10. Answer the following questions:

1. What is the definition of ductility?

2. What is the measure of ductility?

3. What material property is called brittleness?

4. What brittle materials can you name?

5. What way do brittle and ductile materials behave in compression tests?

6. Why is it conventional to divide materials into brittle and ductile?

Unit 5 Strength Under Cyclic Stresses

1. Pronounce the words correctly:

cyclic; gear; combustion; fluctuate; axle; fatigue; intercrystalline; subsequent; utilization.

2. Memorize the following words:

cyclic	- циклический
to be subjected to	- быть подверженным чему-то
to be sufficient	- быть достаточным
to cause smth	- быть причиной чего-то
interior	- внутренность, внутренняя сторона
fatigue	- усталость
combustion	- горение, сгорание
crank gear	- кривошипно-шатунный механизм
internal combustion engine	- двигатель внутреннего сгорания
fluctuating	- колебательный, переменный
to rotate	- вращать
magnitude	- величина
to cause failure	- вызывать /быть причиной повреждения
to penetrate	- проникать

3. Read and Translate the text. Strength under cyclic Stresses

Many machine parts are subjected to cycles of varying stresses during operation. For example, the piston and all parts of the crank gear of an internal combustion engine are subjected to fluctuating forces. Their law of variation is determined by the shape of the indicating diagram and the kinematic characteristics of the mechanism.

The railroad car axle rotating together with the wheels also undergoes cyclic stresses though the external forces maintain their magnitude. This is due to the fact that the points of the rotating axle are alternately in the tension and compression zone.

The number of cycles to failure varies over a very wide range. At high stresses 5 to 10 cycles are sufficient to cause failure. This is well illustrated by the heated bending of a piece of wire.

At present it is an established fact that the structure of a metal does not change under cyclic loads. The origin of fracture is of a purely local nature. A microcrack may form in a region of increased stress due to design, technological to crystals located in the zone of the crack begin to fracture and the crack penetrates into the interior of the body.

The mode of failure is cue to a change in crystalline structure of the metal. This was interpreted formely to be the cause of failure under cyclic stresses. The phenomenon outlined above fatigue, and investigations concerned with strength became known as the analysis of fatigue strength.

The theoretical analysis of fatigue strength involves great difficulties.

The nature of failure is governed by the properties of molecular and crystalline structure of the substance. Неnce, the scheme of a continuous medium that has been employed successfully in the problems considered up to this point cannot serve as a satisfactory basis for analysis in the present case. For the development of a sufficiently well balanced theory of fatigue strength if is necessary to gain a close insight into the properties of cryctal structure and intercrystalline bonds with subsequent utilization of the apparatus of statictics and the probability theory.

4. Find all the Passive constructions in the text. Translate them into Russian.

5. Find all the words with -ed endings in the text. State their origin. Translate the sentences into Russian.

6. Find the sentences with the following prepositional phrases in the text. Translate them into Russian. Then make up your own sentences with the same prepositional phrases:

to depend on, to be subjected to ,to be determined by, due to, to be the cause of smth, to be involved into, to be governed by.

7. Learn the following prepositional phrases by heart. Make up your own sentences using them:

to make a contribution to smth – делать вклад во что-либо

to include smth in smth – включать что-либо во что-либо

to interfere in smth – вмешиваться во что-либо

to make smth of/from smth – делать, создавать что-либо из чего-либо

to divide smth in a number – делить что-либо на какое-то число

to work at smth – работать над чем-либо

to react to smth – реагировать на что-либо

characteristic of smth/smb –характерный для чего-либо, кого-либо