3. COURSE LEARNING OBJECTIVES
● To know the different types of stresses and
strains developed in the member subjected to
axial, bending, shear, torsional & thermal loads.
● To know behaviour & properties of engineering
materials
● To understand the stresses developed in bars,
compounds bars, beams, shafts, and cylinders.
● To understand the concepts of calculation of
shear force and bending moment for beams
with different supports.
● To expose the students to concepts of
Buckling of columns and strain energy.
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4. MODULE-1
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Stresses and Strains: Introduction, Properties
of materials, Stress, Strain and Hooke’s law,
Stress strain diagram for brittle and ductile
materials, True stress and strain, Calculation
of stresses in straight, Stepped and tapered
sections, Composite sections, Stresses due
to temperature change, Shear stress and
strain, Lateral strain and Poisson’s ratio,
Elastic constants and relations between
them.
5. INTRODUCTION
Mechanics of Materials or Strenght of
Materials deals with the study of
mechanism or behaviour of materials
under the action of external loads
within elastic limit. Here external loads
refers to forces,
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6. MECHANICAL PROPERTIES OF MATERIALS
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Some of the Important Mechanical properties are:
Elasticity: It is the ability of the material to regain
it’s original shape and size after the removal of
external load. This property is desirable for
materials used in machines and machine tools.
Steel is perfectly elastic up to certain limit and
more elastic in nature than rubber.
Plasticity: It is the ability of the material to retain
deformation produced due to external load on a
permanent basis. This property is useful in case of
forging, stamping on coins and in ornamental work
7. MECHANICAL PROPERTIES OF MATERIALS
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Ductility: It is the ability of a material to deform to
greater extent before indication of crack when
subjected to tensile load. This is usually expressed
in terms of percentage elongation or percentage
reduction in cross sectional area. This property is
utilized in wire drawing. Mild Steel, aluminium,
copper, tin and lead are some of the ductile
materials.
Brittleness: It is the property of a material which
shows negligible plastic deformation before the
occurrence of fracture. Cast iron, high carbon steel,
concrete, stone, glass, ceramic materials, etc.
8. MECHANICAL PROPERTIES OF MATERIALS
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Strength: It is the ability of the material to resist
the external forces causing various types of
stresses without breakage or rupture.
Stiffness: Stiffness or Rigidity is the ability of the
material to resist deformation under the action of
external load. Modulus of Elasticity is the
measure of Stiffness.
Resilience: It is the ability of the material to
absorb energy when deformed elastically and
release the same when unloaded.
9. MECHANICAL PROPERTIES OF MATERIALS
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Toughness: It is the ability of the material to absorb
energy before the occurrence of fracture.
Malleability: It is the ability of material to deform to
a greater extent before the occurrence of crack,
when it is subjected to compressive force. This
property is utilized in forging, hot rolling, drop
stamping etc.
Hardness: It is the resistance of the material to the
penetration or permanent deformation or
indentation. Indentation test involves pressing a
body of standard shape against the surface of test
specimen. Ex: Brinell, Rockwell and Vicker’s test.
10. MECHANICAL PROPERTIES OF MATERIALS
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CREEP: Whenever a member or part of a
machine is subjected to a constant stress at
high temperature for a longer period of time, it
will undergo a slow and permanent deformation
known as CREEP. This is considered in
designing IC engines, boilers and turbines.
11. STRESS (σ )
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• It is defined as the resistance offered for the
deformation per unit area due to applied external
load. It is usually denoted by the symbol ‘σ ‘.
ie. σ = F/A
• Where F is the external load or force and A is the
cross sectional area.
• The unit commonly used is Mega Pascal (MN/m2)
or 106N/m2 which is numerically equal to N/mm2.
1 Pascal = 1N/m2
1 Kpa (Kilo Pascal) = 1000 N/m2
1 Bar = 100 Kpa =105 N/m2
1MPa (Mega Pascal) = 106N/m2
=1 N/mm2
1GPa (Giga Pascal)=109 N/m2=103 N/mm2
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Stress induced on a plane perpendicular to the
direction of the load applied is known as Direct
Stress or Normal Stress and perpendicular to the
direction of the load applied is known as
Tangential or Shear Stress. When the load tends
to pull apart the particles of the material causing
extension in the direction of the load applied then
the load applied is known as tensile load and the
corresponding stress is Tensile Stress. On similar
lines Push causes contraction and the
corresponding stress is Compressive Stress.
13. Summary
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1. Importance of the course Mechanics of
Materials.
2. Topics to be discussed in Module1.
3. Important Mechanical Properties of Materials
in use.
4. Engineering Applications of the Materials.
14. Slide #12
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TO BE CONTINUED WITH..
Strain, Hooke’s law, Stress strain
diagram for brittle and ductile
materials, True stress and True strain
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