Closed-Form Collapse Moment Equations of Throughwall Circumferentially Cracked Elbows Subjected to In-Plane Bending Moment

2004 ◽  
Vol 126 (3) ◽  
pp. 307-317 ◽  
Author(s):  
J. Chattopadhyay ◽  
A. K. S. Tomar ◽  
B. K. Dutta ◽  
H. S. Kushwaha
Keyword(s):  
Closed Form ◽  
Bending Moment ◽  
Moment Equations ◽  
Element Analysis ◽  
Perfectly Plastic ◽  
Circumferential Crack ◽  
Opening Mode ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Bending Modes

A large throughwall circumferential crack in an elbow subjected to in-plane bending moment can significantly reduce its collapse load. Therefore, it is very important to know the collapse moment of an elbow in the presence of a throughwall circumferential crack. The existing closed-form collapse moment equations of throughwall circumferentially cracked elbows are either too conservative or inadequate to correctly quantify the weakening effect due to the presence of the crack, especially for opening mode of bending moment. Therefore, the present study has been carried out to investigate through elastic-plastic finite element analysis the effect of a throughwall circumferential crack on the collapse moment of an elbow under in-plane bending moment. A total of 72 cases of elbows with various sizes of circumferential cracks (2θ=0–150 deg), different wall thickness (R/t=5–20), different elbow bend radii Rb/R=2,3 and two different bending modes, namely closing and opening have been considered in the analysis. Elastic-perfectly plastic stress-strain response of material has been assumed. Collapse moments have been evaluated from moment-end rotation curves by twice-elastic slope method. From these results, closed-form expressions have been proposed to evaluate collapse moments of elbows under closing and opening mode of bending moment. The predictions of these proposed equations have been compared with 8 published elbow test data and are found to be within ±11% variation except for one case.

The Effect of Throughwall Axial Crack on In-Plane Collapse Moment of Pipe Bend

2007 ◽  
Author(s):  
J. Chattopadhyay ◽  
W. V. Venkatramana ◽  
B. K. Dutta ◽  
H. S. Kushwaha
Keyword(s):  
Degradation Mechanism ◽  
Bending Moment ◽  
Plastic Collapse ◽  
Element Analysis ◽  
Pipe Bend ◽  
Perfectly Plastic ◽  
Axial Crack ◽  
Elastic Perfectly Plastic ◽  
Bending Modes ◽  
Closure Effect

A throughwall axial crack may develop in an elbow or pipe bend due to service related degradation mechanism. It is very important to know the plastic collapse moment (PCM) of an elbow in the presence of a throughwall axial crack. The existing PCM equations of throughwall axially cracked (TAC) elbows are either too conservative or inadequate to correctly quantify the weakening effect due to the presence of the crack. Further, they do not differentiate between closing and opening modes of bending although deformation characteristics under these two modes are completely different. Therefore, the present study has been undertaken to investigate through 3-D elastic-plastic finite element analysis. A total of 84 elbows with various sizes of axial cracks (a/Dm = 0–1), different wall thickness (R/t = 5 — 20), different elbow bend radii (Rb/R = 2,3) and two different bending modes, namely closing and opening have been considered in the analysis. Elastic-perfectly plastic stress-strain response of material has been assumed. Both geometric and material non-linearity are considered in the analysis. Crack closing is observed in most of the cases. To capture the crack closure effect, contact analysis has been performed. Plastic collapse moments have been evaluated from moment — end rotation curves by twice-elastic slope method. From these results, closed-form equations are proposed to evaluate plastic collapse moments of elbows under closing and opening mode of bending moment. The predictions of these proposed equations are compared with the test data available in the literature. Matching between predictions and experimental results is found to be satisfactory.

Closed-Form Plastic Collapse Loads of Pipe Bends Under Combined Pressure and In-Plane Bending

2006 ◽  
Author(s):  
Chang-Sik Oh ◽  
Yun-Jae Kim
Keyword(s):  
Closed Form ◽  
Three Dimensional ◽  
Plastic Collapse ◽  
Plastic Limit ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Bending Mode ◽  
Wide Range ◽  
Plane Bending ◽  
Elastic Perfectly Plastic

Based on three-dimensional (3-D) FE limit analyses, this paper provides plastic limit, collapse and instability load solutions for pipe bends under combined pressure and in-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide plastic collapse loads (using the twice-elastic-slope method) and instability loads. For the bending mode, both closing bending and opening bending are considered, and a wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and collapse load solutions for pipe bends under combined pressure and bending are proposed.

Closed-Form Collapse Moment Equations of Elbows Under Combined Internal Pressure and In-Plane Bending Moment

2000 ◽  
Vol 122 (4) ◽  
pp. 431-436 ◽  
Author(s):  
J. Chattopadhyay ◽  
D. K. Nathani ◽  
B. K. Dutta ◽  
H. S. Kushwaha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Closed Form ◽  
Rotation Curve ◽  
Bending Moment ◽  
Loading Conditions ◽  
Moment Equations ◽  
Element Analysis ◽  
The Moment

Elastic-plastic finite element analysis has been carried out to evaluate collapse moments of six elbows with elbow factors varying from 0.24 to 0.6. The loading conditions of combined in-plane closing/opening bending moment and varying degree of internal pressure are considered in the analysis. For each case, collapse moment is obtained by twice elastic slope method from the moment versus end-rotation curve. Based on these results, two closed-form equations are proposed to evaluate the collapse moments of elbows under combined internal pressure and in-plane closing and opening bending moment. [S0094-9930(00)00103-7]

A Study on Effect of Shape Irregularities on Collapse Loads of Pipe Bends with Critical Circumferential Throughwall Crack under In-Plane Closing Bending

2014 ◽  
Vol 592-594 ◽  
pp. 980-984
Author(s):  
Sumesh Sasidharan ◽  
Arunachalam R. Veerappan ◽  
Subramaniam Shanmugam
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Detrimental Effect ◽  
Bending Moment ◽  
Collapse Load ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Circumferential Crack ◽  
Plane Bending

The presence of thorough wall circumferential cracks has a detrimental effect on collapse load of elbows. The existing theoretical solutions do not correctly quantify the weakening effect due to the presence of the circumferential through wall crack in shape imperfect pipe bends. The present study has been done to investigate the effect of ovality and thinning on the collapse moment of 90° elbow with critical throughwall circumferential crack under in-plane bending moment using elastic-plastic finite element analysis considering large geometry change.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

Elasto-Plastic Coupled Temperature-Displacement Finite Element Analysis of Two-Dimensional Rolling-Sliding Contact With a Translating Heat Source

1991 ◽  
Vol 113 (1) ◽  
pp. 93-101 ◽  
Author(s):  
S. M. Kulkarni ◽  
C. A. Rubin ◽  
G. T. Hahn
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Plastic Material ◽  
Element Model ◽  
Rolling Contact ◽  
Two Dimensional ◽  
Element Analysis ◽  
Element Mesh ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The present paper, describes a transient translating elasto-plastic thermo-mechanical finite element model to study 2-D frictional rolling contact. Frictional two-dimensional contact is simulated by repeatedly translating a non-uniform thermo-mechanical distribution across the surface of an elasto-plastic half space. The half space is represented by a two dimensional finite element mesh with appropriate boundaries. Calculations are for an elastic-perfectly plastic material and the selected thermo-physical properties are assumed to be temperature independent. The paper presents temperature variations, stress and plastic strain distributions and deformations. Residual tensile stresses are observed. The magnitude and depth of these stresses depends on 1) the temperature gradients and 2) the magnitudes of the normal and tangential tractions.

Effect of Core Plasticity on the Post-Buckling Behavior of Debonded Sandwich Beams

2000 ◽  
Author(s):  
Bhavani V. Sankar ◽  
Manickam Narayanan ◽  
Abhinav Sharma
Keyword(s):  
Plastic Material ◽  
Maximum Load ◽  
Face Sheet ◽  
Compression Tests ◽  
Element Analysis ◽  
The Core ◽  
Perfectly Plastic ◽  
The Face ◽  
Post Buckling ◽  
Elastic Perfectly Plastic

Abstract Nonlinear finite element analysis was used to simulate compression tests on sandwich composites containing debonded face sheets. The core was modeled as an elastic-perfectly-plastic material, and the face-sheet as elastic isotropic. The effects of core plasticity, face-sheet and core thickness, and debond length on the maximum load the beam can carry were studied. The results indicate that the core plasticity is an important factor that determines the maximum load.

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.

Effects of Torsion on Equivalent Bending Moment for Limit Load and EPFM Circumferential Pipe Flaw Evaluations

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Weighted Factor ◽  
Elastic Perfectly Plastic

The circumferential flaw evaluation procedures in ASME Boiler and Pressure Vessel Code Section XI nonmandatory Appendix C are currently limited to straight pipes under pressure and bending loads without consideration of torsion loading. The Working Group on Pipe Flaw Evaluation of the ASME Boiler and Pressure Vessel Code is developing guidance for considering the effects of torsion by a mean of an equivalent bending moment, which is a square root of sum square combination of bending moment and torsion load with a weighted factor for torsion moment. A torsion weighted factor, Ce, is established in this paper using large strain finite element limit load analysis with elastic perfectly plastic materials. Planar flaws and nonplanar flaws in a 10.75 in. (273 mm) OD pipe are investigated. Additionally, a finite element J-integral calculation is performed for a planar through wall circumferential flaw with elastic plastic materials subjected to bending and torsion load combinations. The proposed Ce factor for planar flaws is intended for use with the ASME B&PV Code Section XI, Appendix C for limit load and Elastic Plastic Fracture Mechanics (EPFM) circumferential planar flaw evaluations.

Finite Element Limit Loads for Circumferential Through-Wall Cracked Pipe Bends Under In-Plane Bending

2006 ◽  
Author(s):  
Yun-Jae Kim ◽  
Chang-Sik Oh ◽  
Young-Il Kim ◽  
Chi-Yong Park
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Small Strain ◽  
Plastic Limit ◽  
Crack Location ◽  
Perfectly Plastic ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

This paper proposes plastic limit and collapse loads for circumferential through-wall cracked pipe bends under in-plane bending, based on three-dimensional finite element limit analyses. The material is assumed to be elastic-perfectly-plastic, but both the geometrically linear (small strain) and the geometrically nonlinear (large geometry change) options are employed. Regarding crack location, both extrados and intrados cracks are considered. Moreover, for practical application, closed-form approximations of plastic limit and collapse loads are proposed based on the FE results, and compared with corresponding solutions for straight pipes.

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