HTS-SQUID Magnetic Fatigue Detection in Stainless Steel 304
SQUID device
Recent advances in the fabrication of Superconducting Quantum Devices (SQUID) from High Temperature Superconducting (HTS) materials has opened up the possibility of transforming this highly sensitive magnetic field detector into powerful, portable nondestructive evaluation (NDE) probe suitable for industrial applications. The high sensitivity of SQUIDs can be used to synchronously measure the magnetization signals generated by nonmagnetic excitation such as strain, heat, and electrical or optical fields. Measuring a magnetization generated by a strain in a material, reflects the degree of coupling between the magnetic and elastic lattices in the material. Optical ultrasonic techniques are being used to keep the measurement process totally noncontacting. With this technique, new selectivity and capability is introduced into the NDE process for measurement of microstructural properties associated, for instance, with the critical state in high temperature superconducting tapes and fatigue in metals in tape or wire geometry's.
Small fatigue specimens can be easily measured with the HTS-SQUID system shown in the figure. The sketch shows the measurement geometry for scanning a specimen of arbitrary length with 5-10 mm standoff distance under the SQUID sensor.
Variations in fatigue produced magnetic phase precipitates in stainless steel 304 for different stressing levels toward failure.
Noncontacting Laser Ultrasonic Measurements in High Temperature Superconducting Tapes
A pulsed laser is used to locally heat the tape surface, launching elastic waves into and along the tape. Local wave motion is detected by high speed laser interferometry in both the time and frequency domains. The laser detection system employs a Fabry-Perot interferometer or newly developed photorefractive holographic methods to measure the elastic wave displacement locally and in a noncontacting manner along the tape. Measured surface waves yield local information on the thickness and uniformity of the tape fabrication process.
K.L. Telschow, F.W. Bruneel, J.B. Walter, and L. S. Koo, "Noncontacting Ultrasonic and Electromagnetic HTS Tape NDE," IEEE Trans. Appl. Superconductivity, 7(2), 1319-1322, June 1997 — 191kB PDF
Magnetic Critical Current Measurements in Tapes
The critical current of superconducting layers in tapes is generated and detected electromagnetically. Actual probe geometry and specimen tape are shown in the figure. The graph shows the magnetic flux penetration both in and out of the superconducting state. Spatial scanning provides uniformity and local critical current information.
K. L. Telschow, T.K. O'Brien, M. T. Lanagan and D. Y. Kaufman, "Local Critical Current Measurements on BiSrCaCuO/Ag Tape with an Electromagnetic Probe," IEEE Transactions on Applied Superconductivity 3 (1) part III, March 1993, 1643-1646.
K. L. Telschow and L. S. Koo, "An Integral Equation Approach for the Bean Critical State Model in Demagnetizing and Nonuniform Field Geometries," Phys. Rev. B, 50(10), 6923-6928, 1994
K.L. Telschow, L. S. Koo and K.K. Haulenbeek, "Low Field Magnetization Nondestructive Evaluation of HTS Tapes within the Bean Critical State Model," Inst. Phys. Conf. Ser. No. 148, Applied Superconductivity 1995, 423-426.— 45kB PDF
L. S. Koo and K. L. Telschow, "Method for Determining the Critical State Response of Superconductors in Tape Geometry," Phys. Rev. B53, 1996, 8743.
- Contacts:
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Ken Telschow, Ph.D., (208) 526-1264, Send E-mail
Vance A. Deason, (208) 526-2501, Send E-mail