A multi-frequency NDT system for imaging and detection of cracks

Abstract

A real time simultaneous multi-frequency electromagnetic (EM) scanning instrument which operates from 5 kHz to 200 kHz in a step of 5 kHz has been developed. The instrument is based on the latest field-programmable gate array (FPGA) platform and is able to deliver data rate up to 256k/s (32k sample per channel). The system is applied to scanning cracks and defects on stainless steel plates and carbon fibre-reinforced polymer (CFRP) plates. Experiment results show that cracks can be visually identified in the images generated from scanning.