The Computation of Accurate Buckling Pressures of Imperfect Thin-Walled Cylinders

2010 ◽  
Author(s):  
Caitri´ona de Paor ◽  
Denis Kelliher ◽  
Kevin Cronin ◽  
William M. D. Wright
Keyword(s):  
Finite Element ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Small Scale ◽  
Thickness Variation ◽  
Geometrically Nonlinear ◽  
Element Analysis ◽  
Highly Sensitive ◽  
Wall Thickness Variation ◽  
Nonlinear Static

The buckling capacity of thin cylindrical shells subject to uniform external pressure is investigated in this paper. Thin cylindrical shells are known to be highly sensitive to geometric and material imperfections such as wall thickness variation, non-circularity and random geometric imperfections. The effect of imperfection on the buckling load is studied using finite element (FE) models and laboratory experiments. Imperfection measurements are taken on small scale steel cans and these measurements are modelled and analysed using a geometrically nonlinear static finite element analysis. The cans are then tested in the laboratory and the results compared with those predicted by the FE models and theory.

Effects of Diameter to Thickness Ratio and External Pressure on the Velocity of Dynamic Buckle Propagation in Offshore Pipelines

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Z. Omrani ◽  
K. Abedi ◽  
A. R. Mostafa Gharabaghi
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Element Model ◽  
External Pressure ◽  
Thickness Ratio ◽  
Small Scale ◽  
Element Analysis ◽  
Models Comparison ◽  
Buckle Propagation ◽  
Exerted Pressure

In this paper, a numerical study of the dynamic buckle propagation, initiated in long pipes under external pressure, is presented. For a long pipe, due to the high exerted pressure, local instability is likely to occur; therefore, the prevention of its occurrence and propagation are very important subjects in the design of pipelines. The 3D finite element modeling of the buckle propagation is presented by considering the inertia of the pipeline and the nonlinearity introduced by the contact between its collapsing walls. The buckling and collapse are assumed to take place in the vacuum. The numerical results of the nonlinear finite element analysis are compared with the experimental results obtained by Kyriakides and Netto (2000, “On the Dynamics of Propagating Buckle in Pipelines,” Int. J. Solids Struct., 37, pp. 6843–6878) from a study on the small-scale models. Comparison shows that the finite element results have very close agreement with those of the experimental study. Therefore, it is concluded that the finite element model is reliable enough to be used for nonlinear collapse analysis of the dynamic buckle propagation in the pipelines. In this study, the effects of external pressure on the velocity of dynamic buckle propagation for different diameter to thickness ratios are investigated. In addition, the mathematical relations, based on the initiation pressure, are derived for the velocity of buckle propagation considering the diameter to thickness ratio of the pipeline. Finally, a relation for the buckle velocity as a function of the pressure and diameter to thickness ratio is presented.

Nonlinear Finite Element Analysis of Collapse Loads of Cylindrical Shells Subjected to Combined Thermal Loads and External Pressures

2007 ◽  
Author(s):  
Takuya Sato ◽  
Toshiyuki Hirosawa ◽  
Shunji Kataoka
Keyword(s):  
Finite Element ◽  
Cylindrical Shells ◽  
Design Procedure ◽  
External Pressure ◽  
Nonlinear Finite Element ◽  
Plastic Behavior ◽  
Thermal Loads ◽  
Collapse Load ◽  
Element Analysis ◽  
External Pressures

The inner tube of the double-tube reactors used in some chemical process units must be designed to resist buckling. When the inner tube is operated at a higher temperature and at a lower pressure and outer tube is operated at a lower temperature and at a higher pressure, the inner tube will be subjected to combined thermal loads and external pressure. ASME Code Sec. VIII Div. 1 provides a design procedure for shells, based on a B-chart, to ensure against buckling under external pressure, however, additional consideration should be made where plastic deformation may occur due to very large longitudinal thermal loads. In this study, nonlinear finite element analyses were performed to investigate the collapse of thick-walled cylindrical shells subjected to combined thermal loads and high external pressures. Two nonlinearities, a material nonlinearity (elastic-plastic behavior) and a geometric nonlinearity (large deformation), were considered in these analyses. The effects of initial imperfection in the shells (out-of-roundness) as well as of thermal loads were studied. The results showed that the longitudinal thermal loads reduce the plastic collapse load especially when the thermal loads are tensile. It was also shown that the loading sequence has a large effect on the collapse load especially when the thermal stress was larger.

GEOMETRICALLY NONLINEAR FINITE ELEMENT ANALYSIS OF ARBITRARY THIN PLATES

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Saleema Panda ◽  
Manoranjan Barik
Keyword(s):  
Finite Element ◽  
Displacement Function ◽  
Thin Plates ◽  
Element Formulation ◽  
Geometrically Nonlinear ◽  
Element Analysis ◽  
Plate Structures ◽  
Aerospace Applications ◽  
Lagrangian Coordinate ◽  
Nonlinear Static

Many plate structures used especially in naval and aerospace applications undergo deflections that are not small in comparison to the thickness of the plate, but they are still small compared to other dimensions of the plate, so analysis must include the effects of the large displacements on the structures. This report developed an elegant finite element formulation for analyzing the geometrically nonlinear static behavior of arbitrary-shaped thin plates. An arbitrary planform of a whole plate was mapped into a square domain where a cubic serendipity shape function represented the arbitrary geometry. An ACM plate-bending element along with the inplane deformations was considered for the displacement function. The nonlinear formulation was done in the total Lagrangian coordinate system using [N]-notation, and the nonlinear governing equations were solved by Newton Raphson iterative method. It was found that the element was capable of accommodating different geometries just like isoparametric element. The efficacy of the element was shown by comparing the deflections and stresses at critical points of the plates of square, skewed, and circular geometries with previously published results.

Finite Element Analysis for Wall Thickness Variation of Seamless Tube in Stretch Reducing Rolling Process

2011 ◽  
Vol 291-294 ◽  
pp. 532-536 ◽  
Author(s):  
Hui Yu ◽  
Yong Chen ◽  
Xiang Zhong Bai
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wall Thickness ◽  
Three Dimensional ◽  
Longitudinal Direction ◽  
Rolling Process ◽  
Thickness Variation ◽  
Analysis Model ◽  
Element Analysis ◽  
Wall Thickness Variation

According to the geometrical characteristic of workpiece and groove in the stretch reducing rolling process, three-dimensional elastic-plastic finite-element analysis model was established to simulate the metal deformation, the regularities of distribution of wall thickness of transverse direction longitudinal direction were investigated. The analysis was verified by comparing finite element analysis results with on-line measurements. The length of crop ends was determined as well as product bore polygonization. The study provides the foundation for analyzing product defeat and instructing technological design.

Finite Element Analysis of Different Flexure Springs

2010 ◽  
Vol 44-47 ◽  
pp. 2065-2069
Author(s):  
Xi Chen ◽  
Ying Liu ◽  
Hua Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Analysis ◽  
Geometrically Nonlinear ◽  
Advisory Opinion ◽  
Element Analysis ◽  
Radial Stiffness ◽  
The Finite Element Analysis ◽  
High Fatigue ◽  
Nonlinear Static

Flexure spring suspensions have demonstrated the ability to provide long operating lifetimes for cryocoolers. The good flexure spring need high radial stiffness and high fatigue life. The profile curves are very important for flexure spring. In this paper, based on the finite element analysis software (ANSYS), geometrically nonlinear static structural analysis and nonlinear dynamics structural analysis were made to several different flexure springs. The fatigue strength, axial and radial stiffness, modal frequency were calculated and listed. The different performance between linear flexure spring and spiral flexure spring were discussed, which would provide an advisory opinion for the design and application of flexure spring in space cryocooler.

Finite Element Analysis of Composite Cylindrical Shells with and without Cutouts

2012 ◽  
Vol 1 (1) ◽  
pp. 34-38
Author(s):  
B. Siva Konda Reddy ◽  
◽  
CH. Srikanth ◽  
G. Sandeep Kumar ◽  
◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cylindrical Shells ◽  
Element Analysis ◽  
Composite Cylindrical Shells

Fitness for Service Assessments of Bulging and Out-of-Round Structures

2004 ◽  
Author(s):  
Peter Carter ◽  
D. L. Marriott ◽  
M. J. Swindeman
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Model ◽  
External Pressure ◽  
Element Analysis ◽  
Structural Imperfection ◽  
Level 2

This paper examines techniques for the evaluation of two kinds of structural imperfection, namely bulging subject to internal pressure, and out-of-round imperfections subject to external pressure, with and without creep. Comparisons between comprehensive finite element analysis and API 579 Level 2 techniques are made. It is recommended that structural, as opposed to material, failures such as these should be assessed with a structural model that explicitly represents the defect.

Accuracy of Failure Criteria Commonly Used for Ship Collision Simulations

2018 ◽  
Author(s):  
R. Villavicencio ◽  
Bin Liu ◽  
Kun Liu
Keyword(s):  
Finite Element ◽  
Failure Criteria ◽  
Small Scale ◽  
Finite Element Models ◽  
Impact Loads ◽  
Large Scatter ◽  
Element Analysis ◽  
Advantages And Disadvantages ◽  
Ship Collision ◽  
Double Hull

The paper summarises observations of the fracture response of small-scale double hull specimens subjected to quasi-static impact loads by means of simulations of the respective experiments. The collision scenarios are used to evaluate the discretisation of the finite element models, and the energy-responses given by various failure criteria commonly selected for collision assessments. Nine double hull specimens are considered in the analysis so that to discuss the advantages and disadvantages of the different failure criterion selected for the comparison. Since a large scatter is observed from the numerical results, a discussion on the reliability of finite element analysis is also provided based on the present study and other research works found in the literature.

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