• Journal of Industrial Technology
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• v.25 no.B
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• pp.115-120
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• 2005

Impact seismic wave method is a method for non-destructive testing of concrete structure using of stress wave which is propagate and reflected from internal flaws within concrete structure and external surface. In this study, we performed frequency domain method using impact seismic wave test for safety diagnosis of civil engineering structure. And reflection method which is used for one-dimensional target such as tunnel lining and transmission method are compared with each other.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.177-183
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• 1999

The major object of this study is to investigate experimentally the experimental equation by the non-destructive testing methods of ultrasonic pulse velocity, rebound number, combined method of ultrasonic pulse velocity and rebound number, maturity which are applicable to the evaluation of compressive strength of concrete at early ages. Also test result of mix are statistically analyzed to infer the correlation coefficient between the maturity and the compressive strength of concrete. The results show good application of Logistic curve for estimating strength development under various curing temperature. The relation between ultrasonic pulse velocity, rebound number, combined method of ultrasonic pulse velocity and rebound number and compressive strength of concrete have low correlation coefficient, but maturity method show good correlation coefficient.

• Journal of Korean Society of Disaster and Security
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• v.15 no.4
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• pp.11-20
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• 2022

The general non-destructive inspection method for anchor bolts in Korea applies visual inspection and hammering inspection, but it is difficult to check corrosion or fatigue cracks of anchor bolts in the part included in the foundation or in the part where the nut and base plate are installed. In reality, objective investigation is difficult because inspection is affected by the surrounding environment and individual differences, so it is necessary to develop non-destructive inspection technology that can quantitatively estimate these defects. Inspection of the anchor bolts of domestic road facilities is carried out by visual inspection, and since the importance of anchor bolts such as bridge bearings and fall prevention facilities is high, the life span of bridges is extended through preventive maintenance by developing non-destructive testing technology along with existing inspection methods. Through the development of this technology, non-destructive testing of anchor bolts is performed and as a technology capable of preemptive/active maintenance of anchor bolts for road facilities, practical use is urgently needed. In this paper, the possibility of detecting defects in anchor bolts such as corrosion and cracks and reliability were experimentally verified by applying the ultrasonic test among non-destructive inspection techniques. When the technology development is completed, it is expected that it will be possible to realize preemptive/active maintenance of anchor bolts by securing source technology for improving inspection reliability.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.250-255
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• 2007

Steam generator tubes play an important role in safety because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the nuclear power plant. For this reason, the integrity of the tubes is essential in minimizing the leakage possibility of radioactive water. The integrity of the tubes is evaluated based on NDE (non-destructive evaluation) inspection results. Especially ECT (eddy current test) method is usually used for detecting the flaws in steam generator tubes. However, detection capacity of the NDE is not perfect and all of the "real flaws" which actually existing in steam generator tunes is not known by NDE results. Therefore reliability of NDE system is one of the essential parts in assessing the integrity of steam generators. In this study POD (probability of detection) of ECT system for ODSCC in steam generator tubes is evaluated using multivariate logistic regression. The cracked tube specimens are made using the withdrawn steam generator tubes. Therefore the cracks are not artificial but real. Using the multivariate logistic regression method, continuous POD surfaces are evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive evaluation of the cracked tubes. Length and depth of cracks are considered in multivariate logistic regression and their effects on detection capacity are evaluated.

• Computers and Concrete
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• v.7 no.3
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• pp.271-283
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• 2010

Testing of ultrasonic pulse velocity (UPV) is one of the most popular and actual non-destructive techniques used in the estimation of the concrete properties in structures. In this paper, artificial neural network (ANN) approach has been proposed for the evaluation of relationship between concrete compressive strength, UPV, and density values by using the experimental data obtained from many cores taken from different reinforced concrete structures with different ages and unknown ratios of concrete mixtures. The presented approach enables to find practically concrete strengths in the reinforced concrete structures, whose records of concrete mixture ratios are not yet available. Thus, researchers can easily evaluate the compressive strength of concrete specimens by using UPV values. The method can be used in conditions including too many numbers of the structures and examinations to be done in restricted time duration. This method also contributes to a remarkable reduction of the computational time without any significant loss of accuracy. Statistic measures are used to evaluate the performance of the models. The comparison of the results clearly shows that the ANN approach can be used effectively to predict the compressive strength of concrete by using UPV and density data. In addition, the model architecture can be used as a non-destructive procedure for health monitoring of structural elements.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.3
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• pp.321-326
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• 2010

A method that can decide the existence and the severeness of flaws in ceramic materials through the use of non-destructive testing by image processing techniques, is proposed in this paper. The edges of the acquired image are first extracted using Sobel mask and the regions of the image are clustered using another mask after that. Histogram stretching is applied to each of the regions to enhance the image region-wise and objects are extracted by an edge following algorithm. Morphological information is incorporated to remove noise and detect flawed regions. The proposed method can detect flaws in the acquired images and the experimental results also supports that.

• Smart Structures and Systems
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• v.26 no.6
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• pp.735-751
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• 2020

Identification of structure parameters is crucial in Structural Health Monitoring (SHM) context for activities such as model validation, damage assessment and signal processing of structure response. In this paper, guided waves generated by piezoelectric transducers are used for in-situ and non-destructive structural parameter estimation based on Bayesian approach. As Bayesian approach needs iterative process, which is computationally expensive, this paper proposes a method in which an analytical model is selected and developed in order to decrease computational time and complexity of modeling. An experimental set-up is implemented to estimate three target elastic and geometrical parameters: Young's modulus, Poisson ratio and thickness of aluminum and steel plates. Experimental and simulated data are combined in a Bayesian framework for parameter identification. A significant accuracy is achieved regarding estimation of target parameters with maximum error of 8, 11 and 17 percent respectively. Moreover, the limitation of analytical model concerning boundary reflections is addressed and managed experimentally. Pulse excitation is selected as it can excite the structure in a wide frequency range contrary to conventional tone burst excitation. The results show that the proposed non-destructive method can be used in service for estimation of material and geometrical properties of structure in industrial applications.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.591-598
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• 2002

Leakage magnetic flux is occurred in the cracked area of magnetized specimens, and also it changes the magnetic domain area of the magneto-optical film positioned on the specimen. It causes the change of the optical permeability of the magnetic domain on the crack area. So crack images can be obtained easily using this principle. On the other hand, utilizing a laser in this method makes possible to perform a remote sensing by detecting the light intensity contrast between cracked area and normal area. This paper shows the application of non-destructive inspection system taking advantage of magneto-optical method for micro-cracks and presents examples applied to the several types of specimens having fatigue cracks and fabricated cracks using this method. Also the authors prove the possibility of this method as a remote sensing system under the oscillation load considering application to real fields.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.504-512
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• 2003

Simulation programs have been developed and used as an attempt to improve the accuracy of Non-Destructive Evaluation(NDE) techniques. The applicability of these programs is very limited, however, because it is difficult to describe the delicacy of the propagation of stress waves. To investigate the applicability of the finite element analysis for stress wave-based NDE techniques numerical simulation for Impact-Echo method and SASW method is performed. The numerical studies are performed to determine the essential parameters such as contact time of impact load, mesh size and time step size. These studies show that the choice of parameter is very important for improving the accuracy and confidence of the numerical procedure and, thereby, the applicability of the numerical analysis for stress wave-based NDE techniques

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.397-402
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• 2005

The NDT(Non-Destructive Testing) is valid for the defect detection of rolling stocks because it can be used to detect the defect in many invisible parts. For example, fatigue cracks are initiated in press fit parts that suffer from fretting fatigue damage such as the wheel seat and the NDT technique can detect those cracks. But the conventional ICFPD method can not apply to detect such cracks in press fit parts of the axle by some technical problems. In this study, we have introduced the new concept ICFPD method that can be applied in press fit parts of the axle. And we have shown the basic techniques of FEM about the new concept ICFPD method.