scholarly journals Comparison Between Different Approaches for the Evaluation of the Hot Spot Structural Stress in Welded Pressure Vessel Components

2009 ◽  
Author(s):  
Martin Muscat ◽  
Kevin Degiorgio ◽  
James Wood
Keyword(s):  
Fatigue Life ◽  
Pressure Vessel ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Design Stage ◽  
Structural Stress ◽  
Notch Stress ◽  
Weld Toe ◽  
Section Viii ◽  
Division 2

Fatigue cracks in welds often occur at the toe of a weld where stresses are difficult to calculate at the design stage. To circumvent this problem the ASME Boiler and PV code Section VIII Division 2 Part 5 [1] uses the structural stress normal to the expected crack to predict fatigue life using elastic analysis and as welded fatigue curves. The European Unfired Pressure Vessel Code [2] uses a similar approach. The structural stress excludes the notch stress at the weld toe itself. The predicted fatigue life has a strong dependency on the calculated value of structural stress. This emphasizes the importance of having a unique and robust way of extracting the structural stress from elastic finite element results. Different methods are available for the computation of the structural hotspot stress at welded joints. These are based on the extrapolation of surface stresses close to the weld toe, on the linearisation of stresses in the through-thickness direction or on the equilibrium of nodal forces. This paper takes a critical view on the various methods and investigates the effects of the mesh quality on the value of the structural stress. T-shaped welded plates under bending are considered as a means for illustration.

Applicability Evaluation of SS (Structural Stress) Method on Actual Project

2008 ◽  
Vol 580-582 ◽  
pp. 633-636 ◽  
Author(s):  
Kwang Seok Kim ◽  
Joong Kyoo Kang ◽  
Joo Ho Heo ◽  
Sung Geun Lee
Keyword(s):  
Fatigue Life ◽  
Hot Spot ◽  
Fatigue Analysis ◽  
Correlation Factor ◽  
Structural Stress ◽  
Hot Spot Stress ◽  
Notch Stress ◽  
Loading Case ◽  
Application Data ◽  
Applicability Evaluation

The structural stress (SS) method developed by BATTELLE has been studied based on small or mid-size scale specimens. In order to apply the new method, such as SS, on an actual project, it should have application results on actual project. However, SS method didn’t have a lot of application data compared to class procedure using hot spot stress (HSS). In order to find out whether the SS method, for the evaluation of fatigue life, can give reasonable results when it is applied under the same loading suggested by classification societies, it was compared with fatigue lives derived by class. ABS & DNV’s simplified fatigue analysis method were adopted to check the validity of SS method. Before applying complicated loading of class, static loading case was applied, since the class method has their own correlation factor for wave loading. And then, simplified fatigue analysis was performed with more complicated loading cases. From the results of fatigue life calculation, it can be said that SS shows reasonable fatigue lives with respect to HSS or notch stress based fatigue lives.

Applicability Evaluation of SS (Structural Stress) Method on Actual Project

2007 ◽  
Author(s):  
Kwang-Seok Kim ◽  
Joong-Kyoo Kang ◽  
Joo-Ho Heo ◽  
Sung-Geun Lee
Keyword(s):  
Fatigue Life ◽  
Hot Spot ◽  
Fatigue Analysis ◽  
Correlation Factor ◽  
New Method ◽  
Structural Stress ◽  
Hot Spot Stress ◽  
Notch Stress ◽  
Loading Case ◽  
Application Data

The structural stress (SS) method developed by BATTELLE has been studied based on small or mid size scale specimens. In order to apply new method on actual project, the new method such as SS should have application results on actual project. However, SS method didn’t have a lot of application data compared to class procedure using hot spot stress (HSS). In order to find that the SS method for the evaluation of fatigue life can give reasonable results when it is applied under the same loading suggested by classification societies, fatigue lives derived by class and SS method were compared. ABS & DNV’s simplified fatigue analysis method were adopted to check the validity of SS method. Before applying complicated loading of class, static loading case was applied since the class method has their own correlation factor for wave loading. And then simplified fatigue analysis was performed with more complicated loading cases. From the results of fatigue life calculation, it can be said that SS shows reasonable fatigue lives with respect to HSS or notch stress based fatigue lives.

scholarly journals Generalized SCF Formula of Out-Of-Plane Gusset Welded Joints and Assessment of Fatigue Life Extension by Additional Weld

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1249
Author(s):  
Yixun Wang ◽  
Yuxiao Luo ◽  
Yuki Kotani ◽  
Seiichiro Tsutsumi
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Welded Joints ◽  
Life Extension ◽  
Leg Length ◽  
Notch Stress ◽  
Out Of Plane ◽  
Weld Toe ◽  
Effective Notch Stress ◽  
Geometric Effects

The existing S-N curves by effective notch stress to assess the fatigue life of gusset welded joints can result in reduced accuracy due to the oversimplification of bead geometries. The present work proposes the parametric formulae of stress concentration factor (SCF) for as-welded gusset joints based on the spline model, by which the effective notch stress can be accurately calculated for fatigue resistance assessment. The spline model is also modified to make it applicable to the additional weld. The fatigue resistance of as-welded and additional-welded specimens is assessed considering the geometric effects and weld profiles. The results show that the error of SCFs by the proposed formulae is proven to be smaller than 5%. The additional weld can increase the fatigue life by as great as 9.4 times, mainly because the increasing weld toe radius and weld leg length lead to the smaller SCF. The proposed series of S-N curves, considering different SCFs, can be used to assess the welded joints with various geometric parameters and weld profiles.

Design, Manufacture and Safety Aspects of Forged Vessels for High-Pressure Services

1980 ◽  
Vol 102 (1) ◽  
pp. 98-106 ◽  
Author(s):  
G. J. Mraz ◽  
E. G. Nisbett
Keyword(s):  
High Pressure ◽  
Pressure Vessel ◽  
Low Alloy Steels ◽  
Nickel Chromium ◽  
Molybdenum Alloys ◽  
Tension Tests ◽  
Alloy Steels ◽  
Section Viii ◽  
Division 2

Steels at present included in Sections III and VIII of the ASME Boiler and Pressure Vessel Code severely limit its application for high-pressure design. An extension of the well-known AISI 4300 series low alloy steels has long been known as “Gun Steel.” These alloys, which are generally superior to AISI 4340, offer good harden-ability and toughness and have been widely used under proprietary names for pressure vessel application. The ASTM Specification A-723 was developed to cover these nickel-chromium-molybdenum alloys for pressure vessel use, and is being adopted by Section II of the ASME Boiler and Pressure Vessel Code for use in Section VIII, Division 2, and in Section III in Part NF for component supports. The rationale of the specification is discussed, and examples of the mechanical properties obtained from forgings manufactured to the specification are given. These include the results of both room and elevated temperature tension tests and Charpy V notch impact tests. New areas of applicability of the Code to forged vessels for high-pressure service using these materials are discussed. Problems of safety in operation of monobloc vessels are mentioned. Procedures for in-service inspection and determination of inspection intervals based on fracture mechanics are suggested.

Method B Fatigue Screening in ASME BPV Code, Section VIII, Division 2, Part 5

2019 ◽  
Author(s):  
Kenneth Kirkpatrick ◽  
Christopher R. Johnson ◽  
J. Adin Mann
Keyword(s):  
Fatigue Damage ◽  
Pressure Vessel ◽  
Fatigue Analysis ◽  
Damage Factor ◽  
Simple Method ◽  
Mechanical Loads ◽  
Penalty Factor ◽  
Section Viii ◽  
Cyclic Service ◽  
Division 2

Abstract ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 2, Part 5 Method B fatigue screening is intended to be a quick and simple method that is sufficiently conservative to screen components in cyclic service thus not requiring detailed fatigue analysis. The method assesses pressure, thermal, and mechanical loads separately. The basis for each portion of the method is discussed along with an alternative bases for the assessments. Each assessment is reformulated as a fatigue damage factor and all variables are provided so that the intent of each equation is clearly identifiable. A penalty factor will be included in each equation rather than assuming one penalty for all designs, the reformulation creates penalty for non-fatigue resistant designs and reduces the penalty for fatigue resistant designs. Examples are given showing the potentially non-conservative results if a summed damage is not used.

A Study of the Conservatism in ASME BPVC Section VIII Division 2 Opening Design for External Pressure

2019 ◽  
Author(s):  
Barry Millet ◽  
Kaveh Ebrahimi ◽  
James Lu ◽  
Kenneth Kirkpatrick ◽  
Bryan Mosher
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
External Pressure ◽  
The Other ◽  
Finite Element Analyses ◽  
Division 1 ◽  
Section Viii ◽  
Allowable Compressive Stress ◽  
Division 2

Abstract In the ASME Boiler and Pressure Vessel Code, nozzle reinforcement rules for nozzles attached to shells under external pressure differ from the rules for internal pressure. ASME BPVC Section I, Section VIII Division 1 and Section VIII Division 2 (Pre-2007 Edition) reinforcement rules for external pressure are less stringent than those for internal pressure. The reinforcement rules for external pressure published since the 2007 Edition of ASME BPVC Section VIII Division 2 are more stringent than those for internal pressure. The previous rule only required reinforcement for external pressure to be one-half of the reinforcement required for internal pressure. In the current BPVC Code the required reinforcement is inversely proportional to the allowable compressive stress for the shell under external pressure. Therefore as the allowable drops, the required reinforcement increases. Understandably, the rules for external pressure differ in these two Divisions, but the amount of required reinforcement can be significantly larger. This paper will examine the possible conservatism in the current Division 2 rules as compared to the other Divisions of the BPVC Code and the EN 13445-3. The paper will review the background of each method and provide finite element analyses of several selected nozzles and geometries.

scholarly journals An Ability to Adapt and Change

2014 ◽  
Vol 136 (11) ◽  
pp. 36-37
Author(s):  
Madiha El Mehelmy Kotb
Keyword(s):  
Life Cycle ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Electronic Format ◽  
The World ◽  
Regulatory Approach ◽  
Section Viii ◽  
Division 2 ◽  
Service Inspection ◽  
Technical Services

This article reviews about the views of Madiha El Mehelmy Hotb, the Head of the Pressure Vessels Technical Services Division for Regie Du Batiment Du Quedec, on how ASME Boiler and Pressure Vessel Code has evolved over the years. Hotb reveals that during the 1980s, ASME’s regulatory approach covered all aspects of the life cycle of a boiler or a pressure vessel from design to being taken out of service. It also confirmed every step in between – fabrication, installation, repair and modification, and in-service inspection. During later years, the institution moved toward accreditation of authorized inspection agencies, changed the publication cycle from three years to two, eliminated addenda, and restructured the Code committees. New Section VIII and division 2 were written, and the Codes were published in digital electronic format. Hotb believes that the Code will continue to be widely used and adopted in future. It will have a bigger and larger input from all over the world and will have further outreach and adoption by far more countries.

scholarly journals The Influence of Longitudinal Stiffeners on Weld Toe Stress Concentrations in Multi Planar Tubular KK Joints

2007 ◽  
Vol 348-349 ◽  
pp. 409-412
Author(s):  
Charles O. Woghiren ◽  
F.P. Brennan
Keyword(s):  
Stress Concentration ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Stress Concentrations ◽  
Out Of Plane ◽  
Invaluable Tool ◽  
Weld Toe ◽  
Dimensional Parameters ◽  
Stress Concentration Factors ◽  
Jack Up

This paper reports a parametric stress analysis of various configurations of rack plate stiffened multi-planar welded KK joints using the finite element method. The KK joint finds application in the leg structure of offshore Oil & Gas jack-up platforms. The rack plate is a dual purpose element of the joint because it firstly functions as a stiffener which reduces the stress concentration at the brace/chord intersection. This could be an immense contribution to the increase in fatigue life of the joint but other hot spot sites are introduced to the joint. The rack is also used for raising and lowering of the jack-up hull which gives the jack-up platform its jacking capability. Over 120 models using a combination of shell and solid elements were built and analysed within ABAQUS. Non-dimensional joint geometric parameters; β, γ and . were employed in the study with . being defined as the ratio of rack thickness to chord diameter. Stress Concentration Factors (SCFs) were calculated under applied axial and OPB (out-of-plane-bending) loading. Three critical SCF locations were identified for each load case, with each location becoming the most critical based on the combination of the non-dimensional parameters selected for the joint. This is important as careful design can shift the critical SCF from an area inaccessible to NDT to one that can be easily inspected. The SCF values extracted from the models were used to derive six parametric equations through multiple regression analysis performed using MINITAB. The equations describe the SCF at the different locations as a function of the non-dimensional ratios. The equations not only allow the rapid optimisation of multi-planar joints but also can be used to quickly identify the location of maximum stress concentration and hence the likely position of fatigue cracks. This in itself is an invaluable tool for planning NDT procedures and schedules.

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.

A Comparison of Different Design Codes on Fatigue Life Assessment Methods

2016 ◽  
Author(s):  
Jinhua Shi ◽  
Liwu Wei ◽  
Claude Faidy ◽  
Andrew Wasylyk ◽  
Nawal Prinja
Keyword(s):  
Pressure Vessel ◽  
Task Force ◽  
Fatigue Analysis ◽  
Life Assessment ◽  
Design Codes ◽  
Fatigue Life Assessment ◽  
Analysis Methods ◽  
Section Viii ◽  
Division 2 ◽  
Nuclear Association

Different pressure vessel and piping design codes and standards have adopted different fatigue analysis methods. In order to make some contribution to current efforts to harmonize international design codes and standards, a review of fatigue analysis methods for a number of selected nuclear and non-nuclear design codes and standards has been carried out. The selected design codes and standards are ASME Boiler and Pressure Vessel Code Section III Subsection NB and Section VIII Division 2, EN 12952, EN 13445, EN 13480, PD 5500, RCC-M, RCC-MRx, JSME, PNAEG and R5. This paper presents the initial review results. The results of the study could be used as part of the on-going work of the Codes and Standards Task Force of the World Nuclear Association (WNA) Cooperation in Reactor Design Evaluation and Licensing (CORDEL) Working Group.

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