• 제목/요약/키워드: 피로균열 성장률

검색결과 45건 처리시간 0.026초

세라믹 코팅된 1Cr-1Mo-0.25V강의 피로균열성장 특성 (Fatigue crack growth properties of ceramic coated 1Cr-1Mo-0.25V steel)

  • 서창민;김경렬
    • 대한기계학회논문집A
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    • 제21권10호
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    • pp.1674-1682
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    • 1997
  • Fatigue tests were performed to investigate the effect of ceramic coatings as in TiN and TiCN on fatigue crack growth properties of ceramic coated 1Cr-1Mo-0.25V steel with different coating thickness in laboratory air conditions. The experimental results are described with respect to a Paris equation, da/dN=C(.DELTA.K)$^{m}$ , where the crack growth rate of coated specimens provided as similar growth rate as that of the uncoated specimen regardless of coating thickness. Furthermore, it was observed that the type of coating layer had virtually no effect on crack growth rate in the full region of stress intensity factor range. And it was also appeared that the final crack length of TiCN coated specimens was short compared to that of TiN coated, and the substrate specimens, in which it was inferred due to lowering the toughness of coated material from high hardness of TiCN coating layer itself.

수지 혼합비가 FRMLs의 피로균열전파거동과 기계적 성질에 미치는 영향에 관한 연구 (Study on the Effect of Resin Mixture Ratios on the Fatigue Crack Propagation Behavior and Mechanical Property in a FRMLs)

  • 김철웅;손세원
    • 한국정밀공학회지
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    • 제16권8호
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    • pp.149-154
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    • 1999
  • FRMLs(Fiber Reinforced Metal Laminates) is a new type of hybrid materials. FRMLs consists of high strength metal and fiber which are laminated using a structural adhesive bond(epoxy resin). The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical property of Aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA) was cured with methylene dianiline(MDA) with or without accelerator(K-54). Eight kinds of resin mixture ratio were tested for the experiment ; five kinds of FRMLs(1))epoxy & curing agent) and three kinds of FRMLs(2)(epoxy & curing agent & accelerator). FRMLs(2) have a more effective characteristics on the fatigue crack propagation behavior and mechanical property than FRMLs(1)

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크리프-피로상호작용하의 파단수명에 관한 연구 (Study on Fracture Life Under Mutual Interaction of Creep and Fatigue)

  • 조용이;김희송
    • 한국정밀공학회지
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    • 제10권3호
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    • pp.97-106
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    • 1993
  • This is the study on fracture life under the interaction of creep and fatigue. It is difficult to explain the interaction of the creep and fatigue with indication of frequency but the dependency of the time should be considered. The formulation of material varieties causing by interaction of creep and fatigue is required in the accumulative damage method. The strain range partition method requires some of modification corresponding to the changes in temperature and load. All of other method also comprehended with above mentioned problems. Generally, in this field, the variety of stress-strain and suitable parameter is required and connective study between the macro and micro results seems to be insufficient. The linear damage rule is acquiring the support generally but it requires modification in the hgigh temperature instruments. The variety of stress effecting on crack and variety of stress on the metallurgical side are considered to be problems in the future days.

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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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고온에서 원거리 측정 시스템을 활용하기 위한 코팅기술의 응용에 관한 연구 (Coating technique for use with remote measurement system at elevated temperatures)

  • 서창민;남승훈;이해무;김용일;김동석
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2000년도 춘계학술대회 논문집
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    • pp.164-169
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    • 2000
  • The remote measurement system(RMS) as a new experimental method is limited in its application to crack measurements at elevated temperatures because of the oxide layer on the specimen surface. Since TiAlN and Cr coating layers have a high resistance to oxidation and wear, this paper proposed a TiAlN and Cr coating technique for specimens to facilitate the measurement of crack growth behavior using RMS. To investigate the effects of the coating layer, tension and fatigue tests were carried out at room temperature and at 538$^{\circ}C$, using specimens of 1Cr-1Mo-0.25V steel. From the experimental results, it was found that the mechanical properties of the TiAlN and Cr coated specimens were similar to those of the substrate. Accordingly, the TiAlN and Cr coated layer had hardly any influence on the fatigue crack propagation.

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복합응력장 하의 균열부재에 대한 잔류피로수명 평가방법 (Residual fatigue life evaluation method for the cracked components under complex stress fields)

  • 조창희;김상태;권재도
    • 대한기계학회논문집A
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    • 제22권2호
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    • pp.258-267
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    • 1998
  • This study reviews the influence function method(IFM) for calculating stress intensity factors (SIFs, K) and modifies it to apply for the estimating the residual fatigue life for the cracked components under complex stress fields. An IFM has been developed to analyze SIFs for surface cracks which are subjectedto nonuniformly distributed stresses. Through elastic superposition, the influence function method properly accounts for redistribution of stress as the crack grows through the component. This influence function is unique to the given geometry and independent of the loading. Some examples have been provided to show the effectiveness of the IFM including the distributions of K in a residual stress field. The significant effect of residual stress upon fatigue crack growth in a welded component has been demonstrated with the IFM.

과대하중이 피로수명에 미치는 영향에 관한 연구 (A Study on the Effect of Overloading on Fatigue Life)

  • 김경수;신병천;심천식;박진영;조형민
    • 대한조선학회논문집
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    • 제40권3호
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    • pp.45-53
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    • 2003
  • Ships and ocean structures are subjected to random loads caused by irregular waves. The irregularity of amplitude from random loading affects on fatigue crack growth and fatigue life. However the effects of irregularity of loading on fatigue including random loading have not been explained exactly. Therefore in this paper crack growth tests on DENT specimens under constant-amplitude loading including a single tensile overload are conducted to investigate the effect of overload on crack growth rate. The size of plastic zone and crack growth rate before and after a single tensile overloading are measured using ESPI system. Crack growth retardation model that is characterized by crack growth length and the size of plastic zone was proposed and compared with test result. From the research, the validity of proposed model is examined on crack growth retardation, and consequently fatigue life.

2층 고무/코드 적층판의 피로 수명 예측 (Prediction of Fatigue Life in 2 Ply Rubber/Cord Laminate)

  • 임동진;이윤기;윤희석;김민호
    • Composites Research
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    • 제16권3호
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    • pp.9-17
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    • 2003
  • 타이어 벨트층내의 코드간 균열연결 및 층간균열진전을 모사하기 위해 자유단을 갖는 2층 고무/코드 적층시험편에 대한 4~11mm 변위제어 실험을 수행하였다. 자유단의 코드간 균열연결시의 폭방향 균열진전량은 45$^{\circ}$ 경사진 코드들간 길이의 절반에 도달할 때의 측정값으로 하였으며, 이는 탐침법에 의해 측정되었다 또한, 자유단에서 코드들간 균열연결을 모사하기위해 2차원의 이상화된 모델링 기법을 고안하였다. 이론수명은 테어링에너지(균열파단면의 단위면적당 방출에너지)를 이용하여 코드간 균열연결수명(임계값)과 이후 최종파손까지의 수명으로 구분하였으며, 이들을 각기 실험값과 비교하였다. 임계값까지의 수명예측은 실험과 비교하여 약 20%, 최종파손까지 약 65%의 오차가 발생하였다. 따라서, 전체 이론수명은 실험과 비교하여 약 45%의 오차를 발생하였다.

반복-굽힘 모멘트가 A15052/AFRP 적층재의 층간분리 영역과 피로균열진전에 미치는 영향 (The Influence of Cyclic-bending Moment on the Delamination Zone and the Fatigue Crack Propagation in A15052/AFRP Laminates)

  • 송삼홍;김철웅
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.231-237
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    • 2000
  • A15052/AFRP laminates were developed principally to obtain a material with good fatigue strength, in which possible cracks would grow very slowly. Weight savings of more than 30% should be attainable in practice. Also, the crack bridging fibers could still was carry a significant part of the load over the crack, thus the COD and stress intensity factor was reduced at the crack tip. A15052/ AFRP laminates consists of three thin sheets of 5052-H34 aluminum alloy and two layers of [0] unidirectional aramid fiber prepreg. The cyclic-bending moment test was investigated based on applying the five kinds of bending moments. The size of the delamination zone produced between 5052-H34 aluminum alloy sheets and fiber-adhesive layers was measured from ultrasonic C-scan pictures taken around the fatigue crack. In addition, the relationship between the cyclic-bending moment and the delamination zone size was studied and the effect of fiber bridging mechanism was also considered.

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