2. Прочитайте текст снова и письменно ответьте на вопросы:

1. What is a machine?

2. Why have humans used mechanisms and machines?

3. Does the term machine generally apply to an assembly of parts operating together to perform work?

4. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage to the ideal mechanical advantage, isn’t it?

5. Are machines used to transform heat or other energy into mechanical energy known as engines?

Вариант 5

1. Прочитайте и письменно переведите на русский язык текст:

TYPES OF WELDING

1. Welding is a technique used for joining metallic parts usually through the application of heat. This technique was discovered during efforts to manipulate iron into useful shapes.

2. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld.

3. This process can be used with nearly all metals and produces a high-quality weld. However, the rate of welding is considerably slower than in other processes. In shielded metal-arc welding, a metallic electrode, which conducts electricity, is coated with flux and connected to a source of electric current. The metal to be welded is connected to the other end of the same source of current. An electric arc is formed by touching the tip of the electrode to the metal and then drawing it away. The intense heat of the arc melts both parts to be welded and the point of the metal electrode, which supplies filler metal for the weld.

4. This process is used mainly for welding steels. In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process. Submerged arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electroslag welding. It is very efficient but can be used only with steels.

2. Прочитайте текст снова и письменно ответьте на вопросы:

1. What is welding?

2. What kind of gas is used to shield the metal from oxidation?

3. What is the rate of welding process?

4. What is ‘submerged arc welding’?

5. Is electroslag welding an efficient process?

Тексты по направлению

190600.62 "Эксплуатация транспортно-технологических машин и комплексов" вариант 1

1. Прочитайте и письменно переведите на русский язык текст:

ALTERNATIVE VEHICLES

1. At the present rate of production oil supplies will run out rather soon, and we will have to look for other sources of energy.

2. What kind of vehicle will then dominate? Nowadays car makers discuss four promising types of cars: fuel cell cars, electric cars, hybrid cars, and solar electric cars.

3. The electric car has a long history. The first electrical cars were built at the end of the 19^th century, but they couldn’t compete against the internal combustion engine. Success of the electric car depends on the light weight battery, capable of being recharged quickly, and the availability of electric energy.

4. Several U.S. companies already sell electrics. For example, Solar Electric Engineering of Santa Rosa, California, offers Solar Electric’s Destiny 2000 which comes in at $ 28,500, and includes an array of solar cells which provides a tiny bit of power and extends battery life. With its lightweight fiberglass body, the Destiny 2000 can travel 40 to 60 miles on a charge and cruises at 60-70 mph.

5. General Motors produced the electric car named “Impact”. Designed as an electric from top to bottom, the impressive Impact is powered by lead-acid batteries. The Impact easily cruises at 70 to 100 mph, and its range is claimed to be 120 miles at lower speeds.

6. There are many different electric cars around the world. They are used for local deliveries, post offices and the services.

7. The hydrogen/air fuel cells look very hopeful. These do not have to be charged, they generate their own energy from a chemical reaction. They convert fuel energy to electrical energy with better than 80% efficiency. But at present the fuel cells prove too expensive.

8. A hybrid system where electric batteries for city driving would be recharged in highway driving with gasoline fuel is an alternative to the totally electrical system.