• Title/Summary/Keyword: crack growth behavior

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A Prediction of Crack Propagation Rate under Random Loading (랜덤하중에서의 균열전파속도 추정법에 관한 연구)

  • 표동근;안태환
    • Journal of Ocean Engineering and Technology
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    • v.8 no.2
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    • pp.115-123
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    • 1994
  • Under variable amplitude loading conditions, retardation or accelerated condition of fatigue crack growth occurs with every cycle, Because fatigue crack growth behavior varied depend on load time history. The modeling of stress amplitude with storm loading acted to ships and offshore structures applied this paper. The crack closure behavior examine by recording the variation in load-strain relationship. By taking process mentioned above, fatigue crack growth rate, crack length, stress intensity factor, and crack closure stress intensity factor were obtained from the stress cycles of each type of storm ; A(6m), B(7m), C(8m), D(9m), E(11m) and F(15m) which was wave height. It showed that the good agreement with between the experiment results and simulation of storm loads. So this estimated method of crack propagtion rate gives a good criterion for the safe design of vessels and marine structure.

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Assessment of Creep-Fatigue Crack Growth for a High Temperature Component (고온 기기의 크리프-피로 균열성장 평가)

  • Lee, Hyeong-Yeon;Kim, Jong-Bum;Lee, Jae-Han
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.264-268
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    • 2008
  • An assessment of creep-fatigue crack behavior is required to ensure the structural integrity for high temperature components such as fast breeder reactor structures or thermal power plant components operating at an elevated temperature. In this study, an evaluation of creep-fatigue crack growth has been carried out according to the French assessment guide of the RCC-MR A16 for austenitic stainless steel structures. The assessment procedures for creep-fatigue crack growth in the recent version of the A16 (2007 edition) have been changed considerably from the previous version (2002 edition) and the material properties (RCC-MR Appendix A3) have been changed as well. The impacts of those changes on creep-fatigue crack growth behavior are quantified from the assessments with a structural model. Finally the assessment results were compared with the observed images obtained from the structural tests of the same structural specimen.

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An Experimental Study on the Factors that Affect Fatigue Crack Growth Retardation Behavior in S45C Steel (S45C 강의 피로균열전파 지연거동의 영향인자에 관한 실험적 연구)

  • Kim, Seon-Jin;An, Seok-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.3
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    • pp.470-477
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    • 2001
  • Constant ΔK fatigue crack growth tests were performed by applying an intermediate multiple overload for S45C steel. The purpose of the present study is to investigate effects of specimen thickness at various baseline stress intensity factor range levels (ΔK(sub)b), overload application position (a/W) and overload application frequency (OL(sub)HZ) on fatigue crack growth retardation behavior. The principal results are summarized as follows. The amount of retardation for a given ΔK(sub)b level is increased with increasing the baseline stress intensity factor range level for all specimen thickness. The normalized minimum crack growth rate is increased with increasing the specimen thickness, except for ΔK=45MPa√m. The retardation cycle is decreased with increasing a/W and increased with OL(sub)HZ.

An Experimental Study on the Factors that Affect Fatigue Crack Growth Retardation Behavior in SM45C Steel (SM45C 강의 피로균열전파 지연거동에 미치는 영향인자에 관한 실험적 연구)

  • Kim, Seon-Jin;Kim, Jong-Hoon;Ahn, Seok-Hwan
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.55-60
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    • 2000
  • Constant ${\Delta}K$ fatigue crack growth tests were performed applying an intermediate multiple overload for SM45C steel. The purpose of the present study is to investigate the effects of specimen thickness at various baseline stress intensity levels$({\Delta}K_b)$, overload application frequency(a/W) and overload application frequency$(OL_{HZ})$ on fatigue crack growth retardation behavior. The principal results are summarized as follows. The amount of retardation for a given ${\Delta}K_b$ level is increased with increasing the baseline stress intensity level in all specimen thickness. The normalized minimum crack growth rate is increased with increasing the specimen thickness, except for ${\Delta}K=45MPa \sqrt m$. The retardation cycle is decreased with increasing the overload application position and increased with the overload application frequency.

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Prediction d Fatigue Growth Behavior of Short Cracks (짧은 균열의 피로성장거동예측)

  • 최용식;우흥식;한지원
    • Journal of the Korean Society of Safety
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    • v.8 no.4
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    • pp.47-53
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    • 1993
  • The growth of short cracks can be well described in terms of the effective stress intensity factor range, which is calculated on the base of crack closure. The relation between the crack opening SIF and crack length is determined from the experimental results. The crack opening SIF of short cracks, Kop, can be predicted from the crack opening SIF at threshold of long crack, Kop.L. The growth rate of short cracks at notch root can be predicted from the crack opening SIF of short cracks, Kop, and the growth equation of long cracks in region II.

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The Behavior of Crack Growth Rate for APAL and CPAL Patched with FRP Laminate in Aluminum Alloy Plate (알루미늄 합금판재에 FRP 라미네이터를 보강한 APAL 및 CPAL 재의 균열전파속도 거동)

  • 윤한기;정해용;허정원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.4
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    • pp.1013-1022
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    • 1995
  • A hybrid composite (APAL;Aramid Patched ALuminum alloy, CPAL;Carbon Patched ALluminum alloy), consisting of a Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy and carbon/epoxy laminate, was developed. Fatigue crack growth behavior was examined at stress ratios of R=0.2, 0.5. The APAL and CPAL showed superior fatigue crack growth resistance, which may be attributed to the crack bridging effect imposed by the intact fibers in the crack wake.

Fatigue Crack Propagation Behavior in Butt Weldment of SA106 Gr.C Main Steam Pipe Steel

  • Kim, Eung-Seon;Jang, Chan-Su;Kim, In-Sup
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05c
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    • pp.92-97
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    • 1996
  • The fatigue crack propagation behavior in SA106 Gr.C main steam pipe weld joint was investigated in air environment. Crack growth rate tests were conducted on base metal and weld metal at load ratio of 0.1 and 0.3 and at frequency of 10Hz. The fatigue crack growth rates of the base metal and the weld metal were above the ASME reference line and the fatigue crack propagation rate of the weld metal was higher than those of the base metal. Fatigue crack growth rate increased with increasing the load ratio and the effect of the load ratio was more significant in the weld metal. The post weld heat treatment increased the fatigue crack growth rates of the base metal by reducing compressive residual stress and decreased those of the weld metal by reducing weld defects.

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Effect of Peening on Low Temperature Fatigue Strength Behavior of STABILIZER BAR in Suspension Material (현가장치 STABILIZER BAR의 저온피로강도에 미치는 쇼트피닝의 영향)

  • 박경동;정재욱
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.4
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    • pp.58-64
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    • 2004
  • The purpose of this study is to predict the behavior of fatigue crack propagation as one of fracture mechanics on the compressive residual stress. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, and -10$0^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. There is a difference between shot peened specimen and unpeened specimen. Fatigue crack growth rate of shot peened specimen was lower than that of unpeened specimen. Shot peening is improve the resistance of crack growth by fatigue that make a compressive residual stress on surface. That is the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation. Temperature goes down, fatigue crack growth rate decreased.

Generation of Pseudo-Random Load Waves and Preliminary Study on Surface Fatigue Crack Growth under Random Loading (유사랜덤하중파형 작성과 이를 이용한 랜덤하중하의 표면피로 균열진전에 관한 기초적 검토)

  • 송지호;김종한;김정엽
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.125-134
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    • 1989
  • Pseudo-random load waves for fatigue testing were generated by personal computer simulation and preliminary study was performed on the growth behavior of surface fatigue crack under random ladings. The closure behavior and growth rates of surface fatigue crack were significantly influenced by the characteristics of random waves. It was also found that the growth rates of surface fatigue crack under random loadings could not be always described by the effective stress intensity factor based on the concept of crack closure.

A Behavior of Fatigue Crack Growth of Nonmagnetic Steel with Large Grain Size (조대조직을 갖는 비자성강의 피로균열진전거동)

  • Lee, Jong-Hyung;Choi, Seong-Dae;Cheong, Seon-Hwan;Kwon, Hyun-Kyu;Yang, Seong-Hyeon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.3 no.4
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    • pp.88-94
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    • 2004
  • High manganese steel was maintained stability of Non-Magnetics performance. Fatigue tests were carried out under constant stress amplitude, using a non-magnetic high manganese steel. The fatigue crack growth mechanism of the high manganese steel was clarified from results such as observation of crack growth path and fracture surface. The result of getting this study was shown as following: 1) Remarkably ${\Delta}Kth$ of the high manganese steel is big with about 3 times of the general steel product. 2) In the low ${\Delta}K$ value region, da/dN is dependent on Kmax, and in the high ${\Delta}K$ value region, it is dependent on ${\Delta}Keff$. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. 3) It seems to ease the stress concentration of crack tip crack growth behavior in the ${\Delta}Kth$ vicinity by the generation of the secondary crack.

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