无机非金属材料工程专业英语 第6章

in which l0 is the original length（原始长度） before any load is applied, and li is the instantaneous length（瞬时长 度）. Sometimes the quantity li－l0 is denoted as Δl, and is the deformation elongation or change in length at some instant, as referenced to the original length. Engineering strain (subsequently called just strain) is unitless （无量纲）, but meters per meter or inches per inch are often used.
Fundamentals of Materials Science and Engineering
Introduction

Many materials or components, e.g. road wheels of a car, when in service , are subjected to forces or loads. In such situations it is necessary to know the characteristics of the material and to design the member from which it is made such that any resulting deformation will not be excessive and fracture will not occur . The mechanical behavior of a material reflects the relationship between its response or deformation to an applied load or force. Important mechanical properties are strength, hardness, ductility, and stiffness.

Stress （应力）is a measure of an applied mechanical load or force, normalized (归一 化)to take into account cross-sectional area. Two different stress parameters were definedengineering stress and true stress.
Fundamentals of Materials Science and Engineering

yielding adj. Inclined to give way to pressure, or influence. 屈服的。 yield strength 屈服强度 tensile strength 拉伸强度 elongation to fracture 延伸率 Poisson’s ratio 泊松比 proportional limit 比例极限 resilience :The property of a material that enables it to resume its original shape or position after being bent, stretched, or compressed; elasticity. 弹性：使某物质能在弯曲、伸展或收缩后恢复原先的 形状或位置的物体的性能；收缩性.
Fundamentals of Materials Science and Engineering
Chapter 6 Mechanical properties
Fundamentals of Materials Science and Engineering
Why study mechanical properties?

Fundamentals of Materials Science and Engineering

Materials and metallurgical engineers are concerned with producing and fabricating （制造）materials to meet service requirements as predicted by these stress analyses. This necessarily involves an understanding of the relationships between the microstructure (i.e., internal features) of materials and their mechanical properties.
缩截面
标准圆形截 面拉伸试样
标距长度
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Fundamentals of Materials Science and Engineering
(Engineering) strain（工程应变）

Strain represents the amount of deformation induced by a stress; both engineering and true strains are used.
Fundamentals of Materials Science and Engineering
Important terms and concepts:
Anelasticity n.滞弹性
stress n. 应力
ductility n. 延展性，塑性 elastic adj. 弹性的 true stress 真应力 engineering stress 工程应力
Fundamentals of Materials Science and Engineering
safe stress 安全应力 shear 剪切 toughness 韧性 fracture toughness 断裂韧度 impact toughness 冲击韧性 hardness n. 硬度 Rochwell hardness 洛氏硬度 Brinell hardness 布氏硬度 Knoop hardness 努氏硬度 Vichers hardness 维氏硬度 Indenter 压头 Hooke’s law 虎克定律
Upper yielding point
Low yielding point
Stress- strain curve of a low carbon steel specimen
Fundamentals of Materials Science and Engineering
Definition of concepts
elastic recovery 弹性回复 stiffness n. 刚度 modulus of elasticity 弹性模量

deform v. distort/bend/twist： To alter the shape of by pressure or stress. 使变形：通过压力或拉力改变…的形状 Deformation n.变形
Fundamentals of Materials Science and Engineering
What should you be able to do after studying this chapter?

know what a tensile-testing apparatus is used for. Know how stress-strain curve is obtained. Name what are the main mechanical properties。

Fundamentals of Materials Science and Engineering


ascertained: adj. determined replicate vt. duplicate, copy, reproduce, or repeat. 复制：复印、复写、复制或重复 fluctuate vt. vary irregularly , swing 波动,变动 imperative- urgent Professional society 专业协会 ASTM -American Society for Testing and Materials Confine vt. restrict/limit
Fundamentals of Materials Science and Engineering

Four stress-strain test types: Tension, compression, torsion, shear At the onset-A beginning; a start:开始： the onset of a cold.感冒初起 Offset-The start or initial stage; the outset.开始， 开端

Fundamentals of Materials Science and Engineering
Modulus of elasticity（弹性模量）, or Young’s modulus(杨氏模量)
Elasticity n.弹性 strain n. 应变 brittlement n. 脆性 ↔ plastic adj. 塑性的 true strain 真应变 engineering strain 工程应变
Stress-strain curve 应力应变曲线
Fundamentals of Materials Science and Engineering

As a material engineers, it is incumbent (obligatory有义务的) to understand how the various mechanical properties are measured and what these properties represent. In case that you are called upon( ordered; required) to design structures or components using predetermined materials such that unacceptable levels of deformation or failure will not occur, the adequate knowledge on mechanical properties of the material is a matter of life.
Fundamentals of Materials Science and Engineering
Tension test（拉伸试验）
Fundamentals of Materials Science and Engineering
When construct a component or something the like, all these properties of materials should be taken into consideration in the whole process of material selection and structure design.