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

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Prediction of Fatigue Life for Hole-notched Weave CFRP Plate (평직 CFRP 홀 노치재의 피로 수명 예측)

  • Kim, Sang-Young;Kim, Yong-Seok;Kwon, Hee-Whan;Choi, Jung-Hun;Koo, Jae-Mean;Seok, Chang-Sung
    • Composites Research
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    • v.23 no.3
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    • pp.1-6
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    • 2010
  • Recently, CFRP composite is more and more used in the various fields because of a higher specific modulus, chemical property and so on. Most products using CFRP composite are manufactured by construction of components. Various components are joined with those by bolts and pins. Holes for bolts and pins decrease strength and fatigue life of components, because those act as notch in structures. In this paper, we experimentally evaluated the fatigue life of hole-notched and unnotched weave CFRP plate. Then, we compared the two results and proposed an equation for prediction of fatigue life.

A Study on Prediction of Fatigue Life using MFC Sensors (MFC센서를 이용한 피로수명예측에 관한 연구)

  • Lee, Ji-Hoon;Oh, Dong-Jin;Kim, Myung-Hyun
    • Journal of Welding and Joining
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    • v.31 no.6
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    • pp.32-36
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    • 2013
  • The large-scale structures have the possibility that there are defects such as cracks due to stress concentration caused by geometric discontinuities in the structure. In this respect, the assessment of fatigue life and the development of structural health monitoring(SHM) are very important. Fatigue design of structure is typically accomplished either using a set of stress cycle (S-N) data obtained from fatigue tests or using the fracture mechanics approach. The stress intensity factor(SIF) is required for the estimation of fatigue crack propagation life from the linear elastic fracture mechanics (LEFM) perspective. In this study, Macro Fiber Composie(MFC) sensor for the measurement of SIF of two dimensional cracks is used. The SIF based on the piezoelectric constitutive law and fracture mechanics are calculated. The measured values of the SIF are later used for the prediction of the crack propagation life. In this study, the measured value of the SIF and the fatigue life are compared with the theoretical results.

Fatigue Life Evaluation of Spot Weldments of SPC Sheet Including Strain Rate Effect (변형률속도효과를 고려한 일반냉연강판 점용접부의 피로수명평가)

  • Song, Joon-Hyuk;Nah, Seok-Chan;Yu, Hyo-Sun;Kang, Hee-Yong;Yang, Sung-Mo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.1
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    • pp.48-53
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    • 2006
  • A methodology is described for predicting the fatigue life of the resistance spot weldment including strain rate effect. Because it is difficult to perform a physical failure test with high strain rate, an analytical method is necessary to get the mechanical properties of various strain rate, To this end, quasi-static tensile-shear tests at several strain rate were performed on spot weldments of SPC. These test provided the empirical data with the strain rate. With these results, we formulated the function of fatigue life prediction using the lethargy coefficient which is the global material property from tensile test. And, we predicted the fatigue life of spot weldment at dynamic strain rate. To confirm this method for fatigue life prediction, analytical results were compared with the experimental fatigue data.

Life Prediction by Lethargy Coefficient under Dynamic Load (동적인장하중시 무기력상수에 의한 수명 예측)

  • Kwon, S.J.;Song, J.H.;Kang, H.Y.;Yang, S.M.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.7
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    • pp.91-98
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    • 1997
  • Because of a complicated behavior of fatigue in mechanical structures, the analysis of fatigue is in need of much researches on life prediction. A method is developed for the dynamic tensile strength analysis by simple tensile test, which is for the failure life prediction by lethargy coefficient of various materials. Then it is programed to analyze the failure life prediction of mechanical system by virtue of fracture. Thus the dynamic tensile strength analysis is performed to evaluate life parameters as a numerical example, using the developed method.

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Fatigue Life Prediction and Strength Evaluation of Shot Peened Parts (쇼트피이닝한 부재의 피로수명 예측 및 피로강도 평가)

  • Kim, Hwan-Du;Lee, Sun-Bok
    • 한국기계연구소 소보
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    • s.15
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    • pp.75-87
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    • 1985
  • A review was performed on fatigue life prediction and strength evaluation of shot peened parts. Fatigue strength of machine parts can be improved by shot peening due to compressive residual stresses on such parts. Compressive residual stress cannot be uniquely define by peening intensity. Several measuring methods of residual stress and the principle of hole drilling method are presented. Exploratory measurement of residual stress was performed on the shot peened SM35C plate with the hole drilling method. Fatigue life and failure location of shot peened parts under bending load can be predicted by a damage parameter which is incorporated with material properties, residual stress, and applied stress conditions. Some method are presented to predict the fatigue strength of shot peened parts at any given life. Shot peening gives its full benefit to the notched machine parts of high strength steels.

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A Proposal of Parameter to Predict Biaxial Fatigue Life for CF8M Cast Stainless Steels (CF8M 주조 스테인리스강의 2축 피로수명 예측을 위한 파라미터의 제안)

  • Park Joong Cheul;Kwon Jae Do
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.6 s.237
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    • pp.815-821
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    • 2005
  • Biaxial low cycle fatigue test was carried out to predict fatigue life under combined axial-torsional-loading condition which is that of in-phase and out-of-phase for CF8M cast stainless steels. Fatemi-Socie(FS) parameter which is based on critical plane approach is not only one of methods but also the best method that can predict fatigue life under biaxial loading condition. But the result showed that, biaxial fatigue life prediction by using FS parameter with several different parameters for the CF8M cast stainless steels is not conservative but best results. So in this present research, we proposed new fatigue life prediction parameter considering effective shear stress instead of FS parameter which considers the maximum normal stress acting on maximum shear strain and its effectiveness was verified.

Fatigue Life Prediction of FRP Composites under Uniaxial Tension and Pure Torsion Loadings (인장-비틀림 하중에 의한 섬유강화 복합재료의 피로수명 예측)

  • 박성완;이장규
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.04a
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    • pp.352-361
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    • 2003
  • A fatigue damage accumulation model based on the continuum damage mechanics theory was develope(1 where modules decay ratios in tension and shear on used as indicators for damage variables D . In the model, the damage variables are considered to be second-order tensors. Then the maximum principal damage variable, D is introduced According to the similarity to the Principal stress, D is obtained as the maximum eigen value of damage tensor [D']. Under proportional tension and torsion loadings, fatigue lives were satisfactorily predicted at any combined stress ratios using the present model in which the fatigue characteristics only under uniaxial tension and pure torsion loadings on needed. Fatigue life prediction under uniaxial tension and pure torsion loadings, was performed based on the damage mechanics using boundary element method.

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Fatigue Life Prediction of FRP Composites under Uniaxial Tension and Pure Torsion Loadings (인장-비틀림 하중에 의한 섬유강화 복합재료의 피로수명 예측)

  • Park Sung-Oan
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.6
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    • pp.64-73
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    • 2004
  • A fatigue damage accumulation model based on the continuum damage mechanics theory was developed where modulus decay ratios in tension and shear were used as indicators for damage variables D. In the model, the damage variables are considered to be second-order tensors. Then, the maximum principal damage variable, D is introduced. According to the similarity to the principal stress, D is obtained as the maximum eigen value of damage tensor [D]. Under proportional tension and torsion loadings, fatigue lives were satisfactorily predicted at any combined stress ratios using the present model in which the Fatigue characteristics only under uniaxial tension and pure torsion loadings were needed. Fatigue life prediction under uniaxial tension and pure torsion loadings, was performed based on the damage mechanics using boundary element method.

A Study on Prediction of Fatigue Damage Crack Growth for Stiffener Bonded Composite Laminate Panel (보강재 본딩접합 복합재 적층판구조 피로손상 균열진전 수명예측에 대한 연구)

  • Kwon, Jung-Ho;Jeong, Seong-Moon
    • Composites Research
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    • v.26 no.2
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    • pp.79-84
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    • 2013
  • The prediction and analysis procedure of fatigue damage crack growth life for a stiffener bonded composite laminate panel including center hole and edge notch damage, was studied. It was performed on the basis of fatigue damage growth test results on a laminated skin panel specimens and the analysis results of stress intensity factor for the stiffener bonded composite panel. According to the comparison between experimental test and prediction results of fatigue damage growth life, it was concluded that the residual strength and damage tolerance assessment can be carried out along to the edge notch crack growth.

Finite element procedures for the numerical simulation of fatigue crack propagation under mixed mode loading

  • Alshoaibi, Abdulnaser M.
    • Structural Engineering and Mechanics
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    • v.35 no.3
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    • pp.283-299
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    • 2010
  • This paper addresses the numerical simulation of fatigue crack growth in arbitrary 2D geometries under constant amplitude loading by the using a new finite element software. The purpose of this software is on the determination of 2D crack paths and surfaces as well as on the evaluation of components Lifetimes as a part of the damage tolerant assessment. Throughout the simulation of fatigue crack propagation an automatic adaptive mesh is carried out in the vicinity of the crack front nodes and in the elements which represent the higher stresses distribution. The fatigue crack direction and the corresponding stress-intensity factors are estimated at each small crack increment by employing the displacement extrapolation technique under facilitation of singular crack tip elements. The propagation is modeled by successive linear extensions, which are determined by the stress intensity factors under linear elastic fracture mechanics (LEFM) assumption. The stress intensity factors range history must be recorded along the small crack increments. Upon completion of the stress intensity factors range history recording, fatigue crack propagation life of the examined specimen is predicted. A consistent transfer algorithm and a crack relaxation method are proposed and implemented for this purpose. Verification of the predicted fatigue life is validated with relevant experimental data and numerical results obtained by other researchers. The comparisons show that the program is capable of demonstrating the fatigue life prediction results as well as the fatigue crack path satisfactorily.