• 한국정밀공학회지
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• 제18권7호
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• pp.85-90
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• 2001

In order to apply the Leak-Before-Break(LBB)concept to nuclear piping, accurate estimation of J-integral and crack opening displacement(COD) is essential for complex loading, such as combined tension and bending. This paper proposes a new engineering method to estimate J-integral and the COD for circumferential through-wall cracked pipes subject to combined tension and bending loading. The proposed method to estimate the COD is validated against three published pipe test data, generated from a monotonically increasing bending load with a constant internal pressure, which shows excellent agreements.

• 한국산업융합학회 논문집
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• 제4권4호
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• pp.379-386
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• 2001

The lower toughness or brittle materials for mechanical test lead to the additional requirement that applied displacements be controlled with high resolution. Biaxial tension and shear tester using stepper motor with harmonic driver is shown. The device had to be high resolution so that the crack initiation process of slow extension and steady growth could be examined, Grip plates were connected to a linear bearing and actuator. The actuators consisted of stepper motors with harmonic driver connected to pre-loaded ball screw and nut assemblies. The encoders and motor controllers were connected to a personal computer so that arbitrary displacements histories could he prescribed in normal and tangential directions. The linear bearings were used to react loads perpendicular to their axes while allowing low friction, parallel movement of the attached grips. Load cells measured the reactions normal and tangential. the loads measured the reactions were recorded by the computer.

• 대한조선학회논문집
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• 제48권4호
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• pp.375-380
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• 2011

Loading/unloading at sea is necessitated as larger container ships are being used. It is also unavoidable to load/unload at sea during military operations. An experimental cable array robot system, which can be used for loading/unloading at sea, consisting of four cables operated by four motors is designed and built. Even though it has simple structure, it has a large pay-load/robot-weight ratio, flexibility and wide workspace and can be easily built at low cost. In order to plan and control the paths of end-effector, two interpolation methods are introduced and compared. Since the robot is entirely based on cable tension, an analysis of tension is also presented for monitoring and planning purpose.

• Computers and Concrete
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• 제9권2호
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• pp.81-97
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• 2012

This paper presents development of double-K fracture model for the split-tension cube specimen for determining the unstable fracture toughness and initial cracking toughness of concrete. There are some advantages of using of split-tension cube test like compactness and lightness over the existing specimen geometries in practice such as three-point bend test, wedge splitting test and compact tension specimen. The cohesive toughness of the material is determined using weight function having four terms for the split-tension cube specimen. Some empirical relations are also suggested for determining geometrical factors in order to calculate stress intensity factor and crack mouth opening displacement for the same specimen. The results of double-K fracture parameters of split-tension cube specimen are compared with those obtained for compact tension specimen. Finally, the influence of the width of the load-distribution of split-tension cube specimen on the double-K fracture parameters for laboratory size specimens is investigated. The input data required for determining double-K fracture parameters for both the specimen geometries are obtained using well known version of the Fictitious Crack Model.

• 공업화학
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• 제5권5호
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• pp.878-888
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• 1994

ABS 수지의 파단 거동을 살펴 보기 위해 rubber content, molecular weight, lubricant의 종류 및 양과 파단 speed, 주위 환경온도를 변수로 측정한 후 전자현미경 사진으로 그 파단면을 살펴 보았다. Tension하에서 rubber content와 lubricant content는 감소할수록, molecular weight와 tension speed는 증가할수록 strength는 증가하였으며, 파단면은 rubber content, speed, molecular weight는 감소할수록, liquid lubricant를 사용할수록 파단부위 주변의 변형이 일어나지 않았으며, 파단면도 수지가 서로 미끄러져 파단되는 상태가 아닌 상분리와 같은 형상으로 분리파단되었다. Impact하에서 rubber content, molecular weight, 주위 환경온도, lubricant content가 증가할수록 strength도 증가하였으며, 파단면은 사진상의 파단표면적이 작은 것이 높은 strength를 나타내고 있다.

• 한국강구조학회 논문집
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• 제10권4호통권37호
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• pp.721-730
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• 1998

강 구조물의 접합부는 구조물이 안전에 큰 영향을 미치는 부분으로서 이에 대한 연구는 많이 이루어지고 있으나 순수 인장력을 받는 접합부의 블록전단 파단에 대한 연구는 외국에서도 근래에 시작되었으며 현재 국내에서는 연구실적이 없는 상태이다. 본 연구는 최근 우리나라에서 제정된 강구조 한계상태설계기준에 따른 블록전단 산정식의 타당성을 인장력을 받는 ㄱ형강 접합부의 실험에 의하여 규명하고자 한다. 연구방법은 기존의 연구결과의 블록전단 파단형상 및 극한내력을 본 연구와 비교분석하고 기준 산정식의 합당성을 평가하였다. 실험결과 접합부는 2가지 형상, 인장항복 전단파단과 전단항복 인장파단이 일어났으며 실험 파단하중이 기준식에 의한 내력보다 약 15% 크게 나타나고 있어 앞으로 보다 많은 연구에 의해 강구조 한계상태 설계법의 블록전단 산정식에 대한 평가가 필요하다고 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.641-646
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• 2000

This paper describes an experimental investigation on the influence of concrete cover thickness on tension stiffening behavior. Total 36 direct tension specimens were tested with variation of cover thickness. Three different concrete compressive strengths were also considered. After cracking, as the cover thickness becomes thinner and the concrete strength becomes higher, tensile stiffness is decreased. Thereby an increase in cover thickness results in increase of the tensile cracking load and tension stiffening effect. Also the increase in concrete strength results in sudden decrease in tension stiffening effect. Hence, the cover thickness and concrete strength are proved to be important factors in tension stiffening behavior.

• 한국항공우주학회지
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• 제30권4호
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• pp.64-69
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• 2002

축방향 인장 및 압축하중을 받는 점탄성층을 갖는 복합재료 적층보의 동력학적 거동을 해석하였다. 개선된 지그재그 보이론과 지배방정식에 기초한 기하학적 상관식을 이용하여 점탄성층을 갖는 복합재료 적층보를 모델링하였고 이에 기초한 보 유한요소를 개발하였다. 축방향 인장 및 압축하중하의 고유진동수와 감쇠계수는 복소수 유일법을 이용하여 계산하였다. 축방향 인장 및 압축하중이 고유진동수 및 감쇠계수에 미치는 영향을 조사하였다.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.20-27
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• 1998

According as the member of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. And, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic evaluation method for them. In this study, by considering nugget edge of the spot weld part of the IB-type spot welded lap joint under tension-shear load to the ligament crack. fatigue strength of various IB-type spot welded lap joints was estimated with the stress intensity factor(S.I.F.) KIII which is fracture mechanical parameter. We could find that fatigue strength evaluation of the IB-type spot welded lap joints by KIII is more effective than the maximum principal stress ($\sigma$1max) at edge of the spot weld obtained from FEM analysis.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1605-1614
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• 2005

For the last four decades, tension test of notched bars has been performed to investigate the effect of stress triaxiality on ductile fracture. To quantify the effect of the notch radius on stress triaxiality, the Bridgman equation is typically used. However, recent works based on detailed finite element analysis have shown that the Bridgman equation is not correct, possibly due to his assumption that strain is constant in the necked ligament. Up to present, no systematic work has been performed on fully plastic stress fields for notched bars in tension. This paper presents fully plastic results for tension of notched bars and plates in plane strain, via finite element limit analysis. The notch radius is systematically varied, covering both un-cracked and cracked cases. Comparison of plastic limit loads with existing solutions shows that existing solutions are accurate for notched plates, but not for notched bars. Accordingly new limit load solutions are given for notched bars. Variations of stress triaxiality with the notch radius and depth are also given, which again indicates that the Bridgman solution for notched bars is not correct and inaccuracy depends on the notch radius and depth.