bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of the New Post-RCCM Option From Code_Aster Through Benchmark Comparisons With Other Industrial Codes
Authors: Métais Thomas , Plessis Sarah , Miralles Julien 
Published: October 2017

Fatigue is identified as a significant degradation mode that affects nuclear power plants world-wide. The various international codes and standards (ASME, RCC-M, JSME, etc...) offer rules to predict its damaging effect on the locations of the various components of an NPP. These rules, which ensure conservatism and safe operation, have grown in complexity over the years because they have integrated R&D results showing aggravating effects (such as PWR environment degradation) that were not explicitly included in the original analyses (such as Environmental Assisted Fatigue [1] [2]) but also because an economically viable design of components has required optimization and refinement of mechanical assessment methods.
EDF has been developing since 1989 its own in-house FEA code baptised code_aster that is included in the Salome-Meca mechanical package. Salome-Meca is open-access and can be used freely by international users. It is continuously improved with a release at a rate of one new software version per year and it integrates the most recent results obtained by the EDF R&D, in fields as broad as fracture mechanics, XFEM and fatigue.
The fatigue post-processing in code_aster offers a span of criteria (Dang Van, Stress Intensity, etc...) to pick and choose from and even offers the possibility to make up owns one fatigue criteria. It also offers the possibility to post-process fatigue according to the RCC-M rules: this is implemented in code_aster through the so-called POST_RCCM operator.
Recent developments have enabled EDF to update the POST_RCCM operator in order to bridge the gap with modern fatigue industrial codes. The update effort has included in particular the development of a new option to evaluate fatigue for nozzles according to the RCC-M Annex ZE-200 as well as the clarification of the methodologies used for combining time points and transients. In addition, POST_RCCM includes the possibility to perform calculations with integration of environmental effects, with significant freedom to design one’s own corrections. The option is even left open to integrate a correction per the methodology proposed in [2]. The overall work scope and progress as of early 2016 was reported in [3] and is now in its validation phase.
The validation of a fatigue computer code is not an easy task as the full validation using hand calculations would be a highly tedious effort, given the technicality and the multiple choices to make along the various steps of the fatigue analysis. As a result, an accepted way of validating the results obtained with a given code is to perform a benchmark analysis against another industrial fatigue code. This strategy was adopted for the validation of the new POST_RCCM functionalities and this paper presents the work performed and the results obtained.
Stress Intensity Factor Solutions for Crack-Like Anomalies in ERW Seam Welded Pipe
Authors: O’Brian Jennifer , Olson Richard , Young Bruce 
Published: October 2017

In response to the National Transportation Safety Board (NTSB) Recommendation P-09-1, the Department of Transportation (DOT) Pipeline and Hazardous Material Safety Administration (PHMSA) initiated a comprehensive study to identify actions that could be implemented by pipeline operators to significantly reduce longitudinal seam failures in electric resistance weld (ERW) pipe. As part of the project, Task 3 in Phase II was designed to determine more appropriate stress intensity factor solutions for non-standard, axial, crack-like anomalies in ERW seam-welded pipe.
The purpose of this paper is to provide an overview of the normalized stress intensity factor solutions for cold weld (CW), selected seam-weld corrosion (SSWC), and hook crack type anomalies. ERW seams with and without weld caps are also included. The limitations on design space are discussed in the context of presenting results and interpolation and extrapolation schemes beyond that space with infinitely long solutions used as a boundary value. Results are presented in the form of surface plots for various combinations of parameters.
The reports generated during the project are publicly available and are located on the following PHMSA website: http://primis.phmsa.dot.gov/matrix/PrjHome. rdm?prj=390.
Evaluation of the Reaction Moments of Metal Bellows Expansion Joints Subjected to Angular Movement
Authors: Veiga José Carlos , Kavanagh Nelson 
Published: October 2017

The reaction moment calculations of Hinged and Gimbal expansion joints, designed according to the “Standards of Expansion Joint Manufacturers Association” (EJMA), consider the bellows spring rate and pin friction. The reaction moment due to the lateral pressure forces should also be considered. Metal bellows subjected to angular movement extends one side and contracts the opposite, generating a lateral force caused by the media pressure.
This paper evaluates the lateral force reaction moment in a hinged expansion joint with the hardware designed for angular movements. For this purpose prototypes were built and the moments evaluated, simulating actual field conditions.
Thermal Fatigue Crack Propagation in Large Scale Yielding (LSY) Conditions: Pacific Experiment on a 316L Quasi-Structure
Authors: Leopold Gaëlle , Curtit François , Courtin Stéphan 
Published: October 2017

An experimental device was built to study fatigue crack propagation in Large Scale Yielding (LSY) conditions.
This paper deals with results obtained for the first experiment performed on a 316L quasi-structure containing four initial cracks. Crack lengths are measured and thermocouples and strain gauges enabled to follow the test.
A comparison of this experiment was then carried out with an operating transient and measured crack growth rates were compared to the RSE-M PWR codified laws [1].
Flow-Induced Noise of Perforated Plates at Oblique Angles of Incidence
Authors: Vanoostveen Paul , Ziada Samir 
Published: October 2017

This paper investigates experimentally the mechanism of tone generation from flow over a simplified model of a perforated plate. To simplify the geometry to two dimensions, a perforated plate is modeled by a series of rectangular slats with an adjustable gap width between them. This apparatus is tested at various angles of incidence and flow velocities, to identify the conditions favorable to the production of tonal noise.
The results of this research are presented in two main parts. First, the acoustic response of the test plates is documented by means of microphone measurements. It is found that for an angle of incidence between 5 and 30 degrees and a flow velocity of 10 to 30 m/s, tonal noise is produced. Outside of this range of angles, the produced sound is broadband. In the second part, phase-locked particle image velocimetry (PIV) is used to study the flow field. It is found that vortices form in the free shear layer of the gaps between the slats. These vortices impinge on the side of the downstream slat and are then ejected through the gap to the backside of the plate. As these vortices leave the edge of the downstream slat, counter rotating vortices are shed in sympathy with the incident vortices. Vortex pairs are therefore periodically shed which are thought to be the cause of tone generation.
Fatigue Assessment of a Bulged Coke Drum
Authors: Vivas Gabriel A. , Moret Armando J. , Bello Roberto E. , Melian Luis M. , Carmona Jose R. , Araque Egler D. 
Published: October 2017

Coke drums are subjected to batch cycles processing residue from refineries and upgrading the fuel streams back to the plant for further processing. As a result of operating conditions, these vessels are subjected to severe non-uniform thermal gradients that lead to localized hot and cold spots. The predominant failure mode in the coke drum shell is therefore the natural, but unwanted, progression of bulges and corrugations and eventual cracking. According to a coke drum survey coordinated by API in 1996 from 145 coke drums, 57% were found to have shell bulging problems. A common trend to increase profitability in coke drum units is reducing operational cycle length; which aggravates bulging and cracking mechanisms on these vessels.
As part of the bulging monitoring process, laser mapping and bulge severity factor (BSF) analysis were conducted in a total of six coke drums. The vessel that exhibited the most significant bulges was subsequently instrumented with strain gauges and thermocouples in three specific regions. Finite element analyses (FEA) of the instrumented regions were performed using the laser mapping and 2-dimensional temperature gradients as inputs, and compared with the strain gauge measurements. The assessment shows the level of damage produced during operation, as well as the changes in damage from one cycle to the next. The usage factor can be used as a decision criterion by operation personnel for potential changes, as well as aiding in decision making on when to repair, replace or reinforce the sections of interest.
Engineering and Simulations to Investigate and Predict the Failure of the Four Commonly Used Flat Head Designs in Heat Recovery Steam Generators
Authors: Asadi Mahyar , Henry Jeff , Torkildson Steve , Kashani Majid Tanbakuei , Smith Mathew 
Published: October 2017

Failure has been observed to occur on grade P91 alloy flat head closures in Heat Recovery Steam Generators (HRSG), operating at high temperature (>538°C) and high pressure (>125 bar), after a relatively low in-service life. Since creep is expected to be the major failure mechanism, creep analysis and creep life prediction were conducted on four commonly used flat head designs. We have previously shown that failure of welded P91 material is highly dependent on the material properties in the Heat Affected Zone (HAZ). As such we modeled a common multilayer welding procedure to determine the local material properties of both the Coarse Grain and Fine Grain HAZ for each flat head design. Once the final material properties were obtained, we exposed each simulated flat head to typical operational conditions and calculated the total stress (pressure + thermal) and temperature at each node. With this we then used a Deformation Mechanism Map (DMM) for the P91 alloy to determine the creep rate at each node. This allowed us to identify areas that are accumulating creep strain from different creep mechanisms and therefore susceptible to creep and to approximate the creep life.
Finally, a comparison made between the four commonly used flat head designs by ASME to show which design is more desired with respect to welding process.
Numerical Simulation of the Creep Failure of a Steam Reformer Outlet Manifold
Authors: van Zyl Gys , Keltjens Jan , Al-Shawaf Ali 
Published: October 2017

After eleven years of service, a through-thickness crack developed at a circumferential welded joint in the outlet manifold of a steam reformer. The crack led to a minor fire and controlled shutdown of the reformer. The manifold was fabricated from cast 20Cr-30Ni-Nb material, with welds from Inconel 617 nickel base filler.
This paper will present the findings of the failure analysis that was performed to ascertain the cause of the incident. A metallurgical failure analysis was performed to determine the damage mechanism and found clear signs of creep damage, highly localized to the weld. Theoretical calculations and finite element analysis were performed to determine the estimated creep rupture life and found that failure occurred long before the minimum estimated end-of-life.
Further numerical simulations were performed to evaluate the effect of an unusually high number of startup/shutdown cycles. The analyses considered elastic-plastic and inelastic (creep) properties of the weld and base materials and simulated a number of operational cycles where thermal and pressure conditions were cycled between ambient and operational.
The simulations found clear evidence that operational cycles contributed to a dramatic reduction in life through the action of repeated cycles of plastic strain, due to a mismatch in the thermal expansion of the base and weld metals, and creep relaxation. The study concludes with recommendations that can be implemented at fabrication to mitigate this mode of damage.
Design of Threaded Closures for High Pressure Screw Plug Heat Exchangers Designed to ASME Section VIII Div. 2
Authors: Sippy Haresh K. , Chandiramani Dipak K. 
Published: October 2017

Threaded closures for pressure vessels have been in use for decades. Much work has been done to develop safe threaded closures. Threaded closures are very advantageous when there is a need for opening the vessel at intervals for maintenance purposes.
Heat Exchangers are a typical application where there is a need for opening the vessel to get good access to the inside and outside of the tubes for mechanical cleaning, thus maintaining heat transfer efficiency. These are known as Screw Plug Heat Exchangers and are basically U-tube heat exchangers. The tube side normally operates at high pressure and temperature and is closed by a threaded end closure.
Two problems are often encountered in screw plug heat exchangers. These are:
1. Leakage through the gasket at the tubesheet causing intermixing of shell side and tube side fluids, which is unacceptable
2. Jamming of the threaded plug due to deformation of channel barrel
In an earlier paper (PVP2016-63137) these problems were studied for a vessel designed to ASME Section VIII Div. 1. It was found that leakage through the tubesheet gasket could be eliminated by changing the gasket to a grooved metal gasket with covering layers as defined in ASME B16.20.
Preventing leakage from the tubesheet gasket is extremely necessary to get the ultra-low sulphur requirements for clean fuel.
In the work reported in this paper, a procedure for obtaining leak-free performance on a vessel designed to ASME Section VIII Div. 2 was developed and verified using a prototype.
Code formulae for calculation of thickness of various parts normally consider only the need to limit the component stress to be within allowable limits defined in the Code. Allowable stresses for Section VIII Div. 2 construction may be about 18 % higher than the allowable stress for Section VIII Div. 1 construction at design temperature, thereby allowing thinner sections for the same design conditions.
As the thinner sections would deform more, the likelihood of jamming of the end cover could be more severe in ASME Section VIII Div. 2 constructions. Hence this study was additionally undertaken to verify the adequacy of the earlier proposed design methodology, i.e., use of an additional steel ring shrunk fit to the end of the channel to prevent flaring of the channel and jamming of screw threads, for Section VIII Div. 2 constructions.
Evaluation of the Internal Hydrogen-Induced Threshold Stress Intensity Factor in 2.25Cr-1Mo Steels Determined by the Offset Potential Drop Method
Authors: Konosu Shinji , Inoue Takehiro , Murakami Yoshiaki 
Published: October 2017

The single specimen offset potential drop method has been applied to obtain the internal hydrogen-induced threshold stress intensity factor KIH in Cr-Mo steels by using small-sized 12.7-mm-thick ASTM CT-specimens (1/2T-CT).The subcommittee on Hydrogen Embrittlement in the Material Division of the Japan Pressure Vessel Research Council (JPVRC) had been investigating internal hydrogen embrittlement by using 25.4mm thick compact tension specimens (1T-CT(1/2): B = 25.4mm, W = 25.4mm, 2H = 30.5mm), to enable an adequate supply of hydrogen from the uncracked region of the specimen near a crack tip to the crack tip zone during the experiment under normal atmospheric conditions.
In the present study, tests were performed on 1/2T-CT specimens under a mixed load control and grip-displacement control aimed at achieving a reduction in the test execution time. It was found that the threshold stress intensity factors for the 1/2T-CT specimens exhibited virtually the same behavior as those obtained in the previous studies using the 1T-CT (1/2) specimens.
Factors Influencing Nut Factor Test Results
Authors: Brown Warren , Long Stewart 
Published: October 2017

Nut Factor is used to establish a bolt load for a given applied torque in bolted joint assembly. In previous papers the effects of different factors influencing Nut Factor results were examined, which included the type of anti-seize, bolt and nut material, bolt diameter and amount of anti-seize applied. This paper examines those factors further and then includes additional factors which have been shown to have significant effect on the measured Nut Factor.
The knowledge of these factors has been used to adjust the proposed ASTM specification for determining Nut Factor. It is also relevant to application in the field and to ensure that any testing conducted in a laboratory will be applicable in the field.
Consideration of Yield Discontinuity in the Elastic-Plastic Fracture Analysis of Circumferentially Flawed Pipes
Authors: Wang Longjie , Eren Elvin , Wang Bin , Wu Guiyi 
Published: October 2017

This study examined the fracture behaviour of pipes containing surface flaws oriented circumferentially and made from a material that exhibits yield discontinuity (known as Lüders plateau) with the view of making recommendations for the assessment of pipes subject to high level of plasticity.
Starting with the fundamental and first principles, uniaxial tensile tests were carried out with the use of digital image correlation (DIC) to observe the formation and propagation of Lüders bands quantitatively. Finite element (FE) analyses were then carried out to simulate the Lüders banding phenomenon in uniaxial tensile specimens and consequently cracked pipes. Different material models were adopted in FE analyses, including the stress-strain curve with a flat stress plateau neglecting upper yield stress, and the so-called ‘up-down-up’ (UPU) stress-strain curve for refining crack driving force predictions.
The numerical analysis of tensile tests demonstrated that UPU stress-strain model satisfactorily simulated the main macroscopic features of Lüders band observed in the experiment. FE analysis of flawed pipes using both flat and UPU stress-strain curves produced a similar trend in the crack tip opening displacement (CTOD)-strain trajectory as that obtained from large-scale testing. It was seen that the shape of the UPU stress-strain curve, particularly the magnitude of softening, considerably affects the magnitude of crack driving force in the flawed pipe. However, the strain localisation associated with Lüders banding was not observed in the circumferentially flawed pipe in the case of using the flat stress-strain curve. The CTOD crack driving force obtained from simulations was lower than the CTOD obtained from experiments in the Lüders plateau regime, even with the consideration of ductile tearing.
Finally, as a result of this study, recommendations on the optimum choice of material parameters were made for more accurate predictions of crack driving force in the presence of yield discontinuity.
A Comparative Fatigue Analysis Study Based on RCC-M Code and EN13-445 Standard Through Actual Test Cases
Authors: Billon François , Halleguen Julien 
Published: October 2017

This document is aimed at comparing the fatigue analysis methods based on the RCC-M code and on the harmonized standard EN 13445-3 with a view to quantifying the associated deviations and uncertainties, at each step of the calculation, by taking into account every aspect of each code such as calculation thickness of the FE model, physical properties, combination method and fatigue curve.
This comparison study consists in analyzing the 4 Test Cases (TC) described below:
• TC1: Study of the cylindrical-edge transition cone with its upper shell/shell type full-penetration butt weld.
• TC2: Study of the feedwater nozzle (FWN) with its full-penetration weld on the nozzle support ring.
• TC3: Study of the misalignment effect of neutral axes at shell/shell type full-penetration butt weld level.
• TC4: Study of the out-of-roundness effect at shell/shell type full-penetration butt weld level.
The welds considered in this study are full-penetration butt welds whose RCC-M quality is Level 1, whose welding procedure has been qualified, which are dressed, made flush with base metal by grinding and which have been fully (100%) inspected by NDE.
Quantifying Bolt Relaxation During High Temperature Operation
Authors: Brown Warren , Lim Tze-Yew 
Published: October 2017

This paper presents a summary of recent testing into bolt relaxation, which occurs at temperatures above 230°C (450°F). Bolt relaxation is problematic for pressure boundary bolted joints as it can lead to joint leakage in the longer term. In addition, it should be a major consideration at the design phase, with selection of the appropriate bolt material limited not by the creep or yield limit of the material, but by the point where bolt relaxation becomes significant.
Preliminary test results for different bolt materials at different temperatures are presented in this paper. The test results allow for some very high level observations regarding the acceptable design limits for different bolt and nut material combinations.
Development for Manufacture of Refining Reactors Made of 9Cr-1Mo-V Steel
Authors: Nakanishi Tomoaki , Terada Susumu , Yamada Masato , Ikeuchi Tadashi , Maeda Ikuo , Ikeda Tetsunao , Yamashita Ken , Miyamura Takeo , Nanba Shigenobu 
Published: October 2017

9Cr-1Mo-V steel, which was developed for application as a steam generator for fast breed reactors in the 1970s, has a higher strength at high temperatures and has been used for equipment and piping systems in the fossil power industries. ASME, Section VIII, Division 2 [1] gives 9Cr-1Mo-V steel a maximum design temperature of 649°C and an operating temperature of 500°C. And it has higher allowable stresses at 450°C or over, compared to 2¼Cr-1Mo-V steel. Therefore, if this material can be used, more economical pressure vessels operating at 454–500°C can be designed and manufactured.
In our previous study for base metal, a large forged shell ring of 9Cr-1Mo-V steel was manufactured and for base metal welding, cracking susceptibilities and weldability were investigated. For overlay, welding consumables with high resistance to sigma phase embrittlement were developed [2]. In this study, highly efficient welding consumables for tandem SAW designed for circumferential welding of heavy wall shells were developed and welding using the full-scaled shell ring was demonstrated, and then the mechanical properties of the weld metal were evaluated. Results indicated that, regardless of the weld thickness, a minimum of 8 hours postweld heat treatment (PWHT) at 745°C was required to meet hardness and toughness requirements for conventional reactors. The strength of the materials can comply with the Code requirements after 3 cycles of PWHT considering the PWHT in fabrication and after weld repair.
Furthermore, the following new Code Cases and Code revision were proposed and approved in order that pressure vessels can be designed in accordance with ASME, Section VIII, Division 2.
• New Code Case for Fatigue Evaluation
• New Code Case to apply SA-336-F91 in ASME Section VIII, Division 2
• Revision of Table 5A to add SA-336-F91
As a result, it has become possible to design and manufacture refining reactors to operate at 454–500°C.