A New Detection Method of the Surface Broken Wires of the Steel Wire Rope Using an Eddy Current Differential Probe

This paper describes a new detection method of the surface broken wires of the steel wire rope based on the conducting property of the rope. The surface of the steel wire rope is spiral. This spiral characteristic has influence on the eddy current (EC) response signal of the broken wires. Therefore, an EC differential probe is designed to improve the detection accuracy. First, a finite element analysis (FEA) of detecting the broken wires with the EC differential probe is conducted. When the probe scans above the intact part of the steel wire rope, the distribution of the EC in the rope just under the probe is symmetrical about the axis of the rope. Then the output voltage of the differential probe is almost zero. Accordingly, the output voltage is out of balance when the surface broken wires appear. The simulation results show that the effect of the surface alternating peaks and valleys of the rope on the EC response signal of the broken wires can be eliminated by the proposed EC differential probe. Then an experimental platform is built to carry out the scanning detection of different degrees of the surface broken wires. It can be observed that when the probe moves above the broken wires, the output voltage of the differential probe is significantly larger. Finally, the obtained scanning signal is post processed using the wavelet-based denoising method to improve the signal-to-noise rate. The experimental results show that the proposed method can effectively identify the damage degrees of the surface broken steel wires.