Strength of Material

Strength of Material

Mechanical Properties

1. Hardness ;Resist the penetration (impact  load)
2. Strength : Ability of material withstand of material without failure.
3. Elasticity : It regain the original shape after removing load
4. Plasticity : Permanent deformation after removing load.
5. Mali ability : Converts to thin sheet without rupture
6. Ductility : Draw in to thin wire.
7. Brittleness : No deformation takes place & rupture (lake of ductility ) (cast iron)
8. Toughness : absorb energy & plastic deformation without rupture.
9. Fatigue: by repeatedly applied load program me and localized structure damage that occur.
10. Creep : tendency of solid material to move slowly deform permanently under mechanical stress.

Stress : Load applied on particular area.

•  it is tensor quantity 
• unit : N/mm2

Strain : Change in length to original length when force applied on body.

• it has no unit.

Strength of Material

Tensile : when body is subjected to equal and opposite pull.
Compressive : when body is subjected to equal and opposite push.
Thermal stress : stress due to change in temperature.
Linear strain : deformation of bar per unit length in direction of force.
Lateral strain : Direct stress dis accomplished strain in its own direction & opposite kind of strain in every direction at right angle is known.
Poison 's ration = Lateral strain / Linear strain

• it has no unit
• max poison ratio = 0.5 (rubber)

Bulk modulus: Body subjected to 3 mutually perpendicular stress of equal intensity
E = 9KC /(3K+C)

Principle stress & strain:

• 3 planes are mutually perpendicular to each other
• Carries direct stress only
• No shear stress
• 3 direct stress (Max, min, intermediate)

Mohr circle: Graphical method to find Normal tangential resultant stress.

Resilience: Strain energy stored in body due to external loading with in the elastic limit.

Bending Assumption :

• Material is homogeneous.
• obey hook's law.
• Transverse section plane before and after bending.
• Each layer is free to explained.
• Value of young s modulus is same in tension and compression.

Strength of Material

Bending equation:
(M/I)=(SIGMA /Y)=(E/R),
M= Bending Moment
I = Moment of inertia
Y = Distance from center
E = Young 's modulus
R = radius of curvature 

Shear stress in shaft
(Tou/R) = (T/J) = (C x thita )/l
Tou =  Shear stress
R = Radius of shaft
T = torque
J = polar  moment
C = Rigidity
thita = angle of twist
l = length of shaft

Stiffness of spring : load required to produce unit deflection in spring is called stiffness of spring.
vipul baria