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+ Mechanical Engineering Interview Questions and Answers, Question1: What is extrued aluminum? Question2: What is the mechanical advantage of a. Look at the following links for questions that are generally asked for the position of mechanical engineering? 1. Top + Mechanical Engineering Interview. It has over carefully selected interview questions in video format from 49 topics of Mechanical Engineering. These questions are blended with incisive HR .
What is ductile-brittle transition temperature? It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature. Difference between tempering and annealing Ans: Annealing is a process in which work piece is heated up to certain temperature to get desired changes in grain or micro-structure and then allowed to cool slowly in order to relieve the stresses during work treatment.
While tempering is a process wherein hardness and elasticity or ductility can be regain by use of heating and cooling cycle till desired properties can be obtained. What are the advantages of gear drive?
Gear drive is useful for power transmission between two shafts, which are near to each other at most at 1m distance. In addition, it has maximum efficiency while transmitting power. It is durable compare to other such as belts chain drives etc. You can change the power to speed ratio. It increases fuel efficiency. Increases engine efficiency. Need less power input when operated manually.
What is isometric drawing? It is a 3-D drawing used by draftsmen, architects etc What is a Process Flow Diagram? It also has basic information concerning the material balance for the process.
Is it the stress that, produces strain or strain produces stress? A Force applied to an object will cause a displacement. Strain is effectively a measure of this displacement change in length divided by original length.
Stress is the Force applied divided by the area it is applied. What are the points in the stress strain curve for steel? Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.
State Newton's three laws of Motion. The law of inertia: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. Acceleration is produced when a force acts on a mass. The greater the mass of the object being accelerated the greater the amount of force needed to accelerate the object. For every action there is an equal and opposite reaction. State the laws of thermodynamics? Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system.
Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics. First Law: Energy can be neither created nor destroyed. It can only change forms.
In any process in an isolated system, the total energy remains the same. Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.
Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum. What is Hess law? According to the Hess law the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed. Explain what is torque? Torque is the force that causes rotation.
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They are C. In reality, most interviewers are disguised interrogators. They ask tricky questions point blank, and make harsh judgements based on your on-the-spot, spontaneous responses. The challenge for you is how to develop on-the-spot behaviours that are professional and likeable. The only way to ingrain them is to repeatedly work on them in actual environments, until it becomes a habit. But, how can you do that? Why high latent heat of vaporisation is desirable in a refrigerant?
A high latent heat of vaporisation of refrigerant results in small amount of refrigerant and thus lesser circulation system of refrigerant for same tonnage. What is the critical temperature of a refrigerant? Critical temperature is the maximum temperature of a refrigerantrat which it can be condensed into liquid and beyond this it remains gas irrespective of pressure applied.
High temperature in I.
Why efficiency of gas turbines is lower compared to I. Further combustion temperature of I. What do you understand by timed cylinder lubrication? For effective lubrication, lub oil needs to be injected between two piston rings when piston is at bottom of stroke so that piston rides in oi during upward movement. This way lot of lub oil can be saved and used properly.
HUCR is highest useful compression ratio at which the fuel can be used in a specific test engine, under specified operating conditions, without knocking. In some engines glycerine is used in place of water for cooling of engine. Thus weight of coolant gets reduced and smaller riadiator can be used. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four-stroke cycle petrol engine?
In two-stroke engine lub oil is mixed with petrol and thus some lub oil is blown out through the exhaust valves by scavenging and charging air. There is no such wastage in four stroke petrol engine. As compression ratio increases, thermal n increases. How is thermal n affected by weak and rich mixture strength? Thermal n is high for weak mixture and it decreases as mixture strength becomes rich.
How engine design needs to be changed to burn lean mixture? Engine to burn lean mixture uses high compression ratio and the highly turbulent movement of the charge is produced by the geometry of the combustion chamber.
Horse power of I. To which countries these standards belong? What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle? When liquid refrigerant as obtained from condenser is throttled, there are some vapours.
These vapours if carried through the evaporator will not contribute to refrigerating effect. Using a flash chamber at some intermediate pressure, the flash vapour at this pressure can be bled off and fed back to the compression process. The throttling process is then carried out in stages. Similarly compression process is also done in two separate compressor stages. Why pistons are usually dished at top?
What is the function of thermostat in cooling system of an engine? Thermostat ensures optimum cooling because excessive cooling decreases the overall efficiency.
It allows cooling water to go to radiator beyond a predetermined temperature. What are the causes of failure of boiler tubes? 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, and e occasional manufacturing defects.
Failure may occur due to following reasons: The resultant overheating leads to a failure by creep, characterised by the bulging of the tube with the eventual development of a longitudinal split.
Lamination in boiler tubes or score marks arising from the cold drawing of tubes, give rise to premature failure and may promote corrosion at these regions. What are the causes of failure of superheater tubes? Superheater tubes are subjected to the most severe combination of stress, temperature and corrosive environment. In addition to high-temperature strength, resistance to corrosion is also important. Failures in superheater tubes may arise from: Why supercritical boilers use less amount of steel compared to non-supercritical boilers?
Supercritical boilers do not head heavy drum for separation of steam from mixture of water and steam. Out of electric heater and heat pump, which is economical in operation? Heat pump. Which furnace burns low-ash fusion coal and retains most of the coal ash in the slag? Cyclone furnace. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related? What is the effect of friction on flow of steam through a nozzle?
To decrease both mass flow rate and wetness of steam. Why gas turbine power plant needs efficient compressor? Because a large portion of turbine work is eaten away by compressor and its inefficiency will affect net power output and cost of generation. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon? Liquid hydrogen has higher burning velocity.
Why axial flow compressor is preferred for gas turbines for aeroplanes? Because it has low frontal area. What is the effect of inter cooling in gas turbines? It decreases thermal efficiency but increases net output. Why iso-octane is chosen as reference fuel for S.
Iso-octane permits highest compression without causing knocking. Why thermal efficiency of I. Which are the reference fuels for knock rating of S. When effect of variations in specific heats is considered then how do maximum temperature and pressure vary compared to air standard cycle? Temperature increases and pressure decreases. Quantities like pressure, temperature, density, viscosity, etc.
What are these called? Intensive properties. The amount of radiation emitted per scm per sec is called …. Emissive power. Get doubled. How you can define coal? Coal is a naturally occurring hydrocarbon that consists of the fossilised remains of buried plant debris that have undergone progressive physical and chemical alteration, called coalification, in the course of geologic time.
Which pollutant is major greenhouse gas and what is its effect? In order to increase efficiency and reduce CO emissions and other emissions, clear coal technologies are receiving major attention.
What are the important operational performance parameters in design of fuel firing equipment? Fuel flexibility, electrical load following capability, reliability, availability, and maintenance ease. What is the difference between total moisture and inherent moisture in coal? The moisture content of the bulk as sampled is referred to as total moisture, and that of the air dried sample is called inherent moisture.
What elements it reports? Moisture, volatile matter, ash and fixed carbon. Ultimate analysis of coal is elementary analysis. What it is concerned with? Carbon, hydrogen, nitrogen, and sulphur in coal on a weight percentage basis. AFBC Atmospheric fluidised bed combustion process consists of forming a bed of inert materials like finely sized ash or ash mixed with sand, limestone for sulphur removal , and solid fuel particles in a combustor and fluidising it by forcing combustion air up through the bed mixture.
The gas flows thorugh bed without disturbing particles significantly but gas velocity is high enough to support the total weight of bed fluidisation. At slightly higher velocity excess gas passes through the bed as bubbles fluidised bed and gives the bed the appearance of a boiling liquid.
Bubbling fluidised bed combustion BFBC has a defined height of bed material and operates at or near atmospheric pressure in the furnace. Pressurised fluidised bed combustion PFBC system operates the bed at elevated pressure. Exhaust gases have sufficient energy to power a gas turbine, of course, gases need to be cleaned. In fluidised combustion, as ash is removed some unburned carbon is also removed resulting in lower efficiency.
In circulating fluidised bed combustion CFBC system, bed is operated at higher pressure leading to high heat transfer, higher combustion efficiency, and better fuel feed. Circulating fluidised beds operate with relatively high gas velocities and fine particle sizes. The maintenance of steady state conditions in a fast fluidised bed requires the continuous recycle of particles removed by the gas stream circulating bed. The term circulating bed is often used to include fluidised bed systems containing multiple conventional bubbling beds between which bed material is exchanged.
What for Schmidt plot for is used in heat transfer problems? Schmidt plot is a graphical method for determining the temperature at any point in a body at a specified time during the transient heating or cooling period.
In which reactor the coolant and moderator are the same? Pressurised water reactor. What are thermal neutrons? Thermal neutrons are slow neutrons having energy below 1 eV which are in thermal equilibrium with their surroundings. What is big advantage of fast breeder reactor? It has rapid self breeding of fissile fuel during the operation of the reactor, and thus, it offers about sixty times the output with same natural uranium resources through ordinary non-breeder nuclear reactor.
What is the purpose of biological shield in nuclear plants? Biological shield of heavy concrete prevents exposure to neutrons, beta rays and gamma rays which kill living things. Which two elements have same percentage in proximate and ultimate analysis of coal?
Moisture and ash. On ultimate analysis. Which element causes difference in higher and lower heating values of fuel? Which heating value is indicated by a calorimeter and why? Gross heating value because steam is condensed and heat of vapour formed is recovered. State the difference between ultimate and proximate analysis of coal?
In ultimate analysis, chemical determination of following elements is made by weight: Fixed and combined carbon, H, O, N, S, water and ash. Heating value is due to C, H and S. In proximate analysis following constituents are mechanically determined by weight. Moisture, volatile matter, fixed carbon and ash. Heating value is due to fixed carbon and volatile matter.
What is fuel ratio? How the analyses and calorific values of fuels can be reported? It may be reported as a as received or fired wet basis b dry or moisture free basis c combustible or ash and moisture free basis.
What is the difference between nuclear fission and fission chain reaction. 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. Explain difference between fissile and fertile materials. The materials which can give nuclear fission e. U 35, Pu 39, U 33 are fissile materials.
Fertile material itself is not fissionable, but it can be converted to a fissionable material by irradiation of neutrons in a nuclear reactor. What do you understand by fuel cycle in nuclear plants? Fuel cycle a series of sequential steps involved in supplying fuel to a nuclear power reactor. The steps include: Mining, refining uranium, fabrication of fuel elements, their use in nuclear reactor, chemical processing to recover remaining fissionable material, re-enrichment of fuel from recovered material, refabrication of new fuel elements, waste storage etc.
What is heavy water and what is its use in nuclear plants? Water containing heavy isotopes of hydrogen Deuterium is known as heavy water. Heavy water is used as a moderator. Heavy water has low cross section for absorption of neutrons than ordinary water. Heavy water slows down the fast neutrons and thus moderates the chain reaction. What is a converter reactor?
A reactor plant which is designed to produce more fuel than it consumes. The breeding is obtained by converting fertile material to fissile material. Explain nuclear reactor in brief. A plant which initiates, sustains, controls and maintains nuclear fission chain reaction and provides shielding against radioactive radiation is nuclear reactor.
Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off? Accordingly three methods of disposal are: They are stored in water for several months to permit radioactive decay to an accepetable low level.
Which nuclear reactor uses water as a coolant, moderator and reflector? Which reactor produces more fissionable material than it consumes? Breeder reactor. Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium?
Molten salt breeder reactor. Why an increase in area is required to produce an increase of velocity in case of supersonic flow? Increase in area for increase in velocity for supersonic flow is required because the density decreases faster than velocity increases at supersonic speeds and to maintain continuity of mass, area must increase. Under what circumstances would there be an increase in pressure in a divergent nozzle? For subsonic flow at inlet section of a diffuser a lower velocity and higher pressure will exist at the exit section.
For supersonic isentropic flow at the inlet section a higher velocity and lower pressure will exist at the exit but if a shock wave occurs in the diffuser then a higher pressure will exist at the exit. The refrigerant should be such that vapour volume is low so that pumping work will be low.
Water vapour volume is around times compared to R- for a given mass. What is the difference between isentropic process and throttlinglprocess? In isentropic process, heat transfer takes place and in throttling process, enthalpy before and after the process is same. My email id-sasmal gmail.
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