Polyhedral smoothed finite element method for thermoelastic analysis

김호범,임세영 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.12

Thermoelastic analysis by means of three-dimensional polyhedral elements based on the Smoothed Finite elements method (S-FEM), for example nodal Cell-based S-FEM (CS-FEM), Node-based S-FEM (NS-FEM), and Edge-based S-FEM (ES-FEM), was studied. SFEM allows implicit shape functions, making it possible to construct shape functions of S-FEM based polyhedral elements in a straightforward manner. The performance of S-FEM based polyhedral elements was compared with one another and with the conventional finite elements including hexahedral and tetrahedral element. Numerical examples show that the polyhedral elements by means of CS-FEM and ES-FEM provide better accuracy and convergence rate than conventional hexahedral finite elements, while the polyhedral elements by means of NS-FEM leads to spurious mode.

SEA-FEM hybrid analysis for predicting Inter-floor impact noise

Kim, Tae-Min,Kim, Jeung-Tae,Kim, Jung-Soo Elsevier 2018 Applied acoustics Vol.129 No.-

<P><B>Abstract</B></P> <P>A hybrid method for predicting inter-floor impact noise in an apartment house is developed. Statistical Energy Analysis (SEA) is useful for predicting mid- to high-frequency noise by utilizing simple equivalent models of structures that have complex geometry and material properties. For low frequencies with concomitant low modal density, however, the error can be significant. Finite Element Method (FEM) is useful for predicting low frequency noise but entails complex modelling process and can be computation intensive. The inter-floor impact noise contains a significant low frequency component arising from floor vibration engendered by a person walking on the floor. The force of impact at 30–300Hz frequency range excites the first and second bending modes of the floor and causes sound to radiate, and for the component of the sound less than 100Hz, the SEA prediction error can be quite significant. In the present study, a modular hybrid method in which the floor structure is modelled using FEM and the vibration energy transmission through walls is modelled using SEA is proposed. The low frequency vibration of the floor due to impact is analyzed by modelling the floor asa clamped uniform plate while the propagation of vibratory energy to adjacent walls is analyzed by determining CLF and DLF values. The proposed SEA-FEM hybrid analysis method is capable of providing accurate estimation of the impact noise for low-, medium- and high-frequencies. Compared with a FEM−based method, the proposed method is found to yield results that are similar while reducing computation time by 70%.</P>

유한요소해석을 활용한 장신구디자인 사례연구 – 예술장신구 사례를 중심으로 –

민복기 한국기초조형학회 2020 기초조형학연구 Vol.21 No.1

The purpose of this study is to examine the Finite Element Analysis, studied in Applied Mathematics and used in the fields of Civil Engineering and Architecture, and to explore the possibilities of applying it to the field of jewelry. Finite Element Method changes differential equations into different forms and appears as one of the numerical approximation methods. With this mathematical principle background, the linear combination of the certain function’s value sets the external factors such as property and weight in the engineering field, material mechanics and Finite Element Analysis is the evaluation of the structure by approximating the physical displacement of the object. FEA quickly became a computerized simulation technology, and later integrated to utilize CAD modeling data to simulate various physical environments such as strength, heat, flow, and vibration, etc. for effective design. A jewelry is a very small object it has an inevitable condition to be worn on top of the body; therefore, needs to be made with a secure structure but, there has been no case for it with FEA. This research studies the required conditions of this kind of jewelry with new prong structure research that uses FEA and minimizes the number of prongs in the prongs’ structure to two from four or six, and developed new prong structures for the object to float 2mm above the basis for light to pass. In such a case, FEA not only verifies the structural stability but make new concept design exploration possible and can improve productivity and quality through the interpretation of heat and flow in the casting process of the jewelry industry’s production process. Moreover, various physical external forces such as weight, fall or wind can be simulated to construct safer structures for vessel making in the field of Metal Craft as well. 본 연구의 목적은 응용수학분야에서 연구되어 토목, 건축 등의 분야에서 활용되고 있는 유한요소해석에 대해 살펴보고, 이를 장신구 분야에 적용할 가능성을 탐색하는 데 있다. 유한요소법(Finite Element Method; FEM)은미분방정식 문제를 다른 형태로 바꾸고 이 해(解)를 어떤 함수의 일차결합으로 나타내는 수치적인 근사해법(approximation method)의 하나이다. 이러한 수학적 원리를 바탕으로 재료역학 등의 공학분야에서 물성과 하중 등 외부적 요인을 설정하고 대상물의 물리적 변위의 근사값을 도출하여 구조를 해석하는 것이 유한요소해석(Finite Element Analysis; FEA)이다. FEA는 컴퓨터의 계산을 통한 시뮬레이션 기술로 빠르게 정립되었고, 이후 CAD의 모델링데이터를 활용할 수 있도록 통합되어 강도, 열, 유동, 진동 등 다양한 물리적 환경의 시뮬레이션을 통해 효율적 설계를 도출하는데 활용되고 있다. 장신구는 매우 작은 사물이지만 신체 위에 착용되는 필연적 조건을 가지므로 안정적 구조로 제작되어야 하지만 이를 위해 FEA를 활용한 사례는 없었다. 연구자는 이러한 장신구의 요구조건을 충족하는 새로운 난발(Prong)의 구조연구를 위해 FEA를 활용한 난발구조를 연구하였고 4개 혹은 6개로 이루어진 일반적인 난발구조에서 난발의 개수를 최소화하여 2개의 난발구조를 가지도록 하였다, 그리고 빛의 유입을 위해 오브제를 기저부에서 2mm 위로 띄워 고정할 수 있는 난발구조를 개발하였다. 이러한 사례에서와 같이 FEA는 주얼리의 구조안정성 검증 뿐 아니라 새로운 컨셉의 디자인탐색에 도움을 줄 수있고 주얼리산업의 생산과정에서도 열과 유동의 해석을 통해 주조생산성과 품질을 개선시킬 수 있다. 또한 금속공예의 대공분야에서도 하중이나 낙하, 바람 등 다양한 물리적 외력을 시뮬레이션 하여 좀 더 안정적인 구조를도출하는데 활용될 수 있을 것이다.

An edge-based smoothed finite element method for adaptive analysis

Chen, L.,Zhang, J.,Zeng, K.Y.,Jiao, P.G. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.6

An efficient edge-based smoothed finite element method (ES-FEM) has been recently developed for solving solid mechanics problems. The ES-FEM uses triangular elements that can be generated easily for complicated domains. In this paper, the complexity study of the ES-FEM based on triangular elements is conducted in detail, which confirms the ES-FEM produces higher computational efficiency compared to the FEM. Therefore, the ES-FEM offers an excellent platform for adaptive analysis, and this paper presents an efficient adaptive procedure based on the ES-FEM. A smoothing domain based energy (SDE) error estimate is first devised making use of the features of the ES-FEM. The present error estimate differs from the conventional approaches and evaluates error based on smoothing domains used in the ES-FEM. A local refinement technique based on the Delaunay algorithm is then implemented to achieve high efficiency in the mesh refinement. In this refinement technique, each node is assigned a scaling factor to control the local nodal density, and refinement of the neighborhood of a node is accomplished simply by adjusting its scaling factor. Intensive numerical studies, including an actual engineering problem of an automobile part, show that the proposed adaptive procedure is effective and efficient in producing solutions of desired accuracy.

Mean dilatational based finite element formulation for a nearly incompressible nonlinear large deformation analysis

아닉 다스 안토,Hee Keun Cho 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

The finite element method (FEM) is one of the most powerful tools that can be used to solve engineering problems. Standard displacement-based isoparametric elements are the most popular in the engineering community for their simple implementation. However, loworder displacement-based elements exhibit locking in the incompressible. Our proposed formulation is a locking removing method that is free from the need to store any extra integration point. We calculate the modified deformation gradient from the mean dilatation of the element and also modify the finite element equations using the mean dilatation. This method is also different from the B-bar method as the B matrix is not modified, but rather the weak form is linearized for the modified deformation gradient. Therefore, this method is a unique implementation of the average dilatation of the element. Here we also present an implementation algorithm of the proposed formulation and compare the results with available methods.

An Edge-based Smoothed Finite Element Method (ES-FEM) for Dynamic Analysis of 2D Fluid-Solid Interaction Problems

T. Nguyen-Thoi,P. Phung-Van,V. Ho-Huu,L. Le-Anh 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.3

The paper presents an extension of the Edge-based Smoothed Finite Element Method (ES-FEM-T3) using triangular elements forthe dynamic response analysis of two-dimension fluid-solid interaction problems based on the pressure-displacement formulation. Inthe proposed method, both the displacement in the solid domain and the pressure in the fluid domain are smoothed by the gradientsmoothing technique based on the smoothing domains associated with the edges of the triangular elements. Thanks to the softeningeffect of the gradient smoothing technique used in the ES-FEM-T3, the numerical solutions for the coupled systems by the ES-FEMT3are improved significantly compared to those by some other existing FEM methods.

FEM 시뮬레이션을 이용한 tonpilz 트랜스듀서의 먼지 응집 거동

서진원,최균,이호용,Seo, Jin-Won,Choi, Kyoon,Lee, Ho-Yong 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.6

Tonpilz 트랜스듀서를 이용한 미세먼지의 포집 거동을 살펴보기 위하여 유한요소법(FEM) 시뮬레이션을 이용하여 미세먼지의 응집 거동을 모사하였다. 원판형 head mass의 두께와 tail mass의 직경, 그리고 고정 볼트의 깊이를 트랜스듀서의 형상 변수로 고려하였다. 도넛형 압전체의 소재로는 기존의 PZT-4 소재와 서로 다른 특성의 두 가지 압전 단결정에 대하여 그 출력에 미치는 형상 변수의 최적화를 구현하였고 이를 통하여 얻은 트랜스듀서를 이용하였을 때 나타나는 미세먼지의 응집 거동을 다중 물리해석 S/W인 COMSOL을 이용하여 모사하였다. Dust-collecting behavior of tonpilz transducer was simulated with finite-element-method (FEM) software. In order to optimize the performance of tonpilz transducer, the shape factors including the thickness of head mass, the diameter of tail mass and the depth of bolt were analyzed as variables. As a vibrating energy source, the piezoelectric materials was also tested with PZT-4 and two kinds of piezoelectric single crystals. The output power of the transducer was maximized with the shape factors and then the behavior of the dust-collection was demonstrated with the multi-physics software, COMSOL.

유한 요소법을 이용한 하악골 이부 결손수복에 사용된 재건용 금속판의 응력분포에 관한 연구

오정환,한정수,민지현,문성준,이백수,Oh, Jung-Hwan,Han, Jung-Soo,Min, Jee-Hyun,Mun, Sung-Jun,Lee, Baek-Su 대한악안면성형재건외과학회 2008 Maxillofacial Plastic Reconstructive Surgery Vol.30 No.6

Purpose: This study aimed to evaluate distribution and maximal value of mechanical stresses on the reconstruction plate, bridging mandibular symphysis defect, and to optimize the most appropriate locations of the plate to distribute the stress causing the fracture of the plate. Materials and methods: Four types of reconstruction were constructed by different number and location of the reconstruction plates on the 3 D finite element model (FEM) of a human edentulous mandible; Type I: one plate on the inferior border of the anterior mandible, Type II: one plate on the middle of the anterior mandible, Type III: one plate on the superior border of the anterior mandible, and Type IV: two plates on the inferior and superior border of the anterior mandible. Results: The results showed that the maximal stress of type I (234.29 Mpa) was lower than that of type II (260.91 Mpa) and type III (247.37 Mpa), but higher than that of type IV (186.64 Mpa). We could also observe that the stresses are tending to focus on the inner side and inferior part of the plate which connected proximal segment from the vertical load. Conclusions: On the basis of the findings, it was concluded that using a plate on the inferior border of mandible or two plates on the inferior and superior border of mandible are more favorable to distribute mechanical stresses, which could reduce the fracture of the plate.

Finite Element Modeling of the Compression Garments Structural Effect on the Pressure Applied to Leg

Ehsan Ghorbani,Hossein Hasani,Reza Jafari Nedoushan,Nima Jamshidi 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3

Compression garments due to their numerous medical applications have been recently attracted to be mechanicallyanalyzed for their compression mechanism. Predicting the pressures applied to musculoskeletal tissues supported by thesegarments is a good solution for doing such analyzing which could be simply achieved by the help of finite element method. Inthis paper, the main aim was investigating the structural effect of knitted compression garments used for supporting the bodylower-limb musculoskeletal system. Compression garments of weft knitted rib structure containing elastane yarn wereprepared according to the leg’s dimensions of a healthy 27-year old person. Using Kikuhime measuring device, experimentalvalues of the applied pressure were measured in order to be compared with theoretical results. For developing a threedimensionalbiomechanical model for the leg system supported by compression garment, images form computed tomographyscanning methodology was used. Tensile properties of an elastane yarn as the basis for studying the compression garment’smechanical behavior were experimentally measured and then simulated in Abaqus software as a linear viscoelastic material. The results were then applied to multi-scale modeling technique in order to simulate mechanical behavior of the knitted fabricand the compression garment thereof. Combination of both experimental and theoretical results was applied to simulateinteractions between the leg and the compression garment. The results indicated that the pressure values simulated by finiteelement method were predicted with the maximum mean error of 19.64 % and total error mean of 12.29 % compared toexperimental results. Small difference between the measured and simulated values was observed for tibia and fibula becauseof their low soft-tissue volume. The proposed model enables the specialists to present compression garments based on thepatient’s needs and physician prescription which generate the optimal treatment.

CDG 유한요소법을 이용한 수심적분 흐름의 수치모의

김태범(Kim Tae Beom),최성욱(Choi Sung-Uk),민경덕(Min Kyung Duck) 대한토목학회 2006 대한토목학회논문집 B Vol.26 No.5B

본 연구에서는 2차원 수심 적분된 흐름을 모의하기 위한 수치모델을 개발하였다. 유한요소법의 일종인 Characteristic Dissipative Galerkin(COG) 기법을 적용시켜 천수방정식의 수치해를 구한다. 모델 검증을 위해서 l차원 도수문제에 적용하였고, 계산결과와 해석해를 비교할 때 만족스러운 결과를 얻었다. 정상파를 보이는 단면축소 수로에서의 흐름을 모의한 결과, 실험결과와 유사한 수면분포를 얻었다. 이러한 검증 과정을 통해서 본 수치모델을 이용하여 흐름영역이 갑작스럽게 변화하는 경우에도 모의 가능함을 일았다. 또한 180° 만곡수로에 적용한 결과, 만곡부 내측의 유속이 외측에 비해서 크며, 만곡부 내측의 수심은 외측에 비해서 직은 만곡부 흐름특성을 잘 나타내고 있다. 그러나 만곡수로에서 이차류에 의한 운동량의 횡방향 이송을 고려하지 않는 지배방정식의 한계점으로 인해서, 만곡부 끝단을 제외한 만곡부 전체에 걸쳐서 단면상의 종방향 유속이 일정한 분포를 보이고 있다. This paper presents a numerical model for the simulations of 20 depth-averaged flows. The shallow water equations are solved numerically by the Characteristic Dissipative Galerkin (COG) finite element method. For validation, the developed model is applied to the hydraulic jump. The computed results are compared with the analytical solution, revealing good agreement. In addition, flow in a contracting channel showing standing waves is simulated. The calculated water surface profile appears to be qualitatively consistent with the observed data. The foregoing results indicate that the model is capable of simulating the abrupt change in flow field. Next, the model is applied to the flow in a 1800 curved channel. The simulated results show that the velocity near the inner bank is faster than that near the outer bank and the water depth near the inner bank is shallower than that near the outer bank. However, the simulated results show that the velocity distribution across the channel is almost uniform in the bend except the reach close to the end of the bend. This is due to the limitation of the governing equations in which the transverse convection of momentum by the secondary flows along a channel bend is not taken into account.