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Materials Science

Materials Science. Material Selection Classes of Material Properties Properties of Materials. Material selection. Materials are used to make or build objects.

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Materials Science

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  1. Materials Science • Material Selection • Classes of Material Properties • Properties of Materials

  2. Material selection • Materials are used to make or build objects. • During the past 200 years there has been an enormous increase in the range of materials available to us. It is therefore important that the correct materials be used for a particular use. • In Selecting the best material you need to look at 4 things: Physical properties, Cost and Time, Shaping and Forming and Availability.

  3. Selecting the best material – A checklist 1 PHYSICAL PROPERTIES Hardness Tensile Strength Compressive Strength Shear Strength Stiffness Toughness Malleable Corrosive Appearance Weight Conductivity 2 WHAT COST? The materials The extras (fittings etc) SELECTION 3 SHAPING & FORMING Cutting out Moulding Casting Joining 4 AVAILABILITY Are they easy to obtain including fittings.

  4. Classes of Material Properties • General • Chemical • Physicochemical • Mechanical • Thermal • Electrical and magnetic • Acoustical & Optical

  5. General Properties of Engineering Materials • Density or Relative Density • Porosity • Moisture Content • Macrostructure • Microstructure

  6. Chemical Properties of Engineering Materials • Oxide or Compound Composition • Acidity or Alkalinity • Resistance to Corrosion or Weathering

  7. Physicochemical Properties of Engineering Materials • Water-absorptive or water-repellent action • Shrinkage and swell due to moisture change.

  8. Mechanical Properties of Engineering Materials • Some include: • Strength • Tension, compression, shear, and Flexure • Static, impact, and endurance • Stiffness • Elasticity/Plasticity • Ductility/Brittleness • Hardness & wear resistance

  9. Thermal Properties of Engineering Materials • Specific Heat • Expansion • Conductivity Electrical and Magnetic Properties of Engineering Materials • Conductivity • Magnetic permeability • Galvanic action

  10. Acoustical Properties of Engineering Materials • Sound Transmission • Sound Reflection Optical Properties of Engineering Materials • Color • Light transmission • Light reflection

  11. Properties of Materials • Each material has many properties. It is incorrect, for example to describe a material as just ‘strong’ or ‘weak’ as for example concrete is strong in compression but weak in tension. HardnessToughnessStrength BrittlenessMalleabilityDuctility ElasticityPlasticityConductivity DensityFatigueStiffness

  12. Hardness • The ability of a material to resist wear indentation and scratching. An example of a hardness test that can be carried out in the lab. Different materials are used and the depth of indentation measured

  13. Toughness • The ability of a material to withstand blows or sudden impact. Different materials are used, the hammer is swung from the same height each time about a fixed fulcrum. The distance travelled after impact or fracture is used to find toughness

  14. Strength • The ability of a material to withstand forces of tension, compression and torsion Tensile Strength – the ability to withstand pulling forces or Tension forces Compressive Strength – the ability to withstand ‘squeezing’ forces or Compression forces Torsional Strength – the ability to withstand ‘twisting’ forces or Torsion forces

  15. Brittleness • A material that is easily fractured by impact is said to be brittle e.g. Glass The same as the toughness test however those materials that fracture easily are said to be brittle.

  16. Malleability • A material that can be rolled or hammered into shape without rupture. As ring rises the side of Coke can is thinned out

  17. Ductility • A material that can be pulled or stretched into a thin wire or thread. Get picture of wire drawing

  18. Elasticity • The ability of a material to return to its original shape after deformation. Get picture of someone stretching elastic band

  19. Plasticity • The ability of a material to be permanently deformed without fracture..

  20. Conductivity • The ability of a material to allow Heat or electricity to flow through it. Ball Bearing drops from most conductive 1st.

  21. Density • Is the mass of 1 cubic centimetre (cm3) of a substance. (Mass per unit Volume) • Which is heavier a tonne of feathers or a tonne of lead? • Q. Which has the greatest density? Mass Density = Volume

  22. Fatigue • Occurs when materials have become overworked and fracture or fail. Find picture

  23. Stiffness • The ability of a material to resist bending deformation.

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