双管带隔筋件隔筋形状对内外管成形的影响

为了获得综合性能良好的某铝合金双管带隔筋挤压件,对提出的整体挤压成形工艺方案进行有限元模拟,模拟结果中存在折叠、挤压力大、局部强度不足等缺陷.针对所产生缺陷进行成形工艺方案改进,并确定优化后的挤压方案为:双筒带隔筋挤压件连皮在中间,隔筋的上端面倒有呈水滴状的圆弧.通过模拟对改进后的工艺进行验证分析,结果表明:过渡圆角的大小对折叠有较大影响,增大圆角可减小材料向筋部流动的阻力,可以改善材料的流动状态,并获得了最优过渡圆角半径.利用设计的模具进行了实验验证,获得了成形质量良好的挤压件.     

铝合金双筒带隔筋挤压件成形工艺研究

为了获得综合性能良好的铝合金双筒带隔筋挤压件,结合该工件形状特点,首先提出三种整体挤压成形工艺方案。对所提出的成形工艺方案进行有限元模拟,模拟结果中存在折叠、挤压力大、局部强度不够等缺陷。结合产生的缺陷对成形工艺方案进行改进,最终确定优化的挤压方案为双筒带隔筋挤压件连皮在中间,隔筋的上端面呈水滴状的圆弧。     

某复杂盒体零件成形工艺

研究了某复杂盒体,零件属于形状复杂、体积分配不均匀且截面不对称的构件。该盒体在直接采用板料进行挤压过程中,材料出现非等速流动而形成缺陷,影响零件的性能;获得的挤压件开口端不平整,材料利用率低。对该铝合金复杂盒体零件进行计算机有限元模拟,详细分析该盒体在挤压过程中出现的缺陷与不足,并提出合适的解决方案,即增加预成形工艺、改进预成形坯的形状。根据计算机有限元模拟的结果,制定合理的成形工艺路线,即下料-预成形-终成形,确定预成形坯的形状。通过实验验证,获得合格的挤压件。针对此类零件可以通过增加成形次数、优化预成形坯形状等方法来克服成形过程中产生的缺陷,提高材料利用率。     

5A06铝合金带筋盒体件挤压缺陷的模拟分析及优化

为了获得综合性能良好的5A06铝合金带筋盒体挤压件,结合其复杂的形状结构特点,提出采用整体挤压成形工艺方案,对提出的成形工艺方案进行有限元模拟,模拟的结果中存在盒底局部区域填充不饱满,有凹坑、折叠、部分筋条高度不够等缺陷。结合所产生的缺陷分析其产生的原因,改进成形工艺方案,最终确定优化后的挤压方案为:其一增加预成形工序,使得毛坯的分布更加趋近于挤压件的整体结构,同时预成形时先挤出侧筋,以保证底筋充填饱满及侧壁高度达到产品要求且不产生折叠;其二优化模具结构,适当增大凸模筋部圆角半径,同时将盒体底筋对应折叠处的凸模部分缩短10 mm。     

深孔筒形件挤压成形有限元分析

深孔筒形件的成形在挤压成形工艺中是一大难点,成形过程中的温度不易控制,使得模具强度降低,成形后的工件容易产生较大的壁厚差.本文在分析深孔筒形件的挤压工艺的基础上,利用非线性有限元软件MSC/Superform对深孔筒形件的挤压全过程进行了模拟,分29、39、82、91、103这5个时间步进行分析,得出挤压过程中的金属流动趋势;并且对成形过程中挤压件的各个部位的温度场进行分析,模拟出实际挤压过程中模具各个部位的温度,另外还得出了各个挤压工步的载荷--行程曲线,以便对模具及各种成形参数进行优化.最后按照模拟的工艺参数进行了试验,得出符合要求的工件.     

带纵向外筋薄壁筒形件复合流动成形数值模拟与工艺优化

采用传统的切削、挤压方法加工外表面带纵向外筋薄壁筒形件,存在着材料利用率较低、成本较高的问题,因此,提出了一种新的复合流动成形工艺。利用有限元分析软件,研究了预成形压下量、道次减薄量分配比以及滚珠直径等工艺参数对外筋成形效果的影响规律。研究发现:预成形压下量越大,外筋填充效果越好;不同阶段中,滚珠直径对外筋填充效果影响不同;采用两道次成形时,可以显著降低成形过程中的轴向旋压力。以外筋填充率和旋压力作为优化指标,通过正交试验,获得外表面带纵向外筋薄壁筒形件复合流动成形的最佳工艺方案,选取最佳工艺方案,通过试验验证了复合流动成形工艺的可行性,为此类构件的高效、低耗生产提供了理论设计依据。     

基于数值模拟的小应变差筒形件旋压成形方法研究

为了获得变形均匀的筒形件,提出采用有限元数值模拟方法对错距旋压、等距旋压和对轮旋压三种强力旋压成形工艺方案进行分析,介绍了三种强力旋压成形工艺方法及其原理,并制定了相应的成形工艺方案。以20钢筒形件为研究对象,采用MSC.MARC有限元软件,对三种不同的强力旋压成形过程进行了数值模拟。结果表明,旋压成形后工件的内外表面存在一定的应力及应变差;采用对轮旋压所获得筒形件内外表面应力应变差远小于错距旋压及等距旋压,采用等距旋压成形时筒形件内外表面应力应变差最大。     

某复杂铝合金盒形件模具降载方案的优化研究

针对一种形状并非完全对称的盒形件,设计了2种不同结构的凸模,并进行了等温挤压。利用有限元模拟分析软件模拟了挤压过程,分析比较了2种方案的挤压成形结果、凸模的载荷-行程曲线、凸模的等效应变分布等,获得优化的挤压方案,并通过试验对模拟结果进行了验证。结果表明,带有内孔的凸模可以有效地降低挤压过程中的载荷,并获得合格的零件。     

铝合金带筋筒形件成形数值模拟研究

通过有限元模拟软件MSC/superform对某铝合金带筋简形件进行了数值模拟,得到了变形过程的金属流动规律,获得了挤压温度与成形筋高的关系.模拟结果表明,带筋筒形件的塑性变形主要集中在筋部位,筋高随着挤压温度的升高而升高.     

摩托车齿形链链轮成形数值分析与工艺改进

应用有限元分析软件Deform-3D分析了齿形链链轮冷挤压成形初始工艺方案中产生缺陷的原因为:金属流动不合理和最大主应力超过了材料的抗拉强度885 MPa.为解决这一问题,提出了减径挤压成形的改进工艺方案:先缩径再成形齿形.通过数值模拟分析,改进后工艺方案的冷挤压件齿形充填饱满,最大主应力小于材料的抗拉强度.经工艺试验证明,改进的冷挤压工艺方案,可以避免挤压缺陷的产生,获得质量优良的挤压件.     

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。