In a destructive test of a lap joint, what indicates complete fusion between the metals?

• A. Adhesion
• B. Cracking
• C. Fracture of one member with no fusion
• D. Fusion

Answer: (D)

What you’re looking for is complete fusion: the weld metal and the base metals have melted and merged into a single piece across the joint. In a destructive lap-joint test, this means the fracture surface shows a continuous weld zone fused to both pieces, with no unbonded metal or separate interfaces. This indicates that the metals truly tied together during welding, forming a true metallurgical bond.

Adhesion would just be a surface bond without melting through the interface, cracking points to weaknesses or brittle behavior, and a fracture with no fusion shows that the metals never melted together at the joint. Only fusion demonstrates that the metals became one continuous piece in the weld.