凸轮轴数控磨削表面粗糙度的实验研究

针对凸轮轴数控磨削表面加工的质量问题,使用陶瓷结合剂CBN砂轮对凸轮轴进行全数控高速、超高速磨削实验,分析了加工工艺参数对冷激铸铁材料凸轮轮廓不同部位的磨削加工表面粗糙度的影响规律。结果表明:在相同磨削条件下,表面粗糙度值在凸轮升程处最小;凸轮轮廓不同关键部位处的表面粗糙度值随砂轮线速度的增大而减小,随磨削深度的增加而变大。     

全数控凸轮轴高速磨床的研发

介绍全数控凸轮轴高速磨床的设计过程和功能模块,其中包括凸轮轴磨削的理论研究、凸轮轮廓数学模型的建立以及一些关键机械结构的研制.该高速磨床是凸轮轴加工的专业数控没备,采用CBN砂轮,利用磨削点跟随的原理进行磨削加工,提高了凸轮轴的加工精度;同时,将砂轮的线速度提高到120 m/s,大大提高了磨削加工的效率.     

切点跟踪磨削法磨削凸轮轴零件分析

分析了凸轮轴零件的切点跟踪磨削法的磨削运动特点。分析了砂轮中心位移模型,分析了恒线速磨削条件下的凸轮理论转速,进行了凸轮转速的优化。最后对湖南大学开发的MKC200超高速数控非圆轮廓外表面磨床进行了介绍。     

数控凸轮轴磨床保持磨除率恒定的变速磨削研究

计算在数控凸轮轴磨床上加工凸轮时的磨削弧长及凸轮轮廓上任意一点处的极径和曲率半径,推导出保持磨除率基本恒定时凸轮轴转速变化的计算公式。在凸轮轴磨削过程中,保持恒定的磨除率,有利于提高凸轮轴凸轮的表面磨削质量。     

凸轮轴磨削的误差补偿新研究

介绍了凸轮轴磨削的数学模型，提出了当量磨削厚度误差补偿技术，对运动模型进行修正，以保证磨削过程中任意时刻的当量磨削厚度相等。首先由误差补偿模型得出叠加于砂轮架上的位移修正量，再将这一修正量通过砂轮架与头架的联动关系叠加到头架的角速度修正量，从而实现了恒金属去除率磨削，提高了凸轮轮廓的加工精度。     

凸轮轴摆动磨削几何学建模及分析

为研究摆动磨削工艺对表面质量的影响机制,基于恒线速度磨削工艺,分析凸轮旋转一周时凸轮轴角速度和角加速度、砂轮进给速度和加速度的变化规律;对比分析摆动磨削与常规磨削时的接触长度和最大未变形磨屑厚度。结果表明：在不同的凸轮基圆速度下,凸轮轴转动的角速度和角加速度、砂轮进给速度和加速度呈线性增长趋势;摆动磨削可改善磨削表面的质量,且改善效果受磨削参数的影响;磨削深度对磨削表面质量有弱化作用;适当提高砂轮直径、砂轮转速、凸轮速度、摆动幅度、摆动频率可提高磨削表面质量。     

基于Simulink仿真的凸轮轴高速磨削稳定性判定

以凸轮轴高速磨削工艺系统稳定性为研究对象,建立磨削系统的凸轮轴-砂轮-支撑系统动力学模型。通过理论分析与数值计算来辨识磨削力的动态影响因素——凸轮轮廓曲率半径和瞬时磨削深度。基于所建立的磨削动力学模型搭建Matlab/Simulink颤振仿真模型,并从稳定性叶瓣图中选取相应的磨削工艺参数组合进行数值仿真分析,将仿真振动位移时域图所得的稳定性结论与稳定性叶瓣图的磨削稳定区域进行比较,验证了建立的磨削动力学模型和数值仿真方法的有效性。      

数控凸轮磨床的驱动

关干柴油机凸轮轴的加工，以往只能采用靠模凸轮磨床来磨削，现在则采用数控加工方式，根据凸轮型线对角度座标的升程，来编制加工程序，让砂轮按型线的要求往复运动，从而磨削出合格的型线面（图1）。图1中，R为凸轮轴的基圆半径，H为对应角度D的升程，D。为升程起点，r为砂轮半径，凸轮中心A和砂轮中心B在同一水平面上，当A，B间距离为R＋r时，磨削基圆，当凸轮轴转到D。位置时，砂轮按型线要求后退，凸轮型线上升，当D超过叨度时，砂轮按型线要求前进，凸轮型线下降，如果程序恰当，就可以磨出合格的型线面。有了编辑正确的程序，还…     

关于凸轮数控磨削加工的探讨

针对凸轮磨削的特殊性探讨了两轴联动数控凸轮磨床在磨削凸轮轮廓曲线时,砂轮中心的运动规律和被磨凸轮主轴变速规律的问题.并对提高凸轮磨削精度和表面质量所采用的"恒磨削率"及"恒磨削力"和"相对磨削线速度不变"的问题进行了理论上的探讨.     

基于PMAC的凸轮轴变速磨削加工研究

凸轮轴磨削加工是一种特殊的非圆磨削加工,很多实验已证明采用恒速磨削加工的凸轮轴凸轮轮廓存在很多缺陷,而采用变速磨削加工方式可以提高凸轮轴磨削加工精度,并对此已经达成了共识.文章根据文献[1]中提出的凸轮轴变速磨削加工时C轴的变速规律,在基于PMAC的数控凸轮轴磨床实验装置上,利用PMAC的循环程序缓冲区存储大量加工程序代码,实现了凸轮轴磨削加工的变速控制,取得了比较好的控制效果.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.