• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.100-109
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• 2021

This study was examined the tensile strength change of a circular tubular member with artificial sectional damage on its surface to consider surface sectional damage by corrosion. The tensile strength tests were conducted using circular tubular specimens with artificial sectional damage considering sectional damaged height and width on its surface according to the corrosion level. From the tensile strength test results, it is confirmed that tensile strength of the circular tubular specimens was affected by the damaged circumference (damaged width), not damaged length (damaged height) and their tensile failures were appeared at the minimum section of the artificial sectional damage part. Nonlinear finite-element analyses were conducted considering equivalent sectional damage effect on sectional damaged part in tensile specimens to examine the change in the tensile strength of tubular specimens with artificial sectional damage since it is difficult to estimate the sectional damaged surface condition of the specimens clearly. From the nonlinear finite element analysis results for the tensile test specimens, tensile strengths of test specimens with irregular sectional damaged surface were relatively evaluated to be highly decreased than these of FE analysis model with equivalent sectional damage. Therefore, residual tensile strengths of tensile members with irregular sectional damage as local corrosion can be evaluated and predicted using correlation coefficient between tensile test results and FE analysis results with equivalent sectional damage.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.61-66
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• 1999

반복 응력 상태 아래서 알루미나 세라믹의 피로 표면손상 누적현상이 분석되었다. 연속 미끄럼 접촉 시에 발생하는 응력 상태를 재현하기 위해서 동시에 작용하는 수직-수평 반복 압축하중 기법이 사용되었다. 알루미나 구와 평판의 접촉면에서 알루미나 미세 결정의 피로 파손에 의한 마모 입자 형성 기구가 관찰되었고, 반복하중의 횟수와 수직-수평 하중비가 커질수록 마모량은 증가하였다. 반복 접촉하중에 의한 표면손상 누적이 접촉 수직 변위 측정으로 정량화 되었다. 두 접촉 구조물의 강성 (하중-변위 선도의 기울기) 변화가 두 재질의 탄성계수의 변화로 표현되었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.115-115
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• 2009

캐비테이션-에로젼은 침식부식과 유사한 형태의 침식에 의한 손상이다. 즉, 고속의 애체흐름에 노출된 금속 표면을 따라 압력변화에 의해서 생성된 기포들이 파괴되는 것과 관련하여 일어나는 표면손상의 한 형태이다. 본 연구에서는 캐비테이션-에로젼 손상을 억제하기 위하여 WC 서멧을 HVOF 용사하였으며, 캐비테이션-에로젼 특성에 미치는 용사조건의 영향에 중점을 비교분석하였다.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.511-516
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• 2024

The recently enacted detailed guidelines on the performance evaluation of track facilities presented the necessary requirements regarding the evaluation procedures and implementation methods of track performance evaluation. However, the grade of rail surface damage is determined by external inspection (visual inspection), and there is no choice but to rely only on qualitative evaluation based on the subjective judgment of the inspector. Therefore, in this study, we attempted to develop a diagnostic application that can diagnose rail internal defects using rail surface damage. In the field investigation, rail surface damage was investigated and patterns were analyzed. Additionally, in the indoor test, SEM testing was used to construct image data of rail internal damage, and crack length, depth, and angle were quantified. In this study, a deep learning model (Fast R-CNN) using image data constructed from field surveys and indoor tests was applied to the application. A rail surface damage diagnosis application (App) using a deep learning model that can be used on smart devices was developed. We developed a smart diagnosis system for rail surface damage that can be used in future track diagnosis and performance evaluation work.

• Composites Research
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• v.16 no.5
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• pp.15-20
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• 2003

In this paper, the fracture strength of the surface damaged laminates was predicted by applying the fracture strengths of the unflawed and flawed laminates. For prediction, the theoretical equation about the fracture strength of laminates was simplified applying classical laminate theory and was applied to the surface damaged laminates. Lagace's and Tsai's experimental data were used for verifying the theoretical equation. Moreover, to verify the theoretical prediction, an experiment was performed. Surface unflawed laminate and flawed laminates were fabricated and the experiments were made and these results were compared with theoretical predictions. The specimens' fiber direction was same to the tensile direction and the theoretical predictions and the experimental results were showed good agreement. Therefore, by this equation, the fracture strength of structures made of composites will be able to be predicted when the surface of the structures was damaged.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.3-3
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• 2018

산업 발전과 더불어 각종 장비들은 기존에 비해 현저히 가혹한 조건에서 운전되고 있다. 그러한 이유로 고유속, 고회전 등에 기인한 침식 및 캐비테이션 손상이 정적 환경과 비교할 수 없을 정도로 내구성이 저하되어 큰 손상 사고로 이어지는 사례가 다발하고 있다. 아울러 해양환경은 가혹한 부식 조건이므로 동적 손상과 복합적으로 작용하여 그 장비수명은 현저히 단축되고 있는 실정이다. 이를 극복하기 위한 다양한 표면처리 기술이 필요하다고 할 수 있다.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.272-277
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• 1994

The damage of a thin film of Rd6G dye was probed by Surface Second-Harmonic Generation(SSHG) method. A portion of the Rd6G thin film on glass substrate was damaged by 532 nm laser beam, and the damage was probed by detecting intensity variation of SSHG. The result was confirmed through direct observation with optical microscope.oscope.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.139-145
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• 2010

Bending fatigue of aluminium alloy was characterized by acoustic nonlinearity of narrow band laser-generated surface wave. The higher harmonic components generated intrinsically by arrayed line laser beam were analyzed theoretically and acoustic nonlinearity was measured successfully on the surface of fatigue damaged aluminium 6061 alloy. The acoustic nonlinearity increased as a function of fatigue cycles and has close relation with damage level. Consequently, the nonlinear acoustic technique of laser-generated surface wave could be potential to characterize surface damages subjected to fatigue.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.143-143
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• 2016

알루미늄 합금은 내구성과 내식성이 우수할 뿐만 아니라 다양한 표면개질을 통해 그 표면 특성을 더욱 향상시킬 수 있다. 특히 Al-Mg계 5083-H321 Al 합금의 경우 가공성 및 용접성이 우수하여 선체 재료로 널리 이용되는데, 이는 선체중량의 경량화가 가능하여 연료비 절감과 빠른 선속 등 다양한 이점을 지니기 때문이다. 그러나 선속의 고속화에 따라 선체에 가해지는 유체충격이 증가하고 정압 저하에 기인하여 캐비테이션-침식 손상이 증가할 뿐만 아니라 해수환경 특성 상염소이온의 존재로 부식이 가속화되는 등 침식 및 부식의 시너지효과로 손상은 크게 증가한다. 이에 대한 방지대책으로 다양한 표면개질 기법이 제안되고 있으나 강한 충격압이 동반된 캐비테이션 침식-부식 복합 손상 환경에서는 표면처리만으로는 불가능할 수 있다. 따라서 본 연구에서는 양극산화된 5083-H321을 대상으로 캐비테이션 환경 하에서 일정 전위를 인가하여 침식-부식 손상이 최소화되는 최적전위를 규명하고자 한다. 이를 위해 먼저 분극 실험을 통해 재료의 전기화학적 거동을 바탕으로 임의의 전위를 선정하고 해당 전위를 인가한 상태에서 캐비테이션 실험을 실시하였다. 이때 분극실험과 캐비테이션-전기화학 복합실험 모두 $25^{\circ}C$의 해수에서 실시하였으며, 전기화학적 분극실험은 유효면적이 $3.24cm^2$인 시편에 2 mV/s의 분극속도로 0 ~ -3 V 까지 인가하였고, Ag/AgCl 기준전극과 백금대극을 사용하였다. 캐비테이션-전기화학 복합 실험은 정전위를 인가한 상태에서 $30{\mu}m$의 진폭으로 20분간 실시하였으며, 혼팁과 시험편 사이의 거리는 1 mm로 일정하게 유지하였다. 실험 후 표면 손상의 정량적 분석을 위해 인가된 전위별 전류밀도를 비교하고, 무게감소량을 측정하였으며, 손상특성 분석을 위해 3D현미경과 주사전자현미경(SEM)을 통해 표면을 분석하였다.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.585-590
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• 2024

In this study, rail surface defects are increasing due to the aging of urban railway rails, but in the detailed guidelines for track performance evaluation established by the country, rail surface damage is inspected with the naked eye of engineers and simple measuring tools. With the recent enactment of the Track Diagnosis Act, a large budget has been invested and the volume of rail diagnosis is rapidly increasing, but it is difficult to secure the reliability of diagnosis results using labor-intensive visual inspection techniques. It is very important to discover defects in the rail surface through periodic track tours and visual inspection. However, evaluating the severity of defects on the rail surface based on the subjective judgment of the inspector has significant limitations in predicting damage inside the rail. In this study, the rail internal crack characteristics due to rail surface damage were studied. In field measurements, rail surface damage locations were selected, samples of various damage types were collected, and the rail surface damage status was evaluated. In indoor testing, we intend to analyze the correlation between rail surface defects and internal defects using a electron scanning microscope (SEM). To determine the crack growth rate of urban railway rails currently in use, the Gaussian probability density function was applied and analyzed.