某滑阀卡紧故障机理分析(英文)

针对高温工作状况下由滑阀几何形状引起的阀芯径向液压卡紧力进行了理论推导,进行了温度变化对阀芯与阀套配合间隙影响的温度场仿真分析,并对阀芯与阀套做了热应变分析,得到了滑阀顺锥与倒锥结构对阀芯受力的影响及油液、阀体温度不同情况下滑阀流道的温度场分布。通过对计算结果的分析,得出滑阀卡紧故障的原因,为滑阀设计提供了理论参考。     

多路阀滑阀节流槽计算方法研究

工程机械上,多路阀常通过在阀芯节流边加工不同形状的非全周开口节流槽以满足不同阀芯流量控制特性。由于非全周开口节流槽复杂多变的结构特点,传统而相对简单的截面面积计算公式难以完成面积精确的计算。利用CFD仿真软件,对双U节流槽的三维流场压力进行仿真分析,推导了面积与压力变化之间的关系,并根据节流槽液体流动结构形式确定了局部压力损失系数,得到非全周开口计算面积与节流槽结构参数之间的关系方程。通过AMESim软件进行液压系统仿真分析,并最终通过试验进行了验证。研究发现通过该方法能快速准确地完成各种非全周开口滑阀开口面积的设计,对非全周开口滑阀流量设计、液动力预测及其振动和噪声的控制具有重要意义。     

降低机床液压滑阀噪声的措施

由于形成紊流而引起的噪声,其大小主要取决于滑阀节流缝隙的形状。该形状决定于滑阀及其阀体的轮廓形状。为了研究缝隙形状对噪声大小的影响,最好是在同一壳体内变化节流缝隙的形状。这样就使壳体对辐射噪声的影响都是一样的。实验研究中所采用的缝隙形状表示于图1中,其中:a——针状形;б——纵向沟槽形;B——缝隙形;r——圆柱形。     

多路阀主阀芯不同节流槽对其稳态液动力的影响

针对工程机械用多路换向阀在不同工况下稳态液动力过大或不稳定导致滑阀卡滞,从而影响执行机构的可靠性和安全性,以某型号工程机械多路阀为例,设计矩形、半圆形、U形、2U形4种形式节流槽口的阀口,通过Fluent数值模拟研究在不同阀口开度下的流场特征并确定射流角,根据流场计算结果,搭建不同结构节流槽的滑阀模型,分析节流槽口结构形式对阀芯稳态液动力的影响。研究结果表明：随着阀芯节流槽口逐渐开大,矩形、U形、2U形节流槽阀芯所受稳态液动力变化平稳;当阀芯采用U形节流槽时,其单位节流面积受力变化幅度较大,但阀口稳态液动力仍能保持稳定;半圆形节流槽阀芯所受稳态液动力相对不稳定,梯度较大。     

基于CFD的入口节流型滑阀稳态液动力研究

利用计算流体力学(CFD)方法,针对入口节流出口无节流的滑阀阀内流动方式,进行了液动力特性研究。给出了网格细分的规则,以及根据流场计算结果提取液动力的方法。计算了阀芯环形腔截面面积、环形腔长度、出口尺寸及角度、阀口开度等不同滑阀结构参数和工作条件下,入口节流出口无节流流动方式液动力的变化规律,分析了其液动力变化的内在机理。研究结果揭示了该种流动方式下液动力的复杂变化规律,为滑阀的分析和设计提供了参考。     

基于液动力的水压阀阀口设计及试验研究

水压电液比例方向阀是智能化液压支架的核心控制元件,非线性的阀口液动力是影响比例阀性能的关键因素。非全周开口的"锥滑阀"是水压比例阀常采用的结构形式,"锥滑阀"有先节流后密封与先密封后节流两种结构形式。分别建立了两种结构的三维流道模型并进行了网格划分,通过网格无关性验证选取了合适的网格密度。利用CFD仿真方法得到不同阀口开度、不同阀口压差下阀芯所受液动力变化曲线,结果表明:两种"锥滑阀"结构阀口液动力变化趋势相同,先密封后节流结构的阀口液动力要明显小于同等工况下先节流后密封结构的液动力。最后搭建了液动力验证试验系统,通过测量阀口流量和阀口压差间接验证了CFD仿真分析的正确性。     

基于流固热耦合的滑阀温度特性研究

针对中高压系统中,滑阀阀芯、阀套（或阀体）间配合间隙较小,且在使用过程中常出现卡紧现象,建立了液压滑阀的计算流体力学（Computational fluid dynamics,CFD）三维模型和稳态传热模型（FEA）。利用流固热耦合方法,分析黏性加热效应使油液温度升高导致阀芯变形的现象,得出阀芯在不同开口度和不同阀芯材料下的阀芯温度场分布与变形情况,为液压滑阀的设计计算提供了参考。     

基于AMESim的电液控制油缸建模与仿真

简述了电液步进油缸的工作原理与设计特点。建立油缸的数学模型,利用AMESim仿真软件建立该液压系统的仿真模型。研究三通阀不同遮盖量、不同锐边圆角半径以及不同阀口形状等对系统整体性能的影响。结果表明:阀的遮盖量对小位移定位精度影响较大;阀芯工作锐边圆角半径的大小对滑阀小开口时的流量特性有影响,但影响较小;矩形、梯形节流口的过流面积变化率较为恒定,具备良好的调节性能,比较适合在高温环境下工作。研究结果为该型液压缸的工程实践提供指导,为系统的进一步优化提供理论依据。     

具有二个固定节流孔二个可变节流口的正开口四通阀的综合分析

一、二种伺服阀前置级的比较图1为具有二个固定节流孔的正开口四通滑阀,圈2为双喷咀挡板阀,二者的结构形式虽然不同,但从实质上看,二者的组成、原理、功能和等效液压桥路却完全相同。从组成上看,二者都属于具有二个圈定节流孔、二个可变节流口的四通阀。只是图1为滑阀结构,阀口3和4为可变节流窗口;     

超高速冲压滑动夹持成形工位的改善

为提高冲压模具成形速度,研究了用于超高速冲压(UHSS)平台成形母端子PIN和BOX部位冲压模具的滑动夹持成形工位。发现在模具的成形期间,成形滑块表面在半径接触点开始表现出磨损,然后向下产生较长的磨损,分析了滑动表面的几何形状及造成磨损的主要因素,成形滑块在成形期间磨损的主要形式是粘着磨损和分层磨损,夹持块的几何形状和滑动表面的角度是造成磨损的重要原因。对滑动夹持成形工位进行了重新设计,对线性驱动和从动轮廓进行了改进,从开始到结束都采用面滑动,同时原始的滑动面的角度设计变小,减轻了磨损和旋转问题,增加了工位的可调节。     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.