We were
discussing the concept of stress and strain in our previous post; now we are
going further to start our discussion for classifying the stress and strain. Hence,
we will see here the types of stress and strain with the help of this post.

###
**Types of stress**

There are
following type of stresses as displayed in figure here and we will discuss each
type of stress in detail with the help of this post. Basically stresses are
classified in to three types.

1. Direct
stress or simple stress

2. Indirect
stress

3. Combined
stress

Further direct stress or simple stress is classified in two type i.e. normal stress and
shear stress. As it is also displayed in figure, normal stress will be divided
in two type i.e. tensile stress and compressive stress.

Similarly,
indirect stress will also be divided in two type i.e. torsion stress and
bending stress. Above figure displayed here indicates the brief introduction
for the classification of stress in strength of material.

###
**Normal stress**

Normal
stress is basically defined as the stress acting in a direction perpendicular
to the area. Normal stress will be further divided, as we have seen above, in
two types of stresses i.e. tensile stress and compressive stress.

###
**Tensile stress**

Let us see
here the following figure; we have one bar of length L. There are two equal and
opposite pulling type of forces P, acting axially and trying to pull the bar
and this pulling action will be termed as tensile and stress developed in material
of the bar will be termed as tensile stress.

Therefore
we can define the tensile stress as the stress developed in a member due to the
pulling action of two equal and opposite direction of forces. Ïƒ

_{t}is the symbol which is used to represent the tensile stress in a member.
There will
be increase in the length of the bar under the action of tensile loading, but
diameter of the bar will be reduced under the action of tensile loading. Tensile
stress will be determined with the help of following formula.

Tensile stress
(Ïƒ

_{t}) = Resisting force (R) / Cross sectional area (A)
Tensile
stress (Ïƒ

_{t}) =Tensile load or applied load (P) / Cross sectional area (A)
Ïƒ

_{t}Â = P/A###
**Compressive stress**

Let us see
here the following figure; we have one bar of length L. There are two equal and
opposite push type of loading P, acting axially and trying to push the bar and
this pushing action will be termed as compression and stress developed in
material of the bar will be termed as compressive stress.

Therefore
we can define the compressive stress as the stress developed in a member due to
the pushing action of two equal and opposite direction of forces. Ïƒ

_{c}is the symbol which is used to represent the compressive stress in a member.
There will
be decrease in the length of the bar under the action of compressive loading,
but diameter of the bar will be increased under the action of compressive
loading. Compressive stress will be determined with the help of following
formula.

Compressive
stress (Ïƒ

_{c}) = Resisting force (R) / Cross sectional area (A)
Compressive
stress (Ïƒ

_{c}) = Compressive load or applied load (P) / Cross sectional area (A)
Ïƒ

_{c}Â = P/A###
**Shear stress**

Let us see here the following figure; we have two plates and these two plates are
connected with each other with the help of a pin or a rivet as shown in figure.
There are two equal and opposite forces (P) acting tangentially across the
resisting section.

One force
is acting on top plate towards left direction and second force is acting
towards right side as shown in figure and hence such type of loading will try
to shear off the body across the resisting section.

This type
of loading action will be termed as shear loading and stress developed in
material of the body will be termed as shear stress.

Therefore
we can define the shear stress as the stress developed in a member, when member
will be subjected with two equal and opposite forces acting tangentially across
the resisting section. Ï„ is the symbol which is used to represent the shear
stress in a member. Shear resistance R will be equivalent to P here.

Shear
stress (Ï„) = P/A

As we have
seen above in figure, two plates are connected with each other with the help of
a pin and therefore we can also say such type of loading as single shear. Let
we have three plates and these three plates are connected with a pin or rivet,
such type of loading will be termed as double shear. Shear resistance R will be
P/2.

Shear
stress (Ï„) = P/2A

###
**Torsional stress**

Torsional stress is one special type of stress
in a member where one end of member will be secured and other end of member
will be twisted. Let us see one example, let we have one shaft and its one end
is supported by a ball bearing and other end of shaft is free to rotate.

Let if
bearing is seized, then there will be twisting mechanism because one end of
rotating shaft will be fixed due to seized bearing and other end of shaft will
be twisted and therefore there will be produced stress in shaft and that stress
will be termed as torsional stress.

From here,
we can also say that torsional stress will exist in rotating members such as
rotating shaft. Torsional stress will be indicated by symbol

###
**Bending stress**

Let we
have one beam which one end is fixed at A and other end is loaded by force P
and hence beam is deflected here as shown in figure.

Bending stress
will be determined with the help of following formula as displayed here in
following figure.

We will
study and analyze each type of strain in detail in our next post.

###
**Reference:**

Strength of material, By R. K. Bansal

Image Courtesy: Google

We will see another important topic i.e. types of strain in the category of strength of material.

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