Interview Question for Mechanical Engineer
Best mechanical engineer interview question for fresher student
Ques. What is fuel ratio ?
Ans. Fuel ratio is the ratio of its percentage of fixed carbon to volatile matter.
Ques. What is the difference between nuclear fission and fission chain reaction ?
Ans. The process of splitting of nucleus into two almost equal fragments accompanied by release of heat is nuclear fission. Self sustained, continuing, sequence of fission reactions in a controlled manner is fission chain reaction.
Ques. What are the causes of failure of boiler tubes ?
Ans. Boiler tubes ,usually are made from carbon steel and are subject to
(a) high rates of heat transfer,
(b) bending stresses due to uneven heating, especially at expanded or welded joints into headers or drums.
(c) external erosion from burners and flue gas,
(d) possible corrosion on the boiler side,
(e) occasional manufacturing defects.
Failure may occur due to following reasons:
(a) high thermal rating may lead to rapid failure if the internal fluid flow is reduced for any reason. The resultant overheating leads to a failure by creep, characterised by the bulging of the tube with the eventual development of a longitudinal split.
(b) fatigue cracking due to bending stresses occur. These are associated with change of section and weld undercut ,where tubes are expanded or welded into headers.
(c) failure may be arise due to overstresses of a reduced section of metal.
Ques. What is black body ?
Ans. A black body is one which absorbs all radiation falling on it.
Ques. What is critical insulation radius ?
Ans. It is insulation radius at which resistance to heat flow is minimum.
Ques. What is view factor ?
Ans. View factor is dependent upon geometry of the two surfaces exchanging radiation.
Ques. What is Biot number ?
Ans. Biot number is hL/k . This dimensionless number compares the heat transfer coefficient with the internal conductance of a slab. It is the ratio of the conductive to convective resistance of a slab.
Ques. What is Bauschinger effect ?
Ans. According to bauschinger . the limit of proportionality of material does not remain constant but varies according to the direction of stress under cyclic stresses.
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