ISRO Scientist or Engineer Mechanical 2020

Instructions

For the following questions answer them individually

Question 31

‘The state of stress during deep drawing forming operation of a cup is

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Question 32

During turning of a metallic rod at a given condition, the tool life was founded to decrease from 100 min. to 25 min. ool if: cutting speed was increased from 50 $$\frac{m}{min}$$ How muchwill be life of tool if the machined at 80$$\frac{m}{min}$$?

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Question 33

In a single pass rolling operation, the thickness of a 100 mm wideplate is reduced from 20 mm to 15 mm. The roller radius is 125 mm and rotational speed is 8 rpm. The average
flow stress for the plate material is 400 Mpa.The power required for rolling operation in kW is?

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Question 34

A dummyactivity is used in PERT network to describe

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Question 35

In small castings, which of the following allowances can be ignored.

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Question 36

In an arc welding process,two weld coupons were made using two different welding processes. For the first coupon, the voltage, current and welding speed used are 15 V, 300A
and 30 $$\frac{mm}{min}$$ respectively. Whereas the second couponis welded with 60 kV, 200 mA and 25 $$\frac{mm}{s}$$. If the heat transfer efficiency for welding the first coupon is half of that of second coupon, the ratio of heat input per unit lengthis?

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Question 37

In Gas tungsten arc welding (GTAW) which of the following polarity is generally used for getting higher penetration

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Question 38

The laws of adhesive wear, commonly referred to as Archard's law can be expressed as ..................
(If ‘Q’ is the total volume of wear debris produced, ‘W’ is the normal load, ‘L’ is the sliding distance, ‘H’ is the hardness of the softest contacting surfaces being worn away, and ky’is a
non-dimensional wearcoefficient dependent on the materials in contact and their exact degree of cleanliness)

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Question 39

Ina four-barlinkageif ‘S’ is the length of the shortest link, ‘L’ is the length of longestlink and ‘P’ & ‘Q’ are lengthofotherlinks, then the criteria for getting a triple rocker mechanism in which no links will fully rotate is.

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Question 40

The piston of an engine moves with simple harmonic motion. The crank rotates at 120 r.p.m with a stroke of 2 meters. The velocity of the piston, when it is at a distance of 0.8 metre from the center is.

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