bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Variability in Weld Residual Stress
Authors: Cathcart H. , Horne G. , Moffat A. 
Published: November 2019

Abstract
Residual stresses resulting from welds are a key consideration in the design and assessment of piping and pressure vessels. As welding is a variable process, the resulting variability in weld residual stress should be accounted for in design and assessment. This paper investigates the variability in residual stress resulting from flux cored arc welds by performing residual stress measurements on a set of nominally identical welds between 25mm plates of grade DH36 steel. The welds were produced in two environments to assess the impact on residual stress variability: a well-controlled laboratory environment and a less controlled factory environment.
The results showed significant variability in the residual stresses between the welds, with standard deviations up to 25% of the peak value in some locations near the weld center. The welds were two sided and higher variability was measured in the side performed second, with the variability in heat applied appearing to be a key driver of the residual stress variability. A difference was observed between the standard deviations of residual stress in the factory and laboratory samples, with the laboratory samples showing less residual stress variability. Whilst the small number of samples measured prevents firm quantitative conclusions being drawn about the potential differences in residual stress variability between production environments the results do suggest that there is value in further study.
A Critical Review of Recent Fatigue Crack Growth Data in Relation to ASME Code Case N-809
Authors: Mann Jonathan , Currie Chris , Tice David , Platts Norman 
Published: November 2019

Abstract
ASME Code Case N-809 provides Fatigue Crack Growth (FCG) expressions for austenitic stainless steels operating in a primary water environment within a Pressurised Water Reactor (PWR). The code case currently contains different expressions for nominally low-carbon (304L, 316L) and conventional (304, 316) grades.
Since the original work that provided the technical basis for N-809 was completed, an increased amount of FCG data has become available through industry testing, particularly for low-carbon stainless steels. A large database is now available that contains significantly more data than the one used in the original development of the code case. The data cover a wider range of testing conditions (temperature, loading rate, and mean stress) and represent a more diverse population of material types, including multiple heats.
In this paper, the N-809 laws are re-analysed in terms of these new data, with a focus on each of the environmental dependencies that are currently included in the law. In particular, alternative R-ratio expressions from the literature are shown to provide an improved description of the effect of R-ratio for nominally low-carbon materials. The statistical distribution of FCG rates and the treatment of partially retarded data are also investigated as part of the derivation of revised descriptions of best-fit and bounding FCG rates.
The analysis highlights a small amount of potential non-conservatism in the current N-809 description of best-fit FCG rates at higher R-ratios. The current description of upper-bounding behaviour is shown to still be valid, however significant over-conservatism exists at lower R-ratios.
Level Three Assessment of Local Thin Areas in Pipelines Using Web-Enabled FEA
Authors: Brown Donald L. , Spring Daniel W. , Panzarella Charles 
Published: November 2019

Abstract
The fitness-for-service procedures for local thin areas in pipelines trade complexity for conservatism, with more complex procedures being less conservative. In this paper, we outline a procedure for automating the advanced Level 3 assessment procedure outlined in API 579-1/ASME FFS-1 for local thin areas. The outlined procedure is bundled into a web-enabled, industrial trade tool where the minimum data requirements are the same as those for a Level 2 assessment. The procedure can be applied to an entire in-line inspection scan of UT thickness readings and, after calculation, can identify hotspots of local damage. By reducing the inputs to those of a Level 2 assessment procedure, the Level 3 procedure presents as an attractive alternative to the current Level 2 approaches.
Investigation of the Seismic Risk of Industrial Pipe Rack - Piping Systems Accounting for Soil-Structure Interaction
Authors: Karagiannakis George , Di Sarno Luigi 
Published: November 2019

Abstract
Earthquake events have shown that industrial pipe racks lack of a completed design framework that encompasses contemporarily a number of uncertainties such as modelling, seismic action, design and analysis procedures as well as soil conditions. That being said, the seismic behaviour of piping systems has not been assessed up to par recognizing the potential effects of nonbuilding – nonstructural components interaction as well as soil conditions that constitute a decisive parameter particularly for structures that lie on alluvial deposits. In the present work, after reviewing European and American standards and technical literature upon design parameters, the seismic reliability analysis of two pipe rack – piping systems in decoupled and coupled case considering near- and far-field records as well as soil deformability is addressed. As it is illustrated, the classic nonlinear static analysis may overestimate the resistance of racks, common limit states of interstorey drift ratio cannot be applied and the behaviour factor selection may be unjustifiable. Also, soil-structure interaction affects detrimentally the response both of rack and piping system as depicted by the fragility functions.
Study on Active Vibration Control of Seismic Isolation Structure With Variable Gain Using Spectrum Monitoring
Authors: Fujiwara Ukyo , Miura Nanako , Sone Akira 
Published: November 2019

Abstract
In this research, the seismic isolation structure which can switch the active control gains by the characteristics of the earthquake is proposed. As the number of high-rise buildings in urban areas in has increased in recent years, damage due to long-period earthquakes is expected to increase. In this paper, the focus is on the area of velocity response spectrum as an index of long-period earthquake. Then we design the time varying weighting coefficient from the area of the velocity response spectrum obtained from the seismic wave. The long periodicity of the earthquake is judged from the area of the velocity response spectrum calculated from the seismic wave arriving from moment to moment. In addition, we aim to improve the performance of the control system by inputting appropriate control power. We also aimed for energy saving of control by not performing control input within the range where the earthquake does not have a long period. We proposed a method of switching control using time varying weighting factor, designed time varying weighting factor, and confirmed its effectiveness by performing time history response analysis on actual seismic waves.
Review of Ferrite Number (FN) Requirements and Proposed Changes to Code Case N-504-4 and Nonmandatory Appendix Q
Authors: McCracken Steven L. , Segletes David 
Published: November 2019

Abstract
ASME Section XI Nonmandatory Appendix Q and Code Case N-504-4 are routinely used to install full structural weld overlays in the nuclear power industry for repair or mitigation of stress corrosion cracking in austenitic stainless steel weldments. Both Appendix Q and N-504-4 specify a Ferrite Number (FN) and carbon content requirement for the stainless steel weld metal used for the weld overlay to ensure acceptable resistance to stress corrosion cracking. The Ferrite Number (FN) is used in the ASME Code for establishing the delta ferrite content in the deposited weld metal.
Field experience indicates there is often confusion and differing opinion concerning how the Ferrite Number and carbon content requirements of Appendix Q and N-504-4 are satisfied. This is in part due to unavailability of the original technical basis for these requirements. This paper provides a background for the delta ferrite and carbon content requirements, information on influence of delta ferrite and carbon content on stress corrosion cracking and U.S. Nuclear Regulatory Commission (NRC) guidance on the issue. Finally, this paper details a proposed revision of Nonmandatory Appendix Q and N-504-4 to clarify the FN and carbon content requirements.
A Unified Engineering Inelastic Model for 316H Stainless Steel
Authors: Phan V.-T. , Messner M. C. , Sham T.-L. 
Published: November 2019

Abstract
Section III, Division 5 of the ASME Boiler & Pressure Vessel Code provides rules for designing high temperature nuclear components using inelastic analysis. However, the current Code does not provide guidance on suitable inelastic constitutive models to use with this design method nor does it provide Code qualified constitutive models for any of the high temperature Class A materials. This paper describes the development of an inelastic constitutive model for 316H steel, suitable for use with the Division 5 design procedures. The model captures the average response of all Code permissible 316 material as described by a large set of experimental data collected from the literature. The model uses a unified model to describe creep and rate dependent plasticity at high temperature that accounts for the experimentally-observed coupling of these deformation mechanisms. The goal is to incorporate the inelastic model developed here for 316H along with similar models for the other Class A, high temperature materials into Section III, Division 5 to facilitate the use of the design by inelastic analysis method.
Study of the Fracture Toughness in Electron Beam Welds
Authors: Mokhtarishirazabad Mehdi , Simpson Chris , Horne Graeme , Kabra Saurabh , Truman Chris , Moffat Andrew , Mostafavi Mahmoud 
Published: November 2019

Abstract
High energy welding technologies, such as electron beam, have a number of potential benefits including: faster process time, smaller heat affected zone and potentially favourable weld residual stresses. Therefore, they are good candidates for manufacturing complex components for the next generation of nuclear power plants. However, before electron beam can be deployed on a wide scale, further work is required in a number of areas, including how these welds are treated in structural integrity assessments. As an example, the full extent of the effects of complex residual stress (RS) fields, arising from high energy welding technology, on the fracture behaviour of components has not been fully investigated. This understanding is essential for defect tolerance calculations using integrity assessment procedures. In this study, the fracture toughness of austenitic stainless steel 316L plates with various thicknesses (6mm to 25mm), joined by electron beam welding, is evaluated. Residual stresses were measured using non-destructive diffraction and mechanical relief methods (contour method). This is to examine the effect of welding residual stresses on the resistance of the welded component to fracture.
Impact of Including Spiral Wound Bead Width in Gasket Area
Authors: Worden Kathryn , Ruffin Mark 
Published: November 2019

Abstract
Bolted joint and gasket designers currently calculate spiral wound gasket stress in one of three ways. The differences lie in gasket area determination. The first is the historical Boiler & Pressure Vessel Code calculation method of using an effective sealing width which is half or less of the full dimensional width. Found to be inadequate for creating consistently acceptable sealing performance, those promoting and affecting lower leaks rates and emissions opt to use a gasket’s full width to determine gasket area and stress.
The full width of a spiral wound gasket is currently being determined in two different ways among industry participants. Most use the dimensioned outer diameter which includes the bead of winding wire that does not contact the flange surface. Some exclude the width of the bead. Inclusion or exclusion of the bead has a significant impact on gasket seating stress for sealing elements of narrow width as the width of the bead represents a large percentage of the overall dimensions.
In this paper, all three methods will be discussed focusing on gasket stresses for NPS calculated from the preferred method of full width comparing the inclusion and exclusion of the bead width.
TDFAD Analysis of Creep Crack Initiation in 0.5CMV/2.25CrMoV Steel Weldments
Authors: Ejaz M. , Davies C. M. 
Published: November 2019

Abstract
The time dependent failure assessment diagram (TDFAD) is a convenient methodology to simultaneously assess whether a component is likely to fail by brittle, ductile or creep fracture, plastic collapse or creep rupture. In this work, creep toughness data, Kmatc, have been derived from experimental creep crack growth (CCG) tests on compact tension fracture mechanics specimens made of a weldment consisting of 0.5CMV parent material, 2.25CrMo, where the starter crack was located in the heat affected zone (HAZ). Time dependent failure assessment diagrams (TDFADs) are then constructed for each material condition and creep crack initiation (CCI) time predictions were obtained for the CCG tests performed on the weldment samples using both a TDFAD based on either parent and weld material data. The TDFAD based on the weld data provided the most conservative prediction of CCI times thus is recommended for use for weldment samples.
Inclined Surge Line Design Considerations for Analysis and Monitoring
Authors: Oakman Jamie , Gray Mark , Leber Benjamin , Salac Matthew 
Published: November 2019

Abstract
Thermal stratification can occur in pressurizer surge lines when flow rates are low and large temperature differences between the pressurizer fluid and reactor coolant loop fluid exist. NRC Bulletin 88-11 requires that utilities address this issue with respect to the licensing basis. Additionally, significant fatigue usage can develop due to insurges and outsurges from the pressurizer that occur when the temperature difference (ΔT) is large. An important aspect of the surge line fatigue analysis is determination of global pipe moment loads due to insurges, outsurges, and related stratification effects.
The Westinghouse AP1000® plant surge line is designed to limit the global effects of stratification using a surge line geometry that is inclined more than that of the previous generation plants. However, this design provides unique challenges to the analytical solution in comparison to the mostly horizontal geometries in previous PWR designs. The main challenge is due to the location of the stratified fluid hot/cold interface. The horizontal geometry has historically allowed conservative (based on analytical testing) treatment of the stratified interface profile. The inclined geometry requires consideration of positional changes, as the stratified interface moves through the line due to flow changes. Because of this, iterative calculations were required to predict global piping moment loads through the transient histories based on the movement of the stratified interface. Software was developed to solve a series of correlative equations representing moment loads due to pipe temperatures and stratification ΔT within discretized portions of the surge line throughout each transient. The correlative equations, which are based on the matrix solution of piping analysis load cases, predict the global pipe moment loads to a high degree of precision.
The surge line is also a significant location in the online fatigue monitoring program implemented at the sites. The complexity of the design analysis that is reflected in the monitoring model requires a more detailed accounting for the location of the stratification interface, the effect on prediction of moment loadings for controlling locations, and the effect on local stresses at the monitoring locations. This paper describes the approach used to address all of these factors in the design evaluation and subsequent fatigue monitoring application.
Further Work on Analyzing Accuracy and Overall Performance of Torque Tools for Assembling Bolted Flanged Joints
Authors: Rodery Clay D. , Hamilton Scott , Ferguson Neil 
Published: November 2019

Abstract
Over the past two years, the accuracy and repeatability of equipment used to assemble bolted flanged joints have been studied, and progress has been reported in past papers. One of the findings has been that pneumatic torque wrenches demonstrated a broader plus/minus range on bolt stress from the targeted value (e.g., lack of accuracy) than manual or hydraulic torque wrenches. What was notable, however, was that the repeatability of the bolt stress that was achieved did remain consistent with the other types of torque wrenches. Since the repeatability has been shown to be consistent, attention has turned to investigating and determining the reason for the perceived lack of accuracy. One aspect that might account for this is the calibration of the pneumatic torque wrenches.
This paper outlines and documents the research that has recently taken place to identify the parameters that are key elements in improving the accuracy of pneumatic torque wrenches that might form the basis of development of a standard for calibration of powered torqueing equipment.
Study of Simplified Assembly Patterns With Load-Based Feedback and Preemptive Elastic Interaction Compensation
Authors: Richardson Jordan 
Published: November 2019

Abstract
A total of 12 flange assemblies, spanning both class 300 and 600 were instrumented with ultrasonic transducers and observed following differing assembly patterns to gain insight into the BFJ elastic interactions. Each flange assembly was additionally tested to multiple load targets to monitor the overall sensitivity of interaction to load. Analytical work following the data collection led to the development of a simplified installation method and sequencing that dramatically reduces the work effort required to effectively close a joint while being independent of fastener condition or tool selection. The range of validity for the simplified method is further extended with linear multivariate solving techniques and accelerated joint “snugging” to promote joint stiffness. Limits on the acceptable load achievement was set to &lt; 5% error on the average load and &lt; 10% normalized standard deviation to be considered acceptable when targeting Appendix-O calculated loads of ASME PCC-1. Validation of the proposed method was undertaken by the University of Houston at the Bechtel WATC facility with support of Carber Engineering which included full size pressure testing following joint assembly. The observations made from the 60+ full size trials then served to validate FEA work towards the analysis of the remaining sizes of class 300/600 from 4″ to 24″.
Pure Plastic Behavior and the Assumption of Zero Elasticity at the Limit Load
Authors: Marcal Pedro V. , Rainsberger Robert , Fong Jeffrey T. 
Published: November 2019

Abstract
The authors have introduced an analysis based on a modification of the Mooney Rivlin material to obtain an estimate of the plastic behavior of a structure near its failure point. In this paper we generalize the concept of zero elasticity and pure plastic behavior at the limit loads and beyond [1–2]. The theorems of limit analysis assume rigid plastic behavior that is equivalent to zero elasticity. We are concerned with the regions just beyond the limit load, so it is not unreasonable to again assume zero elasticity in this region.
The neglect of elastic behavior allows us to concentrate on large plastic strains that take place at or beyond the limit loads as defined by Limit Analysis [3–4]. We can focus on tearing, Plastic Fracture Mechanics and low-cycle fatigue respectively. In such situations the practice has been adopted to label such state points as ‘Ultimate’ behavior. Here we adopt the same label to refer to behavior at or beyond the limit load, where the full large displacement and work hardening effects can be accounted for by the modified Mooney Rivlin material.
The mechanics of fracture has also been applied to the tearing of Vulcanized rubber by Rivlin and Thomas[5]. This study concerned large nonlinear incompressible strains that were modeled by Mooney Rivlin Materials, Mooney[6]. The Fracture is modeled by the balance of internal and external work caused by the advancing crack surface area [7–8]. One final benefit of the assumption of zero elasticity is its simplification of dynamic analysis.
Pressure Surge Load Estimation on Pipes With Dimensional Reduction and Rayleigh Energy Method
Authors: Seena Abu , Kim Juyoul 
Published: November 2019

Abstract
The pressure surge in pipes due to change in operating conditions exerts an axial load on elbows proportional to the change in momentum of fluid and unbalanced pressure forces. The response of piping structure to such load needs the full time history analysis in three dimensional spaces which is cumbersome process due to high computing memory requirements and long simulation time. In present work it has been shown that using Rayleigh energy balance for each elbow-load configuration, the system can be reduced to equivalent 1D spring mass system and the response can be estimated by solving 1D equation of motion. Then it has been recommended to simulate the response of each elbow which gives good approximation of dynamic amplification of displacement also called as Dynamic Load Factor (DLF). These dynamic load factors for each elbow can be used for the interaction of forces using static equivalent response in 3D space. This approach is pseudo static equivalent analysis where the load amplifications factors DLF are estimated from the dynamic force profile and system response in one-dimensional space. An algorithm is developed for the above explained process. Most of the engineers are using the DLF = 2 for the load estimation due to absence of method to estimate the dynamic load factor. The approach was proposed by Goodling in 1989 and still widely followed in the industry. The present paper discusses uncertainty and inaccuracy involved in performing approximate analysis and shows the significance and need of performing full force time history analysis. The proposed method shows very good agreement with the time consuming 3D full force time history results. There are also limitations for the proposed method. As the spring mass system is simulated with dimensional reduction to single frequency domain, the pipe supports and guides should be properly placed before applying the present approach. It has been shown that with proper support configuration, this simplified approach yields very good approximation of surge load on pipes with reduced time.