STRENGTH OF MATERIALS
Forces on Material
______________________________________________________________________________________
CHAPTER 1
FORCES ON MATERIAL
1.1 Introduction to Strength of Materials
V = shear force
A = area P @ F @ W = force @ load
L = length G = modulus of rigidity @ shear modulus ϕ = shear strain
σ = stress J = polar second moment of area ∆d = deformation of diameter
τ = shear stress d = diameter E = modulus of elasticity @ young’s modulus
T = torque ε = strain ∆L = deformation of length U = strain energy
I = second moment of area @ moment of inertia
ν = poisson’s ratio
Classification of load:
Static load load is stationary and fixed.
e.g: beam that support building.
Dynamic load variable load
e.g: bridge that support variety of vehicle’s loads.
Impact load cause by sudden blows
e.g: nail knocked by hammer.
Armazlin binti Ahamad Arshad 1
, STRENGTH OF MATERIALS
Forces on Material
______________________________________________________________________________________
Fatigue and alternating load happen occasionally for the period of
time.
e.g: rotation of shaft in windmill and
spring swing.
TWO types of main forces: Axial force
Shear force
Axial force tensile force P P
compressive force P
P
P
shear force
Shear force
P
P
P
THREE types of stresses:
Tensile stress
reaction that happen because of the
Compressive stress
force is subjected to the bar
Shear stress
Armazlin binti Ahamad Arshad 2
, STRENGTH OF MATERIALS
Forces on Material
______________________________________________________________________________________
σ = P/A
unit, N/m2 @ Pa
Figure 1.1 : Formula of Stress
Example 1.1
A steel bar with 35mm x 25mm of area is subjected to a tensile load of 40kN. Find the
tensile stress.
Solution
A = 35mm x 25mm ( 35 x 10-3 m ) x ( 25 x 10-3 m )
P = 40kN 40 x 103N
A = ( 35 x 10-3 ) x ( 25 x 10-3 )
= 8.75 x 10-4m2
σ = P/A
= 40 x .75 x 10-4
= 45.71MN/m2
TWO types of strain:
Axial strain deformation that happen because of the force is
Shear strain subjected to the bar
Armazlin binti Ahamad Arshad 3
Forces on Material
______________________________________________________________________________________
CHAPTER 1
FORCES ON MATERIAL
1.1 Introduction to Strength of Materials
V = shear force
A = area P @ F @ W = force @ load
L = length G = modulus of rigidity @ shear modulus ϕ = shear strain
σ = stress J = polar second moment of area ∆d = deformation of diameter
τ = shear stress d = diameter E = modulus of elasticity @ young’s modulus
T = torque ε = strain ∆L = deformation of length U = strain energy
I = second moment of area @ moment of inertia
ν = poisson’s ratio
Classification of load:
Static load load is stationary and fixed.
e.g: beam that support building.
Dynamic load variable load
e.g: bridge that support variety of vehicle’s loads.
Impact load cause by sudden blows
e.g: nail knocked by hammer.
Armazlin binti Ahamad Arshad 1
, STRENGTH OF MATERIALS
Forces on Material
______________________________________________________________________________________
Fatigue and alternating load happen occasionally for the period of
time.
e.g: rotation of shaft in windmill and
spring swing.
TWO types of main forces: Axial force
Shear force
Axial force tensile force P P
compressive force P
P
P
shear force
Shear force
P
P
P
THREE types of stresses:
Tensile stress
reaction that happen because of the
Compressive stress
force is subjected to the bar
Shear stress
Armazlin binti Ahamad Arshad 2
, STRENGTH OF MATERIALS
Forces on Material
______________________________________________________________________________________
σ = P/A
unit, N/m2 @ Pa
Figure 1.1 : Formula of Stress
Example 1.1
A steel bar with 35mm x 25mm of area is subjected to a tensile load of 40kN. Find the
tensile stress.
Solution
A = 35mm x 25mm ( 35 x 10-3 m ) x ( 25 x 10-3 m )
P = 40kN 40 x 103N
A = ( 35 x 10-3 ) x ( 25 x 10-3 )
= 8.75 x 10-4m2
σ = P/A
= 40 x .75 x 10-4
= 45.71MN/m2
TWO types of strain:
Axial strain deformation that happen because of the force is
Shear strain subjected to the bar
Armazlin binti Ahamad Arshad 3
