The update of the ASME III design fatigue curve for stainless steel in conjunction with the Fen model described in the NUREG/CR-6909 report has been criticized since publication. Data used to develop curves and models raises more questions than it answers. Material testing in a simulated light water reactor environment is difficult due to the temperature and pressure involved. The experimental challenge makes it tempting to take shortcuts where they should least be taken. Facing and overcoming the challenges, direct strain-controlled fatigue testing has been performed at VTT using a unique tailored-for-purpose EAF facility. The applicable ASTM standards E 606 and E1012 are followed to provide results that are directly compatible with ASME Code Section III. Several earlier PVP papers (PVP2016-63291, PVP2017-65374) report lower than calculated experimental Fen factors for stabilized stainless steels. In this paper new results, in line with the previous years’ conclusions, are presented for nonstabilized AISI 304L tested with dual strain rate waveforms. To model environmental effects more accurately, an approach accounting for the damaging effect of plastic strain is proposed. A draft Fen model, similar in structure to the NUREG model but with additional parameters, is shown to significantly improve the accuracy of Fen prediction.
{"title":"Low Cycle Fatigue (EAF) of AISI 304L and 347 in PWR Water","authors":"T. Seppänen, J. Alhainen, E. Arilahti, J. Solin","doi":"10.1115/PVP2018-84197","DOIUrl":"https://doi.org/10.1115/PVP2018-84197","url":null,"abstract":"The update of the ASME III design fatigue curve for stainless steel in conjunction with the Fen model described in the NUREG/CR-6909 report has been criticized since publication. Data used to develop curves and models raises more questions than it answers.\u0000 Material testing in a simulated light water reactor environment is difficult due to the temperature and pressure involved. The experimental challenge makes it tempting to take shortcuts where they should least be taken. Facing and overcoming the challenges, direct strain-controlled fatigue testing has been performed at VTT using a unique tailored-for-purpose EAF facility. The applicable ASTM standards E 606 and E1012 are followed to provide results that are directly compatible with ASME Code Section III.\u0000 Several earlier PVP papers (PVP2016-63291, PVP2017-65374) report lower than calculated experimental Fen factors for stabilized stainless steels. In this paper new results, in line with the previous years’ conclusions, are presented for nonstabilized AISI 304L tested with dual strain rate waveforms.\u0000 To model environmental effects more accurately, an approach accounting for the damaging effect of plastic strain is proposed. A draft Fen model, similar in structure to the NUREG model but with additional parameters, is shown to significantly improve the accuracy of Fen prediction.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131056963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Dulieu, V. Lacroix, K. Hasegawa, Yinsheng Li, B. Strnadel
When multiple surface flaws are detected in pressure components, their potential interaction is to be assessed to determine whether they must be combined or evaluated independently of each other. This assessment is performed through the flaw characterization rules of Fitness-For-Service (FFS) Codes. However, the specific combination criteria of surface flaws are different among the FFS Codes. Most of the time, they consist of simple criteria based on distance between flaws and flaw depth. This paper aims at proposing alternative characterization rules reflecting the actual level of interaction between surface planar flaws. This interaction depends on several parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. Thanks to numerous three-dimensional XFEM simulations, best suited combination criteria for surface planar flaws are derived by considering the combined influence of these parameters.
{"title":"Alternative Characterization Rules for Multiple Surface Planar Flaws","authors":"P. Dulieu, V. Lacroix, K. Hasegawa, Yinsheng Li, B. Strnadel","doi":"10.1115/PVP2018-84960","DOIUrl":"https://doi.org/10.1115/PVP2018-84960","url":null,"abstract":"When multiple surface flaws are detected in pressure components, their potential interaction is to be assessed to determine whether they must be combined or evaluated independently of each other. This assessment is performed through the flaw characterization rules of Fitness-For-Service (FFS) Codes. However, the specific combination criteria of surface flaws are different among the FFS Codes. Most of the time, they consist of simple criteria based on distance between flaws and flaw depth. This paper aims at proposing alternative characterization rules reflecting the actual level of interaction between surface planar flaws. This interaction depends on several parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. Thanks to numerous three-dimensional XFEM simulations, best suited combination criteria for surface planar flaws are derived by considering the combined influence of these parameters.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122167071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Limit load solutions have been applied to estimate the collapse load of a component made of ductile material. Worldwide maintenance codes for power plants, such as ASME Boiler and Pressure Vessels Code, Section XI, and JSME fitness-for-service code, describe limit load solutions under the assumption of a single flaw. Detected flaws are, however, not always a single flaw, and adjacent flaws due to stress corrosion cracking have been detected in power plants. Thus, development of a limit load solution to estimate the collapse load in the case of multiple flaws remains an issue of structural integrity evaluation. Under the aim of developing a method for evaluating the effect of multiple flaws on collapse load as a part of a limit load solution, fracture tests of flat plates and pipes with multiple flaws were conducted. Although experimental approaches have been attempted to establish the evaluation method, further efforts are required to incorporate the evaluation procedure into a code rule. Effective parameters for considering reduction of collapse load on the basis of test results for specimens with multiple flaws were identified. Test results clearly show a correlation between collapse load and ratios of net-section areas. This correlation leads to the conclusion that distance parameters and flaw length of a smaller flaw determine the existence of an effect on the collapse load by multiple flaws. To investigate the physical sense of the correlation, finite element analysis (FEA) was performed. The FEA results show that strain distributions at the flaw tip under several conditions correspond at the time of maximum load of the fracture tests regardless of the effect of multiple flaws. Also according to the FEA results, the extent of the strain field is linearly proportional to flaw length. These FEA results are consistent with the correlation obtained by the test results.
{"title":"Limit Load Solution of Non-Aligned Multiple Flaws","authors":"Fuminori Iwamatsu, K. Miyazaki, K. Saito","doi":"10.1115/PVP2018-84809","DOIUrl":"https://doi.org/10.1115/PVP2018-84809","url":null,"abstract":"Limit load solutions have been applied to estimate the collapse load of a component made of ductile material. Worldwide maintenance codes for power plants, such as ASME Boiler and Pressure Vessels Code, Section XI, and JSME fitness-for-service code, describe limit load solutions under the assumption of a single flaw. Detected flaws are, however, not always a single flaw, and adjacent flaws due to stress corrosion cracking have been detected in power plants. Thus, development of a limit load solution to estimate the collapse load in the case of multiple flaws remains an issue of structural integrity evaluation. Under the aim of developing a method for evaluating the effect of multiple flaws on collapse load as a part of a limit load solution, fracture tests of flat plates and pipes with multiple flaws were conducted. Although experimental approaches have been attempted to establish the evaluation method, further efforts are required to incorporate the evaluation procedure into a code rule.\u0000 Effective parameters for considering reduction of collapse load on the basis of test results for specimens with multiple flaws were identified. Test results clearly show a correlation between collapse load and ratios of net-section areas. This correlation leads to the conclusion that distance parameters and flaw length of a smaller flaw determine the existence of an effect on the collapse load by multiple flaws. To investigate the physical sense of the correlation, finite element analysis (FEA) was performed. The FEA results show that strain distributions at the flaw tip under several conditions correspond at the time of maximum load of the fracture tests regardless of the effect of multiple flaws. Also according to the FEA results, the extent of the strain field is linearly proportional to flaw length. These FEA results are consistent with the correlation obtained by the test results.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"12 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134546928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Change in the fatigue life due to application of the mean strain was investigated for Type 316 stainless steel in simulated pressurized water rector (PWR) primary water environment. The tests were conducted by controlling the strain range to 1.2% for different strain rates of 0.4, 0.004, or 0.001%/s. The applied mean strain was 15% in nominal strain. In addition, cold worked specimens were also subjected to the tests without applying the mean strain. The tests using the cold worked specimens were regarded as the tests with the mean strain without increase in surface roughness due to application of plastic deformation. By inducing the cold working at low temperature, the effect of martensitic phase on the fatigue life was also examined. It was shown that the fatigue life of the stainless steel was reduced in the PWR water environment and the degree of the fatigue life reduction was consistent with the prediction model prescribed in the code issued by the Japan Society of Mechanical Engineers (JSME) and NUREG/CR-6909. Increases in peak stress and stress range due to cold working did not cause any apparent influence on the fatigue life. It was also shown that the 10.5 wt% martensitic phase induced by the low temperature cold working and the increase in the surface roughness caused by application of 15% mean strain did not bring about further fatigue life reduction. It was concluded that the effects of the mean strain, cold working, and martensitic phase were minor on the fatigue life in the PWR water environment. The current JSME and NUREG/CR-6909 models were applicable for predicting the reduction in fatigue due to the PWR water environment even if the mean strain or cold working was applied.
{"title":"Influence of Mean Strain on Fatigue Life of Stainless Steel in PWR Water Environment","authors":"M. Kamaya","doi":"10.1115/PVP2018-84461","DOIUrl":"https://doi.org/10.1115/PVP2018-84461","url":null,"abstract":"Change in the fatigue life due to application of the mean strain was investigated for Type 316 stainless steel in simulated pressurized water rector (PWR) primary water environment. The tests were conducted by controlling the strain range to 1.2% for different strain rates of 0.4, 0.004, or 0.001%/s. The applied mean strain was 15% in nominal strain. In addition, cold worked specimens were also subjected to the tests without applying the mean strain. The tests using the cold worked specimens were regarded as the tests with the mean strain without increase in surface roughness due to application of plastic deformation. By inducing the cold working at low temperature, the effect of martensitic phase on the fatigue life was also examined. It was shown that the fatigue life of the stainless steel was reduced in the PWR water environment and the degree of the fatigue life reduction was consistent with the prediction model prescribed in the code issued by the Japan Society of Mechanical Engineers (JSME) and NUREG/CR-6909. Increases in peak stress and stress range due to cold working did not cause any apparent influence on the fatigue life. It was also shown that the 10.5 wt% martensitic phase induced by the low temperature cold working and the increase in the surface roughness caused by application of 15% mean strain did not bring about further fatigue life reduction. It was concluded that the effects of the mean strain, cold working, and martensitic phase were minor on the fatigue life in the PWR water environment. The current JSME and NUREG/CR-6909 models were applicable for predicting the reduction in fatigue due to the PWR water environment even if the mean strain or cold working was applied.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123289452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the framework of a pressurized water reactor primary loop replacement, elbows of different types were produced in cast austenitic stainless steel grade Z3CN 20-09 M. For that type of component, acceptance tests to check the sufficient mechanical properties include room and hot temperature tensile tests, following the RCC-M CMS – 1040 and EN 10002 specifications. A large test campaign on standard 10mm diameter specimens was performed and exhibited a high scattering in yield stress and ultimate tensile strength values. As a consequence, some acceptance tensile tests failed to meet the required minimal values, especially the ultimate tensile strength. Optical and electronic microscopy revealed that the low values were due to the presence of very large grain compared to the specimen gage diameter. However, tensile tests strongly rely on the hypothesis that the specimen gage part can be considered as a representative volume element containing a number of grains large enough so that their variation in size and orientation gives a homogeneous response. To confirm the origin of the scattering, a huge experimental tensile test campaign with specimens of different diameters was conducted. In parallel, FE calculations were also performed. From all those results, it was concluded that it was necessary to improve the RCC-M code for that type of test for cast stainless steel: to do so, a modification sheet was sent and is being investigated by AFCEN.
{"title":"Tensile Tests for Cast Stainless Steel: Evolution of the RCC-M Code","authors":"A. Blouin, M. Couvrat, F. Latourte, J. Soulacroix","doi":"10.1115/PVP2018-84601","DOIUrl":"https://doi.org/10.1115/PVP2018-84601","url":null,"abstract":"In the framework of a pressurized water reactor primary loop replacement, elbows of different types were produced in cast austenitic stainless steel grade Z3CN 20-09 M. For that type of component, acceptance tests to check the sufficient mechanical properties include room and hot temperature tensile tests, following the RCC-M CMS – 1040 and EN 10002 specifications. A large test campaign on standard 10mm diameter specimens was performed and exhibited a high scattering in yield stress and ultimate tensile strength values. As a consequence, some acceptance tensile tests failed to meet the required minimal values, especially the ultimate tensile strength. Optical and electronic microscopy revealed that the low values were due to the presence of very large grain compared to the specimen gage diameter. However, tensile tests strongly rely on the hypothesis that the specimen gage part can be considered as a representative volume element containing a number of grains large enough so that their variation in size and orientation gives a homogeneous response. To confirm the origin of the scattering, a huge experimental tensile test campaign with specimens of different diameters was conducted. In parallel, FE calculations were also performed. From all those results, it was concluded that it was necessary to improve the RCC-M code for that type of test for cast stainless steel: to do so, a modification sheet was sent and is being investigated by AFCEN.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127751684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Vankeerberghen, M. Bruchhausen, R. Cicero, L. Doremus, J. Le-Roux, N. Platts, P. Spätig, Marius Twite, K. Mottershead
INCEFA-PLUS stands for INcreasing safety in nuclear power plants by Covering gaps in Environmental Fatigue Assessment. It is a five year project supported by the European Commission HORIZON2020 program that commenced in mid-2015 and in which sixteen organizations from across Europe participate. Specifically, the effects of mean strain/stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied, these being issues of common interest to all participants. The project will develop proposals for improvements to methods for environmental fatigue assessment of nuclear plant components. Therefore, extensive testing capacity is being solicited in various laboratories across Europe in order to add to the existing amount of published data on environmentally assisted fatigue. Since there currently is no standard on environmental fatigue testing, it was imperative to come up with and agree upon a testing procedure within the consortium to minimize lab-to-lab variations in test results. This was done prior to the first phase of testing, but an update of the procedure was required after review of initial results, when additional potential lab-to-lab differences were identified. The current status of the so-called test protocol, and the key areas of difference found between different testing facilities, will be discussed. Due to the large test matrix within INCEFA-PLUS, distributed amongst various test laboratories, it has been necessary to develop a method to assign a data quality level to each test result, and a minimum data quality requirement for results that will be included in the project’s datasets used for analysis. Furthermore, the project has triggered international interest in facilitating mutual data access, and this requires data is gathered in a common database with data quality ratings applied. Ways to address the evaluation of data quality will be discussed. In a way, both activities, on a test protocol and on data review, jointly contribute to data quality by, respectively, ensuring a pre-test, common test procedure and a post-test, harmonized data evaluation. The large number of participants in the INCEFA-PLUS project presents a unique opportunity to gain consensus on light water reactor environment fatigue testing procedures and data quality assessment from experts working in a range of different organizations. The test protocol and data quality ratings developed within the INCEFA-PLUS project could be adopted by other organizations, or possibly used as the basis for future testing standards documents to harmonize approaches across the nuclear industry.
{"title":"Ensuring Data Quality for Environmental Fatigue: INCEFA-PLUS Testing Procedure and Data Evaluation","authors":"M. Vankeerberghen, M. Bruchhausen, R. Cicero, L. Doremus, J. Le-Roux, N. Platts, P. Spätig, Marius Twite, K. Mottershead","doi":"10.1115/PVP2018-84081","DOIUrl":"https://doi.org/10.1115/PVP2018-84081","url":null,"abstract":"INCEFA-PLUS stands for INcreasing safety in nuclear power plants by Covering gaps in Environmental Fatigue Assessment. It is a five year project supported by the European Commission HORIZON2020 program that commenced in mid-2015 and in which sixteen organizations from across Europe participate. Specifically, the effects of mean strain/stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied, these being issues of common interest to all participants.\u0000 The project will develop proposals for improvements to methods for environmental fatigue assessment of nuclear plant components. Therefore, extensive testing capacity is being solicited in various laboratories across Europe in order to add to the existing amount of published data on environmentally assisted fatigue.\u0000 Since there currently is no standard on environmental fatigue testing, it was imperative to come up with and agree upon a testing procedure within the consortium to minimize lab-to-lab variations in test results. This was done prior to the first phase of testing, but an update of the procedure was required after review of initial results, when additional potential lab-to-lab differences were identified. The current status of the so-called test protocol, and the key areas of difference found between different testing facilities, will be discussed.\u0000 Due to the large test matrix within INCEFA-PLUS, distributed amongst various test laboratories, it has been necessary to develop a method to assign a data quality level to each test result, and a minimum data quality requirement for results that will be included in the project’s datasets used for analysis. Furthermore, the project has triggered international interest in facilitating mutual data access, and this requires data is gathered in a common database with data quality ratings applied. Ways to address the evaluation of data quality will be discussed.\u0000 In a way, both activities, on a test protocol and on data review, jointly contribute to data quality by, respectively, ensuring a pre-test, common test procedure and a post-test, harmonized data evaluation.\u0000 The large number of participants in the INCEFA-PLUS project presents a unique opportunity to gain consensus on light water reactor environment fatigue testing procedures and data quality assessment from experts working in a range of different organizations. The test protocol and data quality ratings developed within the INCEFA-PLUS project could be adopted by other organizations, or possibly used as the basis for future testing standards documents to harmonize approaches across the nuclear industry.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127009478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Métais, A. Morley, L. D. Baglion, D. Tice, G. Stevens, Sam Cuvilliez
Additional fatigue rules within the ASME Boiler and Pressure Vessel Code have been developed over the past decade or so, such as those in Code Case N-792-1 [1], which provides an acceptable method to describe the effects of BWR and PWR environments on the fatigue life of components. The incorporation of environmental effects into fatigue calculations is performed via an environmental factor, Fen, and depends on factors such as the temperature, dissolved oxygen and strain rate. In the case of strain rate, lower strain rates (i.e., from slow transients) aggravate the Fen factor which counters the long-held notion that step (fast) transients cause the highest fatigue usage. A wide range of other factors, such as surface finish, can have a deleterious impact on fatigue life, but their impact on fatigue life is typically considered by including transition sub-factors to construct the fatigue design curve from the mean behavior air curve rather than in an explicit way, such as the Fen factor. An extensive amount of testing and evaluation has been conducted and reported in References [2] [3] [4] [5] [6] [7] and [8] that were used to both revise the transition factors and devise the Fen equations contained in Code Case N-792-1. The testing supporting the definition of Fen was performed on small-scale laboratory specimens with a polished surface finish on the basis that the Fen factor is applicable to the design curve without any impact on the transition factors. The work initiated by AREVA in 2005 [4] [5] [6] suggested, in testing of austenitic stainless steels, an interaction between the two aggravating effects of surface finish and PWR environment on fatigue damage. These results have been supported by testing carried out independently in the UK by Rolls-Royce and AMEC Foster Wheeler (now Wood Group) [7], also on austenitic stainless steels. The key finding from these investigations is that the combined detrimental effects of a PWR environment and a rough surface finish are substantially less than the sum of the two individual effects. These results are all the more relevant as most nuclear power plant (NPP) components do not have a polished surface finish. Most NPP component surfaces are either industrially ground or installed as-manufactured. The previous studies concluded that explicit consideration of the combined effects of environment and surface finish could potentially be applicable to a wide range of NPP components and would therefore be of interest to a wider community: EDF has therefore authored a draft Code Case introducing a factor, Fen-threshold, which explicitly quantifies the interaction between PWR environment and surface finish, as well as taking some credit for other conservatisms in the sub-factors that comprise the life transition sub-factor used to build the design fatigue curve . The contents of the draft Code Case were presented last year [9]. Since then, other international organizations have also made progress on these t
在过去十年左右的时间里，ASME锅炉和压力容器规范中已经制定了额外的疲劳规则，例如规范案例N-792-1[1]中的规则，它提供了一种可接受的方法来描述沸水堆和压水堆环境对部件疲劳寿命的影响。将环境影响纳入疲劳计算是通过环境因子Fen进行的，并取决于温度、溶解氧和应变速率等因素。在应变率的情况下，较低的应变率(即来自慢瞬态)加剧了Fen因子，这与长期持有的阶跃(快速)瞬态导致最高疲劳使用的观念相反。许多其他因素，如表面光洁度，可能对疲劳寿命产生有害影响，但它们对疲劳寿命的影响通常是通过包括过渡子因素来考虑的，以从平均行为空气曲线构建疲劳设计曲线，而不是以明确的方式，如Fen因素。文献[2][3][4][5][6][7]和[8]中已经进行了大量的测试和评估，这些测试和评估用于修正过渡因子并设计Code Case N-792-1中包含的Fen方程。在Fen因子适用于设计曲线且不影响过渡因子的基础上，对具有抛光表面光洁度的小型实验室试样进行了支持Fen定义的测试。2005年由AREVA发起的工作[4][5][6]表明，在奥氏体不锈钢的测试中，表面光洁度和压水堆环境对疲劳损伤的两种加重作用之间存在相互作用。Rolls-Royce和AMEC Foster Wheeler(现为Wood Group)在英国独立进行的测试也支持了这些结果[7]，测试对象也是奥氏体不锈钢。这些调查的关键发现是，压水堆环境和粗糙表面处理的综合有害影响远远小于两个单独影响的总和。这些结果都是更相关的，因为大多数核电站(NPP)组件没有抛光表面。大多数核电厂组件的表面要么是工业地面，要么是在制造时安装的。先前的研究得出结论，明确考虑环境和表面光洁度的综合影响可能适用于广泛的核电厂组成部分，因此将引起更广泛的兴趣:因此，EDF撰写了一份规范案例草案，引入了一个因子，Fen-threshold，该因子明确量化了压水堆环境和表面光光度之间的相互作用，并在构成用于构建设计疲劳曲线的寿命过渡子因子的子因子中获得了一些其他保守性。《法典案例草案》的内容于去年提出[9]。此后，其他国际组织也在这些议题上取得了进展，并形成了自己的看法。所做的工作目前仅适用于奥氏体不锈钢。因此，本文旨在根据迄今收到的意见，对规范案例草案进行更新，并介绍了作为环境疲劳问题国际EPRI合作小组的一部分，正在进行的关于该主题的一些研究和讨论。它旨在为最终版本的en-threshold ASME规范案例达成国际共识。
{"title":"Explicit Quantification of the Interaction Between the PWR Environment and Component Surface Finish in Environmental Fatigue Evaluation Methods for Austenitic Stainless Steels","authors":"T. Métais, A. Morley, L. D. Baglion, D. Tice, G. Stevens, Sam Cuvilliez","doi":"10.1115/PVP2018-84240","DOIUrl":"https://doi.org/10.1115/PVP2018-84240","url":null,"abstract":"Additional fatigue rules within the ASME Boiler and Pressure Vessel Code have been developed over the past decade or so, such as those in Code Case N-792-1 [1], which provides an acceptable method to describe the effects of BWR and PWR environments on the fatigue life of components. The incorporation of environmental effects into fatigue calculations is performed via an environmental factor, Fen, and depends on factors such as the temperature, dissolved oxygen and strain rate. In the case of strain rate, lower strain rates (i.e., from slow transients) aggravate the Fen factor which counters the long-held notion that step (fast) transients cause the highest fatigue usage.\u0000 A wide range of other factors, such as surface finish, can have a deleterious impact on fatigue life, but their impact on fatigue life is typically considered by including transition sub-factors to construct the fatigue design curve from the mean behavior air curve rather than in an explicit way, such as the Fen factor. An extensive amount of testing and evaluation has been conducted and reported in References [2] [3] [4] [5] [6] [7] and [8] that were used to both revise the transition factors and devise the Fen equations contained in Code Case N-792-1.\u0000 The testing supporting the definition of Fen was performed on small-scale laboratory specimens with a polished surface finish on the basis that the Fen factor is applicable to the design curve without any impact on the transition factors.\u0000 The work initiated by AREVA in 2005 [4] [5] [6] suggested, in testing of austenitic stainless steels, an interaction between the two aggravating effects of surface finish and PWR environment on fatigue damage.\u0000 These results have been supported by testing carried out independently in the UK by Rolls-Royce and AMEC Foster Wheeler (now Wood Group) [7], also on austenitic stainless steels. The key finding from these investigations is that the combined detrimental effects of a PWR environment and a rough surface finish are substantially less than the sum of the two individual effects. These results are all the more relevant as most nuclear power plant (NPP) components do not have a polished surface finish. Most NPP component surfaces are either industrially ground or installed as-manufactured.\u0000 The previous studies concluded that explicit consideration of the combined effects of environment and surface finish could potentially be applicable to a wide range of NPP components and would therefore be of interest to a wider community: EDF has therefore authored a draft Code Case introducing a factor, Fen-threshold, which explicitly quantifies the interaction between PWR environment and surface finish, as well as taking some credit for other conservatisms in the sub-factors that comprise the life transition sub-factor used to build the design fatigue curve .\u0000 The contents of the draft Code Case were presented last year [9]. Since then, other international organizations have also made progress on these t","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114651349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fatigue crack growth rates are expressed as a function of the stress intensity factor ranges. The fatigue crack growth thresholds are important characteristics of fatigue crack growth assessment for the integrity of structural components. Almost all materials used in these fatigue tests are ferritic steels. As a result, the reference fatigue crack growth rates and the fatigue crack growth thresholds for ferritic steels were established as rules and they were provided by many fitness-for-service (FFS) codes. However, the thresholds are not well defined in the range of negative stress ratio. There are two types of thresholds under the negative stress ratio. That is, constant thresholds and increment of thresholds with decreasing stress ratios. The objective of this paper is to introduce the thresholds provided by FFS codes and to analyze the thresholds using crack closure. In addition, based on the experimental data, definition of the threshold is discussed to apply to FFS codes. Finally, threshold for ferritic steels under the entirely condition of stress ratio is proposed to the ASME Code Section XI.
{"title":"Definition of Fatigue Crack Growth Thresholds for Ferritic Steels in Fitness-for-Service Codes","authors":"K. Hasegawa, B. Strnadel","doi":"10.1115/PVP2018-84940","DOIUrl":"https://doi.org/10.1115/PVP2018-84940","url":null,"abstract":"Fatigue crack growth rates are expressed as a function of the stress intensity factor ranges. The fatigue crack growth thresholds are important characteristics of fatigue crack growth assessment for the integrity of structural components. Almost all materials used in these fatigue tests are ferritic steels. As a result, the reference fatigue crack growth rates and the fatigue crack growth thresholds for ferritic steels were established as rules and they were provided by many fitness-for-service (FFS) codes. However, the thresholds are not well defined in the range of negative stress ratio. There are two types of thresholds under the negative stress ratio. That is, constant thresholds and increment of thresholds with decreasing stress ratios. The objective of this paper is to introduce the thresholds provided by FFS codes and to analyze the thresholds using crack closure. In addition, based on the experimental data, definition of the threshold is discussed to apply to FFS codes. Finally, threshold for ferritic steels under the entirely condition of stress ratio is proposed to the ASME Code Section XI.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129449326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst most plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth, and, more importantly, on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies. A test methodology using corner cracked tensile specimens, and based on finite element analysis of the specimens to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading has been previously presented. The current paper further develops this approach, enabling it to be utilized to study a range of positive and negative load ratios from R = −2 to R = 0.5 loading, and provides a greater understanding of the development of stress intensity factor within a loading cycle. Test data has been generated in both air and high temperature water environments over a range of loading ratios. Comparison of these data to material specific crack growth data from conventional compact tension specimens and environmental crack growth laws (such as Code Case N-809) enables the impact of crack closure on the effective stress intensity factor to be assessed in both air and water environments. The significance of indicated differences in the apparent level of closure between air and water environments is discussed in the light of accepted growth laws and material specific data.
轻水反应堆冷却剂环境可以显著提高奥氏体不锈钢的疲劳裂纹扩展速率。然而，在这些高温加压水环境中，大多数可用的数据都是通过在正负载比下测试的样品得出的，而大多数植物瞬态涉及显著的压缩和拉伸应力。因此，压缩载荷对环境下疲劳裂纹扩展增强的影响程度，更重要的是，对导致这些增强速率延迟的过程的影响程度尚不清楚，这可能导致当前评估方法过于保守。先前已经提出了一种测试方法，使用角裂拉伸试样，并基于有限元分析试样，以产生完全反向加载时试样的有效应力强度因子Keff。本文进一步发展了这一方法，使其能够用于研究从R = - 2到R = 0.5载荷范围内的正、负载荷比，并对加载周期内应力强度因子的发展提供了更好的理解。测试数据已经在空气和高温水环境中产生，并且在一定的负载比范围内。将这些数据与来自常规压紧拉伸试样的材料特定裂纹扩展数据和环境裂纹扩展规律(如Code Case N-809)进行比较，可以在空气和水环境中评估裂纹闭合对有效应力强度因子的影响。根据公认的生长规律和材料特定数据，讨论了空气和水环境之间表观封闭水平的指示差异的意义。
{"title":"Negative R Fatigue Crack Growth Rate Testing on Austenitic Stainless Steel in Air and Simulated Primary Water Environments","authors":"N. Platts, B. Coult, Wenzhong Zhang, Peter Gill","doi":"10.1115/PVP2018-84252","DOIUrl":"https://doi.org/10.1115/PVP2018-84252","url":null,"abstract":"Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst most plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth, and, more importantly, on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies.\u0000 A test methodology using corner cracked tensile specimens, and based on finite element analysis of the specimens to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading has been previously presented. The current paper further develops this approach, enabling it to be utilized to study a range of positive and negative load ratios from R = −2 to R = 0.5 loading, and provides a greater understanding of the development of stress intensity factor within a loading cycle.\u0000 Test data has been generated in both air and high temperature water environments over a range of loading ratios. Comparison of these data to material specific crack growth data from conventional compact tension specimens and environmental crack growth laws (such as Code Case N-809) enables the impact of crack closure on the effective stress intensity factor to be assessed in both air and water environments. The significance of indicated differences in the apparent level of closure between air and water environments is discussed in the light of accepted growth laws and material specific data.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"156 10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125911832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
After a short review of the 3 Codes in term of flaw evaluation, this paper will consider the Failure Assessment Diagrams (FAD) proposed in each of them. The cracked components are evaluated by a dedicated diagram for margin evaluation of ductile tearing resistance of the components: the elastic stress intensity factor of the crack normalized by the toughness of the material on one axis and the applied stresses normalized by a Reference Stress in the other axis. The 2017 Edition of RSE-M Appendix 5.4 and 5.6, the 2017 Edition of ASME XI Appendix H and the 2016 Edition of API 579 Part 9 will be used in this first comparison.
{"title":"RSE-M - ASME XI - API 579: Comparison of Failure Assessment Diagrams (FAD)","authors":"C. Faidy","doi":"10.1115/PVP2018-84703","DOIUrl":"https://doi.org/10.1115/PVP2018-84703","url":null,"abstract":"After a short review of the 3 Codes in term of flaw evaluation, this paper will consider the Failure Assessment Diagrams (FAD) proposed in each of them.\u0000 The cracked components are evaluated by a dedicated diagram for margin evaluation of ductile tearing resistance of the components: the elastic stress intensity factor of the crack normalized by the toughness of the material on one axis and the applied stresses normalized by a Reference Stress in the other axis.\u0000 The 2017 Edition of RSE-M Appendix 5.4 and 5.6, the 2017 Edition of ASME XI Appendix H and the 2016 Edition of API 579 Part 9 will be used in this first comparison.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123164112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：