A scan type magnetic camera is developed to measure the residual stress generated in the welded part of a tubular-type power transmission tower. The change in strain of the ferromagnetic structure changes the magnetic domain distribution and therefore induces spontaneous magnetization. Thus, the magnetic field intensity distribution measured along the welds correlates with the change in stress generated in the structure. Residual stresses in welds occur more frequently in defects, and consequently, anomalies in the magnetic field strength distribution indirectly indicate the presence of weld failures. Conversely, the scanner is fabricated to be in a chevron shape with an angle of 150 degrees considering the cross section of the twelve-squared shape. Two cylinder-type wheels are arranged on each side of the chevron to prevent slipping. Linearly arrayed giant magnetoresistance (GMR) sensors are arranged on the weld line, and the magnetic field distribution can be measured along the weld. The correlation between the magnetic field intensity and defects is verified by comparing the magnetic field intensity distribution and the ultrasonic signal at the weld.
1. KEPRI report, 2012, Investigation of Failures of 154 kV Tubular-type Transmission Tower
2. Nagarkar V., Gordon J, Vasile S., Gothoskar P., Hopkins F., 1996, “High resolution X-ray sensor for nondestructive evaluation,” Nuclear Science Symposium and Medical Imaging Conference Record, 43, pp 1559-1563.
3. Ito Y., Masuda T., Nagao K., Matsuoka K., 1997, “Ultrasonic testing system for ERW mill,” IAS '97, 2, pp 866-872.
4. Le M., Kim J., Kim S., Lee J., 2016, “Nondestructive Testing of Pitting Corrosion Cracks in Rivet of Multilayer Structures,” International Journal of Precision Engineering and Manufacturing, 17(11), pp 1433-1442.
5. Uchanin V., Najda V., Hristoforou E., 2011, “The Development of Eddy Current Technique for WWER Steam Generators Inspection,” InTech, pp 145-164.
6. Le M., Lee J., Jun J., Kim J., 2013, “Quantitative evaluation of corrosion in a thin small-bore piping system using bobbin-type magnetic camera,” Journal Nondestructive Evaluation, 33(11), pp 56-63.
7. Mix P.E., 2005, “Magnetic Flux Leakage Theory,” in Introduction to nondestructive testing: a training guide, ed: Wiley-Interscience, pp. 73-78.
8. Dubov A., Kolokolnikov S., 2012, “Assessment of the Material State of Oil and Gas Pipelines Based on the Metal Magnetic Memory Method,” Welding in the World, 56(3), pp 11-19.
9. Roskosz M., Rusin A., Kotowicz j., 2010, “The metal magnetic memory method in the diagnostics of power machinery componen,” Journal of Achievements in Materials and Manufacturing Engineering, 43(1), pp 362-370.
10. Dubov A.A, 1995. Diagnostics of boiler tubes with usage of metal magnetic memory. Moscow: Energoatomizdat, pp 112.
11. Kim J., Le M., Park J., Seo H., Jung G., Lee J., 2017, “Measurement of residual stress using linearly integrated GMR sensor array,” Journal of Mechanical Science and Technology. Under review.
6 Page Views
0 PDF Downloads
0 Facebook Shares