提高转接段外套成形质量的优化成形工艺

从缩口成形过程中传力区的受力状态、缩口成形模具的结构缺陷及零件成形回弹等方面分析了某燃气轮机燃烧室转接段外套缩口成形后直径尺寸超差的原因,证实了缩口工艺不适合该零件成形加工.讨论了用胀形工艺取代原来的缩口工艺,使零件在成形过程中受拉应力作用,进行整体胀形,克服了缩口成形过程中压应力使零件变形区壁厚增厚、传力区失稳等问题.同时,胀形模具采用锥形滑块机构的分块式刚性凸模,通过胀形试验确定了凸模的型面尺寸,实现了零件成形回弹的工艺补偿,提高了零件成形质量.     

基于Dynaform的加油口盒成形工艺分析及优化

依靠经验对外形复杂、需要多次拉延才能成形的汽车覆盖件进行模具及工艺设计困难而效率低.基于板料成形模拟软件Dynaform,对某轿车加油口盒的一次拉延可成形性进行了模拟分析.预测该零件在一次成形过程中存在缺陷,由此提出二次拉延成形的工艺方案.针对零件在成形过程中容易出现拉裂和起皱的部位,进行了工艺优化和模拟验证,获得了满意的工艺方案,对该类零件模具工艺设计具有指导意义.     

多楔轮轮毂冲锻成形工艺及影响因素研究

针对某筒形多楔轮轮毂零件的结构特点，基于板料近净成形原理，对其轮毂成形制定了多道次冲锻工艺方案。基于DEFORM-3D软件平台建立了多道次冲锻成形全流程三维有限元模型，通过数值模拟研究了模具结构参数对缩径翻边和镦锻工序中成形缺陷的影响，并分析了成形过程中的等效应变分布与轮毂筒壁壁厚变化情况。结果表明，当两道次缩径翻边步长l₁和l₂的取值范围为12.8～15.6 mm、第1道次缩径翻边圆角半径r₁不小于16 mm时，轮毂筒壁成形结果良好，没有产生失稳和削料。当整形上模圆角半径R为3.5 mm时，镦锻末期在筒壁与凸缘交接处不会产生折叠缺陷。根据模拟结果进行实验验证，成功试制出多楔轮轮毂，验证了工艺制定及参数选择的可靠性，并最终在此基础上制得合格的多楔轮零件。     

加油口冲压工艺设计

通过对圆筒形零件拉深工艺与缩口工艺的对照比较,介绍该零件成形的工艺方案及实验过程。阐述了缩口成形工艺的成形特点,根据成形前后材料体积不变的原则,利用积分计算管子的缩口毛坯高度。并对模具设计与制造中存在的关键技术进行了研究分析。实现了用简单的缩口模具,生产出了合格零件。该模具不仅能保证工艺稳定,而且提高材料利用率和生产效率。因此,对细长的管状类零件,有时用缩口工艺代替拉深工艺可取得更好的效果。     

铝合金壳体成形工艺优化

采用有限元模拟分析了壳体三套成形方案的可行性.结果表明:三套方案均能实现壳体零件无缺陷成形,三个方案凸模最高承受载荷分别为,82.4、121和84.8kN.确定材料利用率为95%和模承受载荷为82.4kN的薄壁管缩口成形工艺为最优方案,并设计模具进行了试验验证.     

组合形活塞销冷镦挤成形工艺方案设计

依据组合形活塞销结构特征,制定了两种多工位冷镦挤成形工艺方案,并应用DEFORM-2D软件对活塞销成形过程进行数值模拟仿真,分析比较了两种方案中金属流动规律、应力分布规律和成形力大小。模拟结果显示:采用制定的两种工艺方案成形活塞销均不会出现折叠、开裂等锻造缺陷,但"两次反挤压+挤锥"的成形工艺方案各工步成形载荷分布更合理。工艺实验结果显示,采用"两次反挤压+挤锥"生产的组合形活塞销满足设计尺寸要求、无折叠和开裂缺陷。数值模拟结果与工艺实验结果相一致,制定的工艺方案可以满足零件塑性成形的设计要求。     

基于Dynaform的消音管液压胀形数值模拟

对管件的液压胀形工艺进行了研究,在此基础上以消音管为例进行了液压胀形数值模拟。基于Dynaform仿真软件,分析了消音管的成形过程,并对其成形极限和厚度变化情况进行了研究。针对液压胀形过程中出现的胀裂缺陷,通过优化加载路径等得到了合格的消音管成形状态,零件的最大变薄率为29. 6%。在数值模拟的基础上,根据最佳工艺方案进行了实际液压胀形试验,比较了仿真结果与试验结果的零件厚度,其相对偏差均在3%以内,并且相对变化趋势一致。研究结果表明,基于数值模拟的液压胀形仿真分析可以准确预测零件成形状态,从而提升设计生产效率。     

基于Deform的汽车法兰盘体零件锻造成形工艺

精密锻件在工艺设计初期通常存在多种成形工艺方案,为确定最合适的工艺,以汽车法兰盘体零件为研究对象,应用CAE分析软件Deform-3D进行了热力耦合数值模拟。由于零件结构复杂,通过分析可知无法一次成形,结合塑性成形技术,初步确定了3种成形工艺方案。首先,从锻件的成形质量及模具使用寿命方面进行了全面的分析和比较。然后,通过建立数学评估模型从应力值、应变值、模具载荷值、零件损伤值等多方面进行优选。结果表明,方案3在锻件质量、模具使用寿命等各方面均存在优势。最后,采用方案3成形工艺进行了生产试验,获得的法兰盘体零件成形饱满,外形良好、无缺陷。通过有限元技术与数学模型的有机结合,能够高效地获得最佳工艺,大大降低试模成本。     

组合形活塞销冷镦挤成形工艺

针对组合形活塞销结构特征和工艺要求,分析该零件的成形难点为:两端圆锥孔的挤压成形和深径比大于2. 5的中心圆孔反挤压。为此,应用DEFORM-2D有限元分析软件对组合形活塞销7工位冷镦挤成形工艺进行数值模拟分析。通过数值模拟分析和工艺方案修订,确定最终的成形工艺方案为:下料-整形-压凹-反挤压-冲孔-第1次挤锥-第2次挤锥,并采用硬质合金YG15制造反挤压凸模,以避免一次反挤压成形时凸模横截面变化处的折断。采用该方案进行工艺实验,实验结果表明:组合形活塞销尺寸满足零件设计要求,无折叠、开裂等锻造缺陷,深孔反挤压凸模使用寿命大于8万件。     

不锈钢进气管扩口工艺设计

介绍一种两端为圆筒、中间为锥部过渡的进气管零件的扩口胀形工艺方案的确定及实施验证过程,阐述不锈钢管扩口胀形工艺成形特点,对扩口胀形过程中的管坯受力状况进行分析,计算管坯扩口毛坯高度、扩口胀形系数和伸长率,对需控制解决的关键性技术进行研究分析,对产品的工艺性作了适当改进。     

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。