Plastic Collapse Analysis of Pipe Bends Under Out-of-Plane Moment and Internal Pressure Loading

2006 ◽  
Author(s):  
Hongjun Li ◽  
Donald Mackenzie
Keyword(s):  
Strain Hardening ◽  
Large Deformation ◽  
Plastic Work ◽  
Deformation Analysis ◽  
Plastic Collapse ◽  
Plastic Response ◽  
Pipe Bend ◽  
Moment Interaction ◽  
Collapse Analysis ◽  
Out Of Plane

Two recently proposed Design by Analysis criteria of plastic collapse based on plastic work concepts, the Plastic Work criterion and the Plastic Work Curvature criterion, are applied to a strain hardening pipe bend arrangement subject to combined pressure and out-of-plane plane moment loading. Calculated plastic pressure-moment interaction surfaces are compared with limit surfaces, large deformation analysis instability surfaces and plastic load surfaces given by the ASME Twice Elastic Slope criterion. The results show that both large deformation theory and material strain hardening have a significant effect on the elastic-plastic response and calculated static strength of the component.

Generation of Plastic Collapse Load Boundaries of a Pressurized Cylindrical Vessel/Radial Nozzle Structure Subjected to Nozzle Bending Loadings Utilizing Various Plastic Collapse Load Techniques

2020 ◽  
pp. 2050115
Author(s):  
Hany Fayek Abdalla
Keyword(s):  
Validation Study ◽  
Cylindrical Vessel ◽  
Plastic Work ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Pipe Bend ◽  
Out Of Plane ◽  
Radial Nozzle ◽  
Nozzle Structure

This research focuses on generating the plastic collapse load boundaries of a cylindrical vessel with a radial nozzle via employing three different plastic collapse load techniques. The three plastic collapse load techniques employed are the plastic work curvature (PWC) criterion, the plastic work (PW) criterion, and the twice-elastic-slope (TES) method. Mathematical based determination of plastic collapse loads is presented and employed concerning both the PWC and the PW criteria. A validation study is initially conducted on a pressurized 90-degree pipe bend structure subjected to in-plane closing bending via finite element analyses along with an elaborate explanation of the mathematical approaches for determining the plastic collapse loads via the PWC and the PW criteria. Outcomes of the validation study revealed very good outcomes for the three techniques. Accordingly, the aforementioned three techniques are utilized to determine the plastic collapse load boundaries of a pressurized cylindrical vessel/nozzle structure subjected to in-plane (IP) and out-of-plane (OP) bending loadings applied on the nozzle one at a time. The TES method revealed considerate limitations when applied within the medium to the high internal pressure spectra. It is shown that both the PWC and the PW criteria outperform the TES method in computing the plastic collapse loads. The vessel/nozzle structure revealed relatively higher plastic collapse moment boundaries under IP bending as compared to OP bending. Conclusively, methodical steps are devised for determining the plastic collapse loads via the PWC and the PW criteria for the ease of systematic application on pressurized structures in general.

Effect of Bend Angle on Gross Plastic Deformation of Pipe Bends for Out-of-Plane Bending: A Study Using Plastic Work Curvature Method

2016 ◽  
Author(s):  
Anindya Bhattacharya ◽  
Sachin Bapat ◽  
Hardik Patel ◽  
Shailan Patel ◽  
Michael P. Cross
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Bending Moment ◽  
Plastic Work ◽  
Bend Angle ◽  
Piping System ◽  
Plastic Collapse ◽  
Pipe Bend ◽  
Out Of Plane ◽  
Plane Bending

Bends are an integral part of a piping system. Because of the ability to ovalize and warp they offer more flexibility when compared to straight pipes. Piping Code ASME B31.3 [1] provides flexibility factors and stress intensification factors for pipe bends. Like any other piping component, one of the failure mechanisms of a pipe bend is gross plastic deformation. In this paper, plastic collapse load of pipe bends have been analyzed for various bend parameters (bend parameter = tRbrm2) under internal pressure and out-of-plane bending moment for various bend angles using both small and large deformation theories. FE code ABAQUS version 6.9EF-1 has been used for the analyses. The goal of the paper is to develop an expression for plastic collapse moment for a bend using plastic work curvature method when the bend is subjected to out-of-plane bending moment and internal pressure as a function of bend angle and bend parameter.

Gross Plastic Deformation of a Hemispherical Head With Cylindrical Nozzle: A Comparative Study

2007 ◽  
Author(s):  
Tomohiro Naruse ◽  
Donald Mackenzie ◽  
Duncan Camilleri
Keyword(s):  
Strain Hardening ◽  
Large Deformation ◽  
Deformation Behaviour ◽  
Limit Load ◽  
Hardening Material ◽  
Cylindrical Nozzle ◽  
Stress Classification ◽  
Moment Interaction ◽  
Design Loads

The plastic load of a hemispherical head with a cylindrical nozzle subject to an internal pressure and/or moment is established using two new plastic criteria; the plastic work curvature (PWC) criterion and the ratio of plastic to total work curvature (RPWC) criterion. The calculated plastic loads are compared to ASME Design by Analysis stress categorization and limit analysis allowable loads. The stress categorization approach is seen to be dependant on the appropriate choice of stress classification lines and the classification of primary, secondary and peak stresses. The limit load approach is simpler to apply but does not consider material strain hardening and/or large deformation behaviour and may often lead to conservative design loads. In the plastic analyses, strain hardening material models and large deformation analyses are considered. The calculated allowable pressure-moment interaction surfaces are assessed and compared for the different methods.

Large Deformation Analysis of an Elastic-Plastic Cantilevered Beam

1989 ◽  
Vol 111 (3) ◽  
pp. 312-315 ◽  
Author(s):  
D. W. Nicholson
Keyword(s):  
Large Deformation ◽  
Numerical Procedure ◽  
Bending Moment ◽  
Elastic Response ◽  
Graphical Form ◽  
Deformation Analysis ◽  
Plastic Response ◽  
Large Deformation Analysis ◽  
Elastic Plastic ◽  
Cantilevered Beam

This study concerns the analysis of the deflection of an elastic-plastic cantilevered beam. Three regions of solution are treated: (i) purely elastic response at low loads; (ii) elastic-plastic response without a hinge, for intermediate loads; and (iii) elastic-plastic response with a hinge for loads corresponding to the fully plastic bending moment at the built-in end. Most existing solutions for this type of problem involve various approximations avoided here, for example, ignoring the elastic part of the strain or using upper bounds based on limit analysis. By avoiding such approximations, the solution given here may be useful as a benchmark for validating finite element codes in the large deformation elastic-plastic regime. Several aspects of the solution are analyzed: (i) the load-deflection relation; (ii) the growth of the elastic-plastic zone; (iii) limiting cases; (iv) the residual configuration; (v) the small bending configuration. A numerical procedure based on Runge-Kutta methods is used, leading to the load-deflection relation in graphical form.

Large Deformation Analysis of a Dielectric Elastomer Membrane

2014 ◽  
Vol 912-914 ◽  
pp. 981-988
Author(s):  
Lei Lei Cui ◽  
Li Li
Keyword(s):  
Large Deformation ◽  
Shooting Method ◽  
Plane Deformation ◽  
Dielectric Elastomer ◽  
Deformation Analysis ◽  
Large Deformation Analysis ◽  
Energy Harvesters ◽  
Out Of Plane ◽  
Dielectric Elastomer Membrane ◽  
Axisymmetric Shape

Due to the capability of high strain, dielectric elastomers are promising for applications as transducers in cameras, robots, valves, pumps, energy harvesters and so on. This paper focuses on the large deformation analysis of a dielectric elastomer membrane.The membrane is initially flat and attached to a disk in the inner circle and to a rigid ring in the outer circle, then a weight is applied to the disk and the membrane deforms into an axisymmetric shape, undergoing large out-of-plane deformation. The membrane is assumed to behave elastically in accordance with the ogden law. The governing equations are derived by combining kinematics and thermodynamics and a set of ordinary differential equations (ODEs) are obtained finally. The ODEs are solved by using shooting method. The obtained results show that the deformation field in the membrane is very inhomogeneous.

scholarly journals A Plastic Load Criterion for Inelastic Design by Analysis

2005 ◽  
Vol 128 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Donald Mackenzie ◽  
Hongjun Li
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Three Dimensional ◽  
Plastic Work ◽  
Plastic Response ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Collapse Behavior ◽  
Three Dimensional Finite Element ◽  
Inelastic Design

The allowable plastic load in pressure vessel design by analysis is determined by applying a graphical construction to a characteristic load-deformation plot of the collapse behavior of the vessel. This paper presents an alternative approach to the problem. The plastic response is characterized by considering the curvature of a plot of plastic work dissipated in the vessel against the applied load. It is proposed that salient points of curvature correspond to critical stages in the evolution of the gross plastic deformation mechanism. In the proposed plastic work curvature (PWC) criterion of plastic collapse, the plastic load is defined as the load corresponding to zero or minimal plastic work curvature after yielding and the formation of plastic mechanisms have occurred. Application of the proposed criterion is illustrated by considering the elastic-plastic response of a simple cantilever beam in bending and a complex three-dimensional finite element analysis of a nozzle intersection. The results show that the proposed approach gives higher values of plastic load than alternative criteria when the material exhibits strain hardening. It is proposed that this is because the PWC criterion more fully represents the constraining effect of material strain hardening on the spread of plastic deformation.

A Criterion for Evaluating Plastic Collapse Load: Plastic Work-Tangent Criterion

2017 ◽  
Author(s):  
Ying Zhang
Keyword(s):  
Pressure Vessel ◽  
Work Load ◽  
Plastic Work ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Plastic Response ◽  
Load Curve ◽  
Plastic Phase ◽  
New Criterion ◽  
Reactor Pressure

A new criterion: plastic work-tangent (PWT) criterion for evaluating plastic collapse load in pressure vessel design by analysis is presented in this paper. According to the plastic work-load curve, when the tangent variation is less than a given value in the plastic phase, the corresponding load is the plastic collapse load. Application of the proposed criterion is illustrated by considering the elastic-plastic response of lower head of reactor pressure vessel (RPV) and nozzle intersection of RPV. It is proposed that this is because the PWT criterion more conveniently to use in finite element soft ANSYS and more efficiently to evaluate the plastic collapse load.

Gross Plastic Deformation of Pipe Bends Under Internal Pressure and In- and Out-of-Plane Bending: A Study on the Sensitivity of the Finite Element Models

2014 ◽  
Author(s):  
Anindya Bhattacharya ◽  
Sachin M. Bapat
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Real Life ◽  
Bending Moment ◽  
Piping System ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Pipe Bend ◽  
Out Of Plane ◽  
Plane Bending

Bends are an integral part of a piping system. Because of the ability to ovalize and warp they offer more flexibility when compared to straight pipes. Piping Code ASME B31.3 [1] provides flexibility factors and stress intensification factors for the pipe bends. Like any other piping component, one of the failure mechanisms of a pipe bend is gross plastic deformation. In this paper, plastic collapse load of pipe bends have been analyzed for various D/t ratios (Where D is pipe outside diameter and t is pipe wall thickness) for internal pressure and in-plane bending moment, internal pressure and out-of-plane bending moment and internal pressure and a combination of in and out-of-plane bending moments under varying ratios. Any real life component will have imperfections and the sensitivity of the models have been investigated by incorporating imperfections as scaled eigenvectors of linear bifurcation buckling analyses. The sensitivity of the models to varying parameters of Riks analysis (an arc length based method) and use of dynamic stabilization using viscous damping forces have also been investigated. Importance of defining plastic collapse load has also been discussed. FE code ABAQUS version 6.9EF-1 has been used for the analyses.

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