1

GATE ME 2003

Subjective

+5

-0

The arc - voltage characteristics of a $$DC$$ power source has a linear power source characteristic of $$V=20+40L,$$ where $$V$$ is the arc voltage in volts and $$L$$ is the arc length in $$cm.$$ The static volt-ampere characteristic of the power source is approximated by a straight line with open circuit voltage $$=80V$$ and short circuit current is $$600Amps,$$ determine the optimum arc length for maximum power

2

GATE ME 2000

Subjective

+5

-0

Two different pairs of sheets of same material are welded by resistance-spot welding. In one pair, the average radius $$(r)$$ of each spherical bridge is $$0.2$$ $$mm$$ and the number of bridges per $$c{m^2}\,\,\left( n \right)$$ is $$25.$$ In another pair, the number of bridges per $$c{m^2}$$ is $$50$$ with the same $$'r'$$ of bridge. The contact resistance $${R_c}$$ per unit area is given by $${R_c} = 0.85$$ $$\left( {\rho /n\pi r} \right)$$ where $$'\,\rho \,'$$ is the resistivity of metal. If the voltage applied is $$5$$ volts and the resistivity of metal is $$2 \times {10^{ - 5}}$$ ohm-cm. The rate of heat generated per $$c{m^2}$$ in each case

3

GATE ME 1999

MCQ (Single Correct Answer)

+5

-1.5

For butt welding $$40mm$$ thick steel plates, when the expected quantity of such jobs is $$5000$$ per month over a period of $$10$$ years, choose the best suitable welding process out of the following available alternatives.

4

GATE ME 1999

MCQ (Single Correct Answer)

+5

-1.5

In butt welding operation on plates, the heat input necessary is given by

$$Q = 8\,K\,{T_c}\,t\,\,\,\left[ {0.2 + {{Vb} \over {4\alpha }}} \right]$$

Where $$K=$$ thermal conductivity,

$${T_c} = $$ temp increases from room temp up to $$MP,$$

$$t=$$ thickness of plate,

$$V=$$ welding speed,

$$b=$$ width of weld,

$$\alpha = thermal diffusivity

Two alloy steel plates as shown in fig are to be welded using a power source rated at $$5$$ $$kVA$$ having a duty cycle of $$75\% .$$ Using the given data, determine the maximum welding speed for the job given in $$mm/s$$

Data : $$K = 45\,W/{m^0}C,\,\,{T_c} = {1450^ \circ }C,$$ and

$$\alpha = 1.2 \times {10^{ - 5}}\,\,{m^2}/s.$$

Questions Asked from Welding Process (Marks 5)

Number in Brackets after Paper Indicates No. of Questions

GATE ME Subjects

Engineering Mechanics

Strength of Materials

Theory of Machines

Engineering Mathematics

Machine Design

Fluid Mechanics

Turbo Machinery

Heat Transfer

Thermodynamics

Production Engineering

Industrial Engineering

General Aptitude