396. Hot die steel, used for large solid dies in drop forging, should necessarily have

1. 1. high strength and high copper content

   
   
   

   2. high hardness and low harden ability

   
   
   

   3. high toughness and low thermal conductivity

   
   
   

   4. high hardness and high thermal conductivity

   
   
   

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1. View Hint View Answer Discuss in Forum

   High toughness for hammering action and low thermal conductivity for retaining higher temperature.

   Correct Option: C

   High toughness for hammering action and low thermal conductivity for retaining higher temperature.

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397. By application of tensile force, the cross sectional area of bar P is first reduced by 30% and then by an additional 20%. Another bar Q of the same material is reduced in cross sectional area by 50% in a single step by applying tensile force. After deformation, the true strain in bar P and bar Q will, respectively be

1. 1. 0.5 and 0.5

   
   
   

   2. 0.58 and 0.69

   
   
   

   3. 0.69 and 0.69

   
   
   

   4. 0.78 and 1.00

   
   
   

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1. View Hint View Answer Discuss in Forum

   True strain
   

   ε = In		Ai
   		Af

   
   

   εT = In		Ai
   		0.8 × 0.7Ai

   
   

   εT = In		1
   		0.56

   
   ε_T = 0.58
   True strain in single step of 50%
   

   εT = In		Ai
   		Af

   
   

   = In		Ai
   		0.5Ai

   
   ε_T = In(2) = 0.693

   Correct Option: B

   True strain
   

   ε = In		Ai
   		Af

   
   

   εT = In		Ai
   		0.8 × 0.7Ai

   
   

   εT = In		1
   		0.56

   
   ε_T = 0.58
   True strain in single step of 50%
   

   εT = In		Ai
   		Af

   
   

   = In		Ai
   		0.5Ai

   
   ε_T = In(2) = 0.693

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398. A solid cylindrical stainless steel work piece of 200 mm diameter and 150 mm height. This component is reduced by 50% in height with flat die in open die forging. Assuming the flow stress of the material as 1000 MPa and the coefficient of friction to be 0.2, the estimated forging force at the end of the stroke is

1. 1. 20.8 kN

   
   
   

   2. 31 kN

   
   
   

   3. 78.6 kN

   
   
   

   4. 78.6 MN

   
   
   

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1. View Hint View Answer Discuss in Forum

   78.6 MN

   Correct Option: D

   78.6 MN

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399. Assertion (A): Cold working of metals results in increase of strength and hardness.
     Reason (R): Cold working reduce the total number of dislocations per unit volume of the material

1. 1. Both A and R are true and R is the correct explanation of A

   
   
   

   2. Both A and R are true but R is not a correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true

   
   
   

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1. View Hint View Answer Discuss in Forum

   A is true but R is false

   Correct Option: C

   A is true but R is false

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400. Consider the following statements: In comparison to hot working, in cold working,
     1. higher forces are required
     2. no heating is required
     3. less ductility is required
     4. better surface finish is obtained.
     Which of the statements given above are correct?

1. 1. 1,2 and 3

   
   
   

   2. 1, 2 and 4

   
   
   

   3. 1 and 3

   
   
   

   4. 2, 3 and 4

   
   
   

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1. View Hint View Answer Discuss in Forum

   1, 2 and 4

   Correct Option: B

   1, 2 and 4

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