Flashcards in Materials Deck (35)

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1

## Define DENSITY

### The mass per unit volume of a material

2

## Equation for DENSITY?

###
Density (kgm^-30= Mass(kg)/Volume(m^3)

D=M

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V

3

## Characteristics of DENSITY

### Density does not vary with size or shape, depends on material only

4

## Define HOOKE'S LAW

### The extension of a material is directly proportional to the force applied to it until the limit or proportionality is reached

5

## Equation for HOOKE'S LAW?

###
Force(N)=spring constant(Nm^-1) x extension (m)

F = KX

6

## What is directly proportional in HOOKE'S LAW?

### Extension and Force applied

7

## What does a tensile force do to a spring?

### Stretch the spring

8

## What does a compressive force do to a spring?

### Compress the spring

9

## When is the limit of proportionality broken?

### As soon as the graph begins to curve

10

## What is the point called when the graph just begins to curve on a force - extension graph?

### The elastic limit

11

## What happens if you continue to apply force beyond the elastic limit?

### The material will become permanently stretched and will be longer than before the force was applied.

12

## What is it called when the material is stretched to a point it will no longer return to original length?

### Plastic deformation

13

## Think of a practical to investigate extension of a material

###
1. Get a ruler, clamp, clamp stand, material and 1kg of weights

2. Set up equipment so weights are hanging off of the material you are testing and the ruler is up against the clamp stand

3. Measure original length before adding additional weight.

4. When original weight measured increase the weights by 100g and record new length

5. Do this until all weights are used.

6. Then unload and record lengths per 100g you take back off

7. Plot a graph of force against extension

14

## What is elastic deformation?

### The material returns to its original state when the force is removed

15

## What happens in terms of the atoms of the material in elastic deformation?

### When under tension the atoms are pulled part form one another. They can move small distances from their equilibrium without changing position in the material. When un-loaded the atoms return to their point of equilibrium

16

## Define STRESS

### Force applied per unit cross-sectional area

17

## Equation for STRESS

###
Stress(Pa or Nm^-2) = force(N)/cross sectional area(m^2)

sigma = F

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A

18

## Define STRAIN

### Extension per unit length before extension

19

## Equation for STRAIN

###
Strain = extension(m)/original length(m)

Large curly E = Delta L

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L

20

## When calculating is a tensile force +ve and a compressive force -ve?

### YES

21

## What does UTS stand for?

### Ultimate Tensile Strength

22

## What is UTS?

### The maximum stress a material can withstand

23

## Where is point of UTS on a stress - strain graph?

### When the gradient is no longer +ve or zero

24

## What is breaking stress?

### When the atoms of a material actually break away from each other causing the material to break

25

## Where on the stress-strain graph is breaking stress?

### At the end of the graph

26

## What is elastic strain energy?

### The energy required or work done to stretch a material and is stored as potential energy

27

## How would you calculate the strain energy on a graph?

### Find the area underneath a force - extension graph

28

## What is the Young's Modulus a measure of?

### The stiffness of a material

29

## Equation for YOUNG'S MODULUS

###
YM= tensile stress/tensile strain

E(Pa or Nm^-2)= Sigma

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Big Curly E

30