Papers by Keyword: EMAT

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Authors: Ik Keun Park, Yong Kwon Kim, Tae Hyung Kim, Yong Sang Cho
Abstract: This paper capitalizes on recent advances in the area of non-contact ultrasonic guided wave techniques. The present technique provides a decent method for nondestructive testing of defect thinning simulating a hidden corrosion or FAC(Flow Accelerated Corrosion) in a thin aluminum plate. The proposed approach is based on using EMAT(Electro-magnetic Acoustic Transducer) to generate guided waves and detect the wall thinning without any coupling. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cut-off measurement allows us to monitor a defect thinning level while a group velocity change can be used to quantify the thinning depth.
Authors: Yang Zhao, Zhong Qing Jia, Guo Rui, Jian Ma, Jiang Feng Song, Ji Hua Sun, Shuai Liu
Abstract: Detection and characterization of defects in metal parts in industrial and commercial settings has typically been carried out by nondestructive ultrasonic inspection systems. The aim of present work is to propose a kind of non-contact nondestructive testing system based on the laser and electro-magnetic acoustic transducer (EMAT) techniques, which is suitable to inspect the defects in metal material. The maximum lift-off value (LOV) of the system is 10 mm. Wavelet threshold method (WTM) is employed to improve the signal to noise ratio (SNR), and the values of SNR increase to 67.42 dB and 64.66 dB for the case of LOV=0 mm and LOV=10 mm, respectively.
Authors: Yong Moo Cheong, Hyun Kyu Jung, Young Suk Kim
Abstract: The leakage of a pipe in nuclear power plants is a significant concern from the point of view of nuclear safety. Because of the geometrical complexity of a pipe and an inaccessibility due to a high radiation, it is difficult to inspect it by the conventional ultrasonic methods. The guided ultrasonic method can be useful for the inspection of a pipe in those harsh environments. Based on the analysis of the dispersion curves for a pipe, a torsional vibration mode, T(0,1) was selected for the detection of cracks. The T(0,1) mode has many advantages, such as a higher sensitivity for a crack from the viewpoint of its non-dispersion characteristics and its wave structure. The torsional mode can be generated by using either an array of electromagnetic acoustic transducers (EMATs) technique or a magnetostrictive sensor technique. The detectability of the cracks was estimated through a series of experiments with artificial notches on a pipe.
Authors: Zhao Ming Zhou, Fu Wan, Lei Wang, Zhang Hua Lian, Yong Chen
Abstract: This paper presents a new wall thickness and ovality measuring method engineered for reliable field use. This paper describes the electromagnetic ultrasonic technique in coiled tubing detection. This paper describes requirements for Coiled Tubing specifications, which measuring different parameters, some of which include diameter, ovality, and wall thickness. This method not only thickness measurements but also ovality measuring will be made. This article discusses the electromagnetic ultrasonic thickness measurement of the system components, and experimental tests have shown. Ovality measurement sensor layout is designed. This paper discusses the development of this new methods, this system is suitable for non-contact, real-time, on-line high-speed data measurements.
Authors: Ik Keun Park, Tae Hyung Kim, Hyun Mook Kim, Yong Kwon Kim, Yong Sang Cho, Won Joon Song
Abstract: In this paper, study on evaluation of thickness reduction in a thin plate with guided waves is presented. Ultrasonic guided wave techniques have been widely studied and successfully applied to various non-destructive tests with the advantage of long range inspection. In addition to application of guided waves to NDT, non-contact methods for ultrasonic wave generation and detection have become very useful and well combined with guided wave techniques due to their capability of ultrasonic wave generation and reception in surface of high temperature or on rough surface. An advanced non-contact technique for detection of thickness reduction simulating hidden corrosion in thin plates using guided waves is proposed. The proposed approach uses EMAT(Electro-Magnetic Acoustic Transducer) for the non-contact generation and detection of guided waves in aluminum plates. Interesting features of the dispersive behavior in selected wave modes are used to detect plate thinning. The experimental results show that the mode cutoff measurements provide a qualitative measurement of thinning detects and change in the mode group velocity can be used as quantitative parameter of thinning depth measurement.
Authors: Yoshihiro Nishimura, Takayuki Suzuki
Abstract: Equations for reconstructing 3D images of internal flaws are presented. Waveforms were measured from a simple reference sample to derive the response function of the probe, and the response function was calculated based on those waveforms. A sample with internal flaws was prepared to evaluate the reconstructed images of internal flaws derived by EMAT using magnetostrictives. 3D-images of an internal flaw could be derived using this response function.
Authors: Le Chen, Yue Min Wang, Hai Quan Geng
Abstract: Shear horizontal (SH) guided waves have been proved to be a viable method in the Non-Destructive Evaluation (NDE). Electromagnetic acoustic transducers (EMAT) can excite SH waves easily. By bonding the Fe-Co alloy to the test sample, the SH guided waves based on magnetostriction effect can be used to detect the flaw in nonferromagnetic material. The principle of exciting and receiving SH waves is introduced, and an experiment is carried out to validate the result.
Authors: Young Gil Kim, Bong Young Ahn, Young Joo Kim, Young Bae Moon, Sung Hwa Kim
Authors: Andreas Sorich, Marek Smaga, Dietmar Eifler
Abstract: The austenitic steel X6CrNiNb1810 (AISI 347) was investigated in isothermal total strain-controlled tests at ambient temperature and T = 300 °C in the LCF-and HCF-range. The phase transformation from paramagnetic austenite (fcc) into ferromagnetic α´-martensite ́(bcc) leads to cyclic hardening and to an increase in fatigue life. At 300 °C no α´-martensite formation was observed in the LCF-range and the cyclic deformation behavior depends basically on cyclic hardening processes due to an increase of the dislocation density, followed by cyclic saturation and softening due to changes in the dislocation structure. In the HCF-range an increase in fatigue life was observed due to ε- and α´-martensite formation. Measurements of the mechanical stress-strain-hysteresis as well as temperature and magnetic properties enable a characterization of the cyclic deformation behavior and phase transformation in detail. The changes in the physical data were interpreted via microstructural changes observed by scanning-and transmission-electron-microscopy as well as by x-ray investigations. Additionally electromagnetic acoustic transducers (EMATs) developed from the Fraunhofer Institute of Non-destructive Testing (IZFP) Saarbrücken were used for an in-situ characterization of the fatigue processes.
Authors: Riichi Murayama, Yoshiyuki Nakata, Yasuhiko Wakibe, Hideki Wada, Yukihisa Imagawa, Tomoyuki Hayashi
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