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2 pages, 159 KiB

Open AccessEditorial

Environmental Fatigue Assessment of Metallic Materials and Components

by Sergio Cicero and Matthias Bruchhausen

Metals 2021, 11(10), 1565; https://doi.org/10.3390/met11101565 - 30 Sep 2021

Viewed by 1320

Abstract

At present, sensitive industrial sectors (such as the nuclear, oil, and gas sectors) face important challenges [...] Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

Research

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13 pages, 2313 KiB

Open AccessArticle

Calculated Shoulder to Gauge Ratio of Fatigue Specimens in PWR Environment

by Igor Simonovski, Alec Mclennan, Kevin Mottershead, Peter Gill, Norman Platts, Matthias Bruchhausen, Joshua L. Waters, Marc Vankeerberghen, Germán Barrera Moreno, Sergio Arrieta Gomez and Radek Novotny

Metals 2021, 11(3), 376; https://doi.org/10.3390/met11030376 - 24 Feb 2021

Cited by 2 | Viewed by 1972

Abstract

A ratio of shoulder to gauge displacements (S2G) is calculated for three different fatigue specimens in a pressurized water environment. This ratio needs to be known beforehand to determine the applied shoulder displacements during the experiment that would result in the desired strain [...] Read more.

A ratio of shoulder to gauge displacements (S2G) is calculated for three different fatigue specimens in a pressurized water environment. This ratio needs to be known beforehand to determine the applied shoulder displacements during the experiment that would result in the desired strain amplitude in the gauge section. Significant impact of both the applied constitutive law and specimen geometry on the S2G is observed. The calculation using the fully elastic constitutive law results in the highest S2G values and compares very well with the analytical values. However, this approach disregards the plastic deformation within the specimens that mostly develops in the gauge section. Using the constitutive laws derived from actual fatigue curves captures the material behaviour under cyclic loading better and results in lower S2G values compared to the ones obtained with the fully elastic constitutive law. Calculating S2G values using elastic–plastic constitutive law based on the monotonic uniaxial tensile test should be avoided as they are significantly lower compared to the ones computed with elastic–plastic laws derived from hysteresis loops at half-life. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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20 pages, 1096 KiB

Open AccessArticle

Characterization of Austenitic Stainless Steels with Regard to Environmentally Assisted Fatigue in Simulated Light Water Reactor Conditions

by Matthias Bruchhausen, Gintautas Dundulis, Alec McLennan, Sergio Arrieta, Tim Austin, Román Cicero, Walter-John Chitty, Luc Doremus, Miroslava Ernestova, Albertas Grybenas, Caitlin Huotilainen, Jonathan Mann, Kevin Mottershead, Radek Novotny, Francisco Javier Perosanz, Norman Platts, Jean-Christophe le Roux, Philippe Spätig, Claudia Torre Celeizábal, Marius Twite and Marc Vankeerberghen Show full author list Hide full author list

Metals 2021, 11(2), 307; https://doi.org/10.3390/met11020307 - 10 Feb 2021

Cited by 7 | Viewed by 2893

Abstract

A substantial amount of research effort has been applied to the field of environmentally assisted fatigue (EAF) due to the requirement to account for the EAF behaviour of metals for existing and new build nuclear power plants. We present the results of the [...] Read more.

A substantial amount of research effort has been applied to the field of environmentally assisted fatigue (EAF) due to the requirement to account for the EAF behaviour of metals for existing and new build nuclear power plants. We present the results of the European project INcreasing Safety in NPPs by Covering Gaps in Environmental Fatigue Assessment (INCEFA-PLUS), during which the sensitivities of strain range, environment, surface roughness, mean strain and hold times, as well as their interactions on the fatigue life of austenitic steels has been characterized. The project included a test campaign, during which more than 250 fatigue tests were performed. The tests did not reveal a significant effect of mean strain or hold time on fatigue life. An empirical model describing the fatigue life as a function of strain rate, environment and surface roughness is developed. There is evidence for statistically significant interaction effects between surface roughness and the environment, as well as between surface roughness and strain range. However, their impact on fatigue life is so small that they are not practically relevant and can in most cases be neglected. Reducing the environmental impact on fatigue life by modifying the temperature or strain rate leads to an increase of the fatigue life in agreement with predictions based on NUREG/CR-6909. A limited sub-programme on the sensitivity of hold times at elevated temperature at zero force conditions and at elevated temperature did not show the beneficial effect on fatigue life found in another study. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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14 pages, 2042 KiB

Open AccessArticle

Investigation on Analysis Method of Environmental Fatigue Correction Factor of Primary Coolant Metal Materials in LWR Water Environment

by Xuejiao Shao, Hai Xie, Yixiong Zhang, Furui Xiong, Xiaoming Bai, Lu Jiang and Qianhua Kan

Metals 2021, 11(2), 233; https://doi.org/10.3390/met11020233 - 30 Jan 2021

Cited by 3 | Viewed by 1852

Abstract

The environmental fatigue correction factor (F_en) is mainly used to analyze the influence of the coolant environment on the fatigue life of primary metal materials. Because the calculation of the transformed strain rate is related to the stress history of the [...] Read more.

The environmental fatigue correction factor (F_en) is mainly used to analyze the influence of the coolant environment on the fatigue life of primary metal materials. Because the calculation of the transformed strain rate is related to the stress history of the component structure, how to determine the strain rate is the most critical step in calculating the F_en. The approaches of the detailed method were given by the Electric Power Research Institute (EPRI) guidelines and RCC-M-2017 Edition Section VI- RPP No. 3 separately, so a gap analysis was performed between the two methods. Furthermore, another average method was also proposed to determine the average strain rate and strain range. Based on the analysis benchmark provided in the EPRI guideline, a simple case study was performed to account for the effect on the fatigue life in applications with different strain rate approaches and different F_en expressions. Finally, two industry case studies were also completed, including on materials of low alloy steel, austenitic stainless steel, and nickel-base alloy. We suggest adopting a more accurate detailed method, and its methodology is recommended to provide more reasonable solutions. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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13 pages, 21021 KiB

Open AccessArticle

Mean Stress Effect on the Fatigue Life of 304L Austenitic Steel in Air and PWR Environments Determined with Strain- and Load-Controlled Experiments

by Philippe Spätig, Jean-Christophe Le Roux, Matthias Bruchhausen and Kevin Mottershead

Metals 2021, 11(2), 221; https://doi.org/10.3390/met11020221 - 27 Jan 2021

Cited by 3 | Viewed by 2136

Abstract

The mean stress effect on the fatigue life of 304L austenitic steel was evaluated at 300 °C in air and pressurized water reactor (PWR) environments. Uniaxial tests were performed in strain-control and load-control modes, with zero mean stress and a positive mean stress [...] Read more.

The mean stress effect on the fatigue life of 304L austenitic steel was evaluated at 300 °C in air and pressurized water reactor (PWR) environments. Uniaxial tests were performed in strain-control and load-control modes, with zero mean stress and a positive mean stress of 50 MPa. A specific procedure was used for the strain-controlled experiments to maintain the strain amplitude and mean stress constant. The strain-controlled data indicate that the application of positive mean stress decreases the fatigue life for a given strain amplitude in air and PWR environments. The data also show that the life reduction is independent of the environments, suggesting that no synergistic effects between the mean stress and the LWR environment occur. The load-controlled experiments confirm that the application of positive mean stress increases fatigue due to cyclic hardening processes. This observation is much less pronounced in the PWR environment. All data were analyzed using the Smith–Watson–Topper (SWT) stress–strain function, which was shown to correlate well with all strain- and load-controlled data with and without mean stress in each environment. In the SWT–life curve representation, the life reduction in the PWR environment was found fully consistent with the NUREG-CR6909 predictions. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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14 pages, 5910 KiB

Open AccessArticle

Environmental Effect on Fatigue Crack Initiation under Equi-Biaxial Loading of an Austenitic Stainless Steel

by Cédric Gourdin, Grégory Perez, Hager Dhahri, Laurent De Baglion and Jean-Christophe Le Roux

Metals 2021, 11(2), 203; https://doi.org/10.3390/met11020203 - 22 Jan 2021

Cited by 3 | Viewed by 2074

Abstract

The lifetime extension of nuclear power stations is considered an energy challenge worldwide. That is why the risk analysis and the study of various effects of different factors that could potentially prevent safe long-term operation are necessary. These structures, often of great dimensions, [...] Read more.

The lifetime extension of nuclear power stations is considered an energy challenge worldwide. That is why the risk analysis and the study of various effects of different factors that could potentially prevent safe long-term operation are necessary. These structures, often of great dimensions, are subjected during their life to complex loading combining varying multiaxial mechanical loads with non-zero mean values associated with temperature fluctuations under a PWR (pressure water reactor) environment. Based on more recent fatigue data (including tests at 300 °C in air and a PWR environment, etc.), some international codes (RCC-M, ASME, and others) have 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 determination of the field of validation of the application of this penalty factor requires obtaining experimental data. The aim of this paper is to present a new device, “FABIME2e” developed in the LISN (Laboratory of Integrity of Structures and Normalization) in collaboration with EDF (Electricity of France) and Framatome. These new tests allow the effect of a PWR environment on a disk specimen to be quantified. This new device combines structural effects such as equibiaxiality and mean strain and the environmental penalty effect with the use of a PWR environment during fatigue tests. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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10 pages, 1795 KiB

Open AccessArticle

On the Influence of the Microstructure upon the Fatigue and Corrosion Fatigue Behavior of UNS N07718

by Christopher Tom Engler, Helmuth Sarmiento Klapper and Matthias Oechsner

Metals 2021, 11(1), 117; https://doi.org/10.3390/met11010117 - 09 Jan 2021

Cited by 2 | Viewed by 2001

Abstract

Due to the challenging operational conditions occurring during drilling, e.g., in the oil and gas industry, the corrosion fatigue (CF) behavior of materials used in drillstring components needs to be well understood. The combination of cyclic mechanic loads and a corrosive environment can [...] Read more.

Due to the challenging operational conditions occurring during drilling, e.g., in the oil and gas industry, the corrosion fatigue (CF) behavior of materials used in drillstring components needs to be well understood. The combination of cyclic mechanic loads and a corrosive environment can affect significantly the integrity of a material, which has to be taken into account when selecting and qualifying materials for drilling equipment. Nickel alloys such as the precipitation-hardenable alloy 718 (UNS N07718) are widely used in many industrial applications including subterranean drilling. In the present study, the fatigue and CF behavior of alloy 718 in three different metallurgical conditions was investigated. The CF behavior of the different conditions was determined using customized rotating bending machines enabling testing in a simulated drilling environment at 125 °C. Results have shown that the fatigue and CF strength of alloy 718 is affected by its microstructural particularities, for instance, the amount of strengthening phases and δ-phase. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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15 pages, 5647 KiB

Open AccessCommunication

Gauge-Strain-Controlled Air and PWR Fatigue Life Data for 304 Stainless Steel—Some Effects of Surface Finish and Hold Time

by Marc Vankeerberghen, Michel De Smet and Christian Malekian

Metals 2020, 10(9), 1248; https://doi.org/10.3390/met10091248 - 16 Sep 2020

Cited by 2 | Viewed by 2592

Abstract

We performed environmental fatigue testing in simulated primary water reactor (PWR) primary water and reference fatigue testing in air in the framework of an international, collaborative project (INCEFA-PLUS), where the effects of mean strain and stress, hold time, strain amplitude and surface finish [...] Read more.

We performed environmental fatigue testing in simulated primary water reactor (PWR) primary water and reference fatigue testing in air in the framework of an international, collaborative project (INCEFA-PLUS), where the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied. Our fatigue lives obtained on machined specimens in air at 300 °C lie close to the NUREG/CR6909 mean air fatigue curve and are in line with INCEFA-PLUS air fatigue lives. Our environmental fatigue lives obtained in simulated PWR primary water at 300 °C lie relatively close to the NUREG/CR6909 mean fatigue curve; derived from the NUREG/CR6909 mean air fatigue curve and the applicable environmental correction factor (Fen). The PWR results show that (1) a polished surface finish has a slightly higher and a ground surface finish a slightly lower fatigue life than the NUREG/CR6909 prediction; (2) the ratio of polished to ground specimen life is ~1.37 at 300 °C and ~1.47 at 230 °C; (3) holds—at zero strain after a positive strain-rate—have a slightly detrimental effect on fatigue life. These results are in line with the INCEFA-PLUS PWR fatigue lives. A novel gauge-strain extensometer was deployed in order to perform a true gauge-strain-controlled fatigue test in simulated PWR primary water. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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19 pages, 4376 KiB

Open AccessArticle

Environmental Fatigue Analysis of Nuclear Structural Components: Assessment Procedures, Loads, and a Case Study

by Sergio Cicero, Thomas Metais, Yuliya Voloshyna, Sam Cuvillez, Sergio Arrieta and Román Cicero

Metals 2020, 10(5), 609; https://doi.org/10.3390/met10050609 - 08 May 2020

Cited by 2 | Viewed by 3339

Abstract

Nowadays, environmental fatigue assessment is mandatory in many countries, in the design and operational stages of nuclear structural components. The analysis of environmental fatigue can be a complex engineering process that is generally performed following national or international procedures. Such procedures are not [...] Read more.

Nowadays, environmental fatigue assessment is mandatory in many countries, in the design and operational stages of nuclear structural components. The analysis of environmental fatigue can be a complex engineering process that is generally performed following national or international procedures. Such procedures are not always based on the same assumptions, and novel analysts may find a confusing variety of documents. Moreover, once a specific procedure has been chosen for the analysis, it is possible to complete the fatigue assessment by using design transients (and loads) or, alternatively, real loads provided by monitoring systems. In this context, this paper provides a comprehensive review of the different environmental fatigue assessment procedures and a brief description of the different types of load inputs (design vs. real data). The work is completed with a case study, in which the (fatigue) cumulative usage factor is estimated in a particular nuclear component by using one of the abovementioned assessment procedures (NUREG/CR-6909) and two options for the load inputs. Full article

(This article belongs to the Special Issue Environmental Fatigue Assessment of Metallic Materials and Components)

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