• 반도체디스플레이기술학회지
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• 제10권3호
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• pp.61-65
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• 2011

The capabilities of finite elements codes allow now accurate simulations of blanking processes when appropriate materials modelling are used. Over the last decade, numerous numerical studies have focused on the influence of process parameters such as punch-die clearance, tools geometry and friction on blanking force and blank profile. In this study, three dimensional finite element analysis is carried out to design a lead frame blanking die using LS-Dyna3D package. After design of the blanking die, an experiment is also carried out to investigate the characteristics of blanking for nickel alloy Alloy42, a kind of IC lead frame material. In this paper, it has been researched the investigation to examine the influence of process parameters such as clearance and air cylinder pressure on the accuracy of sheared plane. Through the experiment results, it is shown that the quality of sheared plane is less affected by clearance and air cylinder pressure.

• Coupled systems mechanics
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• 제7권6호
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• pp.649-668
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• 2018

In this paper, we present a numerical model for fluid-structure interaction between structure built of porous media and acoustic fluid, which provides both pore pressure inside porous media and hydrodynamic pressures and hydrodynamic forces exerted on the upstream face of the structure in an unified manner and simplifies fluid-structure interaction problems. The first original feature of the proposed model concerns the structure built of saturated porous medium whose response is obtained with coupled discrete beam lattice model, which is based on Voronoi cell representation with cohesive links as linear elastic Timoshenko beam finite elements. The motion of the pore fluid is governed by Darcy's law, and the coupling between the solid phase and the pore fluid is introduced in the model through Biot's porous media theory. The pore pressure field is discretized with CST (Constant Strain Triangle) finite elements, which coincide with Delaunay triangles. By exploiting Hammer quadrature rule for numerical integration on CST elements, and duality property between Voronoi diagram and Delaunay triangulation, the numerical implementation of the coupling results with an additional pore pressure degree of freedom placed at each node of a Timoshenko beam finite element. The second original point of the model concerns the motion of the outside fluid which is modeled with mixed displacement/pressure based formulation. The chosen finite element representations of the structure response and the outside fluid motion ensures for the structure and fluid finite elements to be connected directly at the common nodes at the fluid-structure interface, because they share both the displacement and the pressure degrees of freedom. Numerical simulations presented in this paper show an excellent agreement between the numerically obtained results and the analytical solutions.

• 한국전산구조공학회논문집
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• 제22권6호
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• pp.519-525
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• 2009

본 연구에서는 복합재료 적층판에서 균열 생성 및 전파로 이루어지는 계면박리 현상을 모사하기 위하여 응집영역모델을 사용하였다. 응집영역모델을 고려한 유한요소해석을 수행하기 위하여 응집요소를 수식화하였으며, 상용유한요소 프로그램인 Abaqus의 사용자 정의 서브루틴 UEL로 구현하였다. 제안된 응집요소의 타당성과 유효성을 평가하기 위하여 복합재료 적층판의 이중외팔보(double cantilever beam) 시험과 ENF(end notched flexure) 시험결과와 유한요소해석 결과를 비교하였다. 해석 결과는 거시적인 하중-변위 곡선을 비교적 잘 예측하였다. 또한 응집요소를 이용한 유한요소해석시 탄성계수와 응집요소의 크기가 구조물의 하중-변위 곡선에 미치는 영향을 수치적으로 연구하였다. 균열 전파 경로의 격자 의존성을 최소화하고 하중-변위 곡선에 나타나는 지그-재그 현상을 제거하기 위하여 균열 선단에서 충분히 작은 응집요소가 사용되어야 한다.

• Smart Structures and Systems
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• 제20권4호
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• pp.473-481
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• 2017

This study suggests a simple, convenient and non-destructive method for investigation of the Young's modulus detection in stepped shafts which only utilizes the first-order resonant frequency in flexural mode and dimensions of structures. The method is based on the impulse excitation technique (IET) to pick up the fundamental resonant frequencies. The standard Young's modulus detection formulas for rectangular and circular cross-sections are well investigated in literatures. However, the Young's modulus of stepped shafts can not be directly detected using the formula for a beam with rectangular or circular cross-section. A response surface method (RSM) is introduced to design numerical simulation experiments to build up experimental formula to detect Young's modulus of stepped shafts. The numerical simulation performed by finite element method (FEM) to obtain enough simulation data for RSM analysis. After analysis and calculation, the relationship of flexural resonant frequencies, dimensions of stepped shafts and Young's modulus is obtained. Numerical simulations and experimental investigations show that the IET method can be used to investigate Young's modulus in stepped shafts, and the FEM simulation and RSM based IET formula proposed in this paper is applicable to calculate the Young's modulus in stepped shaft. The method can be further developed to detect mechanical parameters of more complicated structures using the combination of FEM simulation and RSM.

• Journal of Advanced Research in Ocean Engineering
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• 제3권1호
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• pp.15-24
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• 2017

This paper explores a series of numerical simulations of dynamic responses of multi-piles (dolphin) type substructures for 2.5MW class offshore wind turbine. Firstly computational fluid dynamics (CFD) simulation was performed to evaluate wave loads on the dolphin type substructures with the design wave condition for the west-south region of Korea. Numerical wave tank (NWT) based on CFD was adopted to generate numerically a progressive regular wave using a virtual piston type wave maker. It was found that the water-piercing area of piles of the substructure is a key parameter determining the wave load exerted in horizontal direction. In the next the dynamic structural responses of substructure members under the wave load were calculated using finite element analysis (FEA). In the FEA approach, the dynamic structural responses were able to be calculated including a deformable body effect of substructure members when wave load on each member was determined by Morison's formula. The paper numerically identifies dynamic response characteristics of dolphin type substructures for 2.5MW class offshore wind turbine.

• Korea-Australia Rheology Journal
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• 제13권2호
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• pp.97-106
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• 2001

Three-dimensional flow analysis was performed by using the control volume finite-element method for design of a profile extrusion die. Because polymer melt behavior is complicated and cross-sectional shape of the profile extrusion die is changing continuously, the fluid flow within the die must be analyzed three-dimensionally. A commercially available polypropylene is used for theoretical and experimental investigations. Material properties are assumed to be constant except for the viscosity. The 5-constant modified Cross model is used for the numerical analysis. A test problem is examined in order to verify the accuracy of the numerical method. Simulations are performed for conditions of three different screw speeds and three different die temperatures. Predicted pressure distribution is compared with the experimental measurements and the results of the previous two-dimensional study. The computational results obtained by using three dimensional CVFEM agree with the experimental measurements and are more accurate than those obtained by using the two-dimensional cross-sectional method. The velocity profiles and the temperature distributions within several cross-sections of the die are given as contour plots.

• Computers and Concrete
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• 제18권5호
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• pp.999-1018
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• 2016

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권5호
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• pp.509-524
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• 2017

Experiments and a numerical simulation were conducted to investigate the deformation and impact behavior of a corroded pipe, as corrosion, fatigue, and collision phenomena frequently occur in subsea pipelines. This study focuses on the deformation of the corrosion region and the variation of the geometry of the pipe under impact loading. The experiments for the impact behavior of the corroded pipe were performed using an impact test apparatus to validate the results of the simulation. In addition, during the simulation, material tests were performed, and the results were applied to the simulation. The ABAQUS explicit finite element analysis program was used to perform numerical simulations for the parametric study, as well as experiment scenarios, to investigate the effects of defects under impact loading. In addition, the modified ASME B31.8 code formula was proposed to define the damage range for the dented pipe.

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

• Steel and Composite Structures
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• 제48권5호
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• pp.507-530
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• 2023

The number of studies investigating the response of concrete-filled tubes (CFTs) under shear has been very limited in the literature. This lack of research has been traditionally reflected in international design standards as rather conservative shear strength predictions for CFTs. The dearth of research on the shear response is even more pronounced for the case of concrete-filled stainless steel tubes (CFSSTs). In line with this, the present study investigates the shear response of circular and square CFSSTs using advanced finite element (FE) analysis. A thorough review of the previous studies on the shear response of carbon steel CFTs is provided along with a summary of past experimental programmes as well as the developed and codified design methods. A comprehensive numerical study is then conducted considering a wide range of circular and square, austenitic and lean duplex CFSSTs with different concrete infills and shear span-to-depth ratios. The effect of the tail length on the shear response is investigated and the minimum required tail length for achieving full shear capacity is established. The simulations are also used to highlight the importance of the dilation of the concrete core in the shear response of concrete-filled tubes and its relationship with the utilised boundary conditions. Furthermore, the numerical results are compared in detail with the predictions of design approaches developed previously for carbon steel CFTs and their accuracy and applicability to the stainless steel counterpart are demonstrated and recommendations are made accordingly.