Welding has been used for decades to create materials from weld metal that were machined to form components and used as a substitute for long lead-time castings, plate and forgings. Past terms like “shapewelding” or “shape melting” have been replaced with “additive manufacturing” to describe the process, but there is debate whether it should be treated as an additive/subtractive manufacturing process or a welding process followed by machining. Welding procedure qualifications verify weld metal properties. The properties of qualified welds are quite predictable when the welding parameters (variables) are controlled. The range of variables to be controlled and the allowable limits vary based on the risk tolerance of the application. These variable qualification limits are covered in various welding qualification codes and standards. In the past, code rules for weld metal buildup were used to qualify additive weld metal, but tighter controls are demanded today. Because of this, ASME Section IX developed and published rules in Code Case 3020 [1] for welding procedure qualifications that are specific to gas metal arc additive manufacturing (GMAAM). The Code Case 3020 qualification rules require testing weld metal properties at the highest and lowest cooling rates to be used in production. Code Case 3020 rules also require testing the thinnest wall section and a thick section for each of those cooling rates. The rules also require that all of the essential and supplementary essential variables used for weld metal joining and operator qualification in ASME Section IX continue to be followed. An ASME supported research project was launched to validate these rules. The project included a design of experiments (DOE), created by subject matter experts and vetted by an advisory committee consisting of designers, fabricators, consultants and metallurgists. Approximately two tons of weld metal was deposited using 24 different sets of welding parameter input configurations as set out by the DOE. Over 300 tensile specimens and over 500 Charpy V-notch (CVN) specimens were taken from various orientations and tested to characterize the weld metal properties. The data was analyzed to determine if the variables and interactions provided statistically significant prediction of the weld metal properties. The degree of isotropy and the extent to which manipulated variables predict weld metal properties are key findings. This paper examines those results, and discusses the relationships as they relate to new and existing code rules.
几十年来，焊接一直被用于从焊接金属中制造材料，这些金属被加工成零件，并被用作长交付周期的铸件、板材和锻件的替代品。过去的术语，如“形状焊接”或“形状熔化”已经被“增材制造”所取代，但它是否应该被视为增材/减材制造过程或焊接过程之后的机械加工存在争议。焊接工艺资格验证焊缝金属性能。当焊接参数(变量)得到控制时，合格焊缝的性能是可预测的。要控制的变量范围和允许的限制根据应用程序的风险承受能力而变化。这些可变的资格限制在各种焊接资格规范和标准中都有规定。在过去，焊接金属积累的规范规则被用来确定添加的焊接金属，但今天需要更严格的控制。因此，美国机械工程师协会(ASME)第九分会制定并公布了规范案例3020[1]中针对气体金属电弧增材制造(GMAAM)的焊接程序资格的规则。规范案例3020鉴定规则要求在生产中使用的最高和最低冷却速率下测试焊缝金属性能。Code Case 3020规则还要求测试每种冷却速率的最薄壁段和最厚壁段。规则还要求继续遵循ASME第IX节中用于焊接金属连接和操作人员资格的所有基本和补充基本变量。一个由ASME支持的研究项目已经启动，以验证这些规则。该项目包括一个实验设计(DOE)，由主题专家创建，并由设计师、制造商、顾问和冶金学家组成的咨询委员会审查。根据美国能源部的规定，使用24套不同的焊接参数输入配置沉积了大约2吨的焊缝金属。从不同方向采集了300多个拉伸试样和500多个夏比v形缺口(CVN)试样，并对焊缝金属性能进行了表征。对数据进行分析，以确定变量和相互作用是否对焊缝金属性能提供统计上显著的预测。各向同性的程度和操纵变量预测焊缝金属性能的程度是关键的发现。本文将检查这些结果，并讨论它们与新的和现有的代码规则相关的关系。
{"title":"A Statistical Study of Mechanical Properties From Mild Steel Welds Deposited via Gas Metal Arc Additive Manufacturing (GMAAM)","authors":"J. B. Schaeffer, Brad Barnhart, T. Melfi","doi":"10.1115/pvp2022-84056","DOIUrl":"https://doi.org/10.1115/pvp2022-84056","url":null,"abstract":"\u0000 Welding has been used for decades to create materials from weld metal that were machined to form components and used as a substitute for long lead-time castings, plate and forgings. Past terms like “shapewelding” or “shape melting” have been replaced with “additive manufacturing” to describe the process, but there is debate whether it should be treated as an additive/subtractive manufacturing process or a welding process followed by machining.\u0000 Welding procedure qualifications verify weld metal properties. The properties of qualified welds are quite predictable when the welding parameters (variables) are controlled. The range of variables to be controlled and the allowable limits vary based on the risk tolerance of the application. These variable qualification limits are covered in various welding qualification codes and standards.\u0000 In the past, code rules for weld metal buildup were used to qualify additive weld metal, but tighter controls are demanded today. Because of this, ASME Section IX developed and published rules in Code Case 3020 [1] for welding procedure qualifications that are specific to gas metal arc additive manufacturing (GMAAM).\u0000 The Code Case 3020 qualification rules require testing weld metal properties at the highest and lowest cooling rates to be used in production. Code Case 3020 rules also require testing the thinnest wall section and a thick section for each of those cooling rates. The rules also require that all of the essential and supplementary essential variables used for weld metal joining and operator qualification in ASME Section IX continue to be followed.\u0000 An ASME supported research project was launched to validate these rules. The project included a design of experiments (DOE), created by subject matter experts and vetted by an advisory committee consisting of designers, fabricators, consultants and metallurgists. Approximately two tons of weld metal was deposited using 24 different sets of welding parameter input configurations as set out by the DOE. Over 300 tensile specimens and over 500 Charpy V-notch (CVN) specimens were taken from various orientations and tested to characterize the weld metal properties. The data was analyzed to determine if the variables and interactions provided statistically significant prediction of the weld metal properties. The degree of isotropy and the extent to which manipulated variables predict weld metal properties are key findings. This paper examines those results, and discusses the relationships as they relate to new and existing code rules.","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122571061","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}
Creep strength-enhanced ferritic (CSEF) steels are widely used in fossil power plants operated in many countries and life management for the components made of these materials are of critical importance for plant operators. In particular, failures in welded joints in softened heat affected zone (HAZ) categorized as type IV failure have taken place widely in piping and boiler headers and prediction of such failure became a urgent requirement to be addressed. Following the simple longitudinal welds, weldments used for attaching various nozzles to main piping or boiler headers became the portions susceptible to type IV failure, stimulating the needs for prediction of their lives also. As a result, it turned out that a more sophisticated approach which can deal with complicated geometries involved in these weldments needs to be developed. With such a background, the authors carried out an internal pressure creep test at 650 °C using the pipe of P91 steel with the outer diameter of 457.2 mm. Outline of testing condition as well as the results including the periodic damage inspection by several methods is presented in the accompanying paper whereas related analytical efforts will be described in this paper. Detailed finite element analyses were performed on nozzles with different geometries, incorporating creep deformation properties of each continuant of welded joint. Moreover, failure criterion based on inelastic strain energy density has been developed for softened HAZ, taking into account of the dependency on temperature, creep strain rate as well as stress triaxiality factor. Results obtained using these properties were compared with the test results in terms of the location and extent of cracking due to creep damage accumulation. They showed reasonable agreement, demonstrating the soundness of the developed approach.
{"title":"Development of Life Estimation Method for Nozzle Welds in Large Scale Piping of Modified 9Cr-1Mo Steel -Part II: Analytical Study","authors":"Yukio Takahashi, H. Shigeyama, M. Yaguchi","doi":"10.1115/pvp2022-84126","DOIUrl":"https://doi.org/10.1115/pvp2022-84126","url":null,"abstract":"\u0000 Creep strength-enhanced ferritic (CSEF) steels are widely used in fossil power plants operated in many countries and life management for the components made of these materials are of critical importance for plant operators. In particular, failures in welded joints in softened heat affected zone (HAZ) categorized as type IV failure have taken place widely in piping and boiler headers and prediction of such failure became a urgent requirement to be addressed. Following the simple longitudinal welds, weldments used for attaching various nozzles to main piping or boiler headers became the portions susceptible to type IV failure, stimulating the needs for prediction of their lives also. As a result, it turned out that a more sophisticated approach which can deal with complicated geometries involved in these weldments needs to be developed.\u0000 With such a background, the authors carried out an internal pressure creep test at 650 °C using the pipe of P91 steel with the outer diameter of 457.2 mm. Outline of testing condition as well as the results including the periodic damage inspection by several methods is presented in the accompanying paper whereas related analytical efforts will be described in this paper. Detailed finite element analyses were performed on nozzles with different geometries, incorporating creep deformation properties of each continuant of welded joint. Moreover, failure criterion based on inelastic strain energy density has been developed for softened HAZ, taking into account of the dependency on temperature, creep strain rate as well as stress triaxiality factor. Results obtained using these properties were compared with the test results in terms of the location and extent of cracking due to creep damage accumulation. They showed reasonable agreement, demonstrating the soundness of the developed approach.","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128555135","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}
This study introduces a datum temperature (DT) calibration approach for improved extrapolation of minimum-creep-strain-rate (MCSR) and stress-rupture (SR) data. The ASME B&PV code III outlines stringent requirements for the approval of materials where each heat is to be tested to 10,000+ hours to be qualified for service. Additionally, components operating at a range of service conditions require tests to be performed at many combinations of stress and temperature. Subsequently, it takes years to decades for new creep-resistant alloys to be implemented due to the number, duration, and costs of tests involved. The increasing demand for new alloys for IGT applications and the desire to reduce qualification time has driven the urge for rapid qualification testing, calibration, and modeling techniques. To that end, a datum temperature (DT) calibration approach is applied to a contemporary creep-damage model for improved long-term extrapolation of creep data. In the DT approach, data across multiple temperatures are mathematically transferred to a datum temperature creating a master curve. This collapse of the data to a single isotherm (i.e. master curve) increases the amount of data available for model calibration. Next, the model is calibrated to the master curve; afterward, the model is transferred back to original temperatures. A DT approach can significantly reduce: the overall duration of creep testing; effort required for model calibration; and eliminate the requirement for temperature-dependent material constants. In this study, the DT calibration method is applied to the continuum-damage-mechanics (CDM)-based Sine-hyperbolic (Sinh) model to extrapolate the MCSR and SR for 18Cr-8Ni (304SS) stainless steel. The MCSR and SR data across multiple isotherms are gathered from the National Institute for Material Science (NIMS) database. Mathematical rules to transfer data to a datum temperature are developed for the Sinh MCSR and SR equations. The Sinh material constants are obtained by creating and fitting the DT master curve. The model is shifted back to the original temperatures and extrapolation credibility is assessed. The normalized mean square error (NMSE), coefficient of determination (R2), and mean square percentage error (MSPE) statistics are employed to analyze the prediction quality. The NMSE at datum temperature is observed to be 2.044 and 0.233 for MCSR and SR, respectively. The corresponding MSPE statistics is low at 0.296 and 0.191. The extrapolation at low stress and high temperature and vice versa is observed to be devoid of any inflection point. The DT approach for Sinh is further verified and validated by comparing against additional MCSR and SR data for 18Cr-12Ni-Mo (316SS) stainless steel that were not used for calibration. It is observed that the Sinh extrapolated MCSR and SR are free of inflection points. Based on the goodness-of-fit of the extrapolations, a recommendation to use DT approach for past and modern creep-damage
{"title":"A Datum Temperature Calibration Approach for Long-Term Minimum-Creep-Strain-Rate and Stress-Rupture Prediction Using Sine-Hyperbolic Creep-Damage Model","authors":"Md. Abir Hossain, M. Haque, C. Stewart","doi":"10.1115/pvp2022-82064","DOIUrl":"https://doi.org/10.1115/pvp2022-82064","url":null,"abstract":"\u0000 This study introduces a datum temperature (DT) calibration approach for improved extrapolation of minimum-creep-strain-rate (MCSR) and stress-rupture (SR) data. The ASME B&PV code III outlines stringent requirements for the approval of materials where each heat is to be tested to 10,000+ hours to be qualified for service. Additionally, components operating at a range of service conditions require tests to be performed at many combinations of stress and temperature. Subsequently, it takes years to decades for new creep-resistant alloys to be implemented due to the number, duration, and costs of tests involved. The increasing demand for new alloys for IGT applications and the desire to reduce qualification time has driven the urge for rapid qualification testing, calibration, and modeling techniques. To that end, a datum temperature (DT) calibration approach is applied to a contemporary creep-damage model for improved long-term extrapolation of creep data. In the DT approach, data across multiple temperatures are mathematically transferred to a datum temperature creating a master curve. This collapse of the data to a single isotherm (i.e. master curve) increases the amount of data available for model calibration. Next, the model is calibrated to the master curve; afterward, the model is transferred back to original temperatures. A DT approach can significantly reduce: the overall duration of creep testing; effort required for model calibration; and eliminate the requirement for temperature-dependent material constants.\u0000 In this study, the DT calibration method is applied to the continuum-damage-mechanics (CDM)-based Sine-hyperbolic (Sinh) model to extrapolate the MCSR and SR for 18Cr-8Ni (304SS) stainless steel. The MCSR and SR data across multiple isotherms are gathered from the National Institute for Material Science (NIMS) database. Mathematical rules to transfer data to a datum temperature are developed for the Sinh MCSR and SR equations. The Sinh material constants are obtained by creating and fitting the DT master curve. The model is shifted back to the original temperatures and extrapolation credibility is assessed. The normalized mean square error (NMSE), coefficient of determination (R2), and mean square percentage error (MSPE) statistics are employed to analyze the prediction quality. The NMSE at datum temperature is observed to be 2.044 and 0.233 for MCSR and SR, respectively. The corresponding MSPE statistics is low at 0.296 and 0.191. The extrapolation at low stress and high temperature and vice versa is observed to be devoid of any inflection point. The DT approach for Sinh is further verified and validated by comparing against additional MCSR and SR data for 18Cr-12Ni-Mo (316SS) stainless steel that were not used for calibration. It is observed that the Sinh extrapolated MCSR and SR are free of inflection points. Based on the goodness-of-fit of the extrapolations, a recommendation to use DT approach for past and modern creep-damage","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126610666","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 recent years, pressure equipment tends to operate under higher temperature and higher pressure with the rapid development of world economy, resulting in greater significance of creep fatigue damage that is strongly temperature and time dependent. This brings new challenges to the design, manufacturing, operation and maintenance management of the high-temperature pressure equipment. The welded structure of high-temperature pressure equipment exhibits heterogenous microstructures with mismatched mechanical properties, as well as the unavoidable weld defects. Damage characterization, life design and failure assessment of welded structures have always been challenging difficulties. Hence, the welded structure is the weakest link for creep fatigue failure. The present paper introduces the research progress on creep fatigue damage assessment method for the welded structures of high-temperature pressure equipment in China, based on the digital image correlation (DIC) technology and the ductility exhaustion theory. It involves in-situ characterization of heterogenous creep deformation of welded joints by using the digital image correlation technology, creep damage assessment of welded structures by finite element modeling, evaluation of strain enhancement effect and life-based creep fatigue strength design of high-temperature welded structures, etc. This method can provide useful guidance for establishing the prevention and control schemes for creep fatigue damage of high-temperature welded structures.
{"title":"Creep Fatigue Damage Assessment of the Welded Structures of High-Temperature Pressure Equipment Based on DIC Technology","authors":"Z. Fan, Yu Zhou, X. Chen","doi":"10.1115/pvp2022-84700","DOIUrl":"https://doi.org/10.1115/pvp2022-84700","url":null,"abstract":"\u0000 In recent years, pressure equipment tends to operate under higher temperature and higher pressure with the rapid development of world economy, resulting in greater significance of creep fatigue damage that is strongly temperature and time dependent. This brings new challenges to the design, manufacturing, operation and maintenance management of the high-temperature pressure equipment. The welded structure of high-temperature pressure equipment exhibits heterogenous microstructures with mismatched mechanical properties, as well as the unavoidable weld defects. Damage characterization, life design and failure assessment of welded structures have always been challenging difficulties. Hence, the welded structure is the weakest link for creep fatigue failure. The present paper introduces the research progress on creep fatigue damage assessment method for the welded structures of high-temperature pressure equipment in China, based on the digital image correlation (DIC) technology and the ductility exhaustion theory. It involves in-situ characterization of heterogenous creep deformation of welded joints by using the digital image correlation technology, creep damage assessment of welded structures by finite element modeling, evaluation of strain enhancement effect and life-based creep fatigue strength design of high-temperature welded structures, etc. This method can provide useful guidance for establishing the prevention and control schemes for creep fatigue damage of high-temperature welded structures.","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132598525","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}
Methods for minimum-creep-strain-rate prediction have evolved. Many models have been proposed, and different calibration techniques are used. Often the limitation of these models for accurate prediction arises due to a lack of long-range data incorporating both the low-stress and high-stress regions. This problem is more prominent for novel materials with very little data and may require long-term creep tests, delaying the material’s qualification. Model calibration against short-range data may lead to an inflection during extrapolation. In this study, a datum temperature (DT) calibration method derived from Parametric Numerical Isothermal Datum (P-NID) is compared with the traditional calibration approach for minimum-creep-strain-rate prediction using Norton power law. Minimum-creep-strain-rate data for Inconel 617 at five temperature levels (800 to 1000°C) and stress ranging from 11 to 122 MPa are used. Two different forms of the Norton power law are calibrated using the traditional approach and the most suitable form for Inconel 617 is selected. Next, the model is calibrated using the datum temperature calibration approach. In the datum temperature method, the data from different temperatures are transferred to a datum temperature creating a wide range of parametric data followed by model calibration against the transferred data at datum temperature. Finally, the model is transferred back to the original temperatures. The traditional approach and datum temperature method results are compared in terms of accuracy, calibration techniques, extrapolation, and limitations for Inconel 617. The datum temperature method is found to be accurate, like the traditional approach, however, requires comparatively less effort during calibration since the model is calibrated against a single temperature instead of multiple temperatures. Thus, the material constants are independent of temperature and stress resulting in stable, inflection-free, and reliable extrapolation over the traditional approach. A step-by-step procedure is provided to derive the datum temperature transformation equations and the calibration method. Finally, a general guideline is provided to apply the datum temperature method to any existing models.
{"title":"Comparison of a Datum Temperature Calibration Method With Traditional Approach for Norton Power Law","authors":"M. Haque","doi":"10.1115/pvp2022-84415","DOIUrl":"https://doi.org/10.1115/pvp2022-84415","url":null,"abstract":"\u0000 Methods for minimum-creep-strain-rate prediction have evolved. Many models have been proposed, and different calibration techniques are used. Often the limitation of these models for accurate prediction arises due to a lack of long-range data incorporating both the low-stress and high-stress regions. This problem is more prominent for novel materials with very little data and may require long-term creep tests, delaying the material’s qualification. Model calibration against short-range data may lead to an inflection during extrapolation. In this study, a datum temperature (DT) calibration method derived from Parametric Numerical Isothermal Datum (P-NID) is compared with the traditional calibration approach for minimum-creep-strain-rate prediction using Norton power law. Minimum-creep-strain-rate data for Inconel 617 at five temperature levels (800 to 1000°C) and stress ranging from 11 to 122 MPa are used. Two different forms of the Norton power law are calibrated using the traditional approach and the most suitable form for Inconel 617 is selected. Next, the model is calibrated using the datum temperature calibration approach. In the datum temperature method, the data from different temperatures are transferred to a datum temperature creating a wide range of parametric data followed by model calibration against the transferred data at datum temperature. Finally, the model is transferred back to the original temperatures. The traditional approach and datum temperature method results are compared in terms of accuracy, calibration techniques, extrapolation, and limitations for Inconel 617. The datum temperature method is found to be accurate, like the traditional approach, however, requires comparatively less effort during calibration since the model is calibrated against a single temperature instead of multiple temperatures. Thus, the material constants are independent of temperature and stress resulting in stable, inflection-free, and reliable extrapolation over the traditional approach. A step-by-step procedure is provided to derive the datum temperature transformation equations and the calibration method. Finally, a general guideline is provided to apply the datum temperature method to any existing models.","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130187588","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 main objective and mission of the European Project ATLAS+ project was to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. ATLAS+ WP3 was focused mainly on ductile tearing prediction for large defects in components. Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as the triaxiality effect, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is today rather limited to R&D or expertise. However, because of the continuous progress in the performance of the calculation tools and accumulated knowledge, in particular by members of ATLAS+, these models can now be considered as relevant for application in the context of engineering assessments. Although there are analytical solutions for calculation of J-Integral values for many standard specimen geometries (i.e. CT or SENT), limited or no formulas are available for more complex structures such as pipes, elbows, T-junctions, pressure vessels etc. Therefore, there is a need to develop a methodology which can be used for derivation of J-R curves for an arbitrary component geometry on the basis of experimental results obtained by testing small size laboratory specimens. To achieve this goal Framatome GmbH used combined local approach (GTN model) and elastic-plastic calculations to determine J-R curves whereas Framatome France used analytical methodologies to derive the J-R curves from local approach results (GTN model). In both cases, the Δa and J values were calculated at the deepest point of the crack front. This paper shows promising results and concludes there is a significant margin in the fracture mechanics assessment based on material properties obtained by testing highly constrained standard specimens compared to more realistic structural situations.
{"title":"ATLAS+ European Project - General Method for the Components J-R Curve Derivation","authors":"T. Nicak, A. Blouin, S. Marie, O. Ancelet","doi":"10.1115/pvp2022-84853","DOIUrl":"https://doi.org/10.1115/pvp2022-84853","url":null,"abstract":"\u0000 The main objective and mission of the European Project ATLAS+ project was to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. ATLAS+ WP3 was focused mainly on ductile tearing prediction for large defects in components. Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as the triaxiality effect, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is today rather limited to R&D or expertise. However, because of the continuous progress in the performance of the calculation tools and accumulated knowledge, in particular by members of ATLAS+, these models can now be considered as relevant for application in the context of engineering assessments.\u0000 Although there are analytical solutions for calculation of J-Integral values for many standard specimen geometries (i.e. CT or SENT), limited or no formulas are available for more complex structures such as pipes, elbows, T-junctions, pressure vessels etc.\u0000 Therefore, there is a need to develop a methodology which can be used for derivation of J-R curves for an arbitrary component geometry on the basis of experimental results obtained by testing small size laboratory specimens.\u0000 To achieve this goal Framatome GmbH used combined local approach (GTN model) and elastic-plastic calculations to determine J-R curves whereas Framatome France used analytical methodologies to derive the J-R curves from local approach results (GTN model). In both cases, the Δa and J values were calculated at the deepest point of the crack front.\u0000 This paper shows promising results and concludes there is a significant margin in the fracture mechanics assessment based on material properties obtained by testing highly constrained standard specimens compared to more realistic structural situations.","PeriodicalId":434925,"journal":{"name":"Volume 4A: Materials and Fabrication","volume":"196 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123656919","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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