• Computational Structural Engineering
• /
• v.8 no.3
• /
• pp.59-66
• /
• 1995

The dynamic responses of structure under impulsive loading have been investigated according to its duration, based on the theory of viscoplasticity which can appropriately represent the effects of plasticity and rheology simultaneously. The viscoplastic model has been implemented into the two-dimensional finite element system to solve plane stress, plane strain or axi-symmetric problems, and the implicit integration scheme, of which solutions are unconditionally stable for relatively large time step length, has been developed to simulate visoplastic straining with deriving the explicit relationship between stress and strain at a material point level. After simulation, one carefully concludes that the duration as well as magnitude of impulsive loading plays an important role in design of structures.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.4
• /
• pp.537-549
• /
• 1999

선형탄성 파괴해석은 균열을 갖는 변형률 경화재료의 파괴거동을 예측하는데 불충분하기 때문에 최근에는 균열 선단 부에서 대규모 소성 역을 갖는 균열 체에 적용할 수 있는 많은 파괴역학개념이 제안되고 있다. 따라서, 본 연구에서는 대규모항복 조건하의 연성파괴를 보이는 평판을 정확하게 해석할 수 있는 새로운 유한요소모델을 제시하고자 한다. 균열 선단 부의 응력 장을 정의하는데 가장 지배적인 파괴매개변수인 J-적분 값과 소성 역의 크기 및 형상을 J-적분법과 등가영역적분법을 통해 파괴거동을 설명할 수 있도록 증분소성이론에 기초를 둔 p-version 유한요소해석이 채택되었다. 제안된 유한요소모델에 의한 수치해석결과는 이론 해와 h-version 유한요소해석과 비교되었다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.7
• /
• pp.645-652
• /
• 2015

In this study, a method for determining Ramberg-Osgood constants for leak-before-break evaluation was investigated. The Ramberg-Osgood constants were calculated for SA312, TP316, and SA-508 Gr.1a in an operating temperature of $316^{\circ}C$. Incremental plasticity, using stress-strain data obtained from experiment, and deformation plasticity, using the Ramberg-Osgood constants, were considered in a finite element analysis. Using incremental plasticity and deformation plasticity, J-integrals and crack opening displacement values were calculated and compared. By comparing the results of incremental plasticity and deformation plasticity, a suitable method for determining Ramberg-Osgood constants for leak-before-break evaluation was confirmed.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.4 s.22
• /
• pp.53-61
• /
• 2006

In th is paper, to predicting the large deformation and cyclic plastic behavior of steel members under loading, 3-Dimensional elastic-plastic FE analysis method is developed by using finite deformation theory and proposed cyclic plasticity model. finite deformation theory, described the large deformation, is formulated by using Updated-lagrangian formulation and Green's strain tensor, Jaumann's derivative of Kirchoff stress. Also, cyclic plasticity model proposed by author is applied to developed analysis method. To verification of developed analysis method, analysis result of steel plate specimen compare to the analysis result using infinitesimal deformation theory and test result. Also, load-displacement and deflection shape, analysis result of pipe-section steel column, compare to test result. The good agreement between analysis result and experiment result shown that developed 3-dimensional finite element analysis can be predict the large deformation and cyclic plastic behavior of steel members.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.11
• /
• pp.753-764
• /
• 2020

In this study, the plastic zone and internal earth pressure of the tunnel were calculated using the following three methods: metal plasticity to analyze the deformation of metal during plastic processing, Terzaghi's earth pressure theory from the geotechnical perspective and modified Terzaghi's earth pressure theory, and slip line theory using Mohr-Coulomb yield conditions. All three methods are two-dimensional mathematical analysis models for analyzing the plane strain conditions of isotropic materials. Using the theory of metallurgical plastics, the plastic zone and the internal earth pressure of the ground were obtained by assuming that the internal pressure acts on the tunnel, so different results were derived that did not match the actual tunnel site, where only gravity was applied. An analysis of the plasticity zone and earth pressure via the slip-line method showed that a failure line is formed in a log-spiral, which was found to be similar to the real failure line by comparing the results of previous studies. The earth pressure was calculated using a theoretical method. Terzaghi's earth pressure was calculated to be larger than the earth pressure considering the dilatancy effect.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.6
• /
• pp.735-746
• /
• 2002

The task of plastic theory is twofold: first, to set up relationships between stress and strain that adequately describe the observed plastic deformation of metals, and second, to develop techniques for using these relationships in studying of the mechanics of metal forming processes, and the anlaysis and design of structures. One of the major problems in the theory of plasticity is to describe the behavior of work-hardening materials in the plastic range for complex loading histories. This can be achieved by formulating constitutive laws either in the integral or differential forms. To adequately predict the response of steel members during cyclic loading, the hardening rule must account for the features of cyclic stress-strain behavior. Neithe of the basic isotropic and kinematic hardening rules is suitable for describing cyclic streess-strain behavior, although a kinematic hardening rule describes the nearly linear portions of the stabilized hystersis loops. There is also a limited expansion of the yield surface as predicted by the isotropic hardening rule. Strong ground motions or wind gusts affect the complex and nonproportional loading histories in the inelastic behavior of structues rather than the proportional loading. Nonproportional loading is defined as externally applied forces on the structure, with variable ratios during the entire loading history. This also includes the rate of time-dependency of the loads. For nonproportional loading histories, unloading may take place along a chord instead of the radius of the load surface. In such cases, the shape of the stress-strain curve has to be determined experimentally for all non-radial loading conditions. The plasticity models including two surface models ae surveyed based on a yield surface and a bound surface that represent a state of maximum stress. This paper is concerned with the improvement of a plasticity models of the two-surface type for structural steel. This is follwed by an overview of plasticity models on structural steel. Finally the need for further research is identified.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.41-48
• /
• 1991

A set of constitutive equations is formulated to predict elastic-plastic strain hardening response of sintered porous iron under combined tension and torsion. The proposed constitutive equations were capable of predicting characteristic behaviors of porous metals. Agreement between theoretical curves and experimental data for elastic-plastic response of sintered porous iron was very good for various initial porosities.

• Journal of the KSME
• /
• v.24 no.2
• /
• pp.83-91
• /
• 1984

소성 이론은 아직 모든 금속성형 문제에 정확한 해를 줄 정도로 충분히 진보되어 있는 상태는 아니지만, 그럼에도 불구하고 실제 공정의 단순화, 가공물의 이상화를 통해 문제를 해석함으로써 가공하중, 금속유동등에 관한 인자들의 영향을 예측하고, 또 원하는 결과를 얻기 위한 적절한 가공조건을 선택할 수 있도록 근사해를 제공하고 있어 실제 공정이 성립하기 전에 행하는 실험적 시도의 량을 충분히 줄일 수 있다. 따라서 여기서는 우선 금속성형에 관련된 수학적 소성 이 론의 기초이론과 소성변형의 해석방법을 소개 하고자 한다.

• Journal of the KSME
• /
• v.22 no.3
• /
• pp.191-195
• /
• 1982

소결 금속(sintered metal)은 기공(pore)의 존재로 성형에 있어서 체적변화를 유발하므로 이제까지 사용되어오던 체적변화를 유발하므로 이제까지 사용되어오던 일반 소성이론(conventional plasticity theory)은 적용할 수 없기 때문에 소결금속에 대한 소성이론을 정립해 오고 있다. 그 발달 과정을 보면 미국과 일본에서 각각 독자적인 방법으로 진행되었는데 미국에서는 Kuhn씨가 포아숀 비(.nu.)를 정의하여 실험적으로 구하고 이것을 기초로 하여 항복조건을 정립하고 응력과 변형도율과의 관계를 유도해 냄과 동시에 알루미늄 분말 소결원판 단조에 적용하여 그 실용성을 예시하였다. 한편 일본에서는 교오토오 대학의 Shima, Oyane등이 연구 정립한 것으로서 다공정 금속과 그 본금속의 항복 응력비와 정수압의 항복 응력에 대한 영향도를 정의하여 실험을 통하여 결정한 다음 항복조건을 만들고 이로부터 응력과 변형율과의 관계, 등가 변형율을 유도하였고 이를 폐금형 압축시험에 적용하였다.

• Computational Structural Engineering
• /
• v.5 no.4
• /
• pp.5-12
• /
• 1992

고체역학의 구성은 크게 탄성론과 소성론(혹은 비탄성론)으로 나눌 수 있다. 전자는 회복가능한 변형을 후자는 회복불가능한 변형을 다루며, 이 두 이론은 응력과 변형의 실험적 관찰에 기초하기 때문에 거시적인 현상론의 성격을 갖고 있다. 체계적으로 잘 정리되어있는 탄성론과는 달리, 소성범위안에서의 복잡한 응력-변형도 관계는 종종 소성론으로 설명되지 않는다. 이점이 많은 연구자들 사이에 완전한 의견의 일치를 보지 못하고 있는 원인이나, 지난 수십년 동안 소성론의 기본틀에 대한 많은 진전이 있었다. 본 고에서는 소성론의 역사에 대한 "간략한" 역사적 고찰과 탄소성 "대변위"를 연구하는 현 역학사회의 관심의 촛점을 소개하고자 한다.