International Journal of Applied Electromagnetics and Mechanics - Volume 59, issue 4

Authors: Fukuoka, Katsuhiro | Hasegawa, Ryo

Article Type: Research Article

Abstract: Non-uniform permeability distributions in steel materials reduce signal-to-noise (S /N ) ratios in eddy current testing (ECT). Therefore, steel materials must be magnetised to reduce magnetic noise. In this study, microcrack detection in spring steel materials using ECT was considered. An ECT system that was able to detect 40-μm-deep crack with S /N ratio of 3 or more was developed. In addition, the depth profile of microcracks using the detection signal was accurately estimated.

Keywords: Eddy current testing (ECT), microcrack, spring steel, signal-to-noise (S∕N) ratio, crack shape estimation

DOI: 10.3233/JAE-171123

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1267-1274, 2019

Authors: Sasayama, Teruyoshi | Enpuku, Keiji

Article Type: Research Article

Abstract: When testing ferromagnetic materials such as iron, low-frequency eddy-current testing (LF-ECT) is used to avoid the skin effect. However, the drawback of LF-ECT is that the signal becomes weak at low frequencies. Furthermore, when the specimen is covered with protective materials, the signal becomes even weak, owing to the large lift-off. To overcome these drawbacks, we utilize a high-temperature superconducting (HTS) coil and a pulse-width modulation (PWM) inverter in the LF-ECT method. Using an HTS coil and a PWM inverter, strong currents are conducted, and the change in the coil resistance can be easily measured. The small impedance change of …the HTS coil is detected by using a Maxwell bridge. The result demonstrates that a steel plate thickness of up to 20 mm can be estimated based upon the measurements of the change in the coil resistance, even when the lift-off is 98 mm. Show more

Keywords: High-temperature superconducting (HTS) coil, low-frequency eddy current testing, pulse width modulation (PWM) inverter

DOI: 10.3233/JAE-171117

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1275-1282, 2019

Authors: Yoshioka, Saijiro | Marumoto, Tatsuya | Gotoh, Yuji

Article Type: Research Article

Abstract: The crude oil which flows inside the steel tube of a heating furnace of an oil-refining plant is gasified by being heated with the burner from the surface outside the steel tube. Since this steel tube is used in Japan for 30 years or more, both the inner side and outer side of the steel tube is carburized. If the carburization depth is increased, the steel tube will be exploded suddenly and a big accident may occur. In this paper, the electromagnetic inspection method for measuring the carburized depth of both the inner side and the outer side of the …steel tube is proposed. The both depth is obtained by evaluating the flux density in layers with and without carburization in the steel tube using the 3-D nonlinear FEM. It is shown that the inspection for the both depth is possible by using the differential electromagnetic characteristics of the layers with and without carburization in the steel tube. Show more

Keywords: Electromagnetic non-destructive inspection, carburization steel tube, both surface and opposite side depth, 3-D finite element method

DOI: 10.3233/JAE-171112

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1283-1290, 2019

Authors: Wondrak, Thomas | Galindo, Vladimir | Stefani, Frank | Jacobs, Ralf T.

Article Type: Research Article

Abstract: The Contactless Inductive Flow Tomography is a procedure that enables the reconstruction of the global flow structure of an electrically conducting fluid by measuring the flow induced magnetic field outside the melt and subsequently solving the associated linear inverse problem. The accuracy of the reconstruction depends on the number and the distribution of the sensors around the vessel. The aim of this investigation is to find a sensor configuration for the reconstruction of a temperature driven flow of a liquid metal in a cylindrical vessel that employs as few sensors as possible without any significant loss of accuracy.

Keywords: Contactless Inductive Flow Tomography, magnetohydrodynamics, integral equations, inverse problems

DOI: 10.3233/JAE-171250

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1291-1296, 2019

Authors: Wang, Dabin | Le, Minhhuy | Kim, Jungmin | Nam, Yun Gwan | Lee, Jinyi

Article Type: Research Article

Abstract: Bleed air ducts are used in aircraft to de-ice fuselage and to heat the cockpit by transferring engine heat. These ducts are made of titanium tubes and are routed in the airframe. Over long-term operation, cracks may appear in the bleed air duct tubes because of the action of moisture and corrosive gas. Therefore, we proposed an electromagnetic testing system for the nondestructive testing of bleed air duct tubes. An unmanned crack detection algorithm, which based on analysis of electromagnetic field distribution, was developed. In addition, locations of cracks in the circumferential and axial directions of the bleed air duct …tube were determined. Show more

Keywords: Bleed air duct, bobbin-type integrated Hall sensor array, electromagnetic testing, crack detection

DOI: 10.3233/JAE-171233

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1297-1303, 2019

Authors: Huang, Xiaoming | Wu, Jianbo | Sun, Yanhua | Kang, Yihua

Article Type: Research Article

Abstract: In magnetic flux leakage (MFL) testing, the scraggly surface of the objects actually consists of “concave” and “bump” defects, however, MFL inspection mechanism is only explained based on magnetic field leakage in the vicinity of the “concave” defects. In order to richen the MFL theory and improve the detection signal analysis, 3D magnetic flux leakage for three typical shapes of “concave” and “bump” defects (i.e., the conical, spherical and rectangular defects) are investigated by building magnetic dipole models. It was found that “bump” defects generate a total different 3D MFL distribution from the “concave” defects, including x , y …and z components of the MFL. Besides, numerical simulations by finite element method are conducted to validate the magnetic dipole models. Show more

Keywords: MFL (magnetic flux leakage), magnetic dipole model, finite element simulation, “concave” and “bump” defects

DOI: 10.3233/JAE-171169

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1305-1312, 2019

Authors: Zhou, Jinhai | Xu, Jiang

Article Type: Research Article

Abstract: Fatigue is one of the common damages in strands for long-term using. Therefore, the detection of fatigue damage in strands is very important to guarantee its reliable operation. In this paper, the feasibility of fatigue damage detection of strands using magnetostrictive guided waves is studied. The coupling efficiency of magnetostrictive guided waves is used to distinguish the fatigue damage of strands. A direct current solenoid magnetizer is used to get the relationship between the strength of bias magnetic field and the peak to peak value of magnetostrictive guided wave signal on fatigue and no fatigue area of a strand. The …coupling efficiency of excitation and receiving process of magnetostrictive guided wave is obtained by the relationship. The results show that the fatigue damage reduces the coupling efficiency of excitation and receiving process of magnetostrictive guided waves. Besides, the optimal bias magnetic field strength which makes the highest coupling efficiency of fatigue area is larger than no fatigue area. These results well verify the feasibility of using magnetostrictive guided wave technology to detect fatigue damage of strands. This study provides a new method for fatigue detection of strands. Show more

Keywords: Strands, fatigue damage, magnetostrictive effect, optimal bias magnetic field, coupling efficiency

DOI: 10.3233/JAE-171153

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1313-1320, 2019

Authors: Li, Hongmei | Zhang, Fuchen | Yang, Bin | Li, Yong

Article Type: Research Article

Abstract: Metal Magnetic Memory Testing (MMMT) technique has been extensively used as a qualitative method to test the position of possible damages in ferromagnetic metal structures. The magneto-mechanical effect and the leakage of magnetic field caused by the discontinuity of structure are largely regarded as two of the critical factors influencing the MMMT signals. In this paper, experiments and calculations were carried out to explore the influences of discontinuous structures on the MMMT signals. Two types of specimens fabricated with different defects were stretched by a tensile testing machine. Leakage magnetic field signals above the specimens were measured by a fluxgate-based …magnetometer. Magnetic charge distributions around the discontinuous structures were calculated based on a reconstruction algorithm using the measured leakage magnetic field signals. The magnetic charge distribution patterns around two different discontinuous structures were compared and some characteristics are summarized. Show more

Keywords: Metal magnetic memory, discontinuous structure, calculated magnetic charge, distribution characteristic

DOI: 10.3233/JAE-171127

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1321-1329, 2019

Authors: Chikami, Tatsuya | Fukuoka, Katsuhiro

Article Type: Research Article

Abstract: In this study, we developed and characterised a method for detecting microcracks in steel materials by eddy current testing (ECT). Magnetic saturation ECT is applied because magnetic noise is generated by steel materials during ECT. Although direct-current (DC) magnetisation is generally used for magnetic saturation ECT, the use of alternate-current (AC) magnetisation offers several advantages. When using AC magnetisation for surface flaw detection, the magnetisation is not influenced by the thickness of the test object owing to the skin effect; therefore, demagnetisation is unnecessary. In this study, we evaluated microcrack detection results obtained using AC magnetisation ECT with different synchronous …positions (conditions) of the magnetisation and ECT; and identified the optimum synchronous position. In addition, the magnetisation distribution in a test object was evaluated by the finite element method analysis and the flaw detection results were verified. Show more

Keywords: Eddy current testing (ECT), steel material, AC magnetisation, microcrack, uniform eddy current probe, magnetic saturation ECT

DOI: 10.3233/JAE-171125

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1331-1339, 2019

Authors: Xu, Jiang | Chen, Guang | Zhou, Jinhai | Li, Yong

Article Type: Research Article

Abstract: Recently, some researchers found that there was a notchfrequency phenomenon when the guided wave propagated in the pre-stressing strand under tension. The notch frequency has a linear relationship with the logarithm of tension. According to their results, a force measurement method for the strand was proposed. However, fatigue damage is often encountered inservice strands. In this paper, we study the effect of fatigue damage on the notch frequency of the pre-stressing strand under tension based on the magnetostrictive guided wave technology. The relationship between the cyclic loading times and the notch frequencies under the same tension is obtained from four …pre-stressing strands. The results show that the notch frequencies are variable with the cyclic loading times. At first, the notch frequency increases slightly, then decreases suddenly, and then increases almost linearly with increasing of the cyclic loading times. Our research indicates that the tension measurement method by using the notch frequency for strands should consider the effect of the fatigue damage. Moreover, the notch frequency can also be employed to evaluate the fatigue damage of strands after 1.85 million cyclic loading times. Show more

Keywords: Notch frequency, fatigue damage, pre-stressing strand, guided wave, magnetostrictive effect

DOI: 10.3233/JAE-171109

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1341-1348, 2019