1250mm辊锻机工作部分刚度有限元分析

通过分析辊锻机的工作原理及性能特点,建立了辊锻机工作部分的三维模型。应用有限元软件,采用线弹性和接触分析办法对自主研发的1250mm辊锻机工作部分进行整体有限元分析,综合考虑机架的变形和锻辊的变形,得出了辊锻机锻辊在辊锻过程中的位移分布,其中第3道次最大变形量最大,为1.7269mm。本文计算出了辊锻机的整体刚度,并与通常锻压机械的许用刚度对比得出,1250mm辊锻机的刚度刚度满足设计要求。     

250mm伺服驱动辊锻机锻辊有限元静力学分析

通过分析伺服驱动辊锻机的工作原理和结构特点,用建模软件搭建三维模型,采用整体施加载荷、各零件单独分析的静力学分析方法,利用仿真软件模拟250 mm伺服驱动辊锻机整体模型在四道次辊锻受到最大辊锻力250 k N时、锻辊在高度方向的变形及受到的应力情况。结果显示:在锻辊四道次变形中,第2道次为最大变形道次,上下锻辊变形之和为0.60991 mm,计算出其刚度为409 k N·mm~(-1),而辊锻机的许用刚度Ch为350~500 k N·mm~(-1),符合刚度标准;在锻辊四道次应力值强度分析中,第4道次Von-Mises应力值最大,有效值达到63.267 MPa,小于辊锻机的许用应力326.8 MPa,完全满足应力值强度的要求,由结果可知,250 mm伺服驱动辊锻机锻辊的刚度强度完全满足要求。     

新型十二辊冷轧板带轧机刚度有限元分析

针对燕山大学设计研发的一种新型十二辊冷轧板带轧机,利用MSC．MARC软件对这种新型十二辊轧机的刚度进行有限元分析。绘制轧制力一变形曲线,计算轧机整体刚度,并对轧机的整体变形进行了细分,分析了各部分变形对工作辊辊缝的影响,为板形和板厚控制提供依据。     

连轧管机垂直刚度的有限元分析

对宝山钢铁股份有限公司宝钢分公司钢管厂Φ140mm全浮动芯棒连轧管机组轧制力及轧辊辊缝变化值进行了在线测定,将轧制力与辊缝变化值的实测结果进行线性拟合,得到轧机的垂直刚度值为5530kN/mm。在对轧机各组成部件受力分析的基础上,利用ABAQUS有限元软件,对轧机各部件分别建模并进行变形计算,得出轧机垂直刚度的模拟值为6110kN/mm。模拟值与实测值的相对误差为10.5%,表明所建有限元模型能够应用于连轧管机刚度的研究。     

轧机刚度的有限元模拟

应用MSC．Marc有限元软件,采用线弹性分析和接触分析方法分别对某四辊冷轧机的机架和辊系进行了模拟,得出二者的变形,进而计算出轧机的整体刚度。将计算结果与实测轧机刚度比较,发现二者有很好的吻合,从而为模拟计算轧机刚度提供了依据。     

LG-730冷轧管机结构力学分析

LG-730冷轧管机是国内最大规格伺服控制型两辊轧机,本文建立了其机架装配应力应变有限元模型,分析了LG-730机架装配在最大载荷下的变形和应力分布,在此基础上,对轧机结构进行了优化:两边机架底座宽度各减小了10 mm,机架筋板厚度由原来的120 mm减小到100 mm,机架两边厚度各减小了20 mm。优化后机架重量降低了,机架的刚度和强度分布更加均匀合理。研究结果对LG-730机架结构设计具有指导意义。     

铁路货车钩尾框精密辊锻过程数值模拟

铁路货车钩尾框锻件为异形长轴类锻件,目前采用自由锻工艺制坯,效率低,质量差,大型自动辊锻机精密辊锻是一种优质高效的先进制坯工艺,用于钩尾框制坯有望取得良好的技术经济效益.以刚塑性有限元法为基础,利用Deform-3D软件对铁路货车钩尾框精密辊锻过程进行三维有限元模拟,揭示了钩尾框辊锻变形过程中金属的流动规律,分析了辊锻成形过程中各道次辊锻过程中模具受载荷情况,以及各道次辊锻过程中的辊锻力矩,为钩尾框精密辊锻工艺及模具设计提供了有效的参考依据.     

四辊轧机刚度的计算分析

利用有限元法计算机架的刚度,用影响函数法计算辊系弹性变形,根据经验公式得到轴承座的变形,进而得到整个工作机座的刚度及各部分变形所占的比例,用有限元分析得到机架的应力分布.计算结果为轧机的改造和轧制规程的制定提供依据.     

大型突变截面连杆制坯辊锻工艺与数值模拟

主要论述了大型突变截面连杆制坯辊锻的关键工艺.以刚塑性有限元法为基础,利用Deform-3D软件,对其进行了三维有限元模拟.揭示了连杆制坯辊锻变形过程中金属的流动规律,分析了辊锻成形过程中各道次辊压坯料各部位应变的分布情况,以及各道次辊锻过程中模具受载情况,从而为连杆辊锻制坯工艺及模具设计提供可靠的理论依据.     

大轴径比工件辊锻过程宽展变形研究

针对现有的塔尔诺夫斯基宽展模型在设计辊锻模具过程中无法获得重剑等大轴径比锻件的辊锻宽展系数的问题，开展了大轴径比锻件平锻实验研究，解析了平锻实验宽展数据，并补充了塔尔诺夫斯基宽展模型。基于扩展后的模型设计了某型重剑剑条14道次的辊锻拔长模具，建立了剑条辊锻拔长过程的塑性有限元模型，模拟了第5道次剑身辊锻拔长过程，并采用应变分析和应力分析得到了辊锻变形区的金属流动规律。结果显示：宽展主要来源于锻件高度方向的压缩变形区，有限元模型预测的宽展量与平锻实验得到的等效宽展量吻合较好。该研究成果可用于指导大轴径比锻件辊锻模具设计及辊锻工艺优化。     

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。