International Journal of Applied Electromagnetics and Mechanics - Volume 33, issue 3-4

Authors: Yamamoto, Toshihiro | Takagi, Toshiyuki | Uchimoto, Tetsuya

Article Type: Research Article

Abstract: This paper proposes a method to reduce noise and extract crack indications from detection signals of a 48-channel ECT system based on its signal phase characteristics. Because this 48-channel ECT system performs two kinds of scanning patterns: U-scan and T-scan, and obtains two sets of signal distributions for one scanning area simultaneously, the proposed method uses a two-stage process that includes so-called main filter and sub filter. Using these two filters imposes more strict conditions on …extracting crack indications so as to reduce more noise. The experimental results show that the proposed filtering method is effective to extract only crack indications from detection signals including complicated noises. Show more

Keywords: Nondestructive inspection, crack detection, eddy current testing, noise reduction, phase characteristics

DOI: 10.3233/JAE-2010-1236

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1179-1184, 2010

Authors: Yang, Fan | Kang, Lihong | He, Wei | Duan, Huiqing

Article Type: Research Article

Abstract: The magnetic field (MF) produced by the bus bars in the urban distribution substation can pollute the environment, and shielding measures should be taken. In the paper the model to calculate the power frequency magnetic field around an urban distribution substation is presented firstly, then the calculation on the magnetic field produced by the three-phase bus bars was carried out, and influence on the magnetic field distribution caused by different parameter was analyzed. The results indicate …that to decrease the magnetic field in the upper floor, it's better to make the distance between the bus bars within 0.4 m, and the height of the bus bars within 0.1 m. Then the shielding measures to eliminate the magnetic field in the upper floor residential housing were investigated, and results indicate that the smaller size of the reinforced grid and the greater diameter of the reinforced bar, the better is the shielding effectiveness. For the shielding of the magnetic field in the up floors, the shielding effectiveness can reach 33.52 dB with an 8 mm thick shielding steel plate used in the floorboard. Considering the economic cost, the shielding grid made of 8# reinforced bars (net size: 0.10*0.10 m^{2} , the diameter of the reinforced bar is 8 mm) is the best for the MF shielding. Show more

Keywords: Magnetic field, distribution substation, bus bar, shielding, concrete and reinforced grid

DOI: 10.3233/JAE-2010-1237

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1185-1194, 2010

Authors: Kosaka, Daigo | Kojima, Fumio | Yamaguchi, Hiroshi

Article Type: Research Article

Abstract: This paper aims at a quantitative nondestructive evaluation of pipe wall thinning using an electromagnetic acoustic transducer. Type 304 stainless steels sample specimens that are fabricated by a semi ellipse were provided for our experiments. First, results of measurement and simulation experiments are shown using the provided test samples. The variety of simulation results showed good agreement with laboratory experimental results. Second, the sensitivity of pulse echo signals with respect to corrosion geometry of pipe wall …is investigated. Finally, the feasibility studies of our sizing methodology are summarized for evaluating FAC and early LDI test samples. Show more

Keywords: Noncontact evaluation, electro magnetic acoustic transducer, flow-accelerated corrosion, liquid droplet impingement erosion, piping

DOI: 10.3233/JAE-2010-1238

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1195-1200, 2010

Authors: Zhang, Weimin | Yuan, Junjie | Mao, Xinyan | Fan, Zhang

Article Type: Research Article

Abstract: Semisinusoidal loads with constant amplitude or increasing amplitude were applied on steel specimens separately in earth magnetic field. The testing results indicated that the variation degree of the magnetic signals was mostly determined by the amplitude of the applied loads. With the load amplitude increasing to plastic loading stage, zero-crossing of the H_{p} (y) distribution curve occurred and stayed at certain position where the curve has large gradient. The zero-crossing position was …exactly the necking point and unchangeable after unloading, which suggested that the plastic failures and microdefects can be identified through testing the H_{p} (y) signals. Show more

Keywords: Cyclic stress, metal magnetic memory effect, magnetic testing, plastic deformation

DOI: 10.3233/JAE-2010-1239

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1201-1209, 2010

Authors: Oshima, Kenichi | Kojima, Fumio

Article Type: Research Article

Abstract: Our study is aimed at developing a practical method for identifying the cracking geometrical shape from surface image obtained by scanning eddy current testing (ECT) probe. A various type of fatigue cracks are made from compact tension (CT) specimen of aluminum alloy samples. ECT signals are collected for those test samples using the absolute pancake probe. We discuss the features of ECT detecting signals of fatigue cracking which are different from electric discharge machining (EDM) crack …signals. Show more

Keywords: Eddy current testing, nondestructive inspection, fatigue cracking

DOI: 10.3233/JAE-2010-1240

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1211-1217, 2010

Authors: Dong, Shiyun | Wang, Dan | Xu, Binshi | Shi, Changliang

Article Type: Research Article

Abstract: A novel method for quantitative characterization of stress concentration based on the tangential component of metal magnetic memory (MMM) signal, H_{p}(x) , was studied via fatigue testing and MMM testing of notched plate samples. In this research, the changing regularity of H_{p}(x) signals is found out. A method to calculate stress concentration factor from H_{p}(x) signals is established, and a new conception of magnetic stress concentration factor …K_{H} , H_{p}(x)_{max} /H_{p}(x)_{ave} , is put forward to quantitatively characterize stress concentration in mechanical components. The research provides the potential possibility of quantitative inspection for metal magnetic memory testing. Show more

Keywords: Stress concentration, metal magnetic memory, quantitative characterization, magnetic stress concentration factor

DOI: 10.3233/JAE-2010-1241

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1219-1223, 2010

Authors: Preda, Gabriel | Rebican, Mihai | Hantila, Florea Ioan

Article Type: Research Article

Abstract: Pulse eddy currents are proposed for detection of cracks in structural conductive, non-magnetic parts. The rectangular pulse accounts for a multi-frequency analysis with the lower harmonics pentrating deeper in the material. An integral-FEM method for simulation of transient eddy-currents and model of defects as zero-thickness, two-dimensional flaws are used. Difference signals peak value depends on crack depth and the peak value moment is delayed for smaller outer defects. The method is effective for defects buried deep …under the surface. Show more

Keywords: Nondestructive testing, pulse eddy-currents, zero-thickness flaws

DOI: 10.3233/JAE-2010-1242

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1225-1229, 2010

Authors: Song, Kai | Kang, Yihua | Sun, Yanhua | Qiu, Chen | Su, Jianke

Article Type: Research Article

Abstract: A variety of defects in continuous steel strip may result in accidents. Traditional MFL (Magnetic flux leakage) testing method can lead to large blind area because steel strip is too broad to be rotated. A new MFL testing method that can inspect omni-directional cracks in steel strip is introduced in this paper. This method is characterized basically by the deep saturation state of steel strip generated. The property of inspection is investigated using 3-D finite element …method. Waveform configurations of the experimental results agree with that of the theoretical predictions. Automatic inspecting equipment has been developed based on the new MFL method principle. Show more

Keywords: MFL testing, strong longitudinal magnetization, omni-directional cracks, steel strip

DOI: 10.3233/JAE-2010-1243

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1231-1236, 2010

Authors: Tanaka, Yoshikazu | Tamoto, Eiji | Fujimoto, Yukio

Article Type: Research Article

Abstract: A contact-type sensor using a piezoelectric film for the guided wave measurement is presented in this paper. Because the piezoelectric film has a piezoelectric effect and flexibility, it is thought to be useful for the guided wave inspection. Thus, a contact-type sensor using a piezoelectric film is presented and some experiments are performed. The experimental results show that the contact-type sensor can receive the T(0,1) mode of the guided wave.

Keywords: Guided wave, Nondestractive inspection, Piezoelectric film

DOI: 10.3233/JAE-2010-1244

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1237-1244, 2010

Authors: Zhou, Zhenggan | Huang, Fengying | Lin, Junming

Article Type: Research Article

Abstract: The conductive or ferromagnetic material with coating layer can be tested by electromagnetic acoustic transducer (EMAT) without pre-treatment. The electro-acoustic converting occurred on the surface of the specimens is mainly concentrated within the skin depth of the eddy current. Thus, the electromagnetic property of the material surface has great influence on the efficiency of EMAT. The eddy current densities induced in the coating of specimens and Lorentz force are calculated with finite element software ANSYS …when EMAT is applied to the 20 steel-based specimens coated with different electrical conductivity materials. With shear wave EMAT, the specimens are tested and the relationship between the amplitude of the first echo wave signal and electrical conductivity of the coating is analysed. The theoretical analysis and experimental results show that under the fixed excitation condition, the higher the electrical conductivity of the coating material, the larger the induced eddy current density and Lorentz force are; the increase of the electrical conductivity of the coating is beneficial to the electromagnetic acoustic excitation and the acquisition of higher voltage amplitudes of the echo waves signals. Show more

Keywords: EMAT, eddy current, lorentz force, FEM, ANSYS

DOI: 10.3233/JAE-2010-1245

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 33, no. 3-4, pp. 1245-1252, 2010