Introduction to Mechanics of Materials, Course content, Objectives, Outcomes, Mechanical Properties.

1. MECHANICS OF
MATERIALS
(AE-106)
LECTURE: 01
Engr. Abdullah Khan
Visiting Lecturer,
Department of Agricultural Engineering.

2. CLASS INFORMATION
• COURSE NAME AND CODE: MECHANICS OF MATERIALS (AE-106)
• CREDIT HOURS: 2
• INSTRUCTOR: ENGR. ABDULLAH KHAN,
DEPARTMENT OFAGRICULTURAL ENGINEERING.
• CONTACT NO.: 0315-9608632
• EMAIL: abdullahkhansaddiqui48@gmail.com
• ADDRESS: STATION KOROONA POST OFFICE SARDHERI TEHSILAND DISTRICT CHARSADDA.
• GRADING CRITERIA: MID TERM = 30%
FINAL TERM = 40%
ASSIGNMENTS = 05%
QUIZZES = 10%
ATTENDANCE = 15%

3. COURSE CONTENT
1. Introduction, types of stresses and strains, elastic limit, modulus of elasticity, yield point.
2. Factor of safety, mechanical properties of materials, stresses due to change of temperature.
3. Poisson’s ratio, elastic constant: young’s modulus, shear modulus, bulk modulus, and relation between elastic
constants.
4. Methods for the determination of stresses on oblique sections.
5. Use of Mohr’s circle to stress problems.
6. Bending moments and shear forces in beams for cantilever beam.
7. Bending moments and shear forces in beams for simply supported beam and over hanging beam.
8. Bending stresses in beams, theory of simple bending, derivation of flexure formula.
Mid Term

4. COURSE CONTENT
9. Center of gravity, moment of inertia, and radius of gyration.
10. Section modulus
11. Deflection of beams; area moment method and mohr’s theorem.
12. Castigliano’s theorem.
13. Failure theories
14. Stresses in thin cylinders and spherical shells.
15. Stresses in composite bars and riveted joints.
16. Torsion theory for shafts of circular section, power transmitted by shaft, torsion combined with bending.
17. Open and closely coiled helical springs subjected to axial loading .
Final term

5. RECOMMENDED STUDY
SOURCES
1. Dr. R.K. Bansal (2009). A text book of Strength of Materials. Fourth edition.
Laxmi Publication Private Ltd, New Delhi.
2. Strength of Material by Professional Staff of Benette College.
3. Shigley, J.E. and C. R. Mischhe, (2000). Mechanical engineering Design. Tenth edition. McGraw Hill
publications Inc. USA.
4. Muvdi, B.B. And W. McNabb. (1984). Engineering Mechanics of Materials. McMillan Publishing CO., New
York.
5. Provided lecture notes.

6. LEARNING OBJECTIVES
To equip the students with
1. The basic understanding of
• Force vectors and their operations, force equilibrium,
• Stresses and strains of a body when the body is subjected to external loads.
2. Provide essential technical basis for the
• Analysis and
• Design of agricultural machinery and civil structures.

7. LEARNING OUTCOMES
Upon the completion of the course, the student should be able
1. To use vectors to represent the force acting on a system and correctly plot free body diagram and check the
equilibrium of a rigid body
2. Know the types of internal loadings, the relationships between stress and strain and the basic mechanical
properties of materials
3. Compute the stress of a beam section due to tension, compression, torsion, bending, shear and combined loading
4. Transform stress (strain) components from one orientation to another learn the concepts for the design of beams

8. WHAT IS MECHANICS OF
MATERIALS?
• Three fundamentals areas of engineering mechanics are
1. Statistics
2. Dynamics
3. Strength of Materials.
Study of the external effects of forces on rigid bodies,
that is, bodies for which the change in shape
(deformation) can be neglected.
In contrast, Strength of Materials deals with the relation
between externally applied loads and their internal
effects on bodies.
The bodies are no longer assumed to the rigid: the
deformations, however small, are of major interest.

9. PROPERTIES OF MATERIALS
Different materials possess different properties
in varying degree and therefore behave in
different ways under given conditions.
Thesepropertiesinclude
Mechanical
Electrical
Thermal
Chemical
Magnetic
Physical
A design engineer is interested in
the behavior of materials under load
which is mechanical in nature, for
the design of machines & structures.
Any material subjected to a load either deforms, yield,
or break, depending upon the magnitude of the load.
We are basically interested in knowing as to how
a particular material will behave under applied
load i.e. In knowing the mechanical properties.

10. WHY TO STUDY TO MECHANICAL
PROPERTIES OF MATERIALS?
An elementary knowledge of the properties of the various
materials enables the designer to decide which particular
material is the best to use for any particular purpose.
An elementary knowledge of the principal processes
by which iron and steel are produced is also essential
to every engineer,
As in specifications of engineering designs and
structures it is frequently stated by which particular
process the material to be employed is to be made.
Certain terms relating to the properties of
materials are constantly being used by
engineers.
The exact meaning of these terms must
therefore be explained at this stage.

11. 1. Tenacity / Strength
It is the resistance offered by a material
when subjected to external loading.
So, stronger the material the greater
the load it can withstand.
Depending upon the type of load applied the
strength can be
Tensile Compressive Shear Torsion
2. Hardness
It is the ability of a material to resist
scratching, abrasion, indentation.
Thus machine cutting tools are
made hard
To prevent them from being
blunted
By contact with the materials
they are intended to cut.
Softness is the converse of Hardness.

12. 3. Brittleness
The property of material to break readily without
much permanent distortion, subjected to shocks.
Usually the tensile strength of brittle materials is
only a fraction of their compressive strength.
Therefore, a non-ductile material is said to be
a brittle material.
Brittle
Material
Should not be considered as lacking strength.
It only shows the lack of plasticity.
Do not have Yield Point on Stress-Strain Diagram + Low Value of E
Glass Cast Iron
Examples
4. Ductility
The property possessed by certain bodies that they
may be drawn out in the direction of their length.
The elongations are permanent.
It enables the material to draw out into
thin wire on application of the load.
Possess the properties both of
tenacity and softness.
The ductility decreases with
increase of temperature.
Mild steel, gold, silver,
copper, aluminum, etc.
Examples

13. 5. Malleability
Malleability of a material is its ability to be flattened
into thin sheets without cracking by hot or cold
working.
A body is said to be malleable when it can be beaten out
and extended in all directions.
Ductility is a tensile property, whereas malleability is a
compressive property
Malleability
increases with
increase of
temperature.
Aluminum, copper, tin, lead,
steel, etc. are malleable
metals.
6. Welding Power
Separate pieces of certain metals, when heated to a
high temperature, may be joined together by
hammering so as to form one piece. Such metals are
said to be weld able.
7. Elasticity
Elasticity of a material is its power of coming back to its
original position after deformation when the stress or
load is removed.
Elasticity is a
tensile
property.
The greatest stress that a material
can endure without taking up
some permanent set is called
elastic limit.

14. 8. Stiffness (Rigidity)
The resistance of a material to deflection is called stiffness
or rigidity.
Stiffness is measured by young’s modulus E.
The higher the value of the young’s
modulus, the stiffer the material.
9. Plasticity
The plasticity of a material is its ability to undergo some
degree of permanent deformation without failure.
Due to this properties various metal can be transformed
into different products of required shape and size.
Plasticity is an important property and widely used in
several mechanical processes like forming, shaping,
extruding and many other hot and cold working processes.
In general,
plasticity increases
with increasing
temperature
This conversion into
desired shape and size
is effected either by the
application of pressure,
heat or both.

15. 10. Toughness 11. Hardenability
The toughness of a material is its ability to withstand
both plastic and elastic deformations.
Toughness is a measure of the amount of energy a material
can absorb before actual fracture or failure takes place.
“The work or energy a material
absorbs is called modulus of
toughness”.
For e.g., If a load is suddenly
applied to a piece of mild steel
and then to a piece of glass the
mild steel will absorb much more
energy before failure occurs.
Thus, mild steel is said to be
much tougher than a glass.
wrought iron, mild
steels
It is a highly desirable
quality for structural
and machine parts to
withstand shock and
vibration.
Hardenability is the degree of hardness that can be
imparted to metal by process of hardening.
The material is heated above a certain temperature and then
suddenly quenched in a cold oil or water bath.
Hardness
does not directly relate to
the hardenability.
Hardenability is indicative of the degree of hardness that
the metal can acquire through the hardening process. i.e.,
Heating or quenching.

16. 12. Impact Strength 13. Resilience
It can be defined as the resistance of the material to
fracture under impact loading.
i.e., Under quickly applied dynamic loads.
Two standard
tests are normally
used to determine
this property.
The IZOD
impact test.
The
CHARPY
test.
Resilience is the capacity of material to absorb
energy elastically.
On removal of the load, the energy stored is released as in
a spring.
The quantity gives capacity
of the material to bear
shocks and vibrations.
The maximum energy
which can be stored in a
body up to elastic limit
is called the proof
resilience.