Electromagnetic Multiphysics Sensing Nondestructive Testing

Abstract

With the continuous improvement of industrialization, there is a huge demand for non-destructive, non-invasive, and non-contact diagnostic mechanisms in maintaining the tested material integrity. Electromagnetic eddy current (EC) technology plays a high-efficient role in near-surface defects detection in metal materials field and it is competent in long-distance rail inspections due to its low energy consumption and high sensitivity. Meanwhile, magnetic flux leakage (MFL) detection methods are widely used to detect pipeline defects. However, it is limited by the detection orientation and magnetization. A new Electromagnetic Structured Coupling sensing of merging Alternating Current Field Measurement (ACFM) and MFL within a multi-parameter system is proposed. The novel structured sensing is highly sensitivity to the detection of both surface and subsurface defects. In order to increase the visualization ability of defect detection, based on a thermal field detection technology triggered by electromagnetic induction mechanism, eddy current thermography (ECT) is an emerging NDT technology which has wide application potential. The principle of ECT is that the excitation coil loaded with alternating current induces eddy current on the near-surface of the conductor material and generates Joule heat simultaneously. The existence of defects will affect the eddy current path, thermal diffusion and infrared radiation process, they will eventually be reflected in the thermograms which are recorded by the infrared camera. ECT also has the advantages of simple system, fast speed, high sensitivity, high resolution, rich spectrum, intuitive results and rich appreciable parameters.