数字化焊接电源系统特征及分析

数字化焊接电源是焊接电源更新换代的先进电源，由于工作环境的特殊性，其实现相对困难，特别是焊接主回路.分析了数字化焊接电源国内外发展现状和数字化电源的特点．针对笔者目前研究的数字化TIG焊机，详细介绍了其全部的结构组成，并根据研究过程中遇到的具体问题，总结了在实现数字化焊接电源过程中必需考虑的综合问题，并在此基础上，讨论了焊接电源控制的控制规律．提出了数字化综合系统平台的思想．指出了DSP(数字信号处理器)在数字化电源和数字化综合系统平台中的优越性和特殊性.     

弧焊电源焊接参数预置系统的发展

阐述了弧焊电源的发展历程,指出与传统的模拟电源相比,数字化弧焊电源的优势和在实际生产中存在的不足。在数字化电源的基础上介绍了弧焊电源焊接参数预置系统的研究现状,详细说明基于模拟电路、单片机、DSP及其他控制方法的预置系统,并分析基于各种控制方法的预置系统的优缺点。预测焊接参数预置系统的发展方向,应使其具有通用性,设计出不依赖于电源的独立焊接参数预置系统,一种预置系统可控制多类焊接电源。     

一体化双丝数字化焊接电源人机交互系统

一体化双丝数字化焊接电源可在一台电源上实现单丝/双丝、CO2/MAG、脉冲MIG、埋弧焊等多种焊接功能。针对此电源用于不同焊接方法时工艺过程不同和焊接参数众多的特点,设计了以ARM+CPLD的人机交互系统。该系统以ARM芯片LM3S828为控制核心,结合CPLD芯片EPM240T100实现数字化参数设置和焊接过程操作,包括:接收焊接开关命令,处理键盘与编码器的操作,焊接参数的选择与输入,利用RS232串行总线和GPIO脚与主控芯片DSP通讯。实验表明所设计的数字化人机系统操作方便,可靠性高。     

数字信号处理器DSP主控GMAW焊接

阐述了焊接过程信息数字处理控制思想，实际研究了数字信号处理器9DSP）在CO2气体保护焊机中的应用，将数字信号处理器（DSP）在送丝系统的柔性化调节，引弧和收弧模式，焊接参数的一元化自调节等方面的应用作了研究和试验，通过研究和样机试验，建立了一套焊接电源的数字化，信息化，柔性化控制平台，并探讨了数字信号处理器（DSP）在CO2焊接领域中的应用优点和前景，并提出了DSP主控GMAW焊接电源全系统框图，试验证明该系统工作稳定可靠，较好地满足了工艺性能，实现了焊机控制的数字化。     

数字化焊接电源系统的特征

介绍了数字化焊接电源系统的概念。分析总结了数字化焊接电源系统的特征和发展方向，提出了数字化焊接电源系统的主要研究内容。指出了数字化焊接电源系统交城为焊接电源的发展趋势。     

数字信号处理器在CO2焊接中的应用

阐述了焊接过程信息数字处理控制思想。对数字信号处理器（DSP）在CO2气体保护焊机中的应用：送丝系统的柔性化调节、引弧和收弧模式、焊接参数的一元化自调节等方面进行了探讨。通过研究和样机试验，建立了一套焊接电源的数字化、信息化、柔性化控制平台，并探讨了数字信号处理器（DSP）在CO2焊接领域中的应用优点和前景。试验证明，该系统工作稳定可靠，较好地满足了工艺性能，基本实现了焊机控制的数字化。     

数字化弧焊电源的现状与分析

随着电力电子技术的大力发展和智能控制技术在焊接领域的应用,焊机的控制已从模拟控制向数字化、智能化方向转变。介绍数字化焊机的核心组成部分——电源,阐述国内外数字化弧焊电源的研究现状,比较数字化弧焊电源与模拟式弧焊电源的优缺点,分析各类弧焊电源的原理和控制方法,概括目前数字化弧焊电源技术存在的问题,并对其发展前景进行了展望。     

基于CAN总线的CO2焊接系统设计

针对CAN总线技术在数据传输中具有可靠性、实时性和灵活性等特点,并能构成分布式系统和成本低等优点,设计了以CAN总线为通信、以ARM为控制芯片的数字化CO2焊接电源系统。实现了整个焊接系统的运行数据与CAN总线控制电路的通信,以及CAN总线与上位机的通信等。根据CO2焊接工艺的特点,编程实现了整个焊接系统的数字化控制。详细说明了CAN总线电路、CAN总线的通信协议设计。本研究对实现焊接系统的智能化控制具有一定的参考价值。     

基于DSP的数字化CO2焊接电源波形控制实现及仿真

采用波形控制可以有效地减少焊接飞溅的产生。本研究在以DSP为核心的CO2焊数字化电源基础上,嵌入波形控制系统,用以提高传统模拟控制的精度、速度和稳定性。本研究使用Simulink建立仿真模型,极大地提高了开发效率。根据焊接现场条件,建立数字化电源控制器的试验测试环境。结果表明,本研究中拟定的波形控制策略能够在这个系统上实现,并且该控制系统具有良好的控制速度和精度。     

基于ARM控制的多功能数字化逆变焊接电源

针对目前传统焊接电源存在的问题.主要讨论了多功能逆变焊接电源由模拟化向数字化改进的设计方法.介绍了硬件电路和软件系统的设计思路,包括如何用ARM处理器实现逆变焊接电源的数字化控制、主电路的设计、控制系统软件功能的设计和实现,最后对设计的样机进行了工艺试验.结果表明.基于ARM的数字化多功能逆变焊接电源具有较好的受控能力,能够满足高质量焊接的需要.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。