模拟的有限元模型，基于此模型对高速铣削加工航空铝合金7050 T7451的切削力、应力和温度进行了有限元模拟.通过铣削力实验测得了同样切削条件下的铣削力值，其值与数值模拟结果比较吻合，证明了所建有限元模型的正确性，从而也表明了采用此模型进行的应力和温度的模拟结果是可信的.铣削加工有限元模拟研究为铝合金切削加工的工艺参数优化、刀具的优选和工艺规划奠定了基础.     

硬铝合金超精密车削残余应力的仿真及试验

为满足超精密车削加工零件低表面应力的使用性能要求,采用有限元和试验相结合的方法,对硬铝合金进行微米级的超精密车削仿真和试验.分析切削过程的切削力和切削温度,研究已加工表面残余应力产生的原因及残余应力的性质,得到切削深度和切削速度对已加工表面残余应力的影响规律.仿真结果表明:金刚石刀具车削硬铝合金,切削温度低,切削力小,但是单位切削力大.切削力是已加工表面形成残余压应力的主导因素.表层残余应力随着切削深度的增加而变大,随着切削速度的增大反而有减小的趋势.在微米级硬铝合金的超精密切削过程中,切削深度对已加工表面残余应力的影响更为显著.进行微米级的超精密车削试验,采用XRD对表层残余应力进行测量,对有限元仿真结果进行了验证,为硬铝合金超精密车削表面残余应力的控制打下理论基础.     

Chemical and electrochemical characterization of artificial sulphate patina on bronze

Copper patinas are generally regarded as aesthetically pleasing and are supposed to protect copper against further corrosion. The preparation of artificial sulphate patina on bronzes has been realized by immersing the bronze into CuSO4 solution. The effect of immersion time on the formation of the patina has been investigated. The sulphate patina obtained with immersion time of 500 h in CuSO4 solution consists of fiat area and crystals. The flat area in the patina is mainly made of cuprite, whereas the crystals are mainly composed of brochantite. The electrochemical measurement of sulphate patina in simulated acid rain with pH 3.1 shows that the protective effectiveness of patina decreases with time and the dissolution of patina is the key factor leading to the degradation of patina. The investigation of the formation mechanism of sulphate patina shows that the cuprite layer forms on the surface of bronze in the initial patination. Then, crystal brochantite grows on the surface of cuprite by the oxidation of cuprite and the incorporation of CuSO4 solution.     

铍青铜正向挤压制品组织与性能的研究

为了进一步了解铍青铜正向挤压制品的组织和性能,分析了铍青铜挤压铸锭组织的不均匀性、挤压棒材淬火后的粗晶环组织、以及挤压棒材的层状组织;同时对挤压棒材力学性能的不均匀性和挤压效应进行了分析.结果表明,提高铍青铜制品的挤压比（R≥15～25）,可以使其组织和性能趋于一致;尽可能减少挤压时的不均匀变形或控制再结晶的进行,可减少或消除粗晶环;减少挤压后坯料柱状晶区,扩大等轴晶区,同时使晶间杂质分散或减少可防止层状组织出现.说明铍青铜铸锭均匀化、挤压温度、变形程度等都是影响挤压效应的因素.     

利用曲率特征虚拟拼接青铜器小碎片的方法

针对青铜器小碎片人工拼接复原耗时费力的问题,提出了一种基于曲率特征的青铜器小碎片虚拟拼接方法．首先分别提取青铜器小碎片的轮廓,并在平滑处理提取结果的基础上计算轮廓的曲率．其次以曲率的局部极大值点作候选角点,再根据支撑域消除圆角点和伪角点．然后计算相邻两角点间的弦长,以弦长作为特征序列进行匹配．最后在平移旋转过程中利用向量模的不变性进行匹配精化处理,得到青铜器小碎片的最终拼接结果．实验结果表明,该方法能够有效地提高拼接效率和匹配效果．     

金刚石车削表面微观形貌形成机理的研究

为了在超精密加工前预测并控制表面粗糙度，提出一种建立圆弧刃车刀金刚石车削表面微观形貌的几何模型的新方法，开发并编写了表面微观形貌的仿真程序，在程序中考虑了刀具几何参数、振动和最小切削厚度对已加工表面特性的影响，通过理论分析和试验研究确定了最小切削厚度与切削刃钝圆半径之间的关系，分析了影响已加工表面粗糙度的若干因素，并在仿真生成的表面微观形貌中成功地加入了随机振动信号，大量切削试验是在自行研制的亚微米CNC超精密机床上进行的，结果表明：利用所建立的表面微观形貌几何模型，能够预测金刚石车削加工将要获得的表面粗糙度。     

A fractal-based model for the microstructure evolution of silicon bronze wires fabricated by dieless drawing

The back-propagation neural(BPN)network was proposed to model the relationship between the parameters of the dieless drawing process and the microstructures of the QSi3-1 silicon bronze alloy.Combined with image processing techniques,grain sizes and grain-boundary morphologies were respectively determined by the quantitative metallographic method and the fractal theory.The outcomes obtained show that the deformed microstructures exhibit typical fractal features,and the boundaries can be characterized quantitatively by speed will cause a smaller grain size together with an elevated fractal dimension.The developed model can be capable for forecasting the microstructure evolution with a minimum error.The average relative errors between the predicted results and the experimental values of grain size and fractal dimension are 3.9% and 0.9%,respectively.     

3D surface topography formation in ultra-precision turning

The generation process of 3D surface topography in ultra-precision turning is analyzed, as the result of superimposing between actual roughness surface, waviness surface and geometrical form texture surface. From the viewpoints of machine technical system and manufacturing process, factors influencing on roughness surface,waviness surface and geometrical form texture surface in ultra-precision turning are discussed further. The 3D topography of ideal roughness surface and actual surface affected by cutting vibration are simulated respectively.     

轴类零件冷缩工艺在生产上的应用

冷缩工艺是无屑加工的新工艺.本文作者结合长春第一汽车制造厂刹车蹄片轴的加工,进行了双轴径同时冷缩的加工方法的试验研究.研究工作取得显著效果,保证了工件精度,使生产效率由班产1300件提高到3000件.文中对工件进行了金相分析、挤压力公式的推导和挤压力计算、模具结构及尺寸的设计、模具材料及润滑剂选择等项研究工作,使该项新工艺建立在科学的基础上.     

微低重力试验多孔青铜气浮转台研制

在微低重力环境模拟中,为降低涡流干扰力矩,设计了基于多孔青铜节流器的气浮转台系统。首先,在止推轴承选型中,对局部多孔质节流器和全多孔质节流器进行了对比分析,发现在气膜厚度20μm条件下,全多孔质节流器承载能力比局部多孔质节流器高40%,因此设计选择全多孔节流器形式;然后,分析了在不同供气压力、不同材料渗透率下,气浮转台止推轴承及径向轴承的承载能力和刚度特性,发现选择较小的材料渗透率能够获得更高的气膜刚度,为气浮转台的结构设计提供了依据。最终研制的气浮转台采用开式止推轴承形式,节流器使用自研的多孔青铜材料,通过精密加工技术,使得加工前后的渗透率保持近似不变。试制成功的气浮转台回转精度小于0.8μm, 150 kg负载下,未出现气锤自激振动现象。气浮转台系统的最大干扰力矩为9×10^-4 N·m。该气浮转台系统不仅可用于微低重力试验,还可应用于超精密加工等领域。