Magnetic Nondestructive Evaluation of Bending Fatigue Damage Using the Drag Force Method

The drag force method shows the potential for applications in the field of nondestructive evaluation of surface-localized material degradation. By analyzing the difference in drag force signature between both forward and backward movement directions, it is possible to deduce whether a part of material was, during a cyclic bending test, subjected to applied cyclic compression or tension. Moreover, the position of the localized stressed region can be indicated. Further quantitative analysis shows that the increase of flexural stress amplitude leads to an increased variation between the drag force difference corresponding to the localized stressed region, and the drag force difference of an unaffected part of the material. The drag force method shows higher sensitivity to surface-related properties than the field-metric magnetic NDE techniques