文档视界 最新最全的文档下载
当前位置:文档视界 › 机械毕业设计英文外文翻译460数字控制 (2)

机械毕业设计英文外文翻译460数字控制 (2)

机械毕业设计英文外文翻译460数字控制 (2)
机械毕业设计英文外文翻译460数字控制 (2)

附录

科技译文:

Numerical Control

Numerical Control(NC) is a method of controlling the movements of machineComponents by directly inserting coded instructions in the form of numerical data(numbers and data ) into the system.The system automatically interprets these data and converts to output signals. These signals ,in turn control various machine components ,such as turning spindles on and off ,changing tools,moving the work piece or the tools along specific paths,and turning cutting fluits on and off.

In order to appreciate the importer of numerical control of machines ,let’s briefly review how a process such as machining has been carried out traditionally .After studying the working drawing of a part, the operator sets up the appropriate process parameters(such as cutting speed ,feed,depth of cut,cutting fluid ,and so on),determines the sequence of operations to be performed,clamps the work piece in a workholding device such as chuck or collet ,and proceeds to make the part .Depending on part shape and the dimensional accuracy specified ,this approach usually requires skilled

operators.Furthermore,the machining procedure followed may depend on the particular operators,and because of the possibilities of human error, the parts produced by the same operator may not all be identical .Part quality may thus depend on the particular operator or even the same operator on different days or different hours of the day. Because of our increased concern with product quality and reducing manufacturing costs,such variability and its effects on product quality are no longer acceptable this situation can be dliminated by numerical control of the mathining operation.

We can illustrate the importance of numerical concrol by the following example. Asume that holes have to be drilled on a part in the positions shown in the picture.In the traditional manual method of machining thid part, the operator positions the drill with respect to the workpiece, using as erfererence points any of the three of the method shown. The operator then proceeds to drill these holes. Let,s assume that 100 parts, having exactly the same shape and dimensional accuracy, have to be dielled. Obviously, this operation is going to be tediious because the operator has to go throuth the same motions again and again. Moreover, the probabiluty is high that, faor warious reasons, some of the paths machined will be different from

orthers. Let`s further assume that during this production run, the order for these paths is changed, so that 10 of the paths now require holes in difficult positions. The machinisst now has to reset the mathine , wehich will be time consuming and subject to error. Such operations can be perfomedeasily by numerical conctrol machines that are capable of producing parts reeatedly and accurately and of handling differeent parts by simply londing differeent part programs.

In numerical control ,data concerning all aspects of the machining operation,such as locations ,speeds,and cutting fluid,are stored on magnetic tape.,cassettes ,floppy or hard disks,or paper or plastic(Mylar,which is a thermoplastic polyester)tape,.Date are stored on punched 25 mm wide paper or plastic tape ,as originally developed and still used .The concept of NC control is that holes in the tape represent specific information in the form of alphanumeric codes ,The presence (on)or absence (off),of these holes is read by sensing devices in the contuol panel ,which then actuate relays and other devices (called hard-wired contuols),These devices control various mechanical and electrical system in the machine .This method eliminnated manual setting of machine positions and tool paths or the use of templates and other

mechanical guides and devices. Conplex operations,such as turning a part having various contours and die sinking in milling machine ,can be carried out.

Numerical control has had a major impact on all aspects of manufacturing operations.It is a widely applied technology ,particularly in the following areas:

a)Machining centers

b)Milling,turning,boring,drilling,and gringing

c)Electrical-discharge,laser-beam,and electron-beam machining

d) Water-jet cutting

e) Punching and nibbling .

f) Pipe bending and metal spinning.

g) Sopt welding and metal spinning.

h) Assembly operations.

Numerical control machines are now used extensively in small-and-medium-quantity(typically 500 parts or less)of a wide variety of parts in small shops and large manufacture facilities. Older machines can be retrofitted with numerical control.

Advantages and Limitations Numerical control has following advantages over conventional method of machine control:

1.Flexibility of operation and ability to produce complex shape with good dimensional accuracy,repeatability,reduced scrap loss,and high production rates ,productivity,and product quality.

2.Tooling costs are reduced,since templates and other fixtures are not required.

3.Machine adjustments are easy to make with minicomputer and digital readout.

4.More operations can be performed with each setup,and less lead time for setup and machining is required compared to conventional methods.Design changes are facilitated,and inventory is reduced.

5.Programs can prepared rapidly and can be recalled at any time utilizing microprocessors,Less paperwork is involved.

6.Faster prototype productiong is possible.

7.Required operator skill is less,and the operator has more time to attend to other tasks in the work area.

The major limitations of NC are the relatively high cost of the equipment and the need for programming and special

maintenance,requiring trained personal.Because NC machines are complex systems,breakdowns can be very costly,so preventive maintenance is essential.However,these limitations are often easily outweighed by the overall economic advantages of NC.

One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control(NC) Controlling a machine tool using a punched tape or stored program is known as numerical control (NC).NC has been defined by the Electronic

Industries.Association(EIA)as "a system in which actions are controlled by the direct insertion of numerical data at some point.The numerical data at some point.The numerical data required to produce a part is known as a part program.

A numerical control machine toll system contains a machine control unit(MCU) and the machine tool itself(Fig

2.16)The MCU is further divided into two elements:The data processing unit(DPU)and the control loops unit (CLU). The DPU processes the code data from the tape or other media and passes information on the position of each axis,required direction of motion,feed rate, and auxiliary function control signals to the CLU. The CLU operates the drive mechanisms of

each of the axes and signals the completion of operation.The DPU sequentially reads the data.When each line has completed execution of operation.The DPU sequentially read the

data.When each line has completed execution as noted by the CLU,another line of data is read.

A data processing unit consists of some or all of the following parts:

1)Data input device such as a paper tape

reader,RS232-C port,etc

2)Data-reading circuits and parity-checking logic

3)Decoding circuits for distributing data among the controlled axes

4)An interpolator,which supplies machine-motion commands between data points for tool motion

A control loops unit,on the other hand consists of the following:

1)Position control loops for all the axes of

motion,where ach axis has a separate control loop

2)Velocity control loops,where feed control is required

3)Deceleration and backlash take up circuits

4)Auxiliary functions control,such as coolant

on/off,gear changes,spindle on/off control

Geometric and kinematics data are typically fed from the DPU to the CLU.

The CLU then governs the physical system based on the data form the DPU.Numerical control was developed to overcome the limitation of human operators,and it has done so.Numerical control machines are more accurate than manually operated machines,they can produce parts more uniformly,they are faster,and the long-run tooling costs are lower.The development of NC led to the development of several Other innovations in manufacturing technology ;

Electic discharge machining

Laser—cuting

Electron beam welding

Numerical control has also made maching tools more versatile their manually operated predecessors . An NC machine tool can automatically produce a wide variety of parts ,each involving an assortment of widely varied and complex machining processes . Numerical control has allowed manufacturers to undertaken the production of part ,each involving an assortment of widely varied and complex machining processes .Numerical control has allowed manufactures to undertaken the production of products that

would not have been feasible from an economic perspective using manually controlled machine tools and processes.

翻译:

数字控制

数控是一种用数字控制机床各部件运动的方法,通过直接向系统输入指令代码(数字和字母)完成的。系统自动将这些指令代码转化成信号输出。这些信号依次控制机床个中部件的运动,比如主轴的启动和停止,刀具的选择,岩指令路径移动刀具和工件,净控制切削液的通断等等。

为了说明数控机床的重要性,我们来简单回顾一下传统机床的加工过程。操作作者研究零件工作图后,调整合适的加工参数(如切削速度,进给量,切削深度,切削液等),安排加工顺序,然后将工件夹紧在夹具(如卡盘或夹头)上,在开始加工。根据所规定的工件形状和尺寸精度,这种加工通常需要熟练的操作加工。而且,其后续加工时由各个操作者完成的。由于存在不可避免的人为误差,即便有同一个人加工出来的零件也不可能完全相同。因此,零件的质量就可能取决于操作者的操作水平,甚至取决于该工人在不同时期或不同时间的状态。由于我们越来越关注加工质量和降低加

工成本,所以我们不再允许存在零件偏差和产品的质量影响,而通过数控加工就可以消除以上这些情况。

我们可以通过以下的例子来说明数控加工的重要性。假如要在图示位置的零件上钻这几个孔,当传统的手工操作机床加工此零件时,操作者可选图示三种方案中的任一种,使钻头与工件的点相对应着,然后钻这些孔。假如要加工100个同样形状,同样尺寸,同样精度的零件,很明显,操作者会觉得很枯燥,因为操作者要一遍一遍重复同样的动作,而且,由于各种原因,有些零件加工出来的不一样的可能性是很高的。我们进一步假设,在操作过程中,零件的加工要求要改变,现在要在不同的位置加工出10个孔,机械师必须马上调整机床,这样既浪费时间又增加了加工误差。而数控机床能够重复而准确地加工工件,而且可通过简单地输入不同程序来加工不同的零件。因此,使用数控机床就可以轻而易举地完成此类加工。

在数控系统中,与加工过程各项相关的数据如工件的定位,切削速度,进给量和切削液,存储在磁盘,盒式录音带,软盘,硬盘,纸袋或塑料袋(热塑性树脂)上。将数据存储在25mm宽的穿孔纸带或塑料带上,这种数据存储方法使用最早并沿用至今。数控的概念就是纸带上的孔表示以字母代码表达的特定信息。这些孔的打开和关闭由控制面板的感应控制,然后驱动继电器和其他机械导向装置。一些复杂操作

如切削具有不同轮廓,外形的零件或在钻床上刻模也可以实现了。

数控加工在制造个方面有着深远的影响,特别在以下的加工领域中广泛使用:

a)加工中心

b)铣,车,镗,钻,磨。

c)放电加工,激光加工和电子束加工。

d)水射流切削。

e)冲孔和分段冲模。

f)弯管和金属旋压

g)点焊,其他焊接和切削加工。

h)装配。

i)数控机床广泛使用在小型或大型机械制造中,加工出品种繁多,小量或中等批量(小于或等于500)的零件。现在也可以用数控改装旧的机床了。

优点和局限性数控加工与传统的机加工相比,具有以下优点:

1、操作简便,能加工出尺寸精度高的复杂形状的工件,重复性好,能降低材料的浪费,生产速度快,生产效率高,加工质量高。

2、降低工具的成本,因为一些模型和工件家具都不需要了。

3、通过微机和数字输出,很容易调整机床。

4、每一步工序可以同时加工很多个零件,与传统的机加工相比,装夹和加工的时间减少了。图样的转换也更容易了。

5、能很快准备好加工工序,微处理器在任何时候都能存储这些工序,手工

用打孔机记录数据或存储程序来控制机床刀具的进给就是数字控制技术(NC)。NC已经被电子工业协会正式定义:数控技术是一种利用所提供的数字数据来控制加工工艺过程的一种体系。这种所需要的数据就是程序。

一个完整的数字控制机床刀具的系统包括了一个机床控制单元(MCU)和机床刀具本身。机床控制单元被进一步分为两部分:一个是数据处理单元,另一个是控制单元。数据处理单元负责处理从纸带或者其他媒介上获得的编码数据并且处理各个轴向的位移,这些数据包括机床运行方向,进给速度,以及CLU的辅助控制信号,从而指导完成整个加工过程。数据控制单元顺序读取这些数据。当每条指令被执行完毕并被CLU记录下来,另外一条指令的数据接着就会被读取。

一条数据处理单元包括下面提到的某些或者全部的部分。

1)数据输入设备像纸带阅读器,磁带阅读器,比

如RS232-C。

2)数据阅读电路和奇偶检验逻辑电路。

3)在各受操纵轴之中分配数据的译码电路。

4)反馈装置,用来接受机床运动数据并调整机床运动状态。

一个控制回路单元,另外还包括以下几个方面:1)所有运动轴的位置控制回路,其中每根轴都有一个单独的回路

2)速度控制回路,只是进给控制所必须的

3)辅助操作控制,例如冷却剂供给,齿轮转换,心轴开关控制

几何学和运动学的数据就是典型地从控制回路单元和数据处理单元获取。数控已经发展到了可以突破人工加工的局限性的水平了。数控机床比手动操作的机床更为准确,它们能更快捷地生产零件,且长时间运转所耗费的加工成本更低。数控技术的发展导致制造技术的其他几个方面革新的发展:

电子清洗机

激光切割机

电子激光焊接

数控也能比以前的手工操作者制造出更多样的机器工具。数控机床工具能够自动生产出广泛多样的零件,并且每种零件

都比传统制造方式有先进的完善的地方。现在数控技术已经可以允许制造者生产出用传统加工方式和由于经济限制所不能生产出的零件,这是一个极大地飞跃。

机械毕业设计英文外文翻译460数字控制 (2)

附录 科技译文: Numerical Control Numerical Control(NC) is a method of controlling the movements of machineComponents by directly inserting coded instructions in the form of numerical data(numbers and data ) into the system.The system automatically interprets these data and converts to output signals. These signals ,in turn control various machine components ,such as turning spindles on and off ,changing tools,moving the work piece or the tools along specific paths,and turning cutting fluits on and off. In order to appreciate the importer of numerical control of machines ,let’s briefly review how a process such as machining has been carried out traditionally .After studying the working drawing of a part, the operator sets up the appropriate process parameters(such as cutting speed ,feed,depth of cut,cutting fluid ,and so on),determines the sequence of operations to be performed,clamps the work piece in a workholding device such as chuck or collet ,and proceeds to make the part .Depending on part shape and the dimensional accuracy specified ,this approach usually requires skilled

机械专业毕业论文外文翻译

附录一英文科技文献翻译 英文原文: Experimental investigation of laser surface textured parallel thrust bearings Performance enhancements by laser surface texturing (LST) of parallel-thrust bearings is experimentally investigated. Test results are compared with a theoretical model and good correlation is found over the relevant operating conditions. A compari- son of the performance of unidirectional and bi-directional partial-LST bearings with that of a baseline, untextured bearing is presented showing the bene?ts of LST in terms of increased clearance and reduced friction. KEY WORDS: ?uid ?lm bearings, slider bearings, surface texturing 1. Introduction The classical theory of hydrodynamic lubrication yields linear (Couette) velocity distribution with zero pressure gradients between smooth parallel surfaces under steady-state sliding. This results in an unstable hydrodynamic ?lm that would collapse under any external force acting normal to the surfaces. However, experience shows that stable lubricating ?lms can develop between parallel sliding surfaces, generally because of some mechanism that relaxes one or more of the assumptions of the classical theory. A stable ?uid ?lm with su?cient load-carrying capacity in parallel sliding surfaces can be obtained, for example, with macro or micro surface structure of di?erent types. These include waviness [1] and protruding microasperities [2–4]. A good literature review on the subject can be found in Ref. [5]. More recently, laser surface texturing (LST) [6–8], as well as inlet roughening by longitudinal or transverse grooves [9] were suggested to provide load capacity in parallel sliding. The inlet roughness concept of Tonder [9] is based on ??e?ective clearance‘‘ reduction in the sliding direction and in this respect it is identical to the par- tial-LST concept described in ref. [10] for generating hydrostatic e?ect in high-pressure mechanical seals. Very recently Wang et al. [11] demonstrated experimentally a doubling of the load-carrying capacity for the surface- texture design by reactive ion etching of SiC

毕业设计外文翻译资料

外文出处: 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题: JDBC接口技术 译文: JDBC是一种可用于执行SQL语句的JavaAPI(ApplicationProgrammingInterface应用程序设计接口)。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口,使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC,很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢?如果有,那么它们之间又是怎样的关系呢? ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统(DBMS)中存取数据的,用C语言实现的,标准应用程序数据接口。通过ODBCAPI,应用程序可以存取保存在多种不同数据库管理系统(DBMS)中的数据,而不论每个DBMS使用了何种数据存储格式和编程接口。 1.ODBC的结构模型 ODBC的结构包括四个主要部分:应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口:屏蔽不同的ODBC数据库驱动器之间函数调用的差别,为用户提供统一的SQL编程接口。 驱动器管理器:为应用程序装载数据库驱动器。 数据库驱动器:实现ODBC的函数调用,提供对特定数据源的SQL请求。如果需要,数据库驱动器将修改应用程序的请求,使得请求符合相关的DBMS所支持的文法。 数据源:由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器,以便ODBC函数调用,但是数据库驱动器本身也执行ODBC函数调用,并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时,数据库驱动器能管理通信协议。当建立起与数据源的连接时,数据库驱动器便能处理应用系统向DBMS发出的请求,对分析或发自数据源的设计进行必要的翻译,并将结果返回给应用系统。 2.JDBC的诞生 自从Java语言于1995年5月正式公布以来,Java风靡全球。出现大量的用java语言编写的程序,其中也包括数据库应用程序。由于没有一个Java语言的API,编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥,比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱,越来越多的公司在Java程序开发上投入的精力日益增加,对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处,比如它并不容易使用,没有面向对象的特性等等,SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1.x 版本中,JDBC只是一个可选部件,到了JDK1.1公布时,SQL类包(也就是JDBCAPI)

毕业设计外文翻译附原文

外文翻译 专业机械设计制造及其自动化学生姓名刘链柱 班级机制111 学号1110101102 指导教师葛友华

外文资料名称: Design and performance evaluation of vacuum cleaners using cyclone technology 外文资料出处:Korean J. Chem. Eng., 23(6), (用外文写) 925-930 (2006) 附件: 1.外文资料翻译译文 2.外文原文

应用旋风技术真空吸尘器的设计和性能介绍 吉尔泰金,洪城铱昌,宰瑾李, 刘链柱译 摘要:旋风型分离器技术用于真空吸尘器 - 轴向进流旋风和切向进气道流旋风有效地收集粉尘和降低压力降已被实验研究。优化设计等因素作为集尘效率,压降,并切成尺寸被粒度对应于分级收集的50%的效率进行了研究。颗粒切成大小降低入口面积,体直径,减小涡取景器直径的旋风。切向入口的双流量气旋具有良好的性能考虑的350毫米汞柱的低压降和为1.5μm的质量中位直径在1米3的流量的截止尺寸。一使用切向入口的双流量旋风吸尘器示出了势是一种有效的方法,用于收集在家庭中产生的粉尘。 摘要及关键词:吸尘器; 粉尘; 旋风分离器 引言 我们这个时代的很大一部分都花在了房子,工作场所,或其他建筑,因此,室内空间应该是既舒适情绪和卫生。但室内空气中含有超过室外空气因气密性的二次污染物,毒物,食品气味。这是通过使用产生在建筑中的新材料和设备。真空吸尘器为代表的家电去除有害物质从地板到地毯所用的商用真空吸尘器房子由纸过滤,预过滤器和排气过滤器通过洁净的空气排放到大气中。虽然真空吸尘器是方便在使用中,吸入压力下降说唱空转成比例地清洗的时间,以及纸过滤器也应定期更换,由于压力下降,气味和细菌通过纸过滤器内的残留粉尘。 图1示出了大气气溶胶的粒度分布通常是双峰形,在粗颗粒(>2.0微米)模式为主要的外部来源,如风吹尘,海盐喷雾,火山,从工厂直接排放和车辆废气排放,以及那些在细颗粒模式包括燃烧或光化学反应。表1显示模式,典型的大气航空的直径和质量浓度溶胶被许多研究者测量。精细模式在0.18?0.36 在5.7到25微米尺寸范围微米尺寸范围。质量浓度为2?205微克,可直接在大气气溶胶和 3.85至36.3μg/m3柴油气溶胶。

机械毕业设计英文外文翻译204机电一体化

附录 INTEGRATION OF MACHINERY (From ELECTRICAL AND MACHINERY INDUSTRY)ABSTRACT Machinery was the modern science and technology development inevitable result, this article has summarized the integration of machinery technology basic outline and the development background .Summarized the domestic and foreign integration of machinery technology present situation, has analyzed the integration of machinery technology trend of development. Key word:integration of machinery ,technology,present situation ,product t,echnique of manufacture ,trend of development 0. Introduction modern science and technology unceasing development, impelled different discipline intersecting enormously with the seepage, has caused the project domain technological revolution and the transformation .In mechanical engineering domain, because the microelectronic technology and the computer technology rapid development and forms to the mechanical industry seepage the integration of machinery, caused the mechanical industry the technical structure, the product organization, the function and the constitution, the production method and the management system has had the huge change, caused the industrial production to enter into “the integration of machinery” by “the machinery electrification” for the characteristic development phase. 1. Integration of machinery outline integration of machinery is refers in the organization new owner function, the power function, in the information processing function and the control function introduces the electronic technology, unifies the system the mechanism and the computerization design and the software which constitutes always to call. The integration of machinery development also has become one to have until now own system new discipline, not only develops along with the science and technology, but also entrusts with the new content .But its basic characteristic may summarize is: The integration of machinery is embarks from the system viewpoint, synthesis community technologies and so on utilization mechanical technology, microelectronic technology, automatic control technology,

机械类毕业设计外文翻译

本科毕业论文(设计) 外文翻译 学院:机电工程学院 专业:机械工程及自动化 姓名:高峰 指导教师:李延胜 2011年05 月10日 教育部办公厅 Failure Analysis,Dimensional Determination And

Analysis,Applications Of Cams INTRODUCTION It is absolutely essential that a design engineer know how and why parts fail so that reliable machines that require minimum maintenance can be designed.Sometimes a failure can be serious,such as when a tire blows out on an automobile traveling at high speed.On the other hand,a failure may be no more than a nuisance.An example is the loosening of the radiator hose in an automobile cooling system.The consequence of this latter failure is usually the loss of some radiator coolant,a condition that is readily detected and corrected.The type of load a part absorbs is just as significant as the magnitude.Generally speaking,dynamic loads with direction reversals cause greater difficulty than static loads,and therefore,fatigue strength must be considered.Another concern is whether the material is ductile or brittle.For example,brittle materials are considered to be unacceptable where fatigue is involved. Many people mistakingly interpret the word failure to mean the actual breakage of a part.However,a design engineer must consider a broader understanding of what appreciable deformation occurs.A ductile material,however will deform a large amount prior to rupture.Excessive deformation,without fracture,may cause a machine to fail because the deformed part interferes with a moving second part.Therefore,a part fails(even if it has not physically broken)whenever it no longer fulfills its required function.Sometimes failure may be due to abnormal friction or vibration between two mating parts.Failure also may be due to a phenomenon called creep,which is the plastic flow of a material under load at elevated temperatures.In addition,the actual shape of a part may be responsible for failure.For example,stress concentrations due to sudden changes in contour must be taken into account.Evaluation of stress considerations is especially important when there are dynamic loads with direction reversals and the material is not very ductile. In general,the design engineer must consider all possible modes of failure,which include the following. ——Stress ——Deformation ——Wear ——Corrosion ——Vibration ——Environmental damage ——Loosening of fastening devices

毕业设计英文翻译

使用高级分析法的钢框架创新设计 1.导言 在美国,钢结构设计方法包括允许应力设计法(ASD),塑性设计法(PD)和荷载阻力系数设计法(LRFD)。在允许应力设计中,应力计算基于一阶弹性分析,而几何非线性影响则隐含在细部设计方程中。在塑性设计中,结构分析中使用的是一阶塑性铰分析。塑性设计使整个结构体系的弹性力重新分配。尽管几何非线性和逐步高产效应并不在塑性设计之中,但它们近似细部设计方程。在荷载和阻力系数设计中,含放大系数的一阶弹性分析或单纯的二阶弹性分析被用于几何非线性分析,而梁柱的极限强度隐藏在互动设计方程。所有三个设计方法需要独立进行检查,包括系数K计算。在下面,对荷载抗力系数设计法的特点进行了简要介绍。 结构系统内的内力及稳定性和它的构件是相关的,但目前美国钢结构协会(AISC)的荷载抗力系数规范把这种分开来处理的。在目前的实际应用中,结构体系和它构件的相互影响反映在有效长度这一因素上。这一点在社会科学研究技术备忘录第五录摘录中有描述。 尽管结构最大内力和构件最大内力是相互依存的(但不一定共存),应当承认,严格考虑这种相互依存关系,很多结构是不实际的。与此同时,众所周知当遇到复杂框架设计中试图在柱设计时自动弥补整个结构的不稳定(例如通过调整柱的有效长度)是很困难的。因此,社会科学研究委员会建议在实际设计中,这两方面应单独考虑单独构件的稳定性和结构的基础及结构整体稳定性。图28.1就是这种方法的间接分析和设计方法。

在目前的美国钢结构协会荷载抗力系数规范中,分析结构体系的方法是一阶弹性分析或二阶弹性分析。在使用一阶弹性分析时,考虑到二阶效果,一阶力矩都是由B1,B2系数放大。在规范中,所有细部都是从结构体系中独立出来,他们通过细部内力曲线和规范给出的那些隐含二阶效应,非弹性,残余应力和挠度的相互作用设计的。理论解答和实验性数据的拟合曲线得到了柱曲线和梁曲线,同时Kanchanalai发现的所谓“精确”塑性区解决方案的拟合曲线确定了梁柱相互作用方程。 为了证明单个细部内力对整个结构体系的影响,使用了有效长度系数,如图28.2所示。有效长度方法为框架结构提供了一个良好的设计。然而,有效长度方法的

信工学院毕业设计外文翻译封面完整版

信工学院毕业设计外文 翻译封面 Document serial number【NL89WT-NY98YT-NC8CB-NNUUT-NUT108】

毕业设计外文资料翻译 专业名称网络工程 班级学号 学生姓名吕帅 指导教师胡硕 填表日期 2015 年 04 月 02 日 Cryptography isone ofthe maintraditional technology andinformation security technology,it is theShannoninformation theory andcryptography theory andtechnology based on thedigital content protection,theuse ofencryptionmethod to complete,i.e.themultimediadata fileis encrypted into ciphertextafter the release,theillegal attackerappearsin the transmission processcannot obtainconfidentialinformation from thetext,so as to achievethe purpose ofcopyright protection andinformation security.Butthis does not completely solve the problem: the spread ofanencrypted filebecause it is notcomprehensibleand hinderthe multimedia information;on the other hand,through themultimedia informationencryptionis easy to causethe attacker'sattention and curiosity,andthere isthe possibility of cracking,and when theinformation isreceivedanddecrypted,theencryptionthe documentandthe document,will no longer be protected,not spared frompiracy.In other words,cryptographycan protectthe transmissionofcontent,and the contentoncedecryptionwill no longer have theprotection.Therefore,there is an urgent need for areplacementorsupplement thecryptographytechnology,itevencan continue to protect thecontent is decryptedincontent.In this way,people put forward thenewconcept ofdigital watermarking,information hiding.Digital watermark isa new direction in thefield of information security technology,is anewtechnologyto protectcopyright and authentication source andintegrality in theopen network environment,the creation ofinformation andpersonal logocreatorthrough digitalwatermarking system toembed the watermarkcan not be perceivedbypeoplein themedia,peoplecan not perceiveon the face ofthe watermark,onlyspecial detector orcomputer softwarethatcan detect thedigital watermarkhidden.

机械类毕业设计外文文献翻译

沈阳工业大学工程学院 毕业设计(论文)外文翻译 毕业设计(论文)题目:工具盒盖注塑模具设计 外文题目:Friction , Lubrication of Bearing 译文题目:轴承的摩擦与润滑 系(部):机械系 专业班级:机械设计制造及其自动化0801 学生姓名:王宝帅 指导教师:魏晓波 2010年10 月15 日

外文文献原文: Friction , Lubrication of Bearing In many of the problem thus far , the student has been asked to disregard or neglect friction . Actually , 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. Also , 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. To 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. As 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

毕业设计外文翻译

毕业设计(论文) 外文翻译 题目西安市水源工程中的 水电站设计 专业水利水电工程 班级 学生 指导教师 2016年

研究钢弧形闸门的动态稳定性 牛志国 河海大学水利水电工程学院,中国南京,邮编210098 nzg_197901@https://www.docsj.com/doc/0b12181585.html,,niuzhiguo@https://www.docsj.com/doc/0b12181585.html, 李同春 河海大学水利水电工程学院,中国南京,邮编210098 ltchhu@https://www.docsj.com/doc/0b12181585.html, 摘要 由于钢弧形闸门的结构特征和弹力,调查对参数共振的弧形闸门的臂一直是研究领域的热点话题弧形弧形闸门的动力稳定性。在这个论文中,简化空间框架作为分析模型,根据弹性体薄壁结构的扰动方程和梁单元模型和薄壁结构的梁单元模型,动态不稳定区域的弧形闸门可以通过有限元的方法,应用有限元的方法计算动态不稳定性的主要区域的弧形弧形闸门工作。此外,结合物理和数值模型,对识别新方法的参数共振钢弧形闸门提出了调查,本文不仅是重要的改进弧形闸门的参数振动的计算方法,但也为进一步研究弧形弧形闸门结构的动态稳定性打下了坚实的基础。 简介 低举升力,没有门槽,好流型,和操作方便等优点,使钢弧形闸门已经广泛应用于水工建筑物。弧形闸门的结构特点是液压完全作用于弧形闸门,通过门叶和主大梁,所以弧形闸门臂是主要的组件确保弧形闸门安全操作。如果周期性轴向载荷作用于手臂,手臂的不稳定是在一定条件下可能发生。调查指出:在弧形闸门的20次事故中,除了极特殊的破坏情况下,弧形闸门的破坏的原因是弧形闸门臂的不稳定;此外,明显的动态作用下发生破坏。例如:张山闸,位于中国的江苏省,包括36个弧形闸门。当一个弧形闸门打开放水时,门被破坏了,而其他弧形闸门则关闭,受到静态静水压力仍然是一样的,很明显,一个动态的加载是造成的弧形闸门破坏一个主要因素。因此弧形闸门臂的动态不稳定是造成弧形闸门(特别是低水头的弧形闸门)破坏的主要原是毫无疑问。

毕业设计外文翻译格式实例.

理工学院毕业设计(论文)外文资料翻译 专业:热能与动力工程 姓名:赵海潮 学号:09L0504133 外文出处:Applied Acoustics, 2010(71):701~707 附件: 1.外文资料翻译译文;2.外文原文。

附件1:外文资料翻译译文 基于一维CFD模型下汽车排气消声器的实验研究与预测Takeshi Yasuda, Chaoqun Wua, Noritoshi Nakagawa, Kazuteru Nagamura 摘要目前,利用实验和数值分析法对商用汽车消声器在宽开口喉部加速状态下的排气噪声进行了研究。在加热工况下发动机转速从1000转/分钟加速到6000转/分钟需要30秒。假定其排气消声器的瞬时声学特性符合一维计算流体力学模型。为了验证模拟仿真的结果,我们在符合日本工业标准(JIS D 1616)的消声室内测量了排气消声器的瞬态声学特性,结果发现在二阶发动机转速频率下仿真结果和实验结果非常吻合。但在发动机高阶转速下(从5000到6000转每分钟的四阶转速,从4200到6000转每分钟的六阶转速这样的高转速范围内),计算结果和实验结果出现了较大差异。根据结果分析,差异的产生是由于在模拟仿真中忽略了流动噪声的影响。为了满足市场需求,研究者在一维计算流体力学模型的基础上提出了一个具有可靠准确度的简化模型,相对标准化模型而言该模型能节省超过90%的执行时间。 关键字消声器排气噪声优化设计瞬态声学性能 1 引言 汽车排气消声器广泛用于减小汽车发动机及汽车其他主要部位产生的噪声。一般而言,消声器的设计应该满足以下两个条件:(1)能够衰减高频噪声,这是消声器的最基本要求。排气消声器应该有特定的消声频率范围,尤其是低频率范围,因为我们都知道大部分的噪声被限制在发动机的转动频率和它的前几阶范围内。(2)最小背压,背压代表施加在发动机排气消声器上额外的静压力。最小背压应该保持在最低限度内,因为大的背压会降低容积效率和提高耗油量。对消声器而言,这两个重要的设计要求往往是互相冲突的。对于给定的消声器,利用实验的方法,根据距离尾管500毫米且与尾管轴向成45°处声压等级相近的排气噪声来评估其噪声衰减性能,利用压力传感器可以很容易地检测背压。 近几十年来,在预测排气噪声方面广泛应用的方法有:传递矩阵法、有限元法、边界元法和计算流体力学法。其中最常用的方法是传递矩阵法(也叫四端网络法)。该方

机械毕业设计外文翻译---装载机发展概况

外文资料翻译 学生姓名: 专业班级:机械设计制造及其自动化04级2班指导教师: 2008年6月

装载机发展概况 Abstract This paper have discussed s.s. ZL-50 type fork-lift truck mainly overall fictitious prototype design as well as some kinds of typical schoolwork operating modes imitate and emulate , include equipment and the overall parts needed build mould. In this design course, have applied ADAMS software and the software of PRO/ENGINEER. ADAMS software is used in the emulation of some kinds of schoolwork operating modes, and the software of PRO/ENGINEER is used to build mould mainly. Through the simulated emulation for some kinds of overall schoolwork operating modes, can see relatively distinctly the overall possible condition in actual schoolwork course that met , can in time modify , have reduced actual design time , have raised production efficiency. The innovation of this design Zhi is in in, imitate and have emulated fork-lift truck the 3 kinds of typical schoolwork operating mode in actual schoolwork, is effect again have imitated in actual schoolwork the hydraulic impact of use, so when being helpful to solve actual loading, the actual problem of meeting the stock that is hard to uninstall can so raise production efficiency. Key words: Fork-lift truck 、fictitious prototype , build mould, emulation, optimization、production efficiency Loader Development China's modern 20 wheel loaders began in the mid-1960s of the Z435. The aircraft as a whole rack, rear axle steering. After years of hard work, the attraction was the world's most advanced technology wheel loader on the basis of the successful development of the power of 162 KW of shovel-fit wheel loaders, stereotypes for Z450 (later ZL50), and in 1971 December 18, formally appraised by experts. Thus the birth of China's first articulated wheel loader, thus creating our industry loader formation and development history. Z450-type loader with hydraulic mechanical transmission, power shift, Shuangqiaoshan drive, hydraulic manipulation, articulated power steering, gas oil Afterburner brake wheel loaders, and other modern, the basic structure of the world's advanced level for the time . Basically represent the first generation of wheeled loading the basic structure. The aircraft in the overall performance of dynamic, and insertion force a rise of power and flexibility, manipulation of light, the higher operating efficiency of a series of advantages. 1978, Heavenly Creations by the Department in accordance with the requirements of machinery, worked out to LIUGONG Z450-based type of wheel loaders series of standards. The development of standards, with reservations Z

相关文档
相关文档 最新文档