• Title, Summary, Keyword: Stiffness Prediction

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Prediction of Mechanical Properties for Spatially Reinforced Composites (공간적으로 보강된 복합재의 기계적 물성치 예측)

  • 유재석;김천곤;홍창선;김광수
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.177-182
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    • 2000
  • This paper predicted the equivalent stiffness of spatially reinforced composites (SRC) using the volume average of a fiber rod and matrix stiffness, and the strength of SRC using the stiffness reduction and the modified Tsai-Wu composite failure theory. Those equivalent engineering constants are used to analyze the mechanical behavior and the failure of SRC structures. Because the distribution of equivalent engineering constants is varying with the change in SRC shape, we made a program that predicts engineering constants of SRC. Both 3-D and 4-D SRC show the smallest tensile modulus and the largest shear modulus at the maximum rotated direction from each rod. Also the strength properties show the same tendency.

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Analysis of the Dynamical Characteristics and Prediction of Stiffness for the Joint between Members (부재간 결합부의 동적 특성 분석 및 강성 예측)

  • Yun, Seong-Ho
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.2
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    • pp.58-64
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    • 2019
  • This paper describes the analysis of dynamic characteristics and prediction of the stiffness for the joint between structural members. In the process of deriving the governing equations, the stiffness values responsible for the moment and shear force were modelled by using linear and torsional springs in the middle of a clamped-clamped beam. The sensitivities of the natural frequency and modal assurance criterion were investigated as a function of the dimensionless linear and torsional spring stiffness. The reliability of the predictions for the linear and torsional stiffness values was verified by the inverse computations of the stiffness matrix. The predictive and exact theoretical stiffness values were compared for the stiffness element in the finite element formulation, and their results show an excellent correlation. It is strongly anticipated that although the proposed methodology is currently limited to the analytical utilization, it will provide a useful tool to estimate unknown joint stiffness values based on the experimental natural frequency and mode shape.

Prediction of effective stiffness on short fiber reinforced composite materials (단섬유 복합재료의 탄성계수 예측)

  • 임태원;한경섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.611-617
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    • 1991
  • Effective stiffness of short fiber composite with a three-dimensional random orientation of fibers is derived theoretically and compared with available experimental data. The laminate analogy and transformed laminate analogy are used for modulus prediction of 2-D and 3-D random composites, respectively. The effective stiffness of random oriented fiber composite can be expressed in terms of longitudinal and transverse stiffnesses of unidirectional composites. The result of transformed laminate analogy is more accurate than other approaches such as, Christensen-Waals equational and Lavengood-Goettler equation, etc. Also the effective properties of random oriented fiber composite can be expressed in terms of fiber and matrix properties such as elastic modulus, shear modulus and Poisson's ratio.

The Analysis of Excavation Behavior Considering Small Strain Stiffness (미소변형율 강성을 고려한 지반굴착 해석)

  • Kim, Young-Min
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.2
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    • pp.21-31
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    • 2010
  • This paper describes research on the prediction of the vertical displacement of surface, horizontal displacements and bending moments in two anchored retaining wall for an excavation by a finite element program. It is very important to consider the appropriate constitutive model for the numerical analysis in excavation behavior. It is shown in this paper that the analyses of excavation considering small strain stiffness gives the more reasonable prediction of the vertical displacement of surface. and the parametric study on the small strain stiffness parameters for excavation analysis has been analysed.

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A Study on the Prediction of Tool Deflection and Precision Machining in Ball End Milling Process (볼 엔드밀 가공에서의 공구 처짐 예측과 정밀 가공에 관한 연구)

  • 조현덕;양민양
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.9
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    • pp.1669-1680
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    • 1992
  • This paper deals with the prediction of cutting force and tool deflection and it's application in the flexible ball end milling process. Machining accuracy is determined by the static stiffness of tool system and the instantaneous cutting force. The static stiffness of tool system consists of the stiffness of holer and the stiffness of ball end mill. The stiffness of holder was obtained from the experimental result, and the stiffness of ball end mill with two flutes was theoretically analyzed by the finite elements method. In cutting process, the instantaneous cutting force is dependent upon the instantaneous feed and pick feed(radial depth of cut) which are varied by tool deflection. For the calculation of cutting force and deflection of ball end mill, iteration method is used with the linear interpolation to the data of cutting force obtained from rigid ball end mill and the data of tool deflection. In this paper, a for enhancing accuracy is discussed. And the selection of helix angle for minimizing machining error is also discussed.

Stiffness Prediction of Spatially Reinforced Composites (공간적으로 보강된 복합재료의 강성예측)

  • 유재석;장영순;이상의;김천곤
    • Composites Research
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    • v.17 no.5
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    • pp.25-38
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    • 2004
  • In this study, the stiffness of spatially reinforced composites (SRC) are predicted by using superposition of a rod and matrix stiffnesses in an arbitrary direction. To confirm the predicted values, the material properties of SRC are measured. The predicted values from the volume average of stiffness matrix are consistent with the tested values in a rod direction, but are inconsistent in an off-rod direction while reverse is true fur the volume average of compliance matrix. Therefore, the harmony function from superposition of stiffness and compliance matrix is introduced. The predicted values from the harmony function are consistent with the tested values in both the rod and the off-rod directions.

Performance Predictions of Tilting Pad Journal Bearing with Ball-Socket Pivots and Comparison to Published Test Results (볼 소켓형 피봇을 갖는 틸팅 패드 저널 베어링의 성능 예측 및 기존 결과와의 비교)

  • Kim, Tae Ho;Choi, Tae Gyu
    • The KSFM Journal of Fluid Machinery
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    • v.20 no.2
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    • pp.63-68
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    • 2017
  • This paper predicts the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with ball-socket pivot and compares the predictions to the published test data obtained under load-between-pad (LBP) configuration. The present TPJB model considers the pivot stiffness calculated based on the Hertzian contact stress theory. Due to the compliance of the pivot, the predicted journal eccentricity agree well with the measured journal center trajectory for increasing static loads, while the early prediction without pivot model consideration underestimates it largely. The predicted pressure profile shows the significant pressure development even on the unloaded pads along the direction opposite to the loading direction. The predicted stiffness coefficients increase as the static load and the rotor speed increase. They agree excellently with test data from open literature. The predicted damping coefficients increase as the static load increases and the rotor speed decreases. The prediction underestimates the test data slightly. In general, the current predictive model including the pivot stiffness improves the accuracy of the rotordynamic performance predictions when compared to the previously published predictions.

Prediction Models for the Stiffness and the Strength of a Double Angle Connection Subjected to Tension (축방향 인장력을 받는 더블앵글 접합부의 강성 및 강도 예측모델)

  • Yang, Jae Guen;Lee, Gil Young;Cheon, Ji Won
    • Journal of Korean Society of Steel Construction
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    • v.19 no.2
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    • pp.201-210
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    • 2007
  • Double-angle connections should be designed with enough stiffness and strength to properly resist various applied loads. Therefore, structural engineers should be able to predict some influential variables and take their effects into account in design. This study was performed to establish the effects of the number of bolts and bolt gage distance on the stiffness and strength of a double-angle connection under tension. Six experimental tests were conducted to describe the effects of these variables by comparing load-displacement relationship curves. In addition, two prediction models were proposed to estimate the initial stiffness and the maximum allowable tensile load based on the results of experimental tests. In the development of these prediction models, the effect of prying action was considered.