Internal Combustion engine

1. 2
R Upadhyai
Mechanical Properties
Mechanical properties of materials are those which affect the mechanical
strength and ability of a material to be molded in suitable shape. Some of the
typical mechanical properties of a material include:
•Strength
•Toughness
•Hardness
•Hardenability
•Brittleness
•Malleability
•Ductility
•Creep and Slip
•Resilience
•Fatigue

2. 3
R Upadhyai
Strength
It is the property of a material which opposes the deformation or breakdown of
material
in presence of external forces or load. Materials which we finalize for our engineering
products, must have suitable mechanical strength to be capable to work under
different
mechanical forces or loads.
Toughness
It is the ability of a material to absorb the energy and gets plastically deformed
without
fracturing. Its numerical value is determined by the amount of energy per unit
volume. Its
unit is Joule/ m . Value of toughness of a material can be determined by stress-strain
characteristics of a material. For good toughness, materials should have good
strength as
well as ductility.
For example: brittle materials, having good strength but limited ductility are not tough
enough. Conversely, materials having good ductility but low strength are also not
tough
enough. Therefore, to be tough, a material should be capable to withstand both high

3. 4
R Upadhyai
Hardness
It is the ability of a material to resist to permanent shape change due to external stress.
There are various measure of hardness – Scratch Hardness, Indentation Hardness and
Rebound Hardness.
Hardenability
It is the ability of a material to attain the hardness by heat treatment processing. It is
determined by the depth up to which the material becomes hard. The SI unit of
hardenability is meter (similar to length). Hardenability of material is inversely
proportional to the weld-ability of material.
Brittleness
Brittleness of a material indicates that how easily it gets fractured when it is
subjected to a
force or load. When a brittle material is subjected to a stress it observes very less
energy
and gets fractures without significant strain. Brittleness is converse to ductility of
material. Brittleness of material is temperature dependent. Some metals which are
ductile
at normal temperature become brittle at low temperature.

4. 5
R Upadhyai
Malleability
Malleability is a property of solid materials which indicates that how easily a material
gets
deformed under compressive stress. Malleability is often categorized by the ability of
material to be formed in the form of a thin sheet by hammering or rolling. This
mechanical property is an aspect of plasticity of material. Malleability of material is
temperature dependent. With rise in temperature, the malleability of material
increases.
Ductility
Ductility is a property of a solid material which indicates that how easily a material
gets
deformed under tensile stress. Ductility is often categorized by the ability of material
to
get stretched into a wire by pulling or drawing. This mechanical property is also an
aspect
of plasticity of material and is temperature dependent. With rise in temperature, the
ductility of material increases.
Creep and Slip
Creep is the property of a material which indicates the tendency of material to move slowly
and deform permanently under the influence of external mechanical stress. It results due to

5. 6
R Upadhyai
Resilience
Resilience is the ability of material to absorb the energy when it is deformed
elastically by
applying stress and release the energy when stress is removed. Proof resilience is
defined
as the maximum energy that can be absorbed without permanent deformation. The
modulus of resilience is defined as the maximum energy that can be absorbed per
unit
volume without permanent deformation. It can be determined by integrating the
stressstrain cure from zero to elastic limit. Its unit is joule/m .
Fatigue
Fatigue is the weakening of material caused by the repeated loading of the material.
When
a material is subjected to cyclic loading, and loading greater than certain threshold
value
but much below the strength of material (ultimate tensile strength limit or yield stress
limit), microscopic cracks begin to form at grain boundaries and interfaces.
Eventually the
crack reaches to a critical size. This crack propagates suddenly and the structure
gets
fractured. The shape of structure affects the fatigue very much. Square holes and
sharp

6. 7
R Upadhyai
One of the important characteristics of the materials is their ability to permit or resist
the flow of electricity.
Materials to be used in electrical equipments can be selected on the basis of
their properties, such as:
(i) Resistivity,
(ii) Conductivity,
(iii) Temperature coefficient of resistance,
(iv) Dielectric strength,
(v) Thermoelectricity, and
Electrical Properties of Materials

7. 8
R Upadhyai
Resistivity:
It is a characteristic property of the material of which the conductor is made. It is that
electrical property of a material due to which, it impedes or resists the flow of electricity
through it.
Conductivity:
The conductivity (σ) is the reciprocal of electrical resistivity.
Temperature Coefficient of Resistance:
It is usually employed to specify the variation of resistivity, ρ with temperature.
Dielectric Strength:
It means the insulating capacity of a material against high voltages. A material
having high dielectric-strength can withstand sufficiently high voltage field across it
before it will breakdown and conduct. A dielectric is an insulator.
Thermoelectricity:
If two dissimilar metals are joined and this junction is then heated, a small voltage in
the millivolt range is produced, and this is known as thermoelectric effect.
Thermoelectric effect forms the basis of the thermocouple operation.

8. 9
R Upadhyai
The Melting or Freezing Point
The melting or freezing point of pure metal is defined as the temperature at which
the solid and liquid phases can exist in stable equilibrium. When a metal is heated to
melting point, the liquid phase appears, and if more heat is supplied, the solid melts
completely at constant temperature.
II. The freezing of a pure liquid on the other hand, may exhibit the phenomena of
supercoiling, the liquid in some cases can be lowered appreciably beyond the
melting point without the appearance of crystals. However, when crystals do not
appear, the mass rapidly assumes the normal temperature of the melting point.
III. The use of mercury in thermometers, manometers and other instruments arises
from its low melting point; the use of tungsten filaments in incandescent high bulbs is
possible because of its extremely high melting point
Boiling Point:
The boiling point of a liquid is the temperature at which its vapour pressure equals to
one atmosphere. The boiling points of the metals except mercury are high. The
boiling point of zinc (907°C) and cadmium (865°C) are sufficiently low so that in
recovery of these metals from their ores the metals are vapourised and condensed.
ADVERTISEMENTS:
Thermal Properties

9. 10
R Upadhyai
Thermal conductivity
It is the property of a material to conduct heat through itself. Materials with high thermal
conductivity will conduct more heat than the ones with low conductivity.
For example, an iron rod will conduct more heat than normal window glass.
Heat Capacity?
The heat capacity of a material can be defined as the amount of heat required to change the
temperature of the material by one degree. The amount of heat is generally expressed in joules or
calories and the temperature in Celsius or Kelvin.
Thermal Expansion
When heat is passed through a material, its shape changes. Generally, a material expands when
heated. This property of a material is called thermal expansion. There can be a change in the area,
volume, and shape of the material.

10. 11
R Upadhyai
A study of chemical properties of materials is necessary because most of the
engineering materials, when they come in contact with other substances with which
they can react, tend to suffer from chemical deterioration.
The chemical properties describe the combining tendencies, corrosion
characteristics, reactivities, solubilities, etc., of substances.
Some of the chemical properties are:
(i) Corrosion resistance.
(ii) Chemical composition.
(iii) Acidity or alkalinity.
(ii) Chemical composition.
Chemical Properties

11. 12
R Upadhyai
Acidity or Alkalinity
Acidity or Alkalinity is an important chemical property of engineering materials. A
material is acetic or Alkane, it is decided by the ph value of the material. Ph value of
a material varies from 0 to 14. Ph value of 7 is considered to be neutral. Ordinary
water is having ph value of 7. The materials which are having ph value below 7 are
called Acetic and Materials which are having ph value greater than 7 are called
alkane. Acidity of Alkalinity of material indicates that how they react with other
materials.
Corrosion Resistance
Corrosion is a gradual chemical or electromechemical attack on a metal by its
surrounding medium. Due to the corrosion, metal starts getting converted into an
oxide, salt or some other compound. Corrosion of a metals is effected by many
factors such as air, industrial atmosphere, acid, bases, slat solutions and soils etc.
Corrosion has a very adverse effect on materials. Due to corrosion, the strength and
life of a material is reduced. Corrosion resistance of a material is the ability of
material to resist the oxidation in atmospheric condition.

12. 13
R Upadhyai
Performance Requirements
The performance requirements describe the attributes that the component or joint must have to
function as required. The attributes can be described in terms of mechanical, electromagnetic, thermal,
optical, physical, chemical, electrochemical, and cosmetic properties.
Reliability Requirements
The reliability of a component or joint refers to its ability to function as required over a specific use
period when exposed to a specific set of use conditions. A component or joint fails once the material
degrades to the point where the component or joint no longer performs as required. The reliability
requirements describe the use conditions to which the materials will be exposed and the expected
response of the materials to the use conditions. Examples of use conditions are exposure to high
temperatures, salt water (corrosion), and vibration.
Selection

13. 14
R Upadhyai
Size, shape, and mass requirements
The size, shape, and mass requirements for a component or joint will have a huge influence on the
materials that can be used. Consider a component that must carry five amperes of current without
heating up by more than 15o C above the ambient temperature. The electrical conductivity for a
component with a 1 mm diameter must be about four times greater than the electrical conductivity for a
component that can be 2 mm in diameter. A bicycle frame that must weight 10 pounds must have frame
tubes made of a lower density material compared to a 20 pound frame. For a component that must
support 200 pounds, the yield stress for the material in a component that must be 0.20 inches diameter
must be much greater compared to the material in a component that can be 0.50 inches in diameter.
Cost requirements
The cost to form a component or joint or purchase a component depends on 1) the materials that
comprise a component or joint, 2) the manufacturing processes used to form a component or joint, 3)
whether a component is custom made or purchased “off-the-shelf supplier”, 4) the quantity of materials
or components being purchased and 5) quality problems associated with a material or component. If
you want to reduce costs, consider what will be required from the materials engineering perspective to
make manufacturing process changes that address items 2 and 5.

14. 15
R Upadhyai
Manufacturing requirements
Companies may require that specific processes be used for fabricating components and building
assemblies or sub-assemblies. Perhaps a company has internal manufacturing capabilities that must
be used or a company is familiar and comfortable with component or joints fabricated using a familiar
manufacturing process.
Restrictions on the processes that can be used to build a product will restrict the materials that can be
used to make components because the materials must be compatible with the processes and other
materials used to make the product. For example, components to be joined using a specific welding,
brazing, or soldering process must be made of materials that enable good joints to be formed using the
specific joining process. This may exclude off-the-shelf components from one or more suppliers
because their components are made of materials that are incompatible with the process. For a custom
component, the restriction may require the use of certain materials in order to form a good joint.

15. 16
R Upadhyai
Industry standards
There are industry standards concerned with the performance and reliability of components and joints.
In some cases, a specific standard will discuss component and joint requirements. For component
specific standards, the standards discuss
•The size and shape of components used for specific applications.
•The materials that can and cannot be used for components used for specific applications.
•The tests required to verify the properties of the materials used to make a component.
Government regulations
Government regulations regarding the materials used in a product are typically related to requirements
on the materials from which components and joints can and cannot be made. The requirements
address the materials that can or cannot be used in a component or joint and the expected quality and
reliability of the materials for specific applications. Every country has its own set of regulations.
Intellectual property requirements
There are many patents regarding the design and manufacture of component or joints. If a patent is
found that is applicable to the component or joint being selected or designed, then the design team has
to decide whether to license the patent or engineer the component or joint order to avoid conflict with
the patent.

16. 17
R Upadhyai
Sustainability requirements
These requirements restrict the materials that can be used in components and joints to materials that
can be re-used or recycled. The requirements might also restrict the manufacturing processes than can
be used to form components and joints to processes that do not harm the environment and do not use
chemicals and materials that are manufactured using environmentally unfriendly processes. The
sustainability requirements for a product become the sustainability requirements for its components
and joints.