Pulsed magnetic apparatus for in situ stress measurement

A pulsed electromagnetic apparatus has been designed and fabricated for the non-destructive evaluation of stress concentration in ferromagnetic material. The apparatus consists of a sensor, a pulsed field generator and a data acquisition system, which is developed in the LabView environment using a data acquisition card. The apparatus has been applied successfully to measure the hysteresis loops and magnetisation curves of Q235 steel under various fixed compressive stresses. The presented measurement for magnetically-open samples showed a good repeatability by locally magnetising the samples to saturation. The magnetic properties derived from the loops and curves are sensitive to applied stress. Remanence B _r is more accurate and suitable for characterising the stress in a material.