Elastic-Plastic Shakedown Assessment of Piping Using a Non-Cyclic Method

2007 ◽  
Author(s):  
Wolf Reinhardt
Keyword(s):  
Boundary Conditions ◽  
Pressure Vessel ◽  
The Other ◽  
Plastic Model ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Class 1 ◽  
Thermal Bending ◽  
Computationally Expensive ◽  
Plastic Shakedown

The analysis for shakedown in nuclear Class 1 piping following NB-3600 of the ASME Boiler and Pressure Vessel Code contains several simplifications and can be overly conservative in some cases and potentially non-conservative in some others. A detailed elastic-plastic analysis following NB-3228.4, on the other hand, is computationally expensive and time consuming because an elastic-plastic model needs to be cycled to stabilization. A non-cyclic method to assess elastic plastic shakedown (absence of ratcheting) has been proposed and is applied to the analysis of some simple straight piping scenarios. Interaction diagrams similar to the Bree diagram are derived for other loading situations, such as thermal bending in conjunction with primary bending. The effect of piping boundary conditions on the ratchet boundary is explored.

A Direct Analysis of Two-Dimensional Elastic-Plastic Rolling Contact

1993 ◽  
Vol 115 (2) ◽  
pp. 227-236 ◽  
Author(s):  
M. Yu ◽  
B. Moran ◽  
L. M. Keer
Keyword(s):  
Finite Element ◽  
Direct Analysis ◽  
Rolling Contact ◽  
Direct Approach ◽  
Two Dimensional ◽  
Elastic Plastic ◽  
Finite Element Calculations ◽  
Plastic Analysis ◽  
Plastic Shakedown ◽  
Residual Problem

A direct approach for elastic-plastic analysis and shakedown is presented and its application to a two-dimensional rolling contact problem is demonstrated. The direct approach consists of an operator split technique, which transforms the elastic-plastic problem into a purely elastic problem and a residual problem with prescribed eigenstrains. The eigenstrains are determined using an incremental projection method which is valid for nonproportional loading and both elastic and plastic shakedown. The residual problem is solved analytically and also by using a finite element procedure which can be readily generalized to more difficult problems such as three-dimensional rolling point contact. The direct analysis employs linear-kinematic-hardening plastic behavior and thus either elastic or plastic shakedown is assured, however, the phenomenon of ratchetting which can lead to incremental collapse, cannot be treated within the present framework. Results are compared with full elastic-plastic finite element calculations and a step-by-step numerical scheme for elastic-plastic analysis. Good agreement between the methods is observed. Furthermore, the direct method results in substantial savings in computational effort over full elastic-plastic finite element calculations and is shown to be a straightforward and efficient method for obtaining the steady state (shakedown) solution in the analysis of rolling and/or sliding contact.

Meaning of Ke in Design-by-Analysis Fatigue Evaluation

2005 ◽  
Vol 128 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Gerry C. Slagis
Keyword(s):  
Stress Range ◽  
Elastic Plastic ◽  
Maximum Value ◽  
Penalty Factor ◽  
Plastic Analysis ◽  
Thermal Bending ◽  
Complex Procedure ◽  
Fatigue Evaluation ◽  
Technical Basis

The ASME Section III Design-by-Analysis rules for pressure-retaining components include a detailed fatigue evaluation based on elastically predicted primary, secondary, and peak stresses. A prerequisite for the fatigue analysis is that the primary-plus-secondary stress range does not exceed 3Sm. If this limit is exceeded, the code provides “Simplified Elastic-Plastic Analysis” rules for the fatigue evaluation. A Ke penalty factor is applied to the elastically predicted alternating stress. The maximum value of Ke (3.3 or 5) is a severe design limitation. Test data indicate that the code specified maximum value of Ke is very conservative. The simplified elastic-plastic rules were originally developed for piping and published in B31.7. When the piping rules were incorporated into Section III in 1971, the B31.7 procedure was replaced by a less complex procedure. The development of the simplified elastic-plastic analysis approach is reviewed to establish the technical basis for the present code rules. The concepts of fatigue, shakedown to elastic action, thermal bending, elastic follow-up, notch factor, and strain redistribution are discussed. Recommendations for changes to the plastic strain correction factor are provided.

Evaluation of Alternate Interpretations Regarding the Conditions for Exclusion of Thermal Bending Stresses in Simplified Elastic-Plastic Stress Analyses

2006 ◽  
Author(s):  
Robert B. Keating ◽  
Richard O. Vollmer
Keyword(s):  
Finite Element Analyses ◽  
Sample Problem ◽  
Secondary Stress ◽  
Elastic Plastic ◽  
Thermal Ratcheting ◽  
Plastic Analysis ◽  
Thermal Bending ◽  
Asme Code ◽  
Bending Stresses ◽  
Simplified Analysis

The ASME Code permits the range of primary plus secondary stress to exceed the stress limit of 3Sm, provided that several key conditions are satisfied. These conditions are provided in Paragraph NB-3228.5, “Simplified Elastic-Plastic Analysis”. The first condition is that the range of primary plus secondary stress intensity, excluding thermal bending stresses, shall be less than 3Sm. The term “thermal bending” is not clearly defined in the Code and at least two Code Interpretations have been issued with differing viewpoints. The first interpretation is that only those stresses due to the radial through-wall temperature distribution may be excluded; the second is that all thermal bending stresses, including thermal discontinuity stresses, may be excluded. In order to investigate the suitability of these two interpretations, elastic-plastic analyses are conducted of a highly restrained sample geometry. First, the sample problem is evaluated using the ASME Code rules for simplified elastic-plastic analysis for thermal ratcheting and fatigue, as required by NB-3228.5. Subsequently, cyclic elastic-plastic finite element analyses are conducted to determine if the simplified analysis rules provide adequate protection with regard to thermal ratcheting and fatigue. These analyses are performed using both interpretations to determine if adequate designs can be achieved for the sample problem selected.

Basis of the Upcoming Changes to the Piping Inelastic Fatigue Design Rules in the ASME Boiler and Pressure Vessel Code Section III, Division 1, Article NB-3600

2015 ◽  
Author(s):  
Timothy M. Adams
Keyword(s):  
Pressure Vessel ◽  
Service Level ◽  
Fatigue Analysis ◽  
Elastic Plastic ◽  
Fatigue Design ◽  
Division 1 ◽  
Class 1 ◽  
Asme Code ◽  
Code Changes ◽  
Near Future

In conducting a Class 1 piping analysis per the simplified rules of the ASME Boiler and Pressure Vessel Code, Section III, Division 1, Article NB-3600, a fatigue analysis is required per paragraph NB-3653 for both Service Level A and Service Level B. The fatigue analysis provides two options. The options are dependent on Equation 10 of subparagraph NB-3653.1. If this equation is met for a given load set pair under consideration, then the analysis proceeds directly to subparagraphs NB-3653.2 through NB-3653.5. If however, Equation 10 is exceeded, the Code allows the use of a simplified Elastic Plastic Analysis as delineated in subparagraph NB-3653.6. The first requirement of NB-3653.6 is that both Equation 12 and Equation 13 must be met. The changes in the seismic design in the last 25+ years have not been appropriately reflected in the subparagraph NB-3653.6(b) Equation 13. Also, the Code provides no clear guidance on seismic anchor motions in paragraph NB-3650. In 2012 ASME Code Committees undertook an action to address these issues. This paper provides the background and basis for Code changes that are anticipated will be implemented in the near future in paragraph NB-3653.6 of the ASME Boiler and Pressure Vessel Code, Section III, Division 1 that will address both of these issues. This implementation will make the Elastic Plastic Fatigue rules of NB-3653.6 consistent with the design by analysis approach of NB-3228.5.

Meaning of Ke in Design-by-Analysis Fatigue Evaluation

2005 ◽  
Author(s):  
Gerry C. Slagis
Keyword(s):  
Stress Range ◽  
Elastic Plastic ◽  
Maximum Value ◽  
Penalty Factor ◽  
Plastic Analysis ◽  
Thermal Bending ◽  
Complex Procedure ◽  
Fatigue Evaluation ◽  
Technical Basis

The ASME Section III Design-by-Analysis rules for pressure-retaining components include a detailed fatigue evaluation based on elastically-predicted primary, secondary, and peak stresses. A pre-requisite for the fatigue analysis is that the primary-plus-secondary stress range does not exceed 3Sm. If this limit is exceeded, the code provides “Simplified Elastic-Plastic Analysis” rules for the fatigue evaluation. A Ke penalty factor is applied to the elastically-predicting alternating stress. The maximum value of Ke (3.3 or 5) is a severe design limitation. Test data indicate that the code specified value of Ke is very conservative. The simplified elastic-plastic rules were originally developed for piping and published in B31.7. When the piping rules were incorporated into Section III in 1971, the B31.7 procedure was replaced by a less complex procedure. The development of the simplified elastic-plastic analysis approach is reviewed to establish the technical basis for the present code rules. The concepts of fatigue, shakedown to elastic action, thermal bending, elastic follow-up, notch factor, and strain redistribution are discussed. Recommendations for changes to the plastic strain correction factor are provided.

Elastic-Plastic Shakedown Evaluation Using ASME Code Section III and Section VIII Methods

2010 ◽  
Author(s):  
David P. Molitoris ◽  
John V. Gregg ◽  
Edward E. Heald ◽  
David H. Roarty ◽  
Benjamin E. Heald
Keyword(s):  
Elastic Analysis ◽  
Acceptance Criteria ◽  
Elastic Plastic ◽  
Division 1 ◽  
Plastic Analysis ◽  
Asme Code ◽  
Section Viii ◽  
American Society ◽  
Plastic Shakedown ◽  
Division 2

Section III, Division 1 and Section VIII, Division 2 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code provide procedures for demonstrating shakedown using elastic-plastic analysis. While these procedures may be used in place of elastic analysis procedures, they are typically employed after the elastic analysis and simplified elastic-plastic analysis limits have been exceeded. In using the Section III, Division 1 and Section VIII, Division 2 procedures for elastic-plastic shakedown analyses, three concerns are raised. First, the Section III, Division 1 procedure is vague, which can result in inconsistent results between analysts. Second, the acceptance criteria contained in both procedures are vague, which can also result in inconsistent results between analysts. Lastly, differences in the procedures and acceptance criteria can result in demonstration of component elastic-plastic shakedown under Section III, Division 1 but not under Section VIII, Division 2. The authors presume that the ASME Code intends to provide similar design and analysis conclusions, which may not be a correct assumption. To demonstrate these concerns, a nozzle benchmark design subject to a representative thermal and pressure transient was evaluated using the two Code elastic-plastic shakedown procedures. Shakedown was successfully demonstrated using the Section III, Division 1 procedure. However, shakedown could not be demonstrated using the Section VIII, Division 2 procedure. The conflicting results seem to indicate that, for the nozzle design evaluated, the Section VIII, Division 2 procedure is considerably more conservative than the Section III, Division 1 procedure. To further assess the conservative nature of the Section VIII, Division 2 procedure, the nozzle benchmark design was evaluated using the same thermal transient, but without a pressure load. While shakedown was technically not observed using the Section VIII, Division 2 acceptance criteria, engineering judgment concluded that shakedown was demonstrated. Based on the results of all the evaluations, recommendations for modifications to both procedures were presented for consideration.

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