• Journal of Power Electronics
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• 제18권5호
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• pp.1489-1500
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• 2018

Partial shading analysis of large-scale photovoltaic (PV) arrays has recently become a theoretically and numerically challenging issue, and it is necessary for PV system designers. The main contributions of this study are the following: 1) A PSIM-based macro-model was employed because it is remarkably fast, has high precision, and has no convergence issues. 2) Three types of equivalent macro-models were developed for the transformation of a small PV sub-array with uniform irradiance to a new macro-model. 3) On the basis of the proposed new macro-model, a tearing method was established, which can divide a large-scale PV array into several small sub-arrays to significantly improve the efficiency improvement of a simulation. 4) Three platforms, namely, PSIM, PSpice, and MATLAB, were applied to evaluate the proposed tearing method. The proposed models and methods were validated, and the value of this research was highlighted using an actual large-scale PV array with 2420 PV modules. Numerical simulation demonstrated that the tearing method can remarkably improve the simulation efficiency by approximately thousands of times, and the method obtained a precision of nearly 6.5%. It can provide a useful tool to design the optimal configuration of a PV array with a given shading pattern as much as possible.

• 한국컴퓨터정보학회논문지
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• 제28권12호
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• pp.89-96
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• 2023

본 논문에서는 GPU기반으로 옷감을 찢는 데 필요한 동적 재메싱를 실시간으로 처리할 수 있는 방법을 제안한다. 얇은 쉘 재질은 물리 기반 시뮬레이션/애니메이션, 게임, 가상현실 등 다양한 분야에서 활용되고 있다. 옷감을 찢는 것은 기하학과 연결 구조를 동적으로 갱신해야 되기 때문에 그 처리 과정이 복잡하고 계산양이 크다. 특히 인터랙티브 콘텐츠를 다루는 분야에서는 이 과정이 빠르게 수행되어야 한다. 대부분의 방법에서는 실시간을 유지하기 위해 저해상도 시뮬레이션을 통해 재메싱을 수행하거나 이미 분할된 패턴을 그대로 이용하기 때문에 동적 재메싱이라고 보기 어려우며, 찢어진 패턴의 품질이 낮다. 본 논문에서는 GPU에 최적화된 동적 재메싱 알고리즘을 새롭게 제안함으로써 고해상도 옷감 찢어짐을 실시간으로 처리할 수 있게 한다. 본 논문에서 제안하는 방법은 사전에 쪼개진 메쉬 형태가 아닌 동적 재메싱이 가능하기 때문에 가상 수술시뮬레이션이나, 실시간을 요구하는 게임 및 가상환경에서 물리 기반 모델링울 할 때 활용될 수 있다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2023년도 제67차 동계학술대회논문집 31권1호
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• pp.353-356
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• 2023

본 논문에서는 GPU 기반으로 옷감을 찢는 데 필요한 동적 재메쉬 기법에 대해서 제안한다. 일반적으로 메쉬를 파괴(Fracture)하거나 찢는 시뮬레이션에서는 안정적인 동역학 계산하는데 있어서 동적 재 메쉬과정에 매우 중요하며 이 과정이 계산양이 가장 크다. 본 논문에서는 GPU 친화적인 동적 메쉬 알고리즘을 새롭게 제안함으로써 옷감 찢기 시뮬레이션을 실시간으로 보여준다.

• 대한조선학회논문집
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• 제36권4호
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• pp.95-104
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• 1999

강 구조물의 대형화에 기인하여 대형 해양구조물, 선박, 교량 및 고층 구조물에서의 극후판의 사용이 지속적으로 증가하고 있으며, 이런 경향은 앞으로도 계속될 것으로 생각된다. 그러나, 극후판을 사용하여 구조물을 시공할 때, 층상균열의 발생이 보고되고 있으며 이것은 극후판의 두께방향 중심부를 따라 분포하는 황, 인등의 불순 개재물 및 용접에 기인하여 발생하는 구속 잔류응력에 의하여 발생하는 것으로 알려져 있다. 연속 주조공법에 의하여 제조되는 극후판의 제조공정의 특성상, 층상균열의 발생은 회피하기가 현실적으로 어려우며, 따라서, 본 논문에서는 강구조물의 층상균열 발생의 감소 방안으로서, 금속학적 측면보다는 용접강도 측면에서 유한요소법에 기초한 전산 프로그램을 사용하여 최적 개선부형상 및 용접순서를 선정하고자 한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 박판성형기술의 진보
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• pp.163-172
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• 1994

The Aerospace and automobile industries have need to avoid sheet-metal forming problem such as incorrect springback after forming and trimming process, excessive thinning/tearing, wrinking/perkering. It is common practice to use costly trial-and-error experimental methods to develop tooling and manufacturing process parameters. Experimentation should be complemented with computer simulation to reduce cost and leadtime in manufacturing and to influence the design of components. In this study, firstly we solved the springback problem after drawing and trimming process of KFP(F100-229) engine airsealing bearing support part(53H00) forming and studied on the effect of several process parameters on the gap between the formed blank and punch shape using the implicit F.E.M code(ABAQUS). Secondly by the three dimensional dynamic analysis using the explicit. F. E. M code (LS-DYNA3D), we studied on the effect of several process parameters which can be used for avoid tearing and wrinking during the drawing process.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1252-1263
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• 2016

This paper presents a numerical method to simulate ductile tearing in cracked components under high strain rates using finite element damage analysis. The strain rate dependence on tensile properties and multiaxial fracture strain is characterized by the model developed by Johnson and Cook. The damage model is then defined based on the ductility exhaustion concept using the strain rate dependent multiaxial fracture strain concept. The proposed model is applied to simulate previously published three cracked pipe bending test results under two different test speed conditions. Simulated results show overall good agreement with experimental results.

• 소성∙가공
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• 제9권3호
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• pp.313-319
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• 2000

Finite element analysis is carried out for simulation of the multi-stage elliptic cup drawing process with the large aspect ratio. The analysis incorporates with shell elements for an elasto-plastic finite element method with the explicit time integration scheme. For the simulation, LS-DYNA3D is utilized for its wide capability of solving forming problems. The simulation result shows that the non-uniform drawing ratio at the elliptic cross section ad the small shoulder radius cause failure such as tearing and wrinkling. The result suggests the guideline to modify the tool shape for prevention of the failure during the drawing process.

• 소성∙가공
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• 제8권1호
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• pp.101-107
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• 1999

The upset forging stage is the initial work in the forging process. It is used to remove the segregation and cavities of the ingot. Specially in handling large sized ingot, an improper upset forging can cause serious surface tearing. However, there is no detail reference for stable upset forging work. To resolve this difficulty, we studied several factors such as upset forging time, temperature varation of ingot, damage, load and stain rate etc., by using the rigid-plastic finite element approach available in the DEFORM code. Numerical simulation results indicated that: the load value of upset forging works shows severe decreasing trend at a certain point, same as strain rate. Also defects were found to be concentrated around the upper and lower portions of the ingot. With these results, we can estimate a guideline for stable upset forging work.

• 소성∙가공
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• 제9권6호
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• pp.598-603
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• 2000

In order to improve trial-and-error based conventional practices for optimizing forming processes, a direct design method to guide iterative design practices, called the ideal forming theory, has been previously developed. In the theory, material elements are required to deform following the minimum Plastic work Path. The theory can be used to determine the ideal initial blank shape needed to best achieve a specified final shape while resulting in optimum strain distributions. In this work, the direct design method based on the ideal forming theory was applied to design initial design shape for VCR deck chassis. Based on the solution of the ideal forming theory, FEM analysis was utilized to evaluate an optimum blank shape to be formed without tearing. Simulation results are in good agreement with experimental data. It was shown that the proposed sequential design procedure based on direct design method and FEM can be successfully applied to optimize the die design Procedure of sheet metal forming processes.

• 한국정밀공학회지
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• 제16권11호
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• pp.148-157
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• 1999

The objective of this study is to investigate the effect of three main chemical compositions(Mg, Zn, Si) on extrudability of 7xxx Al alloy with high tensile strength. A few Al alloys based on 7xxx alloys were metal mold cast with various weight*%) of Mg 0.3-1.2%, Zn 5.0-8.0% and Si 0.4-0.7%, to envestigate the effects of extrudability, as well as mechanical properties. To measure the extrudability of cast billets, maximum extrusion pressure and surface temperature at die exit before tearing occurs were obtained by experiment and simulation of thermo-viscoplastic F.E.M. Also the yield and tensile strength of extruded products were tested.