Quick and clean technology for composite cylinder stability analysis

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Thin-walled cylindrical shells (radius-to-thickness ratio of 160-500) under different loading conditions have been studied for structural stability (Figure 1). Based on this study, guidelines for the selection of the element mesh density have been set. 

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Figure 1. Cylinder load cases

 

A set of problems presented in References [1-5] (Figure 2) has been solved with ESAComp using different mesh densities. The load types considered were axial compression, torsion, and bending. The number of elements in the hoop direction was set to vary from 40 to 240 while the element aspect ratio was set to one. Convergence studies were made and the results are presented for the axial load in Figure 3a. Respectively, results for the torsion and bending cases are shown in Figure 3b. The reserve factor against buckling (indicated on the vertical axis) has been normalized against the value obtained with 240 elements in the hoop direction. A short summary for the problems are presented in the table shown in Figure 2. The deviation (%) indicates the difference between the ESAComp results with respect to the reference results at the converged state. 

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Figure 2. Cylinder configurations

 

As an outcome of this study it can be concluded that in axial load dominated buckling 160 elements are needed in the hoop direction to achieve reasonable accuracy, i.e. the deviation from the converged result is less than 10%. For torsion and bending dominated buckling, 120 elements is a sufficient number to guarantee the same accuracy since in these problems buckling wave lengths are longer. It should be noted that in this study cylinder diameter-to-length ratio was equal or close to one.

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Figure 3. Convergence as a function of elements in the hoop direction

 

The study demonstrates that ESAComp is reliable tool for the design-analysis of cylindrical shells and a valuable benchmark tool to be used together with other software tools. ESAComp capabilities will be demonstrated at the 3rd Int. Conference on Buckling and Postbuckling Behaviour of Composite Laminated Shell Structures in March. See you in Braunschweig!

 

© 2015 Componeering Inc, by Harri Katajisto