Bending experimental study on metal magnetic memory signal based on von Mises yield criterion

摘要

Metal magnetic memory (MMM) is an effective magnetic method in evaluating stress concentration and early damage. To get the normal component of surface spontaneous magnetic signal of the specimen under different loads, three-point flexural test and four-point flexural test of Q235B steel specimens were carried out. Von Mises yield criterion was employed to calculate equivalent stress. The results show that the magnetic signal curve has a strong regularity during loading stage. For a three-point bending specimen, the magnetic signal curve presents "triangle" distribution. For a four-point bending specimen, the magnetic signal curve of the flange and web present "trapezoid" and "saddle" distribution, respectively. The symmetry of magnetic signal curve can be used to determine whether a specimen is under eccentric compression. The main tendency and local extrema of equivalent stress are coinciding with that of magnetic signal. A reasonable qualitative correlation is found between the distribution of equivalent stress and magnetic signal.