• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.263-271
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• 2010

The purposes of this study is to verify the fracture characteristic of steel which is manufactured in Korea, subjected to cyclic loading. This investigation deals with the low cycle fatigue behavior of longitudinal reinforcement in reinforced concrete bridge substructure (piles and columns of piers). Eighty-one specimens of longitudinal reinforcement were tested under axial strain controlled reversed cyclic tests with strain amplitudes. The selected test variables are ratio of tension strain to compression strain, yield stress of longitudinal reinforcement, ratio of diameter of longitudinal steel to clear length of longitudinal steel, size of longitudinal steel and strain amplitudes. Low cycle fatigue behavior and low-cycle fatigue life are investigated and discussed in this paper.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.193-200
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• 2008

Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.19-23
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• 2016

In this study, we have constructed a measuring system to investigate tensile stress measurement of tendons, which is employed in bridges, by means of the non-destructive and non-contact method. The measuring system consists of tensile stress applying apparatus up to 2 GPa, and power supply for ac and dc current to tendon directly to magnetize tendon in circular direction and to coil wound on yoke to magnetize tendon in axial direction. We have used two kinds of tendon, which were produced by different companies, using the measuring system constructed in this work. Two kinds of experiments are carried out in this work; $1^{st}$ experiment : ac current was applied to the tendon and dc current was applied to coil wound on the yoke, and voltage induced from search coil wound on yoke (SCY) was measured and $2^{nd}$ experiment : dc current was applied to the tendon and ac current was applied to coil wound on the yoke, and voltage induced from search coil on tendon (SCT) was measured. In case of $1^{st}$ experiment, voltage induced from SCY was changed below 200MPa tensile stress but the voltage was not increased above 200 MPa. In case of $2^{nd}$ experiment, voltage induced from SCT was decreased up to 1.5 GPa linearly. We expect that $2^{nd}$ experiment could be applied to the non-destructive testing of tensile stress measurement of tendon.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.3-11
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• 1996

본 연구는 고체 추진기관의 각종 밀봉 부에 많이 사용되는 O-링의 설계시 고려되는 각종 형상인자의 변화에 따른 O-링의 거동과 응력 상태를 분석하여 설계 최적조건을 찾기 위한 내용을 다루고 있다. 조립 부의 내외경과 조립 공차, 챔퍼길이와 각도, 조립 홈의 외경, 깊이, 폭, 구성반경, O-링의 내경과 선 직경 등의 설계 변수에 의한 조립부 형상과 재료의 물성치, 유한요소 선택 및 요소 분할, 경계조건, 하중조건, 접촉부 정의 등을 MSC/PATRAN3의 $PCL^{[1]}$/로 프로그래밍 하여 설계변수에 의한 결과 분석을 손쉽게 수행할 수 있도록 시도하였다 고무의 Hyperelastic 물성치는 문헌상의 자료$자료^{[2]}$에 제시된 Ogden 상수를 사용하였으며 추후에는 인장시험, 순수전단시험, 이 축 인장시험을 통해 실험적으로 측정$^{[3]}$ 하여 적용할 예정이다. 고무의 대변형, 대 변형률을 고려한 비선형 응력해석은 MSC/PATRAN3의 Advanced FEA 모듈과 ABAQUS 5.5를 사용하였다. 본 연구에서의 해석결과를 설계변수들의 영향을 비교 분석하는데 사용하였으나 그 정확도가 입증된 상태는 아니며 추후 실제 조립 및 수압시험을 통해 평가할 예정이다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.481-487
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• 1984

The dependence of Lankford's value of rimmed steel sheets on plastic strain in investigated in this paper. It is shown that Gotoh's theory predicts the Lankford's value satisfactorily, if suitable material constants are adopted. In addition the strain dependence of Lankford's value in the balanced biaxially-prestrained steel sheets is studied experimentally.

• The Korean Journal of Rheology
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• v.7 no.2
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• pp.128-138
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• 1995

본 논문에서는 전단띠형성에 있어서 전단변형의 집중화 현상을 이방성 탄소성 재료 에 대해서 해석하였고 소성스핀과 비등방성이 전단띠 형성에 미치는 영향을 연구하였다. 평 면응력 상태에서 소성스핀을 갖고있는 이방성 탄-소성 재료에 대해서 재료 분랑ㄴ정 해서 을 수행하여 변형률 집중화의 시작에 미치는 소성스핀과 비등방성의 효과를 연구하였다. 해 석 결과 이방성 재료에서의 전단띠 형성은 압축 또는 인장의 하중 형태나 이방성 축의 초기 각도 그리고 소성스핀의크기에 따라 그 시작이 촉진되거나 지연되었고 전단띠 생성의 방향 도 달라졌다.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.89-93
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• 1991

A new kind of a non-contact torque sensor which uses the difference of the maximum magnetic inductions as measurand was constructed. The torque sensor utilizes the tensile and compressive stress of two cores which are attached on the rotating shaft. This sensor shows that the linearity was better than 1 %, and the transient torque can be measured at the sampling rate of 10 kHz which is the same as magnetizing frequency of the core.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.277-287
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• 2017

This paper describes the specifications on balanced steel ratio and maximum reinforcement for the design of RC flexural members by the Korean Highway Bridge Design Code based on limit states design. The Korean Highway Bridge Design Code (Limit States Design) is not provide for the balanced steel ratio specification for the calculation of required steel area of RC flexural members design. The maximum steel area limited the depth of the neutral axis at the ultimate limit states after redistribution of the moment, and also recommended the maximum steel area should not exceed 4 percent of the cross sectional area. However, from the maximum neutral axis depth provisions should increase the cross section is calculated to be less the maximum reinforcement area, and according to the 4% of the cross sectional area of the concrete, the tensile strain of the reinforcement is calculated to be greater than double the yielding strain, so can not guarantee a ductile behavior. This study developed a balanced reinforcement ratio that is basis for the required reinforcement calculation for tension-controlled RC flexural members design in the ultimate limit states verification provisons and material properties and applied the ultimate strain of the concrete compressive strength with a simple formular to be applied to design practice induced. And assumed the minimum allowable tensile strain of reinforcement double the yielding strain, and applying correction coefficient up to the ratio of maximum neutral axis depth, proposed maximum steel ratio that can be applied irrespective of the reinforcement yield strength and concrete compressive strength.

• Elastomers and Composites
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• v.47 no.2
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• pp.121-128
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• 2012

Waste EPDM(W-EPDM) collected from the automotive weather strip and the gasket of a laundry machine has not been effectively recycled. Using this W-EPDM powder and other ingredients, i.e., binder(polyolefin resin, polyolefin elastomer, etc.), filler and additives, various economic rubber composites were made by extrusion. In advance of main experiments, the effects of ultrasonic treatment of W-EPDM on the property of rubber composites, comparison in the property of the composites of W-EPDM with those of virgin and devulcanized EPDM, and waste tire rubber were investigated. Also, the properties of the rubber composites extruded with a 12-screw extruder were compared with those extruded with twin-screw extruder. Various W-EPDM composites for synthetic turf filler and car mat were extruded and injection molded, and 3 main properties of tensile strength, elongation and hardness were investigated to develop economical and proper recipes of the rubber composites.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.83-90
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• 2024

This study investigates the 3D printing characteristics of strain hardening cement composites (SHCC) reinforced by PVA fibers. Three SHCC mixtures with diverse fiber volume fractions (1.0% for F1.0 mixture, 1.5% for F1.5 mixture, and 1.8% for F1.8 mixture) were designed. Except for the F1.0 mixture, all mixtures met the necessary conditions for multiple micro-cracking, with higher fiber volume fractions more readily satisfying these conditions. The flow values of three SHCC mixtures were within the 3D printable range of 120~160 mm, exhibiting decreased flow values with increasing the fiber volume fractions. Observation of the printed SHCC surfaces indicated that the F1.0 mixture had a Level-3 (good) rating, while F1.5 and F1.8 were rated as Level-2 (average). Higher fiber volume fractions resulted in poorer surface quality, thus, further research needs to be performed for modulating SHCC mixture suitable for 3D printing. The uniaxial tension behavior showed that the F1.0 mixture failed at lower strain, whereas F1.5 and F1.8 exhibited higher strain performance with multiple micro-cracks occurring.