GATE Mechanical Engineering (ME) 2021 Shift 1 Solved Paper

The resistance spot welding of two 1.55 mm thick metal sheets is performed using welding current of 10000 A for 0.25 s. The contact resistance at the interface of the metal sheets is 0.0001 Ω. The volume of weld nugget formed after welding is 70 mm³. Considering the heat required to melt unit volume of metal is 12 J/mm³, the thermal efficiency of the welding process is_______ % (round off to one decimal place).