• Title, Summary, Keyword: initial shape analysis

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Collapse mechanism for deep tunnel subjected to seepage force in layered soils

  • Yang, X.L.;Yan, R.M.
    • Geomechanics and Engineering
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    • v.8 no.5
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    • pp.741-756
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    • 2015
  • The prediction of impending collapse of deep tunnel is one of the most difficult problems. Collapse mechanism of deep tunnel in layered soils is derived using a new curved failure mechanism within the framework of upper bound theorem, and effects of seepage forces are considered. Nonlinear failure criterion is adopted in the present analysis, and the possible collapse shape of deep tunnel in the layered soils is discussed in this paper. In the layered soils, the internal energy dissipations along velocity discontinuity are calculated, and the external work rates are produced by weight, seepage forces and supporting pressure. With upper bound theorem of limit analysis, two different curve functions are proposed for the two different soil stratums. The specific shape of collapse surface is discussed, using the proposed curve functions. Effects of nonlinear coefficient, initial cohesion, pore water pressure and unit weight on potential collapse are analyzed. According to the numerical results, with the nonlinear coefficient increase, the shape of collapse block will increase. With initial cohesion of the upper soil increase, the shape of failure block will be flat, and with the lower soil improving, the size of collapsing will be large. Furthermore, the shape of collapsing will decrease with the unit weight decrease.

A Study of Bending Using Long Type Coil by Discrete Method (다분할 해석법에 의한 장형코일의 곡가공 연구)

  • Lee, Young-Hwa;Jang, Chang-Doo
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.3
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    • pp.303-308
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    • 2008
  • The induction heating is more efficient for a plate bending because of its easy operation and control of working parameters, compared with the heating by a gas torch. The existing axis symmetric analysis method could neither handle initial curved plates nor be used in the optimization of coil shapes because of its limit of an axis symmetric coil shape. But the proposed method using some discrete part models and analysis processes could overcome these difficulties and show more accurate results in temperatures and deflections of flat or curved plates with initial curvature than those in the existing axis symmetric analysis method. This method is composed of the multi-disciplinary analyses such as an electro magnetic analysis, a heat transfer analysis and a deformation analysis based on inherent strain approach per each step. Traditionally, the coil shape in the induction heating is circular shape and it needs the moving process along heating lines. To overcome this, the 'Long Type Coil' with some linear parallel coils was proposed. It did not need the moving process along heating lines and reduced the heating process time. The results of experiments were compared with those of the simulation.

Practical Determination Method of Initial Cable Forces in Cable-Stayed Bridges (사장교 시스템의 실용적인 초기형상 결정법)

  • Song, Yo-Han;Kim, Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.1
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    • pp.87-95
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    • 2011
  • A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

Blank Design for Sheet Metal Product Based on Direct Design Method (직접설계법에 의한 박판부품의 초기형상설계)

  • 윤정환;김상국;정관수;연의정
    • Transactions of Materials Processing
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    • v.9 no.6
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    • pp.598-603
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    • 2000
  • In order to improve trial-and-error based conventional practices for optimizing forming processes, a direct design method to guide iterative design practices, called the ideal forming theory, has been previously developed. In the theory, material elements are required to deform following the minimum Plastic work Path. The theory can be used to determine the ideal initial blank shape needed to best achieve a specified final shape while resulting in optimum strain distributions. In this work, the direct design method based on the ideal forming theory was applied to design initial design shape for VCR deck chassis. Based on the solution of the ideal forming theory, FEM analysis was utilized to evaluate an optimum blank shape to be formed without tearing. Simulation results are in good agreement with experimental data. It was shown that the proposed sequential design procedure based on direct design method and FEM can be successfully applied to optimize the die design Procedure of sheet metal forming processes.

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Numerical modeling of slipforming operations

  • Lachemi, M.;Elimov, R.
    • Computers and Concrete
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    • v.4 no.1
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    • pp.33-47
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    • 2007
  • Slipforming is a construction method in which the forms move continuously during concrete placement. This paper presents a numerical procedure based on the finite element method to simulate the thermal behavior of concrete during slipforming operations. The validity of the model was successfully tested by simulating a very complex but well documented field case of actual slipforming operations performed during the construction of an offshore concrete oil platform structure. The results obtained have been related to the shape of the concrete "hardened front" in the forms, which allows quick evaluation of the operation. The results of the numerical investigation have shown that the shape of the "hardened front" can be affected by the temperature of the fresh concrete and ambient conditions. For a given initial concrete temperature, there are limitations for the ambient temperature that, when exceeded, can create an unfavorable shape of the concrete "hardened front" in the forms. Similarly, for a given ambient temperature, the initial concrete temperature should not be fall below an established limit in order to avoid unfavorable shape of the "hardened front".

3D Shape Optimization of Electromagnetic Device Using Design Sensitivity Analysis and Mesh Relocation Method (설계민감도해석과 요소망 변형법을 이용한 전자소자의 3차원 형상최적화)

  • ;Yao Yingying
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.7
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    • pp.307-314
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    • 2003
  • This paper presents a 3D shape optimization algorithm for electromagnetic devices using the design sensitivity analysis with finite element method. The structural deformation analysis based on the deformation theory of the elastic body under stress is used for mesh renewing. The design sensitivity and adjoint variable formulae are derived for the 3D finite element method with edge element. The results of sensitivity analysis are used as the input data of the structural analysis to calculate the relocation of the nodal points. This method makes it possible that the new mesh of analysis region can be obtained from the initial mesh without regeneration. The proposed algorithm is applied to the shape optimization of 3D electromagnet pole to net a uniform flux density at the target region.

Development of Forming Technology for Clutch Gear Using Artificial Neural Network (신경망을 이용한 클러치 기어의 정밀성형공법 개발)

  • Kang, Jae-Young;Kim, Byung-Min;Kim, Yeong-Hwan;Kim, Dong-Hawn
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.827-833
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    • 2011
  • Precision forging of gears has a lot of advantages when compared to conventional gear shaping, because it allows the manufacture of gear parts without flash and consequently without the need for subsequent machining operations. In this study, the cold forging process is determined to manufacture the cold forged product for the precision clutch gear used of a commercial automobile, To do this, shape ratio of initial shape having influence the forgeability of forged product is analyzed. The optimal initial shape of clutch gear is designed using the results of DEFORM-3D and the artificial neural network (ANN). The initial shape through the detail analysis results, such as metal flow, distributions of strain can be obtained.

Analysis of Initial Mass Distribution and Facility Shape to Determine Structural Alternative for Hazardous Zone Vulnerable to Debris Flow Disaster (토사재해 위험지역의 구조적 대안 설정을 위한 사태물질 초기 질량분포 및 방어시설물 형상의 영향 분석)

  • Seong, Joo-Hyun;Oh, Seung Myeong;Jung, Younghun;Byun, Yoseph;Song, Chang Geun
    • Journal of the Korean Society of Safety
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    • v.31 no.2
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    • pp.76-82
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    • 2016
  • A 2-D hydrodynamic model for predicting the movement of debris flow was developed. The developed model was validated against a dam break flow problem conducted in EU CADAM project, and the performance of the model was shown to be satisfactory. In order to suggest structural alternative for hazardous zone vulnerable to debris flow disaster, two types of initial mass distribution and two shapes of defensive structure were considered. It was found that 1) the collapse of debris mass initiated with square pyramid shape induced more damage compared with that of cubic shape; and 2) a defensive structure with semi-circular shape was vulnerable to debris flow disaster in terms of debris control or primary defense compared with that of rectangular-shaped structure.

A Study on the Maneuvering Hydrodynamic Derivatives Estimation Applied the Stern Shape of a Vessel (선미 형상을 반영한 조종 유체력 미계수 추정에 관한 연구)

  • Yoon, Seung-Bae;Kim, Dong-Young;Kim, Sang-Hyun
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.1
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    • pp.76-83
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    • 2016
  • The various model tests are carried out to estimate and verify a ship performance in the design stage. But in view of the cost, the model test should be applied to every project vessel is very inefficient. Therefore, other methods of predicting the maneuverability with confined data are required at the initial design stage. The purpose of this study is to estimate the hydrodynamic derivatives by using the multiple regression analysis and PMM test data. The characteristics of the stern shape which has an important effect on the maneuverability are applied to the regression analysis in this study. The correlation analysis is performed to select the proper hull form coefficients and stern shape factors used as the variables in the regression analysis. The comparative analysis of estimate results and model test results is conducted on two ships to investigate the effectiveness of the maneuvering hydrodynamic derivatives estimation applied the stern shape. Through the present study, it is verified that the estimation using the stern shape factors as the variables are valid when the stern shape factors are located in the center of the database.

A Study on the Dynamic Characteristics of Tension Structures according to Initial Tension Forces and Equilibrium Shape (초기인장력과 평형형상을 고려한 인장구조물의 동적 특성에 대한 연구)

  • Chang, Dong Il;Kim, Hak Jae
    • Journal of Korean Society of Steel Construction
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    • v.10 no.1
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    • pp.73-83
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    • 1998
  • Considering dynamic behaviors according to initial tension forces, geometric nonlinearity and the effect of higher eigen modes to participate in dynamic behaviors increase as initial tension forces decrease, and from phase portrait we can realize that period attractors are produced in many area with complexity. If initial tension forxes increase, difference between linear and nonlinear solutions will decrease and the first eigen mode dominate the dynamic behaviors and observing phase portrait, period attractors appear in certain area regularly. These results may offer meaningful informations to nonlinear dynamic analysis using modal reduction methods such as Lanczos modal analysis. And actually nonlinear dynamic analysis needs very large computational efforts. So, if we determine the number of eigen modes to take part in modal analysis corresponding to initial tension forces we will get more accurate data close to exact nonlinear dynamic solutions.

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