What is Four Stroke Engine?

Before starting to know about four stroke engine, we must have the knowledge of what does stroke mean. In this we will go to learn about working, types, main components, application and advantages of 4 stroke engine. I hope that you will really enjoy this.


What is Stroke

When piston moves from TDC to BDC, it is called as 1 stroke. Stroke means movement of something in a direction. Here we mean movement of piston. Before defining 1 stroke we should know about some basic terminology used in four stroke engine.


Main Components of Four Stroke Engine




  • Inlet Manifold: It is a passage for the entry of the fuel inside the cylinder.
  • Exhaust manifold: Passage for the escape of the burnt gases.
  • Intake valve: It is a cam operated valve through which the fuel or air enter within the cylinder.
  • Exhaust valve: It is also a cam operated valve through which the burnt gases escapes out.
  • Spark plug: It is used to generate the spark for the burning of the fuel.
  • Cylinder: It is a part of the engine where piston does reciprocating motion in order to produce all four strokes necessary for the working of an engine.
  • Piston: It is a part of engine which does reciprocation motion within the cylinder. It performs suction, compression, and exhaust process during the working of the four stroke engine.
  • Connecting rod: It connects the piston and crankshaft of the engine. It transfers the power generated by the engine from piston to the crankshaft. And the reciprocating motion of the piston changes to the circular motion.
  • Crankshaft: It is used to convert the reciprocating motion of the piston into circular motion.
  • Crank case: It holds the crankshaft assembly in it and protects them from damage.


Basic Terminology Used in 4 Stroke Engine



  • Bore: The inner diameter of the cylinder is called bore. It is generally expressed or measured in millimeter (mm).
  • Stroke: The distance travelled by the piston from one of its dead center positon to other dead centre position is called stroke. The distance between the two dead centre is called stroke length.
  • TDC: The full form of TDC is Top Dead Centre. It is the maximum upper limit up to which the piston can move.
Basic terminology used in 4 stroke engine

  • BDC: The full form of the BDC is Bottom Dead Centre. It is the lower maximum limit up to which the piston can move.
Basic terminology used in 4 stroke engine

  • Combustion chamber: It is a chamber where the combustion of the fuel takes place
  • Clearance volume: It is the Volume included between the Piston and the Cylinder Head when the Piston is at its Top Dead Center in Vertical Engines and inner Dead Center in Horizontal Engines. The Clearance Volume is generally expressed as percentages of Swept Volume.
  • Swept volume: It is the volume through which the Piston sweeps for its one Stroke. It is equal to the Area of cross section of the Piston multiplied by its Stroke Length. It is also known as swept volume.
  • Total volume: The summation of the clearance and swept volume is called total volume.
  • Compression ratio: The ratio of the total volume to the clearance volume is called compression ratio. For Petrol Engines the value of Compression Ratio is varies from 5:1 to 9:1 and for Diesel Engines varies from 14:1 to 22:1


What is Four Stroke?

There are four stroke in a 4 stroke engine. It means piston moves 4 times to complete its one cycle of power stroke. One cycle of power stroke includes suction, compression, power and exhaust stroke.

1 stroke: suction stroke

In this piston movement is from TDC to BDC

2 stroke: Compression stroke

In this piston movement is from BDC to TDC.

3 stroke: Power stoke

In this the piston movement is from TDC to BDC.

4 stoke: Exhaust stroke

In this the piston moves from BDC to TDC.


What is 4 Stroke Engine?

Any mechanical device which is capable of converting chemical energy of the fuel into mechanical energy is called an engine.
Also in four stroke engine, the chemical energy is converted into mechanical energy in which the piston does four times movement to produce a power stroke ( 2 times from TDC to BDC and 2 times from BDC to TDC).


Types of Four Stroke Engine

The four stroke engine are of two types and these are

1. Petrol engine/ gasoline engine: when petrol is used as a fuel in four stroke engine then it is called as four stroke petrol engine. The construction of petrol engine is slightly different from the diesel engine. In petrol engine there is a spark plug for the combustion of the fuel. And air-fuel mixture is sucked in the cylinder.


2. Diesel engine: When the fuel used in the four stroke engine is diesel than it is called as diesel engine. In diesel engine there is fuel injector for the injection of the fuel within the cylinder. During suction, only air is sucked within the cylinder. Hot compressed Air is used for the burning of the fuel in this type of four stroke engine.



Working of four stroke engine

The various strokes in four stroke engine are

1. Suction stroke

2. Compression stroke
3. Power stroke
4. Exhaust stroke

Let’s understand what actually happens in these strokes one by one in detail.



1. Suction Stroke:

Working of four stroke engine (Suction Stroke)

  • Piston moves from TDC to BDC
  • Opening of intake valve
  • Suction of the air or air fuel-mixture ( air in diesel engine and air-fuel  mixture in petrol engine)

In suction stroke what happens, first the piston moves from TDC to BDC. As the piston moves the inlet valve opens and the air fuel mixture in case of petrol engine and only air in diesel engine enters into the cylinder. The exhaust valve remains closed during this stroke.


2. Compression Stroke

Working of four stroke engine (Compression Stroke)

  • Piston moves from BDC to TDC
  • Compression of air or air-fuel mixture (air in diesel engine and air-fuel mixture in petrol engine)
  • Intake and Exhaust valve remains closed

In compression stroke, the piston moves from BDC to TDC. The inlet and exhaust valve remains closed during this stroke. As the piston moves upward( from BDC to TDC) the compression of air- fuel mixture in case of petrol engine and only air in case of diesel engine takes place. The compression processes completes when piston reaches to the TDC. The compression is done to increase the temperature of the air or air-fuel mixture. The temperature is increased so that it can easily catch fire during sparking in case of petrol engine and spraying of diesel in case of diesel engine.


3. Power/ Expansion/Working Stroke

Working of four stroke engine (Power Stroke)

  • Sparking and burning of the air-fuel mixture in Petrol engine.
  • Burning of diesel by the hot gases.
  • Piston moves from TDC to BDC.
  • Intake and Exhaust valve remains closed.

Petrol engine: The air-fuel mixture is ignited by the spark plug. Due to the ignition the burning process starts. The burning of the air-fuel mixture creates a very high pressure burnt gases. This high pressure burnt gases exerts a thrust on the top face of the piston and it starts to move downward from TDC to BDC. This is the power stroke of the engine. In this stroke we get power which is utilized to run the vehicle. The intake and exhaust valve remains closed during this stroke.

Diesel engine: As the Piston approaches TDC the injection of the diesel in the form of spray by fuel injector takes place. As the diesel sprayed by the fuel injector come in contact with the hot compressed gases it catches fire and burning processes starts. Due to burning high pressure hot burnt gases originates and it puts a very high thrust on the top face of the piston. Due the thrust impact on the piston it starts to move in downward direction i.e. form TDC to BDC. 



4. Exhaust Stroke

Working of four stroke engine (Exhaust Stroke)

  • Piston moves from DBC to TDC.
  • Opening of the Exhaust Valve.
  • Escaping of the hot burnt gases through exhaust valve.

In this stroke the piston moves upward i.e. from TDC to BDC. As the piston moves upward the exhaust valve opens and all the burnt gases left after power stroke starts escaping out of the cylinder. The burnt gases escape out in the environment through exhaust Valve. When the piston reaches at TDC the exhaust process completes. And after this again all the four stroke repeat themselves.


Video of Working of Four Stroke Engine (petrol engine)


Video of working of four stroke Diesel Engine




Application of 4 Stroke Engine

The four stroke engines are generally in motorcycles, cars buses trucks etc.


Advantages of Four Stroke Engine Over Two Stroke Engine

  • It has high fuel efficiency
  • It runs quitter than 2 stroke engine.
  • It remains for last longer than 2 stroke engine and does not cease as quickly.
  • We don’t have to mix oil in the fuel  as done in the 2 stroke engine.
In this article we have studied about four stroke engine. If you like this than don't forget to like us on Facebook. And if you find anything missing than let me know through your commenting. 

Difference between Petrol and Diesel Engine

In this article we will discuss about difference between petrol and diesel engine. The classification of petrol and diesel engine is done on the basis of the respective fuel used by these engines. The engine which uses petrol is called petrol engine while that uses diesel is called diesel engine. Here will discuss all the major differences among these engines.

Difference between Petrol and Diesel Engine

Difference between Petrol and Diesel Engine

There is a lot of difference between petrol and diesel engine and these are as follows:

  • The petrol engine works on Otto cycle whereas diesel engine works on diesel cycle.
  • In petrol engine the air and petrol are mixed in carburetor and it enters into the cylinder. In diesel engine the fuel is first fed into the cylinder by a fuel injector and then gets mixed with air inside the cylinder.
  • In petrol engine first the compression of air and petrol is done and then it is ignited by an electric spark. In diesel engine only the charge of air is compressed and ignition is done by the heat of compressed air.
  • The compression ratio in petrol engine is low as compared with the diesel engine.
  • The power developed in petrol engine is low due to lower compression ratio. In diesel engine the power developed is more due to higher compression ratio.
  • Petrol engine is fitted with spark plug whereas diesel engine is fitted with a fuel injector.
  • In petrol engine the fuel that burns has high volatility. In diesel engine the fuel of less volatility is burnt.
  • Petrol engines are used in light weight vehicles like car, motorcycles, scooters etc. Diesel engines are used in heavy vehicles like buses, trucks, locomotives etc.
  • Fuel consumption in petrol engine is higher than the diesel engine.
  • Petrol engine is lighter whereas diesel engine is heavier.
  • Frequent overhauling is required in petrol engine but overhauling of diesel engine is done after a long time.
  • There is lesser starting problem in petrol engine as compared with diesel engine.
  • Petrol engine has lowered initial and maintenance cost but the initial and maintenance cost of diesel engine is high.

Table for the difference between petrol and diesel engine

S.No
Petrol Engine
Diesel Engine
       1.
The petrol engine works on Otto cycle i.e. on constant volume.
The diesel engine works on diesel cycle i.e. on constant pressure.
         2.
The air and petrol are mixed in the carburetor before they enter into the cylinder.
The fuel is fed into the cylinder by a fuel injector and is mixed with air inside the cylinder.
          3.
The petrol engine compresses a mixture of air and petrol which is ignited by an electric spark.
The diesel engine compresses only a charge of air and ignition is done by the heat of compression.
          4.
Compression ratio is low.
Compression ratio is higher in diesel engine.
          5.
Less power is produced due to lower compression ratio.
Due to higher compression ratio more power is produced.
          6.
Petrol engine is fitted with a spark plug
It is fitted with a fuel injector.
          7.
Burns fuel that has high volatility.
Burns fuel that has low volatility.
      8.
They are used in light vehicles which requires less power
Eg: car, jeep, motorcycle, scooters etc.
They are used in heavy vehicles which require high power.
Eg: bushes, trucks, locomotive etc.

         9.
Fuel consumption in petrol engine is high.
Fuel consumption in diesel engine is less.
        10.
Lighter
Heavier
       11.    
Petrol engine requires frequent overhauling.
Overhauling of diesel engine is done after a long time.
      12.
Lesser starting problem.
Greater starting problem.
      13.
Lower initial cost.
Higher initial cost.
       14.      
Lower maintenance cost.
Higher maintenance cost.


If you found anything incorrect or have doubts regarding above difference between petrol and diesel engine article then comment below.

Image Source: R.B. Gupta

What is Two Stroke Engine?

Here in this article we will discuss about two stroke engine. The topics that we will cover are definition, construction, working, advantages and disadvantages and application of 2 stroke engine.

Two Stroke Engine

The two stroke engine is a reciprocating engine in which the piston does two time movement ( i.e. TDC to BDC and BDC to TDC ) to produce a power stroke.

What is stroke?

When the piston moves from TDC to BDC or BDC to TDC then this movement of piston from TDC to BDC and vice versa is called one stroke.

Construction of two stroke engine

What is Two Stroke Engine?

Main components of a two stroke engine

1. Spark plug: Spark plug is a device which is used to generate spark within the cylinder. The spark produced is used to burn the fuel in the cylinder.

2. Piston: Piston is the reciprocating part of the engine. It is used for the suction and compression of the fuel within the cylinder.

3. Cylinder: it is that part of the two stroke engine which holds piston within it. The inlet and exhaust ports are present in the cylinder. Cylinder head consist of the combustion chamber and the spark plug.

4. Transfer port: It is used to transfer the compressed fuel from crankcase to the cylinder.

5. Connecting rod: It connects the piston and crankshaft. It transfer the power from the piston to the crankshaft.

6. Crank case: It acts as the base of the engine. It supports the crankshaft and camshaft in suitable bearings and provides the arms for supporting the engine on the frame.

7. Crank shaft: It is that part of the engine which is used to convert the reciprocating motion of the engine into the rotating motion with the help of a connecting rod.

8. Exhaust port: It is used to transfer the burnt gases out of the engine.

9. Inlet port: The fresh charge enters into the cylinder through inlet port.

10. Balancing weight: It is the weight used for the balancing of the engine.

Working of a two stroke engine

  • In two stroke engine the suction and exhaust strokes are eliminated.
  • There are only two remaining strokes - these are the compression stroke and power stroke and usually called as upward stroke and downward stroke.
  • Instead of valves, the two stroke engine consists of inlet and exhaust ports.
  • The fresh charge enters into the cylinder through inlet port and burnt gases escapes out through exhaust port.
  • The burnt exhaust gases are forced out through the exhaust port by fresh charge which enters the cylinder nearly at the end of the working stroke through the inlet port.

The two strokes of a two stroke engines are described as follows:

1. Upward stroke:

  • During upward stroke, the piston moves from BDC to TDC and compresses the charge (air-fuel mixture) in the combustion chamber of the cylinder.
  • Because of the upward movement of the piston a partial vacuum is created in the crankcase and this allows the entry of the fresh charge into the crankcase through uncovered inlet port.
  • The exhaust port and the inlet port remains covered when the piston at the TDC.
  • The ignition of the fresh charge is takes place by the spark plug.

Downward stroke:

  • As soon as the combustion of the fresh charge takes place, a large amount of the hot gases is produced which exerts a very high pressure force on the top of the piston. Due to this high pressure force, the piston moves downward and rotates the crankshaft and does useful work.
  • During this stroke the inlet port is covered by the piston and the new charge is compressed in the crankcase.
  • Further downward movement of the piston uncovers first the exhaust port and the transfer port and the exhaust starts through the exhaust port.
  • As soon as the transfer port opens, the charge through it is forced into the cylinder.
  • The charge strikes the deflector on the piston crown, rises to the top of the cylinder and pushes out most of the exhaust gases.
  • The piston is now at BDC position. The cylinder is completely filled with the fresh charge but it is somewhat diluted with the exhaust gases.
  • Finally the cycle event is then repeated. We get two strokes for the single revolution of the crankshaft.

Port Timing diagram for a two stroke cycle engine

What is Two Stroke Engine?

Advantages and disadvantages of two stroke engine over four stroke engine

Advantages:

  • Two stroke engine gives a working stroke for each revolution of the crankshaft. The four stroke engine gives a working stroke for each two revolution of the crankshaft.
  • Power developed by the two stroke engine is twice that developed by the four stroke engine for the same engine speed and volume.
  • Lighter flywheel is required in two stroke engine because of the more turning moment on the crankshaft.
  • For the same power, a two stroke engine is more compact, light and requires less space than a four stroke engine, therefore is used in auto cycles, motorcycles and scooters.
  • It is simpler in construction and mechanism.
  • There is no valve and valve mechanism in it. The ports can be easily designed and covered and uncovered by the movement of the piston itself.
  • It has high mechanical efficiency.
  • It requires fewer spare parts due to its simple design.

Disadvantages:

  • It has high fuel consumption.
  • Thermal efficiency is less than four stroke engine.
  • The charge is diluted by the burnt gases due to incomplete scavenging.
  • It produces greater noise.
  • It does more consumption of the lubricating oil.
  • There is a greater wear and tear of moving parts.

Application of 2 stroke engine:

  • It is used in light weight vehicles like scooters, motorcycles, mopeds etc which uses gasoline as fuel.
  • It is also used in many diesel engines, mainly industrial and marine engines, as well as in some heavy trucks and machinery

Let's check your grasp on the topic

1. Fill in the blanks with appropriate words.
(i). The movement of piston from TDC to BDC or vice versa is known as .....................
(ii). The part of engine that produces spark is called...........................
2. Name all the main components of a 2 stroke engine.
3. Which two strokes are eliminated in these types of engines.
4. Write any two advantages and disadvantages of two stroke engine.
5. Write the function of inlet and exhaust port.

What Is Stress And Strain?

What is Stress?

Whenever an external force is applied on a body then a resisting force is induced in the body. This resisting force acting per unit area of the body is called stress. Under equilibrium condition this resisting force is equal to the applied load. So the stress is also defined as the ratio of applied force to the cross sectional area on which this external force is applied. The force applied on the body is called load.

For better understanding about the stress let’s take an example

What Is Stress And Strain?


Considered a bar of length L, cross section area A and an external force (load) P is applied on the body. Take a section x-x of the bar as shown in the figure. The load at the left of the section induces resisting force R at the right of the bar. And the load at the right of the section x-x as shown in figure above induces a resisting force R at the left of the section. Under equilibrium condition the resisting force remains equal with the applied load. The ratio of resisting force to the cross section area called stress.

stress=(resisting force)/(cross sectional area) = R/A

What is strain?

When an external force is applied on the body then some change in dimension of the body takes place. The ratio of this change in the dimension of the body to the original dimension is called strain.
  • Strain is a dimensional less quantity as it is the ratio of change in dimension to the original dimension.
  • The strain is denoted by the letter ‘e’.
Strain = change in dimension/ original dimension

For example: Considered again a bar of length L, and an external load P in the form of pull is applied on it. Due to this load there is some change in the length of the body. The length of the body increases by the amount dl. The ratio of this change in length (dL) to the original length (L) is called strain.

What Is Stress And Strain?


Strain = change in length/ original length
e = dL/L

Types of Strain

The various types of strain are as follows

1. Tensile strain: When an external load is applied on the body and there is increase in the length of the body. Then the ratio of increase in the length of the body to original length is called tensile strain. Tensile strain is always results in increase in length.

What Is Stress And Strain?

Tensile strain = increase in length/ original length


2. Compressive strain: The ratio of decrease in length of the body to the original length is called compressive strain. The compressive strain is always results in decrease in length of the body.
What Is Stress And Strain?

Compressive strain = decrease in length/ original length

3. Volumetric strain: The ratio of change in volume to the original volume is called volumetric strain.

What Is Stress And Strain?

Volumetric strain = change in volume/ original volume


4. Shear strain: The strain that is produced in the body due to shear stress is called shear strain.

Types of stress

The various types of stress are:

1. Normal stress: The stress that acts in the direction perpendicular to the area is called normal stress.

The normal stress is again of two types and these are

(i). Tensile stress: when a body is subjected to two equal and opposite pulls then the stress induced in the body is tensile stress. The tensile stress results in the increase in the length of the body.
What Is Stress And Strain?
(ii). Compressive stress: The stress induced in a body when it is subjected to equal and opposite pushes is called compressive stress.

What Is Stress And Strain?
  • The compressive stress is always results in the decrease in the length of the body.
  • The compressive stress acts normal to the area and pushes on the area.


(iii). Shear stress: The stress induced in a body, when subjected to two equal and opposite forces which are acting tangentially across the resisting section as a result of which the body tends to shear off across the section, is called shear stress.

What Is Stress And Strain?

  • The strain produced in a body due to shear stress is called shear strain.
  • The shear stress acts tangential to the area.
  • It is denoted by \tau\,.

lets check your grasp on stress and strain

1. The ratio load applied load to the cross section area is called
(i). Stress 
(ii). Strain 
(iii). Shear stress
(iv). Density

2. The ratio of change in dimension to the original dimension is called strain.
(i). True
(ii) False

3. When a body is applied with two equal and opposite push then the stress induced in the body is .............................
(i). Tensile stress
(ii). Tensile strain
(iii) Compressive stress
(iv). Non of these

4. The tensile strain is the ratio of 
(i). Decrease in length to the original length
(ii). Increase in length to the original length
(iii). Increase in volume to the original volume
(iv). None of these

5. Shear stress acts ........................ to the area.
(i). Normal
(ii). Tangential
(iii). Inclined
(iv). None of these

This is all about what is stress and strain?

Difference Between Otto Cycle and Diesel Cycle


We must know about the difference between Otto cycle and Diesel cycle in order to understand the working of automobiles. The present day vehicles that is running one the roads are either works on Otto cycle or Diesel cycle. In this article I will tell you about the major difference between these cycles.

Difference Between Otto Cycle and Diesel Cycle

Difference Between Otto Cycle and Diesel Cycle

The Otto cycle was given by German scientist Otto, in 1876 and diesel cycle was discovered by Dr. Rudolph Diesel in 1897. In Otto cycle the heat addition is takes place at constant volume where as in diesel cycle heat is added at constant pressure. Petrol engines work on Otto cycle and diesel engines work on diesel cycle. In Otto cycle at the time of heat addition, the piston is at TDC where as in diesel cycle when the piston is in backward stroke, the heat addition begins and last at a portion of piston stroke. The Otto cycle has less compression ratio (7:1 to 10:1) but in diesel cycle the compression ratio is high (11:1 to 22:1). In Otto cycle as well as in diesel cycle heat rejection takes place at constant volume. The efficiency of Otto cycle is less as compared with the Diesel cycle.


Table For the Difference Between Otto Cycle and Diesel Cycle 


OTTO CYCLE
DIESEL CYCLE
1.
Heat addition takes place at constant volume.
Heat addition takes place at constant pressure.
2.
Petrol engines work on this cycle.
Diesel engines work on this cycle.
3.
At constant volume, heat rejection takes place.
in diesel cycle also the heat rejection takes place at constant volume.
4.
Compression ratio is less. It is 7:1 to 10:1.
Compression ratio is more. It is 11:1 to 22:1.
5.
Efficiency is less.
Efficiency is more.
6.
Adiabatic expansion takes place during the complete backward stroke of the piston.
After the heat addition is cut-off in the backward stroke, the adiabatic expansion takes place during the remaining portion of stroke.

In this article I have discussed about the difference between Otto cycle and Diesel cycle. if you find anything wrong or missing let me know through your commenting.

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Types of Fluids In Fluid Mechanics

The different types of fluids are: 

Basically the fluids are classified into 5 types and these are

1. Ideal fluid
2. Real fluid
3. Newtonian fluid
4. Non-Newtonian fluid, and
5. Ideal plastic fluid

1. Ideal Fluid: A fluid which can not be compressed and have no viscosity falls in the category of  ideal fluid. Ideal fluid is not found in actual practice but it is an imaginary fluid because all the fluid that exist in the environment have some viscosity. there in no ideal fluid in reality.

2. Real Fluid: A fluid which has atleast some viscosity is called real fluid. Actually all the fluids existing or present in the environment are called real fluids. for example water.

3. Newtonian Fluid: If a real fluid obeys the Newton's law of viscosity (i.e the shear stress is directly proportional to the shear strain) then it is known as the Newtonian fluid.

4. Non-Newtonian Fluid: If real fluid does not obeys the Newton's law of viscosity then it is called Non-Newtonian fluid.

5. Ideal Plastic Fluid: A fluid having the value of shear stress more than the yield value and shear stress is proportional to the shear strain (velocity gradient) is known as ideal plastic fluid.

The graph between the shear stress and velocity gradient for the different types of fluids are given below:

Types of Fluids


lets check your grasp on the topic.

1. Name different types of fluids.
2. A fluid which have atleast some viscosity is known as
(i). Newtonian fluid
(ii). Real fluid
(iii). Ideal fluid
(iv). Ideal Plastic fluid

3. Name the type of fluid which does not obeys the Newton,s law of viscosity.
4. Write true or false for the following
(i). Fluids which are incompressible and have no viscosity is known as real fluid.
(ii). A ideal plastic fluid have the value of shear stress less than the yield value.
(iii). Ideal fluid exist in reality.
(iv). Newtonian fluids obeys the Newton,s law of viscosity.


What is Strain – Strength of Material?

What is strain?, this is a simple and common question generally asked by a person who goes to study about strain in strength of material. In this post I will try my level best to explain you about strain.

What is strain?

What is Strain – Strength of Material

When an external force is applied on a body, there is some change occur in the dimension of the body. The ratio of this change of dimension in the body to its actual length is called strain. 

For example: if you have a bar of length l and an external force P is applied on the bar, then there is some change in the length of the bar. Let the change produced in the bar is dl. Then the strain is the ratio of this change in the length to the original (actual) length. Strain is dimensionless quantity.

Mathematically,

strain= (change in length)/(original length)
e= dl/l

Types of strain:

Strain in mechanics is of four types and these are:
1. Tensile strain: The strain produced in a body due to tensile force is called the tensile strain. The tensile force is always results in increment of the length and decrease in the cross section area of the body. In this case the ratio of the increase in length to the original length is called tensile strain.

2. Compressive strain: The strain appears due to the compressive force is called compressive strain. In compressive force there is a decrease in the dimension of the body. So the ratio of the decrease in the length of the body to the original length is called compressive strain.

3. Volumetric strain: The ratio of the change in the volume of a body to the original volume is called the volumetric strain. In volumetric strain there is a change in the volume of the body due to application of the external forces.

4. Shear strain: The strain which is produced in a body due to shear force is called shear strain.


This is all about what is stress, types of stress and definition of each type of strain in strength of materials.