Advantages of permanent mould casting

Permanent mould casting is a process makes use of a reusable metal mould that made from metal. This process involves pouring molten metal into a mould where cools and solidifies after that mould is opened, casting is removed and mould is reused. Let us have a deep insight into the advantages provided by using this casting process. 

Advantages of permanent mould casting : 

  • Close dimensional tolerance can be obtained. 
  • This process is economical for large scale production as the labour involved in the mould preparation is reduced. 
  • Produce a very good surface finish of the order of 4 microns.
  • Better appearance.
  • This process produces a fine-grained casting with superior mechanical properties because of the metallic mould used.
  • Small cored holes may be produced as compared to sand casting.
  • Inserts can be readily cast in place. 
  • Increases repeatability of casting.
  • Finer grain structure can be obtained.
  • High volume production runs.
  • Less expensive than investment and die casting.

Advantages and disadvantages of centrifugal casting

Centrifugal casting is the process where molten metal is poured into a mould that is rapidly moving around a fixed axis. The molten metal comes into contact with this rotating mould under a pressure provided by centrifugal force gives better filling of the mould. It is mainly used for making parts having the shape of bodies of revolutions because this process provides very high grain density and porosity is almost zero. Now, let us have a deep insight into some more advantages and disadvantages of this process. 


Advantages of centrifugal casting :

  • The mechanical properties of centrifugally cast jobs are better compared to other processes because the inclusions such as slag and oxides get segregated towards the centre and can be removed by machining. 
  • In the solidification process, the pressure acting on the metal causes the porosity to be eliminated giving rise to dense metal.
  • Up to a certain thickness of objects, proper directional solidification can be obtained starting from the mould surface to the centre. 
  • No cores are required for making concentric holes in the case of true centrifugal castings. 
  • There is no need for gates and runners, which increases the casting yield, reaching almost 100%. 
  • The high output obtained through this casting process.
  • Very huge parts can also be produced up to 61 thousand kgs. 
  • The cylindrical shape can easily be obtained.
  • Good for mass production. 
  • No use of gates and risers. 

Disadvantages of centrifugal casting : 

  • The inner surface of the casting is the inaccurate diameter. 
  • Material limitation, not all alloys can be cast. 
  • Highly skilled workers are required. 
  • High initial cost. 
  • An only certain shape which is axisymmetric and having concentric holes are suitable for true centrifugal casting.
  • Wastage of material is high for this process.
  • This process required careful observations by of professionals.
  • Many other casting processes are better than this process because it is a traditional technique.

Brayton cycle

The Brayton cycle is a thermodynamic cycle that can be invented by George Brayton in 1872.

The Brayton cycle is a type of power cycle that utilizes and ideal gas to generate power from a type of fuel used to heat the air.



What is the Brayton cycle?


In the Brayton cycle, two reversible adiabatic processes and two constant pressure process are done in a heat engine. 


Brayton cycle

Process of Brayton cycle :


The Brayton cycle consist of four processes following below :
  • Adiabatic quasi-static process compression process: In this process compressor takes fresh ambient air and compressed it to a higher temperature and pressure. 
  • Constant pressure heat addition process: In this process, compressed air is sent to the combustion chamber where fuel is burnt at constant pressure. 
  • Adiabatic quasi-static expansion process: High-temperature gases expand to the ambient temperature in the turbine and produce the power.
  • Constant pressure heat rejection process: The exhaust gases leave the turbine and air back to its initial condition.

The efficiency of the Brayton cycle :


In general, the thermal efficiency of the Brayton cycle is defined as the ratio of the work output to the heat input at the high temperature.

ŋth = W / QH

For ideal gas can now we expressed in terms of temperature :

ŋth  = NetWork / Heat Input = WT – WC / Qin

      = cp [ (T3 – T4 ) – (T2 – T1) ] / cp (T3 – T2)

      = 1 – [ (T4 – T1) / (T3 – T2) ]

Where,

WT = Work is done by the gas in the turbine
WC = Work was done on the gas in the compressor
cp = Heat capacity ratio 

Types of chain drive

Chains have been classified into three groups like :

  • Hosting chains
  • Conveyor chains
  • Power-transmission chains 
Each type has been discussed below :

Hosting chains :

Hosting chains include an oval link and stud link chains. An oval-link chain is a common form of a hosing chain. It consists of oval links and is also known as coil chain. 

Hosting chains are used for lower speeds only. 

Conveyor chains :

Conveyor chains may be of the detachable or hook-joint type or of the closed-end pintle type. The sprocket teeth are so shaped and spaced that the chain should run onto the off the sprocket smoothly and without interference. The motion of this type of chain is not very smooth. 

Conveyor chains are used for low-speed agricultural machinery. The material of the links is usually malleable cast iron. 

Power transmission chains :

Power transmission chains are made of steel in which the wearing parts are hardened. They are accurately machined and run on carefully designed sprockets. 

They classified into three types :

  • Blockchain: It is mostly used for transmission of power at low speeds. 

  • Roller chain: Roller chain is fixed to the inner link whereas the outer link has a pin fixed to it. There is only sliding motion between pin and bushing. The roller is made of hardened material and is free to turn on the bushing. A good roller chain is quite and wears less as compared to a blockchain. 

  • Silent chain: It is also known as Inverted Tooth Chain. This type of chain is used where maximum quietness is desired. The silent chain doesn't have rollers. The links are shaped as to engage directly with the sprocket teeth. The included angle is either 60 or 75 degree. 

Law of belting

To transmit power from one shaft to another pulley are mounted on the two shafts. A Belt drive is a mechanism in which power is transmitted by the movement of a continuous flexible belt. 

so now let us check it out some information of how to belt drive works? to know more about the law of belting. 

The law of belting states that the centre line of the belt when it approaches a pulley must lie in the midplane of that pulley OR A pulley in that plane must contain the point at which the belt leaves the other pulley. However, when a belt leaving a pulley may be drawn out of the plane of the pulley. 



Law of belting



By following this law of belting, non-parallel shafts may be connected by a flat belt. From the above figure, two shafts with two pulleys are at right angles to each other. Both of these can be observed that the centre line of the belt approaching the larger pulley and it lies in its plane which is also true for the smaller pulley. Also, the points at which the belt leaves a pulley are contained in the plane of the other pulley. 

By observation, it should not possible to operate the belt in the reverse direction without violating the law of belting. Thus, for non-parallel shafts, motion is possible only in one direction. Otherwise, the belt is thrown off the pulley. However, it is possible to run a belt in either direction on the pulleys of two intersecting or two non-parallel shafts with the help of guide pulleys. Thus, the law of belting is still satisfied. 

Greasy friction

If two metallic surfaces are wetted with a small amount of lubricant, a very thin film of the same is formed on each of the surfaces. This thin film is of molecular thickness. It adheres to the surface and is known as absorbed film. 

The property of a lubricant to form a layer of molecular thickness on a metallic surface is known as its oiliness. 

If two lubricants of equal viscosity are used to lubricate two metallic surfaces under identical conditions, it is found that one reduces the friction more than the other and is said to have greater oiliness. 

Now, What is Greasy friction?

The friction of two surfaces, when they are wetted with an extremely thin layer of lubricant and metal-to-metal contact can take place between high spots is known as greasy friction or boundary friction. 

The friction laws governing greasy friction are similar to those for solid or dry friction. 

Laws of friction

There are total five basic laws of friction so now let we check it out one by one.

Experiments have shown that the force of solid friction 

  • is directly proportional to the normal reaction between the two surfaces.
  • opposes the motion between the surfaces.
  • depends upon the materials of the two surfaces.
  • is independent of the area of contact.
  • is independent of the velocity of sliding.
The last of these five laws is not true in the strict sense as it has been found that the friction force decreases slightly with the increase in velocity. 

Types of follower motion

Though the follower can be made to have any type of desired motion, knowledge of existing motion program saves time and labour while designing the cams.

Following are some basic displacement programmes :

  1. Simple Harmonic Motion ( SHM )
  2. Constant Acceleration Deceleration ( Parabolic )
  3. Constant Velocity 
  4. Cycloidal 

Mechanical advantage definition

What is a mechanical advantage?

The ratio of the output force or torque to the input force or torque at any instant OR 
The ratio of force produced by a machine to the force applied to it is called the mechanical advantage of mechanism. 

For any linkage, if friction and inertia forces are ignored and the input torque is applied on one link and resisting torque is on another link then formula for finding mechanical advantage :


Power input = Power output 

 T1w1 = T2w2

So, Mechanical Advantage = T1/T2 = w1/ w2

Thus mechanical advantage is written as the reciprocal of the velocity ratio or the reciprocal of the torque ratio.  

What is moment of a force

The general definition of the moment of force :

Moment of force is defined as a product of force and the moment arm. Now the question arise in your mind that what is moment arm? The moment arm is the perpendicular distance between the line of action of the force and the centre of moments. 

In mechanics moment of force is turning effect produced by force, on a body, on which it acts. 

Moment of force = Force applied × Perpendicular distance from the fixed axis. This formula is applied to calculate the moment of force for balanced as well as unbalanced forces. 


Moment of a force

In the above figure the moment of force = ( P × l ) N-m

If the force is in Newton and moment of force is in meter then the unit of moment of force is Newton-meter ( N-m ).


Lami theorem is applicable only for

Application of Lami's theorem :

Lami's theorem is used to describe an equilibrium of three forces but not for more forces. 

It isn't much used any more since the development of vector algebra in the 1900s. 

Lami's theorem applicable to more than three forces by resolving the system into 3 forces and make sure that none of the three angles is greater than 180°.

Lami's Theorem

Lami's theorem is related to the system of forces like the magnitude of three coplanar, concurrent and non-colinear forces that keeps a body in static equilibrium. 

Lami's theorem statement :


It is stated that if three coplanar forces acting at a point be in equilibrium, then each force is proportional to the sine of the angle between the other two forces. 



Lami's Theorem

Now we consider the three forces A, B and C acting on a particle or rigid body that all forces making respective angles α, β and γ with each other.


Now we can represent the Lami's theorem in mathematically :



A / sinα = B / sinβ = C / sinγ


You also check it out the Lami theorem is applicable only for what type of applications.

System of forces

When a mechanics problem or system has more than one force act on a body, it is known as a system of force OR Force system.

There is a various system of forces following below :
1. Coplanar forces: The forces, whose line of action lie on the same plane that is known as coplaner forces. 

There are four types of coplanar forces system :
  • Collinear force system: When the lines of action of all the forces of a system act along the same line, this force system is called collinear force system.
  • Parallel force system: When the line of action of all the forces of a system is different and parallel to each other, this force system is called a parallel force system. 
  • Concurrent force system: When the forces extended and it passes through a single point this system is called the concurrent force system.  
The point is called the point of concurrency. The lines of actions of all forces meet at the point of concurrency. 
Concurrent forces may or may not be coplanar.

  • Non-concurrent force system: In the system, all the forces do meet at a common point of concurrency, this force system is called non-concurrent force system. 

Parallel forces are an example of this type of force system. 
Non-concurrent forces may be coplanar or non-coplanar.

2. Non-coplanar forces: The forces, whose line of action don't lie on a single plane is called non-coplanar forces or Space forces. 

There is three non-coplanar force system :
  • Parallel force system: When the line of action of all the forces of a system is different and parallel to each other and also both are in a different plane, this force system is called parallel force system. 
  • Non-coplanar concurrent forces: When all the forces in the system meet at one point but their lines of action don't lie on the same plane that type of system is known as non-coplanar concurrent forces.
  • Non-coplanar non-concurrent forces : The forces that are not meet at one point and their lines of actions do not lie on the same plane are called non-coplanar non-concurrent forces.

Resultant force definition

What is the resultant force?

resultant force is defined as a total force acting on the body along with their directions. 


On the other words, it is the single force obtained by combining a system of forces acting on a rigid body and it has the same effect on the rigid body as the original system of forces.


The resultant force may be determined by the following laws :


Parallelogram law of forces :


By this law, two forces acting simultaneously on a particle and it can be represented in magnitude and direction by two adjacent sides of a parallelogram, then their results may be represented in magnitude and direction by the diagonal of a parallelogram which passes through their point of intersection. 



Parallelogram law of force

Similar kind of application applicable for triangle, polygon and for similar types of another shape. 


Resultant of two or more intersecting forces found :


Where two or more intersecting forces are found then for solving resultant of that forces steps given below :


Step -1: First of all resolving all the horizontal forces 

Step -2: Then resolving vertical forces 
Step - 3: Then put all data in the below equation and equate. 
Step - 4: Answer will be the resultant force that what we find. 

R = √ ( ∑horizontal force ) 2 + ( ∑vertical force )2

A number of force acting on a particle will be called in equilibrium when :

∑ horizontal force = 0
∑ vertical force = 0

Resultant force for the two forces that are not parallel or any kind of forces :

Step - 1: Draw a free-body diagram of the object.

Step - 2: Draw coordinate axes on the free-body diagram.
Step -3: Decompose the forces acting on the object into x and y components.
Step - 4: Calculate the x and y component of the resultant force by adding the x and y components of all forces.
Step - 5: Find the magnitude and direction of the resultant force by using x and y component. 

Notes :

If the resultant force acting on a stationary object is zero, the object will remain stationary. 

If the resultant force acting on a moving object is zero, the object will carry on moving at the same speed in the same direction.

Force basic definition

Force is a push or a pull that tends to change the state of uniform motion of an object. 

A force can cause an object to accelerate, slow down, remain in original shape or change shape. 

A force while acing on a body may :
  • Change the motion of a body 
  • Retard the motion of a body 
  • Balance the forces already acting on a body 
  • Give rise to the internal stresses in a body
In order to determine the effects of a force acting on a body, one must know the following characteristics of the forces. 
  • The magnitude of the force
  • The line of action of the force  
  • The nature of the force 
  • The point at which force is acting 
The magnitude of the force is given by in MKS system - kilogram-force ( kgf ) and in SI system - Newton ( N ). 

1 kgf = 9.81 N

There are different types of force. You can check it out below :
  • Applied force
  • Gravitational force
  • Normal force 
  • Frictional force 
  • Air resistance force 
  • Tension force 
  • Spring force 

Ericsson cycle

The Ericsson cycle is a thermodynamic cycle that can be invented by John Ericsson in 1840.

What is the Ericsson cycle?


In the Ericsson cycle, two isothermal processes and two constant pressure process are done in a heat engine. 

This cycle is mostly used in a closed cycle gas turbine. 




Process of Ericsson cycle :


The Ericsson cycle consist of four processes following below :
  • reversible isothermal gas expansion process is air as a working fluid which is heated from the heat addition process so work is done during this process.
  • constant pressure heat transfer or isobaric process is the air passed through the re-generator is released as exhaust gas. The heat absorbed by the re-generator is used during the next part of the cycle. 
  • reversible isothermal gas compression process is air is drawn into the engine is compressed and pressurized air drawn into the air storage sink.
  • constant pressure heat transfer is the compressed air at high pressure passe through the regenerator and absorbs the previously stored heat then flows to the piston and cylinder where it gets expands and produces the work.  

Efficiency of Ericsson cycle :


The efficiency of Ericsson cycle is given by :


                                         Ŋcycle = Wnet / Q =  T1 – T2 / T

Although the thermodynamic process of the Ericsson cycle differ from those of the Carnot cycle both cycles have the same value of the thermal efficiency when both are operating between its T1 and T2.

The Ericsson cycle doesn't have any practical application but is mainly used in a gas turbine employing a large number of stages with insulators, reheaters and heat exchangers.

Stirling cycle

The Stirling cycle is a thermodynamic cycle that can be invented by Robert Stirling in 1845.

What is the Stirling cycle?


In the Stirling cycle, two isothermal processes and two constant volume process are done in a heat engine. Constant volume process is performed with the help of a re-generator to make this cycle reversible.


Stirling cycle PV and TS Diagram


Process of Stirling cycle :


The Stirling cycle consist of four processes following below :
  • reversible isothermal gas expansion process is heat addition process from the external source so work is done during this process.
  • constant volume heat transfer process is internal hear transfer takes place from the gas to the re-generator.  
  • reversible isothermal gas compression process is heat rejection to the external sink.
  • constant volume heat transfer is internal heat is transfer from the re-generator to a gas. 

The efficiency of the Stirling cycle :


The efficiency of the Stirling cycle is the same as that of the Carnot cycle. This is due to the fact that this cycle is also reversible as Carnot cycle. So remember that all reversible cycle have the same efficiency.


                                         Ŋcycle = Wnet / Q =  T1 – T2 / T

Also, the COP of the Stirling cycle and Carnot cycle are the same.

Linishing machine

Linishing is a process of using grinding or belt sanding technique to improve the flatness of a surface. The machine that does this is called the linisher or a Linishing Machine.

Linishing process is one types of the metal finishing process.

There are three types of linishing machine are used. List are following below :
  • Drum linishing machine 
  • Orbital linishing machine 
  • Centerless linishing machine 
Linishing machine use in relation to work piece :
  • Bent tubes
  • Round or Oval tubes 
  • Bars 
  • Cylindrical rode 
  • Metal profiles with square and rectangular section
  • Flat surfaces 
  • Extremities 
Mainly it used for the preparation of the ends of rubber extrusions that will be fused together to make a closed-loop. 

Now you can check it out some product where the linishing machine used : 
  • Shop fittings
  • Urban furniture 
  • Taps components
  • Bathroom fittings 
  • Curtain poles 
  • Lighting equipment 
  • Motorbike handles 
  • Car and motorbike exhaust system 
  • Bicycle parts 
  • Handrails