AJM-WJM-AWJM-USM

Abrasive Jet - Water Jet - Abrasive Water Jet Machining  & Ultrasonic  Machining

Abrasive Jet Machining

1. In advanced machining processes, what is the full form of AJM?
a) Automatic Jet Manufacturing
b) Abrasive Jet Machining
c) Automated Jet Machining
d) Abrasive Jet Manufacturing

Answer: b
Explanation: In advanced machining processes, full form of AJM is Abrasive jet machining.

2. In AJM, which of the following materials are used as abrasive grains?
a) Al₂O₃
b) SiC
c) Glass beads
d) All of the mentioned

Answer: d
Explanation: In Abrasive jet machining, any of the particles mentioned above can be used as abrasive grains.

3. In Abrasive jet machining, work piece material of removed by which of the following means?
a) Vaporization
b) Electro plating
c) Mechanical abrasion
d) Corrosion

Answer: c
Explanation: Abrasive particles hit the surface with high pressure and high velocities, which removes the material.

 

4. Which type of materials can be machined using Abrasive jet machining?
a) Glass
b) Ceramics
c) Hard materials
d) All of the mentioned

Answer: d

Explanation: Materials like ceramics, glass, hard and super hard materials can be machined using Abrasive jet machining.

5. In machining system of AJM, which is the medium of carrying the abrasive grains for machining?
a) Liquids
b) Gases
c) Any fluids
d) None of the mentioned

Answer: b
Explanation: In AJM, different types of gases are used as the medium for carrying abrasives.

6. In machining system of AJM, what is/are the gas/es used for carrying the abrasives?
a) CO₂
b) Air
c) Nitrogen
d) All of the mentioned

Answer: d
Explanation: In AJM, gases like CO₂, air or nitrogen are used to carry the abrasives.

7. What is the pressure of gas that is to be supplied, for carrying the abrasives?
a) 0.1 to 1.0 kg/cm²
b) 2.0 to 8.0 kg /cm²
c) 10.0 to 18.0 kg/cm²
d) 25.0 to 35.5 kg/cm²

Answer: b
Explanation: The pressure of the carrying gas should range between 2 to 8 kg/cm².

8. Which of the following gas, should never be used as the carrier of abrasives?
a) Nitrogen
b) CO₂
c) Oxygen
d) Air

Answer: c
Explanation: Oxygen should not be used as carrier because it causes a violent chemical reaction with abrasives or work piece.

9. What is the frequency of mixing chamber, consisting of gas and abrasives?
a) 10 Hz
b) 30 Hz
c) 50 Hz
d) 70 Hz

Answer: c
Explanation: Mixing chamber consisting of carrier gas and the abrasive grains, vibrates at a frequency of 50 Hz.

10. In Abrasive jet machining, what may be the size of the abrasive grains used?
a) 10 – 40 µm
b) 50 – 100 µm
c) 100 – 150 µm
d) 200 – 300 µm

Answer: a
Explanation: Abrasive grains of size, between 10 – 40 µm can be used for machining.

11. What are the processes where Abrasive jet machining can be used?
a) Cleaning
b) Cutting
c) Deburring
d) All of the mentioned

Answer: d
Explanation: Abrasive jet machining can be used for deburring, cutting, cleaning and for many other heavy duty applications.

12. State whether the following statement is true or false.
“In Abrasive jet machining, commercial grades powders can be used for machining.”
a) True
b) False

Answer: b
Explanation: For AJM, commercial grade powders are not used because their sizes are not classified widely.

13. In machining system of AJM, which of the following controls the relative motion between work piece and nozzle?
a) Cam drives
b) Pantographs
c) Trace mechanisms
d) All of the mentioned

Answer: d
Explanation: Relative motion in Abrasive jet machining can be controlled by the above mentioned means.

14. Masks, which are used to confine the jet stream location on work piece are made of, which type of materials?
a) Copper
b) Glass
c) Rubber
d) All of the mentioned

Answer: d
Explanation: Masks can be made of any of the above-mentioned materials.

Water Jet Machining

1. What is the full form of WJM in advanced machining processes?
a) Water Jack Manufacturing
b) Water Jet Machining
c) Water Jet Manufacturing
d) Water Jack Manufacturing

Answer: b
Explanation: The full form of WJM is water jet machining in advanced machining processes.

2. What is the key element of water jet machining for material removal?
a) Tool Holder
b) Work piece
c) Water jet
d) Power source

Answer: c
Explanation: Water jet is the one, which is used to cut the work piece and to remove material.

3. What is the velocity of the water jet stream in water jet machining?
a) 100 m/sec
b) 300 m/sec
c) 700 m/sec
d) 900 m/sec

Answer: d
Explanation: Velocity of water jet stream that is used in Water jet machining is about 900 m/sec.

4. Which of the following is not a part of machining system of Water jet machining?
a) Transducer
b) Accumulator
c) Jet cutting nozzle
d) Hydraulic pump

Answer: a
Explanation: Transducer is not a part of Water jet machining and other components come under WJM.

5. What is the general power rating of the hydraulic pump, used in WJM?
a) 10 kW
b) 20 kW
c) 30 kW
d) 40 kW

Answer: c
Explanation: The power rating of the motor of hydraulic pump, which is used in WJM is about 30 kW.

6. Which of the following are the components of intensifier present in water jet machining system?
a) Piston
b) Plunger
c) Limit switch
d) All of the mentioned

Answer: d
Explanation: The above mentioned components are present in the intensifier of water jet machining.

7. Intensifier increases the pressure water by which of the following values?
a) 10 – 100 MPa
b) 100 – 200 MPa
c) 200 – 400 MPa
d) 400 – 1000 MPa

Answer: c
Explanation: Use of intensifier is to increase the inlet water pressure to 200 – 400 MPa.

8. On which property of water, will the accumulator in Water jet machining rely on?
a) Density
b) Compressibility
c) Viscosity
d) Velocity

Answer: b
Explanation: Accumulator relies on compressibility of water (12% at 3800bar), in order to maintain a uniform discharge pressure in WJM.

9. What are the values of typical tube diameters in the machining system in WJM?
a) 0.1 to 1 mm
b) 1 to 6 mm
c) 6 to 14 mm
d) 14 to 25 mm

Answer: c
Explanation: Typical tube diameter values range between 6 to 14 mm.

10. What is the expected life of the nozzles used in WJM?
a) 10 hrs
b) 20 hrs
c) 100 hrs
d) 200 hrs

Answer: d
Explanation: The life that is expected from the nozzle, which is a part of machining system, is 200 hrs.

11. Which of the following does not damage the nozzle used in Water jet machining?
a) Particles of dirt
b) Mineral deposits
c) Water
d) All of the mentioned

Answer: c
Explanation: Only dirt particles and mineral deposits are responsible for damage of nozzle.

12. What are the uses of catcher in machining system of Water jet machining?
a) Collecting dirt
b) Collection of debris
c) Reduce noise levels
d) All of the mentioned

Answer: d
Explanation: Catcher in WJM is used to collect the dirt, machined debris and reduce the noise levels.

13. Distance between which components, is the stand-off distance?
a) Nozzle-inlet and work piece top
b) Nozzle-outlet and work piece-top
c) Nozzle-inlet and work piece-bottom
d) Nozzle-outlet and work piece-bottom

Answer: b
Explanation: Stand-off distance is the distance between the top of work piece and nozzle outlet.

14. What is the value of diameter of the jet cutting nozzle in WJM?
a) 0.01 – 0.1 mm
b) 0.1 – 0.3 mm
c) 0.3 – 0.7 mm
d) 0.7 – 1.5 mm

Answer: b
Explanation: In WJM, diameter of the nozzles range between 0.10 – 0.30 mm.

15. What is the value of stand-off distance in Water jet machining?
a) 0.1 – 1 mm
b) 1 – 2 mm
c) 2 – 6 mm
d) 6 – 14 mm

Answer: c
Explanation: Stand-off distance value ranges between 2.5 – 6 mm in Water jet machining.

Abrasive Water Jet Machining

1. In advanced machining processes, what is the full form of AWJM?
a) Automated Water Jet Machining
b) Automated Water Jet Manufacturing
c) Abrasive Water Jet Machining
d) Abrasive Water Jet Manufacturing

Answer: c
Explanation: Full form of AWJM is Abrasive Water Jet Machining.

2. What are all the types of materials, which can be machined using AWJM?
a) Glass
b) Ceramics
c) Concrete
d) All of the mentioned

Answer: d
Explanation: Hard to cut materials, which are mentioned above, can be machined using Abrasive water jet machining.

3. When was Abrasive water jet machining developed first?
a) 1942
b) 1958
c) 1974
d) 1980

Answer: c
Explanation: Abrasive water jet machining was first developed in the year 1974.

4. When compared to the conventional machining, how much times faster, is the Abrasive water jet machining?
a) 5 times
b) 10 times
c) 15 times
d) 20 times

Answer: b
Explanation: Abrasive water jet machining is 10 times faster than the conventional machining.

5. What is the percentage of the abrasives and water in the mixture?
a) 20% water and 80% abrasives
b) 80% water and 20% abrasives
c) 30% water and 70% abrasives
d) 70% water and 30% abrasives

Answer: d
Explanation: Abrasive mixture consists of 70 percent water and 30 percent abrasives.

6. What are the materials used for abrasives in Abrasive water jet machining?
a) SiC
b) Corundum
c) Glass beads
d) All of the mentioned

Answer: d
Explanation: All of the materials mentioned above can be used for making abrasives in Abrasive water jet machining.

7. In the machining system of AWJM, which one accelerates the abrasives to remove material?
a) Water only
b) Water jet stream
c) Feeder
d) None of the mentioned

Answer: b
Explanation: Water jet stream accelerates abrasives but not the water only, to remove material.

8. The introduction of compressed air to the water jet enhances the deburring action.
a) True
b) False

Answer: a
Explanation: Compressed air increases the pressure energy of the jet stream, which enhances the material removal rate.

9. What is the grain size of abrasive particles, which are often used for Abrasive water jet machining?
a) 0.01 – 0.50 µm
b) 10 – 150 µm
c) 200 – 500 µm
d) 500 – 1000 µm

Answer: b
Explanation: Grain size of the abrasive particles range between 10 – 150 µm in Abrasive water jet machining.

10. How is the material removed in Abrasive water jet machining?
a) Vaporization
b) Electron transfer
c) Corrosion
d) Erosion

Answer: d
Explanation: In Abrasive water jet machining, material removal takes place by the erosion of the work piece material using abrasives accelerated by jet stream.

11. Which of the following is not the feed mechanism of the abrasives in AWJM?
a) Side feed
b) Cross feed
c) Central feed
d) All of the mentioned

Answer: b
Explanation: Only side feed and central feed are used in Abrasive water jet machining.

12. In Abrasive water jet machining, how are the abrasives fed into the water jet stream?
a) Suspension
b) Injection
c) All of the mentioned
d) None of the mentioned

Answer: c
Explanation: Abrasives are fed into the water jet stream through suspension or injection.

13. What is the use of delivery system in the machining system of AWJM?
a) To deliver colloidal solution
b) To pump water
c) To fed abrasives
d) None of the mentioned

Answer: b
Explanation: In Abrasive water jet machining, water delivery system is used.

14. In Abrasive water jet machining, intensifier is used to deliver which type of pressure?
a) Very low pressure
b) Low pressure
c) Medium pressure
d) High pressure

Answer: d
Explanation: In AWJM, intensifier is used to deliver high pressure water using pistons with it.

15. In mixing chamber of AWJM, which of the following are mixed?
a) Abrasives and colloidal solution
b) Abrasives and water jet
c) Colloidal and water jet
d) None of the mentioned

Answer: b
Explanation: In mixing chamber, abrasives and water jet stream are mixed.

ULTRASONIC MACHINING

1. Who discovered USM?
a) Balamuth
b) Paul O Flawer
c) Turing
d) Steve John

Answer: a
Explanation: Balamuth was the scientist, who discovered Ultrasonic Machining.

2. What is the full form of USM in advanced machining process?
a) Ultrasound manufacturing
b) Ultrasonic machining
c) UV spectrum manufacturing
d) Ultra sonar machining

Answer: b
Explanation: Full form of USM in advanced machining processes, is Ultrasonic machining.

3. USM removes materials using the ____________ tool.
a) Perpendicularly rotating
b) Perpendicularly oscillating
c) Axially oscillating
d) Inclined oscillating

Answer: c
Explanation: Material is removed using axial oscillating tool.

4. Which is softer material in USM?
a) Tool
b) Work piece
c) Tool & Work piece
d) None of the mentioned

Answer: a
Explanation: Tool is softer than work piece in USM.

5. Frequency of tool’s oscillation in USM ranges between ________
a) 5-10 kHz
b) 10-15 kHz
c) 18-20 kHz
d) 25-50 kHz

Answer: c
Explanation: Frequency used in USM is between 18 – 20 kHz.

6. Amplitude of oscillation of tool in USM ranges between ________
a) 0.1-10 μm
b) 10-40 μm
c) 50-100 μm
d) 100-1000 μm

Answer: b
Explanation: The optimal range used is between 10-40 μm.

7. In which year, discovery of USM took place?
a) 1910
b) 1925
c) 1943
d) 1945

Answer: d
Explanation: Ultrasonic Machining was discovered in 1945.

8. The machining system of USM contains which of the following components?
a) Magnetostrictor
b) Concentrator
c) Tools and slurry
d) All of the mentioned

Answer: d
Explanation: In machining system of USM, the above-mentioned components have to be present.

9. In Ultrasonic Machining, Magnetostrictor is energized at ultrasonic frequency.
a) True
b) False

Answer: a
Explanation: To oscillate, magnetostrictor must be energized to the ultrasonic frequency in USM.

10. Of the following scientists, who discovered magnetostrictor effect?
a) Balamuth
b) Steve O Flawer
c) Joule
d) Turing

Answer: c
Explanation: This effect was discovered by Joule in 1874 at Manchester.

11. In Ultrasonic Machining, magnetostrictor converts magnetic energy into which type of energy?
a) Mechanical energy
b) Electrical energy
c) Thermal energy
d) None of the mentioned

Answer: a
Explanation: Oscillation of magnetostrictor takes place by converting magnetic energy to mechanical energy.

12. What is the value of the amplitude obtained without mechanical amplifier?
a) 0.0001 – 0.001 µm
b) 0.001 – 0.1 µm
c) 1 – 10 µm
d) 10 – 100 µm

Answer: b
Explanation: Relatively very small amplitudes are obtained without amplifier.

13. What is the value of the amplitude obtained when we use mechanical amplifier?
a) 1 – 10 µm
b) 10 – 40 µm
c) 40 – 50 µm
d) 50 – 100 µm

Answer: c
Explanation: Relatively larger amplitudes are obtained when amplifier is used.

14. In USM, tool tips must have low resistance and fatigue strength.
a) True
b) False

Answer: b
Explanation: In USM, tool tips should must have high wear resistance and fatigue strength.

15. At what rate slurry is pumped through nozzle in USM?
a) 10 L/min
b) 25 L/min
c) 50 L/min
d) 75 L/min

Answer: b
Explanation: Slurry is pumped through nozzle at the rate of 25 L/min, L- litres.

Ref: https://www.sanfoundry.com/advanced-machining-questions-answers-water-jet-machining-introduction-machining-system/

R.Satheesh 

GAS TURBINE-Jet and Rocket Propulsion

Jet and Rocket Propulsion

Ref: https://gtu-mcq.com/BE/Mechanical-Engineering/Semester-7/2171910/2139/MCQs?q=6wHWymi73nk=

R.SATHEESH, Asso.Prof

GAS TURBINE-Compressible Flow

Compressible Flow

               Ref: https://gtu-mcq.com/BE/Mechanical-Engineering/Semester-7/2171910/2139/MCQs?q=6wHWymi73nk=

R.SATHEESH, Asso.Prof.,

 

RAC - Vapour Refrigeration Systems

 VAPOUR REFRIGERATION SYSTEM

1. Heat is absorbed by the refrigerant, during vapour compression refrigeration cycle in

(a) Compressor 

(b) Condenser 

(c) Evaporator 

(d) Throttle valve

 

2. In a simple saturated vapour compression cycle, the refrigerant is in superheated condition

(a) before entering compressor 

(b) before entering condenser

(c) before entering throttle valve 

(d) before entering evaporator

 

3. Sub-cooling is a process of cooling the refrigerant in vapour compression refrigeration system

(a) after compression 

(b) before compression 

(c) before Throttling

(d) none of the above

 

4. The order in which main components of vapour compression refrigeration system are used is

(a) compressor-evaporator-condenser-throttle valve

(b) compressor-condenser-evaporator-throttle valve

(c) compressor-throttle valve- evaporator-condenser

(d) compressor-condenser- throttle valve- evaporator

 

5. The oil separator is incorporated in vapour compression refrigeration system

(a) between evaporator and compressor

(b) between compressor and condenser

(c) between condenser and Throttle valve

(d) between throttle valve and evaporator

 

6. In vapour compression refrigeration cycle the following data is available Heat rejected in condenser 

=65 KW  Work done in compressor = 10 kw, then COP( refrigerator) is

(a) 4.5 

(b) 5.5 

(c) 6.5 

(d) not possible to find with the given data

 

7. Following results are tabulated for vapour compression refrigeration cycle.

Enthalpy at suction = 190 kJ/kg

Enthalpy at discharge from compressor = 210 kJ/kg

Enthalpy at exit from condenser = 80 kJ/kg ,    COP of cycle would be

(a)3.5 

(b) 4.5 

(c) 5.5 

(d) 6.5

 

8. For simple saturated vapour compression refrigeration cycle operating between 5°C and 40°C, and the refrigerants being R-11, R-12, R-717 and R-22, the evaporator pressure is lowest for

(a) R-11 

(b) R-12 

(c) R-717 

(d) R-22

 

9. With reciprocating compressor in vapour compression refrigeration system, wet

compression is not desirable because

(a) liquid trapped up in the head of cylinder may damage the compressor valves

(b) COP of the cycle decreases

(c) volumetric efficiency of compressor decreases

(d) mass flow rate per ton of refrigerant increases

 

10. An ideal refrigerant should have

(a) low latent heat of vaporization

(b) high critical temperature

(c) high boiling point

(d) high specific volume of vapour

 

11. The refrigerant leaving throttle valve is

(a) saturated liquid

(b) saturated vapour

(c) superheated vapour

(d) fraction as saturated vapour and remainder as liquid

 

12. Freon group of refrigerants

(a) toxic 

(b) inflammable 

(c) non-toxic and non-inflammable

(d) highly toxic and inflammable

 

13. The leaks of refrigerant from a cycle may be detected by

(a) halide torch test

(b) sulphur candle test

(c) soap and water test

(d) any of the above

 

14. During compression in a vapour compression cycle the refrigerant is super heated

(a) work done is increased

(b) C.O.P is increased

(c) Work done is reduced

(d) Refrigerating effect is reduced

 

15. Heat is rejected by the refrigerant, during vapour compression refrigeration cycle in

(a) Compressor 

(b) Condenser 

(c) Evaporator 

(d) Throttle valve

 

16. Wet compression vapour compression refrigeration cycle means

(a) Vapour compression takes place in wet region

(b) Vapour compression in dry region, but evaporation in wet region

(c) vapour compression in wet region, but leaves in superheated region

(d) None of the above

RAC - Air Refrigeration Systems

 

AIR REFRIGERATION SYSTEM

1. Reversed carnot cycle comprises

(a) two isentropic processes and two adiabatic processes

(b) two isentropic processes and two isothermal processes

(c) two isentropic processes and two isobaric processes

(d) two isentropic processes and two isochoric processes

 

2. Two Carnot Refrigerators are employed, one for ice making and other for comfort cooling

(a) The COP of the refrigerator for ice making is higher than that for other

(b) The COP of the refrigerator for ice making is same as that for the other

(c) The COP of the refrigerator for ice making is lower than that for other

(d) The COP of Carnot refrigerator will depend on refrigerant used

3. A reversed Carnot cycle has a COP of 4. The ratio of higher temperature to lower temperature will be

(a)  1.25        

(b) 1.5

(c) 2            

(d) 2.5

 

4. Carnot refrigerator absorbs heat at -13° C and requires 1 kW for each 6.5 kW of heat absorbed, the COP and temperature of heat rejections respectively

(a) COP = 6.5, t = 27° C     

(b) COP = 7.5, t = 27° C

(c) COP = 6.5, t = 30° C     

(d) COP = 7.5, t = 37° C

 

5. The dense air refrigeration system as compared to open air refrigeration system for same range of temperatures using Bell- Colemann cycle requires.

(a) Same power/Ton of Refrigeration

(b) Lower power/Ton of Refrigeration

(c) Higher power/Ton of Refrigeration

(d) Unpredictable Results

 

6. The amount of heat absorbed by the system at low temperature is

(a) COP

(b) refrigerating effect

(c) work done on the system

(d) refrigeration efficiency

 

7. No refrigerator using reversed Carnot cycle has been constructed because

(a) it is less efficient

(b) it is uneconomical

(c) isentropic portions of cycle require low speeds where as isothermal portions require high speeds

(d) isentropic portions of cycle require high speeds where as isothermal portions require low speeds

 

8. A refrigeration cycle is usually a

(a) open cycle 

(b) closed cycle 

(c) mixed cycle 

(d) Hybrid cycle

 

9. Co-efficient of performance of a Reversed Carnot cycle refrigerator working between higher temperature T2 and lower temperature T1

(a) will increase with increase in T1 keeping T2 fixed

(b) will decrease with increase in T1 keeping T2 fixed

(c) will first increase with increase in T1 and then decrease with increase T1 keeping T2 fixed

(d) None of the above

 

10.Bell-Colemann cycle comprises

(a) two isentropic processes and two adiabatic processes

(b) two isentropic processes and two isothermal processes

(c) two isentropic processes and two isobaric processes

(d) two isentropic processes and two isochoric processes

 

11. The COP of Carnot Refrigerator is 3 and it produces 1 TR. The work that will be done is equal to

(a)  70 kJ/min 

(b) 100 kJ/min 

(c) 200 kJ/min 

(d) 210 kJ/min

 

12. In Bell – Colemann refrigerator for the same temperature range

(a) COP of dense air system is equal to COP of open air system

(b) COP of dense air system is lower than COP of open air system

(c) COP of dense air system is higher than COP of open air system

(d) COP of dense air system may be higher or lower than COP of open air system depending upon  pressure ratio.

 

13. For very high speed planes cruising at Mach number 2.5 and above, the air craft refrigeration system recommended is

(a) Simple evaporative type 

(b) Boot-strap type

(c) Regenerative type 

(d) Boot strap evaporative type

 

14. The air craft system giving Lowest Dry Air Rated Turbine discharge temperature at supersonic cruising speeds of the plane, is

(a) Reduced ambient system of Refrigeration

(b) Boot-strap system of Refrigeration

(c) Regenerative system of Refrigeration

(d) Boot strap evaporative system of Refrigeration

 

15. There are two cooling turbines in

(a) Reduced ambient system of Refrigeration

(b) Boot-strap system of Refrigeration

(c) Regenerative system of Refrigeration

(d) Boot strap evaporative system of Refrigeration

 

16. There are two stages of compression of air in

(a) Reduced ambient system of Refrigeration

(b) Boot-strap system of Refrigeration

(c) Regenerative system of Refrigeration

(d) Simple evaporative system of Refrigeration

 

17. A Bell-Colemann cycle is

(a) reversed Carnot Cycle

(b) reversed Joule Cycle

(c) reversed Rankine cycle

(d) None of the above

 

18. In a refrigeration cycle the heat is rejected by refrigerant at

(a) expansion valve

(b) compressor

(c) condenser

(d) all the above

 

19. A reversible refrigerator working between two fixed temperatures

(a) has the same COP whatever the working substance

(b) has its COP increased for working substance with high enthalpy of evaporation

(c) has its COP increased for working substance with higher specific heats

(d) none of the above