3. Find the answers to the questions in the text.

1. What knowledge satisfies 90% of engineering needs?

2. What non-metallic materials do you know?

3. What factors does the usage of materials depend on?

4. Why are non-metallic materials considered to be the most economical?

5. Give the examples of the major non-metallic engineering application?

6. What are the engineering applications of polymers?

7. Do polymers properties vary significantly, unlike Metals? Prove your answer.

8. What are the advantages, the limitations of polymers applications?

4. Complete the sentences.

1. There are metallic and …

2. The following non-metallic materials … are widely used in engineering.

3. Polymers are …

4. Adhesives can be used to …

5. Glass fibers are used in …

6. The stiffness of plastics is lower …

7. Some plastics can absorb …

5. Match the following English words and word-combinations with their Ukrainian equivalents:

1. non-metallic a. технічний розвиток

2. precious b. обробляти

3. technical development c. звукопоглинання

4. decorative coatings d. неметалевий

5. engineering application e. декоративне покриття

6. plastic wear components f. підшипник

7. bearing g. скловолокно

8. glass fiber h. коштовні метали

9. sound deadening i. застосування в інженерній промисловості

10. to machine j. пластикові утримуючі компоненти

6. True or false statements.

1. Polymers have properties that vary significantly with moderate temperatures and loads.

2. All plastics are flammable.

3. Plastics, polymers glasses are widely used in engineering.

4. The use of polymers for protective coatings is not important.

5. Fluidic devices are used in machine controls.

II. Retell the text “Non-metallic Materials. Advantages and Limitations of Non-metallic Materials for Structural and Wear Application”.

III. Rendering

Glasses. Traditionally, glasses are defined as super-cooled liquids. This is because glasses do not behave like metals, ceramics, or even plastics on cooloing from the molten condition. Most glasses are considered to be just a very viscose liquid when it is a solid.

The properties of glasses very with composition, but some general statements can be made:

1. Glasses are harder than many metals (400 to 600 kg/mm²).

2. Glasses have low ductility; they are brittle.

3. Glasses have a low coefficient of thermal expansion compared with many metals and plastics.

4. Glasses have low thermal conductivity.

5. Glasses can be good electrical insulators.

6. Glasses are resistant to many acids, solvents, and chemicals.

7. Glasses can be used at elevated temperature (up to 820^oC/1508^oF)

8. Glasses are slowly attacked by water.

So, glasses have good mechanical properties, and a wide range of thermal, electrical and optical properties. They have many uses in machines.

Ceramic materials

Indeed, to most people the term “ceramic” means dishes, pottery, porcelain figurines, and the like. But these are not engineering ceramics.

Most of these products are made from natural clays). These clay products are quite weak and useless compared to most engineering ceramics. “Ceramic” materials are more commonly referred to as metalloids. Some common metalloids are boron, germanium, and silicon. Ceramics, formed by the combination of two metallic elements into a compound, are termed intermetallic compounds.

Natural abrasives

Speaking about non-metallic materials we must point out the following natural abrasives used in machine engineering: diamond, corundum, emery, oilstones.

Diamond is used extensively for grinding tungsten- and tantalum-carbide cutting tools, and also glass, stone and ceramics.

Corundum is a mineral composed chiefly of crystallized alumina. The present commercial source of corundum is South Africa (Northern Transvaal). It has been largely replaced by harder, more uniform and efficient, manufactured abrasives.

Emery, a cheap and impure form of natural corundum which has been used for centuries as an abrasive, has been largely superseded by manufactured aluminum oxide for grinding. It is still used to some extent in the metal- and glass-polishing trades. The principal deposits of commercial emery are located in Asia Minor and on the island of Naxos.

Oilstones. Most oilstones used today in metalworking shops are made of manufactured aluminum oxide. The hard variety is used for sharpening tools requiring a very fine edge, such as those of surgeons, engravers, and dentists.

2. Make up a plan in the form of questions.

3. Give the summary of the text according to your plan in a written form.

IV. Comprehensive skills

1. Read and remember.

1. emery [ʹeməri] n наждак

2. garnet [ʹga:nit] n гранат

3. gather pace [ʹgæðə][peis] v крокувати, просуватися

4. gem [dʒem] n коштовний камінь

5. marble [ma:bl] n мармур

6. pumice [ʹpʌmis] pumice n пемза

7. rough [rʌf] adj грубий, нерівний

8. sandpaper [ʹsænd͵peipə] n наждачний папір

9. stick [stik], stuck, stuck [stʌk] v приклеювати

10. vegetable fiber [faibə] n волокно рослинного походження

2. Listen to the text “Natural and synthetic abrasives” and try to understand it.

3. True or false statements.

1. Abrasives are essentially hard and rough materials.

2. Sandpaper is a very expensive abrasive.

3. Hardness of abrasives is measured on the Mohs scale from 1 to 20.

4. In the early 19^th century the research on synthetic abrasives began to gather pace.

5. In 1955 it was shown how artificially prepared diamond could be used as an abrasive.

4. Listen to the text once again and answer the following questions.

1. What is the purpose of abrasives?

2. From what time have abrasives been in use?

3. What are the most important abrasives used through the ages and in, modern times?

4. When did the importance of synthetic abrasives come to the fore?

5. What is the highest rate of the abrasives according to the Mohs scale?

V. Communicative skills

Topic for discussion: The Use of Non-metallic Materials in Engineering.

Unit 4

Topic: Metals. Iron and Steel