• Title, Summary, Keyword: 미소원공결함

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The Influence of the Small Circular Hole Defect on the Fatigue Crack Propagation Behavior in Aluminum Alloys (알루미늄 합금재의 피로크랙 전파거동에 미치는 미소원공결함)

  • Kim, G.H.;Lee, H.Y.
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.6
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    • pp.834-840
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    • 2008
  • We carried out fatigue testing with materials of aluminum alloyC7075-T6, 2024-T4) by rotary bending fatigue tester. We investigated fatigue limit, fatigue crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction to the different small circular hole defect. The summarized result are as follows; Fatigue limit of the smooth specimens were related tensile strength and yield strength. In case of more large applied stress and small circular hole crack defect, the fatigue crack was grown rapidly. The fatigue crack propagation behavior proceed at according to inclusion. Fatigue crack propagation ratio appeared instability and retardation phenomenon in the first half of fatigue life but appeared stability and replied in the latter half. On other hand, this experimental data of the materials are appeared fatigue life predictability.

The Effect of Fatigue Crack Behavior on the Variable Depth of Micro Hole Defects in SM20C at the Symmetric Position (대칭위치에 존재하는 미소원공결함의 깊이변화가 SM20C의 피로균열거동에 미치는 영향)

  • 송삼홍;김성태
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.856-860
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    • 2002
  • The main objective of this study is to consider the effect of fatigue crack behavior on the variable depth of micro hole defects in SM20C at the symmetric position. The fatigue crack propagation test is performed by rotary bending fatigue test machine. The relationship between crack length(2a), cycles(N) and crack growth rate(da/dN) are investigated in this study. The result from the rotary bending fatigue test under the applied stress at 250MPa turned out that the fatigue life illustrated almost constant when the depth of symmetric micro hole deflects is both part A and B at the hope depth(h) = 0.5mm.

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Fatigue Crack Initiation and Propagation From Two Micro Hole Defects (두개의 미소원공결함에서의 피로크랙발생과 전파에 관한 연구)

  • Song, Sam-Hong;Bae, Joon-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.5
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    • pp.842-849
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    • 1997
  • The aim of this study is an investigation of the interaction of two micro hole defects affecting fatigue crack initation life and propagation behavior. The locatio of two micro hole defects was considered as an angle of alignment and the distance between the centers of two micro hole defects. The fatigue cracking behavior is experimented under bending. When micro defects are located close to each other, the fatigue crack initiation lives are varied with their relative locations. In the experiments, the area of local plastic strain strongly played a role in the fatigue crack initiation lives. Therefore we introduce a parameter which contains the plastic deformation area at stress concentrations and propose a fatigue crack initiation life prediction curve. In addition, the directions and propagation rates of fatigue cracks initiated at two micro hole defects are studied experimentally.

A Study on the Fatigue Crack Propagation Behavior in F.F. Shaft Materials of Vehicle with Small Circular Defect at Variable Temperature (미소원공결함을 갖는 자동차 전류구동축재의 온도변화에 따른 피로크랙전파거동에 관한 연구)

  • Lee, S.R.;Lee, D.G.;Chung, J.K.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.185-194
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    • 1998
  • In this study, the rotary bending fatigue test was carried out with two kinds of material, S43C and S50C, using in the Front engine and Front drive wheels(F.F.) of vehicle. The one part of specimens was heated by high frequency induction method(about 1mm depth and $H_RC$ 56~60) and tested environment temperature were $-30^{\circ}C$, $+25^{\circ}C$ and $+80^{\circ}C$ in order to look over the influence of the heat treatment and the temperatures. In the experimented result at $+25^{\circ}C$ and $+80^{\circ}C$, the fatigue life of non-heated specimens were decreased about 35%, but that of heated specimens were decreased about only 5% at $+80^{\circ}C$ more than at $25^{\circ}C$. And in the experiment result at $-30^{\circ}C$ and $+25^{\circ}C$, the non-heated and heated specimens were about 110%, 120% higher fatigue life at $-30^{\circ}C$ than at the $+25^{\circ}C$ each other. On the other hand, the fatigue crack propagation rate of S50C was higher than that of S43C.

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