Buckling of Cylinders With Imperfect Length

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
J. Błachut
Keyword(s):  
Mild Steel ◽  
Axial Compression ◽  
Wall Thickness ◽  
Axial Length ◽  
Small Amplitude ◽  
Thickness Ratio ◽  
Experimental Results ◽  
Dominant Factor ◽  
Buckling Strength ◽  
Perfect Model

Eighteen mild steel cylinders with the length-to-radius ratio, L/R ≈ 2.4 and with the radius-to-wall thickness ratio, R/t ≈ 185 were collapsed by axial compression. Cylinders had variable length at one end of sinusoidal profile. The magnitude of axial imperfection-to-wall thickness ratio, 2A/t, was varied between 0.05 and 1.0. Experimental results show that buckling strength strongly depends on the axial amplitude of imperfection. On average imperfect cylinders, with 2A/t = 1.0, are able to support 49% of experimental buckling load obtained for geometrically perfect model. The largest sensitivity of buckling strength was associated with small amplitude of imperfection in axial length. For example, for axial length imperfection amounting to 25% of wall thickness the buckling strength was reduced by 40%. It appears that the number of sinusoidal waves in the imperfection profile plays a secondary role, i.e., its role in reducing the buckling strength is not a dominant factor. The paper provides experimental details and comparisons with numerical results.

Buckling of Cylinders With Imperfect Length

2013 ◽  
Author(s):  
J. Błachut
Keyword(s):  
Mild Steel ◽  
Axial Compression ◽  
Wall Thickness ◽  
Axial Length ◽  
Numerical Results ◽  
Thickness Ratio ◽  
Experimental Results ◽  
Dominant Factor ◽  
Buckling Strength ◽  
Perfect Model

Eighteen mild steel cylinders with the length-to-radius ratio, L/R ≈ 2.4 and with the radius-to-wall thickness ratio, R/t ≈ 185 were collapsed by axial compression. Cylinders had variable length at one end of sinusoidal profile. The magnitude-to-wall thickness ratio, 2A/t, was varied between 0.05 and 1.0. Experimental results show that buckling strength strongly depends on the axial amplitude of imperfection. On average imperfect cylinders, with 2A/t = 1.0, are able to support 49 % of experimental buckling load obtained for geometrically perfect model. The largest sensitivity of buckling strength was associated with small amplitudes of axial length. For example, for axial length imperfection amounting to 25 % of wall thickness the buckling strength was reduced by 40 %. It appears that the number of sinusoidal waves in the imperfection profile plays a secondary role, i.e., its role in reducing the buckling strength is not a dominant factor. The paper provides experimental details and comparisons with numerical results.

Experimental and finite element study on the single-layer reticulated composite joints

2020 ◽  
Vol 23 (10) ◽  
pp. 2174-2187
Author(s):  
Liang Zheng ◽  
Cheng Qin ◽  
Hong Guo ◽  
Dapeng Zhang ◽  
Mingtan Zhou ◽  
...  
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Axial Compression ◽  
Wall Thickness ◽  
Great Influence ◽  
Single Layer ◽  
Experimental Results ◽  
Steel Pipe ◽  
Cover Plate ◽  
Element Analysis

In this article, a new type of reticulated joint, named the steel–concrete composite reticulated shell joint, is proposed. The proposed reticulated shell joint consists of an inner circular steel pipe, an outer circular steel pipe, a steel cover plate, and internal concrete. Five test specimens were tested under axial compression. The variable study included the wall thickness of the inner and outer circular steel pipes and the radius of the inner circular steel pipe. The test specimens exhibited a high bearing capacity and good plastic deformation ability under axial compression. The test results show that the wall thickness of the outer circular steel pipe and the radius of the inner circular steel pipe have a great influence on the bearing capacity of the steel–concrete composite reticulated shell joint, while the wall thickness of the inner circular steel pipe has little influence on the bearing capacity of the steel–concrete composite reticulated shell joint. Based on the test of the steel–concrete composite reticulated shell joints under axial load, the three-dimensional nonlinear finite element model was used to analyze the mechanical properties of the steel–concrete composite reticulated shell joints under axial compression. The results of the finite element analysis showed good agreement with the experimental results. The formula for calculating the bearing capacity of the joint is derived. By comparing with the experimental results, the calculated results are basically consistent with the experimental results.

The Effect of Shape, Thickness and Boundary Imperfections on Plastic Buckling of Cones

2011 ◽  
Author(s):  
O. Ifayefunmi ◽  
J. Błachut
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Wall Thickness ◽  
Thickness Distribution ◽  
Radial Pressure ◽  
External Pressure ◽  
Combined Loading ◽  
Small Radius ◽  
Worst Case ◽  
Buckling Strength

Three types of imperfections are analysed in the current paper, and they are: (i) Initial geometric imperfections, i.e., deviations from perfect geometry, (ii) Variations in the wall thickness distribution, and (iii) Imperfect boundary conditions. It is assumed that cones are subject to: (a) axial compression only, (b) radial pressure only, and (c) combined loading, i.e., axial compression and external pressure acting simultaneously. Buckling strength of imperfect cones is obtained for all of the cases above. It is shown that the buckling strength is differently affected by imperfections, when cones are subjected to axial compression or to radial external pressure. The response to imperfections along the combined stability envelope is also provided, and these results are first of this type. The finite element analysis, using the proprietary code is used as the numerical tool. Cones are assumed to be from mild steel and the material is modelled as elastic perfectly plastic. Geometrical imperfection profiles are affine to eigenshapes. A number of them are tried in calculations, as well as the effect of them being superimposed. The results indicate that imperfection amplitude and its shape strongly affect the load carrying capacity of conical shells. Also, it is shown that the buckling loads of analyzed cones are more sensitive when subjected to combined loading as compared to their sensitivity under single load conditions. At the next stage, uneven thickness distribution along the cone slant was considered. Variation of wall thickness was assumed to vary in a piece-wise constant fashion. This appears to have a large effect on the buckling strength of cones under axial compression only as compared with that of cones subjected to radial external pressure only. Finally, the effect of variability of boundary conditions on failure load of cones was investigated for two loading conditions, i.e., for axial compression and for radial pressure, only. Results indicate that change of boundary conditions influences the magnitude of buckling load. For axially compressed cones the loss of buckling strength can be large (about 64% for the worst case (beta = 30 deg, the cone not restrained at small radius end). Calculations for radial pressure indicate that the loss of buckling strength is not as acute — with 34% for the worst case (beta = 40 deg, relaxed boundary conditions at the larger radius end). This is an entirely numerical study but references to accompanying experimental programme are provided.

Buckling of Truncated Cones With Localized Imperfections

2012 ◽  
Author(s):  
J. Błachut
Keyword(s):  
Axial Compression ◽  
Wall Thickness ◽  
External Pressure ◽  
Buckling Load ◽  
Buckling Loads ◽  
Conical Shells ◽  
Buckling Strength ◽  
Shape Deviations ◽  
Combined Action ◽  
Axisymmetric Shape

The paper shows that both the inward and outward bulge-type axisymmetric shape imperfections can significantly lower the buckling strength of steel conical shells. The FE results are provided for: (i) axial compression, (ii) external pressure, and (iii) combined action of both loads. Sensitivity of buckling loads to outward bulges has not been generally known or expected. It is shown that the sensitivity of buckling load depends not only on the shape, amplitude but also on the position of the imperfection along the slant. Geometry of recently tested cones was also used in order to assess the influence of measured shape deviations on the buckling strength. The amplitudes of imperfections in these machined models were small (up to 5 % of wall thickness). As a result their influence on the buckling strength was found to be negligible.

RELIABILITY ASSESSMENT OF AXIALLY COMPRESSED COMPOSITE CYLINDRICAL SHELLS WITH RANDOM IMPERFECTIONS

2011 ◽  
Vol 11 (02) ◽  
pp. 215-236 ◽  
Author(s):  
MATTEO BROGGI ◽  
ADRIANO CALVI ◽  
GERHART I. SCHUËLLER
Keyword(s):  
Mathematical Models ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Reliability Assessment ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Experimental Results ◽  
Drastic Decrease ◽  
Different Types ◽  
Probability And Statistics

Cylindrical shells under axial compression are susceptible to buckling and hence require the development of enhanced underlying mathematical models in order to accurately predict the buckling load. Imperfections of the geometry of the cylinders may cause a drastic decrease of the buckling load and give rise to the need of advanced techniques in order to consider these imperfections in a buckling analysis. A deterministic buckling analysis is based on the use of the so-called knockdown factors, which specifies the reduction of the buckling load of the perfect shell in order to account for the inherent uncertainties in the geometry. In this paper, it is shown that these knockdown factors are overly conservative and that the fields of probability and statistics provide a mathematical vehicle for realistically modeling the imperfections. Furthermore, the influence of different types of imperfection on the buckling load are examined and validated with experimental results.

An Experimental Study on the Lateral Impact of Fully Clamped Mild Steel Pipes

1992 ◽  
Vol 206 (2) ◽  
pp. 111-127 ◽  
Author(s):  
N Jones ◽  
S E Birch ◽  
R S Birch ◽  
L Zhu ◽  
M Brown
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Mild Steel ◽  
Failure Modes ◽  
Experimental Results ◽  
Lateral Impact ◽  
Drop Hammer ◽  
Steel Pipes ◽  
Scale Range ◽  
The Impact

This report presents some experimental data that were recorded from 130 impact tests on mild steel pipes in two drop hammer rigs. The pipes were fully clamped across a span which was ten times the corresponding outside pipe diameters which lie between 22 and 324 mm. All of the pipes except five had wall thicknesses of 2 mm approximately and were impacted laterally by a rigid wedge indenter at the mid span, one-quarter span or near to a support. The impact velocities ranged up to 14 m/s and caused various failure modes. Some comparisons between two sets of experimental results indicate that the laws of geometrically similar scaling are almost satisfied over a scale range of approximately five.

An Analysis of the Ultimate Strength of Deck Structures Under In-Plane Loads

1983 ◽  
Vol 20 (03) ◽  
pp. 230-251
Author(s):  
Ygal Shapir ◽  
Gregory J. White
Keyword(s):  
Residual Stresses ◽  
Ultimate Strength ◽  
Experimental Results ◽  
Correction Factors ◽  
Buckling Strength ◽  
Step Procedure ◽  
Simple Program ◽  
Mode Of Failure ◽  
Compressive Loads ◽  
Simple Flow

A step-by-step procedure for determining the mode of failure and the ultimate strength of ship deck structures under in-plane compressive loads is developed. A comparison of several analytical theories for the buckling strength of deck structures in the elastic and inelastic zones is presented and the reason for the approach taken at each step is explained. The final result is a simple flow chart for this procedure and an algorithm which is easily adapted to most computer systems. The procedure is compared with experimental results and a method for determining reasonable size factors of safety (or correction factors) to account for initial deflections, residual stresses, etc., is presented. An example coding in FORTRAN IV for use as a subroutine in larger programs, or as a simple program itself, is given. An example structure is solved to explain each of the steps of the procedure.

The Formation of Tracheae and Tracheoles in Rhodnius prolixus

1958 ◽  
Vol s3-99 (45) ◽  
pp. 29-46
Author(s):  
M. LOCKE
Keyword(s):  
Axial Compression ◽  
Wall Thickness ◽  
Tube Wall ◽  
Rhodnius Prolixus ◽  
Axial Orientation ◽  
Tube Wall Thickness ◽  
Walled Cylinder ◽  
Tangential Orientation

The formation of tracheae in Rhodnius is described by the hypothesis of expansion and buckling. The cuticulin lining is at first a smooth-walled cylinder. Later it expands equally in each direction, increasing in diameter but buckling in the axis. An engineering expression describing symmetrical buckling in a cylinder under uniform axial compression has been applied to this process. Agreement was obtained between the expected and observed values for buckling frequency and tube-wall thickness. The taenidia are formed within the buckles, their amplitude being proportional to the increase in diameter. The axial orientation of the chitin micelles in the lining membrane and the tangential orientation in the taenidia are consistent with their being oriented by the stresses expected during expansion and buckling. The formation of tracheoles may also be described by the expansion and buckling hypothesis.

Effect of pitting defects on the buckling strength of thick-wall cylinder under axial compression

2019 ◽  
Vol 224 ◽  
pp. 226-241 ◽  
Author(s):  
Huakun Wang ◽  
Yang Yu ◽  
Jianxing Yu ◽  
Weipeng Xu ◽  
Haicheng Chen ◽  
...  
Keyword(s):  
Axial Compression ◽  
Thick Wall ◽  
Buckling Strength
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