阻尼溢流阀的建模与动态响应 液压专业毕业设计外文翻译
液压动力系统中英文对照外文翻译文献
中英文对照外文翻译文献(文档含英文原文和中文翻译)原文：FEATURE-BASED COMPONENT MODELS FOR VIRTUALPROTOTYPING OF HYDRAULIC SYSTERMAbstract:This paper proposes a feature-based approach for the virtual prototyping of hydraulic systems. It presents a framework which allows the designer to develop a virtual hydraulic system prototype in a more intuitive manner, i.e. through assembly of virtual components with engineering data. The approach is based on identifying the data required for the development of the virtual prototypes, and separating the information into behaviour, structural, and product attributes. Suitable representations of these attributes are presented, and the framework for the feature-based virtual prototyping approach is established,based on the hierarchical structure of components in a hydraulic system. The proposed framework not only provides a precise model of the hydraulic prototype but also offers the possibility of designing variation classes of prototypes whose members are derived by changing certain virtual components with different features.Key words: Computer-aided engineering; Fluid power systems;Virtualprototyping1.IntroductionHydraulic system design can be viewed as a function-to-form transformation process that maps an explicit set of requirements into a physical realisable fluid power system. The process involves three main stages: the functional specification stage,the configuration design stage, and the prototyping stage.The format for the description of the design in each stage is different.The functional specification stage constitutes the initial design work. The objective is to map the design requirements. To achieve this, the design problems are specified Correspondence and offprint requests to: Dr S. C. Fok, Schoool of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798. The designer must identify the performance attributes, which can include pressure, force, speed, and flowrate, with the required properties such as size, cost, safety and operating sequence. performance requirements for each attribute. In this stage, the design is abstracted in terms of the performance attributes with associated values.The objective of the configuration design stage is to synthesise a hydraulic circuit that performs the required functions conforming to the performance standards within defined constraints. A typical hydraulic system is made up of many subsystems. The smallest building block in a subsystem is the standard hydraulic component (such as valves, cylinders,pumps, etc.). Each type of standard component serves a specific elemental function. The design effort in the configuration design stage is fundamentally a search for a set of optimal arrangements of standard components (i.e. hydraulic circuit) to fulfil the functional requirements of the system. Based on this framework, the designers would normally decompose the overall system functions in terms of subfunctions. This will partition the search space and confine the search for smaller hydraulic subcircuits to perform the subfunctions.Computers are often used to support the configuration design process. For example, Kota and Lee devised a graph-based strategy to automate the configuration of hydraulic circuits. After the development of the hydraulic circuits, digital simulation tools are often used to study and evaluate these configurations. With these tools, designers can compare the behaviour of different circuits and also analyse the effects when subcircuits are combined. In the configuration design stage, the design is traditionally represented as a circuit drawing using standard icons to symbolise the type of standard component. This is a form of directed graph S(C,E) where the circuit S contains components C in the form of nodes with relations between components denoted by edges E.The prototyping stage is the verification phase of the system design process where the proposed hydraulic circuit from the configuration design stage isdeveloped and evaluated. Physical prototyping aims to build a physical prototype of the hydraulic system 666 S. C. Fok et al. using industrial available components. The process of physical prototyping involves the following: Search for appropriate standard components from different manufacturers. Pre-evaluation and selection of components based on individual component cost, size, and specification, and compatibility factors between components. Procurement and assembly of the selected components.Test and evaluate the physical prototype based on the overall system requirements. Use other components or redesign the circuit (or subcircuits)if necessary.Besides dynamics, the development of the physical prototype must take into consideration other factors including structure,cost, and weight. The dynamics data are used to confirm the fluid power system behaviour whereas the geometric information is used to examine the assembly properties. The development of the physical prototype will provide the actual performance,structure, and cost of the design.The main disadvantage of physical prototyping is that it is very tedious and time consuming to look for a set of suitable combinations of standard components from among so many manufacturers. Although the basic functions of the same types of standard component from different manufacturers do not differ, their dynamics, structural and cost characteristics may not be similar, because of design variation. Hence, for a given hydraulic circuit, different combinations of parts from differentmanufacturers can have implications on the resulting system,in terms of dynamics, structure, and cost. Value engineering can be used at this stage to improve the system design by improving the attributes at the component level. This includes maximizing the performance-to-cost ratio and minimising the size-to-performance ratio. Virtual prototyping can be viewed as a computer-aided design process, which employs modelling and simulating tools to address the broad issues of physical layout, operationalconcept, functional specifications, and dynamics analysis under various operating environments. The main advantage of virtual prototyping is that a hydraulic system prototype can be assembled, analysed, and modified using digital computers without the need for physical components, thus saving lead time and cost.The main requirement of a virtual hydraulic system prototype is to provide the same information as a physical prototype for the designer to make decisions.To achieve this, the virtual prototype must provide suitable and comprehensive representations of different data. Furthermore, transformation from one representation to another should proceed formally. Xiang et al. have reviewed the past and current computer-aided design and prototyping tools for fluid power systems. The work revealed that the current tools could not provide a completerepresentation of the design abstractions at the prototyping stage for design judgement. Most of the tools concentrate on the dynamics behaviour. Vital geometrical and product information that relates to the system prototype consideration and evaluation is frequently missing.To advance the development of computer-aided virtual prototyping tools for fluid power systems, there is a need to address the formal representations of different abstractions of behaviour,structural, and product data along with their integration. This paper focuses on these issues and proposes the formalism of a unified component model and the taxonomy based on the feature-based approach. In Section 2, we discuss the feature- based approach focusing on the key information and their representations required for hydraulic system prototyping. Section 3 presents a formalism of the feature-based model and structure for the development of virtual hydraulic system prototypes.The structure is illustrated with an example. Future work and conclusions are given in Section 4.2. Feature-Based ApproachFeatures can be defined as information sets that refer to aspects of attributes that can be used in reasoning about the design, engineering or manufacturing processes. The concept of using features to integrate CAD/CAPP/CAM is not new and there are many papers on the application of this approach in CIM. In all these applications, the feature model is regarded as the basis whereas design by features is the key for the integration. To develop a feature model, the relevant information concerning the design must be identified and grouped into sets based on the nature of the information. The relevant information should contain sufficient knowledge for activities such as design, analysis, test, documentation, inspection, and assembly, as well as support various administrative and logistic functions. Design by features is the process of building a model of the design using features as primitive entities. The feature model provides the standardisation of relevant data. Through the design by features approach, vital knowledge of the design will be generated and stored. Together, the feature model and the design by features approach will provide the essential information, which can be used, not only for the simultaneous consideration of many different concerns with the design, but also to interface the many activities in the design realisation process, including the life cycle support operations. The main drawback of the feature-based design approach is that the feature model should be properly defined . This can be difficult, as features are sets of knowledge that are application dependent. The organisation of the features can also be application specific. Non-trivial data-management problems could arise if the feature model is not properly defined. To avoid these problems, the type,representation and structure of the features should be resolved prior to using the feature-based design methodology. The main concern when developing afeature model is that it is application-specific. In the domain of virtual prototyping of hydraulic systems, the details of the constituent standard components must be able to be used to describe the overall system. The component features are bearers of knowledge about that part. To create a suitable feature model for hydraulic system design based on the assembly of standard components, the relevant information associated with various standard components must be identified and classified. This definition Feature-Based Component Models 667 of the component feature set can then be extended to encompass the subsystem feature set based on the hierarchical structure between the components in the subsystem. In the same manner, a hierarchical structure for the hydraulic system feature representation would evolve by considering the system as a hierarchy of subsystems.The necessary information required for a proper description of the virtual prototype must be no less than that derived by the designer from a physical prototype for decision making. These data should generally include the shape, weight, performance properties, cost, dimensions, functionality data, etc. Comparison with the physical prototyping process, the information required for each standard component could be separated into three distinct groups: behaviour attributes, structural attributes, and product attributes.2.1 Behaviour AttributesThe behaviour of a hydraulic component can be defined in terms of the dynamics characteristics used to satisfy the functional requirements. Consider a hydraulic cylinder connected to a load. Its function is to transmit a force from the stroke of the piston to the load. The maximum force it can transmit can be used to define the functionality and the behaviour requirements can be specified in terms of the desired load acceleration characteristics. Hence for a hydraulic component, behaviour attributes express functionality and can be reflected in the dynamics characteristics. The designer is responsible for the proper definition of the overall system behaviour characteristics in terms of the desired dynamics. A standard component will have its own behaviour and provide a specific plex functions that cannot be achieved by a single standard component are derived using a combination of components. Hence, the behaviour of the standard component will play an important role as the individual behaviours of components together with their arrangement can alter the overall system function .The behaviour of a standard component can be nonlinear and can be dependent on the operating conditions. When two components are combined, it is possible that their behaviours can interact and produce undesired or unintended characteristics. These unwanted behaviours are assumed to have been resolved during the configuration design stage. The hydraulic circuit used in theprototyping stage is assumed to be realisable and without any undesirable interacting behaviours. This means that the output behaviour of a component will provide the input to the subsequent component.The representation of behaviours for hydraulic systems has been widely investigated. These representations include transfer functions, state-space and bond graphs. Transfer functions (for single-input–single-output systems) and state-space equations (for multiple-input–multiple-output systems) are based on the approximation of the dynamics about a nominal operating condition. The power bond graph model is based on the causal effects that describe the energy transformations in the hydraulic system. This approach is appealing for hydraulic system analysis. The main disadvantage is that the derivation of the dynamics equation in a bond graph of a complicated fluid power system can become very tedious. As a result, recent work has concentrated on the used of artificial intelligence to represent the nonlinear mapping between the input and output data, which can be obtained via experimental work. These nonlinear mappings can be accomplished using artificial neural networks .It is quite natural for a hydraulic system designer to use input–output data to describe the behaviour of a hydraulic component. The configuration design of a hydraulic system is often achieved through steps of function decomposition. To design a hydraulic system, the designer often tries to decompose the functions and their requirements down to the component level.译文：基于原型液压系统特征的机构模型摘要：本文为原型液压系统的设计提出了一种基于特征的方法。
液压专业毕业设计科技文献外文翻译--阻尼式溢流阀的建模与动态响应(英语)
Abstract. This paper outlines several possible methods of modelling a passive hydraulic damper with a bypass tube that is opened by a precompressed relief valve. Initially a simple algebraic model is derived which is developed into a more computationally complex model incorporating the dynamics of the internal spring valve and fluid compressibility. Numerical simulations indicate realistic dynamical phenomena and suggest key design parameters. Key words: compressibility, hydraulic damper, nonlinear, relief valve
Figure 4. The required normalised force output against normalised time and velocity for one cycle.
[8–11], to our knowledge the effects of the passive blow-off valve have not been treated in the literature (although relief valves treated on their own have been shown to lead to nonlinear [12, 13] and chaotic dynamics [14].) The resulting model can be used to predict the effect of changing the properties of the damper on the dynamic response. The key features investigated are the sizes of the orifice and bypass tube along with the stiffness and discharge characteristics of the spring and valve respectively. In this paper a simple lumped mass parametric model is derived that incorporates all these effects. The rest of this paper is outlined as follows. Section 2 describes the modelling process used by previous researchers to model Figure 1 as a simplification of an automobile shock absorber. Sections 3 and 4 investigate several possible extensions to the model in Section 2 to take into account the blow-off. First an explicit model is derived to give the force for a given displacement input. The relief valve and compressibility of the fluid are then considered separately. A model for the whole system is then derived. Section 5 gives some results using the different models. There is also a discussion in Section
液压专业必备英文对照教案资料
液压专业词汇hydraulic power 流体传动额定流量rated flowhydraulics 液压技术供给流量supply flowhydrodynamics 液力技术流量系数flower factorhydropneumatics 气液技术滞环hysteresisoperating conditions 运行工况图形符号graphical symbolrated conditions 额定工况液压气动元件图形符号symbols for hydraulic and limited conditions 极限工况pneumatic componentsinstantaneous conditions 瞬态工况流体逻辑元件图形符号symbols for fluid logic steady-state conditions 稳态工况devicesacceptable conditions 许用工况逻辑功能图形符号symbols for logic functions continuous working conditions 连续工况回路图circuit diagramactual conditions 实际工况压力－时间图pressure time diagramefficiency效率功能图function diagramdirection of rotation 旋转方向循环circlenominal pressure 公称压力自动循环automatic cycleworking pressure 工作压力工作循环working cycleinlet pressure 进口压力循环速度cycling speedoutlet pressure出口压力工步phasedifferential pressure pressure drop；压降停止工步dwell phaseback pressure 背压工作工步working phasebreakout pressure 启动压力快进工步rapid advance phasecharge pressure 充油压力快退工步rapid return phasecracking pressure 开启压力频率响应frequency responsepeak pressure 峰值压力重复性repeat abilityoperating pressure 运行压力复现性reproducibilityproof pressure 耐压试验压力漂移driftsurge pressure 冲击压力波动ripplestatic pressure 静压力线性度linearitysystem pressure 系统压力线性区linear regionpilot pressure 控制压力液压锁紧hydraulic lockpre-charge pressure 充气压力液压卡紧stickingsuction pressure 吸入压力变量泵variable displacement pumpoverride pressure 调压偏差泵的控制control of pumprated pressure 额定压力齿轮泵gear pumpair consumption 耗气量叶片泵vane pumpleakage泄漏柱塞泵piston pumpinternal leakage 内泄漏轴向柱塞泵axial piston pumpexternal leakage 外泄漏法兰安装flange mountinglaminar flow 层流底座安装foot mountingturbulent flow 紊流液压马达hydraulic motorcavitation 气穴刚度stiffnessflow rate 流量中位neutral positiondisplacement排量zero position零位集流阀free position flow-combining valve 自由位截止阀cylinder shut-off valve 缸球阀有杆端rod end global(ball) valve针阀needle valve 无杆端rear end闸阀gate valve extend stroke 外伸行程膜片阀retract stroke diaphragm valve 内缩行程蝶阀cushioning butterfly valve 缓冲噪声等级工作行程working stroke noise level放大器amplifier负载压力induced pressure模拟放大器forceanalogue amplifier 输出力数字放大器digital amplifier 实际输出力actual force传感器single-acting cylinder sensor 单作用缸阈值双作用缸threshold double-acting cylinder伺服阀differential cylinder servo-valve 差动缸四通阀伸缩缸telescopic cylinder four-way valve喷嘴挡板valve nozzle flapper 阀液压放大器底板hydraulic amplifier sub-plate颤振manifold block dither油路块阀极性valve polarity 板式阀sub-plate valve流量增益叠加阀sandwich valve flow gain对称度cartridge valve 插装阀symmetry流量极限滑阀slide valve flow limit零位内泄漏null(quiescent) leakage 锥阀poppet valve遮盖阀芯valve element lap零遮盖阀芯位置valve element position zero lap正遮盖over lap check valve单向阀负遮盖液控单向阀pilot-controlled check valve under lap开口梭阀opening shuttle valve零偏压力控制阀pressure relief valve null bias零漂null driftpressure relief valve 溢流阀阀压降sequence valve valve pressure drop 顺序阀分辨率pressure reducing valve 减压阀resolution频率响应平衡阀counterbalance valve frequency response幅值比卸荷阀amplitude ratio unloading valve相位移直动式directly operated type phase lag传递函数pilot-operated type先导式transfer function管路mechanically controlled type 机械控制式flow line硬管manually operated type 手动式rigid tube软管液控式hydraulic controlled type flexible hose工作管路流量控制阀flow control valve working line回油管路固定节流阀return line fixed restrictive valve补液管路replenishing line adjustable restrictive valve 可调节流阀控制管路one-way restrictive valve 单向节流阀pilot line泄油管路调速阀speed regulator valve drain linebleed line放气管路flow divider valve分流阀．压力开关connection pressure switch 接头fitting；脉冲发生器welded fitting pulse generator 焊接式接头液压泵站扩口式接头flared fitting power station空气处理单元air conditioner unit 快换接头quick release coupling压力控制回路flange connection pressure control circuit 法兰接头安全回路弯头elbowsafety circuit差动回路异径接头reducer fitting differential circuit调速回路流道flow pass flow control circuit进口节流回路meter-in circuit 油口port出口节流回路meter-out circuit 闭式油箱sealed reservoir同步回路synchronizing circuit 油箱容量reservoir fluid capacity开式回路bladder accumulator open circuit 气囊式蓄能器闭式回路air contamination closed circuit 空气污染管路布置solid contamination pipe-work 固体颗粒污染管卡液体污染clamperliquid contamination联轴器air filter drive shaft coupling 空气过滤器操作台油雾气lubricator control console控制屏heat exchanger control panel 热交换器避震喉冷却器compensator cooler粘度viscosity加热器heater运动粘度温度控制器thermostat kinematic viscosity密度消声器silencer density含水量duplex filter water content 双筒过滤器闪点过滤器压降flash point filter pressure drop防锈性rust protection 有效过滤面积effective filtration area抗腐蚀性公称过滤精度nominal filtration rating anti-corrosive quality便携式颗粒检测仪压溃压力portable particle counter collapse pressureSolenoid valve 电磁阀填料密封packing sealCheck valve mechanical seal 单向阀机械密封Cartridge valve 径向密封插装阀radial seal Sandwich plate valve rotary seal 旋转密封叠加阀Pilot valve 先导阀活塞密封piston sealPilot operated check valve 液控单向阀rod seal活塞杆密封Sub-plate mount 板式安装；wiper seal 防尘圈密封scraperManifold block 集成块bonded washer 组合垫圈Pressure relief valve 压力溢流阀composite seal 复合密封件Flow valve 流量阀elastomer seal弹性密封件Throttle valve 节流阀NBR ；丁腈橡胶nitrile butadiene rubberDouble throttle check valve ；polytetrafluoroethene聚四氟乙烯双单向节流阀PTFERotary knob 优先控制override control 旋钮Rectifier plate 节流板pressure gauge压力表Servo valve 伺服阀压力传感器electrical pressure transducerProportional valve differential pressure instrument 压差计比例阀Position feedback 液位计位置反馈liquid level measuring instrument渐增流量Progressive flow flow meter流量计．五、伺服阀及伺服系统性能参数电磁铁释放De-energizing of solenoidDynamic response 动态频响DDV-direct drive valve 直动式伺服阀二、介质类NFPA-National Fluid Power Association 美国流体控磷酸甘油酯Phosphate ester (HFD-R)制学会水-乙二醇Water-glycol (HFC)Phase lag 相位滞后乳化液EmulsionNozzle flapper valve 喷嘴挡板阀Inhibitor缓蚀剂Servo-jet pilot valve 合成油射流管阀Synthetic lubricating oilDither 颤振电流Coil impedance 线圈阻抗三、液压安装工程Flow saturation 流量饱和Contamination 污染Linearity 线形度Grout 灌浆Symmetry 对称性Failure 失效Hysterics 滞环Jog 点动Threshold 灵敏度爬行CreepLap 滞后Abrasion 摩擦Pressure gain 压力增益Retract（活塞杆）伸出Null 零位Extension （活塞杆）缩回Null bias 零偏误动作MalfunctionNull shift 零飘Pickling 酸洗Frequency response 频率响应Flushing 冲洗Slope 槽式酸洗曲线斜坡Dipping process液压系统（循环Re-circulation hydraulic system）执行元件（Passivity 钝化actuator）液压缸（cylinder）Nitric acid 柠檬酸液压马达（motor）Argon 氩气液压回路（circuit ）对接焊Butt welding压力控制回路（Socket welding 套管焊pressure control）流量（速度）控制回路（惰性气体焊Inert gas welding speed control）方向控制回路（directional valve control）安全回路（security control 四、管接头）定位回路（position control）卡套式管接头Bite type fittings同步回路（synchronise circuit Tube to tube fittings 接管接头）顺序动作回路（sequeunt circuit）直通接管接头union液压泵（直角管接头union elbow pump）阀（三通管接头union tee valve）压力控制阀（union cross 四通管接头pressure valve）、流量控制阀（flow valveMal stud fittings ）端直通管接头方向控制阀（directional valve）长直通管接头Bulkhead fittings液压辅件（accessory）焊接式管接头Weld fittings普通阀（接头螺母Female connector fittings common valve）插装阀（cartridge valve）变径管接头Reducers extenders叠加阀（superimposed valve 铰接式管接头Banjo fittingsAdjustable fittings/swivel nut 旋转接头。
液压系统建模和仿真SimHydraulics
液压系统建模和仿真SimHydraulics－－液压系统建模和仿真SimHydraulics是液压传动和控制系统的建模和仿真工具，扩展了Simulink?的功能。
使用这个工具可以建立起含有液压和机械元件的物理网络模型，可用于跨专业领域系统的建模。
SimHydraulics提供了构成液压系统的元器件模块库，库中也包括了用于构造其它元件的基本元素模块。
SimHydraulics适用于汽车，航空，国防和工业装备等领域中的各种应用，例如自动变速器，舵面操纵系统和重载驱动装置的建模分析。
SimHydraulics同SimMechanics，SimDriveline和SimPowerSystems一同使用，能够支持对复杂机液系统和电液系统的建模，以分析他们相互交联的影响。
主要功能液压和液压机械系统的物理建模环境超过75个液压和机械元器件模型，包括泵，阀，蓄能器和管路基本液压构造元素库，还有基本机械和运算单元可定制的常用液压流体工作介质SimHydraulics可在Simulink下建立液压系统回路的网络模型，模型表达基于ISO1219流体传动系统标准，并且建立的模型可以同机械和控制器模型相结合。
机械液压和液压系统网络建模使用SimHydraulics可以建立起完整的液压系统模型，过程如同组建一个真实的物理系统。
SimHydraulics使用物理网络方式构建模型：每个建模模块对应真实的液压元器件，诸如油泵，液压马达和控制阀；元件模块之间以代表动力传输管路的线条连接。
这样，就可以通过直接描述物理构成搭建模型，而不是从基本的数学方程做起。
SimHydraulics库提供了75个以上的流体和液压机械元件，包括油泵，油缸，蓄能器，液压管路和一维机构单元，大部分商品化元器件都可以找到对应模型。
SimHydraulics的模型符号符合ISO1219流体动力系统标准，SimHydraulics可以自动从模型原理图综合出描述系统行为特征的方程组。
液压系统设计外文文献翻译
液压系统设计外文文献翻译附录AHydraulic systemC.J.Sexton,S.M.LewisandC.P.PleaseUniversity of Southampton,UKAbstract:A complete hydraulic system consists of five parts, namely, power components, actuators, control components, auxiliary components (accessories) and hydraulic oil. The function of hydraulic system is to help human work, mainly through the implementation of components into the pressure of rotation or reciprocating movement. Other advantages of the hydraulic system include bi-directional movement, overload protection, and variable speed control. In any of the existing powertrain systems, the hydraulic system also has the largest unit mass power ratio. Seals and seals are an important part of hydraulic equipment. Its reliability and service life is an important index to measure the quality of hydraulic system.Keywords: A power element; an actuating element; a control element; an auxiliary element; hydraulic fluidGenerally, there are only three basic ways to transmit power: electrical, mechanical, and hydraulic. Most applications actually combine the three methods into the most efficient and comprehensive system. In order to reasonably determine which method to take, it is important to understand the salient features of the various methods. For example, the hydraulic system transmits power more economically over a long distance than a mechanical system. The hydraulic system, however, has a shorter transmission distance than the electrical system.Hydraulic transmission there are many outstanding advantages, it is widely used, such as the general industrial use of plastics processing machinery, pressure machinery, engineering machinery, machine tools and other mechanical equipment; application of construction machinery, agricultural machinery, automobile and other metallurgical machinery; iron and steel industry, lifting machinery, a roller adjustment device; control gate device in the water conservancy project, riverbed lifting device, bridges and other operating mechanism; high speed turbine power plant equipment, such as nuclear powerplants; ship deck with crane (winch), bow door, bulkhead valve stern thruster; special technology giant antenna with control devices measurement buoys movements such as rotating stage; military industrial control devices used in artillery ship anti rolling devicesaircraft simulation aircraft retractable landing gear and rudder control device device. Special antenna technology control device, measuring buoy, lifting and rotating stage; military artillery unit, ship antirolling device, flight simulation, device and other equipment for rudder control of landing gear and steering device.The function of hydraulic system is to increase the force by changing the pressure. The quality of a hydraulic system depends on the rationality of the system design, the performance of the system components, the pollution prevention and treatment of the system, and the last point is particularly important. In recent years, China's domestic hydraulic technology has greatly improved, and no longer only the use of foreign hydraulic technology for processing.A complete hydraulic system consists of five parts, namely, power components, actuators, control components, auxiliary components (accessories) and hydraulic oil.The function of the power element is to convert the mechanical energy of the prime mover into the pressure energy of the liquid, the oil pump in the hydraulic system, which provides power to the entire hydraulic system. The structure of hydraulic pumps usually include gear pumps, vane pumps and piston pumps.The actuating elements (such as hydraulic cylinders and hydraulic motors) are used to convert the pressure energy of the fluid into mechanical energy and to drive the load in linear reciprocating or slewing motion.Control elements (i.e. hydraulic valves) control and regulate the pressure, flow, and direction of the liquid in the hydraulic system. According to different control functions, the hydraulic valve can be divided into pressure control valve, flow control valve and directional control valve. Pressure control valves are divided into benefits flow valve (An Quanfa), pressure relief valve, sequence valve, pressure relays etc.; flow control valves including throttle valve, regulating valve, diversion valve; directional control valve includes a one-way valve one-way fluid control valve, shuttle valve, reversing valve, etc.. According to different control methods, the hydraulic valve can be divided into switching control valve, fixed value control valve and proportional control valve.The auxiliary components include oil tank, oil filter, oil pipe and pipe joint, sealing ring, quick change joint, high pressure ball valve, hose assembly, pressure measuring joint, pressure gauge, oil level, oil temperature gauge and so on.Hydraulic oil is the medium of transmission of energy in hydraulic system. There are several kinds of mineral oil, emulsion and synthetic hydraulic oil.The function of hydraulic system is to help human work, mainly throughthe implementation of components into the pressure of rotation or reciprocating movement. Hydraulic principle: it is composed of two different sizes of the cylinder is filled with water or oil. Full of water, known as "hydraulic press", full of oil known as "hydraulic press."". Each of two hydraulic cylinders have a movable piston, if put in the small piston on the pressure, according to Pascal's law, the small piston pressure to the piston through the pressure of liquid, the top of the piston will move long distances. The cross-sectional area of the basic small piston is S1, plus a small piston with a downward force F1. Thus, the pressure on the liquid of the small piston, P=F1/S1, can be transmitted equally in all directions. The pressure through the big piston is also P. If the cross sectional area of the piston is S2, pressure F2=P*S2 P pressure piston upward, the cross-sectional area of the small piston is several times, in addition to the small piston small piston force, there will be great pressure, the hydraulic press for pressing plywood, oil, lifting, forging steel.The secret of the hydraulic system's success and versatility lies in its versatility and ease of operation. Hydraulic power transmission will not be restricted, the geometry of the machine as a mechanical system that in addition, hydraulic system is not limited by the physical properties of materials like electrical system, it is almost no amount of power transfer limit. For example, the performance of an electromagnet by steel magnetic saturation limit, on the contrary, the power of hydraulic system only limited by material intensity.In order to increase productivity, enterprises will increasingly rely on automation, which includes remote and direct control of production operations, processing and material handling. The hydraulic power has become an important part of automation, because it has the following four main advantages:1. convenient control, accurate operation by a joystick and a simple button, the hydraulic system operator can immediately start, stop, speed and can provide arbitrary power, position accuracy of 1/10000 inches of position control. A hydraulic system that causes the pilot to lift and drop the landing gear. When the pilot moves the control valve in one direction, the pressure oil flows into a cavity of the hydraulic cylinder and thus falls.2. force, a hydraulic system without the use of heavy gear, pulley lever can simply and effectively less than an ounce of force amplification, produce hundreds of tons of force output.3. constant or constant torque, hydraulic system can not only provide constant change with speed changing or constant torque, it can drive the mobile object per hour from a few inches to several hundred inches per minute per hour. From a few to thousands of revolutions per minute.4. Simple, safe, economical, and in general, hydraulic systems use fewer moving parts than mechanical or electrical systems, so they are easy to run and maintain. This makes the system compact, safe and reliable. For example, a new type of power steering device for vehicles has been phased out of other types of steering power units, which include manual controlsDirection control valve and distributor. Because the steering component is fully hydraulic, there is no universal joint, bearings, gear reducer and other mechanical connections, which makes the system simple and compact. In addition, only very little input torque can produce control force needed to meet the extremely harsh working conditions. It is very important to the operation of space limitations and need a small steering wheel which is necessary to reduce the occasion, operator fatigue.Other advantages of the hydraulic system include bi-directional movement, overload protection, and variable speed control. In any of the existing powertrain systems, the hydraulic system also has the largest unit mass power ratio.The hydraulic system has three disadvantages:1. because the transmission medium (hydraulic oil) in the course of flow, part of the flow velocity is different, resulting in liquid friction, and at the same time, liquid and pipe wall also friction, this is the hydraulic oil temperature rise reasons. Excessive temperature results in more internal and external leakage and reduces mechanical efficiency. At the same time, the hydraulic oil will expand due to the higher temperature. Resulting in an increase in compressibility so that the operation cannot control transmission very well. Solution: high temperature is the hydraulic system's own problems, can only be the biggest mitigation, can not eradicate. The use of better quality hydraulic oil, hydraulic pipe layout, as far as possible to avoid bending, the use of high-quality pipe and pipe fittings, hydraulic valve.2. the vibration of hydraulic system is one of the weak points. The impact of hydraulic oil in the pipeline on the high speed impact and control valve opening and closing is the cause of system vibration. Strong vibrations can cause system control errors, and can cause errors in some of the more complex, sophisticated devices in the system, leading to system failures. Solution: the hydraulic pipe should be fixed, to avoid sharp bends. In order to avoid frequent flow direction changes can not be avoided, shock absorption measures should be done best. The whole hydraulic system should have good vibration reduction measures, while avoiding the influence of the oscillator outside the system.3. the hydraulic system has internal leakage and external leakage, internal leakage refers to the leakage process occurs in the system, such as leakage of hydraulic piston - cylinder, control valve spool and valve leakage between both sides, such as. Although there is no loss of hydraulic oil, but the leakage, the control action has been determined until the system failure. Disclosure refers to the leakage that occurs between the system and the external environment. Hydraulic oil leaks directly into the environment, and in addition to affecting the working environment, there is not enough power to cause system failure. Hydraulic oil leaking into the environment is also dangerous to fire. Solution: use better quality seals to improve the machining accuracy of the equipment.In hydraulic systems and systems, seals are used to prevent leakage of theworking medium and invasion of foreign dust and foreign matter. A sealed element, that is, a seal. Outside leakage will cause waste of working medium, pollute machine and environment, even cause mechanical malfunction and personal accident of equipment. Leakage can cause a drastic drop in volumetric efficiency of hydraulic systems, resulting in insufficient working pressure and even failure to perform work. The small dust particles in the invading system can cause or aggravate the wear of the friction pairs of hydraulic components, and further lead to leakage.As a result, seals and seals are an important part of hydraulic equipment. Its reliability and service life is an important index to measure the quality of hydraulic system. In addition to the clearance seal, the seal is used to control the clearance between the two adjacent surfaces to be below the minimum clearance required for the sealing liquid to pass. In contact sealing, it is divided into two types: self sealing type and self sealing type (i. e. lip seal).附录B液压系统摘要：一个完整的液压系统由五个部分组成，即动力元件、执行元件、控制元件、辅助元件（附件）和液压油。
液压系统知识外文文献翻译、中英文翻译、外文翻译
液压系统知识一个完整的液压系统由五个部分组成，即动力元件、执行元件、控制元件、辅助无件和液压油。
动力元件的作用是将原动机的机械能转换成液体的压力能，指液压系统中的油泵，它向整个液压系统提供动力。
液压泵的结构形式一般有齿轮泵、叶片泵和柱塞泵。
执行元件(如液压缸和液压马达)的作用是将液体的压力能转换为机械能，驱动负载作直线往复运动或回转运动。
控制元件(即各种液压阀)在液压系统中控制和调节液体的压力、流量和方向。
根据控制功能的不同，液压阀可分为压力控制阀、流量控制阀和方向控制阀。
压力控制阀又分为溢流阀(安全阀)、减压阀、顺序阀、压力继电器等；流量控制阀包括节流阀、调整阀、分流集流阀等；方向控制阀包括单向阀、液控单向阀、梭阀、换向阀等。
根据控制方式不同，液压阀可分为开关式控制阀、定值控制阀和比例控制阀。
辅助元件包括油箱、滤油器、油管及管接头、密封圈、压力表、油位油温计等。
液压油是液压系统中传递能量的工作介质，有各种矿物油、乳化液和合成型液压油等几大类。
液压的原理它是由两个大小不同的液缸组成的，在液缸里充满水或油。
充水的叫“水压机”；充油的称“油压机”。
两个液缸里各有一个可以滑动的活塞，如果在小活塞上加一定值的压力，根据帕斯卡定律，小活塞将这一压力通过液体的压强传递给大活塞，将大活塞顶上去。
设小活塞的横截面积是S1，加在小活塞上的向下的压力是F1。
于是，小活塞对液体的压强为P=F1/SI, 能够大小不变地被液体向各个方向传递”。
大活塞所受到的压强必然也等于P。
若大活塞的横截面积是S2，压强P在大活塞上所产生的向上的压力F2=PxS2 ，截面积是小活塞横截面积的倍数。
从上式知，在小活塞上加一较小的力，则在大活塞上会得到很大的力，为此用液压机来压制胶合板、榨油、提取重物、锻压钢材等。
液压传动的发展史液压传动和气压传动称为流体传动，是根据17世纪帕斯卡提出的液体静压力传动原理而发展起来的一门新兴技术，1795年英国约瑟夫•布拉曼(Joseph Braman,1749-1814)，在伦敦用水作为工作介质,以水压机的形式将其应用于工业上,诞生了世界上第一台水压机。
毕业设计论文外文文献翻译机械设计制造及其自动化轴承的摩擦与润滑中英文对照
Friction , Lubrication of BearingIn many of the problem thus far , the student has been asked to disregard or neglect friction . A ctually , friction is present to some degree whenever two parts are in contact and move on each other. The term friction refers to the resistance of two or more parts to movement.Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener and the parts together. Belt drivers, brakes, and tires are additional applications where friction is necessary.The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. A lso , greater power is required to overcome the increased friction. Heat is destructive in that it causes expansion. Expansion may cause a bearing or sliding surface to fit tighter. If a great enough pressure builds up because made from low temperature materials may melt.There are three types of friction which must be overcome in moving parts: (1)starting, (2)sliding,and(3)rolling. Starting friction is the friction between two solids that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. T o produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. The rougher the two surfaces, the greater is starting friction resulting from their movement .Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other. The friction of the two surfaces is known as sliding friction. A s shown in figure ,starting friction is always greater than sliding friction .Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill. This changing of shape , known as deformation, causes a movement of molecules. As a result ,heat is produced from the added energy required to keep the parts turning and overcome friction.The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces. However, even these smooth surfaces may require the use of a substance between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat .Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts. This explains why bronze bearings, soft alloy s, and copper and tin iolite bearings are used with both soft andhardened steel shaft. The iolite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its own lubricant to the points where the pressures are the greatest.Moving parts are lubricated to reduce friction, wear, and heat. The most commonly used lubricants are oils, greases, and graphite compounds. Each lubricant serves a different purpose. The conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other .A second common method of lubrication is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the piston.A lubrication system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity.There are numerous other sy stems of lubrication and a considerable number of lubricants available for any given set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices.Although one of the main purposes of lubrication is reduce friction, any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant.V arieties of lubricationUnlubricated sliding. Metals that have been carefully treated to remove all foreign materials seize and weld to one another when slid together. In the absence of such a high degree of cleanliness, adsorbed gases, water vapor ,oxides, and contaminants reduce frictio9n and the tendency to seize but usually result in severe wear。
液压系统-外文翻译
Hydraulic SystemThere are only three basic methods of transmitting power: electrical, mechanical, and fluid power. Most applications actually use a combination of the three methods to obtain the most efficient overall system. To properly determine which principle method to use, it is important to know the salient features of each type. For example, fluid systems can transmit power more economically over greater distances than can mechanical types. However, fluid systems are restricted to shorter distances than are electrical systems.Hydraulic power transmission system are concerned with the generation, modulation, and control of pressure and flow, and in general such systems include:1.Pumps which convert available power from the prime mover to hydraulic power at the actuator.2.Valves which control the direction of pump-flow, the level of power produced, and the amount of fluid-flow to the actuators. The power level is determined by controlling both the flow and pressure level.3.Actuators which convert hydraulic power to usable mechanical power output at the point required.4.The medium, which is a liquid, provides rigid transmission and control as well as lubrication of components, sealing in valves, and cooling of the system.5.Connectors which link the various system components, provide power conductors for the fluid under pressure, and fluid flow return to tank (reservoir).6.Fluid storage and conditioning equipment which ensure sufficient quality and quantity as well as cooling of the fluid.Hydraulic systems are used in industrial applications such as stamping presses, steel mills , and general manufacturing , agricultural machines , mining industry , aviation , space technology , deep-sea exploration ,transportation , marinetechnology , and offshore gas petroleum exploration . In short, very few people get through a day of their lives without somehow benefiting from the technology of hydraulics.The secret of hydraulic system’s success and widespread use is its versatility and manageability. Fluid power is not hindered by the geometry of the machine as is the case in mechanical systems. Also, power can be transmitted in almost limitless quantities because fluid systems are not so limited by the physical limitations of materials as are the electrical systems. For example, the performance of an electromagnet is limited by the saturation limit of steel. On the other hand, the power limit of fluid systems is limited only by the strength capacity of the material.Industry is going to depend more and more on automation in order to increase productivity. This includes remote and direct control of production operations, manufacturing processes, and materials handling. Fluid power is the muscle of automation because of advantages in the following four major categories.Ease and accuracy of control. By the use of simple levers and push buttons, the operator of a fluid power systems can readily start, stop, speed up or slow down, and position force which provide any desired horsepower with tolerances as precise as one ten-thousandth of an inch.Multiplication of force. A fluid power system (without using cumbersome gears, pulleys, and levers) can multiply forces simply and efficiently from a fraction of an ounce to several hundred tons of output.Constant force or torque. Only fluid power systems are capable of providing constant force or torque regardless of speed changes. This is accomplished whether the work output moves a few inches per hour, several hundred inches per minute, a few revolutions per hour, or thousands of revolutions per minute.Simplicity, safety, economy. In general, fluid power systems use fewer movingparts than comparable mechanical or electrical systems. Thus, they are simpler to maintain and operate. This, in turn, maximizes safety, compactness, and reliability. For example, a new power steering control designed has made all other kinds of power systems obsolete on many off-highway vehicles. The steering unit consists of a manually operated directional control valve and meter in a single body. Because the sterring unit is fully fluid-linked, mechanical linkages, universal joints, bearings, reduction gears, ect . are eliminated. This provides a simple,compact systems.In addition, very little input torque is required to produce the control needed for the toughest applications. This is important where limitations of control space require a small sterring wheel and it becomes necessary to reduce operator fatigue.Additional benefits of fluid power systems include instantly reversible motion, automatic protection against overloads, and infinitely variable speed control. Fluid power systems also have the highest horsepower per weight ratio of any known power source. In spite of all these highly desirable features of fluid power, it is not a panacea for all power transmission problems. Hydraulic systems also have some drawbacks. Hydraulic oils are messy, and leakage is impossible to completely. Also, most hydraulic oils can cause fires if an oil leak occurs in area of hot equipment. There are only three basic methods of transmitting power: electrical, mechanical, and fluid power. Most applications actually use a combination of the three methods to obtain the most efficient overall system. To properly determine which principle method to use, it is important to know the salient features of each type. For example, fluid systems can transmit power more economically over greater distances than can mechanical types. However, fluid systems are restricted to shorter distances than are electrical systems.Hydraulic power transmission system are concerned with the generation, modulation, and control of pressure and flow, and in general such systems include:Pumps which convert available power from the prime mover to hydraulic power at the actuator.Valves which control the direction of pump-flow, the level of power produced, and the amount of fluid-flow to the actuators. The power level is determined by controlling both the flow and pressure level.Actuators which convert hydraulic power to usable mechanical power output at the point required.The medium, which is a liquid, provides rigid transmission and control as well as lubrication of components, sealing in valves, and cooling of the system.Connectors which link the various system components, provide power conductors for the fluid under pressure, and fluid flow return to tank (reservoir).Fluid storage and conditioning equipment which ensure sufficient quality and quantity as well as cooling of the fluid.Hydraulic systems are used in industrial applications such as stamping presses, steel mills , and general manufacturing , agricultural machines , mining industry , aviation , space technology , deep-sea exploration ,transportation , marine technology , and offshore gas petroleum exploration . In short, very few people get through a day of their lives without somehow benefiting from the technology of hydraulics.The secret of hydraulic system’s success and widespread use is its versatility and manageability. Fluid power is not hindered by the geometry of the machine as is the case in mechanical systems. Also, power can be transmitted in almost limitless quantities because fluid systems are not so limited by the physical limitations of materials as are the electrical systems. For example, the performance of an electromagnet is limited by the saturation limit of steel. On the other hand, the power limit of fluid systems is limited only by the strength capacity of the material.Industry is going to depend more and more on automation in order to increase productivity. This includes remote and direct control of production operations, manufacturing processes, and materials handling. Fluid power is the muscle of automation because of advantages in the following four major categories.1. Ease and accuracy of control. By the use of simple levers and push buttons, the operator of a fluid power systems can readily start, stop, speed up or slow down, and position force which provide any desired horsepower with tolerances as precise as one ten-thousandth of an inch.2. Multiplication of force. A fluid power system (without using cumbersome gears, pulleys, and levers) can multiply forces simply and efficiently from a fraction of an ounce to several hundred tons of output.3. Constant force or torque. Only fluid power systems are capable of providing constant force or torque regardless of speed changes. This is accomplished whether the work output moves a few inches per hour, several hundred inches per minute, a few revolutions per hour, or thousands of revolutions per minute.4. Simplicity, safety, economy. In general, fluid power systems use fewer moving parts than comparable mechanical or electrical systems. Thus, they are simpler to maintain and operate. This, in turn, maximizes safety, compactness, and reliability. For example, a new power steering control designed has made all other kinds of power systems obsolete on many off-highway vehicles. The steering unit consists of a manually operated directional control valve and meter in a single body. Because the sterring unit is fully fluid-linked, mechanical linkages, universal joints, bearings, reduction gears, ect . are eliminated. This provides a simple,compact systems.In addition, very little input torque is required to produce the control needed for the toughest applications. This is important where limitations of controlspace require a small sterring wheel and it becomes necessary to reduce operator fatigue.Additional benefits of fluid power systems include instantly reversible motion, automatic protection against overloads, and infinitely variable speed control. Fluid power systems also have the highest horsepower per weight ratio of any known power source. In spite of all these highly desirable features of fluid power, it is not a panacea for all power transmission problems. Hydraulic systems also have some drawbacks. Hydraulic oils are messy, and leakage is impossible to completely. Also, most hydraulic oils can cause fires if an oil leak occurs in area of hot equipment.液压系统仅有以下三种基本方法传递动力：电气，机械和流体。
《自动控制原理》部分中英文词汇对照表(英文解释)
《自动控制原理》部分中英文词汇对照表AAcceleration 加速度Angle of departure分离角Asymptotic stability渐近稳定性Automation自动化Auxiliary equation辅助方程BBacklash间隙Bandwidth带宽Block diagram方框图Bode diagram波特图CCauchy’s theorem高斯定理Characteristic equation特征方程Closed-loop control system闭环控制系统Constant常数Control system控制系统Controllability可控性Critical damping临界阻尼DDamping constant阻尼常数Damping ratio阻尼比DC control system直流控制系统Dead zone死区Delay time延迟时间Derivative control 微分控制Differential equations微分方程Digital computer compensator数字补偿器Dominant poles主导极点Dynamic equations动态方程EError coefficients误差系数Error transfer function误差传递函数FFeedback反馈Feedback compensation反馈补偿Feedback control systems反馈控制系统Feedback signal反馈信号Final-value theorem终值定理Frequency-domain analysis频域分析Frequency-domain design频域设计Friction摩擦GGain增益Generalized error coefficients广义误差系数IImpulse response脉冲响应Initial state初始状态Initial-value theorem初值定理Input vector输入向量Integral control积分控制Inverse z-transformation反Z变换JJordan block约当块Jordan canonical form约当标准形LLag-lead controller滞后-超前控制器Lag-lead network 滞后-超前网络Laplace transform拉氏变换Lead-lag controller超前-滞后控制器Linearization线性化Linear systems线性系统MMass质量Mathematical models数学模型Matrix矩阵Mechanical systems机械系统NNatural undamped frequency自然无阻尼频率Negative feedback负反馈Nichols chart尼科尔斯图Nonlinear control systems非线性控制系统Nyquist criterion柰奎斯特判据OObservability可观性Observer观测器Open-loop control system开环控制系统Output equations输出方程Output vector输出向量PParabolic input抛物线输入Partial fraction expansion部分分式展开PD controller比例微分控制器Peak time峰值时间Phase-lag controller相位滞后控制器Phase-lead controller相位超前控制器Phase margin相角裕度PID controller比例、积分微分控制器Polar plot极坐标图Poles definition极点定义Positive feedback正反馈Prefilter 前置滤波器Principle of the argument幅角原理RRamp error constant斜坡误差常数Ramp input斜坡输入Relative stability相对稳定性Resonant frequency共振频率Rise time上升时间调节时间 accommodation timeRobust system鲁棒系统Root loci根轨迹Routh tabulation（array）劳斯表SSampling frequency采样频率Sampling period采样周期Second-order system二阶系统Sensitivity灵敏度Series compensation串联补偿Settling time调节时间Signal flow graphs信号流图Similarity transformation相似变换Singularity奇点Spring弹簧Stability稳定性State diagram状态图State equations状态方程State feedback状态反馈State space状态空间State transition equation状态转移方程State transition matrix状态转移矩阵State variables状态变量State vector状态向量Steady-state error稳态误差Steady-state response稳态响应Step error constant阶跃误差常数Step input阶跃输入TTime delay时间延迟Time-domain analysis时域分析Time-domain design时域设计Time-invariant systems时不变系统Time-varying systems时变系统Type number型数Torque constant扭矩常数Transfer function转换方程Transient response暂态响应Transition matrix转移矩阵UUnit step response单位阶跃响应VVandermonde matrix范德蒙矩阵Velocity control system速度控制系统Velocity error constant速度误差常数ZZero-order hold零阶保持z-transfer function Z变换函数z-transform Z变换。
液压控制系统-液压液外文文献翻译、中英文翻译
CHAPTER 3HYDRAULIC FLUIDSDuring the design of equipment that requires fluid power, many factors are considered in selecting the type of system to be used—hydraulic, pneumatic, or a combination of the two. Some of the factors are required speed and accuracy of operation, surrounding atmospheric conditions, economic conditions, availability of replacement fluid, required pressure level, operating temperature range, contamination possibilities, cost of transmission lines, limitations of the equipment, lubricity, safety to the operators, and expected service life of the equipment.After the type of system has been selected, many of these same factors must be considered in selecting the fluid for the system. This chapter is devoted to hydraulic fluids. Included in it are sections on the properties and characteristics desired of hydraulic fluids; types of hydraulic fluids; hazards and safety precautions for working with, handling, and disposing of hydraulic liquids; types and control of contamination; and sampling.PROPERTIESIf fluidity (the physical property of a substance that enables it to flow) and incompressibility were the only properties required, any liquid not too thick might be used in a hydraulic system. However, a satisfactory liquid for a particular system must possess a number of other properties. The most important properties and some characteristics are discussed in the following paragraphs.VISCOSITYViscosity is one of the most important properties of hydraulic fluids. It is a measure of a fluids resistance to flow. A liquid, such as gasoline, which flows easily, has a low viscosity; and a liquid, such as tar, which flows slowly, has a high viscosity. The viscosity of a liquid is affected by changes in temperature and pressure. As the temperature of a liquid increases, its viscosity decreases. That is, a liquid flows more easily when it is hot than when it is cold. The viscosity of a liquid increases as the pressure on the liquid increases.A satisfactory liquid for a hydraulic system must be thick enough to give a good seal at pumps, motors, valves, and so on. These components depend on close fits for creating and maintaining pressure. Any internal leakage through these clearances results in loss of pressure, instantaneous control, and pump efficiency. Leakage losses are greater with thinner liquids (low viscosity). A liquid that is too thin will also allow rapid wearing of moving parts, or of parts that operate under heavy loads. On the other hand, if the liquid is too thick (viscosity too high), the internal friction of the liquid will cause an increase in the liquids flow resistance through clearances of closely fitted parts, lines, and internal passages. This results in pressuredrops throughout the system, sluggish operation of the equipment, and an increase in power consumption.Measurement of ViscosityViscosity is normally determined by measuring the time required for a fixed volume of a fluid (at a given temperature) to flow through a calibrated orifice or capillary tube. The instruments used to measure the viscosity of a liquid are known as viscometers or viscosimeters.Figure 3-1.Saybolt viscometer.Several types of viscosimeters are in use today. The Say bolt viscometer, shown in figure 3-1, measures the time required, in seconds, for 60 milliliters of the tested fluid at 100°F to pass through a standard orifice. The time measured is used to express the fluids viscosity, in Saybolt universal seconds or Saybolt furol seconds.Figure 3-2.Various styles of glass capillary viscometers.The glass capillary viscometers, shown in figure 3-2, are examples of the second type of viscometer used. These viscometers are used to measure kinematic viscosity. Like the Saybolt viscometer, the glass capillary measures the time in seconds required for the tested fluid to flow through the capillary. This time is multiplied by the temperature constant of the viscometer in use to provide the viscosity, expressed in centistokes.The following formulas may be used to convert centistokes (cSt units) to approximate Say bolt universal seconds (SUS units). For SUS values between 32 and 100: SUS SUS cST 195226.0-⨯= For SUS values greater than 100: SUS SUS cST 195220.0-⨯=Although the viscometers discussed above are used in laboratories, there are other viscometers in the supply system that is available for local use. These viscometers can be used to test the viscosity of hydraulic fluids either prior to their being added to a system or periodically after they have been in an operating system for a while.Additional information on the various types of viscometers and their operation can be found in the Physical Measurements Training Manual, NA V AIR 17-35QAL-2.Viscosity IndexThe viscosity index (V.I.) of oil is a number that indicates the effect of temperature changes on the viscosity of the oil. A low V.I. signifies a relatively large change of viscosity with changes of temperature. In other words, the oil becomes extremely thin at high temperatures and extremely thick at low temperatures. On the other hand, a high V.I. signifies relatively little change in viscosity over a wide temperature range.Ideal oil for most purposes is one that maintains a constant viscosity throughout temperature changes. The importance of the V.I. can be shown easily by considering automotive lubricants. Oil having a high V.I. resists excessive thickening when the engine is cold and, consequently, promotes rapid starting and prompt circulation; it resists excessive thinning when the motor is hot and thus provides full lubrication and prevents excessive oil consumption.Another example of the importance of the V.I. is the need for high V.I. hydraulic oil for military aircraft, since hydraulic control systems may be exposed to temperatures ranging from below –65°F at high altitudes to over 100°F on the ground. For the proper operation of the hydraulic control system, the hydraulic fluid must have a sufficiently high V.I. to perform its functions at the extremes of the expected temperature range.Liquids with a high viscosity have a greater resistance to heat than low viscosity liquids which have been derived from the same source. The average hydraulic liquid has a relatively low viscosity. Fortunately, there is a wide choice of liquids available for use in the viscosity range required of hydraulic liquids.The V.I. of an oil may be determined if its viscosity at any two temperatures is known. Tables, based on a large number of tests, are issued by the American Society for Testing and Materials (ASTM). These tables permit calculation of the V.I. from known viscosities.LUBRICATING POWERIf motion takes place between surfaces in contact, friction tends to oppose the motion. When pressure forces the liquid of a hydraulic system between the surfaces of moving parts, the liquid spreads out into a thin film which enables the parts to move more freely. Different liquids, including oils, vary greatly not only in their lubricating ability but also in film strength. Film strength is the capability of a liquid to resist being wiped or squeezed out from between the surfaces when spread out in an extremely thin layer. A liquid will no longer lubricate if the film breaks down, since the motion of part against part wipes the metal clean of liquid.Lubricating power varies with temperature changes; therefore, the climatic and working conditions must enter into the determination of the lubricating qualities of a liquid. Unlike viscosity, which is a physical property, the lubricating power and film strength of a liquid isdirectly related to its chemical nature. Lubricating qualities and film strength can be improved by the addition of certain chemical agents.CHEMICAL STABILITYChemical stability is another property which is exceedingly important in the selection of a hydraulic liquid. It is defined as the liquids ability to resist oxidation and deterioration for long periods. All liquids tend to undergo unfavorable changes under severe operating conditions. This is the case, for example, when a system operates for a considerable period of time at high temperatures.Excessive temperatures, especially extremely high temperatures, have a great effect on the life of a liquid. The temperature of the liquid in the reservoir of an operating hydraulic system does not always indicate the operating conditions throughout the system. Localized hot spots occur on bearings, gear teeth, or at other points where the liquid under pressure is forced through small orifices. Continuous passage of the liquid through these points may produce local temperatures high enough to carbonize the liquid or turn it into sludge, yet the liquid in the reservoir may not indicate an excessively high temperature.Liquids may break down if exposed to air, water, salt, or other impurities, especially if they are in constant motion or subjected to heat. Some metals, such as zinc, lead, brass, and copper, have undesirable chemical reactions with certain liquids.These chemical reactions result in the formation of sludge, gums, carbon, or other deposits which clog openings, cause valves and pistons to stick or leak, and give poor lubrication to moving parts. Once a small amount of sludge or other deposits is formed, the rate of formation generally increases more rapidly. As these deposits are formed, certain changes in the physical and chemical properties of the liquid take place. The liquid usually becomes darker, the viscosity increases and damaging acids are formed.The extent to which changes occur in different liquids depends on the type of liquid, type of refining, and whether it has been treated to provide further resistance to oxidation. The stability of liquids can be improved by the addition of oxidation inhibitors. Inhibitors selected to improve stability must be compatible with the other required properties of the liquid.FREEDOM FROM ACIDITYAn ideal hydraulic liquid should be free from acids which cause corrosion of the metals in the system. Most liquids cannot be expected to remain completely no corrosive under severe operating conditions. The degree of acidity of a liquid, when new, may be satisfactory; but after use, the liquid may tend to become corrosive as it begins to deteriorate.Many systems are idle for long periods after operating at high temperatures. This permits moisture to condense in the system, resulting in rust formation.Certain corrosion- and rust-preventive additives are added to hydraulic liquids. Some of these additives are effective only for a limited period. Therefore, the best procedure is to use the liquid specified for the system for the time specified by the system manufacturer and to protect the liquid and the system as much as possible from contamination by foreign matter, from abnormal temperatures, and from misuse.FLASHPOINTFlashpoint is the temperature at which a liquid gives off vapor in sufficient quantity to ignite momentarily or flash when a flame is applied. A high flashpoint is desirable for hydraulic liquids because it provides good resistance to combustion and a low degree of evaporation at normal temperatures. Required flashpoint minimums vary from 300°F for the lightest oils to 510°F for the heaviest oils.FIRE POINTFire point is the temperature at which a substance gives off vapor in sufficient quantity to ignite and continue to burn when exposed to a spark or flame. Like flashpoint, a high fire point is required of desirable hydraulic liquids.MINIMUM TOXICITYToxicity is defined as the quality, state, or degree of being toxic or poisonous. Some liquids contain chemicals that are a serious toxic hazard. These toxic or poisonous chemicals may enter the body through inhalation, by absorption through the skin, or through the eyes or the mouth. The result is sickness and, in some cases, death. Manufacturers of hydraulic liquids strive to produce suitable liquids that contain no toxic chemicals and, as a result, most hydraulic liquids are free of harmful chemicals. Some fire-resistant liquids are toxic, and suitable protection and care in handling must be provided.DENSITY AND COMPRESSIBILITYA fluid with a specific gravity of less than 1.0 is desired when weight is critical, although with proper system design, a fluid with a specific gravity greater than one can be tolerated. Where avoidance of detection by military units is desired, a fluid which sinks rather than rises to the surface of the water is desirable. Fluids having a specific gravity greater than 1.0 are desired, as leaking fluid will sink, allowing the vessel with the leak to remain undetected.Recall from chapter 2 that under extreme pressure a fluid may be compressed up to 7 percent of its original volume. Highly compressible fluids produce sluggish system operation. This does not present a serious problem in small, low-speed operations, but it must be considered in the operating instructions.FOAMING TENDENCIESFoam is an emulsion of gas bubbles in the fluid. Foam in a hydraulic system results fromcompressed gases in the hydraulic fluid. A fluid under high pressure can contain a large volume of air bubbles. When this fluid is depressurized, as when it reaches the reservoir, the gas bubbles in the fluid expand and produce foam. Any amount of foaming may cause pump cavitations and produce poor system response and spongy control. Therefore, defaming agents are often added to fluids to prevent foaming. Minimizing air in fluid systems is discussed later in this chapter.CLEANLINESSCleanliness in hydraulic systems has received considerable attention recently. Some hydraulic systems, such as aerospace hydraulic systems, are extremely sensitive to contamination. Fluid cleanliness is of primary importance because contaminants can cause component malfunction, prevent proper valve seating, cause wear in components, and may increase the response time of servo valves. Fluid contaminants are discussed later in this chapter.The inside of a hydraulic system can only be kept as clean as the fluid added to it. Initial fluid cleanliness can be achieved by observing stringent cleanliness requirements (discussed later in this chapter) or by filtering all fluid added to the system.TYPES OF HYDRAULIC FLUIDSThere have been many liquids tested for use in hydraulic systems. Currently, liquids being used include mineral oil, water, phosphate ester, water-based ethylene glycol compounds, and silicone fluids. The three most common types of hydraulic liquids are petroleum-based, synthetic fire-resistant, and water-based fire-resistant.PETROLEUM-BASED FLUIDSThe most common hydraulic fluids used in shipboard systems are the petroleum-based oils. These fluids contain additives to protect the fluid from oxidation (antioxidant), to protect system metals from corrosion (anticorrosion), to reduce tendency of the fluid to foam (foam suppressant), and to improve viscosity.Petroleum-based fluids are used in surface ships，electro hydraulic steering and deck machinery systems, submarines，hydraulic systems, and aircraft automatic pilots, shock absorbers, brakes, control mechanisms, and other hydraulic systems using seal materials compatible with petroleum-based fluids.SYNTHETIC FIRE-RESISTANT FLUIDS Petroleum-based oils contain most of the desired properties of a hydraulic liquid. However, they are flammable under normal conditions and can become explosive when subjected to high pressures and a source of flame or high temperatures. Nonflammable synthetic liquids have been developed for use in hydraulic systems where fire hazards exist.Phosphate Ester Fire-Resistant FluidPhosphate ester fire-resistant fluid for shipboard use is covered by specification MIL- H-19457. There are certain trade names closely associated with these fluids. However, the only acceptable fluids conforming to MIL-H-19457 are the ones listed on the current Qualified Products List (QPL) 19457. These fluids will be delivered in containers marked MIL-H-19457C or a later specification revision. Phosphate ester in containers marked by a brand name without specification identification must not be used in shipboard systems, as they may contain toxic chemicals.These fluids will burn if sufficient heat and flame are applied, but they do not support combustion. Drawbacks of phosphate ester fluids are that they will attack and loosen commonly used paints and adhesives, deteriorate many types of insulations used in electrical cables, and deteriorate many gasket and seal materials. Therefore, gaskets and seals for systems in which phosphate ester fluids are used are manufactured of specific materials. Naval Ships，Technical Manual, chapter 262, specifies paints to be used on exterior surfaces of hydraulic systems and components in which phosphate ester fluid is used and on ship structure and decks in the immediate vicinity of this equipment. Naval Ships，Technical Manual, chapter 078, specifies gasket and seal materials used. NA V AIR 01-1A-17 also contains a list of materials resistant to phosphate ester fluids.Trade names for phosphate ester fluids, which do not conform to MIL-H-19457 include Pydraul、Skydrol、and Fire Safe.PHOSPHATE ESTER FLUID SAFETY.—as a maintenance person, operator, supervisor, or crew member of a ship, squadron, or naval shore installation, you must understand the hazards associated with hydraulic fluids to which you may be exposed.Phosphate ester fluid conforming to specification MIL-H-19457 is used in aircraft elevators, ballast valve operating systems, and replenishment-at-sea systems. This type of fluid contains a controlled amount of neurotoxic material. Because of the neurotoxic effects that can result from ingestion, skin absorption, or inhalation of these fluids, be sure to use the following precautions:1. Avoid contact with the fluids by wearing protective clothing.2. Use chemical goggles or face shields to protect your eyes.3. If you are expected to work in an atmosphere containing a fine mist or spray, wear a continuous-flow airline respirator.4. Thoroughly clean skin areas contaminated by this fluid with soap and water.5. If you get any fluid in your eyes, flush them with running water for at least 15 minutes and seek medical attention.If you come in contact with MIL-H-19457 fluid, report the contact when you seek medical aid and whenever you have a routine medical examination.Naval Ships，Technical Manual, chapter 262, contains a list of protective clothing, along with national stock numbers(NSN),for use with fluids conforming to MIL-H-19457.It also contains procedures for repair work and for low-level leakage and massive spills cleanup.PHOSPHATE ESTER FLUID DISPOSAL.—Waste MIL-H-19457 fluids and refuse (rags and other materials) must not be dumped at sea. Fluid should be placed in bung-type drums. Rags and other materials should be placed in open top drums for shore disposal. These drums should be marked with a warning label stating their content, safety precautions, and disposal instructions. Detailed instructions for phosphate ester fluids disposal can be found in Naval Ships, Technical Manual, chapter 262, and OPNA VINST 5090.1.Silicone Synthetic Fire-Resistant FluidsSilicone synthetic fire-resistant fluids are frequently used for hydraulic systems which require fire resistance, but which have only marginal requirements for other chemical or physical properties common to hydraulic fluids. Silicone fluids do not have the detrimental characteristics of phosphate ester fluids, nor do they provide the corrosion protection and lubrication of phosphate ester fluids, but they are excellent for fire protection. Silicone fluid conforming to MIL-S-81087 is used in the missile hold-down and lockout system aboard submarines.Lightweight Synthetic Fire-Resistant Fluids In applications where weight is critical, lightweight synthetic fluid is used in hydraulic systems. MIL-H-83282 is a synthetic, fire-resistant hydraulic fluid used in military aircraft and hydrofoils where the requirement to minimize weight dictates the use of a low-viscosity fluid. It is also the most commonly used fluid in aviation support equipment. NA V AIR 01-1A-17 contains additional information on fluids conforming to specification MIL-H-83282.WATER-BASED FIRE-RESISTANT FLUIDS The most widely used water-based hydraulic fluids may be classified as water-glycol mixtures and water-synthetic base mixtures. The water-glycol mixture contains additives to protect it from oxidation, corrosion, and biological growth and to enhance its load-carrying capacity.Fire resistance of the water mixture fluids depends on the vaporization and smothering effect of steam generated from the water. The water in water-based fluids is constantly being driven off while the system is operating. There- fore, frequent checks to maintain the correct ratio of water are important.The water-based fluid used in catapult retracting engines, jet blast deflectors, and weapons elevators and handling systems conforms to MIL-H-22072.The safety precautions outlined for phosphate ester fluid and the disposal of phosphate ester fluid also apply to water-based fluid conforming to MIL-H-22072.CONTAMINATIONHydraulic fluid contamination may be described as any foreign material or substance whose presence in the fluid is capable of adversely affecting system performance or reliability. It may assume many different forms, including liquids, gases, and solid matter of various compositions, sizes, and shapes. Solid matter is the type most often found in hydraulic systems and is generally referred to as particulate contamination. Con- termination is always present to some degree, even in new, unused fluid, but must be kept below a level that will adversely affect system operation. Hydraulic contamination control consists of requirements, techniques, and practices necessary to minimize and control fluid contamination.CLASSIFICATIONThere are many types of contaminants which are harmful to hydraulic systems and liquids. These contaminants may be divided into two different classes—particulate and fluid.Particulate ContaminationThis class of contaminants includes organic, metallic solid and inorganic solid contaminants. These contaminants are discussed in the following paragraphs.ORGANIC CONTAMINATION.—Organic solids or semisolids found in hydraulic systems are produced by wear, oxidation, or polymerization. Minute particles of O-rings, seals, gaskets, and hoses are present, due to wear or chemical reactions. Synthetic products, such as neoprene, silicones, and hypalon, though resistant to chemical reaction with hydraulic fluids, produce small wear particles. Oxidation of hydraulic fluids increases with pressure and temperature, although antioxidants are blended into hydraulic fluids to minimize such oxidation.The ability of a hydraulic fluid to resist oxidation or polymerization in service is defined as its oxidation stability. Oxidation products appear as organicacids,asphaltics,gums,and varnishes. These products combine with particles in the hydraulic fluid to form sludge. Some oxidation products are oil soluble and cause the hydraulic fluid to increase in viscosity; other oxidation products are not oil soluble and form sediment.METALLIC SOLID CONTAMINATION.—Metallic contaminants are almost always present in a hydraulic system and will range in size from microscopic particles to particles readily visible to the naked eye. These particles are the result of wearing and scoring of bare metal parts and plating materials, such as silver and chromium. Although practically all metals commonly used for parts fabrication and plating may be found in hydraulic fluids, themajor metallic materials found are ferrous, aluminum, and chromium particles. Because of their continuous high-speed internal movement, hydraulic pumps usually contribute most of the metallic particulate contamination present in hydraulic systems. Metal particles are also produced by other hydraulic system components, such as valves and actuators, due to body wear and the chipping and wearing away of small pieces of metal plating materials.INORGANIC SOLID CONTAMINATION.—This contaminant group includes dust, paint particles, dirt, and silicates. Glass particles from glass bead penning and blasting may also be found as contaminants. Glass particles are very undesirable contaminants due to their abrasive effect on synthetic rubber seals and the very fine surfaces of critical moving parts. Atmospheric dust, dirt, paint particles, and other materials are often drawn into hydraulic systems from external sources. For example, the wet piston shaft of a hydraulic actuator may draw some of these foreign materials into the cylinder past the wiper and dynamic seals, and the contaminant materials are then dispersed in the hydraulic fluid. Contaminants may also enter the hydraulic fluid during maintenance when tubing, hoses, fittings, and components are disconnected or replaced. It is therefore important that all exposed fluid ports be sealed with approved protective closures to minimize such contamination.Fluid ContaminationAir, water, solvent,and other foreign fluids are in the class of fluid contaminants.AIR CONTAMINATION.—Hydraulic fluids are adversely affected by dissolved, entrained, or free air. Air may be introduced through improper maintenance or as a result of system design. Any maintenance operation that involves breaking into the hydraulic system, such as disconnecting or removing a line or component will invariably result in some air being introduced into the system. This source of air can and must be minimized by prebilling replacement components with new filtered fluid prior to their installation. Failing to prefill a filter element bowl with fluid is a good example of how air can be introduced into the system. Although prebilling will minimize introduction of air, it is still important to vent the system where venting is possible.Most hydraulic systems have built-in sources of air. Leaky seals in gas-pressurized accumulators and reservoirs can feed gas into a system faster than it can be removed, even with the best of maintenance. Another lesser known but major source of air is air that is sucked into the system past actuator piston rod seals. This usually occurs when the piston rod is stroked by some external means while the actuator itself is not pressurized.WATER CONTAMINATION.—Water is a serious contaminant of hydraulic systems. Hydraulic fluids are adversely affected by dissolved, emulsified, or free water. Water contamination may result in the formation of ice, which impedes the operation of valves,actuators, and other moving parts. Water can also cause the formation of oxidation products and corrosion of metallic surfaces.SOLVENT CONTAMINATION.—Solvent contamination is a special form of foreign fluid contamination in which the original contaminating substance is a chlorinated solvent. Chlorinated solvents or their residues may, when introduced into a hydraulic system, react with any water present to form highly corrosive acids.Chlorinated solvents, when allowed to combine with minute amounts of water often found in operating hydraulic systems, change chemically into hydrochloric acids. These acids then attack internal metallic surfaces in the system, particularly those that are ferrous, and produce a severe rust-like corrosion. NA V AIR 01-1A-17 and NSTM, chapter 556, contain tables of solvents for use in hydraulic maintenance.FOREIGN-FLUIDS CONTAMINATION.—Hydraulic systems can be seriously contaminated by foreign fluids other than water and chlorinated solvents. This type of contamination is generally a result of lube oil, engine fuel, or incorrect hydraulic fluid being introduced inadvertently into the system during servicing. The effects of such contamination depend on the contaminant, the amount in the system, and how long it has been present.NOTE: It is extremely important that the different types of hydraulic fluids are not mixed in one system. If different type hydraulic fluids are mixed, the characteristics of the fluid required for a specific purpose are lost. Mixing the different types of fluids usually will result in a heavy, gummy deposit that will clog passages and require a major cleaning. In addition, seals and packing installed for use with one fluid usually are not compatible with other fluids and damage to the seals will result.ORIGIN OF CONTAMINATIONRecall that contaminants are produced from wear and chemical reactions, introduced by improper maintenance, and inadvertently introduced during servicing. These methods of contaminant introduction fall into one of the four major areas of contaminant origin.1. Particles originally contained in the system. These particles originate during the fabrication and storage of system components. Weld spatter and slag may remain in welded system components, especially in reservoirs and pipe assemblies. The presence is minimized by proper design. For example, seam-welded overlapping joints are preferred, and arc welding of open sections is usually avoided. Hidden passages in valve bodies, inaccessible to sand blasting or other methods of cleaning, are the main source of introduction of core sand. Even the most carefully designed and cleaned castings will almost invariably free some sand particles under the action of hydraulic pressure. Rubber hose assemblies always contain some loose particles. Most of these particles can be removed by flushing the hose before installation;。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
阻尼溢流阀的建模与动态响应液压专业毕业设计外文翻译阻尼溢流阀的建模与动态响应作者:richard.eyres@ (英国布里斯托尔大学布里斯托尔工程动态实验室)原文标题：Modelling and Dynamic Response of a Damper with Relief Valve摘要:抽象的。
本文概述了几种可行的方法:一个含有液压阻尼结构的安全阀打开一条旁路管道. 将最初的一个简单的代数模型,推导演变成一个复杂的结合流体动力学和流体压缩性的模型.通过数值仿真来模拟现实现象和设计参数.关键词:流体压缩系数、液压阻尼器、非线性、安全阀1.介绍振动阻尼器在许多应用场合使用,例如汽车减震器上,桥梁的稳定上,直升机和抗震的建筑物。
为了使一个系统不用反复进行实际试验,建立一个模型是至关重要的。
本文将重点阐述一个大型机械系统中的阻尼器,把该阻尼器作为一个独立的模块来研究。
因此它是假定的一个简单且以时间为变量的模型.当输入位移时会产生一种力。
仿制的阻尼器在本质上是一个液压柱塞。
它上面有一个小活塞孔口连接两侧流体使其流动 ,如图1所示。
通过这个原理可对复杂的阻尼器进行研究。
当柱塞两边的压差足够高时,一个锥阀打开,允许流体流过如图2的替代管。
这种情况发生时的阻尼器就称为开阀。
开阀是通过阻尼器套管使油液连通的阀。
油液通过时会对旁路管路产生阻力,管道的压差,决定了阀门开合。
开阀系统和负压差系统是一样，它们与自由阀门不同之处是负压时阀门会处于静止状态以防止第二旁路管中的流体在相反的方向自由流动.这样一种阻尼器,用于指示非线性模型.用于小振幅阻尼或低频运动的应用场合是很重要的.根据阻尼器的性质分类,可决定它可以被应用于以上的哪种工作方式。
这种有不同运作模式的可调阻尼器,广泛应用在陆地和在水上,如汽车高速运行,以及越野。
其他方面的应用有飞机起落架和叶片阻尼器。
当阻尼器在全面运作时,阻尼器可以采取不同的运作方式。
本研究主要目的是试图再现液压减振器测试的显示数据.如图表1和2。
这个数据的显著的特点是:具有滞后性和延迟反应; 在开阀区域有抖动振荡。
图3所示的是一个典型的输入系统线图。
线图显示了活塞阻尼器的位移与时间关系。
时间被定为1个周期,位移如4.3节所述。
输入的主要特征是光滑的周期运动和位移梯度较小的数量变化.。
从这种类型的输入,我们需要一种类似如图4所示的力。
这个力已经恢复到的使开阀上的活塞能够打开,允许直接比较的力。
与时间曲线对应的力表明在反向力处会快速振荡。
在这些区域力的方向并没有改变,没有像期望的那样,有位移梯度显示的几种输出延迟反应。
这种迟滞现象更明显地反映在速度图线反映的力上。
在一个位移输入高频变化的简短响应中,迟滞反应的结果是对输入位移的变化做出反应,同时允许对低频组件做出平稳响应。
一个动态的且完全参数化的模型,比如这个阻尼器,因为压缩弹簧和管道里的液体压迫而受到压力。
如后面图所示,这可能会造成一个复杂的动态响应。
当管段的阻尼器模型, 收到如在图1中的响应[8]的基础上,由此产生的模型可以用来预测阻尼器的动态响应性质变化的效果。
研究的关键内容是, 孔和旁路管路在弹簧刚度和阀的排放特性不同的情况下的尺寸。
在这个文章里简单推导总质量参数模型,将所有这些影响。
2.液压阻尼器广泛应用的两种常见阻尼吸振器为:被动阻尼器;与半主动阻尼器。
被动阻尼器,如液压阻尼器,该阻尼器没有外部输入控制, 在操作和执行上属于完全被动方式。
主动阻尼器有一个外部的能量输入力的响应,以便根据给定的输入来改变力的响应以适合工作环境, 而这可能会导致需求较高的能源. 这也就是半自动阻尼器为何现在变得越来越受欢迎的原因.半自动阻尼器类似于自动阻尼器,不同之处是对于半主动阻尼器,必须给出力的指令,来命令驱动阻尼器。
可以采用一个如图1装置,模拟在流体孔粘滞阻尼。
被动阻尼器的响应在所有时间内是相同的(忽略损失等等)而一个的半主动减振器可能由于机械上孔大小的改变而产生不同反应。
要完全理解这种类型的半主动减振器,重要的是去理解被动的简单情况下,以便推导控制律。
推导出一种参数化模型是必要的,而不是用传递函数的阻尼器建模.更快的解决方案,它可以不考虑物理系统。
例如,孔直径变化就需要进行改造和重新拟合阻尼器模型测试数据。
这除了对参数模型进行验证外,不会被要求实施。
被动阻尼器在许多应用领域使用,例如汽车的冲击吸收系统。
这类系统工作的工作模型都是基于执行一组数学方程。
最终方程都是基于相同的基本方程。
用传递函数,可以产生一个更简单方程.参照图1,由此方程可得阻尼器的力定义式活塞上的受力状态方程,取决于一个给定运动y(t).应用于阻尼器的阀体的惯性和m¨y(t)给出了,在活塞上的力取决于两个腔之间的压力(P1(t)−P2(t)]与活塞由于与假定的面摩擦产生的恒定力的差别。
一个是活塞的截面积。
在稍后参考论文中应该指出,方程(1)不适用于迟滞的表征。
压差(P1(t)−P2(t)],可以归因于粘滞摩擦损失, 通过管口p f和在其出口孔的水头损失ph值的总和。
假设流体不可压缩, 用连续性方程可以来获得体积的变化,(2) 对于小˙y的流量可以假设为层流。
然后可以[16]Poisseuille 方程来表达˙V和pf之间的压力差p两个腔由于粘性在阻尼器的建模和动态响应(3)在这里η是动态粘度、l是长度、d是其孔口直径(假定圆截面)。
结合方程(2)和(3)得到通过孔口粘滞力下列方程其中A是孔的面积。
第二个压力损失是由于ph水头损失(有时叫做节流损失),在其出口孔给出V-压缩流体的速度。
90o出口,c=0.5。
由动量守恒原理得因此这里ρ是液体的密度。
压力差P1−P2等于方程(7)中所描述的损失整体的运动方程,因此是所提供的现有的测试数据不认为摩擦有任何显著影响。
因此d3可以从方程方程(9)省掉。
3.开阀动力学该模型可以推广到更现实的安全阀和开阀区域的动力学过程。
如上面的所述,阻尼器被研究是因为其有一个开阀区域。
在这个区域流体被允许通过旁路阀门,而非让流过活塞的的主孔(见图2)。
这种阀门能够打开一个预先受力的活塞, 使两个腔产生不同的压力差。
由此产生的压差与流体在阀门处的回流管和对面腔不同，如果活塞动力是足够大(F >Fcrit) 将导致阀门开启。
由此产生的回流穿过阀门充当另一个孔。
在可能的最简单的模型下,我们可以把阻尼器视为旁路阻尼管，它用相同的方法、准确地开在经典位置但是呈现不同的几何形状。
这个区与的孔成为这个区域的旁路管而不是A0。
因此我们使用方程(9)四个不同的区域各种系数也随之变动:(一)压力低 (F < Fcrit)、阻尼器处于压缩(˙> 0);y(二)压力高(F > Fcrit)、阻尼器处于压缩(˙> 0);y(三)压力低(F < Fcrit)、阻尼器处在反弹(y˙< 0);以及(四)压力高(F > Fcrit)、阻尼器处在反弹(y˙< 0)。
三个分离的可能性被认为是在接下来的两个部分里。
这些是:更小心处理临界力; 流动中的变化是由于4.1弹性阀，在4.2可压缩性部分。
这些在4.3节总结成一个综合的模型。
在本节中,该系统可以看作是一套明确的公式,而不需要使用时间步进方法。
目标是预测一个给定输入位移F(ωt y =sin( t≈))。
3.1 恒压模型从第二节还不清楚当阀门开启时d3应该是什么的价值。
在方程(9) 由于摩擦而被忽视了。
在试验数据(图4)表明，当速度梯度低而旁路阀门开启速度高时将存在力的补偿。
用方程(9)来计算力，当阀门开启时在这个方程里需要一个常数。
,以防止力处于零时,速度趋于零。
这是包括d3。
这种补偿的作用可以在最简单的情况下使用方程(9) 计算。
一个正弦临界力超过已知值。
通过动作而溢出。
然而输入对阻尼器不会永远都是这么简单。
有待应用物理论证参数是否选择正确。
这个部分描述了一个简化假设,可使模型从低作用力(F < Fcrit)即当阀门关闭时, 过渡到较高作用力(F > Fcrit)即溢流阀打开时的力。
将会用物理方法讨论解释开阀的运动区域, 由于摩擦而产生的影响被忽视了,因为它被假定是很小的。
总体运动方程、忽视过渡区,给出了方程(10)。
在较低的压力下，所有的流量将通过活塞孔口。
由于弹簧的预加压力作用阀将持续关闭。
这将是真是存在的在临界力Fcrit达到临界压力。
在Pcrit图6的临界压力曲线图表明,流速较低时,临界力与ycrit速度将成正比。
以上这种流量的增加产生的力,使阀门打开允许一些的液体流过旁路管。
如果腔1可以被认为是体积比较大, 在压力室1，由于额外的流体流经旁路管而引起的压力改变是可以忽略的。
这就意味着在活塞孔口压差将大致保持常数。
因为力大于临界力,所以洞口流量将保持不变。
这意味着,力的影响由于活塞孔口不变,将等于Fcrit力。
额外的流体通过旁路孔会导致额外的力可以被添加到Fcrit。
如今成为整体方程,指图6,如果假定旁路口的水头损失足够大，来避免产生力速度线性的特性。
这可能导致计算量大的问题需要计算每个开阀。
图6说明了在非物理的参数d(2)的来源，如果临界速度是已知的。
进一步讨论将在第3.2节。
3.2 等效速度模型如果对于一个给定的输入位移的全周期能够通过流体的流动来描述的话，它将会是一个简单分析系统的办法。
这一部分是过对3.1节的扩展,其目的是计算通过孔的假设有效连续流量过渡,并且要考虑到阀的开度。
由于忽略了压缩系数、流量的全向运动，活塞将会完全承受一部分来自流体通过孔(174问:)和水流通过旁路软管(Qb)的压力。
这可以表示为管道两头气流损失(因而相应的压差)必须是平等的，[18]中讨论管网工程与应用。
作为一个简单的例子,这意味着一个更广阔的管道将需要更多的流体通过它来产生相同的水头损失作为相似的情况，不能是较窄的管道。
要定义的损失系数、流量的比值。
参考图6，这个想法可以应用到方程(10)阻尼器的建模和动态响应在图6中的这个例子显示当速度为y1˙时压差为P1。
双方的水头损失在路线和压差上是等效的主要孔的等效速度为Ye，这可以通过方程(10)计算得到,忽略了活塞的惯性和摩擦。
通过旁路管的流量因此可以通过下式得到现在有两个压力P1或力的方程。
4 建模的进一步的作用4．1 由于安全阀的流量改变第3.2节可以扩展到包括安全阀动态弹性。
这个系统有三个部分可以产生压差(忽略压缩性):(a)流量通过活塞孔口;(b)流量通过旁路管;(c)流过阀门。
两个腔压力差如3.2节所述，必须相同。
由孔产生的压力损失必须与旁路管的损失相同。
并与阀门结合在一起,所以Pv是由于流体流过阀门的压力损失 Pb流体流过旁路管的压力损失。
用方程(19)来定义,经过阀门的流量Qv用试验的方法确定的Cp和γ,dv是阀门的直径和α是阀门的锥半角在不可压缩流动的情况下, 由于活塞运动的两种途径的可分为,如(13)。