基于Modelica和Dymola的飞机液压能源系统动态特性仿真

在建立液压能源系统元件动态数学模型基础之上,利用Dymola软件实现液压能源系统动态特性分析通用模型库的构建,并对某型飞机的液压能源系统进行建模和仿真。仿真结果表明,该模型符合实际系统的管路压力和流量脉动特性,在模型中能够获得时域范围内系统任一点的流量压力脉动情况。     

基于Modelica的硫化机液压传动系统仿真

轮胎硫化机液压传动系统显著地表现出连续和离散并存的混杂特性,建立合适的混杂系统模型并对其仿真分析对于产品的设计和分析具有重要意义。将连续的动态方程嵌入Petri网中,引入混杂系统的GHPN建模方法对轮胎硫化机液压传动控制系统建模;在Dymola仿真平台上,使用Modelica语言中的混杂建模技术实现模型的仿真分析。结果表明该方法可有效地建立硫化机液压传动系统的参数化模型。     

面向对象的推进剂加注系统建模与故障仿真

为了在缺乏故障样本的情况下提高液体火箭发动机推进剂加注系统的可靠性和安全性,亟需进行加注系统的建模和故障仿真.为此,采用面向对象的建模方法,提出了在Dymola环境下使用新的建模语言Modelica对加注系统进行建模和仿真的思路,并在理想模型的基础上通过调整模型和改变模型参数的方式进行故障仿真.结果表明,该方法能快速搭建系统模型,并得出有效的故障仿真结果.     

基于Modelica/Dymola的传动丝杠多领域建模与仿真

机电系统的开发需要多领域建模与仿真技术的支持,面向对象物理建模语言Modelica正是为解决复杂物理系统建模与仿真而提出的,而Dymola仿真平台完全支持Modelica语言,使得仿真更加容易实现.传动丝杠系统是一种典型的机电系统,采用Modelica语言对其进行了建模,并在Dymola上进行仿真.仿真结果表明,传动丝杠的伺服系统动态响应性能效果良好,并通过实验验证了仿真的有效性.Modelica/Dymola很好的将机械、电气和控制结合在一起,实现它们之间的无缝连接,而且建模更加形象.     

基于Modelica的多领域伺服系统的研究

在实际应用需求中,跨领域建模与仿真已经变得越来越普遍.面向对象物理建模语言Modelica使多领域建模变得相对简单,并能在完全支持Modelica语言环境下的Dymola平台上进行仿真.采用Modelica语言分别对开环伺服系统和半闭环伺服系统进行了建模,并在Dymola上仿真.仿真结果表明,多领域的伺服系统动态响应性能效果良好,与分析基本上吻合.利用Modelica语言的开放性,根据研究对象的需要建立一些相关的模型,同时也完善了模型库.Modelica/Dymola为伺服系统的研究提供了一种方法.     

直线共轭内啮合齿轮泵流量脉动特性研究

基于面积扫过法计算直线共轭内啮合齿轮泵理论瞬时流量,得到啮合点位置与泵瞬时流量的对应关系,进而求得泵几何流量脉动。产生困油容腔是泵实际运行过程中普遍存在的现象,也是影响泵出口流量平稳性的关键因素。对直线共轭内啮合齿轮泵运行过程进行分析,依据控制容积法将内部流道划分为吸油容腔、排油容腔、齿轮齿间容腔、齿圈齿间容腔和困油容腔。建立直线共轭内啮合齿轮泵AMESim仿真模型,并对泵内部流体运动状态进行分析及仿真验证。结果表明:加入困油容腔的子模型后,该模型能够反映泵实际运行中因困油容腔的产生导致的瞬时流量突变;仿真模型的流量脉动率为2.29%,高于几何流量脉动率(1.71%)。研究结果揭示了泵流量脉动的产生原因及变化规律,为直线共轭内啮合齿轮泵流动特性研究及优化设计工作提供了参考。     

基于振动与流场耦合齿轮泵困油现象分析

为了解决困油现象的历程和困油压力对齿轮泵工作状态的影响,根据困油条件下齿轮泵齿轮的振动模型,由内部流场数值分析,将困油压力作为耦合的条件,建立了困油条件下的齿轮副振动和内部流场耦合的动态模型,并通过对模型解耦,分析困油压力对齿轮副振动的影响以及困油压力的具体表现形式。通过齿轮泵内部流场进行仿真,和对通过传感器采集的振动信号处理分析,明确了困油压力的大小及位置和困油产生冲击的程度,表明所建耦合模型正确可靠,能够用于困油压力预测、振动冲击分析与困油历程的仿真分析。     

变位系数对渐开线内啮合齿轮泵困油容积和流量脉动特性的影响

合理地选取齿轮的变位系数,是降低困油容积和流量脉动的有效措施。为具体分析变位系数对内啮合齿轮泵困油容积和流量脉动系数的影响,根据啮合定理建立渐开线内啮合齿轮泵的数值模型,采用扫过面积法求解内啮合齿轮泵的困油容积和瞬时流量,并分析困油容积和流量脉动随变位系数变化所受到的影响。结果表明：在其他参数保持不变的情况下,总变位系数不变时,随着小齿轮变位系数的增大,困油容积先减小后增大,瞬时流量逐渐增大,流量脉动率减小。     

高阶椭圆齿轮泵低流量脉动的研究（英文）

随着齿轮泵向高压大流量低噪声方向发展,提出了一种低困油、少脉动的高阶椭圆齿轮泵,建立了相应的节曲线模型。通过3-3组合与3-3-3组合在流量和流量脉动率方面的对比,确定3-3-3组合作为高阶椭圆齿轮泵的主要结构。椭圆齿轮的传动比具有一定的变化规律,每个轮齿都有特定的啮合位置,利用坐标变换法分析了高阶椭圆齿轮的齿廓方程,为用CAD建模和仿真分析提供了理论依据。     

高阶椭圆齿轮泵低流量脉动的研究

随着齿轮泵向高压大流量低噪声方向发展,提出了一种低困油、少脉动的高阶椭圆齿轮泵,建立了相应的节曲线模型.通过3-3组合与3-3-3组合在流量和流量脉动率方面的对比,确定3-3-3组合作为高阶椭圆齿轮泵的主要结构.椭圆齿轮的传动比具有一定的变化规律,每个轮齿都有特定的啮合位置,利用坐标变换法分析了高阶椭圆齿轮的齿廓方程,为用CAD建模和仿真分析提供了理论依据.     

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。