Physical Properties

Question 1

Define the words 
Load
Force 
Stress 
Strain
by using them in the same sentence.

Answer 1

A load is applied to a material which exerts a force on the material which produces a stress within a material and
associated strain

Question 2

What are the units for Load?

Answer 2

Kilograms (Kg)

Question 3

What are the units for Force?

Answer 3

Newton (N)

Question 4

Name 3 types of forces

Answer 4

• Uniaxial (single axis)
• Biaxial (2 perpendicular axis)
• Triaxial (equal in all directions)

Question 5

Name 3 uniaxial forces

Answer 5

• Tensile
• Compressive
• Shear

Question 6

What are the units for stress?

Answer 6

Pa

Question 7

What are the units for strain?

Answer 7

No units

Question 8

What is the measure of stiffness

Answer 8

Young’s modulus (E)

Question 9

State Hooke’s Law

Answer 9

Stress (σ) is proportional to strain (ε)

Question 10

What is compliance a measure of?

Answer 10

• Softness

- 1/E (reciprocal to stiffness)

Question 11

What is the proportional limit on an stress-strain curve?

Answer 11

The limit when even if the load is removed the material is permanently damaged

Question 12

What is the ultimate tensile strength on an stress-strain curve?

Answer 12

The fracture point where the material breaks apart

Question 13

What is the yield point on an stress-strain curve?

Answer 13

The point above which strain will increase even with no further increase in stress

Question 14

What is the elastic region on an stress-strain curve?

Answer 14

Region where, if stress is removed the original shape is recoverable

Question 15

What is the plastic region on an stress-strain curve?

Answer 15

Region where, if stress is removed the material is permanently deformed

Question 16

Define resilience

Answer 16

Energy absorbed without permanent deformation

Question 17

Define toughness

Answer 17

Total energy absorbed up to fracture

Question 18

Equation for Poisson’s ratio

Answer 18

Lateral strain / Axial strain

Question 19

Equation for Shear modulus

Answer 19

Shear stress / Shear strain

Question 20

Equation for Bulk modulus (liquids)

Answer 20

Hydrostatic pressure / Shear strain

Question 21

What is a brittle fracture?

Answer 21

• Occurs with little or no plastic deformation

- Low energy absorption

Question 22

What is a ductile fracture?

Answer 22

• Occurs after significant plastic deformation

- High energy absorption

Question 23

What are the 2 steps in a fracture?

Answer 23

• Crack formation (slow)

- Crack propagation (fast)

Question 24

How is direct tensile strength measured?

Answer 24

By gauges and extensometers

Question 25

When measuring direct tensile strength what shape does the specimen need to be in? Why?

Answer 25

- Dumbbell shaped | - Ensures it fractures centrally

Question 26

What is the direct tensile strength test used for?

Answer 26

- Metals - Rigid polymers - Rubbery polymers

Question 27

What is the compressive strength test used for?

Answer 27

- Ceramics - Hard polymers - Dental cements

Question 28

What is the diametral tensile strength test used for?

Answer 28

- Brittle materials

Question 29

What is the diametral tensile strength test NOT used for?

Answer 29

- Ductile materials

Question 30

What are the 2 ways to measure flexural strength?

Answer 30

- 3 point bend test | - 4 point bend test

Question 31

What is the hardness test for metals?

Answer 31

Brinell hardness test

Question 32

What is the hardness test for a range of materials?

Answer 32

Rockwell hardness test

Question 33

What is the hardness test for ceramics, composites and hard plastics?

Answer 33

Knoop hardness test

Question 34

Name the 4 hardness tests

Answer 34

- Brinell hardness test - Rockwell hardness test - Knoop hardness test - Vickers hardness test