• Title, Summary, Keyword: 응력확대계수

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Stress Concentration Factor and Stress Intensity Factor with U-notch and Crack in the Beam (U-노치 및 균열을 갖는 보의 응력집중계수 및 응력확대계수)

  • Seo, Bo Seong;Lee, Kwang Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.5
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    • pp.513-523
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    • 2016
  • The stress concentration factors and stress intensity factors for a simple beam and a cantilever are analyzed by using finite element method and phtoelasticity. Using the analyzed results, the estimated graphs on stress concentration factors and stress intensity factors are obtained. To analyze stress concentration factors of notch, the dimensionless notch length H(height of specimen)/h=1.1~2 and dimensionless gap space r(radius at the notch tip)/h=0.1~0.5 are used. where h=H-c and c is the notch length. As the notch gap length increases and the gap decreases, the stress concentration factors increase. Stress concentration factors of a simple beam are greater than those of a cantilever beam. However, actually, the maximum stress values under a load, a notch length and a gap occur more greatly in the cantilever beam than in the simple beam. To analyze stress intensity factors, the normalized crack length a(crack length)/H=0.2~0.5 is used. As the length of the crack increases, the normalized stress intensity factors increase. The stress intensity factors under a constant load and a crack length occur more greatly in the cantilever beam than in the simple beam.

Stress Intensity Factors of Center Cracked Laminated Composites under Uniaxial Tension (단순인장을 받는 복합 적층재 중앙균열의 응력확대계수)

  • 김성호;오재협;옹장우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.5
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    • pp.1611-1619
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    • 1991
  • 본 연구에서는 Hilton과 Sih의 경우를 확장 적용하여 Fig. 1(b)와 같이 탄성 층 내부에 존재하는 중앙균열선단의 응력확대계수 산출을 위하여 균열부위를 제외하고 는 섬유층과 레진층이 완전히 접착되었다고 가정한 모델을 다음과 같이 설정하였다. 중앙균열을 내재하고 있는 복합재료의 역학적 거동을 해석하기 위하여, 접착레진을 주 로하는 층(resin rich layer)을 중심으로 하여 상하 각1개의 섬유 (fiber)층과 균질한 특성을 갖는 복합재료의 층으로 단순화 하였으며, 이러한 단순화는 적층재에서의 균열 주위의 국부응력을 해석하기 위한 것으로서 복합재료는 레진층이나 섬유층에 비하여 매우 두꺼우므로 반무한체로 이상화 하였다. 선형탄성 이론에 의하여 혼합 경계조건 문제(mixed boundary value problem)로 부터 제2종 Fredholm적분방정식(fredholm int- egral equation of a second kind)을 유도하였으며 수치해석적인 방법에 의하여 응력 확대계수를 구하였다.

A Study on Determination of Stress Intensity Factors for the Interface Crack in Dissimilar AnisotropicMaterials (이방성 이종재료의 접합계면 균열에 대한 응력확대계수 결정에 대한 연구)

  • 이갑래;조상봉;최용식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.3
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    • pp.887-897
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    • 1991
  • 본 연구에서는 이와 같은 배경에서, Fig. 1(f)와 같이 가장 일반적인 이방성 재료가 접합된 경우의 응력확대계수를 명확히 정의하고, 수치해석법으로 구할 수 있는 외삽식을 제안한다. 또한, 탄성문제의 수치해석 방법으로 적은 요소의 분할로써 고 정밀도의 수치해석 결과를 얻을 수 있는 경계요소법(boundary element method:BEM), 특히 저자들이 개발한 복합재료에 대한 2차원 경계요소법 프로그램을 이용하여 이방성 이종재료 접합계면 균열의 응력확대계수를 해석하고, 복합재료내의 섬유방향에 대한 접합계면 균열의 정성적 거동을 고찰하고자 한다.

Calculation of Stress Intensity Factor in a Rotor with a Breathing Crack (개폐균열을 갖는 회전체에서의 응력확대계수 계산)

  • 전오성;이종원;엄윤용;은희준
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.5
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    • pp.1417-1425
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    • 1991
  • 본 연구에서는 파괴역학적 개념을 도입하여 수평 회전체에 존재하는 횡방향 개폐균열의 모형을 설명하고 균열거동을 분석하였으며, 균열의 깊이, 회전속도 및 회 전방향에 따른 균열선단에서의 응력확대 계수를 계산하고 그 특성을 분석하였다.

The analysis of fracture stress using reflection coefficient of surface acoustic wave (탄성표면파의 반사계수를 이용한 파괴응력의 해석)

  • Shin, J.S.;Kim, J.K.;Jun, K.S.
    • The Journal of the Acoustical Society of Korea
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    • v.10 no.3
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    • pp.13-18
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    • 1991
  • In this study, the analysis technique of fracture stress using the reflection coefficient of SAW reflected from a brittle solid with surface crack has been studied. Fracture stress of brittle solid with surface crack has been obtained by the function of the critical stress intensity factor and the maximum normalized stress intensity factor of the crack in the body. And the maximum normalized stress intensity factor of a surface crack can be inferred from a measurement of reflection coefficient of SAW. In experiment, the surface cracks ranging from 0.5mm to 0.9mm in crack depth has been made at the center of each Pyrex disc, and the SAW wedge transducer has been set up for the pitch-catch mode. It has been compared the theoretical values of the fracture stress calculated from the reflection coefficient of SAW with the values of the fracture stress measured from UTM.

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Determination of Stress Intensity Factor for the Crack in Orthotropic Materials Using the Finite Element Method (유한요소법에 의한 직방성재료 내 균열의 응력확대계수 결정)

  • 조형석;강석진;이성근;임원균
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.1
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    • pp.59-65
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    • 2004
  • The stress intensity factors have been widely used in numerical studies of crack growth direction. However in many cases, omissive terms of the series expansion are quantitatively significant, so we consider the computation of such terms. For this purpose, we used the finite element method with isoparametric quadratic quarter-point elements. For examples, infinite square plate with a slant crack subjected to a uniaxial load is analyzed. The numerical analysis were performed for the wide range of crack tip element lengths and inclined angles. The numerical results obtained are compared with the theoretical solutions. Also they were accurate and efficient.

Calculation of Stress Intensity Factor KI Using the Exact Solution in an Infinitely Deep Crack in a Half-Plane (반 무한 평판에 존재하는 반 무한 균열에서 엄밀 해를 이용한 응력확대계수 계산)

  • An, Deuk Man
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.1
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    • pp.7-11
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    • 2017
  • In this study, we develop the exact field of mode I in an infinitely deep crack in a half-plane. Using this field, we obtain the exact stress intensity factor $K_{I}$. From the tractions on the crack faces induced by exact field, we calculate the stress intensity factor of this field. We compare the results with the stress intensity factor calculated using Bueckner's weight function formula and that calculated by using Tada's formula listed in "The Stress Analysis of Cracks Handbook" It was found that Bueckner's formula yields accurate results. However, the results obtained using Tada's formula exhibit inaccurate behavior.

Analysis of Unsteady Propagation of Mode III Crack in Arbitrary Direction in Functionally Graded Materials (함수구배재료에서 임의의 방향을 따라 비정상적으로 전파하는 모드 III 균열해석)

  • Lee, Kwang Ho;Cho, Sang Bong;Hawong, Jai Sug
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.2
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    • pp.143-156
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    • 2015
  • The stress and displacement fields at the crack tip were studied during the unsteady propagation of a mode III crack in a direction that was different from the property graduation direction in functionally graded materials (FGMs). The property graduation in FGMs was assumed based on the linearly varying shear modulus under a constant density and the exponentially varying shear modulus and density. To obtain the solution of the harmonic function, the general partial differential equation of the dynamic equilibrium equation was transformed into a Laplace equation. Based on the Laplace equation, the stress and displacement fields, which depended on the time rates of change in the crack tip speed and stress intensity factor, were obtained through an asymptotic analysis. Using the stress and displacement fields, the effects of the angled property variation on the stresses, displacements, and stress intensity factors are discussed.

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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Stress Intensity Factors for a Center Cracked laminated Composites under Shear Loading (전단하중을 받는 복합 적층재 중앙균열의 응력확대계수)

  • 오재협;김성호;옹장우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.5
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    • pp.838-848
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    • 1992
  • The objective of the study is to provide a theoretical tools for analyzing the fracture of leyered composites with a center crack. It is assumed that the composite is composed of successive accumulation of the fiber layer and resin layer with the fiber layer being perfectly bonded to the resin layer except the region of a center crack. In-plane shear loading (Mode II) and the anti-plane shear loading (Mode III) are considered separately. Boundary value problems are formulated by using a plane theory of elasticity and governing equations are reduced to a Fredholm integral equation of a second kind. The equation is solved numerically and the stress intensity factors are obtained. The normalized Mode II and Mode III stress intensity factors are evaluated for various combinations of material properties and for various geometrical parametes.