Stainless Steel and its type

 

Stainless Steel is defined as that steel which when correctly heat treated and finished, resists oxidation and corrosive attack from most-corrosive media. The different types of stainless steels are as follows:

1. Martensitic stainless steel. The chromium steels containing 12 to 14% chromium and 0.12 to 0.35% carbon is called martensitic stainless steel, as they possess martensitic structure. These steels are magnetic and may be hardened by suitable heat treatment and the hardness obtainable depends upon the carbon content. These steels can be easily welded and machined.

2. Ferritic stainless steel. The steels containing greater amount of chromium (from 16 to 18%) and about 0.12% carbon are called ferritic stainless steels. These steels have better corrosion resistant property than martensitic stainless steels.

3. Austenitic stainless steel. The steel containing high content of both chromium and nickel are called austenitic stainless steels. The most widely used steel contains 18% chromium and 8% nickel. Such a steel is commonly known as 18/8 steel. These steels are non-magnetic and possesses greatest resistance to corrosion and good mechanical properties at elevated temperature.

governing of I.C. engines by moses dhilipkumar

 The process of providing any arrangement, which will keep the engine speed constant (according to the changing load conditions) is known as governing of I.C. engines. Though there are many methods for the governing of I.C. engines, yet the following are important :

1. Hit and miss governing. In this system of governing, whenever the engine starts running at higher speed (due to decreased load), some explosions are omitted or missed. This is done with the help of a centrifugal governor. This method of governing is widely used for I. C. engines of smaller capacity or gas engines.

2. Qualitative governing. In this system of governing, a control valve is fitted in the fuel delivery pipe, which controls the quantity of fuel to be mixed in the charge. The movement of control valve is regulated by the centrifugal governor through rack and pinion arrangement.

3. Quantitative governing. In this system of goverliing, the quality of charge (i.e. air-fuel ratio of the mixture) is kept constant. But the quantity of mixture supplied to the engine cylinder is  varied by means of a throttle valve which is regulated by the centrifugal governor through rack and pinion arrangement.

4. Combination system of governing. In this system of governing, the qualitative and quantitative methods of governing are combined together.

Black exhaust smoke

 BLACK EXHAUST SMOKE

Diagnosis: Not normal

Black exhaust smoke can appear when the vehicle is burning too much fuel. This could be caused by a clogged air filter, malfunctioning fuel injection system, a blocked manifold, or a variety of other issues. A clogged air filter won't hurt your gas mileage thanks to today’s automotive technology, says Consumer Reports, but you’ll pay for it with poor performance. Have your vehicle checked out by a technician to see why your vehicle is burning more fuel than usual.

knocking in I.C. Engines

 

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Detonation or knocking in I.C. Engines – The loud pulsating noise heard within the engine cylinder of an I.C. engine is known as detonation (also called knocking or inking). It is caused due to the propagation of a high speed pressure wave created by the auto-ignition of end portion of unburnt fuel. The blow of this pressure wave may be of sufficient strength to break the piston. Thus, the detonation is harmful to the engine and must be avoided. The following are certain factors which causes detonation:

1.    The shape of the combustion chamber,

2.    The relative position of the sparking plugs in case of petrol engines,

3.    The chemical nature of the fuel,

4.    The initial temperature and pressure of the fuel, and

5.    The rate of combustion of that portion of the fuel which is the first to ignite. This portion of the fuel in heating up, compresses the remaining unburnt fuel, thus producing the conditions for auto-ignition to occur.

The detonation in petrol engines can be suppressed or reduced by the addition of a small amount of lead ethide or ethyl fluid to the fuel. This is called doping.

The following are the chief effects due to detonation:

1.    A loud pulsating noise which may be accompanied by a vibration of the engine.

2.    An increase in the heat lost to the surface of the combustion chamber.

3.    An increase in carbon deposits.

Fluid coupling and its UN known information

  Fluid coupling and its  UN known information

 

It is a device for transmitting rotation between shafts by means of the acceleration and deceleration of a hydraulic fluid (such as oil). Also known as hydraulic coupling. Structurally, a fluid coupling consists of an impeller on the input or driving shaft and a runner on the output or driven shaft. The two contain the fluid. Impeller and runner are bladed rotors, the impeller acting as a pump and the runner reacting as a turbine. Basically, the impeller accelerates the fluid from near its axis, at which the tangential component of absolute velocity is low, to near its periphery, at which the tangential component of absolute velocity is high. This increase in velocity represents an increase in kinetic energy. The fluid mass emerges at high velocity from the impeller, impinges on the runner blades, gives up its energy, and leaves the runner at low velocity.

Hydraulic fluid couplings transfer rotational force from a transmitting axis to a receiving axis. The coupling consists of two toroids — doughnut-shaped objects — in a sealed container of hydraulic fluid. One toroid is attached to the driving shaft and spins with the rotational force. The spinning toroid moves the hydraulic fluid around the receiving toroid. The movement of the fluid turns the receiving toroid and thus turns the connected shaft.

Although fluid couplings use hydraulic fluid within their construction, the mechanism loses a portion of its force to friction and results in the creation of heat. No fluid coupling can run at 100 percent efficiency. Excessive heat production from poorly maintained couplings can result in damage to the coupling and surrounding systems.

A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and/or controlled start-up without shock loading of the power transmission system is essential.

What become your kid ????

 A company ...

 Announced that it needed people for the job,

 Accordingly_

 A lot of people came to the interview.

 Everyone was seated in a hall ...

 Question papers for all,

 Farewell letter was also given.

 Now the company manager spoke,

 '... there are ten questions in this quiz.'

 'You will be allotted five minutes.

 By then you have to answer these questions. '

 'Qualified persons will be selected and given jobs' ....

 Five minutes started ..

 Everyone wrote fast answer that time is limited.

 When the time is up ...

 The manager who bought the farewell paper for everyone said that you gave less time to each one when buying the farewell and we could not write the answer to all the questions except we were able to answer five questions and seven questions.

 Only two of them gave the blank sheet to the manager that he had not written any reply to.

 after that,

 Said the company manager.

 '' Only two people who did not write the answer sheet are eligible to work in this company.

 Others can go home. "

 The same surprise for everyone,

 Everyone asked the company manager to join one.

 _You say we do not work for answering questions correctly.

 How did you get the job done to only those two who did not answer any questions?

 (This is the question that arises in us at this point. Is there a job for those who have answered and those who have not?)

 To which the manager said,

 "Everybody read that tenth question,"

 Everyone who read it went home without being able to speak,

 This is the tenth question.

 # 10) This means that you do not have to answer any of the above questions.

 This is not something to be laughed at.

 Something we all need to think about,

 Wouldn't you have gotten the job if you had set aside two minutes and read the whole question paper?

 For Thought #:

 Except that in this modern age we have to buy a lot of marks by telling children to read step by step,

 No one thinks our children should grow up good and smart ...

Types of mechanical forces

 

A force exerted on a body can cause a change in either the shape or the motion of the body. The unit of force in SI system is the newton (N) and CGS system is dyne. No solid body is perfectly rigid and when forces are applied to it, changes in dimensions occur. Such changes are not always perceptible to the human eye since they are negligible. For example, the span of a bridge will sag under the weight of a vehicle and a spanner will bend slightly when tightening a nut. It is important for civil engineers and designers to appreciate the effects of forces on materials, together with their mechanical properties of materials.

There are three main types of mechanical forces that can act on a body. They are:

1.      Tensile force

2.      Compressive force and

3.      Shear force

1. Tensile force

Tensile force that tends to stretch a material, as shown in the figure 1 below.

Figure 1: Tensile force

For example,

1.      Rubber bands, when stretched, are in tension.

2.      The rope or cable of a crane carrying a load is in tension.

3.      When a nut is tightened, a bolt is under tension.

A tensile force will increases the length of the material on which it acts.

2. Compressive force

Compressive force that tends to squeeze or crush a material, as shown in the figure below.

For example,

A pillar supporting a bridge is in compression.

1. The sole of a shoe is in compression.
2. The jib of a crane is in compression.
3. A compressive force will decrease the length of the material on which it acts.

3. Shear force

Shear force that tends to slide one face of the material over an adjacent face.

For example,

1. A rivet holding two plates together is in shear if a tensile force is applied between the plates as shown in Figure
2. A guillotine cutting sheet metal, or garden shears, each provide a shear force.
3. A horizontal beam is subject to shear force.
4. Transmission joints on cars are subject to shear forces.

A shear force can cause a material to bend, slide or twist.