Publication: Publication Date: 1 June 2016Testing Method:

The standard magnetic flux leakage testing (ML) signals of tangential and normal components were used for evaluating discontinuities. Based on the analysis of ML signal features and their generation mechanisms, the widely used peak-to-peak magnetic flux leakage (MFLpp) value, consisting of “negative” sidelobe features hidden in the test signals actually bears not only on the magnetic flux leakage from discontinuities but also all the magnetic behaviors including the magnetic flow bypass and its relevant “negative” magnetic region. These behaviors need to be modified as evaluation parameters for discontinuities. Unlike MFLpp, a new evaluation parameter, MFLp0, calculated by the height difference between the bump peak and baseline is provided, which eliminates the “negative” sidelobe features and agrees quite well with the single discontinuity ML contribution. The comparison of the evaluation parameters between traditional MFLpp and MFLp0 further indicate that MFLp0 decreases more slowly with the increase of liftoff or offset distance compared to MFLpp, which is helpful in reducing the influence on ML signals caused by unsteady liftoff/offset especially during the course of magnetic sensor shake. Meanwhile, the finite element method and experiments were conducted to confirm these comparisons. The clarity of the ML signal features, their generating mechanisms, and the provided MFLp0 value for evaluating discontinuities are intended to get accurate or even high precision evaluation for tested discontinuities.

References

- Afzal, M., and S. Udpa, “Advanced Signal Processing of Magnetic Flux Leakage Data Obtained from Seamless Gas Pipeline,” NDT&E International, Vol. 35, No. 7, 2002, pp. 449–457.
- Baskaran, R., and M.P. Janawadkar, “Defect Localization by Orthogonally Projected Multiple Signal Classification Approach for Magnetic Flux Leakage Fields,” NDT&E International, Vol. 41, No. 6, 2008, pp. 416–419.
- Centen, P., M.P.H. Weenink, and W. Schuurman, “Minimum-energy Principle for a Free-boundary, Force-free Plasma,” Plasma Physics and Controlled Fusion, Vol. 28, No. 1B, 1986, pp. 347–355.
- Chen, Z., G. Preda, O. Mihalache, and K. Miya, “Reconstruction of Crack Shapes from the MFLT Signals by using a Rapid Forward Solver and an Optimization Approach, IEEE Transactions on Magnetics, Vol. 38, No. 2, 2002, pp. 1025–1028.
- Dutta, S.M., F.H. Ghorbel, and R.K. Stanley, “Simulation and Analysis of
- 3-D Magnetic Flux Leakage,” IEEE Transactions on Magnetics, Vol. 45, No. 4, 2009, pp. 1966–1972.
- Förster, F., “New Findings in the Field of Non-destructive Magnetic Leakage Field Inspection,” NDT&E International, Vol. 19, No. 1, 1986, pp. 3–14.
- Joshi, A., L. Udpa, S. Udpa, and A. Tamburrino, “Adaptive Wavelets for Characterizing Magnetic Flux Leakage Signals from Pipeline Inspection,” IEEE Transactions on Magnetics, Vol. 42, No. 10, 2006, pp. 3168–3170.
- Katoh, M., N. Masumoto, K. Nishio, and T. Yamaguchi, “Modeling of the Yoke-magnetization in MFL-testing by Finite Elements,” NDT&E International, Vol. 36, No. 7, 2003, pp. 479–486.
- Mandache, C., and L. Clapham, “A Model for Magnetic Flux Leakage Signal Predictions,” Journal of Physics D: Applied Physics, Vol. 36, No. 20, 2003, pp. 2427–2431.
- Mandal, K., and D.L. Atherton, “A Study of Magnetic Flux-leakage Signals,” Journal of Physics D: Applied Physics, Vol. 31, No. 22, 1998, pp. 3211–3217.
- Minkov, D., and T. Shoji, “Method for Sizing of 3-D Surface Breaking Flaws by Leakage Flux,” NDT&E International, Vol. 31, No. 5, 1998, pp. 317–324.
- Ravan, M., R.K. Amineh, S. Koziel, N.K. Nikolova, and J.P. Reilly, “Sizing of 3-D Arbitrary Defects using Magnetic Flux Leakage Measurements,” IEEE Transactions on Magnetics, Vol. 46, No. 4, 2010, pp. 1024–1033.
- Romero Ramirez, A., J.S.D. Mason, and N. Pearson, “Experimental Study to Differentiate between Top and Bottom Defects for MFL Tank Floor Inspections,” NDT&E International, Vol. 42, No. 1, 2009, pp. 16–21.
- Snarskii, A.A., M. Zhenirovskyy, D. Meinert, and M. Schulte, “An Integral Equation Model for the Magnetic Flux Leakage Method,” NDT&E International, Vol. 43, 2008, pp. 343–347.
- Stratton, J.A., Electromagnetic Theory, McGraw-Hill, New York, New York, 1941.
- Sun, S., and Y. Kang, “A New MFL Principle and Method Based on Near-zero Background Magnetic Field,” NDT&E International, Vol. 43, No. 4, 2010a, pp. 348–353.
- Sun, Y., and Yihua Kang, “Magnetic Compression Effect in Present MFL Testing Sensor,” Sensors and Actuators A: Physical, Vol. 160, Nos. 1–2, 2010b, pp. 54–59.
- Sun, Y., and Yihua Kang, “The Feasibility MFL inspection for Omni-directional Defects under a Unidirectional Magnetization,” Selected Papers from the 14th International Symposium on Applied Electromagnetics and Mechanics, Part II, Vol. 33, No. 3, 2010c, pp. 919–925.
- Zhiye, D., R. Jiangjun, P. Ying, Y. Shifeng, Z. Yu, G. Yan, and L. Tianwei, “3-D FEM Simulation of Velocity Effects on Magnetic Flux Leakage Testing Signals,” IEEE Transactions on Magnetics, Vol. 44, No. 6, 2008, pp. 1642–1645.

Metrics

Usage | Shares |
---|---|

Total Views 173 Page Views |
Total Shares 0 Tweets |

173 0 PDF Downloads |
0 0 Facebook Shares |

Total Usage | |

173 |