作业帮机械专业英语作文
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篇一：机械专业英语作文
题目：请你用英语就机械领域的一个主题（如车床，螺母等）写一篇科技短文，字数在200以上。
Cutting tools（车刀）
In mechanical engineering high-speed development today, cutting tools of development has become a necessary condition, but we also want to know the kinds of tools and applications in order to complete the cutting work, and maintain the good life of cutter
According to the shape of the lathe tools, we generally use point form part of the car have the following kinds
1. The thick car, mainly used for cutting a lot of excess the diameter size close to need
2. Fine cars, this dao oil-stone available knife, so that the car is very smooth surface.
3. Cutting, only for end of cutting piece, can be used to cut materials. Turning part of the job is produce and deal with scraps of parts, including the blade, and broken broken or roll on scraps of structure, scraps discharge or let store the space of the chip, cutting fluids such as the channel structure elements. The cutting tool in part by the main cutting
edge, deputy cutting edge sword face, Lord, before after face and vice knife knife after surface, the knife sharp edges into. The cutting tool parts and handle department (namely the clamping part) of combining ways mainly have integral, welding type, mechanical clip solid type and welding machinery clip solid type. Mechanical clip solid type lathe tools can avoid hard alloy blades in high temperature and stress of welding crack, and the handle can be repeated use. Mechanical clip solid type lathe tools with screws and linking piece is generally the blades will be clamping, outfit can turn a blade mechanical clip solid type lathe tools. After using blunt blade can turn a continue to use, and parking cutter replacement time turning
Short, thus achieved rapid development
Through the above some introduction, hope everybody can better and faster cutting of workpiece.
篇二：机械专业英语作文1
Mechanical engineering
Engineering Science in life are widely used, especially in mechanical engineering in the application of life is almost throughout life in all its aspects, to automobiles, aircraft, small electric fans, umbrella, all of these and related machinery. The project includes many subjects, but the mechanical engineering is one of the most important subjects, not only because of our life and it is closely related to, but with the progress of the times, people have to rely on mechanical engineering products, in automation today, machine instead of many this is the part of the human labor, improve the efficiency and save time.
As a result of mechanical engineering in every aspect of life, therefore, as an engineer, be faced with a great many challenges, in addition to a solid with knowledge, but also keep pace with the times, familiar with the machinery and related software, can be very good use of software, and as a an engineer, we should try our best to design and produce and closely related to the life of the machine, and can in life play a real role, also have only such, we address and remission now social needs, therefore, the mechanical engineering in the future social development, will play the important role, especially China's case, the industry also is not very developed, machinery can be greater development space.
Before the industrial revolution, machinery is mostly wood structure, wood made by hand by. The development of social economy, the demand for mechanical products. The bulk of the production increasing and precision processing technology progress, promote the mass production method ( interchangeability of parts production, professional division of labor and cooperation, water processing lines and assembly lines ) formation. Study of mechanical products in the manufacturing process, especially when used in the pollution of the environment and natural resources excessive consumption problems and their treatment measures. This is a modern mechanical engineering is an especially important task to grow with each passing day, and its importance.Application of mechanical products. This includes selection, ordering, acceptance, installation, adjustment, operation, maintenance, repair and transformation of the industrial use of machinery and complete sets of machinery and equipment, to ensure that the mechanical products in the long-term use of reliability and economy.
As a student, we are now the most important to learn professional knowledge, only in this way, can we later life and learning, to do its part.
机械工程
工程科学在生活中应用广泛，特别是机械工程在生活中的应用几乎就是遍布了生活中的各个方面，大到汽车、飞机，小到电风扇、雨伞，这些都和机械有关。工程包括很多科目，但是机械工程是最重要的科目之一，不仅是因为它和我们的生活关系密切，而是随着时代的进步，人们已经依赖上机械工程制造出来的产品，而在自动化的今天，机器代替了许多本该是人类该做的部分劳动，提高了效率和节约了时间。
由于机械工程遍布了生活的每一个方面，因此，做为一个工程师，要面临很大且很多的挑战，除了要具备扎实的装也知识外，还要与时俱进，熟悉和机械有关的软件，并要能很好的运用软件，而作为的一个工程师，我们要尽量设计和制造出和生活密切相关的机器，并能够在生活中起到真正的作用，也只有这样，我们解决和缓解现在社会上的需要，因此，机械工程在今后的社会的发展中，还是会起这重要的作用，特别是我国的这样的情况，工业还不是很发达的情况下，机械可发展的空间更大。
工业革命以前，机械大都是木结构的，由木工用手工制成。社会经济的发展，对机械产品的需求猛增。生产批量的增大和精密加工技术的进展，促进了大量生产方法（零件互换性生产、专业分工和协作、流水加工线和流水装配线等）的形成。研究机械产品在制造过程中，尤其是在使用中所产生的环境污染和自然资源过度耗费方面的问题及其处理措施。这是现代机械工程的一项特别重要的任务，而且其重要性与日俱增。机械产品的应用。这方面包括选择、订购、验收、安装、调整、操作、维护、修理和改造各产业所使用的机械和成套机械装备，以保证机械产品在长期使用中的可靠性和经济性。
做为学生，我们现在最重要的学好专业知识，只有这样，我们才能以后是生活和学习中，才能尽自己的一份力量。
篇三：机械专业英语文章中英文对照
英语原文
NUMERICAL CONTROL
Numerical control(N/C)is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols, The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular work part or job. When the job changes, the program of instructions is changed. The capability to change the program is what makes N/C suitable for low-and medium-volume production. It is much easier to write programs than to make major alterations of the processing equipment.
There are two basic types of numerically controlled machine tools：point—to—point and continuous—path(also called contouring).Point—to—point machines use unsynchronized motors, with the result that the position of the machining head Can be assured only upon completion of a movement, or while only one motor is running. Machines of this type are principally used for straight—line cuts or for drilling or boring.
The N/C system consists of the following components：data input, the tape reader with the control unit, feedback devices, and the metal—cutting machine tool or other type of N/C equipment.
Data input, also called “man—to—control link”, may be provided to the machine tool manually, or entirely by automatic means. Manual methods when used as the sole source of input data are restricted to a relatively small number of inputs. Examples of manually operated devices are keyboard dials, pushbuttons, switches, or thumbwheel selectors. These are located on a console near the machine. Dials ale analog devices usually connected to a syn-chro-type resolver or potentiometer. In most cases, pushbuttons, switches, and other similar types of selectors are digital input devices. Manual input requires that the operator set the controls for each operation. It is a slow and tedious process and is seldom justified except in elementary machining applications or in special cases.
In practically all cases, information is automatically supplied to the control unit and the machine tool by cards, punched tapes, or by magnetic tape. Eight—channel punched paper tape is the most commonly used form of data input for conventional N/C systems. The coded instructions on the tape consist of sections of punched holes called blocks. Each block represents a machine function, a machining operation, or a combination of the two. The entire N/C program on a tape is made up of an accumulation of these successive data blocks. Programs resulting in long tapes all wound on reels like motion-picture film. Programs on relatively short tapes may be continuously repeated by joining the two ends of the tape to form a loop. Once installed, the tape is used again and again without further handling. In this case, the operator simply loads and
unloads the parts. Punched tapes ale prepared on type writers with special tape—punching attachments or in tape punching units connected directly to a computer system. Tape production is rarely error-free. Errors may be initially caused by the part programmer, in card punching or compilation, or as a result of physical damage to the tape during handling, etc. Several trial runs are often necessary to remove all errors and produce an acceptable working tape.
While the data on the tape is fed automatically, the actual programming steps ale done manually. Before the coded tape may be prepared, the programmer, often working with a planner or a process engineer, must select the appropriate N/C machine tool, determine the kind of material to be machined, calculate the speeds and feeds, and decide upon the type of tooling needed. The dimensions on the part print are closely examined to determine a suitable zero reference point from which to start the program. A program manuscript is then written which gives coded numerical instructions describing the sequence of operations that the machine tool is required to follow to cut the part to the drawing specifications.
The control unit receives and stores all coded data until a complete block of information has been accumulated. It then interprets the coded instruction and directs the machine tool through the required motions.
The function of the control unit may be better understood by comparing it to the action of a dial telephone, where, as each digit is dialed, it is stored. When the entire number has been dialed, the equipment becomes activated and the call is completed.
Silicon photo diodes, located in the tape reader head on the control unit, detect light as it passes through the holes in the moving tape. The light beams are converted to electrical energy, which is amplified to further strengthen the signal. The signals are then sent to registers in the control unit, where actuation signals are relayed to the machine tool drives.
Some photoelectric devices are capable of reading at rates up to 1000 characters per second. High reading rates are necessary to maintain continuous machine—tool motion；otherwise dwell marks may be generated by the cutter on the part during contouring operations. The reading device must be capable of reading data blocks at a rate faster than the control system can process the data.
A feedback device is a safeguard used on some N/C installations to constantly compensate for errors between the commanded position and the actual location of the moving slides of the machine tool. An N/C machine equipped with this kind of a direct feedback checking device has what is known as a closed-loop system. Positioning control is accomplished by a sensor which, during the actual operation, records the position of the slides and relays this information back to the control unit. Signals thus received ale compared to input signals on the tape, and any discrepancy between them is automatically rectified.
In an alternative system, called an open—loop system, the machine is positioned solely by stepping motor drives in response to commands by a controllers. There is one basic type of NC motions. Point-to-point or Positional Control In point-to-point control the machine tool elements (tools, table, etc.) are moved to programmed locations and the machining operations performed
after the motions are completed. The path or speed of movement between locations is unimportant; only the coordinates of the end points of the motions are accurately controlled. This type of control is suitable for drill presses and some boring machines, where drilling, tapping, or boring operations must be performed at various locations on the work piece. Straight-Line or Linear Control Straight-Line control systems are able to move the cutting tool parallel to one of the major axes of the machine tool at a controlled rate suitable for machining. It is normally only possible to move in one direction at a time, so angular cuts on the work piece are not possible, consequently, for milling machines, only rectangular configurations can be machined or for lathes only surfaces parallel or perpendicular to the spindle axis can be machined. This type of controlled motion is often referred to as linear control or a half-axis of control. Machines with this form of control are also capable of point-to-point control.
The original N/C used the closed—loop system. Of the two systems, closed and open loop, closed loop is more accurate and, as a consequence, is generally more expensive. Initially, open—loop systems were used almost entirely for light-duty applications because of inherent power limitations previously associated with conventional electric stepping motors. Recent advances in the development of electro hydraulic stepping motors have led to increasingly heavier machine load applications.
中文译文
数控技术
数控是可编程自动化技术的一种形式,通过数字、字母和其他符号来控制加工设备。数字、字母和符号用适当的格式编码为一个特定工件定义指令程序。当工件改变时,指令程序就改变。这种改变程序的能力使数控适合于中、小批量生产,写一段新程序远比对加工设备做大的改动容易得多。
数控机床有两种基本形式：点位控制和连续控制(也称为轮廓控制)。点位控制机床采用异步电动机,因此,主轴的定位只能通过完成一个运动或一个电动机的转动来实现。这种机床主要用于直线切削或钻孔、镗孔等场合。
数控系统由下列组件组成：数据输入装置,带控制单元的磁带阅读机,反馈装置和切削机床或其他形式的数控设备。
数据输人装置,也称“人机联系装置”,可用人工或全自动方法向机床提供数据。人工方法作为输人数据唯一方法时,只限于少量输入。人工输入装置有键盘,拨号盘,按钮,开关或拨轮选择开关,这些都位于机床附近的一个控制台上。拨号盘通常连到一个同步解析器或电位计的模拟装置上。在大多数情况下,按钮、开关和其他类似的旋钮是数据输入元件。人工输入需要操作者控制每个操作,这是一个既慢又单调的过程,除了简单加工场合或特殊情况,已很少使用。
几乎所有情况下,信息都是通过卡片、穿孔纸带或磁带自动提供给控制单元。在传统的数控系统中,八信道穿孔纸带是最常用的数据输入形式,纸带上的编码指令由一系列称为程序块的穿孔组成。每一个程序块代表一种加工功能、一种操作或两者的组合。纸带上的整个数控程序由这些连续数据单元连接而成。带有程序的长带子像电影胶片一样绕在盘子上,相对较短的带子上的程序可通过将纸带两端连接形成一个循环而连续不断地重复使用。带子一旦安装好,就可反复使用而无需进一步处理。此时,操作者只是简单地上、下工件。穿孔纸带是在带有特制穿孔附件的打字机或直接连到计算机上的纸带穿孔装置上做成的。纸带制造很少不出错,错误可能由编程、卡片穿孔或编码、纸带穿孔时的物理损害等形成。通常,必须要试走几次来排除错误,才能得到一个可用的工作纸带。
虽然纸带上的数据是自动进给的,但实际编程却是手工完成的,在编码纸带做好前,编程者经常要和一个计划人员或工艺工程师一起工作,选择合适的数控机床,决定加工材料,计算切削速度和进给速度,决定所需刀具类型,仔细阅读零件图上尺寸,定下合适的程序开始的零参考点,然后写出程序清单,其上记载有描述加工顺序的编码数控指令,机床按顺序加工工件到图样要求。
控制单元接受和储存编码数据,直至形成一个完整的信息程序块,然后解释数控指令,并引导机床得到所需运动。
为更好理解控制单元的作用,可将它与拨号电话进行比较,即每拨一个数字,就储存一个,当整个数字拨好后,电话就被激活,也就完成了呼叫。
装在控制单元里的纸带阅读机,通过其内的硅光二极管,检测到穿过移动纸带上的孔漏
过的光线,将光束转变成电能,并通过放大来进一步加强信号,然后将信号送到控制单元里的寄存器,由它将动作信号传到机床驱动装置。
有些光电装置能以高达每秒1000个字节的速度阅读,这对保持机床连续动作是必须的,否则,在轮廓加工时,刀具可能在工件上产生划痕。阅读装置必须要能以比控制系统处理数据更快的速度来阅读数据程序块。
反馈装置是用在一些数控设备上的安全装置,它可连续补偿控制位置与机床运动滑台的实际位置之间的误差。装有这种直接反馈检查装置的数控机床有一个闭环系统装置。位置控制通过传感器实现,在实际工作时,记录下滑台的位置,并将这些信息送回控制单元。接受到的信号与纸带输入的信号相比较,它们之间的任何偏差都可得到纠正。
在另一个称为开环的系统中,机床仅由响应控制器命令的步进电动机驱动定位,工件的精度几乎完全取决于丝杠的精度和机床结构的刚度。有几个理由可以说明步进电机是一个自动化申请的非常有用的驱动装置。对于一件事物,它被不连续直流电压脉冲驱使,是来自数传计算机和其他的自动化的非常方便的输出控制系统。当多数是索引或其他的自动化申请所必备者的时候,步进电机对运行一个精确的有角进步也是理
最初的数控系统采用开环系统。在开、闭环两种系统中,闭环更精确,一般说来更昂贵。起初,因为原先传统的步进电动机的功率限制,开环系统几乎全部用于轻加工场合,最近出现的电液步进电动机已越来越多地用于较重的加工领域。
篇四：机械工程专业英语文章翻译
机
械
题目：
学号：
班级：数控
姓名：康振平
工 程 专 业 英 语 Computer-Aided Design and Manufacturing 20110334304 121
Computer-Aided Design and Manufacturing
计算机辅助设计与制造
Computer-aided design（CAD）involves the use of computers to create design drawings and product models. Computer-aided design is usually associated with interactive computer graphics（known as a CAD system）. Computer-aided design systems are powerful tools and are used in the mechanical design and geometric modeling of products and components.
计算机辅助设计（CAD）是指用计算机来创造设计图纸和产品模型。计算机辅助设计通常是与交互式计算机图形学（称为CAD系统）有关系的。计算机辅助设计系统是功能强大的工具，被用于在机械设计以及产品和零件的几何建模。
In CAD，the drawing board is replaced by electronic input and output devices. When using a CAD system，the designer can conceptualize the object to be designed more easily on the Graphics screen and can consider alternative designs or modify a particular design quickly to meet the necessary design requirements or changes. The designer can then subject the design to a variety of engineering analyses and can identify potential problems （such as an excessive load or deflection）.The speed and accuracy of such analyses far surpass what is available from traditional methods.
在CAD（计算机辅助设计）中，传统的画图板被电子输入和输出设备所替换。当使用CAD系统时，设计者可以使对象概念化以便更容易在图形屏幕上设计，并且可以考虑替代设计或快速地修改一个特定的设计来达到必要的设计要求或变化。因而设计者可以提供多种工程分析并且可以识别潜在的问题（如过负荷或变形）。这些分析的速度和准确性都远远超过了传统的方法。
Draft productivity rises dramatically. When something is drawn once，it never has to be drawn again. it can be retrieved from a library ,and can be duplicated, stretched, sized, and changed in many ways without having to be redrawn。Cut and paste techniques are used
as labor-saving aids.
设计生产率的提高是显著的。当某些图形被绘制一次后，就没必要再画第二次。它可以从图形库中恢复，可以被复制，拉伸，改变大小，和其他许多方面的改变而无需重新绘制。剪切和粘贴技巧作为节省劳力的助手被使用。
CAD makes possible multiview 2D drawings ，and the drawings can be reproduced in different levels of reduction and enlargement. It gives the mechanical engineer the ability to magnify even the smallest of components to ascertain if assembled components fit properly. Parts with different characteristics，such as movable or stationary ，can be assigned different colors on the display.
CAD使二维图纸多重视图变为可能，并且图形可以在大小不同的图层里重生。它使机械工程师有能力放大甚至最小的部件来确定构件是否装配合适。对于具有不同特性的零部件，如移动或静止，可以指定不同的颜色在显示屏上标示。
have even more freedom with the advent of 3-D parts
and manipulate them in endless variations to achieve the desired results. Through finite element analysis ，stresses can be applied to be a computer model and the results graphically displayed，giving the designer quick feedback on any inherent problems in a design before the creation of a physical prototype.
随着三维建模的出现设计师有了更多自由和无限制的修改它们以实现所期望的结果。通过有限元分析，应力加到计算机模型上并且以图形化的方式显示其结果，在产品物理原型生产之前，对设计中的任何内在问题给设计者一个快速的反馈。 Designers
In addition to the design’s geometric and dimensional features，other information （such as a list of materials，specification ，and manufacturing instructions）is stored in the CAD database. Using such information ,the designer can then analyze the economics of alternative designs.
除了设计的几何和尺寸特性之外，其他信息(比如材料清单、规格、和制造说明)都存储在CAD数据库里。利用这些信息，设计师可以分析备选设计的经济性。
Computer-aided manufacturing(CAM) involves the uses of computers and computer technology to assist in all the phases of manufacturing a product，including process and production planning，machining，scheduling，management ，and quality control. Computer-aided design and computer-aided manufacturing are often combined into CAD/CAM systems.
计算机辅助制造(CAM)包括使用计算机和计算机技术来协助制造产品的所有阶段，包括工艺和生产计划，加工，调度，管理，和质量控制。计算机辅助设计和计算机辅助制造常常是和CAD / CAM系统相结合的。
This combination allow the transfer of information from the design stage into the stage of planning for the manufacture of a product，without the need to reenter the data on part geometry manually. The database developed during CAD is stored； then it is processed further，by CAM，into the necessary data and instructions for operating and controlling production machinery，material-handling equipment，and automated testing and inspection for product quality.
这种组合允许一个产品的信息从设计阶段传递到加工规划阶段，而不需要手动重新输入几何部件的数据。计算机辅助设计研发期间存储在数据库，然后通过计算机辅助制造进一步处理，一直到必要的数据和指令的操作和控制生产机械、物料搬运设备，自动化测试和检验产品质量。
In machining operations，an important feature of CAD/CAM is its capability to describe the tool path for various operations，such as NC turning，milling，and drilling. The instructions （programs）are computer generated，and they can be modified by the programmer to optimize the tool path .The engineer or technician can then display and visually check the tool path for possible tool collisions with fixtures or other interferences. The tool path can be modified at any time，to accommodate other part shapes to be machined.
在机械加工中，CAD/CAM的一个重要特征是它有可以描述刀具运动轨迹的能力，如数控车削，铣削，钻孔。指令（程序）是计算机生成的，它们可以由程序员修改优化刀具路径。工程师或技术员可以显示和检查刀具路径可能与夹具或
其他干扰工具碰撞。刀具路径可以随时修改，以适应其他部分的形状被加工。
Some typical applications of CAD/CAM are：（a）programming for NC，CNC，and industrial robots；（b）design of tools and fixtures and EDM electodes；（c）quality control and inspection，for instance，coordinate-measuring machines programmed on a CAD/CAM workstation；（d）process planning and scheduling ；and（e）plant layout.
CAD / CAM的一些典型应用是：（a）数控编程，计算机数控编程和工业机器人；（b）工具和夹具以及电火花电极的设计；（c）质量控制和检查，例如，在CAD / CAM工作站上的坐标测量机编程；（d）工艺规划与调度；和（e）工厂布局。
The emergence of CAD/CAM has had a major impact on manufacturing，by standardizing product development and by reducing design effort，tryout，and prototype work；it has made possible significantly reduced costs and improved productivity. The two-engine Boeing 777 passenger airplane，for example, was designed completed by computer（paperless design ）.The plane is constructed directly from the CAD/CAM software developed（an enhanced CATIA system）and no prototypes or mockups were built ，such as were required for previous models.
CAD/CAM的出现对制造业产生了重大影响，通过产品开发的标准化和减少设计工作量，试用，和原型的工作；它有可能大大降低成本和提高生产力。例如双引擎的波音777客机就是由计算机设计完成（无纸化设计）。这架飞机直接从CAD/CAM软件开发（增强CATIA系统）并没有建立原型或实物模型的情况下制造出来，如以前所需要的的模型。
篇五：机械专业英语文章 中英文对照
Types of Materials
材料的类型
Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials.
材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。他们也把材料分为有机材料(曾经有生命的)和无机材料(从未有生命的)。
For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products.
就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成部分的就是工程材料。
Nonengineering materials are the chemicals, fuels, lubricants, and other materials used in the manufacturing process, which do not become part of the product.
非工程材料则是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成部分的材料。
Engineering materials may be further subdivided into: ①Metal ②Ceramics ③Composite ④Polymers, etc.
工程材料还能进一步细分为：①金属材料②陶瓷材料③复合材料 ④聚合材料，等等。
Metals and Metal Alloys
金属和金属合金
Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility.
金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。
Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and intermetallic compounds become superconductors.
某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些金属和金属化合物能转变成超导体。
What is the difference between an alloy and a pure metal? Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans.
合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。
例如电线中的铜和制造烹饪箔及饮料罐的铝。
Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel, and chromium; and gold jewelry which usually contains an alloy of gold and nickel.
合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。
Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio.
为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。
Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable.
某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用的
What are some important properties of metals?
Density is defined as a material’s mass divided by its volume. Most metals have relatively high densities, especially compared to polymers.
金属有哪些重要特性？
密度定义为材料的质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比较而言。
Materials with high densities often contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.
高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类的一些金属则具有低密度，并被用于既需要金属特性又要求重量轻的场合。
Fracture toughness can be described as a material’s ability to avoid fracture, especially when a flaw is introduced. Metals can generally contain nicks and dents without weakening very much, and are impact resistant. A football player counts on this when he trusts that his facemask won’t shatter.
断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金属一般能在有缺口和凹痕的情况下不显著削弱，并且能抵抗冲击。橄榄球运动员据此相信他的面罩不会裂成碎片。
Plastic deformation is the ability of bend or deform before breaking.
As engineers, we usually design materials so that they don’t deform under normal conditions. You don’t want your car to lean to the east after a strong west wind.
塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有人愿意一阵强烈的西风过后自己的汽车向东倾斜。
However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break.
然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们断裂前通过经历塑性变形来吸收能量。
The atomic bonding of metals also affects their properties. In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires.
金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移动。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。
It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through.
因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子
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