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  • Title/Summary/Keyword: Prediction of the Fatigue Life

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A Study on the Fatigue Life Prediction of Al-2024 with Corrosion (부식을 고려한 항공기재료의 부식피로수명예측 연구)

  • Kim, Wie-Dae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.1
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    • pp.46-51
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    • 2007
  • In this study, test results for fatigue crack propagation of Al-2024-T3511 are presented considering corrosion effects, and fatigue lifes are compared for the cases of corrosion and non-corrosion. Higher corrosion environments show lower fatigue life and faster crack growth. To predict the corrosion fatigue life, a corrosion factor concept is newly introduced and applied in Paris' law. The predicted results show good agreement with experimental data and this corrosion fatigue model can be successfully used for the prediction of fatigue life of aluminum structure with corrosion effects.

Prediction of Shearing Die Life for Producing a Retainer using FE Analysis (유한요소해석을 이용한 리테이너 전단 금형 수명예측)

  • Lee, I.K.;Lee, S.Y.;Lee, S.K.;Jeong, M.S.;Seo, P.K.;Lee, K.H.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.24 no.4
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    • pp.264-271
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    • 2015
  • In the current study, a method was proposed to quantitatively predict the wear and fatigue life of a shearing die in order to determine an effective replacement period for the die. The shearing die model of a retainer manufacturing process was used for the proposed method of quantitative life prediction. The retainer is produced through shearing steps, such as piercing and notching. The shearing die of the retainer is carefully controlled because the dimensional accuracy of the retainer is critical. The fatigue life for the shearing die was predicted using ANSYS considering S-N curves of STD11 and Gerber’s equation. The wear life for the shearing die was predicted using DEFORM-3D considering the Archard’s wear model. Experimental shearing of the retainer was conducted to verify the effectiveness of the proposed method for predicting die life. The fatigue failure of the shearing die was macroscopically measured. The wear depth was measured using a 3D coordinate measuring machine. The results showed that the wear and fatigue life in the FE analysis agree well with the experimental results.

A Study of Crack Propagation and Fatigue Life Prediction on Welded Joints of Ship Structure (II) (선체 용접부의 균열진전 및 피로수명예측에 관한 연구(II))

  • Kim, Kyung-Su;Shim, Chun-Sik;Kwon, Young-Bin;Ko, Hee-Seung;Ki, Hyeok-Geun;Viswanathan, K.K.
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.6
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    • pp.679-687
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    • 2008
  • The fatigue life of ship structure under cyclic loading condition is made up of crack initiation and propagation stages. For a welding member in ship structure, the fatigue crack propagation life is more important than the fatigue crack initiation life. To calculate precisely the fatigue crack propagation life at the critical welding location, the knowledge of the residual stress sensitivity on the fatigue strength is necessary. In this study, thermo elastic-plastic analysis was conducted in order to examine the effect of residual stress on the fatigue crack propagation life. Also the fatigue crack propagation lives considering residual stress were calculated using fatigue crack growth code, AFGROW, on the basis of fracture mechanics. AFGROW is widely used for fatigue crack growth predictions under constant and variable amplitude loading. The reliability of AFGROW on the fatigue of ship structure was confirmed by the comparison of the estimated results with the fatigue propagation test results.

The Study on the Fatigue Life Prediction on Wheels through CAE (CAE를 이용한 자동차용 휠(wheel)의 피로수명 예측기법 연구)

  • 김만섭;고길주;김정헌;양창근;김관묵
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.117-122
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    • 2004
  • The fatigue life in wheels was predicted by simulating the experimental method using Finite-Element analysis. Based on a high frequency fatigue property, calculations of the stresses in wheels were performed by simulating the rotating bending fatigue test. Wheels made of an aluminum alloy(A356.2) were tested using a bending fatigue tester. Results from bending fatigue test showed a linear correlation between bending moment and stress amplitude. Consequently, Finite-Element calculations were performed by a linear analysis. In order to find stress-cycles curves, spoke parts of wheel were tested using a rotary bending fatigue tester. Also, highly accurate Finite-Element analysis requires regression lines and confidence intervals from these results. In conclusion, if the fatigue data related to the material and manufacturing procedure are reliable, the prediction on fatigue lift in wheels can be carried out with high accuracy.

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.

Surface Crack Behavior and the Fatigue Life Prediction of Notched Specimens (표면균열의 거동과 피로수명예측에 관한 연구)

  • 서창민;이정주;정은화;박희범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.5
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    • pp.1097-1103
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    • 1988
  • This paper deals with surface crack behavior and the fatigue life prediction of notched specimens using the relation between surface crack length, a, and the cycle ratio, N/Nf. From the aN/Nf curves, UC(the upper limit curve), LC(the lower limit curve) and MC(the middle limit curve) were assumed and utilized to predict the fatigue life and crack growth rate. The data computed from the three assumed curves were compared with the experimental data. It has been found that in the stable crack growth region (N/Nf=0.30.8) fatigue life can be predicted within 20% errors. Using the characteristics of aN/Nf curve, it is possible to predict the da/dNKmax curve, the da/dNΔKεt curve, and the SNf curve.

Fatigue Life Prediction of SICw/Al Composites by Using the Monte-Carlo Simulation (몬테카르로 시뮬레이션에 의한 SICw/Al 복합재료의 피로수명에측)

  • Ahn, Jeong-Ju;Kwon, Jae-Do;Kim, Sang-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.5
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    • pp.1552-1561
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    • 1996
  • It requires uch time and cost to obtain the fatigue crack growth life and fatigue crack growth path morphlogy from the fatigue crack growth tests. In this study, the Monte-Carlo simulation program was developed to predict the fatigue crack growth lofe and fatigue crack growth path morphology of metal matrix composites. Fatigue crack growth lives of 5%, 10%, 15%, 20%, 25% and 30% SiCw/Al composites were predicted by usign the Monte-Carlo Simulation. And the fatigue crack growth lives of 25% SiCw/Al and Almatrix from Monte-carlo simulation were compared with fatigue life from experiments in order to verify the accuracy of Monte-Carlo Simulation program.

Thermo-Mechancal Fatigue of the Nickel Base Superalloy IN738LC for Gas Turbine Blades (가스터빈 블레이드용 IN738LC의 열기계피로수명에 관한 연구)

  • Fleury, E.;Ha, J.S.;Hyun, J.S.;Jang, S.W.;Jung, H.
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.188-193
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    • 2000
  • A more accurate life prediction for gas turbine blade takes into account the material behavior under the complex thermo-mechanical fatigue(TMF) cycles normally encountered in turbine operation. An experimental program has been carried out to address the thermo-mechanical fatigue life of the IN738LC nickel-base superalloy. In the first phase of the study, out-of-phase and in-phase TMF experiments have been performed on uncoated and coated materials. In the temperature range investigated. the deposition of NiCrAlY air plasma sprayed coating did not affect the fatigue resistance. In the second phase of the study, a physically-base life prediction model that takes into account of the contribution of different damage mechanisms has been applied. This model was able to reflect the temperature and strain rate dependences of isothermal cycling fatigue lives, and the strain-temperature history effect on the thermo-mechanical fatigue lives.

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A Study on Improving the Precision of Quantitative Prediction of Cold Forging Die Life Cycle Through Real Time Forging Load Measurement (실시간 성형하중 계측을 통한 냉간단조 금형수명 정량예측 정밀도 향상 연구)

  • Seo, Y.H.
    • Transactions of Materials Processing
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    • v.30 no.4
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    • pp.172-178
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    • 2021
  • The cold forging process induces material deformation in an enclosed space, generating a very high forging load. Therefore, it is mainly designed as a multi-stage process, and fatigue failure occurs in forging die due to cyclic load. Studies have been conducted previously to quantitatively predict the fatigue limit of cold forging dies, however, there was a limit to field application due to the large error range and the need for expert intervention. To solve this problem, we conducted a study on the introduction of a real-time forging load measurement technology and an automated system for quantitative prediction of die life cycle. As a result, it was possible to reduce the error range of the quantitative prediction of die life cycle to within ±7%, and it became possible to use the die life cycle calculation algorithm into an automated system.

Prediction of the Fatigue Life of Deep Groove Ball Bearing under Radial and Moment Loads -Equivalent Dynamic Loads- (반경방향과 모멘트하중 하에서의 깊은홈 볼베어링의 피로수명 평가 -동등가하중식 제안-)

  • 김완두;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1654-1663
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    • 1994
  • Even if the ball bearing was conservatively designed considering the dynamic capacity and the rating life, sometimes the bearing was early failed on account of the misalignment and the lubricant contaminations etc. Misalignment was generated when bearing-shaft system transmitted large power and when the bearing was inadequately mounted. It was possible to predict the fatigue life of ball bearing under the misalignment considering the motions of ball, cage and raceway, and the factors of the effect on fatigue life. Misalignment affected on ball bearing as radial and moment load and the relationships between misalignment and moment were obtained. In this paper, the analysis of the load distributions between ball and raceway, and the prediction of fatigue life of deep groove ball bearing under radial and moment loads were carried out. And, the new formulation of equivalent dynamic load considering the effects of moment load was proposed.