Nondestructive Testing of Elongated Ferromagnetic Members Based on Extruded Structure

Abstract

The traditional electromagnetic nondestructive testing probe structure includes magnets and yokes, and forms an excitation circuit with the wire rope. The wire rope is excited to a near-saturation state. The magnetic sensor is used for qualitative or quantitative detection of leakage flux from defects. The yoke is essential in the traditional excitation circuit. However, the use of a yoke in a detection probe of such an excitation mechanism has a large volume and is heavy. Through simulation, we improved the magnetization direction and installation position of the permanent magnets. Without a yoke, the permanent magnets were placed in the direction of co-extrusion. The wire rope was excited to near saturation in the permanent-magnet part. However, there was no excitation in the center of the two permanent magnets. The magnetic sensor was placed in the center of two permanent magnets to pick up the magnetic-flux-leakage signal for nondestructive testing of the steel wire rope. This method simplifies the permanent-magnet magnetization. The excitation probe with the yoke removed was also reduced in volume and weight. Through experimental testing, it was proven that the proposed shoving-magnetic-field structure and the traditional detection structure have the same detection effect.