A fatigue sensor system for welded joints in steel structures, capable of providing advanced warning of the rate at which the design life is being consumed.

CrackFirst™
The CrackFirst™ sensor consists of a thin shim of material attached to the target structure close to a critical joint. Under the action of cyclic stress in the structure, a fatigue pre crack at the centre of the shim, introduced during manufacture, extends by fatigue crack growth. This indicates how much of the design life of the adjacent weld has expired and how much remains. It is of most benefit for structures in which fatigue is the primary limit state, especially in situations where inspection and repair is difficult or impossible, or where structural failure would have significant consequences with respect to safety and/or financial loss. Typical applications include cranes, earth moving vehicles, bridges, offshore structures, railway bogies and many more.