bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of Mechanical Behavior of 6XXX Aluminium Alloy due to the Precipitation State During a Thermo-Mechanical Process
Authors: Bardel Didier , Perez Michel , Nelias Daniel , Chaise Thibaut , Garnier Jerôme , Bourlier Florent 
Published: January 2014

The aim of this research is to link the microstructural state and the mechanical properties of an age hardening alloy during a fast heat treatment such as encountered during welding.
A coupled model between precipitation state and mechanical properties is used to predict the yield strength and hardening behavior that can be observed experimentally. The method permits the identification of the kinematic and isotropic contributions in the hardening model. The methodology is applied to a 6061-T6 aluminium alloy which is used in the Jules Horowitz reactor vessel.
The general idea of this methodology is to couple an efficient microstructural model to a mechanical one based on the dislocation theory and ad’hoc experiments. The theoretical background is based on the work of Kampmann and Wagner, known as the KWN model, to account for nucleation, growth/dissolution and coarsening of precipitates. This analysis requires transient thermo-mechanical experimental data. The efficiency of these models and their coupling are shown for a serie 6XXX aluminium alloy which contains β″ and β′ precipitates. Ultimately these models are coupled to a FEA model and allows to predict the distribution of precipitates within each element of the mesh, and subsequently its mechanical behavior.
Evaluation Procedure of Limit Load for Non-Aligned Multiple Flaws
Authors: Iwamatsu Fuminori , Miyazaki Katsumasa , Takazawa Hidekazu , Saito Koichi 
Published: January 2014

The fitness-for-service codes such as the ASME Boiler and Pressure Vessel Code Section XI require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw alignment rule. Worldwide, almost all such codes provide their own alignment rule, often with an unclear technical basis regarding the application of the rule to plastic collapse due to ductile fracture as prescribed by limit load analysis based on a net-section approach. Therefore, evaluation procedures to calculate collapse load for non-aligned multiple flaws have been proposed in various experimental and analytical studies. In these proposals, a collapse load for non-aligned multiple flaws is evaluated using the net-section stress approach in consideration of the ratio of a distance between flaws to a flaw length parameter. However, because each study proposes its own appropriate length and distance parameters, which are based on a few experimental results limited to that study, the applicability of the proposed parameters to evaluation of collapse load for arbitrary flaw sizes and locations is unclear.
In this study, we performed fracture test result on a flat plate with two through-wall flaws in order to determine appropriate parameters for the evaluation procedure of the collapse load for non-aligned multiple flaws. Appropriate parameters were determined by correlation coefficients obtained by comparison of maximum loads of fracture tests and collapse loads of evaluation with various parameters. We found that the appropriate parameters to apply the alignment rule with equations to evaluate collapse load for non-aligned flaws were the ratio of the vertical or direct distance between flaws to the maximum or average flaw length.
Methodology for Numerical Welding Simulation Validation: The Dissimilar Metal Weld Case
Authors: Gilles Ph. , Courtin S. , Vincent R. , Yescas M. , Gommez F. 
Published: January 2014

Welding processes induce residual stresses and distortion in the welded joint and the connected components. For manufacturing purpose distortion is the main issue and up to now the problem is handled by post weld corrective actions. Welding residual stress fields are not considered at the design stage in French codes and standards. However, it is well known that residual stresses are likely to increase the risks of fatigue or corrosion and may cause failure in brittle materials. Ferritic parts of large components are post-weld heat treated; allowing disregarding the influence of residuals stresses thanks to their relief. Preventive measures, including mitigation by fine polishing are undertaken in corrosion sensitive zones. The influence of residual stresses on fatigue is more complex to analyze: in low cycle fatigue, residual stresses should be relieved or redistributed after few cycles with plastic straining, and for high cycle fatigue, residual stress effects are accounted for through a mean stress offsett.
When considered, residual stress fields are often represented in a very crude manner by a membrane distribution of the most influent stress component through the thickness of the structure. In a less rough way, several codes or fitness-for-purpose guidelines (API [1], British standards [2]) propose residual stress profiles relative to several weld configurations. Nevertheless for a given case, the given profiles may differ significantly for several reasons: the degree of conservatism, the number of covered cases, the embedded margins accounting for uncertainties.
Some ill-posed benchmark problems have shown that numerical simulation of residual stresses may deliver very scattered results. AREVA has therefore developed a methodology to validate welding simulations. The scope is limited to fusion welding. The simulations are based on a Thermo-Metallurgical Mechanical model in which the welding energy is represented by an equivalent heat source.
This paper presents the actual state of development of this methodology which will be illustrated through 4 examples of residual fields in Dissimilar Metal Welds. Residual stress measurements have been performed for each of the four mock-ups by different techniques. Based on this important experimental and numerical campaign some actions of improvement of the validation methodology are finally listed.
Environmental Fatigue Factors (NUREG/CR-6909) and Strain Controlled Data for Stabilized Austenitic Stainless Steel
Authors: Solin Jussi , Reese Sven , Karabaki H. Ertugrul , Mayinger Wolfgang 
Published: January 2014

Experimental research on fatigue performance of niobium stabilized stainless steel (1.4550, X6CrNiNb1810 mod) relevant for German NPP primary piping has previously demonstrated good long life performance.
Slow rate fatigue tests in 325 °C PWR water are first time presented and discussed in this paper. Good fatigue performance was measured also in hot water. Our experiments give consistently about doubled lives or 50% smaller Fen factors in compared to predictions by NUREG 6909.
Transferability of the laboratory data, reference and design curves together with the proposed Fen evaluation procedure to component evaluation will be discussed.
Predictions of Fracture Toughness for Weld Material When Adopting a Novel Particle Failure Criterion and a Measured Experimental Particle Distribution
Authors: James Peter , Ford Mike , Jivkov Andrey P. 
Published: January 2014

It is important for safety case justification of the continued use of nuclear power plant that any changes in the ferritic RPV steels’ fracture toughness with temperature, irradiation and geometry can be accounted for, particularly with regards to plant life extension. It has been demonstrated that local approach methods have the potential to provide such estimates by assessing the likelihood of cleavage rupture.
Here a micro-structurally informed, post-processing, local approach methodology with a new rupture criterion is presented. This has been applied to a base and weld material pair, made available under the EU FP7 PERFORM 60 Programme. This material has been selected as tensile and fracture data are available along with results of recently performed analyses to characterise and quantify the size distribution of fracture initiators for the weld material (predominantly found to be alumino-silicates) which is used as an input to the model.
A series of finite element analyses have been performed for two-dimensional three-point bend specimens over a range of temperatures, constraint and irradiation states. Application of the local approach model to these results have then been favourably compared to the experimentally determined toughness. This has been achieved for a range of conditions when using the experimentally determined initiator particle distribution and maintaining the same calibration terms throughout for each material.
Parametric Study of the Coupling Power Factor for the Statistical Energy Analysis of Piping Acoustic Vibration
Authors: Dweib Ahmed H. 
Published: January 2014

Energy-based finite element model is utilized for the evaluation of the Statistical Energy Analysis (SEA) coupling factor and the dependence of the coupling factor on the different system parameters is studied.
Previous research has shown that the coupling factor is largely dependent on the modal densities of the fluid and pipe subsystems, which depend on the pipe dimensional parameters. The coupling factor depends also on the spectrum of the acoustic power generated, which in turn depends on the mass flow rate, the pressure reduction ratio and the characteristics of the pressure-reducing device.
This study is concerned with the piping system parameters, downstream of the pressure-reducing valve. The system parameters selected for consideration are the pipe diameter to thickness ratio D/T and the pipe length to diameter ratio L/D. The study presents the effect of the variation in these two dimensionless parameters on the coupling factor.
The results of the analysis can be used directly in the formulation of SEA power flow equations for large piping systems with multiple sources of acoustic energy as part of the fatigue life evaluation in critical services.
Fatigue of Stainless Steel Components: Toward Codified Rules Improvements
Authors: Faidy Claude 
Published: January 2014

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of French Nuclear Codes: RCC-M, RSE-M and RCC-MRx.
This paper will present comments and proposals for development of these rules associated to Gaps and Needs in order to finalize and justify the AFCEN Codes new rules.
Recently 3 new international R&D results confirm possible un-conservative fatigue material data:
- High cycle fatigue in air for stainless steel,
- Environmental effects on fatigue S-N curve for all materials, and in particular stainless steels,
- Fatigue Crack Growth law under PWR environment for stainless steel.
In front of these new results, AFCEN is working on a 1st set of rules based on existing knowledge:
- Air fatigue curve: mean and design
- PWR Environmental effects with detrimental correction factors
A periodic up-dating of AFCEN proposed rules will be done using French and International R&D programs with a particular attention on harmonization with other Code rules developed in USA, Japan and Germany, in particular.
Acoustic Resonance Experiments in a Reservoir-Pipeline-Orifice System
Authors: Tijsseling Arris S. , Hou Qingzhi , Svingen Bjørnar , Bergant Anton 
Published: January 2014

Acoustic resonance in liquid-filled pipe systems is an undesirable phenomenon that cannot always be prevented. It causes noise, vibration, fatigue, instability, and it may lead to damage of hydraulic machinery and pipe supports. If possible, resonance should be anticipated in the design process and be part of the hydraulic-transients analysis.
This paper describes acoustic resonance tests carried out at Deltares, Delft, The Netherlands, within the framework of the European Hydralab III programme. The test system is a 49 m long pipeline of 206 mm diameter that is discharging water from a 24 m high reservoir through a 240 mm2 orifice to the open atmosphere. The outflow is partly interrupted by a rotating disc which generates flow disturbances at a fixed frequency in the range 1.5 Hz to 100 Hz. In previous studies [1, 2] a similar system was analysed theoretically. Herein experimental data are presented and interpreted. Steady oscillatory behaviour is inferred from pressures measured at four different positions along the pipeline. Heavy pipe vibration during resonance was observed (visually and audibly) and recorded by a displacement transducer.
Fluid Transient Analysis for Safety Valve Vent Stack Using S-RELAP5 Code
Authors: Hsieh Jen-Sheng , Brocheny Pascal 
Published: January 2014

This paper is to present a fluid transient analysis for the safety valve vent stack which is an open discharge system using the AREVA in-house thermal hydraulic code S-RELAP5. S-RELAP5 was developed by AREVA to perform thermal hydraulic analyses. It is a RELAP5-based thermal-hydraulic system code which incorporates features of the NRC RELAP5/MOD2 and RELAP5/MOD3 as well as other improvements. S-RELAP5 deals with one-dimensional two-phase, two-fluid, non-equilibrium hydrodynamic model with a non-condensable gas field.
ASME B31.1-2010 Non-mandatory Appendix II provides formulas for hand calculation of blow down forces at elbow exit and vent pipe. In general, this approach generates only steady state forces. To more accurately calculate forcing functions, S-RELAP5 is a good tool to achieve this task. The purpose of this S-RELAP5 application is to show that the usage of BRANCH and other components in the S-RELAP5 code can effectively simulate the safety valve open system discharge. This is a first-of-a-kind application of the code. Furthermore, this method provides an alternative to the ASME Appendix II hand calculation. In this paper a sample problem from ASME Appendix II is utilized to generate the time history forcing functions to demonstrate the versatility of S-RELAP5. These forcing functions can then be used for the subsequent piping dynamic analysis.
On the Hot Blow-Out Characterization of PTFE-Based Gasket Materials
Authors: Bouzid Abdel-Hakim , Benabdallah Samir 
Published: January 2014

The objective of this work is to improve the HOt Blow-out Test procedure (HOBT) to determine the maximum operating temperature of Teflon-based gaskets. The study aims to analyze the relaxation of these gaskets due to creep at high temperature. The determination of their safe operating temperature limit requires a good knowledge of its capacity to resist creep-relaxation due to temperature exposure in the short and long term. This work investigates the effects cumulative gasket deformation due to thermal cycling, gasket stress level and holding time on the relaxation of these materials. In parallel, an experimental fixture has been developed to measure the thermal expansion coefficient and the short term creep resistance of such materials.
Based on a previous work, the introduction of a fixed number of cycles of heating and cooling in the HOBT test procedure has shown that ratcheting damage may have some impact on reduction of the gasket stress and the temperature limit of PTFE. The effect of holding temperature for a short period of time will also be investigated. The modified HOBT rig allows measurement of the gasket deflection during the test in order to accurately quantify the cumulative permanent deformation. Several types of PTFE-based gaskets will be tested in order to cover a wide range of gaskets to justify the generalization of the modified procedure.
Evaluation on Constraint Effect of Reactor Pressure Vessel Under Pressurized Thermal Shock
Authors: Ogawa Naoki , Yoshimoto Kentaro , Hirota Takatoshi , Sakaguchi Shohei , Oumaya Toru 
Published: January 2014

In recent years, the integrity of reactor pressure vessel (RPV) under pressurized thermal shock (PTS) accident has become controversial issue since the larger shift of RTNDT in some higher fluence surveillance data raised a concern on RPV integrity. Under PTS condition, the combination of thermal stress due to a temperature gradient and mechanical stress due to internal pressure causes considerable tensile stress inside the wall of RPV. Currently, RPV integrity is assessed by comparing stress intensity factor on a crack tip under PTS condition and a reference toughness curve based on the fracture toughness data of irradiated compact specimens. Since PTS loading is large enough to cause plastic deformation, a crack tip behavior on the inner surface of RPV can be explained by elastic-plastic fracture mechanics using the J-integral.
In this study, 3D elastic plastic finite element analyses were performed to assess the crack tip behavior on surface of a RPV under Loss of coolant Accident, which causes one of the most severe PTS condition. In order to quantify the constraint effect on a surface crack, J-Q approach was applied. The constraint effect of a surface crack was compared with a compact specimen and its influence on the fracture toughness was assessed.
As a result, the difference of constraint effect was clearly obtained. And it is recommended to consider constraint effects in the evaluation of structural integrity of RPV under PTS.
Development of Pipe Wall Thinning Evaluation Method and Prediction Tool
Authors: Yoneda Kimitoshi , Morita Ryo , Fujiwara Kazutoshi , Inada Fumio 
Published: January 2014

Flow accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI) are the main pipe wall thinning phenomena in piping system of power plants in Japan. Authors have promoted the development of prediction method to evaluate local thinning trend by FAC/LDI. To apply the method to pipe wall thinning management in power plants, it is required to be transformed into practical tools for easy usage. In Japan, discussion is being made to considerate the introduction of prediction tools into wall thinning management based on wall thickness measurement at present.
Authors have simplified their FAC/LDI models to predict wall thinning trend one-dimensionally along piping layout, and applied to actual thinning data of power plants. With PWR’s FAC data and BWR’s LDI data, maximum thinning rate for each pipe elements were roughly predictable with considerable accuracy. Especially for high thinning rate data, which is important in plant management, the model was able to evaluate within the factor of 2. By installing this model, prediction software “FALSET” was developed, equipped with practical functions for the management. With the further verification and improvement of each function, there are prospects for this software to be utilized as a management tool in power plants.
Impact of Thermal Hazards on Process Buildings Using CFD Techniques
Authors: Raibagkar Anay , Edel Matthew 
Published: January 2014

The impact of thermal hazards on process buildings is an important component of site hazard evaluations. API RP-752 recommends that process facilities analyze thermal hazards and assess their impact to onsite buildings and their occupants. Thermal loads resulting from fires in process units and equipment can have a significant impact on buildings, especially if the building is close to the fire source. Some buildings may be designed for blast and toxic protection, which allows the buildings to be located near process units and equipment, but possibly exposed to thermal hazards from a potential fire.
Screening-level thermal models typically used in process safety applications cannot account for detailed building geometries and how they may affect thermal impact from fire on building occupants. A more robust approach using the Fire Dynamics Simulator Computational Fluid Dynamics (CFD) code has been used in this study to assess the impact of thermal hazards on a target building located downstream of a jet fire. Temperature and radiation increases inside the building due to the thermal loads at the building exterior surface were calculated. The results indicate that buildings can provide protection to occupants depending on exposure time and building/insulation design. The results clearly show that a detailed CFD model can be effectively used to assess the thermal impact of incident radiation on buildings and to assist designers with determining requirements for the building envelope to provide protection to building occupants.
The Application of Combined Buckling Mode Imperfections on Shell Structures
Authors: Laird Sean , Frith Robert 
Published: January 2014

This paper presents the results of a numerical investigation for applying a combination of buckling mode shapes as an initial imperfection to shell geometries under external pressure. The effect that imposed imperfections had on the critical buckling pressure was found to be dependent upon both the shell geometry and the characteristics of the imposed imperfection. Imperfections were generated via linear combinations of the linear elastic buckling mode shapes, with the fundamental mode having the greatest influence. For a number of tests, inclusion of higher order modes into the initial imperfection caused an increase in the critical buckling pressure. This behaviour was observed for both elastic and plastic material models.
For the purpose of limiting the extent of the analysis, the magnitudes of imposed imperfections were maintained within the industry required fabrication tolerances and in particular, acceptable out-of-roundness. The purpose of this paper is to present the methodology and results from this imperfection investigation. Additional testing and discussion may allow a design methodology to be developed that addresses the application of initial imperfections in shells under external pressure.
Fully Automated SCC and Fatigue Crack Propagation Analyses on Deep Semi-Elliptical Flaws
Authors: Sugawara Kota , Koya Hirohito , Okada Hiroshi , Li Yinsheng , Osakabe Kazuya , Kawai Hiroshi 
Published: January 2014

In this paper, some results of crack propagation analyses of deep initially semi-elliptical flaws under assumed residual stress fields are presented. The crack propagation analyses were performed by using a software system that has been developed by Okada and his colleagues. It is based on a conventional finite element program but uses the quadratic tetrahedral finite elements to model the structure with the crack. The finite element model with the crack can be generated in an automated manner. The stress-intensity factor computations are performed by using the virtual crack closure-integral method (VCCM) for the quadratic tetrahedral finite element which was also proposed by Okada and his colleagues. The automatic meshing scheme for the crack propagation analyses has also been developed by the authors.
By the authors’ previous publication, it was shown that the stress intensity factor of deep semi-elliptical surface flaw under assumed residual stress field reached its maximum value at the mid-depth of the crack. Hence, in present study, in order to investigate the feature of the crack propagation of deep surface cracks, we are conducting crack propagation analyses that can predict the crack extension from each point along the crack front for an arbitrary shaped surface flaw. It can also account for material anisotropy in the crack propagation behavior. Then, the SCC crack propagation analyses for a deep semi-elliptical surface flaw in a plate under assumed residual stress fields are being conducted.
The results of the crack propagation analyses suggest that the shapes of the crack after the SCC crack propagation may not be exact semi-elliptic in its shape. In this paper, the analytical procedures and some results are presented. The same analytical procedures can be adopted to perform fatigue crack propagation analyses.