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Flashcards in Physical Properties Deck (34)
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1

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

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

What are the units for Load?

Kilograms (Kg)

3

What are the units for Force?

Newton (N)

4

Name 3 types of forces

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

5

Name 3 uniaxial forces

- Tensile
- Compressive
- Shear

6

What are the units for stress?

Pa

7

What are the units for strain?

No units

8

What is the measure of stiffness

Young's modulus (E)

9

State Hooke's Law

Stress (σ) is proportional to strain (ε)

10

What is compliance a measure of?

- Softness
- 1/E (reciprocal to stiffness)

11

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

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

12

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

The fracture point where the material breaks apart

13

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

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

14

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

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

15

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

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

16

Define resilience

Energy absorbed without permanent deformation

17

Define toughness

Total energy absorbed up to fracture

18

Equation for Poisson's ratio

Lateral strain / Axial strain

19

Equation for Shear modulus

Shear stress / Shear strain

20

Equation for Bulk modulus (liquids)

Hydrostatic pressure / Shear strain

21

What is a brittle fracture?

- Occurs with little or no plastic deformation
- Low energy absorption

22

What is a ductile fracture?

- Occurs after significant plastic deformation
- High energy absorption

23

What are the 2 steps in a fracture?

- Crack formation (slow)
- Crack propagation (fast)

24

How is direct tensile strength measured?

By gauges and extensometers

25

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

- Dumbbell shaped
- Ensures it fractures centrally

26

What is the direct tensile strength test used for?

- Metals
- Rigid polymers
- Rubbery polymers

27

What is the compressive strength test used for?

- Ceramics
- Hard polymers
- Dental cements

28

What is the diametral tensile strength test used for?

- Brittle materials

29

What is the diametral tensile strength test NOT used for?

- Ductile materials

30

What are the 2 ways to measure flexural strength?

- 3 point bend test
- 4 point bend test