comprehensive viva voce question and answer for mechanical engineering
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I want comprehensive viva questions for mechanical engineering
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Questions of the mechanical interview questions


1. Explain the second law of thermodynamics.
Ans. The entropy of the universe increases with time and moves toward a maximum value.

2. What types of pipes are used for steam lines?
Ans. Usually galvanized pipes are not used for steam. Soft steel with bolted or welded fittings are the norm. Pressure and temperature are very important factors to consider in what type of materials to use. Even low pressure steam can be extremely dangerous.

3. What is the difference between the bending center of the torsion center and the elastic center?
Ans. The cutting center is the centroid of a cross section. The center of bending is the center of the twist, which is the point on a beam that can be added a load without torsion. The elastic center is located in the center of gravity. If the object is homogeneous and symmetrical in both directions of the cross section, then they are all equivalent.

4. What is ferrite?
Ans. Magnetic iron rock

5. What is the difference between a projectile movement and a rocket motion?
Ans. A projectile has no motor / rocket in it, so all its momentum is given as it starts up. An example of a projectile would be the pen you throw through a room.
A rocket or missile has an engine / rocket on it so it can accelerate while thus moving and resisting other forces such as gravity.

6. What is a joint?
Ans. These types of joints are used to connect two rods, which are under tension or compressive stress. The ends of the bars are in the form of a bushing and shaft which fit together and the key is driven into a slot which is common to both parts which draws them tightly together. The tensile strength of the steel is proportional to the resistance required to compensate for the stress on the material divided by the number of joints used.

7. What is tin and lead alloy?
Ans. An alloy of tin and lead is commonly referred to as welding. Usually, the weld is a wire with a core of rosin used for welding. The nucleus of the rosin acts as a flux.

8. What does F.O.F. Do they represent in the pipeline design?
Ans. FOF stands for Flange Face. A flange has either type of face:
A) Raised face
B) Flat face
The F.O.F is used to know the exact dimension of the flange to avoid the tiny errors in the measurement in the case of vertical or horizontal pipes.

9. Explain the Otto cycle.
Ans. The Otto cycle can be explained by a pressure volume ratio diagram. Shows the operating cycle of a four-stroke engine. The cycle begins with an intake stroke, closing the intake and moving to the compression stroke, combustion start, power stroke, heat exchange stroke where the heat and exhaust stroke is rejected. It was designed by Nicolas Otto, a German engineer.

10. What is the transmission ratio?
Ans. It is the ratio between the number of revolutions of the pinion gear and a revolution of the idle gear.

11. What is annealing?
Ans. It is a process of heating a material above the temperature of recrystallization and cooling after a specific time interval. This increases the hardness and the resistance if the material.

12. What is the ductile-brittle transition temperature?
Ans. It is the temperature below which the tendency of a material to fracture increases instead of forming. Below this temperature the material loses its ductility. Also called Nil Ductility Temperature.

13. What is a uniformly distributed load?
Ans. A UDL or uniformly distributed load is a load, which extends over a beam such that each unit length is loaded to the same extent.

14. What are the differences between pneumatics and hydraulics?
Ans. 
A) Working fluid: Air pneumatic, hydraulic use Oil
B) Power: Pneumatic power less than hydraulic power
C) Size: the components P are smaller than the components H
D) Leaks: Hydraulic leaks cause fluid to stick around components. In air, air is     filtered into the atmosphere.
E) Tires get power from an air compressor while the hydraulics require a pump
F) Air is compressible, hydraulic oil is not.

15. What is enthalpy?
Ans. The enthalpy is the heat content of a chemical system.

16. What is a positive displacement pump?

Ans. A positive displacement pump causes a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can also be classified as rotary type pumps (eg rotary vane) or lobe pumps similar to oil pumps used in automotive engines. These pumps provide non-pulsating output or displacement unlike alternate pumps. Hence, they are called positive displacement pumps.

17. Why would I use the hydraulics instead of the pneumatics?
Ans. The hydraulic system is suitable for higher forces and precise movements than the tires. This is because hydraulic systems generally operate at significantly higher pressures than pneumatic systems. The movements are more precise (repeatable) because the hydraulics uses an incompressible liquid to transfer energy while the pneumatic uses gases.
Pneumatic systems also have some advantages. They are usually much cheaper than hydraulic systems, can move faster (gas much less viscous than oil) and do not empty oil if they develop a leak.

18. What is isometric drawing?
Ans. It is a three-dimensional drawing used by sketchers, architects, etc.

19. What are the advantages of shifting gears?
Ans. In general, the gear drive is useful for the transmission of power between two axes, which are close to each other (at most 1 m distance). In addition, it has maximum efficiency during power transmission. It is durable compare to others such as straps etc. You can change the energy to the speed ratio.
Advantages: -
It is used to obtain various speeds under different load conditions.
Increases fuel efficiency.
Increases engine efficiency.
It needs less power input when operated manually.

20. What conducts faster heat of copper or brass steel?
Ans. Copper conducts heat faster than steel or brass. Any material that is good for conducting heat is also good for electricity in most cases. The terrible wood to transfer the heat thus is also insulator for electric.

21. How are the pipe flanges electrically insulated?
Ans. The flanges of the pipes are protected against corrosion by means of electrolysis, with dielectric flanges. The piping system is electrically insulated by what is called the sacrificial anode. An easily corrodible metal bag is buried in the ground with a wire that extends from the pipe to the bag so that the sacrificial anode will corrode first. If any electric current charges the pipe, it also serves as ground.

22. What is a Process Flow Diagram?
Ans. A process flow diagram (or System Flowchart) shows the relationships between the major components of the system. It also has basic information about material balance for the process.

23. Where is the pneumatic system used?
Ans. Any system needs redundancy in work needs pneumatic, because the compressor of the pneumatic system has periodic operations (intermittent work, not like hydraulic pump). Compressed air could accumulate in deposits with high pressures and be used even if the compressor failed.

24. Why are gas containers mostly cylindrical?
Ans. The most efficient way to withstand high pressure is a sphere but would be costly to manufacture. A cylinder with a domed upper and a domed bottom (look below, the flat base is actually welded around the outside, the bottom of the gas container is actually vaulted) is a much cheaper way to manufacture while still having good Resistance to resist internal gas pressure.

25. How is the martensite structure formed in steel?
Ans. The transformation of martensite begins when the austenite cools below a certain critical temperature, called matrensite start temperature. As we go below the martensite start temperature, more and more forms of martensite and complete transformation occurs only at a temperature called martensire finishing temperature. The formation of martensite requires the austenite phase to cool rapidly.


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