• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.38-42
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• 2000

In this study, the low velocity impact behavior of the composite laminates has been described by using 3 dimensional nonlinear finite elements. To describe the geometric nonlinearity due to large deformation, the dynamic contact problem is formulated using the exterior penalty finite element method on the base of Total Lagrangian formulation. The incremental decomposition is introduced, and the converged solution is attained by Newton-Raphson Method. The Newmark's constant-acceleration time integration algorithm is used. To make verification of the finite element program developed in this study, the solution of the nonlinear static problem with occurrence of large deformation is compared with ABAQUS, and the solution of the static contact problem with indentation is compared with the Hertz solution. And, the solution of low velocity impact problem for isotropic material is verificated by comparison with that of LS-DYNA3D. Finally the contact force of impact response from the nonlinear analysis are compared with those from the linear analysis.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.163-167
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• 2001

A two-dimensional progressive failure analysis method is presented for the strength characterization of the composite joints under pin loading. The eight-nodes laminated she]1 element is utilized based on the updated Lagrangian formulation. The criteria by Yamada-Sun, Tsai-Wu, and the maximum stress are used for the failure estimation. The stiffness of failed layer is degraded by the complete unloading method. No factor depending on test is included in the finite element analysis except for the material strength and stiffness. Total 20 plate specimens with and without hole are tested to validate the finite element prediction. The Tsai-Wu failure criterion most conservatively estimates the strength of laminate, and the maximum stress criterion yields the highest strength because it does not consider the coupling of the failure modes. The strength by Yamada-Sun method neglecting the matrix failure effect are located between other two methods and shows best agreement with test result for laminate with hole.

• 대한기계학회논문집A
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• 제25권12호
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• pp.1926-1932
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• 2001

In this second part of the paper, the automatic mesh generation and remeshing algorithm using bubble packing method is applied to the nonlinear problem. The remeshing/refinement procedure is necessary in the large deformation process especially because the mesh distortion deteriorates the convergence and accuracy. To perform the nonliear analysis, the transfer of state variables such as displacement and strain is added to the algorithm of Part 1. The equilibrium equation based on total Lagrangian formulation and elasto-viscoplastic model is used. For the numerical experiment, the upsetting process including the contact constraint condition is analyzed by two refinement criteria. And from the result, it is addressed that the present algorithm can generate the refined meshes easily at the largely deformed area with high error.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.662-667
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• 2005

Nonlinear dynamics of active piezolaminated plates are investigated with respect to the thermopiezoelastic behaviors. For largely deformed structures with small strain, the incremental total Lagrangian formulation is presented based on the virtual work principles. A multi field layer wise finite shell element is proposed for assuring high accuracy and non-linearity of displacement, electric and thermal fields. For dynamic consideration of thermopiezoelastic snap through phenomena, the implicit Newmark's scheme with the Newton-Raphson iteration is implemented for the transient response of various piezolaminated models with symmetric or eccentric active layers. The bifurcate thermal buckling of symmetric structural models is first investigated and the characteristics of piezoelectric active responses are studied for finding snap through piezoelectric potentials and the load path tracking map. The thermoelastic stable and unstable postbuckling, thermopiezoelastic snap through phenomena with several attractors are proved using the nonlinear time responses for various initial conditions and damping loss factors. Present results show that thermopiezoelastic snap through phenomena can result in the difficulty of buckling and postbuckling control of intelligent structures.

• 한국생산제조학회지
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• 제8권1호
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• pp.60-66
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• 1999

This study is to develop design sensitivity analysis method based on continuum theory for the actual buckling load of vehicle passenger compartment with respect to sizing design variables. For nonlinear structural analysis, both geometric and material nonlinear effects are considered. The total Lagrangian formulation for incremental equilibrium analysis and one-point linear eigenvalue problem for buckling analysis are utilized. Numerical methods are presented to evaluate design sensitivity expressions, using structural analysis results from FEM code. Optical design of vehicle passenger compartment with buckling constraint solved using Gradient projection method.

• Structural Engineering and Mechanics
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• 제2권2호
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• pp.185-196
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• 1994

In this paper a spline function solution for the ultimate strength of steel members and member structures is derived based on total Lagrangian formulation. The displacements of members along longitudinal and transverse directions are interpolated by one-order B spline functions and three-order hybrid spline functions respectively. Equilibrium equations are established according to the principle of virtual work. All initial imperfections of members and effects of loading, unloading and reloading of material are taken into account. The influence of the instability of members on structural behavior can be included in analyses. Numerical examples show that the method of this paper can satisfactorily analyze the elasto-plastic large deflection problems of planar steel member and member structures.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3441-3453
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• 1996

A finite element anlaysis is performed for large deformations of a felxible beam. The total Lagrangian formulation for a general large deformation, which involves finite rotations, is chosen and the exponential map is used to treat finite rotations from the Eulerian point of view. The finite elements results are confirmed for several cases of deformations through comparison to a first order elasticity solution obtained by numerical integration, and the agreement between the two is found to be excellent. For lateral buckling, the point of vanishing determinant of the resulting unsymmetric tangent stiffness is traced to examine its relationship to bifurcation points. It is found that the points of vanishing determinant is not corresponding to bifurcation points for large deformation in general, which suggests that the present unsymmetric tangent stiffness is not an exact first derivative of internal forces with respect to displacement.

• Structural Engineering and Mechanics
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• 제9권1호
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• pp.99-110
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• 2000

The objective of this paper is to extend the use of the improved degenerated shell element to the linear and the large displacement analysis of plates and shells with laminated composites. In the formulation of the element stiffness, the combined use of three different techniques was made. This element is free of serious shear/membrane locking problems and undesirable compatible/commutable spurious kinematic deformation modes. The total Lagrangian approach has been utilized for the definition of the deformation and the solution to the nonlinear equilibrium equations is obtained by the Newton-Raphson method. The applicability and accuracy of this improved degenerated shell element in the analysis of laminated composite plates and shells are demonstrated by solving several numerical examples.

• 수산해양기술연구
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• 제28권1호
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• pp.79-92
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• 1992

This is analyzed using the finite element method which is appling excellent isoparametric curve element in the aspect of large usages of dynamic responses in which is regarding geometric and material nonlinear of a large scale shell structure of an airplane, a submarine, a ship, and an ocean structure. The solution of dynamic equations is got by direct integration method using time-stepping procedure and regarding Central Difference Method of the both solutions. But because formal matrix factorization is not necessary in each time step and it does not take less time to compute relatively, this method must be regarded very few time steps on the condition. Axisymmatric shell problems are inspected using 8 node Isoparametric element in this paper. Partial axisymmatric spherical shell is used as a model to analyze axisymmatric nonlinear dynamic behavior regarding. Total Lagrangian formulation in geometric nonlinear behavior and elastio-viscoplastic in material nonlinear behavior.

• 한국생산제조학회지
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• 제7권5호
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• pp.106-112
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• 1998

Experience and experiments show that in many cases the buckling limit is reached at a much smaller load level than is predicted by linear buckling analysis. In this paper, it is considered linear and nonlinear of plane vehicle structure and estimates design sensitivity of the cross sectional area that is composed plane vehicle structure and performs optimal design. It compares linear vehicle structure with nonlinear vehicle structure for optima design result that is selected constraint condition of buckling load.