Flashcards in Material Deck (27):

1

## Elasticity

### The property of a body to return to its original shape once the deforming force is removed

2

## Deformation

### The change in shape or size of an object

3

## Elastic Deformation

### An object that deforms that will return to its original shape once the deforming force is removed

4

## Plastic Deformation

### When an object deforms and then when the deforming force is removed the object remains deformed

5

## Tensile force

### Creates tension in an object and will result in an extension

6

## Compressive force

### A force that causes an object to compress

7

## What a force extension graph will look like for a metal

### Will start of straight. Then the limit of proportionality is reached and the gradient will start to change. Then the elastic limit is reached and it will extend more per unit force (gradient decreases) until it reaches the point of fracture

8

## Experiment to observe force-extension of a wire

### Clamp a wire on one end of a table and attach a weight on the other end. The weight should dangle off the table and the wire should be placed over a pulley. Attach a marker to the wire and fix a ruler in position. Add more mass to the weight and record how much the wire extends

9

## Hookes Law

### The extension of an object is proportional to the force that causes it, provided that the elastic limit is not exceeded

10

## Force constant of a spring

### The force required to extend the spring by one unit length

11

## Hookes law in equation form

### F=kx

12

## Area under a force-extension graph

### Work done to stretch the object

13

## What happens to the work done put into stretching a wire that exceeds its elastic limit

###
- At first the work done is causing an increase in elastic potential energy

- Once the material has exceeded its elastic limit the rest of the energy that is input will be converted to heat

14

## Stress

### Force per unit cross sectional area

15

## Strain

### Extension per unit length

16

## Ultimate tensile strength

### The maximum stress that an object can endure before breaking

17

## Equation for youngs modulus

###
Tensile stress / Tensile strain

18

## Young Modulus

### A measure of the stiffness of a material

19

## The overall force constant of two springs in series

### 1/k = 1/(k1) + 1/(k2)

20

## How to work out the ultimate tensile strength from a stress-strain graph

###
The highest point on the graph

21

## How to work out the ultimate tensile strength from a stress-strain graph

###
The highest point on the graph

22

## Experiment to determine Young's Modulus of a wire

### Clamp one end of a wire and attach a weight to the other end. Run the wire over a pulley and mark a point on the wire. Measure the distance from the clamp to the marking. Measure the diameter of the wire with a micrometer and calculate its cross sectional area. Increase mass on the weight and at each step record the extension of the wire. Plot the stress against strain and the YM will be the gradient

23

## Stress-Strain graph of a ductile material

###
At first it is straight and obeys Hooke's Law.

Then the limit of proportionality is reached and the gradient starts to decrease.

The elastic limit is reached and the gradient continues to decrease.

The yield point is reached and the gradient goes negative for a short while before gradually increasing

24

## Elastic limit

###
The maximum stress an object can endure while still behaving elastically. After this point it will not return to its original shape

25

## Stress-Strain graph for a brittle material

### Straight line then breaks

26

## Stress-Strain graph for a polymeric material

### Look in the book its hard to explain

27