Pipe Girth Weld Residual Stress Intensity Factor Profiles for Structural Integrity Assessment

2013 ◽  
Author(s):  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Structural Integrity ◽  
Steel Pipe ◽  
Stress Fields ◽  
Stainless Steel Pipe ◽  
Girth Welds

The influence of the residual stress field in a welded structure on crack growth and fracture is commonly assessed through its contribution to the stress intensity factor (SIF) for the crack of interest. This contribution is most often calculated by assuming a bounding through-thickness residual stress profile for the specific type of weldment with an appropriate SIF solution for the crack location, shape and structure of concern. Although more realistic residual stress profiles for stainless steel pipe girth welds have been developed recently their use, in some cases, leads to an underestimate of the SIF. A new approach is developed for determining bounding SIF values for cracks in residual stress fields of stainless steel pipe girth welds. The forms of the proposed SIF profiles are based on recently published SIF solutions for cracks in periodic residual stress fields [1]. It is shown that the SIF profiles bound those based on a large database of residual stress measurements without being excessively conservative. The outcome is a simple new method for defining more realistic SIF profiles for use in structural integrity assessments of stainless steel pipe girth welds.

Structural Integrity of Penetration Nozzle of Reactor Pressure Vessel Head of PWR Plant

2008 ◽  
Author(s):  
Kiminobu Hojo ◽  
Naoki Ogawa ◽  
Yoichi Iwamoto ◽  
Kazutoshi Ohoto ◽  
Seiji Asada ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Complex Structure ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

A reactor pressure vessel (RPV) head of PWR has penetration holes for the CRDM nozzles, which are connected with the vessel head by J-shaped welds. It is well-known that there is high residual stress field in vicinity of the J-shaped weld and this has potentiality of PWSCC degradation. For assuring stress integrity of welding part of the penetration nozzle of the RPV, it is necessary to evaluate precise residual stress and stress intensity factor based on the stress field. To calculate stress intensity factor K, the most acceptable procedure is numerical analysis, but the penetration nozzle is very complex structure and such a direct procedure takes a lot of time. This paper describes applicability of simplified K calculation method from handbooks by comparing with K values from finite element analysis, especially mentioning crack modeling. According to the verified K values in this paper, fatigue crack extension analysis and brittle fracture evaluation by operation load were performed for initial crack due to PWSCC and finally structural integrity of the penetration nozzle of RPV head was confirmed.

The Effect of the Distance From the Center of a Weld to the Fixed End on the Residual Stress and Stress Intensity Factor of a Piping Weld

2005 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Masanori Numata ◽  
Koichi Saito ◽  
Masahito Mochizuki
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Structural Integrity ◽  
Piping System ◽  
Residual Stress Field ◽  
Fixed Condition ◽  
Simplified Solution ◽  
Fixed End

The fixed conditions of butt welds between straight pipe and valve or pump in the actual piping system are different from those of straight pipes. However, the effect of fixed condition on the residual stress and the stress intensity factor for evaluation of structural integrity of cracked piping is not clear. In this study, the finite element analyses were conducted by considering the differences in the distance from the center of weld to the fixed end L to clarify the effect of fixed condition on the residual stress and the stress intensity factor. For the 600A piping, the residual stress distribution was not affected by the distance L. Furthermore, the stress intensity factor of circumferential crack under the residual stress field could be estimated by using the existing simplified solution for piping.

Fully Automated SCC and Fatigue Crack Propagation Analyses on Deep Semi-Elliptical Flaws

2013 ◽  
Author(s):  
Kota Sugawara ◽  
Hirohito Koya ◽  
Hiroshi Okada ◽  
Yinsheng Li ◽  
Kazuya Osakabe ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Flaw ◽  
Stress Fields

In this paper, some results of crack propagation analyses of deep initially semi-elliptical flaws under assumed residual stress fields are presented. The crack propagation analyses were performed by using a software system that has been developed by Okada and his colleagues. It is based on a conventional finite element program but uses the quadratic tetrahedral finite elements to model the structure with the crack. The finite element model with the crack can be generated in an automated manner. The stress-intensity factor computations are performed by using the virtual crack closure-integral method (VCCM) for the quadratic tetrahedral finite element which was also proposed by Okada and his colleagues. The automatic meshing scheme for the crack propagation analyses has also been developed by the authors. By the authors’ previous publication, it was shown that the stress intensity factor of deep semi-elliptical surface flaw under assumed residual stress field reached its maximum value at the mid-depth of the crack. Hence, in present study, in order to investigate the feature of the crack propagation of deep surface cracks, we are conducting crack propagation analyses that can predict the crack extension from each point along the crack front for an arbitrary shaped surface flaw. It can also account for material anisotropy in the crack propagation behavior. Then, the SCC crack propagation analyses for a deep semi-elliptical surface flaw in a plate under assumed residual stress fields are being conducted. The results of the crack propagation analyses suggest that the shapes of the crack after the SCC crack propagation may not be exact semi-elliptic in its shape. In this paper, the analytical procedures and some results are presented. The same analytical procedures can be adopted to perform fatigue crack propagation analyses.

Bounding Residual Stress Intensity Factor Profiles for Fracture Assessment of Pipe Girth Welds

2015 ◽  
Author(s):  
P. John Bouchard ◽  
Jino Mathew
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Size ◽  
Contour Method ◽  
Stress Measurements ◽  
Axial Residual Stress ◽  
Fracture Assessment ◽  
Girth Welds

The effect of residual stress on potential crack growth and fracture in welded structures is usually assessed through its contribution to the stress intensity factor (SIF) for the crack size and shape of interest. The idea of defining bounding residual SIF profiles for surface breaking circumferential cracks in pipe butt welds was presented at ASME PVP2013. The limiting profiles were based on through-thickness residual stress measurements for eight pipe girth welds. This paper presents new axial residual stress measurements made using the contour method for an Esshete 1250 stainless steel pipe girth weld. A wide variation in the through-wall distribution of axial residual stress around the circumference of the pipe is observed which has a significant effect on calculated values of SIF for postulated surface breaking circumferential cracks. Nonetheless, SIFs based on all of the new measurements (a total of 14 profiles) are comfortably bounded by the simple SIF prescriptions previously published.

The Effect of the Distance From the Center of a Weld to the Fixed End on the Residual Stress and Stress Intensity Factor of a Piping Weld

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Masanori Numata ◽  
Koichi Saito ◽  
Masahito Mochizuki
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Structural Integrity ◽  
Piping System ◽  
Residual Stress Field ◽  
Fixed Condition ◽  
Simplified Solution ◽  
Fixed End

The fixed conditions of butt welds between straight pipe and the valves or pump in an actual piping system are different from those of straight pipes. However, the effect of the fixed condition on the residual stress and the stress intensity factor for the evaluation of the structural integrity of cracked piping is not clear. In this study, finite element analyses were conducted by considering the differences in the distance from the center of weld to the fixed end L, to clarify the effect of the fixed condition on the residual stress and the stress intensity factor. For 600A piping, the residual stress distribution was not affected by L. Furthermore, the stress intensity factors of circumferential cracks under the residual stress field can be estimated by using an existing simplified solution for piping.

Representation and Partitioning of Welding Residual Stress Distributions for Use in Structural Integrity Assessments

2007 ◽  
Author(s):  
Adam Toft ◽  
David Beardsmore ◽  
Peter James ◽  
John Sharples ◽  
Michael Martin
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Structural Integrity ◽  
Stress Distributions ◽  
Intensity Factors ◽  
Polynomial Representations ◽  
Stress Profiles

In order to obtain good estimates of stress intensity factors in a structural integrity assessment, the accuracy with which a residual stress distribution is represented should be commensurate with the importance of localised peaks in residual stress, in particular where such peaks lie within the region under assessment. This paper describes work undertaken to investigate the importance of accurately representing residual stress distributions in structural integrity assessments. This has been carried out by comparing regular polynomial representations of residual stress distributions, combined with available weight function stress intensity factor solutions (as provided in the R6 procedures) with alternative polynomial representations of residual stress distributions, which provide a more accurate fit in the region of the crack. Such improvements in representation of residual stress profiles provide an indication as to how stress intensity factor solutions could, in future, be modified in order to result in improved accuracy of calculated stress intensity factors. Representation by partitioning residual stress profiles into membrane, bending and self-balancing components, in terms of providing a more straight-forward route for curve-fitting of residual stress profiles is considered. The investigation considers several transverse, through-thickness residual stress distributions. Stress intensity factors are calculated for a variety of crack sizes. Representation of the residual stress profiles in the stress intensity factor solutions are compared, as are the results of the stress intensity factor calculations. The conclusions arising provide guidance as to how current methods of curve fitting a residual stress distribution may be improved in cases where current methods may not be accurate. Advice is also provided as to the relative merits of representing residual stress distributions as a set of partitioned components or as a single distribution.

scholarly journals Analysis of Stress Intensity Factor due to Surface Crack Propagation in Residual Stress Fields Caused by Welding

2002 ◽  
Vol 45 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Katsumasa MIYAZAKI ◽  
Masahito MOCHIZUKI ◽  
Satoshi KANNO ◽  
Makoto HAYASHI ◽  
Masaki SHIRATORI ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Surface Crack ◽  
Stress Fields
Sign in / Sign up

Export Citation Format

Share Document