等比式液压机械无级变速器设计与仿真研究

液压机械无级传动是一种多功率流无级传动系统,具有无级调速、高效率的特性,是大功率车辆较理想的传动形式。本文设计了一种新型的等比式液压机械无级变速器,对其无级调速特性进行了分析。在MSC．Easy5中建立了液压机械无级传动系统的计算机仿真模型。提出液压机械无级变速器的传动比控制策略。仿真研究结果表明,该设计方案能够满足车辆动力性能所要求的技术指标。为液压机械无级变速器的工程应用提供了重要的理论参考。     

液压机械无级传动系统储能技术研究

液压机械无级传动是一种多功率流无级传动系统,具有无级调速、高效率的特性,是大功率车辆较理想的传动形式.本文设计了一种新型的等比式液压机械无级变速器,对其无级调速特性进行了分析.并对多段液压机械储能技术进行了理论分析,为储能式多段液压机械传动系统的工程应用提供了重要的理论参考.     

基于液压传动的无级自动变速器模型分析

汽车自动变速器逐步向多挡位方向发展,但挡位愈多,结构愈复杂,体积和质量也会增大;而传统无级变速器工作时效率较低,传动功率较小,且控制系统较复杂,能耗较大。以变量泵与变量马达组成的容积调速回路为基础,建立液压传动的无级自动变速器模型,可有效解决自动变速器与传统无级变速器存在的问题,使变速器的调速特性与发动机特性吻合,为汽车无级自动变速提供一种有效的解决方案。     

行星锥环无级变速器的最大传动能力的研究

推导出了行星锥不同锥顶角及不同锥高系数的最多行星锥数。使用推荐的锥顶角和锥高系数所确定的最多行星锥数,既不会发生锥之间的干涉,也不会发生曲线干涉。分析出了调速环和行星锥的接触点为行星锥上正压力最大的点。给出了在行星锥轮数目最多时,行星锥上正压力最大点在满足许用应力条件下不发生打滑的行星无级变速器最大传动能力公式,并分析了行星无级变速器的设计步骤。     

行星齿轮传动设备无级调速与辅助调速装置的匹配研究

NGW型行星齿轮传动设备的软启动与无级调速是机械传动的发展方向之一,设备的调速范围与辅助调速装置的功率、转速、转矩有关.本文从行星齿轮传动的调速原理人手,采用油马达作为辅助输入,通过分析主电动机和油马达输入转速、转矩的合成规律,研究了行星齿轮传动设备无级调速范围与辅助调速装置的功率、转速、转矩之间的匹配关系及规律.     

行星齿轮功率分流式无级变速器液压控制系统设计

针对无带传动的新型行星齿轮功率分流式无级变速器的传动方案,设计液压控制系统,采用两个换挡电磁阀组合控制相关离合器、制动器工作以实现不同基本挡位,利用数字阀控制起步离合器的平稳起步和基本挡与无级变速挡的平稳换挡。该液压控制系统结构简单,控制方便,具有较好的实用价值。     

新型多段液压机械无级变速器效率特性分析

介绍了泵、马达的近似效率计算公式和闭式变量泵-马达系统效率随转速、油压、排量变化的算法.导出了闭式行星齿轮传动产生功率循环的条件和液压机械无级变速器(HMCVT)典型结构的效率计算公式.描述了包含输入功率、泵马达排量、功率循环等因素时效率计算的合理步骤,对新型多段HMCVT进行了效率计算.结果表明:新型多段HMCVT的平均效率高于0.93,但随传动比、传递功率及转速的变化存在波动;控制传动比在泵排量为零的附近调节,可保证HMCVT高效率工作.     

拉维娜行星齿轮机构的运动分析和传动效率计算

文章以四档拉维娜行星齿轮机构自动变速器为研究对象,通过不同换挡执行元件的组合,得到了它各档的运动规律和各个工作元件之间的运动关系,然后通过运用单排行星齿轮机构一般运动规律的特性方程式列线性方程组求解出了其各档的传动比,同时采用啮合功率法(间接功率法)得到了其各档的传动效率。通过该方法计算出的传动比和传动效率均符合车用变速器的要求,从而得到了一种针对拉维娜行星齿轮机构的新的分析方法。     

采棉机动力换挡行驶传动系统设计与试验

针对采棉机作业工况复杂,提出一种由静液压无级变速与机械式有级变速组配式动力换挡无级调速行驶传动方案。建立采棉机田间采摘、田间运输和公路运输3种工作模式控制逻辑,确定3种模式速度范围。构建动力传动方程,确定采棉机设计参数和液压系统元件选型。搭建采棉机样机进行速比特性田间试验,分析调速特性与变量泵效率特性。结果表明：通过变量泵和变量马达联合调控以及改变机械式有级变速箱传动比,可实现采棉机在田间采摘模式时恒转矩输出,在运输模式时恒功率输出;采棉机田间采摘速度范围为0~8.5 km/h,田间运输速度范围为0~14.5 km/h,公路运输速度为0~27.5 km/h;可实现采棉机全程作业无级调速,满足其行驶动力需求。     

液压机械无级传动在拖拉机上的应用

液压机械传动是一种新型的无级变速装置,该装置适用于大功率拖拉机传动系统。本文主要介绍了它的组成结构和基本原理。分析了液压机械无级变速装置具有的优良传动性能及其在国内外的应用,并指出了液压机械无级传动在我国拖拉机变速器上的应用前景。     

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).     

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.     

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.     

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。