传动比波动幅度约束下的摆线轮齿廓修形量优化

摆线轮齿廓修形对摆线针轮传动机构的承载能力和运行平稳性有重要影响。为获取最优的修形策略和修形量，提出了一种以最小化传动比波动幅度为优化目标、基于内点法的摆线轮齿廓等距-移距复合修形量的优化方法。以单级摆线针轮减速器为例，建立考虑修形后的摆线轮受力平衡方程，以及摆线轮针齿的轮齿接触方程，并通过优化流程将力平衡方程和轮齿接触方程耦合集成，从而实现对3种等距-移距修形组合策略下的修形量进行优化计算，发现正等距加正移距组合修形下的最优修形量可将传动比波动幅度降低40%,最大针齿接触力降低17%,实现更平稳的传动和更好的承载性能，也有利于提高减速器传动精度和寿命。     

摆线齿插齿加工刀具刃形设计

摆线轮是RV减速器中的关键零部件,其设计制造水平对RV减速器的传动性能影响巨大。现阶段,摆线轮制造能力难以适应RV减速器大批量生产的需要。为了提高摆线轮的加工效率,提出采用插齿加工方法加工摆线轮。依据插齿加工运动,建立切削刃设计计算坐标系。基于修形后的摆线轮齿形方程,推导插齿刀理论刃形方程。以某型号RV减速器中的摆线轮参数为例,进行插齿刀理论刃形设计。计算结果表明,设计的插齿刀刃形能与摆线轮齿形时刻处于"点接触"状态,证明提出的插齿刀刃形设计方法是可行的。进而提出了插齿刀前、后刀面的设计方法。最后通过切削仿真证明提出的摆线轮插齿刀刃形设计方法是正确的。     

摆线轮齿廓逆向设计的仿真加工

为了缩短未知修形方式摆线轮加工周期,降低生产成本,提高加工效率,提出一种高阶分段拟合算法,使用该算法可以通过逆向工程的方式实现对未知修形方式摆线轮齿廓的重构。为了验证该算法的合理性,先对已知修形方式的RV320摆线轮齿廓点使用高阶分段拟合算法进行齿廓重构,之后通过VERICUT仿真加工出RV320摆线轮模型,并将仿真加工的RV320摆线轮模型与RV320摆线轮理论模型进行对比,最大加工误差约为0.016 86 mm。之后通过实验加工出RV320摆线轮并对其进行精度检测,检测结果显示通过高阶分段拟合算法加工出的摆线轮符合使用要求,进一步验证了该算法的合理性。由此可得,使用高阶分段拟合算法同样能够实现对未知修形方式摆线轮齿廓的重构,同时也为未知修形方式摆线轮的高精加工提供了一种方法。     

RV减速器摆线轮拓扑修形齿廓研究

为使摆线轮具有良好的啮合性能,根据计算的摆线轮实际工作范围,将摆线轮齿廓分为工作段和非工作段齿廓,采用拓扑修形方法来满足工作段和非工作段的间隙要求。工作段采用转角修形,使修形后工作段为共轭齿廓,并保持一定的齿侧间隙。非工作段采用变等距修形,使齿顶与齿根部分产生合理的间隙,得到合理的修形齿廓。推导了摆线轮拓扑修形齿面方程,可以通过调整修形参数获得满足工作要求的齿廓间隙。从初始啮合间隙、载荷分布、回差分析方面验证了拓扑修形的合理性。     

RV减速器中摆线轮齿形优化修形与参数化设计

为了得到符合实际工作要求的摆线轮齿形,对摆线轮齿形的几种修形方式进行了研究,确定了最佳修形方式为负移距与正等距相组合的修形方式。对多种优化方法进行了分析,选取了两点外插的混合罚函数法来求解,并借助VC++6.0编写绘图程序验证了此种修形方式的合理性。同时利用Pro/E 4.0对摆线轮进行了参数化设计,推导出摆线轮齿廓曲线上的坐标点按齿廓曲线曲率不同分布疏密程度不同的公式,同时借助VC++6.0编制程序计算出摆线轮齿廓曲线上分布的各点的坐标值,为使用数控机床加工摆线轮提供了便利。     

双圆弧谐波齿轮齿形参数化设计仿真与验证

谐波减速器的应用领域对产品性能的要求日益提高，尤其是机器人行业，要求谐波减速器具备高寿命、高精度、高转矩容量等。传统的渐开线齿形由于同时啮合齿对数较少，传动能力有限，难以达到使用要求。而双圆弧谐波齿形能满足上述要求。但目前国产谐波减速器主要还是以渐开线齿形为主，对双圆弧谐波齿形的设计原理基本没有掌握。首先介绍了谐波减速器的研究概况，然后讲述了双圆弧谐波减速器齿轮传动的基本原理和双圆弧齿形计算机辅助设计软件的开发，提出了几种齿形设计中如何提高啮合精度的方法和基于复杂柔轮有限元变形分析的中性曲线的三次样条模型。通过理论计算模型开发出了双圆弧谐波齿轮计算机辅助设计软件，极大地提升了设计开发效率，降低了开发成本。通过有限元分析模拟了柔轮的真实变形，有限元模拟出的柔轮变形齿廓能与刚轮齿廓精确啮合，与理论计算出的刚柔轮齿廓能精确啮合达成一致，证明理论模型计算出的双圆弧齿廓是准确无误的。     

摆线针轮传动中摆线轮齿廓修形技术研究

为确定不同传动要求的摆线针轮传动机构中摆线轮齿廓修形方式及最佳的优化算法,首先对摆线针轮传动中摆线轮齿廓应用最多的"正等距+负移距"和"负等距+正移距"两种组合修形方式进行了分析计算,得到了两种组合修形方式引起的回差大小及修形后摆线轮啮合受力的优劣,确定了不同传动要求的摆线针轮传动机构优先适用的修形方式;对摆线轮齿廓优化算法进行了对比研究,针对"正等距+负移距"组合修形方式确定了优先选用的优化算法;对采用"负等距+正移距"组合修形方式,提出了一种改进的优化算法,将该算法与现有的优化算法进行对比分析,根据实际的装配精度确定了应优先选择的优化算法。     

可靠度约束下摆线针轮减速器加工精度优化北大核心

摆线针轮减速器主要用于高精密传动场合,其在加工过程中,会产生影响传动精度的制造误差。为在实际加工中选取符合传动条件的最优加工参数,基于坐标变换与齿轮共轭接触原理,建立了考虑齿廓修形、制造误差的轮齿接触分析模型,分析了不同种类制造误差对传动误差的灵敏度,并设计一种基于传动可靠度的轮齿修形参数与加工精度优化方法。结果表明,基于DIRECT算法对样本的最佳化计算,可得到一组在许用传动误差条件下制造成本最低的减速器加工参数,且该组加工参数具有高可靠度特性。因此该方法可为制造高可靠度摆线针轮减速机提供理论优化参考。     

RV减速器摆线针轮齿廓修形回差影响分析

针对RV减速器回差精度问题,建立了摆线针轮齿廓修形的回差精度数值分析模型,采用几何法求解各种常见修形方式产生的几何回差,同时考虑摆线针轮传动中的弹性回差,推导出摆线轮齿廓修形的回差影响公式,并讨论了同一摆线轮齿廓修形方式下不同的修形参数与同一修形参数下不同的修形方式对回差的影响,得出在同一修形量的条件下,等距加移距的组合修形方式的回差影响最小,移距修形的回差影响最大。对RV-40E型减速器样机进行试验验证,与传统回差公式相比较,文章推导的回差公式精度提高6%左右。     

RV减速器摆线针轮的有限元接触分析

基于有限元分析方法,研究加载状况下摆线针轮啮合副初始啮合时齿廓对的接触状态。考虑摆线针轮啮合副的齿廓修形和摆线轮齿廓线的建模精度,利用ANSYS自带的APDL语言建立了摆线针轮啮合副的三维模型。考虑有限元网格质量及有限元模型的计算效率,利用VSWEEP命令生成了有限元模型并局部细化了网格。最后考虑摆线针轮的实际工况,建立了摆线针轮的接触对和边界条件。分析结果表明:摆线针轮初始啮合瞬间一共有6个齿参与传力,其中最先接触齿为第6齿,并且在啮合齿廓对附近摆线轮齿及销孔变形比较大。     

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。