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Academic literature on the topic 'P91 martensitic steel'

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Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "P91 martensitic steel"

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Qadr, Hiwa Mohammad, and Ari Maghdid Hamad. "Mechanical Properties of Ferritic Martenstic Steels: A Review." Scientific Bulletin of Valahia University - Materials and Mechanics 17, no. 16 (May 1, 2019): 18–27. http://dx.doi.org/10.2478/bsmm-2019-0003.

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Abstract The word-wide demand for energy is constantly increasing, and therefore ideas around future energy-generation are also on the increase with the aim of meeting this demand. This includes designs for the next generation of nuclear power reactors, such as gas-cooled, liquid-metal-cooled and water-cooled reactors; the goal being to create smarter ways to produce more economical, environmentally-friendly energy. The conditions such reactors would need to meet, present significant design challenges for scientist and engineers, not least around the structural materials and components to use. Depending on the operational conditions, use of elevated- temperature ferritic/martensitic materials such as P91 and P92 steel are favoured by several of the designs for use with out-of-core and in-core applications. The main goal behind this review article is to explain mechanical properties of P91 and P92 steel; these are two types of ferritic/martensitic steels. This reviewer, highlight and discuss the development of ferritic/martenisitc steels for nuclear programmes and to explain the effect of irradiation on mechanical properties of P91 and P92.
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Golański, G., J. Jasak, A. Zieliński, C. Kolan, M. Urzynicok, and P. Wieczorek. "Quantitative analysis of stability of 9%Cr steel microstructure after long-term ageing." Archives of Metallurgy and Materials 62, no. 1 (March 1, 2017): 263–71. http://dx.doi.org/10.1515/amm-2017-0040.

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Abstract The paper presents the results of research on the microstructure of martensitic X10CrMoVNb9-1 (P91) and X13CrMoCo- VNbNB9-2-1 (PB2) steel subject to long-term ageing at the temperature of 620°C and holding times up to 30 000 hours. The microstructural tests of the examined steel types were performed using a scanning microscope Joel JSM - 6610LV and a transmission electron microscope TITAN 80 - 300. The stability of the microstructure of the investigated steels was analyzed using a quantitative analysis of an image, including measurements of the following: the density of dislocations inside martensite/subgrain laths, the width of martensite laths, and the mean diameter of precipitates. It has been concluded that during long-term ageing, the microaddition of boron in PB2 steel significantly influenced the slowing of the process of degradation of the martensitic steel microstructure, as a result of slowing the process of coagulation of M23C6 carbides and Laves phase. It had a favorable effect on the stabilization of lath microstructure as a result of retardation of the processes of recovery and polygonization of the matrix.
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Shi, L., SA Alexandratos, and NP O’Dowd. "Combined finite element and phase field method for simulation of austenite grain growth in the heat-affected zone of a martensitic steel weld." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 1 (January 17, 2018): 13–27. http://dx.doi.org/10.1177/1464420717750999.

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Engineering components operating at high temperature often fail due to the initiation and growth of cracks in the heat-affected zone adjacent to a weld. Understanding the effects of microstructural evolution in the heat-affected zone is important in order to predict and control the final properties of welded joints. This study presents a combined finite element method and phase field method for simulation of austenite grain growth in the heat-affected zone of a tempered martensite (P91) steel weld. The finite element method is used to determine the thermal history of the heat-affected zone during gas tungsten arc welding of a P91 steel plate. Then, the calculated thermal history is included in a phase field model to simulate grain growth at various positions in the heat-affected zone. The predicted mean grain size and grain distribution match well with experimental data for simulated welds from the literature. The work lays the foundation for optimising the process parameters in welding of P91 and other ferritic/martensitic steels in order to control the final heat-affected zone microstructure.
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Vlasák, Tomás, Jan Hakl, Pavel Novák, Jiří Sochor, and Jan Čech. "Creep of Cast Steel P91 with Weld Joint." Materials Science Forum 782 (April 2014): 331–34. http://dx.doi.org/10.4028/www.scientific.net/msf.782.331.

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High-temperature martensitic steel P91, internationally marked GX12CrMoVNbN91, is the material used in the energy industry. Creep and high-temperature corrosion resistances are important properties that affect the application of this material at higher temperatures. Weldment reduces creep properties. This work deals with the quantification of this decrease in the case of material P91. The main focus is except the evaluation of creep test results given to the mathematical description of the weld creep strength reduction. Further metallographic analyses of weld joint after creep exposures were performed.
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Velkavrh, Igor, Joël Voyer, Fevzi Kafexhiu, and Bojan Podgornik. "Creep Rate, Friction, and Wear of Two Heat-Affected Zone Regions of 9–12 wt.% Cr Steels." Metals 11, no. 4 (March 29, 2021): 558. http://dx.doi.org/10.3390/met11040558.

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Coarsening of precipitates can have a profound effect on the mechanical properties of martensitic 9–12 wt.% Cr steels, which are typically used in critical parts of fossil-fuel power plants such as turbines, headers, and main steam pipes. In the present study, changes in precipitates’ size and distribution in the simulated heat-affected zone of two different 9–12 wt.% Cr steels (X20 and P91) after different aging conditions were analyzed and correlated with their creep, friction, and wear behaviors. It was shown that prior to aging, the morphology of the steel matrix (prior austenite grain size and microstructure homogeneity) governed the creep rate and the tribological performance of both steels, while after aging their response was additionally determined by the combination of the number and the size of precipitates. For the selected samples (prepared under identical conditions), number of precipitates was found to be within a narrower range for the X20 steel as compared to the P91 steel. For both steels, aging for a shorter time at the higher temperature yielded significantly higher stationary creep rate values as compared to aging for longer time at the lower temperature. The increase was more pronounced in the P91 than in the X20 steel. Both prior to and after aging, the P91 steel typically provided slightly higher creep resistance than the X20 steel, while the latter provided slightly better tribological performance. Furthermore, as a function of the increasing number of precipitates, static coefficient of friction in air atmosphere was approximately linearly decreasing, while the wear rate initially decreased.
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Rhode, Michael, Tim Richter, Tobias Mente, Peter Mayr, and Alexander Nitsche. "Thickness and microstructure effect on hydrogen diffusion in creep-resistant 9% Cr P92 steel and P91 weld metal." Welding in the World 66, no. 2 (December 9, 2021): 325–40. http://dx.doi.org/10.1007/s40194-021-01218-9.

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Abstract Martensitic 9% Cr steels like P91 and P92 show susceptibility to delayed hydrogen assisted cracking depending on their microstructure. In that connection, effective hydrogen diffusion coefficients are used to assess the possible time-delay. Limited data on room temperature diffusion coefficients reported in literature vary widely by several orders of magnitude (mostly attributed to variation in microstructure). Especially P91 weld metal diffusion coefficients are rare so far. For that reason, electrochemical permeation experiments had been conducted using P92 base metal and P91 weld metal (in as-welded and heat-treated condition) with different thicknesses. From the results obtained, diffusion coefficients were calculated using to different methods, time-lag, and inflection point. Results show that, despite microstructural effects, the sample thickness must be considered as it influences the calculated diffusion coefficients. Finally, the comparison of calculated and measured hydrogen concentrations (determined by carrier gas hot extraction) enables the identification of realistic diffusion coefficients.
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Elarbi, Y., and Béla Palotás. "Microstructural Changes due to Secondary Precipitation Hardening of Martensitic Creep Resistant Steel X20CrMoWV 12 1 (AISI 422)." Materials Science Forum 589 (June 2008): 197–202. http://dx.doi.org/10.4028/www.scientific.net/msf.589.197.

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After development of the well-known T/P91 steel grade in the early 80’s and its long industrial experience since early 90’s, it has been necessary to develop new martensitic creep resistant steels to answer the demand of the power generation industry. New USC (ultra-super critical) boilers require materials with advanced creep properties to reach severe steam parameters. Addition of W to the steel has been found by many researches to be effective to increase creep rupture strength at high temperatures and already used in some developed steel grades such as T/P92, T/P122 and AISI 422 for the USC boilers. Recently, long-term creep strength of the advanced high Cr ferritic steels has been argued regarding the instability of their microstructures at high temperatures over 600 °C. This microstructural instability seems to be enhanced with increasing Cr content or with substitution of Mo by W in the steels. The aim of this paper is concentrated on the investigation of the microstructural development of the studied steel using the Jominy end-face quench test. Different hardness profiles from this test were introduced.
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Ducháček, Petr, and Jiří Janovec. "Heterogeneous Welded Joints (T23-T92; 15CH1M1F-P91)." Key Engineering Materials 647 (May 2015): 147–52. http://dx.doi.org/10.4028/www.scientific.net/kem.647.147.

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The use of new construction materials is increasingly on demand for the construction of new power plants, and for the modernization of existing plants that are at the end of their service life span. Steels such as type P/T92 (modified martensitic 9-12% Cr), and low-alloy steels derived from modified steel 2.5Cr1Mo (ASTM marked P/T23) are considered promising alternatives. In the construction of power units, the so-called heterogeneous joints, which most often consist of a combination of low-alloyed materials and highly-alloyed ones, preferably need to be avoided. These welded joints are often the weak links in the overall construction. Knowledge of the behaviour of creep-resistant steel welded joints is very important for the subsequent evaluation of the life span of the units. This study deals with the degradation of heterogeneous welded joints of steel T23 - T92 and 15CH1M1F - P91, using the commercially available welding materials Thermanit MTS 616 (highly-alloyed), Union I P23; ThermanitP23, Böhler P23-IG and Thermanit (FOX) P23 (low-alloyed). In the heterogeneous welds examined, slight loss of strength of the base material was observed during isothermal heat exposure and extension of the diffusion active zones (i.e., Carbon Depleted Zone (CDZ) and Carbon Enriched Zone (CEZ)). These degradation processes caused structural instability of heterogeneous welds. It was found that the use of low-alloyed welding materials showed superior structural stability than highly-alloyed welds. Additional laboratory analyses are warranted due to the extreme service conditions and the high temperature loads in power units.
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Janulionis, Remigijus, Gintautas Dundulis, and Albertas Grybėnas. "Numerical Research of Fracture Toughness of Aged Ferritic-Martensitic Steel." Metals 10, no. 12 (December 17, 2020): 1686. http://dx.doi.org/10.3390/met10121686.

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Generally, material properties such as the modulus of elasticity, yield strength or fracture toughness are determined by conducting an experiment. Sometimes experimental determination cannot be done due to specific experimental conditions, lack of testing material and so on. Also, experiments are time consuming and costly. Therefore, there arises the need for alternative determination methods. A numerical method for the fracture toughness determination of steel P91 is suggested in this paper. For this purpose, the universal finite element software ABAQUS was used. The numerical simulation of the C(T) specimen tension test was carried out using non-linear simulation for a conditional load PQ determination, and linear simulation for fracture toughness value KQ determination. The suggested method is validated by comparing numerical and experimental tests results. The secondary aim of the paper is the evaluation of the ageing effect on the fracture toughness of steel P91. Thermal ageing of the steel was carried out in an electric furnace at 650 °C up to 11,000 h. As the numerical results had a good coincidence with experimental data at room temperature, the prediction of fracture toughness at elevated temperature, i.e., 550 °C, using numerical method was carried out.
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Yaghi, A. H., T. H. Hyde, A. A. Becker, and W. Sun. "Numerical simulation of P91 pipe welding including the effects of solid-state phase transformation on residual stresses." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 221, no. 4 (October 1, 2007): 213–24. http://dx.doi.org/10.1243/14644207jmda152.

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The methodology of numerically simulating residual stresses in a welded P91 pipe section is described. The finite element (FE) method has been applied to simulate residual axial and hoop stresses generated in the weld region and heat affected zone (HAZ) of an axisymmetric 50-bead circumferentially butt-welded P91 steel pipe, with outer diameter of 145 mm and wall thickness of 50mm. The FE simulation consists of a thermal analysis which is followed by a sequentially-coupled structural analysis. Solid-state phase transformation (SSPT), which is characteristic of P91 steel during welding thermal cycles, has been modelled in the FE analysis by allowing for volumetric changes in steel and associated changes in yield stress due to austenitic and martensitic transformations. Phase transformation plasticity has also been taken into account. Preheat and interpass temperature control has been included in the modelling process. Thermally-obtained temperature contours indicate the size of the weld region, parent metal penetration, and HAZ. Residual axial and hoop stresses have been depicted through the pipe wall thickness as well as along the outer surface of the pipe. The results indicate the importance of including SSPT in the simulation of stresses during the welding of P91 steel.
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Dissertations / Theses on the topic "P91 martensitic steel"

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Zhang, Kuo [Verfasser]. "Characterization and Modeling of the Ratcheting Behavior of the Ferritic-Martensitic Steel P91 / Kuo Zhang." Karlsruhe : KIT Scientific Publishing, 2017. http://www.ksp.kit.edu.

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Zhang, Kuo [Verfasser], and J. [Akademischer Betreuer] Aktaa. "Characterization and Modeling of the Ratcheting Behavior of the Ferritic-Martensitic Steel P91 / Kuo Zhang. Betreuer: Dr. J. Aktaa." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1093559241/34.

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Whitt, Harrison Collin. "Creep and Creep-fatigue Deformation Studies in 22V and P91 Creep-strength EnhancedFerritic Steels." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555603135480185.

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Conference papers on the topic "P91 martensitic steel"

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Golden, Brian, Dongfeng Li, and Noel O’Dowd. "Microstructural Modelling of P91 Martensitic Steel Under Uniaxial Loading Conditions." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97514.

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The changing face of power generation requires an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through microstructurally motivated modelling studies. This paper deals with the comparisons of predictions of the mechanical response of a power plant steel (P91), obtained from a model with a measured microstructure with those obtained from a numerically simulated microstructure. Electron backscatter diffraction (EBSD) is employed to obtain the orientation of the martensitic grain structure of the steel. This information is incorporated within a representative volume element (RVE) to represent the material microstructure. A non-linear, rate dependent, finite strain crystal plasticity model is used to represent the deformation of the material, with the orientation of each finite-element integration point determined from the EBSD analysis. The deformation under uniaxial tension is analysed. Due to the inhomogeneous microstructure strong strain gradients are generated within the RVE even under remote homogenous strain states. It is seen that peak stress/strain states are associated with particular features of the microstructure. The results taken from the model are compared with those obtained with an equiaxed microstructure generated using the Voronoi tessellation method.
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Venkata, Kiranmayi Abburi, and Christopher E. Truman. "Finite Element Simulation of Laser Welding in a P91 Steel Plate." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97339.

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New methods for joining materials used in advanced nuclear power plants are of interest to increase the efficiency and productivity. Optimised joints require narrow heat affected zones, low residual stress, strain and distortion. This requires research into a large range of aspects including the nature of the joining processes, characterisation of the joint materials and the integrity of joints in manufacture and service. Of particular interest is the laser welding of the P91 steel used extensively in the power plants. The objective of this paper is to fully characterise the laser welding process using numerical modelling techniques and compare the measured residual stresses for P91 steel welds induced by the welding process with the predicted residual stresses by numerical simulation. The FE simulation consists of thermal analysis and a sequentially coupled structural analysis. Solid state phase transformation is included in the analysis to account for the volumetric changes due to martensitic transformation during cooling. The neutron diffraction technique is used to measure the residual stresses in the welded plate. The measurements are compared with the simulation results and the characteristics of the residual stress distribution and the influence of phase transformations are discussed.
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Li, Dong-Feng, Brian Golden, and Noel P. O’Dowd. "Modelling of Micro-Plasticity Evolution in Crystalline Materials." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97233.

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In this work, a micromechanical finite element model is presented to investigate micro-plasticity evolution in crystalline materials, with a comprehensive consideration of microstructural interactions, including morphology-based intragranular stress-strain response and the strain gradient induced scale effect. A dislocation-mechanics based crystal plasticity formulation has been employed to account for slip based inelastic deformation. A polycrystalline model has been constructed using the Voronoi tessellation technique to represent the microstructure of a martensitic power plant steel, P91. The model has been validated through a uniaxial tensile test. The effects of strain gradient have been examined at both macroscopic and microscopic levels and the importance of accounting for strain gradient effects in the prediction of local deformation states is discussed for P91.
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Golden, Brian J., Dong-Feng Li, Peter Tiernan, Stephen Scully, and Noel P. O’Dowd. "Deformation Characteristics of a High Chromium, Power Plant Steel at Elevated Temperatures." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45487.

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The changing face of power generation requires an improved understanding of the deformation and failure response of materials that are employed in power plants. Important insights can be obtained through microstructurally motivated modelling studies. With the drive for increased efficiency, there is a corresponding drive towards increasing operating temperatures in conventional power plant. With these increasing temperatures, and with the increased flexibility required of modern power plant working in a mixed energy economy, more robust material testing and modelling tools are required to accurately predict the response of power plant steels. This works deals with the development of a material model for a martensitic steel, P91, relevant to the range of temperatures typically seen in a modern power plant. High temperature (20, 400, 500, 600°C) tensile testing at various strain rates was carried out the steel. Tests were taken to failure and the stress strain response recorded. Electron backscatter diffraction (EBSD) is employed to determine the complex microstructure of the P91 material. This information is incorporated within a representative volume element (RVE) and a nonlinear, rate dependent, finite strain crystal plasticity model used to represent the deformation of the material. The material model was calibrated to each temperature and strain rate to give a robust physically based model that has been fully validated through experimental data.
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Pinto Fernandes, Jorge, Eduardo Manuel Dias Lopes, and Vicente Maneta. "New Steel Alloys for the Design of Heat Recovery Steam Generator Components of Combined Cycle Gas Plants." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59917.

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Demand of Power is growing everyday, mainly due to emerging economies in CRIB countries (China, Russia, India and Brazil). During the last fifty years steam pressure and temperature in power plants have been continuously raised to improve thermal efficiency. Recent efforts to improve efficiency leads to the development of a new generation of Heat Recovery Steam Generator (HRSG) where the Benson Once-Through Technology is applied to improve thermal efficiency. The main purpose of this paper is to analyse the mechanical behaviour of a High Pressure Superheater Manifold by applying Finite Element Modelling (FEM) and a Finite Element Analysis with the objective to analyse stress propagation leading to the study of damage mechanism e.g. Uniaxial Fatigue, Uniaxial Creep for life prediction. The objective of this paper is also to analyse the mechanical properties of the new high temperature resistant materials in the market such as 2Cr Bainitic steels (T/P23, T/P24) and also the 9–12Cr Martensitic steels (T/P91, T/P92, E911 and P/T122). For this study the design rules for construction of power boilers to define the geometry of the HPSH Manifold were applied.
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Alexandratos, Spyridon A., Robert C. Wimpory, Tung-Lik Lee, Padraig Mac Ardghail, Sean B. Leen, and Noel P. O’Dowd. "Comparison of Residual Stress Measurements on Single Bead-on-Plate Welds of a Martensitic Steel Using Neutron Diffraction." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21776.

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Abstract During the welding process, a material is subjected to thermal cycles with rapid heating and cooling rates resulting in residual stress in the weld and the base metal. These residual stress may affect the mechanical performance leading to premature failure of components. Therefore, it is critical to have a detailed knowledge of the residual stress distribution in the weld region as well as in the vicinity in order to predict the service life of components. Due to the high neutron penetration power, neutron diffraction is one of the most useful techniques for nondestructive evaluation of residual stress in welded regions within the bulk. In this paper, neutron diffraction was used to investigate the residual stress distribution within three single bead-on-plate welds of P91 martensitic steel. Residual stress measurements were performed at different neutron diffraction instruments and different methodology of stress determination was applied. Measurements were carried out at the diffractometers Engin-X (ISIS Neutron Source, Rutherford Appleton Laboratory), E3 (BER-II, Helmholtz-Zentrum Berlin) and SALSA (Institut Laue-Langevin). The results of the measurements presented here, were used to determine the variability of the three instruments and compare the effect of different welding parameters on residual stress. The residual stress measurements were also compared with the respective results of the Task Group 1 (TG1) of the European Network on Neutron Techniques standardization for structural integrity (NET).
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Alexandratos, Spyridon A., Lei Shi, and Noel P. O’Dowd. "Parameter Study of a Thermal Analysis of a Bead-on-Plate Weld." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84999.

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Failures in engineering components operating at high temperature often initiate in welded joints, particularly in the heat-affected zone (HAZ) adjacent to a weld. This is due to the inhomogenous microstructure of the weld and adjacent material due to the different thermal histories experienced during the weld cycle. It is therefore important to accurately predict the temperature distributions arising during welding and the subsequent effect on material microstructure. The NET TG1 bead-on-plate weld geometry is examined in this work. This geometry is a single weld bead laid on the surface of an AISI 316L austenite steel plate. Experimental data from the TG1 study are available to validate different weld simulation techniques. Here, a sensitivity study to the thermal properties is carried out and the influence on the HAZ temperatures and grain size is examined. The study shows that the conductivity and the specific heat capacity significantly affect the temperature prediction in the HAZ with a similar influence on predicted grain size following welding. Results are presented for a stainless steel (316L) and a martensitic steel (P91) plate.
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Pohja, Rami H., and Stefan B. Holmström. "A Comparison of Creep-Fatigue Assessment and Modelling Methods." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30640.

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Design codes, such as RCC-MRx and ASME III NH, for generation IV nuclear reactors use interaction diagram based method for creep-fatigue assessment. In the interaction diagram the fatigue damage is expressed as the ratio of design cycles over the allowable amount of cycles in service and the creep damage as the ratio of time in service over the design life. With this approach it is assumed that these quantities can be added linearly to represent the combined creep-fatigue damage accumulation. Failure is assumed to occur when the sum of the damage reaches a specified value, usually unity or less. The fatigue damage fraction should naturally be unity when no creep damage is present and creep damage should be unity when no fatigue damage is present. However, strict fatigue limits and safety factors used for creep rupture strengths as well as different approaches to relaxation calculation can cause a situation where creep-fatigue test data plotted according to the design rules are three orders of magnitude away from the interaction diagram unity line. Thus, utilizing the interaction diagram methods for predicting the number of creep-fatigue cycles may be inaccurate and from design point of view these methods may be overly conservative. In this paper the results of creep-fatigue tests carried out for austenitic stainless steel 316 and heat resistant ferritic-martensitic steel P91, which are included in the design codes, such as RCC-MRx, are assessed using the interaction diagram method with different levels of criteria for the creep and fatigue fractions. The test results are also compared against the predictions of a recently developed simplified creep-fatigue model which predicts the creep-fatigue damage as a function of strain range, temperature and hold period duration with little amount of fitting parameters. The Φ-model utilizes the creep rupture strength and ultimate tensile strength (UTS) of the material in question as base for the creep-fatigue prediction. Furthermore, challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with P91 steel, for the interaction diagram based assessment is discussed.
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Barrett, Richard A., Eimear O’Hara, Padraic E. O’Donoghue, and Sean B. Leen. "High Temperature Low Cycle Fatigue Behaviour of MarBN at 600 °C." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45599.

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The changing face of fossil fuel power generation is such that next generation plants must be capable of operating under (i) flexible conditions to accommodate renewal sources of energy and (ii) higher steam pressures and temperatures to improve plant efficiency. These changes result in increased creep and fatigue degradation of plant components. The key limiting factor to achieving more efficient, flexible plant operation is the development of advanced materials capable of operating under such conditions. MarBN is a new precipitate strengthened 9Cr martensitic steel, with added boron and tungsten, designed to provide enhanced creep strength and precipitate stability at high temperature. Accurate characterisation of this material is necessary so that it can be used under flexible plant operating conditions with high temperature fatigue. This paper presents a combined work program of experimental testing and computational modelling on a cast MarBN material. To characterise and assess the fatigue performance of MarBN, an experimental program of high temperature low cycle fatigue (HTLCF) tests is conducted at a temperature of 600 °C. MarBN is found to give an increased stress range compared to previous P91 steel experiments, as well as considerable cyclic softening. To characterise the constitutive behaviour of the cast MarBN material, a recently developed unified cyclic viscoplastic material model is calibrated and validated across a range of strain-rates and strain-ranges, with good correlation achieved with the measured data throughout.
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Mac Ardghail, Padraig, Richard A. Barrett, Noel Harrison, and Sean B. Leen. "Predictions of ICHAZ Cyclic Thermo-Mechanical Response in GTAW Process for 9Cr Steels." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65794.

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This work is concerned with the development of a modelling framework to predict the effects of tempered-untempered martensite heterogeneity on the thermo-mechanical performance of welded material. A physically-based visco-plasticity model for the inter-critical heat-affected zone (ICHAZ) for 9Cr steels (e.g. P91, P92) is presented in this work, with the ICHAZ represented as a mixture of tempered and untempered martensite. The constitutive model includes dislocation-based Taylor hardening and damage for different material phases. A sequentially-coupled thermal-mechanical welding simulation is conducted to predict the volume fraction compositions for the various weld-affected material zones in a cross-weld specimen. The out-of-phase cyclic thermo-mechanical (25°C to 600°C) performance of notched and plain samples is comparatively assessed for a range of different tempered-untempered martensitic material heterogeneities. It is shown that the heterogeneity in a simulated cross-weld material is highly detrimental to thermal cyclic performance.
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