A Proposed Design Chart to Predict the Inelastic Buckling Pressures for Conical Shells Under Uniform External Pressure

2007 ◽  
Vol 44 (02) ◽  
pp. 77-81
Author(s):  
Carl T. F. Ross
Keyword(s):  
Factor Of Safety ◽  
Random Distribution ◽  
External Pressure ◽  
External Hydrostatic Pressure ◽  
Circular Section ◽  
Inelastic Buckling ◽  
Conical Shells ◽  
Uniform External Pressure ◽  
Design Chart ◽  
Design Charts

The paper presents the theoretical and experimental results obtained when 15 machined circular section conical shells were tested to destruction under uniform external hydrostatic pressure. Three of the shells buckled elastically, but the other 12 buckled inelastically. Previous research has found that the inelastic buckling of such shells with small initial out-of-circularity has defied exact mathematical analysis, due to the fact that the initial out-of-circularity is very small and also of random distribution about the circumference. In this paper these results are used to provide a design chart that enables the inelastic buckling pressures of these vessels to be successfully determined. This design chart should prove to be more accurate, but less conservative, than existing design charts, so that the factor of ignorance is decreased and more reliability can be placed on the true factor of safety.

Plastic General Instability of Ring—Reinforced Conical Shells Under Uniform External Pressure

2007 ◽  
Vol 44 (04) ◽  
pp. 268-277
Author(s):  
Carl T.F. Ross ◽  
Andrew P. F. Little ◽  
Robert Allsop ◽  
Charles Smith ◽  
Marcus Engelhardt
Keyword(s):  
Experimental Tests ◽  
External Pressure ◽  
Elastic Buckling ◽  
Conical Shells ◽  
Uniform External Pressure ◽  
Design Chart ◽  
Circular Conical Shells ◽  
High Degree ◽  
Very High ◽  
Ring Shell

The paper describes experimental tests carried out on three ring-reinforced circular conical shells that suffered plastic general instability under uniform external pressure. In this mode, the entire ring-shell combination buckles bodily in its flank. The cones were carefully machined from EN1A mild steel to a very high degree of precision. The paper also provides a design chart using the results obtained from these three vessels, together with the results of nine other vessels obtained from other tests. All 12 vessels failed by general instability. The design chart allows the possibility of obtaining a plastic knockdown factor, so that the theoretical elastic buckling pressures for perfect vessels can be divided by the plastic knockdown factor, to give the predicted buckling pressure. This method can also be used for the design of full-scale vessels.

scholarly journals Plastic General Instability of Ring-Stiffened Conical Shells under External Pressure

2008 ◽  
Vol 13-14 ◽  
pp. 213-223 ◽  
Author(s):  
Carl T.F. Ross ◽  
G. Andriosopoulos ◽  
Andrew P.F. Little
Keyword(s):  
Finite Element ◽  
Experimental Tests ◽  
Theoretical Work ◽  
External Pressure ◽  
Finite Element Program ◽  
Conical Shells ◽  
Uniform External Pressure ◽  
Design Charts ◽  
Circular Conical Shells ◽  
Element Program

The paper describes experimental tests carried out on three ring-stiffened circular conical shells that suffered plastic general instability under uniform external pressure. The cones were carefully machined from EN1A mild steel to a very high degree of precision. The end diameters of the cones, together with their thicknesses were the same, but the size of their ring stiffeners was different for each of the three vessels. In the general instability mode of collapse, the entire ring-shell combination buckles bodily in its flank. The paper also provides three design charts using the results obtained from these three vessels, together with the results obtained for twelve other vessels from other tests. All 15 vessels failed by general instability. One of these design charts was based on conical shell theory and two of the design charts were based on the general instability of ring-stiffened circular cylindrical shells, using Kendrick’s theory, which were made equivalent to ring-stiffened circular conical shells suffering from general instability under uniform external pressure. The design charts allowed the possibility of obtaining plastic knockdown factors, so that the theoretical elastic buckling pressures, for perfect vessels, could be divided by the appropriate plastic knockdown factor, to give the predicted buckling pressure. The theoretical work is based on the solutions of Kendrick, together with the finite element program of Ross, namely RCONEBUR and the commercial finite element package ANSYS. This method can also be used for the design of full-scale vessels.

Inelastic Shell Instability of Geometrically Imperfect Aluminum Alloy Circular Cylinders under Uniform External Pressure

2008 ◽  
Vol 45 (03) ◽  
pp. 175-181
Author(s):  
Carl T. F. Ross ◽  
Andrew P. F. Little ◽  
Graham Brown ◽  
Aravinthan Nagappan
Keyword(s):  
Aluminum Alloy ◽  
Hydrostatic Pressure ◽  
Analytical Solution ◽  
Structural Design ◽  
External Pressure ◽  
Circular Cylinders ◽  
External Hydrostatic Pressure ◽  
Element Analysis ◽  
Uniform External Pressure ◽  
Design Chart

The paper presents new experimental results on the collapse of unstiffened aluminum alloy circular cylinders suffering elastic and plastic nonsymmetric bifurcation buckling under external hydrostatic pressure. These results complement the results given in two previous Marine Technology papers written by the senior author, which were intended for the structural design of near-perfect unstiffened and ring-stiffened circular conical shells under external hydrostatic pressure. The present paper presents a structural design chart for geometrically imperfect circular cylinders under uniform external pressure, which is more likely to be used than the design charts for the previous near-perfect vessels because it represents the more "usual" case. In addition to an experimental analysis, theoretical analyses were also carried out. An analytical solution by von Mises was used, together with a finite element analysis solution, using the Shell 93 element of the ANSYS computer package. Comparison between ANSYS and the analytical solution was reasonable. A design chart is provided, which looks like it could be quite useful for practical purposes.

Locally imperfect conical shells under uniform external pressure

2013 ◽  
Vol 45 (3) ◽  
pp. 369-377 ◽  
Author(s):  
T. Ghanbari Ghazijahani ◽  
H. Showkati
Keyword(s):  
External Pressure ◽  
Conical Shells ◽  
Uniform External Pressure

Plastic Buckling of Conical Shells

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
J. Błachut ◽  
O. Ifayefunmi
Keyword(s):  
Axial Compression ◽  
Static Stability ◽  
External Pressure ◽  
Single Type ◽  
Simultaneous Action ◽  
External Hydrostatic Pressure ◽  
Conical Shells ◽  
Computer Numerically Controlled ◽  
Experimental Values ◽  
Yield Force

This paper studies the static stability of metal cones subjected to combined, simultaneous action of the external pressure and axial compression. Cones are relatively thick; hence, their buckling performance remains within the elastic-plastic range. The literature review shows that there are very few results within this range and none on combined stability. The current paper aims to fill this gap. Combined stability plot, sometimes called interactive stability plot, is obtained for mild steel models. Most attention is given to buckling caused by a single type of loading, i.e., by hydrostatic external pressure and by axial compression. Asymmetric bifurcation bucklings, collapse load in addition to the first yield pressure and first yield force, are computed using two independent proprietory codes in order to compare predictions given by them. Finally, selected cone configurations are used to verify numerical findings. To this end four cones were computer numerically controlled-machined from a solid steel billet of 252 mm in diameter. All cones had integral top and bottom flanges in order to mimic realistic boundary conditions. Computed predictions of buckling loads, caused by external hydrostatic pressure, were close to the experimental values. But similar comparisons for axially compressed cones are not so good. Possible reasons for this disparity are discussed in the paper.

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