• 비파괴검사학회지
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• 제20권3호
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• pp.221-230
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• 2000

콘크리트 비파괴검사법인 충격공진법의 유용성과 적용 한계를 살펴보기 위하여 실험 및 이론적 연구를 수행하였다. 실험적 연구를 위하여, 다양한 개재물이 포함된 콘크리트 슬래브 공시체를 제작한 후 충격공진법을 적용하여 개재물의 존재 및 매실 위치를 찾아보았다. 공시체들 중 몇 경우에는 개재물의 위치를 정확하게 검출할 수 있었으나, 나머지의 경우에는 검출하지 못하였다. 후자의 경우에 있어서 그 실패 원인을 규명하고, 나아가 본 기법의 유용성을 결정하는 주요 인자들을 알아보기 위하여 유한요소 해석을 수행하였다. 본 연구는 충격공진법의 물리적 이해 증진과 향후 발전에 기여할 것이다.

• 콘크리트학회논문집
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• 제11권4호
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• 한국도로학회논문집
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• 제9권2호
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• pp.89-99
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• 2007

복소수계수 $E^*$로 표현되는 아스팔트 콘크리트의 탄성계수는 아스팔트 포장설계에서 매우 중요한 입력변수다. 일반적으로 아스팔트 콘크리트의 탄성계수는 동탄성 계수시험 (Dynamic Modulus Test)을 사용하여 평가한다. 그러나 동탄성계수시험은 일상적인 시험법으로 적용하기에는 고가의 시험장비, 복잡한 시험장비, 많은 시험시간 등의 문제가 있다. 이에 반하여 충격공진시험(IR: Impact Resonance test)은 비파괴시험으로서 간편한 시험장치, 단순한 시험방법이며 반복성이 뛰어나다. 본 연구의 주요 목적은 충격하중의 타격위치 시편거치 방법 충격하중원의 특성, 신호획득 속도, 신호처리방법 등을 포함한 IR시험의 시험조건의 영향을 평가하는 것이다. 본 연구에서 적용한 모든 시험조건 범위에서 충격공진시험에서 측정된 결과의 변동은 ${\pm}2.7%$ 이내에 들었다.

• 한국안전학회지
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• 제34권5호
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• pp.95-102
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• 2019

Non-destructive methods such as rebound hardness method and ultrasonic method are widely studied for evaluating the physical properties, condition and damage of concrete, but are not suitable for detecting delamination and cracks near the surface due to various constraints of the site as well as the accuracy. Therefore, in this study, the impact resonance method was applied to detect the separation cracks occurring near the surface of the concrete slab and bridge deck. As a next step, the principal component analysis were performed by extracting various features using the FFT data. As a result of principal component analysis, it was analyzed that the reliability was high in distinguishing defects in concrete. This feature extraction and application of principal component analysis can be used as basic data for future use of machine learning technique for the better accuracy.

• 한국도로학회논문집
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• 제16권3호
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• pp.43-50
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• 2014

PURPOSES : The dynamic modulus can be determined by applying the various theories from the Impact Resonance Testing(IRT) Method. The objective of this paper is to determine the best theory to produce the dynamic modulus that has the lowest error as the dynamic modulus data obtained from these theories(Complex Wave equation Resonance Method related to either the transmissibility loss or not, Dynamic Stiffness Resonance Method) compared to the results for dynamic modulus determined by using the Universal Testing Machine. The ultimate object is to develop the predictive model for the dynamic modulus of a Linear Visco-Elastic specimen by using the Complex Wave equation Resonance Method(CWRM) came up for an existing study(S. O. Oyadiji; 1985) and the Optimization. METHODS : At the destructive test which uses the Universal Testing Machine, the dynamic modulus results along with the frequency can be used for determining the sigmoidal master curve function related to the reduced frequency by applying Time-Temperature Superposition Principle. RESULTS : The constant to be solved from Eq. (11) is a value of 14.13. The reduced dynamic modulus obtained from the IRT considering the loss factor related to the impact transmissibility has RMSE of 367.7MPa, MPE of 3.7%. When the predictive dynamic modulus model was applied to determine the master curve, the predictive model has RMSE of 583.5MPa, MPE of 3.5% compared to the destructive test results for the dynamic modulus. CONCLUSIONS : Because we considered that the results obtained from the destructive test had the most highest source credibility in this study, the dynamic modulus data obtained respectively from DSRM, CWRM were compared to the results obtained from the destructive test by using th IRT. At the result, the reduced dynamic modulus derived from DSRM has the most lowest error.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.466-473
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• 2013

Nondestructive evaluation (NDE) technique method using a resonance frequency mode was carried out for heat-treated wood under different conditions. The effect of heat treatment on the bending strength and NDE technique using the resonance frequency by impact hammer and force transducer mode for Korean paulownia, Pinus densiflora, Lidiodendron tulipifera and Betula costata were measured. The heat treatment temperature has been investigated at $175^{\circ}C$ and $200^{\circ}C$, respectively. There were a close relationship of dynamic modulus of elasticity and static bending modulus of elasticity to MOR. In all conditions, It was found that there were a high correlation at 1% level between dynamic modulus of elasticity and MOR, and static modulus of elasticity and MOR. However, the result indicated that correlation coefficient is higher in dynamic modulus of elasticity to MOR than that in static modulus of elasticity to MOR. Therefore, the dynamic modulus of elasticity using resonance frequency by impact hammer mode is more useful as a nondestructive evaluation method for predicting the MOR of heat-treated wood under different temperature and species conditions.

• 콘크리트학회지
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• 제11권1호
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• pp.161-171
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• 1999

본 연구는 비파괴 검사방법인 충격 공진법을 이용하여 결함을 갖는 콘크리트 시험체로부터의 반사신호를 정량적으로 해석하기 위한 연구이다. 충격 공진법은 비교적 저주파의 강한 에너지를 콘크리트내에 가하여 그 반사신호로부터 결함이나 경계층 등을 조사하기 때문에 굵은 골재 등을 포함하고 중량물인 콘크리트 구조물의 탐사에 유용하다. 그러나, 보나 기둥 등의 작은 경계를 갖는 콘크리트 시험체를 대상으로 할 경우에는 각 경계로부터 수평방향을 왕복하는 R-파의 영향이 크기 때문에 결함 또는 경계층으로부터의 반사신호인 수직방향으로부터의 P-파의 세기가 충분히 크지 못하면, 결함 등으로부터의 신호를 검출하기 어렵게 된다. 따라서, 본 연구에서는 시험체의 경계조건과 결함의 위치에 따라 발생 가능한 각 진동모드를 정량적으로 해석하는 방법을 연구하여 결함으로부터의 신호를 검출하는 방법에 대해 검토하였다. 그 결과, 각모서리의 길이가 50cm 이내의 작은 경계조건과 50cm의 깊은 두계를 갖는 콘크리트 시험체내의 결함에 대해서도 콘크리트가 부배합 조건이고 결함의 깊이가 30cm이내일 경우 정량적 탐사가 가능하며, 각 모서리의 크기가 충분히 큰 대형 시험체 조건에서는 보다 용이하고 폭넓게 다양한 조건의 결함 등에 대한 정량적 참사가 가능하였다.

• 콘크리트학회논문집
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• 제22권5호
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• pp.625-632
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• 2010

콘크리트의 탄성계수 결정을 위해 다양한 시험기법이 사용되고 있다. 충격공진시험(IR: impact resonance test)은 비파괴시험으로서 간편한 시험장치와 단순한 시험방법이며 반복성이 뛰어나다. 또한 충격공진시험은 탄성계수 뿐만 아니라 감쇠비 결정이 가능하다. 이 연구에서는 콘트리트 시편에 대한 충격공진시험의 다양한 영향요소(시편거치 방법, 충격하중원의 특성, 신호획득 속도 등)를 평가하고 최적의 시험조건을 제시하였다. 이 연구에서 적용한 모든 시험조건 범위에서 충격공진시험에서 측정된 결과의 변동량은 공진주파수 결정에 있어서 ${\pm}0.3%$, 감쇠비 결정에 있어서 ${\pm}10.0%$로 나타났다. 충격공진시험에서 결정된 탄성계수와 정적시험에서 결정된 탄성계수를 변형률 크기를 고려하여 비교하면 비교적 서로 잘 일치함을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.498-503
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• 2009

This paper presents the vibration problem of the Engine Casing (E/C) "B" deck in the handymax vessel and describes a method to avoid resonance. The first ship of the series did not have any vibration issue on the "B" deck. However, resonance condition occurred when additional machine was installed to the following vessels. To understand the dynamic characteristics of the deck, the normal mode analysis and impact test have been performed. Within the normal operating range of the vessel, the $1^{st}$ natural frequency of the E/C "B" deck is close to the main engine's $6^{th}$ order. Based on these analysis, a reinforcement on the deck was suggested and it proved to be effective. Since actual impact test after the reinforcement also confirmed the resonance avoidance.

• 한국도로학회논문집
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• 제16권3호
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• pp.35-41
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• 2014

PURPOSES : The dynamic modulus for a specimen can be determined by using either the non-destructed or destructed testing method. The Impact Resonance Testing (IRT) is the one of the non-destructed testing methods. The MTS has proved the source credibility and has the disadvantages which indicate the expensive equipment to operate and need a lot of manpower to manufacture the specimens because of the low repeatability with an experiment. To overcome these shortcomings from MTS, the objective of this paper is to compare the dynamic modulus obtained from IRT with MTS result and prove the source credibility. METHODS : The dynamic modulus obtained from IRT could be determined by using the Resonance Frequency (RF) from the Frequency Response Function (FRF) that derived from the Fourier Transform based on the Frequency Analysis of the Digital Signal Processing (DSP)(S. O. Oyadigi; 1985). The RF values are verified from the Coherence Function (CF). To estimate the error, the Root Mean Squared Error (RMSE) method could be used. RESULTS : The dynamic modulus data obtained from IRT have the maximum error of 8%, and RMSE of 2,000MPa compared to the dynamic modulus measured by the Dynamic Modulus Testing (DMT) of MTS testing machine. CONCLUSIONS : The IRT testing method needs the prediction model of the dynamic modulus for a Linear Visco-Elastic (LVE) specimen to improve the suitability.