Materials Science and Technology

Materials Science and Technology is the study of materials and how they can be fabricated to meet the needs of modern technology. Using the laboratory techniques and knowledge of physics, chemistry, and metallurgy, scientists are finding new ways of using metals, plastics and other materials.

Engineers must know how materials respond to external forces, such as compression, torsion, bending, and shear. All materials respond to these forces by elastic deformation. That is, the materials return their original size and form when the external force disappears. The materials may also have permanent deformation or they may fracture. The results of external forces are creep and fatigue.

Compression is a pressure causing a decrease in volume. When a material is subjected to a bending, shearing, or torsion (twisting) force, both the tensile and compressive forces are simultaneously at work. When a metal bar is bent, one side of it is stretched and subjected to a tensional force, and the other side is compressed.

Tension is a pulling force; for example, the force in a cable holding a weight. Under tension, a material usually stretches, returning to its original length if the force does not exceed the material’s elastic limit. Under larger tensions, the material does not return completely to its original condition, and under greater forces the material ruptures.

Fatigue is the growth of cracks under stress. It occurs when a mechanical part is subjected to a repeated or cyclic stress, such as vibration. Even when the maximum stress never exceeds the elastic limit, failure of the material can occur even after a short time. No deformation is seen during fatigue, but small localized cracks develop and patronage through the material until the remaining cross-sectional area cannot support the maximum stress of the cyclic force. Knowledge of tensile stress, elastic limits, and the resistance of materials to creep and fatigue are of basic importance in engineering.

Creep is a slow, permanent deformation that results from steady force acting on a material. Materials at high temperature usually suffer from this deformation. The gradual loosening of bolts and the deformation of components of machines and engines are all the examples of creep. In many cases the slow deformation stops because deformation eliminates the force causing the creep. Creep extended over a long time finally leads to the rupture of the material.

Assignments:

1. General understanding. Answer the questions:

1. What are external forces causing the elastic deformation of materials? Describe those forces that change the form and size of materials.

2. What are the results of external forces?

3. What kinds of deformation are the combinations of tension and compression?

4. What happens if the elastic limit of material is exceeded under tension?

5. What do we call fatigue? When does it occur?

6. What do we call creep? When does this type of permanent deformation take place?

7. What are the results of creep?

2. Find the following words and word combinations in the text:

Отвечать требованиям современной технологии; используя лабораторные методы; новые способы использования металлов; сжатие, растяжение, изгиб, кручение, срез; возвращать первоначальный размер и форму; внешняя сила; постоянная деформация; уменьшение объёма; растягивающие и сжимающие силы; превышать предел упругости материала; повторяющиеся циклические напряжения; разрушение материала; развитие и распространение мелких трещин; сопротивление материалов ползучести и усталости.

3. Say whether these sentences are true (T) or false (F):

1. Elastic deformation helps materials to respond to such forces as tension, compression, torsion etc.

2. When the external force appears the materials return their original size and form.

3. Increasing in volume when the material is pressured is the characteristic of compression.

4. The material never returns to its original length under all kinds of tension.

5. There is no deformation during the fatigue, although some cracks take place here.

6. The example of creep is the gradual loosening of bolts etc.

4. Put the words from column B into the certain gaps in column A. There are two extra words:

A	B
1. … is the growth of cracks under stress.	a) needs; b) length; c) ruptures; d) materials; e) external; f) deformation; g) fatigue.
2. Materials Science and Technology is the study of materials and how they can be fabricated to meet the … of modern technology.
3. Materials at high temperature usually suffer from ... .
4. All materials respond to … forces by elastic deformation.
5. Under larger tensions, the material does not return completely to its original condition, and under greater forces the material … .

5. Translate the following sentences into English:

1. Упругая деформация – это реакция всех материалов на внешние силы, такие, как растяжение, сжатие, скручивание, изгиб и срез.

2. Усталость и ползучесть материалов являются результатом внешних сил.

3. Внешние силы вызывают постоянную деформацию и разрушение материала.

4. Растягивающие и сжимающие силы работают одновременно, когда мы изгибаем или скручиваем материал.

5. Растяжение материала выше предела его упругости дает постоянную деформацию или разрушение.

6. Когда деталь работает долгое время под циклическими напряжениями, в ней появляются небольшие растущие трещины из-за усталости металла.

7. Ползучесть – это медленное изменение размера детали под напряжением.

6. 1) Read the text and divide it into paragraphs; use the phrases below. Render the text:

1. This article is about / the author of the article speaks about … 2. I’d like to call your attention to … 3. One should mention that … 4. It’s interesting to point out that … 5.One should comment upon this question / problem … 6. So / besides / moreover / that is why … 7. On the one hand / on the other hand … 8. In conclusion, I can say that … 9. Considering all the facts …

2) Title the text.

The scientific and technological progress will continue in engineering along two main headlines. Firstly, it is automation, including the creation of “unmanned” industries. Secondly, raising the reliability and extending the service life of machines.

This certainly requires new technology. The machines modules on a large scale are well suited for “unmanned” industries.

Intense work is being carried out on new robots. What we need is not merely manipulators which can take up a workpiece and pass it on, but robots which can identify objects, their position in space, etc.

We also need machines that would trace the entire process of machining. Some have been designed and are manufactured. Modern engineering thinking has created new automated coal digging complexes and machine systems, installations for the continuous casting of steel, machine tools for electrophysical and electrochemical treatment of metals, unique welding equipment, automatic robot transfer lines and machine tool modules for flexible industries.

New technologies and equipment have been designed for most branches of engineering.

In the shortest time possible the engineers are also start producing new generators of machines and equipment which would allow manufactures to increase productivity several times and to find a way for the application of advanced technologies.

Large reserves in extending service life for machines can be found in the process of designing. At present, advanced methods have been evolved for designing machines proceeding from a number of criteria. Automatic design systems allow for an optimizing of the solutions in design and technologies when new machined are still in the blueprint stage.

A promising reserve in increasing the life of parts is strengthening treatment. In recent years new highly efficient methods have been found.

First and foremost of them is the vacuum plasma methods for coating components will hard alloy compounds, such as nitrides and carbides of titanium, tungsten and boron. Methods have been designed for reinforcing machine parts most vulnerable to wear and tear, such as in grain harvesters, to make them last several times longer.

Thus, it is not merely quantity engineers and scientists are after, rather it is a matter of major characteristics. In other words, this is a matter of quality, and not of the mere number of new machines, apparatuses and materials.

UNIT 3

Read the text: