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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 36, Issue 3 - Jun 2016
Volume 36, Issue 2 - Apr 2016
Volume 36, Issue 1 - Feb 2016
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Analysis of Time Domain Active Sensing Data from CX-100 Wind Turbine Blade Fatigue Tests for Damage Assessment
Choi, Mijin ; Jung, Hwee Kwon ; Taylor, Stuart G. ; Farinholt, Kevin M. ; Lee, Jung-Ryul ; Park, Gyuhae ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 93~101
DOI : 10.7779/JKSNT.2016.36.2.93
This paper presents the results obtained using time-series-based methods for structural damage assessment. The methods are applied to a wind turbine blade structure subjected to fatigue loads. A 9 m CX-100 (carbon experimental 100 kW) blade is harmonically excited at its first natural frequency to introduce a failure mode. Consequently, a through-thickness fatigue crack is visually identified at 8.5 million cycles. The time domain data from the piezoelectric active-sensing techniques are measured during the fatigue loadings and used to detect incipient damage. The damage-sensitive features, such as the first four moments and a normality indicator, are extracted from the time domain data. Time series autoregressive models with exogenous inputs are also implemented. These features could efficiently detect a fatigue crack and are less sensitive to operational variations than the other methods.
An Efficient and Accurate Method for Calculating Nonlinear Diffraction Beam Fields
Jeong, Hyunjo ; Cho, Sungjong ; Nam, Kiwoong ; Lee, Janghyun ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 102~111
DOI : 10.7779/JKSNT.2016.36.2.102
This study develops an efficient and accurate method for calculating nonlinear diffraction beam fields propagating in fluids or solids. The Westervelt equation and quasilinear theory, from which the integral solutions for the fundamental and second harmonics can be obtained, are first considered. A computationally efficient method is then developed using a multi-Gaussian beam (MGB) model that easily separates the diffraction effects from the plane wave solution. The MGB models provide accurate beam fields when compared with the integral solutions for a number of transmitter-receiver geometries. These models can also serve as fast, powerful modeling tools for many nonlinear acoustics applications, especially in making diffraction corrections for the nonlinearity parameter determination, because of their computational efficiency and accuracy.
Diffraction Corrections for Second Harmonic Beam Fields and Effects on the Nonlinearity Parameter Evaluation
Jeong, Hyunjo ; Cho, Sungjong ; Nam, Kiwoong ; Lee, Janghyun ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 112~120
DOI : 10.7779/JKSNT.2016.36.2.112
The nonlinearity parameter is frequently measured as a sensitive indicator in damaged material characterization or tissue harmonic imaging. Several previous studies have employed the plane wave solution, and ignored the effects of beam diffraction when measuring the non-linearity parameter
. This paper presents a multi-Gaussian beam approach to explicitly derive diffraction corrections for fundamental and second harmonics under quasilinear and paraxial approximation. Their effects on the nonlinearity parameter estimation demonstrate complicated dependence of
on the transmitter-receiver geometries, frequency, and propagation distance. The diffraction effects on the non-linearity parameter estimation are important even in the nearfield region. Experiments are performed to show that improved
values can be obtained by considering the diffraction effects.
Application of Nonlinear Ultrasonic Method for Monitoring of Stress State in Concrete
Kim, Gyu Jin ; Park, Sun Jong ; Kwak, Hyo Gyoung ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 121~129
DOI : 10.7779/JKSNT.2016.36.2.121
As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members.
Study on the Defects Detection in Composites by Using Optical Position and Infrared Thermography
Kwon, Koo-Ahn ; Park, Hee-Sang ; Choi, Man-Yong ; Park, Jeong-Hak ; Choi, Won Jae ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 130~137
DOI : 10.7779/JKSNT.2016.36.2.130
Non-destructive testing methods for composite materials (e.g., carbon fiber-reinforced and glass fiber-reinforced plastic) have been widely used to detect damage in the overall industry. This study detects defects using optical infrared thermography. The transient heat transport in a solid body is characterized by two dynamic quantities, namely, thermal diffusivity and thermal effusivity. The first quantity describes the speed with thermal energy diffuses through a material, whereas the second one represents a type of thermal inertia. The defect detection rate is increased by utilizing a lock-in method and performing a comparison of the defect detection rates. The comparison is conducted by dividing the irradiation method into reflection and transmission methods and the irradiation time into 50 mHz and 100 mHz. The experimental results show that detecting defects at 50 mHz is easy using the transmission method. This result implies that low-frequency thermal waves penetrate a material deeper than the high-frequency waves.
Measurement of Elastic Constants by Simultaneously Sensing Longitudinal and Shear Waves as an Overlapped Signal
Seo, Hogeon ; Song, Dong-Gi ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 138~148
DOI : 10.7779/JKSNT.2016.36.2.138
Measurement of elastic constants is crucial for engineering aspects of predicting the behavior of materials under load as well as structural health monitoring of material degradation. Ultrasonic velocity measurement for material properties has been broadly used as a nondestructive evaluation method for material characterization. In particular, pulse-echo method has been extensively utilized as it is not only simple but also effective when only one side of the inspected objects is accessible. However, the conventional technique in this approach measures longitudinal and shear waves individually to obtain their velocities. This produces a set of two data for each measurement. This paper proposes a simultaneous sensing system of longitudinal waves and shear waves for elastic constant measurement. The proposed system senses both these waves simultaneously as a single overlapped signal, which is then analyzed to calculate both the ultrasonic velocities for obtaining elastic constants. Therefore, this system requires just half the number of data to obtain elastic constants compared to the conventional individual measurement. The results of the proposed simultaneous measurement had smaller standard deviations than those in the individual measurement. These results validate that the proposed approach improves the efficiency and reliability of ultrasonic elastic constant measurement by reducing the complexity of the measurement system, its operating procedures, and the number of data.
Third Harmonic Generation of Shear Horizontal Guided Waves Propagation in Plate-like Structures
Li, Weibin ; Xu, Chunguang ; Cho, Younho ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 149~154
DOI : 10.7779/JKSNT.2016.36.2.149
The use of nonlinear ultrasonics wave has been accepted as a promising tool for monitoring material states related to microstructural changes, as it has improved sensitivity compared to conventional non-destructive testing approaches. In this paper, third harmonic generation of shear horizontal guided waves propagating in an isotropic plate is investigated using the perturbation method and modal analysis approach. An experimental procedure is proposed to detect the third harmonics of shear horizontal guided waves by electromagnetic transducers. The strongly nonlinear response of shear horizontal guided waves is measured. The accumulative growth of relative acoustic nonlinear response with an increase of propagation distance is detected in this investigation. The experimental results agree with the theoretical prediction, and thus providing another indication of the feasibility of using higher harmonic generation of electromagnetic shear horizontal guided waves for material characterization.
Parametric Study of Rectangular Coil for Eddy Current Testing of Lamination
Wang, Pengfei ; Zeng, Zhiwei ;
Journal of the Korean Society for Nondestructive Testing, volume 36, issue 2, 2016, Pages 155~159
DOI : 10.7779/JKSNT.2016.36.2.155
Eddy current testing (ECT) is an important nondestructive testing technology for the inspection of flaws in conductive materials. However, this widely used technology is not suitable for inspecting lamination when a conventional pancake coil is used because the eddy current (EC) generated by the pancake coil is parallel to the lamination and will not be perturbed. A new method using a rectangular coil placed vertical to the work piece is proposed for lamination detection. The vertical sections of the rectangular coil induce ECs that are vertical to the lamination and can be perturbed by the lamination. A parametric study of a rectangular coil by finite element analysis was performed in order to examine the capability of generating vertical EC.