Detection of crack in austenitic stainless steel with high sensitive magnetic sensor

This study attempt to detect cracks in austenitic stainless steel by Magnetic Flux Leakage Technique with a high sensitive magnetic sensor. If a specimen is subjected to the stress, the magnetic properties change or the martensite phase is formed due to the plastic deformation or the stress induced phase transformation. When the generated phase is martensite, this local change of magnetic property can be detected by measuring the Magnetic Flux Leakage with a sensitive magnetic sensor. In order to verify the MFL due to the above effect, we first calculate the MFL in the vicinity of a crack in austenitic stainless steel by the use of FEM analysis. Subsequently, we measure the MFL with respect to a SUS304 specimen with fatigue crack and a welded SUS316 specimen with SCCs. It is found that the location and the shape of the welded part, the fatigue crack and the SCC can be visualized by the MFLT with a high sensitive magnetic sensor. (author)