数控机床三维空间误差建模及补偿技术研究

为了提高数控机床的加工精度,解决由机床三维空间误差引起的工件加工质量降低的问题,在研究多体系统理论误差建模技术的基础上,提出离线补偿和嵌入式补偿两种补偿策略。离线补偿是基于数控加工程序的修正补偿,将机床三维空间误差映射到数控加工程序,通过修改加工程序实现对机床的三维空间误差补偿;嵌入式补偿是基于数控系统的在线补偿,将机床三维空间误差融合到数控系统中,通过修正数控系统中的数据流实现对机床的三维空间误差补偿。实验表明,在不影响机床可靠性的前提下,两种补偿策略均显著提高了数控机床的加工精度。     

华中8型短电弧数控机床进给伺服控制研究

放电间隙是短电弧加工的重要参数,其直接影响加工效率及质量,存在测量及控制难的问题。提出了一种基于短电弧电流和电压的阴极工具进给伺服控制方法,进行了短电弧加工状态采集系统的设计,实现了电流、电压、温度、压力等信息的准确采集和交互,并基于华中8型数控系统二次开发平台,研制了专用数控系统,完成了基于采集反馈信息的阳极工具伺服控制,对航空发动机部件进行了短电弧加工验证。相关测试结果表明,短电弧专用数控系统稳定、可靠,具有良好的工程应用价值。     

基于数据库的电火花电弧复合加工在线补偿方法

电火花电弧复合加工技术具有加工效率高、节能环保的优点,但在加工难加工材料时存在工具电极损耗严重、补偿困难等问题。为此,提出了基于数据库的电火花电弧复合加工在线补偿方法。基于大量实验数据构建的工艺数据库,建立了加工轨迹长度计算的数学模型,获得了加工轨迹的补偿长度,利用机床控制程序进行电极的在线均匀补偿,并利用该补偿方法进行了电极损耗的在线补偿试验。结果表明:基于数据库进行在线补偿后,可提高工件的加工精度。     

短电弧加工机床数控系统设计与实现

为解决高硬度、高强度难加工导电材料的高效去除加工难度、以及短电弧机床机理研究和数控化应用的需要,设计并制作数控短电弧加工机床.分析现有数控系统软硬件特点及类型,并针对短电弧加工机床的要求,研制开发一套开放式数控系统.实际运行结果表明,该系统达到了设计要求.     

数控机床热变形误差补偿技术

热变形误差是影响机床加工精度的重要因素之一,通过实时热变形误差补偿可以提高数控机床加工精度.本文在分析产生机床热误差的原理的基础上, 探讨了热误差的测量方法,利用多元线性回归方法建立了机床热变形与温升之间的数学模型.应用数控系统的PLC补偿功能,对XH178加工中心加工过程中的热误差进行了实时补偿.实验结果表明误差补偿量达到80%以上.     

开放式数控系统摩擦补偿的实现

摩擦是引起数控机床换向误差的主要因素之一,降低了数控机床的加工精度。在机床换向时,摩擦力表现出非常强的非线性,不利于机床的高精度控制。在搭建的开放式数控系统平台上,通过对速度环施加脉冲补偿量实现了对摩擦的补偿,有效降低了轮廓误差。     

支持多任务的高精度数控机床控制系统设计

深入研究了数控机床软硬件实现方案,给出了机床数控系统中微处理器和运动控制芯片的型号.重点对数控系统中多任务的调度策略进行研究,给出了基于RT-Linux内核的任务调度方案,在解决多任务调度的同时保证了部分任务的实时性.除此之外,研究在数控机床加工过程中提高加工精度的方法,分析了工件加工过程中,对精度有影响的加工数据的传递过程,设计了有助于提高加工精度的机床数据处理过程.     

数控机床圆精度及补偿技术研究

数控机床误差的检测对于提高加工精度具有重要意义。对现有检测方法进行分析后,采用一种基于Renishaw QC20-W球杆仪的圆轨迹测量方法,获得加工中心误差信息,使用激光干涉仪通过数控系统对其进行误差补偿,提高机床动态性能。     

利用宏程序实现FANUC反向间隙自动测量与补偿

针对传统使用百分表手动检测数控机床反向间隙过程中人工介入较多,测量效率低等缺点,提出了一种结合高精度测头和FANUC数控系统G31高速跳转信号,利用宏程序实现"傻瓜"式一键操作进行反向间隙自动测量与自动补偿的方案。分析了自动检测系统的检测原理,介绍了系统的硬件电气连接,给出了关键宏程序代码。最后以Renishaw激光干涉仪为工具,比较了利用该方法自动测量和补偿反向间隙前后的机床精度。试验数据证明该自动检测系统能有效地调整机床的反向间隙,从而提高机床的定位精度。     

短电弧加工不同直径电极间隙流场研究

在短电弧加工过程中,利用流体软件Fluent对不同的电极直径加工间隙流场进行仿真,通过极间流场中的压力场与速度场间接得出加工屑排除的变化规律,并通过实验进行验证。结果发现:电极直径的增大可以促进加工屑从加工间隙排出,减少因间隙颗粒的堆积而产生的短路现象,从而避免“二次放电”;当加工深度不变时,电极直径的大小与工件材料的去除率呈正相关,证明短电弧加工过程中存在“面积效应”;电极直径的相对变化对工件表面质量没有明显的改善,即对表面粗糙度的影响不大。     

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.