基于PC控制技术的伺服机械压力机控制系统设计

伺服机械压力机是"数控一代"的机械压力机,其控制系统直接影响压力机的功能和性能。在对伺服机械压力机控制要求进行分析的基础上,基于PC控制技术,对伺服机械压力机的控制系统进行了设计,包括:控制器的选择、控制构架的搭建、曲轴与滑块位置的检测以及滑块轨迹的规划与控制等。采用基于PC的控制器,开发了实验样机,并对典型伺服冲压工艺进行了实验测试。实验结果表明,该伺服机械压力机的控制系统可实现包含变速、停止和反向等运动的伺服冲压工艺的规划控制,具有良好的控制性能。     

三类伺服阀控制电液伺服加载系统的分析

以三类伺服阀控制马达的电液伺服加载系统为对象，分别建立了三类阀控制马达伺服加载系统的数学模型并进行了频率特性分析，通过对系统进行的动态仿真分析，得出了不同伺服阀对电液伺服加载系统的影响特性。     

数控液压伺服系统设计与应用

为提高液压系统控制精度,采用数控液压伺服控制取代传统的电液伺服控制。介绍数控液压伺服系统的组成,重点介绍数控液压伺服阀的结构和工作原理,并介绍该系统的应用领域。该系统采用PLC控制步进电机,不仅能够满足数控液压系统的快速性和可靠性要求,而且大大降低成本。     

直动式电液伺服阀控制系统的建模与仿真研究

在介绍直动式电液伺服阀的基础上,建立了直动式电液伺服阀伺服控制系统的数学模型以及S imu link仿真框图,对其进行仿真,并对仿真结果进行了分析。     

伺服焊枪的精度与电极力控制特性分析

伺服焊枪是一种基于伺服电极控制的新型焊枪,为促进伺服焊枪在车身制造中的应用,对焊枪的精度特性与电极力控制特性进行分析。研究表明,伺服焊枪的传动误差、回程误差能够满足电极位移在线检测要求;对比分析伺服焊枪与气动焊枪的电极力控制特性,结果表明:在预压阶段伺服焊枪对工件的冲击力更小,达到预压力时间更短,在通电焊接阶段伺服焊枪热膨胀力波动较小,具有更精确的电极力控制能力,利于熔核的形成,使基于变电极力控制的焊接工艺规范成为可能。     

数控液压伺服系统组成及工作原理

为了提高液压系统控制精度,将传统的电液伺服控制方式改为数控液压伺服控制方式.充分利用先进的计算机技术,采用PLC控制步进电机,不仅能够满足数控液压系统的快速性和可靠性要求,而且大大降低了成本.     

数控机床伺服参数优化技术研究及应用

给出数控机床伺服控制系统三闭环控制结构,介绍每个控制环的控制原理。给出伺服参数优化流程,以及速度环、位置环和圆度优化的具体测试项目、伺服参数和优化方法。根据三轴立式加工中心存在的问题,进行了单轴伺服参数优化和圆度优化,给出了优化前后伺服参数和控制性能的对比。优化后三轴立式加工中心的加工节拍减少了2.3 s,圆插补加工误差减小到10 μm以内。     

交流伺服控制技术在板坯连铸结晶器调宽中的应用

西门子交流伺服控制技术是当今世界先进伺服控制技术,本文介绍了西门子全数字交流伺服(CUMC)控制系统在连铸机结晶器调宽系统中的应用,分析了交流伺服控制系统的优点.     

大型热模锻水压机的电液伺服控制系统

在大型热模锻水压机上，采用电液伺服控制技术对主阀分配器和水压机活动横梁的行程进行位置闭环控制，重点介绍伺服位置控制的原理及功能，控制系统的线性化处理及R．V．D．T校准。     

射流管伺服比例阀

对伺服阀与比例阀的结构、性能、抗污染能力及价格等特点进行了比较.介绍了某研究所研制的射流管伺服比例阀.其采用了前置独立式直杆型射流放大器、外接式滤油器及过滤模块等新技术,进一步提高了整阀的抗污染性能并降低了生产成本.安装接口按ISO4401的有关标准设计,可方便地替代国外同类型的伺服阀、伺服比例阀及比例阀;该阀的控制性能及精度完全等同于伺服阀,但对油液的要求等同于比例阀,成本只为国外同类伺服比例阀的1/3-2/3,可广泛运用于航空航天及各类工业控制场合.     

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.