Study on Collapse Characteristics and CSRF Method for 45 Deg Cylinder-to-Cylinder Intersections

2012 ◽  
Author(s):  
Takuro Honda ◽  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Plastic Strain ◽  
High Stress ◽  
Elastic Analysis ◽  
Collapse Pressure ◽  
Elastic Plastic ◽  
Replacement Method ◽  
Inelastic Analysis ◽  
Collapse Strength ◽  
Collapse Characteristics ◽  
Plastic Analysis

It is known that the collapse strength of complex three dimensional structures is hard to evaluate accurately with elastic analysis, and more accurate results require the use of inelastic analysis. A cylinder-to-cylinder acute lateral intersection is one of basic structures of process plants. It is known that a high stress concentration occurs at an acute lateral more than 90 deg-lateral. In general, the area replacement method and the elastic analysis are applied for the design of acute lateral. However, these results may provide overly-conservative designs. In the previous work, the authors proposed CSRF (Collapse Strength Reduction Factor) method. The CSRF was defined as a ratio of the simple cylinder collapse pressure to the cylinder-to-cylinder collapse pressure. The proposed CSRF method provided more reasonable design than the elastic analysis. In this paper, the concept of the CSRF was redefined by using the maximum allowable working pressure. The CSRF were evaluated on the 45 deg and 90 deg-laterals based on the area replacement method, the elastic analysis, the limit load analysis and the elastic plastic analysis to study the collapse characteristics of 45 deg-laterals. The 45 deg-laterals are weaker than 90 deg-laterals, and inelastic analysis provides greater strength of 45 deg-laterals than elastic analysis. The results of elastic plastic analysis showed that overly-large plastic strain occurs on 45 deg-laterals. This plastic strain should be evaluated in addition to the collapse pressure.

Study on Collapse Characteristics of Cylinder-to-Cylinder Intersections by Inelastic Finite Element Analysis

2009 ◽  
Author(s):  
Shunji Kataoka ◽  
Asako Miyakawa ◽  
Takuya Sato
Keyword(s):  
Three Dimensional ◽  
Limit Load ◽  
Reduction Factor ◽  
Elastic Analysis ◽  
Membrane Stress ◽  
Strength Reduction Factor ◽  
Element Analysis ◽  
Collapse Pressure ◽  
Inelastic Analysis ◽  
Collapse Strength

It is known that the collapse strength of complex three-dimensional structures cannot be evaluated accurately with elastic analysis, and more accurate results require the use of inelastic analysis. A typical example is cylinder-to-cylinder intersection. In this paper, the relationship of collapse loads and local primary membrane stresses of cylinder-to-cylinder intersections was examined. First, elastic analysis of the cylinder-to-cylinder intersections with various combinations of diameter and thickness under internal pressure was conducted. The local primary membrane stress (PL) obtained from the analysis was normalized by the general primary membrane stress (Pm) the ratio of PL/Pm defining the Stress Intensification Factor (SIF). The results revealed that SIF was directly influenced by the geometries. Secondly, limit load analysis was conducted on the same structures and the collapse pressure was obtained. The Collapse Strength Reduction Factor (CSRF) defined as the ratio of the run pipe collapse pressure to the cylinder-to-cylinder collapse pressure was proposed. The CSRF was also found to be influenced by the geometries. Comparing the result of SIF with CSRF, it is clear that the evaluation by SIF is overly-conservative and the proposed concept of CSRF provides more accurate evaluation of the cylinder-to-cylinder intersections. Furthermore, the basic data for the intersections with uniform thickness can also be applied to the reinforced intersections.

The Elastic-Plastic Analysis of Tubes—IV: Thermal Ratchetting

1992 ◽  
Vol 114 (2) ◽  
pp. 236-245 ◽  
Author(s):  
W. Jiang
Keyword(s):  
Steady State ◽  
Plastic Strain ◽  
Centrifugal Force ◽  
Kinematic Hardening ◽  
Elastic Plastic ◽  
External Pressures ◽  
Plastic Analysis ◽  
Steady Solutions ◽  
Number Of Cycles

This paper continues the investigation of the shakedown behavior of tubes subjected to cyclic centrifugal force and temperature, and sustained internal and external pressures. It is found that when ratchetting occurs, the plastic strain builds up with each cycle, but finally reaches a steady state after a large number of cycles for kinematic hardening materials. The steady solutions for three kinds of ratchetting behavior are found and given in this paper.

Proposal of Use of Mises Criteria for Elastic Analysis in Appendix 9 of ASME Section VIII Division 3

2020 ◽  
Author(s):  
Susumu Terada
Keyword(s):  
Flow Stress ◽  
Plastic Collapse ◽  
Elastic Analysis ◽  
Stress Evaluation ◽  
Stress Theory ◽  
Elastic Plastic ◽  
Primary Stress ◽  
Plastic Analysis ◽  
Section Viii ◽  
Von Mises

Abstract The stress evaluation by elastic analyses for protection against plastic collapse in Appendix 9 is based on maximum shear stress theory (Tresca theory). On the other hand, the stress evaluation by elastic-plastic analysis and design equations by flow stress for design pressure for cylindrical shell and spherical shell in KD-221 is based on distortion energy yield stress theory (von Mises theory). With regard to materials with low and intermediate Sy/Su, in particular the primary stress evaluation based on Tresca stress for elastic analysis in current Div.3 is much more conservative than that based on flow stress equations similar to elastic-plastic analysis from experimental results. In Section VIII Div.2, von Mises yield criterion is used for stress evaluation for elastic analysis because it matches experimental results more closely than Tresca yielding criterion and is also consistent with plasticity algorithms used in elastic-plastic analysis. Therefore in Div.3 von Mises stress should be used for elastic analysis in the same way as in Sec. VIII Div.2. For materials with high Sy/Su, the primary stress evaluation based on von Mises criterion for elastic analysis is less conservative than that based on flow stress equations similar to elastic-plastic analysis because of a difference in design factor of 1.5 for elastic analysis and 1.732 for flow stress equations. Therefore, we propose using von Mises criterion for protection against plastic collapse with design correction factor using Sy/Su in Appendix 9 in order to remove excessive conservativeness for materials with low and intermediate Sy/Su. The validity of this proposal is shown in this paper.

A Shell-Element–Based Elastic Analysis Predicting Welding-Induced Distortions for Ship Panels

2007 ◽  
Vol 51 (02) ◽  
pp. 128-136
Author(s):  
Gonghyun Jung
Keyword(s):  
Numerical Model ◽  
Three Dimensional ◽  
Shell Element ◽  
Significant Loss ◽  
Buckling Analysis ◽  
Elastic Analysis ◽  
Plastic Strains ◽  
Elastic Plastic ◽  
Distortion Analysis ◽  
Plastic Analysis

A new numerical model, Q-Weld (Edison Welding Institute, Columbus, OH), which is a shell-element-based elastic analysis, is proposed for the prediction of the distortion induced in ship panels. Based on the results of the three-dimensional thermal-elastic-plastic analyses, it was found that the shell element-based model excluding the geometry of fillet welds and including only transverse and longitudinal plastic strains is valid without significant loss of accuracy. The developed Q-Weld predicts well-agreed distortions with the three-dimensional thermal-elastic-plastic analysis and demonstrates its potential in welding-induced distortion analysis, including buckling analysis.

Effects of Local Peak Stress Distribution on the Ratchet Limit

2002 ◽  
Author(s):  
Nobuyoshi Yanagida ◽  
Masaaki Tanaka ◽  
Norimichi Yamashita ◽  
Yukinori Yamamoto
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Plastic Strain ◽  
Equivalent Stress ◽  
Equivalent Plastic Strain ◽  
Peak Stress ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Elastic Plastic ◽  
Plastic Analysis

Alternative stress evaluation criteria suitable for Finite Element Analysis (FEA) proposed by Okamoto et al. [1],[2] have been studied by the Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) in Japan. Thermal stress ratchet criteria in plastic FEA are now under consideration. Two criteria are proposed: (1) Evaluating variations in plastic strain increments, and (2) Evaluating the width of the area in which Mises equivalent stress exceeds 3Sm. To verify of these criteria, we selected notched cylindrical vessel models as prime elements. To evaluate the effect of the local peak stress distribution on these criteria, cylindrical vessels with a semicircular notch on the outer surface were selected for this analysis. We used two notch configurations for our analysis, and the stress concentration factor for the notches was set to 1.5 and 2.0. We conducted elastic-plastic analysis to evaluate the ratchet limit. Sustained pressure and alternating enforced longitudinal displacements which causes secondary stress were used as parameters for the elastic-plastic analysis. We found that when no ratchet was observed, the equivalent plastic strain increments decreased and the area in which Mises equivalent stress exceeds 3Sm are below the certain range.

A Simplified Technique for Shakedown Load Determination of a 90 Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic In-Plane Bending

2005 ◽  
Author(s):  
Hany F. Abdalla ◽  
Maher Y. A. Younan ◽  
Mohammed M. Megahed
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Internal Pressure ◽  
High Heat ◽  
Heat Fluxes ◽  
Elastic Analysis ◽  
Pipe Bend ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Plane Bending

In this paper a simple technique is presented to determine the shakedown load of a 90 degree pipe bend subjected to constant internal pressure and cyclic in-plane bending using the finite element method. Through the proposed technique, the shakedown load is determined without performing time consuming cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown load is determined through performing only two analyses namely; an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown load is determined through the calculation of the residual stresses developed in the pipe bend. In the elastic analysis, performed only once and stored, an in-plane closing moment is applied preserving structure stresses within the material elastic range. In the elastic-plastic analysis, a constant internal pressure, below the pressure to cause yielding, is applied in addition to an increasing moment magnitude that causes the material yield strength to be exceeded. For verification purposes, the results of the simplified technique are compared to the results of full cyclic loading finite element simulations where the pipe bend is subjected to constant internal pressure and cyclic in-plane closing moment loading. In order to have confidence in the proposed technique, it is applied beforehand on the Bree cylinder [1] subjected to constant internal pressure and cyclic high heat fluxes across its wall. The results of the proposed technique showed very good correlation with the, analytically determined, Bree diagram of the cylinder.

Elastic-Plastic Analysis of the Maximum Postulated Flaw in the Beltline Region of a Reactor Vessel

1982 ◽  
Vol 104 (4) ◽  
pp. 278-286 ◽  
Author(s):  
H. G. deLorenzi
Keyword(s):  
Plastic Flow ◽  
Deformation Theory ◽  
Surface Flaw ◽  
Elastic Analysis ◽  
Elastic Plastic ◽  
Surface Flaws ◽  
Plastic Analysis ◽  
Design Calculations ◽  
Tension Loading ◽  
Design Pressure

A maximum postulated surface flaw in the beltline region of a PWR pressure vessel has been analyzed under elastic-plastic conditions. The analysis was performed using 3-D finite element methods, and the deformation theory of plasticity was used to describe the plastic flow of the material. The calculations were carried out for the internal pressure varying from the design pressure up to approximately twice the design pressure. The results show that at the design pressure the plastic flow of the material around the crack front is so small that an elastic analysis is adequate. However, the commonly used approach of treating the flaw in the vessel as a surface flaw in a flat plate under far field tension loading is nonconservative. At a pressure of approximately 50 percent over the design pressure the energy release rate derived from an elastic analysis starts to deviate from the value obtained from an elastic-plastic calculation. The elastic result now starts to be nonconservative and at twice the design pressure the elastic analysis will clearly underestimate the severity of the crack. A 2-D elastic-plastic plane strain approximation will on the other hand grossly overestimate the severity of the crack. A realistic 3-D elastic-plastic analysis is, therefore, needed to estimate the safety factors of surface flaws and to serve as benchmarks for the development of simpler design calculations.

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.

Elastic-Plastic Deformation of a Single Grooved Flat Plate Under Longitudinal Shear

1963 ◽  
Vol 85 (4) ◽  
pp. 585-591 ◽  
Author(s):  
Michael F. Koskinen
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Plastic Zone ◽  
Flat Plate ◽  
High Stress ◽  
Longitudinal Shear ◽  
Elastic Plastic ◽  
Semiempirical Equation ◽  
Stress Levels ◽  
Plastic Case

The development of plastic strain is followed from the elastic through the partially plastic to the fully plastic condition for a nonstrainhardening material. Adjacent to the zone of deformation in the fully plastic case is a region of limited plastic deformation. The growth of the plastic zone is compared with predictions based on the elastic-plastic solution for a semi-infinite solid and the elastic solution for a plate. Agreement is good at low stress levels. At high stress levels, a relatively simple semiempirical equation is proposed. Predictions based on elasticity theory alone are shown to be seriously in error.

ASME III Fatigue Assessment Plasticity Correction Factors for Austenitic Stainless Steels

2014 ◽  
Author(s):  
Julian Emslie ◽  
Chris Watson ◽  
Keith Wright
Keyword(s):  
Preliminary Investigation ◽  
Austenitic Stainless Steels ◽  
Strain Range ◽  
Equivalent Strain ◽  
Elastic Analysis ◽  
Correction Factors ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Asme Code ◽  
Ratio Correction

ASME III NB-3200 provides a method for carrying out fatigue calculations using a simplified elastic-plastic analysis procedure. This allows a correction to elastic analysis to be performed in place of a full elastic-plastic analysis. Two mutually exclusive factors are described: the Poisson’s ratio correction accounts for surface stress exceeding the yield strength of the material and the Ke factor accounts for gross section plasticity. The recently released ASME Code Case N-779 provides a more complex but less onerous calculation of the Ke factor. Correction factors from the JSME and RCC-M codes have also been considered in this paper. The conservatism of different plasticity correction factors has been examined by calculating a ratio between the equivalent strain range from elastic-plastic Finite Element (FE) models and the strain range from elastic FE models and comparing this to calculated plasticity correction factors. Results show the potential for both the current ASME and Code Case Ke corrections to under-predict the strains when compared to those from an elastic-plastic FE assessment. A preliminary investigation has been carried out into an alternative correction factor based on linearised stress and local thermal stress ranges. This addresses the discontinuity between the two correction methods for surface and sectional plasticity which has been identified as a feature of the ASME correction methodology.

Sign in / Sign up

Export Citation Format

Share Document