Welded joints in a tubular-type transmission tower (TTT) are potential locations for stress concentration zones (SCZs) owing to the thermal effects caused by welding and external loads during operation. The SCZs degrade the quality of welded joints and need to be inspected at an early stage by nondestructive testing methods. In this study, a metal magnetic memory (MMM) technique is presented for the inspection of SCZs in the welded joints of a TTT. The MMM system uses four pairs of fluxgate sensors to measure the weak residual magnetic field on the welded surface without an external magnetic source; each fluxgate sensor pair can measure the normal and tangential magnetic field components on the welding surface. The SCZs can be areas of welding discontinuities or of early stages of discontinuity initiation (before the existence of defects); thus, not all SCZs inspected by the MMM technique will have defects. For further evaluation of the state of the welds at the SCZs, the A-scan ultrasonic testing technique is used to determine the existence of discontinuities at the SCZs that were detected by the MMM technique. Thus, a fast and reliable assessment result of the welded joints can be obtained. A failed 154 kV TTT welding specimen was used in the experiment, and it was found that defects existed in some of the SCZs.
Bao, S., M. Fu, Y. Gu, and H. Lou, 2017, “Quantitative Characterization of Stress Concentration of Low-Carbon Steel by Metal Magnetic Memory Testing,” Materials Evaluation, Vol. 75, No. 3, pp. 397–405.
Dapino, M.J., R.C. Smith, F.T. Calkins, and A.B. Flatau, 2002, “A Coupled Magnetomechanical Model for Magnetostrictive Transducers and its Application to Villari-Effect Sensors,” Journal of Intelligent Material Systems and Structures, Vol. 13, No. 11, pp. 737–747.
Dubov, A.A., 1995, Diagnostics of Boiler Tubes with Usage of Metal Magnetic Memory, Moscow: Energoatomizdat, p. 112.
Dubov, A.A, and S. Kolokolnikov, 2012, “Assessment of the Material State of Oil and Gas Pipelines Based on the Metal Magnetic Memory Method,” Welding in the World, Vol. 56, Nos. 3–4, pp. 11–19.
Dubov, A.A, A. Dubov, and S. Kolokolnikov, 2014, “Application of the Metal Magnetic Memory Method for Detection of Defects at the Initial Stage of Their Development for Prevention of Failures of Power Engi-neering Welded Steel Structures and Steam Turbine Parts,” Welding in the World, Vol. 58, No.2, pp. 225–236.
Ito, Y., T. Masuda, K. Nagao, and K. Matsuoka, 1997, “Ultrasonic Testing System for ERW Mill,” IAS ‘97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting, 5–9 October 1997, New Orleans, LA, doi: 10.1109/IAS.1997.628963.
KEPRI, 2012, “Investigation of Failures of 154 kV Tubular-type Transmis-sion Tower”, internal report, KEPRI, Korea.
Le, M., J. Jun, J. Kim, and J. Lee, 2013, “Nondestructive Testing of Train Wheels Using Differential-Type Integrated Hall Sensor Matrixes Embedded in Train Rails,” NDT & E International, Vol. 55, pp. 28–35.
Le, M., J. Kim, S. Kim, and J. Lee, 2016, “Nondestructive Testing of Pitting Corrosion Cracks in Rivet of Multilayer Structures,” International Journal of Precision Engineering and Manufacturing, Vol. 17, No.11, pp. 1433–1442.
Le, M., H. Vu, J. Kim, C.S. Angani, and J. Lee, 2014, “Quantitative Evalua-tion of Corrosion in a Thin Small-Bore Piping System using Bobbin-Type Magnetic Camera,” Journal of Nondestructive Evaluation, Vol. 33, No. 1, pp. 74–81.
Mix, P.E., 2005, “Magnetic Flux Leakage Theory,” in Introduction to Nonde-structive Testing: A Training Guide, 2nd edition, Wiley, Hoboken, New Jersey, pp. 73–78.
Nagarkar, V.V., J.S. Gordon, S. Vasile, P. Gothoskar, and F. Hopkins, 1996, “High Resolution X-ray Sensor for Non-Destructive Evaluation,” IEEE Transactions on Nuclear Science, Vol. 43, No. 3, pp. 1559–1563.
Roskosz, M., 2011, “Metal Magnetic Memory Testing of Welded Joints of Ferritic and Austenitic Steels,” NDT & E International, Vol. 44, No. 3, pp. 305–310.
Uchanin, V., and V. Najda, 2011, “The Development of Eddy Current Technique for WWER Steam Generators Inspection,” Steam Generator Systems: Operational Reliability and Efficiency, ed. Valentin Uchanin, InTech, pp. 145-164.
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