Abstract Summary
Fatigue in steel components is of major importance for the safety of infrastructures. Early detection of fatigue cracks in such structures means that appropiate repairs can be performed before the damage becomes too severe. Despite the need for a reliable early detection method for this type of damage, detection is notoriously difficult. Therefore, there is a need for innovative detection methods to improve or complement the current monitoring systems. In the search for a new method to monitor the early growth of fatigue cracks, the magnetic stray field generated by the magnetisation of the steel component becomes interesting because the strength and direction of the magnetic stray field are strain-dependent. The behaviour of the magnetic field during fatigue loading has received little research so far. Our main research question is if the magnetic stray can provide a sufficient information in the onset and development of this damage. To investigate the evolution of the magnetic stray field under fatigue loads, laboratory tests with a cyclic tensile load have been performed on several CT-specimens made of steel with different stress ratios. During each test, data were collected using four different measurement techniques: a conventional crack gauge (CG), digital image correlation (DIC), acoustic emission (AE) sensors and a magnetic field (MF) sensor. By comparing the data from these different measurement techniques, the effectiveness of magnetic field sensors in the early detection of fatigue crack growth is assessed.
