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GATE 2022 ME: Production Engineering Quiz - 6

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Question 1

The voltage length characteristic of a direct current (dc) arc is given by
V = (20 + 40 L) Watts
Where, L is the length of the arc in cm. The power source characteristic is approximated by a straight line with an open circuit voltage = 80 V and a short circuit current = 1000 amp. The optimum arc length is _________ (in cm).

Question 2

For resistance spot welding of two sheets each of 2 mm thickness, a current of 3000 ampere was passed for 0.2 s. The total resistances was 50 micro-ohms. The heat energy utilised for welding is 72.88 J and the melting energy per unit volume is 2.9 J/mm3. The weld nugget can be

Question 3

Which theory explains microscopic level of surfaces that has crevices, cracks and pores?

Question 4

Two 8 mm thick steel plates are placed 5 mm apart and welded by a butt joint. Welding is carried out at 20 V. Heat transfer efficiency is 0.80. If the heat required to melt steel is 10 J/mm3 and melting efficiency is 0.625. The weld current  is 200 A. The welding speed (in mm/s) is ___________.

Question 5

Resistance spot welding is performed on two plates of 1.5 mm thickness with 6 mm diameter electrode, using 15000 A current for a time duration of 0.25 seconds. Assuming the interface resistance to be 0.0001Ω, the heat generated( W-sec) to form the weld is

Question 6

For spot welding of two steel sheets (base metal) each of 3 mm thickness, welding current of 10000 A is applied for 0.2 s. The heat dissipated to the base metal is 1000 J. Assuming that the heat required for melting 1 mm3 volume of steel is 20 J and interfacial contact resistance between sheets is 0.0002Ω, the volume (in mm3) of weld nugget is _________.
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Oct 12ESE & GATE ME