齿轮液压泵的结构合理性探讨

在简介了传统的双齿轮泵流量波动大、结构受力对称性差、易产生泄露和磨损等不足基础上,指出研发齿轮泵新型泵体结构的必要性。简要分析了平衡式多齿轮泵、多联齿轮泵、平衡式复合泵的基本原理和结构特征,分析了各自的排量、流量、传动件受力情况等动态特性,提出了改善齿轮泵受力状况、减少磨损、降低泄露、减少流量波动的途径。指出高压化、低流量脉动、低噪声、大排量、变排量、集成化是齿轮泵的发展方向。     

谐波式齿轮泵的流量脉动分析

运用轮齿啮合理论几何运动规律对谐波式齿轮泵的流量特性进行研究,推导出了瞬时流量的计算公式,并与内啮合齿轮泵的流量脉动进行对比。     

活齿泵的试验研究

活齿泵融合了活齿传动理论和内啮合齿轮泵原理，并具有活齿传动结构紧凑、多齿啮合、传动平稳的特点，能够满足液压泵的各种要求。并通过试验验证了活齿泵流量均匀性好的优点。     

一种内啮合行星式自动送料机构

介绍了典型冲压自动化生产的组合模式。提出一种内啮合行星式自动送料机构,并对这种机构的工作原理、运动特性进行了分析与讨论。研究结果表明,内啮合行星式送料机构具有结构紧凑、送料行程大、加速度特性好、运行平衡可靠等优点,可用于多工位自动化冲压件的2d、3d自动送料。     

基于齿廓曲线的外啮合齿轮泵排量计算

渐开线外啮合齿轮泵以结构简单、造价低廉等优点而在矿山、工程等领域应用广泛,但目前关于精准计算其瞬时流量、排量的文献较少。为此,基于齿轮啮合机制、轮齿齿廓性质以及转角和啮合点的关系,建立齿轮泵瞬时输出流量的数学及仿真模型。针对齿轮泵重合度、齿轮变位、卸荷槽、侧隙等影响因素对模型进行论证,进而提出一种精准计算渐开线外啮合齿轮泵排量的方法,并采用Simulink仿真软件对不同类型外啮合齿轮泵的瞬时流量进行仿真模拟。同时利用3种不同型号齿轮泵验证排量公式,其最大误差在5%以内。验证计算模型有效性后,基于MATLAB设计了齿轮泵计算辅助平台,实现了外啮合齿轮泵瞬时流量、排量性能可视化,以简化计算流程,适应工程化应用。     

内啮合齿轮泵内部泄漏流量的建模与实验

根据流体间隙流动特性,分析了内啮合齿轮泵内部结构及其泄漏通道,建立了内部泄漏流量的数学模型;结合NB型内啮合齿轮泵完成了内部泄漏流量的仿真分析并进行了实验验证,为研究内啮合齿轮泵的内部泄漏、容积效率和动态特性提供了理论依据。     

内外啮合齿轮泵与马达传动的特性分析

为了实现齿轮泵输出流量的定级变化、齿轮马达输出转矩和转速的定级变化,设计了内外啮合型齿轮泵和马达,将内外啮合齿轮泵和马达组成传动系统。以内3外2型为例,对内外啮合型齿轮泵和马达的原理进行了分析:泵具有5个独立的油液输出口,通过不同组合可以组成11中不同的供油方式;马达有5个进油口,在普通连接下可以输出11种转矩与转速,在差动连接下可以输出6种转矩与转速。分析结果表明:在内外啮合齿轮泵和马达的传动系统中,通过改变泵的供油组合方式、马达的连接方式,可以定级的改变马达转矩与转速,拓宽了齿轮泵和马达的适应领域。     

考虑行星轮不平衡影响下的啮合边带特征研究北大核心

啮合边带特征是齿轮箱故障诊断关注的指标,针对行星轮不平衡引起的啮合边带的调制特征未知问题,通过分析振动的传递路径,建立考虑行星轮不平衡质量与时变啮合刚度和太阳轮浮动多因素耦合的行星轮系振动模型。基于该振动模型分析同相位和顺序相位结构特点的行星传动在行星轮不平衡影响下的啮合边带特征;通过与健康状态下系统啮合边带特征的对比,揭示行星轮不平衡引起的啮合边带调制机理;同时分析在不同运行转速和负载工况下行星轮不平衡对啮合边带调制的影响规律,结果表明啮合边带易受转速和负载影响。     

多齿轮变量齿轮泵瞬时流量特性仿真分析

针对齿轮泵存在振动与噪声的问题,提出了一种新型结构多齿轮变量齿轮泵。依据流量特性理论分析,采用MATLAB软件编写程序对瞬时流量特性进行仿真分析。结果表明：与普通外啮合齿轮泵相比,该变量泵不仅可以改变排量,使瞬时流量显著增加、流量脉动大幅降低,而且实现了对泵体振动与噪声的有效控制,具有良好的流量特性品质。     

一种新型内啮合齿轮泵的设计计算与制造

1.问题的提出在液压传动和润滑供油中,渐开线外啮合齿轮泵由于“空穴”现象转速不能太高,所以泵的每分钟流量受到限制。另外,外啮合齿轮泵由于受到“外啮合”的影响,所以体积也不会太小。内啮合齿轮泵与外啮合齿轮泵相比,其体积小,并且可通过增大配油窗口以避免“空穴”现象来提高泵的转速,流量可以增大,这在工业实践中是很有意义的。当外转子齿廓曲线左右侧各为一段圆弧,内转子齿廓曲线为短幅外摆线的等距线时,可以圆满地实现上述啮合传动,提高泵的液压特性。油泵的装配简图及内外转子齿形如图1所     

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.