Fatigue cracking in a welded component almost always starts from welds and there is a risk that it may extend to the point of catastrophic failure. Although this should not happen if good design rules are followed, there are often uncertainties as to the actual loading, which may occur. For engineering critical applications, this implies a need for regular inspections, which may prove to be problematical because of difficult access, the resolution limitation of some NDT methods and the relatively high costs involved.

A project consortium involving TWI, UMIST, the Fatigue Monitoring Bureau (FMB), Caterpillar and GE Aviation, and supported by the DTI, has developed a simple fatigue gauge which, when attached to or installed on a component, can give advance warning of structural failure and provide an estimate of its remaining life. The great advantage of such gauges, apart from the relative simplicity of inspection, is that when suitable located, they are subjected to exactly the same loading history as the structure, therefore providing extremely accurate information of fatigue damage. The gauge can be interrogated remotely to measure the level of fatigue.