Local post welding heat treatment (PWHT) is a popular method to reduce the residual stress of bigger weld structures. In this paper, the weld residual stresses before and after local PWHT were investigated. The results show that there are larger axial stresses concentration in weld toe and an inconsistent deformation along axial direction during heating stage which may leads to crack. The residual stresses in outer surface are decreased greatly after local PWHT. An optimized local PWHT with auxiliary heating (AH) temperature 800°C and width 800mm were proposed. The axial stress and deformation inconsistent in weld can be reduced by AH, thus leads to the reduction of crack risk in weld toe.
{"title":"An Optimized Heat Treatment Process to Reduce the Weld Residual Stress by Auxiliary Heating","authors":"Yun-Xu Luo, Gao Teng, Wenchun Jiang","doi":"10.1115/pvp2019-93112","DOIUrl":"https://doi.org/10.1115/pvp2019-93112","url":null,"abstract":"\u0000 Local post welding heat treatment (PWHT) is a popular method to reduce the residual stress of bigger weld structures. In this paper, the weld residual stresses before and after local PWHT were investigated. The results show that there are larger axial stresses concentration in weld toe and an inconsistent deformation along axial direction during heating stage which may leads to crack. The residual stresses in outer surface are decreased greatly after local PWHT. An optimized local PWHT with auxiliary heating (AH) temperature 800°C and width 800mm were proposed. The axial stress and deformation inconsistent in weld can be reduced by AH, thus leads to the reduction of crack risk in weld toe.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"178 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78511771","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}
Sung-Ho Yoon, Tae-Young Ryu, M. Kim, Jaeboong Choi, Ik-joong Kim
Single-Edge-Notched-Bending (SENB) specimen is mainly used for fracture characteristics test of pipe material. However, there is also a disadvantage in that it does not sufficiently simulate the fracture characteristics of thin pipes due to the difference in boundary effect between the SENB specimen and the actual pipe. The Single-Edge-Notched-Tensile (SENT) specimen can be used as complementary test method due to its less boundary effect compared to the SENB specimen. In this study, the SENT specimen which are fabricated with API X 70 carbon steel was simulated ductile fracture behavior by using finite-element-analysis (FEA). To simulate ductile fracture behavior, Gurson-Tvergaard-Needleman (GTN) model was applied. GTN model is a kind of damage model that describes the behavior of ductile fracture through three steps of void changes : nucleation, growth, and coalescence. And GTN model is composed of three constitutive equations and nine parameters. In order to develop the GTN ductile fracture model for API X 70 carbon steel, five kinds of tensile specimen tests were simulated by FEA. In addition, we analyzed the influence of parameters of GTN model through analysis and developed optimal material parameters for API X 70 carbon steel. Finally, the ductile fracture behavior of the SENT specimen was simulated and the FEA results of SENT specimen was compared with actual SENT specimen test.
单侧切口弯曲(SENB)试样主要用于管道材料断裂特性试验。但也存在一个缺点，即由于SENB试样与实际管道的边界效应不同，不能充分模拟细管的断裂特征。与SENB试样相比，单侧缺口拉伸试样具有较小的边界效应，因此可以作为补充试验方法。采用有限元分析方法模拟了API X 70碳钢试样的韧性断裂行为。为了模拟韧性断裂行为，采用了Gurson-Tvergaard-Needleman (GTN)模型。GTN模型是一种通过成核、长大、聚并这三步空穴变化来描述韧性断裂行为的损伤模型。GTN模型由3个本构方程和9个参数组成。为了建立API X 70碳钢的GTN韧性断裂模型，采用有限元法对5种拉伸试样进行了模拟。此外，通过分析分析GTN模型参数的影响，制定了API X 70碳钢的最佳材料参数。最后，模拟了试件的韧性断裂行为，并将试件的有限元分析结果与实际试件试验结果进行了比较。
{"title":"Development of GTN Model Parameters for Simulating Ductile Fracture Behavior of X 70 Carbon Steel SENT Specimens","authors":"Sung-Ho Yoon, Tae-Young Ryu, M. Kim, Jaeboong Choi, Ik-joong Kim","doi":"10.1115/pvp2019-93542","DOIUrl":"https://doi.org/10.1115/pvp2019-93542","url":null,"abstract":"\u0000 Single-Edge-Notched-Bending (SENB) specimen is mainly used for fracture characteristics test of pipe material. However, there is also a disadvantage in that it does not sufficiently simulate the fracture characteristics of thin pipes due to the difference in boundary effect between the SENB specimen and the actual pipe. The Single-Edge-Notched-Tensile (SENT) specimen can be used as complementary test method due to its less boundary effect compared to the SENB specimen. In this study, the SENT specimen which are fabricated with API X 70 carbon steel was simulated ductile fracture behavior by using finite-element-analysis (FEA). To simulate ductile fracture behavior, Gurson-Tvergaard-Needleman (GTN) model was applied. GTN model is a kind of damage model that describes the behavior of ductile fracture through three steps of void changes : nucleation, growth, and coalescence. And GTN model is composed of three constitutive equations and nine parameters. In order to develop the GTN ductile fracture model for API X 70 carbon steel, five kinds of tensile specimen tests were simulated by FEA. In addition, we analyzed the influence of parameters of GTN model through analysis and developed optimal material parameters for API X 70 carbon steel. Finally, the ductile fracture behavior of the SENT specimen was simulated and the FEA results of SENT specimen was compared with actual SENT specimen test.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"136 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79467517","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}
Kawami Kazuyoshi, B. An, T. Iijima, S. Fukuyama, M. Imaoka, Hiroyasu Tamai, Tamura Motonori, A. Kinoshita, Toshiyuki Tanaka
Hydrogen barrier coating is a promising technology for preventing hydrogen embrittlement in metals. In this study, characterizations of hydrogen barrier films coated on surfaces of austenitic stainless steel, SUS304 of the Japanese Industrial Standard (JIS), by wet coating processes applied electro-polishing and chemical oxidation method are carried out using cross-sectional transmission electron microscopy (TEM) analyses, and then slow strain rate tensile (SSRT) tests are performed in 1.1MPa hydrogen and nitrogen gases at room temperature. The hydrogen barrier films show 200–300nm total thickness of compositionally modulated Chromium oxide dense layer. The SSRT results reveal that both the elongation and reduction of area are decreased in hydrogen gas compared with those in nitrogen gas for the non barrier-coated specimens but no significant differences appear for the barrier-coated specimens. The fracture surface of the non barrier-coated specimen shows quasi-cleavagy cracking in hydrogen gas while that of the barrier-coated specimen shows only ductile dimple fracture in hydrogen gas, indicating that the coated films effectively prevent the hydrogen embrittlement of SUS304 stainless steel in hydrogen.
{"title":"Wet Coated Thin Barrier Films to Prevent Hydrogen Embrittlement on SUS304 Stainless Steel","authors":"Kawami Kazuyoshi, B. An, T. Iijima, S. Fukuyama, M. Imaoka, Hiroyasu Tamai, Tamura Motonori, A. Kinoshita, Toshiyuki Tanaka","doi":"10.1115/pvp2019-93260","DOIUrl":"https://doi.org/10.1115/pvp2019-93260","url":null,"abstract":"\u0000 Hydrogen barrier coating is a promising technology for preventing hydrogen embrittlement in metals. In this study, characterizations of hydrogen barrier films coated on surfaces of austenitic stainless steel, SUS304 of the Japanese Industrial Standard (JIS), by wet coating processes applied electro-polishing and chemical oxidation method are carried out using cross-sectional transmission electron microscopy (TEM) analyses, and then slow strain rate tensile (SSRT) tests are performed in 1.1MPa hydrogen and nitrogen gases at room temperature. The hydrogen barrier films show 200–300nm total thickness of compositionally modulated Chromium oxide dense layer. The SSRT results reveal that both the elongation and reduction of area are decreased in hydrogen gas compared with those in nitrogen gas for the non barrier-coated specimens but no significant differences appear for the barrier-coated specimens. The fracture surface of the non barrier-coated specimen shows quasi-cleavagy cracking in hydrogen gas while that of the barrier-coated specimen shows only ductile dimple fracture in hydrogen gas, indicating that the coated films effectively prevent the hydrogen embrittlement of SUS304 stainless steel in hydrogen.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85582712","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}
H. Takamizawa, J. Katsuyama, Y. Ha, T. Tobita, Y. Nishiyama, K. Onizawa
The heat-affected zone (HAZ) of reactor pressure vessel (RPV) steels is known to show large scatter in Charpy impact properties because it has inhomogeneous microstructure due to thermal histories of multi-pass welding for butt-welded joints. The correlation between mechanical properties and microstructure such as grain size, phase-fraction, martensite-austenite constituent, on the characteristics of HAZ of un-irradiated materials was investigated. Neutron irradiation was conducted at Japanese Research Reactor −3 (JRR-3) operated by JAEA. The neutron irradiation susceptibility was evaluated based on post-irradiation examinations consisting of mechanical testing and microstructural analysis. In the experiments, typical RPV steel plate and their weldment were prepared. Simulated HAZ materials that have representative microstructures such as coarse-grain HAZ (CGHAZ) and fine-grain HAZ (FGHAZ) were also prepared based on the thermal histories calculated by finite element analysis. For un-irradiated materials, a part of simulated HAZ materials showed a higher reference temperature of the master curve method than that of the base metal (BM). The irradiation hardening of HAZ was almost the same or lower than that of the BM, and the shift of reference temperature for HAZ materials was comparable with that of BM.
{"title":"Susceptibility to Neutron Irradiation Embrittlement of Heat-Affected Zone of Reactor Pressure Vessel Steels","authors":"H. Takamizawa, J. Katsuyama, Y. Ha, T. Tobita, Y. Nishiyama, K. Onizawa","doi":"10.1115/pvp2019-94011","DOIUrl":"https://doi.org/10.1115/pvp2019-94011","url":null,"abstract":"\u0000 The heat-affected zone (HAZ) of reactor pressure vessel (RPV) steels is known to show large scatter in Charpy impact properties because it has inhomogeneous microstructure due to thermal histories of multi-pass welding for butt-welded joints. The correlation between mechanical properties and microstructure such as grain size, phase-fraction, martensite-austenite constituent, on the characteristics of HAZ of un-irradiated materials was investigated. Neutron irradiation was conducted at Japanese Research Reactor −3 (JRR-3) operated by JAEA. The neutron irradiation susceptibility was evaluated based on post-irradiation examinations consisting of mechanical testing and microstructural analysis. In the experiments, typical RPV steel plate and their weldment were prepared. Simulated HAZ materials that have representative microstructures such as coarse-grain HAZ (CGHAZ) and fine-grain HAZ (FGHAZ) were also prepared based on the thermal histories calculated by finite element analysis. For un-irradiated materials, a part of simulated HAZ materials showed a higher reference temperature of the master curve method than that of the base metal (BM). The irradiation hardening of HAZ was almost the same or lower than that of the BM, and the shift of reference temperature for HAZ materials was comparable with that of BM.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"71 7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83614743","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}
Structural components are regularly exposed to cyclic thermal stresses which can induce plastic deformation within them. The accumulation of plastic deformation will eventually lead to failure of the component. The creep behaviour a material exhibits depends upon the magnitude and sign of the prior loading the material was subjected to. This idea was investigated by conducting tests on a section of 316H stainless steel header at 550°C. Both negative and positive plastic strain were applied upon loading followed by load controlled creep to investigate the influence of prior loading upon the accumulation of creep strain. These tests resulted in more creep strain being accumulated after compressive prior loading as opposed to tensile prior loading. This result is significantly influenced by intergranular strains which come from elastic and plastic anisotropy. The experimental results have been compared to the results of an existing crystal plasticity finite element (CPFE) model and there is good agreement between the two sets. Validation of the CPFE model is important for understanding the behaviour of 316H and being able to accurately predict the hysteresis loop this material produces which can provide vital information when conducting life assessments.
{"title":"The Influence of Prior Plastic Loading on the Accumulation of Creep Strain in 316H Stainless Steel","authors":"Megan Taylor, A. Mamun, D. Knowles","doi":"10.1115/pvp2019-93639","DOIUrl":"https://doi.org/10.1115/pvp2019-93639","url":null,"abstract":"\u0000 Structural components are regularly exposed to cyclic thermal stresses which can induce plastic deformation within them. The accumulation of plastic deformation will eventually lead to failure of the component. The creep behaviour a material exhibits depends upon the magnitude and sign of the prior loading the material was subjected to. This idea was investigated by conducting tests on a section of 316H stainless steel header at 550°C. Both negative and positive plastic strain were applied upon loading followed by load controlled creep to investigate the influence of prior loading upon the accumulation of creep strain. These tests resulted in more creep strain being accumulated after compressive prior loading as opposed to tensile prior loading. This result is significantly influenced by intergranular strains which come from elastic and plastic anisotropy. The experimental results have been compared to the results of an existing crystal plasticity finite element (CPFE) model and there is good agreement between the two sets. Validation of the CPFE model is important for understanding the behaviour of 316H and being able to accurately predict the hysteresis loop this material produces which can provide vital information when conducting life assessments.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84883947","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}
Lifetime assessment of steam turbine components has become more and more important for the past years. Tower solar turbines experience a greater number of start-ups than those operating in base-load plants and high levels of thermal stress occurs during fast start-up, which both have a significant impact on lifetime. To achieve the fastest start-up time without reducing the lifetime of solar turbine it is essential to fully understand the thermal behavior of the turbine components during start-up. A series of experiments have been carried on a combined cycle steam turbine. The operation mode and inlet parameters of experiment unit are similar to tower solar turbine, so the new thermal model of heat transfer coefficient based on these experiment data can be used for the start-up research of tower solar turbine. A Finite Element (FE) turbine model is created and analyzed with the new thermal model in many start-up cases such as warm start, hot start to seek for an optimized start-up mode.
{"title":"An Optimized Start-Up Mode of Tower Solar Turbines With Heat Transfer Coefficient Model Based on Experiment Data","authors":"L. Xiaoxiao, C. Gang, Wang Peng","doi":"10.1115/pvp2019-94049","DOIUrl":"https://doi.org/10.1115/pvp2019-94049","url":null,"abstract":"\u0000 Lifetime assessment of steam turbine components has become more and more important for the past years. Tower solar turbines experience a greater number of start-ups than those operating in base-load plants and high levels of thermal stress occurs during fast start-up, which both have a significant impact on lifetime. To achieve the fastest start-up time without reducing the lifetime of solar turbine it is essential to fully understand the thermal behavior of the turbine components during start-up. A series of experiments have been carried on a combined cycle steam turbine. The operation mode and inlet parameters of experiment unit are similar to tower solar turbine, so the new thermal model of heat transfer coefficient based on these experiment data can be used for the start-up research of tower solar turbine. A Finite Element (FE) turbine model is created and analyzed with the new thermal model in many start-up cases such as warm start, hot start to seek for an optimized start-up mode.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"132 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84918130","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 2205 duplex stainless steel (DSS) was pre-stretched to 5% and subsequently aged at 850 °C for 0–120 minutes, to explore the effects of pre-strain and aging treatment on the corrosion behavior of the DSS in 6% FeCl3 solution at 50 °C for 72 hours. The microstructure, hardness and corrosion behavior of the pre-strained and aged DSS were investigated based on statistical data and physical metallurgy in comparison with the counterparts without pre-strain. The results showed that the sigma (σ) phase precipitated firstly in δ-ferrite grain boundaries and then in δ-ferrite/γ-austenite (δ/γ) phases boundaries by consuming the volume fraction of δ-ferrite. The volume fraction of σ phase in the DSS with and without pre-strain increased with increasing aging times following a classical Johnson-Mehl-Avrami (JMA) relationship, and the kinetics of the precipitation of σ phase was accelerated by pre-strain throughout the aging time of 60–120 min. The hardness of the non-pre-strained DSS (NP-DSS) was lower than that of pre-strained DSS (P-DSS) throughout 0–120 min at 850 °C. The hardness of NP-DSS increased continuously with increasing aging time, and the hardness of P-DSS decreased firstly and then increased continuously with increasing aging time. The aged NP-DSS displayed a gradually serious pitting with increasing aging time, and the corresponding corrosion behavior of the aged P-DSS exhibited pitting firstly and then mainly cracking, and the pitting occurred in the vicinity of δ/σ and γ/σ boundaries.
{"title":"Effect of Pre-Strain and Aging Heat Treatment on the Corrosion Behavior for 2205 Duplex Stainless Steel in 6% FeCl3 Solution","authors":"Chengsi Zheng, Qingnan Fei, W. Kong, Z. Ai","doi":"10.1115/pvp2019-93244","DOIUrl":"https://doi.org/10.1115/pvp2019-93244","url":null,"abstract":"\u0000 A 2205 duplex stainless steel (DSS) was pre-stretched to 5% and subsequently aged at 850 °C for 0–120 minutes, to explore the effects of pre-strain and aging treatment on the corrosion behavior of the DSS in 6% FeCl3 solution at 50 °C for 72 hours. The microstructure, hardness and corrosion behavior of the pre-strained and aged DSS were investigated based on statistical data and physical metallurgy in comparison with the counterparts without pre-strain. The results showed that the sigma (σ) phase precipitated firstly in δ-ferrite grain boundaries and then in δ-ferrite/γ-austenite (δ/γ) phases boundaries by consuming the volume fraction of δ-ferrite. The volume fraction of σ phase in the DSS with and without pre-strain increased with increasing aging times following a classical Johnson-Mehl-Avrami (JMA) relationship, and the kinetics of the precipitation of σ phase was accelerated by pre-strain throughout the aging time of 60–120 min. The hardness of the non-pre-strained DSS (NP-DSS) was lower than that of pre-strained DSS (P-DSS) throughout 0–120 min at 850 °C. The hardness of NP-DSS increased continuously with increasing aging time, and the hardness of P-DSS decreased firstly and then increased continuously with increasing aging time. The aged NP-DSS displayed a gradually serious pitting with increasing aging time, and the corresponding corrosion behavior of the aged P-DSS exhibited pitting firstly and then mainly cracking, and the pitting occurred in the vicinity of δ/σ and γ/σ boundaries.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79765610","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 susceptibility of 316L-type austenite stainless steel to hydrogen was quantified by means of SSRT results and low-cycle fatigue life measurement. Both tests were conducted in the air condition after being charged with high-pressure hydrogen gas of 10 MPa and a temperature of 300°C for 120 hours. In addition, SSRT tests in gaseous hydrogen at a pressure of 10 MPa were also performed and compared to the tests conducted in hydrogen pre-charged and as-received conditions. The 0.2% yield strength and tensile strength did not show there to be a considerable difference between hydrogen pre-charging and the as-received conditions, whereas the gaseous hydrogen condition revealed a remarkable degradation in tensile properties, especially in terms of fracture elongation. In the case of fatigue life test, a considerable influence of hydrogen pre-charging in fatigue life properties was observed in the high strain amplitude regime whereas the measured values in the low strain deformation region are consistently comparable to that in the as-received condition. Fatigue limit was not affected by hydrogen pre-charging.
{"title":"Ductility and Fatigue Strength Loss of a Hydrogen-Charged 316L Austenitic Stainless Steel","authors":"U. Baek, T. Nguyen, S. Nahm, K. Ryu","doi":"10.1115/pvp2019-93180","DOIUrl":"https://doi.org/10.1115/pvp2019-93180","url":null,"abstract":"\u0000 The susceptibility of 316L-type austenite stainless steel to hydrogen was quantified by means of SSRT results and low-cycle fatigue life measurement. Both tests were conducted in the air condition after being charged with high-pressure hydrogen gas of 10 MPa and a temperature of 300°C for 120 hours. In addition, SSRT tests in gaseous hydrogen at a pressure of 10 MPa were also performed and compared to the tests conducted in hydrogen pre-charged and as-received conditions. The 0.2% yield strength and tensile strength did not show there to be a considerable difference between hydrogen pre-charging and the as-received conditions, whereas the gaseous hydrogen condition revealed a remarkable degradation in tensile properties, especially in terms of fracture elongation. In the case of fatigue life test, a considerable influence of hydrogen pre-charging in fatigue life properties was observed in the high strain amplitude regime whereas the measured values in the low strain deformation region are consistently comparable to that in the as-received condition. Fatigue limit was not affected by hydrogen pre-charging.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91391301","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 pipeline industry has traditionally utilized the “double stroke” concept to define line pipe yielding for limiting plastic deformation of the pipeline during hydrostatic pressure testing. Practice showed that double stroke may define a nominal yield point lying between the elastic limit and the offset yield strength. Recently, a set of field hydrostatic tests were conducted on an X70 pipeline at Enterprise Products, and the test pressure at double stroke was as high as 129% of SMYS, but the von Mises stress was less than the actual yield strength. The entire pipeline was thought in the elastic conditions at double stroke during the hydrostatic testing. It is well recognized that the classical Tresca and von Mises yield criteria determines a lower and an upper bound of the limit load at yielding, and a newly proposed Zhu-Leis yield criterion determines a medium result of the two classical solutions. Extensive full-scale tests have confirmed that the Zhu-Leis yield solution is the best prediction of experimental data on average. This paper attempts to use the more accurate Zhu-Leis yield criterion to reanalyze the real-world hydrostatic tests of the X70 pipeline to see if pipe yielding occurs and to determine pipe diameter expansion at double stroke during the hydrostatic pressure testing.
{"title":"Determination of Pipeline Yielding Occurred in Hydrostatic Pressure Testing","authors":"Xian-Kui Zhu","doi":"10.1115/pvp2019-93087","DOIUrl":"https://doi.org/10.1115/pvp2019-93087","url":null,"abstract":"\u0000 The pipeline industry has traditionally utilized the “double stroke” concept to define line pipe yielding for limiting plastic deformation of the pipeline during hydrostatic pressure testing. Practice showed that double stroke may define a nominal yield point lying between the elastic limit and the offset yield strength. Recently, a set of field hydrostatic tests were conducted on an X70 pipeline at Enterprise Products, and the test pressure at double stroke was as high as 129% of SMYS, but the von Mises stress was less than the actual yield strength. The entire pipeline was thought in the elastic conditions at double stroke during the hydrostatic testing.\u0000 It is well recognized that the classical Tresca and von Mises yield criteria determines a lower and an upper bound of the limit load at yielding, and a newly proposed Zhu-Leis yield criterion determines a medium result of the two classical solutions. Extensive full-scale tests have confirmed that the Zhu-Leis yield solution is the best prediction of experimental data on average. This paper attempts to use the more accurate Zhu-Leis yield criterion to reanalyze the real-world hydrostatic tests of the X70 pipeline to see if pipe yielding occurs and to determine pipe diameter expansion at double stroke during the hydrostatic pressure testing.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78674958","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}
Dissimilar Metal Welds (DMW) are commonly found between the ferritic low alloy steel heavy section components and the austenitic stainless steel piping sections in nuclear power plants. In the EPR™ design which is the latest FRAMATOME Pressurized water reactor (PWR) these DMW involve a narrow gap technology with no buttering, and only one bead per layer of a nickel base alloy weld filler metal (Alloy 52). In order to assess the thermal aging performance of this relatively new narrow gap DMW design, a significant internal R&D program was launched some years ago. Several representative mock-ups were thoroughly characterized in the initial condition as well as in the thermal aged condition, up to 50,000 hours aging at 350°C. The characterisations were focused on the fusion line between the ferritic low alloy steel (LAS) and the nickel base alloy since a particular microstructure is present in this area, especially in the carbon depleted area of the Heat Affected Zone (HAZ) which is often regarded as the weak zone of the weld joint. Metallography, hardness, nanohardness, chemical analyses, and Atom Probe Tomography, as well as fracture toughness tests were carried out on different specimens in different thermal aging conditions. The results show that the fracture toughness behaviour in the ductile-brittle domain of the low alloy steel carbon depleted HAZ at the interface with the alloy 52 weld metal of the DMWs is excellent, even for a thermal ageing equivalent to 60 years at service temperature. This was found in spite of the carbon depleted zone of the HAZ, the variations of hardness, chemical composition, particularly the carbon gradients, and the thermal aging effect induced by phosphorous segregation at grain boundaries.
{"title":"Thermal Aging Assessment and Microstructural Investigations of Alloy 52 Dissimilar Metal Welds for Nuclear Components","authors":"M. Yescas, P. Joly, F. Roch","doi":"10.1115/pvp2019-93120","DOIUrl":"https://doi.org/10.1115/pvp2019-93120","url":null,"abstract":"\u0000 Dissimilar Metal Welds (DMW) are commonly found between the ferritic low alloy steel heavy section components and the austenitic stainless steel piping sections in nuclear power plants. In the EPR™ design which is the latest FRAMATOME Pressurized water reactor (PWR) these DMW involve a narrow gap technology with no buttering, and only one bead per layer of a nickel base alloy weld filler metal (Alloy 52).\u0000 In order to assess the thermal aging performance of this relatively new narrow gap DMW design, a significant internal R&D program was launched some years ago. Several representative mock-ups were thoroughly characterized in the initial condition as well as in the thermal aged condition, up to 50,000 hours aging at 350°C. The characterisations were focused on the fusion line between the ferritic low alloy steel (LAS) and the nickel base alloy since a particular microstructure is present in this area, especially in the carbon depleted area of the Heat Affected Zone (HAZ) which is often regarded as the weak zone of the weld joint. Metallography, hardness, nanohardness, chemical analyses, and Atom Probe Tomography, as well as fracture toughness tests were carried out on different specimens in different thermal aging conditions. The results show that the fracture toughness behaviour in the ductile-brittle domain of the low alloy steel carbon depleted HAZ at the interface with the alloy 52 weld metal of the DMWs is excellent, even for a thermal ageing equivalent to 60 years at service temperature. This was found in spite of the carbon depleted zone of the HAZ, the variations of hardness, chemical composition, particularly the carbon gradients, and the thermal aging effect induced by phosphorous segregation at grain boundaries.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89427980","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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