Тошкент Давлат Техника Университети “Амалий инглиз тили” кафедраси

2. Read the text and answer to the questions

1. 
   Which alloys are used in all branches of machine-building?
   
2. 
   How are ferrous and non-ferrous alloys fabricated?
   
3. 
   What are the main ferrous materials?
   
4. 
   In what way can the properties of steels be improved?
   
5. 
   What non-ferrous alloys are used in industry?
   
6. 
   What are the main properties of aluminium-base alloys?
   
7. 
   What is mechanical strength?
   

In 1910 Captain Robert Scott, the famous British polar explorer, fitted out an expedition to the South Pole, at that time still a terra incognita. The expedition went forward through the lifeless ice desert of the Antarctic, leaving behind small boxes of food and cans of kerosene for the explores to use them on the way back. At the beginning of 1912 the expedition finally reached its destination but to the men’s great disappointment they found a note there which made it clear that they had been preceded by the Norwegian explorer Roald Amundsen one month earlier. However, Captain Scott’s worst misfortune was yet to come. On the way back they found out that the expedition was left without kerosene: the cans were empty. The kerosin had leaked out. The people, exhausted, freezing and hungry, could not either warm themselves up or prepare anything to eat. The result was awful – Captain Scott and his friends soon died. What was the reason for the mysterious disappearance of the kerosene? Why did the expedition so carefully planned end so tragically? What was Captain Scott’s mistake? It was quite simple: the kerosene cans had been soldered with tin. The explorers were ignorant of the fact that at freezing temperatures tin “catches a cold”, first losing its luster and becoming dull grey and then turning into powder. This phenomenon – “tin plague” – led to the tragedy of the expedition. Meanwhile this fact was known as early as the Middle Ages. At the end of the 19th century a train carrying bars of tin was sent from Holland to Russia. When the cars were unsealed in Moscow they contained some grey and useless powder – it was Russian winter which had played a wicked trick on the buyers of tin. At about the same period a well-equipped expedition set out for Siberia. It seemed everything had been taken care of to ensure its success, except one thing: tin dishes had been taken. The result was that after a while spoons and bowls had to be carved from wood if the expedition was to go any further. At the very beginning of the 20th century a shocking incident occurred at an army in St. Petersburg: it was discovered, that all tin buttons had vanished from the soldiers’ uniforms and the boxes that were supposed to contain such buttons were full of a grey powder. The contents of the boxes were analyzed. The substance in them was tin. It was the chemical phenomenon known as ‘tin plague’. What are the processes that cause tin to disintegrate? Only after discovering X-rays metallurgists enabled to take a look inside the metal and study its crystalline structure. Tin (and other metals) seems to have different crystalline forms under different circumstances. The properties of different crystalline forms differ from the properties of the original metal. Thus, at a temperature of minus 33°C tin turns into a powder (tin plague) and at a temperature below13°C a new modification – grey tin – is formed. It l oses the properties of metal and becomes a semiconductor.

ANSWERS
EXERCISE 1.
1. Radiyning kashf etilishi asosiy atom tuzilishi tushunchasini o'zgartirdi.
2. Qurilishdagi har qanday nosozliklar inson o’limiga va qimmatga tushishiga olib kelis
hi mumkin.
3. Bugungi kunda zamonaviy yuqori tezlikdagi transport energetika uskunasining rivojlanishi mavjud muhandislik materiallarining ishdan chiqish xususiyatlarining ahamiyatini oshirdi.
4. Boshqariladigan kosmik kemalarni loyihalashning hozirgi asosiy muammosi bu katta raketa divigatellarining vibratsiyasidir.
5. Elektron mikroskopning yaratilishi metallarni charchash fenomini yaxshiroq tushunish imkonini berdi
6. Hozirda ko'plab olimlar ichki yonuv dvidatellarida zaharli gazlarni nazorat qilish ustida ish olib borishmoqda .
7. Reaktiv dvigatellarda yuqori quvvatli kompozit materiallar ba'zilarida titanium qotishmalarini almashtirishi mumkin .
8. Titandan foydalanish o'sishi kutilganidan ko'proq oshdi.