• 소음진동
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• 제8권1호
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• pp.132-138
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• 1998

The dynamic response of symmetric cross-ply and angle-ply composite laminated plates under impact loads is investigated using a higher order shear deformation theory. A modified Hertz law is used to predict the impact loads and a four node finite element is used to model the plate. By using a higer order shear deformation theory, the out-of-plane shear stresses, which can be a crucial factor in the failure of composite plates, are determined with significant accuracy. This is accomplished by using a stress recovery technique using the in-plane stresses. The results compared with previous investigations showed good agreement. It can be seen that this method of analyzing impact problems is more efficient than current three dimensional methods in terms of time and expense.

• 한국정밀공학회지
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• 제10권4호
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• pp.109-117
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• 1993

Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

• 대한토목학회논문집
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• 제14권1호
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• pp.93-103
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• 1994

본(本) 논문(論文)에서는 내부(內部)힌지가 있는 평면(平面) 뼈대구조(構造)의 기하학적(幾何學的)인 비선형(非線型)을 수행하기 위한 두 가지 해석방법(解析方法) 즉, 유한분절법(有限分節法)과 유한요소법(有限要素法)을 제시한다. 유한분절법(有限分節法)의 경우에는 내부(內部)힌지에 대한 경계조건(境界條件)이 고려된 평형방정식(平衡方程式)과 힘-변위(變位) 관계식(關係式)을 직접(直接) 적분(積分)하여 엄밀한 접선강도(接線剛度) 매트릭스를 유도한다. 유한요소법(有限要素法)의 경우에는 내부(內部)힌지와 전단변형(剪斷變形)의 영향이 고려된 Hermitian 다항식(多項式)을 형상함수(形狀凾數)로 사용하여 탄성(彈性) 및 기하학적(幾何學的)인 강도(剛度)매트릭스를 산정한다. 제시된 이론(理論)의 정확성(正確性)과 타당성(妥當性)을 입증(立證)하기 위하여, 선택된 예제(例題)의 해석결과(解析結果)를 제시한다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권5호
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• pp.1-11
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• 2017

This study focused on the ultimate behaviors(ultimate strength and fracture mode ) of single shear bolted connection with austenitic sainless steel(STS201) and curling effect on the ultimate strength using finite element analysis based on test results. Main variables are end distance in the parallel direction to loading and edge distance in the perpendicular direction to loading. The validation of finite element analysis procedures was verified through the comparisons of ultimate strength, fracture mode and curling(out-of-plane deformation) occurrence between test results and numerical predictions. Curling was observed in both test and analysis results and it reduced the ultimate strength of single- shear bolted connections with relatively long end distances. Strength reduction ratios caused by curling were estimated quantitatively by maximum 19%, 32%, respectively for specimens with edge distance, 48 mm and 60 mm compared with strengths of uncurled connections with restrained out-of-plane deformation. Finally, analysis strengths were compared with current design strengths and it is found that design block shear equations did not provide the accurate predictions for bolted connections with strength reduction by curling.

• 대한치과교정학회지
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• 제42권4호
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• pp.159-168
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• 2012

Objective: The aims of this study were to investigate mandibular deformation under clenching and to estimate its effect on the stability of orthodontic mini-implants (OMI). Methods: Three finite element models were constructed using computed tomography (CT) images of 3 adults with different mandibular plane angles (A, low; B, average; and C, high). An OMI was placed between #45 and #46 in each model. Mandibular deformation under premolar and molar clenching was simulated. Comparisons were made between peri-orthodontic mini-implant compressive strain (POMI-CSTN) under clenching and orthodontic traction forces (150 g and 200 g). Results: Three models with different mandibular plane angles demonstrated different functional deformation characteristics. The compressive strains around the OMI were distributed mesiodistally rather than occlusogingivally. In model A, the maximum POMI-CSTN under clenching was observed at the mesial aspect of #46 (1,401.75 microstrain [${\mu}E$]), and similar maximum POMI-CSTN was observed under a traction force of 150 g (1,415 ${\mu}E$). Conclusions: The maximum POMI-CSTN developed by clenching failed to exceed the normally allowed compressive cortical bone strains; however, additional orthodontic traction force to the OMI may increase POMI-CSTN to compromise OMI stability.

• Computers and Concrete
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• 제9권1호
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• pp.35-50
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• 2012

The 2D representative volume element (RVE) for softening quasi-brittle materials like concrete is determined. Two alternative methods are presented to determine a size of RVE in concrete subjected to uniaxial tension by taking into account strain localization. Concrete is described as a heterogeneous three-phase material composed of aggregate, cement matrix and bond. The plane strain FE calculations of strain localization at meso-scale are carried out with an isotropic damage model with non-local softening.

• Structural Engineering and Mechanics
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• 제8권6호
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• pp.623-637
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• 1999

This paper presents a four-noded quadrilateral $C^0$ strain plate element for the analysis of thick laminated composite plates. The element formulation is based on: 1) the third-order shear deformation theory; 2) assumed strain element formulation; and 3) interrelated edge displacements and rotations along element boundaries. Unlike the existing displacement-type composite plate elements based on the third-order theory, which rely on the $C^1$-continuity formulation, the present plate element is of $C^0$-continuity, and its element stiffness matrix is evaluated explicitly. Because of the third-order expansion of the in-plane displacements through the thickness, the resulting theory and hence elements do not need shear correction factors. The explicit element stiffness matrix makes the present element more computationally efficient than the composite plate elements using numerical integration for the analysis of thick layered composite plates.

• 소성∙가공
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• 제1권1호
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• pp.95-103
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• 1992

The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

• Structural Engineering and Mechanics
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• 제33권4호
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• pp.447-484
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• 2009

The spatially coupled buckling, in-plane, and lateral bucking analyses of thin-walled Timoshenko curved beam with non-symmetric, double-, and mono-symmetric cross-sections resting on elastic foundation are performed based on series solutions. The stiffness matrices are derived rigorously using the homogeneous form of the simultaneous ordinary differential equations. The present beam formulation includes the mechanical characteristics such as the non-symmetric cross-section, the thickness-curvature effect, the shear effects due to bending and restrained warping, the second-order terms of semitangential rotation, the Wagner effect, and the foundation effects. The equilibrium equations and force-deformation relationships are derived from the energy principle and expressions for displacement parameters are derived based on power series expansions of displacement components. Finally the element stiffness matrix is determined using force-deformation relationships. In order to verify the accuracy and validity of this study, the numerical solutions by the proposed method are presented and compared with the finite element solutions using the classical isoparametric curved beam elements and other researchers' analytical solutions.

• 한국분말재료학회지
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• 제29권4호
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• pp.303-308
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• 2022

The plastic deformation behavior of additively manufactured anisotropic structures are analyzed using the finite element method (FEM). Hill's quadratic anisotropic yield function is used, and a modified return-mapping method based on dual potential is presented. The plane stress biaxial loading condition is considered to investigate the number of iterations required for the convergence of the Newton-Raphson method during plastic deformation analysis. In this study, incompressible plastic deformation is considered, and the associated flow rule is assumed. The modified return-mapping method is implemented using the ABAQUS UMAT subroutine and effective in reducing the number of iterations in the Newton-Raphson method. The anisotropic tensile behavior is computed using the 3-dimensional FEM for two tensile specimens manufactured along orthogonal additive directions.