• 한국해안해양공학회지
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• 제6권1호
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• pp.51-60
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• 1994

여유고에서 오염물질의 이동과 확산을 효율적으로 모의할 수 있는 Lagragian 기법을 이용한 1차원 수치모델이 재발되어 미국 플로리다주의 Burnt Store Isles의 수로망(canal network)으로 유입되는 오염물질에 대해서 적용되었다. 본 수력학 모델은 음해법으로 수치해석되었다. 수치 영역은 크게 주수로와 여유고(storage)로 대별되며 지수로(finger canal)와 지류(tributary)들은 수로망을 단순화하기 위하여 여유고로 간주되었다. 수치실험 결과는 현장실험결과와 비교하여 비교적 잘 일치하고 있음을 보여준다.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2442-2449
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• 2002

This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

• 소성∙가공
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• 제25권1호
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• pp.49-55
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• 2016

Electrohydraulic forming (EHF) is a high-speed forming process that uses an electric arc discharge in water. Shock waves resulting from the electric arc discharge are propagated to the blank through water and the blank moves toward the die. Advantages of EHF include improved formability due to the high-speed process and reduction of the bouncing effect. In the current study, a numerical simulation of EHF was developed using LS-DYNA. In the simulation, the model for the electric arc was assumed as an adiabatic gas expansion and an Arbitrary Lagrange-Eulerian (ALE) multi material formulation was used to describe the interaction between the electric arc and the water. In order to model the Fluid-Structure Interaction (FSI), a coupling mechanism was used. The blank of Al 1100-O was simulated using shell elements. The results of the simulation showed that the blank was deformed due to the pressure propagation of water and the bouncing effect did not affect the formability of blank.

• 한국정밀공학회지
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• 제29권6호
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• pp.632-639
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• 2012

A fully coupled thermo-mechanical model is adopted to study the temperature distribution and the material deformation in friction stir welding(FSW) process. Rotational speed is most important parameters in this research. Three dimension results under different process parameters were presented. Result indicate that the maximum temperature is lower than the melting point of the welding material. The higher temperature gradient occurs in the leading side of the workpiece. The maximum temperature can be increased with increasing the tool angular velocity, rpm in the current numerical modeling. In this research ABAQUS Ver.6.7 is to analyze a fully coupled thermo-mechanical model. ALE(Arbitrary Lagrangian-Eulerian) finite element formulation is used for the large deformation in FSW process and using the Mass scaling for the analysis time efficiency.

• Wind and Structures
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• 제16권5호
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• pp.411-431
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• 2013

A computational study of vortex-induced transverse vibrations of a cylinder with low mass-damping is presented. An Arbitrary Lagrangian-Eulerian (ALE) formulation of the Unsteady Reynolds-Averaged Navier-Stokes equations (URANS), along with the Spalart-Allmaras (SA) one-equation turbulence model, are coupled conservatively with rigid body motion equations of the cylinder mounted on elastic supports in order to study the amplitude and frequency response of a freely vibrating cylinder, its flow-induced motion, Vortex Street, near-wake flow structure, and unsteady loading in a moderate range of Reynolds numbers. The time accurate response of the cylinder from rest to its limit cycle is studied to explore the effects of Reynolds number on the start of large displacements, motion amplitude, and frequency. The computational results are compared with published physical experiments and numerical studies. The maximum amplitudes of displacements computed for various Reynolds numbers are smaller than the experimental values; however, the overall agreement of the results is quite satisfactory, and the upper branch of the limit-cycle displacement amplitude vs. reduced velocity response is captured, a feature that was missed by other studies. Vortex shedding modes, lock-in phenomena, frequency response, and phase angles are also in agreement with experiments.

• Coupled systems mechanics
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• 제1권4호
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• pp.361-379
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• 2012

This paper presents a fully coupled three-dimensional solver for the analysis of interaction between pulsatile flow and large deformation structure. A partitioned time marching algorithm is employed for the solution of the time dependent coupled discretised problem, enabling the use of highly developed, robust and well-tested solvers for each field. Conservative transfer of information at the fluid-structure interface is combined with an effective multi-predict-correct iterative scheme to enable implicit coupling of the interacting fields at each time increment. The three-dimensional unsteady incompressible fluid is solved using a powerful implicit time stepping technique and an ALE formulation for moving boundaries with second-order time accurate is used. A full spectrum of total variational diminishing (TVD) schemes in unstructured grids is allowed implementation for the advection terms and finite element shape functions are used to evaluate the solution and its variation within mesh elements. A finite element dynamic analysis of the highly deformable structure is carried out with a numerical strategy combining the implicit Newmark time integration algorithm with a Newton-Raphson second-order optimisation method. The proposed model is used to predict the wave flow fields of a particular flow-induced vibrational phenomenon, and comparison of the numerical results with available experimental data validates the methodology and assesses its accuracy. Another test case about three-dimensional biomedical model with pulsatile inflow is presented to benchmark the algorithm and to demonstrate the potential applications of this method.