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Tesi etd-11262006-211639


Thesis type
Tesi di laurea specialistica
Author
Del Medico, Francesco
email address
dlmfra@libero.it
URN
etd-11262006-211639
Title
Buckling of laminated-composite cylindrical shells under axial compression
Struttura
INGEGNERIA
Corso di studi
INGEGNERIA MECCANICA
Commissione
Relatore Ing. Biagi, Michele
Relatore Prof. Bertini, Leonardo
Relatore Prof. Beghini, Marco
Parole chiave
  • Galerkin
  • shell
  • buckling
  • composite
Data inizio appello
13/12/2006;
Consultabilità
parziale
Data di rilascio
13/12/2046
Riassunto analitico
A deep investigation upon stability of laminated-composite cylindrical shells under axial compression is presented and analytical methods for shell design criteria are demonstrated and discussed.<br><br>In the first part the classical Donnell-type solution of the buckling problem of geometrically perfect cylindrical shells is presented; a comparison between the results found out with this solution and those obtained with Finite Elements Analysis in NASTRAN highlights the need of different approaches for orthotropic shells. New algorithms SOLBUC-1 and SOLBUC-2 are proposed and appear in good accordance with FEM results.<br><br>In the second part, an analysis of experimental results on a selected group of laminated-composite cylindrical shells puts in evidence the high sensibility of these structures to geometrical imperfections.<br><br>NASA approach currently used in industry is based on the introduction of &#34;knock-down factors&#34; that, infact, yield over-conservative Critical Buckling Loads; new design approaches are proposed leading to a good mark-up in comparison to NASA results.<br><br>In particular, an analytical solution of non-linear fourth-order partial differential stability equations considering axis-symmetrical imperfection is presented in new algorithm SOLDIF and leads to new Buckling Load &#34;knock-down factors&#34;. These new &#34;knockdown factors&#34; appear substantially improved and hence less conservative than the corresponding &#34;knockdown factors&#34; presently used in the industry.<br><br>Furthermore, the results show that the improved analytical-based knockdown factor presented always yields a safe estimate of the buckling load of the shells examined in this work.
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