계층적 B-스플라인을 이용한 스플라인 유한요소법의 국부 세분화에 관한 연구

하주환(Zoo-Hwan Hah),김현중(Hyun-Jung Kim),윤성기(Sung-Kie Youn) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.8

본 연구에서는 NURBS 의 국부 세분화 방법 중 하나인 계층적 B-스플라인을 이용해 스플라인 유한요소법의 국부 세분화를 수행하는 방법을 제안한다. 세분화가 필요한 영역에 전역 격자로부터 계층적으로 생성된 국소 격자를 중첩시켜 국부 세분화를 수행한다. 국소 격자의 매듭 벡터와 제어점은 전역 격자로부터 추출된 후 세분화 되는 과정을 거친다. 생성된 국소 격자에 적절한 연속성 조건을 부여 함으로써 전역 격자와 국소 격자의 연속성을 유지 한다. 제안된 방법을 이용해 수치 예제의 해석을 수행하였다. 이를 통해 기존 NURBS 기반 스플라인 유한요소법에 비해 제안된 방법의 효율성을 검증하였다. A new local refinement scheme for spline finite element method has been proposed; this scheme involves the use of hierarchical B-spline. NURBS has been widely used in CAD; however, the local refinement of NURBS is difficult due to its tensor-product property. In this study, we attempted to use hierarchical B-splines as local refinement strategy in spline FEM. The regions of high gradients are overlapped by hierarchically-created local meshes. Knot vectors and control points in local meshes are extracted from global meshes, and they are refined using specific schemes. Proper compatibility conditions are imposed between global and local meshes. The effectiveness of the proposed method is verified on the basis of numerical results. Further, it is shown that by using a proposed local refinement scheme, the accuracy of the solution can be improved and it could be higher than that of the solution of a conventional spline FEM with relatively lower degrees of freedom.

주조공정에서의 효율적인 열응력 해석을 위한 이종해석기법의 연계

곽시영(Si Young Kwak),임채호(Chae Ho Lim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.8

본 논문에서 유한차분법(FDM)과 유한요소법(FEM)을 연계하여 주조공정 해석을 수행하는 이종해석기법을 제안하였다. 수치해석기법으로는 FDM, FEM, BEM 등 다양한 기법이 있으며, 대부분의 공학문제는 각각의 현상에 적합한 수치해석기법을 사용하여 해석을 수행하고 있다. 일반적으로, FDM 또는 FVM 은 유동 및 열전달 해석에, FEM 은 열응력 해석에 많이 적용되고 있지만 복합적인 공학 문제를 해결하기 위해서 각각 수치해석기법을 연동한 해석의 필요성이 점점 증가하고 있다. 따라서, 본 논문에서는 3 차원 공간에서 FDM 을 사용하여 응고 및 열 전달 해석을 수행하고, 계산된 온도 데이터를 FEM 해석장에 적합하게 변환하여 열응력 해석을 수행하는 FDM/FEM연계해석 방법을 제시하였다. 그리고 제시한 해석방법을 주조 공정 해석에 적용한 결과, 요소생성 등의 해석작업과 해석속도 면에서 효율적으로 해석을 수행할 수 있었다. This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.

Preangulated TMA T-loop spring의 적용 위치 변화에 따른 견치의 초기 응력 분포에 대한 유한 요소법적 연구

김정민,차경석,이진우 대한치과교정학회 1999 대한치과교정학회지 Vol.29 No.5

본 연구는 상악 견치, 상악 제 2 소구치, 상악 제 1 대구치의 유한요소 모델을 제작하였고 0.018×0.025인치 Stainless steel wire를 고정원 강화를 위해 상악 제 2소구치와 제 1대구치에 위치시켰다. 0.017×0.025인치 T-loop spring의 전후방적 위치에 따른 응력 분포를 알아보기 위해 T-loop spring의 중간이 견치와 제 1대구치 거리의 중간에 위치하는 것과, 2mm전방에 위치하는 것, 2mm후방에 위치하는 것의 3가지 유한 요소모델을 제작하였다. 이 T-loop spring을 6mm 강제변위시켜 발생하는 힘을 각 치아에 적용시켰으며, 견치에서 발생하는 힘과 응력에 대하여 다음과 같은 결론을 얻었다. 1. 3가지 형태 모두에서 유사한 크기의 후방견인력을 보였다. 2. 3가지 형태 모두에서 유사한 크기와 비슷한 형태의 응력 분포를 보였다. 3. 3가지 형태 모두에서 회전 중심은 치근단 2/3부분에 보였다. 4. 2mm 전방 위치된 T-loop spring과 2mm 후방 위치된 T-loop spring에 각각 함입력과 정출력을 보이지만 그 크기가 작아서 응력 양상에 영향을 주지 못한다. The purpose of this study was to find the difference of stress distribution on canine altered by the application point of preangulated T-loop spring. For this study, the finite element models of upper left canine, upper left second premolar and upper left first molar were made. Also, the finite element models of 0.017×0.025 inch preangulated, preactivated T-loop spring and 0.018×0.025 inch stainless steel wire were made. Three types of T-loop spring were made : the middle of activated T-loop is positioned in accordance with the middle position of instance of bracket position of both the canine and first molar, 2mm anterior, 2mm posterior. We compared the forces and the distribution of stress that were generated by difference of position of T-loop spring. The results were as follows. 1. All of the 3 types of T-loop spring showed the similar retraction forces. 2. All showed the similar amount & pattern of stress distribution. 3. The centers of rotation of canine in 3 types of T-loop spring were same and were positioned between C and D plane. 4. The canine showed the intrusive force by 2mm anterior positioned T-loop spring, but the extrusive force by 2mm posterior positioned T-loop spring. Neverthless, because of the small amount of the forces, the effect of vertical force was not significant.

유한요소법을 이용한 자성유체의 거동예측을 위한 수치적 모델링

서재형(Jae-Hyeong Seo),이무연(Moo-Yeon Lee),서이수(Lee-Soo Seo) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.1

The objective of this study is numerically analyzed the behavior characteristics of the magnetic fluid in a closed rectangular container using finite element method (FEM). The governing equations are solved with magnetization and Maxwell equations for consideration of rotating effect of the magnetite particle. Then the discretized equations are solved with boundary conditions of the velocity and temperature. The developed model is validated with the results of Davis (1983) and Fusegi et al. (1991) has a good agreement within 5.5 % and 2.7 %, respectively.

LED 접합온도 예측에 대한 연구

한지원(Ji-Won Han),이경우(Kham Lee),이명훈(Myoung-Hun Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

LED is a solid-state semiconductor device which directly converts electrical energy into light. Thermal problem caused by the heat generated within the LED itself is still a bottleneck to limit the stability, reliability and lifetime of LED.<SUP>1)</SUP> The detail finite element method of LED package was created by ABAQUS. The obtained results indicates that experimental data and FEM analysis offer temperature of 5% error for reliability. The temperature of 9Via hole is measured lower than 3via hole.

FEM 해석을 이용한 mN급 MEMS 추력 측정 시스템 설계

류영석(Youngsuk Ryu),서대반(Daeban Seo),이종광(Jongkwang Lee) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.12

mN급 마이크로 추력기의 성능 평가에 적합한 시스템을 설계하기 위해 FEM 해석을 수행하여 MEMS 기반 추력 측정 시스템의 형상 최적화를 수행하였다. 추력 측정 시스템은 원형 박막 구조를 가지며 추력 측정을 위해 압저항 센서를 사용하였다. 압저항 센서의 높은 민감도를 확보하기 위해서 시스템은 동일 추력 대비 높은 응력을 발생시킬 수 있는 시스템으로 설계되어야 한다. FEM 해석을 통해 목표 추력 범위 내에서 원형 박막의 크기와 두께에 따른 응력 변화를 확인하여 형상 최적화를 수행하였다. In order to design a system suitable for the performance evaluation of mN level micro thrusters, an FEM simulation was performed to optimize shape of MEMS based thrust measurement system. The thrust measurement system is based on a circular membrane structure and a piezoresistive sensor is used for thrust measurement. To obtain the high sensitivity of the piezoresistive sensor, the system should be designed as a system, which has higher stress under the applied thrust. Through the FEM simulation, the optimization was performed by analyzing the stress variation according to the diameter and thickness of the circular membrane within designed thrust range.

FEM과 ADS를 이용한 최적화에 관한 연구

김민주,이승수,전언찬 동아대학교 생산기술연구소 2001 生産技術硏究所硏究論文集 Vol.6 No.2

This study is an investigation for the ADS optimum design by using FEM. We write out program which express ADS perfectly and reduce the required time for correcting of model to the minimum in solution and manufacture result. We complete algorithm which can plan optimum forming of model by feedback error information in CAE. For that, we draw up ADS program which modeling rachet wheel by using visual LISP and telegraph to ANSYS, structural solution program, we can solve stress solution. Then we correct model by feedback date obtaining in solution process, repeat course following stress solution again and do modeling rachet wheel for optimum forming. That is our aim. As a result of experience, we can develope automatic design program using Visual LISP and exhibit ADS as modeling third dimension CAD for optimum design. Also, we develop optimum design algorithm using ADS and FEM. In racket wheel, greatest equivalence stress originates in key groove comer and KS standard is proved the design for security.

유한요소법과 반응표면법을 이용한 250 ㎾급 견인 유도전동기 최적설계

이중호(Jung Ho Lee),윤태원(Tae Won Yun) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.6

This paper deals with the optimum design criteria for the premium efficiency of 250 ㎾ traction induction motor, using response surface methodology (RSM) and finite element method (FEM). The focus of this paper is found firstly a design solution through the comparison of torque according to rotor bar shape, rotor dimensions variations. And secondly a mixed resolution with central composite design (CCD) is introduced and analysis of variance (ANOVA) is conducted to determine the significance of the fitted regression model. The proposed procedure allows to be optimized the rotor copper bar shape, rotor slot, rotor dimensions starting from an existing motor or a preliminary design.

유한요소법을 이용한 냉각홴의 진동 및 간섭에 관한 연구

서종휘(Seo, Jong-Hwi),송하종(Song, Ha-Jong),박태원(Park, Tae-Won),김주용(Kim, Joo-Yong),정일호(Jung, Il-Ho) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.9

A CFA(cooling fan assembly) is composed of a fan, motor and shroud, which is at the back of the automotive radiator. By forcing the wind to pass, the CFA controls the cooling performance of the radiator. The noise and vibration of the CFA may be primarily due to the resonance between the CFA and engine. The Interference among the fan, shroud and radiator by deformation is considered when the CFA is designed. In this paper, in order to analyze the structural vibration of the CFA for automobiles, a finite element model of the CFA is established by using a commercial FEM code. After the finite element modeling, the natural frequencies and the mode shapes are obtained from the FE analysis. The natural frequencies are obtained from the vibration test as well. Then, the results of the vibration test are compared with those of the FE analysis. The natural frequencies obtained by experiment have a great similarity to the results from FE model. We have confirmed the validity of the FE model and verify the structural safety for the resonance. The stress and displacements are obtained from FE analysis. We have confirmed the safety for the interference and failure.

유한요소법을 이용한 네오디움 영구자석의 코어 설계

허관도(Kwan-Do Hur),예상돈(Sang-Don Ye) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.5

Permanent magnets have recently been considered as device that can be used to control the behavior of mechanical systems. Neodymium magnets, a type of permanent magnet, have been used in numerous mechanical devices. These are permanent magnets made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. The magnetic selection, magnet core design and mechanical errors of the magnetic component can affect the performance of the magnetic force. In this study, the coercive force, residual induction, and the dimensions of the design parameters of the magnet core are optimized. The design parameters of magnet core are defined as the gap between the magnet and the core, the upper contact radius, and the lower thickness of the core. The force exercised on a permanent magnet in a non-uniform field is dependent on the magnetization orientation of the magnet. Non-uniformity of the polarization direction of the magnetic has been assumed to be caused by the angular error in the polarization direction. The variation in the magnetic performance is considered according to the center distance, the tilt of the magnetic components, and the polarization direction. The finite element method is used to analyze the magnetic force of an optimized cylindrical magnet.