Method for disassembly of two elements welded by ultrasound and element able to be welded by ultrasound to another element to the implementation of said method

A pair of elements comprising:

• a first element;
• a second element ultrasonically welded to the first element, said second element comprising, at a front surface, an energy director that concentrates the heating during ultrasonic welding and forms a material junction after the ultrasonic welding with a corresponding surface of the first element after the ultrasonic welding;
• and
• a wire attached to the second element at a first location and passing through the energy director at a second location, the wire having suitable mechanical characteristics making it able to cut the energy director while remaining attached to the second element at the first location, wherein said wire separates the energy director subsequent to ultrasonic welding of the second element to the first element to free the second element from the first element.