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This set of Advanced Machining Processes Multiple Choice Questions & Answers (MCQs) focuses on “EDM-Heat Affected Zone (HAZ)”.

1. What are the values of temperatures obtained in Electro discharge machining?
a) 1000 to 2000 oC
b) 2000 to 4000 oC
c) 4000 to 8000 oC
d) 8000 to 12000 oC

Explanation: The temperature attained while machining in Electro discharge machining are from 8000 to 12000 oC.

2. What is the value of thickness of recast layer obtained when power of 5 µJ is given?
a) 1 µm
b) 3 µm
c) 5 µm
d) 7 µm

Explanation: When a power of 5 µJ is given, recast layer thickness of 1 µm is obtained.

3. What are the values of thickness of recast layers in Electro discharge machining?
a) 0.001 to 0.025 µm
b) 0.01 to 0.25 µm
c) 1 to 25 µm
d) 10 to 250 µm

Explanation: In Electro discharge machining, the value of thickness of recast layers ranges from 1 to 25 µm.

4. In Electro discharge machining, some annealing of the work piece can be expected _____ the machined surface.
a) On
b) Just below
c) Above
d) At bottom

Explanation: Annealing of some part of the work piece in EDM can be expected just below the machined surface.

5. The depth of the annealed surface is _____ to the amount of power used in machining operation.
a) Directly proportional
b) Inversely proportional
c) Exponential
d) All of the mentioned

Explanation: The depth of annealed surface in EDM is proportional to the amount of power used.

6. What are the values of thickness of annealed surface obtained while machining using EDM?
a) 1 to 25 µm
b) 50 to 200 µm
c) 200 to 500 µm
d) 500 to 1000 µm

Explanation: Values of annealed surface thickness range from 50 µm to 200 µm.

7. In EDM, choosing electrodes that produce which type of machining reduces the annealing effect?
a) Stable
b) Unstable
c) Uneven
d) All of the mentioned

Explanation: In Electro discharge machining, choosing the electrodes which produce more stable machining reduces the annealing effect.

8. What happens to the fatigue strength of alloys if altered surfaces are produced in Electro discharge machining?
a) Increases
b) Reduces
c) Enhances
d) Improves

Explanation: The altered surface layers that are produced in Electro discharge machining, significantly reduces the fatigue strength of alloys.

9. The altered layers formed during the process of EDM consists of which of the following?
a) Tempered layers
b) Heat affected zones
c) Intergranular precipitates
d) All of the mentioned

Explanation: Altered layers consists of recast layers, tempered layers, HAZs and intergranular precipitates in EDM.

10. During roughing process through Electro discharge machining, what is the thickness of layer formed?
a) <0.075 mm
b) <0.125 mm
c) <0.500 mm
d) <0.750 mm

Explanation: The thickness of layer obtained after machining is <0.127 mm in EDM.

11. During finishing process through Electro discharge machining, what is the value thickness of layer formed?
a) <0.075 mm
b) <0.125 mm
c) <0.500 mm
d) <0.750 mm

Explanation: The thickness of layer obtained during EDM finishing is <0.075 mm.

12. Which of the following processes can be used for restoration of fatigue properties?
a) Low-stress grinding
b) Chemical machining
c) Reheat treatment
d) All of the mentioned

Explanation: For removal of altered layers processes such as low-stress grinding, chemical machining, reheat treatment, metallurgical type coating and application of shot peening.

13. State whether following statement is true or false regarding the HAZ in EDM.
“In EDM, post treatment to recover fatigue strength is not recommended.”
a) True
b) False