• Structural Engineering and Mechanics
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• v.35 no.6
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• pp.659-676
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop new finite elements for uniaxial and bending fatigue life prediction. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite elements for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure for each element in structural components. The performance of the fatigue finite elements is demonstrated by the fatigue life predictions from Al6061-T6 aluminum and Ti-6Al-4V. Results are compared with experimental results and analytical predictions.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.19-24
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• 2004

The mode I stress intensity factor ($K_I$) of a newly proposed slow-crack-growth-test (Notched Ring Test, NRT) specimen was found using finite-element method. The theoretical $K_I$ value of NRT was not available in any references and could not be solved analytically. At first, in order to verify the accuracy of the finite-element approach, published $K_I$ values of several cracks were calculated and compared with finite-element results. The results were in excellent agreement within inherent errors of theoretical $K_I$. Finally the $K_I$ of NRT was found using 2- and 3-dimensional finite-element methods and expressed as a function of the applied load.

• Computational Structural Engineering
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• v.7 no.2
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• pp.111-120
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• 1994

Cracks in rubber bonded to a rigid material such as steel are analyzed with the aid of a mixed finite element technique. Firstly the weak form is derived for finite element analysis of an incompressible material, and the Mooney-Rivlin form is assumed for the constitutive modeling of rubber. The numerical results from finite element analysis is examined to confirm the accuracy and convergence of solution by way of comparison to other numerical results. The interpretation of the J-integral for large elastic deformation as the energy release rate is confirmed, and the J-integral is calculated for varing crack length. The crack growth stability is discussed using the result of finite element analysis.

• Advances in nano research
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• v.15 no.5
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• pp.411-422
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• 2023

In the present study, the axial vibration of the nanorods is investigated in the framework of the doublet mechanics theory. The equations of motion and boundary conditions of nanorods are derived by applying the Hamilton principle. A finite element method is developed to obtain the vibration frequencies of nanorods for different boundary conditions. A two-noded higher order rod finite element is used to solve the vibration problem. The natural frequencies of nanorods obtained with the present finite element analysis are validated by comparing the results of classical doublet mechanics and nonlocal strain gradient theories. The effects of rod length, mode number and boundary conditions on the axial vibration frequencies of nanorods are examined in detail. Mode shapes of the nanorods are presented for the different boundary conditions. It is shown that the doublet mechanics model can be used for the dynamic analysis of nanotubes, and the presented finite element formulation can be used for mechanical problems of rods with unavailable analytical solutions. These new results can also be used as references for the future studies.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.379-386
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• 2000

This paper presents the results of finite element analysis on the seismic response of a soil-reinforced segmental retaining wall subjected to a prescribed earthquake record. The results of finite element analysis indicate that the maximum wall displacement occurs at the top, exhibiting a cantilever type of wall movement. Also revealed is that the increase in reinforcement force is more pronounced in the upper part of the reinforced zone, resulting in a more or less uniform distribution. None of the design guidelines appears to be able to correctly predict the dynamic force increase when compared with the results of finite element analysis. The calculation model adopted by the NCMA guideline, however, appears to compare better with the results of finite element analysis as well as field survey than the FHWA guideline. Based on the findings from this study, a number of implications to the current design methods are discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.101-108
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• 2000

This paper presents the results of finite element analysis on the seismic response of a soil-reinforced segmental retaining wall subjected to a prescribed earthquake record. The results of finite element analysis indicate that the maximum wall displacement occurs at the top, exhibiting a cantilever type of wall movement. Also revealed is that the increase in reinforcement force is more pronounced in the upper part of the reinforced zone, resulting in a more or less uniform distribution. None of the design guidelines appears to be able to correctly predict the dynamic force increase when compared with the results of finite element analysis. The results demonstrated that there exist critical stiffness and length of reinforcement beyond which further increase would not contribute to additional reinforcing effect. Based on the findings from this study, a number of implications to the current design methods are discussed.

• Transactions of Materials Processing
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• v.16 no.8
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• pp.590-595
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• 2007

This paper introduces a new approach to take account of bending history in finite element inverse analysis during sheet metal forming process. A modified membrane element was adopted for finite element inverse analysis so that bending-unbending energy was additionally imposed in the total plastic energy, predicting bending-unbending regions using the geometry of the final shape and tools. An algorithm was applied to a cylindrical cup deep drawing process. The blank shape and the distribution of the thickness strain were compared with those obtained from the incremental finite element analysis in order to evaluate the effect of the bending history. The algorithm reduced the difference between the results of the inverse analysis from those of the incremental analysis due to bending history. The analysis was also carried out with the variation of the thickness of the initial blank to investigate the effect of bending deformation. The results showed that the difference was remarkably reduced as the thickness of the initial blank increased. This indicates that the finite element inverse analysis cooperated with the suggested scheme is useful to obtain more accurate results, especially when bending effects are significant.

• The Pure and Applied Mathematics
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• v.12 no.2 s.28
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• pp.153-159
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• 2005

We investigate the error estimates of the h and p versions of the finite element method for an elliptic problems. We present theoretical results showing the p version gives results which are not worse than those obtained by the h version in the finite element method.

• Transactions of Materials Processing
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• v.3 no.2
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• pp.156-166
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• 1994

An arbitrary Lagrangian-Eulerian (ALE) finite element method has been developed. The finite element formation is derived and implemented for rigid-viscoplastic materials. The developed computer program is applied to the analysis of axisymmetric square die extrusion, which has many difficulties with updated Lagrangian approach. The results are compared with those from updated Largrangian approach. The results are compared with those from updated Lagrangian finite element program. Updating scheme of time dependent variables and mesh control are also examined.

• Journal of Welding and Joining
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• v.22 no.4
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• pp.59-64
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• 2004

The purpose of this study is to investigate the influence of weld bead profiles on stress concentration factors of double V groove butt-welded joints. The influence of three parameters such as toe radii, flank angles and bead heights on the stress concentration factors is studied by finite element analysis. It is shown that the three parameters have similar effects on the stress concentration factors. Finally a formula to estimate the stress concentration factors considering the three parameters and others is proposed and estimated results are compared with the results obtained by finite element analysis.