Alternating Flux Leakage Testing Research Articles

Proposal of Electromagnetic Inspection Method of Outer Side Defect on Steel Tube With Steel Support Plate Using Optimal Differential Search Coils

Steel tubes are used in the heat exchanger in the petrochemical plant or the steam generator in the fast breeder reactor. Since these steel tubes in the heat exchanger or steam generator are stored as a bundle by the support steel plate (baffle), it is necessary to inspect the existence of defects from the inside of each tube. In these steel tubes, the defects are generated between the steel tube and the baffle at the outer side of steel tube. In this paper, problems in applying the alternating flux leakage testing method for the inspection of the outer side defect on steel tube with the baffle are examined using 3-D nonlinear FEM. Moreover, the differential type search coils that detect the leakage flux from the outer side defect on steel tube are proposed. The optimal dimension of the differential search coils is determined using the Rosenbrock's method or the evolution strategy.

Inspection of Outer Side Defect on Steel Tube with Support Steel Plate using Alternating Flux Leakage Testing

Inspection of Outer Side Defect on Steel Tube with Support Steel Plate using Alternating Flux Leakage Testing

Three-Dimensional FEM Analysis of Electromagnetic Inspection of Outer Side Defects on Steel Tube Using Inner Coil

Steel tubes are used in the heat exchanger in the petrochemical plant. Since these steel tubes in the heat exchanger are stored as a bundle, it is necessary to inspect the defects of these tubes from the inside of tube. In this paper, problems in applying the alternating flux leakage testing method for the inspection of the outer side defect on steel tube are examined using 3-D finite element method. The features of detecting property of outer side defect using an inner coil at low-frequency are investigated by analyzing the flux and current distribution. It is shown that the inspection of the outer side defect on a steel tube with cooling aluminum fin is possible using the proposed method

Proposal of detecting method of outer side crack by alternating flux leakage testing using 3-D nonlinear FEM

It is known that the detection of cracks on the outer side of steel plate is possible using the dc flux leakage testing. If the examined steel plate is thin, the outer side crack may be detected by alternating flux leakage testing. The merit of the alternating flux leakage testing method is that a cheap coil is used for detecting the leakage flux from the crack. In this paper, the inspection method of outer side crack of the steel plate using the alternating flux leakage testing is proposed. The component |Bx| of the leakage flux parallel to the surface of steel is utilized for detecting the crack. The behavior of leakage flux is examined using a three-dimensional edge-based hexahedral FEM (finite element method). It is shown that the outer side crack can be inspected by detecting the parallel (x-) component of leakage flux

Proposal of Detecting Method of Plural Cracks and Their Depth by Alternating Flux Leakage Testing: 3-D Nonlinear Eddy Current Analysis and Experiment

Alternating magnetic flux leakage testing is used for the detection of cracks on the surface of steel plates. In this paper, a new technique and precise inspection of how to detect plural cracks and their depth, which are located at very short distances from each other, is proposed. The leakage flux density of the parallel (x) component is used for the distinction of the plural cracks. Moreover, the depth of plural cracks is obtained by changing the exciting frequency and by detecting the perpendicular (z) component of leakage flux. The behavior of leakage flux is examined using three-dimensional edge-based hexahedral finite-element methods and compared with experimentation. The effect of hysteresis on magnetic phenomena is also examined.

Study on problems in detecting plural cracks by alternating flux leakage testing using 3-D nonlinear Eddy current analysis

The alternating magnetic flux leakage testing is used for the detection of cracks in a steel plate. A new technique of how to detect plural cracks, which are located at a very short distance from each other, using the parallel (x-) component of the leakage flux density is proposed. The behavior of leakage flux is examined using a three-dimensional edge-based hexahedral finite-element method. The effects of dimensions of search coils and cracks on the detection accuracy are illustrated.

3-D nonlinear eddy current analysis of factors affecting the evaluation of alternating flux leakage testing

3-D nonlinear eddy current analysis of factors affecting the evaluation of alternating flux leakage testing

Evaluation of alternating flux leakage testing using 3D nonlinear eddy current analysis and experiment

AbstractAlternating magnetic flux leakage testing has been applied in the inspection process for detecting cracks on the surface of steel. To develop a precise inspection method, the flux and eddy current distribution should be investigated taking into account the nonlinearity of steel. This paper describes 3D numerical analysis and experiment for this testing. The property of leakage flux from the crack of steel under ac excitation is investigated using the 3D edge‐based hexahedral finite element method. It is shown that the 3D analysis is obligatory in the precise analysis of magnetic phenomena of this testing. The effect of crack width and depth of leakage flux is clarified, and the relationship between the lift off and the amplitude of leakage flux is also illustrated. The characteristic of leakage flux is confirmed by a verification experiment. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 8–15, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10085