Low-frequency nondestructive analysis of cracks in multilayer structures using a scanning magnetic microscope

Abstract

The use of a scanning magnetic microscope (SMM) with a high temperature superconducting quantum interference device (SQUID) for quantitative measurements in eddy current nondestructive analysis (NDA) is presented. The SQUID has been used to detect the weak magnetic field variations around a small defect, close to a structural part generating an intensive magnetic field. The experimental data for a deep crack close to a rivet in a multilayer conducting plate have been taken in a RF-shielded environment and discussed in the light of the theoretical predictions. The results show that eddy current NDA can distinguish subsurface crack signals from wider structural signals, with defects located 10 mm below the surface. Moreover, in order to visualize the structure of the probing current when a circular induction coil is used, the simulation of eddy currents in a thick unflawed conducting plate has been carried out.

Design and analysis of a hybrid magnetic shielding system: application for the magnetic non-destructive testing of circuits

“…With the rapid development of weak magnetic signal detection, high-precision magnetic sensors, such as superconducting quantum interference devices (SQUIDs), have been widely used. With the use of these detectors, the accuracy of magnetic field detection has been highly improved and they are applied in various domains, including encephalography [1], spacecraft [2] and crack detection [3]. In these areas, magnetic non-destructive testing is a core concept and has been a popular concern for its research value and business prospects.…”