9 Materials. Vocabulary Properties and processes. Kick off

Transcription

1 9 Materials Kick off 1 Look at the pictures. Use two words from the list to say why each material has been used. cheap flexible light stiff strong Vocabulary Properties and processes 1 Look at the definitions. Then complete the table of adjectives and their opposites using the words in the list. brittle easily broken. Glass is brittle. dense heavy in relation to size. Hard rock, such as granite, is dense. 1 nylon rope EXAMPLE Because it's strong and flexible. ductile (of metal) can be stretched and yet retain its strength. Copper is ductile. elastic will spring back to its original shape when stretched. Rubber is elastic. plastic will keep its new shape when stretched or bent. A copper wire is plastic. ductile expensive light soft stiff weak Adjectives elastic plastic strong 1 2 brittle flexible 3 hard 4 5 heavy cheap 6 dense We form some nouns by modifying adjectives. Add -ity or -ness to complete the nouns. 4 carbon fibre bicycle frame 5 rubber tyre 2 Can you name one other construction material that fits each of the five descriptions in 1? Nouns strength weak ' ductility brittle 2 flpxihil ' stiffness hard ' softness lightness heavi ^ dens ^ Note: We usually say low cost and high cost rather than cheapness and expensiveness.

2 Materials 65 In this unit describing tlie properties of materials describing manufacturing processes comparatives and superlatives discussing a stress-strain curve listening to a conversation about a problem with a material i Look at the adjectives and definitions. What products can you name that have these properties? durable lasting a long time, not wearing out malleable able to be hammered into shape tough can withstand cracking under shock smooth having an even surface It's my job 1 Discuss the questions. 1 Why do you think it takes longer to build an oil platform than a standard ship? 2 What is the main material used in shipbuilding? 3 What conditions or environmental factors are important design considerations for ships? 4 Look at the industrial processes. Use the words to complete the sentences. 2 (JT* Listen and check your answers. casting forging 1 is one of the oldest industrial processes. Hammers or weights force malleable material into the desired shape. 2 is useful for creating a long piece with a complex profile. A compressive force pushes the material through a hole to shape it. This process works with both ductile and brittle materials. 3 Iron is a heavy material, and it's also brittle when cast. In it's heated to 1260 C and poured into useful shapes such as frying pans. 4 is used to turn ductile materials like copper and aluminium into sheet. 3 Listen again. Answer the questions. 1 What are the main products of Mr Kim's company? 2 What two parts of the company does Mr Kim's team work the most closely with? 3 What does Mr Kim help the other teams to do? 4 What property of steel can cause problems for shipbuilders? 5 What is the name for steel combined with other metals? 6 What is the name for damage caused to materials by sea water? 7 What is the name for parts that, if they failed, would cause the failure of a structure? 8 What is Mr Kim's role while a ship is being built? 4 In small groups, discuss the questions. 1 Why must every oil platform be unique and made to order? 2 Why don't shipbuilders use 'amazing new materials'? 3 Why is cooperation important in shipbuilding? 5 Would you like to do Mr Kim's job? Why / why not?

3 66 Unit 9 Language spot Comparatives and superlatives 1 Look at the information. Complete the sentences with the words in the list. better cheaper less brittle more brittle more expensive the best the cheapest the least brittle the most brittle the most expensive the worst worse Metals - price per tonne Steel - $700 Aluminium alloy - $1950 Copper - $7600 Titanium - $ Steel is. 2 Copper is 3 Titanium is. 4 Steel is Metals - ductility. than aluminium alloy. than aluminium alloy.. metal. very ductile copper metal. and brittleness low carbon steel high carbon steel very brittle cast iron 5 High carbon steel is. 6 Low carbon steel is _ 7 Cast iron is 8 Copper is. metal.. metal. _ than cast iron.. than copper. Lightweight bicycle frames - performance :' good j ' steel aluminium titanium very good carbon fibre 9 Carbon fibre is 10 Aluminium is _ material,.than steel. 11 Steel is choice for a Hghtweight frame. 12 The performance is steel is than the performance of carbon fibre. Complete the sentences with the correct form of the adjectives in the list. brittle ductile flexible heavy soft weak 1 The tonnes.. ship we made last year weighed Glass, which is _. material used in the production of our mobile phones, may break if the phone is dropped. 3 Because it is aluminium can be cut by high carbon steel. 4 If the component fails, it will always fail at point. 5 The pipe needs to bend several times as we pass it into the structure, so we don't want it to be stiff. We should choose pipe we can find. 6 Copper is used for wire because it is than most other metals. 3 Find five things around you and compare them. Use comparatives and superlatives. EXAMPLES The concrete floor is denser than the wooden ceiling. The glass in the windows is the most brittle material in the room.» Go to Giammai lefeience p 122 Number talk strength, stiffness, and toughness 1 Read the text. Then complete the sentences with the words in the list. Young's modulus is a mathematical description of how a material behaves when it is stretched. The unit of Young's modulus is the gigapascal (GPa). Steel typically has a Young's modulus of 200 GPa, while rubber has a Young's modulus of 3 GPa. The same force will stretch rubber more than steel. Engineers and scientists test and calculate the Young's modulus of materials using machines that stretch a material and measure its behaviour. The measurements are used to produce an ~ extension-load graph for the s material. Load is measured in newtons and extension is,, extension (mm) measured in millimetres. ^ Extension-load graph for rubber

4 Materials 67 less lower millimetres more newtons stiff 1 The Young's modulus of a material expresses how the material is. 2 The same force will stretch steel than rubber. 3 Rubber has a Young's modulus than steel. 4 Rubber will stretch than steel before it breaks. 5 The amount that the material stretches is expressed in 6 The force applied to cause stretching is expressed in Speaking Discussing a stress-strain curve 1 Match the diagrams with the materials. 2 Read the text. Answer the questions. In Unit 4, we talked about stress and strain. Engineers use stress-strain graplis to show the strength, stiffness, and toughness of materials. Stress-strain graphs are produced using load-extension data. Stress and strain are calculated using the cross sectional area of the material and its original length. Graphs for soft, flexible materials such as rubber often have curved lines and show large strains before they break. Graphs for many stronger, stiffer materials such as steel and glass fibre are linear They start with straight lines and show less strain before they break. Which of these graphs shows rubber? Which shows glass fibre? strain strain 3 Using the words stress and strain, explain why rubber, not glass, is used for car tyres. 4 Which of these is most likely the Young's modulus for iron and which for aluminium? Which material is stiffer? 190 GPa 70 GPa strain % strain % 1 low carbon steel 3 wood (pine) 2 glass plate 4 copper 2 Match each description with the correct material and graph in 1. a The graph is linear right up to the breaking point. It is not as strong as steel, and it is more brittle than wood. b The graph is linear at first, then there is a sharp change and the graph curves. It is stronger than wood and is the stiffest of these materials. c This graph is non-linear. The material reaches its tensile strength, then it forms a neck. The stress measured by the original area falls until the material breaks at the neck. The material is the most ductile. d The graph is linear, then there is a short curve before failure. This material is brittle but not as brittle as glass. 3 Work in pairs. Student A, go to p.l09. Student B, go to p.ll3.

5 68 Unit 9 Aluminium (chemical symbol: Al) is the most common metal in the Earth's crust and the third most common element after oxygen and silicon. crust mantle liquid outer core solid inner core Reading Aluminium 1 Discuss the questions. 1 What properties does aluminium have? 2 What products are made from aluminium? 3 What processes form aluminium into shapes we can use? 2 Read the first paragraph of the text. Check your answers. Our good frienci Al 3 Read the whole text. Answer the questions. 1 What properties make aluminium a good material for aircraft? 2 What is a typical Young's modulus of aluminium alloy? 3 What property protects aluminium from corrosion? 4 Name three properties that make aluminium a good material for soft drinks cans. 5 What properties make aluminium a good material for electrical transmission? 4 Discuss the questions. 1 Since aluminium is stronger than wood, why do we still use wood for building houses? 2 There is plenty of aluminium in the Earth so why should we recycle it? 3 How do you think they make pure aluminium stronger? 4 Why can't we use very strong but brittle materials for building aircraft? Aluminium is everywhere Aluminium is a lightweight, high-strength metal, resistant to corrosion and easily recycled. When alloyed with other elements, it can be processed by casting, rolling, extruding, or forging. This makes it a favourite material of engineers in almost every field, from construction, rail transport, and aviation to the electrical industry, and many more. Strength and malleability Some aluminium alloys can be as strong as many steels, and its ductility and malleability mean it is easy to form. Its Young's Modulus, about 70 GPa, is about 33% of steel, and it's less dense than steel. Without aluminium there would be no air transport. Corrosion resistance Aluminium is highly reactive. This means that it changes chemically when it comes into contact with certain other substances. When aluminium is exposed to oxygen, it reacts. The result is a strong but thin oxide film on the surface of the aluminium. If the film is damaged, it forms again in most conditions. This gives aluminium excellent corrosion resistance. It also makes aluminium easy to colour and decorate. This, along with ease of recycling, makes it perfect for drinks cans and other food packaging. Conductivity Its high electrical conductivity - combined with its lightness and strength - mean that aluminium is used more frequently than copper for overhead power cables. Aluminium's conductivity is lower than copper's, but engineers prefer the lower density and cost of aluminium. aluminium aluminum

6 Listening An aircraft wing spar problem 1 Look at the picture of an aircraft wing. Answer the questions. Rear wing wing spars tap^red end of wing spar 1 What properties do engineers look for in materials for aeroplane parts? 2 Why are testing and quality control especially important in aeroplane manufacture? 3 What types of problems would you expect to find in the manufacture of wing spars? Q Listen to two engineers discussing a problem with a wing spar and the results of some tests that were done on it. Choose the correct option to complete the sentence. 1 The problem with the wing spar was that it was a incomplete b cracked c broken 2 The tensile test showed that the material was a low quality b incorrect c within tolerances 3 The impact tests found a problem with the spar's a fracture toughness b thickness c yield strength 4 The spar was formed by a rolhng b extrusion c casting 5 The problem was caused by a human error b incorrect adjustment of the milling machine c impurities in the aluminium 6 The problem can be solved by changing a manufacturing technique b suppliers c the spar's design 7 The next step is to a stop the project c go back to the design engineers b do more tests Checklist Assess your progress in thiis unit. Tick (/) tine statements whiich are true. I can describe the properties of materials I can describe manufacturing processes I can use comparatives and superlatives I can discuss a stress-strain curve Key words Adjectives brittle dense ductile durable flexible malleable smooth tough Nouns alloy corrosion density ductility extension-load graph property stress-strain graph Why do you think it is necessary to test real components rather than just material samples when changing to new materials?