# Physical Properties Flashcards

1
Q
```Define the words
Force
Stress
Strain
by using them in the same sentence.```
A

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

2
Q

What are the units for Load?

A

Kilograms (Kg)

3
Q

What are the units for Force?

A

Newton (N)

4
Q

Name 3 types of forces

A
• Uniaxial (single axis)
• Biaxial (2 perpendicular axis)
• Triaxial (equal in all directions)
5
Q

Name 3 uniaxial forces

A
• Tensile
• Compressive
• Shear
6
Q

What are the units for stress?

A

Pa

7
Q

What are the units for strain?

A

No units

8
Q

What is the measure of stiffness

A

Young’s modulus (E)

9
Q

State Hooke’s Law

A

Stress (σ) is proportional to strain (ε)

10
Q

What is compliance a measure of?

A
• Softness

- 1/E (reciprocal to stiffness)

11
Q

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

A

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

12
Q

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

A

The fracture point where the material breaks apart

13
Q

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

A

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

14
Q

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

A

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

15
Q

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

A

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

16
Q

Define resilience

A

Energy absorbed without permanent deformation

17
Q

Define toughness

A

Total energy absorbed up to fracture

18
Q

Equation for Poisson’s ratio

A

Lateral strain / Axial strain

19
Q

Equation for Shear modulus

A

Shear stress / Shear strain

20
Q

Equation for Bulk modulus (liquids)

A

Hydrostatic pressure / Shear strain

21
Q

What is a brittle fracture?

A
• Occurs with little or no plastic deformation

- Low energy absorption

22
Q

What is a ductile fracture?

A
• Occurs after significant plastic deformation

- High energy absorption

23
Q

What are the 2 steps in a fracture?

A
• Crack formation (slow)

- Crack propagation (fast)

24
Q

How is direct tensile strength measured?

A

By gauges and extensometers

25
Q

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

A
• Dumbbell shaped

- Ensures it fractures centrally

26
Q

What is the direct tensile strength test used for?

A
• Metals
• Rigid polymers
• Rubbery polymers
27
Q

What is the compressive strength test used for?

A
• Ceramics
• Hard polymers
• Dental cements
28
Q

What is the diametral tensile strength test used for?

A
• Brittle materials
29
Q

What is the diametral tensile strength test NOT used for?

A
• Ductile materials
30
Q

What are the 2 ways to measure flexural strength?

A
• 3 point bend test

- 4 point bend test

31
Q

What is the hardness test for metals?

A

Brinell hardness test

32
Q

What is the hardness test for a range of materials?

A

Rockwell hardness test

33
Q

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

A

Knoop hardness test

34
Q

Name the 4 hardness tests

A
• Brinell hardness test
• Rockwell hardness test
• Knoop hardness test
• Vickers hardness test