• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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• pp.50-54
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• 2002

Influences of bending strain on the critical current ($I_c$) in Ag-sheathed Bi-2223 superconducting tapes at 77K were investigated. The effect of bending mode on the bending strain characteristics was discussed in viewpoints of sample geometry, n-value and damage morphology. Especially, in this paper, we reported the $I_c$ behavior in Ag alloy sheathed Bi-2223 multifilamentary superconducting tapes under hard bending. As a result, $I_c$ degradation behavior of the hard bending appeared remarkably than the case of easy bending, but it did not influence greatly on the n-value.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.84-87
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• 2000

Square tubes used for vehicle structure components have an important role on keeping its stiffness and preserving occupant safety in vehicle collision and rollover in which it experience axial collapse, bending collapse or both. Bending collapse, which absorbs kinetic energy of the impact and retains a survival space for the occupant, is a dominant failure mode in oblique collision and rollover. Thus, in this paper, the bending collapse characteristics such as the maximum bending moment and energy absorption capacity of the square tube replaced by light-weight material were evaluated and presented. The bending test of cantilever tubes which were fabricated with aluminum, GFRP and aluminum/ GFRP hybrid by co-curing process was performed. Then the maximum bending moment and the energy absorption capacity from the moment-angle curve were evaluated. Based on the test results, it was found that aluminum/ GFRP hybrid tube can show better specific energy absorption capacity compared to the pure aluminum or GFRP tube and can convert unstable collapse mode which may occur in pure GFRP tube to stable collapse mode like a aluminum tube in which plastic hinge is developed.

• 한국정밀공학회지
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• 제14권9호
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• pp.37-44
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• 1997

In this paper the bending collapse characteristics of square and rectangular steel tubes were studied with the pure bending test machine which apply pure bending moment without imposing shear and tensile forces. Under pure bending moment, delayed buckling modes occur and depend on test length and shape of section. For delayed mode, the endrgy of bending moment is absorbed by strain hardening energy. The pre- dictions of maximum moment and moment-rotation angle curve from those concepts are in good agreement with experimental observations.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.6-11
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• 2004

The influences of mixed strain mode of bending-tension on the critical current. Ic in externally reinforced Bi-2223 tapes and their interaction were investigated in this study. A test fixture which providing a mixed deformation mode of bending-tension to HTS tapes has been newly devised. When the total strain induced in the tape in the mixed strain mode was expressed by the superposition of the bending and tensile strains the irreversible strain for the critical current degradation of Bi-2223 tapes increased, as compared with the simple bending mode case. The $I_c$ degradation at the region exceeding the irreversible strain showed a medium between the simple bending case and the simple tension case. As the initial bending strain imparted increased , namely as the diameter of mandrel adopted decreased. the apparent irreversible strain in Bi-2223 tapes increased . but the increment became smaller As a result. it can be found that the tension to be applied to bent Bi-2223 tapes during cabling should be smaller. as the mandrel diameter becomes smaller.

• Geomechanics and Engineering
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• 제20권1호
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• pp.9-18
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• 2020

Three-point bending specimens have been used to investigate the mixed mode fracture of green sandstone. Dimensionless stress intensity factors and T-stresses were calculated first by using the finite element method for various crack lengths, crack angles and span to length ratios. It is shown that three-point bending specimens can provide the whole range of mode mixities from pure mode I to pure mode II, provided suitable values are chosen for the crack angle and span to length ratio. The fracture test results were also used to compare with predictions of different criteria. These comparisons show that modified criteria including the influence of the T-stress agree better with experiment than the conventional criteria but that no one criterion matches perfectly the test results.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.134-138
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• 2003

The influences of mixed mode of bending-tension on the Ic degradation and their interaction on the strain effect were evaluated in this study. A test fixture which applies a mixed deformation mode of bending-tension to HTS tapes has been newly devised. When the strain induced in the tape due to the mixed deformation mode was expressed as a total tensile strain, the irreversible strain to the critical current degradation of Bi-2223 tapes increased when compared with the case of simple bending mode, and the value at both ends were larger than that at the central region of the bend part. The Ic degradation behavior at the region exceeding the irreversible strain showed quiet a rapid drop of the Ic when compared with the simple bending cases. As the applied bending strain increased namely as the diameter of mandrel adopted decreased, the apparent irreversible strain of Bi-2223 tapes increased However, the increment decreased as the mandrel diameter decreased. As a result, it could be found that the tension to be applied to the Bi-2223 tapes during cabling of HTS tapes should be smaller, as the mandrel diameter becomes smaller.

• 한국지반공학회논문집
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• 제36권3호
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• pp.25-36
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• 2020

동토의 세립분 함유량에 따른 파괴특성을 파악하기 위해 -10℃의 온도에서 다양한 세립분 함유량과 초기 노치(notch)의 위치를 조정한 직사각형 공시체를 제작하여 Three-point bending 시험을 수행하였다. 시험결과를 바탕으로 동토의 mode I 파괴인성(fracture toughness)을 산정하였으며, 하중-변형 곡선의 최대점까지의 fracture energy를 산정하여 동토의 mixed-mode(mode I + II) 파괴특성을 파악하였다. 시험결과, 최대하중 및 mode I 파괴인성은 세립분 함유량 10%까지 증가하다가 15%에서 다시 감소하는 경향을 나타내었다. 또한, 노치의 위치가 공시체 중심에서 멀어질수록 mode II 하중의 증가로 인해 균열이 진행하는데 필요한 fracture enenrgy가 증가하는 것으로 나타났으며, 세립분 함유량이 증가할수록 mode II 하중의 증가비율 또한 증가하는 것으로 나타났다.

• 산업기술연구
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• 제17권
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• pp.213-218
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• 1997

This study is concerned with characteristics of bending collapse of aluminum members with multi-cell section. Aluminum is light so it is compatible of being used for vehicle structures members. Bending collpase behaviors of aluminum members with multi-cell section are very complex and tension failure mode are occured in experiment. In this paper, the aluminum members are modeled to be able to represent the tension failure mode and, characteristics of bending collapse of aluminum members with multi-cell section by experimental method are compared with the results of PAM-CRASH.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.51-73
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• 2014

A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cable-stayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

• Wind and Structures
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• 제29권3호
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• pp.163-175
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• 2019

Multispan suspension bridges make a good alternative to single-span ones if the crossed strait or river width exceeds 2-3 km. However, multispan three-tower suspension bridges are found to be very sensitive to the wind load due to the lack of effective longitudinal constraint at their central tower. Moreover, at certain critical wind speed values, the aerostatic instability with sharply deteriorating dynamic characteristics may occur with catastrophic consequences. An attempt of an in-depth study on the aerostatic stability mode and damage mechanism of three-tower suspension bridges is made in this paper based on the assessment of strain energy and dynamic characteristics of three particular three-tower suspension bridges in China under different wind speeds and their further integration into the aerostatic stability analysis. The results obtained on the three bridges under study strongly suggest that their aerostatic instability mode is controlled by the coupled action of the anti-symmetric torsion and vertical bending of the two main-spans' deck, together with the longitudinal bending of the towers, which can be regarded as the first-order torsion vibration mode coupled with the first-order vertical bending vibration mode. The growth rates of the torsional and vertical bending strain energy of the deck after the aerostatic instability are higher than those of the lateral bending. The bending and torsion frequencies decrease rapidly when the wind speed approaches the critical value, while the frequencies of the anti-symmetric vibration modes drop more sharply than those of the symmetric ones. The obtained dependences between the critical wind speed, strain energy, and dynamic characteristics of the bridge components under the aerostatic instability modes are considered instrumental in strength and integrity calculation of three-tower suspension bridges.