• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.105-114
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• 2016

When impact load is applied to a plate structure, a common phenomenon that occurs in structures is plastic deformation accompanied by a large strain and eventually it will experience a fracture accordingly. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is formed by line heating and by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper-Symonds model and Johnson-Cook model with the assumption that strain rate can be neglected when strain rate is less than the intermediate speed is verified through comparing the present numerical results with those in references. This paper ends with describing the future study.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.239-240
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• 2010

This study make samples of fiber into a variable condition with strain-hardening cement composite(SHCC) and evaluate the mechanical properties, results from experiment can be used to construction of database for development and application of SHCC.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.309-314
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• 2000

Rubber is used as a primary suspension component in a vehicle or a mechanical structure. The aim of this study is to establish a procedure for measuring the material properties of rubber and to analyze the differences of material properties of virgin rubber and heat aged rubber. The effect of mechanical conditioning was shown and included in the procedures of tensile. compression. simple shear. and pure shear tests. In addition. using engine oil was recommended for compression test in order not to have barrelling. Moreover, based on the material properties of vil·gin rubber and heat aged rubber. equations of C10 and IRHD were proposed as a function of heat aging temperature and time.

• Journal of the Korean Geosynthetics Society
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• v.8 no.4
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• pp.27-34
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• 2009

In this paper, characteristics of shear strength and deformation of geosynthetics-reinforced slag materials are described. In order to investigate the effect of geosynthetics on shear strength and deformation behavior of slags, when they are reinforced with geosynthetics or geomat such as PET mat, large triaxial tests were performed under consolidated-drained condition. The materials used in the study are real ones as they are in the field, so that the scale effect of samples disappeared. From the large triaxial tests, it was observed that the stress-strain relationship of geosynthetics-reinforced slags shows relatively small dilatancy and weak tendency of strain hardening, compared with that of slags without reinforcement. The shear strength parameters such as apparent cohesion and internal friction angle increase with PET mat reinforcement, consequently result in about 1.2 (for low confining pressure) to 1.4 (for high confining pressure) times of shear strength of un-reinforced sample. Therefore, the adoption of geomat-reinforced slag layers leads to an increase in the factor of safety for embankment design on soft soil formations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.161-171
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• 1993

The aim of this study is to provide the stress-strain behavior of hardening geological materials such as rock or concrete on three dimensional spaces by using Desai model based on plastic theory. To validate proposed model, truly triaxial tests with high pressure under variety of stress paths in which three principal stresses were controlled independently using concrete materials were performed. The main results are summerized as follows: 1. Various stress paths for hardening materials used are satisfactorily explained by performing the truly triaxial test with high pressure. This is very important to investigate constitutive equations for materials like rock or concrete. 2. Since the proposed yield function is continuous, it avoids the singularity point at the intersection of two function in the previous models, thus, reducing the difficulties for computer implementation. 3. Analytic predictions for yielding behavior on $J_1-{\sqrt{J_{2D}}}$ octahedral and triaxial plane, as well as volumetric strain and stress-strain behavior agree well with experimental results.

• Composites Research
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• v.36 no.5
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• pp.369-376
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• 2023

This study focuses on investigating the influence of epoxy polymer crosslinking density, a crucial aspect in composite material matrices, on the yield surface using molecular dynamics simulations. Our approach involved generating epoxy models with diverse crosslinking densities and subjecting them to both uniaxial and multiaxial deformation simulations, accounting for the elasto-plastic deformation behaviors. Through this, we obtained key mechanical parameters including elastic modulus, yield point, and strain hardening coefficient, all correlated with crosslinking conversion ratios. A particularly noteworthy finding is the rapid expansion of the yield surface in the biaxial compression region with increasing crosslinking ratios, compared to the uniaxial tensile region. This unique behavior led to observable yield surface variations, indicating a significant pressure-dependent relationship of the yield surface considering plastic strain and crosslinking conversion ratio. These results contribute to a deeper understanding of the complex interplay between crosslinking density and plastic mechanical response, especially in the aspect of multiaxial deformation behaviors.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.909-912
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• 2008

Fiber is an important ingredient in strain-hardening cementitious composite (SHCC), which can control fracture of cementitious composite by bridging action. The properties of reinforcing fiber, as tensile strength, aspect ratio and elastic modulus, have great effect on the fracture behavior of SHCC. But SHCC has serious problem as drying shrinkage because silica powder is used to make SHCC in order to improve bond strength between reinforcing fibers and cement matrix. Therefore, curing method (period and temperature) is very important for SHCC to show high tensile performance. a variety of experiments have being performed to access the performance of SHCC recently. This research emphasis is on the mechanical properties of SHCC made in Polyvinyl alcohol (PVA), Polyethylene (PE) fibers and steel cord (SC), and how curing method affects the composite property, and ultimately its strain-hardening performance.

• Elastomers and Composites
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• v.39 no.1
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• pp.42-50
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• 2004

In this work, the diglycidylether of bisphenol A (DGEBA) and modified polyurethane (PU) blends were initiated by N-benzylpyrazinium hexafluoroantimonate (BPH). The cure and fracture toughness of neat DGEBA with the addition of PU were investigated. The cure properties of DGEBA/PU blend system were examined by DSC and near-IR measurements. The fracture touhtness were investigated by measuring the critical stress intensity factor ($K_{IC}$) and the critical strain energy release rate ($G_{IC}$). According to the results, the maximum values of owe activation energy ($E_a$) and conversion (${\alpha}$) were found at 10 phr of PU. Also the $K_{IC}$ showed a similar behavior with the results of conversion. These results were probably due to increase of crosslinking density in the blends resulted from increase of the hydrogen bonding between the hydroxyl groups of DGEBA and isocyanate groups of PU.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.937-939
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• 2005

의료영상의 3차원 모델링은 의학 연구 및 교육, 환자 치료를 위해 보다 정확한 정보를 제공 할 수 있다. 따라서 본 논문에서는 동맥경화가 발생된 위치를 정확하게 파악하고 빠르게 진단하는데 도움을 줄 수 있도록 3차원 개인 혈관모델의 자동생성 기법을 제안한다. 개인별 3차원 혈관모델을 생성하기 위하여 개인에 따라 모양이 다른 혈관조영사진에서 추출된 혈관영역을 기반으로 표준 모델을 변형 및 조정한다. 즉, 표준모델을 2차원으로 투영시킨 영상과 개인별 2차원 혈관영상에 대응되는 특징점을 추출하고 각 특징점의 이동량을 계산한 뒤 이 결과를 3차원으로 역 투영시킴으로써 변형된 새로운 혈관 모델을 생성한다. 3차원 혈관모델을 통하여 질병의 진행 및 차도를 환자들이 시각적으로 확인할 수 있으므로 높은 안정감을 주며 빠르고 정확한 진단으로 오진율을 감소시킬 것으로 기대된다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.59-62
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• 2003

Kinds, shapes and fraction ratios of fibers have influence on properties of HPFRCC(High-Performance Fiver Reinforced Cementitious Concrete ) like bending strength, strain capacity and fracture toughness. For example, hydrophilic fibers have different chemical bond strength from hydrophobic fibers, fiber shapes influence on fiber pull-out and rupture, and fiber volume fraction influence on bending strength. In this study, to estimate influences of kinds, shapes and fraction ratios of fibers, we make HFRCC with 3 kind of fiber in various volume fraction of fiber and compare cracking, bending strength and fracture toughness. As the results, bending strength of HPFRCC was increased as fiber volume fraction was Increase and fiber tensile strength was increase, and strain capacity and fracture toughness of HFRCC was higher in fiber pull-out fracture than in fiber rupture fracture. And HFRCC showing pseudo strain hardening has higher fiber reinforce efficiency than others.