Investigating And Testing Materials Flashcards
How Would You Test Tensile Strength in the Workshop
Tensile Strength is the ability to resist stretching or pulling forces.
This can be tested in a workshop by 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 defects under the load and/or how much load each material can bear with the least deflection.
The less deflection under load, the more tensile strength the material has.
How Would You Test Toughness in the Workshop
This test establishes how much impact force the material can absorb. Materials 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 materials may head or even shatter.
How Would You Test Hardness in the Workshop
You can test hardness by testing the resistance to surface indentation.
This can be done 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 Would You Test Malleability and Ductility in the Workshop
This test can be used ti test both ductility and malleability using one test piece.
Secure the test piece in a vice. Try to bend the test piece to 90°. 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 Would You Test Corrosion in the Workshop
This test can be used determine the rate of corrosion for a material when exposed to environmental effects such as rain or sun.
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 length of time. Materials can then be visually inspected for surface corrosion. Depending on the indented product function, further material testing such as toughness or hardness could then be carried out.
How Would You Test Electrical Conductivity in the Workshop
Electrical conductivity can be tested using a multimeter. Collect material samples of the same dimensions and, on the top surface, mark a set distance between the two ends of the material sample. This distance is the spacing for each probe of the multimeter. Place the probes on the distance marks and measure the resistance on the multimeter. The higher the resistance, the lower the conductivity.
How Would You Test Thermal Conductivity in the Workshop
Thermal conductivity can be tested using a thermometer. Collect material sample of the same dimensions. Measure a set distance from one end of the material on which to place a thermometer. A Bunsen burner is lit under the end of the material. Record the time 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.
What possible variables need to be kept the same for Material Testing
- Size of material sample being tested
- Environmental conditions
- Testing Equipment
- Force Applied
- Method of force application
- Position of force application
- Individual taking measurements
How Would You Test Tensile Strength in an Industrial Setting
A standard test piece is placed into a tensometer machine and held in clamps at each end. One clamp is fixed and the other moves in a worm drive gear mechanism. As the worm drive travels at a constant rate, the test piece is put under tension. As the test piece is stretched, the load and distance travelled is plotted, giving information on elastic limit, yield point, maximum load and final breaking point after ‘necking’.
How Would You Test Toughness in an Industrial Setting
The Izod impact test is used to test the toughness of a material. A notched test piece is held vertically in the vice of the test machine. A pendulum is released form a set position and swings to strike the test piece. The energy absorbed by the test piece is calculated from the height the pendulum swings to after it hits the test piece. The material that absorbs the most impact is toughest.
This is shown by the distance the pendulum swings after breaking the material. The further it swings, the less energy the sample absorbs and the more brittle the material.
How Would You Test Hardness in an Industrial Setting
One type of test for Hardness is the Rockwell test.
A preload is applied to the material sample using a diamond indented which breaks through just the surface of the material. The preload is the datum or zero reference position. An additional load is then applied to the test material and held for a predetermined length of time (dwell time). The load is then released and the distance between the preload and the applied load is measured, and the hardness of the material calculated. The smaller the indentation depth, the harder the material.
How Would You Test Ductility and Malleabilty in an Industrial Setting
A bend test is used to determine how well a material can withstand cracking during one continuous bend. A ductile material will have a lot of plastic deformation prior to failure.
The test piece is placed into a bending machine and held, supported at the ends. A mandrel or plunger loads the test piece at the centre and bends it to a predetermined angle, or until the test piece fractures. The material is then inspected for cracks or defects. Cracks on the outer bend indicate the level of ductility. Cracks on the inside of the bend indicate the level of malleability.
What is Non-destructive Testing
Non-destructive testing (NDT) is usually carried out on products such as large castings where there is a likelihood of an internal defect or imperfection which would not be detected by other methods. There are two standard NDT methods: ultrasonic and x-ray
What 2 types of Non-destructive testing are there?
- Ultrasonic
- X-ray
How does Ultrasonic Testing Work?
A transducer generates sound waves which are pulsed into the material. The intensity of the reflected sound waves signal is recorded on a display unit. The sound waves travel through the material and if there are any defects such as cracks in the sound waves’ paths, the sound energy will be partially reflected and shown on the display unit.
