• 대한기계학회논문집A
• /
• 제31권10호
• /
• pp.1009-1016
• /
• 2007

Finite element alternating method has been suggested and used effectively to obtain the fracture parameters in assessing the integrity of cracked structures. The method obtains the solution from alternating independently between the FEM solution for an uncracked body and the crack solution in an infinite body. In the paper, the finite element alternating method is extended in order to obtain the elastic-plastic stress fields of a three dimensional inner crack. The three dimensional crack solutions for an infinite body were obtained using symmetric Galerkin boundary element method. As an example of a three dimensional inner crack, a penny-shaped crack in a finite body was analyzed and the obtained elastc-plastic stress fields were compared with the solution obtained from the finite element analysis with fine mesh. It is noted that in the region ahead of the crack front the stress values from FEAM are close to the values from FEM. But large discrepancy between two values is observed near the crack surfaces.

• Composites Research
• /
• 제24권3호
• /
• pp.31-38
• /
• 2011

본 연구에서는 우주 파편들과의 초고속 충돌로부터 우주 구조물을 보호하기 위한 새로운 하이브리드 복합재료 쉴드가 제안되었다. 제안된 쉴드의 유한요소 모델을 구성하고, 에너지 흡수율을 예측하기 위해서 유한 요소 해석을 수행하였다. 최종모델의 해석에 앞서 각 구성 요소인 알루미늄 판, PMMA 판 그리고 중간층인 직물 섬유의 해석이 먼저 수행되었으며, 각 요소의 유한요소 모델의 타당성이 검증되었다. 해석에 사용된 재료 물성은 고 변형률 속도에서의 재료 물성들을 예측하여 사용하였으며, 해석 결과 개별 요소의 에너지 흡수율이 직물섬유를 제외하고는 잘 맞음을 확인하였다. 이후 하이브리드 복합재료 쉴드의 유한 요소 모델을 구성하였고, 직물섬유의 구속 조건을 고정과 비 구속의 두 가지로 나누어 해석을 수행하여 비교하였다. 이를 통해서 비구속 삽입된 섬유를 이용한 하이브리드 쉴드가 섬유 풀아웃 현상이 잘 구현되었고, 이로 인해 에너지 흡수율이 향상 될 수 있음을 최종 확인하였다.

• 대한토목학회논문집
• /
• 제11권1호
• /
• pp.45-53
• /
• 1991

지하구조물은 물체력과 초기응력이 지배적인 하중조건이 되며, 무한 또는 반무한영역을 경계로 한다. 또한 굴착면 주위에는 응력집중에 의해 비선형 거동이 발생한다. 본 논문에서는 경계요소법으로 물체력과 초기응력을 해석하기 위하여 영역적분은 경계 적분화하였다. 물체력에 대한 영역적분은 Galerkin텐서와 발산정리를 사용한 방법과 극좌표를 이용한 직접적분 방법으로 경계적분화하였고, 초기응력에 대한 영역적분은 극좌표를 이용한 직접적분 방법을 응용하여 경계적분화하였다. 경계요소해석 결과는 유한요소해석 결과와 비교하여 검증하였고 검증된 경계요소 프로그램을 비선형 유한요소 프로그램과 조합하여 굴착면 주위에 발생하는 비선형 거동을 합리적으로 해석하도록 하였다. 경계요소법에서 고려하기 어려운 물체력과 초기응력에 대한 영역적분을 경계적분화하여 효율적으로 해석할 수 있었으며, 조합해석 방법으로 비선형 거동을 합리적으로 해석할 수 있었다. 본 연구의 결과는 지하구조물의 해석에 유용하게 사용될 수 있을 것으로 기대된다.

• Journal of Magnetics
• /
• 제18권2호
• /
• pp.130-134
• /
• 2013

Most electrical machines like motor, generator and transformer are symmetric in terms of magnetic field distribution and mechanical structure. In order to analyze these problems effectively, many coupling techniques have been introduced. This paper deals with a coupling scheme for open boundary problem of symmetric and periodic structure. It couples an analytical solution of Fourier series expansion with the standard finite element method. The analytical solution is derived for the magnetic field in the outside of the boundary, and the finite element method is for the magnetic field in the inside with source current and magnetic materials. The main advantage of the proposed method is that it retains sparsity and symmetry of system matrix like the standard FEM and it can also be easily applied to symmetric and periodic problems. Also, unknowns of finite elements at the boundary are coupled with Fourier series coefficients. The boundary conditions are used to derive a coupled system equation expressed in matrix form. The proposed algorithm is validated using a test model of a bush bar for the power supply. And the each result is compared with analytical solution respectively.

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

• Geomechanics and Engineering
• /
• 제7권5호
• /
• pp.495-524
• /
• 2014

To investigate the soil-pile interactive performance under lateral loads, a set of laboratory model tests was conducted on remoulded test bed of soft clay and medium dense sand. Then, a simplified boundary element analysis had been carried out assuming floating pile. In case of soft clay, it has been observed that lateral loads on piles can initiate the formation of a gap, soil heave and the tension crack in the vicinity of the soil surface and the interface, whereas in medium dense sand, a semi-elliptical depression zone can develop. Comparison of test and boundary element results indicates the accuracy of the solution developed. However, in the boundary element analysis, the possible shear stresses likely to be developed at the interface are ignored in order to simplify the existing complex equations. Moreover, it is unable to capture the influence of base restraint in case of a socketed pile. To bridge up this gap and to study the influence of the initial stress state and interface parameters, a field based case-study of laterally-loaded pile in layered soil with socketed tip is explored and modelled using the finite element method. The results of the model have been verified against known field measurements from a case-study. Parametric studies have been conducted to investigate the influence of the coefficient of lateral earth pressure and the interface strength reduction factor on the results of the model.

• 한국소음진동공학회논문집
• /
• 제23권3호
• /
• pp.226-233
• /
• 2013

Individual differences in head-related transfer functions(HRTFs) were calculated using boundary element(BE) models for three Korean adults. The BE models for the individuals were developed from the computerized tomography(CT) images of the individuals. The BE models were composed of the head, pinna, and ear canal. The frequency-dependent impedance boundary conditions were imposed on the skin, hair, and tympanic membrane. The HRTFs calculated from the individual BE models showed large difference above 2 kHz in magnitude and in the locations of peaks and valleys of the frequency spectrums, which should be considered in virtual auditory sound field. The identified individual differences in the HRTFs demonstrate that the developed BE models can be utilized successfully in order to obtain the HRTFs information of individuals.

• Structural Engineering and Mechanics
• /
• 제70권5호
• /
• pp.535-549
• /
• 2019

This study aimed to develop a high-order shear deformation theory to predict the free vibration of hybrid cross-ply laminated plates under different boundary conditions. The equations of motion for laminated hybrid rectangular plates are derived and obtained by using Hamilton's principle. The closed-form solutions of anti-symmetric cross-ply and angle-ply laminates are obtained by using Navier's solution. To assess the validity of our method, we used the finite element method. Firstly, the analytical and the numerical implementations were validated for an antisymmetric cross-ply square laminated with available results in the literature. Then, the effects of side-to-thickness ratio, aspect ratio, lamination schemes, and material properties on the fundamental frequencies for different combinations of boundary conditions of hybrid composite plates are investigated. The comparison of the analytical solutions with the corresponding finite element simulations shows the good accuracy of the proposed analytical closed form solution in predicting the fundamental frequencies of hybrid cross-ply laminated plates under different boundary conditions.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2002년도 추계 학술발표회 논문집
• /
• pp.106-113
• /
• 2002

In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used for a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted for soil. These two fields are coupled using FE-BE coupling technique In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, the dynamic response analyses of interface spring elements are performed. As a result, less spring stiffness makes the natural frequency decrease and the resonant amplitude increase.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1995년도 추계학술대회논문집
• /
• pp.102-108
• /
• 1995

Internal contact scheme between two free surfaces on one deforming body has been proposed by using the penalty method. It has been imposed to be internal boundary condition on two-dimensional thermo-viscoplastic finite element method so as to analyze one deforming body, which has two free surfaces penetrating each others. Analysis of side pressing with a circular void and a inclined elliptic hole have been carried out in order to verity the proposed contact scheme. A finite element code imposed internal boundary condition has been applied to two-dimensional analysis of free forging of large ingot with a void. Through the analysis, effects of working parameters in order to consolidate voids have been investigated.