Application of Nondestructive Testing Based on DC Superconducting Quantum Interference Device

A nondestructive evaluation system based on DC Superconducting quantum interference device (DC SQUID) had been set up. Using the system the remnant magnetic field of a stainless steel sample crashed by force was tested. By electromagnetism excited, the magnetic field distribution on the surface of an aluminum slate with inner hole was measured. In addition the relation between SQUID response to defect and exciting frequency was discussed.