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.

유한요소법을 이용한 초음파 진동 공구혼 설계에 관한 연구

이봉구(Bong-Gu Lee),김광래(Kwang-Lae Kim),김강은(Kang Eun Kim) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.6

Conical horn is used in many high frequency ultrasonic horns, to achieve a longitudinal vibration mode across a wide ultrasonic tool horn output surface. Modal analysis is method for designing tuned ultrasonic tool horn and for the prediction natural frequency of ultrasonic tool horn vibration mode. The design of ultrasonic horn is based on prototype estimate obtained by FEM analysis. The FEM simulated ultrasonic tool horn is built and characterized experimentally through laser vibrometer and electrical impedance analysis. In this paper, FEM analysis is developed to predict the natural frequency of ultrasonic tool horn and use of in the optimal design of ultrasonic horn shape.

유한요소해석을 이용한 연성재료의 나노인덴테이션에 관한 연구

한승우(S. W. Han),이현우(H. W. Lee),이학주(H. J. Lee),고순규(S. G. Ko),김재현(J. H. Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

Nano-indentation is used for measuring mechanical properties of thin films such as elastic modulus and hardness. For ductile materials, pile-up around the indenter causes the calculation of inaccurate projected contact area. This phenomenon was found by measurement of indentation shape using an atomic force microscope. In present study finite element analysis of nano-indentation was performed to compensate the effects of pile-up on the contact area. The result of finite element analysis was compared with that of nano-indentation for a ductile material. The analysis has demonstrated that the true contact area is greater than that calculated by nano-indentation. It is verified that the consideration of the effects of pile-up in nanoindentation for ductile materials using the finite element method is reasonable.

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.

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.

유한요소법을 이용한 다단포머-냉간단조품용 공정설계시스템 개발에 관한 연구

박철우(Chul Woo Park),강정훈(Jung Hun Kang),김철(Chul Kim),김문생(Moon Saeng Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.10

This paper deals with an automated computer-aided process planning and die design system by which designer can determine operation sequences even if they have a little experience in process planning and die design by multi-former for quasi-axisymmetric cold forging product. The approach to the system is based on knowledge-based rules and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLiSP for the AutoCAD using a personal computer. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM softwares, DEFORM and ANSYS, to form a useful package. The system is composed of three main modules. The process planning and die design module considers several factors, such as the complexities of preform geometry, punch and die profiles, specifications of available multi-former, and the availability of standard parts. As the system using 2D geometry recognition is integrated with the technology of process planning, die design, and CAE analysis, the standardization of die parts for wheel bolt requiring cold forging process is possible. The developed system makes it possible to design and manufacture quasi-axisymmetric cold forging product more efficiently.

유한요소법을 이용한 스패어 휠 캐리어용 토크리미터의 해석

염상훈(Sanghoon Yeom),이성범(Seong Beom Lee),한정훈(Jeonghun Han) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5

Existing spare wheel carrier in way of Link chain cause accidents like fall while driving because Link chain has several problems such as tangle, damage. To solve this problem, we hope to develop spare wheel carrier in the way of Wire rope. In significant part which has complex mechanism like Torque limiter, Anti turn around device, Anti loosen device in Wire rope type wheel carrier, analysis using FEM(Finite Element Method) is required because simple theoretical calculation has high risk in trial and error. Torque limiter is one of important part to prevent Spare wheel"s falling when cam shaft has too much Torque. In this study, we want to verify pilot design through analysis of Torque limiter using FEM. For this, we will compare and analyze the torque in Torque limiter by using ANSYS which is FEA(Finite Element Analysis) software.

FEM을 이용한 고속기어 치형 수정에 관한 연구

반재삼,이경원,김규하,조규종 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.1

The stable driving condition of high speed gear is approached by shape modifications of a gear tooth. Recently, many gear designers are using FEM for the design and the manufacture of a high precision gear. In this paper, it is aimed to drive in stable sound level through the modification of the tooth and the shape of a gear. The simulation is used to understand the effect of holes for the decrement of weight and the stress variation for the tooth modification. beam elements used to simulate the same condition as a real gear drive by FEM. The driven gear is simulated to 60,000rpm for the tooth modification.