bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Improved Method of Evaluating the Stress Intensity Factor for a Penetrating Circumferential Defect in a Self-Balancing Residual Stress Field in a Weld
Authors: Wei Liwu , Shi Jinhua , Buckland John 
Published: December 2016

It is required to determine the stress intensity factor (SIF) contributed from a through-wall residual stress distribution when assessing the structural integrity of a welded joint containing flaws. By decomposing the through-wall residual stress distribution into a membrane stress component (σm), bending stress component (σb) and self-balancing stress component (σsb), the total SIF from the through-wall residual stress distribution (Ktotal) comprises Km (due to σm), Kb (due to σb) and Ksb (due to σsb). Km and Kb can be relatively easy to determine as there are standard solutions available for common geometries and flaw types. However, it is not straightforward to calculate Ksb owing to the arbitrary distribution of the self-balancing stress component. In particular, no SIF solutions are available for a through-wall penetrating defect in a plate or a cylinder subjected to an arbitrary through-wall self-balancing stress distribution other than for three special distributions (cosine, triangular and square distributions). Neglecting the contribution of σsb to the Ktotal could significantly underestimate the crack driving force, thus leading to a non-conservative assessment of limiting defect size.
Therefore, the calculation of Ksb for a though-wall penetrating defect in a plate or a cylinder under an arbitrary stress distribution is of the primary concern in this work. Understandably, finite element analysis (FEA) can be used to calculate the Ksb in these situations, but it is costly to perform such analysis. In this work, a simple method is proposed for estimating Ksb due to the self-balancing component which has a different distribution from the cosine, triangular and square distributions. This method is an extension of the approach adopted by Annex Q, BS 7910:2013 in dealing with the calculations of Ksb resulted from the σsb profiles which are decomposed from the proposed upper bound through-wall welding residual stress profiles. Some typical through-wall welding residual stress distributions are investigated with the proposed method in estimation of the Ksb for a through-wall penetrating defect in a plate or a cylinder. Discussion and highlights are given in the aspects of the effects of welding residual stress profiles on SIFs, the implications for limiting defect sizes, and the likelihood of underestimating the Ksb when using the equation established in R6 Revision 4 with a cosine distribution for any other distributions.
Guidelines for MACA: The Optimization of Corrosion Allowance
Authors: Taagepera Jaan , Boyak Craig 
Published: December 2016

Excess capacity in the design of a pressure vessel can be recognized in a maximum allowable working pressure (MAWP). This pressure value is the result of the calculations for minimum thickness, in the new condition, being rounded up to the next nominal plate thickness and then working the formulae to establish limiting pressure based on the actual thickness used.
Another variable which may be optimized is the design temperature. Raising the design temperature tends to result in a reduced allowable stress. Once a plate thickness has been determined, the necessary allowable stress can be back calculated. From this allowable stress, an optimized design temperature can be determined.
Excess capacity can also be recognized in the form of increased corrosion allowance or MACA, the Maximum Allowable Corrosion Allowance. This is particularly helpful in the maintenance and inspection realms where life extension or unexpected thinning can force an unplanned shutdown of the unit, a fitness for service evaluation, or repair once the specified corrosion allowance is exhausted.
This paper presents a set of guidelines or rules for establishing a MACA based optimization for the design of new pressure vessels.
Sensitivity Analyses for a PWR SCC Case Using the Probabilistic Loss-of-Coolant-Accident (Pro-LOCA) Software
Authors: Young Bruce A. , Lee Sang-Min , Scott Paul M. 
Published: December 2016

As a means of demonstrating compliance with the United States Code of Federal Regulations 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary piping systems for nuclear power plants exhibit an extremely low probability of rupture, probabilistic fracture mechanics (PFM) software has become increasingly popular. One of these PFM codes for nuclear piping is Pro-LOCA which has been under development over the last decade. Currently, Pro-LOCA is being enhanced under an international cooperative program entitled PARTRIDGE-II (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE - Phase II).
This paper focuses on the use of a pre-defined set of base-case inputs along with prescribed variation in some of those inputs to determine a comparative set of sensitivity analyses results. The benchmarking case was a circumferential Primary Water Stress Corrosion Crack (PWSCC) in a typical PWR primary piping system. The effects of normal operating loads, temperature, leak detection, inspection frequency and quality, and mitigation strategies on the rupture probability were studied. The results of this study will be compared to the results of other PFM codes using the same base-case and variations in inputs. This study was conducted using Pro-LOCA version 4.1.9.
Inclusion of Warm Pre-Stress Concept in French RPV Structural Integrity Assessment
Authors: Moinereau Dominique , Ait-Bachir Malik , Chapuliot Stéphane , Marie Stéphane , Jacquemoud Clémentine , Tanguy Benoit 
Published: December 2016

Evaluation of the fracture resistance of nuclear reactor pressure vessel (RPV) regarding the risk of brittle fracture is a key point in the structural integrity assessment of the component (RPV). Such approach is codified in French RSE-M code, based on a very conservative methodology. With respect to long term operation, an improvement of the present methodology is necessary and in progress to reduce this conservatism.
One possible significant improvement is the inclusion of the warm pre-stress (WPS) concept in the assessment. After a short description of the WPS concept, the process engaged in France to allow inclusion of WPS in the integrity assessment is presented.
In a first step, experimental and numerical studies have been conducted in France by EDF, CEA and AREVA (also including international collaborations and projects) to demonstrate and validate the beneficial effect of WPS on the brittle fracture resistance of RPV steels. A large panel of experimental results and data is now available obtained on small, medium and large scale specimens on representative RPV steels (including highly irradiated RPV materials). These data have been included in a specific WPS experimental database.
Main experiments have been interpreted by refined computations, based on elastic plastic analyses and local approach to cleavage fracture.
In a second step, a new criterion (ACE criterion) has been proposed by French organizations (AREVA, CEA and EDF) for an easy simplified evaluation of warm pre-stress effect on the brittle fracture resistance of RPV steels. Accuracy and conservatism of the criterion is verified by comparison to experimental data results and numerical analyses.
Finally, implementation of the WPS effect in the French RSE-M code (for in service assessment) is in progress, based on the ACE criterion.
The present paper summarizes all these steps leading to codification of WPS in RSE-M code.
Evolution of Fatigue Post-Processing Methods in the EDF Open-Access FEA Code ASTER
Authors: Métais Thomas , Plessis Sarah , Chau The-Hiep , Le Roux Jean-Christophe 
Published: December 2016

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 that were not included in the original analyses (such as Environmental Assisted Fatigue [1]) 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 open-source 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 one owns fatigue criteria. It also offers the possibility to post-process fatigue according to the RCC-M rules (POST_RCCM operator).
Recent developments have enabled to update the POST_RCCM operator to make it bridge the gap with modern fatigue industrial codes as well as to integrate the EAF calculations per the methodology proposed in [2]. The work is currently ongoing within EDF R&D and will give birth to a stabilized and validated version of the code by end of 2016.
This paper presents the updates and the new possibilities of the POST_RCCM operator and gives an update of the work as of early 2016.
Modifications of the 2016 Edition of the RCC-M Code to Account for Environmentally Assisted Fatigue
Authors: Courtin Stéphan , Métais Thomas , Triay Manuela , Meister Eric , Marie Stéphane 
Published: December 2016

The French nuclear industry has to face nowadays a series of challenges it did not have to face a decade ago. The most significant one is to ensure a reliable and safe operation of Nuclear Power Plants (NPP) in a context of both an ageing reactor fleet and new builds. The new constructions need rules that integrate a strong operation feedback while the older NPPs need rules that will guarantee the life extension beyond 40 years of operation.
In this context, a new edition of the French RCC-M Code is planned for 2016. This new edition integrates the modifications made to the Code as a result of Requests for Modification (RM), which can be submitted by anyone and which help to continuously improve the quality and robustness of the Code.
Concerning fatigue analyses, the RCC-M Code steering committee has acknowledged end of 2014 the reception of two RM to modify the fatigue design curve for austenitic stainless steels and Nickel base alloys, as well as to integrate environmental effects in the fatigue evaluation for austenitic stainless steel components. The contents of these two RM were based on the proposals presented in Reference [1].
AFCEN required a technical review of these two RM and this task was performed by a working group composed by French and international experts. This process concluded to the approval of these two RM to be integrated to the 2016 edition of the RCC-M Code. This paper offers a presentation of these two new Rules in Probation Phase (RPP), this format being quite similar to Code Cases proposed by ASME Code.
Rationalizing Sampling of Pipe Material Properties for Probabilistic Pipe Fracture Analyses
Authors: Olson Richard , Young Bruce 
Published: December 2016

One element of probabilistic pipe fracture analyses is an assessment of the stability of cracks under applied load. If the load at some time step is greater than the cracked section can sustain, the state of the pipe is reported as ruptured. Another element of probabilistic pipe fracture analyses is the calculation of the crack opening displacement (COD) value which is used as an input to a leak rate calculation. Both of these analyses typically require pipe material properties that are sampled from a probabilistic distribution characterized by a mean value and some variance about the mean. Such properties include yield strength, ultimate strength, Ramberg-Osgood stress-strain curve coefficients, and fracture toughness curve parameters such as initiation toughness and tearing parameters.
From a procedural perspective, it is tempting to sample all of the relevant parameters independently. However, in some instances, the assumption of independence leads to nonsensical conditions such as yield being greater than ultimate; yield and ultimate being completely disconnected from the underlying Ramberg-Osgood description of the stress-strain curve; J-R toughness curves that are convex instead of concave; or initiation J values as low as zero.
This paper provides a suggested approach to sampling material properties for probabilistic pipe fracture analyses. The approach maintains consistency between yield, ultimate and the underlying Ramberg-Osgood stress-strain curve, and sets reasonable cutoff limits on the properties that are sampled. Equations for ensuring consistency among the related parameters are given along with justifications for the sampling limits, and an example of application of the proposed methodology.
Hydrostatic Testing of Pressure Vessels at Calculated Test Pressure Using ASME Sec.VIII Div.2
Authors: Nawandar Suresh K. , Kasliwal Rashi , Gopalakrishnan Shyam , Mathkar Ameya 
Published: December 2016

Pressure vessels designed for the internal pressure are required to be subjected to hydrostatic test after completion of their fabrication. Two methods are provided in the ASME Sec. VIII Div.2 to calculate the minimum test pressure. One method is based on the Maximum Allowable Working Pressure of the vessel or the MAWP and the other is based on the highest permissible pressure of the vessel at the test condition. This latter pressure is also known as the ‘calculated’ test pressure or the pressure based on the Maximum Allowable Pressure in new and cold condition or the MAP. In either case, the induced primary membrane stress, Pm, shall satisfy the below condition Pm≤0.95*Sy where, Sy is the yield strength of the material at the test temperature.
It is common to notice in many User’s Design Specifications (UDS), the requirement to test the vessels at the ‘calculated’ test pressure.
In the year 2007, major changes were made to ASME Sec.VIII Div.2. Some changes that had relevance to the hydrostatic testing were the change in the basis of the allowable stress at room temperature to the yield strength for most materials, increase in the factor on the test pressure basis to 1.43 and the corresponding increase in permissible limits on the induced primary membrane stress to 0.95*Sy.
It is noted in pressure vessels, built with cylindrical shells and(/or) with hemispherical dished heads with materials whose maximum allowable stresses at room temperature were dependent on the yield strength, that the membrane stress induced when subjected to ‘calculated’ test pressure exceeded the Code limit of 0.95*Sy. Increasing the thickness of the shell and(/or) head did not result in containing the stresses below 0.95*Sy as such an increase in thickness resulted in proportional increase in the MAP values and therefore, further increase of the test pressure.
The objective of this paper is to first derive the actual membrane stress induced in the vessel subjected to the ‘calculated’ test pressure and provide an engineering solution to the problem of induced stress exceeding the Code limit in order to achieve Code as well as the UDS compliance.
Influence of Restraint Stiffness and Preload on Distribution of Reaction Loads
Authors: Johnson Joshua , McKeel Charles , Leduc Daniel 
Published: December 2016

With recent advancements in the production of plastic materials the use of woven plastic webbings (Nylon, Polyester, etc) has increased due to decreased cost, increased load rating, greater ease of use over chains, and an increasingly proven history of use. However a common misconception is that chains and plastic webbing can be interchanged as long as the webbing has a sufficient load rating.
Packages in transport are commonly secured by an arrangement of rigid blocks (chock blocks) at the base and chains, cables, or straps to the top. Analysts are apt to evaluate restraint loads by distributing the prescribed shipping loads based on relatively simple free body diagrams, assuming rigid body mechanics. However, due to the lower stiffness of plastic webbing these rigid body assumptions are not always valid, and may lead to incorrect or misleading results.
Considerations for Baseline NDE of Pressure Vessels
Authors: Lu James , Antalffy Leslie P. , Millet Barry , Smythe Dennis 
Published: December 2016

ASME B&PV Code, Section VIII “Rules for Construction of Pressure Vessels” do not have requirements for baseline examination by vessel manufacturers. However many Owners require baseline data to establish as-built conditions of pressure vessels. Capturing baseline data at the manufacturing stage in a manner suitable for the Owner’s operations can preclude the need for post installation or preservice examination. Baseline NDE data can be easily referenced and compared to inservice inspection results to determine if any specific damage mechanisms manifest during operation and subsequently develop into damages to the vessel. Baseline NDE data can also provide guidance on inspection scheduling and damage monitoring. Therefore baseline examination in manufacturing phase is important to post-construction inspection and evaluation activities.
This paper discusses baseline NDE considerations based on pressure vessel service conditions and damage mechanisms. It presents a systematic approach to acquire baseline NDE data in Manufacturers’ shops, including Owner’s role, Manufacturer’s responsibilities and design considerations to allow NDE access to all welds. Topics include examination location reference systems and baseline NDE methods, techniques, and tools that facilitate comparison to inservice examination. This paper also provides an example on implementing baseline NDE of a typical pressure vessel.
All-Purpose Packing Cups for Hyper Compressor
Authors: Maggi Carmelo , Wojnar Jan , Tognarelli Leonardo 
Published: December 2016

Hyper compressors are designed for LDPE production, compressing ethylene up to 3500bar with only two stages of compression, in order to reach conditions for the polymerization. The high operating and fluctuating pressure strongly impact design and life of all cylinder components.
The packing cups are among the most stressed components of a hyper compressor cylinder. They are particularly subjected to very high pulsating pressures, thus fatigue and wear. Therefore, they are periodically replaced during maintenance and are critical for availability of the hyper compressor.
A typical hyper compressor packing assembly contains 5 to 6 disc shaped packing cups that contain the plunger sealing rings at the internal diameter. The packing cups are provided with lube oil ducts to lubricate the sealing elements. Typically these ducts extend axially through the assembly to the injection points. For that purpose each packing cup could have a different number of lube oil passages. Moreover, at the external diameter are located passages for packing cooling oil. For these reasons each of the packing cups is a unique part with different machining features.
In order to optimize the availability of spare parts and standardize the product, a new design of hyper compressor packing cups has been evaluated, called further “all-purpose packing cup”. The idea was to make the packing cups all equal to each other, and potentially to reduce manufacturing and warehousing costs.
This idea has been realized by introducing in a single all-purpose cup, multiple sectors angularly offset with each other. Each sector contains the oil ducts required for a given cup position in the assembly. By rotating the cup about the plunger axis by e.g. 90° or 180° the desired sector can be activated (put in fluid communication with adjacent lube oil ducts). In this way the “all-purpose packing cup” can be mounted in each of the 5 to 6 different positions in the packing assembly.
The all-purpose cup design has been analyzed by a well validated FEA approach on the high cycle fatigue and flaw propagation safety margins. The analysis was performed considering all multiple possible load combinations where, depending on the assembly configuration, different active lube oil holes (holes that deliver oil to the plunger) were pressurized while all remaining ducts were left unpressurized.
Hardness and Microstructural Evolution of a JRQ A533 Cl.1 Steel Submitted to Thermal Annealing
Authors: Medina Almazán A. Liliana , Ovando Ramírez Lizandra S. , Auger Thierry 
Published: December 2016

For operation of existing nuclear power plants (NPPs) beyond their design lifetime (up to 80 years), one of th7e main issues is the assessment of the performance of its structures, systems and components (SSC) during the period of extended operation. The reactor pressure vessel (RPV) is one of the components that could determine the lifetime of a NPP. Neutron irradiation at the temperature of operation of the nuclear reactors facilitates the chemical equilibrium of the alloying elements of the RPV steels, especially copper, while producing nanoscale precipitates (Cu, Mn-Ni-Si, and ∼M6C carbides) that leads to embrittlement [1–4]; by the other side, neutron irradiation also produces dislocation loops. Both, nanoscale precipitates and dislocation loops, produce loss of toughness and hardness increase. One of the proposals to manage the RPV time life is the thermal annealing, however there are still some concerns about its application, one of them is a possible detrimental effect by the development of new microstructural features that could lead to thermal embrittlement. Thus it is important to have data about the microstructural and hardness evolution of the RPV steels submitted to thermal annealing treatments.
The results of thermal treatments (450°C, 500°C and 550°C) performed in a A533 C1.1 (JRQ) steel during 0.5 to 1000 hours are presented in this work. JRQ steel has a bainitic microstructure, but well separated ferrite and bainite islands are observed at high magnification. The hardness evolution of such islands as a function of the thermal treatment is correlated with the number of precipitates present after thermal treatment as well as with the chemical evolution in these microconstituents. Thermal treatments of JRQ steel at 450, 500 and 550°C promoted the increase of hardness in both, bainite and ferrite. For the thermal treatment at 550°C, it is observed a maximum of the number of precipitates per μm2 in the treatments during 500 hours, which coincides with the depletion of the alloying elements in the bainite matrix and a decrease of Vickers microhardness (HV) in bainite. Cooper rich nanoprecipitates have been observed in the samples treated at 550°C during 500 and 1000 hours. The Cu content in the nanoprecipitates increase according the ageing time.