scholarly journals Snap-Through of the Very Shallow Shell with Initial Imperfection

2016 ◽  
Vol 16 (2) ◽  
pp. 43-48
Author(s):  
Jozef Havran ◽  
Martin Psotný
Keyword(s):  
Boundary Conditions ◽  
Nonlinear Analysis ◽  
Shallow Shell ◽  
Initial Imperfection ◽  
Limit Load ◽  
External Pressure ◽  
Load Level ◽  
Nonlinear Equilibrium ◽  
Load Displacement ◽  
Ansys System

Abstract Elastic shallow shell of translation subjected to the external pressure is analysed in the paper numerically by FEM. Nonlinear equilibrium paths are calculated for the different boundary conditions. Special attention is paid to the influence of initial imperfection on the limit load level of fundamental load-displacement path of nonlinear analysis. ANSYS system was used for analysis, arclength method was chosen for obtain fundamental load-displacement path of solution.

scholarly journals Slender metal web stability analysis: Impact of initial imperfection on the mode of buckling

2020 ◽  
Vol 313 ◽  
pp. 00006
Author(s):  
Martin Psotný
Keyword(s):  
Initial Imperfection ◽  
Iteration Algorithm ◽  
Initial Shape ◽  
Aspect Ratios ◽  
Nonlinear Approach ◽  
Linearized Problem ◽  
Nonlinear Equilibrium ◽  
Post Buckling ◽  
Ansys System ◽  
Raphson Iteration

The post buckling of a rectangular slender web in compression has been analyzed. Shapes of a buckling area obtained from the nonlinear analysis have been compared with buckling modes from the linearized problem for various aspect ratios. Effects of initial shape imperfections upon the analysis have been investigated using nonlinear approach. To trace the complete nonlinear equilibrium curves, specialized code based on FEM was created. The Newton-Raphson iteration algorithm was used, load versus displacement control was changed during the process of calculation. Obtained results were verified using Ansys system, in this case arc-length method was activated for overcoming critical points.

Elastic-Plastic Axisymmetric Failure of Swedge-Stiffened Cylindrical Pressure Hull Under External Pressure

1993 ◽  
Vol 37 (02) ◽  
pp. 176-188
Author(s):  
Cho-Chung Liang ◽  
Ming-Fung Yang ◽  
Hung-Wen Chen
Keyword(s):  
Hydrostatic Pressure ◽  
Plastic Zone ◽  
Nonlinear Analysis ◽  
External Pressure ◽  
Geometrically Nonlinear ◽  
Pressure Loading ◽  
Geometrically Nonlinear Analysis ◽  
Elastic Plastic ◽  
Load Displacement ◽  
Distribution Of Stresses

An elastoplastic and geometrically nonlinear analysis of two of Ross's swedge-stiffened pressure hulls subjected to hydrostatic pressure loading is presented. Three commonly used swedge forms—trapezoidal, triangular, and sinusoidal-shaped—are considered. Comparisons on the responses of these three swedge-stiffened shapes are included. The load/displacement relations as well as the distribution of stresses with plastic zone spread phenomena are also illustrated.

Effect of a Bending Stiffness on the Load-Displacement Path of Von Mises Truss

2015 ◽  
Vol 769 ◽  
pp. 43-48
Author(s):  
Martin Psotny ◽  
Jozef Havran
Keyword(s):  
Theoretical Models ◽  
Load Level ◽  
Buckling Analysis ◽  
Iteration Algorithm ◽  
Linear Solution ◽  
Nonlinear Equilibrium ◽  
Von Mises ◽  
Ansys System ◽  
Raphson Iteration ◽  
Linear Buckling Analysis

Von Misses truss is one of the best examples to explain nature of non-linear solution and define the snap-through. Linear buckling analysis and nonlinear finite element approaches are compared in presented paper. At the present time theoretical models for the evaluation of the ultimate load assume a structure with imperfections. The peculiarities of the effect of the magnitude and mode of initial imperfections are investigated. Effect of member stiffness on the load level in critical point of nonlinear solution, as well as the relative position with respect to the critical load from buckling analysis are analyzed. To obtain the nonlinear equilibrium paths, Newton-Raphson iteration algorithm has been used. Obtained results are compared with those gained using ANSYS system.

Buckling of Circular Cylindrical Shells Using a Displacement Function

1974 ◽  
Vol 96 (4) ◽  
pp. 1322-1327
Author(s):  
Shun Cheng ◽  
C. K. Chang
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Displacement Function ◽  
Combined Loading ◽  
Trial Solution ◽  
Governing Differential Equation ◽  
Circular Cylindrical Shells ◽  
The Stability

The buckling problem of circular cylindrical shells under axial compression, external pressure, and torsion is investigated using a displacement function φ. A governing differential equation for the stability of thin cylindrical shells under combined loading of axial compression, external pressure, and torsion is derived. A method for the solutions of this equation is also presented. The advantage in using the present equation over the customary three differential equations for displacements is that only one trial solution is needed in solving the buckling problems as shown in the paper. Four possible combinations of boundary conditions for a simply supported edge are treated. The case of a cylinder under axial compression is carried out in detail. For two types of simple supported boundary conditions, SS1 and SS2, the minimum critical axial buckling stress is found to be 43.5 percent of the well-known classical value Eh/R3(1−ν2) against the 50 percent of the classical value presently known.

Ruga mechanics of soft-orifice closure under external pressure

2021 ◽  
Vol 477 (2249) ◽  
Author(s):  
Hanxun Jin ◽  
Alexander K. Landauer ◽  
Kyung-Suk Kim
Keyword(s):  
Surface Layer ◽  
Limit Load ◽  
Phase Evolution ◽  
External Pressure ◽  
Soft Material ◽  
Buckling Mode ◽  
Cross Sectional ◽  
Threefold Symmetry ◽  
Instability Modes ◽  
Symmetry Mode

Here, we report the closure resistance of a soft-material bilayer orifice increases against external pressure, along with ruga-phase evolution, in contrast to the conventional predictions of the matrix-free cylindrical-shell buckling pressure. Experiments demonstrate that the generic soft-material orifice creases in a threefold symmetry at a limit-load pressure of p / μ  ≈ 1.20, where μ is the shear modulus. Once the creasing initiates, the triple crease wings gradually grow as the pressure increases until the orifice completely closes at p / μ  ≈ 3.0. By contrast, a stiff-surface bilayer orifice initially wrinkles with a multifold symmetry mode and subsequently develops ruga-phase evolution, progressively reducing the orifice cross-sectional area as pressure increases. The buckling-initiation mode is determined by the layer's thickness and stiffness, and the pressure by two types of the layer's instability modes—the surface-layer-wrinkling mode for a compliant and the ring-buckling mode for a stiff layer. The ring-buckling mode tends to set the twofold symmetry for the entire post-buckling closure process, while the high-frequency surface-layer-wrinkling mode evolves with successive symmetry breaking to a final closure configuration of two- or threefold symmetry. Finally, we found that the threefold symmetry mode for the entire closure process provides the orifice's strongest closure resistance, and human saphenous veins remarkably follow this threefold symmetry ruga evolution pathway.

Localization and Propagation of Instabilities in Long Shallow Panels Under External Pressure

1994 ◽  
Vol 61 (4) ◽  
pp. 755-763 ◽  
Author(s):  
T. L. Power ◽  
S. Kyriakides
Keyword(s):  
Constant Pressure ◽  
Limit Load ◽  
Solution Procedure ◽  
External Pressure ◽  
Uniform Pressure ◽  
Membrane Tension ◽  
Pressure Loading ◽  
Shallow Arches ◽  
Subsequent Deformation ◽  
Static Conditions

This paper discusses the response of long, shallow, elastic panels to uniform pressure loading. Under quasi-static conditions, the deformation of such panels is initially uniform along their length, and their response has the nonlinearity and instabilities characteristic of shallow arches. Shallower panels deform symmetrically about the midspan and exhibit a limit load instability. For less shallow panels, the response bifurcates into an unsymmetric mode before the limit load is achieved. A formulation and a solution procedure are developed and used to analyze the response of such panels beyond first instability. It is demonstrated in both cases that following the first instability the deformation ceases to be axially uniform and locqlizes to a region a few arch spans in length. A drop in pressure accompanies this localized collapse and causes unloading in the remainder of the panel. Subsequent deformation is confined to this region until membrane tension arrests the local collapse. Further deformation can occur at a constant pressure and takes the form of spreading of the collapsed region along the length of the panel. The lowest pressure at which this can take place (propagation pressure) can be significantly lower than the pressure associated with first instability.

scholarly journals Free Vibration Analysis of the Unified Functionally Graded Shallow Shell with General Boundary Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Dongyan Shi ◽  
Shuai Zha ◽  
Hong Zhang ◽  
Qingshan Wang
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Vibration Analysis ◽  
Shallow Shell ◽  
Shear Deformation Theory ◽  
Free Vibration Analysis ◽  
Functionally Graded ◽  
General Boundary ◽  
Volume Distribution ◽  
General Boundary Conditions

The free vibration analysis of the functionally graded (FG) double curved shallow shell structures with general boundary conditions is investigated by an improved Fourier series method (IFSM). The material properties of FG structures are assumed to vary continuously in the thickness direction, according to the four graded parameters of the volume distribution function. Under the current framework, the displacement and rotation functions are set to a spectral form, including a double Fourier cosine series and two supplementary functions. These supplements can effectively eliminate the discontinuity and jumping phenomena of the displacement function along the edges. The formulation is based on the first-order shear deformation theory (FSDT) and Rayleigh-Ritz technique. This method can be universally applied to the free vibration analysis of the shallow shell, because it only needs to change the relevant parameters instead of modifying the basic functions or adapting solution procedures. The proposed method shows excellent convergence and accuracy, which has been compared with the results of the existing literatures. Numerous new results for free vibration analysis of FG shallow shells with various boundary conditions, geometric parameter, material parameters, gradient parameters, and volume distribution functions are investigated, which may serve as the benchmark solution for future researches.

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