This set of Advanced Machining Processes Multiple Choice Questions & Answers (MCQs) focuses on “LBM-Material Removal”.
1. What is the material removal mechanism of Laser beam machining process?
a) Melt and evaporate
b) Electro chemical corrosion
c) Mechanical erosion of materials
d) Electro chemical dissolution
View Answer
Explanation: The material is removed by melting and evaporation in Laser Beam Machining process.
2. Physics of laser is very complex due to which of the reasons below?
a) Scattering loss
b) Reflection loss
c) Scattering & Reflection loss
d) None of the mentioned
View Answer
Explanation: Physics of laser is very complex because of scattering and reflection losses.
3. What happens when the heat is diffused into bulk material?
a) Phase change occurs
b) Melting occurs
c) Vaporization may take place
d) All of the mentioned
View Answer
Explanation: The heat diffusion into bulk material causes phase change, melting or vaporization in the materials.
4. State whether the following statement is true of false regarding LBM.
“In LBM, high intensity laser beams are recommended for more material.”
a) True
b) False
View Answer
Explanation: High intensity laser beams are not recommended since they form a plasma plume near surface of material.
5. What happens to the process efficiency if plasma plumes are formed in LBM?
a) Increases
b) Enhances
c) Decreases
d) Improves
View Answer
Explanation: In Laser beam machining, the process efficiency is reduced due the absorption and scattering loses when plasma plumes are formed.
6. Machining of LBM takes place when power density is ____________ than what is lost by conduction and radiation.
a) Greater
b) Smaller
c) Lower
d) Same as
View Answer
Explanation: Machining of laser takes place when power density is greater than what is lost by conduction, convection and radiation.
7. Which of the following phenomenon take place before melting and evaporating in LBM?
a) Conduction
b) Reflection
c) Absorption
d) All of the mentioned
View Answer
Explanation: Material in LBM is removed through several effects such as conduction, absorption, reflection following melting and evaporation.
8. What happens to the material removal rate when reflectivity is higher?
a) Will decrease
b) Will increase
c) Will enhance
d) Remains same
View Answer
Explanation: In LBM, as the reflectivity of the metals is increased the material removal rates of the process are decreased.
9. Reflectivity of the materials depends on which of the following factors?
a) Wave length
b) Properties of material
c) Surface finish
d) All of the mentioned
View Answer
Explanation: Reflectivity of the materials depends on wavelength, the properties of materials, surface finish and temperature.
10. How much amount of incident radiation is reflected at lower power densities?
a) 10 percent
b) 20 percent
c) 50 percent
d) 90 percent
View Answer
Explanation: Most of the metals reflect nearly 90 percent of incident radiation if the power densities are low.
11. How are minimum energies required for plastics when compared to that required for metals?
a) Lower than
b) Higher than
c) Same as
d) None of the mentioned
View Answer
Explanation: The minimum energies required for plastic are lower than that required for metals.
12. Which of the following has high machining speeds in Laser Beam Machining?
a) Metals
b) Non metals
c) Metal alloys
d) All of the mentioned
View Answer
Explanation: Non metallic material machine at higher speeds than metallic ones due to higher reflectivity in metallic materials.
Sanfoundry Global Education & Learning Series – Advanced Machining.
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