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Production Engineering Test 4
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  • Question 1/9
    1 / -0
    The temperature employed in brazing is
  • Question 2/9
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    In an arc welding process, a spherical nugget of diameter 13 mm is mode using 25 V potential and current of 300 A. If the heat transfer efficiency is 0.91 and the specific melting energy is 1 J/mm3, then melting efficiency = 
  • Question 3/9
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    A resistance spot-welding operation is performed on two pieces of 1.5 mm thick sheet steel using 12000 amps current for a duration of 0.20 second. The electrodes are 6 mm in diameter at the contacting surfaces. Resistance is assumed to be 0.0001 ohms and the resulting weld nugget is 6 mm in diameter and 2.5 mm thick. The unit melting energy for the metal is 12 J/mm3. What portion of heat generated was used to form the weld?
  • Question 4/9
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    The total heat supplied in arc welding is 1000 J/mm. The melting efficiency is 45%. Welding speed is 9 mm/s. The rate of melting is 20 J/mm3. Calculate the area of the joint obtained in mm2.
  • Question 5/9
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    Two metallic sheets of thickness 2 mm each are spot welded by passing a current of 11000 A for 0.1 sec. The density of spot weld nugget is 10 gm/cc. If the maximum indentation allowed is 15 % of thickness and the specific melting energy is 1390 J/gm, then the following statements are true. (Use resistance = 300 μΩ)
  • Question 6/9
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    The power source characteristics and the voltage length characteristics of on DC are given by I2 = - 400 (V – 80) and V = 30 + 10 ℓ, where ‘L’ is arc length in mm, V is voltage and I is current. What is the change in welding current (A) for arc length change from 3.8 mm to 4 mm? 
  • Question 7/9
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    In an MIG welding operation, the power source characteristic is given as \({V_p} = 40 - \frac{I}{{64}}\), where Vp = Voltage, I = current. If the are length characteristic is Va = 3 la + 27

    Where Va = voltage, la = arc-length in mm, then the following are true

  • Question 8/9
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    A power source designed for a spot-welding process has current as a function of time given by I = 100,000t, where I is in amp and t in second. The sheet metal being spot welded is low carbon steel whose unit melting energy is 10 J/mm3. The resistance of the process is 85 micro-ohms, nugget formed is disk shape of diameter = 4 mm and thickness = 2 mm. 25% of the energy generated from the source is used to form the nugget. The time for which the current must be applied to perform the spot-welding operation is _____ seconds. (Correct upto two decimals)
  • Question 9/9
    1 / -0

    What is percentage decrease in maximum output current that can be drawn at 100% duty cycle from a welding source rated at 600 A at 60% duty cycle

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