1
GATE PI 2010
MCQ (Single Correct Answer)
+2
-0.6
During open die forging process using two flat and parallel dies, a solid steel disc of initial radius $$({R_{IN}})\,\,200mm$$ and Initial height $$({H_{IN}})\,\,50mm$$ attains a height $$({H_{FN}})$$ of $$30mm$$ and radius of $${R_{FN}}$$. Along the die-disc interfaces

(i) The coefficient of friction $$\left( \mu \right)$$ is :
$$\,\,\,\,\,\,\,\mu = 0.35\left[ {1 + {e^{ - {R_{IN}}/{R_{FN}}}}} \right]$$

(ii) In the region $${R_{SS}}\,\, \le \,\,r\,\, \le \,\,{R_{FN}},$$ sliding friction prevails and
$$\,\,\,\,\,\,P = \sqrt 3 .K.{e^{2\mu \left( {{R_{IN}} - r} \right)/{H_{FN}}}}$$ and $$\tau = \mu \,p$$

Where $$p$$ and $$\tau $$ are the normal and the shear stress respectively; $$K$$ is the shear yield strength of steel and $$r$$ is the radial distance of any point
(i) In the region $$0\, \le \,r\, \le \,{R_{IN}}.$$ sticking condition prevails

The value of $$RSS$$ (in $$mm$$ ), where sticking condition changes to sliding friction is

A
$$241.76$$
B
$$254.55$$
C
$$265.45$$
D
$$278.20$$
2
GATE PI 2010
MCQ (Single Correct Answer)
+2
-0.6
In a rolling process, the roll separating force can be decreased by
A
Reducing the roller diameter
B
Increasing friction between the rolls and the metal
C
Reducing front tension to rolled material
D
Providing back up rollers
3
GATE PI 2010
MCQ (Single Correct Answer)
+1
-0.3
Hot die steel, used for large solid dies in drop forging, should necessarily have
A
high strength and high copper content
B
High hardness and low hardenability
C
High toughness and low thermal conductivity
D
High hardness and high thermal conductivity
4
GATE PI 2010
MCQ (Single Correct Answer)
+1
-0.3
Cold shut (lap) may occur in products obtained by:
A
Casting
B
Forging
C
Machining
D
Welding
EXAM MAP