• Title/Summary/Keyword: macro-element approach

Search Result 33, Processing Time 0.021 seconds

Numerical Analysis Method of 2-D Dynamic Characteristics of Magnetic Field in Squirrel Cage Induction Motor Considering End-ring (농형회전자의 엔드링(End-ring)을 고려한 유도전동기 자계의 2차원적 동특성 수치해석 방법)

  • 김영중;임달호
    • The Transactions of the Korean Institute of Electrical Engineers
    • /
    • v.41 no.9
    • /
    • pp.1003-1012
    • /
    • 1992
  • This paper presents and analysis method for designing a squirrel cage induction motor, which is aimed at analyzing the dynamic characteristics of magnetic field. This scheme is capable of estimating the effects of slot harmonics due to the rotation of rotor by utilizing Macro-airgap element combination, Voltage source treatment and Time difference algorithm. Furthermore, this strategy presents and approach which effectively compensates for end-ring of rotor. And direct convergence method is applied for considering a magnetic nonlinearity in core. In addition to the precision and the convergence study of algorithm, comparisons with experimental values prove the accuracy of this analysis method.

An Estimation of Korea's Import Demand Function for Fisheries Using Cointegration Analysis (공적분분석을 이용한 우리나라 수산물 수입함수 추정)

  • 김기수;김우경
    • The Journal of Fisheries Business Administration
    • /
    • v.29 no.2
    • /
    • pp.97-110
    • /
    • 1998
  • This paper tries to estimate Korea's import demand function for fisheries using cointegration analysis. The estimation function consists of one dependent variable-import quantity of fisheries(FTIW) and two independent variables-relative price(RP) between importable and domestic products and real income(GDP). As it has been empirically found out that almost all of time series of macro-variables such as GDP, price index are nonstationary, existing studies which ignore this fact need to be reexamined. Conventional econometric method can not analyze nonstationary time series in level. To perform the analysis, time series should be differenciated until stationarity is guaranteed. Unfortunately, the difference method removes the long run element of data, and so leads to difficulties of interpretation. But according to new developed econometric theory, cointegration approach could solve these problems. Therefore this paper proceeds the estimation on the basis of cointegration analysis, because the quartly variables from 1988 to 1997 used in the model is found out to be nonstationary. The estimation results show that all of the variables are statistically significant. Therefore Korea's import demand for fisheries has been strongly affected by the variation of real income and the relative price.

  • PDF

Asymptotic Expansion Homogenization of Permeability Tensor for Plain Woven Fabrics (평직에 대한 투과율 계수의 균질화)

  • Song, Young-Seok;Youn, Jae-Roun
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2005.04a
    • /
    • pp.134-136
    • /
    • 2005
  • Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

  • PDF

A Experimental Study and FE Analysis of the Forming Process with Milli-Component Forming (미세 성형 부품의 성형 공정 해석 및 실험)

  • Ku T. W.;Kang B. S.;Oh S. I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2001.05a
    • /
    • pp.235-238
    • /
    • 2001
  • Milli-structure components are classified as a component group whose size is between macro and micro scales, that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In this study, milli-structure rectangular cup drawing is analyzed and measured using the finite element method and experiment. Generally, milli-structure containers or cases like cellular phone vibrator consist of rectangular-shaped drawing to save installation space. A systematic approach is established for the design and the experiment of the forming processes for rectangular milli-structure cases. To verify the simulation results, the experimental investigations were also carried out on a real industrial product. The numerical analysis by FEM shows good agreement with the experimental results in view of the deformation shape of the product.

  • PDF

Mesoscopic study on historic masonry

  • Sejnoha, J.;Sejnoha, M.;Zeman, J.;Sykora, J.;Vorel, J.
    • Structural Engineering and Mechanics
    • /
    • v.30 no.1
    • /
    • pp.99-117
    • /
    • 2008
  • This paper presents a comprehensive approach to the evaluation of macroscopic material parameters for natural stone and quarry masonry. To that end, a reliable non-linear material model on a meso-scale is developed to cover the random arrangement of stone blocks and quasi-brittle behaviour of both basic components, as well as the impaired cohesion and tensile strength on the interface between the blocks and mortar joints. The paper thus interrelates the following three problems: (i) definition of a suitable periodic unit cell (PUC) representing a particular masonry structure; (ii) derivation of material parameters of individual constituents either experimentally or running a mixed numerical-experimental problem; (iii) assessment of the macroscopic material parameters including the tensile and compressive strengths and fracture energy.

Sintering Multi-scale Virtual Reality

  • Olevsky, Eugene A.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
    • /
    • 2006.09a
    • /
    • pp.264-265
    • /
    • 2006
  • The directions of further developments in the modeling of sintering are pointed out, including multi-scale modeling of sintering, on-line sintering damage criteria, particle agglomeration, sintering with phase transformations. A true multi-scale approach is applied for the development of a new meso-macro methodology for modeling of sintering. The developed macroscopic level computational framework envelopes the mesoscopic simulators. No closed forms of constitutive relationships are assumed for the parameters of the material. The model framework is able to predict the final dimensions of the sintered specimen on a global scale and identify the granular structure in any localized area for prediction of the material properties.

  • PDF

Analysis of side-plated reinforced concrete beams with partial interaction

  • Siu, W.H.;Su, R.K.L.
    • Computers and Concrete
    • /
    • v.8 no.1
    • /
    • pp.71-96
    • /
    • 2011
  • Existing reinforced concrete (RC) beams can be strengthened with externally bolted steel plates to the sides of beams. The effectiveness of this type of bolted side-plate (BSP) beam can however be affected by partial interaction between the steel plates and RC beams due to the mechanical slip of bolts. To avoid over-estimation of the flexural strength and ensure accurate prediction of the load-deformation response of the beams, the effect of partial interaction has to be properly considered. In this paper, a special non-linear macro-finite-element model that takes into account the effects of partial interaction is proposed. The RC beam and the steel plates are modelled as two different elements, interacting through discrete groups of bolts. A layered method is adopted for the formulation of the RC beam and steel plate elements, while a special non-linear model based on a kinematic hardening assumption for the bolts is used to simulate the bolt group effect. The computer program SiBAN was developed based on the proposed approach. Comparison with the available experimental results shows that SiBAN can accurately predict the partial interaction behaviour of the BSP beams. Further numerical simulations show that the interaction between the RC beam and the steel plates is greatly reduced by the formation of plastic hinges and should be considered in analyses of the strengthened beams.

A Historical Approach to the Development of Democracy and the Archival Society in Korea (한국 기록관리와 '거버넌스'에 대한 역사적 접근)

  • OH, Hang-Nyeong
    • The Korean Journal of Archival Studies
    • /
    • no.11
    • /
    • pp.15-40
    • /
    • 2005
  • 'Governance' is a subject that is widely discussed these days in the government and the academic world. I think that the new concept, 'governance', is a strategy to develop the democracy of the society in its institutional and functional aspects. When we are going to discuss about governance, public records and their relationships, without understanding the meaning of 'public' in Korea, we cannot expect to discuss the matter precisely. It is said that Korean public service sectors are awash with authoritarianism and unreasonableness, and that they are at the center of seething corruption and bribe scandals. It is the legacy that the regimes adopted in the aftermath of the Japanese colonial rule for 35 years. The colonial legacy included not simply the practice of the Japanese colony, but also people who had collaborated the Japanese. The American military government and Rhee, Sung-Man regime also appointed the same officials to government posts. As was the same case in other areas including economy, press, education, politics, law, etc. In this point of view, "Righting historical wrongs", a controversial issue now in Korea, aims at establishing the right relationships between an individual and the public, and eventually laying the foundation of democracy for future generation, a procedure of achieving good governance. Apparently, Korea has made progress in developing democracy, as well as in reforming the government policy and organization. Many independent commissions are performing the projects instead of the government institutions that mandated to do the job, but has not played their roles. The e-government projects in Korea was launched in 2001 by the former administration. However, the confusion of records-management after the promulgation of the act is the result of the lack of strategy and the inconsistency of the vision. Good record-keeping supports effective, transparent and accountable government. Accountability is a key element of good governance. It is a recognized fact that without information, there is no guidance for decision-making, and accountability. Thus without records, there is no accountability for the decisions of actions. Transparency means that the decisions taken and their enforcement are carried out based on led-out rules and regulations. When both accountability and transparency are non-existent, good governance is bound to fail. Archival institutions have to give an attention to inner-governance because of the new trend of archival practice, namely 'macro-appraisal'. This 'macro-appraisal' is a kind of a functions-based approach. However, macro-appraisal focuses not just on function, but on the three-way interaction of function, structure and citizen, which combined reflect the functioning of the state within civil society, that is to say, its governance. In conclusion, the public and democracy are major challenges in the Korean society. The so-called good governance requires good record management. In this respect, records managers are in the front line of instituting good governance, and achieving better public and democracy for future generation, a procedure of achieving good governance.

Multiscale Finite Element Analysis of Needle-Punched C/SiC Composites through Subcell Modeling (서브셀 모델링을 통한 니들 펀치 C/SiC 복합재료의 멀티스케일 유한요소해석)

  • Lim, Hyoung Jun;Choi, Ho-Il;Lee, Min-Jung;Yun, Gun Jin
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.34 no.1
    • /
    • pp.51-58
    • /
    • 2021
  • In this paper, a multi-scale finite element (FE) modeling methodology for three-dimensional (3D) needle-punched (NP) C/SiC with a complex microstructure is presented. The variations of the material properties induced by the needle-punching process and complex geometrical features could pose challenges when estimating the material behavior. For considering these features of composites, a 3D microscopic FE approach is introduced based on micro-CT technology to produce a 3D high fidelity FE model. The image processing techniques of micro-CT are utilized to generate discrete-gray images and reconstruct the high fidelity model. Furthermore, a subcell modeling technique is developed for the 3D NP C/SiC based on the high fidelity FE model to expand to the macro-scale structural problem. A numerical homogenization approach under periodic boundary conditions (PBCs) is employed to estimate the equivalent behavior of the high fidelity model and effective properties of subcell components, considering geometry continuity effects. For verification, proposed models compare excellently with experimental results for the mechanical behavior of tensile, shear, and bending under static loading conditions.

Life Prediction of Composite Pressure Vessels Using Multi-Scale Approach (멀티 스케일 접근법을 이용한 복합재 압력용기의 수명 예측)

  • Jin, Kyo-Kook;Ha, Sung-Kyu;Kim, Jae-Hyuk;Han, Hoon-Hee;Kim, Seong-Jong
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.11 no.9
    • /
    • pp.3176-3183
    • /
    • 2010
  • A multi-scale fatigue life prediction methodology of composite pressure vessels subjected to multi-axial loading has been proposed in this paper. The multi-scale approach starts from the constituents, fiber, matrix and interface, leading to predict behavior of ply, laminates and eventually the composite structures. The multi-scale fatigue life prediction methodology is composed of two steps: macro stress analysis and micro mechanics of failure based on fatigue analysis. In the macro stress analysis, multi-axial fatigue loading acting at laminate is determined from finite element analysis of composite pressure vessel, and ply stresses are computed using a classical laminate theory. The micro stresses are calculated in each constituent from ply stresses using a micromechanical model. Three methods are employed in predicting fatigue life of each constituent, i.e. a maximum stress method for fiber, an equivalent stress method for multi-axially loaded matrix, and a critical plane method for the interface. A modified Goodman diagram is used to take into account the generic mean stresses. Damages from each loading cycle are accumulated using Miner's rule. Monte Carlo simulation has been performed to predict the overall fatigue life of a composite pressure vessel considering statistical distribution of material properties of each constituent, fiber volume fraction and manufacturing winding angle.