Method and device including primary and auxiliary magnetic poles for nondestructive detection of structural faults

摘要

A magnetic inspection device for detecting structural faults in elongated magnetically permeable objects has two primary and opposite poles which induce a magnetic flux to place the object at least near magnetic saturation. At least one auxiliary pole is positioned on the inspection device between the primary poles and serves to change the level of the magnetic flux induced by the primary poles so as to induce eddy currents during relative movement of the inspection device and the object. At least one sensor positioned on the inspection device detects eddy current changes which are representative of structural faults.