Early stage fatigue damage characterization in aluminum alloys and stainless steels with Meandering Winding Magnetometer technology

It is shown that pre-crack and early stage fatigue damage can be characterized by a new sensor technology, the Meandering Winding Magnetometer (MWM). This new technology consists of a conformable sensor, the MWM, and associated measurement grids that are model based. Measurements on type 304 stainless steel indicated that damage is readily detectable at 20% of life (N/N F = 0.2) and causes a 1.5% conductivity loss. Near failure the conductivity loss in the crack-free region was approximately 4%. In 2024 aluminum the onset of detectable fatigue damage was observed at approximately 50% of total life. For the probe geometry employed, the conductivity loss in the microcrack region iust prior to failure was 7%: in the macrocrack region it reached 13%.