A measure of the equivalent shear stress amplitude from a prismatic hull in the principal coordinate system

“…is the square root of the amplitude of the second invariant of the random deviatoric stress tensor, R i ( ) , with i = 1 to 5 , are the semi-axes of the five-dimension prismatic hull circumscribed to the loading path of, √ J 2a ( ) , obtaining by applying an orthogonal transformation using a matrix composed by the five eigenvectors of the principal axes of the loading path, as discussed in [15].…”

Section: Probabilistic Fatigue Model For the Stochastic Viscoelastic mentioning

confidence: 99%

“…In this study, the estimation of, √ J 2a ( ) , is based on the first two statistical moments (mean and variance) of the semi-axes, R i ( ) , of a five-dimension prismatic hull circumscribing the loading path of, √ J 2a ( ) , as discussed in [15]. In this case, among the strategies normally employed to estimate the distribution of extreme values over a period of time, the developments made by Preumont [16] are retained here, in which the statistical moments of, R i ( ) , are given by:…”

Section: Probabilistic Fatigue Model For the Stochastic Viscoelastic mentioning

confidence: 99%

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Fatigue damage investigation and optimization of a viscoelastically damped system with uncertainties

Gonçalves

Rosa

Lima

2019

J Braz. Soc. Mech. Sci. Eng.

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The need for larger and more efficient structures has led to the development of numerical models to approach real-world complex behaviors. Normally, engineering systems consider deterministic parameters, while in real-world situations, they are subjected to parametric uncertainties, resulting in differences between the calculated responses. This work is devoted to performing numerical and computational studies of fatigue damage analyses of viscoelastically damped systems in the frequency domain subjected to parametric uncertainties. Here, the discretization of the random field is performed using the finite element method combined with the Karhunen-Loève expansion and the fatigue damage index is estimated by applying the so-called Sines' global criterion. Optimization techniques were applied in order to obtain the optimal design of surface viscoelastic treatments in terms of fatigue. Therefore, the main contribution intended for the present study is to show the importance of considering optimal-robust parameters to estimate the failure probability of engineering structures with constrained viscoelastic layers. After presenting the underlying foundations, the numerical results are presented and the main features of the proposed methodology are highlighted.

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“…Such stresses imply a risk of fatigue failure which must be taken into account during the design stage to ensure structural integrity. In this study, we are concerned with the infinite fatigue life, that is based on the greatest stress values reached during the service life Khalij et al, 2010). By taking into account their randomness, this leads us to study their multivariate extreme value distributions.…”

Section: Introductionmentioning

confidence: 99%

Generation of stationary Gaussian processes and extreme value distributions for high-cycle fatigue models - application to tidal stream Turbines

Suptille¹,

Pagnacco²,

Khalij³

et al. 2012

J. Braz. Soc. Mech. Sci. & Eng.

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The operating environment of tidal stream turbines is random due to the variability of the sea flow (turbulence, wake, tide, streams, among others). This yields complex time-varying random loadings, making it necessary to deal with high cycle multiaxial fatigue when designing such structures. It is thus required to apprehend extreme value distributions of stress states, assuming they are stationary multivariate Gaussian processes. This work focus on such distributions, addressing their numerical simulation with an analytical description. For that, we first focused on generating one-dimensional Gaussian processes, considering a band-limited white noise in both the narrow-band and the wide-band cases. We then fitted the resulting extreme value distributions with GEV distributions. We secondly extended the generation method to the correlated two-dimensional case, in which the joint extreme value distribution can be obtained from the associated margins. Finally, an example of application related to tidal stream turbines introduces a Bretschneider spectrum, whose shape is commonly encountered in the field of hydrology. Comparing the empirical calculations with the GEV fits for the extreme value distributions shows a very well agreement between the results. Nomenclature Acronyms AR = Average Random EV D = Extreme Value Distribution GEV = Generalized Extreme Value IFFT = Inverse Fast Fourier Transform MA = Moving Average PSD = Power Spectrum Density Operators arg [•] = argument of the complex number • E [•] = statistical expectation of • Prob [•] = probability of the event •

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A measure of the equivalent shear stress amplitude from a prismatic hull in the principal coordinate system

Cited by 15 publications

References 20 publications

Investigations of the quadrature phase impact on the behavior of the Liu & Mahadevan’s criterion for fully reversed bending–torsion experiments

Investigations of the quadrature phase impact on the behavior of the Liu & Mahadevan’s criterion for fully reversed bending–torsion experiments

Fatigue damage investigation and optimization of a viscoelastically damped system with uncertainties

Generation of stationary Gaussian processes and extreme value distributions for high-cycle fatigue models - application to tidal stream Turbines

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