31. The binary phase diagram of metals P and Q is shown in the figure. An alloy X containing 60% P and 40% Q (by weight) is cooled from liquid to solid state. The fractions of solid and liquid (in weight percent) at 1250°C, respectively, will be
    

1. 1. 68.0% and 32.0%

   
   
   

   2. 32.0% and 68.0%

   
   
   

   3. 22.2% and 77.8%

   
   
   

   4. 77.8% and 22.2%

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   

   Mass fraction of liquid, wL =	Cl - Cα
   	Cα - Cl

   
   

   wL =	68 - 40	= 0.778
   	68 - 32

   
   w_L = 77.8%
   w_s = 1 - w_L = 1 - 77.8
   w_s = 22.2%

   Correct Option: C

   
   

   Mass fraction of liquid, wL =	Cl - Cα
   	Cα - Cl

   
   

   wL =	68 - 40	= 0.778
   	68 - 32

   
   w_L = 77.8%
   w_s = 1 - w_L = 1 - 77.8
   w_s = 22.2%

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32. For cutting double start screw threads of pitch 1.0 mm on a lathe, the thread cutting tool should have a feed rate of

1. 1. 0.5 mm/rev

   
   
   

   2. 1.0 mm/rev

   
   
   

   3. 2.0 mm/rev

   
   
   

   4. 4.0 mm/rev

   
   
   

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1. View Hint View Answer Discuss in Forum

   Pitch = 1mm
   Start = Double Start
   Feed rate = 2 × 1 = 2 mm/res.

   Correct Option: C

   Pitch = 1mm
   Start = Double Start
   Feed rate = 2 × 1 = 2 mm/res.

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33. A circular hole of 25 mm diameter and depth of 20 mm is machined by EDM process. The material removal rate (in mm³/min) is expressed as 4 × 10⁴ IT^–1.23 where I = 300 A and the melting point of the material, T = 1600° C. The time (in minutes) for machining this hole is (correct to two decimal places).

1. 1. 2.1431 min

   
   
   

   2. 7.1431 min

   
   
   

   3. 78.1431 min

   
   
   

   4. 9.1431 min

   
   
   

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1. View Hint View Answer Discuss in Forum

   MRR = 4 × 10⁴ IT^{– 1.23} mm³/min
   Volume required to remove.
   

   =	π	D² × L =	π	25² × 20 = 9817.477 ,,³
   	4		4

   
   MRR = 4 × 10⁴ × I × T^{– 1.23}
   = 4 × 10⁴ × 300 × (1600)^{– 1.23}
   = 1374.40 mm³/min
   

   Time required =	9817.77	= 7.1431 min
   	1374.4

   Correct Option: B

   MRR = 4 × 10⁴ IT^{– 1.23} mm³/min
   Volume required to remove.
   

   =	π	D² × L =	π	25² × 20 = 9817.477 ,,³
   	4		4

   
   MRR = 4 × 10⁴ × I × T^{– 1.23}
   = 4 × 10⁴ × 300 × (1600)^{– 1.23}
   = 1374.40 mm³/min
   

   Time required =	9817.77	= 7.1431 min
   	1374.4

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34. Metal removal in electric discharge machining takes place through

1. 1. ion displacement

   
   
   

   2. melting and vaporizatron

   
   
   

   3. corrosive reaction

   
   
   

   4. plastic shear

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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35. The non-traditional machining process that essentially requires vacuum is

1. 1. electron beam machining

   
   
   

   2. electro Chemical machining

   
   
   

   3. electro Chemical discharge machining

   
   
   

   4. electro discharge machining

   
   
   

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1. View Hint View Answer Discuss in Forum

   EBM requires vaccum chamber and therefore collision of accelerated electron is avoided with the air molecules to obtain fine machining.

   Correct Option: A

   EBM requires vaccum chamber and therefore collision of accelerated electron is avoided with the air molecules to obtain fine machining.

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