焊缝对压力机强度的影响分析

为了分析焊缝对机身强度和刚度的影响,首先建立压力机的三维和有限元模型,研究中忽略焊缝内部材质和焊接质量的影响,并对筋板和机身主板进行模型处理。观察对比焊缝宽度不同的情况下,机身强度和刚度值变化,总结筋板焊缝与相应坡口大小相适合的数据,最后对比分析了考虑焊缝和不考虑焊缝对机身和筋板影响的差异,为压力机设计时筋板焊缝宽度的选择提供一定依据。     

Q345高强钢T型接头焊接变形机理的数值模拟研究

为了研究T型接头的变形机理,本文以通用有限元分析软件MSC.Marc为平台,开发了用于模拟焊接温度场、应力场和应变场的热-弹-塑性非线性有限元计算方法。在所开发的计算方法中,采用了双椭球高斯体积移动热源模型来模拟焊接的热输入,以生死单元技术考虑焊缝成形,数值模拟了低合金高强钢Q345的T型接头焊接残余应力与变形。研究结果表明,T型接头的角变形主要取决于两个因素:翼缘板上下表面的温差以及翼缘板的板厚。其中翼缘板上下表面的温差是角变形的驱动力,温差越大,角变形越大;而板厚(刚度)是角变形的阻力,板厚(刚度)越大,则变形的阻力越大。     

异步电机转子端环导条的真空电子束焊工艺

针对典型的异步电机用铜及铜合金端环导条开展了真空电子束焊试验研究。通过先行铬铜试块电子束焊缝成形试验,获得了优异的"钉楔状"自熔焊缝,同时测试了不同束流强度下的熔深和表面熔宽;通过模拟实际T形接头的电子束焊接束偏量试验,确定了铬铜端环与纯铜导条电子束焊接时的最佳束偏量;某型异步电机端环导条实物验证结果表明,真空电子束焊下的端环导条焊接电阻显著低于感应钎焊的,接头导电性能更优,拉伸试验结果显示焊缝抗拉强度高于母材的。     

基于Inventor的角焊缝几何参数对结构强度影响分析

根据Inventor对焊接构件有限元计算结果,研究焊接件结构强度随焊缝不同几何参数变化的关系。研究表明:焊脚长度越大,Mises等效应力和接触应力越小,但焊脚长度超出板厚后,结构应力变化不再明显;焊缝截面面积相等,焊缝坡度呈18.4°时,Mises等效应力最小,能够很好满足结构疲劳强度,坡度呈60°时Mises等效应力最大,而接触应力在坡度呈65°时最小;由于焊脚长度不同,相同焊喉高度的焊缝,结构应力并不相等。研究结果为合理选择焊缝几何参数,提高结构强度提供理论依据。     

曲线焊缝位置对拼焊板焊缝移动的影响规律研究

焊缝位置对拼焊板成形性能有重要影响。在盒形件冲压和有限元模拟中,发现焊缝位置对焊缝移动尤其是法兰处焊缝移动有重要影响。通过简化研究模型,布置不同位置焊缝,进行U形件冲压有限元模拟。根据分析数据,建立几何分析模型,研究了焊缝位置对焊缝移动的影响规律。结果表明,法兰处的焊缝移动主要和焊缝与材料流动方向之间的夹角、材料流动量有关。材料流动量越大,法兰处焊缝移动越大。当材料流动量一致时,法兰处焊缝与材料流动方向之间角度越大,法兰处焊缝移动越大。     

铝钢异种材料电弧熔钎焊接技术的研究

为了减轻车身重量,铝合金正被广泛的应用到汽车车身用中.而铝合金与汽车用钢板的连接问题是铝合金得以广泛应用的关键.本研究通过钨极氩弧焊和冷金属过渡焊两种电弧熔钎焊接方法实现铝合金与低碳钢的连接,研究了两种焊接方法的焊缝成型、接头拉剪强度以及金属间化合物的成分差异,并与传统的铆接接头进行比较.研究表明,电弧熔钎焊具有较高的接头拉剪强度和较小的接头重量.由于冷金属过渡焊的热输入量低,使得其焊缝成型相对较好,且其接头拉剪强度值已达到母材强度的85％.     

焊接工艺参数对E309L药芯焊丝焊缝金属铁素体数的影响

采用铁素体测试仪、Schaeffler图及WRC-1992图3种测试方法,研究了不同焊接工艺参数对E309L药芯焊丝焊缝金属铁素体数(Ferrite number, FN)的影响。结果表明,焊缝金属FN随焊接电参数的改变变化最大,气体流量居中,焊丝伸出长度最小;适当地增大焊丝伸出长度和气体流量可以降低FN;焊缝金属中N元素对气体流量、焊丝伸出长度的变化比较敏感,WRC-1992图法因考虑了N元素的作用,测试结果更准确,而铁素体测试仪法适合测试正常焊接工艺参数下的FN;随着焊接电参数、焊丝伸出长度、气体流量的增大,Schaeffler图法测试焊缝金属FN均逐渐减小。     

镀锌钢板的激光焊接工艺与接头力学性能研究

对DP780镀锌钢板进行激光对接焊接,研究了其焊接工艺参数变化对接头力学性能的影响。结果表明,激光功率越大或焊接速率越小时,热输入量越大,焊缝深度和宽度越大。焊缝和热影响区显微硬度高于母材,达到450~475HV。随着激光功率或焊接速率的增大,接头抗拉强度、屈服强度和伸长率先增大后减小。激光功率为1.4 kW、焊接速率为0.9 m/min时,抗拉强度为933.5 MPa,屈服强度为671.5 MPa,伸长率为13.1%。     

车身激光深熔焊焊缝的缺陷消除与工艺优化研究

分析了焊装车间某白车身主焊、侧围激光深熔焊焊缝质量问题,提出几种焊缝常见质量缺陷,并对这些质量缺陷提出优化方案。通过调整机器人轨迹并优化板材匹配等手段,解决了常见的焊缝切割和气孔造成的功能性质量问题,提高了焊缝的连接强度。     

机器结构焊缝强度设计的若干经验法则

机器结构焊缝设计的特点焊缝强度通常是相对于母材强度而言。当焊件的两块钢板厚度不相等时,以其中薄件的板厚作为焊缝强度计算的依据。所谓焊缝设计中的等强度原则,是指焊缝强度等于其中薄板的强度。焊缝的等强度设计原则,适用于桥梁、建筑等按强度条件设计的工程结构。机器结构(指机体、底座、床身和立柱等基础大件)的设计不同于桥梁、容器等工程结构设计,它不是按强度条件,而是按刚度条件设计的。所以,机器结构的形状不仅复杂,而     

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).     

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.     

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.     

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。