Definition
A change in the physical properties of a metal caused by repeated bending, flexing, or cold working, in which the metal becomes harder, stiffer, and more brittle. Work-hardened metal loses ductility and is more likely to crack under further stress.
Plain English
When metal is bent or flexed over and over, it gradually becomes harder and more brittle until it eventually cracks. The metal has not been heated — the change comes purely from being worked.
Context Anchor
Seen in aircraft maintenance, especially when discussing sheet metal, brackets, tubing, or any metal part that has been bent, straightened, or formed.
Derivation
The term is literal: the metal is 'hardened' by being 'worked.' Naming it this way distinguishes it from heat treatment, which is the other main way metal hardness is changed.
Why Pilots Care
Excessive work hardening during repairs can make aircraft aluminum parts brittle and prone to cracking, affecting airworthiness.
Analogy
Bend a paperclip back and forth. The first bends are easy, but soon the metal stiffens at the bend point — and then it snaps. That stiffening before the snap is work hardening.
Intuition Check
Work hardening does not mean a mechanic worked hard on the part. It means the metal itself became harder because it was forced into a new shape.
Example Sentence 1
The mechanic replaced the bracket because repeated vibration had caused work hardening near the mounting hole.
Example Sentence 2
Repeated bending of a control cable can cause work hardening that leads to fatigue failure.