Stress Indices for Circumferential Fillet Welded and Socket Welded Joints

2002 ◽  
Author(s):  
Edward A. Wais ◽  
E. C. Rodabaugh ◽  
R. Carter
Keyword(s):  
Test Data ◽  
Welded Joints ◽  
Stress Indices ◽  
Accurate Evaluation ◽  
Class 1

This paper presents the results of an investigation of the Stress Indices for circumferential fillet welded or socket welded joints which are required for ASME Section III Class 1 systems. The history or background of the basis of the various indices is reviewed and summarized. New values for the indices are suggested based on new test data and analysis. These changes will result in a more accurate evaluation of circumferential fillet welded or socket welded joints.

Investigation of Stress Indices and Directional Loading of Eccentric Reducers

2003 ◽  
Author(s):  
Edward A. Wais ◽  
E. C. Rodabaugh ◽  
R. Carter
Keyword(s):  
Test Data ◽  
Stress Indices ◽  
Piping Systems ◽  
Class 1

Stress indices and stress intensification factors are used in the design of piping systems that must meet the requirements of ASME Section III for Class 1 and Class 2 systems. This study reviews the present values for eccentric reducers and provides new test data for comparison, which takes into account the directionality of the loading. Suggestions are presented which significantly improve the evaluation of reducers.

Fatigue Strength Reduction Factors for Welded Joints: Another View

2007 ◽  
Author(s):  
Arturs Kalnins
Keyword(s):  
Standard Deviation ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Test Data ◽  
Welded Joints ◽  
Welded Joint ◽  
Fatigue Curve ◽  
Strength Reduction ◽  
Initial Estimate ◽  
Curve Fit

The paper distinguishes between FSRFs that are used for two different purposes. One is to serve as a guideline for an initial estimate of the fatigue strength of a welded joint. That is the purpose of the FSRFs that are given in the ASME B&PV Code and various accompanying documents. If that estimate renders the fatigue strength inadequate, an FSRF can be sought that is limited to the joint under consideration. The paper shows how such FSRFs can be determined from fatigue test data. In order to make it possible to read the allowable cycles from the same design fatigue curve as that used for the FSRFs of the guidelines, a Langer curve [defined by equation (2) in the paper] is used to curve fit the data. The appropriate FSRF is obtained by minimizing the standard deviation between this curve and the data. The procedure is illustrated for girth butt-welded pipes. The illustration shows that for the data used in the analysis, a constant FSRF is applicable to less than one million cycles but not to the high-cycle regime.

Qualification of the Notch Stress Approach for the Fatigue Assessment of Welded Pressure Equipment and Power Plant Components

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Ralf Trieglaff ◽  
René Stößlein ◽  
Fabian Hauser
Keyword(s):  
Test Data ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Hot Spot ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Notch Stress

The fatigue assessment of welded joints in different engineering disciplines is usually based on nominal, structural or notch stresses on one hand (elastic concept using component fatigue curves of load controlled test data) and local strains on the other hand (elasto-plastic concept using material fatigue curves of strain-controlled push-pull test data of un-notched and polished standard specimens). The concepts of the first mentioned group are implemented in widespread standards and recommendations such as [1] to [3]. The fatigue assessment procedure of the European standard for unfired pressure vessels (EN 13445-3, Clause 17 & 18 and related annexes) [4] is currently under revision with one focus on the elaboration of user friendly fatigue assessment options for welded components [5]. The current state of the art focuses on the application of an adapted structural hot spot stress approach to the fatigue assessment of welded pressure equipment [5]. Although this is a significant step forward, the implementation of a notch stress approach can furtherly increase the fatigue assessment options by detailed weld seam analysis. The paper focuses on respective methodological proposals and application examples of typical welded joints. The finite element analysis as part of the procedure has to be harmonized with the requirements of the assessment procedure. Of course, the compatibility of the hot spot stress approach and a notch stress approach has to be guaranteed for individual examples. The direct comparison of the different approaches allows for a qualitative evaluation of methods. The application of an appropriate master fatigue curve FAT100 and the limitations with regard of stress/strain ranges in the low cycle fatigue (LCF) regime as well as the fatigue assessment of welded joints with mild weld toe notches is the subject of special considerations. The latest recommendations of German Welding Society (DVS) [6] constitute a reference for the last two subjects raised.

Stress Index Development for Special Elbows

2009 ◽  
Author(s):  
J.-M. Kim ◽  
H.-C. Song ◽  
S.-Y. Kang ◽  
S.-H. Park ◽  
J.-S. Yang ◽  
...  
Keyword(s):  
Finite Element ◽  
The Other ◽  
Stress Index ◽  
Piping System ◽  
Element Analysis ◽  
Finite Element Program ◽  
Stress Indices ◽  
Reactor Coolant ◽  
Class 1 ◽  
Asme Code

The reactor coolant piping system is designed to be in compliance with the requirements of Class 1 piping of Section III of the ASME Boiler and Pressure Vessel Code. Stress indices are required to evaluate the nuclear Class 1 piping. The reactor coolant system of Kori 1 nuclear power plant consists of a 2-loop system, each having two special elbows: one is the reducing elbow with a non-uniform thickness, and the other is the elbow with a splitter installed inside the elbow. However, stress indices for special elbows are not specified in NB-3683.7 of the ASME Code. In this paper, we computed the stress indices of special elbows for pressure and moment loads by the finite element analysis. The linear elastic method was used for the analysis with the finite element program, ANSYS, and the solid element (SOLID 45) was selected to model the geometry. The finite element model of the special elbows included a straight segment of pipe on each end of the elbows. The uniformly distributed internal pressure was applied to the pipe and elbow. The equivalent axial blow-off load was applied to one end, and the translational degree of freedom was fixed at the other end of the model. The moment was applied to one end, and the boundary condition was fixed at the other end of the model. Based on the analysis results, it is concluded that stress indices, except B1, in NB-3683.7 of the ASME Code can be used for special elbows conservatively. More analyses are required to apply B1 index to the special elbows.

Investigation of Torsional Stress Intensification Factors and Stress Indices for Girth Butt Welds in Straight Pipe

2002 ◽  
Author(s):  
Edward A. Wais ◽  
E. C. Rodabaugh ◽  
R. Carter
Keyword(s):  
Carbon Steel ◽  
Test Data ◽  
Straight Pipe ◽  
Butt Weld ◽  
Bending Tests ◽  
Butt Welds ◽  
Stress Indices ◽  
Stress Intensification Factor ◽  
Torsional Test ◽  
Fatigue Evaluation

The basis for fatigue evaluation of ASME Section III Class 2, 3 and B31.1 piping is the girth butt weld where the Stress Intensification Factor (SIF) is defined to be 1.0. The SIFs for other components are based on comparison to the butt welds. This SIF of 1.0 for butt welds is based on extensive bending tests on carbon steel straight pipe which are reviewed and summarized in this study. The results of new test data, including torsional test data, are presented. The authors are unaware of any previous torsional tests on carbon steel straight pipe. This new data leads to suggested changes in the codes taking into account the directionality of the loading.

Effect of Radial Offset Between Welded Back to Back Elbows on Their C2 Stress Index

2010 ◽  
Author(s):  
R. Balakrishnan ◽  
W. Reinhardt
Keyword(s):  
Finite Element ◽  
Welded Joint ◽  
Element Model ◽  
Stress Index ◽  
Element Analysis ◽  
Butt Weld ◽  
Stress Indices ◽  
Special Cases ◽  
Piping Systems ◽  
Class 1

Pipe bends and elbows in process and power plant piping systems are sometimes added to provide additional flexibility along with their primary function of changing the direction of fluid flow. In special cases, piping systems may have double bends or elbows welded back to back with or without straight pipe in between. Due to manufacturing inaccuracies, back-to-back welded elbows may have a radial offset at the welded joint. Assessment of Class 1 piping following NB-3600 requires consideration of the C2 stress index of the girth butt weld, which is to be multiplied with the elbow C2 index. As an alternative, the C2 stress index may be calculated by finite element analysis using the maximum linearized membrane plus bending stress intensity. The effect of offset between the elbows at the welded joint on the elbow C2 stress indices is studied in this paper. Double elbows with elbow angles ranging from 30° to 90° and a radial offset of 1/32″ and 3/32″ at the weld are considered. Double elbows model with no weld in between and finite element model with single elbow are analyzed for comparison. The effect of angle between the bend planes of the two back-to-back elbows is studied. Results from the analyses are compared with C2 stress indices calculated as per NB-3680.

scholarly journals Experimental Data Assessment and Fatigue Design Recommendation for Stainless-Steel Welded Joints

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 723 ◽  
Author(s):  
Peng ◽  
Chen ◽  
Dong
Keyword(s):  
Stainless Steel ◽  
Fatigue Strength ◽  
Structural Steel ◽  
Fatigue Test ◽  
Test Data ◽  
Welded Joints ◽  
Steel Structures ◽  
Design Codes ◽  
Inverse Slope ◽  
Fatigue Design

Stainless steel possesses outstanding advantages such as good corrosion resistance and long service life. Stainless steel is one of the primary materials used for sustainable structures, and welding is one of the main connection modes of stainless-steel bridges and other structures. Therefore, fatigue damage at welded joints deserves attention. The existing fatigue design codes of stainless-steel structures mainly adopt the design philosophy of structural steel. In order to comprehensively review the published fatigue test data of welded joints in stainless steel, in this paper, the fatigue test data of representative welded joints of stainless steel were summarized comprehensively and the S–N curves of six representative stainless-steel welded joints were obtained by statistical evaluation. The comparison of the fatigue strength from existing design codes and fatigue test data was performed, and the results showed that the fatigue strength of welded joints of stainless steel was higher than that of structural-steel welded joints. The flexibility of regression analysis with and without a fixed negative inverse slope was discussed based on the scatter index. It was found that the fatigue test data of stainless-steel welded joints are more consistent with the S–N curve regressed by a free negative inverse slope. In this paper, a design proposal for the fatigue strength of representative welded joints of stainless steel is presented based on the S–N curve regressed by the free negative inverse slope.

Investigation of Flexibility Factors and Stress Indices for Class 1 Curved Piping

2010 ◽  
Author(s):  
Nima Zobeiry ◽  
Ali Asadkarami ◽  
Wolf Reinhardt
Keyword(s):  
Bending Moment ◽  
Finite Element Models ◽  
3D Finite Element ◽  
Stress Indices ◽  
Curved Pipes ◽  
Class 1 ◽  
Realistic Assessment ◽  
Asme Code ◽  
The Given ◽  
Limited Scope

In the analysis of piping, consideration of the behaviour of bends and elbows is essential. Due to the ovalization phenomenon, the bends exhibit more flexibility under bending moment loading than straight pipes, while generating comparatively higher stresses. This has been recognized in the ASME Code for Class 1 piping, where flexibility factors and stress indices have been given for curved pipes. It has been understood that the values of stress indices given in the Code are conservative. As a result, extensive research has been performed to obtain lower values, as allowed by the Code. However, these studies have been performed separately from the flexibility factors, where research is generally lacking. The Code recognizes that the given flexibility factors have limited scope of use and more work on this issue has been proposed. It is evident that a more realistic assessment of pipe bends has to be based on revised stress indices and flexibility factors. In this paper, a number of compound bends are studied, where on one hand the stress indices are conservative and on the other the flexibility factors of the Code may not be applicable. For this purpose, the behaviour of these bends is simulated using 3D finite element models. Using these models and by comparison to the flexibility and stresses in straight pipes, flexibility factors and stress indices for the bends are obtained. A comparison to the values in the literature and discussion of different factors contributing to these values are presented.

Background for Changes in the 1981 Edition of the ASME Nuclear Power Plant Components Code for Controlling Primary Loads in Piping Systems

1982 ◽  
Vol 104 (4) ◽  
pp. 351-361 ◽  
Author(s):  
S. E. Moore ◽  
E. C. Rodabaugh
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Plastic Deformations ◽  
Stress Indices ◽  
Nominal Pressure ◽  
Piping Systems ◽  
Class 1 ◽  
Bending Stresses ◽  
Plant Components

Section III of the ASME Boiler and Pressure Vessel Code contains simplified design formulas for placing bounds on the plastic deformations in nuclear power plant piping systems. For Class 1 piping a simple equation is given in terms of primary load stress indices (B1 and B2) and nominal pressure and bending stresses. The B1 and B2 stress indices reflect the capacities of various piping products to carry load without gross plastic deformation. In this paper, the significance of the indices, nominal stresses, and limits given in the Code for Class 1 piping and corresponding requirements for Class 2 and Class 3 piping are discussed. Motivation behind recent (1978–1981) changes in the indices and in the associated stress limits is presented.

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