• Title/Summary/Keyword: viscoelastic analysis

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Nonlinear Viscoelastic Analysis of Reticulated Spatial Truss Composed of Composite Materials (복합재료 그물형 공간 트러스의 점탄성적 비선형 해석)

  • Han, Sung Cheon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.6
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    • pp.661-672
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    • 2001
  • The present study is concerned with the arc-length method in the investigation of the large deflection behavior of spatial structures with composite materials. This study should be able to trace the main equilibrium path by automatically varying the arc-length size of individual solution steps with the variation of the curvature of the nonlinear equilibrium path. A quasi-elastic method is used for the solution for viscoelastic analysis of the reticulated spatial structures. Elastic modulus of composite materials is defined by micro mechanical materials modeling method and nonlinear equilibrium path is traced with various load types. To demonstrate the effectiveness of the present strategies, numerical examples of reticulated spatial truss is given and compared with solutions using other methods.

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Viscoelastic Analysis of Stress Intensity Factor for Interface Edge Crack in a Unidirectional Liminate (단일방향 복합재료의 공유면에 존재하는 계면 모서리균열의 점탄성 해석)

  • 이상순;김범식
    • Computational Structural Engineering
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    • v.10 no.1
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    • pp.129-134
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    • 1997
  • Interfacial stress singularity in a unidirectional two-dimensional laminate model consisting of an elastic fiber and a viscoelastic matrix has been investigated using the time-domain boundary element method. First, the interfacial singular stresses between the fiber and the matrix of a unidirectional laminate subjected to a uniform transverse tensile strain have been investigated near the free surface, but without any defect or any edge crack. Such a stress singularity might lead to fiber-matrix debonding or interfacial edge cracks. Then, the overall stress intensity factor for the case of a small interfacial edge crack of length a has been computed.

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Viscoelastic Analysis for Behavior of Edge Cracks at the Bonding Interface of Semiconductor Chip (반도체 칩 접착 계면에 존재하는 모서리 균열 거동에 대한 점탄성 해석)

  • 이상순
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.3
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    • pp.309-315
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    • 2001
  • The Stress intensity factors for edge cracks located at the bonding interface between the elastic semiconductor chip and the viscoelastic adhesive layer have been investigated. Such cracks might be generated due to stress singularity in the vicinity of the free surface. The domain boundary element method(BEM) has been employed to investigate the behavior of interface stresses. The overall stress intensity factor for the case of a small interfacial edge crack has been computed. The magnitude of stress intensity factors decrease with time due to viscoelastic relaxation.

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Viscoelastic Bending, Vibration and Buckling Analysis of Laminated Composite Plates on Two-parameter Elastic Foundation (2개 매개변수를 갖는 탄성지반위에 놓인 복합재료 적층판의 점탄성적 휨, 진동 좌굴해석)

  • Han, SungCheon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.5
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    • pp.443-455
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    • 2001
  • An energy method has been used for an elastic formulation of bending vibration and buckling analysis of laminated composite plates on two-parameter elastic foundations. A quasi-elastic method is used for the solution of viscoelastic analysis of the laminated composite plates. The third-order shear deformation theory is applied by using the double-fourier series. To validate the derived equations the obtained displacements for simply supported orthotropic plates on elastic foundations are compared with those of LUSAS program Numerical results of the viscoelastic bending vibration and buckling analysis are presented to show the effects of layup sequence number of layers material anisotropy and shear modulus of foundations.

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Study on the Nonlinear Characteristic Effects of Dielectric on Warpage of Flip Chip BGA Substrate

  • Cho, Seunghyun
    • Journal of the Microelectronics and Packaging Society
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    • v.20 no.2
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    • pp.33-38
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    • 2013
  • In this study, both a finite element analysis and an experimental analysis are executed to investigate the mechanical characteristics of dielectric material effects on warpage. Also, viscoelastic material properties are measured by DMA and are considered in warpage simulation. A finite element analysis is done by using both thermal elastic analysis and a thermo-viscoelastic analysis to predict the nonlinear effects. For experimental study, specimens warpage of non-symmetric structure with body size of $22.5{\times}22.5$ mm, $37.5{\times}37.5$ mm and $42.5{\times}42.5$ mm are measured under the reflow temperature condition. From the analysis results, experimental warpage is not similar to FEA results using thermal elastic analysis but similar to FEA results using thermo-viscoelastic analysis. Also, its effect on substrate warpage is increased as core thickness is decreased and body size is getting larger. These FEA and the experimental results show that the nonlinear characteristics of dielectric material play an important role on substrate warpage. Therefore, it is strongly recommended that non-linear behavior characteristics of a dielectric material should be considered to control warpage of FCBGA substrate under conditions of geometry, structure and manufacturing process and so on.

Enhanced First-Order Shear Deformation Theory for Thermo-Mechanical-Viscoelastic Analysis of Laminated Composite Structures (복합재료 적층 구조물에 대한 열-기계-점탄성 연성 거동 예측을 위한 개선된 일차전단변형이론)

  • Kim, Jun-Sik;Han, Jang-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.4
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    • pp.53-59
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    • 2022
  • In this study, an enhanced first-order shear deformation theory is proposed to efficiently and accurately predict the thermo-mechanical-viscoelastic coupled behavior of laminated composite structures. To this end, transverse shearstress and displacement fields are independently assumed, and the strain-energy relationship between these fields issystematically established using the mixed variational theorem (MVT). In MVT, the transverse shear stress fields are obtained from the third-order zigzag model, whereas the displacement fields of the conventional first-order model are considered to amplify the benefits of numerical efficiency. Additionally, a transverse displacement field with a smooth parabolic distribution is introduced to accurately predict the thermal behavior of composite structures. Furthermore, the concept of Laplace transformation is newly employed to simplify the viscoelastic problem, similar to the linear-elastic problem. To demonstrate the performance of the proposed theory, the numerical results obtained herein were compared with those available in the literature.

Bending and Vibration Analysis of Elastic and Viscoelastic Laminated Composite Structures using an Improved Higher-order Theory (개선된 고차이론을 이용한 복합재료 적층구조물의 탄성 및 점탄성적 휨, 진동해석)

  • Han, Sung Cheon;Yoo, Yong Min;Park, Dae Yong;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.1-12
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    • 2002
  • To obtain more accurate responses of laminated composite structures, the effect of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of in-plane displacements with respect to the thickness coordinate need to be considered in the analysis. The improved higher-order theory is used to determine the deflections and natural frequencies of laminated composite structures. A quasi-elastic method is used for the solution of viscoelastic analysis of the laminated composite plates and sandwiches. Solutions of simply-supported laminated composite plates and sandwiches are obtained and the results are compared with those by the 3D elasticity theory and other theories. The improved theory proposed in this paper is shown to predict the deflections and natural frequencies more accurately than all other theories.