Testing of materials in industry

Question 1

What is the definition of ‘tensile strength’?

Answer 1

The tensile strength of a material can be defined as, ‘the ability of a material to stretch without breaking or snapping’

Question 2

Describe a method suitable for determining the tensile strength of a piece of material

Answer 2

A piece of material is clamped in a vice. A fixed weight is hung from the end. The amount of deflection, is a measure of its resistance and tensile strength

Question 3

What is the definition of ‘elasticity’?

Answer 3

The elasticity of a material can be defined as, ‘the ability of a material to absorb force and flex in different directions, returning to its original position’

Question 4

Describe how the elasticity of a material can be tested

Answer 4

A piece of material is clamped in a vice. A fixed weight is hung from the end and the material bends / deflects. When the weight is quickly removed, the material ‘springs back’. The amount of deflection, is a measure of its elasticity

Question 5

What is the definition of ‘toughness’?

Answer 5

The toughness of a material can be defined as, ‘the ability of a material to absorb sudden shock without breaking or shattering

Question 6

What is a school workshop test for establishing the toughness of a material?

Answer 6

hit a sample of material with a hammer, whilst it is secured in an engineers vice. If it survives the blow, without bending too far, it can be said to be tough. If it shatters, it can be said to be brittle

Question 7

What is an industrial method of measuring the toughness of sample materials?

Answer 7

A pendulum is allowed to ‘swing’ from a set starting position. The resulting ‘distortion’ to the sample material can be measured on the scale. This gives an indication of the materials toughness

Question 8

What is the definition of ‘hardness’?

Answer 8

The hardness of a material can be defined as, ‘the ability of a material to resist scratching, wear and tear and indentation’.

Question 9

Why is it important to carry out tests on a material, to help determine its physical properties?

Answer 9

It is important to carry out tests to determine a material’s physical properties to determine how useful the material is for a particular function

Question 10

Describe a basic test for measuring the hardness of a material

Answer 10

Using a centre punch to ‘indent’ the surface of a material, is a basic test. Different materials require a different amount of force to form an indent. This makes it possible to compare the hardness of a selection of materials

Question 11

What is a more sophisticated method of measuring the hardness of a material?

Answer 11

A more sophisticated method of measuring the hardness of a material, is to drop a ‘plug’ down a tube. When the ‘plug’ hits the material below, the surface will suffer an indent. The indent produced on different materials, can be compared. Consequently, the smaller the indent, the harder the material

Question 12

How can a hand file be used to measure the hardness of a material?

Answer 12

When using a hand file to ‘file’ a material, the force / effort required can be felt physically . Filing a selection of materials to the same degree, allows the hardness of each to be compared

Question 13

How does a Hardness Testing Machine work?

Answer 13

A sample test material is clamped on the table. As the operator rotates the table handles, the table is moved upwards until it comes in contact with the ‘test point’. The dial is set to ‘0’.
Further turning of the table handles increases pressure between the surface of the sample material and the ‘test point’. The resulting indentation is measured on the dial. This gives a measure of the samples ‘hardness’

Question 14

How does a Tensile Testing Machine work?

Answer 14

A sample test material is securely clamped between the top and lower vices. The tensile dial is set to ‘0’. A motor is turned on, slowly moving the top vice away from the lower vice, stretching the test material. When the test material ‘snaps’, the final tensile dial reading is taken, displaying the tensile strength of the sample

Question 15

How does a Ductility Testing Machine work? 🦆

Answer 15

A test sample of steel wire, is secured between the fixed vice and the rotating vice of the ductility tester. The test material is then twisted by rotating the handle. The ductility of the test sample is determined by the number of times the handle rotates, before the sample breaks. The type of fracture also indicates the ductility properties of the wire

Question 16

How does an Elasticity Testing Machine Work?

Answer 16

The test material is secured between the fixed vice and the moving vice. The dial is set to ‘0’. A motor then controls the moving vice, allowing it to traverse (move) a set distance from left to right. The material is then allowed to return to its original position, when the motorised vice returns to ‘0’.
The amount of left and right movement is slowly increased, with the vice returning to its original position. This tests the flexibility of the material. Eventually the amount of movement is such that the material cannot return / flex back to its original position. The dial measures this distance and it is a measure of the materials elasticity

Question 17

What is ‘conductivity’?

Answer 17

The conductivity of a material can be defined as, ‘the ability of a material to conduct electricity or heat’

Question 18

What is a suitable test for measuring electrical conductivity?

Answer 18

A voltmeter is used to measure resistance. The probes are set to the same distance on each sample. The resistance is a measure of the materials conductivity

Question 19

What is a suitable test for measuring thermal conductivity?

Answer 19

A bunsen burner is placed at one end of a piece of material and a temperature meter at the other end. The time it takes for the temperature to change at the opposite end of the material is recorded. If a selection of materials of the same length and section are tested in this way, their conductivity can be compared

Question 20

What is the definition of ductility? 🦆

Answer 20

The ductility of a material can be defined as, ‘the ability of a material to change shape (deform) usually by stretching along its length’

Question 21

What is the definition of malleability?

Answer 21

The malleability of a material can be defined as, ‘the ability of a material to be reshaped in all directions without cracking’

Question 22

What is a single workshop test that can help determine the ductility and malleability of a material?

Answer 22

A piece of tube is placed over a piece of material and used as a lever. The material is folded to 90 degrees. Cracks / damage on the outside of the bend represents a lack of ductility. Cracks / damage on the inside of the bend represents a lack of malleability

Question 23

List the names of three common steels

Answer 23

• Mild Steel
• Medium Carbon Steel
• High Carbon Steel

Question 24

What is the carbon content of Mild Steel?

Answer 24

0.4%

Question 25

What is the carbon content of Medium Carbon Steel?

Answer 25

0.8%

Question 26

What is the carbon content of High Carbon Steel?

Answer 26

1.2%

Question 27

Why is High Carbon Steel suitable for hardening and tempering?

Answer 27

Mild steel and medium carbon steel don’t have enough carbon to change their crystalline structure