MOST IMPORTANT MECHANICAL ENGINEERING INTERVIEW QUESTIONS .

A Most asking question during Technical Interviews:


1.)What causes hardness in steel ?
How heat treatment alters properties of steel ?

Ans: The shape and distribution of the carbides in the iron determines the hardness of the steel.Carbides can be dissolved in austenite is the basis of the heat treatment of steel.If steel is heated above the A critical temperature to dissolve all the carbides, and then cooled, suitable cooling through the cooling range will produce the desired size and distribution of carbides in the ferrite,imparting different properties.

2.)What is the difference between streamline body and bluff body ?

Ans: In streamline body the shape is such that separation in flow occurs past the nearmost part of the body so that wake formed is small and thus friction drag is much greater than pressure drag. In bluff body the flow gets separated much ahead of its rear resulting in large wake and thus pressure drag is much greater than the friction drag.

3.)Define hydraulically efficient channel cross section ?

Ans: The shape of such section is that which produces minimum wetted perimeter for a given area of flow and carries maximum
flow.

4.)What is the difference between alpha iron, delta iron and gamma iron ?

Ans: The bcc form of iron exists between room temperature and 910°C, and between 1400°C and the melting point at 1539°C. The lower temperature form is known as "alpha"-iron and the higher temperature form as "delta"-iron. The face-centered cubic form existing between 910°C and 1400°C is referred to as"gamma-iron".

5.)Explain the difference between the points of inflexion and contraflexure?

Ans: At points of inflexion in a loaded beam the bending moment is zero and at points of contraflexure in loaded beam the bending moment changes sign from increasing to decreasing.




6.)What do you understand by eutectic ?

Ans: It is mechanical mixture of two or more phases which solidify simultaneously from the liquid alloy.

7.)Under what condition a convergent divergent nozzle required ?

Ans: When pressure ratio is greater than critical pressure ratio.

8.)What is the difference between isotropic material and homogeneous material ?

Ans: In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions.

9.)What do you understand by catenary cable ?

Ans: A cable attached to the supports and carrying its own weight.

10.)What is the difference between basic hole and basic shaft ?

Ans: A basic hole is one whose lower deviation is zero and in case of basic shaft the upper deviation is zero.


11.)In which process internal energy remains constant ?

Ans: Isothermal process.

12.)What happens if gasoline is used in a Diesel engine? Will diesel engine 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.

13). 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.

14.).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.

15.)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.
For More Interview Questions Like Boiler and Mechanical Power.


16.)Define surface tension ?

Ans: Surface tension of a liquid is the work that must be done to bring enough molecules from inside the liquid to the surface to form one new unit area of that surface. (Its unit is Nm/m2 or N/m).

17.)State Archimedes principle ?

Ans: Any weight, floating or immersed in a liquid, is acted upon by a buoyant force equal to the weight of the liquid displaced. This force acts through the center of buoyancy, i.e. the e.g. of the displaced liquid.

18.). Distinguish between a jig and fixture ?

Ans: Jig clamps and locates parts in positive manner and guides cutting tools (drills, reamers, taps etc). Fixture is bolted or fixed securely to the machine table so that work is in correct location ship to the cutter. Fixtures are used for mass milling, turning and grinding, etc.

19.). In which type of flow the stream lines, streak lines and path lines are identical ?

Ans: In steady flow.

20.) Define Piston Rings?

A piston ring is a split ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.