• Transactions of Materials Processing
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• v.7 no.3
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• pp.233-245
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• 1998

A new approach has been proposed for the incremental analysis of the nonsteady state large deformation of planar anisotropic elastic-plastic sheet forming. A mathematical brief review of a constitutive law for the incremental deformation theory has been presented from flow theory using the minimum plastic work path for elastic-plastic material. Since the material embedded coordinate system(Lagrangian quantity) is used in the proposed theory the stress integration procedure is completely objective. A new return mapping algorithm has been also developed from the general midpoint rule so as to achieve numerically large strain increment by successive control of yield function residuals. Some numerical tests for the return mapping algorithm were performed using Barlat's six component anisotropic stress potential. Performance of the proposed algorithm was shown to be good and stable for a large strain increment, For planar anisotropic sheet forming updating algorithm of planar anisotropic axes has been newly proposed. In order to show the effectiveness and validity of the present formulation earing simulation for a cylindrical cup drawing and front fender stamping analysis are performed. From the results it has been shown that the present formulation can provide a good basis for analysis for analysis of elastic-plastic sheet metal forming processes.

• Composites Research
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• v.13 no.2
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• pp.51-60
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• 2000

Filament wound pressure vessels have been studied for the efficient design tool to consider the variation of fiber angles through-the thickness direction. Filament winding patterns were simulated from semi-geodesic fiber path equation to calculate fiber path on arbitrary surface. Finite element analyses were performed considering fiber angle variation in longitudinal and thickness directions by ABAQUS. For the finite element modeling of the pressure tank, the 3-dimensional layered solid element was utilized. From the stress results of pressure tanks, maximum stress criterion in transverse direction was applied to modify material properties for failed region. In the end of each load increment, resultant layer stresses were compared with a failure criterion and properties were reduced to 1/10 for a failed layer. Results of progressive failure analysis were compared with two experimental data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.725-731
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• 1985

In this study the rigid-plastic finite element method is used in order to study the deformation characteristics of solid cylinder upsetting. The effects of friction and aspect ratios on the effective strain distribution, axial stresses at the die-material interface, radial displacements, strain components, grid distortion on the meridional cross-section and gradual changes of outer profile are studied analyzed and compared with the experiments for commercially pure aluminum and .alpha.-brass. The agreement between numerical (or theoretical)and experimental results is shown to be acceptable for the engineering purpose.

• Computational Structural Engineering
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• v.11 no.1
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• pp.179-190
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• 1998

A geometrically nonlinear finite element formulation of spatial cable networks is presented using two cable elements. Firstly, derivation procedures of tangent stiffness and mass matrices for the space truss element and the elastic catenary cable element are summarized. The load incremental method based on Newton-Raphson iteration method and the dynamic relaxation method are presented in order to determine the initial static state of cable nets subjected to self-weights and support motions. Furthermore, static non-linear analysis of cable structures under additional live loads are performed based on the initial configuration. Challenging example problems are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate static nonlinear behaviors of cable nets.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.21-28
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• 1987

The paper describes the analysis of large displacement problems including instability phenomena. The element used in this is a degenerated isoparametric shell element with eight nodes. Total Lagrangian formulation has been adopted in this study using Newton-Raphson iteration method with incremental load. The linear stability analyses performed usually for the initial position can be repeated at several advanced fundamental states on the non-linear buckling path. Thus a current estimate of the failure load is given. The numerical examples of a cylindrical panel under uniform load, simply supported plate under axial load, and clamped plate under uniform load are carried out. The examples applying degenerated isoparametric elements to bifurcation buckling and nonlinear collapse problems are also performed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.121-125
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• 2010

In this study, we have constructed this algorithm that theoretical method for prediction performance of the internal ballastic analysis. And we have confirmed reliability, compared the value calculated by realized program with the value computed by modeling program. A basic concept of algorithm expresses combustion phenomenon to move each factor(node) according to the time increment like as Finite element method. And we have confirmed this realized program has sufficient possibility to utilize in the internal ballastic analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1429-1437
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• 1992

A new finite element formulation based on the relaxation type hereditary integral is presented for a time-domain analysis of isotropic, linear viscoelastic problems. The semi-discrete variational approximation and elastic-viscoelastic correspondence principle are used in the theoretical development of the proposed method. In a time-stepping procedure of final, linear algebraic system equations, only a small additional computation for past history is required since the equivalent stiffness matrix is constant. The viscoelasticity matrices are derived and the stress computation algorithm is given in matrix form. The effect of time increment and Gauss point numbers on the numerical accuracy is examined. Two dimensional numerical examples of plane strain and plane stress are solved and compared with the analytical solutions to demonstrate the versatility and accuracy of the present method.

• Journal of the Society of Disaster Information
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• v.13 no.3
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• pp.286-295
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• 2017

In this study, it is compared various coefficients of subgrade reaction for application of numerical analysis based on measured data by using various theories and empirical formula. The ratio of the maximum and minimum value is 6.80 at the top of wall but it is 1.06 at the maximum displacement point depends on change of calculated coefficient of subgrade reaction. The data of displacement were generally similar considering an increment of a coefficient of subgrade reaction. And the results of comparison of the displacement at the maximum displacement point by numerical analysis and measured data show similar displacement shape.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.105-117
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• 1994

A finite element procedure which can trace plastic collapse behavior of plane frame structures under small and large deformation is presented. The member is assumed to be prismatic and straight, and has the rectangular or I cross section. For the elasto-plastic analysis, the concept of plastic hinge is introduced and the incremental displacement method is applied. The limit state condition of the plastic hinge is considered under the combined condition of a bending moment and an axial force. Numerical examples are presented in order to demonstrate the validity and efficiency of the proposed procedure.

• Computational Structural Engineering
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• v.9 no.1
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• pp.151-159
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• 1996

A finite element formulation based on the CFT(Compression Field Theory) concept such as the effect of compression softening in cracked concrete, and macroscopic and rotating crack models etc. was presented for the nonlinear behaviour of structural concrete. In this category, tangential or secant material stiffnesses for cracked concrete were also defined and discussed in view of the iterative solution schemes for nonlinear equations. Considering the computational efficiency and the ability of modelling the post-ultimate behaviour as major concerns, the incremental displacement solution algorithm involving initial material stiffnesses and the relaxation procedure for fast convergence was adopted and formulated in a type of 8-noded quadrilateral isoparametric elements. The analysis program NASCOM(Nonlinear Analysis of structrual Concrete by FEM : Monotonic Loading) developed baed on the CFT constitutive relationships and the incremetal solution strategy described enables the predictions of strength and deformation capacities in a full range. crack patterns and their corresponding widths, and yield extents of reinforcement. As the verfication purpose of NASCOM, the prediction of Cervenka's panel test results including the load resistance and the deformation history was made. A limited number of predictions indicate a good correlation in a general sense.