J. Solin, J. Alhainen, T. Seppänen, H. E. Karabaki, W. Mayinger
Strain controlled LCF testing extended to 10 million cycles revealed an abrupt endurance limit enforced by secondary hardening. In elevated temperatures the ε-N curve is rotated and endurance limit is lowered, but not vanished. When very low strain rates are applied at 325°C in simulated PWR environment, fatigue life is reduced, but far less than predicted according to NUREG/CR-6909. It is possible, but not probable that the difference is due to different stainless grades studied. We assume that the test method plays a more important role. We have repeatedly demonstrated in different tests campaigns that interruptions of straining with holds aiming to simulate steady state normal operation between fatigue relevant cycles can notably extend the fatigue endurance. Further proof is again presented in this paper. The suspected explanation is prevention of strain localization within the material microstructure and also in geometric strain concentrations. This actually suggests, that hold effects should be even more pronounced in real components. Cyclic behavior of austenitic steels is very complex. Transferability of laboratory data to NPP operational conditions depends on test environment, temperature, strain rate and holds in many ways not considered in current fatigue assessment procedures. In addition to penalty factors, also bonus factors are needed to improve transferability. Furthermore, it seems that the load carrying capacity of fatigued stainless steel is not compromised before the crack growth phase. Tensile tests performed after fatigue tests interrupted shortly before end-of-life condition in 325°C (N ≈ 0.85 × N25) showed strength and ductility almost identical to virgin material. This paper provides new experimental results and discusses previous observations aiming to sum up a state of the art in fatigue performance of German NPP primary loop materials.
{"title":"Cyclic, Monotonic and Fatigue Performance of Stabilized Stainless Steel in PWR Water and Research Laboratory","authors":"J. Solin, J. Alhainen, T. Seppänen, H. E. Karabaki, W. Mayinger","doi":"10.1115/PVP2018-84935","DOIUrl":"https://doi.org/10.1115/PVP2018-84935","url":null,"abstract":"Strain controlled LCF testing extended to 10 million cycles revealed an abrupt endurance limit enforced by secondary hardening. In elevated temperatures the ε-N curve is rotated and endurance limit is lowered, but not vanished. When very low strain rates are applied at 325°C in simulated PWR environment, fatigue life is reduced, but far less than predicted according to NUREG/CR-6909. It is possible, but not probable that the difference is due to different stainless grades studied. We assume that the test method plays a more important role.\u0000 We have repeatedly demonstrated in different tests campaigns that interruptions of straining with holds aiming to simulate steady state normal operation between fatigue relevant cycles can notably extend the fatigue endurance. Further proof is again presented in this paper. The suspected explanation is prevention of strain localization within the material microstructure and also in geometric strain concentrations. This actually suggests, that hold effects should be even more pronounced in real components.\u0000 Cyclic behavior of austenitic steels is very complex. Transferability of laboratory data to NPP operational conditions depends on test environment, temperature, strain rate and holds in many ways not considered in current fatigue assessment procedures. In addition to penalty factors, also bonus factors are needed to improve transferability. Furthermore, it seems that the load carrying capacity of fatigued stainless steel is not compromised before the crack growth phase. Tensile tests performed after fatigue tests interrupted shortly before end-of-life condition in 325°C (N ≈ 0.85 × N25) showed strength and ductility almost identical to virgin material.\u0000 This paper provides new experimental results and discusses previous observations aiming to sum up a state of the art in fatigue performance of German NPP primary loop materials.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"64 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":"114119596","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}
G. Wilkowski, Y. Hioe, E. Kurth, E. Punch, M. Uddin, F. Brust, K. Bagnoli, Greger L. Pioszak
Leak-Before-Break (LBB) has been applied in various industries for decades, and this paper explores using it for a new application. In the refining industry, various process units contain hydrogen at elevated temperatures where high temperature hydrogen attack (HTHA) can occur. This mechanism involves the reaction between hydrogen and carbides to form methane, but also the diffusion of hydrogen occurs in the steel. Under certain temperature and hydrogen partial pressures, the methane formation can cause grain boundary cavitation which leads to fissuring and eventually macroscopic cracking. Generally one designs to avoid such cracking from occurring following the so-called “Nelson Curves” contained in API RP 941; however, in recent years it has been found that non-stress relieved carbon steels are susceptible to HTHA below the original API 941 curve. As a result, the refining industry has experienced a number of leaks in piping and vessels. This paper presents some developmental efforts to apply LBB to non-stress relieved seamless carbon steel piping girth welds susceptible to (HTHA) cracking in refinery applications. Much of this approach builds on analyses, results, and experience from the commercial nuclear industry LBB efforts over the last 30 years. This paper will discuss the results of both mechanical testing as well as detailed modelling efforts to evaluate LBB technology to this new application for circumferential cracks, which to date implies that LBB may be applicable to seamless pipe girth welds. Cracks in tees or other components were not addressed in this work. Axial cracks in seam welds are not addressed in this work.
先漏后破(LBB)技术已经在各行各业应用了几十年，本文探讨了将其应用于新的领域。在炼油工业中，各种工艺装置在高温下含有氢气，高温氢侵蚀(HTHA)可能发生。这一机理包括氢与碳化物反应生成甲烷，但也包括氢在钢中的扩散。在一定的温度和氢分压下，甲烷的形成会引起晶界空化，导致裂纹，最终形成宏观开裂。一般来说，按照API RP 941中所谓的“纳尔逊曲线”进行设计，以避免这种开裂的发生;然而，近年来发现，在原始API 941曲线以下，未去应力的碳钢容易受到HTHA的影响。因此，炼油行业经历了管道和容器的多次泄漏。本文介绍了在炼油厂易开裂的无应力无缝碳钢管道环焊缝上应用LBB的一些发展努力。这种方法在很大程度上建立在过去30年商业核工业LBB工作的分析、结果和经验的基础上。本文将讨论机械测试的结果以及详细的建模工作，以评估LBB技术在圆周裂纹中的新应用，迄今为止，这意味着LBB可能适用于无缝管环焊缝。三通或其他部件的裂缝在这项工作中没有得到解决。接缝焊缝的轴向裂纹在本工作中未得到解决。
{"title":"Initial Developments for LBB Application to HTHA Sensitive Non-Stress Relieved Carbon Steel Girth Welds in Refinery Plants","authors":"G. Wilkowski, Y. Hioe, E. Kurth, E. Punch, M. Uddin, F. Brust, K. Bagnoli, Greger L. Pioszak","doi":"10.1115/PVP2018-84669","DOIUrl":"https://doi.org/10.1115/PVP2018-84669","url":null,"abstract":"Leak-Before-Break (LBB) has been applied in various industries for decades, and this paper explores using it for a new application. In the refining industry, various process units contain hydrogen at elevated temperatures where high temperature hydrogen attack (HTHA) can occur. This mechanism involves the reaction between hydrogen and carbides to form methane, but also the diffusion of hydrogen occurs in the steel. Under certain temperature and hydrogen partial pressures, the methane formation can cause grain boundary cavitation which leads to fissuring and eventually macroscopic cracking. Generally one designs to avoid such cracking from occurring following the so-called “Nelson Curves” contained in API RP 941; however, in recent years it has been found that non-stress relieved carbon steels are susceptible to HTHA below the original API 941 curve. As a result, the refining industry has experienced a number of leaks in piping and vessels. This paper presents some developmental efforts to apply LBB to non-stress relieved seamless carbon steel piping girth welds susceptible to (HTHA) cracking in refinery applications. Much of this approach builds on analyses, results, and experience from the commercial nuclear industry LBB efforts over the last 30 years. This paper will discuss the results of both mechanical testing as well as detailed modelling efforts to evaluate LBB technology to this new application for circumferential cracks, which to date implies that LBB may be applicable to seamless pipe girth welds. Cracks in tees or other components were not addressed in this work. Axial cracks in seam welds are not addressed in this work.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"107 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":"124232148","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}
V. Paiva, G. Gonzáles, R. D. Vieira, J. Maneschy, R. B. Vieira, J. Freire
The present paper combines the fatigue properties rapid assessment approach using uniaxial test specimens proposed by Risitano and co-workers with the nondestructive testing (NDT) inspection approach proposed by Sakagami and co-workers to monitor the onset of fatigue in a reduced scale pipeline test specimen that was previously dented and subsequently subjected to cyclic pressure loading. In addition to the use of the conventional infrared (IR) thermographic method, the present paper uses a self-reference lock-in IR thermography method based on Thermoelastic Stress Analysis (TSA) and its deviation from traditional applications due to the presence of fatigue damage and plastic strains. The paper concludes showing that is possible to predict and monitor and detect fatigue initiation and damage using IR and TSA techniques applied to the thin wall pipe loaded under cyclic hydrostatic pressure.
{"title":"Fatigue Monitoring of a Dented Piping Specimen Using Infrared Thermography","authors":"V. Paiva, G. Gonzáles, R. D. Vieira, J. Maneschy, R. B. Vieira, J. Freire","doi":"10.1115/PVP2018-84597","DOIUrl":"https://doi.org/10.1115/PVP2018-84597","url":null,"abstract":"The present paper combines the fatigue properties rapid assessment approach using uniaxial test specimens proposed by Risitano and co-workers with the nondestructive testing (NDT) inspection approach proposed by Sakagami and co-workers to monitor the onset of fatigue in a reduced scale pipeline test specimen that was previously dented and subsequently subjected to cyclic pressure loading. In addition to the use of the conventional infrared (IR) thermographic method, the present paper uses a self-reference lock-in IR thermography method based on Thermoelastic Stress Analysis (TSA) and its deviation from traditional applications due to the presence of fatigue damage and plastic strains. The paper concludes showing that is possible to predict and monitor and detect fatigue initiation and damage using IR and TSA techniques applied to the thin wall pipe loaded under cyclic hydrostatic pressure.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"18 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":"126657730","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}
Following the flaw indications found in summer 2012 in two Belgian Reactors Pressure Vessels (RPV), WENRA recommended [1] the nuclear safety authorities in Europe to verify the material quality and integrity of the RPV in a 2-step approach: 1) a comprehensive review of the manufacturing and inspection records of the forgings of the RPV, 2) an additional UT examination of the base material of the vessels if needed. In this context, and to consolidate scientific basis on this issue, IRSN, the French technical safety organization, conducted, with CEA support, a test program aiming at studying the consequences of hydrogen flakes in large forgings of primary equipment (RPV, steam generator, pressurizer). Framatome provided the material to be investigated, namely two blocks of a steam generator vessel shell in 18MND5 steel: a block without flake — the reference block — and a block including a high density of hydrogen flakes. This shell — so called VB395 — was rejected because of an incident which occurred during the degassing heat treatment. Fracture toughness has been evaluated from 85 tests in the ductile range and the ductile-to-brittle transition range of the material. The test results on usual 0.5T-CT specimens were compared to those on specimens containing a hydrogen flake replacing the fatigue precrack. The latter were interpreted using 3D elastic-plastic X-FEM simulations allowing the modelling of the irregular flake geometry. Furthermore, large scale bending specimens with multiple flakes have been tested at −100°C. These tests were interpreted thanks to 3D X-FEM simulations allowing the analysis of the hydrogen flake interaction in terms of KJ.
{"title":"Mechanical Behaviour of a Forged Ferritic Steel Shell Containing Numerous Hydrogen Flakes","authors":"C. Jacquemoud, I. Delvallée-Nunio","doi":"10.1115/PVP2018-84087","DOIUrl":"https://doi.org/10.1115/PVP2018-84087","url":null,"abstract":"Following the flaw indications found in summer 2012 in two Belgian Reactors Pressure Vessels (RPV), WENRA recommended [1] the nuclear safety authorities in Europe to verify the material quality and integrity of the RPV in a 2-step approach: 1) a comprehensive review of the manufacturing and inspection records of the forgings of the RPV, 2) an additional UT examination of the base material of the vessels if needed.\u0000 In this context, and to consolidate scientific basis on this issue, IRSN, the French technical safety organization, conducted, with CEA support, a test program aiming at studying the consequences of hydrogen flakes in large forgings of primary equipment (RPV, steam generator, pressurizer).\u0000 Framatome provided the material to be investigated, namely two blocks of a steam generator vessel shell in 18MND5 steel: a block without flake — the reference block — and a block including a high density of hydrogen flakes. This shell — so called VB395 — was rejected because of an incident which occurred during the degassing heat treatment.\u0000 Fracture toughness has been evaluated from 85 tests in the ductile range and the ductile-to-brittle transition range of the material. The test results on usual 0.5T-CT specimens were compared to those on specimens containing a hydrogen flake replacing the fatigue precrack. The latter were interpreted using 3D elastic-plastic X-FEM simulations allowing the modelling of the irregular flake geometry.\u0000 Furthermore, large scale bending specimens with multiple flakes have been tested at −100°C. These tests were interpreted thanks to 3D X-FEM simulations allowing the analysis of the hydrogen flake interaction in terms of KJ.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"18 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":"134599692","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. Bifano, Lyle E. Breaux, Anthony J. Feller, R. Brodzinski
Commonly used piping vibration screening limits are typically justified by experience and lack a well-documented technical basis. This paper presents technical background for future Level 1 Fitness-for-Service (FFS) vibration screening criteria. The criteria assess the risk of fatigue in process piping due to bending mode type vibrations. Finite element analysis (FEA) of 20,000 randomly generated candidate-piping models and high-cycle welded joint fatigue curves for both constant amplitude and variable amplitude loading form the stress limits and basis for the proposed criteria. Most importantly, the proposed criteria aligns with historically used allowable vibration limits rooted in substantial experience. The allowable stress basis implemented in this paper considers periodic and random vibrations making it applicable to situations of mechanically induced, two-phase flow induced, turbulent-induced vibration of single-phase process fluid, or wind-induced, which may be manifested as either periodic or random. To reduce conservatism, limits are set for butt-welded and non-butt welded mainline piping to prevent use of a single blanket limit that may lead to unnecessary piping support alterations/additions, or costly piping configuration changes and unit downtime. Furthermore, the proposed Level 1-type criteria are consistent with previously proposed FFS Level 2 and 3 piping vibration fatigue evaluations [1] intended for inclusion in the ASME FFS-1/API 579 (API 579) Fitness for Service Standard [2].
{"title":"New Fatigue Screening Criteria for the Fitness-for-Service Assessment of In-Service Process Piping Vibrations","authors":"M. Bifano, Lyle E. Breaux, Anthony J. Feller, R. Brodzinski","doi":"10.1115/PVP2018-84847","DOIUrl":"https://doi.org/10.1115/PVP2018-84847","url":null,"abstract":"Commonly used piping vibration screening limits are typically justified by experience and lack a well-documented technical basis. This paper presents technical background for future Level 1 Fitness-for-Service (FFS) vibration screening criteria. The criteria assess the risk of fatigue in process piping due to bending mode type vibrations. Finite element analysis (FEA) of 20,000 randomly generated candidate-piping models and high-cycle welded joint fatigue curves for both constant amplitude and variable amplitude loading form the stress limits and basis for the proposed criteria. Most importantly, the proposed criteria aligns with historically used allowable vibration limits rooted in substantial experience. The allowable stress basis implemented in this paper considers periodic and random vibrations making it applicable to situations of mechanically induced, two-phase flow induced, turbulent-induced vibration of single-phase process fluid, or wind-induced, which may be manifested as either periodic or random. To reduce conservatism, limits are set for butt-welded and non-butt welded mainline piping to prevent use of a single blanket limit that may lead to unnecessary piping support alterations/additions, or costly piping configuration changes and unit downtime. Furthermore, the proposed Level 1-type criteria are consistent with previously proposed FFS Level 2 and 3 piping vibration fatigue evaluations [1] intended for inclusion in the ASME FFS-1/API 579 (API 579) Fitness for Service Standard [2].","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"53 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":"131383352","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}
A. Martín, C. Pétesch, Y. Lejeail, P. Lamagnère, T. Lebarbé, J. Garcia, Gaetano Aiello
RCC-MRx Code is the result of the merger of the RCC-MX 2008, developed in the context of the research reactor Jules Horowitz Reactor project, and the RCC-MR 2007, which established rules applicable to the design of components operating at high temperature and to the Vacuum Vessel of ITER. This code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires) in 2012, 2015, and a new edition will be published by the end of 2018. This new edition integrates a significant evolution for the rules dedicated to the ratchetting evaluation through the so-called “efficiency diagram rule”. This rule was initially developed to present a less penalizing rule than the classical “3 Sm” rule and to analyze the interaction between creep and ratchetting in the high temperature domain. Since the first edition of RCC-MR code, several modifications have been made to this rule to improve its representativeness for this kind of damage. These modifications were motivated and justified by numerous experimental tests. The last significant evolution is thus the occasion to present through this article, the background of this rule, the major evolutions already incorporated in the code and also the on-going developments.
{"title":"Efficiency Diagram Alternative Rule for Ratchetting: Historical Background, Overview, On-Going Developments","authors":"A. Martín, C. Pétesch, Y. Lejeail, P. Lamagnère, T. Lebarbé, J. Garcia, Gaetano Aiello","doi":"10.1115/PVP2018-84161","DOIUrl":"https://doi.org/10.1115/PVP2018-84161","url":null,"abstract":"RCC-MRx Code is the result of the merger of the RCC-MX 2008, developed in the context of the research reactor Jules Horowitz Reactor project, and the RCC-MR 2007, which established rules applicable to the design of components operating at high temperature and to the Vacuum Vessel of ITER.\u0000 This code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires) in 2012, 2015, and a new edition will be published by the end of 2018.\u0000 This new edition integrates a significant evolution for the rules dedicated to the ratchetting evaluation through the so-called “efficiency diagram rule”. This rule was initially developed to present a less penalizing rule than the classical “3 Sm” rule and to analyze the interaction between creep and ratchetting in the high temperature domain.\u0000 Since the first edition of RCC-MR code, several modifications have been made to this rule to improve its representativeness for this kind of damage. These modifications were motivated and justified by numerous experimental tests.\u0000 The last significant evolution is thus the occasion to present through this article, the background of this rule, the major evolutions already incorporated in the code and also the on-going developments.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"104 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":"127982885","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}
G. Ozeki, A. Yokobori, T. Ohmi, T. Kasuya, N. Ishikawa, S. Minamoto, M. Enoki
Hydrogen induced cracking occurs at the welded position of the structure due to concentration of hydrogen during cooling process of welding. In order to prevent the hydrogen induced cracking, Pre-Heat Treatment (PHT) is conducted. However, since PHT takes high cost, it is important to find out the suitable PHT condition based on computational mechanics. One of authors has been proposed α multiplication method which magnifies the hydrogen driving term in the diffusion equation to find out detailed behaviors of hydrogen concentration around a local stress field. In this study, in order to clarify the effect of PHT on hydrogen diffusion and concentration behaviors, a coupled analysis of heat transfer – thermal stress – hydrogen diffusion combining with α multiplication method was conducted for the model of y-grooved weld joint under various PHT conditions. This analytical method is as follows. At first, heat transfer analysis was conducted by finite difference method (FDM). And, temperature at each grid obtained by heat transfer analysis was interpolated to each node for thermal stress analysis by the finite element method (FEM). Then, thermal stress was calculated for each node using the interpolated temperature. After that, thermal stress obtained by this analysis was interpolated to each grid point for analysis of hydrogen diffusion by FDM. Using the interpolated thermal stress, stress driven hydrogen diffusion analysis was performed. By conducting sequentially these calculations mentioned above, hydrogen diffusion and concentration behaviors during cooling process were analyzed. The temperature of weld metal was 1500°C. And at initial state, hydrogen was introduced in weld metal. Thermal stress analysis was conducted under plane strain condition. As a result, hydrogen diffusion and concentration behaviour at weld joint during cooling process was found to be typical at the site of maximum hydrostatic stress and to be affected not only the gradient of hydrostatic stress but also the gradient of diffusion coefficient induced by temperature distribution.
{"title":"Effect of Pre-Heat Treatment on Hydrogen Concentration Behavior of y-Grooved Weld Joint Based on a Coupled Analysis of Heat Transfer-Thermal Stress-Hydrogen Diffusion","authors":"G. Ozeki, A. Yokobori, T. Ohmi, T. Kasuya, N. Ishikawa, S. Minamoto, M. Enoki","doi":"10.1115/PVP2018-84178","DOIUrl":"https://doi.org/10.1115/PVP2018-84178","url":null,"abstract":"Hydrogen induced cracking occurs at the welded position of the structure due to concentration of hydrogen during cooling process of welding. In order to prevent the hydrogen induced cracking, Pre-Heat Treatment (PHT) is conducted. However, since PHT takes high cost, it is important to find out the suitable PHT condition based on computational mechanics. One of authors has been proposed α multiplication method which magnifies the hydrogen driving term in the diffusion equation to find out detailed behaviors of hydrogen concentration around a local stress field.\u0000 In this study, in order to clarify the effect of PHT on hydrogen diffusion and concentration behaviors, a coupled analysis of heat transfer – thermal stress – hydrogen diffusion combining with α multiplication method was conducted for the model of y-grooved weld joint under various PHT conditions.\u0000 This analytical method is as follows. At first, heat transfer analysis was conducted by finite difference method (FDM). And, temperature at each grid obtained by heat transfer analysis was interpolated to each node for thermal stress analysis by the finite element method (FEM). Then, thermal stress was calculated for each node using the interpolated temperature. After that, thermal stress obtained by this analysis was interpolated to each grid point for analysis of hydrogen diffusion by FDM. Using the interpolated thermal stress, stress driven hydrogen diffusion analysis was performed. By conducting sequentially these calculations mentioned above, hydrogen diffusion and concentration behaviors during cooling process were analyzed. The temperature of weld metal was 1500°C. And at initial state, hydrogen was introduced in weld metal. Thermal stress analysis was conducted under plane strain condition.\u0000 As a result, hydrogen diffusion and concentration behaviour at weld joint during cooling process was found to be typical at the site of maximum hydrostatic stress and to be affected not only the gradient of hydrostatic stress but also the gradient of diffusion coefficient induced by temperature distribution.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"1996 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113966411","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}
K. Yoshimoto, T. Hirota, H. Sakamoto, Oshikiri Masato, K. Tsutsumi, Murakami Takeshi
Miniature compact tension (Mini-C(T)) specimen can be an effective tool by utilizing together with Master Curve (MC) methodology for fracture toughness evaluation of irradiated reactor pressure vessel (RPV) steels. Recently, Mini-C(T) specimen has been incorporated into the Japanese standard test method related to MC methodology, JEAC4216-2015 and several studies were found focusing on applicability of Mini-C(T) specimen to irradiated RPV materials. However, there exist some other issues to be resolved considering application to irradiated materials. One of them is violation against the limitation criteria for ductile crack growth (DCG) specified in the standards. In general, upper shelf energy (USE) of RPV materials tends to decrease as well as shift in Charpy transition temperature due to neutron irradiation embrittlement. It may cause reduction in resistance of material against DCG and this leads to the problem peculiar to low USE materials such that the limitation for DCG might be dominant rather than that for KJclimit. Therefore, it is possible to fail to obtain valid KJc data even within valid temperature range of MC methodology, i.e. −50°C ≤ T-To ≤ 50°C, for low USE materials using Mini-C(T) specimens. In this study, the RPV steel with USE lower than 68J was made simulating reduction of USE due to neutron irradiation. Fracture toughness tests were performed using Mini-C(T) specimens as well as the standard 1T-C(T) specimens. Based on the test results, the validity for DCG limitation was also evaluated for each datum by post-test observation of fracture surface. Additionally, effectiveness of added side grooves and double thickness of specimen was examined as a countermeasure for Mini-C(T) specimen.
{"title":"Study on Applicability of Master Curve Methodology Using Miniature C(T) Specimen to a Reactor Pressure Vessel With Low Upper Shelf Energy","authors":"K. Yoshimoto, T. Hirota, H. Sakamoto, Oshikiri Masato, K. Tsutsumi, Murakami Takeshi","doi":"10.1115/PVP2018-84994","DOIUrl":"https://doi.org/10.1115/PVP2018-84994","url":null,"abstract":"Miniature compact tension (Mini-C(T)) specimen can be an effective tool by utilizing together with Master Curve (MC) methodology for fracture toughness evaluation of irradiated reactor pressure vessel (RPV) steels. Recently, Mini-C(T) specimen has been incorporated into the Japanese standard test method related to MC methodology, JEAC4216-2015 and several studies were found focusing on applicability of Mini-C(T) specimen to irradiated RPV materials. However, there exist some other issues to be resolved considering application to irradiated materials. One of them is violation against the limitation criteria for ductile crack growth (DCG) specified in the standards. In general, upper shelf energy (USE) of RPV materials tends to decrease as well as shift in Charpy transition temperature due to neutron irradiation embrittlement. It may cause reduction in resistance of material against DCG and this leads to the problem peculiar to low USE materials such that the limitation for DCG might be dominant rather than that for KJclimit. Therefore, it is possible to fail to obtain valid KJc data even within valid temperature range of MC methodology, i.e. −50°C ≤ T-To ≤ 50°C, for low USE materials using Mini-C(T) specimens.\u0000 In this study, the RPV steel with USE lower than 68J was made simulating reduction of USE due to neutron irradiation. Fracture toughness tests were performed using Mini-C(T) specimens as well as the standard 1T-C(T) specimens. Based on the test results, the validity for DCG limitation was also evaluated for each datum by post-test observation of fracture surface. Additionally, effectiveness of added side grooves and double thickness of specimen was examined as a countermeasure for Mini-C(T) specimen.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"126 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":"116093913","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}
The standard Master Curve (MC) deals only with materials assumed to be homogeneous, but MC analysis methods for inhomogeneous materials have also been developed. Especially the bi-modal and multi-modal analysis methods are becoming more and more standard. Their drawback is that these methods are generally reliable only with sufficiently large data sets (number of valid tests, r ≥ 15–20). Here, the possibility of using the multi-modal analysis method with smaller data sets is assessed, and a new procedure to conservatively account for possible inhomogeneities is proposed.
{"title":"Assessment of Master Curve Material Inhomogeneity Using Small Data Sets","authors":"K. Wallin","doi":"10.1115/PVP2018-84297","DOIUrl":"https://doi.org/10.1115/PVP2018-84297","url":null,"abstract":"The standard Master Curve (MC) deals only with materials assumed to be homogeneous, but MC analysis methods for inhomogeneous materials have also been developed. Especially the bi-modal and multi-modal analysis methods are becoming more and more standard. Their drawback is that these methods are generally reliable only with sufficiently large data sets (number of valid tests, r ≥ 15–20). Here, the possibility of using the multi-modal analysis method with smaller data sets is assessed, and a new procedure to conservatively account for possible inhomogeneities is proposed.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"6 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":"128833832","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}
Small punch test specimens are widely used for a long time as they are simple to produce and requires only a small volume of material. This fact is advantageous especially for high activity materials but also for assessment of operational damage in components materials when component integrity and strength may not be affected. In the same time, no test standard exists and several different specimen types and test procedures have been developed in different place. Thus, to unify this activity, considerable attention has been paid since 2012 to the standardization of small punch test technique within the American Society of Testing and Materials (ASTM). In 2016 a large InterLaboratory Study has been launched within the ASTM subcommittee E10.02 - Behavior and Use of Nuclear Structural Materials, involving 12 laboratories and 6 evaluated structural materials from the nuclear and non-nuclear power plant components. Paper describes the current status of ASTM standardization, results of the InterLaboratory Study, first analysis of the results with respect to some important test parameters, lessons learned and open questions remaining to be solved for the successful completion of the standardization process.
{"title":"Interlaboratory Study for Small Punch Testing Preliminary Results","authors":"M. Brumovsky, R. Kopřiva","doi":"10.1115/PVP2018-84142","DOIUrl":"https://doi.org/10.1115/PVP2018-84142","url":null,"abstract":"Small punch test specimens are widely used for a long time as they are simple to produce and requires only a small volume of material. This fact is advantageous especially for high activity materials but also for assessment of operational damage in components materials when component integrity and strength may not be affected. In the same time, no test standard exists and several different specimen types and test procedures have been developed in different place.\u0000 Thus, to unify this activity, considerable attention has been paid since 2012 to the standardization of small punch test technique within the American Society of Testing and Materials (ASTM). In 2016 a large InterLaboratory Study has been launched within the ASTM subcommittee E10.02 - Behavior and Use of Nuclear Structural Materials, involving 12 laboratories and 6 evaluated structural materials from the nuclear and non-nuclear power plant components.\u0000 Paper describes the current status of ASTM standardization, results of the InterLaboratory Study, first analysis of the results with respect to some important test parameters, lessons learned and open questions remaining to be solved for the successful completion of the standardization process.","PeriodicalId":128383,"journal":{"name":"Volume 1A: Codes and Standards","volume":"31 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":"114292770","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}
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