There was a really good article on stranded wire used in non cramping terminal devices.
Wire strands compress and then vibration causes the strands to shift and gradually loosen.
A ferrule is a crimped-on copper terminal that provides a solid end to the wire for clamp-on terminals in battery chargers, AC inlets , etc.
Daryl
s/y Intuition - PSC 31 #54
Daryl Clark