• Geotechnical Engineering
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• v.3 no.4
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• pp.7-20
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• 1987

This study was performed to investigate the effect of time-dependent creep on the deformation analysis of multi-dimensional consolidation using the finite element method for young Sedimentary clay. It was assumed that the creep in the clay had occured during consolidation. In the analysis, the Modified cam-clay theory originated from the critical state theory was used as the constitutive equation, in which a term equivalent to the creep was supplemnted. The results of the analysis were in good agreement with the observed values in the field.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.301-306
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• 1999

Cu/Cr/polyimide 계에서 금속박막 두께와 폴리이미드 표면의 플라즈마 전처리 조건에 따른 필 테스트 결과로부터 Park와 Yu의 X-선 측정에 의한 방법과 Moidu등의 이론적 방법을 통애 Cr/polyimide 계면균열의 계면파괴에너지를 구했다. 두 방법으로 구한 박막의 소성일과 계면파괴어네지는 대부분의 경우에 대해 서로 잘 일치하였으며, 이와 같은 실험적 방법과 이론적 방법 모두 계면파괴에너지의 측정에 유용함을 알 수 있었다. 계면파괴에너지는 박막 두께에 거의 무관하였으며, 0.03, 0.036 그리고 0.05 W/$\textrm{cm}^2$의 rf플라즈마 밀도에 대해 각각 $46.8\pm$17.8, $170.3\pm$42.9 그리고 $253.9\pm$44.4 J/$\m^2$의 계면파괴에너지를 얻었다.

• Computational Structural Engineering
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• v.9 no.1
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• pp.65-76
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• 1996

The initiation and growth of microcracks or microvoids inside concrete results in the progressive degradation of concrete. This damage processing along processing along with plastic deformation is main cause of nonlinear behavior of concrete. In this study, a continuum damage model of concrete is developed for the analysis of the nonlinear behavior of concrete due to damage and elasto-plastic deformation. Anisotropic damage tensor is used to describe the anisotropy of concrete and hypothesis of equivalent elastic energy is used to define the effective elastic tensor. The damage model including the damage evolution law and constitutive equation is derived with damage variable and damage surface which is defined by damage energy release rate by using the Helmholtz free energy and dissipation potential based on the thermodynamic principles. By adopting a typical plasticity model of concrete, plasticity of concrete is included to this model. Afinite element analysis program implemented with this model was developed and finite element analysis was performed for the analyses of concrete subjected to uniaxial and biaxial loadings. Comparison of the results of analysis with those of experiments and other models shows that the model successfully predicts the nonlinear behavior of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.817-820
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• 2008

이 논문은 초고강도 섬유보강 I형 보의 거동을 Diana를 사용하여 3차원 유한요소해석을 수행하였다. 보통 또는 고강도 콘크리트의 구성방정식과 달리 초고강도 섬유보강 콘크리트의 재료적 특성 즉, 인장 변형률 강화를 고려한 탄-소성 파괴 역학적 모델을 제안하여 해석에 반영하였다. 인장영역에서는 인장 변형률 강화를 고려한 다차원 고정 균열 규준을 사용하였고, 압축영역에서는 associated flow rule을 고려한 Drucker-Prager Criterion을 채택하였다. UHPFRC(Ultra-High Performance Fiber Reinforced Concrete) I형 보의 하중변형관계, 최초 균열, 최초 대각 균열, 극한상태 등의 결과를 실험결과와 비교하여 해석법의 유용성을 입증하였다.

• Transactions of Materials Processing
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• v.33 no.1
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• pp.5-11
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• 2024

The development of a next-generation hydrogen compressor, a key component in the expansion of hydrogen charging infrastructure, is in progress. In order to improve compression efficiency and durability, it is important to optimize the precision forming and shearing processes of the diaphragm, which is the bellows unit cell, as well as the optimization of diaphragm shape itself. In this study, we aim to show that die and process design technology that can synchronize the inner and outer shearing points of the diaphragm for the precision forming of product can be constructed based on a numerical simulation. First, the damage model that can predict the fracture points will be determined using the shear load and shear zone measurements obtained by performing a blanking test of AISI-633 stainless steel. Next, we will explain the overall procedure based on numerical analysis model how to determine the shearing points according to the deformation pattern of urethane die for various shearing die design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.528-535
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• 2011

In the present, the formation of shear band under a simple shear deformation is investigated using a rate-independent elastic-plastic constitutive relations. Moreover, the strain gradient terms are incorporated to obtain a non-local plastic constitutive relation, which in turn represented using combined two-back stress hardening model. Then, the continuum damage model is also included to the proposed model. The post-localization behavior are studied by introducing a small imperfection in a work piece. The strain gradient affects the shear localization significantly such that the intensity of shear band decreases as the strain gradient coefficient increases when the J2 flow theory is employed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.1046-1052
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• 2007

Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which was operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreased the thermal load and strain of the cooling channel structure. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.802-807
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• 2007

Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was also conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which is operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion data were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreases the thermal load and strain of the cooling channel. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.149-157
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• 2004

Residual stresses can have a significant influence on the fatigue lives of structural engineering components. For the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Significant advances have been made in recent years fur obtaining accurate and reliable determinations of residual stress distributions. These include both experimental and numerical methods. The purpose of this study is to simulate peening process with the help of the finite element method in order to predict the magnitude and distribution of the residual stresses in accordance with the parameters, which are, e.g. shot velocity, shot diameter, shot impact angle, shot shape, distance between two impinging shots, and material parameters.

• Geotechnical Engineering
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• v.6 no.4
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• pp.19-32
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• 1990

Generally foundation is composed of complicated multi - layers. Primary objective of this study is to perform numerical analysis on the distribution of stresses on the subgrade with the variation of constitutive equations, the structures and the depth of layer, rigidity, loading condition, etc. Multi - layered soils has been treated as Burmister's elastic model. However, in this research it was intended to analyzed the distribution of stresses on the subgrade with all of the multi - layered soils by using the EVP(elasto - viscoplastic) model, one of the numerical program based on the Biot's equation as governing equation. The numerical results are compared with those by the Burmister's and the Fox'method, which in turn proves to be satisfactory. This research is aiming at investigating the mechanism of stress transfer within a foundation by using computer program for multilayers foundation.