• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.200-203
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• 2007

Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) with different growth methods by performing an in-situ tensile testing in a scanning electron microscope. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator. We also obtained different tensile load of carbon nanotube with different growth methods.

• 에너지공학
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• 제24권4호
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• pp.55-62
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• 2015

It is expected that the size of welding defect affects the mechanical performance of welded medium density polyethylene (MDPE) pipe joints. In this study, butt fusion welded MDPE pipe joints with a single spherical or planar defect of various sizes were studied using experimental crush testing and also by finite element method. The crush test showed that the mechanical performance of crush was not affected by the size and geometry of a single welding defect when the defect size was increased to 45% of the pipe's wall thickness. The simulation results indicated that the effect of the single welding defect on the Von Mises stress distribution near the defect explained the reason of the test results.

• 한국지진공학회논문집
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• 제24권4호
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• pp.189-196
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• 2020

In this study, two full-scale gravity load-designed reinforced concrete corner beam-column joints were tested by being subjected to uniand bi-directional cyclic lateral loading. The test variable was loading type: uni- or bi-directional loading. To investigate the effect of the loading type on the cyclic behavior of joint specimens, damage progression, force-deformation relation, contribution of joint deformation to total drift, joint stress-strain response, and cumulative energy dissipation were investigated. The test data suggest that bidirectional loading can amplify damage accumulation in the joint region.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.210-211
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• 2021

This study introduces and demonstrates the application of an experimental regime for anti-seismic performance evaluation of waterproofing materials to used for concrete pile walls. Concrete pile walls are subject to high degree of seismic load, and the occurring stress can affect the waterproofing integrity of the structure, but there is currently no existing methodology or standard for evaluating this property of waterproofing materials. To propose and conduct this evaluation, a new testing apparatus was designed and manufactured intended to be able to test an installed waterproofing material's seismic resistance performance.

• 비파괴검사학회지
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• 제34권2호
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• pp.148-154
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• 2014

광탄성기법은 주응력 차이와 주응력 방향을 측정할 수 있는 편리한 기법이다. 일반적인 재래식 광탄성기법에서는 광탄성 파라미터를 측정하기 위해서는 수작업으로 한 지점씩 측정해야 하므로 많은 시간이 소요되며 광탄성 데이터 측정과 식별에 숙련이 필요하다. 프린지 위상이동법은 최근에 개발되어 광역학분야에서 프린지 데이터를 측정하고 해석하기 위해 편리하게 사용되고 있다. 이 논문은 photoflex (우레탄고무일종) 재질의 마름모 평판 중심점을 지나는 수평선상의 응력분포를 측정하기 위한 실험적 연구이다. 마름모 평판시편의 수평선상에서는 등경프린지 또는 주응력 방향이 일정하므로 4-버켓 위상이동법의 적용이 가능하다. 이 방법은 원형편광기에서 검광판을 $0^{\circ}C$, $45^{\circ}C$, $90^{\circ}C$, 그리고 $135^{\circ}C$ 회전시켜 얻은 4개의 광탄성 프린지를 필요로 한다. 이 방법으로 측정된 실험 결과는 유한요소해석 결과와 정량적으로 비교하였으며, 두 결과가 근접하게 일치되었다.

• Computers and Concrete
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• 제10권1호
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• pp.1-18
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• 2012

This paper presents the details of studies conducted on hollow concrete block masonry (HCBM) units and wall panels. This study includes, compressive strength of unit block, ungrouted and grouted HCB prisms, flexural strength evaluation, testing of HCBM panels with and without opening. Non-linear finite element (FE) analysis of HCBM panels with and without opening has been carried out by simulating the actual test conditions. Constant vertical load is applied on the top of the wall panel and then lateral load is applied in incremental manner. The in-plane deformation is recorded under each incremental lateral load. Displacement ductility factors and response reduction factors have been evaluated based on experimental results. From the study, it is observed that fully grouted and partially reinforced HCBM panel without opening performed well compared to other types of wall panels in lateral load resistance and displacement ductility. In all the wall panels, shear cracks originated at loading point and moved towards the compression toe of the wall. The force reduction factor of a wall panel with opening is much less when compared with fully reinforced wall panel with no opening. The displacement values obtained by non-linear FE analysis are found to be in good agreement with the corresponding experimental values. The influence of mortar joint has been included in the stress-strain behaviour as a monolith with HCBM and not considered separately. The derived response reduction factors will be useful for the design of reinforced HCBM wall panels subjected to lateral forces generated due to earthquakes.

• 한국소음진동공학회논문집
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• 제18권9호
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• pp.937-942
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• 2008

이 논문은 건설이 완료된 700MW급 발전소의 시운전 기간 중 주 급수펌프 임펠러에서 반복적으로 발생된 웨어링 이탈 및 고착, 슈라우드 손상 그리고 축 절단 등의 절손이 부분부하 조건에서 증폭되는 압력맥동과 연관이 있는 것으로 규명되었다.

• 대한기계학회논문집A
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• 제36권5호
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• pp.529-535
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• 2012

본 논문의 목적은 계장화 압입시험과 유한요소해석을 이용하여 아연도금강판의 기계적 물성을 추정하는 것이다. 먼저 인장시험을 통하여 유한요소해석에 요구되는 두께에 따른 아연도금강판의 기계적 물성을 획득하였으며, 이를 이용하여 유한요소해석을 수행하여 특정지점에서의 소성 응력 및 변형률을 획득하였다. 이러한 유한요소해석의 유효성은 계장화 압입시험의 하중-변위선도와 비교를 통하여 검토하였다. 유한요소해석을 통하여 구한 진응력-진변형률 곡선을 인장시험 결과와 비교하여 이의 정확성을 검증하였으며 또한 이를 바탕으로 대표 응력 및 변형률 산출지점을 재평가하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.223-226
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• 2009

The plastics are widely utilized in the inside of vehicles. The dynamic tensile characteristics of auto-body plastics are important in a prediction of deformation mode of the plastic component which undergoes the high speed deformation during car crash. This paper is concerned with the dynamic tensile characteristics of the auto-body plastics at intermediate strain rates. Quasi-static tensile tests were carried out at the strain rate ranged from 0.001/sec to 0.01/sec using the static tensile machine(Instron 5583). Dynamic tensile tests were carried out at the strain rate ranged from 0.1/sec to 100/sec using the high speed material testing machine developed. Conventional extensometry method is no longer available for plastics, since the deformation of plastic is accompanied with localized deformation. In this paper, quasi-static and dynamic tensile tests were performed using ASTM IV standard specimens with grids and images from a high speed camera were analyzed for strain measurement. True stress-strain relations and the actual strain rates at each deformation step were obtained by processing load data and deformation images, assuming the plastics to deform uniformly in each grid.

• 콘크리트학회지
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• 제6권1호
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• pp.89-100
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• 1994

프리스트레스 프리텐숀 보의 전달길이를 위하여 콘크리트의 변형율에 의하여 부착력을 계측하는 간접적인 방법을 일반적으로 사용하여 왔다. 이 트랜스퍼 실험은 실제 보에서 행하여지므로, 실제 상태의 정착부착력을 계측할 수 있다는 장점이 있으나, 최대 정착부착응력과 부착강비를 구하기 난해하며, 그 결과가 매우 분산되어 있으므로, 구조 설계자가 안전한 적정기준을 이해하고 선택하기 어렵다. 콘크리트의 변형을 측정하지 않아도 PS 강선의 정착부착 성능을 얻을 수 있는 대안을 소개하였다. 실제 보에서 PS강재의 긴장을 풀 때와 유사한 상황에서 정축부착 응력을 직접 구하였다. 하중재하부에서 풀려진 PS강선의 긴장력은 하중재하부쪽 강선의 단면증가를 가져오고, 콘크리트 블록에 정착부착력을 발생시키며, 다른 방향(고정부 쪽)으로 슬립을 유발시킨다. 두 개의 중공 로드셀로 양단하중을 최대 부착응력 또는 전면슬립이 일어날 때까지 계측하였다. 프리텐션 콘크리트보의 정착부착 길이를 구하기 위하여 이 방법을 기존의 트랜스퍼 실험방법과 병행하여 사용할 것을 제안한다.