2. Read and translate the following text into Ukrainian. The Main Joints ­

The joints of machine elements are either permanent or detachable. Detachable joints (bolted, key and splined types) can be disassembled and reassembled without destroying their elements.

Permanent joints (riveted, welded, glued, etc.) can be disconnected only by destroying the welded seam, rivets or other elements of the joint.

Welded Joints

The permanent joints obtained by welding have won uni­versal recognition in modern mechanical engineering and construction.

Welding is the process of jointing a number of metal pieces by raising the temperature at the joint so that the metal becomes plastic or fluid. In the first case the welded pieces are united by pressure.

The basic advantages of welding over the riveted joints are:

1. Economy of material and lighter weight of the structure owing to:

(a) better utilization of metal elements (plates, angles) since their working sections are not weakened by the rivet holes, consequently the sections of welded pieces can be made smaller than the sections of riveted elements, for the same acting forces;

(b) possibility of using butt joints requiring no cover straps;

(c) lighter weight of the joining elements (rivets weigh more than welds).

2. Less labour is required since there is no need for mark­ing out and drilling or punching holes; riveting consumes much more labour than welding which can be auto­mated

3. Possibility of joining curvilinear parts

4. Tightness and impermeability of the joint

5. Noiselessness (riveting is inevitably accompanied by noise)

At present, the basic types of welding are gas welding, electric resistance welding and electric arc welding.

Gas welding. The welded metal is heated to a melting temperature. This temperature is attained by burning combustible gases (acetylene, hydrogen) in oxygen. Acetylene produces a high temperature which ensures the welding of thick metal parts (up to 40 mm thick).

Gas welding is resorted to for joining elements made of low carbon steels, thin steel sheets, cast-iron, non-ferrous metals and alloys.

A great part in the fabrication of welded structures is played by gas cutting of metal. The cuts are produced by burning the metal in a jet of oxygen.

Electric resistance welding. In this case metal is heated to a plastic state by the current passing through the joint between the elements (to be welded after which these elements are joined) by pressing them together.

Electric resistance welding is used for butt-joining strips and rounds (butt welding) and for lap-joining thin sheets of metal (spot welding, roll welding).

3. Find the answer to the questions:

1. What kinds of the joints of machine elements are known?

2. What are the basic advantages of welding?

3. What are the basic types of welding?

4. When is gas welding used for?

5. When is electric resistance welding used for?

4. Complete the sentences:

1. The joints of machine elements are … .

2. Welding is the process of jointing a number of metal pieces … .

3. … is heated to a melting temperature.

4. … is played by gas cutting of metal.

5. … is used for butt-joining strips and rounds.

5. Match the following English words with their Ukrainian equivalents.

1. joint a. будівництво, конструкція

2. construction b. тиск, нажим

3. plastic c. з’єднання

4. pressure d. пластмаса

5. resort e. застосовувати

6. fabrication f. заклепка, клепати

7. rivet g. обхват, перемичка

8. strap h. полоса

9. strip i. підробка

10. element j. елемент, частина

6. Translate sentences into English.

1. Зварне з’єднання утворюється зварюванням з’єднувальних деталей.

2. Зварювання – один із самих прогресивних і поширених способів одержання нероз’ємних з’єднань.

3. Зварювання застосовують не тільки як спосіб з’єднання деталей, але як технологічний спосіб виготовлення самих деталей.

4. Зварні конструкції мають великі переваги:

- простіша технологія підготовчих операцій;

- безшумність процесу зварювання;

- помітне зниження ваги конструкцій і економія матеріалу.