• Title/Summary/Keyword: 굽힘효과

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An Analysis of Axisymmetric Deep Drawing by the Energy Method (에너지법에 의한 축대칭 디프드로잉의 해석)

  • 양동열;이항수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.51-61
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    • 1993
  • A systematic approach of the energy method is proposed for analysis of axisymmetric deep drawing in which the total deforming region is divided into five sections by the geometric characteristic. The corresponding solution is found through optimization of the total energy dissipation with respect to some parameters assumed in the kinematically admissible velocity field defined over each region. The sheet blank is divided into three-or five-layers to consider the bending effect. For the evaluation of frictional energy, it is assumed that the blank holding force acts on the outer rim of the flange and that the contact pressure acting on punch shoulder or die shoulder has uniform distributions, respectively. The computed results by the present method are compared with the experiment and the computed results by the elastic-plastic finite element method for the distribution of thickness strain and the relation between the punch stroke and punch load. The results for the case of multi-layers show better agreements than for the case of a single layer in load vs. stroke relation and strain distribution. It is thus shown that the multi-layer technique can be effectively employed in analyzing axisymmetric deep drawing in connection with the energy method.

Static and Dynamic Analyses of Bending Problems Using 3-Dimensional 10-Node Equivalent Element (3차원 10절점-상당요소에 의한 굽힘문제의 정적.동적해석)

  • 권영두;윤태혁
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.117-130
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    • 1997
  • In this paper, a modified 10-node equivalent solid element(MQM10 element), which has smallest degrees of freedom among 3-dimensional solid elements accounting bending deformation as well as extensional and shear deformations of isotropic plates, is proposed. The proposed MQM10 element exhibits stiffer bending stiffness due to the reduction of degrees of freedom from 20-node element or Q11 element. As an effective way to correct the relative stiffness stiffening phenomenon, the modification equation of Gauss sampling points is proposed. The quantity of modification is a function of Poisson's ratio. The effectiveness of MQM10 element is tested by applying it to several examples. It is noted that the results of static and free vibration analysis of isotropic plates using MQM10 elements show a good agreement with those using 20-node element.

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Effect of Graphite Powder Addition on the Mechanical Properties of Carbon/Carbon Composites (흑연분말의 첨가가 탄소/탄소 복합재료의 물성에 미치는 영향)

  • 신준혁;황성덕;강태진
    • Composites Research
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    • v.13 no.2
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    • pp.72-80
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    • 2000
  • Effect of graphite powder addition on the mechanical properties of carbon fiber reinforced carbon composites (C/C composites) was investigated. Greenbody (G/B) with 0~30wt.% graphite powder addition to phenol resin was prepared and carbonized at $1000^{\circ}C$ to make C/C composites. Flexural strengths of 20wt.% graphite powder additions showed maximum values in the both case of G/B and C/C composites. But, at the graphite addition over 20wt.%, there was negative effect due to the matrix inhomogeneity. Flexural strength of cured resin without graphite Powder was higher than that with graphite. However, flexural strength of carbonized resin with graphite increased three times as much as that of carbonized resin without graphite. Because the addition of graphite powder effects the restraint of shrinkage after carbonization and the deflection of crack path. In Mode II ENF test, energy release rates($G_{II}$) of G/B and C/C composites with the 20w1.% addition of graphite were both increased. But, the addition of graphite was more effective to the increase of $G_{II}$ in C/C composites than that in G/B.

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Microstructural Morphology and Bending Performance Evaluation of Molded Microcomposites of Thermotropic LCP and PA6 (액정폴리머/폴리아미드6 미시복합재료의 내부구조 및 기계적 굽힘성능 평가)

  • ;Kiyoshi Takahashi
    • Composites Research
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    • v.12 no.6
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    • pp.53-64
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    • 1999
  • Microstructural morphology and bending strengths of moulded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) have been studied as a function of epoxy fraction. Injection-moulding of a composite plaque at a temperature below the melting point of the LCP fibrils generated a multi-layered structure: the surface skin layer with thickness of $65\;-\;120{\mu\textrm{m}}$ exhibiting a transverse orientation; the sub-skin layer with an orientation in the flow direction; the core layer with arc-curved flow patterns. The plaques containing epoxy 4.8vol% exhibited superior bending strength and large fracture strain. With an increase of epoxy fraction equal to and beyond 4.8vol%, geometry of LCP domains was changed from fibrillar shape to lamella-like one, which caused a shear-mode fracture. An analysis of the bending strength of the composite plaques by using a symmetric layered model beam suggested that addition of epoxy component altered not only the microstructural geometry but also the elastic moduli and strengths of the respective layers.

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Analysis Study on the Damage of Crack Happening with the Bending at CFRP Plate due to Stacking Angle (적층각도에 따른 CFRP 평판에서의 굽힘으로 발생한 크랙 파손에 관한 해석적 연구)

  • Hwang, Gue-wan;Cho, Jae-ung
    • Journal of the Korea Convergence Society
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    • v.8 no.3
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    • pp.185-190
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    • 2017
  • This study investigates the bending stress, shear stress and deformation energy happening at the inner fiber structure when the bending moment is applied to he specimen with flat shape composed of carbon fiber. As CFRP is composed of innumerable fibers with multi-axes, the stress under bending condition can be effectively distributed. Theses stresses is shown to increase again at the starting point as this angle of $60^{\circ}$. Therefore, the condition at the stacking angle of $60^{\circ}$ is seen to become most adequate under the state where the bending stress happens. On the basis of this study result, the damage property by the bending at the plate due to stacking angle was examined through the analytic approach. it is thought that this study can be devoted to the safe design for damage prevention and durabilty improvement. Also, the esthetic sense can be shown as the designed factor of shape with flat plate is grafted onto the convergence technique.

Change in Gastrocnemius Pennation Angle According to Ankle Dorsiflexion among University Students (일부 대학생의 발목관절 발등굽힘 각도 변화에 따른 장딴지근 깃각의 차이)

  • Kim, Ji-Seon;Seo, Byoung-Do;Shin, Hyung-Soo;Shin, Hee-Joon;Ju, Joung-Youl
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.12
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    • pp.8684-8690
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    • 2015
  • This study aimed to investigate the influence of the ankle dorsiflexion angle ($0^{\circ}$, $10^{\circ}$, and $20^{\circ}$) on the effectiveness of gastrocnemius stretching angle. The subjects of this study were 25 young man and female women. In all participants, the pennation angle of the medial head of the gastrocnemius was evaluated using ultrasonography at an ankle dorsiflexion angle of $0^{\circ}$, $10^{\circ}$, or $20^{\circ}$. Repeated measures analysis of variance was uesd to test for differences between ankle dorsiflexion angles. The independent t-test was performed to determine the significance of sex differences. The results of this study showed that the gastrocnemius pennation angle decreased as the ankle dorsiflexion angle increased, with significant interaction between each angle of ankle dorsiflexion angle (p<0.01). Sex comparison showed that the pennation angle was greater in man than in women, but the difference was not significant (p>0.05). According to the sex the gastrocnemius pennation angle is decreased as the ankle dorsiflexion angle increased (p<0.01). These results suggest that the end range of dorsiflexion is more beneficial for gastrocnemius stretching than a small range. Further studies are needed to investigate the influence of other factors, such as stretching angle and application time, on gastrocnemius stretching.

Mechanical and Electrical Reliability of Silver Nanowire Film on Flexible Substrate (유연기판 위에 제작된 Silver Nanowire 필름의 기계 및 전기적 신뢰성 연구)

  • Lee, Yo Seb;Lee, Won Jae;Park, Jin Yeong;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.4
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    • pp.93-99
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    • 2016
  • In this paper, we investigated the mechanical and electrical reliability of silver nanowire (AgNW) films. In particular, the durability and reliability of AgNW films were studied when the AgNW film was subjected to the bending deformation under current flow. The electrical durability of AgNW was evaluated by observing changes in heat generation and current density occurring in AgNW through voltage and current tests. The AgNW film showed a constant resistance change up to a bending radius of 2 mm and 200,000 cycles in the bending fatigue tests. The over-coating layer has an effect of improving the durability of the AgNW film. In the case of AgNW with the over-coating layer, heat was uniformly dissipated on the surface of AgNW film, whereas in the case of AgNW film without the over-coating layer, heat was generated locally. In the bending test under the current flow, the current density of the AgNW film was continuously decreased up to 52.4%. During bending, the AgNW was deformed due to mechanical deformation such as tensile, bending and sliding of the AgNW, consequently contact resistance of the AgNW was increased, leading to a electrical breakdown of AgNW by Joule heating. It was found that the application of the over-coating layer can improve the electrical and mechanical reliability of the AgNW film.

Development of an Angle Estimation System Using a Soft Textile Bending Angle Sensor (소프트 텍스타일 굽힘 각 센서를 이용한 각도 추정 시스템 개발 )

  • Seung-Ah Yang;Sang-Un Kim;Joo-Yong Kim
    • Science of Emotion and Sensibility
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    • v.27 no.1
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    • pp.59-68
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    • 2024
  • This study aimed to develop a soft fabric-based elbow-bending angle sensor that can replace conventional hard-type inertial sensors and a system for estimating bending angles using it. To enhance comfort during exercise, this study treated four fabrics (Bergamo, E-band, span cushion, and polyester) by single-walled carbon nanotube dip coating to create conductive textiles. Subsequently, one fabric was selected based on performance evaluations, and an elbow flexion angle sensor was fabricated. Gauge factor, hysteresis, and sensing range were employed as performance evaluation metrics. The data obtained using the fabricated sensor showed different trends in sensor values for the changes in the angle during bending and extending movements. Because of this divergence, the two movements were separated, and this constituted the one-step process. In the two-step process, multilayer perceptron (MLP) was employed to handle the complex nonlinear relationships and achieve high data accuracy. Based on the results of this study, we anticipate effective utilization in various smart wearable and healthcare domains. Consequently, a soft- fabric bending angle sensor was developed, and using MLP, nonlinear relationships can be addressed, enabling angle estimation. Based on the results of this study, we anticipate the effective utilization of the developed system in smart wearables and healthcare.

Structural Behavior of Thin-Walled, Pretwisted Composite Beams (초기 비틀림 각을 갖는 박벽 복합재료 보의 정적 거동 해석)

  • Park, Il-Ju;Hong, Dan-Bi;Jung, Sung-Nam
    • Composites Research
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    • v.20 no.6
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    • pp.15-20
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    • 2007
  • In this work, the structural response of thin-walled, composite beams with built-in twist angles is analyzed using a mixed beam approach. The analytical model includes the effects of elastic couplings, shell wall thickness, and torsion warping. Reissner's semi-complimentary energy functional is used to describe the beam theory and also to deal with the mixed-nature in the beam kinematics. The bending and torsion related warpings introduced by the non-zero pretwist angles are derived in closed-form through the proposed beam formulation. The theory is validated with available literature and detailed finite element analysis results for rectangular solid section beams with elastic couplings. Very good correlation has been obtained for the cases considered.

A Structural Analysis of Sandwich Plate with Unsymmetrical FRP Thick Faces (두껍고 비대칭인 FRP면재를 갖는 Sandwich 평판의 구조해석)

  • Ik-Tai Kim;Ki-Sung Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.1
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    • pp.132-140
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    • 1995
  • The structural behavior of sandwich plates with unsymmetricaly thick faces are analysed using Raleigh-Ritz Energy method by comparing the bending stresses, shear stresses, local bending stresses, membrane stresses of skin and core materials including local bending effect. As for sandwich materials, the combination of two types of face materials and three types of core materials are used in the analysis.

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