• Title, Summary, Keyword: Kinked Crack

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An Extension Behavior of an Interface Kinked Crack by CED (CED에 의한 계면굴절균열의 진전거동)

  • 권오헌
    • Journal of the Korean Society of Safety
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    • v.11 no.2
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    • pp.9-15
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    • 1996
  • The characteristics on the extension of the CED(Crack energy density) concept to the interface kinked crack problems in a dissimilar material are examined. Each mode contributions of CED are found by symmetric and antisymmetric components and domain independent integrals. Finite element calculation is carried out to simulate the Interface kinked crack growth on bimaterial. The focus is the establishment of fracture criterion with CED and finding the orientation of crack extension. From the results, a prediction about the extension behavior of an interface kinked crack can be done. And we show that CED can be a parameter to indicate fracture criterion at an Interface kinked crack.

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The Evaluation of the Kinked Interface Crack Behavior in Dissimilar Materials by CED (CED에 의한 계면굴절균열의 진전거동평가)

  • Kwon, O.H
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.3
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    • pp.414-422
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    • 1997
  • The characteristics on the extension of the CED(Crack Energy Density) concept to the interface kinked crack problems in a dissimilar are examined. Each mode contributions of CED are found by symmetric and antisymmetric conponents and domain independent integrals. Finite element calculation is carried out to simulate the interface kinked crack growth on a bimaterial. The focus is the establishment of fracture criterion with CED and finding the orientation of crack extension. From the results, a prediction about the extension behavior of an interface kinked crack can be done. And we show that CED can be a parameter to indicate fracture criterion at an interface kinked crack.

An Integral Equation for Kinked Cracks in Finite Plane Bodies (유한영역에서의 꺾인균열 해석을 위한 적분방정식 적용 연구)

  • 서욱환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2138-2144
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    • 1993
  • An integral equation representation of cracks was presented which differs from well-known "dislocation layer" representation. In this new representation, the equations are written in terms of the displacement discontinuity across the crack surfaces rather than derivatives of the displacement-discontinuity. It was shown in that the new technique is well-suited to the treatment of kinked cracks. In the present paper, this integral equation representation is coupled to the direct boundary-element method for the treatment of finite bodies containing kinked cracks. The method is demonstrated for two-dimensional finite domains but extension to three-dimensional problems would appear to be possible. The resulting approach is shown to be simple, yet very accurate. accurate.

Fatigue Crack Retardation and Retardation Mechanism in Variable Loading (The Effects of Crack Tip Branching in Crack Growth Retardation)

  • Song, Sam-Hong;Kwon, Yun-Ki
    • International Journal of Precision Engineering and Manufacturing
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    • v.3 no.3
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    • pp.76-81
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    • 2002
  • In order to study the fatigue crack and retardation mechanism in variable loading, the effects of crack tip branching in crack growth retardation were examined. The characteristics of crack tip branching behavior were considered with respect to microstructure and crack tip branching angle was examined. Crack tip branching was observed along the grain boundary of finite and pearlite structure. It was found that the branching angle ranges from 25 to 53 degrees. Using the finite element method, the variable of crack driving farce to branching angle was examined. The effective crack driving farce (K$\_$eff/) decreased as the branching angle increased. The rate of decrease was 33% for kinked type and 29% for forked one. It was confirmed that the effect of crack tip branching is a very important factor in crack growth retardation. Therefore, crack branching effect should be considered in building the hypothetical model to predict crack growth retardation.

A Study on Mode III Kinked Crack Analysis Using Displacement-Discontinuity Method (변위 불연속 방법에 의한 모드 III 꺾인 균열 해석 연구)

  • 서욱환
    • Journal of Welding and Joining
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    • v.18 no.4
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    • pp.104-110
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    • 2000
  • An integral equation representation of cracks was presented, which differs from well-known "dislocation layer" representation. In this new representation, an integral equation representation of cracks was developed and coupled to the direct boundary-element method for treatment of cracks in plane finite bodies. The method was developed for in-plane (modes I and II) loadings only. In this paper, the method is formulated and applied to mode III problems involving smooth or kinked cracks in finite region. The results are compared to exact solutions where available and the method is shown to be very accurate despite of its simplicity.implicity.

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The Prediction of Crack Growth Retardation Behavior by Crack Tip Branching Effects (Fatigue Behavior in variable Loading Condition) (균열가지 효과를 고려한 균열 성장 지연 거동 예측 (변동하중하에서의 피로거동))

  • 권윤기
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.8 no.2
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    • pp.126-136
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    • 1999
  • We studied on crack growth retardation in single overloading condition. Crack tip branching which as the second mechanism on crack growth retardation was examined. Crack tip branching was observed to kinked type and forked type. It was found that the branching angle range was from 25 to 53 degree. The variations of crack driving force with branching angle were calculated with finite element method The variation of {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and total crack driving force(K) were examined respectively So {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and K mean to mode I, II and total crack driving force. Present model(Willenborg's model) for crack growth retardation prediction was modified to take into consideration the effects of crack tip branching When we predicted retardation with modified model. it was confirmed that predicted and experimental results coincided with well each other.

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AN INTEGRAL EQUATION FOR KINKED CRACKS APPLIED TO MODE III IN FINITE PLANE BODIES (유한영역에서의 모드 III 꺾인균열 해석을 위한 적분방정식 적용연구)

  • Sur, Ukhwan
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.2 no.1
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    • pp.111-129
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    • 1998
  • An integral equation representation of cracks was presented, which differs from well-known "dislocation layer" representation. In this new representation, an integral equation representation of cracks was developed and coupled to the direct boundary-element method for treatment of cracks in plane finite bodies. The method was developed for in-plane(modes I and II) loadings only. In this paper, the method is formulated and applied to mode III problems involving smooth or kinked cracks in finite region. The results are compared to exact solutions where available and the method is shown to be very accurate despite of its simplicity.

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A Fracture Mechanics Approach on Delamination and Package Crack in Electronic Packaging(l) -Delamination- (반도체패키지에서의 층간박리 및 패키지균열에 대한 파괴역학적 연구 (1) -층간박리-)

  • 박상선;반용운;엄윤용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2139-2157
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    • 1994
  • In order to understand the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the stress intensity factor, T-stress and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the delamination are investigated taking into account the temperature dependence of the material properties, which simulates as more realistic condition. As the crack length increases the J-integral increases, which suggest that the crack propagates if it starts growing from the small size. The effects of the material properties and molding process temperature on stress intensity factor, T-stress is and J-integral are less significant than the chip size for the practical cases considered here. The T-stress is negative in all eases, which is in agreement with observation that interfacial crack is not kinked until the crack approaches the edge of the leadframe.

A Fracture Mechanics Approach on Delamination and Package Crack in Electronic Packaging(ll) - Package Crack - (반도체패키지에서의 층간박리 및 패키지균열에 대한 파괴역학적 연구 (2) - 패키지균열-)

  • 박상선;반용운;엄윤용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2158-2166
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    • 1994
  • In order to understand the package crack emanating from the edge of leadframe after the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the M-integral and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the package crack are investigated taking into account the temperature dependence of the material properties, which simulates a more realistic condition. If the temperature dependence of the material properties is considered the result of analysis conforms with observations that the crack is kinked at between 50 and 65 degree. However, in case of constant material properties at the room temperature it is found that the J-integral is underestimated and the kink crack angle is different form the observation. The effects of the material properties and molding process temperature on J-integral and crack angle are less significant that the chip size for the cases considered here. It is suggested that the geometric factors such as ship size, leadframe size are to be well designed in order to prevent(or control) the occurrence and propagation of the package crack.