bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Peak Excitation Frequency on Seismic Fatigue Damage of Plant Pipelines
Authors: Inada Fumio , Sakai Michiya , Morita Ryo , Tamura Ichiro 
Published: October 2020

Abstract
In a previous report, a new method of calculating the approximate seismic cumulative fatigue damage of plant pipelines was developed, in which the sum of the cumulative absolute velocities (CAV) of the pipeline response per cycle was calculated, and the result was applied to the allowable vibration velocity described in the ASME Operation and Maintenance (O/M) code 2012. The new method provided a conservative value of cumulative fatigue damage. In this present study, a parameter showing the effect of a concentrated mass attached to the tip of a cantilever pipe was obtained as a function of the ratio of the concentrated mass to the mass of the cantilever pipe by eigenmode calculation using ABAQUS. In the previous report, the new method was based on the relative response of the pipeline, whereas in this present study, the application of the method was expanded to evaluations using the CAV of the excitation input for each cycle. We conducted the fast forward simulation of a real earthquake to determine the effect of the peak frequency change on cumulative fatigue damage, and we found that the response of cumulative fatigue damage at the peak frequency tends to decrease with increasing peak excitation frequency, which was consistent with the results obtained using the previously reported new method. Both the new method and the newly expended method are based on the ASME O/M code, and the results obtained by these methods suggest that the peak frequency tends to affect general pipelines. In the calculations, when the configuration of the pipeline is fixed and the mode shape does not change, the cumulative fatigue damage was found to decrease with increasing peak frequency of input acceleration. If the mode shape changes with the peak input acceleration frequency, then cumulative fatigue damage is affected. Moreover, if the participation factor has a larger value in a higher mode, the cumulative fatigue damage also has a larger value.
Extension of PASCAL4 Code for Probabilistic Fracture Mechanics Analysis of Reactor Pressure Vessel in Boiling Water Reactor
Authors: Lu Kai , Katsuyama Jinya , Li Yinsheng 
Published: October 2020

Abstract
In Japan, Japan Atomic Energy Agency has developed a probabilistic fracture mechanics (PFM) analysis code, PASCAL4, for probabilistic evaluation of reactor pressure vessels (RPVs) in pressurized water reactors (PWRs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) events. Besides severe PTS events, however, transients associated with normal operations, such as the cooldown and heatup transients associated with reactor shutdown and startup, respectively, should also be considered in the integrity assessment of RPVs in both PWRs and boiling water reactors (BWRs). With regard to a heatup transient, because temperature is at its minimum, and tensile stress at its maximum on the RPV outer surface, outer surface crack and embedded crack near the RPV outer surface should be taken into account. To extend the applicability of PASCAL4, we improved the code to include analysis functions for these cracks. The improved PASCAL4 can be used to run PFM analyses of RPVs subjected to both cooldown (including PTS) and heatup transients. In this paper, improvements made to PASCAL4 are firstly described, including the incorporated stress intensity factor solutions and the corresponding calculation methods for vessel outer surface crack and embedded crack near the outer surface. Using the improved PASCAL4, PFM analysis examples for a Japanese BWR-type model RPV subjected to thermal transients including a low temperature overpressure event and a heatup transient are presented.
An Effect of Bearing Surface Angle at Bolt Head on the Nut Factor and Contact Area Ratio in Tightening Bolted Joints
Authors: Shirakawa Atsushi , Sawa Toshiyuki 
Published: October 2020

Abstract
Bolted joints are used in many industrial products such as mechanical structures, automobiles, airplanes, chemical plants, and so on. In designing bolted joints, the bolt preload in the joints should be determined appropriately and rationally for preventing accidents due to bolt loosening and fracture. Also, in actual bolt tightening, it is important that the bolts should be fastened with a designed bolt preload range. Several methods for tightening bolts are well known, one of which is the torque clamping method. In this method, the designed bolt preload can be obtained by a controlled tightening torque. The relationship between the tightening torque and bolt preload is assumed to be linear in the elastic range, and the bolt preload is often calculated from the tightening torque using the nut factor. However, in some cases, where the relationship between the tightening torque and the bolt preload is not linear. One of the reasons is the effect of bearing surface angle at bolt head. In this study, the effect of the bearing surface angle at the bolt head on the nut factor is examined experimentally. Also, it is known that the bearing surface angle at the bolt head affects the contact stress at the bearing surface of the joint member. The contact area ratio is newly proposed and obtained. As a result, a method to obtain an appropriate bearing surface angle at the bolt head and tightening torque range is proposed, taking the effect of contact area ratio factor into account.
Utilisation Limits of 1¼Cr½Mo (SA387-11-2) Steel in High Plate Thickness
Authors: Detemple Ingo , Philippi Bastian , Maffert Jörg 
Published: October 2020

Abstract
Technical requirements for petrochemical reactor steels have proliferated in the last decade. The need to increase economic benefits together with higher operating temperatures and pressures are leading to the construction of higher capacity reactors with thicker walls.
Also, more and more severe and sometimes conflicting requirements in these specifications make it difficult, to derivate a steel design, e.g. in terms of chemical composition and processing parameters, for an optimized balance between quality demands and economical aspects.
The design of pressure vessel for petrochemical industry is based on mechanical properties and the design method, which are given by the construction code.
Consideration of Special Effects for the Application of an Optimized Fracture Mechanics Approach for the RPV Assessment: Project CAMERA
Authors: Obermeier Florian , Hein Hieronymus , May Johannes , Kobiela Julia , Kaiser Marco 
Published: October 2020

Abstract
A large database for fracture toughness data according to the standard ASTM E1921 in the brittle and brittle to ductile transition region was generated within the former research programs CARINA and CARISMA for materials used in western pressurized water reactor (PWR) reactor pressure vessels (RPV). These programs confirmed successfully the application of the Master Curve approach for German RPVs. With respect to the RPV proof of safety during plant operation, in particular for integrity assessments considering the event of a Pressurized Thermal Shock (PTS) further relevant issues appeared in terms of the use of suitable fracture toughness curves for components and of the quantification of safety margins for the irradiated material state:
• Validity of fracture toughness curve and Master Curve respectively in the irradiated state at higher test temperatures (ductile material region)
• Verification of the WPS effect (warm pre-stress) in the irradiated state for representative loading paths and materials
• Impact of material inhomogeneities on the fracture toughness
• Transferability of specimen-specific effects on the safety-related RPV integrity assessment
To address these open issues a follow-up project was initiated called CAMERA (Consideration of special effects for the application of an optimized fracture mechanics approach for the RPV safety assessment). One main aspect within this program is to assess the possibility of describing the whole fracture toughness curve including the upper shelf based on empirical T0 correlations and the effect of a load case related warm pre-loading.
Material tests are carried out and evaluated according to ASTM E1820 to get the crack extension resistance as a function of stable crack extension (J-R curves) in the transition to the ductile region and according to ASTM E1921 (WPS) in the lower shelf region and transition region. The least-square fit curves (J-R) as well as the effect of warm pre-stress are determined for several types of irradiated and unirradiated RPV base and weld metals.
The results serve to expand the application window of the Master Curve concept to the ductile region and to complete the fracture toughness curve over the entire temperature range from lower shelf until operating temperature also considering the load scenario based on the effect of warm pre-stress. This paper will summarize and discuss the results of the material tests performed.
Elasto-Visco-Plastic Buckling of Thick Anisotropic Shells: Numerical Buckling Predictions and Experiments
Authors: Jacquet Nicolas , Tardif Nicolas , Elguedj Thomas , Garnier Christophe 
Published: October 2020

Abstract
This work is focused on elasto-visco-plastic (EVP) buckling of thick shell structures. In particular we are interested in predicting accurately the buckling risk of stainless steel components of nuclear fast sodium reactor working under high pressure and at high temperature (around 180 bar and 500 °C). We follow a modeling/experimental approach to solve this problem.
The set-up of relevant experiments at such high temperature being complex, we work with a representative material that shows similar EVP and buckling behavior at room temperature. The representative material is an alloy mostly composed of tin, silver and copper, commonly named Sn 3.0 Ag 0.5 Cu. The elasto-visco-plastic constitutive model of the material was first characterized using tensile tests on notched specimen at room temperature under various strain rates, and the model parameters identified using finite element model updating (FEMU). In a second step we performed in plane compressive buckling tests of thick plates for various displacement rates. Surface 3D displacements were acquired using three cameras and digital image correlation.
It is well known for thick plates that linearized tangent moduli derived from Levy-Mises flow theory does not give accurate elasto-plastic buckling prediction. Linearized tangent moduli derived from Hencky’s deformation theory gives more accurate buckling prediction for thick plates. This numerical phenomenon known as buckling paradox was well correlated to experiments in the literature. This paradox is applied here to thick plates, with EVP constitutive model, in order to predict buckling.
Finally, finite element (FE) modeling of the buckling experiments was performed. Plates are modeled using SHB8PS solid shell elements. Solid shell elements allow direct displacement correlation with experiments and accurate through the thickness behavior with a 3D material model. The numerical modeling includes real plate geometry obtained using post machining measurements, experimental boundary conditions derived from the DIC (Digital Image Correlation) results and the previously identified constitutive material law. Buckling risk is tested at each loading step of the incremental algorithm using the tangent operator derived with the Hencky’s deformation theory.
Numerical results show a very good correlation with the experimental results on load and displacement history as well as buckling critical load and buckling mode.
Implementation of Ductile Damage Models to Determine Constraint Parameters for Ductile Materials: Phase 1 — Generic Constraint Conditions
Authors: Beswick J. , James P. , Sharples J. 
Published: October 2020

Abstract
It has been observed that steels which are operating in the ductile regime demonstrate greater resistance to tearing under conditions of reduced crack-tip constraint. Constraint is influenced by both geometry and load conditions. For example, fracture toughness specimens with shorter cracks relative to wall thickness, or those subjected to tension as opposed to bending, will demonstrate reduced constraint. Constraint may be quantified by an elastic T-Stress or the elastic-plastic Q parameter.
R6, a set of structural integrity guidelines widely used in the nuclear industry, suggests that the effective fracture toughness of a material at reduced constraint may be calculated using a material-specific toughness locus. To define this locus, it is usually necessary to perform laboratory tests on the material at various levels of constraint, which are both expensive and time consuming. For cleavage (low-temperature) fracture, it is also possible to consult look-up tables, which require the calculation of the Weibull stress parameter.
This paper details findings from an investigation into a method to determine the parameters defining failure loci for steels. The work involves the use of finite element analysis and two damage models which consider void growth in ductile materials. The first model is the Rice and Tracey model, which determines void growth based on stress triaxiality and plastic strain, and the second is the GTN local approach, which considers void initiation, growth and coalescence to define a yield surface for the material. The yield surface is governed by numerous parameters which enable the definition of the void volume fraction of the material at the various stages preceding fracture.
Previous work has demonstrated independence of the parameters used to define the toughness loci to the critical void size when defined using the Rice and Tracey approach. The work presented in this paper demonstrates similar behaviour using the GTN model, with independence of the constraint benefit to the governing parameters. The toughness determined using the GTN approach is calculated from J-R type curves obtained by simulating crack growth in idealised constraint scenarios: specifically applying a T-Stress to boundary layer models, where a boundary layer model is an idealised high constraint scenario.
It is shown in this paper that, whilst independence is demonstrated to the GTN parameters, there are discrepancies between the toughness loci derived using the GTN model and those using the Rice and Tracey approach. The reasons for this are discussed and are predicted to be due to load order effects, in that constraint reduces through loading, which may not be captured accurately using the boundary layer model. An introduction to the next phase of work, which does accurately include these effects, is also provided.
Damage Assessment of Similar Martensitic Welds Under Creep, Fatigue and Creep-Fatigue Loading
Authors: Bender Thorben , Klenk Andreas , Weihe Stefan 
Published: October 2020

Abstract
For the assessment of welds under high-temperature conditions in the creep or creep-fatigue regimes, the knowledge on the damage location and its temporal evolution are of high importance. The failure behavior of similar welds of ferritic-martensitic steels in the creep regime is well known. For creep-fatigue loading, the behavior of welds is still subject to research but it seems that the heat affected zone (HAZ) limits the lifetime of welded components as well. This local failure behavior is not reflected in design guidelines using weld reduction factors or in typical assessment approaches. The evaluation of local strains and stresses in the HAZ is unavoidable. For the improvement of design and inspection guidelines, a more detailed consideration of weld behavior is of interest.
In this paper, an overview of current developments in the assessment of welds under creep, fatigue, and creep-fatigue loading conditions is given. An assessment approach for creep damage and failure, including the prediction of rupture time and location, is presented. The assessment is based on numerical analyses considering the different behavior of base material and HAZ represented by three different subzones. The approach is validated with the simulation of a uniaxial cross weld, creep crack, and component tests. Whereas the creep behavior of the HAZ compared to base metal is quite well known, there is only little knowledge of their fatigue behavior. Using a set of fatigue tests on HAZ, base metal specimens and cross weld specimens, the influence of fatigue and creep-fatigue loading on the lifetime and failure location of a weld will be discussed. For the numerical simulations, a viscoplastic material law of Chaboche type is used and an evaluation of the local strains in the HAZ allows an attempt to explain the observed failure locations.
PWHT Exemptions for Carbon Steel in B31.3: An EPC Contractor’s Perspective
Authors: Rensman Jan-Willem , Kraayeveld George 
Published: October 2020

Abstract
In the 2014 edition of the ASME B31.3 Code [1], thick, P-No. 1 carbon steel pipe became exempt from Postweld Heat Treatment (PWHT) under the condition of preheating at 95°C (200°F) and multi-pass welding. The decision whether to apply PWHT or not is left to the designer but no further guideline is provided. The impression is that the need for PWHT is only corrosion/service related, and not beneficial or necessary for the integrity of the piping. Several publications [2][3][4] have addressed these changes and highlighted that this might lead to potentially unsafe situations.
This paper will critically review the arguments used for the justification of the PWHT exemption for carbon steel and show that many arguments are invalid or incomplete. It will discuss the implications for the performance of materials and predict possible failure scenarios. It will then provide estimates of typical PWHT cost eliminated by the current rules. It will provide an EPC contractor’s perspective on the current ASME B31 rules with practical approaches that may be taken to mitigate the risks. Finally, recommendations to the ASME B31 committees involved in PWHT exemption will be provided.
Alternative Design Approach by Finite Element Analysis for High Pressure Equipment
Authors: Trinca Giovan Battista , Ronchi Nicola , Fusari Fausto , Fiordaligi Emanuele 
Published: October 2020

Abstract
Components that are subject to pressure, typical of the pressure vessel industry, can be designed using such calculation methods as “Design by Rule-DBF” or “Design by Analysis-DBA”. DBA, based on the FEM, is used increasingly often because, in addition to providing a reduction in thickness due to the lower uncertainty on the calculation, it helps to verify and study physical phenomena and complex geometry that are otherwise difficult to research while offering a more intuitive usability of the results. In this paper we wish to offer, in an educative and qualitative manner, a general overview of DBA from the creation of the model to obtaining the results, describing the types of analysis that can be carried out according to the constitutive model of the material used and the degree of accuracy that can be achieved. At the end, we cover some case studies in which DBA has been successfully used to verify design or particular conditions (such as heat treatments) for pressure vessels fabrication. The DBA calculation, described in this paper, is used with the same computational methods for high, medium or low pressure components, but it is clear that the most significant reduction in thickness is for high pressure components such as reactors, which is why the DBA calculation is particularly appreciated for this type of equipment. In the context of this paper “high pressure equipment” means when the ratio of the inner diameter to thickness of the walls is &lt; 30.
Advanced Structural Integrity Assessment Tools for Safe Long Term Operation: ATLAS+ Project — Status of the Activities of the WP3 on Modelling in 2020
Authors: Blouin Arnaud , Marie Stéphane , Nicak Tomas , Timperi Antti , Gill Peter 
Published: October 2020

Abstract
The main objective and mission of the ATLAS+ project is to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems.
ATLAS+ WP3 focuses mainly on ductile tearing prediction for large defect in piping and associated components: Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as triaxiality effects, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is currently rather limited to R&D expertise. However, because of the continuous progress in the performance of calculation tools and accumulated knowledge, in particular by members of the ATLAS+ consortium, these models can now be considered as relevant for application in the context of engineering assessments.
WP3 has been planned to:
• Illustrate the implementation of these models for industrial applications through the interpretation of large scale mock-ups (with cracks in weld joints for some of them),
• Make recommendations for the implementation of the advanced models in engineering assessments,
• Correct data from the conventional engineering approach by developing a methodology to produce J-Δa curve suitable case by case, based on local approach models,
• Improve the tools, guidance and procedures for undertaking leak-before-break (LBB) assessments of piping components, particularly in relation to representing structural representative fracture toughness J-Resistance curves and the influence of weld residual stresses.
To achieve these goals, WP3 is divided into 4 sub-WPs and this paper presents the progress of the work performed in each sub-WP after 36 months of activities.
Evaluation by Two-Dimensional Finite Element Analysis of the Effect of Number of Weld Layers on the Residual Stress Profile in Stainless Steel Pipe Welds
Authors: Zumpetta Alexandra K. , Stockdale Andrew W. , Hicks Trevor G. , Mabe William R. , Coughlin Jessica L. 
Published: October 2020

Abstract
Tensile residual stresses associated with stainless steel pipe welds can promote in-service cracking and influence the need for inspections. Previous research via finite element analysis (FEA) [1] and experimental characterization [2] has shown that welds in thick wall pipe can produce compressive residual stresses at the inner diameter (ID) surface. However, research that has evaluated the relationship between the number of weld layers, stemming from different weld bead sizes, and the resulting pipe residual stress profiles is limited. This investigation used two-dimensional (2D) FEA to evaluate the influence of the number of weld layers (resulting from different weld bead sizes) on the ID surface and through-wall residual stress profiles for varying stainless steel pipe radii, thicknesses, and weld joint geometries. The findings herein are compared to previous experimental results [2]. The results demonstrated that for the larger pipe sizes and the welding conditions investigated, increasing the number of weld layers (reducing individual weld bead sizes) reduced the ID surface tensile axial residual stresses. In the larger pipe sizes, the magnitude of the tensile residual stresses extending through (into) the pipe wall is also reduced with an increased number of weld layers. The FEA results show that the weld joint geometry may not affect the residual stress profiles as strongly as do the number of weld layers, based on the similarities in the tensile stress values for the joint geometries that were evaluated.