• Journal of the Korea Convergence Society
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• v.5 no.1
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• pp.23-27
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• 2014

In case eccentric load is applied at compact tension specimen, the propagation behavior due to existence or nonexistence of hole, numbers and positions of holes near crack is investigated in this study. Strain energy, displacement and stress happened in specimen are examined through simulation analysis. And stress intensity factor is obtained by the basis of strain energy and deformation. When defect or hole exists in structure, the possibility of fracture can be thought to be verified by using the study result.

• Computational Structural Engineering
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• v.4 no.3
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• pp.99-106
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• 1991

Flexural load-deflection relationships for steel fiber reinforced concrete(SFRC) are dependent on the tensile and compressive constitutive behaviors of the material, which may be refined in the presence of strain gradients under flexural loads. Considering the relatively large amount of flexural test results available for steel fiber reinforced concrete, and the relative ease of conducting such tests in comparison with direct tension tests, it seems to be important to obtain basic information on the tensile constitutive behavior of SFRC from the result of flexural tests. For this purpose "System Identification" technique was used for interpretating the flexural test data and it was successful in obtaining optimum sets of main parameters which explain the tensile constitutive behavior of SFRC under flexure.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1069-1074
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• 1999

본 연구에서는 PbZr(sub)0.53Ti(sub)0.47O$_3$(PZT) 박막을 복수 도포함에 따른 박막내의 응력을 온도의 함수로 실시간(in situ) 측정하였으며, 응력발생의 원인에 박막의 건조, 열분해(pyrolysis), 치밀화 및 결정화 현상과 연관시켜 설명하였다. 도포직후 단층박막에 생성된 55MPa의 인장응력은 가열됨에 따라$ 300^{\circ}C$-$350^{\circ}C$에서 최대 145MPa로 증가하였으며, 박막내의 응력은 모든 온도구간에서 항상 인장응력을 나타내었더. 다층도포시 $650^{\circ}C$까지 열처리 주기를 완료한 층이 두꺼워질수록 새로 도포한 층의 영향은 점차 감소하였으며, 9층박막에 이르러서는 가열과 냉각에 따라 응력이 동일하게 변화하였다. 응력측정 결과 다층박막의 치밀화는 $350^{\circ}C$에서 시작되어 $520^{\circ}C$-$550^{\circ}C$ 부근에서 완료되는 것으로 나타났으며 치밀화가 시작하는 온도는 미세경도 측정결과와 일치하였다. $PbTiO_3$(PT)와 달리 PZT 다층박막은 Si 기판 위에서 perovskite로의 결정화가 일어나지 않았다.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.491-498
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• 2001

The failure phenomenon of overlaid concrete structures, such as surface crack and peel-off failure in the contact zone, was investigated due to temperature shock(rainfall). To investigate this failure phenomenon, the surface tensile stress, and the shear stress, the vertical tensile stress in the contact zone were analysed using the non-linear stress-strain relationship of material such as strain-hardening- and strain-softening diagrams. Rainfall intensity, overlay thickness and overlay material were the main variables in the analyses. It is assumed that the initial temperature of overlaid concrete structures was heated up to 55$\^{C}$ by the solar heat. With a rain temperature 10$\^{C}$ and the rainfall intensity of nR=1/a, tR=10min, 60min, the stress states of overlaid concrete structures were calculated. The result shows that only fictitious cracks occurred in the overlay surface and no shear bond failure occurred in the contact zone. The vortical tensile stress increasing with overlay thickness was proved to be the cause of peel-off failure in the contact zone. The formulae for relationship between the vertical tensile stress and overlay thickness, material properties were derived. Using this formulae, it is possible to select proper material and overlay thickness to prevent failure in the contact zone due to temperature shock caused by rainfall.

• Journal of Korean Association for Spatial Structures
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• v.10 no.3
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• pp.57-64
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• 2010

Uniaxial tensile tests of ETFE membrane are performed in this paper. Three kinds ETFE membrane with different thickness are used in the tests. The tensile strength, the tensile strain at break and the stress-strain curve are obtained from the tests. Futhermore, The cycle loading test of ETFE membrane is carried out through using different values of cycle stress. The residual strain, the relaxation of stress and the change of the elastic modulus of foil are investigated. In the creep test, three kinds of temperature (25, 40 and 60 $^{\circ}C$)and three kinds of stress(3,6and9 MPa) are set respectively and the creep time lasts 24 hours.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.72-75
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• 2005

The profiles of the second-order higher harmonics during B-H hysteresis loop have been measured as functions of the tensile stress in grain-oriented $3.2{\%}$ Si steels. The observed harmonics profiles have been analyzed in terms of the nonlinear, asymmetric magnetization which reflects the domain reorientation under the field. The field interval of the second-order higher harmonics is related to the nucleation and annihilation fields and a measurement method for the magnetostriction is proposed using the harmonics profiles under tensile stress.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.343-354
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• 2008

A new method is suggested herein to measure the virgin earth stresses by means of a borehole. This novel concept is basically a combination of borehole stress relieving and borehole fracturing techniques. The destressing of the borehole is achieved by means of inducing thermal tensile stresses at the borehole periphery by using a cryogenic fluid such as Liquid Nitrogen($LN_2$). The borehole wall eventually develops fractures when the induced thermal stresses exceed the existing compressive stresses at the borehole periphery in addition to the tensile strength of the rock. The above concept is theoretically analyzed for its potential applicability to interpret in situ stress levels from the tensile fracture stresses and the corresponding borehole wall temperatures. Coupled thermo-mechanical numerical simulations are also conducted using FLAC3D, with thermal option, to check the validity of the proposed techniques. From the preliminary theoretical and numerical analysis, the method suggested for the measurement of in situ stresses appears to be capable of accurate estimation of the virgin stresses by monitoring tensile crack formation at a borehole wall and recording the wall temperatures at the time of crack initiation.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.45-52
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• 2002

It has been known that tensile residual stresses occurring by the thermal expansion coefficient mismatch between fiber and matrix is a cause of the weak strength of metal matrix composites(MMCs). In order to solve this problem, TiNi alloy fiber was used as a reinforced material in TiNi/A16001 shape memory alloy composite in this study. TiNi alloy fiber improves the tensile strength of the composite by causing compressive residual stress in matrix on the basis of its shape memory effect. Pre-strain was imposed to generate the compressive residual stresses inside the TiNi/A16001 shape memory alloy composites. AE technique was used to quantify the microscopic damage behavior of the composite at high temperature. The effect of applied pre-strains on the AE behavior was also evaluated.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.395-400
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• 2001

The Split Hopkinson Pressure Bar(SHPB) technique, a special experimental apparatus, has been used to obtain the material behavior under high strain rate loading condition. In this paper, dynamic deformation behaviors of the PMMA under high strain rate tensile loading are determined using SHPB technique.

• Magazine of the Korea Concrete Institute
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• v.2 no.1
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• pp.79-90
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• 1990

The purpose of this paper is to study on the effect of cutting off tension bars in reinforced concrete beams. that is, the ultimate strength, the failure mode and thl} tension stress distribution through the span. To achieve this purpose, a full-scale frame and seven small scale model beams (five rectangular and two T-section beams) were tested. The four main model specimens and two speciml}ns without cutting off tension bars 1,'{ere analyzed as plane stmss element with package program ADINA. As a result of test and analysis, the shorter' distance bet ween the reaction point and the cutting off point, the higher the ultimate strength of a bl}am will be when other physical properties are equal.