scholarly journals Buckling of simply supported GLARE cylindrical panels subjected to uniform compression

2021 ◽  
Vol 349 ◽  
pp. 01004
Author(s):  
Costas Kalfountzos ◽  
George Bikakis ◽  
Efstathios Theotokoglou
Keyword(s):  
Logarithmic Scale ◽  
The Finite Element Method ◽  
Uniform Compression ◽  
Simply Supported ◽  
Glass Fiber Composites ◽  
Composite Layers ◽  
Cylindrical Panels ◽  
Curvature Parameter ◽  
Analytical Formulas ◽  
Buckling Coefficient

In this article, the elastic buckling behaviour of cylindrical GLARE (GLAss REinforced) panels with classically simply supported boundary conditions under uniaxial compression is investigated using the finite element method (FEM) and eigenvalue buckling analysis. The buckling coefficient-curvature parameter diagrams of five GLARE grades are obtained and studied along with the diagrams of two glass-fiber composites and monolithic 2024-T3 aluminum, using validated FEM models. It is found that aluminium has a stronger impact on the buckling behaviour of the GLARE panels than the composite layers. From the constructed buckling coefficient - curvature parameter diagrams in double logarithmic scale it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter of the panels. Based on this finding, appropriate regressions are implemented in order to derive approximate analytical formulas of the buckling coefficient as a function of the curvature parameter for the considered materials.

Deterministic and probabilistic buckling response of fiber–metal laminate panels under uniaxial compression

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Costas D. Kalfountzos ◽  
George S.E. Bikakis ◽  
Efstathios E. Theotokoglou
Keyword(s):  
Glass Fiber ◽  
Buckling Load ◽  
Sensitivity Analyses ◽  
Logarithmic Scale ◽  
Content Type ◽  
Buckling Behavior ◽  
Fiber Metal Laminate ◽  
Curvature Parameter ◽  
Buckling Coefficient ◽  
Fiber Metal

Purpose The purpose of this paper is to study the deterministic elastic buckling behavior of cylindrical fiber–metal laminate panels subjected to uniaxial compressive loading and the investigation of GLAss fiber-REinforced aluminum laminate (GLARE) panels using probabilistic finite element method (FEM) analysis. Design/methodology/approach The FEM in combination with the eigenvalue buckling analysis is used for the construction of buckling coefficient–curvature parameter diagrams of seven fiber–metal laminate grades, three glass-fiber composites and monolithic 2024-T3 aluminum. The influences of uncertainties concerning material properties and laminate dimensions on the buckling load are studied with sensitivity analyses. Findings It is found that aluminum has a stronger impact on the buckling behavior of the fiber–metal laminate panels than their constituent uni-directional or woven composites. For the classical simply supported boundary conditions, it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter when the diagrams are plotted in double logarithmic scale. The probabilistic calculations demonstrate that there is a considerable probability to overestimate the buckling load of GLARE panels with deterministic calculations. Originality/value In this study, the deterministic and probabilistic buckling response of fiber metal laminate panels is investigated. It is shown that realistic structural uncertainties could substantially affect the buckling strength of aerospace components.

The Effect of Curvature and Torsion on the Temperature Distribution in a Helix

1985 ◽  
Vol 52 (3) ◽  
pp. 529-532 ◽  
Author(s):  
D. D. Sayers ◽  
M. C. Potter
Keyword(s):  
Differential Equation ◽  
Finite Element Method ◽  
Partial Differential Equation ◽  
Temperature Distribution ◽  
Strong Dependence ◽  
Maximum Temperature ◽  
Nonuniform Heating ◽  
The Finite Element Method ◽  
Curvature Parameter ◽  
Curvature And Torsion

Traditional analysis treats the helix as a straight wire with the effects of nonuniform heating, torsion, and large curvature ignored. Using a helical coordinate system the governing partial differential equation including these effects is derived. The equation is then solved numerically using the finite element method. The results indicate a strong dependence of the temperature on the torsion parameter when the curvature parameter is significant. As the curvature parameter increases, the temperature distribution becomes skew-symmetric and the maximum temperature in the helix increases. Nonuniform heating influences the temperature distribution independent of the curvature and torsion.

Study on Flexibility of Intracranial Vascular Stents Based on the Finite Element Method

2018 ◽  
Vol 35 (4) ◽  
pp. 465-474 ◽  
Author(s):  
L. Liu ◽  
H. Jiang ◽  
Y. Dong ◽  
L. Quan ◽  
Y. Tong
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Cantilever Beam ◽  
Beam Model ◽  
The Finite Element Method ◽  
Simply Supported Beam ◽  
Bending Deformation ◽  
Vascular Stents ◽  
Simply Supported ◽  
Loading Method

ABSTRACTFlexibility is a particularly important biomechanical property for intracranial vascular stents. To study the flexibility of stent, the following work was carried out by using the finite element method: Four mechanical models were adopted to simulate the bending deformation of stents, and comparative studies were conducted about the distinction between cantilever beam and simply supported beam, as well as the distinction between moment-loading method and displacement-loading method. A complete process as implanting a stent including compressing, expanding and bending was also simulated, for analyzing the effects of compressing and expanding deformation on stent flexibility. At the same time, the effects of the arrangement and the number of bridges on stent flexibility were researched. The results show that: 1. A same flexibility index was obtained from cantilever beam model and simply supported beam model; displacement-loading method is better than moment-loading for simulating the bending deformation of stents. 2. The flexibility of stent with compressing and expanding deformation is lower than that in the initial form. 3. Crossly arranging the neighboring bridges in axial direction, can effectively improve the stent flexibility and reduce the flexibility difference in various bending directions; the bridge number, has proportional non-linear correlation with the stent rigidity as well as the maximum moment required for bending the stent.

scholarly journals PERFORMANCE BASED DESIGN OF UNBRACED STEEL FRAMES EXPOSED TO NATURAL FIRE SCENARIOS

2016 ◽  
Author(s):  
Carlos Couto ◽  
Thiago Silva ◽  
Martina Carić ◽  
Paulo Vila Real ◽  
Davor Skejić
Keyword(s):  
Fire Resistance ◽  
Steel Frames ◽  
Design Methods ◽  
The Other ◽  
Performance Based Design ◽  
The Finite Element Method ◽  
Natural Fire ◽  
Fire Scenarios ◽  
Buckling Coefficient ◽  
Structural Engineers

<p>According to the Eurocode 3 Part 1-2 (EN1993-1-2) (CEN 2005b), it is possible for structural engineers to consider physical based thermal actions and to do performance based design instead of using prescriptive rules based on nominal fire curves. However, some uncertainties remain in the use of such approaches. This study focus on the clarification of the use of the simplified design methods to assess the fire resistance of unbraced steel frames exposed to fire. On the other hand, a recent study (Couto et al. 2013) suggests the use of a buckling coefficient of 1.0 for all the columns except those belonging to the first storey of a pinned framed where 2.0 should be taken instead and it is unclear if the consideration of such values for the buckling lengths is adequate when using performance based designs.</p>In this study, a comparison is made between simple and advanced calculation models and it is demonstrated that the simple design methods, using the suggested buckling coefficients to calculate the fire resistance of the frames are safe sided when compared to the use of advanced calculations using the finite element method (FEM).

Reduction in the Critical Moment for Lateral Torsional Buckling of Coped Beams

2015 ◽  
Vol 797 ◽  
pp. 3-10 ◽  
Author(s):  
Karolina Brzezińska ◽  
Roman Bijak
Keyword(s):  
Computational Analysis ◽  
Reduction Factor ◽  
Bottom Flange ◽  
The Finite Element Method ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
End Plate ◽  
Analytical Formulas ◽  
Beam Section ◽  
Plate Connection

The paper presents a computational analysis of the effect constructional details of coped connections, assumed to be a fork support in calculations, on the critical LTB moment values. On the basis of analytical formulas by Lindner [1], a formula, having a simple form, was derived for the reduction factor rn for the critical LTB moment. The parameters for the formula were presented in a tabular form, taking into account the beam section (IPE/HEA), the type of beam to end-plate connection (Types 1-3), the load type (q / P) and the way the load is applied (top / bottom flange). The correctness of the derived formula was validated on the basis of the analytical results and the Finite Element Method results obtained with the Abaqus/CAE software. In the program, the beam geometric dimensions and connections were represented as volumetric finite elements. Additionally, the dimensions of the end-plate for IPE and HEA section series were arranged in a systematic manner following the British catalogue.

Transverse Ribs Affect the Stability of Steel-Concrete Composite Box Beams

2014 ◽  
Vol 587-589 ◽  
pp. 1663-1667
Author(s):  
Chong Yang Zhou ◽  
Jian Rong Yang ◽  
Wan Wan Jiang
Keyword(s):  
Finite Element Method ◽  
The Finite Element Method ◽  
Box Girder ◽  
Linear Buckling ◽  
Box Beams ◽  
Buckling Coefficient ◽  
Stiffening Ribs ◽  
The Stability ◽  
Lateral Bracing ◽  
Linear Buckling Analysis

The paper uses the finite element method to the specific structure of the linear buckling analysis to study the steel - concrete buckling coefficient changes when the changes and adjustments in the case of composite box girder structure different density transverse stiffening ribs buckling coefficient bracing spacing, Thus obtained that the almost linear relationship between the change in distance between the transverse stiffening ribs and buckling coefficient. Meanwhile get when bracing spacing when a valid range, coefficient of variation of buckling structure is not particularly obvious. Which is to adjust the spacing and lateral bracing number of stiffening ribs provide a space.

Buckling of an Elliptical Plate With Simply Supported Edge Under Uniform Compression

1976 ◽  
Vol 43 (3) ◽  
pp. 455-458 ◽  
Author(s):  
Kenzo Sato
Keyword(s):  
Plate Theory ◽  
Mathieu Functions ◽  
Elliptical Plate ◽  
Buckling Mode ◽  
Uniform Compression ◽  
Simply Supported ◽  
Aspect Ratios ◽  
Thin Plate Theory ◽  
The Stability ◽  
Circular Functions

On the basis of the ordinary thin plate theory, the stability of a simply supported elliptical plate subjected to uniform compression in its middle plane is considered by the use of circular functions, hyperbolic functions, Mathieu functions, and modified Mathieu functions which are solutions of the equilibrium equation of the buckled plate. The first five eigenvalues for the buckling mode symmetrical about both axes are calculated numerically for a variety of aspect ratios of the ellipse. The limiting cases of a circular plate and of an infinitely long strip are also discussed.

Optimal Forms of Shallow Cylindrical Panels With Respect to Vibration and Stability

1986 ◽  
Vol 53 (1) ◽  
pp. 135-140 ◽  
Author(s):  
R. H. Plaut ◽  
L. W. Johnson
Keyword(s):  
Surface Area ◽  
Fundamental Frequency ◽  
Axial Load ◽  
Cylindrical Panel ◽  
Buckling Load ◽  
Material Surface ◽  
Uniform Thickness ◽  
Simply Supported ◽  
Cylindrical Panels

Thin, shallow, elastic, cylindrical panels with rectangular planform are considered. We seek the midsurface form which maximizes the fundamental frequency of vibration, and the form which maximizes the buckling value of a uniform axial load. The material, surface area, and uniform thickness of the panel are specified. The curved edges are simply supported, while the straight edges are either simply supported or clamped. For the clamped case, the optimal panels have zero slope at the edges. In the examples, the maximum fundamental frequency is up to 12 percent higher than that of the corresponding circular cylindrical panel, while the buckling load is increased by as much as 95 percent. Most of the solutions are bimodal, while the rest are either unimodal or trimodal.

scholarly journals Four-sphere head model for EEG signals revisited

2017 ◽  
Author(s):  
Solveig Næss ◽  
Chaitanya Chintaluri ◽  
Torbjørn V. Ness ◽  
Anders M. Dale ◽  
Gaute T. Einevoll ◽  
...  
Keyword(s):  
Analytical Formula ◽  
Mathematical Expression ◽  
Head Model ◽  
The Finite Element Method ◽  
Sphere Model ◽  
Eeg Signals ◽  
Scalp Eeg ◽  
Spherical Head ◽  
Analytical Formulas ◽  
Eeg Recordings

AbstractElectric potential recorded at the scalp (EEG) is dominated by contributions from current dipoles set by active neurons in the cortex. Estimation of these currents, called ’inverse modeling’, requires a ’forward’ model, which gives the potential when the positions, sizes, and directions of the current dipoles are known. Different models of varying complexity and realism are used in the field. An important analytical example is the four-sphere model which assumes a four-layered spherical head where the layers represent brain tissue, cerebrospinal fluid (CSF), skull, and scalp, respectively. This model has been used extensively in the analysis of EEG recordings. Since it is analytical, it can also serve as a benchmark against which numerical schemes, such as the Finite Element Method (FEM), can be tested. While conceptually clear, the mathematical expression for the scalp potentials in the four-sphere model is quite cumbersome, and we observed the formulas presented in the literature to contain errors. We here derive and present the correct analytical formulas for future reference. They are compared with the results of FEM simulations of four-sphere model. We also provide scripts for computing EEG potentials in this model with the correct analytical formula and using FEM.

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