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.

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.

Tensile and Fatigue Failure of 17-4 PH Martensitic Stainless Steels in Presence of Hydrogen Depending on Frequency and Heat Treatment

2020 ◽  
Author(s):  
Jean-Gabriel Sezgin ◽  
Junichiro Yamabe
Keyword(s):  
Fatigue Life ◽  
Hydrogen Gas ◽  
Relative Reduction ◽  
Low Alloy Steels ◽  
Notched Specimen ◽  
Acceleration Ratio ◽  
Paris Law ◽  
Alloy Steels ◽  
Life Tests ◽  
Surface Morphologies

Abstract Slow-strain-rate tensile (SSRT) and fatigue-life tests were carried out on 17-4PH martensitic stainless steel with an ultimate tensile strength (UTS) of ∼ 1 GPa. The specimens were precharged by exposure to hydrogen gas at pressures of 35 MPa or 100 MPa at 270°C for 200 h. The SSRT tests used smooth axisymmetric specimens made of two grades of 17-4PH (H1150 and H900) differing by the UTS due to their thermal history. No degradation of the UTS was observed for both H1150 and H900 grades. However, the relative reduction in area (RRA) was 0.31 for H1150 or 0.11 for H900, translating a difference in their hydrogen sensitivity. Both grades presented different fracture-surface morphologies: a mixture of quasi-cleavage (QC) and intergranular (IG) facets for H1150 and cleavage (C) facets for H900. Circumferentially-notched axisymmetric specimens made of H1150 were used for the fatigue-life tests in the [10−3 Hz;10 Hz] frequency range. Our previous study on low-alloy steels with UTS of around 950 MPa demonstrates that the fatigue life of a circumferentially-notched specimen with a sharp notch can be successfully predicted from the fatigue crack growth (FCG) property following the Paris law. This study used the same specimen geometry and a BCC steel with a similar UTS value; hence, the FCG behavior was investigated from the fatigue-life test of the notched specimen. As a result, the degradation of fatigue lives attributed to the FCG acceleration was observed in presence of hydrogen. A FCG acceleration ratio bounded to 30 was observed in the high-cycle regime, accompanied by QC facets. A FCG acceleration ratio bounded to ∼100 was observed in the low-cycle regime, accompanied by QC and IG facets. A FCG model accounting for the interaction of elementary mechanisms was proposed and succeeded in predicting the FCG acceleration ratio observed on H1150. This model was also successfully applied to a low-alloy steel with a comparable UTS (1002 MPa) tested in gaseous hydrogen.

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.

scholarly journals DURABILITY OF THE OIL PIPELINE SYSTEMS UNDER ENVIRONMENTAL EFFECTS

2019 ◽  
Vol 18 (4) ◽  
pp. 564-576
Author(s):  
Sabah M Beden ◽  
Ali A Battawi ◽  
A J Shahrum
Keyword(s):  
Fatigue Life ◽  
Environmental Effects ◽  
Gaseous Hydrogen ◽  
Mechanical Resistance ◽  
Low Alloy Steels ◽  
Metallic Materials ◽  
Oil Pipeline ◽  
System A ◽  
Alloy Steels ◽  
High Level

Recent discoveries of petroleum and gas reserves in environments with severe operationalconditions metallic materials, carbon and low alloy steels, have pushed and prompted theneed to find alternatives. The presence of gaseous hydrogen may cause the suffering ofhydrogen damage and embrittlement. The effect of hydrogen and temperature on fatigue lifeproperties, have pushed the utilization of steel procurement specification even stricter thanthey used to be. The main modifications concern the mechanical resistance, toughness at lowtemperatures weld ability and resistance to embrittlement related to hydrogen.Aiming to enhance the reliability and operation of pipelines system, a study based on theelastoplastic fracture was carried out to determine high level prediction for the fatigue life,as well as to evidence the toughness resistance of the used materials. The materials testedhere are API 5L X70 and X100 micro alloyed steels. Hydrogen had affecting the materialproperties, which are reducing the toughness and an influence spotted in Charpy tests.

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.

BETHLEHEM HOT-ROLLED SHEET XF SERIES

Alloy Digest ◽  
1992 ◽  
Vol 41 (1) ◽  
Keyword(s):  
Tensile Properties ◽  
High Strength ◽  
Rolled Sheet ◽  
Low Alloy Steels ◽  
Bend Strength ◽  
Bethlehem Steel Corporation ◽  
Alloy Steels ◽  
Steel Corporation ◽  
Hot Rolled ◽  
Minimum Yield

Abstract BETHLEHEM HOT-ROLLED SHEET XF SERIES alloys B50XF, B60XF, B70XF and B80XF are high strength low alloy steels. The numbers in the alloy designations refer to minimum yield strengths. The steels are made using ladle desulfurization which virtually eliminates harmful stringer type inclusions. The steels were developed for parts that are difficult to form using conventional high strength low alloy steels. This datasheet provides information on composition, microstructure, hardness, tensile properties, and bend strength as well as deformation, and fatigue. It also includes information on forming and machining. Filing Code: SA-383. Producer or source: Bethlehem Steel Corporation. Originally published August 1981, Bethlehem B50XF thru B80XF.

CYCLOPS L2

Alloy Digest ◽  
1977 ◽  
Vol 26 (10) ◽  
Keyword(s):  
Fracture Toughness ◽  
Physical Properties ◽  
Tensile Properties ◽  
Tool Steel ◽  
Heat Treating ◽  
Low Alloy Steels ◽  
Good Resistance ◽  
Alloy Steels ◽  
Hardened Condition

Abstract CYCLOPS L2 is the tool steel counterpart of one of the widely used chromium-vanadium low-alloy steels. It exhibits exceptional strength, toughness and resistance to fatigue; it may be used where these characteristics are more important than extreme hardness. Cyclops L2 has only modest hardenability but it has good resistance to abrasion and wear in the hardened condition. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, and joining. Filing Code: TS-325. Producer or source: Cyclops Corporation.

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