Tuesday, May 26, 2015

written Exam Question for Mechanical Engineers

written Exam Question for Mechanical Engineers


1. Draw the stress-strain curve for Mild steel. Bangladesh Bank, Assistant Director (Mech.) -2013
2. What is modulus of Elasticity/Shear Stress? Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Modulus of Rigidity/Shear Stress- within Elastic Limit, Ʈ ∞Ø, Ʈ = CØ , C= Ʈ/Ø,
Where C= Modulus of Rigidity, Ø= Shear Strain and Ʈ= Shear Stress
3. What is Modulus of Elasticity/young Modulus? Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Modulus of Elasticity - within Elastic Limit, ð ∞€, ð =E. € , E= ð /€,
Where E= Modulus of Elasticity, ð = Stress and = Strain
4. What is tonne of Refrigeration?  Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Tonne of Refrigeration: The amount of refrigeration effect produced by uniform melting of one tonne (1000 Kg) of ice from and at 0°C in 24 hours.
5. What is Jigs and Fixtures?  Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Jigs: Jigs are used for holding and grinding the tool in drilling, reaming or taping operation
Fixtures: Fixtures are used for holding the work in milling, grinding, planning or turning operations.

6. What is Newtonian Fluid? RPCL, Assistant Manager (Mech.)-2013
Answer:
A Newtonian fluid- whose viscosity does not change with the rate of deformation or shear strain is known as Newtonian Fluid.
7. Write the operations carried out in Lathe machines. Dhaka Wasa, Assistant Engineer (Mech.)-2009, Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
Operations which can be carried out in lathe machines-
>Knurling, >Threading, >Boring, >Chamfering, >Taper Turning > Plain Turning, >Step Turning
8. Which alloy based metal is Babbit metal? Asusganj Power Station, Assistant Engineer (Mech.) -2010
Answer:
Babbit Metal is a tin base alloy containing 88% tin, 8% antimony, and 4% copper.
9. Write down the Euler’s Column theory. Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
Euler’s Column Theory, P= π2.E.I./C.l2
10. What is coefficient of Concentration (Cc)? . Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
Coefficient of Concentration (Cc): It is defined as the ratio of area of jet at vena contracta (ac) to the area of orifice (a).
11. What is coefficient of Velocity (Cv)? . Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
Coefficient of Velocity (Cv): It is defined as the ratio of actual velocity of the jet  at vena contracta to the theoretical velocity.
12. What is cavitations?  Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Cavitation- The formation, growth and collapse of vapor filled cavities or bubbles in a flowing liquid due to local fall in fluid pressure are called cavitation.
13. Write down the advantages of Gas Turbine (GT). Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
Advantages of GT-
a) Need not warm time b) Low weight and size c) Less floor space d) Quick start up and shut down e) High thermal efficiency f) Minimal transmission loss g) Less installation cost
14. What is hot working process? Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Hot working- The working of metal above the re-crystallization temperature is called hot working.
15. What are the Boiler Mountings? Bangladesh Bank, Assistant Director (Mech.) -2013
Answer:
Boiler Mountings are- Water level Indicator, Pressure Gauge, Safety valve, steam stop valve, Blow off cock, Fusible Plug
16. For a small scale industry, the fixed cost per month is Tk. 5000. The variable cost price per product is Tk. 20 and sell price is Tk. 30. The break even Production per month? Bangladesh Ordinance Factory, Assistant Engineer (Mech.) -2010
Answer:
Let, X= Break Even Production per month
5000+20x =30x, x=500
17. Draw the Performance curve of Centrifugal pump. EGCB, Assistant Engineer (Mech.) -14
Answer:




               













18. Write down the comparison between petrol and Diesel Engine. BRTA, Assistant Director (Mech.) -2012
Answer:
Petrol Engine
Diesel Engine
A petrol Engine draws a mixture of petrol and air during suction stroke.
A Diesel Engine only draws air during suction stroke.
The pressure at the end of compression is 10 bar.
The pressure at the end of compression is 35 bar.
The combustion of fuel takes place approximately at constant volume.
The combustion of fuel takes place approximately at constant pressure.
A petrol engine compression ratio is approximately 6 to 10 bar.
A Diesel Engine compression ratio is approximately from 15 to 25 bar
The Thermal efficiency is up to 26%.
The thermal Efficiency is up to 40%.

9. Draw the temperature profile of Counter flow and Parallel flow heat exchanger. Bangladesh Bank, Assistant Director (Mech.) -2012
Answer:
20. What is cetane Number? RPCL , Assistant Manager (Mech.) -2013
Answer:
Cetane Number- The percentage by volume of a cetane in a mixture of cetane and -methyl naphthalene which has the same ignition delay as the given fuel when tested in a specified test engine under specified condition is as cetane numb

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