Question

Aluminum strips of $2mm$ thickness are joined together by a resistance spot welding process by applying an electric current $6000A$ and $0.15second$. The heat required for melting aluminum is $2.9J/m{m}^3$. The diameter and thickness of the weld nugget are found to be $5mm$ and $2.5mm$ respectively. Assuming the electrical resistance to be $75$ micro ohms, the percentage of total energy utilzed in forming the wed nugget is

• A. $28$
• B. $65$
• C. $72$
• D. $35$

Answer 1

The correct option is D $35$

$\text{Energy generated}=I^{2}RT$

$=(6000{)}^2\times 75\times {10}^{-6}\times 0.15=405J$

$\text{Energy required}=2.9J/m{m}^3\times \text{Vol of nugget}$

$=2.9\times \frac{\pi }{4}\times 5^2\times 2.5=142.35\text{Joules}$

$\text{\% of energy utilized in weld nugget formation}$

$=\frac{142.35}{405}\times 100=35\text{\%}$