Testing Materials How do materials behave under different conditions? May 29, 2009
Which to Use..? <ul><li>In pairs, summarise the key characteristics of the 4 main material classes: </li></ul><ul><ul><li>...
Which to Use..? <ul><li>In pairs, summarise the key characteristics of the 4 main material classes: </li></ul><ul><ul><li>...
 
Testing Materials Materials behave differently when we put them under stress. This is due to the object  and  the material...
<ul><li>How will a spring behave under tension? </li></ul><ul><li>Measure the extension for different masses (0g to 300g) ...
Hooke’s Law <ul><li>Robert Hooke, who in 1676 stated,  </li></ul><ul><li>The power ( sic .) of any springy body is in the ...
Hooke’s Law <ul><li>But what happened when you added more springs? </li></ul><ul><li>Does it change the shape of the graph...
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Designer Materials 2

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Designer Materials 2

  1. 1. Testing Materials How do materials behave under different conditions? May 29, 2009
  2. 2. Which to Use..? <ul><li>In pairs, summarise the key characteristics of the 4 main material classes: </li></ul><ul><ul><li>Metals Ceramics Polymers Composite </li></ul></ul><ul><ul><li>Think about the properties that we discussed last lesson… </li></ul></ul><ul><ul><li>List some examples... </li></ul></ul>
  3. 3. Which to Use..? <ul><li>In pairs, summarise the key characteristics of the 4 main material classes: </li></ul><ul><ul><li>Metals - Tough. Strong in tension . Can have plastic properties. E.g. Iron, Steel, Copper. </li></ul></ul><ul><ul><li>Ceramics - Stiff. Strong in compression . Week in tension. Brittle. E.g. Cement, Diamond, Porcelain. </li></ul></ul><ul><ul><li>Polymers - Long chain molecules. Some are brittle. Some are very elastic. Some are tough. E.g polythene. Cotton, leather. </li></ul></ul><ul><ul><li>Composite - More than 1 material. Has properties of each material e.g. reinforced concrete with steel bars). </li></ul></ul>
  4. 5. Testing Materials Materials behave differently when we put them under stress. This is due to the object and the material. <ul><li>Example: </li></ul><ul><li>If you sit on a match it will snap </li></ul><ul><li>But a chair made of the same material holds your weight </li></ul>
  5. 6. <ul><li>How will a spring behave under tension? </li></ul><ul><li>Measure the extension for different masses (0g to 300g) and record results into a table. DO NOT DAMAGE SPRING!!! </li></ul><ul><li>Plot the results onto a graph - Mass vs. Extension </li></ul><ul><li>What happens if you add another sprint next to the first? Next to it or attached to it…? </li></ul>x m
  6. 7. Hooke’s Law <ul><li>Robert Hooke, who in 1676 stated, </li></ul><ul><li>The power ( sic .) of any springy body is in the same proportion with the extension. </li></ul><ul><li>announced the birth of elasticity. Hooke's statement expressed mathematically is, </li></ul><ul><li>F = k . x </li></ul><ul><li>where F is the applied force (and not the power, as Hooke mistakenly suggested), x is the deformation of the elastic body subjected to the force F , and k is the spring constant (i.e. the ratio of previous two parameters). </li></ul>
  7. 8. Hooke’s Law <ul><li>But what happened when you added more springs? </li></ul><ul><li>Does it change the shape of the graph? </li></ul><ul><li>Does it change the spring constant? </li></ul><ul><li>How can we get around this..? </li></ul><ul><li>For homework - work out if we could work out a consistent constant </li></ul>

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