基于高速开关阀的湿式离合器缓冲控制系统研究

湿式离合器是大功率液力机械传动装置重要的传动部件，其工作状态直接影响设备的安全可靠运作。为了提高湿式离合器工作效率，通过分析离合器的工作原理，基于电磁式高速开关阀设计一种用于湿式摩擦离合器的液压控制系统，构建液压系统模型，通过 MATLAB/Simulink仿真求解该液压系统的压力输出信号。计算结果显示：该液压系统可以用于控制湿式离合器的接合，能够为湿式离合器提供稳定的接合油压缓冲信号。     

手自一体变速器液压控制系统设计

由液力变矩器加定轴式齿轮变速器组成的手自一体变速器,取消了行星齿轮变速机构,提高了传动效率.笔者根据定轴式齿轮变速机构的传动方案,提出了采用湿式多片摩擦离合器作为换挡执行机构,设计了液压控制系统,实现了由数字阀控制液力变矩器的锁止,用比例电磁溢流阀控制系统压力以满足传递不同的转矩要求,两个电磁阀组合控制各挡离合器工作来自动换挡.简化了液压控制系统,降低了控制难度,具有较好的实用价值.     

干式DCT离合器活塞位移控制研究及试验

简要介绍干式DCT液压控制系统,分析其工作原理及主要特点。深入分析离合器活塞位移控制系统的结构及工作原理,利用EASY5软件对其控制特性进行仿真研究,并通过试验验证仿真的正确性,为离合器扭矩传递的控制打下了基础,同时为控制策略的制定及控制系统的开发提供了依据。     

湿式离合器液压执行系统建模与仿真

针对湿式离合器液压执行系统,在分析其工作原理和结构的基础上,在机械域和液压域上分别对关键组成部分比例压力电磁阀和离合器油缸活塞建立数学模型,并采用AMESim软件对湿式离合器的液压执行系统进行建模;为了验证所搭建模型的有效性,在给定不同的激励电流情况下分析系统的动态响应;针对所搭建的AMESim模型,采用传统PID控制算法和基于模型的前馈+反馈控制算法控制输出油压,对比验证了跟踪效果。仿真结果表明:搭建的模型具有良好的动态特性,前馈+PID反馈的控制算法较PID算法的控制效果更好。     

湿式双离合器动态充油特性与主油压相关性研究

湿式双离合器充油特性是开发双离合器自动变速器离合器控制系统的关键之一。在考虑液压系统的液阻、液感、液容以及电磁阀液动力的前提下,建立了离合器压力控制系统以及各液压元件在充油过程中的动态模型,并利用AMESim对其进行动态仿真,通过试验验证了所建模型的正确性与有效性。仿真和试验结果发现:由于离合器电磁阀阀芯液动力的存在,离合器充油时的压力响应速度与系统主线压力设置呈非单调关系,存在最优区间。基于此研究结果,通过优化系统主线压力设置可以有效提高离合器充油速度,改善建压时间。     

气动高精度压力控制系统的建模及特性分析

为实现气缸容腔的高精度压力控制,设计一种采用比例压力阀控制、缓冲储气罐和无摩擦气缸串联的双闭环高精度压力控制系统.建立了该类系统完整的数学模型,模型包含阀口流动的非线性、储气罐和气缸内的压力动态、比例阀的动力学、储气罐和气缸连接管路的模型和基于实验数据的气体泄漏模型.仿真分析了气源压力、气源温度、储气罐容积、连接管路长度和直径等关键参数对系统动态性能和控制性能的影响,为压力控制系统各参数的选择和控制器的设计提供理论依据.     

双向缓冲缸对锻造操作机行走机构特性影响的分析研究

利用AMESim系统仿真软件对锻造操作机双向缓液压油缸的内部结构进行建模与仿真分析,研究双向缓冲液压缸对锻造操作机大车行走机构的影响,分析双向缓冲液压缸的动态特性与工作原理。通过对锻造操作机大车行走机构启动和停止动作过程的液压系统进行仿真分析研究,揭示出液压缓冲缸双侧活塞的位移变化减小了控制大车行走换向阀的冲击,使得行走马达转速和转矩变化平缓,增加了锻造操作机的平稳性。采用贺德克测量仪测量行走换向阀口压力,验证仿真结果的准确性。     

基于优化非线性控制的液压制动系统压力跟踪仿真研究

为提高车辆制动过程中控制系统的响应速度,设计车辆液压制动非线性PID控制优化系统,并对制动压力跟踪效果进行仿真。给出车辆液压制动系统平面图,分析车辆行驶和制动过程中液压系统的工作原理。采用数学模型对车辆液压制动系统进行简化,针对输入的不确定性设计了非线性PID控制系统。采用遗传算法对非线性PID控制系统进行优化,给出了液压制动非线性PID控制系统的优化流程。在不同初始状态和不同压力信号条件下,采用MATLAB软件对制动压力跟踪误差进行仿真,并与优化前的仿真结果进行对比和分析。结果表明:在非线性PID控制系统中,液压制动压力跟踪误差较大,控制参数调整速度较慢;在遗传算法优化后的非线性PID控制系统中,液压制动压力跟踪误差较小,控制参数调整速度较快。采用遗传算法优化非线性PID控制系统,可以提高整个系统的反应速度,获得良好的制动效果。     

基于神经网络PID控制的液静压轴承等膜厚度研究

针对液静压轴承外部负载改变时、油膜厚度发生变化、从而出现轴承的承载力及阻尼性降低的问题,设计等油膜厚度的主动式控制方法。以比例压力阀作为压力补偿元件,控制回路以供油压力、工作台位移、油腔流量及工作压力作为回馈。计算保持稳态补偿膜厚差所需的供压压力差值作为压力阀的PID控制参数值,再结合类神经网络经训练参数找出最佳PID控制器参数,进行位移补偿控制,达到稳态等膜厚控制。实验结果表明,神经网络PID控制器比其他神经网络控制器具有更快的暂态振荡收敛,并迅速达到等膜厚的目标。     

摆锤式冲击试验台液压系统的设计

设计一种对被试件抗冲击性和可靠性进行试验的冲击试验台,介绍该冲击试验台液压系统的设计和工作原理;设计使用湿式液压离合器水平自动冲击,防止二次冲击,安全可靠;并应用AMESim对系统动态性能进行仿真分析,结果表明该液压系统能够满足设计要求。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.