Y. Javadi, Alistair Hutchison, R. Zimermann, D. Lines, Nina E. Sweeney, M. Vasilev, E. Mohseni, R. Vithanage, C. Macleod, G. Pierce, J. Mehnen, A. Gachagan
Residual Stress (RS) in engineering components can lead to unexpected and dangerous structural failures, and thus represent a significant challenge to quality assurance in both welding and metal additive manufacturing (AM) processes. The RS measurement using the ultrasonic method is based on the acoustoelasticity law, which states that the Time-of-Flight (ToF) of an ultrasonic wave is affected by the stress field. Longitudinal Critically Refracted (LCR) waves have the highest sensitivity to the stress in comparison with the other type of ultrasonic waves. However, they are also sensitive to the material texture which negatively affects the accuracy of the RS measurement. In this paper, a Phased Array Ultrasonic Testing (PAUT) system, rather than the single element transducers which are traditionally used in the LCR stress measurement technique, is innovatively used to enhance the accuracy of RS measurement. An experimental setup is developed that uses the PAUT to measure the ToFs in the weld, where the maximum amount of tensile RS is expected, and in the parent material, stress-free part. The ToF variations are then interpreted and analyzed to qualify the RS in the weld. The same measurement process is repeated for the Wire Arc Additive Manufacture (WAAM) components. Based on the results, some variations between different acoustic paths are measured which prove that the effect of the residual stress on the ultrasonic wave is detectable using the PAUT system.
{"title":"Development of a Phased Array Ultrasonic System for Residual Stress Measurement in Welding and Additive Manufacturing","authors":"Y. Javadi, Alistair Hutchison, R. Zimermann, D. Lines, Nina E. Sweeney, M. Vasilev, E. Mohseni, R. Vithanage, C. Macleod, G. Pierce, J. Mehnen, A. Gachagan","doi":"10.1115/pvp2022-85023","DOIUrl":"https://doi.org/10.1115/pvp2022-85023","url":null,"abstract":"\u0000 Residual Stress (RS) in engineering components can lead to unexpected and dangerous structural failures, and thus represent a significant challenge to quality assurance in both welding and metal additive manufacturing (AM) processes. The RS measurement using the ultrasonic method is based on the acoustoelasticity law, which states that the Time-of-Flight (ToF) of an ultrasonic wave is affected by the stress field. Longitudinal Critically Refracted (LCR) waves have the highest sensitivity to the stress in comparison with the other type of ultrasonic waves. However, they are also sensitive to the material texture which negatively affects the accuracy of the RS measurement. In this paper, a Phased Array Ultrasonic Testing (PAUT) system, rather than the single element transducers which are traditionally used in the LCR stress measurement technique, is innovatively used to enhance the accuracy of RS measurement. An experimental setup is developed that uses the PAUT to measure the ToFs in the weld, where the maximum amount of tensile RS is expected, and in the parent material, stress-free part. The ToF variations are then interpreted and analyzed to qualify the RS in the weld. The same measurement process is repeated for the Wire Arc Additive Manufacture (WAAM) components. Based on the results, some variations between different acoustic paths are measured which prove that the effect of the residual stress on the ultrasonic wave is detectable using the PAUT system.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"19 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":"126783803","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}
D. Hitchcock, T. Krentz, A. Mullins, C. James, Qianhui Liu, Siyang Wang, Samruddhi Gaikwad, M. Urban
Safe and reliable fueling components are essential for large scale deployment of H2 fuel. Field data has shown that existing materials used in dispensing hoses do not meet current standards for component reliability. Currently modern copolymerization methods are under investigation to create a new platform for inner hose technologies using self-healable copolymers. Ideally these inexpensive self-healable copolymer inner layers will reduce the cost of H2 delivery hoses and extend their service life beyond 25,000 refills. In this work gas driven hydrogen permeability measurements were performed on a variety of self-healing copolymer membranes all of which have exhibited excellent self-healing properties in previous studies. Copolymers were prepared with Poly(2,2,2-trifluoroethyl methacrylate/n-butyl acrylate) [p(TFEMA/nBA)] and Poly(methyl methacrylate/nbutyl acrylate) [p(MMA/nBA)]. Measurements were performed through a range of temperatures and source pressures. Additionally, the effects of composition, copolymer ratio, and molecular weight on the hydrogen permeability, solubility, and diffusivity were all studied. As expected, hydrogen permeation through the samples is proportional to the source pressure and inversely proportional to the molecular weight of the polymer. In general, the self-healing copolymers exhibit hydrogen permeabilities consistent with literature data for similar elastomers. These results suggest this class of self-healable copolymers may be promising candidates for use as inexpensive inner layers in hydrogen dispensing hoses with extended service life.
{"title":"Hydrogen Permeability of Self-Healing Copolymers for Use in Hydrogen Delivery Applications","authors":"D. Hitchcock, T. Krentz, A. Mullins, C. James, Qianhui Liu, Siyang Wang, Samruddhi Gaikwad, M. Urban","doi":"10.1115/pvp2022-84051","DOIUrl":"https://doi.org/10.1115/pvp2022-84051","url":null,"abstract":"\u0000 Safe and reliable fueling components are essential for large scale deployment of H2 fuel. Field data has shown that existing materials used in dispensing hoses do not meet current standards for component reliability. Currently modern copolymerization methods are under investigation to create a new platform for inner hose technologies using self-healable copolymers. Ideally these inexpensive self-healable copolymer inner layers will reduce the cost of H2 delivery hoses and extend their service life beyond 25,000 refills.\u0000 In this work gas driven hydrogen permeability measurements were performed on a variety of self-healing copolymer membranes all of which have exhibited excellent self-healing properties in previous studies. Copolymers were prepared with Poly(2,2,2-trifluoroethyl methacrylate/n-butyl acrylate) [p(TFEMA/nBA)] and Poly(methyl methacrylate/nbutyl acrylate) [p(MMA/nBA)]. Measurements were performed through a range of temperatures and source pressures. Additionally, the effects of composition, copolymer ratio, and molecular weight on the hydrogen permeability, solubility, and diffusivity were all studied. As expected, hydrogen permeation through the samples is proportional to the source pressure and inversely proportional to the molecular weight of the polymer. In general, the self-healing copolymers exhibit hydrogen permeabilities consistent with literature data for similar elastomers. These results suggest this class of self-healable copolymers may be promising candidates for use as inexpensive inner layers in hydrogen dispensing hoses with extended service life.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"180 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":"133444623","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}
Over the last decade, multiple carbon steel flanges brittle fracture failures have led the industry to issue a global alert on standard ASTM A105 flanges toughness values at temperatures higher than −20°F (−29°C), the minimum temperature allowed by the current editions of ASME B16.5 and ASME B31.3. The ASME BPV VIII Subgroup Toughness penalized these components by assigning the material the UCS-66 Curve A and modified UCS-66(c) to limit the minimum temperature of standard A105 flanges to 0°F (−18°C), unless the flanges have been normalized and manufactured to fine grain practice, after which they can be used down to the temperature permitted by ASME B16.5. In order to determine whether these changes would provide acceptable toughness values, nineteen (19) flanges were purchased from local manufacturers in both as-forged and normalized conditions and were subjected to several tests including charpy testing at various temperatures, McQuaid-Ehn, hardness testing, metallography, grain sizing, and chemical analysis. The results suggest that complying with UCS-66(c) does not necessarily guarantee acceptable toughness results for flanges that were normalized and manufactured to fine grain practice, and this is attributed to low Mn:C ratios and possibly uncontrolled heat treatment procedure. On the other hand, a number of non-normalized standard flanges have been found to provide very low toughness values at temperatures as high as 32°F (0°C), despite the current state of UCS-66(c) allowing use down to a minimum temperature of 0°F (−18°C). In view of the above, this paper discusses and evaluates some of the possible additional technical requirements that users could specify to minimize the risk of brittle fracture on standard ASTM A105 flanges, as well as a number of methods to guarantee better toughness performance in standard flanges.
{"title":"Flanges Impact Testing Exemption Assessment","authors":"Roberto Robles, M. Muñoz, Antonio Santana","doi":"10.1115/pvp2022-84867","DOIUrl":"https://doi.org/10.1115/pvp2022-84867","url":null,"abstract":"\u0000 Over the last decade, multiple carbon steel flanges brittle fracture failures have led the industry to issue a global alert on standard ASTM A105 flanges toughness values at temperatures higher than −20°F (−29°C), the minimum temperature allowed by the current editions of ASME B16.5 and ASME B31.3. The ASME BPV VIII Subgroup Toughness penalized these components by assigning the material the UCS-66 Curve A and modified UCS-66(c) to limit the minimum temperature of standard A105 flanges to 0°F (−18°C), unless the flanges have been normalized and manufactured to fine grain practice, after which they can be used down to the temperature permitted by ASME B16.5.\u0000 In order to determine whether these changes would provide acceptable toughness values, nineteen (19) flanges were purchased from local manufacturers in both as-forged and normalized conditions and were subjected to several tests including charpy testing at various temperatures, McQuaid-Ehn, hardness testing, metallography, grain sizing, and chemical analysis. The results suggest that complying with UCS-66(c) does not necessarily guarantee acceptable toughness results for flanges that were normalized and manufactured to fine grain practice, and this is attributed to low Mn:C ratios and possibly uncontrolled heat treatment procedure. On the other hand, a number of non-normalized standard flanges have been found to provide very low toughness values at temperatures as high as 32°F (0°C), despite the current state of UCS-66(c) allowing use down to a minimum temperature of 0°F (−18°C).\u0000 In view of the above, this paper discusses and evaluates some of the possible additional technical requirements that users could specify to minimize the risk of brittle fracture on standard ASTM A105 flanges, as well as a number of methods to guarantee better toughness performance in standard flanges.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"5 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":"115234618","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}
Many existing pieces of plant equipment do not have original impact test data or suffer from a loss in toughness over time. As a result, the ability to remove material for testing can be of significant value. Often, extraction of sufficient material for conducting fracture toughness testing necessitates weld repair to fill in the sample location. Some equipment may also require stress relief. Use of subsize test specimens that minimizes the amount of material removed can permit local thin area acceptance criteria to be met and avoids weld repair in most cases. However, for subsize specimens that are substantially smaller than conventional geometries, it is important to examine the limits within which a valid J integral can be measured when tests display significant amount of ductility. Standards like ASTM E1820-20 provide restrictions on the maximum J integral (Jmax) based on specimen thickness (B), uncracked ligament length (bo) as well as maximum crack growth Δa. These limits ensure the stress-strain fields at the crack tip are well described by J, a condition referred to as J dominance. In the first phase of this project, detailed 3D FEA analyses of subsize compact tension C(T) specimens (commonly called mini-CT) have been performed to explore the criteria necessary to obtain a valid measurement of J. This is generally considered to be a function of the materials hardening exponent, mode of loading, and the specimen dimensions. One methodology to examine if J controlled crack growth exists is to evaluate the crack tip stress field, and compare this to the theoretical HRR solution. In the case of the mini-CT, due to limitations associated with the small specimen size and extent of yielding across the uncracked ligament, the two parameter J-A2 solution was used to extend the range of J dominance. Additional modification of J-A2 is made by accounting for the effect of global bending on crack tip opening stress (J-A2-M) following the procedures developed by Zhu et al. [1] and Chao et al. [2] for SEN(B) specimens. The results of this study indicate that Jmax for the mini-CT may be given as Jmax<(Bn,bo)σo5 for typical pressure vessel steels. Where Bn is the specimen net thickness, bo is the ligament length and σo is the yield stress. However, test results as well as consideration for plastic collapse suggest that while a valid measurement of initiation J (Ji) may be possible, the extent of J controlled crack growth is more restrictive than the ASTM E 1820-20 limit of Δa = 0.25bo, and may be closer to 0.08 bo.
许多现有的工厂设备没有原始的冲击试验数据，或者随着时间的推移而遭受韧性损失。因此，去除用于测试的材料的能力可能具有重要的价值。通常，为了提取足够的材料进行断裂韧性测试，需要进行焊缝修复以填充样品位置。有些设备可能还需要减压。使用小尺寸试样可以最大限度地减少材料的去除量，从而满足局部薄区域的验收标准，并在大多数情况下避免焊接修复。然而，对于比传统几何形状小得多的亚尺寸试样，当试验显示大量延性时，检查有效J积分可以测量的极限是很重要的。ASTM E1820-20等标准根据试样厚度(B)、未开裂韧带长度(bo)以及最大裂纹扩展Δa对最大J积分(Jmax)进行了限制。这些极限确保了裂纹尖端的应力-应变场被J很好地描述，这种情况被称为J优势。在这个项目的第一阶段，详细的三维有限元分析的亚尺寸致密拉伸C(T)试样(通常称为迷你ct)已经执行，以探索必要的标准，以获得有效的测量J.这通常被认为是一个函数的材料硬化指数，加载模式和试样尺寸。检验J控制裂纹扩展是否存在的一种方法是评估裂纹尖端应力场，并将其与理论HRR解进行比较。在mini-CT的情况下，由于与小样本尺寸和未裂韧带屈服程度相关的限制，使用两参数J- a2溶液来扩大J优势的范围。根据Zhu et al.[1]和Chao et al.[2]为SEN(B)试样开发的程序，通过考虑整体弯曲对裂纹尖端开启应力(J-A2- m)的影响，对J-A2进行了额外的修改。研究结果表明，对于典型的压力容器钢，微型ct的Jmax可取为Jmax<(Bn,bo)σo5。式中，Bn为试样净厚度，bo为韧带长度，σo为屈服应力。然而，试验结果以及对塑性破坏的考虑表明，虽然可以有效地测量起裂J (Ji)，但J控制裂纹扩展的程度比ASTM E 1820-20的极限Δa = 0.25bo更为严格，可能更接近0.08 bo。
{"title":"Evaluation of Validity Criteria for Subsize Compact Tension Specimens Using a Bending Modified J-A2 Solution","authors":"K. Bagnoli, G. Thorwald, R. Holloman, Y. Hioe","doi":"10.1115/pvp2022-81773","DOIUrl":"https://doi.org/10.1115/pvp2022-81773","url":null,"abstract":"\u0000 Many existing pieces of plant equipment do not have original impact test data or suffer from a loss in toughness over time. As a result, the ability to remove material for testing can be of significant value. Often, extraction of sufficient material for conducting fracture toughness testing necessitates weld repair to fill in the sample location. Some equipment may also require stress relief. Use of subsize test specimens that minimizes the amount of material removed can permit local thin area acceptance criteria to be met and avoids weld repair in most cases. However, for subsize specimens that are substantially smaller than conventional geometries, it is important to examine the limits within which a valid J integral can be measured when tests display significant amount of ductility. Standards like ASTM E1820-20 provide restrictions on the maximum J integral (Jmax) based on specimen thickness (B), uncracked ligament length (bo) as well as maximum crack growth Δa. These limits ensure the stress-strain fields at the crack tip are well described by J, a condition referred to as J dominance. In the first phase of this project, detailed 3D FEA analyses of subsize compact tension C(T) specimens (commonly called mini-CT) have been performed to explore the criteria necessary to obtain a valid measurement of J. This is generally considered to be a function of the materials hardening exponent, mode of loading, and the specimen dimensions. One methodology to examine if J controlled crack growth exists is to evaluate the crack tip stress field, and compare this to the theoretical HRR solution. In the case of the mini-CT, due to limitations associated with the small specimen size and extent of yielding across the uncracked ligament, the two parameter J-A2 solution was used to extend the range of J dominance. Additional modification of J-A2 is made by accounting for the effect of global bending on crack tip opening stress (J-A2-M) following the procedures developed by Zhu et al. [1] and Chao et al. [2] for SEN(B) specimens. The results of this study indicate that Jmax for the mini-CT may be given as Jmax<(Bn,bo)σo5 for typical pressure vessel steels. Where Bn is the specimen net thickness, bo is the ligament length and σo is the yield stress. However, test results as well as consideration for plastic collapse suggest that while a valid measurement of initiation J (Ji) may be possible, the extent of J controlled crack growth is more restrictive than the ASTM E 1820-20 limit of Δa = 0.25bo, and may be closer to 0.08 bo.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"31 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":"115231695","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}
Romy Welschen, F. Gillemot, I. Simonovski, O. Martin, M. Adamech, J. Petzová, Rebeca Hernández, R. Kopřiva, Frederiki Naziris, Boy Molenaar, M. Kolluri
Miniature / sub-sized specimen test methods for the mechanical characterization of metallic alloys like the small punch test (SPT) have the benefit that only small quantities of material are needed to perform a reasonable number of tests. This makes such tests in particular interesting if only limited quantities of material are available for mechanical characterization, like irradiated specimens from reactor pressure vessel (RPV) surveillance programs of light water reactors (LWRs). The SPT only requires small discs of 8mm diameter and 0.5mm thickness and such specimens can be manufactured from broken Charpy impact test specimens that were previously tested within RPV surveillance programs. With the publication of EN 10371 earlier in 2021 the SPT is now a standardized test that can be used in principle to determine tensile, creep, fracture toughness properties and ductile-to-brittle transition temperatures (DBTTs). However, fabrication and testing of irradiated SPT specimens remotely in hot cell environments has several practical challenges. Any deviation in specification as laid down in the standard can lead to variations in test outcome. To address this issue an SPT Round Robin exercise on VVER RPV steel 15Kh2NMFA reference material has been performed in the context of the Horizon 2020 Euratom project STRUMAT-LTO. Several research organizations, namely NRG, EK/CER, JRC, VUJE, CIEMAT and UJV, have participated in this round robin exercise to validate sample manufacturing, test procedures and test equipment and to determine tensile properties and DBTTs of the above RPV steel. In this paper results and conclusions of the STRUMAT-LTO SPT round robin exercise are presented.
{"title":"Round Robin Analysis of Small Punch Testing on 15Kh2NMFA Reference Material","authors":"Romy Welschen, F. Gillemot, I. Simonovski, O. Martin, M. Adamech, J. Petzová, Rebeca Hernández, R. Kopřiva, Frederiki Naziris, Boy Molenaar, M. Kolluri","doi":"10.1115/pvp2022-83811","DOIUrl":"https://doi.org/10.1115/pvp2022-83811","url":null,"abstract":"\u0000 Miniature / sub-sized specimen test methods for the mechanical characterization of metallic alloys like the small punch test (SPT) have the benefit that only small quantities of material are needed to perform a reasonable number of tests. This makes such tests in particular interesting if only limited quantities of material are available for mechanical characterization, like irradiated specimens from reactor pressure vessel (RPV) surveillance programs of light water reactors (LWRs). The SPT only requires small discs of 8mm diameter and 0.5mm thickness and such specimens can be manufactured from broken Charpy impact test specimens that were previously tested within RPV surveillance programs. With the publication of EN 10371 earlier in 2021 the SPT is now a standardized test that can be used in principle to determine tensile, creep, fracture toughness properties and ductile-to-brittle transition temperatures (DBTTs). However, fabrication and testing of irradiated SPT specimens remotely in hot cell environments has several practical challenges. Any deviation in specification as laid down in the standard can lead to variations in test outcome. To address this issue an SPT Round Robin exercise on VVER RPV steel 15Kh2NMFA reference material has been performed in the context of the Horizon 2020 Euratom project STRUMAT-LTO. Several research organizations, namely NRG, EK/CER, JRC, VUJE, CIEMAT and UJV, have participated in this round robin exercise to validate sample manufacturing, test procedures and test equipment and to determine tensile properties and DBTTs of the above RPV steel. In this paper results and conclusions of the STRUMAT-LTO SPT round robin exercise are presented.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"8 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":"117183157","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. Hayashi, T. Ogawa, Shuichi Yoshida, M. Itatani, Toshiyuki Saito
Cases of stress corrosion cracking (SCC) in Ni-base alloy weld metals welded to the low alloy steel (LAS) in reactor pressure vessel (RPV) components have led to discussions on the possibility of SCC propagating into the RPV. In the previous study, the fracture mode of dissimilar metal welds (DMWs) of LAS and Ni-base alloy weld has been investigated by using a large-scale, heavy forged steel part named “bottom head ring” of the RPV, manufactured for a recent boiling water reactor (BWR). The fracture loads evaluated using the elastic-plastic fracture mechanics (EPFM) methodology have showed fairly good agreement with the maximum loads in the fracture tests on plate specimens with a semi-elliptical surface crack. All the fracture tests have successfully demonstrated the applicability of the fracture assessment methodology based on EPFM to the DMWs of RPV components. In the fracture tests on the plate specimens, a periodic unloading condition was applied in order to obtain specimen compliance: inverse of the gradient in the load-displacement relationship under unloading. The compliances were evaluated from the crack mouth opening displacement (CMOD) data that have been obtained for large CMOD of more than 10 mm at fracture. The results of detailed evaluations of the ductile crack extension behavior based on the evaluated compliance indicated that the ductile crack extension occurred near the maximum load. Evaluations of the J–Δa relationships of the plate specimens based on the CMOD data were also performed by finite element analyses (FEA) according to the proposed method. The J–R curves obtained for the plate specimens commonly showed similar behaviors of having significantly higher J for the small Δa range from 0 to about 2 mm than that for the compact tension (C(T)) specimen, indicating a difference in the plastic constraint in the crack tip between the two types of specimens. These results demonstrate that the method proposed in this study is highly useful for evaluating the J–Δa relationship of the fracture test specimen. Fracture assessments using the J–R curves of the plate specimens provided a better prediction of the fracture load than that using the J–R curve of the conventional C(T) specimen. All the results supported the applicability of the EPFM methodology in the fracture evaluation, shown in the previous work.
{"title":"Study on Ductile Crack Extension and Fracture Behavior in Plate Specimen With a Semi-Elliptical Surface Crack Using a BWR Reactor Pressure Vessel Material","authors":"T. Hayashi, T. Ogawa, Shuichi Yoshida, M. Itatani, Toshiyuki Saito","doi":"10.1115/pvp2022-84606","DOIUrl":"https://doi.org/10.1115/pvp2022-84606","url":null,"abstract":"\u0000 Cases of stress corrosion cracking (SCC) in Ni-base alloy weld metals welded to the low alloy steel (LAS) in reactor pressure vessel (RPV) components have led to discussions on the possibility of SCC propagating into the RPV. In the previous study, the fracture mode of dissimilar metal welds (DMWs) of LAS and Ni-base alloy weld has been investigated by using a large-scale, heavy forged steel part named “bottom head ring” of the RPV, manufactured for a recent boiling water reactor (BWR). The fracture loads evaluated using the elastic-plastic fracture mechanics (EPFM) methodology have showed fairly good agreement with the maximum loads in the fracture tests on plate specimens with a semi-elliptical surface crack. All the fracture tests have successfully demonstrated the applicability of the fracture assessment methodology based on EPFM to the DMWs of RPV components.\u0000 In the fracture tests on the plate specimens, a periodic unloading condition was applied in order to obtain specimen compliance: inverse of the gradient in the load-displacement relationship under unloading. The compliances were evaluated from the crack mouth opening displacement (CMOD) data that have been obtained for large CMOD of more than 10 mm at fracture. The results of detailed evaluations of the ductile crack extension behavior based on the evaluated compliance indicated that the ductile crack extension occurred near the maximum load. Evaluations of the J–Δa relationships of the plate specimens based on the CMOD data were also performed by finite element analyses (FEA) according to the proposed method. The J–R curves obtained for the plate specimens commonly showed similar behaviors of having significantly higher J for the small Δa range from 0 to about 2 mm than that for the compact tension (C(T)) specimen, indicating a difference in the plastic constraint in the crack tip between the two types of specimens. These results demonstrate that the method proposed in this study is highly useful for evaluating the J–Δa relationship of the fracture test specimen. Fracture assessments using the J–R curves of the plate specimens provided a better prediction of the fracture load than that using the J–R curve of the conventional C(T) specimen. All the results supported the applicability of the EPFM methodology in the fracture evaluation, shown in the previous work.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"1 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":"128276992","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 this paper, a strain-based failure assessment is performed on a canister made of stainless steel when a spent nuclear fuel dry storage system goes through a drop accident, to investigate the effects of strain rate on strain-based failure assessment results. The KORAD-21 multi-purpose dry storage container system developed for interim storage and transportation at the Korea Radioactive Waste Agency (KORAD) is considered. A finite element (FE) analysis is performed on a 1m puncture drop of the KORAD-21 model. Based on the FE results, the canister under a 1m puncture drop is evaluated by two different criteria: (1) strain-based acceptance criteria suggested in ASME Boiler and Pressure Vessels Code Section III, Appendix FF, “Strain-based acceptance criteria for energy-limited events” and (2) the Johnson-Cook fracture strain model based on experimental data. The difference between the two criteria is that the Johnson-Cook fracture strain model expresses the true fracture strain as a function of stress triaxiality and strain rate, whereas the formula in App. FF establishes strain limit (combination of uniform strain and true fracture strain) as a function of stress triaxiality only. In this study, the safety margins of Appendix FF are analyzed by comparing the failure assessment results for canister drop simulation with those applying the Johnson-Cook fracture strain model.
{"title":"Effects of Strain Rate on Strain-Based Failure Assessment of Cask 1m-Puncture Drop for 304 Stainless Steel","authors":"H. Kim, Jun-Min Seo, Ji-Hye Kim, Yun‐Jae Kim","doi":"10.1115/pvp2022-83765","DOIUrl":"https://doi.org/10.1115/pvp2022-83765","url":null,"abstract":"\u0000 In this paper, a strain-based failure assessment is performed on a canister made of stainless steel when a spent nuclear fuel dry storage system goes through a drop accident, to investigate the effects of strain rate on strain-based failure assessment results. The KORAD-21 multi-purpose dry storage container system developed for interim storage and transportation at the Korea Radioactive Waste Agency (KORAD) is considered. A finite element (FE) analysis is performed on a 1m puncture drop of the KORAD-21 model. Based on the FE results, the canister under a 1m puncture drop is evaluated by two different criteria: (1) strain-based acceptance criteria suggested in ASME Boiler and Pressure Vessels Code Section III, Appendix FF, “Strain-based acceptance criteria for energy-limited events” and (2) the Johnson-Cook fracture strain model based on experimental data. The difference between the two criteria is that the Johnson-Cook fracture strain model expresses the true fracture strain as a function of stress triaxiality and strain rate, whereas the formula in App. FF establishes strain limit (combination of uniform strain and true fracture strain) as a function of stress triaxiality only. In this study, the safety margins of Appendix FF are analyzed by comparing the failure assessment results for canister drop simulation with those applying the Johnson-Cook fracture strain model.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"1 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":"115658487","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}
NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. Most tanks have between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents results which consider weld residual stress and fracture assessment of some layered pressure vessels. This is part of the much larger probabilistic fitness for service evaluation of these tanks. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Because the tanks have low toughness the weld residual stress state has an important effect on the fitness for service of these tanks and are tabulated for use in the probabilistic code.
{"title":"Weld Residual Stress Modeling of and Fracture Assessment of Layered Pressure Vessels","authors":"F. Brust","doi":"10.1115/pvp2022-85958","DOIUrl":"https://doi.org/10.1115/pvp2022-85958","url":null,"abstract":"\u0000 NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. Most tanks have between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents results which consider weld residual stress and fracture assessment of some layered pressure vessels. This is part of the much larger probabilistic fitness for service evaluation of these tanks. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Because the tanks have low toughness the weld residual stress state has an important effect on the fitness for service of these tanks and are tabulated for use in the probabilistic code.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"109 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":"122701363","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 paper intends to contribute to a better understanding of how normalizing cooling rate affects toughness of SA – 350 LF2 Class 1 forgings. This is a sensitive material widely used in pressure vessels fabrication when toughness requirements are applicable. Three pieces from the same forging were normalized at 870°C for two hours. Each of them was subjected to a different cooling rate from normalizing to room temperature, being the temperature in the center of the piece registered by thermocouples every two seconds. Test specimens were extracted for impact testing at −46°C and metallographic examination. Subsequently, the normalized samples were cut out in two and subjected to two simulated post weld heat treatment at 630°C. Further specimens for metallographic characterization and impact testing were taken. It can be concluded that normalizing cooling rate has a pivotal role in the morphology of pearlite, and hence in its ability to offset the deterioration of toughness in the post weld heat treatment due to iron carbide precipitation by means of pearlite spheroidization.
{"title":"Effect of Normalizing Cooling Rate on Impact Toughness of ASME SA – 350 LF2 CL1 Forgings","authors":"R. Hernández Soto, J. M. Gómez de Salazar","doi":"10.1115/pvp2022-84549","DOIUrl":"https://doi.org/10.1115/pvp2022-84549","url":null,"abstract":"\u0000 This paper intends to contribute to a better understanding of how normalizing cooling rate affects toughness of SA – 350 LF2 Class 1 forgings. This is a sensitive material widely used in pressure vessels fabrication when toughness requirements are applicable.\u0000 Three pieces from the same forging were normalized at 870°C for two hours. Each of them was subjected to a different cooling rate from normalizing to room temperature, being the temperature in the center of the piece registered by thermocouples every two seconds. Test specimens were extracted for impact testing at −46°C and metallographic examination. Subsequently, the normalized samples were cut out in two and subjected to two simulated post weld heat treatment at 630°C. Further specimens for metallographic characterization and impact testing were taken.\u0000 It can be concluded that normalizing cooling rate has a pivotal role in the morphology of pearlite, and hence in its ability to offset the deterioration of toughness in the post weld heat treatment due to iron carbide precipitation by means of pearlite spheroidization.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"37 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":"134201465","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 XFEM (Extended Finite Element Method) has emerged as a reliable tool for structural engineers to study fracture problems. This method was introduced in 1999 as an alternative to the solution of models with inclusions and discontinuities. As it is a recent method and despite being available in most of the commercial software, the modeling with XFEM lacks assessment on the sensitivity of the method in terms of mesh refinement and other parameters that need to be suitable for building the model. This experimental and numerical study explores the Extended Finite Element Method to predict ductile crack propagation of typical fracture specimens made of a pressure vessel ASTM A285 steel. First, a detailed parametric study is conducted to reproduce the load versus displacement curve obtained from a fracture toughness test using deep crack bend samples. Then, after calibrating the model parameters, the model is used to predict the response of specimens with different levels of crack-tip triaxiality. For this purpose, shallow crack bend specimens with and without side grooves are modeled and compared to experimental toughness tests. Overall, a good agreement between experimental and numerical responses was observed.
{"title":"Calibration and Verification of XFEM Model to Predict Ductile Fracture","authors":"Israel Pereira, D. Sarzosa","doi":"10.1115/pvp2022-84341","DOIUrl":"https://doi.org/10.1115/pvp2022-84341","url":null,"abstract":"\u0000 The XFEM (Extended Finite Element Method) has emerged as a reliable tool for structural engineers to study fracture problems. This method was introduced in 1999 as an alternative to the solution of models with inclusions and discontinuities. As it is a recent method and despite being available in most of the commercial software, the modeling with XFEM lacks assessment on the sensitivity of the method in terms of mesh refinement and other parameters that need to be suitable for building the model. This experimental and numerical study explores the Extended Finite Element Method to predict ductile crack propagation of typical fracture specimens made of a pressure vessel ASTM A285 steel. First, a detailed parametric study is conducted to reproduce the load versus displacement curve obtained from a fracture toughness test using deep crack bend samples. Then, after calibrating the model parameters, the model is used to predict the response of specimens with different levels of crack-tip triaxiality. For this purpose, shallow crack bend specimens with and without side grooves are modeled and compared to experimental toughness tests. Overall, a good agreement between experimental and numerical responses was observed.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"1 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":"124486666","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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