Definition
A form of bearing damage in which small indentations or dents are pressed into the smooth race surface by the rolling elements (balls or rollers). It is caused by static overload, severe impact, or vibration while the bearing is not rotating, and it leaves a pattern of evenly spaced marks that produce roughness and noise once the bearing is back in service.
Plain English
Tiny dents pressed into the smooth track inside a bearing by the balls or rollers, usually from a hard knock or heavy load while the bearing wasn't turning. Once those dents are there, the bearing feels rough and runs noisily.
Context Anchor
Seen in aircraft maintenance when inspecting wheel bearings, engine accessory bearings, or other rotating parts that must turn smoothly.
Derivation
Named after Swedish engineer Johan August Brinell, who developed the Brinell hardness test in the late 1800s. That test measures hardness by pressing a hardened ball into a metal surface and measuring the dent. A bearing that has been brinelled has, in effect, had the same kind of dent pressed into its race -- which is why the damage carries his name.
Why Pilots Care
Brinelling damages bearings and can produce vibration, accelerated wear, or sudden failure in flight-critical components.
Analogy
It is like pressing a marble hard into soft metal or clay and leaving a small round dent. Once the dent is there, a rolling part can bump over it instead of moving smoothly.
Intuition Check
Brinelling is not ordinary surface wear. It means the bearing surface has been permanently dented by force.
Example Sentence 1
After the hard landing, the mechanic inspected the main wheel bearings for signs of brinelling before returning the aircraft to service.
Example Sentence 2
Brinelling in the propeller hub can create noticeable vibration that must be corrected before flight.