• 대한의용생체공학회:의공학회지
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• 제19권5호
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• pp.495-502
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• 1998

Y.C. Fung[1]에 의한 연조직의 점탄성에 관한 수학적 모델이론 (Fung's Quasi-linear vlscoelastic theory)을 이용하여 인간의 인두조직의 점탄성(vlscoelatlcity)특성을 측정하기 위하여 반복성하중(cyclic load) ,응력완화 (tensile stress relaxation), incremental load, 그리고 일축성인장 (uniaxial tensile) 시험 등을 실시하였다. 실험적으로 측정한 인두조직의 점탄성특성이 이미 조사된 다른 조직의 점탄성특성과 정량적으로 비교되었다. 인두조직의 점탄성특성의 정량화를 위하여 Y.C.Fung의 수학적 모델이 적용되었는데 응력완화(tensile stress relaxation) 시험 측정결과로부터 도출된 표준화된 응력완화(reduced stress relaxation)함수 G(t)와 일축성인장(uniaxial tensile)시험에서 도출된 탄성반응(elastic response)함수 5(t)를 이용하여 시간에 따른 응력의 궤적을 산출하여 이를 반복성 하중(cyclic load)실험에서 측정된 결과와 비교, 분석하였다. 이러한 인두조직의 점탄성특성에 관한 연구결과는 향후 유한요소를 이용한 인두의 생체역학적 모델의 기본 데이터로 이용될 수 있다.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.435-450
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• 2016

Experimental studies were conducted on 36 grouted splices to investigate their mechanical performance under four loading schemes: (1) incremental tensile loading, (2) repeated tensile loading, (3) cyclic loading at high stress, and (4) cyclic loading at large strain. Load-deformation responses of the grouted splices under cyclic loadings were featured with pinching effect and stiffness degradation compared to those responses under tensile loadings. The shape of the hysteresis loops of load-deformation curves was similar to that under incremental tensile loading. For the purpose of structural analysis, stress-strain relationships were presented for grouted splices under various loadings.

• Journal of Welding and Joining
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• 제34권4호
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• pp.28-33
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• 2016

The purpose of this study is to evaluate the redistribution of transverse residual stress in the multi-pass FCA butt weld of YP47 in the hatch coaming top plate of ultra large size containership under the tensile cyclic load. In order to do it, the configuration of modified H type specimen including restraint length was first designed to simulate the restraint condition of the butt weld in hatch coaming top plate. FE analysis procedure for evaluating the transverse residual stress was verified by comparing the calculated mean and surface residual stresses with the measured results in the test specimen. After that, the effect of the cyclic load on the redistribution of transverse residual stress was evaluated by comprehensive FEA. From the results, it was found that although the maximum transverse residual stress decreased with an increase in the applied maximum load, the effect of the cyclic load on the mean residual stress is small enough to be negligible. It is because the maximum stress of the ship corresponding to the probability of 10E-8 is less than 70% of yield stress of the weld.

• Geomechanics and Engineering
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• 제14권2호
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1784-1787
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• 2008

Molecular dynamics (MD) simulations are used to analyze behavior of copper nanowires under cyclic loading. The embedded atom method (EAM) potential is employed to represent atomic interaction. Cyclic load is applied in two ways (Forward Tension / Reverse Compression and Forward Compression / Reverse Tension). The results show that dislocations are piled up as a result of plastic deformation during alternate tensile and compressive loading. After cyclic loading with a change of direction, yield stress decreases in consequence of the effect by the dislocation pileups. On the other hand, under FC/RT cyclic load, phase transformation represent associated with mechanical twinning. And copper nanowire can return to almost former undeformed condition during tensile loading at 300K.

• 콘크리트학회논문집
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• 제14권2호
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• pp.239-248
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• 2002

철근 콘크리트 면부재의 주기거동을 나타내기 위하여 소성모델과 손상모델의 통합구성모델을 개발하였다. 인장-압축을 받는 콘크리트의 응력은 개념적으로 콘크리트의 스트럿 작용에 의한 압축응력과 인장균열에 의한 인장응력의 합으로 정의하였다. 인장균열의 비등방손상에 의하여 영향을 받는 압축파괴의 등방손상을 나타내기 위하여 다중파괴기준을 갖는 소성모델을 사용하였으며, 다중균열 방향에서 인장응력-변형률 관계를 나타내기 위하여 다중고정균열손상모델과 인장균열의 소성유동모델의 개념을 사용하였다. 이러한 통합모델은 주기 인장-압축 상태의 철근 콘크리트의 거동측성, 즉 다중 인장균열 방향, 점진적으로 회전하는 균열 손상, 콘크리트의 압축파괴를 나타낼 수 있다. 제안된 구성모델은 유한요소해석에 적용되었으며, 주기하중을 받는 철근 콘크리트 전단패널 및 전단벽에 대한 기존의 실험결과들과의 비교를 통해 검증되었다.

• Journal of Welding and Joining
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• 제24권3호
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• pp.55-59
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• 2006

This paper is concerned with a study on cyclic bending load of bus folding door pillar including adhesive bonding and spot welding. Three specimen types were used such as spot welding, I-type adhesive bonding and M-type adhesive bonding in this study. The tensile-shear tests were carried out to evaluate the tensile-shear strength of these three specimen types. Also four-point bending tests were carried out to evaluate the static and dynamic bending load. From the results, using adhesive bonding has a better effect on the static and dynamic bending load than using spot welding. Therefore, manufacturing better structural products can be expected by applying hybrid welding using adhesive and spot welding to those.

• 한국압력기기공학회 논문집
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• 제15권2호
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• pp.31-39
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• 2019

Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1446-1455
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• 2000

Fatigue crack initiation and propagation behavior under cyclic biaxial loading has been investigated using thin-walled tubular specimen with a hole. Two types of biaxial loading system, i.e. cyclic tensile loading with super-imposed static torsional load and cyclic torsional loading with superimposed static tensile load, with various values of the biaxial loading ratio, $\tau$ s/ $\sigma$ max (or $\tau$ max/ $\sigma$s) were employed. Fatigue tests show that fatigue crack near the hole initiates and propagates at 900 and 450 direction to the longitudinal direction of the specimen under cyclic tensile and torsion loading with static biaxial stress, respectively, and the static biaxial stress doesn't have any great influence on fatigue crack initiation and growth direction. Stress analysis near the hole of the specimen shows that the crack around the hole initiates along the plane of maximum tangential stress range. Fatigue crack growth rates were evaluated as functions of equivalent stress intensity factor range, strain energy density factor range and crack tip opening displacement vector, respectively. It is shown that the biaxial mode fatigue crack growth rates can be relatively consistently predicted with these cyclic parameters.

• Steel and Composite Structures
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• 제30권2호
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• pp.171-183
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• 2019

As China's infrastructure continues to grow, concrete filled steel tubular (CFST) structures are attracting increasing interest for use in engineering applications in earthquake prone regions owing to their high section modulus, high strength, and good seismic performance. However, in a corrosive environment, the seismic resistance of the CFST columns may be affected to a certain extent. This study attempts to investigate the mechanical behaviours of square CFST members under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were subjected to a reversed cyclic load and tested. Third, comparisons between the test results and the predicted ultimate strength by using four existing codes were carried out. It was found that the corrosion leads to an evident decrease in yield strength, elastic modulus, and tensile strain capacity of steel plates, and also to a noticeable deterioration in the ultimate strength, ductility, and energy dissipation of the CFST members. A larger axial force ratio leads to a more significant resulting deterioration of the seismic behaviour of the columns. In addition, the losses of both thickness and yield strength of an outer steel tube caused by corrosion should be taken into account when predicting the ultimate strength of corroded CFST columns.