주기 구조를 이용한 Partial H-plane Filter

김동진,정우성,이정해,Kim Dong-Jin,Chung Woo-Sung,Lee Jeong-Hae 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.8

In this paper, a compact partial H-plane filter with periodic structure is proposed. Guided wavelength of periodic structure' is reduced by slow wave effect. Cross-section and length of partial H-plane filter with periodic structure are considerably reduced by 75% and 30%, respectively, as compared with conventional E-plane filter. In addition, spurious responses of the bandpass filter are improved. To design bandpass filter with periodic structure, we have analyzed a periodic structure of partial H-plane waveguide and derived equations of the periodic filter. Measured results are in good agreement with simulated results. 본 논문에서는 주기 구조를 이용한 소형화된 partial H-plane필터를 제안하였다. 주기 구조의 관내 파장은 저속파의 영향으로 인해 그 크기가 줄어든다. 주기 구조를 이용한 partial H-plane 필터는 일반적인 E-plane 필터보다 단면적과 길이가 각각 75%, 30% 축소되었다. 또한 대역 통과 필터의 스퓨리어스 응답 특성이 향상되었다. 주기 구조를 이용한 대역 통과 필터를 설계하기 위해 partial H-plane 도파로의 주기 구조가 해석되었고, 설계식이 유도되었다. 측정된 결과는 시뮬레이션 결과와 잘 일치함을 확인할 수 있었다.

면내조합하중과 횡압 하의 선박 이중판 설계시스템 구축

함주혁 한국해양공학회 2019 韓國海洋工學會誌 Vol.33 No.2

A design system was developed for the doubler plate of a ship structure simultaneously subjected to in-plane loads and lateral pressure based on general dimensions and those of a representative ship structure. An equivalent design equation that considers various structural design parameters was derived by introducing the equivalent plate thickness theory, and the design of the doubler plate reinforcement of the ship structure was developed. A hybrid structural design system was established for a doubler plate simultaneously subjected to in-plane loads and lateral pressure consisting of two modules: an optimized design module and a double plate strength & design review module. The practical application of this design system was illustrated to show its usability. It was found that the design safety of the doubler plate was ensured, and this system could be used as an initial design guide to review the double plate reinforcement for a dent or corrosion of the ship plate members. Using the developed design system would make it possible to obtain a more reasonable doubler plate structure that considers the rational reinforcement of plate members of ship structures. In addition, a more reliable structural analysis using a strength evaluation process can be performed to verify the efficiency of the optimum structural design for the doubler plate structure.

In-Plane Dynamics Characteristics and Multi-Objective Optimization of Negative Poisson’s Ratio Honeycomb Structure with Power Function Curve

Zhu Yifan,Xu Feng Xiang,Guan Yijie,Zou Zhen,Duan Libin,Du Zhanpeng,Ma Hongfeng 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5

As an alternative to the conventional concave hexagonal honeycomb structure (CHHS), a negative Poisson’s ratio honeycomb structure with power function curve (NHPC) was devised. The relationship between the power function exponent (PFE) and normalized power function coefficient (NPFC) of honeycomb structure and its equivalent Poisson’s ratio (EPR) was explored to identify the range of variables required for the negative Poisson’s ratio effect. To investigate the in-plane mechanical properties and energy absorption characteristics of NHPC, the deformation mode, dynamic response, and energy absorption characteristics under various impact velocities were studied by constructing an in-plane impact simulation model. The results showed that NHPC obviously exhibited a negative Poisson’s ratio effect on medium and low impact velocities, and the deformation was primarily uniform. As the NPFC increased, the honeycomb structure was less prone to stress concentration, while the peak crushing force (PCF) and the specific energy absorption (SEA) declined and the plateau stress increased. A multi-objective optimization experiment was operated with low PCF and high SEA as the targets within the range of design variables in order to generate the optimal NHPC. According to the experimental findings, the improved NHPC showed a 25.48 % reduction in PCF and a 19.29 % increase in SEA. This paper provides theoretical recommendations for improving the energy absorption and structural optimization of the honeycomb structure.

Deformation estimation of plane-curved structures using the NURBS-based inverse finite element method

Runzhou You,Liang Ren,Tinghua Yi,Hongnan Li 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.1

An accurate and highly efficient inverse element labelled iPCB is developed based on the inverse finite element method (iFEM) for real-time shape estimation of plane-curved structures (such as arch bridges) utilizing onboard strain data. This inverse problem, named shape sensing, is vital for the design of smart structures and structural health monitoring (SHM) procedures. The iPCB formulation is defined based on a least-squares variational principle that employs curved Timoshenko beam theory as its baseline. The accurate strain‒displacement relationship considering tension‒bending coupling is used to establish theoretical and measured section strains. The displacement fields of the isoparametric element iPCB are interpolated utilizing nonuniform rational B-spline (NURBS) basis functions, enabling exact geometric modelling even with a very coarse mesh density. The present formulation is completely free from membrane and shear locking. Numerical validation examples for different curved structures subjected to different loading conditions have been performed and have demonstrated the excellent prediction capability of iPCBs. The present formulation has also been shown to be practical and robust since relatively accurate predictions can be obtained even omitting the shear deformation contributions and considering polluted strain measures. The current element offers a promising tool for real-time shape estimation of plane-curved structures.

경계요소법을 이용한 평면변형율요소의 확률해석

전정배,윤성수,박진선,이형렬,Jeon, Jeong-Bae,Yoon, Seong-Soo,Park, Jin-Seon,Lee, Hyeong-Ryeol 한국농공학회 2012 한국농공학회논문집 Vol.54 No.4

The objectives of this study is intended to analyze stresses using the boundary element method and probability analysis for agricultural structure. Loads and material properties are an important factor when analyzing the structure. Until now, designing structure, loads and material properties are applied deterministic value. However, load and material properties involve uncertainties due to those change probabilistic and deterministic methods could not consider uncertainties. To solve these problems, the reliability analysis based on probability properties scheme was developed. Reliability analysis is easy to approach to analysis frame structure, however it has limitation when solving plane stress strain problems a kind of agricultural structures. The BEM (Boundary Element Method) is able to analysis plane strain problems by boundary conditions. Thus, this study applied boundary element method to analysis plane strain problem, load and material properties as a probabilistic value to calculate the analytical model using Monte Carlo simulations were developed.

등기하개념을 이용한 평면구조물의 자유진동해석

이상진 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.9

Isogeometric concept is introduced to carry out free vibration analysis of plane structures. The geometry of structures is represented by usingnon-uniform rational B-spline surface (NURBS) and its basis function is consistently used in the formulation of plane stress element. Inaddition, multi-patch strategy is introduced to deal with the openings in building. The performance of the present isogeometric plane stresselement is investigated by using five numerical examples. From numerical results, it is found to be that the isogeometric concept cansuccessfully identify reliable natural frequencies and associated mode shapes of plane structures with/without openings in efficient way. 평면구조물의 자유진동해석을 수행하기 위해 등기하 해석개념이 도입되었다. 구조물의 기하학적 형상은 비균일 유리 B-스플라인(NURBS)으로 표현하였다. 또한 비균일 유리 B- 스플라인의 기저함수를 평면 응력 요소의 정식화에 일관되게 사용하였다.  또한 건물의 개구부를 표현하기 위해서 멀티 패치를 도입하였다. 본 연구를 통해서 구현된 등기하 평면응력요소의 성능은 다섯가지 수치예제를 통하여 조사하였다. 수치해석결과로부터 등기하개념은 구조물의 개구부 유무에 상관없이 충분한 신뢰성을 가지는 고유 진동수와 모드형상을 성공적으로 계산하였다.

유사 평면변형률 유한요소를 사용한 실린더 문제의 해석

권영두(YOUNG-DOO KWON),권현욱(HYUN-WOOK KWON),신상목(SANG-MOK SHIN),이찬복(CHAN-BOK LEE) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.5

Long cylinder, subjected to internal pressure, is important in the analysis and design of nuclear fuel rod structures. In many cases, long cylinder problems have been considered as a plane strain condition. However, strictly speaking, long cylinder problems are not plane strain problems, but rather a general plane strain (GPS) condition, which is a combination of a plane strain state and a uniform strain state. The magnitude of the uniform axial strain is required, in order to make the summation of the axial force zero. Although there has been the GPS element, this paper proposes a general technique to solve long cylinder problems, using several pseudo-general plane strain (PGPS) elements. The conventional GPS elements and PGPS elements employed are as follows: axisymmetric GPS element (GA3), axisymmetric PGPS element (PGA8/6), 2-D GPS element (G10), 3-D PGPS element (PG20/16), and reduced PGPS elements (RPGA6, RPG20/16). In particular, PGPS elements (PGA8/6, PG20/16) can be applied in periodic structure problems. These finite elements are tested, using several kinds of examples, thereby confirming the validity of the proposed finite element models.

등기하해석법을 이용한 자유진동 평면구조물의 위상최적화

이상진(Lee, Sang-Jin),배정은(Bae, Jungeun) 대한건축학회 2018 大韓建築學會論文集 : 構造系 Vol.34 No.6

Isogeometric concept is introduced to find out the optimum layout of plane structure under free vibration. Eigenvalue problem is formulated and numerically solved in order to obtain natural frequencies and mode shapes of plane structures. For the exact geometric expression of the structure, the Non-Uniform Rational B-spline Surface (NURBS) basis functions is employed and it is also used to define the material density functions. A node-wise design variables is adopted to deal with the updating of material density in topology optimization (TO). The definition of modal strain energy is employed to achieve the maximization of fundamental frequency through its minimization. The verification of the proposed TO technique is performed by a series of benchmark test for plane structures.

Fourier series expansion method for plated-structures

Deng, Jiann-Gang,Cheng, Fu-Ping Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.8 No.4

This work applies a structural analysis method based on an analytical solution from the Fourier series which transforms a half-range cosine expansion into a static solution involving plated structures. Two sub-matrices of in-plane and plate-bending problems are also formulated and coupled with the prescribed boundary conditions for these variables, thereby providing a convenient basis for a numerical solution. In addition, the plate connection are introduced by describing the connection between common boundary continuity and equilibrium. Moreover, a simple computation scheme is proposed. Numerical results are then compared with finite element results, demonstrating the numerical scheme's versatility and accuracy.

Influence of structural anisotropy on the stress relaxation behavior of anisotropic rocks

( Chuangzhou Wu ),( Hyun-sic Jang ),( Bo-an Jang ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Time-dependent characteristics, such as creep and stress relaxation, are among the crucial design parameters which govern the long-term stability and serviceability of underground structures located in the rock mass. However, the past studies on the time-dependent properties of rocks have commonly neglected the effect of structural anisotropy on rock located a round deep openings. A series of biaxial compression tests were performed to investigate the stress relaxation behavior of greenschist rock considering the effects of structural anisotropy and directional dependence of applied loading with foliation planes. The laboratory findings revealed that the rock specimen exhibited three distinct stages of relaxation behavior. The specimens subjected to vertical and lateral loads acting parallel to the foliation plane showed a higher stress relaxation and creep strain accumulation. Moreover, when specimens were subjected to creep along vertical direction, their lateral sides showed signs of stress relaxation, which in turn could affect the strength and stability of the surrounding rock. These results are promising and innovative which cannot be achieved using traditional creep test (uniaxial and triaxial creep test). The test results are compared with published data in the literature to understand the influence of the foliation plane on the magnitude and time to attain the maximum stress relaxation. Test findings are practically significant in view of design and stability of long deep-buried tunnels.