1,721,087 research outputs found
On the performance of advanced three-dimensional models for cylindrically bent plates subjected to arbitrary boundary conditions
No full textBased on recent researches (e.g. [1–3]) aimed at approaching the three-dimensional dynamical values (natural frequencies and mode shapes) of multilayered plates subjected to classical although arbitrary boundary conditions, the interest of the present communication is based on the attempt to test the pres- ent simple analytical approach while preserving the accuracy of the results within the frame of the exist- ing modern calculators. Such an attempt has been previously pursued by the present author through the classical theorem of virtual displacements along with the adoption of the global piecewise smooth func- tions (GPSFs) [4]; as is shown by Messina and Rollo [2] and Messina [3], such a formalization has allowed one to deal with a multilayered architecture as if the plates were made up of a single layer sub- jected to classical arbitrary boundary conditions with, these latter, even dealt with through only three distinct functional bases. The fact that any explicit continuity conditions of the relevant interfacial stress components are not explicitly introduced could be worth mentioning. The above-mentioned analyses left, however, open questions; indeed, Messina [3] noticed certain boundary conditions as mainly respon- sible for a low convergence of eigenvalues to the expected exact three-dimensional counterparts.
After investigating the mentioned influence of boundary conditions [3], this writer became aware of static analyses of possible relevant interest. In particular, this writer noticed with extreme interest the paper by Vel and Batra [5] to which the attention of this note is essentially addressed. Vel and Batra [5] analysed the generalized plane strain deformations from a static point of view and by using the Eshelby– Stroh formalism. In spite of the different nature of the problem (static in [5], dynamic in [1,3]) we must accept the fact that a possible slack convergence at exact values in a static analysis is a particular aspect of its dynamic counterpart and vice versa.
Therefore, this author discusses the performance of the Eshelby–Stroh formalism, illustrated by Vel and Batra [5], in comparison to the capability of an analytical model to deal with multilayered plates as if they were made up of a single layer architecture [1,3] within the frame of static deformations. Interestingly the comparison will show how sometimes the explicit introduction of the required natural boundary conditions can reduce the accuracy of the results. Moreover, it is shown how the GPSFs bring remarkable benefits when used to model multilayered plates; the benefits can even increase when the GPSFs are used in multiple dimensions rather than only through the thickness of the plate. In passing, and finally, the present comparison shows a slight disagreement with Vel and Batra [5] for few transver- sal stress component distributions; this slight disagreement, however, is definitely of extremely minor importance when compared to the clean and helpful frame offered by the analysis of [5]
DETECTING DAMAGE IN BEAMS THROUGH DIGITAL DIFFERENTIATOR FILTERS AND CONTINUOUS WAVELET TRANSFORMS
No full textSeveral papers that have recently appeared in the literature have shown the potential offered by certain
mathematical tools (wavelets) for detecting damage in systems such as transversally vibrating beams.
However, although the applications shown by different authors suggest that the tools show promise, the
literature lacks a clear and concise collocation of the wavelets with respect to these previous methods that
show similar (if not identical in certain circumstances) performances. In this paper, the continuous wavelet
transforms (cwts) are discussed and compared, from a theoretical and numerical point of view, with those
methods known as differentiator operators. Such differentiator operators adopted as filters are also able
(similarly to the cwts) to reduce unwanted high frequency noise. Therefore, literature concerning
differentiator filters in the digital signal processing area is investigated and several digital filters, known and
modified, are analyzed and compared withth e cwts in the presence of Gaussian noise. The theoretical
aspects are discussed in both the non-transformed and Fourier transformed domain. This study results in
an attempt to provide an elucidation on the effectiveness and the need to use the considered methods
(differentiator filters and/or cwts) for detecting damage in transversally vibrating beams
Three dimensional free vibration analysis of cross-ply laminated plates through 2D and exact models
No full textDiagnostica di sistemi strutturali mediante l'analisi di sensibilità di parametri modali: un approccio numerico-sperimentale
No full textTesi di Dottorato di Ricerca, discussa presso Università degli Studi di Napoli "Federico II"
Analyses of freely vibrating cross-ply laminated plates in conjunction with adaptive global piecewise-smooth functions (A-GPSFs)
No full textRefinements of damage detection methods based on wavelet analysis of dynamical shapes
No full textAbstractThis manuscript aims at illustrating significant refinements concerning the use of wavelets, when these latter are used in the guise of continuous wavelet transforms (CWT) for identifying damage on transversally vibrating structural components (e.g. beams, plates and shells). The refinements regard the presentation of wavelet-algorithms which are aimed at significantly reducing those border distortions normally arising during a wavelet-damage detection procedure. The main advantage of the algorithms is that they are self-contained, namely: (i) the wavelet transforms do not undergo any own variation and their application follows the convolution laws established in the past; (ii) it is not necessary to design a specific boundary wavelet; (iii) no significant analytical treatment neither of the wavelets nor of the signal is required and, finally, (iv) the algorithms can be adapted to different boundary conditions and different physical situations. Besides all the specified advantages, the wavelet-damage detection procedure is still carried out by excluding historical data. The effectiveness of the algorithms is shown through numerical and experimental examples. These latter are illustrated along with reduced outliers of experimental estimation through a related consistent statistical procedure
Free vibrations of multilayered plates based on a mixed variational approach in conjunction with global piecewise-smooth functions
No full textFree vibrations of multilayered doubly-curved shells based on a mixed variational approach and global piecewise-smooth functions
No full textDanneggiamenti locali su componenti meccanici elementari mediante trasformate indina continua e filtri digitali derivatori: identidicazioni numeriche e sperimentali
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