• Title/Summary/Keyword: CTS시험편

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Method to measure $K_ I$,$K_ I1$ and J-integral for CTS specimen under mixed mode loading (혼합모드 하중을 받는 CTS 시험편에서 $K_ I$,$K_ I1$ 와 J-적분의 측정방법)

  • Hong, K.J;Kang, K.J
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.11
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    • pp.3498-3506
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    • 1996
  • A loading device to be used in fracture experiment is presented. It's loading angle can be adjusted from $-45^{\circ}$ to $105^{\circ}$ at intervals of $15^{\circ}$ for a CTS ( compact tension-shear) specimen, so that it is to be useful to measure mixed mode toughness. The equations to give the $K_ I$, $K_ I1$ and J-integral for the experiment are evluated though finite elemetn analysis in which the loading procedure is simulated and the behaviors of the specimen such as load-displacement curve are estimated. In the course of the evaluation the values $K_ I$, $K_ I1$ and J-integral calculated through recentrly released numerical methods are employed as the reference ones.

An Experimental Study on the Fatigue Crack Propagation Behavior in CTS Specimen under Mode II Loading (모드 II 하중을 받는 CTS 시험편의 피로균열 전파거동에 관한 실험적 연구)

  • Song, Sam-Hong;Lee, Jeong-Moo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.7
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    • pp.1217-1226
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    • 2003
  • The purpose of this paper is to investigate fatigue crack behavior under shear(Mode II) loading. Various specimens and devices have been used in order to produce Mode II loading in fatigue experiments for shear crack propagation. But, there is not sufficient comparisons of experimental results between Mode II and others loading modes, because of characteristics of applied loads and specimens. So, compact tension shear(CTS) specimens were used in this paper to investigate the propagation behavior of Mode II by comparing the experimental results between loading modes. We firstly observed the characteristics which was showed in Mode II experiment using CTS specimens. The experimental results under Mode II loading were compared with fatigue crack behavior under Mode I and Mixed-mode I+II loading. The characteristics for initiation and propagation behavior under Mode II loading was investigated by such comparisons.

Fatigue Crack Propagation Behavior in CTS Specimen Under Mixed-Mode Loading with Hole Defefects (원공 결함을 갖는 CTS 시험편의 혼합모드 하중 하에서의 피로균열 전파거동)

  • Song, Sam-Hong;Shin, Seung-Man;Lee, Jeong-Moo;Seo, Ki-Jeong
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.137-142
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    • 2003
  • In this study, the propagation behavior of fatigue crack effected hole defects was investigated under mixed-mode I+II loading. To create mixed-mode stress field at crack tip, the compact tension shear (CTS) specimen and loading device were used in this tests. The propagation experiments of fatigue crack were performed by changing of the loading application angle(${\phi}$) and the distance(L) estimated from pre-crack tip to hole center located side by side by side with a pre-crack. As L changes, the variation for propagation aspect of fatigue crack, fatigue life and crack propagation rate were examined under mixed-mode loading. Under mixed-mode loading, the propagation rate of fatigue crack increased while the propagation direction changed dramatically because of the interference of hole defects.

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An Experimental Study on the Fatigue Crack Propagation Behavior Under Mixed-Mode Single Overload (혼합모드 단일과대하중 하의 피로균열 전파거동에 관한 실험적 연구)

  • Song, Sam-Hong;Lee, Jeong-Moo;Hong, Suck-Pyo
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.119-124
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    • 2003
  • In this study, retardation behavior of fatigue crack under single overloading of the mixed mode I+II state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I loading overloading afterwards. We examined the observed deformation aspects, variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. It has been confirmed that the retardation behavior did not immediately appear and the retardation length was short when the component of mixed-mode overload was changed.

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Fatigue Crack Propagation Behavior under Mixed Mode Loading (혼합모드 하중에서의 피로균열 전파거동)

  • 송삼홍;이정무;최병호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.481-484
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    • 2000
  • Practical structures are subject not only to tension but also to shear and torsional loading. Even under uniaxial loading, when the load is not perpendicular to the crack plane, mixed mode crack can occur. Hence, it is necessary to evaluate the fatigue behavior under mixed mode loading. In this study, the propagation behavior of the fatigue crack of the STS304 steels under mixed mode loading condition was investigated. The mode I and II stress intensity factors of CTS specimen were calculated using elastic finite element method with experimental results. The fatigue crack propagation under mixed mode was evaluated by the effective stress intensity factor proposed by Tanaka.

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The Characteristics of Fatigue Crack Propagation Behavior in Shear Load (전단하중 하의 피로균열 전파거동의 특징)

  • Lee, Jeong-Moo;Song, Sam-Hong
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.302-307
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    • 2004
  • This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

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The Mixed Mode fatigue Crack Propagation Behavior with the Variation of Stress Ratio (응력비 변화에 따른 혼합모드 피로균열 전파거동)

  • Song, Sam-Hong;Choi, Ji-Hoon;Lee, Jeong-Moo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.11
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    • pp.2287-2296
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    • 2002
  • Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0$^{\circ}$, 30$^{\circ}$, 60$^{\circ}$ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.

Fatigue Crack Propagation Behavior in STS304 under Mixed Mode Loading (혼합모드 하중에서의 STS304의 피로균열 전과거동)

  • Song, Sam-Hong;Lee, Jeong-Moo
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.9
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    • pp.131-139
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    • 2001
  • The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failure occur from cracks subjected to mixed mode loadings. Hence, it is necessary to evaluate the fatigue behavior under mixed mode loading. Under mixed mode loading conditions, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. The mode I and II stress intensity factors of CTS specimen were calculated using elastic finite element method. The propagation behavior of the fatigue crack of the STS304 steeds under mixed mode loading condition was evacuated by using stress intensity factors $K_I$ and $K_II. The MTS criterion and effective stress intensity factor were applied to predict the crack propagation direction and the fatigue crack propagation rate.

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Fracture Criterion and Fatigue Crack Growth Behavior of Rail Steel Under Mode I & Mixed Mode Loading (단일 및 혼합모드 하중하에서의 레일강의 파괴조건 및 피로균열진전거동)

  • Kim, Jung-Kyu;Lee, Jong-Sun;Kim, Chul-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.6 s.165
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    • pp.1039-1047
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    • 1999
  • It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

Effects by the Magnitude of Shear Load on the Formation and Propagation of Mode II Branch Cracks (전단하중의 크기가 모드 II 분기균열의 형성과 전파에 미치는 영향)

  • 이정무;송삼홍
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.487-490
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    • 2004
  • In this paper, we investigated the characteristics of initiation and propagation behavior for fatigue crack observed by changing various shapes of initial crack and magnitudes of loading in modified compact tension shear(CTS) specimen subjected to shear loading. In the low-loading condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack face grew to a main crack. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. The propagation path of fatigue crack under the Mode II loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

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