JOB INTERVIEW QUESTIONS

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS:-

1. What is Difference between Hardness and Toughness?

Ans. Toughness is the ability of a material to absorb energy.
Hardness is the ability of a material to withstand wear.

2.What does F.O.F Stand for Piping Design?

Ans.Face of Flange, The F.O.F (Raised face and Flat face) is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipe lines.

3.Difference between Performance and Efficiency?

Ans.The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance.

Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.

1. What is knurling?

: Knurling is a machining process normally carried our on a centre lathe. The act of Knurling creates a raised criss-cross pattern on a smooth round bar that could be used as a handle or something that requires extra grip.

2. What is the mechanical advantage of a double pulley?

: It only takes half the effort to move an object but twice the distance.

3. What is extrued aluminum?

: Extrusion is the process where a metal or a metal bar is pulled through a mandrel to elongate it and/or give it a final shape.
Extruded Aluminum is a common form of making small aluminum wire, bars or beams and many varieties of small non-structural, decorative pieces.

4. What is a Newtonian fluid?

: A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

1)What is Sentinel Relief Valve?
Ans. It’s a special type valve system. The valve will open when exhaust casing pressure is excessive (high). The valve warns the operator only; it is not intended to relieve the casing pressure.

2)What is the difference between Specification,Codes, Standards?
Ans. Specification is describing properties of any type of materials. Code is procedure of acceptance and rejection criteria.
Standard is accepted values and compare
other with it.

3.) What is difference between Welding and Brazing?

Ans. In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together. In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.

1.)What are two essential conditions of perfect gas ?

Ans: It satisfies equation of state and its specific heats are constant.

2.). Enthalpy and entropy are functions of one single parameter. Which is that ?

Ans: Temperature.

3.)What is caustic embrittlement ?

Ans: It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of rivetted joints and around the rivet holes.

4.)Why large boilers are water tube type ?

Ans: Water tube boilers raise steam fast because of large heat transfer area and positive water circulation. Thus they respond faster to fluctuations in demand. Further single tube failure does not lead to catastrophy.

VERY IMPORTANT QUESTION:-

Q:-Difference between internal combustion engines and external combustion engines?

Answer:- In an *Internal Combustion Engine*, the Fuel is burnt in the cylinder or vessel eg. Diesel or Petrol engine used in Cars.
In an *External Combustion Engine*, the internal working fuel is not burnt. Here the fluid is being heated from an external source. The fuel is heated and expanded through the internal mechanism of the engine resulting in work. eg. Steam Turbine, Steam engine Trains.
* Internal engine has its energy ignited in the cylinder. like 99.9% of engines today.
* An external combustion example is a steam engine where the heating process is done in an boiler out side the engine.

So in fact we can define internal combustion engine develops its operating pressure by burning fuel directly in the engine. Gasoline engines, Wankel engines, diesels, gas turbines are all internal combustion. External combustion engines burn the fuel outside the engine and use it to heat an operating fluid which then is used to operate the engine. Steam locomotives, steam turbines, and Stirling engines are external combustion

Why can't we use petrol in diesel engine?

Petrol has a lower ignition temperature and is more inflammable than diesel.The compression ratio in diesel engine is very much higher than petrol engine, so if petrol is used in diesel engine there will be lot of knocking( the phat phat sound like that of Enfield)
and chances are the engine ll be greatly damaged and there is a chance of fire hazard resulting in personal injury.

Its just like eating grass instead of rice.
Of course you can eat but, at once you won't feel anything and day by day you will face problems related to stomach, digestion, etc.
Like this, if you use petrol instead of diesel, the vehicle will work but it will stuck and trouble at the middle.

Q. Why I-section beam is preferred for heavy loading?

Ans.Cross sectional shape I, giving many benefits. It is very good for giving stiffness (less deformation on loading) and to withstand higher bending moments (as a result of heavy loading) on comparison with other cross-sectional shapes of same area. Also, it is very easy to manufacture. It will have more moment of inertia.


What is the difference between pump and compressor ?
When we use pump and When we use compressor?

Ans:-Basically a Pump is used for liquid or fluid to transform it to a much high pressure head while a Compressor is used for gases to transform from low to a much high pressure.
From Mechanical Engineering point of view liquid is incompressible so Compressor cannot be used for liquid substances. 


Q. WHY HAVE EIGHT CYLINDERS IN AN ENGINE? WHY NOT HAVE ONE BIG CYLINDER OF THE SAME DISPLACEMENT OF EIGHT CYLINDERS INSTEAD?

A. There are a couple of reasons why a big 4.0-liter engine has eight half-liter cylinders rather than one big 4-liter cylinder. The main reason is smoothness. A V-8 engine is much smoother because it has eight evenly spaced explosions instead of one big explosion. Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders (1 liter) through their compression strokes, but with one big cylinder you would have to compress 4 liters instead