冷精整直齿轮和组合凹模弹性变形规律

采用有限元模拟和试验研究相结合的方法对倒档直齿轮冷精整成形中凹模和齿件的弹性变形规律进行研究。分别沿齿形方向和齿向方向对凹模和齿件的弹性变形特点进行分析,并将两者综合预测冷精整齿件的尺寸偏差。结果表明,凹模和齿件的弹性变形量沿渐开线齿面呈空间不均匀分布的特性是导致齿件精度低的主要原因。为实现直齿轮的精度控制,提出一种基于厚壁圆筒理论的齿形模具修正方法,利用应力外圈的预应力作用实现模腔修正,并进行试验研究,结果表明模具修正后的试验齿件的尺寸精度达到国标IT6级。     

冷精整直齿轮弹性回复行为研究及模具结构优化

研究了直齿圆柱齿轮冷精整工艺中,冷精整模具尺寸参数对齿轮尺寸精度的影响。建立了直齿圆柱齿轮冷精整工艺的三维弹塑性有限元模型,利用三维有限元模拟软件进行模拟分析,得到了冷精整凹模中,工作带导入角和工作带高度2个参数同齿轮回弹量之间的变化规律,并进一步分析了工作带入口角度对齿形翘曲程度的影响。对直齿轮冷精整工艺进行物理试验验证,所得结果与有限元分析一致,两者间的最大相对误差不超过5%。     

直齿轮冷精锻钢坯卸压孔直径对模具弹性变形的影响

针对直齿轮冷精锻成形过程中，模具因承受较大的成形载荷产生弹性变形，进而影响成形齿轮的成形精度等问题，基于径向分流法设计了不同卸压孔直径的钢坯，建立了坯料塑性成形与模具应力分析的有限元模型，研究了不同卸压孔直径对模具弹性变形的影响。根据模具型腔的弹性变形量，采用反补偿法修正了齿模齿廓曲线，并比较了修正前后锻件的变形量。结果表明：随着卸压孔直径的增大，模具弹性变形量先增大后减小，在卸压孔直径d₀=Φ20 mm时，模具的弹性变形量最小；模具不同高度的齿腔轮廓平面的弹性变形量变化形势一致，但增量幅度不同；上轮廓平面变形量最大且齿根到齿顶波动幅度大，峰值位于齿顶；齿模齿形修正后锻件的弹性变形量减小了28.6%。设计了3组不同d₀的坯料进行成形实验，实验结果与仿真结果基本吻合，通过减小模具弹性变形量可以提高锻齿的尺寸精度。     

基于数值模拟的齿轮冷精整齿向精度预测

应用Deform-3D软件对载重汽车用直齿圆柱齿轮进行了挤压成形后的冷精整工艺数值模拟分析,得到了不同精整量下齿轮的齿向误差,进一步总结出精整量对齿向误差的影响规律,并预测出最佳精整量.模拟结果显示齿轮齿向误差随着精整量的增加先减小后变大,当精整量为0.15 mm时齿向误差最小为0.026 mm,此时齿向精度为8级.针对模拟结果进行了冷精整工艺试验并对精整件进行了齿向精度检测,检测结果表明精整后可将齿向精度由11级提高到为8级,此结果与模拟得到的预测结果相一致.     

冷成形直齿锥齿轮齿形回弹分析及凹模修正

针对直齿锥齿轮冷成形工艺,采用塑性有限元法,对成形过程进行数值模拟,分析了各阶段坯料流动情况及产品卸载后的回弹规律。结果显示,在齿高方向,最小回弹在最大齿厚0.02mm处,沿齿顶或齿根逐渐增大,接近齿顶处回弹值达到最大为0.14mm。选用反补偿修正法对齿形凹模二次修正,获得满足所需精度的目标齿轮,最大偏差值为-0.025mm。研究表明,通过数值模拟回弹分析与修正,可以获得较高齿形精度的直齿锥齿轮产品,缩短了模具制造周期,降低了成本。     

高精度锥齿轮冷闭式锻造齿模修形及加工电极设计

精密成形时弹性变形是影响锻件尺寸精度的重要因素。本文采用数值模拟的方法,以锥齿轮冷闭式锻造精密成形工艺为对象,模拟了锥齿轮的冷闭式锻造成形过程,揭示了在有预应力的工况下模具弹性膨胀变形及锥齿轮锻件出模后弹性回复的变化规律。根据模拟结果,分别绘制了模具弹性膨胀和锻件出模回弹后的齿形曲线。在定量分析了两者对齿轮精度的综合影响之后,运用反补偿法预先修正齿形凹模,并进行了齿模电极的设计。研究结果对齿轮精度的提高提供了重要参考。     

行星齿轮精锻工艺分析与试验研究

根据齿轮精度检验的指标,提出了精度控制需要注意的问题,并针对每个问题提出解决办法。在系统分析热精锻和冷锻成形过程中齿形、齿面、弹性变形及模具寿命等问题的基础上,确定了热精锻-冷精整工艺流程,完成了精锻件及热精锻模的设计。对不同坯料尺寸和镦粗比的热精锻工艺过程进行了试验研究,分析了坯料和镦粗比对齿形充满的影响。研究结果表明,采用直径小于分锥角小端直径的坯料,选定镦粗比1．5进行热锻成形,锻造的热精锻齿轮齿形、齿顶充满效果较好,冷精整后的齿形饱满准确,在对氧化铁皮进行彻底清理后,锻件表面质量良好。     

大模数直齿轮温冷锻精整量的优化选择

文章针对大模数直齿圆柱齿轮中空分流冷精整工艺中,冷精整量这一关键工艺参数,采用广义胡克定律计算公式得出精整量的最小值,并建立了直齿圆柱齿轮基于中空分流的正向冷挤压精整工艺的三维弹塑性有限元模型,利用DEFORM-3D软件进行模拟分析,得到了齿面冷精整量与齿轮锻件的相对壁厚同齿面回弹量之间的变化规律;采用实验方法验证了模拟结果的正确性。研究结果对于大模数直齿圆柱齿轮冷精整量的优化选择,具有重要的指导意义与参考价值。     

变形热对齿轮冷锻精度影响的数值模拟研究

在有、无变形热产生的条件下,采用刚塑性热力耦合有限元法,对冷精锻直齿圆柱齿轮成形过程进行了模拟,并且完成了直齿轮冷锻模具弹性变形和工件弹性回复的模拟。由模拟结果可知:变形热的产生及热量传导能对齿轮精度产生很大的影响;由于在不同温度下材料的膨胀系数以及弹性模量不同,在有变形热的条件下,成形力有所降低,模具弹性变形和工件弹性回复量增大。     

弧齿锥齿轮冷锻回弹的数值模拟及数字化修形

冷锻时弹性变形是影响弧齿锥齿轮锻件尺寸精度的主要因素.利用有限元数值模拟软件DEFORM-3D模拟了弧齿锥齿轮的冷闭塞式锻造过程,并对模具弹性变形及锻件回弹的规律进行了分析.根据模拟结果,运用反补偿法及基圆修正法预先对模具型腔进行了修正,以保证弧齿锥齿轮锻件的尺寸精度.     

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。