1. Preparation…  Need ceramic mug  Alu tin  Plastic cup  ELASTIC BAND  SPRING

2. PHF110: Basic Physics and Materials Lecture 1b: Materials’ Properties 27 th November 2015

3. Human Time Periods Nano Age? Graphene? ???? Silicon AgePlastics Age Stone age Middle ages Industrial Rev Machine Age Renaissance Bronze age 6000-2500 BC1300-1000 BC Iron age 2.5 million BC Figurines 28,000 BC Flint Pottery 14,000 BC Bronze sword Iron tools Plastic artefacts Electronics

4. Materials Science PropertiesProcessingMicrostructure Melting temperature Ductility Hardness …… Facts Casting Injection moulding Forging Rolling …… Processes Grain structure Chemical distribution Phases Particles …… Features

5. Materials science – an (everyday) example End plug Barrel Cartridge Lid Ink Point(?) Insert Tip Ball Question: How many different materials?

6. A More complex example… Question: How many different materials? Answer: Many – all with tailored properties

7. Materials Science  The understanding of properties is extremely important for correct materials selection and use Processing Microstructure Casting Injection moulding Forging Rolling …… Processes Grain structure Chemical distribution Phases Particles …… Features Properties

8. Intended Learning Outcomes  Define a few common properties of materials  Describe some materials’ properties – note as we go along  Recommend basic materials properties requirements for simple applications

9. Materials grouping  3 Objects, 3 materials, 1 function  You instinctively know which is which.  What properties do they have? MetalCeramicPolymer

10. Some Properties  Melting / freezing / boiling point  Strength  Elasticity / plasticity  Ductility  Hardness  Toughness  Electrical and thermal conductivity  There are MANY more to learn about!

11. Strength (General)  OED: “ability to sustain the application of force without breaking or yielding”  ED: “…refers to a level of stress at which there is a significant change in the state of the material, e.g., yielding or rupture”  However, it’s not quite as simple as that…  What is yielding and rupture? What is stress?

12. Yielding  The point at which a material no longer exhibits linear-elastic behaviour Elastic means reversible! 2. Small load F  bonds stretch 1. Initial F  Linear- elastic 3. Unload return to initial

13. Plastic means permanent! Plastic Deformation (Metals) 1. Initial2. Small load3. Unload planes still sheared F  elastic + plastic bonds stretch & planes shear  plastic

14. Plastic Deformation (Polymers)  Deformation stages  Crystallites separate (reversible)  Rotation of crystallites (irreversible)  Separation of segments  Orientation of segments and amorphous

15. Load and displacement vs stress and strain = 1 unit of load 100 apples Small CSA Large CSA = 100 apples

16. Load and displacement vs stress and strain Displacement, δ Original length, L o

17. Stress vs strain  Allow us to relate load to load bearing area  And displacement to overall length of the piece  Calculating them is very simple: original area before loading  = F t A o 2 m N Area, A o F t F t lolo  = δ l o m m

18. Stress and Strain  We can measure the amount of stress required to cause a strain – Stress –strain curve  This curve can tell us quite a lot of information

19. Stress – Strain Curve (metals)

20. Plastic Deformation (Polymers)  Deformation stages  Crystallites separate (reversible)  Rotation of crystallites (irreversible)  Separation of segments  Orientation of segments and amorphous

21. Stress – Strain Curve (polymers)

22. Stiffness  OED: “the force required to produce unit deflection or displacement of an object”  ED: “For a structure, stiffness is the ratio of the force divided by the displacement. When discussing materials, substitutes for force, and substitutes for displacement”  NOTE: stiffness is altered by the structure  We describe material stiffness by defining a modulus stress strain

23. The Young Modulus – the measure of stiffness  Symbol E  E= stress / strain = σ / ε  Units?  Some common values?  Many uses! For example; medical

24. Property Kitchen Stiff Strong Weak Not Stiff

25. Ductility A measure of a material’s ability to undergo plastic deformation before fracture  After a tensile test a ductile material will have formed a neck – check your polymer sample  Useful for  Wire drawing  Can making – deep drawing  Rolling  NOTE: Not the same as malleability

26. Hardness A measure of a materials ability to resist deformation by indentation or abrasion (scratching)  Scratching - Moh’s scale  Indentation

27. Moh’s scale – scratch resistance  Qualitative measure of hardness  Quantitative methods discussed in Week 3 1234567891010 TalcDiamon d Glass Steel Aluminiu m

28. Indentation Methods  A known mass is applied to a material through a hard indenter for a known time  Deformation of the material is measured  Gives a quantitative measure of hardness

29. toughness A measure of the amount of energy a material absorbs as it fractures  Can be affected by speed of test (impact)  Specimen geometry important – Notch sensitivity  Can be ascertained (low speed load application) from stress-strain curve

30. Electrical conductivity The ease with which an electrical current may flow within the material  Electricity is conducted by electron transport within the material  Controlled by the bond types  Metals – metallic bonding = good conductor  Ceramics – ionic bonding = poor conductor  Polymers – covalent bonding = poor conductor

31. Comparison of some (general) properties Material class Electrical conductivity HardnessToughnessTensile strength DuctilityMelting temp MetalGoodMediumHigh MediumHigh CeramicPoorHighLow V.High PolymerPoorLow Very highLow  VERY generalised table  Missing properties include:  Cost, formability, availability, recyclability, chemical resistance, density and many many more!

32. Materials selection  Screwdriver is made of 2 materials  Steel and Perspex  What properties do they have which make them suitable?

33. Consider important properties for these items…  Safety goggles?  Pen (think of the different parts)?  Fizzy drinks bottle?  Touch screen of a smart phone?  What properties do they require and why?

34. Intended Learning Outcomes  Define a few common properties of materials  Describe some materials’ properties  Recommend basic materials properties requirements for simple applications