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Abstract

The approach to numerical analyses was changed by the introduction of Eurocodes . The EN 1993-1-6 standard allows taking into account imperfections on the shape of a buckling form from a linear elastic bifurcation analysis. The article analyses the first ten forms of imperfection from a linear elastic bifurcation analysis on the reduction of the capacity of a cylindrical shell. Calculations were made using finite element methods.

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Authors and Affiliations

K. Schabowicz
Ł. Zawiślak
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Abstract

In this paper, the authors investigate a cylindrical shell reinforced by carbon nanotubes. The critical buckling load is calculated using analytical method when it is subjected to compressive axial load. The Mori-Tanaka method is firstly utilized to estimate the effective elastic modulus of composites having aligned oriented straight CNTs. The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. There is presented a study on the effects of CNTs volume fraction, thickness and aspect ratio of the shell, CNTs orientation angle, and the type of supports on the buckling load of cylindrical shells. Furthermore the effect of CNTs agglomeration is investigated when CNTs are dispersed none uniformly in the polymer matrix. It is shown that when the CNTs are arranged in 90 degrees direction, the highest critical buckling load appears. Also, the results are plotted for different longitudinal and circumferential mode numbers. There is a specific value for aspect ratio of the cylinder that minimizes the buckling load. The results reveal that for very low CNTs volume fractions, the volume fraction of inclusions has no important effect on the critical buckling load.

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Authors and Affiliations

Jafar Eskandari Jam
Esmail Asadi
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Abstract

The work is devoted to a horizontal tank composed of cylindrical shell closed with ellipsoidal heads and supported at the ends. The tank is loaded with internal or external pressure. For the first load case, a strength condition was formulated, for the other one -the condition of stability of the structure. An optimization model was formulated, in which the mass of the tank subject to the strength and stability conditions was assumed as an objective function. Optimal proportions of geometric dimensions for a family of the tanks of various capacities provided with heads of various convexities were determined. The results were presented in the form of plots. A function was proposed that approximated the solution and could be useful for purposes of designing of the tanks.
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Authors and Affiliations

Krzysztof Magnucki
ORCID: ORCID
Jerzy Lewiński
Piotr Stasiewicz
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Abstract

Cylindrical shells made of composite material form one of the major structural parts in aerospace structures. Many of them are acoustically thick, in which the ring frequencies are much higher than their critical frequencies. In this work, sound radiation behaviour of acoustically thick composite cylinders is presented. Based on the structural and acoustic wave number diagrams, the modal average radiation resistances in the frequency band of interest are theoretically determined. The structural wavenumbers are determined considering transverse shear deformation. The results show lesser sound radiation between the critical and ring frequencies, and significant sound radiation near the ring frequency and beyond. In the absence of the present results the radiation efficiency is considered to be unity at all frequencies beyond the critical frequency, including near the ring frequency. The radiation resistances of the same cylinder are determined experimentally and they are in very good agreement with the theoretical estimates. As part of this investigation, an expression for determining the ring frequency of composite cylinder is also presented.
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Bibliography

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Authors and Affiliations

S. Josephine Kelvina Florence
1
K. Renji
2

  1. Structures Group, U. R. Rao Satellite Centre, Bangalore, India-560017
  2. Advanced Technology Development Group, U. R. Rao Satellite Centre Bangalore, India-560017

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