A comparative study of electromagnetic NDE methods and Quantum Well Hall Effect sensor imaging for surface-flaw detection in mild steel welds


Following on from the success and industrial interest in Non-Destructive Evaluation (NDE) applications of Quantum Well Hall Effect (QWHE) sensors, a study was conducted to establish the detection capabilities and general performance of low frequency QWHE imaging for surface-breaking flaw detection and comparing them to Magnetic Particle Inspection (MPI), Eddy Current Testing (ECT) and Alternating Current Field Measurement (ACFM).

In this study, a probe consisting of a QWHE sensor, illuminating electromagnet and sensor circuitry was controlled using an automated XY scanner with a measurement step size of 250 µm to simulate an integrated array of QWHE sensors of 250 µm pitch. This probe was used to apply a 3 mT 100 Hz frequency magnetic field to map the surface magnetic field and Magnetic Flux Leakage (MFL) response of five bespoke dressed mild steel weld samples made by Sonaspection.

These samples contained 15 surface-breaking flaws of varying length from 3 to 11 mm; mainly longitudinal toe and centre-line cracks, representative of certain typical industrial requirements of one of our industrial partners.

The same samples were also subjected to MPI, ECT and ACFM provided by leading industrial companies using their own qualified personnel, equipment and procedures. The outcomes and performance of each NDE technique including QWHE imaging were then compared and evaluated.