bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Welding-Induced Plasticity in Austenitic Steel Weldments
Authors: Muránsky Ondrej , Hamelin Cory J. , Tran Minh , Braham Chedly , Smith Michael C. 
Published: December 2016

Historically, weld residual stresses (WRS) have been used as the primary validation parameter for welding simulations, largely due to the importance of predicting WRS for structural integrity assessments. However, the extent of welding-induced plasticity (WIP) caused by the plastic flow of near-weld material is also an important characteristic affecting weld performance. WIP has been shown to negatively affect weld integrity, since the associated accumulation of defects (dislocations) in the material will accelerate the nucleation of macro-scale defects that lead to component failure. Information on WIP is particularly important when attempting to validate the constitutive models used for weld simulation, and can assist with the proper definition of material yield strength.
The present study highlights two approaches to assess WIP in welded structures. The first approach involves the development of a micro-hardness correlation to infer the level of WIP across the near-weld region. The second approach uses electron backscatter diffraction (EBSD) data to directly calculate the average crystal misorientation in the region of interest, which is proportional to the amount of geometrically necessary dislocations present. The dissimilar approach to determine WIP between the two characterization methods allows a degree of confidence in the results obtained, therefore providing an accurate dataset for weld model validation. To exemplify this point, the two approaches are used to characterize WIP across a three-pass slot weld in AISI 316 steel (NeT TG4 specimen), and the results are compared to weld modelling predictions.
Predicting an Optimal Inter-Pass Temperature to Mitigate Residual Stress and Distortion in Ferritic Steel Weldments
Authors: Sun Yongle , Hamelin Cory J. , Smith Michael C. , Edwards Lyndon 
Published: December 2016

The residual stress and distortion found in multi-pass welds are often influenced by the prescribed inter-pass temperature. In ferritic steel components, the severity of this influence is affected by solid-state phase transformation (SSPT) kinetics, which will depend on the overall heat input and cooling conditions. The development of an optimised welding procedure to mitigate weld residual stress (WRS) and distortion in these components can therefore necessitate an extensive test matrix, varying both preheat and inter-pass temperatures as well as the transient weld heat input.
Computational parametric studies provide an opportunity to dramatically reduce the cost and time associated with the development of welding procedure specifications. Welding procedures can be simulated using validated modelling approaches to examine parametric sensitivity and gain insights into optimal conditions for a given welding task. In the present study, a three-pass tungsten inert gas (TIG) groove weld in SA508 Gr.3 Cl.1 ferritic steel is numerically investigated using the ABAQUS finite element code with a user defined subroutine to incorporate the effect of SSPT kinetics. Parametric sensitivity is assessed whereby a representative heat input is applied to simulate weld deposition for each pass, and the inter-pass temperature is varied to examine its effect on WRS and distortion in the weldment. The implications of the overall heat input on cross-weld microstructure are also presented using this approach.
FEM Stress Analysis of Long-Term Sealing Performance for Bolted Pipe Flange Connections With PTFE Blended Gaskets Under Elevated Temperature
Authors: Sato Koji , Sawa Toshiyuki , Kobayashi Takashi 
Published: December 2016

Mechanical characteristics of bolted pipe flange connections with PTFE blended gaskets under elevated temperature are examined using FEM calculations and experiments. Firstly, the basic characteristics of the PTFE blended gaskets are measured such as the stress-strain curves, the thermal expansion coefficient and the relationship between the contact gasket stress and the leak rate at room temperature and some high temperature. The leak rates of the gasket at the averaged gasket stress are measured using the rigid platen. In addition, the creep characteristics of the gaskets are measured using the rigid platen under elevated temperature. Then, using the gasket basic characteristics measured above, the FEM calculations are carried out to analyze the mechanical characteristics such as 1) changes in axial bolt forces (the load factor), 2) the contact gasket stress distributions, 3) flange hub stress. Then, the sealing performance of bolted pipe flange connections is predicted using the contact gasket stress distributions obtained from the FEM calculations and the relationship between the gasket stress and the leak rate.
In the FEM calculations, the value of the load factor due to the internal pressure is obtained as φg = 0.12. Furthermore, the sealing performance in long-term is estimated using the change in the axial bolt forces (creep) and the contact gasket stress distributions under heat cycle and internal pressure. For verification of the FEM calculations, the experiments were performed to measure the load factor (change in axial bolt forces), the leak rate of the connection at each temperature, and the hub stress. The FEM results are in a fairly good agreement with the measured results. In addition, the reduction in the contact gasket stress due to the heat cycle, internal pressure and the creep is demonstrated and the effect of the nominal diameter of pipe flanges on the sealing performance is shown.
Experimental and Numerical Evaluation of Fracture Toughness on Electron Beam Welded Joint in Al6061-T6
Authors: Rekik W. , Ancelet O. , Gardin C. , Hamon F. 
Published: December 2016

In order to ensure the integrity of structures, failure assessment is required. In this context, the fracture behavior of an electron beam (EB) welded joint on thick plate of aluminum alloy 6061-T6 used for structural components of experimental nuclear reactors was investigated. In the particular case of welded structures, the tearing resistance is strongly dependent on the mismatch of the welded joint and the local behavior of each metallurgical zone.
For a reliable analysis, the tensile mechanical behavior of each position of the welded joint was precisely determined by the use of a new measurement prototype. The toughness behavior under different configurations was then evaluated on CT specimens. From these experimental results a mechanical behavior contrast was highlighted. In fact, the fusion zone presents the lowest yield stress and a gradient is observed in the heat affected zone until the material behavior reaches of the base metal yield stress. On the contrary, the toughness of the welded zone is the highest and decreases strongly in the heat affected zone according to an exponential function until the base metal toughness is reached.
Dynamic Effects on Fracture Toughness for Ferritic Steel in the Ductile-to-Brittle Transition
Authors: Jacquemoud C. , Delvallée-Nunio I. , Balestreri F. 
Published: December 2016

Dynamic loading effects on fracture toughness of ferritic steel have been evaluated in the ductile-to-brittle transition, considering loading rates representative of object drops. To verify that the design fracture toughness curve, initially defined from static tests, remains conservative for the integrity assessment of object submitted at low temperature to a dynamic impact due to a drop, experiments on 16MND5 ferritic steel have been performed.
A three-point bending set-up and a thermal chamber have been designed in order to perform dynamic fracture tests on large Single Edge-notched Bending SE(B) specimens, at very low temperature. Considering that the reference temperature of the material is −122°C (defined from quasi-static tests), dynamic drop tests have been performed at −120°C, −80°C and 0°C in order to cover the ductile-to-brittle transition of the material. A shift of +80°C of the reference temperature has been observed with the increase in the stress intensity rate, from less than 1 MPa.m0.5/s in quasi-static tests to values up to 105 MPa.m0.5/s for the dynamic SE(B) tests.
Numerical simulations of the tests, compared to classical static analysis, have confirmed that the effects of inertia and viscosity on fracture toughness are negligible at these temperatures (<0°C). Equivalent static analysis appears sufficient to study such dynamic tests.
Environmental Fatigue Evaluation Considering Transient Stress History for Piping
Authors: Kim Youn-Jung , Kang Sun-Yeh , Park Byung-Jong , Kim Gee-Seok , Kim Hyun-Min 
Published: December 2016

The environmental fatigue evaluation for piping is performed based on conservative formulas and environmental correction factors (Fen) calculation because of the difficulty of finding transient strain history and to reduce the cost of the analysis. Therefore, more sophisticated analyses using a finite element model of piping would be required to meet Code requirement (cumulative fatigue usage factor including the environmental effects, CUFen < 1).
The environmental fatigue evaluation was performed considering the transient stress history for pressurizer surge and spray piping. The stress histories due to the thermal moment and thermal gradient through the wall thickness were evaluated using a three-dimensional piping system model. The strain rate for Fen calculation was calculated in accordance with draft Code Case 10-293 and 14-1177.
For the purpose of comparison, environmental fatigue usage factors and Fen are calculated based on the ASME Code NB-3600 rules. The differences of Fen, CUF, and CUFen are reviewed between the methods using NB-3200 rule and NB-3600 rule.
Finally, this paper shows that environmental fatigue evaluation considering transient history is an effective method in lowering the environmental CUF value of the piping.
Nuclear In-Service Inspection Codes ASME Section XI and RSE-M Codes Comparisons
Authors: Faidy Claude 
Published: December 2016

This paper will compare two major In-Service Inspection Nuclear Codes: the Boiler and Pressure Vessel Code Section XI developed by ASME on the one hand and French RSE-M developed by AFCEN on the other hand. These two Codes cover totally or partially:
- General Introduction
- In-service and pre-service inspection program
- In-service inspection techniques and qualifications
- Surveillance in Operation
- Flaw evaluation
- Repair-Replacement
- Quality Assurance and Documentation
- Appendices and Code Cases
A general presentation of the two Codes will be developed and followed by a general comparison.
To conclude, the paper will consider two particular examples for detailed comparison:
- K stress intensity factor handbooks comparison for circumferential flaws in cylinder: ASME Code Appendix A3000 and RSE-M Code Appendix 5-4, last published editions
- analysis of longitudinal crack in steam generator tubes
A Probabilistic Approach to Predicting Pipework Failures in High Temperature Environments
Authors: Cannell Benjamin , Lloyd David , ElAgha Feras , Knowles David 
Published: December 2016

Structural integrity assessments are traditionally undertaken using lower bound deterministic approaches whereby the worst combination of loads, operating conditions and material properties are assumed. This can lead to excessively conservative predictions which give pessimistic outlooks for plant life. A more representative approach which allows for consideration of acceptable levels of reliability of a component / system can be achieved through use of probabilistic assessment methods. A probabilistic approach aims to capture the uncertainties in the plant conditions, system loads and material properties (including degradation in-service).
This paper outlines a focused approach to undertaking a ‘Monte-Carlo’ probabilistic assessment of thin stainless steel pipework in high temperature environments considering failure due to creep rupture and plastic collapse whereby known or estimated statistical distributions of the assessment inputs are randomly sampled. The method is undertaken in Excel using VBA and it is developed to provide a transparent, quick and easy approach for a probabilistic assessment.
Tensile Testing and Analysis of Notched Low Alloy Steel Specimens
Authors: Wormsen Anders , Kirkemo Finn , Hagner Torulf 
Published: December 2016

Notched axisymmetric specimens of two high strength low alloy steels used frequently in the subsea industry have been tensile tested to failure in air and in a 3.5% NaCl artificial seawater solution with cathodic protection (CP). The aim of the testing was to provide input to an initial assessment of elastic-plastic static load-capacity analysis of low alloy steels with material and quality control requirements according to ISO 13628-7 (ISO-7). The tensile testing in seawater with CP was performed in order to investigate whether hydrogen as formed by the CP system may have an effect on the ductility and strength that needs to be taken into account in the static load-capacity analysis and hence in design.
Local and global static load-capacity criteria from ASME VIII Div. 3 (Div.3), ISO-7, NORSOK U-001 (U-001) and API 6X (6X) have been considered for the notched specimens. Recommendations regarding elastic-plastic static load-capacity analysis of subsea equipment are given. The specimens tested in seawater with CP were found to have a reduced ductility and strength compared to the corresponding specimens tested in air. Further testing in seawater with CP is recommended before it can be concluded whether the environmental effect of the hydrogen needs to be included in the static load-capacity analysis of high strength low alloy steels.
Some Practical Aspects of Class 1E Actuator Qualification on Comparing Test Levels and Design Basis Event Loading
Authors: Farrell Ronald S. 
Published: December 2016

All power operated valve actuators that perform a critical safety function in nuclear power plants must be backed by testing to demonstrate they are capable of reliably performing their safety related function. Such actuators are denoted Class 1E and must be qualified according to IEEE-382 “Standard for Qualification of Actuators for Power-Operated Valve Assemblies with Safety-Related Functions for Nuclear Power Plants” which states that a Class 1E Actuator is essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal, or otherwise essential in preventing significant release of radioactive material to the environment. Qualification of these actuators involves type testing where one or several test specimens that adequately represent and span the entire represented fleet undergo rigorous testing commensurate with expected service. Then, for each application, an evaluation is performed to show how specific loading is enveloped with margin by the testing. IEEE-382 is a specific application of the more general IEEE-323 “Standard for Qualifying Class 1E Equipment for Nuclear Power Generation Stations” containing general requirements applicable to all Class 1E equipment; then, the rules of IEEE-323 add useful clarification to those of IEEE-382.
This paper describes actual type testing of a gas-hydraulic actuator where planned levels were not reached at all times for every test due to test apparatus limitations and shows that the resulting intermittently off target test levels need not envelope loading for all times compared to specific applications. IEEE-382 requires an evaluation showing that test conditions meet specific service conditions plus acceptable margin; however, demonstrating that margin also exists in the range of achieved test levels demonstrates that specified service conditions are adequately included even though specified levels are not enveloped at every time or frequency due to the test apparatus limit anomalies. One practical example is given that logically compares the achieved seismic test levels with a sample required load case for a line mounted valve assembly. Another example compares results from a simulated design basis environmental accident event involving high temperature steam with a sample expected event curve. Rather than compare test and application level by level and curve by curve, the physical effect of the loading, such as stress level, is compared between the test specimen and the application. It is concluded that test levels need not envelope requirements at every point if it can be shown and documented that important physical aspects including stress level, deflection magnitude, absorbed vibration cycles, and energy involvement are enveloped with the required margin.
Computational Simulation for Evaluation of Food Softening Treatment Vessel Using Underwater Shockwave
Authors: Higa Yoshikazu , Shimojima Ken , Iyama Hirofumi , Higa Osamu , Takemoto Ayumi , Itoh Shigeru , Yasuda Atsushi 
Published: December 2016

To clarify the characteristics of the shock wave propagation in food and treatment food vessel, the finite element models of the food, surrounding water, source of high-pressure and its vessel were developed using commercial finite element software HyperWorks (Altair®) RADIOSS®.
By conducting a series of numerical simulations, the pressure distribution in the foods has been observed. From a comparison between computational results and experimental ones corresponding to food hardness using creep meter, it is also revealed that the food softening treatment is highly dependent on the incident shockwave and the reflected one.
Reduction of Fugitive Emissions From Bolted Flanged Connections by Using PTFE Blended Gasket
Authors: Kobayashi Takashi , Sato Koji , Muramatsu Akira , Sawa Toshiyuki 
Published: December 2016

Gasket is the key element which determines the tightness of bolted flanged connection. PTFE blended gaskets which have recently been developed and come onto the market have a superior sealing performance as well as the chemical and temperature resistances and can contribute to reduce fugitive emissions. This paper deals with the sealing behaviors of the PTFE blended gasket and the tightness of a bolted flanged connection in which the gasket is used. The gasket is mainly composed of PTFE and graphite and has a high tightness and heat resistance up to 300 degree C. The creep characteristic is improved by the graphite filler.
In this paper, the estimation method of the tightness of bolted flanged connections based on the sealing behavior of gasket is demonstrated. The estimated results are validated by experiments using a flange connection.
It is shown that the leak rate below the tightness class 4 defined in the Room Temperature Tightness Test (ROTT, Pressure Vessel Research Council) can be obtained using the PTFE blended gasket.
Damage Characterization of Heat Resistant Steels After Long Service in Reforming Plants
Authors: Alvino Antonello , Antonini Alessandra , Lega Daniela , Mennuti Canio , Tonti Andrea 
Published: December 2016

ASTM A 297 grade HP steels are widely employed for radiant tubes in reforming furnaces: this class of heat resistant alloys shows high creep and corrosion resistance, ensuring good performances in extreme pressure and temperature conditions. The typical microstructure of such materials is an austenitic matrix surrounded by a network of interdendritic carbides, which contain chromium and other carbide forming elements, namely Nb, Ti, W, Zr and Y.
During long service life, these high strength materials may suffer aging or even severe damage, especially when process conditions allow coke deposition, or maintenance procedures are not carried properly.
Service aging can be summarized, for HP steels, in terms of microstructure degradation: coalescence and coarsening of interdendritic precipitates, precipitation of secondary carbides in the austenite matrix and transformation of niobium-rich carbides in the G-phase silicide are the typical phenomena occurring on the microstructure of these alloys during service. Carburization can also occur in radiant tubes, since their inner wall side is exposed to hydrocarbon-rich process fluids: carbon diffuses into the metal matrix, causing massive precipitation of chromium-rich carbides. The alloy corrosion resistance is then reduced, resulting in surface attack, cracks development and a general wastage of the material. Furthermore, the high temperatures, which tubes are exposed to, can also induce creep, especially if a local tube overheating occurs: cavities and microcracks, mainly localized at precipitates, are the typical evidences of creep damage on HP steels.
The present work is aimed on the damage characterization of several radiant tubes in HP alloys, after long term service aging in reforming plants. We employed optical and electron microscopy, EDX elements mapping and mechanical tests, in order to characterize and evaluate the various damages affecting the alloys.
Microstructure evolution has been detected in all the analyzed tubes, but we found that such a phenomenon was strictly influenced by the chemical composition of each alloy, so that in presence of small amounts of titanium and tungsten, the chemical evolution of the secondary phases was appreciably contained. Creep also was observed in all the investigated tubes and its extent was found to be related to both alloy composition and process conditions. These latter have assumed to be the main driving factor for carburization, since we observed that slight differences in temperature, pressure, chemical composition of the process fluid and tube maintenance dramatically conditioned the performances of each tube. Massive precipitation and material degradation, in fact, were found in some cases, but, on the other side, no appreciable evidence of carburization damage was observed on other cases.
PWR Effect on Crack Initiation Under Equi-Biaxial Loading Development of the Experiment
Authors: Perez G. , Gourdin C. , Courtin S. , Le Roux J. C. 
Published: December 2016

Fatigue lifetime assessment is essential in the design of structures. Under-estimated lifetime predictions may generate overly conservative usage factor values and hence result in unnecessary in-service inspections.
In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like: Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History...
In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.
To formally integrate these effects, some international codes have already proposed and suggested a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which has to be multiplied by the usual fatigue usage factor.
The aim of this paper is to present a new device “FABIME2E” developed in the LISN in collaboration with EDF and AREVA. These new tests allow quantifying accurately the effect of PWR environment on semi-structure specimen. This new device combines the structural effect like equibiaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.