• Structural Engineering and Mechanics
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• 제30권6호
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• pp.665-678
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• 2008

The beams components subjected to the loading such as axial, bending and cyclic thermal loads were studied in this research. The used constitutive equations are those of elasto-plasticity coupled to ductile and/or creep damage. The nonlinear kinematic hardening behavior was considered in elastoplasticity modeling. The unified damage law proposed for ductile failure and fatigue by the author of Sermage et al. (2000) and Kachanov's creep damage model applied to cyclic creep and low cycle fatigue of beams. Based on the results of the analysis, the shakedown limit loads were determined through the calculation of the residual strains developed in the beam analysis. The iterative technique determines the shakedown limit load in an iterative manner by performing a series of full coupled elastic-plastic and continuum damage cyclic loading modeling. The maximum load carrying capacity of the beam can withstand, were determined and imposed on the Bree's interaction diagram. Comparison between the shakedown diagrams generated by or without creep and/or ductile damage for the loading patterns was presented.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.9-12
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• 2000

The importance of the role of plastic spin in the rate-dependent response of materials at large deformations is the main objective of this work. After a brief presentation of a general consitutive framework for visco-rigid plasticity at large strains an isotropic/kinematic hardening and a visco-rigid plastic model are used to analyze the stress-strain response under simple shear. A clear understanding of the role of plastic spin is achieved by obtaining numerical analyzed results for different stress values in which the plastic spin consititutive parameters interrelaste with the strain rate and other more conventional model constants, Especially this paper is concerned with introducing behaviors of Al7075

• 소성∙가공
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• 제18권4호
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• pp.329-335
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• 2009

In order to better predict the springback for friction stir welded DP590 steel sheet, the combined isotropic-kinematic hardening was formulated with considering the permanent softening behavior during reverse loading. As for yield function, the non-quadratic anisotropic yield function, Yld2000-2d, was used under plane stress condition. For the verification purposes, comparisons of simulation and experiments were performed here for the unconstrained cylindrical bending, the 2-D draw bending tests. For two applications, simulations showed good agreements with experiments.

• 소성∙가공
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• 제26권1호
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• pp.41-47
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• 2017

Cyclic behavior of advanced high strength steel sheets was measured using an inverse-optimization approach with pre-straining and bending. First, tensile specimens were pre-strained, and three-point bending was conducted for the pre-strained specimens. By using the inverse finite element optimization, the combined isotropic-kinematic hardening parameters that minimize the error between the measured and predicted bending force-displacement curves. The measured cyclic behavior agreed well with the cyclic behavior measured by sheet tension-compression test, which confirms the validity of the measuring procedure based on inverse optimization.

• Structural Engineering and Mechanics
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• 제75권1호
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• pp.101-108
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• 2020

The present study intends to analyze damage in thin-walled steel cylinders undergoing constant internal pressure and thermal cycles through use of anisotropic continuum damage mechanics (CDM) model coupled with nonlinear kinematic hardening rule of Chaboche. Materials damage in each direction was defined based on plastic strain and its direction. Stress and strain distribution over wall-thickness was described based on the CDM model and the return mapping algorithm was employed based on the consistency condition. Plastic zone expansion across the wall thickness of cylinders was noticeably affected with change in internal pressure and temperature gradients. Expansion of plastic zone over wall-thickness at inner and outer surfaces and their boundaries demarking elastic and plastic regions was attributed to the magnitude of damage induced over thermomechanical cycles on the thin-walled samples tested at various pressure stresses.

• 한국농공학회지
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• 제44권4호
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• pp.114-122
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• 2002

Up to now, many constitutive models for clay have been proposed and studied based on the elasto-plastic or elasto-viscoplastic theory and it has been recognized that the effect of time on the loading process is a salient feature. In the present study, cyclic behavior characteristics of clay was studied with a viscoelastic-viscoplastic constitutive model for clay based on the non-linear kinematic hardening rule. In order to examine the behavior of clay several cyclic untrained triaxial tests and also their numerical simulations were performed. As results of that, it was found that the proposed model can well describe cyclic behaviors of clay such as frequency dependent characteristics, and have the high feasibility of numerical simulation for dynamic analysis.

• 소성∙가공
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• 제23권5호
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• pp.297-302
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• 2014

The current paper introduces work that was conducted during the development of a stamping die for a reinforce center pillar made from high strength steel. In the current study, the Bauschinger effect on the springback analysis was studied by comparing simulation results with real panels, which are currently in production. For a complicated part shape, quantitative measurements of the deformed shape are not easy in general to obtain. An adjustment procedure of the shape data for some chosen sections has been suggested to improve the accuracy of the quantitative measurements. The results show that the kinematic hardening model provides more accurate results.

• 소성∙가공
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• 제9권4호
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• pp.395-403
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• 2000

Formation of Shear Band under the adiabatic condition is widely observed In the engineering materials during rapidly forming process lot a thermally rate-dependent material. The shear band stems from evolution of a narrow region in which an intensive plastic flow occurs. The shear band often plays a role of a precursor of the ductile fracture during a forming process. The objective of this study is to investigate the localization behavior using numerical method. In this work, the implicit finite difference scheme is employed due to the ease of convergence and the numerical stability It is noted that physical and mechanical properties of materials determine how the shear band is formed and then localized. Material properties can be characterized with inertia number dissipation number and diffusion number. It is observed that the dimensionless numbers effect on localization. Using a parametric study, comparison was made between CRS-1018 steel with WHA (tungsten heavy alloy). The deformation behavior of material in this study include an isotropic hardening as well as thermal softening. Moreover, this study suggests that a kinematic hardening constitutive relation be required to predict a more accurate strain level at a shear band.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 춘계학술발표대회 개요집
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• pp.264-266
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• 2000

In this study, analysis of creep-fatigue behavior of low alloy steel weld was performed. An interface was employed along the crack plane to simulate the interface between base metal and weld metal. A trapezoidal waveshapes was loaded cyclically and analysis result was compared with that of monotonic load. The material was assumed as elastic-plastic-secondary creeping material. Because the isotropic hardening plasticity model used in the last study cannot simulate the behavior of material under cyclic load, the linear kinematic hardening plasticity model was used. The behavior of strain field and $C_{t}$ parameter was obtained.d.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1592-1597
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• 2009

Ratcheting is a cyclic accumulation of strain under a cyclic loading. It is a kind of mechanisms which generate cracks in rail steels. Though some experimental and numerical study has been performed, modeling of ratcheting is still a challenging problem. In this study, an elastic-plastic constitutive equation considering non-linear kinematic hardening and isotropic hardening was applied. Under the tangential stress of the contact stresses, a cyclic stress-strain relation was obtained by using the model. Strain under repeated cycles was accumulated.