• 비파괴검사학회지
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• 제9권1호
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• pp.83-89
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• 1989

Effects of the microstructure and the testing conditions for the detectability of the small flaw in ultrasonic testing have been studied. The detectability of the flaw was influenced not only by the grain size but also by the microstructure of the test piece. This is considered to be caused by randomization of the matrix which influences the elastic anisotropy of the grain. It was found that the detectability was improved as the frequence became higher and the beam size became smaller. The experimental results indicate that ultrasonic backscattering measurement is one of the promising methods to evaluate the detectability of the flaw indirectly.

• 비파괴검사학회지
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• 제9권2호
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• pp.18-24
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• 1989

Computer-aided high frequency ultrasonic is applied to aluminum oxide(85w%, 94w%, 96w%, and 99w%) MOR(modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, elastic modulus, shear modulus, and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different fate setting method using 50MHz center frequency 1 inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows good reliability as compared with resonance method. Sintered density variation of $0.025g/cm^{3}$, that is 0.6% of theoretical density in $Al_{2}O_{3}$ samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.

• 비파괴검사학회지
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• 제26권1호
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• pp.30-39
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• 2006

Feasibility is studied for an application of the mass-spring lattice model (MSLM), a numerical model previously developed for unidirectional composites, to the numerical simulation of ultrasonic inspection of austenitic welds modeled as transversely isotropic. Fundamental wave processes, such as propagation, reflection, refraction, and diffraction of ultrasonic waves in such an inspection are simulated using the MSLM. All numerical results show excellent agreement with the analytical results. Further, a simplified model of austenitic weld inspection has been successfully simulated using the MSLM. In conclusion, a great potential of the MSLM in numerically simulating ultrasonic inspections of austenitic welds has been manifested in this work, though significant further efforts will be required to develop a model with field practicality.

• 비파괴검사학회지
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• 제21권6호
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• pp.607-611
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• 2001

초음파검사 시스템은 검사자, 검사장비, 검사절차서로 구성되어진다. 따라서 각각의 구성의 성능에 따라 초음파검사의 신뢰도가 좌우되며, 또한 검사환경이나 검사체의 재질, 결함의 유형에 따라서도 검사의 신뢰도는 영향을 받게된다. 이러한 다양한 인자들로 인해 비파괴검사의 신뢰도를 평가하는 것이 쉽지 않다. 본 연구에서는 로지스틱 모델과 몬테 카를로 시뮬레이션을 이용하여 초음파검사의 신뢰도를 척도할 수 있는 검출확률을 평가하고자 한다. 신뢰도 평가의 유용성을 검증하기 위해 원진배관에 대한 순회시험의 데이터에 신뢰도 평가 모델을 적용하였다.

• 비파괴검사학회지
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• 제36권2호
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• pp.121-129
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• 2016

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.

• 비파괴검사학회지
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• 제32권4호
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• pp.401-409
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• 2012

초음파 시험은 접착계면에서 발생하는 미접착 결함을 검출할 수 있는 다른 비파괴 시험보다 미접착 검출 능력이 월등히 뛰어나다. 하지만, 스틸 연소관, 내열 고무, 라이너 및 추진제로 구성된 고체 추진기관은 각 재질의 음향 임피던스의 큰 차이와 반사파의 중첩 때문에 초음파 신호를 분석하기에는 많은 어려움 있다. 그러므로 고체 추진기관의 미접착 결함을 검출하기 위한 초음파 시험은 자동화된 C-Scan 시스템을 이용하여 스틸 연소관과 내열 고무 계면의 극히 제한된 영역에서 적용되어 왔다. 기존의 초음파 시험은 대부분의 초음파가 음향 임피던스가 낮은 고무 재질에서 흡수되므로 고체 추진기관의 라이너와 추진제 사이의 미접착 결함을 검출할 수 없었고, 이런 문제점을 해결하기 위하여 초음파 공진법을 사용하여 주파수 스펙트럼으로부터 공진 주파수를 분석하였다. 본 논문은 초음파 공진 특성을 이용하여 라이너와 추진제 사이의 미접착 결함을 검출할 수 있는 기법에 대해 자세히 기술하였다.

• 비파괴검사학회지
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• 제29권3호
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• pp.242-247
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• 2009

The ability of time reversal techniques to focus ultrasonic beams on the source location is important in many aspects of ultrasonic nondestructive evaluation. In this paper, we investigate the time reversal beam focusing of ultrasonic array sensors on a defect in layered media. Numerical modeling is performed using the commercially available software which employs a time domain finite difference method. Two different time reversal approaches are considered - the through transmission and the pulse-echo. Linear array sensors composed of N elements of line sources are used for signal reception/excitation, time reversal, and reemission in time reversal processes associated with the scattering source of a side-drilled hole located in the second layer of two layer structure. The simulation results demonstrate the time reversal focusing even with multiple reflections from the interface of layered structure. We examine the focusing resolution that is related to the propagation distance, the size of array sensor and the wavelength.

• 비파괴검사학회지
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• 제21권1호
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• pp.1-21
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• 2001

It will be shown how models can simulate all the elements of an ultrasonic NDE measurement system, including the pulser/receiver, cabling, transducer(s), and the acoustic/elastic waves fields. When combined, these models form what is called the electroacoustic measurement model. It will be demonstrated how this electroacoustic measurement model can be used to conduct parametric transducer and system studies and how the model can form the basis for experimentally characterizing all the elements of the ultrasonic measurement system, using purely electrical measurements.

• 비파괴검사학회지
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• 제26권3호
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• pp.153-161
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• 2006

A simulation program SIMULTSONIC is under development at CNDE to help determine and/or help optimize ultrasonic probe locations for inspection of complex components. SIMULTSONIC provides a ray-trace based assessment for immersion and contact modes of inspection. The code written in Visual C++ operating in Microsoft Windows environment provides an interactive user interface. In this paper, a description of the various features of SIMULTSONIC is given followed by examples illustrating the capability of SIMULTSONIC to deal with inspection of canonical objects such as pipes. In particular, the use of SIMULTSONIC in the inspection of very thin-walled pipes (with 450 urn wall thickness) is described. Ray trace based assessment was done using SIMULTSONIC to determine the standoff distance and the angle of oblique incidence for an immersion mode focused transducer. A 3-cycle Hanning window pulse was chosen for simulations. Experiments were carried out to validate the simulations. The A-scans and the associated B-Scan images obtained through simulations show good correlation with experimental results, both with the arrival time of the signal as well as with the signal amplitudes.

• 비파괴검사학회지
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• 제37권2호
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• pp.115-121
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• 2017

The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke's equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at $300^{\circ}C$ for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke's equation. The results showed that the variations in these parameters were in good agreement with each other.