液压滑动工作台低速爬行的预防和消除

针对液压滑动工作台在低速运行时经常出现的爬行现象，从滑动工作台的设计、制造、使用、维护等方面进行了全面的分析，提出了相应的预防和消除爬行现象的措施。     

液压爬行现象探析及对策

液压爬行是影响液压缸低速运动性能的主要因素，从相对移动的金属表面的摩擦力特征入手，通过对液压滑台的试验研究，提出减小液压缸动、静摩擦力的差别以及提高传动系统的刚性是消除液压爬行的主要途径。     

半液压卸荷复合导轨技术在大型数控滚齿机中的应用

针对大型数控滚齿机床在使用中出现的低速爬行问题,提出了半液压卸荷复合导轨技术,阐述了立柱液压卸荷结构的工作原理,分析了数控滚齿机立柱(X轴)水平移动定位影响因素。结果表明:该机构可减小机床立柱移动时动静摩擦因数的差异,为解决大型机床的低速爬行问题提供了一种有效途径。     

大惯量矢量变频液压复合调速系统仿真研究

针对大惯量、时变负载变频液压调速的低速控制与调速精度问题,将节流调速和矢量变频液压调速有机结合.建立大惯量矢量变频液压复合调速系统;创建系统数学模型,在研究系统的主要影响因素基础上简化数学模型;利用MATLAB SIMULINK构建仿真模型并分析系统动态性能.仿真结果表明:矢量变频液压调速速度跟踪精度高,并对转动惯量和负载扰动表现较强的鲁棒性;节流调速增加了液压变频调速的低速稳定性;该复合调速系统获得了理想的调速效果.     

直驱式船舶舵机系统的低速特性建模与仿真

船舶舵机系统是重要的船舶操纵设备,它的性能直接影响船舶的稳定性和安全性。采用直驱式容积控制(DDVC)技术,克服传统液压舵机系统效率低、噪声大的缺点,设计了高性能舵机液压系统。针对在低速情况下,直驱式舵机系统所受的摩擦干扰、容积和机械损失、转矩干扰,建立了直驱式船舶舵机系统模型,并且基于AMESim/Simulink的联合仿真对该系统在理想状态和低速状态下的特性进行分析。结果表明:系统中的摩擦、转矩干扰等非线性因素导致直驱式舵机低速运动时出现了爬行和死区现象,严重影响了系统运动的平稳性,需要通过相应的摩擦补偿控制来消除或减小其对低速性能的影响。     

曲轴连杆低速大扭矩液压马达低速特性的仿真研究

本文建立了曲轴连杆低速大扭矩液压马达进口节流系统的数学模型。推导了低速域马达输出轴角速度随时间变化的理论解析式,采用计算机仿真手段,研究了马达自身因素及系统因素对低速稳定性的影响,通过动态仿真验证了理论分析的正确性。     

进油节流调速液压回路爬行现象的建模与仿真分析

本文通过对低速传动系统产生爬行现象原因的分析，建立了表征进油节流调速回路动态特性的非线性数学模型，进行了计算机仿真分析。     

大型推弯式弯管机超低恒速液压控制系统研究

为了获得高质量的大直径薄壁弯头,通过中频感应加热液压推弯式弯管机对管材实现弯制,而超低恒速控制是大型推弯式弯管机保障弯头质量的关键技术问题之一。从实际工况出发,在分析油缸爬行问题的基础上,通过数字液压技术的阀控实现系统的超低恒速,避免弯制过程的低速爬行现象。结果表明:系统保证了油缸的低速稳定性,避免了弯制过程出现颤动及弯弧起皱现象,并易于为工程实际所用。     

液压滑台低速不稳定性机理与控制的研究

根据低速不稳定性的振动机理,推导出“液压弹簧”对液压滑台运行中速度稳定性的影响。通过建立力学模型和系统的运动微分方程,分析了主要影响因素,并提出相应措施,从而控制了加速度的波幅大小,使滑台达到低速稳定的目的。     

液压振动台建模与加速度波形失真度分析

针对液压振动台波形失真度大的现象,建立了液压振动台非线性数学模型,开展仿真分析,揭示液压振动台加速度波形失真度的主要原因.采用状态反馈的方法,选取系统共振频率附近作为工作点,线性化系统模型,以改善系统特性,仿真结果表明,该方法可以有效降低液压振动台波形失真度.     

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.     

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.     

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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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.