LVDT位置反馈现场调试专用工具

本文涉及电厂汽轮机高、中压主汽门,高、中压调门开度的反馈装置——LVDT,解决了调试过程中人力、工时、环境、干扰等多项问题。机组运行过程中,由DCS向现场调门发送开度信号来自动调节流量、压力等参量,而获取现场阀门开度的唯一手段就是现场的位置反馈装置传送回控制室CRT的电流信号,如果反馈的信号和送出的信号偏差超过一定数值,就会造成系统的不稳定现象,可能造成整个机组切换手动,造成不必要的损失。而由于机组车头处温度较高,电子器件损坏概率直线上升,备件更换的频率也随之上升,所以位置反馈的校验装置就显得更加重要了。位置反馈不准确则意味着无法真实反映阀门的开度,而阀门的开度直接控制了进油/进气量,对机组的负荷量和设备的正常运转均会带来影响。电厂汽轮机高、中压主汽门,高、中压调门是对汽轮机负荷进行调节的关键运行设备,而LVDT位置反馈是电厂运行人员对这些门开度进行连续监测的唯一途径,它的准确性直接影响电厂机组的负荷情况。以往的调试方法费时、费力,且存在安全隐患。现按现场LVDT装置接头的规格,自制一工具,将电流表串入现场回路中,使调试人员能在现场单独观测电流变化,实现现场调试、现场观测,减少环境干扰、提高检修效率。     

假肢接受腔硅胶材料的力学性能研究

采用HY0580的压缩试验机,在反复压缩模式下模拟假肢接收腔/硅胶材料界面,研究了4种不同表面结构的硅胶内衬套材料的力学压缩性能。结果表明:4种不同表面结构的硅胶内衬套材料在载荷分别为0.5 N、3 N、7 N、10 N的试验工况下进行压缩试验时,都是在相同载荷(4.5 N)时出现平台期;在同等载荷的情况下,因1和4号硅胶材料正反两面均为光面,表面微凸体不高,粗糙度较小,2和3号材料与皮肤接触的反面上微凸体较高,粗糙度较大,故1号和4号材料的变形比2号和3号小,说明材料表面的各种纹路对缓解皮肤的压力有一定作用,硅胶材料反面上的粗大微凸体,增加了与皮肤的粘结性,有利于降低皮肤摩擦损伤的风险,提高残肢患者穿戴舒适性。     

基于UG打印机支架多工位级进模设计

级进模向导（PDW）是UG软件的一个重要功能模块,PDW提供了毛坯布局、废料设计、工序排样、标准件设计、模架设计、冲裁设计、镶块组设计、让位槽设计等功能。打印机支架按工序设置了冲导正孔、冲安装孔、成形凹坑、冲废料、折弯、Z折弯、冲载体废料7个工位,完成全部工位后,便可得到一个完整的冲压成品制件。PDW能自动执行级进模的设计和细化工作,使用PDW可以极大地提高级进模设计效率。     

Mice embryology: A microscopic overview

In this work, we studied the embryology of mice of 12, 14, and 18 days of gestation by gross observation, light microscopy, and scanning electron microscopy. Grossly, the embryos of 12 days were observed in C‐shaped region of the brain, eye pigmentation of the retina, first, second, and third pharyngeal arches gill pit nasal region on the fourth ventricle brain, cervical curvature, heart, liver, limb bud thoracic, spinal cord, tail, umbilical cord, and place of the mesonephric ridge. Microscopically, the liver, cardiovascular system and spinal cord were observed. In the embryo of 14 days, we observed structures that make up the liver and heart. At 18 days of gestation fetuses, it was noted the presence of eyes, mouth, and nose in the cephalic region, chest and pelvic region with the presence of well‐developed limbs, umbilical cord, and placenta. Scanning electron microscopy in 18 days of gestation fetuses evidenced head, eyes closed eyelids, nose, vibrissae, forelimb, heart, lung, kidney, liver, small bowel, diaphragm, and part of the spine. The results obtained in this work describe the internal and external morphology of mice, provided by an integration of techniques and review of the morphological knowledge of the embryonic development of this species, as this animal is of great importance to scientific studies. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

过渡金属作用下的金刚石石墨化机理研究*

从电子和原子角度解释了过渡金属对金刚石石墨化催化作用的机理,即过渡金属具有空d轨道,并且在某一面上与金刚石(111)面原子符合对准原则。为了验证此结论,基于第一性原理建立铬、铁、钴、钛、铂、铝、铜原子与金刚石原子的作用模型,进行仿真计算,得到不同过渡金属对金刚石石墨化的影响规律。仿真结果表明：Cr、Fe、Co、Ti、Pt作用下的金刚石结构出现不同程度的石墨化现象,而Al、Cu作用下的金刚石无石墨化现象。不同金属作用下金刚石原子结构的平面度由小到大依次为铁、铬、钴、钛、铂、铝、铜;碳原子间方差由小到大依次为铁、铬、钴、铂、钛、铝、铜;系统能量变化由大到小的顺序依次为铁、铬、钴、铂、钛。通过比较,铁、铬、钴原子对金刚石石墨化具有明显的催化作用,铂、钛原子有一定的催化作用,而铝、铜原子则无催化作用。当金属具有空d轨道且与金刚石在一定面上符合对准原则,未配对电子越多,金属对金刚石石墨化的催化作用越强;反之,当金属价电子层无d轨道或d轨道电子是充满状态时,金属对金刚石石墨化无催化作用。该研究为利用金刚石石墨化机理刃磨金刚石刀具提供了理论基础。     

Gait definition and successive gait-transition method based on energy consumption for a quadruped

In nature,to realize the smooth motion for different speeds,the continuous gait transition is usually required for the quadrupeds.Thus,the gait simulation of quadrupeds is a requisite step to obtain the stable and energy-efficient gait for the walking machines.In this paper,the definitions of the two gait parameters,phasic difference and duty factor are presented,which can determine the gait of the quadrupeds.Then,several typical gaits of the quadrupeds are analyzed such that the seven standard gaits and corresponding parameters are summarized.Additionally,the variance law of the two parameters,which determine the relationship of gait transition,is analyzed.Furthermore,the quadruped gait derivative spectrum (QGDS) is proposed and the gait definition of the quadrupeds is presented.To minimize the power consumption,the choice criterion of gait,the optimal gait in terms of the motion speed,duty factory,and power consumption for the walking machines,is developed.Last,the continuous variance of the gait is implemented by the simulation of the gait transition from walk to trot,which evaluate the choice criterion and transition of gait.     

NOVEL METHOD OF REALIZING THE OPTIMAL TRANMISSION OF THE CRANK—AND—RPCKER MECHANISM DESIGN

A novel method of realizing the optimal transmission of the crank-and-rocker mechanism is presented,The optimal combination design is made by finding the related optimal transmission parameters ,The diagram of the optimal transmission is drawn ,In the diagram,the relation among minimum transmission angle,the coeffcient oftravel speed variation,the oscillating angle of the rocker and the length of the bars is shown,concisely,conveniently and directly,The method possesses the main characteristic,That is is to achieve the optimal transmission parameters under the transmission angle by directly choosing in the diagram,according to the given requirements ,The characteristics of the mechanical transmission can be improved to gain the optimal transmission effect by the method,Especially,the method is simple and convenient in practical use.     

重载汽车变速器试验用传动箱的传动系统设计

主要介绍了如何在设计阶段延长传动箱齿轮使用年限,通过对传动箱的设计、制造、使用、维护进行全面调研,同时对试验传动箱不同规格的汽车变速器时的试验传动箱齿轮负荷进行了测定,进而对设计方案参数、润滑、齿轮、轴进行了理论分析和计算,按照系统工程学,作了设计、制造、润滑、使用等全系铳的分析。通过分析认为,这是一个系统设计的成功范例。     

Dynamic characteristics of a planetary gear system based on contact status of the tooth surface

Studies on the planetary gear have attracted considerable attention because of its advantages, such as compactness, large torque-to-weight ratio, vibrations, and high efficiency, which have resulted in its wide applications in industry, wind turbine, national defense, and aerospace fields. We have established a novel dynamic model of the planetary gear transmission by using Newton’s theory, in which some key factors such as time-variant meshing stiffness, phase relationships, and tooth contact characteristics are considered. The influences of gear axial tipping, operating conditions, and the meshing phase on the contact characteristics and the dynamic characteristics were researched systematically. It was found that the contact area of the tooth surface was moved due to the axial gear tipping, which obviously affected the meshing stiffness. With the increase in the inclination angle of the sun gear, the meshing stiffness decreases, which produces an evident influence on the high natural frequency in the planetary transmission system. In terms of the dynamic characteristics of the system, the component of rotating frequency appeared in the dynamic meshing force of the sun gear and the planetary gear. Moreover, the floating track of the center wheel varied significantly and exhibited an oval distribution as the inclination angle of the sun gear changed. When the inclination angle of the sun gear increased, the rotating frequency component increased significantly, but the other meshing frequency components remained unchanged; meanwhile, the deformation of the floating track also increased. If the inclination angle of the sun gear changes, the vibration state of the system and the collision impact could become more serious, and the lifetime of the planetary transmission system will reduce. Furthermore, when the load was increased, we found that the gear-tooth contact zone transformed from line contact to surface contact, the meshing stiffness increased, the effect of high natural frequency on the planetary transmission system became more evident, but its low-order natural frequency remained stable. With regard to the dynamic characteristics of the system, the components of the major frequency at the external gearing remained unchanged, but the rotation frequency of the sun gear and the meshing frequency amplitude increased linearly with the increase in load. In conclusion, the variation in the meshing stiffness of the planetary gear system had minor impact on the low-order natural frequency, but had a significant impact on the high natural frequency of the planetary transmission system due to the phase variation of the gear.     

Axial stress waves in an elastic–perfectly-plastic bar

A bar, made from an elastic–perfectly plastic material, fixed at one end, suddenly has an axial load applied at the other end. After its sudden application, the load is held constant. If the load is less than half the yield load for the bar, and in the absence of damping, the load causes a stress wave to pass up and down the bar, all behaviour being elastic. At any point within the bar length, the stress varies, in a stepwise fashion, between zero, and twice the stress corresponding to the applied load. This is the classical elastic solution. However, if the load is greater than half the yield load, when the stress wave first hits the fixed end, yielding will occur, and a simple model is proposed in this paper to allow for yielding. The model incorporates two zones separated by the stress wave, as in the elastic solution, together with a third zone, concentrated, and adjacent to the fixed support, in which all plastic straining takes place. The paper describes and verifies the model, and presents the predictions that it gives for various levels of load.     

Study on the applicability of four flumes in small rectangular channels

Different experiments and numerical simulation research were carried out in order to explore the hydraulic characteristics and applicability of the cutthroat flume, NACA airfoil-shaped flume, airfoil pillar-shaped flume, and optimized airfoil-shaped flume in rectangular channels. The four flumes with contraction ratios of 0.4, 0.5, and 0.6 in rectangular channels were tested under 144 free-flow conditions. Based on the Fluent software, standard k-ε three-dimensional turbulence model and volume of fluid (VOF) method were utilized for numerical simulation in each working condition. The principle of critical flow was used to analyze the correlation between the discharge, the contraction ratio, and the upstream water depth. This correlation was used to obtain the discharge calculation formulas of the cutthroat flume, NACA airfoil-shaped flume, airfoil pillar-shaped flume, and optimized airfoil-shaped flume in rectangular channels. The Froude number in front of the flume, the backwater height, the critical submergence degree, the velocity distribution, the head loss, the discharge measurement formula, and the accuracy were studied and compared. It can be concluded from the results that the cutthroat flume, NACA airfoil-shaped flume, airfoil pillar-shaped flume, and optimized airfoil-shaped flume all have good applicability in rectangular channels. Moreover, the hydraulic characteristics of all the four flumes meet the water measurement specifications in the irrigation area. The upstream Froude number of the NACA airfoil-shaped flume is the smallest, whereas the backwater height and head loss of the cutthroat flume and optimized airfoil-shaped flume are the smallest. It is also worth noting that the critical submergence degree of the optimized airfoil-shaped flume is the highest, with an average value of 0.85. The discharge measurement formulas of the four flumes have been deduced using the correlation between the discharge, the contraction ratio, and the upstream water depth. It was found that the average errors between the calculated discharge and the measured discharge of the four flumes are 3.17%, 2.17%, 1.53%, and 2.29%, respectively, which are less than 5%, and therefore meet the discharge measurement requirements. In the agricultural irrigation system and flow monitoring system, the hydraulic characteristics of the four flumes can provide a reference and basis for the selection of flumes in the rectangular channel.     

智能排爆机器人机械手部设计及其优化

利用排爆机器人技术结合现代设计方法,并根据结构特点,以质量最轻最优为目标,以几何尺寸、蜗轮齿面疲劳强度、蜗杆特性系数、模数、齿数、等为约束条件,对排爆机器人的机械手部进行了结构优化,使得机械手部结构好、质量轻、运动灵活.     

一种小型灌装机的设计

设计了一种小型回转式塑杯灌装机,主要进行了总体传动控制方案的设计、机械部分设计和控制部分设计.其中控制部分设计包括PLC控制落杯、灌装、封口、退杯等的协调工作及电机间歇运动;步进电动机的起动电路;气动系统实现落杯、退杯等.     

穿梭车用伸缩货叉的设计研究

基于穿梭车的货到人拣选系统中,伸缩货叉是穿梭车上物料搬运的执行机构,它的合理设计是保证穿梭车轻巧、快速、精准的关键。文中进行伸缩货叉的研发设计,通过总体规划设计,确定伸缩货叉的性能参数;通过分析常用结构形式的弊端,合理设计伸缩货叉各部件结构,使伸缩货叉具有较大行程、足够强度的同时,结构先进合理,简单紧凑,外形尺寸小,方便选材,成本低,传动平稳,定位精确,易于操作,更加具有市场竞争力。     

广州地铁车辆内装设计

对广州地铁4、5号线车辆的内装饰设计,即客车顶板、侧、端墙板、地板,客室和司机室座椅、客室扶手立柱吊环、车窗,司机室前窗、后端门、司机室和客室侧门等,进行了简要地介绍。针对该城市的自身特点,从结构的设计和色调的搭配,设计出了符合该城市自身特点的轨道车辆。     

浅谈平/槽轮铸件的试制

船舶舱盖用轮子是舱盖开起的关键部件,根据船舶服役的区域不同,轮子必须符合强度、低温冲击、延伸、表面硬度等要求。对于QT700-2的厚大型、高牌号球铁产品,在国内使用的场合并不多见。随着造船行业向亚洲特别是中国的转移,我们必须解决相关零部件的国产化问题。为此,笔者通过与铸造行业的专家一起努力、选择具有相当制造技术水平的专业工厂,共同研究、探讨、试制了平/槽轮球铁产品,并获得成功。平/槽轮铸件的试制成功,既解决了企业产品的交货难问题、并产生了较好的经济效益,也为国内厚大型、高牌号球铁产品的铸造提供了宝贵的经验。     

基于制造网格的产品资源协同平台研究和应用

针对钢铁汽车产业链具有的动态性、分布性、异构性和自治性的特点,提出了覆盖生产制造、贸易服务、加工配送和下游客户等企业单元的虚拟钢铁汽车产业链网络结构,构建了基于制造网格的产品资源协同平台系统框架,分为规则层、共性层、工具层、应用层、服务层;最后,通过在某钢铁集团、加工中心、第三方物流提供商和下游汽车客户之间的成功应用验证了系统的实用性和有效性。     

单级齿轮系统拍击特性研究

用数值仿真法和映射法研究了齿轮系统的拍击振动特性。通过研究每一次碰撞之间的映射关系、每一拍击周期之间的映射关系,得出的结论是:激励幅值的大小是影响系统拍击性能的一个重要因素;当激励幅值增大时,齿轮碰撞速度也增大,在一定条件下,将发生齿背碰撞;当激励幅值变化时,齿轮系统的初始脱齿状态也将发生变化,由此导致系统产生1周期、2周期、多周期甚至准周期拍击振动;转速波动的二次谐波分量对系统拍击性能的影响与基频分量的影响基本相同,因此,忽略二次谐波将导致较大的误差。用周期性拍击过程之间的映射关系研究齿轮系统的拍击特性,会带来很大的方便。     

表面粗糙度对不对中滑动轴承润滑特性的影响

以活塞式航空发动机滑动轴承为研究对象,综合考虑轴颈倾斜和轴瓦表面形貌等因素对轴承润滑特性的影响,建立滑动轴承润滑分析模型;以高斯随机表面、分形曲面、非高斯随机表面分别模拟轴瓦表面的粗糙程度,分析轴颈不对中和表面粗糙度耦合作用下油膜压力、端泄流量、承载力和轴承力矩等参数随偏心率和转速的变化规律。研究结果表明:考虑轴瓦表面形貌后轴承最大油膜压力变大,最小油膜厚度有小幅度减小;随着偏心率和转速增加,最大油膜压力、端泄流量、轴承承载力、工作力矩均增加;随着偏心率增加,考虑表面形貌时(高斯表面、分形表面、非高斯表面)的轴承油膜压力、承载力、工作力矩均变大;随着转速的增加,考虑表面形貌时的轴承润滑特性均变大,尤其是高斯表面,润滑特性变化较明显。     

联轴节的质量对平衡精度的影响

由于联轴节与被平衡工件连接时,联轴节会产生附加质量,该附加质量对工件的平衡精度有很大影响。分析了联轴节的质量、附加质量、主转动惯量之间的关系,及联轴节附加质量对平衡精度的影响。通过分析得知联轴节的附加质量与联轴节的形式、重量、尺寸有关,附加质量和强度两者是互相制约的。因此,联轴节必须具有与所传递转矩相适应的强度。在保证联轴节扭转刚度的前提下,使其具有最小的外形尺寸、重量和主转动惯量,才能降低联轴节质量对平衡精度的影响,确保其在生产中具有稳定的工作性能和使用寿命。