MATERIAL PROPERTIES PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 18. MATERIAL PROPERTIES

 

A Tensile strength and deformation When materials are exposed to forces, such as tension (stretching forces ) and compression (crushing forces ), they deform – that is, they change shape. The type of deformation depends on the type of force that is applied. B Elasticity and plasticity Some materials can extend significantly, but still return to their original shape. A material’s ability to do this is called elasticity. Rubber is an example of a very elastic material – it can be elastically deformed to a considerable extent. C Stages in elastic and plastic deformation The graph below shows the typical extension behaviour of ductile materials in tensile testing – where a sample bar is subjected to a progressively increasing tensile force. Points 0-1 The extension of the bar is proportional to the increase in tension. For example, when tension increases by 10%, length increases by 10% Point 1 The bar reaches the limit of proportionality. Beyond the point, length begins to increase at a slightly greater rate than tension.   EXERCISES 18.1 Complete the sentences using the words in the box. You will need to use one word twice. Look at A opposite to help you. compression deformation elongation extension tension 1. A stretching force is called _____________. 2. A crushing force is called _____________. 18.2 Match the two parts to make correct sentences. Look at B and C opposite to help you. 1. If a material is stiff 2. If a material is brittle 3. If a material is plastic 4. If a material yields 5. If a material fractures 6. If a material is elastically deformed. 18.3 Complete the magazine article about springs using words from A, B and C opposite.

ANSWER KEY