机械工程专业英语_原文翻译

5.1 Introduction

Conventional machining is the group of machining operations that use single- or multi-point tools to remove material in the form of chips. Metal cutting involves removing metal through machining operations. Machining traditionally takes place on lathes, drill presses, and milling machines with the use of various cutting tools. Most machining has very low set-up cost compared with forming, molding, and casting processes. However, machining is much more expensive for high volumes. Machining is necessary where tight tolerances on dimensions and finishes are required.

5.1 译文

传统机械加工是一组利用单刃或者多刃刀具以切屑形式去除材料的加工方式。金属切削意味着通过机械加工去除金属。传统的机械加工都是利用不同的刀具在车床、钻床和铣床上进行的。与成型加工、锻压和铸造工艺相比，大多数机械加工的生产准备成本都较低，然而如果是大批量生产，其成本要高得多。当对零件的尺寸公差和光洁度要求较高时，机械加工是很有必要的。

5.2 Turning and Lathe

Turning is one of the most common of metal cutting operations. In turning, a workpiece is rotated about its axis as single-point cutting tools are fed into it, shearing away excess material and creating the desired cylindrical surface. Turning can occur on both external and internal surfaces to produce an axially-symmetrical contoured part. Parts ranging from pocket watch components to large diameter marine propeller shafts can be turned on a lathe.

Apart from turning, several other operations can also be performed on lathe.

axially ['?ksi?li] adv.轴向地symmetrical [si'metrik?l] a. 对称的

cylindrical [si'lindrikl] a.圆柱形的contoured ['k?ntu?d] a.显示轮廓的，与某种形体轮廓相吻合的

译文:

在金属切削加工操作中，车削是最常见的一种。在车削过程中，工件绕其轴线回转，单刃车刀沿工件进给，切除掉多余的材料，最后形成要求的圆柱形表面。车削可以加工外面和内表面以形成具有轴对称的成形工件。从怀表的零件到大直径的船用螺旋桨轴都可以在车床上加工。

除了车削，还有另外几种加工操作都可以在车床上进行。

Boring and internal turning. Boring and internal turning are performed on the internal surfaces by a boring bar or suitable internal cutting tools. If the initial workpiece is solid, a drilling operation must be performed first. The drilling tool is held in the tailstock, and the latter is then fed against the workpiece. When boring is done in a lathe, the work usually is held in a chuck or on a face plate. Holes may be bored straight, tapered, or to irregular contours. Boring is essentially internal turning while feeding the tool parallel to the rotation axis of the workpiece.

译文:

利用镗杆或合适的内圆车刀可以进行镗削和车内圆。如果工件毛坯是实心的，首先要钻孔。钻头安装在尾架上，后者向工件进给。如果在车床上进行镗削加工，工件通常装夹在卡盘或者花盘上。镗出的孔可以是直孔、锥孔或者不规则轮廓。当将刀具沿工件的回转轴线平行进给时，镗削实际上就是车内圆。

Facing. Facing is the producing of a flat surface as the result of a tool’s being fed across the end of the rotating workpiece. Unless the work is held on a mandrel, if both ends of the work are to be

faced, it must be turned around after the first end is completed and then the facing operation repeated. The cutting speed should be determined from the largest diameter of the surface to be faced.

Facing may be done either from the outside inward or from the center outward. In either case, the point of the tool must be set exactly at the height of center of rotation.

Because the cutting force tends to push the tool away from the work, it is usually desirable to clamp the carriage to the lathe bed during each facing cut to prevent it from moving slightly and thus producing a surface that is not flat. In the facing of casting or other materials that have a hard surface, the depth of the first cut should be sufficient to penetrate the hard material to avoid excessive tool wear.

mandrel ['m?ndr?l] n.车床心轴clamp [kl?mp] v. 夹紧，夹住

carriage [‘k?rid?] n.大刀架，拖板penetrate ['penitreit] v. 穿透，渗透

tool wear 刀具磨损

译文:

车端面可以加工出一个平面，它是当车刀沿回转工件的端面横向进给的结果。除非工件固定在心轴上，如果工件两端都要车端面，必须将一端加工完成后，将工件调头，重复进行车端面加工。车削速度必须由所加工表面的最大直径来决定。车端面可以由外向内也可以由中心向外进行。无论哪种情况，刀尖必须准确地与回转中心对正。由于切削力有将车刀推离工件的趋势，通常最可行的就是在车端面时将拖板卡紧在床身上以避免车刀轻微移动造成加工表面不平整。在对具有硬质表面的铸件或其他材料进行车端面加工时，首次切深要足以穿透硬质材料从而避免过度的刀具磨损。

Parting. Parting is the operation by which one section of a workpiece is severed from the remainder by means of cutoff tool. Because cutting tools are quite thin and must have considerable overhang, this process is less accurate and more difficult. The tool should be set exactly at the height of axis of rotation, be kept sharp, have proper clearance angles, and be fed into the workpiece at a proper and uniform feed rate.

remainder [ri'meind?]剩余物，余数overhang ['?uv?'h??] vt.悬于...之上n.伸出;突出uniform ['ju:nif?:m] a.相同的,一致的n.制服;军服clearance angles 后角

译文:

切断是一种利用切断刀（割刀）将工件的一部分与其剩余部分脱离的加工方法。由于切断刀非常薄而且处于悬臂状态，因此这种加工方法不太精确而且加工起来常常比较困难。切断刀必须准确地对正回转轴，保持锋利，具有合适的后角，以合适、不变的进给率沿工件进给。

Threading. Threading can be considered as turning since the path to be travelled by the cutting tool is helical. However, there are some major differences between turning and threading. While in turning, the interest is in generating a smooth cylindrical surface, in threading the interest is in cutting a helical thread of a given form and depth which can be calculated from the formulae.

译文:

车螺纹可以看作是车削，只是车刀所形成的加工轨迹是螺旋线。但二者也存在一些不同之处。车削主要考虑能否生成光滑的圆柱形表面，而车螺纹注重的是能否切出具有按公式计算出来的规定形状和深度的螺旋线。

There are two basic requirements for thread cutting.

?An accurately shaped and properly mounted tool is needed because thread cutting is a

form-cutting operation. The resulting thread profile is determined by the shape of the tool and its position relative to the workpiece.

?The second by requirement is that the tool must move longitudinally in a specific relationship to the rotation of workpiece, because this determines the lead of the thread. This requirement is met through the use of the lead screw and the split unit, which provide positive motion of carriage relative to the rotation of spindle

form-cutting operation 成形加工longitudinally [l?:?d?i'tju:din?li] adv.纵向

lead screw 丝杠split unit 开合机构

译文:

车螺纹有两个基本要求：首先，由于车螺纹是一种成形加工，因此车刀必须具有准确的形状而且要安装合适。所切出的螺纹外形是由车刀形状和它与工件的相对位置决定的。其次，车刀的纵向进给与工件的回转运动具有特定的关系，因此这决定了螺纹的导程。这个条件可以通过采用丝杠和开合机构得到满足，它们可以实现拖板相对于主轴回转运动的精确可靠的运动

1. Engine lathes 普通车床

2. Vertical lathes 立式车床

3. Turret lathes 转塔车床

5. Contouring lathes 仿形车床

6. Universal lathes 万能车床

Lathe bed is foundation of the engine lathe, which heavy, rugged casting is made to support the working parts of the lathe. The size and mass of the bed gives the rigidity necessary for accurate engineering tolerances required in manufacturing. On top of the bed are machined slideways that guide and align the carriage and tailstock, as they are move from one end of the lathe to the other. rugged adj. 健壮，坚固mass n. 质量slideways n.导轨床身是普通车床的基础，它是由沉重而坚固的铸件制作而成的，其目的是为了支撑车床的工作部件。床身的尺寸和质量要使车床具有足够的刚性以保证制造过程中获得所需的工程公差。床身上的导轨可以引导和对准拖板和尾座，使它们可以从车床的一端移动到另一端。?Headstock is clamped atop the bed at left-hand end of the lathe and contains the motor that drives the spindle whose axis is parallel to the guideways through a series of gears housed within the gearbox. The function of gearbox is to generate a number of different spindle speeds.

?atop adv. 在(…)顶上

?gearbox 齿轮箱

床头箱（主轴箱）紧固在床身上面的左端，内装有电机，它通过变速箱内的一组齿轮来驱动主轴转动，主轴的轴线平行于导轨。变速箱的功能是可以产生不同的主轴转速。

? A spindle gear is mounted on the rear of the spindle to transmit power through the change gears to the feeding box that distributes the power to the lead screw for threading or to the feed rod for turning.

?on the rear of 在…的尾部

?change gears 挂轮

?lead screw 丝杠

?feed rod 光杠

主轴齿轮安装在主轴的尾部，通过挂轮把动力传递到进给箱，如果是车螺纹，进给箱将动力分配到丝杠上；如果是车削，就将动力分配到光杠上。

?The spindle has a through hole extending lengthwise through which bar stocks can be fed if continuous production is used. The hole can hold a plain lathe center by its tapered inner surface and mount a chuck, a face plate or collet by its threaded outer surface.

?taper n.坡度，锥形v.锥度加工

?collet n.夹头

主轴有一个纵向通孔，如果连续加工棒料，通孔就用来实现棒料的送料。这个通孔具有一个内锥面，可以安装普通车床的中心顶尖。主轴的外表面车有螺纹，可以安装卡盘，花盘或夹头。

Carriage assembly is actually an H-shaped block that sits across the guideways and in front of lathe bed. The function of the carriage is to carry and move the cutting tool longitudinally. It can be moved by hand or by power and can be clamped into position with a locking nut. The carriage is composed of the cross slide, compound rest, tool saddle, and apron.

拖板组件实际上是一个H形的铸件，位于床身的前端并横跨在导轨上。拖板的功能带动刀具纵向移动，这个可以通过手动或者自动完成。利用锁紧螺母可以将其卡紧在所需位置。拖板组件由横拖板，小刀架，刀架鞍板和溜板箱组成。

?The cross slide is mounted on the dovetail guideways on the top of the saddle and it moved back and forth at 90°to the axis of the lathe by the cross slide lead screw. The lead screw can be hand or power activated.

?dovetail 燕尾槽

横拖板安装在刀架鞍板上部的燕尾槽导轨上。它利用横拖板丝杠于车床轴线成90度夹角的方向上前后移动。丝杠可以手动或者自动驱动。

?The compound rest is mounted on the cross slide and can be swiveled and clamped at any angle in a horizontal plane. The compound is typically used for cutting chamfers or tapers, but must also be used when cutting thread. The compound rest can only be fed by hand. There is no power to compound rest. The cutting tool and tool holder are secured in the tool post which is mounted directly to the compound rest.

?swivel ['sw?v?l] v.旋转

小刀架安装在横拖板上，它可以在水平面内转动或夹紧在任意角度位置。小刀架主要用来倒角和加工锥面，在车削螺纹时也必须用到小刀架。小刀架只能手动进给，没有动力传到小刀架上。刀具和刀夹被卡紧在直接安装在小刀架上的刀座上。

The tool saddle is an H shaped casting mounted on the top of the guideways and houses the cross slide and compound rest. It makes possible longitudinal, cross and angular feeding of the tool bit. ?刀架鞍板是一个安装在导轨上部的H形铸件，容纳有横拖板和小刀架。它可以实现刀尖的纵向、横向和斜向进给。

The apron is attached to the front of the carriage and contains the gears and feed clutches which transmit motion from the feed rod or lead screw to carriage and cross slide. When cutting screw threads, power is provided to the gearbox of the apron by the lead screw. In all other turning operations, it is the feed rod that drives the carriage.

?溜板箱位于拖板的前端，里面装有齿轮和将运动从光杠或丝杠传递至拖板或横向拖板的进给离合器。当切制螺纹时，动力通过丝杠传递到溜板箱中的变速齿轮箱。在其它车削加工时，依靠光杠来驱动拖板。

?Tailstock is composed of a low base and the movable part of the tail-stock proper, the transverse adjustments being made with a cross screw furnished with a square head. The two parts are hold together by the holding-down bolts which secure the tailstock to the bed.

?transverse adj. 横向的，横切的；n. 横轴

?holding-down bolts 压紧螺栓

尾座由底座和尾座体的可移动部件组成。课移动部件的横向调整有带有四方头的横向丝杠来完成。底座和可移动部分通过压紧螺栓连接在一起并将尾座固定在床身上。

6.1

Traditional or conventional machining, such as turning, milling, and grinding etc.,

uses mechanical energy to shear metal against another substance to create holes or remove material. Non-traditional machining processes are defined as a group of processes that

remove excess material by various techniques involving mechanical, thermal, electrical or chemical energy or combinations of these energies but do not use a sharp cutting tool as it

is used in traditional manufacturing processes. 传统的或常规的加工，如车削，铣削，磨削等，利用机械能剪金属与另一个物质创造孔或删除材料。非传统加工工艺被定义为一组过程清除多余的材料的各种技术，涉及机械，热，电或化学能源或组合这些能量，但不要用锋利的切割工具，它采用的是传统的制造工艺

[1]

Extremely hard and brittle materials arc difficult to be machined by traditional

machining processes. Using traditional methods to machine such materials means

increased demand for time and energy and therefore increases in costs; in some cases traditional machining may not be feasible. Traditional machining also results in tool wear

and loss of quality in the product owing to induced residual stresses during machining.

Non-traditional machining processes, also called unconventional machining process or advanced manufacturing processes, are employed where traditional machining processes

are not feasible, satisfactory or economical due to special reasons as outlined below:

非常硬脆材料难加工的传统加工过程。用传统方法加工的材料需求增加的时间和精力，因此成本增加；在某些情况下

传统加工可能是不可行的。传统加工也导致刀具磨损质量损失在产品由于加工引起的残余应力。非传统加工工艺，又称为非常规加工过程或先进的制造工艺，采用传统的加工工艺是不可行的，令人满意的或经济由于特殊原因概述如下：

1. Very bard fragile materials difficult to clamp for traditional machining;很难夹巴德脆性材料加工；

2. When the workpiece is too flexible or slender,当工件太灵活或纤细，

3. When the shape of the part is too complex;当形状的部分是太复杂；

4. Parts without producing buns or inducing residual stresses.无生产面包或诱导残余应力。Traditional machining can be defined as a process using mechanical (motion) energy.

Non-traditional machining utilizes other forms of energy; the three main forms of energy

used in non-traditional machining processes are as follows:传统加工可以被定义为一个过程中使用机械（运动）的能量。特种加工利用其他形式的能量；三种主要形式的能量用于非传统加工工艺如下：

1. Thermal energy;热能量；

2. Chemical energy-化学能,

3. Electrical energy.电力能源

Several types of non-traditional machining processes have been developed to meet

extra required machining conditions. When these processes are employed properly, they

offer many advantages over traditional machining processes. The common non-traditional machining processes are described in the following section.几种类型的非传统加工工艺已满足

额外所需的加工条件。当这些过程是正确使用，他们提供了许多优势，传统的加工工艺。常见的非传统

加工过程是描述在下面的部分。

6.2 Electrical Discharge Machining (EDM)电火花加工（电火花）

Electrical discharge machining (EDM) sometimes is colloquially referred to as spark machining, spark eroding, burning, die sinking or wire erosion. It is one of the most

widely used non-traditional machining processes. The main attraction of EDM over

traditional machining processes such as metal cutting using different tools and grinding is

that this technique utilizes thermoelectric process to erode undesired materials from the

workpiece by a series of rapidly recurring discrete- electrical sparks between workpiece

and electrode.电火花加工（电火花）有时是通俗称为火花机械加工，电火花加工，燃烧，开模或侵蚀。这是一个最

广泛使用的非传统加工工艺。主要景点的电火花加工过传统加工工艺等金属切削用不同的工具和研磨这种技术利用热电过程不受欢迎的材料的侵蚀工件通过一系列的快速离散-电火花加工和电极。

[2]

The traditional machining processes rely on harder tool or abrasive material to

remove the softer material whereas non-traditional machining processes such as EDM

uses electrical spark or thermal energy to erode unwanted material in order to create

desired shapes. So, the hardness of the material is no longer a dominating factor for EDM process.传统的加工工艺很难依靠工具或研磨材料拆下软的材料，而非传统加工工艺如电火花使用电火花或热能量侵蚀有害物质为创造所需的形状。因此，材料的硬度不再是一个主导因素电火花过程。

EDM removes material by discharging an electrical current, normally stored in a

capacitor bank, across a small gap between the tool (cathode) and the workpiece (anode) typically in the order of 50 volts/l0 amps. As shown in Fig-6. 1, at the beginning of EDM operation, a high voltage is applied across the narrow gap between the electrode and the workpiece. This high voltage induces an electric field in the insulating dielectric that is

present in narrow gap between electrode and workpiece. This cause conducting particles suspended in the dielectric to concentrate at the points of strongest electrical field. When

the potential difference between the electrode and the workpiece is sufficiently high ,the dielectric breaks down and a transient spark discharges through the dielectric fluid,

removing small amount of material from the workpiece surface. The volume of the

material removed per spark discharge is typically in the range of 10-5 to 10-6 mm3. The gap

is only a few thousandths of an inch, which is maintained at a constant value by the servomechanism that actuates and controls the tool feed.电容器组，在一个小的差距之间的工具（阴极）和工件（阳极）通常在50伏特/ 10安培。如在fig-6。1年初，电火花加工经营，高电压应用于缩小之间的差距电极和工件。这种高电压诱导电场绝缘介质是目前在窄间隙的电极与工件之间。这导致导电粒子悬浮介质中的集中点的最大电场。什么时候

电位差的电极与工件之间的足够高，介质崩溃和一个短暂的火花放电通过流体介质，除少量材料从工件表面。体积的

材料去除每火花放电通常范围在10 - 5到10 - 6毫米。差距只有千分之几

7.1 Introduction

Quality and accuracy are major considerations in making machine parts or structures. Interchangeable parts require a high degree of accuracy to fit together. With increasing accuracy or less variation in the dimension, the labor and machinery required to

manufacture a part is more cost intensive.[l] Any manufacturer should have a thorough knowledge of the tolerances to increase the quality and reliability of 'a manufactured part

with the least expense.质量和精度的主要因素在制造机器零件或结构。零件的互换性要求高精度的配合。随着越来越多的准确性或少变化的尺寸，劳动和机械要求制造一个部分是成本密集。[ 1 ]任何厂商应该有一个透彻的

知识的公差，提高质量和可靠性的一部分用最少的费用。

An engineering drawing must be properly dimensioned in order to convey the

designer's intent to the end user. Dimensions of parts given on blueprints and

manufactured to those dimensions should be exactly alike and fit properly. Unfortunately,

it is impossible to make things to an exact or dimension. Most dimensions have a varying degree of accuracy and a means of specifying acceptable limitations in dimensional

variance so that a manufactured part will be accepted and still function. It is necessary that

the dimensions, shapes and mutual position of surfaces of individual parts are kept within

a certain accuracy to achieve their correct and reliable functioning. Routine production processes do not allow maintenance (or measurement) of the given geometrical properties

with absolute accuracy.工程图纸必须是适当的尺寸来传达设计师的意图最终用户。在图纸和零件尺寸制造这些方面应该是完全一样的，好的。不幸的，这是不可能让事情精确或尺寸。大多数方面有不同的程度的准确性和可接受的限制手段指定尺寸方差，制造部分将被接受和功能仍然。这是必要的尺寸，形状和相互位置的表面上的个别部分被保持在一定的精度，实现正确的和可靠的运作。日常生产过程不允许维持（或测量）的几何性质绝对精度

[2] Actual surfaces of the produced parts therefore differ from实际表面产生不同的部位

ideal surfaces prescribed in drawings. Deviations of actual surfaces are divided into four

groups to enable assessment, prescription and checking of the permitted inaccuracy during production:理想的表面在图纸规定。偏差的实际表面分为四组，使评估，处方和检查的允许误差在生产：

1. Dimensional deviations;尺寸偏差；

2. Shape deviations;形状偏差；

3. Position deviations;位置偏差

4. Surface roughness deviations.表面粗糙度偏差。

As mentioned above, it is principally impossible to produce machine parts with

absolute dimensional accuracy. In fact, it is not necessary or useful. It is quite sufficient

that the actual dimension of the part is found between two limit dimensions and a

permissible deviation is kept with production to ensure correct functioning of engineering products. The required level of accuracy of the given part is then given by the dimensional tolerance which is prescribed in the drawing. The production accuracy is prescribed with regards to the functionality of the product and to the economy of production as well. The principal factor used to set a tolerance for a dimension should be the function of the

feature being controlled by the dimension. Unnecessarily tight tolerances lead to high cost

of manufacture resulting from more expensive manufacturing methods and higher reject

rates.如上所述，它主要是不可能产生的机械零件绝对尺寸精度。事实上，它是不必要或有用。这是很充分的

，零件的实际尺寸是两国之间的极限尺寸和允许偏差是确保正确的运作与生产工程产品。所需的准确度的特定部分给出的尺寸宽容是在绘图。生产精度是明关于该产品的功能和经济的生产等。本主要用于设置一个公差尺寸应该是功能的特征所控制的尺寸。不必要的紧公差导致成本高制造更昂贵的制造方法和较高的拒绝率。

7 2 Tolerances公差

Tolerance is the total amount that a specific dimension is permitted to vary. It is the

difference between the maximum and the minimum limits for the dimension. To

understand tolerances, you should understand some of the definitions associated with the determination of a tolerance. These definitions may be generally categorized as relating to size, allowance, or fit.宽容的总金额，具体尺寸允许有所不同。它是之间的差异最大和最小极限尺寸。到理解公差，你应该了解一些定义与测定误差。这些定义大致可归类为有关大小，补贴，或适合。

Size. The size of an object or its mate is (mown as nominal, basic, or design size.

Allowance. The difference between the largest allowable shaft size and the smallest

hole diameter is termed as the allowance. [3] The quality of the fit is characterized by the allowance value.大小。物体的大小或其配偶（割的名义，基本设计，或大小。津贴。之间的差异最大允许轴尺寸和最小的孔直径被称为津贴。[ 3 ]符合质量的特点是津贴的价值。

Fit. clearance, interference, or transition fit refer to how the object 'its ski

assembly.适合的。清除，干扰，或过渡配合指对象“滑雪组件。

To specify the size of an object, we dimension it with a nominal size, basic size, and

actual size shown in Fig.7.1.指定对象的大小尺寸，我们用公称尺寸，基本尺寸，和实际尺寸显示在fig.7.1。

Nominal size (basic size). It is the designation used for general identification and

usually expressed in common fractions. It is an exact theoretical size of a part from which

limit dimensions are computed. The nominal size of a part should be selected from the preferred dimension series indicated by the national standard.(4J (shown in Fig.7.Ia)

limit size. It includes upper limit size and lower limit size which are allowable extreme

sizes of a part Fox example, the limits for a hole arc 1500 (lower limit) and 1.501 (upper

limit) and for a shaft I .499 (upper limit) and 1.497 (lower limit), shown in Fig.7. I b.

Actual size. It is the measured size of the finished part, shown in Fig.7.Ic.l公称尺寸（基本尺寸）。它是一般用于鉴定和命名通常表示分数。这是一个确切的理论的一部分，极限尺寸的计算。标称尺寸的一部分，应选择从首选尺寸系列的国家标准。（4j（显示在图7。自动化）极限尺寸。它包括上限和下限尺寸大小是容许极限狐狸大小的部分，限制洞弧1500（下限）和1.501（上限制）和一个轴我。499（上限）和1.497（下限），显示在图7。我B实际尺寸。它是衡量大小的成品，显示在图7。我集成电路。

Deviations, allowance refer to size allowable variations.

Deviations. The upper and lower deviations obtained by subtracting basic size from

limit size. For example, a hole dimensioned as 2.000.0004, thus upper deviation is

+0.0004 and lower deviation is -0.0004.

Allowance. The intentional difference between the maximum material limits of

mating parts. This is a minimum clearance (positive allowance) or maximum interference (negative allowance) between mating parts.

Tolerances can be expressed in either of two ways.

Bilateral Tolerances. A bilateral tolerance is a tolerance in which variation is

permitted in both directions from a specified dimension. Examp1e is 2.00010.0004. For

this expression, the dimension of the part would be permitted to vary between 1.996 and

2.004 for a total tolerance of 0.008.

The actual size of the object may be larger or smaller than the stated size limitation if

there can be equal variation in both directions. The plus and minus limitations combine to

form a single value.[5J

Unilateral Tolerances. A unilateral tolerance is a tolerance in which variation is

permitted only in one direction from the specified dimension. Example is 2.OOO;" For

this expression. the dimension of the part would be permitted to vary between 2.000 and

2.008 for a total tolerance of 0.008.

Unilateral tolerance expression has the advantage that they are easier to check on

drawings and that the change in the tolerance can be made with the least disturbance to

other dimensions.

7 3 Fits

How mating parts or assemblies fit together with component parts is referred to as fit,

which includes clearance fit, interference fit, or transition fit, see Fig. 7.3.

Fit is the general range of tightness resulting from the application of a specific

combination of allowance and tolerances in the design of mating parts.

Clearance fit. It is a fit enabling a clearance between the hole and shaft in the

coupling. The lower limit size of the hole is greater or at least equal to the upper limit size

of the shaft.

lnterfertnee fit It is a fit always ensuring some interference between the hole and

shaft in the coupling. The upper limit size of the bole is smaller or at least equal to the lower limit size of the shaft.

Transition fit. It is a fit where (depending on the actual sizes of the hole and shaft)

both clearance and interference may occur in the coupling. Tolerance zones of the hole and shaft partly or completely interfere.

8.1 Introduction

To ensure that the workpiece is produced according to the specified shape,

dimensions and tolerances, it is essential that workplace should be appropriately located and clamped on the machine tool.[11 Production devices are generally workholders

with/without tool guiding/setting arrangement These are called jigs and fixtures. A fixture is a production tool that locates, holds and supports the workpiece securely so that each part is machined within the specified limits. It must correctly locate a work-piece in a given orientation with respect to a cutting tool or measuring device, or with respect to another component, as for instance in assembly. Such location must be invariant in the sense that the devices must clamp and secure the workpiece in that location for the particular processing operation. Fixtures are generally used in machining (milling, planning, shaping and turning, etc.) and other manufacturing operations, such as welding, heat treatment, machining inspection and assembly etc. Jigs are provided with tool guiding elements such as drill bushes. They direct the tool to the c erect position on the workpiece. Jigs are rarely clamped on the machine table because it is necessary to move the jig on the table to align the various bushing in the jig with the machine spindle.

8.2 Advantages of Jigs and Fixtures

Productivity. Jigs and fixtures eliminate individual marking, positioning and

frequent checking, which reduces operation time and increase productivity. Interchangeability. Jigs and futures facilitate uniform quality in manufacture. There

is no need for selective assembly. Any part of machine fits properly in assembly and all similar components are interchangeable

Skill reduction. Jigs and fixtures simplify locating and clamping of the workpieces.

Tool guiding elements ensure correct position of the tools with respect to the workpieces.

There is no need for skillful setting of the workpiece of tool. Any average person can be trained to use jigs and fixtures, the replacement of a skilled workman with unskilled labor can effect substantial saving in labor cost.

Cost reduction. Higher production rate, reduction in scarp, easy assembly and

savings in labor costs result in substantial reduction in the cost of workpieces produced with jigs and fixtures.

8.3 TM Location of The Workpiece

A body that is completely free in space has twelve degrees of freedom shown in Fig.8.l.

It can rotate about or have linear movement along each of the three mutually perpendicular axes XX. YY or IZ, so it has six freedoms of rotation and six freedoms of translation.[2] When workpiece is located, it must be constrained from moving in any direction, so these freedoms are eliminated or restricted to ensure that the operation is performed with the required accuracy. This can be done by six locations in the case of the body shown in Fig.8.1, which is known as six-point locating principle. It is illustrated in Fig.8.2.

The bane of the component is resting on three locating pins which is the minimum number of points upon which it will foxily seat. The three adjacent locating surfaces of the workpiece art resting against 3, 2 and I pint respectively, which prevent 9 degrees of freedom. The test three degrees of freedom are arrested by three external forces usually provided directly by clamping. Some of such forces may be attained by friction. If more than six points art used, the additional points will be surplus and unnecessary and would therefore be redundant constraints.

There are three general forms of location: plane, concentric, and radial.[3] Plane locators locate a workpiece from any surface. The surface may be flat, curved, or have an irregular contour. In most applications, plane-locating devices locate a part by its external surfaces, Fig.8.3a. Concentric locators, for the most part, locate a workpiece from a central axis. This axis may or may not be in the center of the workpiece. The

most-common type of concentric location is a locating pin placed in a bole. Some workpieces, however, might have a cylindrical projection that requires a locating hole in the fixture, as shown in Fig.8.3b. The third type of location is radial. Radial locators restrict the movement of a workpiece around a concentric locator, Fig.8.3c. In many cases, locating is performed by 4 combination of the three locating methods.

In machining practice, depending on concrete requirements, not all the twelve degrees

of freedom are necessary to be restricted.[4] In Fig.8.4a, on the workpiece, a slot should be machined and so its freedom of movement in all directions should be restricted. In

Fig-8.4b, however, the machining of a stepped surface needs only ten degrees of freedom being restricted. And from Fig-8.4c, it can be seen that since only the upper surface should be machined (e.g., 2 surface grinding), restricting three degrees of freedom is enough. Another condition to avoid in workholder design is redundant or duplicate location. Redundant locators restrict the same degree of freedom more than once. The workpieces. in Fig.8.5 show several examples. The part at Fig.8.Sa shows bow a flat surface can be redundantly located. The part should be located on only one, not both, side surfaces. Since the sizes of parts can vary, within their tolerances. 7be example at Fig. 8.Sb points out the same problem with concentric diameters. Either diameter can locate the part, but not both. The example at Fig.8.Se shows the difficulty with combining bole and surface location. Either locating method, locating Qom the holes or from the edges, works well if used alone. When the methods are used together, however, they cause a duplicate condition. The condition may result in parts that cannot be loaded or unloaded as intended.

9.1

A gear drive system is one where a motor turns a series of gears to do work. It plays a very important role of transmitting power, achieving conveying and adjusting torque in numerous industrial equipment like machine tool, automobile, engineering machinery, agricultural machinery and construction machinery.

In general gear drive is useful for power transmission between two shafts which are

near to each other (at most at 1 m distance) ) and also it has maximum efficiency. The gear that supplies the power is called the input gear and the gear that does the actual work at the other end of the gear drive is the output gear. While transmitting power, it is durable compare to other drive systems such as belts, chain drives etc.

Gears are compact, positive-engagement power transmission elements in gearing transmission; they determine the speed, torque, and direction of rotation of driven machine elements.[l] Gear types may be grouped into five main categories: Spur, Helical, Bevel, Hypoid, and Worm. Typically, shaft orientation, efficiency, and speed determine which of these types should be used for a particular application. This section on gearing and gear drives describes the major gear types; it evaluates how the various gear types are combined into gear drives and considers the principal factors that affect gear drive.

9.2

Spur gears have straight teeth cut parallel to the rotational axis. The tooth form is

based on the involute curve shown in Fig.9.1. Practice has shown that this design accommodates mostly rolling rather than sliding contact of the tooth surfaces.[2] The involute curve is generated during gear machining processes using gear cutters with straight sides.

Near the root of the tooth, however, the tool traces a trochoidal path, Fig.92,

providing a heavier, and stronger, root section. Because of this geometry, contact between the teeth occurs mostly as rolling rather than sliding. Since less heat is produced by this rolling action, mechanical efficiency of spur gears is high, often up to 99%. Some sliding does occur, however. And because contact is simultaneously across the entire width of the meshing teeth, a continuous series of shocks is produced by the gear. These rapid shocks result in some objectionable operating noise and vibration.[3] Moreover, tooth wear results from shock loads at high speeds. Noise and wear can be minimized with proper lubrication. Spur gears are the least expensive to manufacture and the most commonly used, especially for drives with parallel shafts. The three main classes of spur gears are: external tooth, internal tooth, and rack-and-pinion.

External-tooth gear,. The most common type of spur gear, Fig.9.3, has teeth cut on

the outside perimeter of mating cylindrical wheels, with the larger wheel called the gear and the smaller wheel the pinion. The simplest arrangement of spur gear, is a single pair

of gears called a single reduction stage, where output rotation is in a direction opposite that of the input In other words, one is clockwise while the other is counter-clockwise. Higher net reduction is produced with multiple stages in which the driven gear is rigidly connected to a third gear. This third gear then drives a mating fourth gear that serves as

output for the second stage. In this manner, several output speeds on different shafts an

be produced from a single input rotation.

Internal (ring) Gears. Ring gears produce an output rotation that is in the same

direction as the input, Fig.9.4. As the name implies, teeth are cut on the inside surface of a cylindrical ring, inside of which are mounted a single external-tooth spur gear or set of external-tooth spur gees, typically consisting of three or four larger spur gears (planets) usually surrounding a smaller central pinion (sun). Normally, the ring gear is stationary, causing the planets to orbit the sun in the same rotational direction as that of the sun. For this reason, this class of gear is often *referred to as a planetary system. The orbiting motion of the planets is transmitted to the output shaft by a planet carrier. In an alternative planetary arrangement, the planets may be restrained to orbit the sun and the ring left free to move. 'This causes the ring gear to rotate in a direction opposite that of the sun. By allowing both the planet carrier and the ring gear to rotate, a differential gear drive is produced, the output speed of one shaft being dependent on the other.

Rack-and-pinion gears. A straight bar with teeth cut straight across it, Fig. 9.5, is

called a rack. Basically, this rack is considered to be a spur gear unrolled and laid out flat. Thus, the rack-and pinion is a special case of spur gearing. The rack-and-pinion is useful in converting rotary motion to linear and vice versa. Rotation of the pinion produces linear travel of the rack. Conversely, movement of the rack causes the pinion to rotate. The

rack-and-pinion is used extensively in machine tools, lift trucks, power shovels, and other heavy machinery where rotary motion of the pinion drives the straight-line action of a reciprocating part. Generally, the rack is operated without a sealed enclosure in these applications, but some type of cover may be provided to keep dirt and other contaminants from accumulating on the working surfaces. [4]

9.3 Helical Gears .

Helical gearing differs from spur gearing in that helical teeth arc cut across the gear

face at an angle rather than straight, Fig.9.6. Thus, the contact line of the meshing teeth progresses across the face from the tip at one end to the root of the other, reducing the noise and vibration characteristic of spur gears. Also, several teeth are in contact at any one time, producing a more gradual loading of the teeth that reduces wear substantially. The increased amount of sliding action between helical gear teeth, however, places greater demands on the lubricant to prevent metal-to-metal contact and resulting premature gear failure, Also, since the teeth mesh at an angle, a side thrust load is produced along each gear shaft. Thus, thrust bearings must be used to absorb this load so that the gears are held in proper alignment.

10.1

The word "hydraulics" generally refers to power produced by moving liquids, which

also means an application of fluid mechanics to engineering devices involving liquids, usually water or oil. [1] Hydraulics deals with such problems as the flow of fluids through pipes or in open channels, the design of storage dams, pumps, and water turbines, and

with other devices for the control or use of liquids, such as nozzles,* valves, jets, and flowmeters, etc.[2] Modem hydraulics is defined

as the use of confined liquid to transmit power,

multiply force, or produce motion. Though

hydraulic power in the form of water wheels and

other simple devices has been in use for

centuries, the principles of hydraulics weren't

formulated into scientific law until the 17th

century. It was then that French philosopher

Blaise Pascal discovered that liquids cannot be compressed. He discovered a law which states: pressure applied on a confined fluid is transmitted in all directions with equal force on equal areas. To better understand Pascal's Law, let's use a bottle full of liquid as an example shown in Fig. 10.1. Let's say the bottle has a 1 square inch opening. If we were to apply 10 pounds of force on a cork at the opening, 10 pounds of force would be applied equally to all sides of the bottle. This is expressed as 10 psi or 10 pounds of force per square inch. So 10 psi represents the fluid pressure of the system.

A hydraulic or hydraulic power transmission is a drive- or transmission system that

uses a hydraulic fluid under pressure to drive machinery. Such a system basically consists of (shown in Fig.10.2):

Generator part of the transmission. In general a hydraulic pump, driven by an

electric motor, a combustion engine or a windmill.

Valves, filters, piping etc. To guide and control the system.

Actuator part of the transmission. A hydraulic motor or hydraulic cylinder to

converts hydraulic energy into mechanical energy to drive the machinery.

10.2 Hydraulic Pump

When a hydraulic pump operates, it performs two functions. First, its mechanical

action creates a vacuum at the pump inlet which allows atmospheric pressure to force liquid from the reservoir into the inlet line and then to the pump. Second, its mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.

A pump produces liquid movement or flow: it does not generate pressure. It produces

the flow necessary for the development of pressure which is a function of resistance to fluid flow in the system. For example, the pressure of the fluid at the pump outlet is zero for a pump not connected to a system (load). Further, for a pump delivering into a system, the pressure will rise only to the level necessary to overcome the resistance of the load.

All pumps may be classified as either positive-displacement or non-positive-displacement Most pumps used in hydraulic systems are positive-displacement.[3]

A positive-displacement pump is one that displaces (delivers) the same amount of

liquid for each rotating cycle of the pumping element Constant delivery during each cycle is possible because of the close-tolerance fit between the pumping element and the pump case. That is, the amount of liquid that slips the pumping element in a positive-displacement Pump is minimal and negligible compared with the theoretical maximum possible delivery. The delivery per cycle remains almost constant, regardless of changes in pressure against

which the pump is working. Note that if fluid slippage is substantial, the pump is not operating properly and should be repaired or replaced.

Positive-displacement pumps can be of either fixed or variable displacement. The

output of a fixed displacement pump remains constant during each pumping cycle and at a given pump speed. The output of a variable displacement pump can be changed by

altering the geometry of the displacement chamber.

The positive-displacement principle is well illustrated in the reciprocating-type pump,

the most elementary positive-displacement pump, Fig.l0.3. As the piston extends, the partial vacuum created in the pump chamber draws liquid from the reservoir through the inlet check valve into the chamber. The partial vacuum helps seat firmly the outlet check valve. The volume of liquid drawn into the chamber is known because of the geometry of the pump case, in this example, a cylinder.

As the piston retracts, the inlet check valve reseats, closing the valve, and the force of

the piston unseats the outlet check valve, forcing liquid out of the pump and into the system. The same amount of liquid is forced out of the pump during each reciprocating cycle.

All positive-displacement pumps deliver the same volume of liquid each cycle (regardless of whether they are reciprocating or rotating). It is a physical characteristic of the pump and does not depend on driving speed. However, the faster a pump is driven, the more total volume of liquid it will deliver.

11.1 Introduction

Direct-drive technology contributes to higher machine (or system) throughput with

quicker acceleration and higher top speeds compared with gear-or belt-driven designs.[l] Also, the motor has no brushes to replace. In direct-drive motion, the motor is directly connected to its driven load without intervening ball screws, pulleys, gearboxes, timing belts, or other components. Numerous manufacturers displayed direct-drive motion technology either in the form of low-speed rotary motors or high-speed linear motors.

11. Direct-Drive linear (DDL) Motion

This distinct motion technology eliminates all rotary-to-linear conversion devices

between motor and load-such as ball screws, gear boxes, rack-and-pinions, and belts, to obtain high-dynamic performance in a growing number of applications.

DDL motors. Core of a typical DDL system is the linear motor. Linear motors are a

special class of synchronous brushless servo motor. They work like rotary motors, but are opened up and rolled out flat. Through the electromagnetic interaction between a coil assembly (primary part) and a permanent magnet assembly (secondary part), the electrical energy is converted to linear mechanical energy with a high level of efficiency.[2] Other common names for the primary component are motor, moving part, slider or glider, while the secondary part is also called magnetic way or magnet track Several linear motor design variants exist.

Three DDL Motors. (See Fig. 11.1 and Fig.11.2) Different manufacturing groups have

specialized in one or another of three basic linear motor configurations-flat bed, U-channel and tubular. Each motor has its intrinsic advantages and limitations, but drawbacks specific to one motor type can often be sidestepped by using either of the two alternatives.

Flat bed motors, while offering unlimited travel and the highest drive force, exert considerable and undesirable magnetic attraction between the load carrying forcer and the motor's permanent magnet track. This attraction force requires bearings that support the extra load.

With its ironless core, the U-channel motor has low inertia and thus maximum agility. However, the forcer's load carrying magnetic coils travel deep within the U-Channel frame, restricting beat removal. [3]

The simplest to install, tubular linear motors are' rugged and thermally efficient. Furthermore, they provide drop-in replacements for ballscrew and pneumatic positioners. The tubular motor's permanent magnets are encased in a stainless steel tube (Thrust Rod), which is supported at both ends. Without additional thrust rod support, load travel is limited to 2 to 3 meters, depending on Thrust Rod diameter.

Mature, yet advancing. Bosch Rexroth, Electric Drives and Controls Division, regards

DDL motor systems to be a mature technology, yet one that continues to make incremental advancements. [4) The company cites examples, such as improved coolant jacket designs that minimize temperature differential between stator and machine bed, optimized magnet shapes to reduce force ripple and material cost, and magnet tracks protected by stainless steel covers supplied pre-assembled in various lengths, to case system installation and operation.

Some functions, such as force /torque ripple compensation, nanometer-level interpolation, and ultra-high resolution sinusoidal feedback, are said to result in superior dynamic/static stiffness and motion accuracy.[5] Additionally, automatic commutation functions can eliminate the need for absolute feedback or Hall-effect sensor boxes, although they're supported as well.

Another feature is enhanced vibration suppression, which reduces machine resonance

and settling time. It also eliminates vibration due to machine resonance and load disturbances. This function automatically detects and suppresses oscillation frequencies under I kHz. A notch filter is also available to control frequencies of 1 kHz and above.

Advantages. Manufacturers have moved beyond specialized semiconductor industry

usage to provide advanced performance in a host of applications. In fact, with ten times the speed and ten times the operating life of ballscrews, linear direct drive technology is often the only solution to modem productivity-enhancing automation.

Linear direct drives offer the following advantages over conventional solutions for generating linear motions consisting of a rotary motor and a mechanical power transmission Component:

1. Much higher velocities;

2. Much higher acceleration;

3. Much higher positioning accuracy without overshoot;

4. Direct force build-up;

S. Maintenance-free, backlash-free drive;

6. High static and dynamic stiffness under load;

7. Control loop stability due to optimal mass snatching.

12.1 Introduction

One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC). Prior to the advent of NC, all machine tools were manually operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related and limited to the skills of the operator. Numerical control represents the first major step away from human control of machine tools.

12.3/NC and CNC

Numerical control means the control of machine tools and' other manufacturing systems through the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool. An NC machine toot 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 undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tools and processes.

The original NC systems were vastly different from those used today. The machines

had hardwired logic circuits. The instructional programs were written on punched paper, which was later replaced by magnetic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. The development of a concept known as direct numerical control (DNC) solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. [I] In direct numerical control, machine tools are tied ,via a data transmission link, to a boss computer. Programs for operating the machine tools are stored in the host computer and fed to the machine tool as needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the host computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control.

The development of the microprocessor allowed for the development of programmable logic controllers (PLCs) and microcomputers.(21 These two technologies allowed for the development of computer numerical control (CNC). With CNC, each machine tool has a PLC or a microcomputer that serves the same purpose. This allows programs to be input and stored at each individual machine tool. It also allows programs to be developed off-line and downloaded to the individual machine tool. CNC solved the problems associated with downtime of the host computer, but it introduced another problem known as data management The same program might be loaded to ten different microcomputers with no communication among them. This problem is in the process of being solved by local area networks that connect microcomputers for better data management.

12.3 Construction of CNC Machines

CNC machine tools are complex assemblies. In general, any CNC machine tool

consists of the following units:

1. Computers;

2. Control systems;

3. Drive motors;

4. Tool changers.

According to the construction of CNC machine tools, CNC machines work in the following (simplified) manner.

1. The CNC machine control computer reads a prepared program and translates it into machine language, which is a programming language of binary notation used on computers, not on CNC machines.

2. When the operator starts the execution cycle, the computer translates binary codes

into electronic pulses which are automatically sent to the machine's power units.

The control units compare the number of pulses sent and received.

3. When the motors receive each pulse, they automatically transform the pulses into rotations that drive the spindle and lead screw, causing slide or table movement The

part on the milling machine table or the tool in the lathe turret is driven to the

position specified by the program.[3)

Computers. CNC machines use an on-board computer that allows the operator to

read, analyze, and edit programmed information, while NC machines require operators to make a new tape to alter a program. In essence, the computer is what distinguishes CNC from NC.

As with all computers, the CNC machine computer works on a binary principle using only two characters, I and 0. for information processing. The computer reacts on precise time impulses from the circuit. There are two states, a state with voltage, I and a state without voltage, 0. Series of ones and zeroes are the only states that the computer distinguishes. called machine language, it is the only language the computer understands. When creating the program, the programmer does not care about the machine language; he or she simply uses a list of codes and keys in the meaningful information. Special built-in software compiles the program into machine language and the machine moves the tool by its servomotors.[4]

Modern CNC machine use 32-bit processors in their computers that allow fast and accurate processing of information. Ms results in savings of machining time.

Control Systems. There are two types of control systems on NCICNC machines:

open-loop and closed-loop. The overall precision of the machine is determined by the type of control loop used

The open-loop control system does not provide positioning feedback to the control

unit. The movement pulses are sent out by the control and received by a special type of servomotor called a stepping motor. The number of pulses that the control sends to the stepping motor controls the amount of the rotation of the motor. The stepping motor then proceeds with the next movement command. Since this control system only counts pulses and cannot identify the discrepancies in positioning, the control has no way of knowing

that the tool did not reach the proper location. The machine will continue this inaccuracy until somebody finds the error.

The open-loop control can be used in applications in which there is no change in load conditions, such as NC drilling machine. The advantage of the open-loop control system is that it is less expensive, since it does not require the additional hardware and electronics needed for positioning feedback. The disadvantage is the difficulty of detecting a positioning error.

In the closed-loop control system, the electronic movement pulses are sent from the control to the servomotor, enabling the motor to rotate with each pulse. The movements are detected and counted by a feedback device called transducer. With each step of movement, a transducer sends a signal back to the control, which compares the current position of the driven axis with the programmed position. When the numbers of pulses sent and received match, the control starts sending out pulses for the next movement. Closed-loop systems are very accurate. Most have an automatic compensation for error, since the feedback device indicates the error and the control makes the necessary adjustments to bring the slide back to the position. They use AC, DC, or hydraulic servomotors.

Drive Motors. The drive motors control the machine slide movement on NC/CNC equipment.

They come in four basic types:

1. Stepping motors;

2. DC servomotors;

3. AC servomotors;

4. Fluid servomotors.

Stepping Motors convert a digital pulse, generated by the microcomputer unit (MCU), into a small step rotation. Stepping motors have a certain number of steps that they can travel. The number of pulses that the MCU sends to the stepping motor, controls the amount of the rotation of the motor. Stepping motors are mostly used in applications where low torque is required.

Stepping motors are used in open-loop control systems, while AC, DC, or hydraulic servomotors are used in closed-loop control systems.

Direct Current (DC) servomotors are variable-speed motors that rotate in response to

the applied voltage. They are used to drive a lead screw and gear mechanism. DC servos provide higher-torque output than stepping motors.

Alternative Current (AC) servomotors are controlled by varying the voltage

frequency to control speed. They can develop more power than a DC servo. They are also used to drive a lead screw and gear mechanism.

Fluid, or hydraulic, servomotors are also variable speed motors. They are able to produce more power, or more speeds in the case of pneumatic motors, than electric servomotors.

Tool Changers. Most of the time, several different cutting tools are used to produce a

part The tool must be replaced quickly for the next machining operation. For this reason, the majority of NGCNC machine tools are equipped with automatic tool changers, such as magazines on machining centers and turrets on turning centers (Fig. 12.1).They allow

tool changing without the intervention of the operator. Typically, an automatic tool changer grips the tool in the spindle, pulls it out, and replaces it with another tool. On

most machines with automatic tool changers, the turret or magazine can rotate in either direction, forward or reverse.

13.1

In 1968, an NC machine was marketed, which could automatically change tools, so

that many different processes could be done on one machine. Such a machine became

known as a "machining center"-a machine that can perform a variety of processes and change tools automatically while under programmable control. The computer-controlled machining centers have the required flexibility and versatility that other individual

machine tools do not have, so they often become the first choice in machine-tool selection.

In describing the individual machining processes and machine tools in Unit 5, it was

noted that each machine, regardless of how highly it is automated, is designed to perform basically the same type of operations, such as turning, boring, drilling, milling, broaching, planning, or shaping. Note, for example, that the parts shown in Fig. 13.1 have a variety of complex geometric features and that all of the surface on these parts require different

types of machining operations (such as milling, facing, boring, drilling, reaming, or threading) to meet certain specific requirements concerning shapes, features, dimensional tolerances, and surface finish.

If some form of machining is required or if it is needed to finish machine these parts

to their final shapes more economically, then it is obvious that none of the machine tools described in Unit 5 individually could produce these parts completely. We also note that, traditionally, machining operations are performed by moving the workpiece from one machine tool to another until all of the required machining operations are completed

13.2 The Concept of Machining Centers

The traditional method of machining parts using different types of machine tools has been and continues to be a viable and efficient manufacturing method. It can be highly automated in order to increase productivity, and it is indeed the principle behind transfer lines (also called dedicated manufacturing lines, ME). Commonly used in high-volume or mass production, transfer lines consist of several specific machine tools arranged in a logical sequence.

The workpiece (such as an automotive engine block) is moved from station to station

with a specific machining operation performed at each station, after which it is transferred

to the next machine for another specific machining operation, and so on. There are situations, however, where transfer lines are not feasible or economical, particularly when

the types of products to be processed are changed rapidly due to factors such as product demand or changes in product shape or style. It is a very expensive and time-consuming process to rearrange these machine tools to respond to the needs for the next production cycle. An important concept developed in the late 1950s is that of machining centers.

A machining center is an advanced, computer-controlled machine tool that is capable

of performing a variety of machining operations on different surfaces and different orientations of a workpiece without having to remove it from its workholding device or

fixture. The workpiece generally is stationary, and the cutting tools rotate as they do in milling, drilling, honing, tapping, and similar operations. Whereas in transfer lines or in typical shops and factories the workpiece is brought to the machine, note that in machining centers, it is the machining operation that is brought to the workpioce.

In referring to the word workpiece, we also should point out that the workpiece in a machining center also includes all types of tooling. Tooling can include forming and cutting tools, cutters and tool holders, tool shanks for holding tool inserts, molds for casting, male and female dies for forming, punches for metal-working and powder metallurgy, rams for extrusion, workholding devices, and fxturing-all of which also have to be manufactured. Since the geometries are often quite complicated and a variety of machining operations are performed, these tools arc produced commonly in machining centers.

14.1

If we examine the word control, we find several meanings given in the dictionary. e.g., command, direct, govern, and regulate. Thus, a control system may be regarded as a group of physical components arranged to direct the flow of energy to a machine or process in such a manner as to achieve the desired performance.

The word automatic means self-moving or self-acting; thus an automatic control

system is a self-acting control system.

An important distinction applied to control systems, whether automatic or otherwise,

is that between open-loop and closed-loop operation. Automatic control, including this distinction, can perhaps be best introduced by means of a simple example.

14.2 Open-Loop Control and Closed-Loop Control

In this example, let it be desired to maintain the actual water level c in the tank as

close as possible to a desired level r. The desired level will be called the system input, and the actual level the controlled variable or system output. Water flows from the tank via a valve V, and enters the tank from a supply via a control valve VV. The control valve is adjustable, either manually or by some type of actuator. This may be an electric motor or a hydraulic pneumatic cylinder. Very often it would be a pneumatic diaphragm actuator. In general, increasing the pneumatic pressure above the diaphragm pushes it down against a spring and increases valve opening.

Open-Loop Control. In this form of control, the valve is adjusted to make output c

equal to input r, but not readjusted continually to keep the two equal. Open-loop control, with certain safeguards added, is very common. For example, in the context of sequence control, that is, guiding a process through a sequence of predetermined steps. However,

for systems such as the one at hand, this form of control will normally not yield high performance. A difference between input and output, a system error e-r-c would be expected to develop, due to two major effects:

1. Disturbances acting on the system;

2. Parameter variations of the system.

These are prime motivations for the use of feedback control. For the water level example, pressure variations upstream of V and downstream of V, can be important distinbances affecting inflow and outflow, and hence the level. A sudden or gradual change of flow resistance of the valves due to foreign matter or valve deposits represents a

《机械工程专业英语教程》课文翻译

Lesson 1 力学的基本概念 1、词汇： statics [st?tiks] 静力学；dynamics动力学；constraint约束；magnetic [m?ɡ＇netik]有磁性的；external [eks＇t?:nl] 外面的, 外部的；meshing啮合；follower从动件；magnitude [＇m?ɡnitju:d] 大小；intensity强度，应力；non-coincident [k?u＇insid?nt]不重合；parallel [＇p?r?lel]平行；intuitive 直观的；substance物质；proportional [pr?＇p?:??n?l]比例的；resist抵抗，对抗；celestial [si＇lestj?l]天空的；product乘积；particle质点；elastic [i＇l?stik]弹性；deformed变形的；strain拉力；uniform全都相同的；velocity[vi＇l?siti]速度；scalar[＇skeil?]标量；vector[＇vekt?]矢量；displacement代替；momentum [m?u＇ment?m]动量； 2、词组 make up of由……组成；if not要不，不然；even through即使，纵然； Lesson 2 力和力的作用效果 1、词汇： machine 机器；mechanism机构；movable活动的；given 规定的，给定的，已知的；perform执行；application 施用；produce引起，导致；stress压力；applied施加的；individual单独的；muscular [＇m?skjul?]]力臂；gravity[ɡr?vti]重力；stretch伸展，拉紧，延伸；tensile[tensail]拉力；tension张力，拉力；squeeze挤；compressive 有压力的，压缩的；torsional扭转的；torque转矩；twist扭，转动；molecule [m likju:l]分子的；slide滑动; 滑行；slip滑，溜；one another 互相；shear剪切；independently独立地，自立地；beam梁；compress压；revolve (使)旋转；exert [iɡ＇z?:t]用力，尽力，运用，发挥，施加；principle原则, 原理，准则，规范；spin使…旋转；screw螺丝钉；thread螺纹； 2、词组 a number of 许多；deal with 涉及，处理；result from由什么引起；prevent from阻止，防止；tends to 朝某个方向；in combination结合；fly apart飞散； 3、译文： 任何机器或机构的研究表明每一种机构都是由许多可动的零件组成。这些零件从规定的运动转变到期望的运动。另一方面，这些机器完成工作。当由施力引起的运动时，机器就开始工作了。所以，力和机器的研究涉及在一个物体上的力和力的作用效果。 力是推力或者拉力。力的作用效果要么是改变物体的形状或者运动，要么阻止其他的力发生改变。每一种

部编版七年级上册语文第15课《诫子书》课文原文及教案

部编版七年级上册语文第15课《诫子书》课 文原文及教案 课文 【作者】诸葛亮【朝代】三国时期 夫君子之行，静以修身，俭以养德。非淡泊无以明志，非宁静无以致远。夫学须静也，才须学也，非学无以广才，非志无以成学。淫慢则不能励精，险躁则不能治性。年与时驰，意与日去，遂成枯落，多不接世，悲守穷庐，将复何及！ 教案 教学目标： 1、掌握关键词句，理解文章内容。 2、研读课文，积累名言警句。 3、背诵课文，汲取精神养料。 课时安排：1课时 教学过程 一、导入 作者：诸葛亮（181-234），字孔明，琅玡阳都（今山东沂南南）人，三国时蜀汉政治家、军事家。他一生立志“兴复汉室，还于旧都”，为此鞠躬尽瘁，死而后已；他更以淡泊明志，宁静致远的高风亮节言传身教，惠及子女。今天让我们一起走进他的《诫子书》，聆听他对子女、后人的谆谆教诲。《诫子书》，告诫儿子的

一封家书。 二、初读课文 老师范读，学生勾画生字词。注意句子的停顿。 如：夫/君子之行，静以/修身，俭以/养德。 非淡泊/无以明志，非宁静/无以致远。 非学/无以广才，非志/无以成学。 淫慢/则不能励精，险躁/则不能治性。 年时/与驰，意与/日去，遂成/枯落，多不/接世，悲守/穷庐，将复/何及！ 学生自由读课文。 听朗读录音，体味语调、语速的变化，揣摩作者情感。 学生再自由读一遍课文。 三、精读课文。 1、小组合作，借助注释疏通文意，互相质疑解难，尝试翻译课文。 难点：(1)词语广才——增长才干。励精——振奋精神。治性——修养性情。驰——疾行，指迅速逝去。 （2）句子非淡泊无以明志，非宁静无以致远。非学无以广才，非志无以成学。年与时驰，意与日去，遂成枯萎，多不接世。 提醒学生翻译课文时不能直译的便意译，无论哪种译都要保留原句的句式特征。以第二个句子为例：年华随着时光飞驰，意志随着岁月流逝，最终枯败零落，对社会无益······ 2、总结交流： 四人一组互相翻译课文，交流指正。选2名学生朗读自己的

《化学工程与工艺专业英语》课文翻译 完整版

Unit 1 Chemical Industry 化学工业 1.Origins of the Chemical Industry Although the use of chemicals dates back to the ancient civilizations, the evolution of what we know as the modern chemical industry started much more recently. It may be considered to have begun during the Industrial Revolution, about 1800, and developed to provide chemicals roe use by other industries. Examples are alkali for soapmaking, bleaching powder for cotton, and silica and sodium carbonate for glassmaking. It will be noted that these are all inorganic chemicals. The organic chemicals industry started in the 1860s with the exploitation of William Henry Perkin‘s discovery if the first synthetic dyestuff—mauve. At the start of the twentieth century the emphasis on research on the applied aspects of chemistry in Germany had paid off handsomely, and by 1914 had resulted in the German chemical industry having 75% of the world market in chemicals. This was based on the discovery of new dyestuffs plus the development of both the contact process for sulphuric acid and the Haber process for ammonia. The later required a major technological breakthrough that of being able to carry out chemical reactions under conditions of very high pressure for the first time. The experience gained with this was to stand Germany in good stead, particularly with the rapidly increased demand for nitrogen-based compounds (ammonium salts for fertilizers and nitric acid for explosives manufacture) with the outbreak of world warⅠin 1914. This initiated profound changes which continued during the inter-war years (1918-1939). 1．化学工业的起源 尽管化学品的使用可以追溯到古代文明时代，我们所谓的现代化学工业的发展却是非常近代（才开始的）。可以认为它起源于工业革命其间，大约在1800年，并发展成为为其它工业部门提供化学原料的产业。比如制肥皂所用的碱，棉布生产所用的漂白粉，玻璃制造业所用的硅及Na2CO3. 我们会注意到所有这些都是无机物。有机化学工业的开始是在十九世纪六十年代以William Henry Perkin 发现第一种合成染料—苯胺紫并加以开发利用为标志的。20世纪初，德国花费大量资金用于实用化学方面的重点研究，到1914年，德国的化学工业在世界化学产品市场上占有75%的份额。这要归因于新染料的发现以及硫酸的接触法生产和氨的哈伯生产工艺的发展。而后者需要较大的技术突破使得化学反应第一次可以在非常高的压力条件下进行。这方面所取得的成绩对德国很有帮助。特别是由于1914年第一次世界大仗的爆发，对以氮为基础的化合物的需求飞速增长。这种深刻的改变一直持续到战后（1918-1939）。 date bake to/from: 回溯到 dated: 过时的，陈旧的 stand sb. in good stead: 对。。。很有帮助

机械工程专业英语翻译 华中科技大学版 李光布

1.机械设计过程 机械设计的最终目标是生产一种满足客户需求的有用产品，而且这种产品安全，高效，可靠，经济，实用。当回答这个问题时，广泛地思考，我将要设计的产品或系统的客户是谁？ 在产品设计之前，了解所有客户的期望和期望是至关重要的。营销专业人员经常被用来管理客户期望的定义，但是设计师可能会把他们作为产品开发团队的一部分。 许多方法被用来确定客户想要什么。一种被称为质量功能部署或QFD的流行方法寻求（1）识别客户期望的所有特征和性能因素，以及（2）评估这些因素的相对重要性。QFD过程的结果是产品的一组详细功能和设计要求。 考虑设计过程如何配合为客户提供令人满意的产品所必须发生的所有功能以及在产品的整个生命周期中为产品提供服务也很重要。事实上，重要的是考虑产品在使用寿命后如何处置。影响产品的所有这些功能的总和有时被称为产品实现过程或PRP。PRP中包含的一些因素如下： ?营销功能来评估客户的要求 ?研究确定可在产品中合理使用的可用技术 ?可以包含在产品中的材料和组件的可用性 ?产品设计和开发 ?性能测试 ?设计文件 ?供应商关系和采购职能 ?考虑全球材料采购和全球营销 参加工作的技能 ?物理工厂和设施可用

?制造系统的能力 生产计划和生产系统的控制 ?生产支持系统和人员 ?质量体系要求 ?销售操作和时间表 ?成本目标和其他竞争性问题 ?客户服务要求 ?产品在生产，操作和处置过程中的环境问题 ?法律要求 ?金融资本的可用性 你可以添加到这个列表吗？您应该能够看到，产品的设计只是综合过程的一部分。在本文中，我们将更加注意设计过程本身，但必须始终考虑设计的可生产性。产品设计和制造过程设计的同时考虑通常被称为并行工程。 2.机械设计所需的技能 产品工程师和机械设计师在日常工作中使用广泛的技能和知识。这些技能和知识包含在以下内容中： ?素描，技术制图和计算机辅助设计 ?材料的性质？材料加工*和制造过程 ?化学的应用，如腐蚀防护，电镀和喷漆 静力学动力学材料的强度，运动学和机制 流体力学，热力学和传热 ?流体动力，电气现象的基本原理和工业控制

土木工程专业英语原文及翻译

土木工程专业英语原文 及翻译 文档编制序号：[KKIDT-LLE0828-LLETD298-POI08]

08 级土木(1) 班课程考试试卷 考试科目专业英语 考试时间 学生姓名 所在院系土木学院 任课教师 徐州工程学院印制 Stability of Slopes Introduction Translational slips tend to occur where the adjacent stratum is at a relatively shallow depth below the surface of the slope:the failure surface tends to be plane and roughly parallel to the slips usually occur where the adjacent stratum is at greater depth，the failure surface consisting of curved and plane sections． In practice, limiting equilibrium methods are used in the analysis of slope stability. It is considered that failure is on the point of occurring along an assumed or a known failure surface．The shear strength required to maintain a condition of limiting equilibrium is compared with the available shear strength of the soil，giving the average factor of safety along the failure surface．The problem is considered in two dimensions，conditions of plane strain being assumed．It has been shown that a two-dimensional analysis gives a conservative result for a failure on a three-dimensional(dish-shaped) surface． Analysis for the Case of φu =0 This analysis, in terms of total stress，covers the case of a fully saturated clay under undrained conditions, . For the condition immediately after construction．Only moment equilibrium is considered in the analysis．In section, the potential failure surface is assumed to be a circular arc. A trial failure surface(centre O，radius r and length L a where F is the factor of safety with respect to shear strength．Equating moments about O：

诫子书原文加拼音及译文版

jièzǐshū 《诫子书》 zhūgěliàng 诸葛亮 fūjūn zǐzhīxíng jìng yǐxiūshēn jiǎn yǐyǎng dé 夫君子之行，静以修身，俭以养德，fēi dàn bówúyǐmíng zhìfēi níng jìng wúyǐzhìyuǎn fūxué非淡泊无以明志，非宁静无以致远。夫学xūjìng yěcái xūxuéyěfēi xuéwúyǐguǎng cái fēi zhì须静也，才须学也，非学无以广才，非志wúyǐchéng xuéyín màn zébùnéng lìjīng xiǎn zào zébùn éng 无以成学。淫慢则不能励精，险躁则不能zhìxìng nián yǔshíchíyìyǔrìqùsuìchéng kūluò 治性。年与时驰，意与日去，遂成枯落，duōbùjiēshìbēi shǒu qióng lújiāng fùhéjí 多不接世，悲守穷庐，将复何及！ [译文] 君子的行为操守，从宁静来提高自身的修养，以节俭来培养自己的品德。不恬静寡欲无法明确志向，不排除外来干扰无法达到远大目标。学习必须静心专一，而才干来自学习。所以不学习就无法增长才干，没有志向就无法使学习有所成就。放纵懒散就无法振奋精神，急躁冒险就不能陶冶性情。年华随时光而飞驰，意志随岁月而流逝。最终枯败零落，大多不接触世事、不为社会所用，只能悲哀地坐守着那穷困的居舍，其时悔恨又怎么来得及？ 这篇文章当作于蜀汉建兴十二年（元234年），是诸葛亮晚年写给他八岁的

儿子诸葛瞻的一封家书。诸葛亮一生为国，鞠躬尽瘁，死而后已。他为了蜀汉国家事业日夜操劳，顾不上亲自教育儿子，于是写下这篇书信告诫诸葛瞻。

(完整版)机械工程专业英语词汇

陶瓷ceramics 合成纤维synthetic fibre 电化学腐蚀electrochemical corrosion 车架automotive chassis 悬架suspension 转向器redirector 变速器speed changer 板料冲压sheet metal parts 孔加工spot facing machining 车间workshop 工程技术人员engineer 气动夹紧pneuma lock 数学模型mathematical model 画法几何descriptive geometry 机械制图Mechanical drawing 投影projection 视图view 剖视图profile chart 标准件standard component 零件图part drawing 装配图assembly drawing 尺寸标注size marking 技术要求technical requirements 刚度rigidity 内力internal force 位移displacement 截面section 疲劳极限fatigue limit 断裂fracture 塑性变形plastic distortion 脆性材料brittleness material 刚度准则rigidity criterion 垫圈washer 垫片spacer 直齿圆柱齿轮straight toothed spur gear 斜齿圆柱齿轮helical-spur gear 直齿锥齿轮straight bevel gear 运动简图kinematic sketch 齿轮齿条pinion and rack 蜗杆蜗轮worm and worm gear 虚约束passive constraint 曲柄crank 摇杆racker 凸轮cams

专业英语原文和翻译

Basic Control Actions and Industrial Automatic Control An automatic controller compares the actual value of the plant output with the desired value, determines the deviation, and produces a control signal which will reduce the deviation to zero or to a small value.The manner in which the automatic conroller produces the control signal is called the control action. Classifications of industrial automatic controllers Induetrial automatic controllers may be classified according to their control action as: ·two-position or on-off controllers; ·proportional controllers; ·integral controllers; ·proportional-plus-integral controllers; ·proportional-plus-derivative controllers; ·proportional-plus-derivative-plus-integral controllers. Most industrial automatic controllers use eletricity or pressurized fluid such as oil or air as power sources. Automatic controllers may also be classified according to the kind of power employed in the operation, such as pneumatic controllers, hydraulic controllers, or electronic controllers.What kind of controller to use must be decided by the nature of the plant and the operating conditions,including such considerations as safety, availability, reliability, accuracy, weight, and size? Elements of industrial automatic controllers An automatic controller must detect the actuating error signal, which is usually at a very low power level, and amplify it to a sufficiently high level. Thus, an amplifier is necessary. The output of an automatic controller is fed to a power device, such as a pneumatic motor or valve, a hydraulic motor, or an electric motor. The controller usually consists of an error detector and amplifier. The measuring element is a device that converts the output variable into another suitable variable, such as a displacement, pressure, or electric signal, which can be used for comparing the output to the reference input signal. This element is in the feedback path of the closed-loop system. The set point of the controller must be converted to a reference input of the same units as the feedback signal from the measuring element. The amplifier amplifies the power of the actuating error signal, which in turn operates the actuator. The actuator is an element which alters the input to the plant according to the control signal so that the feedback signal may be brought into correspondence with the reference input signal. Self-operated controllers In most industrial automatic controllers, separate units are used for the measuring element and for the actuator. In a very simple one, however, such as a self-operated controller, these elements are assembled in one unit. Self-operated controllers utilize power developed by the measuring element and are very simple and inexpensive. The set point is determined by the adjustment of the spring force. The controlled pressure is measured by the diaphragm. The actuating error signal is the net force acting on the diaphragm. Its position determines the valve opening. The operation of self-operated controller is as follows: Suppose that the output pressure is lower than the reference pressure, as determined by the set point. Then the downward spring force is greater than the upward pressure force, resulting in a downward movement of the diaphragm. This increases the flow rate and raises the output pressure.

机械工程专业英语翻译合集

1.我们可以把钢再次加热到临界温度以下的某一温度，然后在慢慢让其冷却。We can heat the steel again to a temperature below the critical temperature, then cool it slowly. 2.无论任何简单的机床，都是由单一元件即通称为机械零件或部件组成的。However simple, any machine is a combination of individual components generally referred to as machine elements or parts. 3.这些金属不都是好的导体。 All these metals are not good conductors. 4. 在做带电实验的时候，再怎么小心都不为过。 You can't be too careful in performing an experiment. 5.利用发电机可以把机械能转变成电能。 The mechanical energy can be changed back into electrical energy by means of a generator or dynamo. 6.假定电源输入的电压保持不变。 Assume that the voltage input of the power supply remains the same. 7.化石燃料是发电过程中最为频繁使用的能源。 Fossil fuels are most frequently used source daring the power generation process. 8单个机械零件的可靠性成为评估整台机器使用寿命的基本因素。 The individual reliability of machine elements becomes the basis for estimating the overall life 9.说我们生活在一个电子时代，这一点都不夸张。 It's no exaggeration to say that we live in an electronic age. 10.发动机的转速不应超过最大允许值。 Engine revolution should not exceed the maximum permissible. 11.如能从大型核电站获得成本极低的电力，电解氢的竞争能力就会增强。（Electrolytic hydrogen）。 If extremely low-cost power were ever to become available from large nuclear power plants, electrolytic hydrogen would become competitive. 12.电子技术提供了一种新的显示时间的方法。 A new way of displaying time has been given by electronics. 13.远距离输电需要高压，安全用电需要低压。 High voltage is necessary for long transmission line while low voltage for safe use. 14.铝的电阻大约是同等尺寸的铜的1.5倍。 The resistance of aluminum is approximately half again as great as that of copper for the same dimensions = size 15.In fact,it is impossible for no force to be exerted on a body,since in this world everything is subject to the for ce of gravity. 事实上，物体不受外力作用是不可能的，因为在这个世界上任何物体都要受到重力的作用。 16.In a thermal power plant,all the chemical energy is not

诫子书字词与全文翻译

15 诫子书 原文：夫君子之行，静以修身，俭以养德。非淡泊无以明志，非宁静无以致远。夫学须静也，才须学也，非学无以广才，非志无以成学。淫慢则不能励精，险躁则不能治性。年与时驰，意与日去，遂成枯落，多不接世，悲守穷庐，将复何及！ 译：君子的品行，依靠内心安静集中精力来修养身心，依靠俭朴节约的作风来培养品德。不清心寡欲，就没有什么可以拿来使自己实现远大目标。学习必须静心专一，增长才干必须刻苦学习，不刻苦学习就无法增长才干，没有坚定不移的志向就无法使学业成功。放纵懈怠就不能振奋精神，轻薄浮躁就不能修养性情。年纪随同时光而疾速逝去，意志随同岁月而消失，最终像枯枝落叶凋落、衰残，对社会没有任何贡献，只有悲伤地困守在自己的穷家破舍里，到那时再悲伤叹息又怎么来得及! 字词： 1.夫：助词，用于句首，表示发端。 2.君子：指有才德的人。 3.静：屏除杂念和干扰，宁静专一。（原文指淡泊宁静） 4.以：连词，表示后者是前者的目的。（“以观沧海”“以塞忠谏之路”） 5.之：的，助词。 6.养德：培养品德。 7.淡泊：内心恬淡，不慕名利。淡，恬淡。泊，安静，恬静。 8.宁：宁静，安定。 9.远：远大目标。（形容词活用作名词）

10.无以：没有什么可以拿来，没办法。（以：同样表目的） 11.明志：明确志向。明，明确、坚定。志，（坚定不移的）志向。 12.致远：达到远大目标。致，达到。 13.广才：增长才干。（名词活用作动词） 广，增长（形容词活用作动词）才：才干（名词） 14.淫慢：放纵懈怠。淫，放纵。慢，懈怠。 15.励精：振奋精神。励，振奋。 16.险躁：轻薄浮躁。与上文“宁静”相对而言。险，轻薄。 17.能：能够。 18.治性：修养性情。治，修养。 19.年与时驰：年纪随同时光而疾速逝去。 年：年纪。驰，疾行，指迅速逝去。 20.意与日去：意志随同岁月而消失。意：意志。 21.遂：最终，终于。 22.日；岁月。原指太阳。这里指消失。 23.枯落：凋落，衰残。比喻人年老志衰，没有用处。（本指树叶凋落） 24.多不接世：意思是，大多对社会没有任何贡献。 接，承接。世，社会。 25.守：困守。 26.穷庐：穷困潦倒之人住的陋室。 27.将复何及：又怎么来得及。将，连词，又。复，又；再。何，怎么。及，来得及。

测绘专业英语原文和部分翻译(1-39)

Table of Contents Uuit 1 What is Geomatics? （什么是测绘学） (2) Unit 2 Geodetic Surveying and Plane Surveying（大地测量与平面测量） (6) Unit 3 Distance Measurement（距离测量） (10) Unit 4 Angle and Direction Measurement（角度和方向测量） (14) Unit 5 Traversing （导线测量） (17) Unit 6 Methods of Elevation Determination（高程测量方法） (21) Unit 7 Robotic Total Station （智能型全站仪） (25) Unit 8 Errors in Measurement（测量工作中的误差） (29) Unit 9 Basic Statistical Analysis of Random Errors (32) Unit 10 Accuracy and Precision （准确度和精度） (35) Unit 11 Least-Squares Adjustment (38) Unit 12 Geodesy Concepts (40) Unit 13 Geoid and Reference Ellipsoid (42) Unit 14 Datums, Coordinates and Conversions (44) Unit 15 Map Projection (46) Unit 16 Gravity Measurment (48) Unit 17 Optimal Design of Geomatics Network (50) Unit 18 Construction Layout （施工放样） (53) Unit 19 Deformation Monitoring of Engineering Struvture (56) Unit 20 Understan ding the GPS（认识GPS） (59) Uuit 21 Understanding the GPS (II) 认识GPS(II) (62) Unit 22 Competition in Space Orbit（太空轨道上的竞争） (64) Unit 23 GIS Basics（GIS 的基础） (69) Unit 24 Data Types and Models in GIS GIS中的数据类型和模型 (75) Unit 25 Digital Terrain Modeling（数字地面模型） (79) Unit 26 Applications of GIS (83) Unit 27 Developments of photogrammetry (87) Unit 28 Fundamentals of Remote Sensing （遥感的基础） (90) Unit 29 Digital Image Processing and Its Applications in RS (94) Unit 30 Airborne Laser Mapping Technology（机载激光测图技术） (99) Unit 31 Interferometric SAR(InSAR) (102) Unit 32 Brief Introduction toApplied Geophysics (104) Unit 33 Origon of Induced Polarization (105) Unit 34 International Geoscience Organization (108) Unit 35 Prestigious Journals in Geomatics (110) Unit 36 Relevant Surveying Instrument Companies (115) Unit 37 Expression of Simple Equations and Scientific Formulsa (116) Unit 38 Professional English Paper Writing (119) Unit 39 Translation Techniques for EST (127)

机械工程专业英语 翻译

2、应力和应变 在任何工程结构中独立的部件或构件将承受来自于部件的使用状况或工作的外部环境的外力作用。如果组件就处于平衡状态,由此而来的各种外力将会为零,但尽管如此,它们共同作用部件的载荷易于使部件变形同时在材料里面产生相应的内力。 有很多不同负载可以应用于构件的方式。负荷根据相应时间的不同可分为: (a)静态负荷是一种在相对较短的时间内逐步达到平衡的应用载荷。 (b)持续负载是一种在很长一段时间为一个常数的载荷, 例如结构的重量。这种类型的载荷以相同的方式作为一个静态负荷; 然而,对一些材料与温度和压力的条件下,短时间的载荷和长时间的载荷抵抗失效的能力可能是不同的。 (c)冲击载荷是一种快速载荷(一种能量载荷)。振动通常导致一个冲击载荷, 一般平衡是不能建立的直到通过自然的阻尼力的作用使振动停止的时候。 (d)重复载荷是一种被应用和去除千万次的载荷。 (e)疲劳载荷或交变载荷是一种大小和设计随时间不断变化的载荷。 上面已经提到，作用于物体的外力与在材料里面产生的相应内力平衡。因此,如果一个杆受到一个均匀的拉伸和压缩，也就是说, 一个力,均匀分布于一截面,那么产生的内力也均匀分布并且可以说杆是受到一个均匀的正常应力,应力被定义为 应力==负载 P /压力 A, 因此根据载荷的性质应力是可以压缩或拉伸的,并被度量为牛顿每平方米或它的倍数。 如果一个杆受到轴向载荷，即是应力，那么杆的长度会改变。如果杆的初始长度L和改变量△L已知，产生的应力定义如下: 应力==改变长△L /初始长 L 因此应力是一个测量材料变形和无量纲的物理量 ,即它没有单位;它只是两个相同单位的物理量的比值。 一般来说,在实践中,在荷载作用下材料的延伸是非常小的, 测量的应力以*10-6的形式是方便的, 即微应变, 使用的符号也相应成为ue。 从某种意义上说，拉伸应力与应变被认为是正的。压缩应力与应变被认为是负的。因此负应力使长度减小。 当负载移除时，如果材料回复到初始的，无负载时的尺寸时，我们就说它是具有弹性的。一特定形式的适用于大范围的工程材料至少工程材料受载荷的大部分的弹性, 产生正比于负载的变形。由于载荷正比于载荷所产生的压力并且变形正比于应变, 这也说明,当材料是弹性的时候, 应力与应变成正比。因此胡克定律陈述, 应力正比于应变。 这定律服从于大部分铁合金在特定的范围内, 甚至以其合理的准确性可以假定适用于其他工程材料比如混凝土，木材，非铁合金。 当一个材料是弹性的时候，当载荷消除之后，任何负载所产生的变形可以完全恢复,没有永久的变形。

诫子书原文及翻译

《诫子书》原文及翻译 原文：夫君子之行，静以修身，俭以养德。 字词：夫：助词，用于句首，表示发端。君子：指有才德的人。静：屏除杂念和干扰，宁静专一。（原文指淡泊宁静）以：连词，表示后者是前者的目的。（“以观沧海”“以塞忠谏之路”）之：的，助词。养德：培养品德。 译文：君子的品行，依靠内心安静集中精力来修养身心，依靠俭朴节约的作风来培养品德。原文：非淡泊无以明志，非宁静无以致远。 字词：淡泊：内心恬淡，不慕名利。淡，恬淡。泊，安静，恬静。宁：宁静，安定。远：远大目标。（形容词活用作名词）明志：明确志向。明，明确、坚定。志，（坚定不移的）志向。致远：达到远大目标。致，达到。 译文：不清心寡欲，就没有什么可以拿来使自己实现远大目标。 原文：夫学须静也，才须学也， 字词： 译文：学习必须静心专一，增长才干必须刻苦学习， 原文：非学无以广才，非志无以成学。 字词：广才：增长才干。（名词活用作动词）广，增长（形容词活用作动词）才：才干（名词）无以：没有什么可以拿来，没办法。（以：同样表目的） 译文：不刻苦学习就无法增长才干，没有坚定不移的志向就无法使学业成功。 原文：淫慢则不能励精，险躁则不能治性。 字词：.淫慢：放纵懈怠。淫，放纵。慢，懈怠。励精：振奋精神。励，振奋。险躁：轻薄浮躁。与上文“宁静”相对而言。险，轻薄。.能：能够。治性：修养性情。治，修养。 译文：放纵懈怠就不能振奋精神，轻薄浮躁就不能修养性情。 原文：年与时驰，意与日去， 字词：.年与时驰：年纪随同时光而疾速逝去。年：年纪。驰，疾行，指迅速逝去。 意与日去：意志随同岁月而消失。意：意志。日；岁月。原指太阳。这里指消失。 译文：年纪随同时光而疾速逝去，意志随同岁月而消失， 原文：遂成枯落，多不接世， 字词：遂：最终，终于。枯落：凋落，衰残。比喻人年老志衰，没有用处。（本指树叶凋落）多不接世：意思是，大多对社会没有任何贡献。接，承接。世，社会。 译文：最终像枯枝落叶凋落、衰残，对社会没有任何贡献， 原文：悲守穷庐，将复何及！ 字词：.守：困守。穷庐：穷困潦倒之人住的陋室。将复何及：又怎么来得及。将，连词，又。复，又；再。何，怎么。及，来得及。 译文：只有悲伤地困守在自己的穷家破舍里，到那时再悲伤叹息又怎么来得及!