Effect of an Axisymmetric Imperfection on the Plastic Buckling of an Axially Compressed Cylindrical Shell

1979 ◽  
Vol 46 (1) ◽  
pp. 125-131 ◽  
Author(s):  
S. Gellin
Keyword(s):  
Cylindrical Shell ◽  
Axial Compression ◽  
Thin Shells ◽  
Plastic Range ◽  
Imperfection Sensitivity ◽  
Plastic Buckling ◽  
Elastic Range ◽  
Long Cylindrical Shell ◽  
Axisymmetric Shape ◽  
Shape Imperfection

The effect of a sinusoidal axisymmetric shape imperfection on the plastic buckling of a long cylindrical shell under axial compression is studied. The load at which nonaxisymmetric bifurcation from the axisymmetric state occurs is determined as a function of the imperfection amplitude for relatively thin shells. Imperfection-sensitivity in the plastic range is contrasted with that in the elastic range.

The Preferred Mode Shape in the Linear Buckling of Circular Cylindrical Shells Under Axial Compression

1965 ◽  
Vol 32 (4) ◽  
pp. 793-802 ◽  
Author(s):  
P. Mann-Nachbar ◽  
W. Nachbar
Keyword(s):  
Cylindrical Shell ◽  
Aspect Ratio ◽  
Axial Compression ◽  
Probability Distributions ◽  
Thin Shells ◽  
Thin Cylindrical Shell ◽  
Linear Buckling ◽  
Manufacturing Tolerances ◽  
Circular Cylindrical Shells ◽  
Circumferential Waves

The chessboard buckle pattern in the solution of the linearized Donnell equations for buckling of a thin, cylindrical shell under axial compression is so sensitive to uncertainties in shell dimensions that the number of circumferential waves and the aspect ratio of the buckles is indeterminate. This problem is treated statistically. Shell dimensions are treated as random variables with probability distributions dependent on nominal values and manufacturing tolerances. Distributions for aspect ratio and number of circumferential waves are found by a Monte-Carlo technique. It is found that the linear theory does contain a mechanism for distinguishing among buckle modes. There is always a preferred buckle mode. For thin shells and attainable manufacturing tolerances, the aspect ratio of the preferred mode is closer to one than that of any other possible mode, and the corresponding number of buckles is large.

Effect of Post-Weld Heat Treatment on the Plastic Buckling of Welded Cylindrical Shells

2012 ◽  
Author(s):  
Ji Wang ◽  
Zhiping Chen ◽  
Chulin Yu
Keyword(s):  
Heat Treatment ◽  
Cylindrical Shell ◽  
Residual Stresses ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Weld Zone ◽  
Stress Relief ◽  
Post Weld Heat Treatment ◽  
Plastic Buckling ◽  
Weld Heat

Storage tanks, silos and other welded cylindrical shell structures are usually constructed of rolled panels which are joined by patterned circumferential and longitudinal welds. Cold-formed residual stresses are produced during the cold bending process of steel panels, and obvious deformations and uneven distributed welding residual stresses are also produced because of the welding process. Studies have shown that residual stresses could weaken the critical buckling load of welded cylindrical shells under axial compression. Stress-relief post-weld heat treatment (PWHT) is a process that heats the workpiece gradually to 500∼650 °C, holding the temperature 0.5 hours then reducing the temperature slowly. Two cylindrical shell specimens are fabricated in this paper, and one is processed with stress-relief PWHT, while the other is not. The magnitude and distribution of residual stresses near the weld zone in each specimen are measured with an X-ray diffraction-based measurement system (named iXRD by the manufacturer), and initial imperfections and critical load of the specimens are obtained by the use of an axial buckling experiment platform. Thereafter, numerical simulations are conducted with measured geometric imperfections and residual stresses exerted into the finite element model. Finally, comparison of the critical loads of both cylindrical shell specimens is made, showing the effects of residual stresses on the plastic buckling of cylindrical shells under axial compression.

Buckling Load Estimation of Two-way Grid Domes Stiffened by Diagonal Braces Under Vertical Load

2021 ◽  
Vol 62 (1) ◽  
pp. 7-23
Author(s):  
Shiro Kato ◽  
Shoji Nakazawa ◽  
Yoichi Mukaiyama ◽  
Takayuki Iwamoto
Keyword(s):  
Slenderness Ratio ◽  
Fem Analysis ◽  
Buckling Load ◽  
Vertical Load ◽  
Imperfection Sensitivity ◽  
Plastic Buckling ◽  
Elastic Plastic ◽  
Alternative Formula ◽  
Efficient Scheme ◽  
Estimation Scheme

The present study proposes an efficient scheme to estimate elastic-plastic buckling load of a shallow grid dome stiffened by diagonal braces. The dome is circular in plan. It is assumed to be subject to a uniform vertical load and to be supported by a substructure composed of columns and anti-earthquake braces. Based on FEM parametric studies considering various configurations and degrees of local imperfections, a set of formulations are presented to estimate the elastic-plastic buckling load. In the scheme, the linear buckling load, elastic buckling load, and imperfection sensitivity are first presented in terms of related parameters, and the elasticplastic buckling load is then estimated by a semi-empirical formula in terms of generalized slenderness ratio using a corresponding plastic load. For the plastic load, the present scheme adopts a procedure that it is calculated by a linear elastic FEM analysis, while an alternative formula for the plastic load is also proposed based on a shell membrane theory. The validity of the estimation scheme is finally confirmed through comparison with the results based on FEM nonlinear analysis. The formulations are so efficient and simple that the estimation may be conducted for preliminary design purposes almost with a calculator. .

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