Download presentation

1
Deforming Solids

2
Stretching a spring Strain energy Stretching materials Describing deformation

3
Stretching a Spring

4
**Hooke’s Law states that**

The extension is proportional to the force The spring will go back to its original length when the force is removed So long as we do not exceed the elastic limit

5
Graphs

6
Interpreting Graph Strain Energy

7
Strain Energy Stored ability to do work due to stretching or compression or displacement 𝑬 𝒔 = 𝟏 𝟐 𝐤 𝒙 𝟐

8
**Combination of Springs**

9
**Deformation of Rubber Band**

Hysteresis

10
**Deformation of Rubber Band**

Hysteresis

11
**Elastic versus Plastic**

Elastic Behaviour Material has the ability to go back to its original shape Elastic Limit A point where beyond it the material is permanently deformed

12
**Elastic versus Plastic**

Plastic Behaviour Material has been permanently deformed but not broken

13
**Describing Deformation**

Stress Measure of force required to cause a particular deformation Force per unit area Pressure Units: Nm2 Pascal 𝑺𝒕𝒓𝒆𝒔𝒔= 𝑭 𝑨

14
**Describing Deformation**

Strain Resulting deformation Extension divided by original length Dimensionless quantity 𝑺𝒕𝒓𝒂𝒊𝒏= ∆𝑳 𝑳 𝒐

15
Testing Materials

16
**Describing Deformation**

Young Modulus, Y Ratio of tensile stress to tensile strain Units: Nm-2 Pascal 𝒀= 𝑺𝒕𝒓𝒆𝒔𝒔 𝑺𝒕𝒓𝒂𝒊𝒏 𝒀= 𝑭𝑳 𝒐 𝑨∆𝑳

18
**Some interesting values of Young Modulus**

DNA ~ 108 Pa spaghetti (dry) ~ 109 Pa cotton thread ~ 1010 Pa plant cell walls ~ 1011 Pa carbon fullerene nanotubes ~ 1012 Pa

19
Materials

20
Graph

21
**Interpreting Graph Slope = Young Modulus Ultimate Tensile Stress**

Maximum stress a material can withstand before breaking Slope = Young Modulus

23
**Measuring Young Modulus**

24
**Measuring Young Modulus**

25
**Measuring Young Modulus**

26
**Measuring Young Modulus**

27
**Describing Deformation**

Curve A shows a brittle material. Strong The fracture of a brittle material is sudden and catastrophic Example: cast iron

28
**Describing Deformation**

Curve B is quite brittle and slightly ductile Brittle but deforms before breaking Example: steel

29
**Describing Deformation**

Curve C is a ductile material Deforms permanently Drawn into thin wires Examples are copper and gold

30
**Describing Deformation**

Curve D is a plastic material. Deforms permanently Deformation is not proportional to stress applied Example is polyethylene

31
Materials

Similar presentations

© 2020 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google