3-Methods for investigating and testing materials

• Materials testing


  Used to help select the most appropriate material for a product or application
• When testing different materials

  1. Use the same size of material for each test

  2. Make sure the environmental conditions are the same

  3. Use the same testing equipment and technique (including force applied and position of force)

  4. Use one person to take all test measurements
• Simple workshop tests


  • Use basic tools and equipment
• Simple workshop tests


  • Tensile, toughness, hardness, malleability and ductility tests
• Tensile test


  Less deflection under load means the material has more tensile strength
• Toughness test


  Tough materials absorb impact, brittle materials bend or shatter
• Hardness test


  The smaller the indent, the harder the material
• Malleability and ductility test


  Cracks on the outside indicate a lack of ductility, cracks on the inside indicate a lack of malleability
• Corrosion testing involves placing equally sized material samples outside in an area exposed to the effects of weather and leaving for a set length of time
• Electrical conductivity test


  1. Collect material samples of the same dimensions, mark a set distance, place multimeter probes, measure resistance

  2. The higher the resistance, the lower the conductivity
• Thermal conductivity test


  1. Collect material samples of the same dimensions, measure a set distance from one end and place a thermometer, light a Bunsen burner under the other end, record the time it takes for the temperature to reach the set point

  2. The shorter the time, the higher the thermal conductivity of the material
• Industrial tests


  • Usually carried out in a lab with specific testing machinery, using standardised test pieces of materials
• Tensile strength test


  1. A tensometer machine tests for tensile strength

  2. The standard test piece is held in a clamp at each end, one clamp is fixed and the other moves, putting the material under tension

  3. The test piece is stretched, the load and distance traveled is plotted, giving information on elastic limit, yield point, maximum load and final breaking point
• Toughness test


  1. The Izod impact test is used to test the toughness of a material

  2. A notched test piece is held vertically in the vice of the machine, a pendulum is released from a set position to strike the test piece

  3. The energy absorbed by the test piece is calculated from the height the pendulum swings to after it hits the test piece

  4. The material that absorbs the most impact is the toughest and gives the least pendulum swing
• Hardness test


  1. The Rockwell, Brinell and Vickers pyramid tests are used to test the hardness of a material

  2. All involve a load being applied to a material with the resultant indentation determining the hardness

  3. The smaller the indentation, the harder the material
• Non-destructive testing (NDT)


  • Carried out on products rather than material samples, the product is not destroyed during testing, used to find defects in the material
  • Methods include ultrasonic and x-ray
• Malleability and ductility test

  1. The test piece is placed into a bending machine and held, supported at the ends

  2. A mandrel or plunger loads the test piece at the centre and bends it to a predetermined angle or until the test piece fractures

  3. Cracks on the outer bend indicate the level of ductility, cracks on the inside of the bend indicate the level of malleability
• Corrosion testing


  Material samples of equal size are placed into a simulated weather environment and left for a set length of time, materials can then be inspected for surface corrosion
• Thermal conductivity test


  A square-shaped material test piece is placed between two temperature controlled plates, the temperature is increased at a controlled rate and the heat flow through the material is measured by heat flow sensors