Skip to main content

Part - 6 Most commonly asked Mechanical Interview Questions with answer

Most commonly asked Mechanical Interview Questions 

 1.          Why Entropy decreases with increase in temperature?

 Ans.      ds=dQ/T Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.

2.           Why different types of sound are produced in different bikes, though they run on SI Engines?

 Ans.       Engine specifications are different in different manufactures like as Bore Diameter (CC), Ignition timing. Also the exhaust passage takes more responsible for sound.

3.           How much Watt means 1Hp?

 Ans.       746.2 Watt

 4.           Explain Bicycle Rear Wheel Sprocket working?

 Ans.      Rear wheel sprocket works under the principle of ratchet and pawl.

5.          Definition of Octane Number and Cetane Number?

 Ans.     Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine.
Cetane No.- Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.

6.         Which Mechanism is used in Automobile gearing System?

 Ans.     Differential mechanism

7.            When Crude Oil is Heated, Which Hydro Carbon comes first?

 Ans.       Natural gas (Gasoline)… at 20 Celsius

8.           How to calculate Bearing number ti Diameter of the inner and outer?

 Ans.      Divide the shaft diameter size by 5, it will give last two digit of the bearing no. and according to type of load we have to choose the type of bearing and that will give prior number of the bearing.

9.           The Fatigue life of a part can be improved by?

 Ans.       Improving the surface finish by Polishing & providing residual stress by Shot peening.

10.          What happens if gasoline is used in a Diesel Engine, Diesel Engine will work?

 Ans.        No, It will not work, as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast.

11.          Poisson's Ratio is Higher in, Rubber/Steel/Wood?

 Ans.       When a material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression. This phenomenon is called the Poisson effect. Poisson’s ratio is a measure of the Poisson effect.
For rubber = 0.5
For steel = 0.288
For wood < 0.2

Thus Poisson’s ratio is higher in RUBBER.
See related more FAQs  <<<< Click Here >>>>

Labels:

Popular posts from this blog

FILLET WELD FRACTURE TEST

FILLET WELD FRACTURE TEST Object :  To break the joint through the weld to permit examination of the fracture surfaces for flaws and to check root penetration and fusion. Method: The specimen is cut to length and a saw cut, normally 2 mm deep, is made along the center of the weld face. The specimen is fractured by bending or hammer blows. Reporting Results: Thickness of parent material.  Throat thickness and leg length.  Location of fracture. Appearance of joint after fracture. Depth of penetration / lack of penetration or fusion.
Read more

Part -5 Most commonly asked Mechanical Interview Questions

Most commonly asked Mechanical Interview Questions with answer 1. Why the Centrifugal Pump is called High Discharge pump? Ans. Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is given in the following formulae: Centrifugal force F= (M*V2)/R. Where, M-Mass V-Velocity R-Radius 2. How Cavitation can be eliminated by Pump? Ans. Cavitation means bubbles are forming in the liquid. To avoid Cavitation, we have to increase the Pump size to One or Two Inch To increase the pressure of the Suction Head  Decrease the Pump Speed. 3. Why Cavitation will occur in Centrifugal Pump and not in Displacement Pump? Ans. The form...
Read more

Vickers Hardness Test

Vickers Hardness Test:- The Vickers hardness test method consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between opposite faces subjected to a load of I to I 00 kgf. The full load is normally applied for I 0 to 15 seconds. The two diagonals of the indentation left in the surface of the material after removal of the load are measured using a microscope and their average calculated. The area of the sloping surface of the indentation is calculated. The Vickers hardness is the quotient obtained by dividing the kgf load by the square mm area of indentation. F= Load in kgf d = Arithmetic mean of the two diagonals, di and d2 in mm HV = Vickers hardness When the mean diagonal of the indentation has been determined the Vickers hardness may be calculated from the formula, but is more convenient to use conversion tables. The Vickers hardness should be reported like 800 HV/10, which means a Vickers...
Read more