• Title, Summary, Keyword: 응력완화시험

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Stress Relaxation Test of Granite under Water-Saturated Triaxial Condition (화강암의 응력완화현상에 관한 수침삼축시험)

  • 서용석
    • The Journal of Engineering Geology
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    • v.10 no.3
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    • pp.217-223
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    • 2000
  • Microcracks that consist of quarry planes of granite are an essential factor affecting the long-term behavior of granite. In this paper, fine-grained granite distributed in the Tsukuba area of Japan was selected and microcracks were measured by using scanline method. In addition, a new relaxation testing equipment was developed to carry out stress relaxation test under water-saturated triaxial condition. Based on the relaxation test results with the initial stress level of 75%, the axial stress is decreased by 39%-49% just after the start of the tests, and the totally relaxed stress is 10∼24 MPa in 190 ERT (Elapsed relaxation time, hour). In addition, the relaxed stress is increased with the density of cracks which are parallel to axial load direction.

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Stress Relaxation and Nonlinear Viscoelastic Model of PAN-PVC Copolymers (PAN-PVC 공중합체의 응력완화와 비선형 점탄성 모델)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.45 no.4
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    • pp.250-255
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    • 2010
  • From the three element non-Newtonian model of one non-Newtonian viscoelastic Maxwell elements and a elastic spring, the stress relaxation equation was derived. The various model parameters of this equation were evaluated by appling the experimental results of stress relaxation to the stress relaxation equation. The theoretical curves calculated from this model parameters agreed with the experimental stress relaxation curves. From the parameters of nonlinear viscoelastic model, the hole volume, fine structure, viscoelastic properties and mechanical properties of polymer fibers were studied. The experiments of stress relaxation were carried out using the tensile tester with the solvent chamber. The stress relaxation curves of the two types polyacrylonitrile-polyvinylchloride copolymer and another two types PVC monofilament fibers were obtained in air and water of various temperatures.

Self Diffusions and Rheological Properties of Polyamide Polymer Materials in Various Solvents (용매 환경에서의 폴리아미드 고분자 재료의 자체확산과 유변학적인 특성)

  • Kim, Nam Jeong
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.4
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    • pp.1050-1059
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    • 2019
  • The self diffusion, hole volume, and flow thermodynamic parameters of polyamide fibers were calculated from rheological parameters and crystallite size in order to study of flow segments in amorphous region. The stress relaxation of polyamide filament fibers were carried out in air and various solvents at various temperatures using the tensile tester with the solvent chamber. The rheological parameters were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model. It was observed that the rheological parameters of these polyamide filament fibers are directly related to the relaxation spectra, self diffusion, viscosities, and activation energies of flow segments.

Rheological Model Analysis of Acorn Starch Gels by Stress Relaxation Test (응력완화시험에 의한 도토리 전분겔의 물성론적 모형 분석)

  • 김영아;이혜수
    • Korean journal of food and cookery science
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    • v.5 no.1
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    • pp.49-52
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    • 1989
  • Stress relaxation tests with different percent deformation were performed for crude and refined starch gels of acorn. With no relation to percent deformation, refined starch gel had higher initial stress ($\sigma_e$) and lower equilibrium stress ($\sigma_e$) than crude starch gel. But the ratio of equilibrium stress to initial stress ($\sigma_e$/$\sigma_o$) was minimum at 60 percent deformation. The analysis of relaxation curves by successive residual method revealed that the rheological behavior of acorn starch gels could be expressed by generalized Maxwell model. The element numbers of models for crude and refined starch gel were 7-element and 5-element at 60 percent deformation, and 5-element and 3-element at 45 percent deformation, respectively.

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Self Diffusion Coefficients and Free Hole Volumes of Poly(acrylonitrile)-poly(vinyl chloride) Copolymers (Poly(acrylonitrile)-poly(vinyl chloride) 공중합체의 자체 확산 계수와 유동 자유 홀부피)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.46 no.3
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    • pp.245-250
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    • 2011
  • The self diffusions and hole volumes of amorphous region of poly(acrylonitrile)-poly(vinyl chloride) fibers were investigated by experiments of stress relaxation. The experiments of stress relaxation were carried out using the tensile tester with the solvent chamber. The flow parameters of filament fibers were obtained by applying the experimental stress relaxation curves to the theoretical equation of stress relaxation. From the flow parameters, the hole volumes, self diffusions, viscosities and thermodynamic parameters of solid polymers were calculated. It was observed that the flow parameters of these samples are directly related to the hole volumes, self diffusions and flow activation energies of flow segments.

Thermodynamic Properties and Self Diffusions from Rheological Parameters of Eyring-Halsey Model (Eyring-Halsey 모델의 유동파라메타로부터 열역학 성질과 자체 확산)

  • Kim, Nam Jeong
    • Journal of the Korean Chemical Society
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    • v.58 no.3
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    • pp.251-257
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    • 2014
  • The stress relaxation of poly(methyl acrylate)-poly(acrylonitrile) copolymer samples were carried out in air and distilled water at various temperatures using the tensile tester with the solvent chamber. The rheological parameters were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Eyring-Halsey non-Newtonian model. The self diffusion, hole volume, viscosities, and thermodynamic parameters of copolymer samples were calculated from rheological parameters and crystallite size in order to study of flow segments in amorphous region. It was observed that the rheological parameters of these copolymer samples are directly related to the self diffusion, hole volume, viscosities, and thermodynamic parameters of flow segments.

Stress Relaxation of Poly(methyl acrylate)-Poly(acrylonitrile) Copolymers (Poly(methyl acrylate)-Poly(acrylonitrile) 공중합체의 응력완화)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.47 no.3
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    • pp.223-230
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    • 2012
  • The rheological parameters of poly(methyl acrylate)-poly(acrylonitrile) copolymers were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Eyring-Halsey non-Newtonian model. The experimentals of stress relaxation were carried out using the tensile tester with the solvent chamber. The determination of rheological parameters was performed from computer calculation. It was observed that the rheological parameters of these copolymer samples are directly related to the self diffusions and viscosities and activation energies of flow segments.

Reduction of Coupling in Tensile and Flexure Composite Specimens (인장 및 굽힘 복합재료 시험편의 커플링 완화 방안)

  • 정일섭
    • Composites Research
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    • v.12 no.2
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    • pp.82-90
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    • 1999
  • The mechanical properties of generally orthotropic materials are conventionally measured by performing off-axis tensile and flexure tests. However, the inevitable coupling between tension and shear in case of tensile test or bending and twisting in flexure test case induces nonuniform displacement and stress fields. Consequential stress concentration along the boundary of specimens would result in inaccurate modulus and underestimated strength. This paper proposes the variation of specimen geometry in terms of appropriate obliquity of loaded boundary. For the purpose, classical lamination theory is transformed into skewed coordinate, and characteristic equations for both of unidirectional and laminated composite specimens are formulated. Finite element analysis is employed to show the validity of the skewedness in tensile and bending test specimens.

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Experimental and Theory for Relaxation Spectrum of Polyacrylonitrile-Poly(vinyl chloride) Copolymers (Polyacrylonitrile-Poly(vinyl chloride) 공중합체 완화스펙트럼의 실험과 이론적인 고찰)

  • Kim, Nam-Jeong
    • Polymer Korea
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    • v.35 no.3
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    • pp.232-237
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    • 2011
  • The relaxation spectra of polyacrylonitrile-poly(vinyl chloride) copolymer filament fibers were obtained by applying the experimental stress relaxation curves to the theoretical equation of relaxation spectrum. The theoretical equation of relaxation spectrum was derived from the Ree-Eyring and Maxwell model. The experimental of stress relaxation was carried out using a tensile tester with a solvent chamber. The determination of relaxation spectra was performed by computer calculation. From the relaxation spectra, the fine structures, viscoelastic properties and hole volumes of solid polymers were studied. It was observed that the relaxation spectra of these samples were directly related to the distribution of molecular weights and self diffusions of flow segments.

A Study on the Mathematical Modeling of Human Pharyngeal Tissue Viscoelasticity (인두조직의 점 탄성특성의 수학적모델링에 관한 연구)

  • 김성민;김남현
    • Journal of Biomedical Engineering Research
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    • v.19 no.5
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    • pp.495-502
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    • 1998
  • A mathematical model of viscoelasticity on the material property of human pharyngeal tissue utilizing Y.C. Fung's Quasi-linear viscoelastic theory is proposed based on cyclic load, stress relaxation, incremental load, and uniaxial tensile load tests. The material properties are characterized and compared with other biological materials' results. The mathematical model is proposed by combining two characteristic functions determined from the stress relaxation and uniaxial tensile load tests. The reduced stress relaxation function G(t) and elastic response function S(t) are obtained from stress relaxation test and uniaxial tensile load test results respectively. Then the model describing stress-time history of the tissue is implemented utilizing two functions. The proposed model is evaluated and validated by comparing the model's cyclic behaviour with experimental results. The model data could be utilized as an important information for constructing 3-dimensional biomechanical model of human pharynx using FEM(Finite Element Method).

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