PH8151 Engineering Physics Chapter 1

1.3. ENGINEERING STRESS-STRAIN DIAGRAM

Learning Resource : Apparatus and Procedure for Tensile Test

(1) Tensile testing using an automated Universal Testing

Machine - Youtube channelMaterials Science 2000

URL:https://youtu.be/D8U4G5kcpcM

(2) Tensile testing and plotting of stress-strain graph -

Youtube channelTool Notes

URL:https://youtu.be/uWgnBNOy-rA

1.3 Engineering Stress-Strain Diagram

The feformation in which stress and strain are proportional is calledelastic deformation.
For elastic deformation, a plot of stress (ordinate) versus strain (abscissa) results in a
linear relationship, called Hooke’s law, as shown in Figure1.6.

Stress-Strain Diagram

(medium-carbon (0.3–0.6% C) steel)

Strain (ε )

1

2

3

5

Stress (

σ =

F/A

) 0

Fracture

Ultimate

tensile

strength

Slope=E Beginning of necking

yield

strength

4

Elastic limit

Yield point

E=

σ

ε

= Elastic modulus (Young's modulus)

Necking leading to fracture

Neck

Steel specimen

Tensile load

direction

Figure 1.6: Stress-Strain Diagram- Description of Mechanical Properties.

Hooke’s Law

Within elastic limit, stress (‡) is directly proportional to strain (‘). Or‡Ã‘.

With E as the proportionality constant, called theelastic modulus, we have

‡=E‘. Or Elastic Moldulus,E=

‡

‘

(1.2)

PH8151 7 LICET