外文翻译-提高材料利用率.doc

外文翻译题 目 Improve material utilization 学生姓名 XXX 学号 12XXXXXXXXX 所在学院 XX学院 专业班级 XXXX 指导教师 XX _ 完成地点 陕西理工学院 2015年 06 月 8 日提高材料利用率1.材料的物理性能在选择工业用材料时，许多工程师通常都只考虑其平均的宏观性能，因为这些特性是由工程实验确定的，而很少考虑其微观特性。但有些工程师由于其专业范围或所从事工作的需要，也考虑其微观性能。材料的平均性能包括制造过程的波动引起的缺陷、组织的变化以及密度变化。微观性能则与原子、分子以及它们的相互作用有关。为了使材料可直接用于工业，也为了在开发新材料时对可有的性能进行评估，因而需对材料的这些问题进行研究。当研究物质的微观性能与材料的平均性能之间的关系时，为了不至于将明显矛盾的概念混淆，就应了解造成材料具有各种性能的原因。这些性能有一般的，微观的、宏观的。一般性能则是以上提到的平均性能，这些性能属经典物理学的范畴，微观特性主要是由量子力学理论来解释，而宏观特性则是要由相对论来说明。相对论涉及的是类似行星那样大的物体或接近于光速的物体，同时也适合于较小的物质，如高速运行的亚原子粒子。对于核工程师、研究粒子加速器的电气工程师，相对论也有一定的地位。而对于生产工程师，相对论仅是学术上的兴趣，或是只因学科上的完整性而被提及。2.材料的机械性能在确定了材料的重要物理性能之后，就必须考虑其机械性能（如屈服强度和硬度）。机械性能具有结构敏感性，因为它们取决于晶体结构的类型及结合力，特别是取决于晶体内容或晶粒边界上缺陷的特性。区分金属与其他材料的一个重要特性是其塑性及在强度没有减少的条件下塑性变形的能力。设计时，延伸率为515%则可使其承受突然的动态过载。为了适应这类载荷而不破坏，材料应具有动态韧性、较大的弹性模量以及经过断裂之前产生足够的塑性变形以消耗能量的能力。为了预测材料受载后的特性，工程师需要材料机械性能的可靠数据。手册中的数据是普通合金在68F时的平均特性。设计时最常用的数据是拉伸屈服强度、硬度、弹性模量，在其他温度时（除68F之外）的屈服强度。设计者很少用到抗蠕变特性、缺口敏感性、冲击强度以及疲劳强度。材料厂商的样本中通常也提供最新的或完整的数据。在手册中很难找到生产工程中所需的象强重比、单位体积的成本以及对特定工作环境的承受能力等数据。材料的主要机械性能及其对设计的重要影响的简单回顾可使读者熟悉每一种试验的重要性。3.材料的选择各类实用的材料在不断增长，而每种材料都具有各自的特点、应用范围及优缺点。当今制造业中常用的材料有：铁和钢（碳钢、合金钢、不锈钢、工具钢和模具钢）。有色金属及其合金（铝、镁、铜、镍、钛、超耐热合金、高熔点金属、铍、锆、低熔点合金以及贵金属）。塑料（热塑塑料、热固塑料及合成橡胶）。陶瓷、玻璃陶瓷、玻璃、石墨、金刚石。复合材料（增强塑料、金属基符合材料、陶瓷基复合材料、蜂窝结构复合材料）。(1)材料性能当选择产品的材料时，首先要考虑的是材料的机械性能：强度、韧性、塑性、硬度、弹性、疲劳强度、抗蠕变性。材料的强重比以及刚度与重量比也是重要的特性，特别是用于航空及汽车工业的材料。铝、钛及增强塑料的上述二种比值比钢和铸铁的高。当然，产品及其零件材料的机械性能应根据产品发挥其预定功能的工作条件来选定。然后才考虑材料的物理性能如密度、比热、热膨胀性、导热性、熔点、导电特性及导磁特性。在较差的以及正常的工作环境下材料的化学性能也有重要的作用。材料的抗氧化性能、抗腐蚀性、性能的普遍降低、毒性、可燃性也都是要考虑的重要因素。例如，某些商务航空灾难性事故中，许多人员的死亡就是由于机舱内非金属材料燃烧释放的有毒烟雾所造成的。材料的制造性能决定了它们是否能用相对简便的方法铸造成型、机械加工、焊接、热处理等。将材料加工成所需形状的方法可能对产品的最终性能及使用寿命产生不利的影响。(2)利用率及成本原材料、加工过的材料及制成零件的利用率和成本是制造中的主要问题。材料选择的经济性与从技术上考虑材料性能和特点是同样重要的。如果原材料或加工过的材料或制成的零件不适合于所要求的数量、形状和尺寸，则应选择其替代品和选择其他加工方法，这就可能对产品成本起重要的影响。例如，若我们需要一根某一直径的圆棒，但这种尺寸并不是标准尺寸，那么必须购买较大直径的棒料，并通过某些加工方法（如切削加工，在模具中拉拔或磨削）加工至所需尺寸。供需的可靠性也影响其成本，大多数国家都进口许多生产上必不可少的原料，应注意，美国也依靠进口原料。显然，这取决于与其他国家的政治关系。用不同的方法对材料进行加工，其费用就不同，有些加工需要贵重机械，有些需要较大的劳动强度，有些需要具有专门技术的人员或受过高等教育的人员或经过专门训练的人员。(3)外观、使用寿命、处理方法材料被加工成产品之后的外观对用户产生较大的影响，其色泽、外观感觉及表面纹理都是在决定购置产品时要考虑的特性。使用时间以及与使用相关的现象（如磨损、疲劳、蠕变及尺寸稳定性等）也是重要的因素，这些现象对产品的性能有很大的影响，如不加以控制，就可能使产品完全失效。同样，产品中各材料的相容性也是重要的。摩擦、磨损及其它现象都可能缩短产品的使用寿命或导致产品破损。例如，由不同材料所制成的配合件间的电蚀作用就会腐蚀零件。在人们意识到要保持清洁与健康环境的时代，产品使用寿命期之后材料的回收利用及适当的处理变得日益重要。例如，应注意生物可降解的包装材料、可重复使用的玻璃瓶及铝制饮料罐的回收利用。有毒废物及材料的恰当处理也是一个重要问题。Improve material utilization1 Physical Properties of MaterialsIn the selection of materials for industrial applications, many engineers normally refer to their average macroscopic properties, as determined by engineering tests, and are seldom concerned with microscopic considerations. Others, because of their specialty or the nature of their positions, have to deal with microscopic properties.The average properties of material are those involving matter in bulk with its flaws, variations in composition, and variations in density that are caused by manufacturing fluctuations. Microscopic properties pertain to atoms, molecules, and their interactions. These aspects of material are studied for their direct applicability to industrial problems and also so that possible properties in the development of the new materials can be estimated.In order not to become confused by apparently contradictory concepts when dealing with the relationship between the microscopic aspects of matter and the average properties of materials, it is wise to consider the principles that account for the nature of matter at the different levels of our awareness. These levels are the commonplace, the extremely small, and the extremely large. The commonplace lever deals with the average properties already mentioned, and the principles involved are those set forth by classical physics. The realm of the extremely small is largely explained by means of quantum mechanics, whereas that of the extremely large is dealt with by relativity.Relativity is concerned with very large masses, such as planets or stars, and large velocities that may approach the velocity of light. It is also applicable to smaller masses, ranging down to subatomic particles, when they move at high velocities. Relativity has a definite place in the tool boxes of nuclear engineers and electrical engineers who deal with particle accelerators. For production engineers, relativity is of only academic interest and is mentioned here for the sake of completeness. 2 Mechanical Properties of MaterialsOnce the important physical properties of a material have been established, mechanical properties such as yield strength and hardness must be considered. Mechanical properties are structure-sensitive in the sense that they depend upon the type of crystal structure and its bonding forces, and especially upon the nature and behavior of the imperfections that exits within the crystal itself or at the grain boundaries.An important characteristic that distinguishes metals from other material is their ductility and ability to be deformed plastically without loss in strength. In design, 5 to 15 percent elongation provides the capacity to withstand sudden dynamic overloads. In order to accommodate such loads without failure, materials need dynamic toughness, high moduli of elasticity, and the ability to dissipate energy by substantial plastic deformation prior to fracture.To predict the behavior of a material under load, engineers require reliable data on the mechanical properties of materials. Handbook data is available for the average properties of common alloys at 68. In design, the most frequently needed data are tensile yield strength, hardness, modulus of elasticity, and yield strengths at temperatures other than 68. Designers less frequently use resistance to creep, notch sensitivity, impact strength, and fatigue strength. Suppliers catalogs frequently give more recent or complete data.Production-engineering data that is seldom found in handbooks include strength-to-weight ratios, cost per unit volume, and resistance to specific service environments.A brief review of the major mechanical properties and their significance to design is included to ensure that the reader is familiar with the important aspects of each test.3 Selecting MaterialsAn ever-increasing variety of materials is available, each having its own characteristics, applications, advantages, and limitations. The following are the general types of materials used in manufacturing today:Irons and steels (carbon, alloy, stainless, and tool and die steels)Nonferrous metals and alloys (aluminum, magnesium, copper, nickel, titanium, superalloys, refractory metal, beryllium, zirconium, low-melting alloys, and precious metals)Plastics (thermoplastics, thermosets, and elastomers)Ceramics, glass ceramics, glasses, graphite and diamond.Composite materials (reinforced plastics, metal-matrix and ceramic-matrix composites, and honeycomb structures).（1）Properties of materialsWhen selecting materials for products, we first consider their mechnical properties: strength, toughness, ductility, hardness, elasticity, fatigue, and creep. The strength-to-weight and stiffness-to-weight ratios of material are also important, particularly for aerospace and automotive applications. Aluminum, titanium, and reinforced plastics, for example, have higher ratios than steels and cast irons. The mechanical properties specified for a product and its components should of course be for the conditions under which the product is expected to function. We then consider the physical properties of density, specific heat, thermal expansion and conductivity, melting point, and electrical and magnetic properties. Chemical properties also play a significant role in hostile as well as normal environments.Oxidation corrosion, general degradation of properties, toxicity, and flammability of materials are among the important factors to be considered. In some commercial airline disasters, for example, many deaths have been caused by toxic fumes from burning nonmetallic materials in the aircraft cabin. Manufacturing properties of materials determine whether they can be cast formed, machined, welded, and heat treated with relative ease. The method used to process materials to the desired shapes can adversely affect the products final properties and service life.（2）Availability and costAvailability and cost of raw and processed materials and manufactured components are major concerns in manufacturing. Competitively, the economic aspects of material selection are as important as the technological considerations of properties and characteristics of materials. If raw or processed material or manufactured components are not available in the desired quantities, shapes, and dimensions, substitutes and/or additional processing will be required, which can contribute significantly to product cost. For example, if we need a round bar of a certain diameter and it is not available in standard form, then we have to purchase a larger rod and reduce its diameter by some means, such as machining, drawing through a die, or grinding. Reliability of supply, as well as demand, affects cost. Most countries import numerous raw materials that are essential for production. Note the reliance of the United States on imported raw materials. The broad political implication of such reliance on other countries is self-evident. Different costs are involved in processing materials by different methods. Some methods require expensive machinery, others require extensive labor, and still others require personnel with special skills or a high level of education or specialized training.（3）Appearance, service life, and disposalThe appearance of materials after they have been manufactured into pro