1,721,044 research outputs found
The influence of an initial twisting on tapered beams undergoing large displacements
Full text linkThe behaviour of pre-twisted and tapered beams (such as turbine or helicopter blades) is characterized by stress distributions that may be quite different from those of the usual beam theory, yielding couplings among bending, twisting and traction. We propose a physical–mathematical model for tapered beams that accounts for the effects of the pre-twist of the cross-sections along the centre-line. The beam centre-line may undergo large displacements, while its cross-sections see small warping both in- and out of their plane. Supposing infinitesimal strain, a variational approach provides the field equations, which are
perturbed in terms of a small geometric ratio and shall be solved numerically in general. However, analytical closed-form solutions exist in some cases, such as for isotropic beams with pre-twisted, bi-tapered elliptic cross-sections; they are presented and compared with the results of nonlinear 3D-FEM simulations
Correction to: On inner constraints in plane circular arches (Archive of Applied Mechanics, (2004), 74, 3-4, (212-222), 10.1007/s00419-004-0344-7)
No full textThe series expansions in Eq. (16) of [1] for trigonometric functions depending on a small evolution parameter shall be corrected
Beamlike models for the analyses of curved, twisted and tapered horizontal-axis wind turbine (HAWT) blades undergoing large displacements
No full textContinuous ongoing efforts to better predict the mechanical behaviour of complex beamlike structures, such as wind turbine blades, are motivated by the need to improve their performance and reduce the costs. However, new design approaches and the increasing flexibility of such structures make their aeroelastic modelling ever more challenging. For the structural part of this modelling, the best compromise between computational efficiency and accuracy can be obtained via schematizations based on suitable beamlike elements. This paper addresses the modelling of the mechanical behaviour of beamlike structures which are curved, twisted and tapered in their unstressed state and undergo large displacements, in- and out-of-plane cross-sectional warping, and small strains. A suitable model for the problem at hand is proposed. Analytical and numerical results obtained by its application are presented and compared with results from 3D FEM analyses
Natural frequencies of parabolic arches with a single crack on opposite cross-section sides
No full textWe study natural vibration of elastic parabolic arches, modeled as plane curved beams susceptible to elongation, shear, and bending, exhibiting small concentrated cracks. The crack is simulated by springs between regular chunks, with stiffness evaluated following stress concentration in usual crack opening modes. We evaluate and compare the linear dynamic response of the undamaged and damaged arch in nondimensional form. The governing equations are turned into a system of first-order differential equations that are solved numerically by the so-called matricant. The original contribution of this study lies in highlighting the dependence of the variation of the first natural frequencies on the crack location not only along the axis but also on opposite sides of the cross-section. We obtain the relative variations of the first frequencies in terms of the two crack locations. The result of this direct problem provides information on the possibility to detect such locations, and gives indications on structural monitoring and damage identification
On inner shearing constraints for a direct beam model coarsely describing warping
No full textWe investigate inner shearing constraints for a direct one-dimensional beam model coarsely describing warping. In particular, we study how they affect the field equations for the elastic buckling of open thin-walled beams. We show that the distinction between the axes of the shear centres and of the centroids is crucial for the kinematics of the beam, and to derive expression of reactive actions, hence of buckling critical conditions. We also show how a suitable definition of the warping inertial action and properly introduced inner shearing constraints yield the field equations of the literature for the beam in a general dynamic setting. © 2013 Springer Science+Business Media Dordrecht
A DIRECT ONE-DIMENSIONAL BEAM MODEL FOR THE FLEXURAL-TORSIONAL BUCKLING OF THIN-WALLED BEAMS RID C-9350-2009
No full textIn this paper, the direct one-dimensional beam model introduced by one of the authors is refined to take into account nonsymmetrical beam cross-sections. Two different beam axes are considered, and the strain is described with respect to both. Two inner constraints are assumed: a vanishing shearing strain between the cross-section and one of the two axes, and a linear relationship between the warping and twisting of the cross-section. Considering a grade one mechanical theory and nonlinear hyperelastic constitutive relations, the balance of power, and standard localization and static perturbation procedures lead to field equations suitable to describe the flexural-torsional buckling. Some examples are given to determine the critical load for initially compressed beams and to evaluate their post-buckling behavior
The effect of warping on the dynamics of thin-walled beams
No full textthis contribution presents the effect of a coarse warping descriptor on the first natural angular frequencies of a clamped-clamped thin-walled beam with non-symmetric cross-sections. By means of a direct one-dimensional model, leading to ordinary differential field equations, the linear dynamics of such a pattern scheme is investigated. The effect of warping and warping constraints is taken into account, and the results are compared with those of a numerical commercial code and of a recent set of laboratory experiments. The agreement is satisfactory; we describe the investigations completing this contribution, which are in due course
"Un modello modnodimansionale per l'analisi della biforcazione flesso-torsionale di travi di spessore sottile"
No full textXVII Congresso Nazionale di Meccanica Teoria ed Applicata, Firenze 11-15 settembre 200
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