When you stretch something tight. New anchor chains are stretched or have tention applied to them to near breaking point befor being used on a ship. Tention can be used on a spring just prior to its loosing it's elasticity. Almost anything can have tention applied to it as it is a force.
As a point of interest, still water has tention applied to it as demonstrated by the Water Spiders which can walk on its surface.
No, it is mechanical caused by the spring trying to retain the shape it was made due to it's composition and shape.
taper is the wrong way not enough tentsion have to adjust the guides drive safe