Bifurcation Buckling Versus Limit Load Instabilities of Elastic-Plastic Tubes Under Bending and External Pressure

1991 ◽  
Vol 113 (1) ◽  
pp. 43-52 ◽  
Author(s):  
G. T. Ju ◽  
S. Kyriakides
Keyword(s):  
Limit Load ◽  
External Pressure ◽  
Experimental Results ◽  
Offshore Pipelines ◽  
Elastic Plastic ◽  
Combined Loads ◽  
Bifurcation Buckling ◽  
Load Types ◽  
T Values

Commonly used procedures for installing offshore pipelines can induce substantial bending to the line in the presence of external pressure. These combined loads can lead to catastrophic collapse of the structure. For typically used steels and higher diameter-to-thickness ratios (D/t), bending is limited by a bifurcation type of instability; for lower D/t values, the structures exhibit limit load types of instabilities. Similar distinctions can be made for bending in the presence of external pressure. Previous work (Corona and Kyriakides, 1988) addressed primarily the limit load types of instabilities. In this paper, this analysis is extended to include bifurcation instabilities. The predictions from the two types of analyses are critically compared to experimental results and recommendations about the regime of applicability of each are made.

An Approximate Model for an Elastic-Plastic Pipe Element Under Combined Loading

1975 ◽  
Vol 97 (1) ◽  
pp. 22-28 ◽  
Author(s):  
L. D. Larson ◽  
W. F. Stokey ◽  
W. E. Franzen
Keyword(s):  
Strain Hardening ◽  
Axial Load ◽  
Analytical Approach ◽  
Limit Load ◽  
Approximate Model ◽  
Experimental Results ◽  
Combined Loading ◽  
Elastic Plastic ◽  
Plastic Pipe ◽  
Plastic Analysis

An approximate model for the elastic-plastic analysis of a pipe element under combined loading is developed. The model is obtained by generalizing a limit load solution for combined pressure, bending, torsion and axial load to include strain hardening. For various combinations of loading of tubes, curvatures and twist angles are predicted and compared with experimental results and those predicted by a more rigorous analytical approach. The comparison shows that good results are obtained from the approximate model.

scholarly journals Simulation of the External Pressure Influence on the Micro-Structural Evolution of a Single Crystal Ni-Based Superalloy

2011 ◽  
Vol 278 ◽  
pp. 247-252
Author(s):  
Inmaculada Lopez-Galilea ◽  
Stephan Huth ◽  
Suzana Gomes Fries ◽  
Ingo Steinbach ◽  
Werner Theisen
Keyword(s):  
Single Crystal ◽  
Microstructural Evolution ◽  
Phase Field ◽  
Structural Evolution ◽  
Field Method ◽  
External Pressure ◽  
Experimental Results ◽  
Alloying Elements ◽  
Phase Field Method

The phase field method has been applied to simulate the microstructural evolution of a commercial single crystal Ni-based superalloy during both, HIP and annealing treatments. The effects of applying high isostatic pressure on the microstructural evolution, which mainly retards the diffusion of the alloying elements causing the loss of the orientational coherency between the phases is demonstrated by the simulation and experimental results

Clamped torispherical shells under external pressure — some new results

1988 ◽  
Vol 23 (1) ◽  
pp. 9-24 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Failure Mode ◽  
External Pressure ◽  
Spherical Cap ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Modes Of Failure ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Initial Geometric Imperfections ◽  
The One

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells. A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.

Elastic-plastic collapse of 3-D damaged cylindrical shells subjected to uniform external pressure

2004 ◽  
Vol 10 (4) ◽  
pp. 343-349 ◽  
Author(s):  
X. W. Zhao ◽  
J. H. Luo ◽  
M. Zheng ◽  
H. L. Li ◽  
M. X. Lu
Keyword(s):  
Cylindrical Shells ◽  
External Pressure ◽  
Plastic Collapse ◽  
Uniform External Pressure ◽  
Elastic Plastic

Nondimensional Parameters and Equations for Buckling of Anisotropic Shallow Shells

1994 ◽  
Vol 61 (3) ◽  
pp. 664-669 ◽  
Author(s):  
M. P. Nemeth
Keyword(s):  
Laminated Shells ◽  
Shallow Shells ◽  
Fundamental Parameters ◽  
Combined Loads ◽  
Vlasov Equations ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Z Parameter ◽  
Shear Buckling ◽  
Doubly Curved

A procedure for deriving nondimensional parameters and equations for bifurcation buckling of anisotropic shallow shells subjected to combined loads is presented. First, the Donnell-Mushtari-Vlasov equations governing buckling of symmetrically laminated doubly curved thin elastic shallow shells are presented. Then, the rationale used to perform the nondimensionalization of the buckling equations is presented, and fundamental parameters are identified that represent measures of the shell orthotropy and anisotropy. In addition, nondimensional curvature parameters are identified that are analogues of the well-known Batdorf Z parameter for isotropic shells, and analogues of Dunnell’s and Batdorf s shell buckling equations are presented. Selected results are presented for shear buckling of balanced symmetric laminated shells that illustrate the usefulness of the nondimensional parameters.

Reinforced concrete slabs on yielding supports under dynamic load

2021 ◽  
Vol 23 (3) ◽  
pp. 109-117
Author(s):  
G. I. Odnokopylov ◽  
Z. R. Galyautdinov ◽  
V. B. Maksimov
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
High Efficiency ◽  
Experimental Results ◽  
Displacement Velocity ◽  
Concrete Slabs ◽  
Elastic Plastic ◽  
Deformation Stage ◽  
Reinforced Concrete Slabs

The paper presents the experimental results of strength and deformability of reinforced concrete slabs on yielding supports arranged along the perimeter under the dynamic loading. Crushable ring-shaped inserts deforming at the elastic, plastic and curing stages are considered as yielding supports. The displacement, velocity and acceleration are evaluated depending on the deformation stage of yielding supports. The high efficiency is shown for the use of yielding supports, which leads to a significant reduction in the structure displacement, strain, and stress.

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.

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