• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.52-58
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• 2014

Plastic deformation of roadbed influences the stability and maintenance of concrete slab track. Long-term plastic deformation in a railway roadbed is generated primarily due to accumulated inelastic strains caused by repeated passing of trains. Prediction of cumulative plastic deformation is important in cost-effective maintenance of railway tracks as well as for the safe operation of trains. In this study, the vertical displacements in railway roadbeds with different thicknesses of reinforced roadbed were computed. Parameters of the power model for cumulative plastic strain were calibrated by using the data from triaxial tests and full-scale loading tests. Results of three-dimensional finite element analyses of standard roadbed sections provide us with design guidelines for the selection of the thickness of reinforced roadbed.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.33-44
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• 1999

An energy balance procedure is developed to incorporate the effects of earthquake duration which involves the effect of cyclic loading and the corresponding cumulative plastic deformation. Particular emphasis is given to the flexural failure of non-seismically designed columns of reinforced concrete frames. For this, conceptual strength deterioration models for columns, governed by concrete, anchorage failure and longitudinal steel fracture due to low-cycle fatigue, are proposed. It is evident that the energy-based method has good agreement with the experimental data and is able to predict the failure mode.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.15-22
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• 2003

The fatigue crack growth model is derived and the retardation model is proposed. The fatigue crack growth model considers the residual plastic stretch on the crack surface which results from the plastic deformation at the tip of fatigue crack. The fatigue crack growth rate is calculated by using the cumulative fatigue damage and plastic strain energy in the material elements at the crack tip. This model gives the crack growth rate in reasonable agreement with test data for aluminum alloy AL6061-T651 and 17-4PH casting steel. The fatigue crack growth retardation model is based on the residual plastic stretch produced from a tensile overload which reduced the plastic strain range of the following load cycles. A strip-yield model of a crack tip plasticity is used for the calculation of a plastic zone size. The proposed retardation model characterized the observed features and delayed retardation of the fatigue crack growth under tensile overload.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.235-240
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• 1996

본 연구에서는 고온의 천이 열하중을 받는 304 SS 재질의 액체금속로 원통용기에 대하여 진행성 변형기구인 열적 라체팅(thermal ratcheting) 변형거동을 해석하였다. 재료의 반복 소성을 나타내는 구성식으로서 Chaboche모델을 이용하였으며 이 모델의 적용을 위하여 ABAQUS의 사용자 프로그램을 개발하였다. 열천이 과정이 반복되는 동안에 축방향의 온도분포 이동에 따른 탄소성 해석을 수행한 결과 소성변형이 각 싸이클마다 누적되어 점진적 변형이 일어났으며 이 해석결과를 시험치와 비교함으로써 해석의 타당성을 검토하였다. 반복 소성거동에 대한 Chaboche 모델을 이용하면 천이 열하중을 받는 304 SS. 재질의 고온구조물에 대하여 라체팅 거동을 정량적으로 평가 할 수 있는 것으로 나타났다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.185-186
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• 2009

In the present study, the deformation capacity of slender shear walls with thin web was studied. As reported by other researchers, web-crushing and rebar-fracture, developing by inelastic deformation after flexural yielding, were considered as the governing failure modes of walls. To address the effect of the longitudinal elongation on web-crushing and rebar-fracture, the longitudinal elongation was predicted by using truss model analysis. The failure criteria by web-crushing and rebar-fracture were defined as a function of the longitudinal elongation. The proposed method was applied to 17 shear wall specimens with boundary columns, and the prediction results were compared with the test results. The results showed that proposed method predicted the maximum deformations and failure modes of the wall specimens with reasonable precision.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.169-172
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• 2008

Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions..

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.19-26
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• 2003

Plastic and creep deformations of a solder joint on thermal cycle play an important role in the reliability of optical telecommunication components. Solder joint strain is increased with the thermal cycle time and it causes mis-alignments and power loss in the optical component. Furthermore, the component can be failed since the deformation exceed the limitation of the fatigue life. We applied the finite element analysis method to solve the problem of the solder joint reliability on thermal cycle. Plastic and creep deformations are calculated by the finite element method. And, the fatigue lire is predicted by using creep-fatigue prediction models with calculated strains. The temperature conditon of the analysis was referred from the Telcordia reliability schedule (-40 to 75). Also, the three ramp renditions, 1/min, 10/min and 50/min, and dwelling time were considered to analyze the differences of results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.195-204
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• 2004

A series of constant creep and repeated creep tests are performed to investigate the behavior of visco-elasto-plastic materials of chemical grouted sands. In the result of constant creep test, the material exhibits three types of shear strain : elastic, plastic, viscoelastic. The elastic, plastic and viscoelastic strains are linear, i.e., the strains are proportional to the stresses for loading. Good agreement is found between the predicted viscoelastic and test results by the power law and the generalized model. In the repeated creep test, the instantaneous recoverable strain is time-independent and the magnitude of accumulated plastic strain increases with number of cycles. Also it is seen that the accumulated plastic strains are approximately proportional to stress. There are no significant differences between test results predicted values for first cycle, and the differences increase relatively insignificantly with number of cycles.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.409-413
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• 2006

The accumulated deformation due to the undrained creep causes the general stability problem for the overall soil mass. In this study, the time-dependent constitutive equation, into which a damage law, modified cam clay model, and Perzyna's generalized viscous theory were incorporated, was derived microscopically. The model prediction agreed well with the experimental result including the case of the undrained creep rupture.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.785-796
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• 2008

Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions.