• 한국전자통신학회논문지
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• 제15권1호
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• pp.101-106
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• 2020

본 연구는 다양한 어셈블리 부품의 용접부 내부결함을 검사하기 위한 초음파 탐상 장비 개발에 관한 것이다. 본 연구에서는 초음파 탐상을 위하여 시스템의 모션제어 S/W, 초음파 송수신기 제어, 결함 판정 기준 설정 등의 계측 S/W 등이 설계되었으며, 양품과 불량품의 비교분석을 하기 위하여 용접결함 불량품 샘플워크 등도 제작되었다. 이와 같은 구성으로 이루어진 시스템을 통하여 어셈블리 부품 용접부의 결함 위치 및 깊이에 대한 자동검사 기능을 수행할 수 있었으며, 종전에 전문가에 의해 이루어졌던 용접부의 내부결함에 대한 판단을 시스템이 수행하도록 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.181-184
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• 2008

콘크리트는 비교적 내화성이 있는 재료이다. 그러나 화재 등의 고온에 장기 노출될 경우는 콘크리트 강도 등이 급격하게 저하하는 현상이 발생한다. 이와 같은 경우, 저강도 콘크리트를 일반 비파괴검사 강도추정식을 이용하여 추정하는 것은 적절하지 않다. 이 문제를 해결하기 위해 각종 배합조건의 콘크리트시편을 200, 400, 600, $800^{\circ}C$의 온도변화 조건에서 가열한 후, 초음파속도와 콘크리트강도간의 상관관계를 분석하였다. 아울러 이들 결과를 통해 고온에서 손상된 콘크리트 비파괴검사 강도추정식을 제안하였다.

• Journal of Welding and Joining
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• 제23권5호
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• pp.43-48
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• 2005

Conventional non-destructive techniques for inspection of the weld in pipelines require significant test time and high cost. Ultrasonic guided waves have been widely studied and successfully applied to various non-destructive tests with advantage of the long-range inspection. In this paper, a study on the application of ultrasonic guided waves to the long-range inspection of the pipeline is presented using a long-range guided wave inspection system, Wavemaker SE16, GUL. The characteristics and setup of the long-range guided wave inspection system and experimental results in pipes of with various diameter are introduced. The experimental results in mock-up pipes with cluster type detects show that the minimum detectable wall thickness reduction with this guided wave system is $2\~3\%$ in the pipe cross section area. And the wall thickness reduction of $5\%$ in cross section area can be detected when actual detection level is used. Therefore, the applicability of the guided wave systeme to long-range inspection of wall thickness reduction in pipes is verified.

• 한국정밀공학회지
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• 제15권7호
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• pp.149-159
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• 1998

The importance of soundness and safety evaluation in weld zone using by the ultrasonic wave has been recently increased rapidly because of the collapses of huge structures and safety accidents. Especially, the ultrasonic method that has been often used for a major non-destructive testing(NDT) technique in many engineering fields plays an important role as a volume test method. Hence, the defecting any defects of weld Bone in austenitic stainless steel type 304 using by ultrasonic wave and neural network is explored in this paper. In order to detect defects, a distance amplitude curve on standard scan sensitivity and preliminary scan sensitivity represented of the relation between ultrasonic probe, instrument, and materials was drawn based on a quantitative standard. Also, a total of 93％ of defect types by testing 30 defect patterns after organizing neural network system, which is learned with an accuracy of 99％, based on ultrasonic evaluation is distinguished in order to classify defects such as holes or notches in experimental results. Thus, the proposed ultrasonic wave and neural network is useful for defect detection and Ultrasonic Non-Destructive Evaluation(UNDE) of weld zone in austenitic stainless steel 304.

• Interaction and multiscale mechanics
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• 제3권2호
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• pp.173-191
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• 2010

Damage detection plays a very important role to the maintenance of bridge structures. Traditional damage detection methods are usually based on structural dynamic properties, which are acquired from pre-installed sensors on the bridge. This is not only time-consuming and costly, but also suffers from poor sensitivity to damage if only natural frequencies and mode shapes are concerned in a noisy environment. Recently, the idea of using the dynamic responses of a passing vehicle shows a convenient and economical way for damage detection of bridge structures. Inspired by this new idea and the well-established tap test in the field of non-destructive testing, this paper proposes a new method for obtaining the damage information through the acceleration of a passing vehicle enhanced by a tapping device. Since no finger-print is required of the intact structure, this method can be easily implemented in practice. The logistics of this method is illustrated by a vehicle-bridge interaction model, along with the sensitivity analysis presented in detail. The validity of the method is proved by some numerical examples, and remarks are given concerning the potential implementation of the method as well as the directions for future research.

• Advances in concrete construction
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• 제8권1호
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• pp.9-19
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• 2019

This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.

• Structural Engineering and Mechanics
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• 제81권6호
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• pp.737-750
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• 2022

Timber-Concrete Composite construction system consists of combining timber beam or deck and concrete with different connectors. Different fastener types are used in Timber-Concrete Composite systems. In this paper, the effects of two types of fasteners on structural behavior are compared. First, the notches were opened on timber beam, and combined with reinforced concrete slab by fasteners. This system is called as Notched Connection System. Then, timber beam and reinforced concrete slab were combined by new type designed fasteners in another model. This system is called as Notched-Slab Approach. Two laboratory models were constructed and bending tests were performed to examine the fasteners' effectiveness. Bending test results have shown that heavy damage to concrete slab occurs in Notched Connection System applications and the system becomes unusable. However, in Notched-Slab Approach applications, the damage concentrated on the fastener in the metal notch created in the slab, and no damage occurred in the concrete slab. In addition, non-destructive experimental measurements were conducted to determine the dynamic characteristics. To validate the experimental results, initial finite element models of both systems were constituted in ANSYS software using orthotropic material properties, and numerical dynamic characteristics were calculated. Finite element models of Timber-Concrete Composite systems are updated to minimize the differences by manual model updating procedure using some uncertain parameters such as material properties and boundary conditions.

• Computers and Concrete
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• 제29권 6호
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• pp.433-444
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• 2022

Concrete's compressive strength is widely studied in order to understand many qualities and the grade of the concrete mixture. Conventional civil engineering tests involve time and resources consuming laboratory operations which results in the deterioration of concrete samples. Proposing efficient non-destructive models for the prediction of concrete compressive strength will certainly yield advancements in concrete studies. In this study, the efficiency of using radial basis function neural network (RBFNN) which is not common in this field, is studied for the concrete compressive strength prediction. Complementary studies with back propagation neural network (BPNN), which is commonly used in this field, have also been carried out in order to verify the efficiency of RBFNN for compressive strength prediction. A total of 13 input parameters, including novel ones such as cement's and fly ash's compositional information, have been employed in the prediction models with RBFNN and BPNN since all these parameters are known to influence concrete strength. Three different train: test ratios were tested with both models, while different hidden neurons, epochs, and spread values were introduced to determine the optimum parameters for yielding the best prediction results. Prediction results obtained by RBFNN are observed to yield satisfactory high correlation coefficients and satisfactory low mean square error values when compared to the results in the previous studies, indicating the efficiency of the proposed model.

• 콘크리트학회논문집
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• 제14권5호
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• pp.782-788
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• 2002

콘크리트 구조물의 설계, 시공관리 그리고 내력판정 등을 위해서는 콘크리트의 압축강도를 알아야 하는데 미리 제작해 놓은 공시체가 없을 경우 비파괴 시험을 통해 압축강도를 예측하는 방법이 많이 사용되고 있다. 지금까지 수많은 비파괴 방법이 제안되었지만 그 중 가장 널리 사용되는 것이 반발도법과 초음파 속도법이며, 두 방법을 혼합한 복합법 등이 현재 많이 사용되고 있다. 국내에서도 이에 대한 연구가 많이 수행되어 여러 추정식이 개발되어 있지만 대부분 외국에서 개발된 비파괴 강도 추정식을 사용하고 있으며 국내의 콘크리트 구조물에 적용하기에는 무리가 따른다고 할 수 있으며, 특히 재령에 따른 반발도의 변화에 관해서는 외국에서 제한된 소수의 연구결과만이 발표되었을 뿐 국내에서는 거의 없는 실정이다. 본 연구에서는 국내 실정에 적합한 비파괴 강도 추정식의 제안을 목적으로 국내 대학 및 연구기관에서 수행된 연구결과를 바탕으로 일반 강도 범위에서 물-시멘트비, 재령의 및 양생조건에 따른 반발도 및 복합법에 의한 강도와 재령의 영향을 분석하였다. 재령이 비파괴 강도에 미치는 영향을 구명하기 위해 28일 회귀식을 모든 재령에 적용하는 단일회귀식 방법과 재령별로 회귀식을 적용하는 방법의 두 가지로 분석을 수행하여 재령계수를 제안하였다. 단일회귀식을 사용하여 반발도법과 복합법으로 구한 재령계수는 반발도나 강도와는 무관한 재령만의 함수가 되어 콘크리트의 물성치를 고려할 수 없지만, 재령에 따른 회귀식을 사용하여 구한 재령계수는 재령뿐만 아니라 반발도와 강도의 함수가 되며 고강도 콘크리트일수록 재령계수들이 작아지는 것으로 나타났다. 그리고 재령에 따른 회귀식을 사용한 경우 반발도와 강도에 따른 재령계수의 변화를 고려할 수 있으므로 더 합리적인 것으로 판단되며, 본 연구에서 제안된 재령계수를 국내의 콘크리트 강도 비파괴 추정식 제안에 있어 도움이 될 수 있는 참고자료로 제시하고자 한다.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1161-1161
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• 2001

Rapid cost-effective methods of measuring wood quality are extremely important to tree improvement programs where it is necessary to test large numbers of trees. Non-destructive sampling of a forest can be achieved by using increment cores generally removed at breast height. At CSIRO Forestry and Forest Products methods for the rapid, non-destructive measurement of wood properties and wood chemistry based on increment core samples have been developed. In this paper the application of near infrared (NIR) spectroscopy to the prediction of a range solid wood properties, including density, longitudinal modulus of elasticity (E$\sub$L/) and microfibril angle (MFA), is described. Experiments conducted on individual species (Eucalyptus delegatensis and Pinus radiata), the two species combined and a number of mixed species from several genera are reported. NIR spectra were obtained from the radial/longitudinal face of each sample and used to develop calibrations for the measured physical properties. When the individual species were used the relationships between laboratory determined data and NIR fitted data were good in all cases. Coefficients of determination (R$^2$) ranging from 0.77 for MFA to 0.93 for stick density were obtained for E. delegatensis and R$^2$ ranging from 0.68 for MFA to 0.94 for strip density were obtained for P. radiata. The calibration statistics for the combined E. delegatensis and P. radiata samples were similar to those found for the individual species. As these results indicated that it might be possible to produce general calibrations based on samples from a number of species of a single genus or samples from a number of different genera, a wide range of species was subsequently tested. Good relationships were obtained for both density and E$\sub$L/. These calibrations had R$^2$ that were slightly lower than those determined using individual species and standard errors that were higher. The mixed species calibrations, when applied to the E. delegatensis and P. radiata sample sets, provided good estimates of density (stick and strip) and E$\sub$L/. The results demonstrated that a mixed species calibration, that encompasses wide variation in terms of, wood anatomy, chemistry and physical properties, could be used to rank trees. Experiments reported in this paper demonstrate that solid wood properties can be estimated by NIR spectroscopy. The method offers a rapid and non-destructive alternative to traditional methods of analysis and is applicable to large-scale non-destructive forest resource assessment, and to tree breeding and silvicultural programs.