3) Methods For Investigating And Testing Materials

Question 1

Describe the simple workshop test for toughness

Answer 1

Place material in vice and hit with hammer

Question 2

Describe the simple workshop test for hardness

Answer 2

Use a dot punch to produce an indent in the sample material. The smaller the indent, the harder the material

Question 3

Describe the simple workshop test for tensile strength

Answer 3

Clamp each end of the material and place weights on one end. less deflection under load means the material has more tensile strength

Question 4

State the simple workshop test for malleability and ductility

Answer 4

Place sample in vice and bend to 90°. Cracks on the outside indicate a lack of ductility. Cracks on the inside indicate a lack of malleability

Question 5

State the simple workshop test for corrosion

Answer 5

Place the material sample outside in an area exposed to weather and leave for a set amount of time

Question 6

States the simple workshop test for electrical conductivity

Answer 6

Place multimeter probes at each end of the sample. Measure the resistance on the multimeter. The higher the resistance, the lower the conductivity.

Question 7

State the simple workshop test for thermal conductivity

Answer 7

Light a Bunsen burner under the other end of material. Record the time it takes for the temperature to read the set point at the other end of the sample. The shorter the time it takes, the higher the thermal conductivity of the material

Question 8

State the industrial test for tensile strength

Answer 8

A tensometer machine is used
The standard test piece is held in a clamp at each end
One clamp is fixed and moves on a worm drive gear mechanism
The test piece is stretched, the load and distance travelled is plotted, giving information on elastic limit, yield point, maximum load & final breaking point after ‘necking’

Question 9

State and describe the name of the industrial test used to test toughness

Answer 9

The Izod impact test
A notched piece is held vertically the vice of the machine
A pendulum is released from a set position and swings to strike the piece
The energy absorbed by the test piece is calculated from the height the pendulum swings after it hits the test please
The material for absorbs the most impact is the toughest and it gives the least pendulum swing
Brittle materials absorb less energy and the pendulum swings further

Question 10

State the three industrial tests for hardness

Answer 10

The Rockwell test,
The Brinell test
Vickers pyramid test

Question 11

State a general description of industrial hardness tests

Answer 11

All hardness tests involve a load being applied to the material with the resultant indentation determining its hardness. The smaller the indentation the harder the material

Question 12

Describe the Rockwell test

Answer 12

A pre-load is applied to the material using a diamond indenter
Diamond is used because it will not deform under load
Preload is the datum position
And additional load his van applied to the test material and held for a predetermined length of time (dwell time)
The load is released and the distance between the preload and applied load is measured

Question 13

Describe the Brinell test

Answer 13

A hardened standard sized steel ball is forced into the material’s surface using a preset load and the diameter of the indent in the surface is measured

Question 14

Describe the Vickers Pyramid test

Answer 14

Used for very hard materials
Uses a diamond Square based pyramid to indent the surface of the material
A microscope is then used to measure the size of the indent

Question 15

Give two facts about nondestructive testing (NDT)

Answer 15

1) It is used for products rather than materials

2) The product is not destroyed during testing.

Question 16

State to nondestructive testing methods

Answer 16

Ultrasonic sound waves and x-rays

Question 17

State the difference between the simple workshop test and industrial test for malleability

Answer 17

The only difference is the test piece is placed into a bending machine and a manual or plunger loads to test piece at the centre and bends to a predetermined angle or until the piece fractures

Question 18

State the difference between the simple workshop test for corrosion and V industrial test

Answer 18

The only difference is that it is simulated in a lab

Question 19

State the difference between the simple workshop test for thermal conductivity and the industrial test

Answer 19

In the industrial 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 placed on the surface of the material.