food technology, its application and other things

1. Comprehensive
discussion on
material
properties
Presented by
Asif Rahaman
Roll: 34900721068
Dept: ME Sem: 6
Sub: Design of machine elements

2. CONTENTS
Department of Mechanical
Discussion on various material properties
References
Introduction
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3. Introductio
n
Department of Mechanical
Mechanical properties are defined as how materials react to loads or external forces. It is very
important to understand the mechanical properties of engineering materials for creating
components and structures that are reliable, efficient, and safe. They are essential in
establishing a material’s suitability for particular applications across a range of technical
disciplines. Basically, a material’s response to loads or external forces is described by its
mechanical properties. They comprise traits such as flexibility, power, toughness, the degree
of hardness, and more.
Mechanical properties are as follows:
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 Yield Strength
 Tensile Strength
 Brittleness
 Poisson’s Ratio
 Hardness
 Thermal Expansion
 Wear Resistance
 Stiffness
 Ductility
 Malleability
 Toughness
 Resilience
 Creep
 Fatigue

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 Yield Strength
The maximum stress a material can withstand without permanently
deforming is known as yield strength.
It has various phenomena:
 Upper Yield Point: Certain substances have an upper yield point, which
is indicated by a sharp decline in the stress-strain curve after a peak. In
some applications, this phenomenon, which is more typical of materials
like steel with a low carbon content, can cause instability.
 Lower Yield Point: Various materials have a lower yield point, which is
indicated by a sharp reduction in stress just as plastic deformation
begins. For example, certain alloys.
 Yield Strength without Yield Point: Many plastics, for example, lack
an apparent yield point. They show a progressive change from elastic to
plastic deformation instead.
Material Properties
Fig-1: Stress-strain curve

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Material Properties
 Tensile Strength
The maximum stress a material can withstand before breaking under strain is known
as tensile strength. It is a key metric used in the fields of materials science and
engineering in order to assess a material’s capacity for carrying loads and forecast
how it will react under tensile loading.
 Brittleness
The opposite of ductility is brittleness. Materials that are brittle only slightly bend
plastically before breaking. When a material is in the elastic range, it reacts to stress
by being stretched, but once the tension is gone, it returns to its former size and
shape. Hooke’s Law, which asserts the stress is directly proportional to strain within a
material’s elastic limit, governs this property.
Fig-2: Tensile specimen
Fig-3: Brittleness

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 Ductility
A material’s ductility is its capacity to pull out into a thin wire when subjected to a tensile strain. Plastic
and strength are both required for ductile material. Gold, mild steel, copper, aluminium, nickel, zinc,
and tin are examples of ductile materials. Ductility is often expressed in terms of percentage
elongation and percentage area decrease. Tensile properties are assumed to include ductility.
Plasticity and tensile strength are combined in ductile material.
 Stiffness
A material’s stiffness is determined by its capacity to withstand
deformation when stressed. The elasticity modulus serves as a proxy for
stiffness. A material has a high degree of stiffness or rigidity if it only
deforms slightly when subjected to load. The aluminium beams are less
rigid or stiff than steel beams.
Material Properties
Fig-4: Ductility

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Material Properties
 Poisson’s Ratio
Poisson’s ratio gauges a material’s lateral contraction after axial deformation. It is the difference
between axial and lateral strain. There are three types of Poisson’s Ratio:
 Positive Poisson’s Ratio (0<v<0.5): Whenever an axial load is applied to the majority of
common materials, the material responds by compressing laterally. This indicates that although
the lateral strain is negative, it is smaller in absolute terms than the axial strain, leading to a
positive Poisson’s Ratio.
 Negative Poisson’s Ratio (−1<ν<0): In a few designed materials, such as some foams and
composites, the side strain is positive when axial tension is applied. The result is a negative
Poisson’s Ratio.
 Zero Poisson’s Ratio (ν=0): When an axial load is given to a perfect incompressible material,
there is no lateral strain. This means under axial loading, the material’s lateral dimensions do not
change.

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Material Properties
 Hardness
Hardness is a material’s resistance to piercing, scratching, or erosion. A tougher
substance is less susceptible to deformation because it has stronger atomic
bonds. The depth or size of an indentation made by a typical indenter under a
specific load is frequently used to measure the property.
Types of Hardness Tests:
 Brinell Hardness Test: Under a specific load, the surface of the material is
pressed into by a steel ball, generally 10 mm in diameter. The resulting
indentation’s diameter is determined, and the hardness rating is computed.
Softer materials or ones with tough grain structures are good choices for this
test.
 Knoop Hardness Test: Due to the tiny size of the indentation, the Knoop
Hardness Test is often applied to thin and weak materials.
 Shore Hardness Test: This test, which generally applies to elastomers and
polymers, determines the amount of depth of penetration of a certain indenter
with a specific geometry and spring force.
Fig-5: Hardness testing

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Material Properties
 Thermal Expansion
A material’s dimensions changing as a result of temperature changes is
known as thermal expansion. With variations in temperature, various
materials expand or contract to differing degrees.
Types of Thermal Expansion
 Linear Thermal Expansion: A material’s change in length due to a shift
in temperature is referred to as linear thermal expansion.
 Area Expansion: This notion applies when working with two-
dimensional items like sheets or surfaces.
 Volume Expansion: This process is important in three-dimensional
items like solids and liquids.
 Anisotropic Thermal Expansion: It is the ability of different materials
to display distinct thermal expansion behavior in various directions.
Fig-6: Expansion contraction of
electric wire

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Material Properties
 Wear Resistance
The material’s capacity to withstand degradation and wear when in touch with other surfaces is
known as wear resistance.
Types of Wear Resistance:
 Abrasive Wear: It occurs when sharp particles collide with the surface of a substance, causing
material to be removed through scratching, grinding, or cutting.
 Adhesive Wear: It is the process by which material is transferred from one surface to another
as a result of adhesive forces.
 Erosive Wear: It is commonly seen in applications involving high-velocity liquids or particles and
is brought on by the impact of solids, droplets of liquid, or gases on a material’s surface.
 Fretting Wear: Surface damage results from repeated micro-sliding and impacting between two
surfaces in localized contacts that are subjected to minor relative motion.
 Corrosive Wear: In environments where materials have been exposed to both mechanical and
chemical degradation, corrosive wear combines the effects of both wear and corrosion.

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Material Properties
 Malleability
Material’s malleability refers to its capacity to endure heat or cold working
while being rolled, flattened, or hammered into thin sheets. Plastic should
be used for malleable materials, although strength is not required.
Malleability is regarded as a compressive quality. Examples of malleable
metals are soft steel, wrought iron, Al, Cu, Sn, and Pb.
 Toughness
It refers to a material’s capacity to sustain bending without breaking under heavy impact loads. When a
substance is heated, its toughness reduces. The area under the stress-strain curve, which is another
way to measure it, shows how much energy a unit volume of the material has absorbed after being
stressed all the way to failure. For instance, mild steel will absorb far more energy before failing if a load
is rapidly applied to it before being applied to a piece of glass. Mild steel is therefore thought to be far
more durable than glass.
Fig-7: Toughness

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Material Properties
 Resilience
Resilience is the ability of a material to absorb energy while enduring shock and impact
loads. The quantity of energy absorbed per unit volume within the elastic limit is
typically used to describe it. Maximum energy which can be stored in a body up to
elastic limit is called the proof resilience and the Proof resilience per unit volume is
called modulus of resilience.
 Creep
A part is going to experience creep, which is a slow and irreversible deformation, if it is exposed to a
steady tension at a high temperature over a protracted length of time. When designing IC engines,
boilers, and turbines, property is taken into account. Viscous flow is the most basic type of creep
deformation. The image below illustrates the three phases of a standard creep curve. The initial creep
begins quickly and then slows down. However, the rate of the secondary creep is quite constant. Tertiary
Creep, which began in the third stage but was speeded up, ends when the material ruptures or fractures.
It is related to both grain boundary void generation and necking.
Fig-8: Stress vs strain

13. Reference
s
Department of Mechanical
1. V. Raghavan, “Material Science and Engineering’,
Prentice Hall of India Private Limited, 1999.
2. R.K. Bansal, Strength of Materials, Laxmi
Publications
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14. Thank You.