Shakedown Limits for Hillside Nozzles in Cylindrical Vessels

2017 ◽  
Author(s):  
Ahmed K. Bakry ◽  
Chahinaz A. Saleh ◽  
Mohammad M. Megahed
Keyword(s):  
Internal Pressure ◽  
Superposition Method ◽  
Nonlinear Superposition ◽  
Cyclic Pressure ◽  
Fea Model ◽  
Direct Technique ◽  
Out Of Plane ◽  
High Pressure Range ◽  
Bending Loads ◽  
Shakedown Limit

This research paper is concerned with the mechanical behavior of the cylindrical vessels with hillside nozzles when subjected to both pressure and nozzle bending loads in cyclic forms. The influence of hillside angle on shakedown (SD) limits of the connection under cyclic pressure and combined steady pressure with cyclic nozzle bending is investigated. A shell FEA model is built for the assembly using five different hillside angles ranging from 0° to 40°. Shakedown limits are determined by a direct technique known as the Nonlinear Superposition Method (NSM). Bree diagrams for cyclic out of plane opening (OPO) / in plane (IP) nozzle moments combined with steady internal pressure are determined. The results show an increase in both OPO and IP shakedown moments as the hillside angle is increased. In addition, the OPO shakedown limit moments for all hillside angles was found to be insensitive to the level of internal pressure in contrary to IP shakedown moment which starts to reduce with pressure for the high pressure range.

Shakedown Limits for Hillside Nozzles in Cylindrical Vessels

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Ahmed K. Bakry ◽  
Chahinaz A. Saleh ◽  
Mohammad M. Megahed
Keyword(s):  
Internal Pressure ◽  
High Pressures ◽  
Superposition Method ◽  
Analysis Model ◽  
Element Analysis ◽  
Nonlinear Superposition ◽  
Direct Technique ◽  
Out Of Plane ◽  
Shell Finite Element ◽  
Shakedown Limit

This research paper is concerned with the mechanical behavior of the cylindrical vessels with hillside nozzles when subjected to both pressure and nozzle bending loads in cyclic forms. The influence of hillside angle on shakedown (SD) limits of the connection under cyclic pressure and combined steady pressure with cyclic nozzle bending is investigated. A shell finite element analysis model is built for the assembly using five different hillside angles ranging from 0 deg to 40 deg. Shakedown limits are determined by a direct technique known as the nonlinear superposition method (NSM). Bree diagrams for cyclic out of plane opening (OPO)/in plane (IP) nozzle moments combined with steady internal pressure are determined. The results show an increase in both OPO and IP shakedown moments as the hillside angle is increased. In addition, the OPO shakedown limit moments for all hillside angles were found to be insensitive to the level of internal pressure; this differs from the IP shakedown moment which starts to decrease with pressure for the high pressures.

Shakedown Boundary of a 90–Degree Back–to–Back Pipe Bend Subjected to Steady Internal Pressures and Cyclic Out–of–Plane Bending Moments

2014 ◽  
Author(s):  
Hany F. Abdalla
Keyword(s):  
Internal Pressure ◽  
Bending Moment ◽  
Bending Moments ◽  
Pipe Bend ◽  
Structure Comparison ◽  
Out Of Plane ◽  
Plane Bending ◽  
Shakedown Limit ◽  
Elastic Shakedown ◽  
Internal Pressures

Ninety degree back–to–back pipe bends are extensively utilized within piping networks of modern nuclear submarines and modern turbofan aero–engines where space limitation is considered a supreme concern. According the author’s knowledge, no shakedown analysis exists for such structure based on experimental data. In the current research, the pipe bend setup analyzed is subjected to a spectrum of steady internal pressures and cyclic out–of–plane bending moments. A previously developed direct non–cyclic simplified technique, for determining elastic shakedown limit loads, is utilized to generate the elastic shakedown boundary of the analyzed structure. Comparison with the elastic shakedown boundary of the same structure, but subjected to cyclic in–plane bending moments revealed a higher shakedown boundary for the out–of–plane bending loading configuration with a maximum bending moment ratio of 1.4 within the low steady internal pressure spectrum. The ratio decreases towards the medium to high internal pressure spectrum. The simplified technique outcomes showed excellent correlation with the results of full elastic–plastic cyclic loading finite element simulations.

Guidelines for FEA Modeling of Cylinder-to-Cylinder Intersection

2004 ◽  
Author(s):  
Liping Xue ◽  
G. E. O. Widera
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Wall Thickness ◽  
Finite Element Models ◽  
Element Analysis ◽  
Fea Model ◽  
Fea Modeling ◽  
Out Of Plane

The purpose of this paper is to develop a definitive set of guidelines for carrying out finite element analysis (FEA) modeling of cylinder-to-cylinder intersections. By studying the stresses in the neighborhood of such intersections subjected to internal pressure and external moments (in-plane and out-of-plane moments) resulting from the use of various finite element models, the effects of number of elements along the nozzle circumference, number of elements through the wall thickness and element sizes in the direction perpendicular to nozzle circumference are investigated. Finally, general guidelines are proposed for setting up a FEA model of cylinder-to-cylinder intersections.

Shakedown Limit Load Determination for a Kinematically Hardening 90-Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic Bending

2007 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Material Behavior ◽  
Pipe Bend ◽  
Cyclic Bending ◽  
Perfectly Plastic ◽  
Shakedown Limit

A simplified technique for determining the shakedown limit load of a structure employing an elastic-perfectly-plastic material behavior was previously developed and successfully applied to a long radius 90-degree pipe bend. The pipe bend is subjected to constant internal pressure and cyclic bending. The cyclic bending includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending moment loadings. The simplified technique utilizes the finite element method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full cyclic loading finite element simulations or conventional iterative elastic techniques. In the present paper, the simplified technique is further modified to handle structures employing elastic-plastic material behavior following the kinematic hardening rule. The shakedown limit load is determined through the calculation of residual stresses developed within the pipe bend structure accounting for the back stresses, determined from the kinematic hardening shift tensor, responsible for the translation of the yield surface. The outcomes of the simplified technique showed very good correlation with the results of full elastic-plastic cyclic loading finite element simulations. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes. The generated shakedown diagrams are compared with the ones previously generated employing an elastic-perfectly-plastic material behavior. These indicated conservative shakedown limit moments compared to the ones employing the kinematic hardening rule.

The Effect of Initial Forces on the Hydroelastic Vibration and Stability of Planar Curved Tubes

1974 ◽  
Vol 41 (2) ◽  
pp. 355-359 ◽  
Author(s):  
J. L. Hill ◽  
C. G. Davis
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Constant Curvature ◽  
Elastic Limit ◽  
Center Line ◽  
Finite Element Technique ◽  
Line Shapes ◽  
Circular Arcs ◽  
Out Of Plane ◽  
Element Technique

The effect of initial forces on the vibration and stability of curved, clamped, fluid conveying tubes is analyzed by the finite-element technique. The tubes are initially planar with general center-line shapes approximated by constant curvature arcs. The effect of internal pressure is included. Numerical results are presented with, and without, the effects of the initial in-plane forces, for circular arcs S, L, and spiral configurations. Neglecting initial forces results in out-of-plane buckling, while including these forces prevents buckling within the elastic limit, in all configurations studied.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

A Theoretical and Experimental Analysis of the Bending Behavior of Unbonded Flexible Pipes

2014 ◽  
Author(s):  
Tatiana Vargas-Londoño ◽  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Structural Response ◽  
Experimental Tests ◽  
Theoretical Models ◽  
External Pressure ◽  
Local Behavior ◽  
Flexible Pipes ◽  
Floating System ◽  
Bending Loads

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of the pipe that have to be properly evaluated in order to ensure integrity of the line. Research has been done on the local behavior of flexible pipes under combined axisymmetric loads as well as under bending loads. However, there is a lack of research combining both axisymmetric and bending loads, as also in the study of the strains in the tensile amour layers of the pipes, aspects which are important for the calibration of theoretical models to predict such behavior. Based on that, this study aims to evaluate the local behavior of flexible pipes under combinations of axisymmetric (tension, and internal pressure) and bending loads via a series of experimental tests in a 9.13″ I.D pipe. In the experimental tests, the behavior of the pipe was studied for three load combinations: i) bending combined with tension; ii) bending combined with internal pressure; and iii) bending combined with tension and internal pressure. Based on these tests, the authors obtained the strains in the tensile armor layer, axial elongation due to tension, axial reaction forces due to internal pressure, and deflection due to bending. These measurements were used to calibrate a theoretical model devoted to simulate the pipe’s response, getting accurate results for stiffness and stresses of the pipe in each scenario.

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 of GRP Pipe Bends Under Out-of-Plane Flexure with and Without Pressure

1993 ◽  
Vol 207 (2) ◽  
pp. 133-141
Author(s):  
R Kitching ◽  
P Myler
Keyword(s):  
Internal Pressure ◽  
Polyester Resin ◽  
Design Procedure ◽  
Out Of Plane ◽  
Failure Loads ◽  
Smooth Pipe ◽  
Plane Bending ◽  
Chopped Strand Mat ◽  
Plane Flexure

Tests to failure have been carried out on six smooth pipe bends constructed by hand lay-up from polyester resin and glass in the form of chopped strand mat. The failure loads under out-of-plane bending only are compared with those where this type of loading is combined with internal pressure. The results are discussed in relation to the design procedure adopted in BS 7159: 1989.

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