Structural modal reanalysis using automated matrix permutation and substructuring

부승환 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.1

In this paper, a new efficient method for structural modal reanalysis is proposed, which can handle large finite element (FE) models requiring frequent design modifications. The global FE model is divided into a residual part not to be modified and a target part to be modified. Then, an automated matrix permutation and substructuring algorithm is applied to these parts independently. The reduced model for the residual part is calculated and saved in the initial analysis, and the target part is reduced repeatedly, whenever design modifications occur. Then, the reduced model for the target part is assembled with that of the residual part already saved; thus, the final reduced model corresponding to the new design is obtained easily and rapidly. Here, the formulation of the proposed method is derived in detail, and its computational efficiency and reanalysis ability are demonstrated through several engineering problems, including a topological modification.

Automated static condensation method for local analysis of large finite element models

부승환,오민한 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.6

In this paper, we introduce an efficient new model reduction method, named the automated static condensation method, which is developed for the local analysis of large finite element models. The algebraic multilevel substructuring procedure is modified appropriately, and then applied to the original static condensation method. The retained substructure, which is the local finite element model to be analyzed, is defined, and then the remaining part of the global model is automatically partitioned into many omitted substructures in an algebraic perspective. For an efficient condensation procedure, a substructural tree diagram and substructural sets are established. Using these, the omitted substructures are sequentially condensed into the retained substructure to construct the reduced model. Using several large practical engineering problems, the performance of the proposed method is demonstrated in terms of its solution accuracy and computational efficiency, compared to the original static condensation method and the superelement technique.

Welding simulation using a reduced order model for efficient residual stress evaluation

신한섭,부승환 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.4

In this paper, to evaluate the residual stress of welded structures efficiently, we propose a welding simulation method utilizing a reduced order model. To construct the reduced order model, a finite element model is divided into a target part and an omitted part. For the heat transfer analysis, a thermal boundary condition is newly defined and applied to the target part, to compensate for the heat loss induced by neglecting the omitted part. For the thermal elastic plastic analysis, a reduced model for the target part is constructed using the automated static condensation method. The performance of the proposed welding simulation method adopting the reduced order model is verified by solving several welding problems, and it effectively reduces computational costs while predicting the residual stress with little loss of accuracy.

Block-partitioned Rayleigh–Ritz method for efficient eigenpair reanalysis of large-scale finite element models

정연호,부승환,Yim Solomon C 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.3

In this manuscript, we propose a new effective method for eigenpair reanalysis of large-scale finite element (FE) models. Our method utilizes the matrix block-partitioning algorithm in the Rayleigh–Ritz approach and expresses the Ritz basis matrix using thousands of block matrices of very small size. To avoid significant computational costs from the projection procedure, we derive a new formulation that uses tiny block computations instead of global matrix computations. Additionally, we present an algorithm that recognizes which blocks are changed in the modified FE model to achieve computational cost savings when computing new eigenpairs. Through selective updating for the recognized blocks, we can effectively construct the new Ritz basis matrix and the new reduced mass and stiffness matrices corresponding to the modified FE model. To demonstrate the performance of our proposed method, we solve several practical engineering problems and compare the results with those of the combined approximation method, the most well-known eigenpair reanalysis method, and ARPACK, an eigenvalue solver embedded in many numerical programs.

고성능 수치해석 라이브러리를 적용한 진동해석 프로그램 개발

고도현,부승환 해양환경안전학회 2021 해양환경안전학회지 Vol.27 No.1

선박 및 해양구조물과 같은 대형 유한요소모델의 진동 특성을 평가하기 위해 고유치 해석 및 가진 주파수에 따른 응답 계산을 필수적으로 수행해야 한다. 하지만 이러한 해석들은 과도한 전산 장비와 계산 시간이 요구되어 고성능 해석 프로그램의 개발이 필요하다. 특히 선형연립방정식에서 발생하는 역행렬 계산 및 고유치 해석 시에는 상당한 전산 해석 시간이 발생하기 때문에 최신 고성능 라이브러리를 적용함으로써 이를 개선할 수 있다. 본 연구에서는 병렬식 선형연립방정식 계산 라이브러리인 PARDISO와 고성능 고유치 해석 라이 브러리인 ARPACK을 적용하여 빠르고 정확한 해석이 가능한 진동해석 프로그램을 개발하였다. 끝으로 개발된 해석 프로그램의 정확도와 효율성을 검증하기 위해 여러 선박해양공학 수치 예제를 사용하였고, 상용 유한요소 프로그램인 ABAQUS와의 결과 비교 검토를 통해 개발된 진동해석 프로그램의 신뢰성을 검증, 제시하였다. In order to evaluate the vibrational characteristics of huge finite element models such as ships and offshore structures, it is essential to perform eigenvalue analysis and frequency response analysis. However, these analyzes necessitate excessive equipment and computation time, which require the development of a high-performance analysis program. In particular, a considerable computational analysis time is required when calculating the inverse matrix in a linear system of equations and analyzing the eigenvalue analysis. Therefore, it can be improved by applying the latest high-performance library. In this paper, the vibration analysis program that enables fast and accurate analysis was developed by applying ‘PARDISO’, a parallel linear system of equation calculation library, and ‘ARPACK’, a high-performance eigenvalue analysis library. To verify the accuracy and efficiency of proposed method, we compare ABAQUS with proposed program using numerical examples of marine engineering.

재해석 기법을 이용한 설계 변경된 보강판의 효율적인 구조모드해석

박준범,부승환 해양환경안전학회 2018 해양환경안전학회 학술발표대회 논문집 Vol.2018 No.11

A new block assembly method for shipbuilding at sea

Bilin Zhang,부승환,김진균 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.5

In this paper, we introduce a new method for assembly of shipbuilding blocks at sea and present its feasibility focusing on structural safety. The core concept of this method is to assemble ship building blocks by use of bolting, gluing and welding techniques at sea without dock facilities. Due to its independence of dock facilities, shipyard construction capability could be increased considerably by the proposed method. To show the structural safety of this method, a bulk carrier and an oil tanker were employed, and we investigated the structural behavior of those ships to which the new block assembly method was applied. The ship hull models attached with connective parts are analyzed in detail through finite element analyses, and the cargo capacity of the bulk carrier is briefly discussed as well. The results of these studies show the potential for applying this new block assembly method to practical shipbuilding.

강성응축기법을 이용한 국부 비선형 정적 해석

신한섭,오민한,부승환 해양환경안전학회 2021 해양환경안전학회지 Vol.27 No.1

본 연구에서는 국부 비선형 정적 해석을 효율적으로 수행하기 위하여 강성응축(Static condensation)을 활용한 해석기법을 제시하였다. 강성응축기법은 자유도 기반의 유한요소 모델 축소기법이며, 해석 모델을 관심 대상(Target) 부분과 응축되어 생략될(Omitted) 부분으 로 구분한다. 본 연구에서는, 관심 대상 부분에는 비선형 영역, 생략될 부분에는 선형 영역으로 지정하였고, 선형 영역에 대응되는 강성 행렬 및 하중 벡터를 비선형 영역, 즉 관심 대상 부분으로 모두 응축하였다. 모델 응축 후에는 비선형 영역에 대한 강성 행렬 및 하중 벡터만으로 이루어진 축소 모델을 구성하였으며, 이 축소 모델만을 뉴턴-랩슨 반복(Newton-Raphson iteration)을 통해 갱신하여 효율적으로 비선형 해석을 수행하였다. 끝으로, 제안된 기법을 다양한 수치 예제에 적용하여 해석기법의 효율성과 신뢰성을 제시하였다. In this study, an analysis technique using static condensation is proposed for an efficient local nonlinear static analysis. The static condensation method is a model reduction method based on the degrees of freedom, and the analysis model is divided into a target part and a condensed part to be omitted. In this study, the nonlinear and linear parts were designated to the target and the omitted parts, respectively, and both the stiffness matrix and load vector corresponding to the linear part were condensed into the nonlinear part. After model condensation, the reduced model comprising the stiffness matrix and the load vector for the nonlinear part is constructed, and only this reduced model was updated through the Newton-Raphson iteration for an efficient nonlinear analysis. Finally, the efficiency and reliability of the proposed analysis technique were presented by applying it to various numerical examples.

SUS304L 겹침 용접부에 대한 극저온에서의 인장 및 피로강도에 관한 실험적 연구

김경수(KYUNG-SU KIM),부승환(SEUNG-HWAN BOO),박창열(CHANG-YOUL PARK),조영근(YOUNG-GUN CHO),이정수(JEUNG-SOO LEE) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.3

As LNG tank is operated around -162 ℃ an experimental approach all the cryogenic temperature tensile and fatigue strengths of SUS304L lap joint weld is very important at the design stage of membrane type LNG tank. In this study, in order to estimate the tensile and fatigue strengths of SUS304L lap joint weld at cryogenic temperature condition, tensile and fatigue tests were conducted. Also, S-N curves are presented with statistical testing method recommended by JSME. As a result of the experimental approach, the design fatigue of fatigue strength is proposed and that is expected to be useful for membrane type LNG tank design.

향상된 동적 부구조법의 소개

김진균(Jin-Gyun Kim),부승환(Seung-Hwan Boo),이필승(Phill-Seung Lee) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4