• Steel and Composite Structures
• /
• 제26권3호
• /
• pp.347-360
• /
• 2018

The aim of this paper is to evaluate the accuracy and reliability of the available bond-slip laws which are being used for the numerical modeling of Fiber Reinforced Polymer (FRP)/concrete interfaces. For this purpose, a set of Reinforced Concrete (RC) beams retrofitted with external FRP were modeled using the 3D nonlinear Finite Element (FE) approach. All considered RC beams have been previously tested and the corresponding experimental data are available in the literature. The failure modes of these beams are concrete crushing, steel yielding and FRP debonding. Through comparison of the numerical and experimental results, the effectiveness of each FRP/concrete bond-slip model for the prediction of the structural behavior of externally retrofitted RC beams is assessed. The sensitivity of the numerical results against different modeling considerations of the concrete constitutive behavior and bond-slip laws has also been evaluated. The results show that the maximum allowable stress of FRP/concrete interface has an important role in the accurate prediction of the FRP debonding failure.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.1038-1043
• /
• 2003

There are many industrial applications including thin-body structures such as fins. For the numerical modeling of radiation of sound from thin bodies, the conventional boundary element method (BEM) using the Helmholtz integral equation fails to yield a reliable solution. Therefore, many researchers have tried to solve the thin-body acoustic problems. In the area of the design sensitivity analysis (DSA) and optimization methods, however, there has been just a few study reported. Especially fur the thin-body acoustics, however, no further study in the DSA and optimization fields has been reported. In this research, the normal derivative integral equation is adopted as an analysis formulation in the thin-body acoustics, and then used for the sizing DSA and optimization. Since the gradient-based method is used for the optimization, it is important to have accurate gradients (design sensitivities) of the objective function and constraints with respect to the design variables. The DSA formulations are derived through chain-ruled derivatives using the finite element method (FEM) and BEM by using the direct differentiation and continuum variation concepts. The proposed approaches are implemented and validated using a numerical example.

• 전자공학회논문지T
• /
• 제35T권1호
• /
• pp.75-81
• /
• 1998

본 논문은 장방형 다이아프램 형상과 단일형 피에조저항 전단응력 스트레인 게이지 와의 관계를 해석하여 최적의 전단응력 압력센서를 설계하기 위한 것이다. 다이아프램상의 전단응력을 시뮬레이션 하기 위하여 유한요소법 분석 프로그램 ANSYS 5.1를 사용하였다. 시뮬레이션 결과는 다이아프램 형상비가 3일때 스트레인 게이지의 위치는 중앙에서, 크기는 전체 장방형 다이아프램 크기의 8%를 점유할때 온도에 안정적이고, 최대 감도를 가진다는 것을 조사하였다.

• 지구물리와물리탐사
• /
• 제5권2호
• /
• pp.78-83
• /
• 2002

본 논문에서는 유한 요소법과 민감도를 이용한 역산 알고리즘을 결합하여 물리 탐사에서 많이 사용되는 시추공-시추공 모형의 2차원 푸리에 정식화에 따른 역산문제에 적용하였다. 역산기법의 효율향상을 위해 웨이브렛의 다중 분해능 특성을 응용한 기법을 적용하였고 타당성은 수치해석을 통한 데이터를 이용하여 검증하였다. 이론모형으로는 석회암 지하공동을 존재한다고 설정하여 이론모형 지하공동모형에 16개의 전류 및 전위 전극을 사용하여 계산을 행하였다. 본 연구에 의해서 지하공동과 같은 작은 영역의 불연속 매질일 경우, 이 역산법이 정확하고 적용이 용이한 해석법임을 알 수 있었다. .

• Journal of Electrochemical Science and Technology
• /
• 제4권1호
• /
• pp.41-45
• /
• 2013

Platinum is a well known element which shows a significant electrocatalytic activity in many important applications. In glucose sensor, because of the poisoning effect of reaction intermediates and the low surface area, the electrocatalytic activity towards the glucose oxidation is low which cause the low sensitivity. So, we fabricate a nanoporous PtZn alloy electrode by deposition-dissolution method. It provides a high active surface and a large enzyme encapsulating space per unit area when it used for an enzymatic glucose sensor. Glucose oxidase was immobilized on the electrode surface by capping with PEDOT composite and PPDA. The composite and PPDA also can exclude the interference ion such as ascorbic acid and uric acid to improve the selectivity. The surface area was determined by cyclic voltametry method and the surface structure and the element were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX), respectively. The sensitivity is $13.5{\mu}A/mM\;cm^2$. It is a remarkable value with such simply prepared senor has high selectivity.

• International Journal of Automotive Technology
• /
• 제8권2호
• /
• pp.193-201
• /
• 2007

The present paper deals with the application of the explicit finite element code, PAM-CRASH, to simulate the crash behavior of steel thin-walled tubes with various cross-sections subjected to axial loading. An isotropic elastic, linear strain-hardening material model was used in the finite element analysis and the strain-rate sensitivity of mild steel was modeled by using the Cowper-Symonds constitutive equation with modified coefficients. The modified coefficients were applied in numerical collapse simulations of 11 types of thin-walled polygon tubes: 7 convex polygon tubes and 4 concave polygon tubes. The results show that the thin hexagonal tube and the thick octagonal tube showed relatively good performance within the convex polygon tubes. The crush strengths of the hexagonal and octagonal tubes increased by about 20% and 25% from the crush strength of the square tube, respectively. Among the concave tubes, the I-type tube showed the best performance. Its crush strength was about 50% higher than the crush strength of the square tube.

• 한국기계가공학회지
• /
• 제18권2호
• /
• pp.58-64
• /
• 2019

This paper describes the analysis of dynamic characteristics and prediction of the stiffness for the joint between structural members. In the process of deriving the governing equations, the stiffness values responsible for the moment and shear force were modelled by using linear and torsional springs in the middle of a clamped-clamped beam. The sensitivities of the natural frequency and modal assurance criterion were investigated as a function of the dimensionless linear and torsional spring stiffness. The reliability of the predictions for the linear and torsional stiffness values was verified by the inverse computations of the stiffness matrix. The predictive and exact theoretical stiffness values were compared for the stiffness element in the finite element formulation, and their results show an excellent correlation. It is strongly anticipated that although the proposed methodology is currently limited to the analytical utilization, it will provide a useful tool to estimate unknown joint stiffness values based on the experimental natural frequency and mode shape.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.446-451
• /
• 2007

An Improved finite element model updating method to address the numerical difficulty associated with ill-conditioning and rank-deficiency. These difficulties frequently occur in model updating problems, when the identification of a larger number of physical parameters is attempted than that warranted by the information content of the experimental data. Based on the standard Bounded Variables Least-squares (BVLS) method, which incorporates the usual upper/lower-bound constraints, the proposed method is equipped with new constraints based on the correlation coefficients between the sensitivity vectors of updating parameters. The effectiveness of the proposed method is investigated through the numerical simulation of a simple framed structure by comparing the results of the proposed method with those obtained via pure BVLS and the regularization method. The comparison indicated that the proposed method and the regularization method yield approximate solutions with similar accuracy.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1995년도 추계학술발표회논문집(1)
• /
• pp.480-486
• /
• 1995

Turbulent flow field in a subchannel of bare rod bundles has been numerically simulated using the control volume based finite element method. Launder & Ying model of Reynolds stress and Lam & Bremhorst low-Reynolds number model are implemented in k-$\varepsilon$ equations and momentum equations. Secondary flows are simulated using the stream function and vorticity approach. The control volume based finite element method enable to use the upwind scheme (donor cell scheme). Sensitivity of the constants in the models are studied, and proper values are found to get the close result to the measured flow distributions.

• Structural Engineering and Mechanics
• /
• 제2권3호
• /
• pp.245-256
• /
• 1994

A new axisymmetric crack model is proposed on the basis of p-version of the finite element method limited to theory of small scale yielding. To this end, axisymmetric stress element is formulated by integrals of Legendre polynomial which has hierarchical nature and orthogonality relationship. The virtual crack extension method has been adopted to calculate the stress intensity factors for 3-D axisymmetric cracked bodies where the potential energy change as a function of position along the crack front is calculated. The sensitivity with respect to the aspect ratio and Poisson locking has been tested to ascertain the robustness of p-version axisymmetric element. Also, the limit value that is an exact solution obtained by FEM when degree of freedom is infinite can be estimated using the extrapolation equation based on error prediction in energy norm. Numerical examples of thick-walled cylinder, axisymmetric crack in a round bar and internal part-thorough cracked pipes are tested with high precision.