• Journal of Welding and Joining
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• v.19 no.5
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• pp.499-505
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• 2001

In order to classify the mechanical phenomena of thermal elasto-plastic behavior on the multi-spot welded joints, this study has tried to carry out three-dimensional thermal elasto-plastic analysis on them. However, because the shape of multi-spot welded joints is not taxi-symmetric, unlike the cafe of single-spot welded joint, the solution domain for simulation should be three dimension. Therefore, in this paper, firstly, the three-dimensional thermal elasto-plastic program is developed by an iso-parametric finite element method. Secondly, from the results analyzed by developed program, this has clarified mechanical characteristics and their production mechanism on single and multi-spot waled joints. Moreover, it has been intended to make clear effects of pitch length on welding residual stresses, plastic strain of multi-spot welded joints.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.72-80
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• 1996

During the shape rolling process the influence of reduction ration and taper of shape roller on deformation and limit of ductile fracture such as free surface cracks developing in the workpiece has been studied. The deformation behaviours were analyzed by the 3-dimensional elasto-pastic finite element method and the conditions of ductile fracture were determined from 3-dimensional elasto-plastic finite element method and modified Cockrogt-Latham criterion. The deformed geometry and prediction of ductile fracture by 3-dimensional elasto-plastic finite element method are compared with experimental results The calcuated results are in good agreements with experimental data. The analysis used in the study was found to be effective in predicting the shape rolling process.

• Journal of Korean Association for Spatial Structures
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• v.6 no.4 s.22
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• pp.63-72
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• 2006

Fundamental equations of a member to analysis the elasto-plastic buckling analysis based on the deflection method are derived in this paper, and its validity and accuracy are shown by the numerical examples. The model discussing in the present paper has three elasto-plastic springs which are located at the both ends and center of a member and two elastic beam elements between them. The elasto-plastic springs represent the elasto-plastic behavior of the member and elastic beam element represents buckling behavior of the member. Numerical example shows the validity of this formulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1196-1202
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• 2004

A meshfree multi-scale method has been presented for efficient analysis of elasto-plastic problems. From the variational principle, problem is decomposed into a fine scale and a coarse scale problem. In the analysis only the plastic region is discretized using fine scale. Each scale variable is approximated using meshfree method. Adaptivity can easily and nicely be implemented in meshree method. As a method of increasing resolution, partition of unity based extrinsic enrichment is used. Each scale problem is solved iteratively. Iteration procedure is indispensable for the elasto-plastic deformation analysis. Therefore this kind of solution procedure is adequate to that problem. The proposed method is applied to Prandtl's punch test and shear band problem. The results are compared with those of other methods and the validity of the proposed method is demonstrated.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.687-696
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• 2006

An efficient numerical method is developed to estimate the elasto-plastic post-buckling strength of space-framed structures. The inelastic ultimate strength of beam-columns and frames is evaluated by the parametric study. Applying the improved plastic hinge analysis that evaluate the gradual stiffness decrease effects due to spread of plasticity, elasto-plastic post-buckling behavior of steel frames is investigated considering the various residual stress distributions. Introducing the plastification parameter that represent pread of plasticity in the element and performing parametric study of equivalent element force and member idealization, finite-element solutions for the elasto-plastic analysis of space frames are compared with the results by plastic region analysis, shell elements and experimental results.

• Earthquakes and Structures
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• v.7 no.3
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• pp.333-347
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• 2014

Multi-scale model can take both computational efficiency and accuracy into consideration when it is used to conduct elasto-plastic seismic response analysis for complex steel bridges. This paper proposed a method based on pushover analysis of member sharing the same section pattern to verify the accuracy of multi-scale model. A deck-through type steel arch bridge with a span length of 200m was employed for seismic response analysis using multi-scale model and fiber model respectively, the validity and necessity of elasto-plastic seismic analysis for steel bridge by multi-scale model was then verified. The results show that the convergence of load-displacement curves obtained from pushover analysis for members having the same section pattern can be used as a proof of the accuracy of multi-scale model. It is noted that the computational precision of multi-scale model can be guaranteed when length of shell element segment is 1.40 times longer than the width of section where was in compression status. Fiber model can only be used for the predictions of the global deformations and the approximate positions of plastic areas on steel structures. However, it cannot give exact prediction on the distribution of plastic areas and the degree of the plasticity.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.395-402
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• 2000

Recently, the deep excavations have been peformed to utilize the under ground space. As the ground excavation is deeper, the damage of the adjacent structure and the ground occurs frequently. The analysis of the retaining structures is necessary to the safety of the excavation works. There are many methods such as elasto-plastic, FEM, and FDM to analyze the displacement of the retaining structure. The elasto-plastic method is generally used in practice. In this thesis, GEBA-1 program by the Nakamura-Nakajawa elasto-plastic method was developed. The program for Windows was used the Visual Basic 6.0, and the Main of the program consists of three subroutines, SUB1, SUB2, and SUB3. The lateral displacement of the wall was analyzed by the developed program GEBA-1, SUNEX, and EXCAD, and compared with the measured displacement by the Inclinometer(at three excavation work sites). The excavation method of each site is braced retaining wall using H-pile. Each excavation depth is 14m, 14m, or 8.2m. The results of the analyses are the followings ① In the multi-layer soil, the lateral displacement by the GEBA-1 and EXCAD which is considering the distribution of the strut load is equal to the measured displacement. Elasto-plasto programs can't consider the change of the ground water in clay. Therefore, the analysis displacement was expected only 20% of the measured wall displacement. ③ At the final excavation step, the maximum lateral displacement of analysis and field occurred 7∼18m at the 85∼92% of the excavation depth. ④ The maximum lateral displacement in clay, as 50mm, occurred on the ground surface.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.1
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• pp.36-41
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• 2005

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.10a
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• pp.16-21
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• 1990

Recently, the finite element method has been sucessfully extended to treat the rather couplet phenomena such as nonlinear buckling problems which are of considerable practical interest. In this study, a finite element program to evaluate the elasto-plastic buckling stress is developed. The Stowell's deformation theory for the plastic buckling of flat plates, which is in good agreement with experimental results, is used to evaluate bending stiffness matrix. A bifurcation analysis is performed to compute the elasto-plastic buckling stress. The subspace iteration method is employed to find the eigenvalues. The results are compared with corresponding enact solutions to the governing equations presented by Stowell and also with experimental data due to Pride. The developed program Is applied to obtain elastic and elasto-plastic buckling stresses for various loafing cases. The effect of different plate aspect ratio is also investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.185-192
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• 1988

Computation of the elasto-plastic solution of ball indentation was carried out by the quadratic programming method. The problem was formulated as an elasto-plastic contact problem under the assumption of small displacement and small deformation and then transformed into a minimization problem. Finite element approximation resulted in a quadratic programming problem. Numerical and experimental study were done with aluminium Al 2024-T351 and commercially pure copper. The computed load-displacement curves were in good agrement with those obtained from experiments. Tabor's relationship for representative strains was also examined. Stress distributions were found to resemble closely those results available in the literature.