• 제목/요약/키워드: random loading

검색결과 225건 처리시간 0.028초

짧은 피로균열의 랜덤하중하의 균열닫힘 및 진전거동 (Part I: 균열닫힘 거동 상세) (Crack Closure and Growth Behavior of Short Fatigue Cracks under Random Loading (Part I : Details of crack Closure Behavior))

  • 이신영;송지호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 춘계학술대회논문집A
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    • pp.79-84
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    • 2000
  • Crack closure and growth behavior of physically short fatigue cracks under random loading are Investigated by performing narrow- and wide-band random loading tests for various stress ratios. Artificially prepared two-dimensional, short through-thickness cracks are used. The closure behavior of short cracks under random loading is discussed, comparing with that of short cracks under constant-amplitude loading and also that of long cracks under random loading. Irrespective of random loading spectrum or block length, the crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history, contrary to the behavior of long cracks that the crack opening load under random loading is nearly the same as or slightly higher than constant-amplitude results. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks.

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짧은 피로균열의 랜덤하중하의 균열닫힘 및 진전거동(Part II : 진전거동 및 진전수명예측) (Crack Closure and Growth Behavior of Short Fatigue Cracks under Random Loading (Part II : Growth Behavior and Growth Life Prediction))

  • 이신영;송지호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.141-146
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    • 2000
  • Crack closure and growth behavior of physically short fatigue cracks under random loading are investigated by performing narrow- and wide-band random loading tests for various stress ratios. The importance of the crack closure phenomenon is examined by predicting the growth lives of short cracks using obtained crack opening behavior. Artificially prepared two-dimensional, short through-thickness cracks are used. The crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks. Most of the life prediction ratios are within the factor of 2 scatter band except several data at very short crack sizes, indicating that crack growth predictions based on the measured crack opening data are excellent. From the results obtained in this study, it can be concluded that crack closure is the primary factor governing fatigue crack growth of short cracks under random loading as well as under constant-amplitude loading.

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알루미늄 합금의 랜덤하중 하에서 발생한 피로파면 해석 방법 (Fractographic Analysis Method of Fatigue Fracture Surface under Program and Random Loading for Aluminum Alloy)

  • 김상태;최성종;양현태;이희원
    • 대한기계학회논문집A
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    • 제27권12호
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    • pp.2055-2060
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    • 2003
  • Striation is a typical pattern observed on the fatigue fracture surface and the spacing is known to correspond to a macroscopic fatigue crack growth rate, and many models for the predict in the formation of such striation have been proposed. However, these theories and methods can't be applied under random loading spectrum. In this study, the fatigue tests were carried out on aluminum alloy under random loading spectrum. The fatigue fracture surfaces were observed in the scanning electron microscope (SEM) and great quantities of SEM micrographs were synthesized and saved in computer system. The space and morphology of several large-scale striations, which are expected to from at the relatively greater load range in loading block, were observed. The crack length for each loading blocks was decided in consideration of regularity and repetition of those striations. It is shown that the applicability of fractographic methods on the fatigue fracture surface under random loading spectrum.

신경회로망을 이용한 변동하중 하에서의 균열열림점 자동측정 (Automatic Determination of Crack Opening Loading under Random Loading by the Use of Neural Network)

  • 강재윤;송지호;김정엽
    • 대한기계학회논문집A
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    • 제24권9호
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    • pp.2283-2291
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    • 2000
  • The neural network method is applied to automatically measure the crack opening load under random loading. The crack opening results obtained are compared with the visual measured results. Fatigue crack growth under random loading is predicted using the crack opening data measured by the neural network method, and the prediction results are compared with experimental ones. It is found that the neural network method can be successfully applied to consistently measure the crack opening load under random loading and also gives some results different from the results by visual measurement.

랜덤하중하의 피로균열진전 데이터를 이용한 ${\Delta}K_{eff}$ 평가법의 정량적 평가 (A Quantitative Evaluation of ${\Delta}K_{eff}$ Estimation Methods Based on Random Loading Crack Growth Data.)

  • 구자석;송지호;강재윤
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.208-213
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    • 2004
  • Methods for estimation of the effective stress intensity factor range (${\Delta}K_{eff}$) are evaluated for narrow and wide band random loading crack growth test data of 2024-T351 aluminum alloy. Three methods of determining $K_{op}$, visual measurement, ASTM offset compliance method, and the neural network method proposed by Kang and Song, and three methods of estimating ${\Delta}K_{eff}$, conventional, the 2/PI0 and 2/PI methods proposed by Donald and Paris, are compared in a quantitative manner by using the results of fatigue crack growth life prediction under random loading. For all $K_{op}$ determination methods discussed, the 2/PI0 and 2/PI methods of estimating ${\Delta}K_{eff}$ provide better results than conventional method for narrow and wide band random loading data.

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랜덤하중 하에서 피로균열진전예측 방법들의 비교 (A comparative study of methods to predict fatigue crack growth under random loading)

  • 최병익;강재윤;이학주;김정엽
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.235-240
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    • 2003
  • Methods to predict fatigue crack growth are compared in a quantitative manner for crack growth test data of 2024-T351 aluminum alloy under narrow and wide band random loading. In order to account for the effect of load ratio, crack closure model, Hater's equation and NASGRO's equation have been employed. Load interaction effect under random loading has been considered by crack closure model, Willenborg's model and Wheeler's model. The prediction method using the measured crack opening results provides the best result among the prediction methods discussed for narrow and wide band random loading data.

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랜덤하중 하에서 피로균열진전예측 방법들의 비교 (A Comparative Study of Methods to Predict Fatigue Crack Growth under Random Loading)

  • 이학주;강재윤;최병익;김정엽
    • 대한기계학회논문집A
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    • 제27권10호
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    • pp.1785-1792
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    • 2003
  • Methods to predict fatigue crack growth are compared in a quantitative manner for crack growth test data of 2024- T351 aluninum alloy under narrow and wide band random loading. In order to account for the effect of load ratio, crack closure model, Hater's equation and NASGRO's equation have been employed. Load interaction effect under random loading has been considered by crack closure model, Willenborg's model and Wheeler's model. The prediction method using the measured crack opening results provides the best result among the prediction methods discussed for narrow and wide band random loading data.

Random loading identification of multi-input-multi-output structure

  • Zhi, Hao;Lin, Jiahao
    • Structural Engineering and Mechanics
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    • 제10권4호
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    • pp.359-369
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    • 2000
  • Random loading identification has long been a difficult problem for Multi-Input-Multi-Output (MIMO) structure. In this paper, the Pseudo Excitation Method (PEM), which is an exact and efficient method for computing the structural random response, is extended inversely to identify the excitation power spectral densities (PSD). This identified method, named the Inverse Pseudo Excitation Method (IPEM), resembles the general dynamic loading identification in the frequency domain, and can be used to identify the definite or random excitations of complex structures in a similar way. Numerical simulations are used to reveal the the difficulties in such problems, and the results of some numerical analysis are discussed, which may be very useful in the setting up and processing of experimental data so as to obtain reasonable predictions of the input loading from the selected structural responses.

다축 Random Dynamic 하중을 받는 대차 저널박스의 피로수명평가 (Fatigue Life Assessment of Journal Box Attached to Bogie under Multiaxial Random Dynamic Loading)

  • 박상구;김승섭;한성욱;박근수;우관제
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2009년도 춘계학술대회 논문집
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    • pp.1125-1131
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    • 2009
  • This paper presents the evaluation of fatigue life for a journal box attached to rolling stock bogie under random dynamic loading condition. Because a journal box was under random dynamic loading conditions, the fatigue life assessment due to these loads requires the analysis considering the multiaxial effect of random dynamic loading. To do this work, the finite element analysis has been conducted to calculate random dynamic response using multiaxial acceleration data. Then, the fatigue life assessment of component has been conducted using vibration fatigue analysis applying the power spectral densities of the responses obtained through the FEA The results of fatigue life assessment were compared to the damage from the strain measurement. This study shows that can be evaluated the fatigue life assessment considering real service condition about a component attached to rolling stock bogie.

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Stress Analysis of Top Hat Type Structure for Random Loading

  • M. J. Jhung;Kim, Y. B.;Lee, J. B.
    • Nuclear Engineering and Technology
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    • 제29권6호
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    • pp.476-487
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    • 1997
  • To resolve several arguments raised for the current analysis of a structure like top hat, which is composed of flange, cylinder and plate, the dynamic response analysis is performed for the full and half models. The dynamic characteristics are investigated for full and half models and the results are compared between them. The responses such as bolt reactions and stresses due to random loading are also obtained using the analysis capabilities between commercial programs which have the routine for the random vibration analysis. Several general purpose structural analysis programs are used to get the response due to the random loadings. Also the application of the random loading and the effect of correlations such as fully correlated, partially correlated and fully uncorrelated cases are studied and the general directions for the generation of design loads due to random loading are suggested.

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