Stress Classification Using the R-Node Method

2006 ◽  
Author(s):  
Ihab F. Z. Fanous ◽  
R. Seshadri
Keyword(s):  
Experimental Data ◽  
Complex Geometries ◽  
Element Analysis ◽  
Shell Elements ◽  
Linear Elastic ◽  
Stress Classification ◽  
Wide Range ◽  
Asme Code ◽  
Section Viii ◽  
Division 2

The ASME Code Section III and Section VIII (Division 2) provide stress classification guidelines to interpret the results of a linear elastic finite element analysis. These guidelines enable the splitting of the generated stresses into primary, secondary and peak. The code gives some examples to explain the suggested procedures. Although these examples may reflect a wide range of applications in the field of pressure vessel and piping, the guidelines are difficult to use with complex geometries. In this paper, the r-node method is used to investigate the primary stresses and their locations in both simple and complex geometries. The method is verified using the plane beam and axisymmetric torispherical head. Also, the method is applied to analyze 3D straight and oblique nozzle modeled using both solid and shell elements. The results of the analysis of the oblique nozzle are compared with recently published experimental data.

Stress Classification Using the r-Node Method

2006 ◽  
Vol 129 (4) ◽  
pp. 676-682 ◽  
Author(s):  
Ihab F. Z. Fanous ◽  
R. Seshadri
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Complex Geometries ◽  
Element Analysis ◽  
Shell Elements ◽  
Linear Elastic ◽  
Stress Classification ◽  
Wide Range ◽  
Asme Code ◽  
Division 2

The ASME Code Secs. III and VIII (Division 2) provide stress-classification guidelines to interpret the results of a linear elastic finite element analysis. These guidelines enable the splitting of the generated stresses into primary, secondary, and peak. The code gives some examples to explain the suggested procedures. Although these examples may reflect a wide range of applications in the field of pressure vessel and piping, the guidelines are difficult to use with complex geometries. In this paper, the r-node method is used to investigate the primary stresses and their locations in both simple and complex geometries. The method is verified using the plane beam and axisymmetric torispherical head. Also, the method is applied to analyze 3D straight and oblique nozzles modeled using both solid and shell elements. The results of the analysis of the oblique nozzle are compared with recently published experimental data.

Evaluating the Effect of Nozzle Weld Stiffness When Using Shell Finite Element Models for ASME Code Evaluations

2012 ◽  
Author(s):  
Bryan Dunlap ◽  
Hassan Ziada ◽  
John Julyk
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Shell Element ◽  
Finite Element Models ◽  
Shell Elements ◽  
Asme Code ◽  
Section Viii ◽  
Shell Finite Element ◽  
Code Compliance ◽  
Division 2

Typically the use of SHELL finite elements to model nozzle/vessel interfaces will not include details of the weld at the interface. The omission of the weld details from SHELL element models is due to the difficulty in implementing such details and the assumption that additional interface stiffness due to the weld will have a negligible effect on results at locations of interest for Code evaluation. This study will demonstrate a proposed method for modeling weld details with SHELL elements and then evaluate the magnitude of the weld stiffness effect on results and Code compliance. The method of modeling the weld details with SHELL elements used in this study will follow the guidance provided by ASME BPVC Section VIII, Division 2, Annex 5.A [2] for such interfaces. Models of nozzle/vessel interfaces will be shown comparing results of SOLID element models with and without the weld detail, and then SHELL element models both with and without the weld detail. The results from these models will be evaluated and recommendations for future modeling and evaluation of nozzle/shell interfaces with SHELL elements will be offered.

Analysis of Shells of Noncircular Cross Section

2004 ◽  
Author(s):  
Jack E. Helms ◽  
Michael W. Guillot
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Thin Wall ◽  
Element Analysis ◽  
Noncircular Cross Section ◽  
Division 1 ◽  
Asme Code ◽  
Minimum Requirements ◽  
Section Viii ◽  
Tank Design

Minimum requirements for the design of shells of noncircular cross section are given in Appendix 13 of Section VIII, Division 1 of the ASME Code. The ASME Section XII Committee is re-examining the design of noncircular shells as part of their activities on cargo tank design. In this study finite element analysis is used to model a thin-wall noncircular shell. The results of the analysis are compared to experimental data provided by RTL, Inc.

Applicability of Design Rules for Openings in Shells, ASME B&PV Code, Section VIII, Division 2 - A Case Study

2021 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Krishnakant V. Pudipeddi ◽  
Subramanyam V. R. Sripada
Keyword(s):  
Stress Analysis ◽  
Failure Modes ◽  
Element Analysis ◽  
Design Rules ◽  
Area Method ◽  
Replacement Method ◽  
Local Stresses ◽  
Pressure Area ◽  
Section Viii ◽  
Division 2

Abstract The Pressure-Area method is recently introduced in the ASME Boiler and Pressure Vessel (B&PV) Code, Section VIII, Division 2 to reduce the excessive conservatism of the traditional area-replacement method. The Pressure-Area method is based on ensuring that the resistive internal force provided by the material is greater than or equal to the reactive load from the applied internal pressure. A comparative study is undertaken to study the applicability of design rules for certain nozzles in shells using finite element analysis (FEA). From the results of linear elastic FEA, it is found that in some cases the local stresses at the nozzle to shell junctions exceed the allowable stress limits even though the code requirements of Pressure-Area method are met. It is also found that there is reduction in local stresses when the requirement of nozzle to shell thickness ratio is maintained as per EN 13445 Part 3. The study also suggests that the reinforcement of nozzles satisfy the requirements of elastic-plastic stress analysis procedures even though it fails to satisfy the requirements of elastic stress analysis procedures. However, the reinforcement should be chosen judiciously to reduce the local stresses at the nozzle to shell junction and to satisfy other governing failure modes such as fatigue.

Two-Step Approach of Stress Classification and Primary Structure Method

1999 ◽  
Vol 122 (1) ◽  
pp. 2-8 ◽  
Author(s):  
Ming-Wan Lu ◽  
Yong Chen ◽  
Jian-Guo Li
Keyword(s):  
Primary Structure ◽  
Peak Stress ◽  
Classification Problem ◽  
Linearization Method ◽  
Equivalent Linearization ◽  
Element Analysis ◽  
Primary Stress ◽  
Stress Classification ◽  
The Finite Element Analysis ◽  
Asme Code

A key problem in engineering applications of “design by analysis” approach is how to decompose a total stress field obtained by the finite element analysis into different stress categories defined in the ASME Code III and VIII-2. In this paper, we suggest a two-step approach (TSA) of stress classification and a primary structure method (PSM) for identification of primary stress. Together with the equivalent linearization method (ELM), the stress classification problem is well solved. Some important concepts and ideas discussed by Lu and Li [Lu, M. W., and Li, J. G., 1986, ASME PVP-Vol. 109, pp. 33–37; Lu, M. W., and Li, J. G., 1996, ASME PVP-Vol. 340, pp. 357–363] are introduced. They are self-limiting stress, multi-possibility of stress decomposition, classification of constraints, and primary structures. For identification of peak stress, a modified statement of its characteristic and a “1/4 thickness criterion” are given. [S0094-9930(00)00201-8]

User’s Design Specification Preparation for 2¼Cr-1Mo-¼V Reactors in Accordance With ASME Section VIII, Division 2 Code and Code Case 2605

2013 ◽  
Author(s):  
Radoslav Stefanovic ◽  
Alicia Avery ◽  
Kanhaiya Bardia ◽  
Reza Kabganian ◽  
Vasile Oprea ◽  
...  
Keyword(s):  
Operating Temperature ◽  
Design Specification ◽  
Element Analysis ◽  
Analysis And Evaluation ◽  
Reheat Cracking ◽  
Inelastic Analysis ◽  
Allowable Stresses ◽  
Section Viii ◽  
Fatigue Evaluation ◽  
Division 2

Today’s hydroprocessing reactor manufacturers use 2¼Cr–1Mo–¼V steel to build lighter reactors than conventional Cr-Mo reactors. Manufacturing even lighter hydroprocessing reactors has been enabled with the introduction of the new ASME Section VIII Division 2 Code, initially released in 2007. The higher allowable stresses in the new Division 2 for these Vanadium-modified steels permits even lighter reactors to be built while maintaining suitable design margins. The new Division 2 Code requires additional engineering to ensure safe design. One of the challenges the engineer is faced with, is preparation of the User’s Design Specification (UDS) including new and more stringent requirements for fatigue evaluation. As the operating temperature of the rector is higher than 371°C, engineers have to evaluate the fatigue life of the reactor in accordance with Code Case 2605 (CC2605). CC2605 requires inelastic analysis and evaluation effects of creep. Vanadium-modified reactors require additional care during fabrication to prevent higher hardness around weld areas, reheat cracking, and reduced toughness at lower temperatures in the “as welded” condition. This paper provide guidance for the preparation of an ASME Section VIII Division 2 User’s Design Specification including process descriptions of all the cycles expected for the life of the rector and analysis requested by CC2605. An example of such an analysis, including finite element analysis results, is provided in this paper. Requirements to provide the material specification is also discussed with an emphasis on prevention of reheat cracking, hardenability, and temper and hydrogen embitterment.

Evaluation of ASME Pressure Vessel Code Prohibitions on Rod and Bar Stock and Potential Remedies

2014 ◽  
Author(s):  
John J. Aumuller ◽  
Vincent A. Carucci
Keyword(s):  
Pressure Vessels ◽  
Early 20Th Century ◽  
Economic Disadvantage ◽  
User Experiences ◽  
The Public ◽  
Division 1 ◽  
Asme Code ◽  
Billet Material ◽  
Section Viii ◽  
Division 2

The ASME Codes and referenced standards provide industry and the public the necessary rules and guidance for the design, fabrication, inspection and pressure testing of pressure equipment. Codes and standards evolve as the underlying technologies, analytical capabilities, materials and joining methods or experiences of designers improve; sometimes competitive pressures may be a consideration. As an illustration, the design margin for unfired pressure vessels has decreased from 5:1 in the earliest ASME Code edition of the early 20th century to the present day margin of 3.5:1 in Section VIII Division 1. Design by analysis methods allow designers to use a 2.4:1 margin for Section VIII Division 2 pressure vessels. Code prohibitions are meant to prevent unsafe use of materials, design methods or fabrication details. Codes also allow the use of designs that have proven themselves in service in so much as they are consistent with mandatory requirements and prohibitions of the Codes. The Codes advise users that not all aspects of construction activities are addressed and these should not be considered prohibited. Where prohibitions are specified, it may not be readily apparent why these prohibitions are specified. The use of “forged bar stock” is an example where use in pressure vessels and for certain components is prohibited by Codes and standards. This paper examines the possible motive for applying this prohibition and whether there is continued technical merit in this prohibition, as presently defined. A potential reason for relaxing this prohibition is that current manufacturing quality and inspection methods may render a general prohibition overly conservative. A recommendation is made to better define the prohibition using a more measurable approach so that higher quality forged billets may be used for a wider range and size of pressure components. Jurisdictions with a regulatory authority may find that the authority is rigorous and literal in applying Code provisions and prohibitions can be particularly difficult to accept when the underlying engineering principles are opaque. This puts designers and users in these jurisdictions at a technical and economic disadvantage. This paper reviews the possible engineering considerations motivating these Code and standard prohibitions and proposes modifications to allow wider Code use of “high quality” forged billet material to reflect some user experiences.

Technical Basis for ASME Section VIII Code Case 2235 on Ultrasonic Examination of Welds in Lieu of Radiography

2000 ◽  
Vol 123 (3) ◽  
pp. 338-345 ◽  
Author(s):  
Mahendra D. Rana ◽  
Owen Hedden ◽  
Dave Cowfer ◽  
Roger Boyce
Keyword(s):  
Fracture Mechanics ◽  
Linear Elastic Fracture Mechanics ◽  
Acceptance Criteria ◽  
Ultrasonic Examination ◽  
Linear Elastic ◽  
Division 1 ◽  
Section Viii ◽  
Elastic Fracture ◽  
Technical Basis ◽  
Division 2

In 1996, Code Case 2235, which allows ultrasonic examination of welds in lieu of radiography for ASME Section VIII Division 1 and Division 2 vessels, was approved by the ASME B&PV Code Committee. This Code Case has been revised to incorporate: 1) a reduction in minimum usable thickness from 4″ (107.6 mm) to 0.5″ (12.7 mm), and 2) flaw acceptance criteria including rules on multiple flaws. A linear elastic fracture mechanics procedure has been used in developing the flaw acceptance criteria. This paper presents the technical basis for Code Case 2235.

A New Method of Stress Linearization for Design by Analysis in Pressure Vessel Design

2014 ◽  
Vol 598 ◽  
pp. 194-197
Author(s):  
Hong Jun Li ◽  
Qiang Ding ◽  
Xun Huang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
New Method ◽  
Stress Distributions ◽  
Bending Stress ◽  
Element Analysis ◽  
Stress Tensors ◽  
Section Viii ◽  
Division 2

Stress linearization is used to define constant and linear through-thickness FEA (Finite Element Analysis) stress distributions that are used in place of membrane and membrane plus bending stress distributions in pressure vessel Design by Analysis. In this paper, stress linearization procedures are reviewed with reference to the ASME Boiler & Pressure Vessel Code Section VIII Division 2 and EN13445. The basis of the linearization procedure is stated and a new method of stress linearization considering selected stress tensors for linearization is proposed.

Applications of Code Case 2605 for Fatigue Evaluation of Vessels Made in 2.25Cr-1Mo-0.25V Steels Slightly Into Creep Range

2010 ◽  
Author(s):  
Susumu Terada
Keyword(s):  
Fatigue Curve ◽  
Time Dependent ◽  
Inelastic Analysis ◽  
Asme Code ◽  
Section Viii ◽  
Preliminary Study ◽  
Number Of Cycles ◽  
Fatigue Evaluation ◽  
Division 2 ◽  
Made In

The current Section VIII Division 2 of ASME code does not permit method A of paragraph 5.5.2.3 to be used for the exemption from fatigue analysis when the design allowable stress is taken in the time dependent temperature range. Method B of paragraph 5.5.2.4 also cannot be used because it requires the use of the fatigue curve which is limited to 371 ° C and below the needed temperature. Code Case 2605 is a rule for fatigue evaluation of 2.25Cr-1Mo-0.25V steels at temperatures greater than 371 ° C and less than 454 ° C. An inelastic analysis including the effect of creep shall be performed for all pressure parts according to Code Case 2605. Especially, a full inelastic analysis shall be performed using the actual time-dependent thermal and mechanical loading histograms for the lateral nozzle based on preliminary study. It takes much time to perform this inelastic analysis for all full histograms and obtain the fatigue evaluation results when large number of cycles of full pressure is specified in user’s design specification. This paper provides sample analysis results for nozzles and clarifies issue of implementation of Code Case 2605. Then, the proposal of simplification and modification of Code Case 2605 from these results are proposed.

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