• Computational Structural Engineering
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• v.8 no.2
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• pp.103-113
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• 1995

Since the mechanical properties of the rubber connectors used in the vehicle structures are sensitive on the dynamic characteristics of the system, they must be exactly evaluated. In this paper, both finite deformation theory and Hookean model are considered to calculate the stiffness coefficients of rubber connectors. An expert system is developed by using finite element method. When the equivalent stiffness coefficients on the same kinds of isolators used in actual vehicles were emperically examined, the results were largely dispersed due to the lack of the quality control on the material properties. To compensate the errors caused by the mathematical modeling and the mechanical properties, a practical method which identifies the shear and bulk moduli of rubber with the experimented overall force-deformation curves is suggested and applied to the engine isolators of vehicle.

• Journal of KSNVE
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• v.7 no.1
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• pp.61-69
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• 1997

Despite of the development in the finite element method, it is difficult to get the finite element model describing the dynamic characteristics of the complex structure exactly. Therefore a number of different methods have been developed in order to update the finite element model of a structure using vibration test data. This paper outlines the basic formulation for the frequency response function based updating method. One important advantage of this method is that the intermediate step of performing an eigensolution extraction is unnecessary. Using simulated experimental data, studies are conducted in the case of 10 DOF discrete system. The solution of noisy and incomplete experimental data is discussed. True measured frequency response function data are used for updating the finite element model of a beam and a plate. Its applicability to the joint identification is also considered.

• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.39-46
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• 2007

Different backcalculation results for the same material properties are caused by different structural geometry. In this paper, based on real simulation results for typical pavement systems using 3-dimensional FE models, modified AREA graphs are proposed to graphically backcalculate modulus of elasticity of slab and subgrade based on center deflection and AREA. In modified graph for single infinity slab models, deflection and AREA are increased in deeper depth to bedrock. But, effects of depth to bedrock more than 4.0 meters on backcalculation results are negligible. And, center deflection and AREA generated from multifinite slab models are larger than those of single infinity slab models with same depth to bedrock.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.17-28
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• 2012

In this study, we suggest a method for material property evaluation by dual-triangular pyramidal indenters using the reverse analysis. First, we demonstrated that load-displacement curves of conical and triangular pyramidal indenters are different for the same material. For this reason, an independent research on the triangular pyramidal indenter is needed. From FE indentation analyses on various materials, we then investigated the relationships among material properties, indentation parameters and load-displacement curves. From this, we established property evaluation formula using dual-triangular pyramidal indenters having two different half-included-angles. The approach provides the values of elastic modulus, yield strength and strain-hardening exponent within an average error of 3% for various materials.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.829-836
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• 2001

A dependable boundary reconstruction technique is proposed. The finite element method is used for the analysis of the direct heat conduction problem to realize the deformable grid system. An appropriate strategy for grid update is suggested. A complete sensitivity analysis is performed to obtain the derivatives required for restoration of the optimal boundary. With the result of the sensitivity analysis, the unknown boundary is sought using the sequential quadratic programming. The method is applied to reconstruction of boundaries with sinusoidal, step, and cavity form. The overall performance of the proposed method is examined by comparison between the estimated the exact boundaries.

• The Journal of the Acoustical Society of Korea
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• v.30 no.7
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• pp.368-376
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• 2011

Piezoelectric composites have been widely used in broadband acoustic transducers because of their lower acoustic impedance and higher electro-mechanical coupling factor. However, their complex structure has placed many limitations on the design of various transducers. This paper suggests the methodology to substitute the 1-3 piezocomposites by a single-phased material that has properties equivalent to those of the piezocomposites. The resonant method and finite element analysis (FEA) are used to derive the equivalent properties that can accurately depict resonant properties at various vibration modes of the piezocomposites. Validity of the suggested method is confirmed by comparing frequency characteristics of fabricated 1-3 piezocomposite specimens and FEA models. Further, accuracy of the derived material constants is checked by applying the equivalent properties to FEA models of the single phase material for various resonant modes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.51-56
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• 2006

부유식 해상공항과 같은 초대형 부체 구조물(VLFS)의 연안역 설치 후 발생할 수 있는 배후의 해빈변형을 예측하기 위한 토대를 마련하기 위한 기초 연구를 수행하였다. 이를 위해 일정 사면을 가진 천해역에서의 실험 결과를 통하여 비교적 수심이 깊은 곳에 설치된 매립식 구조물 배후에서의 파랑 및 해빈류를 개관하였으며, 매립식 및 부유식 해상 구조물 설치 시 주변 해역의 파랑 및 해빈류장을 계산하였다. 파랑장에 있어서 라프라스 방정식 토대로 유한요소법을 도입한 3차원 파랑 변형 계산을 수행함으로써 매립식 및 부유식 구조물 모두에 대해 적용 가능하였으며, 해상 구조물의 설치 형식이 매립식 및 부유식 경우에 대해 파랑, 해빈류 분포의 변화를 관찰할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1281-1286
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• 2003

A line search algorithm to increase a convergence in Newton's method is developed and applied to nonlinear finite element analysis. The algorithm is based on the slack line search theory which is an efficient algorithm to determine initial acceleration coefficient, variable backtracking algorithm proposed by some researchers, and convergence criterion based on residual norm. Also, it is capable of avoiding exceptional diverging conditions. Developed program is tested in metal forming simulation such as forging and ring rolling. Numerical result shows the validity of the algorithm for a highly nonlinear system .

• Transactions of Materials Processing
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• v.4 no.4
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• pp.302-321
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• 1995

A method of determining an optimum blank shape for the non-circular deep drawing process is investigated. The rigid-plastic finite element method is introduced and the computer program code is developed. The ideal shape of a drawn cup with uniform wall height is assumed and metal flow is traced back-ward step by step to predict an initial blank shape of the ideal cup. For examples of the non-circular deep drawing products, three cases of drawn cup with quadrilateral punch shape are considered and optimum blank shapes for each case are proposed and compared with experimental results.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.228-232
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• 2010

두 가지 어류 이동용 여수로 설계안에 대하여 유한요소법 기반의 레블�V 기법을 이용하여 흐름을 모의하고 적용성을 검토하였다. 첫 번째 설계안은 저수지에서 여수로로 직각 형태의 유입부를 가지고 있으며, 두 번째 설계안은 부드러운 곡면 형태의 유입부를 가지고 있다. 수치해석 결과를 자유수면의 위치, 압력분포 등의 특성을 중심으로 여수로 수리모형 실험 결과와 비교하였다. 그 결과, 직각 형태의 유입부를 갖는 설계안의 경우, 유입부의 응력분포의 영향으로, 평탄하지 않은 자유수면형과 압력분포를 보이는 것을 관찰할 수 있었다. 반면에 곡선형태의 유입부를 갖는 여수로의 경우에는 수면형과 압력분포에서 완만한 변화를 보이는 것이 관측되었다. 여수로 정상부에서 대기압보다 작은 부압의 분포는 두 가지 설계안 모두 비슷한 분포를 보였다. 여수로의 출구부에서는 측면부에서는 와류의 영향으로 인하여 수면의 상승을 관찰할 수 있었다. 결론으로서 곡면 유입부 형태의 여수로가 완만한 천이역을 갖고 있으며, 어류이동측면에서 유리함을 확인할 수 있었다.