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25 best mechanical engineering interview questions and answers pdf free download. 1. Mechanical Engineering Interview questions and. Download Mechanical Engineering Interview Questions PDF from here and prepare accordingly. Check More: Interview Questions and Answers . If you possess degree or diploma in mechanical engineering, you can. Download Most Important Mechanical Interview Questions and Answers pdf Book for Fresher Engineering & Diploma Candidates – Below we.
They will looking for leadership. If you did project in group work, they will find out your leadership quality by related question. What safety precautions should be observed while working in the workshop? Keep shop floor clean, free from oil and other slippery materials. Wear proper dress and avoid loose clothing and loose hair. Wear shoes and avoid chapels. Avoid playing, loose talk and funning inside the shop floor. Keep good housekeeping and put all unnecessary items and rejected items in scrap box.
Learn everything about the machine before starting and clear all the doubts. Keep a safe distance from rotating and sliding parts.
Never store inflammable materials inside or around the shop. Never play with electricity, fire, parts with sharp edge etc. Keep fire buckets and extinguishers ready for use. What are the precautions to be taken to avoid fire? The buckets along with sand should be placed inside the workshop. Switches and other electrical parts must be made of fireproof material.
Carbon dioxide gas should be place at required points in special containers. Fire extinguishers of suitable type should be placed at accessible places. What do you mean by First Aid? First Aid is immediate and temporary care given to a person who affected accidental injury or a sudden illness before the arrival of doctor.
What is a Drawing? It is a graphical representation of a real thing to define and specify the shape and size of a particular object by means of lines. What is Engineering Drawing? A drawing which is worked out an engineer for the engineering purpose is known as Engineering Drawing. Explain briefly the following lines used in Engineering drawing? These are terminated with arrowheads. Difference between 'Thermodynamics and Heat Transfer'?
Thermodynamics mainly deals with the transfer of energy in form of heat or work between systems and surroundings with other systems in form of either heat or work in equilibrium conditions. When there is change in one state, which was in equilibrium state and starting to change in other equilibrium state, this information helps to determine heat or work interactions due to this process.
While Heat transfer deals with non equilibrium heat exchange or transfer due to temperature gradient while in thermodynamics, during thermal equilibrium No temperature gradient no heat exchange is possible. Explain in an orderly manner how the force in the member of a truss be detected using the method of joint.
The steps required to calculate the force are as follows: The reaction at the support has to be first calculated. Once the reaction is calculated the direction of force of the member is made to make it tensile.
On getting the result to be negative the direction assumed is wrong and this implies the force being compressive in nature. A joint needs to be selected whose 2 members are not known. The lami's theorem is used on the joint on which less than three forces are acting.
After the above process is complete the free body diagrams of the joint needs to be made. Since the system is in equilibrium the condition of Summation of V and H must result in zero. After the above step the resolution of forces method needs to be used on the joint on which more than 4 forces are acting. What is mechanism? A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.
What is annealing? It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material. 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. Isothermal process. What is temper embrittlement in alloy steels and what are its effects?
Embrittlement attack is usually intergranular in metals, i. It imparts a tendency to fail under a static load after a given period of time in those alloy steels which are susceptible to embrittlement. What are whiskers? Whiskers are very small crystals which are virtually free from imperfections and dislocations.
What is Bauschinger effect? According to Bauschinger, the limit of proportionality of material does not remain constant but varies according to the direction of stress under cyclic stresses. What is the difference between heat capacity and specific heat of a material? Explain the rule to find specific heat of aqueous solutions.
For aqueous solutions of salts, the specific heat can be estimated by assuming the specific heat of the solution equal to that of the water alone. What do you understand by latent heat? Give four examples of latent heats. For pure substances, the heat effects accompanying changes in state at constant pressure no temperature change being evident are known as latent heats. Examples of latent heats are: Define the terms free energy and free enthalpy.
What is their significance and importance? It is equal to the work during a constant-volume isothermal reversible nonflow process. For reversible isothermal steady-flow processes or for reversible constant-pressure isothermal nonflow processes, change in free energy is equal to net work. What is polytropic process? Under what conditions it approaches isobaric, isothermal, and isometric process? In which reversible process no work is done? No work is done in isometric process.
Out of constant pressure and constant volume lines on TS diagram which line has higher slope? And whether slope is constant or variable? Constant volume line. Slope is variable. Whether entropy is intensive property or extensive property? Entropy is extensive property. In which process fluid expands but does no work? Throttling process. What is the difference between scavenging and supercharging? Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends.
Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes. Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion?
Why entropy change for a reversible adiabatic process is zero? Because there is no heat transfer in this process.
What are two essential conditions of perfect gas? It satisfies equation of state and its specific heats are constant. Enthalpy and entropy are functions of one single parameter. Which is that?
Why rate of condensation is higher on a polished surface compared to rusty surface? Polished surface promotes drop wise condensation and does not wet the surface.
How much resistance is offered to heat flow by drop wise condensation? What is the relationship between COP of heating and cooling? When maximum discharge is obtained in nozzle? At the critical pressure ratio. Under what condition the work done in reciprocating compressor will be least? It is least when compression process approaches isothermal.
For this purpose, attempts are made to cool the air during compression. What is the difference between stalling and surging in rotary compressions? Stalling is a local phenomenon and it occurs when How breaks away from the blades. Surging causes complete breakdown of flow and as such it affects the whole machine.
Why the electric motor of a fan with backward curved blades is never got overloaded under any condition? For higher flow, power consumption gets lower. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio?
Isentropic efficiency of axial flow compressor is higher. What is the name given to portion of thermal energy to be necessarily rejected to environment? What is pitting? How it is caused?
Non uniform corrosion over the entire metal surface, but occuring only in small pits is called pitting. It is caused by lack of uniformity in metal. What is caustic embrittlement? It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of rivetted joints and around the rivet holes. Which impurities form hard scale and which impurities soft scale?
Sulphates and chlorides of lime and magnesium form hard scale, and carbonates of lime and magnesium form soft scale. What is the difference between hard water and soft water? Hard water contains excess of scale forming impurities and soft water contains very little or no scale forming substances. Which two elements in feed water can cause corrosion of tubes and plates in boiler? Acid and oxygen in feed water lead to corrosion. What should be done to prevent a safety valve to stick to its seat?
Safety valve should be blown off periodically so that no corrosion can take place on valve and valve seat. Why large boilers are water tube type? Water tube boilers raise steam fast because of large heat transfer area and positive water circulation. Thus they respond faster to fluctuations in demand.
Further single tube failure does not lead to catastrophy. What type of boiler does not need a steam drum? Super-critical pressure boiler. Why manholes in vessels are usually elliptical in shape? Elliptical shape has minimum area of opening and thus plate is weakened the least. Further it is very convenient to insert and take out the cover plate from elliptical opening.
Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water condition in boiler drum?
High drum level does not allow steam separation to be effective and some water can be carried over with steam which is not desirable for steam turbine. Why boiler is purged every time before starting firing of fuel? Purging ensures that any unburnt fuel in furnace is removed, otherwise it may lead to explosion.
What is the principle of mechanical refrigeration? A volatile liquid will boil under the proper conditions and in so doing will absorb heat from surrounding objects. 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.
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