Review and Consideration of Unsettled Problems on Evaluation of Fatigue Damage in LWR Water

2006 ◽  
Vol 129 (1) ◽  
pp. 186-194
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi
Keyword(s):  
Fatigue Life ◽  
Mechanical Test ◽  
Low Alloy Steels ◽  
Test Results ◽  
Considerable Effort ◽  
Test Conditions ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Life Reduction ◽  
Year 2000

Reduction in the fatigue life of structural materials of nuclear components in Light Water Reactor (LWR) water was initially detected and examined by the authors in the 1980s, who subsequently directed considerable effort to the development of a method for evaluating this reduction quantitatively. Since the first proposal of equations to calculate environmental fatigue life reduction for carbon and low-alloy steels was published in 1985 by Higuchi and Sakamoto (J. Iron Steel Inst. Jpn. 71, pp. 101–107), many revisions were made based on a lot of additional fatigue data in various environmental and mechanical test conditions. The latest models for evaluation using Fen of the environmental fatigue life correction factor were proposed for carbon and low alloy steels in the year 2000 and for austenitic stainless steel, in 2002. Fen depends on some essential variables such as material, strain rate, temperature, dissolved oxygen and sulfur concentration in steel. The equation for determining Fen is given by each parameter for each material. These models, having been developed three to five years ago, should be properly revised based on new test results. This paper reviews and discusses five major topics pertinent to such revision.

Review and Consideration of Unsettled Problems on Evaluation of Fatigue Damage in LWR Water

2005 ◽  
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi
Keyword(s):  
Fatigue Life ◽  
Mechanical Test ◽  
Low Alloy Steels ◽  
Test Results ◽  
Considerable Effort ◽  
Test Conditions ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Life Reduction ◽  
Year 2000

Reduction in the fatigue life reduction of structural materials of nuclear components in LWR water was initially detected and examined by the authors in the 1980s, who subsequently directed considerable effort to the development of a method for evaluating this reduction quantitatively. Following the establishment of equations to calculate environmental fatigue life reduction for carbon and low alloy steels in 1985 by Higuchi and Sakamoto [1], appeared based on numerous new fatigue data obtained under various environmental and mechanical test conditions. The latest models for evaluation using Fen of the environmental fatigue life correction factor were proposed for carbon and low alloy steels in the year 2000 and for austenitic stainless steel, in 2002. Fen depends on some essential variables such as material, strain rate, temperature, dissolved oxygen and sulfur concentration in steel. The equation for determining Fen is given by each parameter for each material. These models, having been developed three to five years ago, should be properly revised based on new test results. This paper reviews and discusses five major topics pertinent to such revision.

Revised Proposal of Fatigue Life Correction Factor Fen for Carbon and Low Alloy Steels in LWR Water Environments

2004 ◽  
Vol 126 (4) ◽  
pp. 438-444 ◽  
Author(s):  
Makoto Higuchi
Keyword(s):  
Fatigue Life ◽  
Correction Factor ◽  
Light Water Reactor ◽  
Low Alloy Steels ◽  
Light Water ◽  
High Temperature Water ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Life Reduction ◽  
Temperature Water

The fatigue life of carbon and low alloy steels decreases with reduction in strain rate in high temperature water such as in the case of a light water reactor coolant. The fatigue life reduction also depends on temperature and dissolved oxygen. The fatigue life correction factor Fen has been proposed as a method to assess the fatigue life reduction in such environments. Three different models for calculating Fen for carbon and low alloy steels have been proposed by Higuchi et al., Chopra et al., and Mehta. These models were compared using considerable environmental fatigue data that were tested and published in Japan and USA and piled up in the database “JNUFAD” by the author. These models give somewhat different results in the specific conditions and a revised model for calculating Fen is thus proposed by remedying the particular drawbacks of each. In this model, the same formula is used for carbon and low alloy steels and S*,T*,O*, and ε˙* are adopted in the formula after reevaluating every parameter. The revised proposal shows better correlation with the test data than the previous models.

Proposal of Fatigue Life Equations for Carbon and Low-Alloy Steels and Austenitic Stainless Steels as a Function of Tensile Strength

2013 ◽  
Author(s):  
Hiroshi Kanasaki ◽  
Makoto Higuchi ◽  
Seiji Asada ◽  
Munehiro Yasuda ◽  
Takehiko Sera
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Room Temperature ◽  
Austenitic Stainless Steels ◽  
Low Alloy Steels ◽  
Strength Based ◽  
Fatigue Data ◽  
Current Design ◽  
Alloy Steels

Fatigue life equations for carbon & low-alloy steels and also austenitic stainless steels are proposed as a function of their tensile strength based on large number of fatigue data tested in air at RT to high temperature. The proposed equations give a very good estimation of fatigue life for the steels of varying tensile strength. These results indicate that the current design fatigue curves may be overly conservative at the tensile strength level of 550 MPa for carbon & low-alloy steels. As for austenitic stainless steels, the proposed fatigue life equation is applicable at room temperature to 430 °C and gives more accurate prediction compared to the previously proposed equation which is not function of temperature and tensile strength.

Revised and New Proposal of Environmental Fatigue Life Correction Factor (Fen) for Carbon and Low-Alloy Steels and Nickel Base Alloys in LWR Water Environments

2006 ◽  
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi ◽  
Akihiko Hirano ◽  
Yuichiro Nomura
Keyword(s):  
Fatigue Life ◽  
Dissolved Oxygen ◽  
Strain Rate ◽  
Test Data ◽  
Base Alloy ◽  
Low Cycle Fatigue ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Nickel Base ◽  
Fatigue Life Reduction

Low cycle fatigue life of carbon and low alloy steels reduces remarkably as functions of strain rate, temperature, dissolved oxygen and sulfur in steel in high temperature water simulating LWR coolant. A model for predicting such fatigue life reduction was first proposed in the early 1980s and since then has been revised several times. The existing model established in 2000 is used for the MITI Guideline [6] and the TENPES Guideline [7] which stipulate procedures for evaluating environmental fatigue damage at LWR plants in Japan. This paper presents the most recent environmental fatigue evaluation model derived based on additional fatigue data provided by the EFT Project over the past five years. This model differs not significantly with previous version but does provide more accurate equations for the susceptibility of fatigue life to sulfur in steel, strain rate, temperature and dissolved oxygen. Test data on environmental fatigue of nickel base alloys are available only to a limited extent and there is yet no model for predicting fatigue life reduction in such an environment. The EFT Project has made available considerable environmental fatigue test data and developed a new model for calculating Fen of nickel base alloys. The contribution of environment to fatigue of nickel base alloy is much less compared to that in austenitic stainless steel.

Evaluation of Fatigue Damage in LWR Water With and Without Threshold and Moderation Factor

2003 ◽  
Author(s):  
Makoto Higuchi ◽  
Kazuya Tsutsumi ◽  
Katsumi Sakaguchi
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Power Plants ◽  
Light Water Reactor ◽  
Low Alloy Steels ◽  
Light Water ◽  
Water Reactor ◽  
Fatigue Data ◽  
Fatigue Life Reduction

During the past twenty years, the fatigue initiation life of LWR structural materials, carbon, low alloy and stainless steels has been shown to decrease remarkably in the simulated LWR (light water reactor) coolant environments. Several models for evaluating the effects of environment on fatigue life reduction have been developed based on published environmental fatigue data. Initially, based on Japanese fatigue data, Higuchi and Iida proposed a model for evaluating such effects quantitatively for carbon and low alloy steels in 1991. Thereafter, Chopra et al. proposed other models for carbon, low alloy and stainless steels by adding American fatigue data in 1993. Mehta developed a new model which features the threshold concept and moderation factor in Chopra’s model in 1995. All these models have undergone various revisions. In Japan, the MITI (Ministry of International Trade and Industry) guideline on environmental fatigue life reduction for carbon, low alloy and stainless steels was issued in September 2000, for evaluating of aged light water reactor power plants. The MITI guideline provide equations for calculations applicable only to stainless steel in PWR water and consequently Higuchi et al. proposed in 2002 a revised model for stainless steel which incorporates new equations for evaluation of environmental fatigue reduction in BWR water. The paper compares the latest versions of these models and discusses the conservativeness of the models by comparison of the models with available test data.

Observation of Fatigue Crack Initiation and Propagation for Carbon and Low-Alloy Steels in Oxygenated Water at Elevated Temperature

2006 ◽  
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Elevated Temperature ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Low Alloy Steels ◽  
Test Conditions ◽  
Alloy Steels ◽  
Crack Initiation Life ◽  
Temperature Water

Low cycle fatigue life of structural materials in LWR plants decreases remarkably in elevated temperature water depending on strain rate, temperature, water chemistry and material properties. The maximum reduction rate in fatigue life for carbon and low alloy steels is over 100 in severe conditions. Fatigue life is composed of fatigue crack initiation life and consequent propagation life. It is important to know the proportion of crack initiation life to propagation life in water environment when developing a model to estimate fatigue crack initiation life. The beachmark imprinting method was used to monitor fatigue crack initiation and consequent propagation. Environmental test conditions varied widely from severely accelerated conditions of high temperature and dissolved oxygen to mild conditions of lower temperature and oxygen. Fatigue crack initiation life could be determined using the beachmark imprinting method for all test conditions. Based on obtained test results, the susceptibility of each parameter in NWC and the relationships between NWC/NW and environmental fatigue life correction factor Fen under various conditions are discussed, but a good relationship could not be detected due to widely scattered data and a model to predict fatigue crack initiation life could not be proposed.

scholarly journals Tensile Testing of Carbon Steel in High Pressure Hydrogen

2007 ◽  
Author(s):  
Andrew Duncan ◽  
Poh-Sang Lam ◽  
Thad Adams
Keyword(s):  
High Pressure ◽  
Carbon Steel ◽  
Alternative Energy ◽  
Room Temperature ◽  
Structural Integrity ◽  
Mechanical Test ◽  
Low Alloy Steels ◽  
Test Results ◽  
Alloy Steels ◽  
Pressure Hydrogen

An infrastructure of new and existing pipelines and systems will be required to carry and to deliver hydrogen as an alternative energy source under the hydrogen economy. Carbon and low alloy steels of moderate strength are currently used in hydrogen delivery systems as well as in the existing natural gas systems. It is critical to understand the material response of these standard pipeline materials when they are subjected to pressurized hydrogen environments. The methods and results from a testing program to quantify hydrogen effects on mechanical properties of carbon steel pipeline and pipeline weld materials are provided. Tensile properties of one type of steel (A106 Grade B) in base metal, welded and heat affected zone conditions were tested at room temperature in air and high pressure (10.34 MPa or 1500 psig) hydrogen. A general reduction in the materials ability to plastically deform was noted in this material when specimens were tested in hydrogen. Furthermore, the primary mode of fracture was changed from ductile rupture in air to cleavage with secondary tearing in hydrogen. The mechanical test results will be applied in future analyses to evaluate service life of the pipelines. The results are also envisioned to be part of the bases for construction codes and structural integrity demonstrations for hydrogen service pipeline and vessels.

Reactor Water Environmental Fatigue

2003 ◽  
Author(s):  
William J. O’Donnell
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Corrosion Fatigue ◽  
Low Alloy Steels ◽  
Nuclear Plants ◽  
Alloy Steels ◽  
Stress Concentration Factors ◽  
Rapid Transients ◽  
License Renewal ◽  
Fatigue Life Reduction

Existing nuclear plants were designed based on fatigue data obtained entirely in air environments. We now seek to extend the life of these plants, recognizing that many conservatisms were included in the fatigue stress calculations, stress concentration factors and lumped transients. Since we know how these plants were operated, we can quantify the cyclic rates and coolant chemistry. This makes it feasible to use environmental fatigue life evaluation technology which takes credit for the reduced corrosion fatigue damage which occurs during more rapid transients and for reduced dissolved oxygen levels which produce lesser corrosion fatigue damage in carbon and low alloy steels. Accordingly, the use of Fen environmental fatigue life reduction factors which depend on the cyclic rates, coolant chemistry and temperature are quite useful for evaluating the safe fatigue life of aging plants and for license renewal.

Development of New Design Fatigue Curves in Japan: Proposal of a New Fatigue Evaluation Method

2018 ◽  
Author(s):  
Seiji Asada ◽  
Akihiko Hirano ◽  
Toshiyuki Saito ◽  
Yasukazu Takada ◽  
Hideo Kobayashi
Keyword(s):  
Stainless Steels ◽  
Evaluation Method ◽  
Austenitic Stainless Steels ◽  
Fatigue Tests ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Stress Effect ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Evaluation

In order to develop new design fatigue curves for carbon steels & low-alloy steels and austenitic stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). The study on design fatigue curves was actively performed in the subcommittees. In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database (≈6000 data) was constructed and the accurate best-fit curves of carbon steels & low-alloy steels and austenitic stainless steels were developed. Design factors were investigated. Also, a Japanese utility collaborative project performed large scale fatigue tests using austenitic stainless steel piping and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect, surface finish effect and size effect. Those test results were provided to the subcommittee and utilized the above studies. Based on the above studies, a new fatigue evaluation method has been developed.

Effect of Plasticity on Fatigue Life of Welded Nuclear Component With Local Brittle Zone

2003 ◽  
Author(s):  
Jong-Sung Kim ◽  
Se-Hwan Lee ◽  
Tae-Eun Jin
Keyword(s):  
Fatigue Life ◽  
Tensile Properties ◽  
Stress Amplitude ◽  
Low Alloy Steels ◽  
The Finite Element Method ◽  
Fatigue Lifetime ◽  
Nuclear Component ◽  
Alloy Steels ◽  
Brittle Zone ◽  
Produce Strain

The local brittle zone (LBZ), which has lower tensile properties as well as lower fracture toughness than base metal and weldment, can occur on the heat affected zone (HAZ) of some nuclear components made of low alloy steels due to the carbide coarsening by multi-pass welding and post-weld heat treatment. These variations of material strengths across the welds due to the LBZ can produce strain concentrations when the stress amplitude is large enough to cause cyclic plastic flow. But, it is difficult to find the previous researches about a relation between the fatigue life of LBZ on real nuclear components and plasticity. So, in this study, the microstructures and tensile properties of HAZ on nuclear components are predicted by using the semi-analytical method, and the fatigue lifetimes of welds on nuclear components with the LBZ are evaluated by the finite element method considering the local plasticity and the variations of tensile properties, and the fatigue analysis procedure of ASME B&PV Code Sec.III. Finally, the effect of LBZ on nuclear components on fatigue lifetime is reviewed.

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