1. What is the density of a material?

2. What are the units of density? Where low density is needed?

3. What are the densities of water, aluminium and steel?

4. A measure of what properties is stiffness? When stiffness is important?

5. What is Young modulus?

6. What is strength?

7. What is yield strength? Why fracture strength is always greater than yield strength?

8. What is ductility? Give the examples of ductile materials. Give the examples of brittle materials.

9. What is toughness?

10. What properties of steel are necessary for the manufacturing of: a) springs, b) car body parts, c) bolts and nuts, d) cutting tools?

11. Where is aluminium mostly used because of its light weight?

Exercise 4.3. Find the following words and word combinations in the text:

1. количество массы в единице объема

2. килограмм на кубический метр

3. мера сопротивления деформации

4. отношение приложенной силы на единицу пло­щади к частичной упругой деформации

5. жесткая конструкция

6. прочность на сжатие

7. способность материала деформироваться не раз­рушаясь

8. поглощать энергию путем деформации

9. обратно пропорционально квадрату размера де­фекта

10. постепенное изменение формы

11. повышенные температуры

12. высокие растягивающие усилия

Exercise 4.4. Translate into English the following:

1. Плотность измеряется в килограммах на куби­ческий метр.

2. Большинство материалов имеют более высокую плотность, чем вода и тонут в воде.

3. Плотность материала очень важна, особенно в авиации.

4. Модуль Юнга — отношение приложенной силы к упругой деформации данного материала.

5. Чем более металл жесткий, тем менее он дефор­мируется под нагрузкой.

6. Когда металл растягивают, он сначала течет, то есть пластически деформируется.

7. Свинец, медь, алюминий и золото — самые ков­кие металлы.

8. Сопротивление ползучести является очень важ­ным свойством материалов, которые используются в авиационных моторах.

UNIT 5

MATERIALS TECHNOLOGY

TEXT A. CHANGES IN MATERIALS TECHNOLOGY

TEXT В . WORKING WITH NEW MATERIALS

TEXT C. METAL CASTING - A BASIC MANUFACTURING   PROCESS

TEXT D. METAL CUTTING

TEXT A. CHANGES IN MATERIALS TECHNOLOGY

Since the technology of any age is founded upon the materials of the age, the era of new materials will have a profound effect on engineering of the future.

Not only new materials, but related, and equally important, new and improved and less wasteful processes for the shaping, treating and finishing of both traditional and new materials are continuously being developed.

It is important that an engineer should be familiar with them. These include casting, injection molding and rotational molding of components of ever increasing size, complexity and accuracy; manufacture of more complex components by powder metallurgy techniques; steel forming and casting processes based on new, larger and more mechanized machines, giving reduced waste and closer tolerances; the avoidance of waste in forging by the use of powder metallurgy or cast pressforms and new finishing processes for metals and plastics, just to name a few. A high proportion of these processes is aimed at the production of complex, accurate shapes with a much smaller number of operations and with far less waste than the traditional methods of metal manufacture.

Joining techniques have developed to unprecedented level of sophisti­cation and are also providing opportunities for economies. It is necessary to mention that these newer techniques allow the manufacture of complicated parts by welding together simpler sub-units requiring little machining; such assemblies can be made from a variety of materials. The methods can also be used effectively for assembly, allowing savings to be made in both materials and machine utilization.

The brief review of new processes above has indicated that a new materials technology is rapidly emerging, providing new opportunities and challenges for imaginative product design and for more efficient manufacture.

 Exercise 5.1.Translate the sentences, which of them are not correct.

1. Joining techniques have developed to the high level of sophistication.

Joining techniques are developing to a high level of sophistication. 2. The review of new processes has indicated that a new materials technology is rapidly developing. The review of new processes is indicating that a new materials technology is rapidly developing. 3. The avoidance of waste in forging has been achievedby the use of powder metallurgy. The avoidance of waste in forging is being achieved by the use of powder metallurgy.

Exercise 5.2.Translate the sentences:

1. They also undertake the training of people who want to work at the new plant but do not have the required qualification. 2. The students know how to conduct this experiment. 3. The students know how they have to conduct this experiment. 4. He shows me the results of his work. 5. He shows me what results he has obtained. 6. There is a growing need for engineers who are familiar with the fundamental problems in metal processing and manufacturing. 7. There is a growing need for engineers familiar with the fundamental problems in metal processing and manufacturing. 8. When new types of autos are designed all the latest achievements of scientific and engineering progress are taken into account. 9. When designing new types of autos all the latest achieve­ments of scientific and engineering progress are taken into account.

10. On receiving his diploma the engineer does not finish his education.

11. When the engineer receives his diploma he does not finish his education.

Exercise 5.3. Answer the questions:

1. Is materials technology changing nowadays? 2. What do new manufacturing processes include? 3. What are they aimed at? 4. Can complicated parts be manufactured by welding together simpler sub-units? 5. Can these assemblies be made from a variety of materials? 6. What has the brief review of new materials and processes indicated? 7. Why is it necessary for an engineer to know these processes?

TEXT В . WORKING WITH NEW MATERIALS

A successful design is almost always a compromise among highest performance, attractive appearance, efficient production, and lowest cost. Achieving the best compromise requires satisfying the mechanical requirements of the part, utilizing the most economical material that will perform satisfactorily, and choosing a manufacturing process compatible with the part design and material choice. Stating realistic requirements for each of these areas is of the utmost importance.

The rapidity of change in materials technology is typified by the fact that plastics, a curiosity at the turn of the 20th century, are now being used in volumes which have for many years exceeded those of all the non-ferrous metals put together, and which are beginning to rival steel.

The changes which are taking place are, of course, not only quan­titative. They are associated with radical changes in technology — in the range and nature of the materials and processes available to the engi­neer.

The highest specific strength (i.e. the strength available from unit weight of material) now available comes from non-metals, such as fibreglass, and from metals, such as berillium and titanium, and new ultra­high strength steels.

Fibre technology, in its modern form, is of more recent origin than plastics, but composites based on glass and/or on carbon fibres are already being applied to pressure vessels, to lorry cabs and to aircraft engines, and may well replace aluminium for the skin and structure of aircraft. An all-plastic car has been exhibited: nearly the whole car, except the engine and transmission is of plastics or reinforced plastics.

It is not only plastics and their reinforcement which are changing the materials scene. Ceramics too are gaining an increasing foothold. Their impact as tooling materials in the form of carbides, nitrides and oxides is also well known — cutting tools made of these materials are allowing machining rates which had previously been considered quite impossible,

Silicon nitride seems to offer particular promise for a wide variety of applications. Among these is liquid metal handling. Pumps for conveying liquid aluminium are now on trial which could revolutionize the foundry industry. Silicon nitride is also being tested for the bearing surfaces of the Wankel rotary engines which are being developed as potential replace­ments for the conventional piston engines of our motor cars. And ce­ramic magnets have replaced the traditional steel pole-piece plus cop­per field coil for providing the engineering field for many electric motors.

It is clear that the number of combinations of all kinds of original trends in the production of new materials is practically unlimited. This, in turn, opens new realms for the designing of still cheaper, effective and unthinkably perfected, compared to that we have today, machines and mechanisms.

Exercise 5.4. Make up questions to the text B.

TEXT C. METAL CASTING -A BASIC MANUFACTURING PROCESS

One of the basic processes of the metalworking industry is the production of metal castings. A casting may be defined as "a metal object obtained by allowing molten metal to solidify in a mold", the shape of the object being determined by the shape of the mold cavity. A foundry is a commercial establishment for producing castings.

Numerous methods have been developed through the ages for producing metal castings but the oldest method is that of making sand castings in the foundry. Primarily, work consists of melting metal in a furnace and pouring it into suitable sand molds where it solidifies and assumes the shape of the mold.

Most castings serve as details or component parts of complex machines and products. In most cases they are used only when they are machined and finished to specified manufacturing tolerances providing easy and proper assembly of the product.

At present the foundry industry is going through a process of rapid transformation, owing to modern development of new technological methods, new machines and new materials. Because of the fact that casting methods have advanced rapidly owing to the general mechanical progress of recent years there is today no comparison between the quality of castings, the complexity of the patterns produced and the speed of manufacture with the work of a few years ago.

TEXT D. METAL CUTTING

Cutting is one of the oldest arts practiced in the stone age, but the cutting of metals was not found possible until the 18th century, and its detailed study started about a hundred years ago.

Now in every machine-shop you may find many machines for working metal parts, these cutting machines are generally called machine-tools and are extensively used in many branches of engineering. Fundamentally all machine-tools remove metal and can be divided into the following categories: