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

BEND TESTS

BEND TESTS Object:   To determine the soundness of weld metal, heat affected zone and weld zone.These tests may also be used to give some measure of the ductility of the weld zone. It is not usual to use transverse and longitudinal bend tests for the same application. Method:   All specimens to be removed and prepared without causing significant distortion or heating. The cap and root are ground flush. The specimen is bent by the movement of a former of prescribed diameter, the relevant side of the specimen to be placed in tension. Angle of bend and diameter of former should be as specified in the appropriate standard. Reporting Results: Thickness of specimen Direction of bend (root or face) Angle of bend Diameter of former Appearance of joint after bending e.g. type and location of flaws
Read more

SIDE BEND TEST

SIDE BEND TEST Object: To determine the soundness of the weld metal and HAZ in a cross section. This may be preferred to the transverse bend test on thick materials. It is also used on processes or procedures expecting lack of fusion (e.g. thick plate using MIG). Method: The testing method is the same as that used for transverse bends except the cap and root are not ground flush, to allow testing across the complete weld. Report Results: Width and thickness of specimen.  Angle of bend. Diameter of former. Appearance of joint after bending e.g. type and location of flaws.
Read more

Chemical compositions of steel

Chemical Composition :-  The chemical composition of steel is of great importance since it determines the potential mechanical properties of the finished steel product and controls the degree of corrosion resistance and weld- ability of the material For this reason structural steel specifications always provide a table of chemical composition limits within which the steel producer must develop his own particular recipe. The purpose of the specified chemical composition is not to provide the detailed chemical formula necessary to produce a certain type of steel but to provide safeguards. The steel producer is informed that he must keep within the limits which are deemed to be acceptable for the type of steel considered. Within these limits, which may be broad or narrow, the steel producer has complete freedom to use his skill and knowledge to make steel with the required mechanical properties. Each producer selects a combination of quantities of elements, which fall within the r...
Read more