• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.177-181
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• 2001

Nondestructive testing(NDT) is one of the fundamental tools to improve the quality of commercial and industrial products. NDT is potentially a major application of interferometry. Interferometry(ESPI, Shearography, ect) has successfully been applied in various industrial environments such as high performance aircraft, home appliance, automotive, and laminates on engine structures, etc. Today's industry demands high performance components with toughest mechanical features and ultimate safety standards. Especially in automotive and aircraft industry the development process focuses on tailor-made design and solutions to meet customer specifications. To reconcile economy, ligh-weight construction has become a key issue. Many companies are looking for new advanced NDT techniques to archive cost efficiency over the limitations of classical methods. ESPI and shearography allow a rapid, full field and 3D-measurement without contact. In this paper recent applications of ESPI and shearography for NDT are described. Advanced features of classical techniques are specified and new applications in material and component testing are presented.

• Journal of Mechanical Science and Technology
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• v.16 no.2
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• pp.147-154
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• 2002

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K$\_$IC/) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating the 7c consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimate K$\_$IC/, using the K$\_$IC/ versus excess temperature (i.e., T-FATT) correlation that is available in the literature for CrMoV rotor steel.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.6
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• pp.616-621
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• 2003

There are various Non-Destructive Evaluation (NDE) techniques used for measurement of residual stresses in material, such as magnetic methods, X-ray diffraction, Ultrasonic velocity measurement etc. The capabilities, applications and limitations of these techniques for evaluation of cold work/plastic deformation were studied and compared. Mild steel plates were subjected to different degree of cold deformation and were analyzed by Magneto-mechanical Acoustic Emission (MAE), Barkhausen Noise (BN) and magnetic properties (hysteresis loop parameters analysis). Further, these specimens were analyzed by X-ray diffraction and ultrasonic velocity measurements. The microhardness measurement and microstructure studies of these cold worked plates were also carried out. The results of all these studies and comparison of different techniques are discussed in this paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.6
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• pp.577-582
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• 2003

This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.469-476
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• 2008

Condition based maintenance(CBM) for the preventive diagnosis of important equipments related to safety or accident in power plant is essential by using the suitable methods based on actual power plant conditions. To improve the reliability and accuracy of the measured value at the minute leak situation, and also to monitor continuously internal leak condition of power plant valve, the development of a diagnosis and monitoring technique using multi-measuring method should be performed urgently. This study was conducted to estimate the feasibility of multi-measuring method using three different methods such as acoustic emission(AE) method, thermal image measurement and temperature difference$({\Delta}T)$ measurement that are applicable to internal leak diagnosis for the power plant valve. From the experimental results, it was suggested that the multi-measuring method could be an effective way to precisely diagnose and evaluate internal leak situation of valve.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.3
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• pp.162-168
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• 2006

Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

• Journal of the Korean Society for Nondestructive Testing
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• v.7 no.2
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• pp.27-34
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• 1988

Recently, it is gradually raised necessity that thickness of thin film is measured accurately and managed in industrial circles and medical world. In this study, regarding to the thickness of film which is in opaque object and is beyond distance resolution capacity, thickness measurement was done by MEM-cepstrum analysis of received ultrasonic wave. In measurement results, film thickness which is beyond distance resolution capacity was measured accurately. And within thickness range that don't exist interference, thickness measurement by MEM-ceptrum analysis was impossible.

• Journal of the Korean Society for Nondestructive Testing
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• v.2 no.1
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• pp.10-16
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• 1982

This study was carried out to measure the flaw height of welds in consideration of the effective probe angle in ultrasonic oblique detection. Specimens with inserted artificial flaws were made and flaw heights were estimated from detecting these specimens. Two different methods were applied to estimate flaw heights. From the result of the experiment, flaw height could be measured within the accuracy of 15% percent error and the difference between the probe distance method and beam path method is about 5% relatively small. It is considered that the results obtained this experimental study could be helpful informal ions for measuring flaw height.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.296-304
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• 2000

Radar is becoming a popular tool for condition assessment of concrete structures. The advancement of radar method to concrete structures requires a systematic approach, which incorporates the fundamentals of radar theory and the characteristics of concrete as a material with electromagnetic properties. The research work presented in this paper deals with the establishment of effective measurement area for radar measurements, the determination of concrete thickness using radar, and the calculation of the dielectric constant of concrete from radar measurements. As results, formulas have been suggested to determine optimum measurement area for concrete, using radar and concrete thickness has been successfully identified for specimens used in this work. In the experiments, five concrete specimens which have the dimensions of 900mm (length) $\times$ 600mm (width) with thickness variation from 50mm to 250mm are used.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.357-365
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• 2014

Purpose: The continued increase in the world population has triggered an increased demand for food. Cereal grains, flour, and their products constitute the staple diet for most of the world's population. This high demand for food, particularly for cereal-based products, has been exploited for commercial gain through adulteration of food materials. We provide a thorough review of the current developments and limitations of modern, nondestructive analytical techniques used for detection of adulterants in cereals and their products and compare them with conventional methods. Results: Adulterated food poses a serious health risks to humans, animals, and the ecosystem in general. Over the last few decades, the adulteration industry has developed fraudulent practices that often outsmart conventional methods of detection and quality control. Therefore, technological advancements to aid in detection and measurement of adulterants in food products and to ensure food quality and safety are critically important to consumers worldwide. Conclusion: There is a continuous demand for development of nondestructive technology to improve the accuracy and efficiency of detection, measurement, and qualification of adulterants in cereals and other food materials.