| Structural Monitoring |  | CrackFirst Fatigue Sensor |
CrackFirst is a fatigue testing sensor for welded joints in steel structures that is capable of providing advanced warning of the rate at which the design life is being used. Unlike a typical strain gauge which monitors the amount of strain at the point it is attached to the structure, the CrackFirst fatigue testing sensor senses the actual amount of fatigue damage suffered.
The CrackFirst fatigue testing sensor consists of a thin 0.25mm thick 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. The sensor design is such that the extent of crack growth in the shim is proportional to the cumulative fatigue damage for a welded joint subject to 
the same loading. It has been designed for use on common steel structures which see cyclic loading, such as ships, earth moving machines, bridges and cranes, and is of most benefit where 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.
As the CrackFirst fatigue testing sensor provides information on the rate at which the design life is being expended, it can be used to set inspection levels according to usage, rather than elapsed time. The physical condition of the fatigue testing sensor is irreversible, so sensors remain serviceable for many years. It is also possible to retrofit sensors, provided that prior service is taken into account.
| Copyright © Strainstall Monitoring 2012 | Home | Contact Us | Site Map |