伺服液压缸非对称静压支承结构对比仿真分析

静压支承能够实现金属间无需直接接触,以达到纯液体摩擦,大大减小两者之间的摩擦力。伺服液压缸导向套可采用静压支承来减小摩擦,提高液压缸使用寿命。但在特殊工况下,液压缸往往还受到径向偏载力,针对新型非对称静压支承结构进行了油膜性能研究。利用Fluent软件分别对传统四垫静压支承和新型非对称静压支承结构进行流场仿真,对比在不同进口压力、不同活塞杆速度、不同偏心量下的压力云图分布及其摩擦力变化。通过分析压力云图,比较两种不同静压支承结构的承载性能。仿真结果表明:新型非对称静压支承结构的摩擦力小,当活塞杆受到径向偏载时能够自适应达到平衡。     

液体静压技术在伺服油缸中的应用

本文介绍一种用于液压伺服缸中的圆锥形液体静压轴承，分析了油缸活塞运动速度对轴承静压支承力的影响，阐述了圆锥形液体静压轴承的设计方法。     

腔内孔式回油液体静压轴承

一、前言实践证明,液体静压轴承能适应高精度、高效率和重型的机床主轴系统的性能要求,因此,液体静压轴承在这三种类型机床上得到了广泛的应用。而过去广泛采用的定压式静压轴承中,可变节流形式的静压轴承,其油膜刚度较高,但结构比较复杂,在中小型机床上应用受到一定的限制。能否设法在固定节流形式的基础上,经济合理地提高油膜刚度,这就是我们设计和试验新的型式静压轴承的指导思想。同时,我们在新结构的设计中,还考虑了主轴挠度在轴承油膜范围内对油膜刚度的影响,而将主轴挠度的不利因素转化为对提高油膜刚度的有利因素。新的结构型式——腔内孔式回油液体静压轴     

不同节流方式的静压轴承承载性能研究

静压轴承节流器对轴承的承载能力和油膜刚性起决定性作用.根据静压轴承节流作用机理,推导和建立毛细管、小孔、滑阀反馈、薄膜反馈4种节流方式下的静压轴承承载能力和油膜刚性的数学模型,对4种节流方式下的静压轴承油膜承载性能进行计算与分析.计算结果表明:采用固定节流器的静压轴承油膜刚性较差、承载能力低,采用可变节流器的静压轴承承载能力较高,理论上可达到无穷大的油膜刚度.     

新型静压支承结构液压缸力学性能分析与实验

传统液压缸多采用导向环和密封圈组合密封的方式,普遍存在内耗高、响应速度慢、抗偏载力差等问题。在静压支承理论的基础上,提出一种新型椭圆形静压支承结构液压缸及其设计方法。采用理论计算和模拟仿真相结合的方式,对比分析了传统型、矩形静压腔和椭圆形静压腔液压缸的抗偏载力、摩擦力的大小及其主要影响因素。仿真结果表明：静压支承式液压缸的抗偏载能力和摩擦力性能均明显优于传统结构液压缸,且椭圆形静压腔结构具有明显优势。最后,设计实验测试平台,通过实验验证了上述计算模型和仿真模拟的正确性。     

动静压轴承定义的初议

流体润滑状态可以分为动力润滑与静力润滑两种方式,与此相应分为动压轴承与静压轴承。动力润滑利用轴颈(或轴承)的旋转自己产生能支承外载荷的油膜压力。静压轴承利用外部的泵油装置给流体加压形成油膜压力,因此它与速度无关,但增加一套泵油装置。最近,为了充分发挥两种润滑方式的特点,把动力与静力的润滑方式结合于一体,出现了动静压轴承。严格地说,任何静压轴承只要轴颈(或轴承)是旋转的,必定会有动压效应,因此,轴     

一种轧辊静压轴承的瞬态响应分析方法

静压轴承是轧机轧辊中承受径向载荷最直接的部件。对轧辊静压轴承进行瞬态响应分析是轧机设计的关键环节,其动力学特性直接影响到轧机的生产效率及轧制精度。本文在建立静压轴承的Reynolds方程及其边界条件的基础上,分析静压轴承的流量连续状态,并联合能量方程和温-粘关系方程对Reynolds方程进行迭代求解。在考虑油膜力的非线性条件下,运用动态油膜力代替线性刚度、阻尼系数,建立静压轴承的动力学方程,并采用Newmark-β法迭代求解该方程,得到了静压轴承的瞬态响应,为静压轴承动力学分析提供一种新思路。以某型号四腔静压轴承为例进行了瞬态响应计算,结果验证了本方法在进行静压轴承瞬态响应分析的有效性。     

基于CFD的静压转台油膜特性分析与油腔设计

针对静压转台回转运动精度不足的问题,以数控磨床的扇形液体静压转台为对象,对单个静压支承结构的位移率和设计间隙进行理论计算,得到油膜承载力与位移率和设计间隙之间的关系。对油腔内部流场进行仿真计算,得到不同油腔结构对油腔流场中承载性能产生的影响规律;根据仿真结果和转台的参数要求选取合适的油腔结构,设计了扇形静压转台;通过流固耦合分析,验证油腔设计的合理性;通过油膜刚度试验,验证了油腔设计的可行性。     

静压支承摩擦副的一种最优化设计法

引言在静压支承设计中,我们可以采用恒定油膜厚度设计理论和设计方法,首先选取一个理想的油膜厚度h,然后依据该设计理论的油膜刚度最大值条件,确定出一个保证实现上述要求的液阻比,当液阻比确定后,如何合理地设计静压支承面的几何尺寸呢?这是一个非常重     

对阻尼槽型滑靴新设计理论的探讨

一、引言在轴向柱塞泵中,滑靴的设计已开始采用静压支承理论。滑靴静压支承设计理论,从阻尼观点建立的流动模型来看,阻尼管型滑靴,是液流经过固定阻尼和可变阻尼串联的油膜流动来实现静压支承的,如图1所示。对于阻尼槽型滑靴是液流经过固定阻尼与可变阻尼相并联的并联阻尼后再与一可变阻尼串联的油膜流动来实现静压支承的,如图2所示。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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