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주기하중을 받고 있는 금속의 시간의존적 소성 모델 비교
Dongkeon Kim,Gary Dargush 한국복합신소재구조학회 2013 복합신소재구조학회논문집 Vol.4 No.1
In real world applications, the response of structures may be dependent on the rate of loading and thus can be affected by transient loading, especially when the rate of loading is significant. In such situations, the rate of loading may become a major issue to understand structures during earthquake excitation or under blast or high velocity impact. In some cases, the rate effect on structures under strong earthquake excitation cannot be ignored when attempting to understand inelastic behavior of structures. M any researchers developed the constitutive theories in cyclic plasticity and viscoplasticity. In this study, numerical simulation by cyclic visocoplasticity models is introduced and analyzed. Finally, the analytical results are compared with experimental results as a means to evaluate and verify the model.
Unified Space-Time Finite Element Methods for Dissipative Continua Dynamics
Kim, Jinkyu,Dargush, Gary F.,Roh, Hwasung,Ryu, Jaeho,Kim, Dongkeon World Scientific Publishing Company 2017 International journal of applied mechanics Vol.9 No.2
<P>Based upon the extended framework of Hamilton’s principle, unified space-time finite element methods for viscoelastic and viscoplastic continuum dynamics are presented, respectively. For numerical efficiency, mixed time-step algorithm in time- and displacement-based algorithm in space are adopted. Through analytical investigation, we demonstrate that the Newmark’s constant average acceleration method and the present method are the same for viscoelasticity. With spatial eight-node brick elements, some numerical simulations are undertaken to validate and investigate the performance of the present non-iterative space-time finite element method for viscoplasticity.</P>
Extended framework of Hamilton's principle in heat diffusion
Kim, J.,Dargush, G.F.,Lee, H.S. Pergamon Press ; Elsevier Science Ltd 2016 International journal of mechanical sciences Vol.114 No.-
Based upon the extended framework of Hamilton's principle, a variational formulation in heat diffusion, as well as second sound phenomena is developed. This formulation is compatible with the initial and boundary conditions of a well-posed heat problem, and it correctly accounts for the governing partial differential equations, as its Euler-Lagrange equations. Thus, this new formulation provides a sound base to develop various unified space-time finite element methods. In order to validate the finite element representation over both space and time in the context of this formulation, two-dimensional lower-order space-time finite element methods are also developed with numerical investigations on representative examples.
A two surface plasticity model for the simulation of uniaxial ratchetting response
김동건,Gary F. Dargush,신성우,허종완 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1
In this study, a two surface plasticity model was developed and used to simulate the uniaxial ratchetting response of CS 1026 steel. Most cyclic plasticity models used in ratchetting simulations are Chaboche-type nonlinear kinematic hardening models, which deal with dynamic recovery terms considering the back stress tensor. This paper describes the ratchetting simulation of steel by the two surface model based on yield theory following both isotropic and kinematic hardening rules in order to obtain enhanced ratchetting response. The parameters used in the simulation were obtained from a parametric study and were determined from the initial range and stabilized range of CS 1026 steel. In addition, the two surface model was validated by comparing the results of a ratchetting simulation with experimentally determined maximum axial strain per cycle. The ratchetting responses obtained from the two surface model are an improved simulation results compared with results from bilinear and kinematic hardening models.
Cyclic damage model for E-shaped dampers in the seismic isolation system
김동건,Gary F. Dargush,허종완 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.8
The objective of this study is to apply a constitutive damage model for cyclic response of E-shaped dampers as well as metal and metallic plate dampers in order to be used in more broad areas such as material and component levels. The seismic isolation system used as sliding bearings and metallic dampers undergoes almost elastoplastic behavior due to seismic excitation. Accordingly, a two surface damage model is applied to understand inelastic behavior and to evaluate the potential damaged state of E-shaped dampers in the seismic isolation system. This damage model is originally formulated through a thermodynamic approach based on the entropy production equation. The cyclic damage model proposed in this study can be implemented into a user subroutine in the finite element (FE) software ABAQUS. Finally, the numerical results for E-shaped energy dissipation devices in the seismic isolation system are compared with the experimental test results so as to check the validity of the proposed model.
A Rate Dependent Plasticity Model under Cyclic Loading of Metals
김동건,Kim, Dongkeon,Dargush, Gary F. Korean Society for Advanced Composite Structures 2013 복합신소재학회논문집 Vol.4 No.1
In real world applications, the response of structures may be dependent on the rate of loading and thus can be affected by transient loading, especially when the rate of loading is significant. In such situations, the rate of loading may become a major issue to understand structures during earthquake excitation or under blast or high velocity impact. In some cases, the rate effect on structures under strong earthquake excitation cannot be ignored when attempting to understand inelastic behavior of structures. Many researchers developed the constitutive theories in cyclic plasticity and viscoplasticity. In this study, numerical simulation by cyclic visocoplasticity models is introduced and analyzed. Finally, the analytical results are compared with experimental results as a means to evaluate and verify the model.
주기하중을 받고 있는 금속의 시간의존적 소성 모델 비교
김동건 ( Dong Keon Kim ),( Gary F. Dargush ) 한국복합신소재구조학회 2013 복합신소재구조학회논문집 Vol.4 No.1
In real world applications, the response of structures may be dependent on the rate of loading and thus can be affected by transient loading, especially when the rate of loading is significant. In such situations, the rate of loading may become a major issue to understand structures during earthquake excitation or under blast or high velocity impact. In some cases, the rate effect on structures under strong earthquake excitation cannot be ignored when attempting to understand inelastic behavior of structures. M any researchers developed the constitutive theories in cyclic plasticity and viscoplasticity. In this study, numerical simulation by cyclic visocoplasticity models is introduced and analyzed. Finally, the analytical results are compared with experimental results as a means to evaluate and verify the model.