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1、,English on Mechanical Engineering Lesson 3 Mechanical Properties of Metals,Text,Mechanical properties are the characteristic responses of a material to applied forces. Knowledge of mechanical properties of materials is essential in order to construct a mechanically sound structure such as a bridge
2、on the river. Mechanical properties can be determined by conducting experimental tests on the material samples. Some important mechanical properties of materials are: strength (in tension, compression, shear, bending and torsion), stiffness (strength), ductility, impact strength, hardness and toughn
3、ess.,Materials Sustain Loads On Tension,Materials Sustain Loads On Shear,Materials Sustain Loads on bending,Materials Sustain Loads on torsion,Text,1. Strength The Strength of a material may be defined as the ability of the material to sustain loads without undue distortion or failure. Material shou
4、ld be adequately strong when subjected to tension, compression, shear, bending or torsion as per the intended use. For example, the crankshaft of an automobile should have sufficient torsion strength. ,2. Stiffness Stiffness is the ability of a material or shape to resist elastic deflection. For ide
5、ntical shapes, the stiffness is proportional to the modulus of elasticity. A material which deforms less under a given load is stiffer than one which deforms more. 3.Ductility Ductility refers to the capacity of a material to undergo deformation under tension without rupture as in a wire drawing ope
6、ration.,Text,4. Impact Strength Impact strength is the strength of a material when subjected to high rates of loading, usually in bending, tension or torsion. The amount of energy required to fracture the material by a single blow is measured by means of a Charpy impact test. 5. Hardness Hardness is
7、 the resistance of a material to plastic deformation usually by indentation. However, the term may refer to stiffness or refer to resistance to scratching, abrasion or cutting. Tests, such as Vickers, Briell and Rockwell, are generally employed to measure hardness.,6.Toughness Toughness refers to th
8、e ability of a material to withstand bending or the application of shear stresses without fracture. By this definition, copper is extremely tough but cast iron is not.,1、property n. 特征, 特性,财产, 性质 2、characteristic a. 特有的, 典型的 response n. 回答, 响应, 反应 characteristic response 特征响应 3、essential a. 本质的, 基本的
9、; n. 实质, 要素 4、construct vt. 建造, 构造, 创立 5、sound a.可靠的，坚固的 vi. 发出声音 n.声音 6、conduct v. 实施, 传导；n. 行为, 操行 7、sample n. 标本, 样品, 试样, 范例 8、sustain vt. 支撑, 维持, 持续 9、undergo vt. 经历,支撑, 忍受 10、subject vt.使屈从于.,经受住n. 主语adj. 受制于 11、resistance n. 抵抗, 阻力, 电阻 12、withstand vt.抵挡, 经受住,Words and Expressions:,13、strength
10、 n. 强度, 力量,兵力, 浓度 14、tension n. 拉紧, 拉力, 张力, 牵力 15、compression n. 压缩, 压榨 16、shear v. 剪切, 修剪, 剪 17、bend v. 弯曲, 屈服; n. 弯曲 18、torsion n 扭转, 转矩 19、stiffness n.刚度,刚性, 坚硬, 硬度 20、ductility n. 展延性, 柔软性,顺从 21、impact n. 冲击, 影响, vt.撞击, 22、toughness n. 韧性, 坚韧, 刚性 23、hardness n. 硬度, 24、distortion n. 扭曲, 变形, 曲解, 失
11、真 25、deformation n. 变形 26、deform v. 使变形 27、deflection n. 偏差,变形 偏斜, 偏转 28、failure n. 破坏,失败,破产 美不及格 29、rupture v. 破裂, 裂开 n.破裂, 决裂, 敌对, 割裂 30、fracture n. 破裂, 骨折; v. (使)破碎, (使)破裂 31、crankshaft n. 机曲轴 32、elastic a. 弹性的 反义词：plastic 弹性的 33、identical a. 同一的, 同样的ID card n.身份证 34、modulus n. 系数, 模数 the modulus
12、 of elasticity弹性模数,35、indentation n. 压痕，印凹痕 36、scratch n. 划痕，抓痕 vt. 刮,擦, 抓, 挖 37、abrasion n. 磨损 cut n切削 v.切(割、削) 38、shape n. 型材,型钢 39、blow vt. 冲击,吹 40、Charpy impact test 摆锤式冲击试验 41、applied forces 外力、张力、作用力 42、crankshaft 曲轴 43、automobile 汽车 44、wire drawing operation 拉丝工艺 45、high rates of loading 高速载荷
13、 46、stresses 内应力,Notes A knowledge of mechanical properties of materials is essential in order to construct a mechanically sound structure such as a bridge on the river 材料的力学性能对于构建一个可靠的力学构件（如河流上的桥梁）是非常重要的。 to be essential：相当于to be important，其含义为“重要”。 in order to：引出一个目的状语，其中such as 可用于列举，其义为：例如，诸如。 T
14、he strength of a material may be defined as the ability of the material to sustain loads without undue distortion or failure 材料的强度可定义为，材料受载而不失效或过分变形的能力。 to be defined as：被定义为to sustain loads without undue distortion or failure：动词不定式短语，充当目的状语。, For identical shapes, the stiffness is proportional to t
15、he modulus of elasticity 对于同样的型材,刚度与弹性模量成比例。 to be proportional to：与成比例 The amount of energy required to fracture the material by a single blow is measured by means of a Charpy impact test 一次冲击击碎材料所需能量可通过摆锤式冲击试验测得。 required to fracture the material by a single blow：过去分词短语，充当定语，修饰energy。 by means of：
16、用方法，通过方式,a. strength b. stiffness c. ductility d.impact strength e. hardness f.toughness, the capacity of a material to undergo deformation under tension without rupture as in a wire drawing operation the resistance of a material to plastic deformation usually by indentation the ability of a material or shape to resist e
