• 제목/요약/키워드: 피로 J-integral범위

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미소 원공결함을 갖는 Cr-Mo-V강의 고온피로 크랙전파거동 (A Study on the Fatigue Crack Propagation Behavior of Cr-Mo-V Alloy with Micro Defects at High Temperature.)

  • 송삼홍;강명수
    • 한국정밀공학회지
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    • 제13권12호
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    • pp.70-77
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    • 1996
  • Fatigue tests were carried out at high temperature on a Cr-Mo-V steel in order to assess the fatigue life of components used in power plants. The characteristics of high temperature fatigue were divided in terms of cycle-dependent fatigue and time-dependent fatigue, each crack propagation rate was examined with respect to fatigue J-integral range, .DELTA. J$_{f}$and creep J-integral range, .DELTA. J$_{c}$. The fatigue life was evaluated by analysis of J-integral value at the crack tip with a dimensional finite element method. The results obtained from the present study are summarized as follows : The propagation characteristics of high temperature fatigue cracks are determined by .DELTA. J$_{f}$for the PP(tensile plasticity-compressive plasticity deformation) and PC(tensile plasticity - compressive creep deformation) stress waveform types, and by .DELTA. J$_{c}$for the CP(tensile creep- compressive plasticity deformation) stress waveform type. The crack propagation law of high temperature fatigue is obtained by analysis of J-integral value at the crack tip using the finite element method and applied to examine crack propagation behavior. The fatigue life is evaluated using the results of analysis by the finite element method. The predicted life and the actual life are close, within a factor of 2.f 2.f 2.

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1.5Cr-0.67Mo-0.33V강의 열피로 크랙전파 거동 (Thermo-Mechanical Fatigue Crack Propagation Behaviors of 1.5Cr-0.67Mo-0.33V Alloy)

  • 송삼홍;강명수
    • 대한기계학회논문집
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    • 제19권9호
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    • pp.2133-2141
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    • 1995
  • The thermo-mechanical fatigue tests were performed on the specimens extracted from 1.5Cr-0. 67Mo-0.33V alloy. The characteristics of thermo-mechanical fatigue crack propagation were examined and reviewed in view of fracture mechanics. The results obtained from the present study are summarized as follows : (1) The propagation characteristics of isothermal low-cycle fatigue crack are dominated by .DELTA.J$_{f}$ in case of PP waveform, and .DELTA.J$_{c}$ in case of CP waveform. (II)The propagation characteristics of thermo-mechanical fatigue crack are dominated by .DELTA.J$_{c}$ for in-phase case, and by .DELTA.J$_{c}$ for out-of-phase. The present results were in good agreement with the equation of propagation law for isothermal low-cycle fatigue crack in case of thermo-mechanical fatigue.tigue.e.

J적분에 의한 SB41강의 피로균열 진전 특성 평가 (Description of crack growth behavior of SB41 steel in terms of J integral)

  • 배원호;김상태;이택순
    • 대한기계학회논문집
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    • 제14권6호
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    • pp.1568-1575
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    • 1990
  • 본 연구에서는 중앙균열을 가진 SB41강의 평판이 하중제어와 변형률제어 피로 상태에서 소규모 항복, 대규모 항복, 또는 전면 항복의 각 응력에서 피로균열 진전 속 도와 J적분 범위, .DELTA.J와의 관계를 조사하는 한편, 피로균열 진전 속도를 지배하는 국 소적 역학 인자인 균열선단 개구변위, COD와 균열 진전 속도와 관계 및 그 특성을 고 찰하였다.

크리이프-피로 상호작용하의 균열성장속도 예측에 관한 연구 (A Study on Prediction of Crack growth Rate Under Creep-Fatigue Interaction)

  • 주원식;조석수
    • 한국해양공학회지
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    • 제9권2호
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    • pp.98-111
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    • 1995
  • High temperature low cycle fatigue shows that cycle-dependent crack growth owing to cyclic plastic deformation occurred simultaneosly with time-dependent crack growth owing to intergranular deformation. Consequently, to estimate crack growth rate uniquely, many to investigators have proposed various kinds of parameters and theories but these could not produce satisfactory results. Therefore the goal of this study is focused on prediction of crack growth rate using predominant damage rule, linear cumulative damage rule and transitional parameter ${\Delta}J_c/{\Delta}J_f$. On the basis of these sinusoidal loading waveform at 600$^{\circ}C$ and 700$^{\circ}C$.

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SB41 강의 표면 피로균열 진전 특성에 관한 연구 (A Study on the Fatigue Crack Growth Behavior of Surface Cracks)

  • 배원호;김상태;이택순
    • 대한기계학회논문집
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    • 제15권3호
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    • pp.916-923
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    • 1991
  • 본 연구에서는 표면 균열이 있는 평판의 탄소성 피로하중 상태에서 성장하는 균열 형태의 변화와, 작용하는 응력의 크기에 따른 균열 개페구 특성의 변화를 연구하 였다.또, 유효 응력 확대계수 범위, .DELTA.K$_{eff}$와 J적분범위, .DELTA.J가 탄소성 응력 상태에서의 표면 피로균열 진전속도를 나타내는 역학양으로 사용되는데 따른 적합성등 을 검토하였다.

표면결함재에 관한 탄소성 파괴역학에 의한 피로수명 예측 (Fatigue Life Prediction by Elastic-Plastic Fracture mechanics for Surface Flaw Steel)

  • 강용구;서창민;이종식
    • 한국해양공학회지
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    • 제9권2호
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    • pp.112-122
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    • 1995
  • In this work, prediction of fatigue life and fatigue crack growth are studied. 4th order polynominal function is presented to describe the crack growth behaviors from artifical pit of SM45C steel. Crack growth curves obtained from 4th order polyminal growth equations are in good agreement with experimental data The crack growth behaviors at arbitrary stress levels and investigated by the concept of elastic-plastic fracture mechanics using ${\Delta}J$. Fatigue life prediction are carried out by numerical integral method. Prediction lives obtained by proposed method in this study, is in good agreement with the experimental ones. Life prediction results calculated by using of ${\Delta}J$ better than those of ${\Delta}K$.

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SUS 304 강의 크리프 온도역에 있어서 피로균열성장거동에 관한 연구 (A Study on Fatigue Crack Growth Behavior at a Creep Temperature Region in SUS 304 Stainless Steel)

  • 주원식;오세욱;조석수
    • 대한기계학회논문집
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    • 제18권3호
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    • pp.548-554
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    • 1994
  • The high temperature fatigue crack growth behavior of SUS 304 stainless steel at $550^{\circ}C$ and $650^{\circ}C$ was investigated under various kinds of stress ratio and frequency in sinusoidal waveform on the basis of the non-linear fracture mechanics. The result arranging crack growth rate by modified J-integral J' showed influence of stress ratio and frequency. All the data obtained under the test at $550^{\circ}C$ were plotted within data band of da/dN-${\triangle}J_f$ relationship for cycle-dependent crack growth. On the basis of static creep and cycle-dependent data band; both time- and cycle-dependent crack growth behavior was observed under loading conditions at $650^{\circ}C$, but cycle-dependent crack growth behavior predominantly appeared and time-dependent crack growth behaviour was little observed under loading conditions at $550^{\circ}C$. Fractographic examinations for fracture surface indicated that the fracture mode was generally transgranular. The stripes were found on fracture surface and each stripe was accompanied by a crack tip blunting and an abrupt increase in the load-point displacement. The $J'_{an}$ had a validity in case of $650^{\circ}C, but scarcely had it in case of $550^{\circ}C$.