Fatigue of Stainless Steel Components: Toward Codified Rules Improvements

2013 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Environmental Effects ◽  
Stainless Steels ◽  
High Cycle Fatigue ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Correction Factors ◽  
Cycle Fatigue ◽  
The Past

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of French Nuclear Codes: RCC-M, RSE-M and RCC-MRx. This paper will present comments and proposals for development of these rules associated to Gaps and Needs in order to finalize and justify the AFCEN Codes new rules. Recently 3 new international R&D results confirm possible un-conservative fatigue material data: - High cycle fatigue in air for stainless steel, - Environmental effects on fatigue S-N curve for all materials, and in particular stainless steels, - Fatigue Crack Growth law under PWR environment for stainless steel. In front of these new results, AFCEN is working on a 1st set of rules based on existing knowledge: - Air fatigue curve: mean and design - PWR Environmental effects with detrimental correction factors A periodic up-dating of AFCEN proposed rules will be done using French and International R&D programs with a particular attention on harmonization with other Code rules developed in USA, Japan and Germany, in particular.

Fatigue of Stainless Steel Components: Toward Codified Rules Improvements

2013 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Environmental Effects ◽  
Stainless Steels ◽  
High Cycle Fatigue ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
The Past

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of RCC-M, RSE-M and RCC-MRx. This paper will present comments and proposals for development of these rules associated to Gaps and Needs in order to finalize and justify the AFCEN Codes new rules. Recently 3 new international R&D results confirm possible un-conservative fatigue material data: - High cycle fatigue in air for stainless steel, - Environmental effects on fatigue S-N curve for all materials, and in particular stainless steels, - Fatigue Crack Growth law under PWR environment for stainless steel. In front of these new results, AFCEN is working on a 1st set of rules based on existing knowledge: - Air fatigue curve - PWR Environmental effects A periodic up-dating of AFCEN proposed rules will be done using French and International R&D programs with a particular attention on harmonization with other Code rules developed in USA, Japan and Germany, in particular.

Status of French Road Map to Improve Environmental Fatigue Rules

2012 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stainless Steel ◽  
Environmental Effects ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Stress Effects ◽  
The Past ◽  
Road Map ◽  
The Status ◽  
Load Effects ◽  
Section Viii

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of RCC-M and ASME Codes [1, 2]. This paper will present the major technical improvements to obtain reasonable evaluation of potential fatigue damage through EDF road map. Recently new results [3] confirm possible un-conservative fatigue material data: - High cycle fatigue in air for stainless steel, - Environmental effects on fatigue S-N curve for all materials - Fatigue Crack Growth law under PWR environment for stainless steel. In front of these new results, EDF has developed a “Fatigue Road Map” to improve the different steps of Codified fatigue rules. A periodic up-dating of proposed rules in the different French Codes: RCC-M, RCC-MRx and RSE-M with research of harmonization with other Code rules developed in USA, Japan and Germany in particular, will be done on a yearly basis. During the past 15 years, many results have been obtained through fatigue tests of stainless steel materials: - mean and design fatigue curve in air, - environmental effects on fatigue curves, - plasticity effects, - bi-axial load effects, - mean stress effects, - stress indices, - transferability from small to large specimen, - weld versus base metal. In parallel, many new developments have been made in non-nuclear pressure equipment industry: like the reference stress of ASME Section VIII or the structural stress of EN 13445. These methods are mainly well adapted to fatigue pressure cycling. In front of that situation, the French nuclear code organization needs to propose reliable rules for new design and for operating plants. Different proposals are under discussion and the status of the EDF proposals are presented in the paper. The consequences could be important for the utilities because a large part of the in-service inspection program is connected to some fatigue usage factor level between 0.5 and 1.

Study on Fatigue Behaviors of 0Cr21Mn17Mo2N0.83 High Nitrogen Stainless Steels

2020 ◽  
Vol 861 ◽  
pp. 89-94
Author(s):  
You Yang ◽  
Wei Feng Tang
Keyword(s):  
Solid Solution ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Fracture ◽  
Stainless Steels ◽  
Room Temperature ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
High Nitrogen

High cycle fatigue behaviors of 0Cr21Mn17Mo2N0.83 high nitrogen stainless steels at forged and solid solution state were investigated. High cycle fatigue tests were carried out up to 107cycles at a stress ratio R=0.1 and frequency of 70Hz on specimens using a high frequency fatigue machine. Fatigue fracture surfaces of specimens that in the high cycle fatigue tests were observed using a scanning electron microscope for revealing the micro-mechanisms of fatigue crack initiation and propagation. The results showed that the fatigue limit of test alloys at room temperature is 865.25 MPa (as-forged alloy) and 736.10MPa (solid solution alloy), respectively. The micro-fatigue fracture surface of the test alloys included three representative regions. These regions are fatigue initiation area, fatigue crack propagation area and fatigue fracture area. Fatigue cracks of the test alloys initiate principally at the precipitates, inclusion or uneven stress concentration sites of alloy surface, and propagate along the grain boundary. The fatigue striations of fatigue crack propagation area are very clear. The fatigue fracture of test specimens show the rupture characteristics of quasi cleavage and dimple fracture. The room temperature fatigue properties of as-forged alloy are generally higher than that of the solid solution high nitrogen stainless steel according to the S-N curves fitting results.

EDF/NRC High-Cycle Fatigue Database Proposal

2015 ◽  
Author(s):  
T. P. Métais ◽  
G. Stevens ◽  
G. Blatman ◽  
J. C. Le Roux ◽  
R. L. Tregoning
Keyword(s):  
Stainless Steels ◽  
Data Exchange ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Austenitic Stainless Steels ◽  
Nuclear Regulatory Commission ◽  
Fatigue Curve ◽  
Research Data ◽  
Cycle Fatigue ◽  
Fatigue Data

Revised fatigue curves for austenitic stainless steels are currently being considered by several organizations in various countries, including Japan, South Korea, and France. The data available from laboratory tests indicate that the mean air curve considering all available austenitic material fatigue data may be overly conservative compared to a mean curve constructed from only those data representative of a particular type of material. In other words, developing separate fatigue curves for each of the different types of austenitic materials may prove useful in terms of removing excess conservatism in the estimation of fatigue lives. In practice, the fatigue curves of interest are documented in the various international design codes. For example, in the 2009 Addenda of Section III of the ASME Boiler and Pressure Vessel (BPV) Code [1], a revised design air fatigue curve for austenitic materials was implemented that was based on NRC research models [2]. More recently, in Japan, various industrial groups have joined their efforts to create the Design Fatigue Curve Sub-committee (DCFS) with the objective to reassess the fatigue curves [3]. In France, EDF/AREVA and CEA are developing a new fatigue curve for austenitic stainless steels [4]. More specifically, in 2014, EDF presented a paper on high-cycle fatigue analysis which demonstrated that the factor on the strain amplitude could be reduced from 2 to 1.4 for the RCC-M austenitic stainless steel grades [5]. Recently, discussions between EDF and the U.S. Nuclear Regulatory Commission (NRC) have led both parties to recognize that there is a need to exchange worldwide research data from fatigue testing to promote a common, vetted database available to all researchers. These discussions have led EDF and NRC to pursue a collaborative agreement and associated fatigue data exchange, with the intent to assemble all available fatigue data for austenitic materials into a standardized format. The longer term objective is to perform common analyses on the consolidated set of data. This paper summarizes the intent and of the preliminary results of this cooperation and also provides insights from both organizations on possible future activities and participation in the global exchange of fatigue research data.

High-Cycle-Fatigue Characterization of an Additive Manufacturing 17-4 PH Stainless Steel

2021 ◽  
Vol 877 ◽  
pp. 49-54
Author(s):  
Lorenzo Maccioni ◽  
Lorenzo Fraccaroli ◽  
Yuri Borgianni ◽  
Franco Concli
Keyword(s):  
Stainless Steel ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Crack Nucleation ◽  
High Surface ◽  
Testing Machine ◽  
Volume Ratio ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Traction Test

On the one hand, many mechanical components manufactured through additive technologies are optimized in terms of stiffness/weight or strength/weight thanks to lattice structures. On the other hand, the high complexity of these components often impedes further finishing operations and, therefore, the fatigue strength can be compromised. The high surface to volume ratio together with the high roughness, typical of additive manufactured components, promote the crack nucleation. In this paper, the High-Cycle-Fatigue (HCF) behavior of the 17-4 PH stainless steel (SS) was characterized. Cylindrical samples, manufactured via Selective Laser Melting (SLM) with an EOS M280, were tested in the as-build condition through a STEPLab UD04 fatigue-testing machine. In particular, a preliminary quasi-static traction test was performed on a sample to obtain the yield strength (σY = 570 MPa) and the ultimate tensile strength (UTS = 1027 MPa). Fatigue tests were performed on samples at different stress levels in order to characterize the whole Stress-Number of cycles (S-N) curve (Wöhler diagram). More specifically, the stair-case method combined with the Dixon approach were exploited to calculate the fatigue limit (σF = 271 MPa). The obtained results were compared with those present in literature for the same material and they are coherent with previous researches

scholarly journals Short/small fatigue crack growth, thresholds and environmental effects: a tale of two engineering paradigms

2021 ◽  
Vol 39 (2) ◽  
pp. 165-175
Author(s):  
Russell J. H. Wanhill ◽  
Stefanie E. Stanzl-Tschegg
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Steam Turbine ◽  
Crack Growth ◽  
Environmental Effects ◽  
High Cycle Fatigue ◽  
Materials Science ◽  
Fatigue Cracks ◽  
Cycle Fatigue ◽  
Metal Fatigue

Abstract This paper results from mutual discussions on the review ‘When do small fatigue cracks propagate and when are they arrested?’ in Corrosion Reviews, 2019; 37(5): 397–418. These discussions have arisen from the two engineering paradigms characterizing our fatigue research: (i) an aerospace research and technology remit for metallic airframes, and (ii) a materials science research programme supporting a methodology for steam turbine low pressure (LP) blade operations. In our opinion, this paper is of interest for other investigators of metal fatigue with respect to design requirements, life predictions and assessments. In more detail, the paper considers the fatigue design methodologies for airframes and steam turbine LP blades. This includes short/small fatigue cracks, fatigue crack growth thresholds, high-cycle fatigue (HCF) and very-high-cycle fatigue (VHCF), and the relevance of environmental effects (corrosion and corrosion fatigue).

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