Добавил:
Upload Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Інженерна мех. 3 курс Гудкова.doc
Скачиваний:
9
Добавлен:
20.11.2019
Размер:
382.46 Кб
Скачать
  1. Resume, what do Properties of Materials imply? Tell about Mechanical, Physical, Chemical, Dimensional properties of Materials particularly.

Unit 3

Topic: Non-metallic materials

I. Reading skills

1. Pre-reading tasks

a) You will read a text about non-metallic materials. Do you know what factors the usage of materials depends on?

  • Think over the examples of the major non-metallic engineering materials and make a list of them.

b) Read and memorize the following words and word-combinations in their specialized meanings.

аbrasive [əʹbreisiv] n шліфувальний матеріал

absorb [əbʹsƆ:b] v поглинати

adhesive [ədʹhi:siv] n матеріал, що зв’язує

application [͵æpliʹkei∫(ə)n] n застосування

boron [ʹbƆ:rƆn]  n бор

cam [kæm] n кулачок, кулачковий диск

caster [ʹka:stə] n ливарник, ролик

clay [klei] n глина

cutting [ʹkʌtiŋ] tool n ріжучий інструмент

deaden [ʹdedn] v ослабляти, заглушати

detent [diʹtent] n клямка, гачок

elastomer [iʹlæstəmə] n еластомер

elevated [ʹeliveitid] (temperature) adj висока (температура)

expansion [iksʹpæn∫(ə)n] n розширення

flammable [ʹflæməbl] adj легкозаймистий

gear [giə] n шестерня, зубчаста передача

germanium [dʒə: ʹmeiniəm]   n германій

grind [graind] v шліфувати, полірувати

insulation [insjuʹlei∫(ə)n]   n ізоляція, ізоляційний матеріал

intricate [ʹintrikit] (shape) adj скляна (форма)

lb.-Libra [ʹlaibrə] n фунт

metalloid [ʹmetəlƆid] n неметал

moderate [ʹmƆd(ə)rit] (temperature) adj помірна (температура)

molten [ʹməult(ə)n] (condition) adj розплавлений (стан)

plain bearing [ʹbeəriŋ] n підшипник ковзання

quench [kwent∫]  v загартувати

reinforced [ri:inʹfƆ:st] adj підвищеної міцності (жорсткості)

roll [rəul] v вертіти, обертати

shield [∫i:ld] v заслоняти, пропускати

shock resistance [∫Ɔk] [riʹzist(ə)ns] n опір, протидія удару, поштовху

silicon [ʹsilikən] n кремній

slide [slaid] n ковзна частина механізму, повзун, каретка

stiffness [ʹstifnis] n жорсткість

transmit [trænzʹmit] v проводити, пропускати

wear [weə] v тримати, мати

yield [ji:ld] strength n межа міцності на текучість

2. Read and translate the following text into Ukrainian.

Non-metallic materials. Advantages and limitations of non-metallic materials

For structural and wear applications

The engineering mechanic should become familiar with a few plastics, a few ceramics, a few tool steel, and so on; it will be found that these will satisfy maybe 90% of engineering needs. Save the remaining 10% of material problems for the metallurgist.

As it is pointed out, there are non-metallic and metallic materials. The usage of materials depends on its properties, availability, economics factors.

The following non-metallic materials: plastics, polymers, glass are widely used in engineering. And though mechanical properties are usually significantly lower than those of Metals, non-metallic materials are the most economical. The commonest plastics and metals cost approximately $ 0.30/lb. Some of the new exotic polymers can cost as much as $ 30/lb, and the precious metals as much as $ 3.000/lb.

Technical development states, that plain bearings are the major plastic engineering application. Plastic wear components are widely used in the design of rolling elements, slides, cams, gears, casters, detents, and hundreds of other specific machine components.

In the case of glass-or asbestos-filled or reinforced plastics, the hardest possible mating surface is a mandate for good service life.

The importance of the use of polymers for protective and decorative coatings is obvious. Polymers are the highest corrosion-resistant materials. Adhesives, a powerful application of polymeric materials, can be used to simplify many designs and fabrication procedures.

The high-silica glasses have excellent thermal shock resistance. These glasses can be heated red hat and water quenched without cracking. Glass fibers are used in insulation, sound deadening. Glasses can be used to shield or to transmit radiation. Photosensitive glasses are chemically machined into intricate shapes for fluidic devices used in machine controls.

Plastics

Though polymers are widely used in coating, adhesives, and elastomers, every engineer must know that, unlike metals, polymers have properties that vary significantly with moderate temperatures and loads. The following are some of indiosyncracies of plastics to be considered in the design of load-bearing members:

1. Plastics, or more correctly polymeric materials, expand with temperature at a rate many times greater than a metal.

2. The stiffness of plastics is an order of magnitude lower than the stiffness of metals.

3. Plastics permanently deform under load at room temperature and at stresses below their yield strength.

4. Some plastics are flammable.

5. Some plastics can absorb significant amounts of moisture and change size.

6. Fatigue data are not readily available.