Advanced Nondestructive Evaluation I

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Authors: Hee Jun Jung, Sung Jin Song, Chang Hwan Kim, Joo Young Yoo, Young Hwan Choi, Suk Chull Kang, Myung Ho Song
Abstract: For inspection of steam generator tubes in nuclear power plants using eddy current testing, it is a very crucial task to extract the flaw signal from signals compounded by flaws and supporting structures. To perform such an important task, the multifrequency eddy current testing method is widely adopted. In this study, we explore the performance of a linear mixing technique based on the discrete cosine transform method by experiments. The results obtained using the DCT based method agree very well to those obtained by commercial software demonstrating the effectiveness of the approach.
Authors: Hyang Beom Lee
Abstract: To obtain the simulated eddy current testing (ECT) signals of steam generator (SG) in nuclear power plant (NPP), nodal-based finite element (FE) analysis with magnetic vector potential (MVP) is usually used. To perform the numerical analysis, we derive the governing equation in terms of MVP and electric scalar potential (ESP) from Maxwell’s equations. To insure the uniqueness of solution, gauge condition has to be considered. In eddy current problems, Coulomb gauge condition (CGC) is usually used. In 2-D or 3-D axis-symmetric analysis, CGC is included during formulation and ESP is eliminated using some special assumption. Because CGC is not used during the formulation in 3-D analysis, we have to include artificially. And because of the heavy computation cost for 3-D analysis modified magnetic vector potential (MMVP) is used by elimination ESP. In this paper, effects of artificial treatment of CGC and elimination of ESP on ECT signal are investigated in order to help for obtaining accurate numerical simulation results.
Authors: Kil Mo Koo, Sang Baik Kim, In Chul Lim, Chul Moo Sim, Yong Moo Cheong, Chi Seong Park
Abstract: In this experiment, a residual water level gaging in a bellows tube is implemented by appling the immersion ultrasonic technique. The bellows tube is located in a complex structure. Since it is located at considerable depth implemented, it is difficult to approach it from the outside working area, which has a residual water level after a drainage of the water in it, because a structure like the bellows has a peak and mold shape.
Authors: Jin Feng Ding, Yi Hua Kang, Xin Jun Wu
Abstract: Failure of the drill pipe thread is always a very serious problem which may result in serious accidents and rework during the drilling of oil wells. Rupture crack of the drill pipe thread may result in great economic and labour losses, so they need to be inspected periodically. As the drill pipe thread is not a smooth surface and is in the end area of drill pipes, it is very difficult to be inspected by traditional Non-destructive testing (NDT) methods. According to the experiment results and the requirement of the working conditions in the field, a local MFL inspection method, which is the most adaptive inspection method, is determined. Laboratory testing and field experience show that this inspection method can detect the crack as small as 0.6mm (depth) in the thread root and thus reduces the risks of drilling failure. This local MFL inspection method can inspect flaws of the drill pipe thread that occur in practice exactly and quickly, and it has very wide application perspectives.
Authors: Bum Joon Kim, Byeong Soo Lim, Sung Jin Song, Young H. Kim
Abstract: This work investigates the relationship between the creep-fatigue life and ultrasonic test of creep-fatigue damage. Under the creep-fatigue interaction, the main cause of life reduction is the initiation and growth of microvoid with increasing hold time. The number/size of microvoid/cavity, the fraction of cavity area varied with the hold time. Therefore, the life evaluation using the microvoid with the variation of hold time is very informative for safety of components in power plants. In this study, using the heat resisting alloy, P122 steel for USC (ultra super critical) power plant, the creep-fatigue tests with various hold times and their ultrasonic inspection were carried out for the purpose of evaluation for creep-fatigue life. The results obtained by Rayleigh surface wave of backscattered ultrasound were compared and analyzed with the experimental parameters. The good agreement between the experimental life and the predicted life was obtained.
Authors: Jung Suk Lee, Jae Il Jang, Keun Bong Yoo, Dong Il Kwon
Abstract: An indentation fracture toughness model is applied to estimate non-destructively the fracture toughness of power plant materials such as ASTM A53 and ASME SA335 P91. Fracture toughness evaluated using the model showed good agreement with current standard fracture toughness test results.
Authors: Yang Ki Hyun, Soon Ho Won, Jae Ho Jang, In Bae Kim
Abstract: Evolution of microstructure due to service exposure to high temperature has a strong effect performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of Fe2Mo-type laves phases and coarsening of M23C6-type carbides are the primary cause of degradation of mechanical properties such as creep resistance, tensile strength and toughness. Therefore creep tests have been carried out on modified 9Cr-1Mo steels to examine the effect of aging and stress on the creep strength. Additionally vibrating sample magnetometer is used to measure hysteresis loop.
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: Hak Joon Kim, Sung Jin Song, Lester W. Schmerr
Abstract: For the proper interpretation of ultrasonic measurement results from a side-drilled hole (SDH) using a rectangular transducer, it is very helpful to have a complete ultrasonic measurement model. A highly efficient ultrasonic beam model of a rectangular transducer and an accurate scattering model of a SDH are currently available. However, to develop such a complete measurement model, a reference model for the system efficiency factor is also needed. In this study a reference model suitable for a rectangular transducer is given and combined with existing models to develop a complete ultrasonic measurement model that can the predict ultrasonic signals from a SDH. Based on this model, we have calculated the ultrasonic signals from a SDH at different transducer orientations and compared the model-based predictions with experiments.
Authors: Sung Jin Song, Joon Soo Park, Hak Joon Kim, Un Hak Seong, Suk Chull Kang, Young Hwan Choi
Abstract: In this study, the expanded multi-Gaussian beam model is adopted to develop a model to calculate the ultrasonic beam fields radiated from an ultrasonic phased array transducer. Combining this beam model with three other components including time delays, a far-field scattering model and a system efficiency factor, we develop a complete ultrasonic measurement model for predicting the phased array ultrasonic signals that can be captured from a flat-bottom hole in a steel specimen in a pulse-echo set-up using an array transducer mounted in a solid wedge. This paper describes the complete model developed with its key ingredients.

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