弧面分度凸轮三维实体模型的建立

文章给出了弧面分度凸轮工作轮廓面上点坐标的通用计算公式,在此基础上阐述利用UG/Freeform Modeling模块与C 语言相结合生成弧面分度凸轮的工作曲面,以实现弧面分度凸轮的三维实体建模.为弧面分度凸轮机构的研究与开发及其动力学仿真奠定了基础.     

弧面分度凸轮理论轮廓面的计算

提高凸轮的加工质量是目前弧面分度凸轮研究的一个重点。但无论是其静态几何量测量,还是加工误差分析,首先要解决的是凸轮理论轮廓面的计算。本文在对弧面分度凸轮轮廓面详尽分析的基础上,论述了弧面分度凸轮理论轮廓面的计算以及ＶｉｓｕａｌＣ＋＋５．０开发的面向凸轮加工精度分析的理论轮廓面计算软件包。该软件包可应用于凸轮ＣＡＤ、ＣＡＭ、ＣＡＱ等子系统。     

弧面分度凸轮宏程序数控编程的研究

介绍弧面分度凸轮NC加工数据的计算算法.利用FANUC-0i数控系统的用户宏程序编制出弧面分度凸轮的数控加工程序,并且在弧面凸轮专用数控铣床上进行验证.该方法与传统方法相比程序简洁且通用性强,可显著提高编程效率.     

钢球滚子弧面分度凸轮机构的三维建模及运动仿真

介绍钢球滚子弧面分度凸轮机构三维模型的建立和运动仿真过程.根据包络蜗杆分度机构啮合原理得到弧面凸轮廓面方程,并求得钢球滚子中心轨迹点.实现钢球滚子弧面分度凸轮机构组件三维几何模型的建立和装配,并对钢球滚子弧面分度凸轮机构进行运动仿真.分别用简谐运动曲线和修正正弦曲线进行对比验证,结果表明:建立的三维模型是正确的和可行的,修正正弦曲线能够使弧面分度凸轮的运动更加平稳.     

弧面分度凸轮工作轮廓曲面的三维网格模型设计

针对孤面分度凸轮几何参数和运动参数繁多以及滚子类型和运动规律曲线多样的特点,描述了弧面分度凸轮工作轮廓曲面的生成方法及其方程,并在此基础上,利用MATLAB编程语言,开发出具有统一用户界面的弧面分度凸轮工作轮廓曲面三维网格设计程序,缩短了设计周期,提高了设计精度.     

弧面分度凸轮的材料选择与热处理工艺分析

弧面凸轮分度机构主要用于间歇运动,如各类自动机、生产线上的传动机构,它具有高速度、高精度、高稳定的性能,分度准确,因此应用广泛。但弧面分度凸轮加工比较困难,工作中要合理保护,充分发挥其优良性能,弧面凸轮的材料合理选择和热处理工艺的正确安排比较关键。本文仔细分析了弧面分度凸轮工作环境,合理地选择材料,正确进行热处理工艺分析,从而使零件工作性能达到满意的效果。     

圆柱分度凸轮的精确建模与数控编程

应用UG的二次开发工具UG/Grip开发了圆柱分度凸轮的建模系统,实现了圆柱分度凸轮的三维数字化精确建模,再利用UG CAM模块的可变轴曲面轮廓铣对凸轮沟槽进行数控编程与加工,提高了圆柱分度凸轮数控加工的质量和效率。     

数控加工中心ATC弧面分度凸轮运动学问题研究

推导了弧面凸轮压力角和诱导主曲率的计算公式，对数控加工中心凸轮式自动换刀机械手(ATC)弧面分度凸轮的压力角和曲率进行了详细的分析，为ATC的优化设计和研究提供了理论基础，有助于ATC机构产品系列化的完成。     

弧面分度凸轮机构参数化设计与仿真

以弧面分度凸轮机构为研究对象，基于VC＋＋面向对象的方法及Pro／ENGINEER二次开发技术，建立了弧面分度凸轮参数化设计系统，该系统给出了界面友好的参数输入对话框，能够完成机构参数的自动综合和凸轮轮廓的自动生成，具有直观性、易于操作和调整，并在Pro／ENGINEER环境下进行装配、仿真与干涉检测，验证了设计的合理性。     

滚珠型单头弧面分度凸轮实体建模及加工仿真研究

目前对单头弧面分度凸轮实体建模有很多研究方法,大多数研究的弧面分度凸轮实体建模过程比较复杂,不仅建模周期比较长,而且实际加工周期也比较长,导致了凸轮设计的效率偏低,不能满足凸轮小批量生产的要求。对此,文章采取了滚珠型单头弧面分度凸轮实体建模的方法,通过Matlab软件选择出优良的滚珠运动规律曲线,编程曲线程序计算出运动规律曲线的对应三维坐标点,保持为文本格式后导入到三维建模软件Pro/E中,从而生成转盘上面的滚珠实际运动轨迹曲线,在运动规律曲线上画出一个圆形,尺寸等于滚珠直径,采用扫略切除命令完成弧面分度凸轮的创建,最后把弧面分度凸轮模型保存为IGES格式,导入到Mastercam软件中进行加工仿真。同时,文中与其它弧面分度凸轮建模及加工仿真进行了对比分析,对比结果显示,文中研究的凸轮不仅建模周期特别短,大约都缩短了67%左右,而且加工仿真时间也特别短,大约缩短了50%左右,因此为弧面分度凸轮的建模与加工仿真提供了参考数据。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.