Created by: Mohamad Fikree Bin Alias Lecturer Politeknik Tuanku Sultanah Bahiyah

JJ310 - Strength of Material

OUTLINEO Hookes LawO Young Modulus, E O Tensile test O Stress-strain diagram

Refresh the memory back..O Stress

O Strain

What is Hookes Law?O Stress applied to the material is directly

proportional to the strain provided the elastic limit of the material is not exceeded. O Applied to all elastic material including steel. O E.g. bungee jumping rope.

Young Modulus, EO The ratio of linear stress to the linearO O O O

O

strain. Also known as elasticity modulus. Elastic value of the material. Value of E differ depending on the material type. E , strength of the material e.g. E steel higher than aluminum.

EStress

Unit?Strain

, stress

Esteel aluminum

, strain

#2 Find the slope!!

Example of E

Got the answer? 100 kN/m2

STRESS VS STRAIN GRAPHStress, (kN/m2) 100 80 60 40 20 0 0.2 0.4 0.6 Strain, 0.8

Based on the graph, find the value of Elasticity modulus.

we know:

So? What to do next? #1 Make sure it is a STRESS VS STRAIN GRAPH!!

Tensile TestO Test to measure:O Elasticity point O Maximum tension strength O Yield point O Break point

O Different material different value.

Tensile Test

Aluminum Tensile Test

Stress-strain diagramP = ratio limit A = elasticity limit Y = yield point S = max tension strength B = break pointA

*credits to substech.com

Tensile Test

before

after

nec k before

after

Tensile TestWhat should you know? 1. Yield stress 2. Max tension stress 3. % elongation 4. % area reduction

Stress-strain diagramP = ratio limit A = elasticity limit Y = yield point S = max tension strength B = break pointA

*credits to substech.com

Lets try it out#1 A tensile test towards a steel rod with diameter of 14.35mm and original length of 56mm being conducted. These are the results recorded: Load, kN 0 20 40 0.061 60 0.092 80 0.122

Length Increment, 0 0.031 mm Final length of rod = 65.6mm

Final Diameter of rod = 11.45mm i. Draw a load versus length increment graph and find the slope value. ii. Calculate: a. E value b. % elongation c. % area reduction

E value without strain vs stress graph..LOAD VERSUS LENGTH GRAPH80 70 60 50 40 30 20 10 0 0.2 0.4 0.6 0.8 Length, L (mm) What happen if we find the slope? Can we find these values in the graph? we know: Load,P (kN)

Another one!!#2 A tensile test being conducted on a material diameter of 5.64mm and length of 22mm. Given:Maximum tension stress = 512 MN/m2 Minimum yield stress = 210 MN/m2 % elongation = 20% Find these values: a) Maximum load can be applied to the material b) Final length of the material c) Minimum load applied to the material during yield point