Characterization of Surface-Breaking Cracks Using One Tangential Component of Magnetic Leakage Field Measurements

We propose a procedure for full characterization of rectangular surface-breaking cracks based on measurements of only one tangential component of the magnetic field with the magnetic flux leakage (MFL) technique. The parameters of interest include orientation, length, and depth of the cracks. We assume that the length and the depth of the investigated cracks are much larger than the crack width, so that the variation of the MFL response with respect to the width is negligible. Our procedure employs fast direct methods that provide reliable estimation of the crack parameters in three separate consecutive steps. We propose denoising and correction techniques as well. We confirmed the accuracy of the methods by simulations based on the finite-element method (FEM) as well as by experimental MFL observations. A procedure is proposed for full characterization of rectangular surface breaking cracks based on measurements of only one tangential component of the magnetic field with the magnetic flux leakage (MFL) technique. The parameters of interest include orientation, length and depth of the cracks. We assume that the length and the depth of the investigated cracks are much larger than the crack width such that the variation of the MFL response with respect to the width is negligible. The proposed procedure employs fast direct methods which provide reliable estimation of the crack parameters in three separate consecutive steps. De-noising and correction techniques are proposed as well. The accuracy of the proposed estimation methods is examined via simulations based on the finite element method (FEM) as well as experimental MFL data.

[1]  L. Udpa,et al.  Adaptive Wavelets for Characterizing Magnetic Flux Leakage Signals from Pipeline inspection , 2006, INTERMAG 2006 - IEEE International Magnetics Conference.

[2]  Satish Udpa,et al.  Advanced signal processing of magnetic flux leakage data obtained from seamless gas pipeline , 2002 .

[3]  David L. Atherton,et al.  Finite element calculation of magnetic flux leakage detector signals , 1987 .

[4]  D. Jiles,et al.  Analytical approach for fast computation of magnetic flux leakage due to surface defects , 2005, INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005..

[5]  Gui Yun Tian,et al.  3D magnetic field sensing for magnetic flux leakage defect characterisation , 2006 .

[6]  L. Tsay,et al.  Sulfide stress corrosion cracking and fatigue crack growth of welded TMCP API 5l X65 pipe-line steel , 2001 .

[7]  G. Park,et al.  Improvement of the sensor system in magnetic flux leakage-type nondestructive testing (NDT) , 2002 .

[8]  Baldev Raj,et al.  A new optical technique for detection of defects in ferromagnetic materials and components , 2000 .

[9]  Alberto Pignotti,et al.  Nonlinear model of flaw detection in steel pipes by magnetic flux leakage , 1995 .

[10]  William Lord.  Electromagnetic Methods of Nondestructive Testing , 1985 .

[11]  F. M. Haggag.  Innovative SSM Technology Determines Structural Integrity of Metallic Structures : Example Applications for Pressure Vessels and Oil and Gas Pipelines , 2006 .

[12]  M. Sadiku.  Numerical Techniques in Electromagnetics , 2000 .

[13]  S B Palmer,et al.  The magnetic leakage field of surface-breaking cracks , 1986 .

[14]  R. Polikar,et al.  Adaptive noise cancellation schemes for magnetic flux leakage signals obtained from gas pipeline inspection , 2001, 2001 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.01CH37221).

[15]  Lynann Clapham,et al.  A model for magnetic flux leakage signal predictions , 2003 .

[16]  David L. Donoho,et al.  De-noising by soft-thresholding , 1995, IEEE Trans. Inf. Theory.

[17]  Wenhua Han,et al.  A modified wavelet transform domain adaptive FIR filtering algorithm for removing the SPN in the MFL data , 2006 .

[18]  R. C. Juvinall.  Engineering Considerations of Stress, Strain, and Strength , 1967 .

[19]  Satish S. Udpa,et al.  Invariance transformations for magnetic flux leakage signals , 1996 .

[20]  P. Wild,et al.  Magnetic flux leakage inspection of tailor-welded blanks , 2002 .

[21]  Jin Tao,et al.  Research on a Recognition Algorithm for Offshore-Pipeline Defects during Magnetic-Flux Inspection , 2005 .