2. Прочитайте текст снова и письменно ответьте на вопросы:

1. What is corrosion?

2. Does electrochemical corrosion usually affect metallic materials?

3. Why are some metals more resistant to corrosion than others?

4. Do some metals have naturally slow or fast reaction kinetics?

5. Why is graphite an extreme example?

Вариант 3

1. Прочитайте и письменно переведите на русский язык текст:

ENGINE LATHE

1. The most versatile machines of the lathe group are engine lathes. They are used for metal-cutting operations and for cutting threads. Because of their ability to perform various kinds of work they require a great degree of skills to operate. A worker skilled in the use of a lathe is called a turner.

2. Engine lathes vary in size. The size of the engine lathe is based upon two measurements - approximate largest diameter that can be revolved over the ways and the total bed. The engine lathe is fitted with a carriage and cross-slide for clamping and holding the cutting tool. In engine lathe the cutting tools are generally guided by the machine tools itself, in other words, they are operated mechanically, while in some lathes the cutting tools are guided by hand.

3. The engine lathe consists essentially of the following basic parts: the bed, the headstock, the tailstock and the carriage. All the principal units are mounted on a bed. The bed has the ways or guides along which the carriage and the tailstock travel. The bed is a strong easting which functions as a base for supporting and aligning the rest of the machine. The work is damped and rotated by the headstock. The headstock is located and firmly bolted to the left-hand side of the bed and carries a pair of bearings in which the spindle rotates. Many modern lathes have a motor built into the headstock with the spindle serving as the motor shaft.

4. The tailstock is located at the right-hand side of the bed. It is a casting carrying a non-rotating sleeve, which can be advanced or retracted by means of the revolving screw. The tailstock may be moved anywhere along the lathe bed and can be damped in place at any point. The cutting tool is traversed in both the longitudinal and cross directions, as well as at an angle, by means of the carriage.

2. Прочитайте текст снова и письменно ответьте на вопросы:

1. What are the most versatile machines of the lathe group?

2. Why do the engine lathes require a great degree of skills?

3. What basic parts does the engine lathe consist of?

4. What is the function of the lathe bed?

5. How is the work damped and rotated?

Вариант 4

1. Прочитайте и письменно переведите на русский язык текст:

A MACHINE

1. A machine is any mechanical or organic device that transmits or modifies energy to perform or assist in the performance of tasks. It normally requires an input as a trigger, and transmits the modified energy to an output, which performs the desired task.

2. Humans have used mechanisms and machines to amplify their abilities. The primary difference between simple tools and simple mechanisms or machines is a power source and a somewhat independent operation. The term machine generally applies to an assembly of parts operating together to perform work. Generally these devices decrease the intensity of an applied force, altering the direction of the force or transforming one form of motion or energy into another.

3. The mechanical advantage of a machine is the ratio between the resistance or load, and the force required to overcome it, although this ratio is not entirely accurate as force is required to overcome friction, as well. To compensate for this, mechanical advantage is calculated as the ratio between the distance moved by the force applied, and the distance moved by the force not applied. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). Functioning physical machines are always less than 100% efficient.

4. Inefficiency of a machine is the degree or percentage to which a machine does not accomplish the work it could do without the restrictions of friction. Modern power tools, automated machine tools, and human operated power machinery complicate this definition greatly. Machines used to transform heat or other energy into mechanical energy are known as engines.