Testing and Numerical Simulation of Magnetic Fields Affected by Presence of Fatigue Cracks

摘要

Growing applications of high strength steels, which are more sensitivernto fatigue, harsher operative environments, and increasing economicrnvalue of ship- and offshore structures, such as FPSOs and FLNGs,rnincrease the need for asset integrity management systems. Presently,rnthere are many nondestructive testing methods available. Magneticrnmethods to monitor fatigue cracks are not yet fully exploited and seemrnpromising due to the possibility of passive monitoring using the Earthrnmagnetic field as source. Measurements and numerical simulationsrnshow that magnetic fields in steel structures are affected by thernpresence of fatigue cracks. A sign change of the out-of-plane magneticrnfield density can be observed in the vicinity of a crack. Therefore, therncrack can be detected by modern Hall probes. This makes it possible torndevelop a passive crack monitoring system based on magnetism.