3-Methods for testing materials

Question 1

Why are materials tested?

Answer 1

To help select the most appropriate material for an application

Question 2

How can a fair test be created?

Answer 2

• use same size of material for each test
• Control environmental conditions
• Use the same equipment and methods
• use one person to take all the measurements

Question 3

How is Hardness tested using simple workshop tools?

Answer 3

a Dot punch and force from a hammer is applied to the material. The smaller the indent the harder the material

Question 4

How is Malleability and ductility tested using simple workshop tools?

Answer 4

Material is bent to an angle of 90 degrees, if the material cracks on the inside it indicates a lack of malleability, if the material cracks on the outside then it indicates a low ductility

Question 5

How is corrosion tested using simple workshop tools?

Answer 5

Place materials outside, exposed to weather conditions for a set length of time, they can then be visually inspected for surface corrosion

Question 6

How is electrical conductivity tested using simple workshop tools?

Answer 6

• Tested using multimeter probes , the higher the resistance recorded, the lower the conductivity

Question 7

How is thermal conductivity tested using simple workshop tools?

Answer 7

• Measure a length of the material and place a thermometer on one side and a lit bunsen burner on the other
• Establish a set temperature for the other side of the product to reach
• The shorter time it takes, the higher the thermal conductivity

Question 8

What is an industrial test?

Answer 8

Carried out in a lab, using specific testing machinery, and standardised pieces of materials

Question 9

Industrial tests - Tensile strength

Answer 9

• A tensometer machine is used
• The material is held in a clamp at each end, one end will pull on the material (creates tension)
• The material will stretch and the load and distance travelled is plotted
• This gives us information of elastic limit, yield point, maximum load, and final breaking point

Question 9

Industrial tests - Toughness

Answer 9

• Izod Impact test
• A notched material is held vertically in a vice
• A pendulum is released and will swing to strike the test piece, The energy absorbed by the material is calculated from the height the pendulum swings after impact
• A tougher material will absorb more impact and cause a lower swing

Question 10

Industrial tests - What are the three types of tests for hardness

Answer 10

• Rockwell
• Brinell
• Vickers pyramid

Question 11

Industrial tests - Rockwell test for hardness

Answer 11

• Initial load applied to break the surface of the material using a diamond indenter
• An additional load is then applied and held for a length of time (dwell time)
• The load is released and the distance between the initial load and applied load is measured

Question 12

Industrial tests - Brinell test for Hardness

Answer 12

• Hardened standard sized steel ball is forced into the materials surface using a pre set load
• The diameter of the surface indent is measured

Question 13

Industrial tests - Vickers pyramid test for hardness

Answer 13

• Used for very hard materials
• Diamond square based pyramid is indented into the surface of the material
• A microscope is then used to measure the indent size

Question 14

What is non-destructive testing (NDT)

Answer 14

method carried out on products rather than material samples, the product is not destroyed in the process, it is just used to find defects in the material

Question 15

What are the two standard NTD methods

Answer 15

• Ultrasonic: Sound waves are pulsed into a material, different sounds indicate faults
• X-ray: image is projected onto a display screen allowing to observe tiny details such as hairline cracks

Question 16

Industrial tests - Malleability and ductility

Answer 16

• Material is placed in a bending machine and is held at both ends
• A plunger will apply a load to the middle of the material and bend it until a predetermined angle or fracture
• cracks on the outer bend indicate the level of ductility
• Cracks on the inside indicate the level of malleability

Question 17

Industrial tests - Corrosion

Answer 17

Similar to the simple method, however the materials will be left in a simulated weather environment

Question 18

Industrial tests - Electrical conductivity

Answer 18

the same as the workshop method.
- Mark a set distance at each end
- place a multimeter probe on each mark
- Measure the resistance, the lower it is the more conductivity

Question 19

Industrial tests - Thermal Conductivity

Answer 19

• Heat flow meter
• Square shaped material is placed between two temperature controlled plates
• The temperature is increased at a controlled rate and the conductivity can then be measured using heat flow sensors