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배터리 전극 설계를 위한 응력-확산 완전연계 멀티스케일 해석기법
장성민,문장혁,조경재,조맹효,Chang, Seongmin,Moon, Janghyuk,Cho, Kyeongjae,Cho, Maenghyo 한국전산구조공학회 2013 한국전산구조공학회논문집 Vol.26 No.6
In this paper, we device stress-diffusion full coupling multiscale analysis method for battery electrode simulation. In proposed method, the diffusive and mechanical properties of electrode material depend on Li concentration are estimated using density function theory(DFT) simulation. Then, stress-diffusion full coupling continuum formulation based on finite element method(FEM) is constructed with the diffusive and mechanical properties calculated from DFT simulation. Finally, silicon nanowire anode charge and discharge simulations are performed using the proposed method. Through numerical examples, the stress-diffusion full coupling method shows more resonable results than previous one way continuum analysis. 본 논문에서는 배터리 전극 해석을 위한 응력-확산 완전 연계 멀티스케일 해석기법을 고안하였다. 제안된 방법에서는 먼저 리튬농도에 따른 확산계수 및 기계적 물성을 계산하였다. 이를 고려하여 확산에 의한 응력뿐만 아니라 응력에 의한 확산 거동 변화까지 모두 고려한 응력-확산 완전연계 연속체 모델을 유한요소 기반으로 구성하였다. 이를 통해 실리콘 나노와이어 음극의 충/방전 전산 모사를 수행하였다. 이러한 해석결과를 통하여 기존의 확산에 의한 응력 연속체 모델보다 더 실제와 가까운 해석결과를 제안된 방법이 보여줌을 확인할 수 있었다.
리튬이온 배터리의 실리콘 전극의 응력-확산 연계 멀티스케일 해석
장성민(Seongmin Chang),문장혁(Janghyuk Moon),조경재(Kyeongjae Cho),조맹효(Maenghyo Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Silicon(Si) is a promising material for Li-ion batteries negative electrode due to high theoretical Li storage capacity (4.4 Li atoms per a Si atom). However, Si electrode has poor cycling performance because large volume change up to 380% occurs in the Si electrode charge and discharge cycles. The diffusion coupled stress caused by the large volume change causes the internal fracture of Si electrode. Hence, stress-diffusion coupled analysis is required for the accurate analysis and design of the silicon electrodes. In this study, a mixed-form finite element framework is formulated to simulate the full coupling between stress and diffusion. Moreover, the change of diffusion coefficient and elastic properties according to the Li concentration is estimated using the first principle method, atomic level computational techniques, and the change of properties is applied in continuum finite element model. Through the stress-diffusion coupled multiscale method, we analysis the stress of electrode in various size, charge rate and shape during the charge and discharge process.
이차전지 실리콘 전극의 대변형을 고려한 양방향 응력-확산 연계 멀티피직스해석
장성민(Seongmin Chang),문장혁(Janghyuk Moon),조맹효(Maenghyo Cho) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Silicon (Si) is a promising candidate material for anode (negative electrode) of secondary batteries due to high theoretical lithium (Li) storage capacity. Si is swollen by up to 300% when it absorbs Li. This large deformation results in miss-match stress. Due to the stress, micro cracks may propagate during charging and discharging, resulting in fracture. As a result, the Si electrode exhibits low cycle performance. In order to improve cycle performance of Si anode, it is necessary to accurately analysis the relationship between the diffusion of Li and the stress. In this paper, we devised a multiphysics analysis technique that accurately implements the large volume expansion due to the diffusion of Li and takes into account the two-way coupled effect between the stress and diffusion.
고유치 평형방정식과 부구조화 기법을 이용한 대형 구조 시스템 식별 기법
장성민(Seongmin Chang),백승민(Sungmin Baek),조맹효(Maenghyo Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Even with the increased computational capacity and improved FEM techniques, a large amount of computational time and computer resources are still required to identify large and complex structural system. In our previous study, overall system responses are estimated from the limited experimental system responses using an advanced reduction technique to prevent increases of the unknown parameters due to the limited system response and to satisfy the balance eigenvalue equations in the least square sense. Although the previous method reduces calculation time and enhances the convergence of solution, the previous method is not efficient to be applied to large scale-system identification. Thus, in this study, we improve the previous method through applying the sub-structuring technique. In the system identification, employment of reduction methods for efficient computations generates transformation errors and these errors deteriorate the identification results. In order to avoid this trouble resulting from the reduction transformation error, the iterated improved reduced system (IIRS) is now applied in the sub-structuring level. The proposed identification method in the large scale problem is demonstrated through a number of numerical examples.
복합 규칙성을 가진 구조물의 효과적인 해석을 위한 다단계 균질화기반 해석 프레임워크
전영재,장완재,장성민,Youngjae Jeon,Wanjae Jang,Seongmin Chang 한국전산구조공학회 2023 한국전산구조공학회논문집 Vol.36 No.1
전산 자원의 발달로 여러 부품들이 결합된 전체 구조물에 대한 해석이 가능해져 해석에 필요한 계산 시간과 데이터의 양이 증가하였다. 이러한 전체 구조물에는 같은 부품이 반복되어 규칙성을 가지는 경우가 많다. 이러한 반복적인 구조물에 균질화 기법을 적용하면 효과적인 해석이 가능하다. 상용 프로그램의 일반적인 균질화 모듈에서 단위 구조는 모든 방향으로 반복된다고 가정한다. 하지만 실제 구조물들은 여러 단위 구조가 복잡하게 반복되는 경우가 많아 기존 균질화 기법을 적용하는데 어려움이 있다. 본 논문에서는 복잡한 반복성을 고려하는 다단계 균질화 기법을 제안한다. 제안된 균질화 기법은 구조물을 여러 영역으로 나누어 균질화를 수행하는 형태로 기존 기법보다 정확한 해석이 가능하다. Because of the development of computational resources, an entire structure in which many components are combined can be analyzed. To do so, the calculation time and number of data points are increased. In many practical industry structures, there are many parts with repeated patterns. To analyze the repetitive structures effectively, a homogenization method is usually employed. In a homogenization module, including commercial programs, it is generally assumed that a unit cell is repeated in all directions. However, the practical industry structures usually have complicated, repeated patterns or structures. Complicated patterns are difficult to address using the conventional homogenization method. Therefore, in this study, a multilevel homogenization method was devised to consider complex regularities. The proposed homogenization method divides the structure into several areas and performs multiple homogenizations, resulting in a more accurate analysis than that provided by the previous method.