Fatigue Assessment of a Weld Joint of a Pressure Vessel

2005 ◽  
Author(s):  
Arturs Kalnins ◽  
Vic Bergsten ◽  
Mahendra Rana
Keyword(s):  
Fatigue Strength ◽  
Internal Pressure ◽  
Weld Joint ◽  
Pressure Vessel ◽  
Structural Stress ◽  
Constant Amplitude ◽  
Fatigue Assessment ◽  
Full Penetration ◽  
Notch Stress ◽  
Number Of Cycles

A full-penetration weld on both sides between a shell and a flat head is evaluated for fatigue strength by four methods, two based on structural stress and two on notch stress. Internal pressure is cycled with constant amplitude. The allowable cycles are calculated by each method. The number of cycles for the same geometry and loading varies widely, ranging from 4,835 to 137,000.

The Simplified Method for Fatigue Assessment of the European Pressure Vessel Standard EN 13445

2013 ◽  
Author(s):  
Fernando Lidonnici
Keyword(s):  
Pressure Vessel ◽  
Cyclic Load ◽  
Pressure Range ◽  
Pressure Fluctuations ◽  
Worked Examples ◽  
Fatigue Curve ◽  
Fatigue Assessment ◽  
Full Penetration ◽  
Simplified Method ◽  
Number Of Cycles

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method for fatigue assessment. Use of the simplified method is limited to cases where the cyclic load is mainly given by pressure fluctuations. The stress ranges needed for the evaluation of the allowable number of cycles are calculated only on the basis of the pressure range and of the maximum allowable pressure of each vessel component, obtained from the normal design formulae. Suitable tables are provided in order to establish, for each vessel component, a relationship between the stress range and the pressure range. Other tables are provided in order to define a suitable fatigue curve on the basis of the so called “Weld Class”: curves with higher values of stress ranges are given for full penetration welds having better NDT testing, while curves with lower stress ranges are given for not fully penetrated welds with poor or no NDT testing. Since only the plain Design by Formulae is needed for the use of the method, no FEM calculations are required. The simplified method may therefore give a suitable simple and economic solution in many common cases of cyclic loading. In this paper two worked examples have been provided in order to compare the results of fatigue calculations made with the simplified method with the results obtained by means of a complete F.E.M. stress analysis.

Fatigue Assessment of a Weld Joint Subjected to Thermal Stresses

2005 ◽  
Author(s):  
Arturs Kalnins
Keyword(s):  
Weld Joint ◽  
Thermal Stresses ◽  
Elastic Stress ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Structural Stress ◽  
European Standard ◽  
Full Penetration ◽  
Cyclic Service ◽  
Number Of Cycles

Fatigue analysis is performed for a full-penetration weld joint, welded from both sides, connecting a cylindrical vessel to a flat head. It is subjected to a repeated transient cycle of ambient temperature inside the vessel. No pressure is cycled. Finite element heat transfer and elastic stress analyses are performed, and stress ranges are calculated. The allowable number of cycles for cyclic service is obtained by two structural stress methods. One is a method proposed for the ASME Boiler and Pressure Vessel code and the other is in the European Standard for unfired pressure vessels. It is found that for the same geometry and loading the former would permit 136,000 or 36,000 cycles while the latter would permit 8,000 cycles.

scholarly journals Methods for Structural Stress Determination according to EN 13445-3 Annex NA – Comparison with other Codes for Unfired Pressure Vessels

2018 ◽  
Vol 165 ◽  
pp. 10003
Author(s):  
Ralf Trieglaff ◽  
Jürgen Rudolph ◽  
Martin Beckert ◽  
Daniel Friers
Keyword(s):  
Pressure Vessel ◽  
Pressure Vessels ◽  
Structural Stress ◽  
Stress Determination ◽  
User Friendliness ◽  
Fatigue Assessment ◽  
Shell Elements ◽  
European Working ◽  
The Status

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 – Design methods with the aim of reaching a significant increase in user-friendliness and a clear guideline for the application. This paper is focused on the new informative annex NA ”Instructions for structural stress oriented finite elements analyses using brick and shell elements”. As an essential amendment for the practical user, the determination of structural stress ranges for fatigue assessment of welds is further specified in this new annex. Different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses. This paper will give a short overview of the proposed approaches of structural stress determination in annex NA of the revised EN 13445-3. It will present the status of the approaches based on the results of fatigue analyses according to EN 13445-3 Clause 18 for different application examples. For verification purposes, the results of the approaches proposed in EN 13445-3 are compared with the results of other pressure vessel design codes for nuclear and non-nuclear application.

scholarly journals Notch Stress Intensity Factor (NSIF)-Based Fatigue Design to Assess Cast Steel Porosity and Related Artificially Generated Imperfections

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1097
Author(s):  
Manuel Schuscha ◽  
Michael Horvath ◽  
Martin Leitner ◽  
Michael Stoschka
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fatigue Strength ◽  
Intensity Factor ◽  
Cast Steel ◽  
Experimental Investigations ◽  
Fatigue Assessment ◽  
Notch Stress Intensity Factor ◽  
Fatigue Design ◽  
Notch Stress

Shrinkage porosities and non-metallic inclusions are common manufacturing process based defects that are present within cast materials. Conventional fatigue design recommendations, such as the FKM guideline (“Forschungskuratorium Maschinenbau”), therefore propose general safety factors for the fatigue assessment of cast structures. In fact, these factors mostly lead to oversized components and do not facilitate a lightweight design process. In this work, the effect of shrinkage porosities on the fatigue strength of defect-afflicted large-scale specimens manufactured from the cast steel G21Mn5 is studied by means of a notch stress intensity factor-based (NSIF-based) generalized Kitagawa diagram. Additionally, the mean stress sensitivity of the material is taken into account and establishes a load stress ratio enhanced diagram. Thereby, the fatigue assessment approach is performed by utilizing the defects sizes taken either from the fracture surface of the tested specimens or from non-destructive X-ray investigations. Additionally, a numerical algorithm invoking cellular automata, which enables the generation of artificial defects, is presented. Conclusively, a comparison to the results of the experimental investigations reveals a sound agreement to the generated spatial pore geometries. To sum up, the generalized Kitagawa diagram, as well as a concept utilizing artificially generated defects, is capable of assessing the local fatigue limit of cast steel G21Mn5 components and features the mapping of imperfection grades to their corresponding fatigue strength limit.

Sensitivity of Fatigue Assessment to the Use of Different Reference S-N Curves

2003 ◽  
Author(s):  
Xiaozhi Wang ◽  
Zhan Cheng
Keyword(s):  
Loading Condition ◽  
Offshore Structures ◽  
Constant Amplitude ◽  
Fatigue Assessment ◽  
Tubular Joints ◽  
Environment Effects ◽  
Assessment Approach ◽  
The Difference ◽  
Offshore Industry ◽  
Number Of Cycles

The S-N curve based fatigue assessment approach is the most widely used one in both ship and offshore industry, in contrast with a fracture mechanics approach. The S-N approach, implemented by either simplified or spectral method, has to apply S-N curves to calculate fatigue strength. The S-N curve, which represents the number of cycles (N) of a constant amplitude stress range (S) that will cause a fatigue failure, is normally developed based on experimental data. Which S-N curve should be applied to a particular detail depends very much on the geometry of the detail, welding information as well as loading condition. There are various S-N curves published by different institutions, e.g., S-N curves published by UK HSE, IIW, AWS etc. The newly developed ABS “Guidance on Fatigue Assessment of Offshore Structures”, [1], proposes the ABS S-N curves, in which two categories of joints, tubular and non-tubular, are included, and both size and environment effects are taken into account. However, the application in Gulf of Mexico is also influenced by API recommendations. In API RP 2A, AWS S-N curves are referred, which in US practice is accepted for fixed (buoyant and non-buoyant) platform deck structures. The objective of this paper is to address the difference between different S-N curves and to present the detailed results of fatigue assessment by using different S-N curves for non-tubular joints. Conclusions made based on the study provide more background on the S-N curve application in fatigue assessment.

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.

Notch-Stress Analysis by FE Submodeling

1997 ◽  
Vol 119 (2) ◽  
pp. 243-244 ◽  
Author(s):  
E. Weiß ◽  
J. Rudolph ◽  
A. Lietzmann
Keyword(s):  
Finite Element ◽  
Fatigue Strength ◽  
Stress Analysis ◽  
Carrying Capacity ◽  
Pressure Vessel ◽  
Load Carrying Capacity ◽  
Finite Element Analyses ◽  
Notch Stress ◽  
Solid Models ◽  
Load Carrying

This paper presents experiences in detailed finite element analyses of pressure vessel components with respect to load-carrying capacity and fatigue strength. The application of the submodeling technique for shell-to-solid models is discussed.

Comparison of Methods for Structural Stress Determination According to EN 13445-3 Annex NA

2017 ◽  
Author(s):  
Ralf Trieglaff ◽  
Martin Beckert ◽  
Jürgen Rudolph ◽  
Fabian Hauser
Keyword(s):  
Pressure Vessel ◽  
Working Group ◽  
Structural Stress ◽  
Stress Determination ◽  
User Friendliness ◽  
Fatigue Assessment ◽  
Shell Elements ◽  
European Working ◽  
Detailed Assessment

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 - Design methods to reach a significant increase in user-friendliness and a clear guideline for the application. This paper is focused on the new informative annex NA “Instructions for structural stress oriented finite elements analyses using brick and shell elements”. As an essential amendment for the practical user the determination of structural stress ranges for fatigue assessment of welds is further specified in this new annex. Different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses. This paper will give an overview of the proposed approaches of structural stress determination in annex NA of the revised EN 13445-3. It will present the results of fatigue analyses according to EN 13445-3 Clause 18 from a round robin test with participants of the German working group for different application examples. The estimated structural stress ranges for the proposed approaches of structural stress determination will be compared. This comparison leads to general remarks and open points for the different approaches. Furthermore it is concludes that further comparisons, e.g. with results of other pressure vessel design codes are desirable.

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