Methods of investigating and testing materails Flashcards
What are the two main categories of testing?
Simple workshop tests (comparative) and Scientific measured tests (industrial).
Name some Practical workshop tests?
Tensile testing, toughness testing, hardness testing, malleability/ductility testing, corrosion testing and conductivity testing.
Name some Industrial tests?
Tensile testing, toughness testing, hardness testing, ductility/malleability testing and non-destructive testing.
What variables do we need to check when testing?
1) Size of material sample being tested
2) Environmental conditions
3) Testing equipment
4) Force applied
5) Method of force application
6) Position of force application
7) Individual taking measurements
How is Tensile testing done in the workshop?
Clamping material samples of the same length and thickness into a vice and applying a load such as weights to the unclamped end. This method can be used to see how much the material deflects under the load and/or how much the load each material can bear with the least deflection. The less the deflection under load, the more tensile strength the material has.
How is Toughness testing done in the workshop?
Material samples are clamped into a vice. Each sample is then hit with the same force, using a hammer. Tough materials will absorb the impact, whereas brittle may bend or even shatter.
How is Hardness testing done in the workshop?
There are two aspects: abrasive wear and resistance to surface indentation.
Abrasive wear is tested by running a file over the surface of the material, using the same force for each material sample. The material with the fewest scratches is the hardest.
Resistance to surface indentation is tested by using a dot punch and a hammer. The material sample is fully supported underneath and the dot punch is placed onto the material surface. The dot punch is hit once with a hammer, using the same force for each material sample. The smaller the indent, the harder the material.
How is malleability/ductility testing done in the workshop?
Secure the test piece in a vice. Try to bend the test piece to 90 degrees. Cracks or surface damage on the outside of the bend indicates a lack of ductility. Cracks or surface damage on the inside of the bend indicates a lack of malleability.
How is Corrosion testing done in the workshop?
All test pieces should be the same size. Materials can simply be placed outside in an area exposed to weather effects and left for a certain amount of time. Materials then can be visually inspected for surface corrosion.
How is Conductivity testing done in the workshop?
There are two types of conductivity testing: electrical conductivity and thermal conductivity.
Collect material samples of the same dimensions and, on the top surface, mark a set distance between the two ends of the material sample. Place the probes on the distance marks and measure the resistance on the multimeter. The higher the resistance, the lower the conductivity.
Collect materials samples of the same dimensions. Measure a set distance from one end of the material on which to place the thermometer. A bunsen burner is lit under the other end of the material. Record the time it takes for the temperature to reach the set point at the other end of the material sample. The shorter the time it takes to reach the set temperature, the higher the thermal conductivity of the material.
