Work Bounds and Associated Deformation of Cyclically Loaded Creeping Structures

1973 ◽  
Vol 40 (4) ◽  
pp. 921-927 ◽  
Author(s):  
A. R. S. Ponter ◽  
J. J. Williams
Keyword(s):  
Internal Pressure ◽  
Cycle Time ◽  
Characteristic Time ◽  
Plastic Material ◽  
Bending Moment ◽  
Perfectly Plastic ◽  
State Of Stress ◽  
The Difference ◽  
Work Done ◽  
Walled Cylinder

In this paper the deformations of a beam subject to cyclic bending moment and a thick-walled cylinder subject to cyclic internal pressure are investigated for an elastic/time hardening/perfectly plastic material. Bounds [1, 2] are computed on the work done by the applied loads over a cycle when the material has reached a cyclic state of stress. The bounds provide the extreme states when the cycle time is either large or small compared with a characteristic time of the material. It is found that the difference between the bounds is generally very small. This result is discussed in relation to recent work by Williams and Leckie [3].

Elastic-plastic stress analysis of a cracked thick-walled cylinder

1983 ◽  
Vol 18 (4) ◽  
pp. 253-260 ◽  
Author(s):  
C L Tan ◽  
K H Lee
Keyword(s):  
Internal Pressure ◽  
Stress Analysis ◽  
Plastic Material ◽  
Boundary Integral ◽  
Hardening Material ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Walled Cylinder ◽  
Plastic Stress

The boundary integral equation (BIE) method for two-dimensional elastic-plastic stress analysis is applied to an internally pressurized thick-walled cylinder containing a radial crack. Two different types of material are considered, namely, an elastic-perfectly plastic material and a work-hardening material. The loading conditions applied include the case when the internal pressure also acts on the crack faces, and the case when it does not. Results are presented showing the plastic zone development in the cylinder and the variations of the fracture mechanics parameter, the J line integral, with increasing internal pressure.

The ratchetting of a cylinder subjected to internal pressure and alternating axial deformation

1993 ◽  
Vol 28 (4) ◽  
pp. 277-282 ◽  
Author(s):  
D N Moreton
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Plastic Material ◽  
Yield Criterion ◽  
Axial Deformation ◽  
Simple Experiment ◽  
Perfectly Plastic ◽  
Thin Walled ◽  
Elastic Perfectly Plastic ◽  
Walled Cylinder

A thin-walled cylinder subjected to a continuous internal pressure and an alternating axial deformation is shown to exhibit ratchetting. This ratchetting manifests itself as a growth in the diameter of the cylinder and a reduction in its wall thickness. For an elastic-perfectly-plastic material the ratchetting rates are established and the boundaries of ratchetting behaviour determined. These ratchetting rates are compared with the results from a simple experiment and other available data. It is noted that the analysis is very sensitive to the yield criterion adopted.

On Thick-Walled Cylinder Under Internal Pressure

2003 ◽  
Vol 125 (3) ◽  
pp. 267-273 ◽  
Author(s):  
W. Zhao ◽  
R. Seshadri ◽  
R. N. Dubey
Keyword(s):  
Internal Pressure ◽  
Strain Curve ◽  
Stress Strain ◽  
Piecewise Linearization ◽  
Elastic Plastic ◽  
Plastic Cylinder ◽  
Parametric Functions ◽  
The Difference ◽  
New Formulation ◽  
Walled Cylinder

A technique for elastic-plastic analysis of a thick-walled elastic-plastic cylinder under internal pressure is proposed. It involves two parametric functions and piecewise linearization of the stress-strain curve. A deformation type of relationship is combined with Hooke’s law in such a way that stress-strain law has the same form in all linear segments, but each segment involves different material parameters. Elastic values are used to describe elastic part of deformation during loading and also during unloading. The technique involves the use of deformed geometry to satisfy the boundary and other relevant conditions. The value of strain energy required for deformation is found to depend on whether initial or final geometry is used to satisfy the boundary conditions. In the case of low work-hardening solid, the difference is significant and cannot be ignored. As well, it is shown that the new formulation is appropriate for elastic-plastic fracture calculations.

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.

A limit load solution for a thick-walled cylinder with a fully circumferential crack under axial tension

2009 ◽  
Vol 44 (6) ◽  
pp. 407-416 ◽  
Author(s):  
P J Budden ◽  
Y Lei
Keyword(s):  
Finite Element ◽  
Plastic Material ◽  
Yield Criterion ◽  
Limit Load ◽  
Cylinder Wall ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Von Mises ◽  
Inside Radius ◽  
Walled Cylinder

Limit loads for a thick-walled cylinder with an internal or external fully circumferential surface crack under pure axial load are derived on the basis of the von Mises yield criterion. The solutions reproduce the existing thin-walled solution when the ratio between the cylinder wall thickness and the inside radius tends to zero. The solutions are compared with published finite element limit load results for an elastic–perfectly plastic material. The comparison shows that the theoretical solutions are conservative and very close to the finite element data.

A Finite Element Based Study on the Elastic-Plastic Transition Behavior in a Hemisphere in Contact With a Rigid Flat

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
S. Shankar ◽  
M. M. Mayuram
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Plastic Material ◽  
Plastic Region ◽  
Real Contact Area ◽  
Real Contact ◽  
Perfectly Plastic ◽  
The Difference ◽  
Elastic Perfectly Plastic ◽  
Green Model

An axisymmetrical hemispherical asperity in contact with a rigid flat is modeled for an elastic perfectly plastic material. The present analysis extends the work (sphere in contact with a flat plate) of Kogut–Etsion Model and Jackson–Green Model and addresses some aspects uncovered in the above models. This paper shows the critical values in the dimensionless interference ratios (ω∕ωc) for the evolution of the elastic core and the plastic region within the asperity for different Y∕E ratios. The present analysis also covers higher interference ratios, and the results are applied to show the difference in the calculation of real contact area for the entire surface with other existing models. The statistical model developed to calculate the real contact area and the contact load for the entire surfaces based on the finite element method (FEM) single asperity model with the elastic perfectly plastic assumption depends on the Y∕E ratio of the material.

Strength Limit of Thimble Tube With Material Plasticity Under Bending Moment and Axial Compression Force

2018 ◽  
Author(s):  
Hisashi Koike ◽  
Masaji Mori ◽  
Daisuke Fujiwara ◽  
Takashi Shimomura
Keyword(s):  
Fuel Assembly ◽  
Seismic Event ◽  
Plastic Material ◽  
Bending Moment ◽  
Normal Operation ◽  
Beam Model ◽  
Allowable Limit ◽  
Perfectly Plastic ◽  
Asme Code ◽  
Elastic Perfectly Plastic

The thimble tube, which is made of Zircaly-4, is one of the main components of a PWR fuel assembly. The thimble tube has an important role as a structural member of the skeleton. Another role of the thimble tube is to guide a rod cluster control assembly (RCCA) for insertion during the reactor operation, and the function has to be assured not only in normal operation but in a seismic event. In a horizontal seismic event, the fuel assembly vibrates laterally, which gives bending moment to the thimble tube. In addition, axial compressive force acts on the thimble tube in a vertical seismic event. The integrity of the thimble tube has to be maintained while this force and moment act. Mitsubishi has confirmed by the elastic stress analysis that the stress of the thimble tube is lower than the limit value requested for the seismic event. The stress evaluation method is based on the ASME code. The ASME code also describes the limit analysis which is available when the predicted stress is beyond elastic region of the material. In the analysis, the material is assumed to be elastic-perfectly plastic, and the maximum load that the structure can carry is calculated. For the reason mentioned above, the allowable limit of the thimble tube should be determined as a function between the force and the moment. We are planning to examine the allowable limit experimentally. As a step before testing, an analytical approach for the limit is discussed in this paper. Firstly, the allowable limit is calculated by a beam model assuming elastic-perfectly plastic material, based on the ASME code. Secondly, a 3D model analysis with elastic-plastic material is performed to predict the practical strength. Based on the comparison with the analysis using elastic-perfectly plastic material, ASME based limit is considerably conservative compared with the one with the actual stress-strain curve. Conversely, this means there is enough room to rationalize the allowable limit. As the future work, the experiment will be conducted to obtain the practical limit of the thimble tube and to verify the analysis results.

Plastic Collapse Load for Vessel With External Flaw Simultaneously Subjected to Internal Pressure and External Bending Moment: Experimental and FEA Results

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Shinji Konosu ◽  
Masato Kano ◽  
Norihiko Mukaimachi ◽  
Hiroyuki Komura ◽  
Hiroyuki Takada
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Pressure Ratio ◽  
Safety Margin ◽  
Bending Moment ◽  
Plastic Instability ◽  
Plastic Collapse ◽  
Collapse Load ◽  
The Status ◽  
Work Done

This paper is based on work done to establish the validity of a simple engineering approach to assess plastic collapse for a vessel with a local thin area (LTA). The approach is based on a recently developed p-M (internal pressure ratio and external bending moment ratio) diagram, which is an easy way to visualize the status of a vessel with a LTA simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point (Mr,pr) lies inside the p-M line, the vessel with the LTA is judged to be safe. Numerous experiments and finite element analyses for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are similar to those calculated under the proposed p-M line based on the measured yield stress. The p-M line adopted in the Ibaraki fitness for service (FFS) rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0–3.0, about 1.5–4.0 for the TES loads at LTA, and 2.5–6.5 for the plastic instability (break) loads.

FEM Stress Analysis and Mechanical Characteristics of Bolted Pipe Flange Connections With PTFE Blended Gaskets Subjected to External Bending Moments and Internal Pressure

2017 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Riichi Morimoto ◽  
Takashi Kobayashi
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Bending Moment ◽  
Leak Rate ◽  
Bending Moments ◽  
Four Point Bending ◽  
Sealing Performance ◽  
The Difference ◽  
Good Agreement

In designing of pipe flange connections with gaskets, it is important to examine the mechanical characteristics of the connections subjected to external bending moments due to earthquake such as the changes in hub stress, axial bolt forces and the contact gasket stress distribution which governs the sealing performance. One of the authors developed the PTFE blended gaskets and the authors examined the mechanical characteristics of the connections with the PTFE blended gaskets under internal pressure. However, no research was done to examine the mechanical characteristics of the connections with the newly developed PTFE blended gasket subjected to external bending moment due to earthquake. The objectives of the present study are to examine the mechanical characteristics of the connection with PTFE blended gasket subjected to external bending moment and internal pressure and to discuss the difference in the load order to the connections between the internal pressure and the external bending moments. The changes in the hub stress, the axial bolt force and the contact gasket stress distribution of the connection are analyzed using FEM. Using the obtained the gasket stress distribution and the fundamental data between the gasket stress and the leak rate for a smaller test gasket, the leak rate of the connection with the gasket is predicted under external bending moment and internal pressure. In the FEM calculations, the effects of the nominal diameter of pipe flanges on the mechanical characteristics are shown. In the experiments, ASME class 300 4 inch flange connection with 2m pipes at both sides is used and the test gasket is chosen as No.GF300 made by Nippon Valqua Industries, ltd. Four point bending moment is applied to the connection. The FEM results of the hub stress and the axial bolt forces are in a fairly good agreement with the experimental results. In addition, the FEM results of the leak rate are fairly coincided with the measured results.

Limit Load Solutions of the Orthotropic Thick-Walled Pipe Subjected to Internal Pressure, Bending Moment and Torsion Moment

2019 ◽  
Author(s):  
Min Xu ◽  
Yujie Zhao ◽  
Binbin Zhou ◽  
Xiaohua He ◽  
Changyu Zhou
Keyword(s):  
Analytical Solution ◽  
Yield Strength ◽  
Internal Pressure ◽  
Yield Criterion ◽  
Bending Moment ◽  
Limit Load ◽  
Pure Bending ◽  
Pure Torsion ◽  
Torsion Moment ◽  
The Difference

Abstract Based on the Hill yield criterion, the analytical solutions of the limit load of orthotropic thick-walled pipes under pure internal pressure, bending moment and torsion are given respectively. The simplified Mises analytical solution and finite element results of limit load for isotropic thick-walled pipe are obtained. The solution verifies the reliability of the analytical solution. The paper discusses the difference of limit load of isotropic and orthotropic pipes under the conditions of pure internal pressure, pure bending moment and pure torsion moment. It is concluded that the influence of material anisotropy on the limit load is significant. The limit load of pipe under pure internal pressure is mainly determined by circumferential yield strength, pure bending is only related to axial yield strength and pure torsion moment is related to the yield strength in the 45° direction and radial yield strength.

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