Scanning waveform analysis of a room-temperature-probe SQUID NDE system

A room-temperature-probe SQUID NDE system with high mobility and excellent spatial resolution has been developed for detecting the internal cracks of metallic material. Here, the sensing probe is composed of quadruple excitation coils and double D-shape pickup coils. It is connected to the input coil surrounding the SQUID sensor to transfer a magnetic field of eddy current. Following the previous demonstration of its good spatial resolution and high sensitivity, a signal mechanism for the scanning waveform is further proposed in this study to explain the scanning non-directionality of the system and analyze the internal cracks. Both fine and wide single cracks and multi-cracks with dense and spare intervals are valid. Moreover, the model is in good agreement with the test results.