• Title/Summary/Keyword: random loading

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A Stochastic Analysis of Crack Propagation Life under Constant Amplitude Loading (균일진폭 하중하에서의 확률론적 균열진전 수명해석)

  • 윤한용;양영순;윤장호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.9
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    • pp.1691-1699
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    • 1992
  • The experimental results of fatigue crack propagation under constant amplitude loading show that intra-and inter-specimen variability exist. In this paper, a stochastic model for the estimation of mean and variance of crack propagation life is presented To take into account the intra-specimen variability, the material resistance against crack propagation is treated as an 1-dimensional spatial stochastic process, i. e. random field, varying along the propagation path. For the inter-specimen variability, C in paris equation is assumed to be a random variable. Compared with experimental results reported, the present method well estimate the variation in fatigue crack propagation life. And it is confirmed that the thicker the specimen thickness is, the less the variation of propagation life is.

Fatigue Crack Propagation Life Assessment of T-joint Fillet Weldment Considering Residual Stress under Random Loading (변동하중하의 잔류응력을 고려한 십자형 용접부의 잔존 수명 예측에 관한 연구)

  • Kim, Sung-Hoon;Kim, Kyung-Su;Lee, Jang-Hyun;Yoo, Chang-Hyuk;You, Won-Hyo;Yoo, Mi-Ji
    • Journal of Welding and Joining
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    • v.29 no.2
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    • pp.46-55
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    • 2011
  • This paper deals with the crack propagation life assessment of T-joint welded structure where typical fatigue cracks have been frequently initiated when the marine vessels experience the storm load. Welding residual stresses are calculated to investigate its effects on the fatigue life. Thereafter the residual stress distribution was applied to the AFGROW life prediction program, which incorporated the loading, the welding residual stress, and the geometric shape of the structure. The fatigue tests of the T-joint welded specimen under storm loading show the beach mark clearly generated on the fractured section of the weldment. The crack propagation life estimated based on the beach mark is compared with that of AFGROW to validate the life prediction. Based on the results, the evaluation method of the remaining fatigue life for T-joint fillet weldment of marine vessel's cargo hold with random load or storm load was established.

Generation of Pseudo-Random Load Waves and Preliminary Study on Surface Fatigue Crack Growth under Random Loading (유사랜덤하중파형 작성과 이를 이용한 랜덤하중하의 표면피로 균열진전에 관한 기초적 검토)

  • 송지호;김종한;김정엽
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.125-134
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    • 1989
  • Pseudo-random load waves for fatigue testing were generated by personal computer simulation and preliminary study was performed on the growth behavior of surface fatigue crack under random ladings. The closure behavior and growth rates of surface fatigue crack were significantly influenced by the characteristics of random waves. It was also found that the growth rates of surface fatigue crack under random loadings could not be always described by the effective stress intensity factor based on the concept of crack closure.

Stochastic ship roll motion via path integral method

  • Cottone, G.;Paola, M. Di;Ibrahim, R.;Pirrotta, A.;Santoro, R.
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.2 no.3
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    • pp.119-126
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    • 2010
  • The response of ship roll oscillation under random ice impulsive loads modeled by Poisson arrival process is very important in studying the safety of ships navigation in cold regions. Under both external and parametric random excitations the evolution of the probability density function of roll motion is evaluated using the path integral (PI) approach. The PI method relies on the Chapman-Kolmogorov equation, which governs the response transition probability density functions at two close intervals of time. Once the response probability density function at an early close time is specified, its value at later close time can be evaluated. The PI method is first demonstrated via simple dynamical models and then applied for ship roll dynamics under random impulsive white noise excitation.

Parameter Sensitivity Study on Fatigue Crack Propagation Life Under Random Loadings (Random하중하의 피로크랙 진전수명에 대한 파라미터의 영향도평가)

  • 윤한용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.46-50
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    • 1993
  • The sensitivity study to evaluate the effects of parameters on the fatigue crack propagation life under the constant loadings is executed in the previous study of the authors. It is shown that the effect of the crack opening ratio is large comparatively. The purpose of this paper is to evaluate the effects of parameters on the fatigue crack propagation life under the random loadings. A new method of evaluation of the effective stress under the random loadings is developed. The sensitivity study of parameters on the fatigue crack propagation life under the random loadings is executed by using it.

Quasi-static cyclic displacement pattern for seismic evaluation of reinforced concrete columns

  • Yuksel, E.;Surmeli, M.
    • Structural Engineering and Mechanics
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    • v.37 no.3
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    • pp.267-283
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    • 2011
  • Although earthquakes generate random cyclic lateral loading on structures, a quasi-static cyclic loading pattern with gradually increasing amplitude has been commonly used in the laboratory tests because of its relatively low cost and simplicity compared with pseudo-dynamic and shake table tests. The number, amplitudes and sequence of cycles must be chosen appropriately as important parameters of a quasi-static cyclic loading pattern in order to account for cumulative damage matter. This paper aims to reach a new cyclic displacement pattern to be used in quasi-static tests of well-confined, flexure-dominated reinforced concrete (RC) columns. The main parameters of the study are sectional dimensions, percentage of longitudinal reinforcement, axial force intensity and earthquake types, namely, far-fault and near-fault.

Evaluation of structural dynamic responses by stochastic finite element method

  • Li, Q.S.;Fang, J.Q.;Liu, D.K.
    • Structural Engineering and Mechanics
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    • v.8 no.5
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    • pp.477-490
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    • 1999
  • The uncertainties associated with structural parameters and dynamic loading are identified and discussed. Structural parametric uncertainties are treated as random variables and dynamic wind load is simulated as a random process. Dynamic wind-induced responses of structures with parametric uncertainties are investigated by using stochastic finite element method. The formulas for structural dynamic reliability analysis considering the randomness of structural resistance and loading are proposed. Two numerical examples of high-rise structures are presented to illustrate the proposed methodology. The calculated results demonstrate that the variation in structural parameters indeed influences the dynamic response and the first passage probability evaluation of structures.

Random Vibration and Harmonic Response Analyses of Upper Guide Structure Assembly to Flow Induced Loads (유체유발하중을 받는 상부안내구조물의 랜덤진동 및 조화응답해석)

  • 지용관;이영신
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.1
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    • pp.59-68
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    • 2002
  • The cylindrical Upper Guide Structure assembly of the reactor intervals wish the Core Support Barrel and the Inner Barrel Assembly is subjected to flow induced loads horizontally which include random pressure fluctuation due to turbulent flow and pump pulsation pressures. The purpose of this papers is to perform random vibration and harmonic response analyses fort flow induced loads. The dynamic response characteristics due to random turbulence and pump pulsation loads were evaluated using the lumped mass beam model. Especially the model considered the annulus effects due to water gaps existing between cylindrical structures such as the Upper Guide Structure Barrel, the Core Support Barrel, and the Inner Barrel Assembly. The effect of the Inner Barrel Assembly inside the Upper Guide Structure assembly was studied. The peak dynamic responses lot each loading condition due to the addition of IBA were affected by the natural frequencies of the structures. Therefore the peak dynamic responses of the structures should be conservatively obtained from evaluation of dynamic analysis for various loading conditions.

Comparison of Discrete Noise with Broadband Noise from Small-scaled UH-1H Rotor (축소형 UH-1H 로터에서의 광역소음과 이산소음의 비교)

  • Ryu, Ki-Wahn
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.1
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    • pp.20-25
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    • 2005
  • The thickness, loading, and broadband noise generated from the trailing edge of the UH-1H main rotor are numerically compared each other. The Kocureck and Tangler's prescribed wake model is adopted to represent the wake geometry during the hovering motion. Three tip Mach numbers of $M_{T}$ = 0.2, 0.4, and 0.8, are selected to analyze the effects of different tip Mach numbers. At $M_{T}$ = 0.8, in considering the A-weighting and audible frequency band, the random noise is smaller than the tonal noises such as the thickness and the loading noise which have the low frequency characteristics. Especially most of the random noise frequency spread on the ultrasound region. On the other hand, below $M_{T}$ = 0.4, the band of random noise moves to the audible frequency region, and the random noise becomes larger than the tonal noise. It turns out that the random noise analysis of the rotor should be necessary at low speed operating condition.

A Probabilistic Analysis of Soil- Structure Interaction Subjected to Seismic Loading (지진에 대한 지반-구조물 상호작용의 확률론적 연구)

  • Lee, In-Mo;Kim, Yong-Jin;Lee, Jeong-Hak
    • Geotechnical Engineering
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    • v.6 no.2
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    • pp.5-20
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    • 1990
  • In the seismic analysis of structures, where the dynamic soil-structure interaction (DSSI) is considred, earthquake input motions as well as dynamic soil properties are random in nature. To take into account the random nature of both the input motions and the dynamic soil properties systematically, a probabilistic analysis of the DSSI subjected to seismic loading is proposed in this paper, The complex response method formulized by the elastic half space theory, the random vibration theory, and the Rosenblueth's two-point estimate method are combined for the proposed probabilistic analysis. The conclusions drawn from this study are as follows ' 1) The uncertainty bands of the earthquake input motions proposed by Kanai-Tajimi as well as those of the dynamic properties are large the coefecients of variation of those parameters tinge from 0.4 to 0.6. 2) The uncertainties of the dynamic soil properties are more sensitive to the structural responses than those of the input motion parameters. 3) The effect of correlations between the input motion parameters and the dynamic soil properties is negligible.

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