Ferrous and non-ferrous metals
In general metals are used in various constructions and different industries. For example, thousands of miles of railway track. All metals are divided into ferrous and non-ferrous metals. Ferrous metals are iron and its alloys (steel, cast iron etc.). Especially ferrous metals are of great importance. Machine tools and machinery, steamships and locomotives, automobiles and aeroplanes, rails and bridges, razor blades are turned out by the steel industry.
Non-ferrous are metals and alloys the main component of which is not iron but another element. It may be copper, aluminium, zinc. That's why copper and aluminium are belonged to as non-ferrous metals. Non-ferrous metals are extracted from minerals such as magnesite (magnesium carbonate), tinstone (tin oxides) etc. Non-ferrous metals have some characteristics. They are: high electric and heat conductivity, high corrosion resistance, non-magnetic qualifies, light weight and easiness to fabrication.
Task 24. Match the following words with their Russian equivalents:
| non-ferrous metal | a | медь | |
| an alloy | b | инструмент | |
| a railway | c | мост | |
| a network | d | цветной металл | |
| a tool | e | сплав | |
| a bridge | f | железная дорога | |
| copper | g | сеть |
1. ____, 2. ____, 3. ____, 4. ____, 5. ____, 6. ____, 7. ____.
Task 25. Read the text again and complete the spidergram.
Task 26. Complete the following sentences:
1. Ferrous metals _____________________________________________________.
2. __________________________________________, steamships and locomotives, automobiles and aeroplanes _______________________________________________.
3. _______________________________are referred to as non-ferrous metals.
4. ___________________are divided into ________________________________.
5. In general, _______________________________________________________.
6. _______________________________________have some characteristics.
Task 27. Read the following statements and say whether they are right or wrong. Correct false statements.
1. Thousands of miles of railway track form an intricate network of steel over the world, helping to carry daily billions of freight for different industries.
2. Copper, aluminium and some other metals are not referred to non-ferrous metals.
3. All metals are divided into ferrous and non-ferrous metals.
4. Metals in general and especially ferrous metals are of great importance in various constructions.
5. Ferrous metals are iron and its alloys.
6. Non-ferrous metals are extracted from minerals such as magnesite, tinstone etc.
Task 28. Put the following sentences in negative and
interrogative form.
1. All metals are divided into ferrous and non-ferrous metals.___________________
_______________________________________________________________________
2. Ferrous metals are iron and its alloys. ___________________________________
_______________________________________________________________________
3. Ferrous metals are of great importance in various constructions. ______________
_______________________________________________________________________
4. Non-ferrous are metals and alloys the main component of which is iron. ________
_______________________________________________________________________
5. Copper, aluminium and some other metals are referred to as non-ferrous metals. _
_______________________________________________________________________
Unit III.
Bridges and tunnels.
Task 1. Read and translate the text.
Early bridges.
Bridges are structures built over a river, railroad track, road, lakes, ravines, canyons, highways or some other obstacle. They allow people or vehicles to cross from one side to another.
Bridges must be built strong enough to safely support their own weight as well as the weight of the people and vehicles that pass over it. The bridge must also withstand natural occurrences that include weathering, earthquakes, strong winds, and freezing and thawing.
There's no doubt you've seen a bridge, and it's almost as likely that you've traveled over one. If you've ever laid a plank or log down over a stream to keep from getting wet, you've even constructed a bridge. Bridges are truly ubiquitous -- a natural part of everyday life. The type of bridge used depends on various features of the obstacle. The main feature that controls the bridge type is the size of the obstacle. How far is it from one side to the other? This is a major factor in determining what type of bridge to use.
In ancient times the first bridges made by humans were probably spans of wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement.
Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope which was capable of binding and holding in place materials used in early bridges.
The greatest bridge builders of antiquity were the ancient Romans. The Romans built arch bridges and aqueducts that could stand in conditions that would damage or destroy earlier designs. The Romans built long, arched spans, many of which are still standing. The Romans also used cement, which reduced the variation of strength found in natural stone. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost then later rediscovered.
Rope bridges, a simple type of suspension bridge, were used by the Inca civilization in the Andes Mountains of South America, just prior to European colonization in the 1500s.
Bridges built during the Middle Ages usually rested on crude stone arches with heavy piers (intermediate supports) that were a great obstruction to river traffic, and their roadways were often lined with small shops.
The best known early American design is the New England covered bridge. Colonial American bridge builders were willing to run the risk of rot or fire in exchange for such savings in time and manpower. Beginning with Abraham Darby's bridge at Coalbrookdale in 1779, most bridges began to be built of cast and wrought iron. Robert Stephenson, an English engineer, designed and built a bridge of this type across Menai Strait in North Wales (1850). Another is Victoria Bridge across the St. Lawrence at Montreal. The disadvantage of cast iron for bridges is its low tensile strength. During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich, Johannes Grubenmann, and others.
With the Industrial Revolution in the 19th century, truss systems of wrought iron were developed for larger bridges, but iron did not have the tensile strength to support large loads. With the advent of steel, which has a high tensile strength, much larger bridges were built, many using the ideas of Gustave Eiffel.
Task 2. Put a question tag.
1. The bridge must withstand natural occurrences that include weathering, earthquakes, strong winds, ________________?
2. The main feature that controls the bridge type is the size of the obstacle, _______
__________?
3. The greatest bridge builders of antiquity were the ancient Romans, ___________?
4. Cement reduced the variation of strength found in natural stone, _____________?
5. Since 1779 most bridges began to be built of cast and wrought iron, _____________?
6. Robert Stephenson designed and built a bridge of this type across Menai Strait, ________________?
7. During the 18th century there were many innovations in the design of timber, _________________?
8. Iron did not have the tensile strength to support large loads, ___________?
9. Steel has a high tensile strength, ______________?
Task 3. Translate the following words.
| ravine | fiber | ||||
| obstacle | rope | ||||
| withstand | mortar | ||||
| span | suspension | ||||
| log | crude | ||||
| plank | pier | ||||
| ubiquitous | rot | ||||
| crossbeam | wrought iron | ||||
| reed | cast iron | ||||
| bamboo poles | tensile | ||||
| cavern | truss system | ||||
| deciduous | lashing |
Task 4. Match the parts of word combinations.
| railroad | a | weight | |
| to support | b | a plank | |
| natural | c | civilization | |
| to lay | d | track | |
| to cross | e | bridges | |
| mortar | f | caverns | |
| Inca | g | occurrences |
Task 5. Make up your own sentences with them.
Task 6. Write out from the text above the events which took place in the indicated period of time.
1. The Roman era
2. The Middle Ages
3. Since 1779
4. The Industrial Revolution
Task 7. Answer the following questions.
1. What is a bridge by definition?
2. Why must bridges be strong enough?
3. Were bridges a natural part of antique people’s life?
4. Why were the Romans different in building bridges?
5. What civilization used rope bridges?
6. What were Darby's bridges made of?
7. Was low tensile strength of cast iron for bridges advantage or disadvantage?
8. Did iron have the tensile strength to support large loads during the Industrial Revolution?
Task 8. Fill in the blanks using the words below.
Romans, obstacle, humans, century, wooden, wet, cement, stone, plank, feature, timber, bridges, many, ancient.
1. __________are structures built over a river, railroad track, road etc.
2. They laid a ___________ or log down over a stream to keep from getting ___________.
3. The main ____________ that controls the bridge is the size of the _________.
4. In _________ times the first bridges made by ________ were probably spans of ____________ logs.
5. The ___________ also used ___________, which reduced the variation of strength found in natural ____________.
6. During the 18th ____________ there were ____________ innovations in the design of ____________ bridges by Hans Ulrich and others.
Task 9. Read the text again. Entitle each part.
Task 10. Retell the text above.
Task 11. Translate the text into English.
В России первые железные мосты появились в 1780-е г.г. и отличались от европейских тем, что были большей частью именно железными, а не чугунными. Один из них был сделан по проекту Дж. Кваренги для парка в Царском селе. Затем последовала серия мостов, изготовленная на Сестрорецком оружейном заводе. Два железных моста 1793-1794 находятся в Таврическом саду в Петербурге. Эти памятники инженерного искусства лишь по случайности удалось спасти от сноса - совершенство их конструкции таково, что долгое время их считали произведениями значительно более позднего времени.
В начале XIX в. в Петербурге появляется новый тип мостов - "из полых чугунных ящиков", первым из которых был "Бердов мост" (1805-1806) на одном из притоков Невы. В 1807 г. Гесте составил для Петербурга первый в мире образцовый проект чугунного моста и в 1810-20-е гг. в городе появилось около десяти этих сооружений, казавшихся в то время необычно легкими.
Первое десятилетие XIX в. стало временем возникновения мостов вантовой конструкции (или американо-европейской системы); начало их строительству было положено американцем Джоном Фидлеем, юристом по образованию, рассматривавшим строительство мостов как дополнительное средство заработка. В это же время идея вантового моста пришла в голову архитектора Витберга. Интересен факт отсутствия точных расчетов конструкции в первых железных мостах. До 1820-х гг. расчеты заменялись моделью в 1/3 величины реальной постройки, что объясняется неустойчивостью качества выплавки железа в ранний период.
Task 12. Come up with the best title for the text above.
Task 13. Read and translate the text.