Novel Remote NDE Technique for Pipes Combining HTS-SQUID and Ultrasonic Guided Wave

This paper describes basic research of a novel remote nondestructive evaluation (NDE) technique for pipes combining high-sensitive high-temperature superconductor superconducting quantum interference device (HTS-SQUID) and ultrasonic guided waves. Measurements of magnetic signals due to acoustic emission (AE) and ultrasonic-guided waves on a steel pipe were demonstrated using an HTS-SQUID gradiometer. To convert the guided waves into magnetic signals, the inverse magnetostrictive effect of a magnetized nickel thin plate glued around the pipe's circumference was utilized. An AE sensor and alternative magnetized nickel thin plate with wound coil were used as AE and ultrasonic-guided wave transmitters. Magnetic signals due to AE and ultrasonic guided waves were successfully measured by the HTS-SQUID gradiometer, which was set above the nickel film with a lift-off of about 2 mm.