基于Simulink的液压缓冲器动态特性分析

为研究液压缓冲器的缓冲特性,根据伯努利方程建立了该液压缓冲装置的数学模型。利用Simulink的图形化建模仿真工具,在该平台下搭建了缓冲器的计算模型,根据Simulink模型对结构参数进行了仿真计算,并分析了流液孔等参数对缓冲性能的影响。分析结果表明:沟槽起始深度越深、节流口长度越短,缓冲的效果越好。该模型为液压缓冲器提供了一个参数化的设计工具,便于不同工况下的液压缓冲器设计,具有一定的工程意义。     

某型飞机尾橇缓冲器动态性能分析和试验方法研究北大核心

对某型飞机的尾橇缓冲器的动态性能分析和试验方法进行研究。推导全油液式尾橇缓冲器阻尼力数学模型,并基于该数学模型建立了落震仿真分析模型,通过仿真得到该尾橇缓冲器的动态特性并判断是否符合性能要求;以理想缓冲曲线为基准,通过若干套阻尼孔构型的缓冲器冲击试验,得到最接近设计状态的理想阻尼孔构型。分析和试验方法可用于指导全油液式尾橇缓冲器的设计与验证,对尾橇缓冲器的研发工作具有一定的参考价值。     

一种被动式液压缓冲器原理及工作过程仿真研究

提出了一种被动式液压缓冲器的设计方案,对其工作原理进行了分析,建立了缓冲过程的数学模型,并仿真研究了缓冲器不同参数对缓冲效果的影响.仿真结果表明:缓冲器的结构参数、初始速度和负载质量均对缓冲加速度波形影响较大,可以通过调整缓冲器的结构参数获得满意的缓冲效果.     

基于ADAMS与Simulink工程车辆油气悬架非线性建模分析

工程车辆油气悬架建模存在诸多非线性影响因素,根据其结构特点和工作原理,基于气体状态方程和油液孔口出流方程建立其非线性数学模型;并以此为基础搭建Simulink数学模型和ADAMS油气悬架试验台多体动力学模型;为验证模型准确性,搭建油气悬架试验台,进行油气悬架动态特性试验,获得激励频率变化对油气悬架动态特性的影响规律。对比分析联合仿真和试验结果验证了非线性数学模型和联合仿真模型的准确性与可靠性,为工程车辆油气悬架系统的特性研究及整车动力学特性研究提供了参考。     

高速液压缸平板节流缓冲过程的研究

探讨了一种可用于高速液压缸的平板节流的缸内缓冲装置的结构和原理，建立了其相应的数学模型，并在此基础上进行了系统仿真，利用仿真结果分析了模型结构参数对缓冲效果的影响，仿真结果与试验结果基本一致，从而验证了这种节流缓冲方式的合理性和有效性。     

车用液压缓冲器动态特性研究

为研究履带车辆平衡肘限位液压缓冲器的工作特性,在分析液压缓冲器缓冲机制的基础上,建立了缓冲过程的数学模型.采用四阶龙格-库塔数值计算方法,运用MATLAB编程进行仿真计算,得出缓冲器动态特性曲线.对影响液压缓冲器缓冲特性的因素进行了分析.研究结果表明:合理选择活塞与缸壁的缝隙、节流孔的大小及位置对缓冲器的缓冲性能非常重要;冲击载荷的初速度对缓冲器的最大缓冲力影响很大,而冲击质量对最大缓冲力影响很小.     

一种多孔式液压缓冲器的设计与优化

针对目前多孔式液压缓冲器优化设计中缓冲曲线不够理想,且未全面考虑结构参数影响的设计优化问题,建立多孔式液压缓冲器的数学模型和AMESim仿真模型,对活塞直径、复位弹簧刚度、环形间隙、阻尼孔间距和孔径等主要结构参数进行仿真研究;以此为依据,基于遗传算法对其主要结构参数、阻尼孔间距和孔径进行优化,结果表明:优化后的缓冲器峰值压力降低13%,平均阻抗力提高6%,缓冲曲线更加接近理想缓冲曲线。     

航空发动机叶片MPAW修复传热建模及冷却方法

热源参数和冷却速度是影响钛合金叶片焊接修复质量的关键因素.基于脉冲热源叠加原理和高斯分布特性,建立了焊接热源的数学模型,根据夹具实体结构建立了焊接修复有限元模型,通过COMSOL进行传热过程建模,并通过试验对热源模型进行了验证.根据传热仿真结果分析了夹具的传热特性,设计了夹具的冷却结构和流体参数.通过建立典型位置的参数化表面,对比分析了采用冷却方法之后最高温度变化情况并进行了焊接试验.结果表明,热源模型与实际吻合度较好,采用的换热方法可有效提升焊接修复效果.     

渐变式液压缓冲器的设计与仿真研究

为得到渐变节流液压缓冲器理想缓冲特性,提出一种基于理想缓冲过程的节流杆外部轮廓曲线的建模方法。该方法是在分析渐变式液压缓冲器缓冲机制的基础上,建立了阻尼孔两侧等流量方程,推导出节流杆的外部轮廓尺寸方程,并利用MATLAB数值分析方法,绘制出节流杆轮廓曲线。把所得的轮廓曲线应用于实际缓冲过程中,对得到的缓冲特性曲线进行分析,验证了该建模方法的可行性,并对不同冲击载荷的碰撞情况进行对比。结果表明:通过该建模方法得到的缓冲器具有理想的缓冲特性,并能安全缓冲掉小于额定值的冲击能量。     

车辆换挡缓冲阀充油特性的研究

以车辆换挡缓冲阀为研究对象,建立了缓冲阀工作过程的数学模型。然后利用Matlab/simulink分析了其结构参数对缓冲压力特性的影响。结果表明,缓冲阀芯和节流孔直径对缓冲压力特性的影响较大,缓冲弹簧和回位弹簧的刚度对缓冲压力特性有一定的影响。最后通过试验验证了缓冲阀数学模型的准确性。     

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。