• Structural Engineering and Mechanics
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• 제3권4호
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• pp.383-390
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• 1995

A 2-D four-noded finite element which contains a ${\lambda}$ singularity is developed. The new element is compatible with quadratic standard isoparametric elements. The element is tested on two different examples. In the first example, an edge crack problem is analyzed using two different meshes and different integration orders. The second example is a crack perpendicular to the interface problem which is solved for different material properties and in turn different singularity order ${\lambda}$. The results of those examples illustrate the efficiency of the proposed element.

• Structural Engineering and Mechanics
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• 제5권2호
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• pp.127-135
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• 1997

Patch recovery attempts to derive a more accurate stress filed over a particular element than the finite element shape function used for that particular element. Elements that have a free edge being the boundary to the structure have particular stress relationship that can be incorporated to the stress field to improve the accuracy of the approximation.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.353-361
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• 2022

Linear Elastic Fracture Mechanics (LEFM) has been developed by applying stress analysis to determine the stress intensity factor (SIF, K). The finite element method (FEM) is widely used as a standard tool for evaluating the SIF for various crack configurations. The prediction accuracy can be achieved by applying an adaptive Delaunay triangulation combined with a FEM. The solution can be solved using either direct or iterative solvers. This work adopts the element-by-element preconditioned conjugate gradient (EBE-PCG) iterative solver into an adaptive FEM to solve the solution to heal problem size constraints that exist when direct solution techniques are applied. It can avoid the formation of a global stiffness matrix of a finite element model. Several numerical experiments reveal that the present method is simple, fast, and efficient compared to conventional sparse direct solvers. The optimum convergence criterion for two-dimensional LEFM analysis is studied. In this paper, four sample problems of a two-edge cracked plate, a center cracked plate, a single-edge cracked plate, and a compact tension specimen is used to evaluate the accuracy of the prediction of the SIF values. Finally, the efficiency of the present iterative solver is summarized by comparing the computational time for all cases.

• 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.

• 비파괴검사학회지
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• 제20권2호
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• pp.91-101
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• 2000

초음파 탐촉자로부터 방사된 음장을 모델링하는 것은 초음파 측정 모델을 구성하는 첫 번째 단계이며, 그 정확도를 결정짓는 핵심 요소이기 때문에 지금까지 다양한 연구가 진행되었다. 본 논문에서는 지금까지 제안된 다양한 기법 중에서 현재 널리 사용되고 있는 Rayleigh-Sommerfeld 적분 모델, 경계회절파모델(boundary diffraction wave model), 가장자리요소모델(edge element model)에 대해 간략하게 논의하고, 이 세가지 모델을 적용하여 평면 원형 및 사각형 초음파 탐촉자의 방사 음장을 계산하고, 각 기법의 정확성과 계산 효율을 비교하였다.

• Steel and Composite Structures
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• 제46권4호
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• pp.565-575
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• 2023

This study represents a numerical research in vibration and buckling of functionally graded material (FGM) beam comprising edge crack by using finite element method (FEM) and multilayer perceptron (MLP). It is assumed that the material properties change only according to the exponential distributions along the beam thickness. FEM and MLP solutions of the natural frequencies and critical buckling load are obtained of the cracked FGM beam for clamped-free (C-F), hinged-hinged (H-H), and clamped-clamped (C-C) boundary conditions. Numerical results are obtained to show the effects of crack location (c/L), material properties (E₂/E₁), slenderness ratio (L/h) and end supports on the bending vibration and buckling properties of cracked FGM beam. The FEM analysis used in this paper was verified with the literature, and the fundamental frequency ratio ($\overline{P_{cr}}$) and critical buckling load ratio ($\overline{{\omega}}$) results obtained were compared with FEM and MLP. The results obtained are quite compatible with each other.

• Nuclear Engineering and Technology
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• 제56권8호
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• pp.3180-3187
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• 2024

Rupture disk corrosion test (RDCT) method has been recently developed for real-time measurement of initiation of stress corrosion cracking (SCC) in a high-temperature water. This work presents a parametric study on the stress distribution of a thin disk specimen of RDCT to consider the fixture shape and friction using finite element analysis (FEA). The FEA results showed a dome-shaped deformation of the specimen. From the stress analysis as a function of friction coefficient, it was suggested that the maximum stress was applied around the dome-edge, which was invariant with change to the friction coefficient. This indicates that friction between the fixture and the specimen has little effect on stress distribution. On the other hand, the stress analysis as a function of a rounded-corner radius (Rc) revealed the location at which the maximum stress was applied shifted from the dome edge to the dome center as Rc increased. From SCC initiation tests using the RDCT apparatus in a primary water environment, it was found that SCC initiates at the dome edge when Rc is 0.5 mm, while SCC initiates near the disk center when Rc is 2.0 mm. This experimental result is in good agreement with the results of FEA.

• 한국정밀공학회지
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• 제15권6호
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• pp.159-166
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• 1998

The problem of interface crack in the bonded structures has received a great deal of attention in recent years. In this paper the aluminum bonded single lap-joint containing the interface edge crack is investigated. The tensile load and the average shear stress of the adhesive joints which have different crack length are obtained from the static tensile tests. The critical value of crack length to provoke the interface fracture is determined to a/L=0.4, where a is the interface crack length and L is the adhesive lap-length. The fracture mechanical parameters are introduced to confirm the existence of the critical crack length. The compliance and the stress intensity factors are calculated using the displacement and the stress near the interface crack tip by the boundary element method. These numerical results support the experimental results that the critical value of a/L is 0.4. It is known that the compliance and the stress intensity factors are the efficient parameters to estimate the bonded single lap-joint containing the interface edge crack.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.9-12
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• 2002

A parametric study has been conducted to investigate the effect of the geometry on the strength of an unidirectional and fabric hybrid laminated composite joint. Tests are conducted for the specimens with nine different edge-to-hole diameter or width-to-hole diameter ratios. For the finite element analysis, the characteristic length method is used, and the tests for determining the characteristic length are performed additionally. Nonlinear contact problem between the pin and laminate is modeled by the gap element in MSC/NASTRAN. Tsai-Wu failure criteria is applied to the stress on the characteristic curve. The finite element and experimental results shows good agreement in strength of composite joint. Results of the parametric study shows the effect of the geometry is remarkable in the specimens with width-to-hole diameter ratio less than 2.8 and edge-to-hole diameter ratio less than 1.4.

• Tribology and Lubricants
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• 제28권6호
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• pp.272-277
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• 2012

Finite element analysis was carried out using wafer-scale and particle-scale models to understand the mechanism of the fast removal rate(edge effect) at wafer edges in the chemical-mechanical polishing process. This is the first to report that a particle-scale model can explain the edge effect well in terms of stress distribution and magnitude. The results also revealed that the mechanism could not be fully understood by using the wafer-scale model, which has been used in many previous studies. The wafer-scale model neither gives the stress magnitude that is sufficient to remove material nor indicates the coincidence between the stress distribution and the removal rate along a wafer surface.