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Minimum number of weld pass layers versus pipe wall thickness 

Minimum number of weld pass layers versus pipe wall thickness 

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Conference Paper
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For supporting fitness-for-service (FFS) assessment, this paper presents a method for providing a full field description of through-thickness residual stress profiles for pipe girth welds, beyond weld locations (e.g., at weld centerline and weld toe). The paper starts with a brief introduction of the finite element modeling procedure used in this s...

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... of weld pass layers as a function of wall thickness is shown in Fig. 9 based on the present study. Note that the vertical axis should be identified as the number of through- thickness layers which often consists of more than one weld ...

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Citations

... Residual stress through-thickness estimation at distances away from the weld is practically nonexistent in these FFS codes, which can result in overly conservative assessments when applying fracture mechanicsbased structural integrity procedures [21]. During the defect assessment of regions in the proximity of welded joints [6] and residual stressinduced stress corrosion cracking in tube sheet welds [19,21,22], residual stress upper bound profiles at a distance away from the weld become important and information of which is not available in these FFS codes. ...
... Residual stress through-thickness estimation at distances away from the weld is practically nonexistent in these FFS codes, which can result in overly conservative assessments when applying fracture mechanicsbased structural integrity procedures [21]. During the defect assessment of regions in the proximity of welded joints [6] and residual stressinduced stress corrosion cracking in tube sheet welds [19,21,22], residual stress upper bound profiles at a distance away from the weld become important and information of which is not available in these FFS codes. Moreover, the available upper bound profiles in FFS codes [14][15][16][17][18] have been found to show drastic inconsistencies, considering different welding processes, weld geometries and weld joint configurations [23]. ...
... Upper bound profiles prescribed in FFS codes, as shown in Figs. 1 and 4 for BS7910, are based on polynomial curve fits on selected welded components [14,16,18], supplemented with finite element results [26]. However, recent research has demonstrated that residual stress estimation profiles at a distance away from the weld can be significant, where component geometry pipe radius to thickness ratio (r/t) [27][28][29] and heat input [19,21,22] are identified as distinct parameters. Residual stress profiles in FFS codes are determined in terms of circumferential girth welds and longitudinal seam welds. ...
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The distribution of residual stresses in welded joints plays an important role within the fracture evaluation guidelines recommended in structural integrity assessment codes such as BS7910, API 579 RP-1/ASME FFS-1 and R6. The residual stress profile recommendations in these standards are based on extensive experimental results and finite element modelling (FEM) based parametric residual stress evaluations at the weld centerline and weld toe positions. The upper bound residual stresses' profiles based on these recommendations vary significantly from one type of welding process to another for a given weld configuration with identical welding conditions. These fitness-for-service codes (FFS) depict great variability in estimating residual stress profiles during defect assessment, as BS 7910 & R6 recommends a constant profile at a distance away from welds and API 579 provides a single curve for all locations in the axial direction. Thus, conservatism is widely associated with these recommended profiles in fracture potential evaluation and assessments, leading to suboptimal recommendations. In this manuscript, a detailed review is undertaken of residual stress estimation in various FFS codes, showing vast variability among them for locations away from the weld toe on girth welds. Key distinct parameter characteristics , pipe radius to thickness ratio and heat input are detailed and found to have a significant effect on residual stress profiles in structural integrity assessment, using a stress decomposition technique. These recommendations establish an overall analysis of the interrelationship between key parameters, considering a generalized broad range of applications. A framework is proposed, based on the current review, for conducting detailed investigation by employing thermomechanical numerical modelling, coupled with measurement results (nondestructive and semi-destructive) from an experimental study, as input to machine-learning algorithms for application guidance to engineers.
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... where A w represents weld fusion area which can be estimated based on a given joint preparation or available weld macrograph. A closed form solution for estimating plastic zone extent d p measured from weld fusion (see [24,[27][28]) can be obtained. Then, its estimation can be written in a simple form as: ...
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... x is a dimensionless coordinate parameter along through-thickness direction with ID atx ¼ À1 and OD atx ¼ 1. The self-equilibrating term s s:e: ðxÞ is given by Eq. (8) in Part I [1]. ...
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... It should be noted that the over-estimated yield zone through Eqs. (9), (10) according to R6 [2] can be largely eliminated by the plastic zone estimation method recently given by Song et al [8]. Contour plots of the residual stress distributions are shown inFig. ...
... The material used in this parametric analysis is 2¼ CrMoeV steel. Material properties can be found in Ref. [8] and not repeated here due to space limitation. Annealing initiation temperature is set at 1200 C in the unified weld material model [18]. ...
... Due to space limitation, only results of Single-V joint type are presented here, as shown inFig. 8. Results on other joint types and thicknesses (such as Double-V, Narrow Groove) can be found in Refs. [8,17]. 4.1. ...
... The plot is not shown here due to space limitations. As such, r/t ratio can be characterized as an independent parameter that controls residual stress distributions as discussed in [22]. ...
... The plot is not shown here due to space limitations. As such, r/t ratio can be characterized as an independent parameter that controls residual stress distributions as discussed in [22]. ...
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... The plot is not shown here due to space limitations. As such, r/t ratio can be characterized as an independent parameter that controls residual stress distributions as discussed in [22]. ...
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