Plastic Collapse and the Controlling Failure Pressures of Thin 2:1 Ellipsoidal Shells Subjected to Internal Pressure

1979 ◽  
Vol 101 (1) ◽  
pp. 64-72 ◽  
Author(s):  
G. D. Galletly ◽  
R. W. Aylward
Keyword(s):  
Internal Pressure ◽  
Strain Hardening ◽  
Failure Modes ◽  
Companion Paper ◽  
Plastic Collapse ◽  
Collapse Pressure

In the first part of the paper, plastic collapse pressures of thin 2:1 ellipsoidal shells are determined. The effects of E, σyp and strain hardening, S, on the collapse pressure are presented and discussed. The second part of the paper is concerned with the controlling failure pressures of internally pressurized 2:1 ellipsoidal shells. This involves the consideration of both plastic collapse pressures and asymmetric buckling pressures (the latter were obtained from a companion paper). Curves of the controlling failure pressures versus D/t are given for several values of σyp and S. Both aluminum and steel shells are considered. Dimensionless buckling and collapse pressures are also tabulated and some very simple formulas for both failure modes are suggested which should be useful to designers.

Plastic Collapse of Thin Internally Pressurized Torispherical Shells

1979 ◽  
Vol 101 (4) ◽  
pp. 311-320 ◽  
Author(s):  
S. K. Radhamohan ◽  
G. D. Galletly
Keyword(s):  
Strain Hardening ◽  
Yield Stress ◽  
Material Properties ◽  
Parametric Study ◽  
Companion Paper ◽  
Experimental Results ◽  
Plastic Collapse ◽  
Approximate Design ◽  
Mode Of Failure ◽  
Hardening Coefficient

The plastic collapse pressures of internally pressurized thin torispherical shells are given in the present paper. The influence of both the geometric parameters (i.e., r/D, RS/D and D/t) and the material properties (yield stress σyp and the strain-hardening coefficient) on the plastic collapse pressures were investigated. Both steel and aluminium shells were analyzed and, based on the present parametric study, approximate design equations for calculating the plastic collapse pressures are suggested. The asymmetric buckling pressures, pcr, for torispherical shells (obtained from a companion paper) are also compared with the plastic collapse pressures, pc, to determine which are the lower and, thus, control the mode of failure. In addition, the approximate design equations for pcr and pc are compared with some experimental results on small machined models; the agreement between theory and test was quite good.

A simple formula for prediction of plastic collapse pressure of steel ellipsoidal heads under internal pressure

2020 ◽  
Vol 156 ◽  
pp. 106994
Author(s):  
Jinyang Zheng ◽  
Zekun Zhang ◽  
Keming Li ◽  
Yehong Yu ◽  
Chaohua Gu
Keyword(s):  
Internal Pressure ◽  
Simple Formula ◽  
Plastic Collapse ◽  
Collapse Pressure

Comparison of Ellipsoidal and Equivalent Torispherical Heads Under Internal Pressure: Buckling, Plastic Collapse and Design Rules

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Jinyang Zheng ◽  
Yehong Yu ◽  
Yehong Chen ◽  
Keming Li ◽  
Zekun Zhang ◽  
...  
Keyword(s):  
Failure Modes ◽  
Good Prediction ◽  
Plastic Collapse ◽  
Design Equation ◽  
Fe Method ◽  
Shape Deviation ◽  
Design Rules ◽  
Collapse Pressure ◽  
Current Design ◽  
The Difference

Abstract Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII and EN13445-3, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate shape deviation between the two types of heads. Then we compare elastic–plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse (bursting). It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling of ellipsoidal heads based on the geometric equivalency approaches result in uneconomical design. In addition, experimental and numerical results show that such heads experience geometric strengthening. The finite element (FE) method considering the effect of geometric strengthening provides a good prediction of plastic collapse pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design. Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for bursting of ellipsoidal and torispherical heads.

Comparison of Ellipsoidal and Equivalent Torispherical Heads Under Internal Pressure: Buckling, Plastic Collapse and Design Rules

2019 ◽  
Author(s):  
Jinyang Zheng ◽  
Keming Li ◽  
Yehong Yu ◽  
Zekun Zhang ◽  
Wenzhu Peng ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Failure Modes ◽  
Bursting Pressure ◽  
Good Prediction ◽  
Plastic Collapse ◽  
Design Equation ◽  
Fe Method ◽  
Shape Deviation ◽  
Design Rules ◽  
Current Design

Abstract Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate the shape deviation between the two types of heads. Then we compare the elastic-plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse. It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling failure based on the geometric equivalency approaches result in uneconomical design. Nevertheless, the shape deviation has little effect on plastic collapse pressures of ellipsoidal and equivalent torispherical heads, showing that the geometric equivalency approaches are applicable for such heads that fail by plastic collapse (bursting). In addition, the experimental and numerical results show that such heads experience geometric strengthening. The FE method considering the effect of geometric strengthening provides a good prediction about plastic collapse (bursting) pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design. Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to the buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for the bursting of ellipsoidal and torispherical heads subjected to internal pressure.

Plastic Collapse Assessment of Thick Vessels Under Internal Pressure According to Various Hardening Rules

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
A. Chaaba
Keyword(s):  
Internal Pressure ◽  
Strain Hardening ◽  
Limit Analysis ◽  
Limit State ◽  
Plastic Behavior ◽  
Plastic Collapse ◽  
Perfectly Plastic ◽  
Von Mises ◽  
Hardening Rules ◽  
Collapse Assessment

This paper aims to deal with plastic collapse assessment for thick vessels under internal pressure, thick tubes in plane strain conditions, and thick spheres, taking into consideration various strain hardening effects and large deformation aspect. In the framework of von Mises’ criterion, strain hardening manifestation is described by various rules such as isotropic and/or kinematic laws. To predict plastic collapse, sequential limit analysis, which is based on the upper bound formulation, is used. The sequential limit analysis consists in solving sequentially the problem of the plastic collapse, step by step. In the first sequence, the plastic collapse of the vessel corresponds to the classical limit state of the rigid perfectly plastic behavior. At the end of each sequence, the yield stress and/or back-stresses are updated with or without geometry updating via displacement velocity and strain rates. The updating of all these quantities (geometry and strain hardening variables) is adopted to conduct the next sequence. As a result of this proposal, we get the limit pressure evolution, which could cause the plastic collapse of the device for different levels of hardening and also hardening variables such as back-stresses with respect to the geometry change.

Post-Buckling Failure Modes of X65 Steel Pipe: An Experimental and Numerical Study

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Nima Mohajer Rahbari ◽  
Mengying Xia ◽  
Xiaoben Liu ◽  
J. J. Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Failure Modes ◽  
Bending Test ◽  
Bending Load ◽  
Post Buckling ◽  
X65 Steel ◽  
Bending Loads ◽  
Buckling Failure ◽  
Longitudinal Strains

In service pipelines exhibit bending loads in a variety of in-field situation. These bending loads can induce large longitudinal strains, which may trigger local buckling on the pipe's compressive side and/or lead to rupture of the pipe's tensile side. In this article, the post-buckling failure modes of pressurized X65 steel pipelines under monotonic bending loading conditions are studied via both experimental and numerical investigations. Through the performed full-scale bending test, it is shown that the post-buckling rupture is only plausible to occur in the pipe wall on the tensile side of the wrinkled cross section under the increased bending. Based on the experimental results, a finite element (FE)-based numerical model with a calibrated cumulative fracture criterion was proposed to conduct a parametric analysis on the effects of the internal pressure on the pipe's failure modes. The results show that the internal pressure is the most crucial variable that controls the ultimate failure mode of a wrinkled pipeline under monotonic bending load. And the post-buckling rupture of the tensile wall can only be reached in highly pressurized pipes (hoop stress no less than 70% SMYS for the investigated X65 pipe). That is, no postwrinkling rupture is likely to happen below a certain critical internal pressure even after an abrupt distortion of the wrinkled wall on the compressive side of the cross section.

Failure Analysis of Tubular Hydroforming

2000 ◽  
Author(s):  
Z. C. Xia
Keyword(s):  
Internal Pressure ◽  
Process Parameters ◽  
Deformation Theory ◽  
Failure Modes ◽  
Tensile Loading ◽  
Failure Criteria ◽  
Material Anisotropy ◽  
Governing Equations ◽  
Compression Load ◽  
Failure Diagram

Abstract A mathematical analysis of failure developments for tubular hydroforming under combined internal pressure and end feeding is presented in this paper. Under considerations are two distinct failure modes, namely the bursting and the wrinkling. Bursting is an instability phenomenon where the tube can’t sustain any more tensile loading. Splitting usually follows due to extreme deformations in the bursting area. Wrinkling is due to high compression load, which deteriates the qulity of the final product. The deformation theory of plasticity is utilized in this study that takes into account of material anisotropy. The governing equations for the onset of both failure modes are established. The results are presented as Hydroforming Failure Diagram in the End Feed – Internal Pressure space. A parametric study of the failure criteria for a variety of materials and process parameters is performed. It is shown that the material anisotropy plays a significant role. The results provide guidelines for product designers and process engineers for the avoidance of failure during hydroforming. The validity and applicability of current study are also discussed.

A New Method for Preventing Plastic Collapse of Ellipsoidal Head Under Internal Pressure

2021 ◽  
Author(s):  
Keming Li ◽  
Jinyang Zheng ◽  
Zekun Zhang ◽  
Chaohua Gu ◽  
Ping Xu
Keyword(s):  
Internal Pressure ◽  
New Method ◽  
Plastic Collapse
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