Stimulated by the thread on headset brinelling, a quick internet search turned up a lot of information, including this interesting article:
http://en.wikipedia.org/
True brinelling is impact damage, in which the race material is pushed aside to form a crater around the ball bearing, without any loss of material. False brinelling has a similar appearance to the naked eye, but the mechanism is fretting, which involves wear and loss of material, with or without corrosion.
The following paragraph, however, I couldn't quite follow, and wondered if someone could comment or clarify:
"Until recently, bicycle headsets tended to suffer from false brinelling in the "straight ahead" steering positions, due to small movements caused by flexing of the fork. Good modern headsets incorporate a plain bearing to accommodate this flexing, leaving the ball race to provide pure rotational movement."
The writer may have ventured out onto thin ice here.
John Hurley
Austin, Texas, USA