Crack Initiation Under Equibiaxial Fatigue, Development of a Particular Equibiaxial Fatigue Device

2013 ◽  
Author(s):  
S. Bradaï ◽  
C. Gourdin ◽  
S. Courtin ◽  
J. C. Leroux ◽  
C. Gardin
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Nuclear Power ◽  
Strain State ◽  
Biaxial Tension ◽  
Strain Tensor ◽  
Austenitic Stainless Steels ◽  
Fatigue Loading ◽  
New Device ◽  
Fatigue Development

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data on austenitic stainless steels is available. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. For this reason, a new experimental data must be obtained on the considered material with a strain tensor in equi-biaxial tension. The aim of this paper is to present a new device “FABIME2” developed in the LISN in collaboration with EDF and AREVA. This new device allows accurate quantification of the effects of both equi-biaxial strain state as well as structure (such as mean stress) on the fatigue life. A Finite Element Modeling is also performed in order to obtain a precise description of the strain state in the specimen.

scholarly journals Equi-Biaxial Loading Effect on Austenitic Stainless Steel Fatigue Life

2014 ◽  
Author(s):  
S. Bradaï ◽  
C. Gourdin ◽  
S. Courtin ◽  
J. C. Le Roux ◽  
C. Gardin
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Nuclear Power ◽  
Biaxial Loading ◽  
Biaxial Tension ◽  
Strain Tensor ◽  
Austenitic Stainless Steels ◽  
Fatigue Loading ◽  
Fatigue Lifetime ◽  
Biaxial Fatigue

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. The aim of this paper is to present the experimental results obtained with a device “FABIME2” developed in the LISN in collaboration with EDF and AREVA. The specimen geometry is optimized by FEM (Cast3M) simulation in order to obtain a stress concentration localized in the central region during the test. This device allows accurate quantification of the effects of both equi-biaxial strain state as well as structure (such as mean stress) on the fatigue life.

Specificity of Crack Initiation under Equibiaxial Fatigue: Development of a New Experimental Device

2014 ◽  
Vol 891-892 ◽  
pp. 1329-1334
Author(s):  
Soumaya Bradaï ◽  
Cédric Gourdin ◽  
Stephan Courtin ◽  
Jean Christophe Leroux ◽  
Catherine Gardin
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Strain State ◽  
Structural Parameters ◽  
Strain Tensor ◽  
Fatigue Loading ◽  
Experimental Program ◽  
Mean Stress ◽  
New Device ◽  
Fatigue Development

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in-service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equibiaxial fatigue damage. Hence this requires obtaining experimental data on the considered material and with a strain tensor in equibiaxial tension. This paper describes an experimental program on austenitic stainless steel carried out on the new experimental fatigue device FABIME2 developed in the LISN in collaboration with EDF and AREVA. This new device allows accurate quantification of the effects of both equibiaxial strain state as well as structural parameters (such as mean stress) on the fatigue life. It also allows studying the complexity of combinations between potential detrimental effects like surface roughness, mean stress and equibiaxial loading. Different load ratios can be tested by adjusting the loading conditions. A Finite Element Modeling is performed in order to obtain a precise description of the strain state in the specimen. The results of the on-going test campaign will be presented.

scholarly journals Equi-Biaxial Loading Effect on Austenitic Stainless Steel Fatigue Life

2015 ◽  
Author(s):  
S. Bradaï ◽  
C. Gourdin ◽  
S. Courtin ◽  
J. C. Le Roux ◽  
C. Gardin
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Numerical Study ◽  
Strain Tensor ◽  
Austenitic Stainless Steels ◽  
Nuclear Industry ◽  
Image Correlation ◽  
Biaxial Fatigue ◽  
The Impact

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. Two calibration tests (with strain gauges and image correlation) were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to −1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components.

Stiffness Degradation of Digital Polypropylene Under Fatigue Loading: Investigations via 3-Dimensional Polyjet Printed Coupons

2020 ◽  
Author(s):  
Ravi Pratap Singh Tomar ◽  
Furkan I. Ulu ◽  
Ajit Kelkar ◽  
Ram V. Mohan
Keyword(s):  
Experimental Data ◽  
Regression Analysis ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Damage State ◽  
3 Dimensional ◽  
Accumulated Damage ◽  
Polyjet Printing

Abstract The utilization of additively manufactured parts is gaining popularity in functional applications. Polymer-based additive manufacturing (AM) parts are utilized in a variety of engineering applications for automotive, aerospace, and energy. AM printed parts are however newer class of materials, and structural performance of these materials is not fully understood completely, and very limited exists currently on precisely performance of Polyjet printed parts and associated digital materials under fatigue loading. This paper investigates the stiffness degradation under tension-tension fatigue loading of digital polypropylene using homogenous 3-Dimensional test coupons formed using PolyJet printing. Homogeneous 3-Dimensional test configuration employed in the present study eliminates the process-induced limitations of traditional ASTM D638 2D fatigue test coupons for AM processed materials. Fatigue data is analyzed to present an empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclic loading. Further, the actual damage accumulation due to cyclic loading with the predicted model is compared. Modeling of the S-N diagram provides a better estimation of fatigue life and fatigue life modeling of AM printed test coupons and is obtained via linear regression analysis of experimental data with high correlation coefficient R2 (0.9971). The analytical model of the accumulated damage state is based on the stiffness degradation and is derived from the regression analysis of experimental data of stiffness degradation at different loading percentages assuming a polynomial of degree 4. Present study provides insight into the fatigue damage state and cyclic performance of digital polypropylene from Polyjet printing.

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

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 203 ◽  
Author(s):  
Cédric Gourdin ◽  
Grégory Perez ◽  
Hager Dhahri ◽  
Laurent De Baglion ◽  
Jean-Christophe Le Roux
Keyword(s):  
Nuclear Power ◽  
Biaxial Loading ◽  
Fatigue Crack Initiation ◽  
Austenitic Stainless Steels ◽  
Complex Loading ◽  
Fatigue Curve ◽  
Mean Values ◽  
Term Operation ◽  
New Device ◽  
Penalty Factor

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.

scholarly journals PWR effect on crack initiation under equi-biaxial loading development of the experiment

2019 ◽  
Vol 20 (6) ◽  
pp. 619
Author(s):  
Cédric Gourdin ◽  
Gregory Perez ◽  
Hager Dhahri ◽  
Stéphan Courtin ◽  
Jean Christophe Le Roux ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Biaxial Loading ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Structural Effect ◽  
Fatigue Tests ◽  
Pressurized Water ◽  
Term Operation ◽  
New Device ◽  
Penalty Factor

The lifetime extension of the nuclear power stations is considered as an energy challenge worldwide. That is why, the risk analysis and the study of various effects of different factors that could potentially represent a hazard to a safe long term operation are necessary. The methodology for fatigue dimensions of the Pressurized Water Reactor components (PWR) is based on the use of design curves established from test carried out in air at 20 °C on smooth specimens by integrating safety coefficient that covers the dispersion of tests associated with the effects of structures. 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 CEA-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 equi-biaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.

A Review of the Effects of Coolant Environments on the Fatigue Life of LWR Structural Materials

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
O. K. Chopra ◽  
W. J. Shack
Keyword(s):  
Fatigue Life ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Crack Initiation ◽  
Austenitic Stainless Steels ◽  
Structural Materials ◽  
Low Alloy Steels ◽  
Asme Code ◽  
Alloy Steels

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies design curves for the fatigue life of structural materials in nuclear power plants. However, the effects of light water reactor (LWR) coolant environments were not explicitly considered in the development of the design curves. The existing fatigue-strain-versus-life (ε-N) data indicate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. Under certain environmental and loading conditions, fatigue lives in water relative to those in air can be a factor of 15 lower for austenitic stainless steels and a factor of ≈30 lower for carbon and low-alloy steels. This paper reviews the current technical basis for the understanding of the fatigue of piping and pressure vessel steels in LWR environments. The existing fatigue ε-N data have been evaluated to identify the various material, environmental, and loading parameters that influence fatigue crack initiation and to establish the effects of key parameters on the fatigue life of these steels. Statistical models are presented for estimating fatigue life as a function of material, loading, and environmental conditions. An environmental fatigue correction factor for incorporating the effects of LWR environments into ASME Code fatigue evaluations is described. This paper also presents a critical review of the ASME Code fatigue design margins of 2 on stress (or strain) and 20 on life and assesses the possible conservatism in the current choice of design margins.

Study of Crack Propagation Under Fatigue Equibiaxial Loading

2014 ◽  
Author(s):  
S. Bradaï ◽  
C. Gourdin ◽  
C. Gardin
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Life ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Thermal Fatigue ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
316L Austenitic Stainless Steel

In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. As a consequence, the potential impact of multiaxial loading on the fatigue life of components is a major concern. However, few experimental data are available about austenitic stainless steels. It is essential to improve the fatigue assessment methodologies taking into account the potential equibiaxial fatigue damage. It implies obtaining experimental data on the considered material, with a strain tensor corresponding to equibiaxial tension. Many multiaxial criteria, based on thermal fatigue tests or uniaxial fatigue tests, were proposed by Von Mises, Zamrik and other researchers [cited in 1]. Yet, additional thermal fatigue tests and isothermal equibiaxial fatigue tests must be carried out. In this context, a new experimental fatigue device FABIME2 [cited in 2] is developed, in the LISN, in collaboration with EDF and AREVA, in order to characterize accurately the possible equibiaxiality effect on the fatigue behavior of the 316L austenitic stainless steel. This paper is focused on the identification of a new criterion in order to be able to take into account the possible effect to the equibiaxial loading on fatigue life. It will be identified by a comparison of experimental results and numerical predictions. In this aim, a test campaign with several experiments was realized on the new FABIME2 device, in order to determine the crack growth rate from an equibiaxial fatigue loading. Propagation tests were carried out on 316L austenitic stainless steel CT specimens, at room temperature, in order to obtain the Paris law [cited in 3]: (crack growth rate da/dN versus the applied stress intensity factor range ΔK). The crack growth is followed throughout equibiaxial test. This allows obtaining, the da/dN evolution, and the corresponding ΔK values. A finite element modeling done with CASTEM®, will be proposed to simulate the crack propagation in the FABIME2 specimen using a 3-dimensional approach, considering a semi-elliptical crack shape.

Fatigue Life of the Strain Hardened Austenitic Stainless Steel in Simulated Pressurized Water Reactor Primary Water

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Nicolas Huin ◽  
Kazuya Tsutsumi ◽  
Thierry Couvant ◽  
Gilbert Henaff ◽  
Jose Mendez
Keyword(s):  
Fatigue Life ◽  
Power Systems ◽  
Stress Corrosion ◽  
Environmental Degradation ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Nuclear Power ◽  
Austenitic Stainless Steels ◽  
Primary Water ◽  
Degradation Of Materials

Over the last 20 years or so, many studies have revealed the deleterious effect of the environment on fatigue life of austenitic stainless steels in primary water reactor (PWR) primary water. The fatigue life correlation factor, so-called Fen, which corresponds to the ratio of fatigue life in air at room temperature to that in water under reactor operating conditions, has been standardized to consider the effect on fatigue life evaluation, and the formulations are function of strain rate and temperature due to their noticeable negative effect compared with other factors (Chopra and Shack, 2007, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials,” Final Report, Report No. NUREG/CR-6909, ANL-06/08; Codes for Nuclear Power Generation Facilities, 2009, "Environmental Fatigue Evaluation Method for Nuclear Power Plants," JSME S NF1-2009, The Japan Society of Mechanical Engineers, Tokyo, Japan). However, mechanism causing fatigue life reduction remains to be cleared. As one of the possible approaches to examine the underlying mechanism of environmental effect, the authors focused on the effect of plastic strain, because it could lead microstructural evolution on the material. In addition, in the case of stress corrosion cracking (SCC), it is well known that the strain-hardening prior to exposure to the primary water can lead to remarkable increase of the susceptibility to cracking (Vaillant et al., 2009, “Stress Corrosion Cracking Propagation of Cold-Worked Austenitic Stainless Steels in PWR Environment,” 14th International Conference on Environmental Degradation of Materials in Nuclear Power Systems; Couvant et al., 2009, "Development of Understanding of the Interaction Between Localized Deformation and SCC of Austenitic Stainless Steels Exposed to Primary PWR Environment," 14th International Conference on Environmental Degradation of Materials in Nuclear Power Systems). However, its effect on fatigue life has not necessarily been cleared yet. The main effort in this study addressed the effect of the prior strain-hardening on low cycle fatigue life in the primary water. A plate of 304LSS was strain hardened by cold rolling or tension prior to fatigue testing. The tests were performed under axial strain control at 300 °C in primary water including B/Li and hydrogen, and in air. The effect on environmental fatigue life was investigated through a comparison of Fen in experiments and in regulations, and also the effect on the fatigue limit defined at 106 cycles was discussed.

scholarly journals PWR Effect On Crack Initiation Under Equi-biaxial Loading

2018 ◽  
Vol 165 ◽  
pp. 16005
Author(s):  
Cédric Gourdin ◽  
Hager Dhahri ◽  
Grégory Perez ◽  
Stéphan Courtin ◽  
Jean-Christophe Le Roux ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Biaxial Loading ◽  
Austenitic Stainless Steels ◽  
Complex Loading ◽  
Fatigue Curve ◽  
Structural Effect ◽  
Mean Values ◽  
Term Operation ◽  
New Device ◽  
Penalty Factor

The lifetime extension of the nuclear power stations is considered as 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 mechanical loads, multiaxial, with nonzero mean values associated with temperature fluctuations and also PWR environment. Based on more recent fatigue data (including tests at 300°C in air and 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 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 the effect of PWR environment on disk specimen. This new device combines the structural effect like equi-biaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.

Sign in / Sign up

Export Citation Format

Share Document