A high pressure material testing system (max. pressure: 140 MPa, temperature range: −80 ∼ 90 °C) was developed to investigate the testing method of material compatibility for high pressure gaseous hydrogen. In this study, SSRT and fatigue life test of JIS SUS304 and SUS316 austenitic stainless steel were performed in high pressure gaseous hydrogen at room temperature, −45, and −80 °C. These testing results were compared with those in laboratory air atmosphere at the same test temperature range. The SSRT tests were performed at a strain rate of 5 × 10−5 s−1 in 105 MPa hydrogen gas, and nominal stress-strain curves were obtained. The 0.2% offset yield strength (Ys) did not show remarkable difference between in hydrogen gas and in laboratory air atmosphere for SUS304 and SUS316. Total elongation after fracture (El) in hydrogen gas at −45 and −80 °C were approximately 15 % for SUS304 and 20% for SUS316. In the case of fatigue life tests, a smooth surface round bar test specimen with a diameter of 7 mm was used at a frequency of 1, 0.1, and 0.01 Hz under stress rate of R = −1 (tension-compression) in 100 MPa hydrogen gas. It can be seen that the fatigue life test results of SUS304 and SUS316 showed same tendency. The fatigue limit at room temperature in 100 MPa hydrogen gas was comparable with that in laboratory air. The room temperature fatigue life in high pressure hydrogen gas appeared to be the more severe condition compared to the fatigue life at low temperature. The normalized stress amplitude (σa / Ts) at the fatigue limit was 0.37 to 0.39 for SUS304 and SUS316 austenitic stainless steels, respectively.
{"title":"Effect of High Pressure Gaseous Hydrogen on Fatigue Properties of SUS304 and SUS316 Austenitic Stainless Steel","authors":"T. Iijima, H. Enoki, J. Yamabe, B. An","doi":"10.1115/PVP2018-84267","DOIUrl":"https://doi.org/10.1115/PVP2018-84267","url":null,"abstract":"A high pressure material testing system (max. pressure: 140 MPa, temperature range: −80 ∼ 90 °C) was developed to investigate the testing method of material compatibility for high pressure gaseous hydrogen. In this study, SSRT and fatigue life test of JIS SUS304 and SUS316 austenitic stainless steel were performed in high pressure gaseous hydrogen at room temperature, −45, and −80 °C. These testing results were compared with those in laboratory air atmosphere at the same test temperature range. The SSRT tests were performed at a strain rate of 5 × 10−5 s−1 in 105 MPa hydrogen gas, and nominal stress-strain curves were obtained. The 0.2% offset yield strength (Ys) did not show remarkable difference between in hydrogen gas and in laboratory air atmosphere for SUS304 and SUS316. Total elongation after fracture (El) in hydrogen gas at −45 and −80 °C were approximately 15 % for SUS304 and 20% for SUS316. In the case of fatigue life tests, a smooth surface round bar test specimen with a diameter of 7 mm was used at a frequency of 1, 0.1, and 0.01 Hz under stress rate of R = −1 (tension-compression) in 100 MPa hydrogen gas. It can be seen that the fatigue life test results of SUS304 and SUS316 showed same tendency. The fatigue limit at room temperature in 100 MPa hydrogen gas was comparable with that in laboratory air. The room temperature fatigue life in high pressure hydrogen gas appeared to be the more severe condition compared to the fatigue life at low temperature. The normalized stress amplitude (σa / Ts) at the fatigue limit was 0.37 to 0.39 for SUS304 and SUS316 austenitic stainless steels, respectively.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84157884","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}
It has long been recognised that a defect experiencing a state of low constraint shows improved fracture properties when compared to the same defect in a highly constrained state. Fracture test specimens have, therefore, been designed in such a way as to generate a state of high constraint at the crack tip in order to ensure that the properties measured are conservative. Where a defect, in practice, is not highly constrained then using the fracture toughness measured from a standard test piece leads to an overly pessimistic assessment. With the move toward more accurate design and assessment due to the availability of advanced computational tools, it is advantageous to take this excessive conservatism into account. A particular case that is of interest is the effect that constraint has on the onset of upper shelf temperature (OUST). The OUST is typically defined as the intersection of the fracture toughness loci representing the 5% probability of cleavage and the 50% probability of ductile initiation. This paper details a method which can be used to predict the shift in OUST using the toughness scaling method proposed by Anderson and Dodds and extended to account for the influence of constraint on ductile initiation.
{"title":"Predicting the Effect of Low Constraint on the Onset of Upper Shelf Temperature","authors":"C. Seal, A. Sherry","doi":"10.1115/PVP2018-84606","DOIUrl":"https://doi.org/10.1115/PVP2018-84606","url":null,"abstract":"It has long been recognised that a defect experiencing a state of low constraint shows improved fracture properties when compared to the same defect in a highly constrained state. Fracture test specimens have, therefore, been designed in such a way as to generate a state of high constraint at the crack tip in order to ensure that the properties measured are conservative. Where a defect, in practice, is not highly constrained then using the fracture toughness measured from a standard test piece leads to an overly pessimistic assessment. With the move toward more accurate design and assessment due to the availability of advanced computational tools, it is advantageous to take this excessive conservatism into account. A particular case that is of interest is the effect that constraint has on the onset of upper shelf temperature (OUST). The OUST is typically defined as the intersection of the fracture toughness loci representing the 5% probability of cleavage and the 50% probability of ductile initiation. This paper details a method which can be used to predict the shift in OUST using the toughness scaling method proposed by Anderson and Dodds and extended to account for the influence of constraint on ductile initiation.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81740341","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 integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as those associated with lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper uses mechanistic modelling to define the limits of applicability of the NFAD approach in terms of ρ/a, where ρ is the notch root radius and a is the notch depth. The work concludes that the NFAD can be used to assess notches with ρ/a values of up to unity.
{"title":"Limits of Applicability of the Notch Failure Assessment Diagram","authors":"A. Horn, C. Aird","doi":"10.1115/PVP2018-85062","DOIUrl":"https://doi.org/10.1115/PVP2018-85062","url":null,"abstract":"Structural integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as those associated with lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper uses mechanistic modelling to define the limits of applicability of the NFAD approach in terms of ρ/a, where ρ is the notch root radius and a is the notch depth. The work concludes that the NFAD can be used to assess notches with ρ/a values of up to unity.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"17 Suppl 2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80249984","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. Sarzosa, R. Savioli, C. Ruggieri, A. Jivkov, J. Beswick
This work presents recent improvements in the micromechanical failure criterion based on the Weibull stress (σw) concept for prediction of cleavage fracture in ferritic steels. The model is applied in SE(B) specimens extracted from an ASTM A533 pressure vessel steel having different levels of stress triaxiality at the crack tip. Nonlinear 3D finite element models with dimensions matching the tested specimens were built to provide the necessary crack tip stresses at the fracture process zone for calculation of the σw-J evolution from wich the variation of characteristic toughness values (J0) between different cracked geometries can be estimated. Application of this methodology for the material used at this study is able to predict J0 for SE(B) specimens with very shallow crack size ratio a/W = 0.05, short crack a/W = 0.2 and deep crack a/W = 0.4. The reported fracture toughness values for specimens having very shallow crack size ratio is an additional contribution of this study.
{"title":"A Local Approach to Assess Effects of Specimen Geometry on Cleavage Fracture Toughness in Reactor Pressure Vessel Steels","authors":"D. Sarzosa, R. Savioli, C. Ruggieri, A. Jivkov, J. Beswick","doi":"10.1115/PVP2018-85063","DOIUrl":"https://doi.org/10.1115/PVP2018-85063","url":null,"abstract":"This work presents recent improvements in the micromechanical failure criterion based on the Weibull stress (σw) concept for prediction of cleavage fracture in ferritic steels. The model is applied in SE(B) specimens extracted from an ASTM A533 pressure vessel steel having different levels of stress triaxiality at the crack tip. Nonlinear 3D finite element models with dimensions matching the tested specimens were built to provide the necessary crack tip stresses at the fracture process zone for calculation of the σw-J evolution from wich the variation of characteristic toughness values (J0) between different cracked geometries can be estimated. Application of this methodology for the material used at this study is able to predict J0 for SE(B) specimens with very shallow crack size ratio a/W = 0.05, short crack a/W = 0.2 and deep crack a/W = 0.4. The reported fracture toughness values for specimens having very shallow crack size ratio is an additional contribution of this study.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78721328","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 computation of mass flow rates through crack-like defects in piping systems of light water reactors requires typically the description of two-phase flow conditions. The computed discharge rate depends on the crack opening area, the thermal-hydraulic modeling of the flow, and the flow resistance of the crack. Several models have been proposed to characterize the critical flow through crack-like defects. An evaluation of advantages and shortcomings of the different models with regard to the interaction of the three different parts (crack opening area, thermal-hydraulic modeling, flow resistance) has been performed. In this paper, the flow resistance modeling from several approaches is discussed, and compared with a database from eight different testing programs. Five different flow models are applied to analyze a database of more than 800 leak rate measurements for subcooled water from twelve different experimental programs. It is shown that the correct modeling of the flow resistance is crucial for a best estimate reproduction of the measured data. It turns out that generally, equilibrium models are about as good as non-equilibrium models. The data were processed with the GRS software WinLeck which includes different analytical approaches for the calculation of crack sizes and leak rates in piping components. The most reliable results within the model selection are produced by the CDR model (Critical Discharge Rate) of the ATHLET code (Analysis of Thermal-hydraulics of Leaks and Transients) developed by GRS. As a conclusion, the accurate modeling of form losses and frictional pressure losses for critical discharge flow rates through crack-like leaks are essential for a reliable prediction of flow rates. Uncertainties in leak rate computations results arise due to the lack of information about the flow geometry and its associated drag. The assumed flow resistance of a through-wall crack influences the computed leak rate as significant as the phase-change- and flow-models. The manifest difference between equilibrium models (Pana, Estorf) and non-equilibrium models (Henry, ATHLET-CDR) seems to be less significant than the pressure loss issue. One can conjecture that, for crack-like through-wall defects, friction effects play a more important role than non-equilibrium effects.
{"title":"Leak Rate Computation: Flow Resistance vs. Thermal-Hydraulic Aspect","authors":"K. Heckmann, J. Sievers, F. Weyermann","doi":"10.1115/PVP2018-84534","DOIUrl":"https://doi.org/10.1115/PVP2018-84534","url":null,"abstract":"The computation of mass flow rates through crack-like defects in piping systems of light water reactors requires typically the description of two-phase flow conditions. The computed discharge rate depends on the crack opening area, the thermal-hydraulic modeling of the flow, and the flow resistance of the crack. Several models have been proposed to characterize the critical flow through crack-like defects. An evaluation of advantages and shortcomings of the different models with regard to the interaction of the three different parts (crack opening area, thermal-hydraulic modeling, flow resistance) has been performed.\u0000 In this paper, the flow resistance modeling from several approaches is discussed, and compared with a database from eight different testing programs. Five different flow models are applied to analyze a database of more than 800 leak rate measurements for subcooled water from twelve different experimental programs. It is shown that the correct modeling of the flow resistance is crucial for a best estimate reproduction of the measured data. It turns out that generally, equilibrium models are about as good as non-equilibrium models. The data were processed with the GRS software WinLeck which includes different analytical approaches for the calculation of crack sizes and leak rates in piping components. The most reliable results within the model selection are produced by the CDR model (Critical Discharge Rate) of the ATHLET code (Analysis of Thermal-hydraulics of Leaks and Transients) developed by GRS.\u0000 As a conclusion, the accurate modeling of form losses and frictional pressure losses for critical discharge flow rates through crack-like leaks are essential for a reliable prediction of flow rates. Uncertainties in leak rate computations results arise due to the lack of information about the flow geometry and its associated drag. The assumed flow resistance of a through-wall crack influences the computed leak rate as significant as the phase-change- and flow-models. The manifest difference between equilibrium models (Pana, Estorf) and non-equilibrium models (Henry, ATHLET-CDR) seems to be less significant than the pressure loss issue. One can conjecture that, for crack-like through-wall defects, friction effects play a more important role than non-equilibrium effects.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88882685","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}
S. Oliver, C. Simpson, A. James, C. Reinhard, D. Collins, M. Pavier, M. Mostafavi
Nuclear reactor pressure vessels must be able to withstand thermal shock due to emergency cooling during a loss of coolant accident. Demonstrating structural integrity during thermal shock is difficult due to the complex interaction between thermal stress, residual stress, and stress caused by internal pressure. Finite element and analytic approaches exist to calculate the combined stress, but validation is limited. This study describes an experiment which aims to measure stress in a slice of clad reactor pressure vessel during thermal shock using time-resolved synchrotron X-ray diffraction. A test rig was designed to subject specimens to thermal shock, whilst simultaneously enabling synchrotron X-ray diffraction measurements of strain. The specimens were extracted from a block of SA508 Grade 4N reactor pressure vessel steel clad with Alloy 82 nickel-base alloy. Surface cracks were machined in the cladding. Electric heaters heat the specimens to 350°C and then the surface of the cladding is quenched in a bath of cold water, representing thermal shock. Six specimens were subjected to thermal shock on beamline I12 at Diamond Light Source, the UK’s national synchrotron X-ray facility. Time-resolved strain was measured during thermal shock at a single point close to the crack tip at a sample rate of 30 Hz. Hence, stress intensity factor vs time was calculated assuming K-controlled near-tip stress fields. This work describes the experimental method and presents some key results from a preliminary analysis of the data.
{"title":"Measurements of Stress During Thermal Shock in Clad Reactor Pressure Vessel Material Using Time-Resolved In-Situ Synchrotron X-Ray Diffraction","authors":"S. Oliver, C. Simpson, A. James, C. Reinhard, D. Collins, M. Pavier, M. Mostafavi","doi":"10.1115/PVP2018-84676","DOIUrl":"https://doi.org/10.1115/PVP2018-84676","url":null,"abstract":"Nuclear reactor pressure vessels must be able to withstand thermal shock due to emergency cooling during a loss of coolant accident. Demonstrating structural integrity during thermal shock is difficult due to the complex interaction between thermal stress, residual stress, and stress caused by internal pressure. Finite element and analytic approaches exist to calculate the combined stress, but validation is limited. This study describes an experiment which aims to measure stress in a slice of clad reactor pressure vessel during thermal shock using time-resolved synchrotron X-ray diffraction.\u0000 A test rig was designed to subject specimens to thermal shock, whilst simultaneously enabling synchrotron X-ray diffraction measurements of strain. The specimens were extracted from a block of SA508 Grade 4N reactor pressure vessel steel clad with Alloy 82 nickel-base alloy. Surface cracks were machined in the cladding. Electric heaters heat the specimens to 350°C and then the surface of the cladding is quenched in a bath of cold water, representing thermal shock. Six specimens were subjected to thermal shock on beamline I12 at Diamond Light Source, the UK’s national synchrotron X-ray facility. Time-resolved strain was measured during thermal shock at a single point close to the crack tip at a sample rate of 30 Hz. Hence, stress intensity factor vs time was calculated assuming K-controlled near-tip stress fields. This work describes the experimental method and presents some key results from a preliminary analysis of the data.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77128663","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}
Yongjoon Kang, Seung-Gun Lee, G. Kim, Sang-hoon Lee, Sangwoo Song, Sung-Sik Kang
The effect of simulated post-weld heat treatment (PWHT) on the mechanical properties and microstructure of P-No. 1 materials was investigated and the suitability of the exemption requirements of simulated PWHT as specified in ASME Section III Division 1 Subsection NX-2211 was evaluated. SA-516 Gr. 60 and 70 carbon steel plates and SA-106 Gr. B carbon steel pipe were employed, and the materials were subjected to the simulated PWHT with holding temperatures of 610, 650, 690, and 730 °C for 8 hours. Both the tensile strength and lateral expansion of the materials tested in this study showed a tendency to decrease with increasing holding temperature of the simulated PWHT. In some cases, the materials after the simulated PWHT cannot satisfy those mechanical requirements.
研究了模拟焊后热处理(PWHT)对P-No合金力学性能和组织的影响。对1种材料进行了调查，并评估了ASME Section III Division 1小节NX-2211中规定的模拟PWHT豁免要求的适用性。采用SA-516 Gr. 60和70碳钢板和SA-106 Gr. B碳钢管，分别在610、650、690和730℃的温度下进行8小时的模拟PWHT。随着模拟PWHT保温温度的升高，材料的抗拉强度和横向膨胀率均呈下降趋势。在某些情况下，模拟PWHT后的材料不能满足这些力学要求。
{"title":"Effect of Simulated Post-Weld Heat Treatment on the Mechanical Properties and Microstructure of P-No. 1 Carbon Steels","authors":"Yongjoon Kang, Seung-Gun Lee, G. Kim, Sang-hoon Lee, Sangwoo Song, Sung-Sik Kang","doi":"10.1115/PVP2018-84605","DOIUrl":"https://doi.org/10.1115/PVP2018-84605","url":null,"abstract":"The effect of simulated post-weld heat treatment (PWHT) on the mechanical properties and microstructure of P-No. 1 materials was investigated and the suitability of the exemption requirements of simulated PWHT as specified in ASME Section III Division 1 Subsection NX-2211 was evaluated. SA-516 Gr. 60 and 70 carbon steel plates and SA-106 Gr. B carbon steel pipe were employed, and the materials were subjected to the simulated PWHT with holding temperatures of 610, 650, 690, and 730 °C for 8 hours. Both the tensile strength and lateral expansion of the materials tested in this study showed a tendency to decrease with increasing holding temperature of the simulated PWHT. In some cases, the materials after the simulated PWHT cannot satisfy those mechanical requirements.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90667153","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 represent a challenge for structural integrity assessments of nuclear plants due to the complex microstructure and variation in properties over short length scales. This paper presents the findings of a study aimed at investigating the fracture behaviour of a dissimilar metal weld of SA508-4N steel joined to 316LN stainless steel via a filler weld of Alloy 82. Fracture toughness observations have shown the crack growth direction extended from the SA508-4N heat affected zone into the Alloy 82 weld metal. Finite element modelling has been used to simulate the fracture toughness testing with the crack-tip positioned in different material regions. The results have shown that the location of the crack-tip in relation to the fusion boundary and material properties being sampled by the plastic zone has a significant effect on the fracture behaviour of the dissimilar metal weld. Finally X-ray tomography of tested material has provided significant insights into the level of initial porosity within the dissimilar metal weld and development of ductile damage in the materials surrounding the crack-tip. This has been used to infer parameters for a continuum ductile damage model that is used to simulate crack growth.
{"title":"Advanced Assessment of Ductile Fracture Behaviour in Dissimilar Metal Welds Using X-Ray Tomography","authors":"W. Brayshaw, A. J. Cooper, A. Sherry, P. James","doi":"10.1115/PVP2018-84014","DOIUrl":"https://doi.org/10.1115/PVP2018-84014","url":null,"abstract":"Dissimilar metal welds represent a challenge for structural integrity assessments of nuclear plants due to the complex microstructure and variation in properties over short length scales. This paper presents the findings of a study aimed at investigating the fracture behaviour of a dissimilar metal weld of SA508-4N steel joined to 316LN stainless steel via a filler weld of Alloy 82. Fracture toughness observations have shown the crack growth direction extended from the SA508-4N heat affected zone into the Alloy 82 weld metal. Finite element modelling has been used to simulate the fracture toughness testing with the crack-tip positioned in different material regions. The results have shown that the location of the crack-tip in relation to the fusion boundary and material properties being sampled by the plastic zone has a significant effect on the fracture behaviour of the dissimilar metal weld. Finally X-ray tomography of tested material has provided significant insights into the level of initial porosity within the dissimilar metal weld and development of ductile damage in the materials surrounding the crack-tip. This has been used to infer parameters for a continuum ductile damage model that is used to simulate crack growth.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81009849","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 is focussed on establishing more simplified Leak-before-Break (LbB) guidance for inclusion into Section III.11 of the R6 procedure. The approach adopted has involved the development of a universal software tool for LbB simplified assessments which can be used to perform initial scoping calculations to demonstrate typical LbB cases. It is envisaged that this simplified methodology will enable plant assessment engineers to be more informed on which sites on plant are likely to have LbB successfully applied and to be able to undertake LbB assessments in a more simplistic way than is currently available. Using the developed software tool, a range of LbB calculations for different cracks and loading conditions have been performed to provide guidance on where LbB is more likely to be applied on plant. Loading conditions include primary and secondary stresses, where through-wall changes have been accounted for. The pipe geometries included in this study have been defined by the inner radius and the wall thickness, calculated by minimum pipe thickness required according to meet the design rules of ASME III. The pipe inner radius varies from 40mm to 200mm (80mm to 400mm inner diameter (ID)). All pipe outer diameters are less than 0.5m. All cracks considered in this study are through-wall and circumferential. Pipe material properties are chosen to be broadly representative of an Austenitic Stainless Steel, where the fracture toughness varies from 100 to 180MPa√m and the yield stress is 150MPa.
{"title":"Simplified LBB Guidance: Stage 1 — Development of a New Software Tool and Initial Scoping Calculations","authors":"Peter Gill, J. Sharples, C. Aird","doi":"10.1115/PVP2018-84926","DOIUrl":"https://doi.org/10.1115/PVP2018-84926","url":null,"abstract":"This study is focussed on establishing more simplified Leak-before-Break (LbB) guidance for inclusion into Section III.11 of the R6 procedure. The approach adopted has involved the development of a universal software tool for LbB simplified assessments which can be used to perform initial scoping calculations to demonstrate typical LbB cases. It is envisaged that this simplified methodology will enable plant assessment engineers to be more informed on which sites on plant are likely to have LbB successfully applied and to be able to undertake LbB assessments in a more simplistic way than is currently available. Using the developed software tool, a range of LbB calculations for different cracks and loading conditions have been performed to provide guidance on where LbB is more likely to be applied on plant. Loading conditions include primary and secondary stresses, where through-wall changes have been accounted for. The pipe geometries included in this study have been defined by the inner radius and the wall thickness, calculated by minimum pipe thickness required according to meet the design rules of ASME III. The pipe inner radius varies from 40mm to 200mm (80mm to 400mm inner diameter (ID)). All pipe outer diameters are less than 0.5m. All cracks considered in this study are through-wall and circumferential. Pipe material properties are chosen to be broadly representative of an Austenitic Stainless Steel, where the fracture toughness varies from 100 to 180MPa√m and the yield stress is 150MPa.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73096292","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}
Said El Chamaa, Mitesh Patel, M. Wenman, C. Davies
Hydrogen pick-up in zirconium alloys can lead to their structural failure, which is an important problem in the nuclear industry. This investigation focuses on modelling the accumulation of hydrogen in the vicinity of loaded V-notches in four-point bend Zircaloy-4 specimens. In order to account for the anisotropic diffusivity of hydrogen in hexagonal close-packed α-zirconium, a multiscale methodology is proposed to compute notch-tip hydrogen profiles. This methodology unifies continuum scale stress analysis, using the finite element approach, and atomistic scale stress analysis, using the elastic dipole tensor of point defects. The steady state notch-tip hydrogen profiles are determined for different notch geometries and crystal orientations. It was found that hydrogen enhancement is greater but more localised for sharper notches with a smaller flank angles, which is the expected effect of stress. It was also found that hydrogen enhancement is greater if the notch opening plane coincides with the prism plane as opposed to the basal plane. This anisotropic effect is a consequence of the trigonal symmetry of the hydrogen interstitialcy.
{"title":"Multiscale Stress-Diffusion Analysis of Notch-Tip Hydrogen Profiles in Zircaloy-4","authors":"Said El Chamaa, Mitesh Patel, M. Wenman, C. Davies","doi":"10.1115/PVP2018-84555","DOIUrl":"https://doi.org/10.1115/PVP2018-84555","url":null,"abstract":"Hydrogen pick-up in zirconium alloys can lead to their structural failure, which is an important problem in the nuclear industry. This investigation focuses on modelling the accumulation of hydrogen in the vicinity of loaded V-notches in four-point bend Zircaloy-4 specimens. In order to account for the anisotropic diffusivity of hydrogen in hexagonal close-packed α-zirconium, a multiscale methodology is proposed to compute notch-tip hydrogen profiles. This methodology unifies continuum scale stress analysis, using the finite element approach, and atomistic scale stress analysis, using the elastic dipole tensor of point defects. The steady state notch-tip hydrogen profiles are determined for different notch geometries and crystal orientations. It was found that hydrogen enhancement is greater but more localised for sharper notches with a smaller flank angles, which is the expected effect of stress. It was also found that hydrogen enhancement is greater if the notch opening plane coincides with the prism plane as opposed to the basal plane. This anisotropic effect is a consequence of the trigonal symmetry of the hydrogen interstitialcy.","PeriodicalId":23651,"journal":{"name":"Volume 6B: Materials and Fabrication","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79817661","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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