Allowable External Flaws and Acceptance Standards for High Toughness Ductile Pipes Subjected to Bending Moment and Internal Pressure

2020 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Valery Lacroix ◽  
Vratislav Mares
Keyword(s):  
Internal Pressure ◽  
Small Diameter ◽  
Bending Moment ◽  
Limit Load ◽  
High Toughness ◽  
Asme Code

Abstract Failure stresses for ductile high toughness pipes are predicted by Limit Load Criteria based on a net section stress concept. Allowable flaws of the Acceptance Standards provided by the Article IWB-3514 in the ASME B&PV Code Section XI were determined by the Limit Load Criteria. The allowable flaws are applicable for ductile high toughness pipes with circumferential internal and external flaws. Authors have developed more precise equations using the Limit Load Criteria, which is called Modified Limit Load Criteria, hereafter. As the results of the Modified Limit Load Criteria, failure stresses for external flawed pipes are always smaller than the failure stresses obtained by the Limit Load Criteria provided by the ASME Code Section XI. It seems that the allowable flaw sizes of the Acceptance Standards provided by the ASME Code Section XI are less conservative for external flaws. The objective of this paper is to demonstrate difference of failure stresses by the Limit Load Criteria and Modified Limit Load Criteria for external flawed pipes. In addition, the allowable flaws of the Acceptance Standards are examined by large and small diameter pipes with external flaws using the Modified Limit Load Criteria.

Fully Plastic Failure Stresses and Allowable Crack Sizes for Circumferentially Surface Cracked Pipes Subjected to Tensile Loading

2021 ◽  
Author(s):  
Kunio Hasegawa ◽  
David Dvorak ◽  
Vratislav Mares ◽  
Bohumir Strnadel ◽  
Yinsheng Li
Keyword(s):  
Experimental Data ◽  
Bending Moment ◽  
Limit Load ◽  
Tensile Loading ◽  
Crack Size ◽  
Plastic Failure ◽  
Circumferential Crack ◽  
Asme Code ◽  
American Society ◽  
Better Than

Abstract Fully plastic failure stresses for circumferentially surface cracked pipes subjected to tensile loading can be estimated by means of limit load criteria based on the net-section stress approach. Limit load criteria of the first type (labelled LLC-1) were derived from the balance of uniaxial forces. Limit load criteria of the second type are given in Section XI of the ASME (American Society of Mechanical Engineering) Code, and were derived from the balance of bending moment and axial force. These are labelled LLC-2. Fully plastic failure stresses estimated by using LLC-1 and LLC-2 were compared. The stresses estimated by LLC-1 are always larger than those estimated by LLC-2. From the literature survey of experimental data, failure stresses obtained by both types of LLC were compared with the experimental data. It can be stated that failure stresses calculated by LLC-1 are better than those calculated by LLC-2 for shallow cracks. On the contrary, for deep cracks, LLC-2 predictions of failure stresses are fairly close to the experimental data. Furthermore, allowable circumferential crack sizes obtained by LLC-1 were compared with the sizes given in Section XI of the ASME Code. The allowable crack sizes obtained by LLC-1 are larger than those obtained by LLC-2. It can be stated that the allowable crack size for tensile stress depends on the condition of constraint of the pipe, and the allowable cracks given in Section XI of the ASME Code are conservative.

Limit Load Interaction of Welded Piping Branch Junctions Subjected to Combined Internal Pressure and Bending

2005 ◽  
Vol 297-300 ◽  
pp. 685-690 ◽  
Author(s):  
Fu Zhen Xuan ◽  
Pei Ning Li ◽  
Shan Tung Tu
Keyword(s):  
Parabolic Equation ◽  
Internal Pressure ◽  
Small Diameter ◽  
Limit Load ◽  
Fe Analysis ◽  
Diameter Ratio ◽  
Linear Finite Element ◽  
The Individual ◽  
Linear Expression ◽  
Parameter Influence

Systematic detailed non-linear finite element (FE) analysis are described for limit load interaction of piping branch junctions subjected to internal pressure and bending. The results show that for the tees with a small diameter ratio, the limit load interaction closes to the linear expression; as diameter ratio d/D increasing, the interaction relationship tends to parabolic equation; for the piping branch junction with diameter ratio equaling to unit, the limit load combinations is approximately quadratic. Compared to the individual limit bending value, internal pressure slightly increases the bending capability as it is in the range of 0.2£P/PL£0.4, especially for the cases of the main pipe with thinner wall. A closed limit load solution is obtained from the FE results through accommodating the geometrical parameter influence, and validated by using experimental 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.

Failure Bending Moment for Pipes With an Arbitrary-Shaped Circumferential Flaw

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Akira Shibuya ◽  
Nathaniel G. Cofie
Keyword(s):  
Bending Moment ◽  
Limit Load ◽  
Surface Flaw ◽  
Piping System ◽  
Load Carrying Capacity ◽  
Constant Depth ◽  
Load Carrying ◽  
Geometrical Shapes ◽  
Asme Code ◽  
Good Agreement

When a flaw is detected in a stainless steel piping system, an evaluation has to be performed to determine its suitability for continued operation. The failure bending moment of the flawed pipe can be predicted by limit load criterion in accordance with Appendix E-8 in the JSME S NA-1-2008 and/or Appendix C in the ASME Code Section XI. However, in these current codes, the limit load criterion is only calculated for the case of pipes containing a single flaw with constant depth, although the actual flaw depth is variable along the circumferential direction. Particularly, geometrical shapes of stress corrosion cracks are generally complex. The objective of this paper is to propose a method by formula for predicting the load-carrying capacity of pipes containing a circumferential surface flaw with any arbitrary shape. The failure bending moment is obtained by dividing the surface flaw into several subflaw segments. Using this method, good agreement is observed between the numerical solution and the reported experimental results. Several numerical examples are also presented to show the validity of the proposed methodology. Finally, it is demonstrated that three subflaw segments are sufficient to determine the collapse bending moment of a semi-elliptical surface flaw using the proposed methodology.

Effects of Bending Moment and Torsion on the Internal Pressure Limit Load of Locally Thinned Pipes

2011 ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Internal Pressure ◽  
Pipe Wall ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Structural Factors ◽  
Stress Evaluation ◽  
Pressure Limit ◽  
Wall Thinning

The pipe wall thinning stress evaluation procedures in Code-Case N-597-2 [1] of the ASME Boiler and Pressure Vessel (B&PV) Code are essentially based on Construction Code [2] stress evaluation. Stresses in the hoop and the axial directions are evaluated separately to meet the Construction Code allowable stress. Using Construction Code rules for local pipe wall thinning stress evaluation in Class 2 & 3 piping may be too restrictive. An alternative approach is to use the limit loads of locally wall thinned pipe in conjunction with an appropriate Z-Factor and the structural factors of the ASME B&PV Section XI, Appendix C [3]. Such approach may require a combined effect of pressure, bending, axial load and torsion loads on locally thinned pipe. In this paper, the effects of bending moment and torsion on the internal pressure limit load of locally thinned straight pipes are investigated. Large strain finite element limit load analysis with elastic - perfectly plastic materials are performed for a parametric matrix of piping models with various pipe R/t ratios, flaw depths, axial and transverse flaw extents. Based on the results, the allowable pressure for axial flaws in C-5420 of the ASME B&PV Section XI, Appendix C [3] may be used for piping local wall thinning as an alternative evaluation procedure to the current minimum pipe wall thickness evaluation procedure in the Code Case N-597-2 [1].

Limit Load Analysis of As-Fabricated Pipe Bends With Low Ovality Under In-Plane Closing Moment Loading and Internal Pressure

2018 ◽  
Author(s):  
Sherif S. Sorour ◽  
Mostafa Shazly ◽  
Mohammad M. Megahed
Keyword(s):  
Internal Pressure ◽  
Failure Modes ◽  
Bending Moment ◽  
Limit Load ◽  
Element Analysis ◽  
Pipe Bend ◽  
Bending Process ◽  
Piping Systems ◽  
Geometrical Imperfections ◽  
Pipe Bending

Pipe bends are critical components in piping systems where their failure modes are quite different from straight pipes. The objective of the present work is to investigate the limit loads of pipe bends with actual As-fabricated shape obtained from pipe bending process as compared to bends with Ideal and Assumed imperfect shapes. The present work is conducted by using nonlinear finite element analysis and is performed in two steps. The first step is achieved by simulating rotary pipe bending process with ball mandrel to obtain the actual as-fabricated shape of the 90° pipe bend. The process simulation was verified against published experimental data. In the second step, the pipe bend is subjected to different combinations of simultaneous loads consisting of internal pressure and In-plane closing bending moment. Results are provided for limit load curves for pipe bends with as-fabricated geometries and bends with ideal shape and assumed geometrical imperfections.

Determination of Shakedown Limit Load for a 90-Degree Pipe Bend Using a Simplified Technique

2006 ◽  
Vol 128 (4) ◽  
pp. 618-624 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Internal Pressure ◽  
Bending Moment ◽  
Limit Load ◽  
Heat Fluxes ◽  
Bench Mark ◽  
Pipe Bend ◽  
Elastic Plastic ◽  
Shakedown Limit

In this paper a simplified technique is presented to determine the shakedown limit load of a 90-degree pipe bend subjected to constant internal pressure and cyclic in-plane closing bending moment using the finite element method. The simplified technique determines the shakedown limit load without performing time consuming full elastic-plastic cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit load is determined by performing two finite element analyses namely; an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown limit load is determined through the calculation of the residual stresses developed in the pipe bend. In order to gain confidence in the simplified technique, the output shakedown limit moments are used to perform full elastic-plastic cyclic loading simulations to check for shakedown behavior of the pipe bend. The shakedown limit moments output by the simplified technique are used to generate the shakedown diagram of the pipe bend for a range of constant internal pressure magnitudes. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. In order to get acquainted with the simplified technique, it is applied beforehand to a bench mark shakedown problem namely, the Bree cylinder (Bree, J., 1967, J. Strain Anal., 3, pp. 226–238) problem. The Bree cylinder is subjected to constant internal pressure and cyclic high heat fluxes across its wall. The results of the simplified technique showed very good correlation with the analytically determined Bree diagram of the cylinder.

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