The Experts below are selected from a list of 53016 Experts worldwide ranked by ideXlab platform
Francesco Pellicano - One of the best experts on this subject based on the ideXlab platform.
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dynamic stability and sensitivity to geometric imperfections of strongly compressed circular cylindrical shells under dynamic Axial Loads
Communications in Nonlinear Science and Numerical Simulation, 2009Co-Authors: Francesco PellicanoAbstract:Abstract In the present paper, the dynamic stability of circular cylindrical shells is investigated; the combined effect of compressive static and periodic Axial Loads is considered. The Sanders–Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration; Lagrange equations are used to reduce the nonlinear partial differential equations to a set of ordinary differential equations. The dynamic stability is investigated using direct numerical simulation and a dichotomic algorithm to find the instability boundaries as the excitation frequency is varied; the effect of geometric imperfections is investigated in detail. The accuracy of the approach is checked by means of comparisons with the literature.
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dynamic instability and chaos of empty and fluid filled circular cylindrical shells under periodic Axial Loads
Journal of Sound and Vibration, 2006Co-Authors: Francesco Pellicano, Marco AmabiliAbstract:Abstract In the present paper the dynamic stability of circular cylindrical shells subjected to static and dynamic Axial Loads is investigated. Both Donnell's nonlinear shallow shell and Sanders–Koiter shell theories have been applied to model finite-amplitude static and dynamic deformations. Results are compared in order to evaluate the accuracy of these theories in predicting instability onset and post-critical nonlinear response. The effect of a contained fluid on the stability and the post-critical behaviour is analyzed in detail. Geometric imperfections are considered and their influence on the dynamic instability and post-critical behaviour is investigated. Chaotic dynamics of pre-compressed shells is investigated by means of nonlinear time-series techniques, extracting correlation dimension and Lyapunov exponents.
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stability and vibration of empty and fluid filled circular cylindrical shells under static and periodic Axial Loads
International Journal of Solids and Structures, 2003Co-Authors: Francesco Pellicano, Marco AmabiliAbstract:Abstract In the present study, the dynamic stability of simply supported, circular cylindrical shells subjected to dynamic Axial Loads is analysed. Geometric nonlinearities due to finite-amplitude shell motion are considered by using the Donnell’s nonlinear shallow-shell theory. The effect of structural damping is taken into account. A discretization method based on a series expansion involving a relatively large number of linear modes, including axisymmetric and asymmetric modes, and on the Galerkin procedure is developed. Axisymmetric modes are included; indeed, they are essential in simulating the inward deflection of the mean oscillation with respect to the equilibrium position and in describing the axisymmetric deflection due to Axial Loads. A finite length, simply supported shell is considered; the boundary conditions are satisfied, including the contribution of external Axial Loads acting at the shell edges. The effect of a contained liquid is investigated. The linear dynamic stability and nonlinear response are analysed by using continuation techniques and direct simulations.
Shao Yongbo - One of the best experts on this subject based on the ideXlab platform.
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analysis of stress concentration factor of welded tubular k joints subjected to Axial Loads
Journal of Ship Mechanics, 2010Co-Authors: Shao YongboAbstract:The geometrical and numerical modelling of welded tubular K-joints is presented in this study.The stress concentration factors along the weld toe in the hot spot stress region for tubular K-joints subjected to balanced Axial Loads are obtained through experimental tests on two large-scale tubular K-joints.The accuracy of the numerical stress concentration factors is verified from experimental results.The effect of the geometrical parameters on the stress concentration factor of tubular K-joints under Axial Loads is investigated based on the finite element results of 1 008 K-joints models with different geometries.Finally,a set of parametric equations to predict the stress concentration factor of a tubular K-joint subjected to balanced Axial Loads is proposed,and these parametric equations are deduced from nonlinear regression and curve fitting technique.The accuracy of the parametric equations is also evaluated.
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parametric equation of stress intensity factor for tubular k joint under balanced Axial Loads
International Journal of Fatigue, 2005Co-Authors: Shao Yongbo, Lie Seng TjhenAbstract:In this paper, an automatic mesh generation method, which is for a uni-planar tubular K-joint containing an arbitrary surface crack located along the chord weld toe, is developed for producing the complete finite element mesh model. Using the proposed model, the stress intensity factors along the crack front have been evaluated by an interaction J-integral method in this study. To evaluate the reliability and accuracy of the numerical stress intensity factor results, a full-scale K-joint specimen was tested to failure. Using alternating current potential drop (ACPD) technique, the crack growth rate is captured and the stress intensity factors of the specimen are obtained using Paris' equation. It has been found that numerical stress intensity factor results agree with experimental results quite well. Thereafter, altogether 5120 numerical models of tubular K-joints containing a surface crack at the crown subjected to balanced Axial Loads have been analyzed. A parametric stress intensity factor equation has then been proposed. The accuracy of the proposed stress intensity factor equation has been assessed by comparing the computing results from the equation with the numerical results. Error analysis has been conducted and it shows that the proposed equation can provide reliable and accurate estimation of stress intensity factor for cracked tubular K-joints under balanced Axial Loads.
Philip W. Loveday - One of the best experts on this subject based on the ideXlab platform.
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Guided Wave Propagation as a Measure of Axial Loads in Rails
Proceedings of SPIE, 2010Co-Authors: Philip W. Loveday, Paul D. WilcoxAbstract:Guided wave propagation has been proposed as a means to monitor the Axial Loads in continuously welded railway rails although no practical system has been developed. In this paper, the influence of Axial load on the guided wave propagation characteristics was analyzed using the semi-analytical finite element method, extended to include Axial Loads. Forty modes of propagation were analyzed up to a maximum frequency of 100 kHz. The sensitivity of the modes to Axial load or changes in elastic modulus was formulated analytically and computed. In practice, by using separation of signals in time it would only be possible to separate the mode with the greatest group velocity over a reasonable distance. It was found that the influence of Axial load on the wavelength of such a mode should be measureable. However, the influence of changes in the elastic modulus due to temperature is expected to be an order of magnitude larger. In order to develop a practical measurement technique it would be necessary to eliminate or compensate for this and other influences.
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semi analytical finite element analysis of elastic waveguides subjected to Axial Loads
Ultrasonics, 2009Co-Authors: Philip W. LovedayAbstract:Predicting the influence of Axial Loads on the wave propagation in structures such as rails requires numerical analysis. Conventional three-dimensional finite element analysis has previously been applied to this problem. The process is tedious as it requires that a number of different length models be solved and that the user identify the computed modes of propagation. In this paper, the more specialised semi-analytical finite element method is extended to account for the effect of Axial load. The semi-analytical finite element method includes the wave propagation as a complex exponential in the element formulation and therefore only a two-dimensional mesh of the cross-section of the waveguide is required. It was found that the stiffness matrix required to describe the effect of Axial load is proportional to the mass matrix, which makes the extension to existing software trivial. The method was verified by application to an aluminium rod, where after phase and group velocities of propagating waves in a rail were computed to demonstrate the method.
Patrice Cartraud - One of the best experts on this subject based on the ideXlab platform.
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mechanical modeling of helical structures accounting for translational invariance part 2 guided wave propagation under Axial Loads
International Journal of Solids and Structures, 2013Co-Authors: Fabien Treyssede, Ahmed Frikha, Patrice CartraudAbstract:This paper corresponds to the second part of a study that aims at modeling helical structures accounting for translational invariance. In the Part 1 of this paper, the static behavior has been addressed using a helical homogenization approach which provides the stress state corresponding to Axial Loads. The latter is considered as a prestressed state, for elastic wave propagation analysis in helical waveguides, which is the subject of the Part 2 of this paper. Non destructive testing of springs and multi-wire strands is a potential application of the proposed model. Accounting for translational invariance, the elastodynamic equations of prestressed helical structures yield a 2D problem posed on the cross-section, corresponding to a so-called semi-analytical finite element (SAFE) formulation. For helical springs, the numerical model is validated with an analytical solution corresponding to a Timoshenko beam approximation. It is shown that the influence of the prestressed state is significant at low frequencies. Finally, a seven-wire strand subjected to Axial Loads is considered. The computed dispersion curves are compared to experimental data. Good agreement is obtained for the first compressional-like modes and their veering central frequency.
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Analytical modeling of synthetic fiber ropes subjected to Axial Loads. Part I: A new continuum model for multilayered fibrous structures
International Journal of Solids and Structures, 2007Co-Authors: Seyed Reza Ghoreishi, Patrice Cartraud, Peter Davies, Tanguy MessagerAbstract:Synthetic fiber ropes are characterized by a very complex architecture and a hierarchical structure. Considering the fiber rope architecture, to pass from fiber to rope structure behavior, two scale transition models are necessary, used in sequence: one is devoted to an assembly of a large number of twisted components (multilayered), whereas the second is suitable for a structure with a central straight core and six helical wires (1 + 6). The part I of this paper first describes the development of a model for the static behavior of a fibrous structure with a large number of twisted components. Tests were then performed on two different structures subjected to Axial Loads. Using the model presented here the Axial stiffness of the structures has been predicted and good agreement with measured values is obtained. A companion paper presents the second model to predict the mechanical behavior of a 1 + 6 fibrous structure.
Marco Amabili - One of the best experts on this subject based on the ideXlab platform.
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dynamic instability and chaos of empty and fluid filled circular cylindrical shells under periodic Axial Loads
Journal of Sound and Vibration, 2006Co-Authors: Francesco Pellicano, Marco AmabiliAbstract:Abstract In the present paper the dynamic stability of circular cylindrical shells subjected to static and dynamic Axial Loads is investigated. Both Donnell's nonlinear shallow shell and Sanders–Koiter shell theories have been applied to model finite-amplitude static and dynamic deformations. Results are compared in order to evaluate the accuracy of these theories in predicting instability onset and post-critical nonlinear response. The effect of a contained fluid on the stability and the post-critical behaviour is analyzed in detail. Geometric imperfections are considered and their influence on the dynamic instability and post-critical behaviour is investigated. Chaotic dynamics of pre-compressed shells is investigated by means of nonlinear time-series techniques, extracting correlation dimension and Lyapunov exponents.
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stability and vibration of empty and fluid filled circular cylindrical shells under static and periodic Axial Loads
International Journal of Solids and Structures, 2003Co-Authors: Francesco Pellicano, Marco AmabiliAbstract:Abstract In the present study, the dynamic stability of simply supported, circular cylindrical shells subjected to dynamic Axial Loads is analysed. Geometric nonlinearities due to finite-amplitude shell motion are considered by using the Donnell’s nonlinear shallow-shell theory. The effect of structural damping is taken into account. A discretization method based on a series expansion involving a relatively large number of linear modes, including axisymmetric and asymmetric modes, and on the Galerkin procedure is developed. Axisymmetric modes are included; indeed, they are essential in simulating the inward deflection of the mean oscillation with respect to the equilibrium position and in describing the axisymmetric deflection due to Axial Loads. A finite length, simply supported shell is considered; the boundary conditions are satisfied, including the contribution of external Axial Loads acting at the shell edges. The effect of a contained liquid is investigated. The linear dynamic stability and nonlinear response are analysed by using continuation techniques and direct simulations.
