Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high ratio of performance to cost. On the other hand, the weak graphite flakes present in gray cast iron act as stress concentrators and negatively affect the strength of this material. It is therefore important to know the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, a tensile test of gray cast iron was carried out using a plate specimen in a scanning electron microscope, and the microscopic deformation was observed on the surface of specimen. Particularly, the change in the size of graphite flakes during the tensile test was examined, and the observed trend was discussed. We found from the experimental results that the dimensional changes in the graphite flakes varied in the observed area, and that the final fracture occurred in an area where a relatively large dimensional change was observed. This suggests that the fracture location or the critical parts of gray cast iron, can be predictable from the dimensional changes of the graphite flakes at an early stage of deformation.
{"title":"Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron","authors":"N. Tada, T. Uemori","doi":"10.1115/PVP2018-85124","DOIUrl":"https://doi.org/10.1115/PVP2018-85124","url":null,"abstract":"Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high ratio of performance to cost. On the other hand, the weak graphite flakes present in gray cast iron act as stress concentrators and negatively affect the strength of this material. It is therefore important to know the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, a tensile test of gray cast iron was carried out using a plate specimen in a scanning electron microscope, and the microscopic deformation was observed on the surface of specimen. Particularly, the change in the size of graphite flakes during the tensile test was examined, and the observed trend was discussed. We found from the experimental results that the dimensional changes in the graphite flakes varied in the observed area, and that the final fracture occurred in an area where a relatively large dimensional change was observed. This suggests that the fracture location or the critical parts of gray cast iron, can be predictable from the dimensional changes of the graphite flakes at an early stage of deformation.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121762791","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}
P. L. Delliou, A. Dahl, Christophe Sonnefraud, W. Vincent
Some components of the main primary circuit of PWR nuclear power plants contain nickel-base alloy 600 parts (steam generator (SG) tubes, steam generator partition plates, lower internal radial supports). It is well known that this alloy is prone to stress corrosion cracking in the primary water environment. In 2002, surface cracks were discovered for the first time in SG partition plates of EDF 900 MWe NPP. The integrity of the SG containing these cracks must be demonstrated for all operating conditions, including accidental conditions. Due to the high tensile consolidation rate and the high fracture toughness of alloy 600, this was proved using limit load analysis. However, for a thorough demonstration, an experimental program was launched at EDF/R&D to better understand the behaviour of cracks in this high fracture toughness material. Centre Cracked Tensile (CCT) specimens were selected for this experimental program, being closer to the industrial case than conventional CT specimens. Two tests have been conducted at room temperature on large CCT specimens containing a semi-elliptical crack. The paper presents the design of the CCT tests, the material characterisation, the main results of the tests and their numerical interpretation.
{"title":"Experimental Results and Numerical Analyses of Tests Conducted on Large Alloy 600 Centre Cracked Tensile Specimens","authors":"P. L. Delliou, A. Dahl, Christophe Sonnefraud, W. Vincent","doi":"10.1115/PVP2018-84280","DOIUrl":"https://doi.org/10.1115/PVP2018-84280","url":null,"abstract":"Some components of the main primary circuit of PWR nuclear power plants contain nickel-base alloy 600 parts (steam generator (SG) tubes, steam generator partition plates, lower internal radial supports). It is well known that this alloy is prone to stress corrosion cracking in the primary water environment. In 2002, surface cracks were discovered for the first time in SG partition plates of EDF 900 MWe NPP. The integrity of the SG containing these cracks must be demonstrated for all operating conditions, including accidental conditions. Due to the high tensile consolidation rate and the high fracture toughness of alloy 600, this was proved using limit load analysis. However, for a thorough demonstration, an experimental program was launched at EDF/R&D to better understand the behaviour of cracks in this high fracture toughness material. Centre Cracked Tensile (CCT) specimens were selected for this experimental program, being closer to the industrial case than conventional CT specimens.\u0000 Two tests have been conducted at room temperature on large CCT specimens containing a semi-elliptical crack. The paper presents the design of the CCT tests, the material characterisation, the main results of the tests and their numerical interpretation.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134215874","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}
Fernando Tallavo, M. Pandey, M. Jyrkama, N. Christodoulou, G. Bickel, B. W. Leitch
A key element of the fuel channel life cycle management in CANDU® nuclear reactors is to prevent contact between the pressure tube (PT) and the calandria tube (CT) in a fuel channel. By preventing PT-CT contact, the development of hydride blisters and delayed hydride cracking of the PT can be avoided. The PT-CT contact is a result of in-reactor deformation due to irradiation induced creep of the fuel channel assembly. Excessive sagging of the PT can also interfere with the free passage of the fuel bundles when the channel is refueled. Contact of the CT with reactor control mechanisms located horizontally between the fuel channels can result from excessive sag of the CT. The prediction of dimensional changes due to in-reactor creep and the time of PT-CT contact is calculated using finite element modeling of the fuel channel with appropriate creep constitutive laws describing PT and CT deformation. The three-dimensional nature of creep deformation of fuel channels can be approximated by a one-dimensional finite element model (1D-FEM), which is a computationally tractable problem. However, the simplifications of a 1D-FEM model come at the expense of loss of prediction accuracy. This paper compares creep deformation analysis of fuel channels using 1D-FEM and 3D-FEM models. The comparison is based on PT and CT sag profiles as well as on PT-CT gap at different time intervals during service of the fuel channel. Results from the comparative analysis show that the 1D-FEM model predicts greater values of PT-CT gap. The difference in gap predicted between both FEM models increases rapidly when the minimum gap is located in the outlet span. At 250,000 equivalent full power hours, the 1D-FEM model overestimate the gap by 1.12 mm with respect to the 3D-FEM model.
{"title":"A Comparative Evaluation of Finite Element Modeling of Creep Deformation of Fuel Channels in CANDU® Nuclear Reactors","authors":"Fernando Tallavo, M. Pandey, M. Jyrkama, N. Christodoulou, G. Bickel, B. W. Leitch","doi":"10.1115/PVP2018-84982","DOIUrl":"https://doi.org/10.1115/PVP2018-84982","url":null,"abstract":"A key element of the fuel channel life cycle management in CANDU® nuclear reactors is to prevent contact between the pressure tube (PT) and the calandria tube (CT) in a fuel channel. By preventing PT-CT contact, the development of hydride blisters and delayed hydride cracking of the PT can be avoided. The PT-CT contact is a result of in-reactor deformation due to irradiation induced creep of the fuel channel assembly. Excessive sagging of the PT can also interfere with the free passage of the fuel bundles when the channel is refueled. Contact of the CT with reactor control mechanisms located horizontally between the fuel channels can result from excessive sag of the CT. The prediction of dimensional changes due to in-reactor creep and the time of PT-CT contact is calculated using finite element modeling of the fuel channel with appropriate creep constitutive laws describing PT and CT deformation. The three-dimensional nature of creep deformation of fuel channels can be approximated by a one-dimensional finite element model (1D-FEM), which is a computationally tractable problem. However, the simplifications of a 1D-FEM model come at the expense of loss of prediction accuracy. This paper compares creep deformation analysis of fuel channels using 1D-FEM and 3D-FEM models. The comparison is based on PT and CT sag profiles as well as on PT-CT gap at different time intervals during service of the fuel channel. Results from the comparative analysis show that the 1D-FEM model predicts greater values of PT-CT gap. The difference in gap predicted between both FEM models increases rapidly when the minimum gap is located in the outlet span. At 250,000 equivalent full power hours, the 1D-FEM model overestimate the gap by 1.12 mm with respect to the 3D-FEM model.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114328978","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 change in operation of conventional power plants — due to the increasing use of renewable energies — from a stationary to a more flexible operation, causes additional stresses to the components by a high amount of smaller load cycles. This fact results in a demand for validated new concepts to estimate fatigue life especially for welded joints which are the weak parts within the piping. Resulting from the measured stains during operation in the LCF regime, a non-linear fracture mechanics based concept was chosen. For the development and validation of the model, different experiment types are carried out using various types of specimens. To consider the influence of different microstructures within a welded component, specimens made of X6CrNiNb18-10 (AISI 347) with the microstructure found in the base material on the one side, and as found in the HAZ on the other side are used. To take the influence of a mechanical and microstructural notch into account, notched specimens of X6CrNiNb18-10 (AISI 347), and welded specimens made of X6CrNiNb18-10 (AISI 347, base material) and X5CrNiNb19-9 (weld material) are used. Experiments are performed with all types of specimens with an increasing complexity from constant amplitude loading to operational loading. The developed nonlinear fracture mechanics based lifetime model uses the effective cyclic J-Integral normalized to the crack length to replace crack growth calculation by a linear damage accumulation. To consider the loading history an algorithm for the calculation of crack opening and crack closure is used. The advantages of this approach are shown by a comparison with damage calculations based on the damage parameter by Smith, Watson and Topper and based solely on the strain ranges. The differences in the concepts will be highlighted and used for further considerations of how to advance the lifetime prediction model for variable amplitudes. The presented work gives an overview of the preliminary results of the current work on the AiF research project 18842 N ‘Extended damage concepts for thermomechanical loading under variable amplitudes and plastic deformation’.
{"title":"Fatigue Life of Welded Joints of AISI 347 Stainless Steel Under Thermomechanical and Variable Amplitude Loading","authors":"A. Bosch, S. Schackert, M. Vormwald, C. Schweizer","doi":"10.1115/PVP2018-84705","DOIUrl":"https://doi.org/10.1115/PVP2018-84705","url":null,"abstract":"The change in operation of conventional power plants — due to the increasing use of renewable energies — from a stationary to a more flexible operation, causes additional stresses to the components by a high amount of smaller load cycles. This fact results in a demand for validated new concepts to estimate fatigue life especially for welded joints which are the weak parts within the piping. Resulting from the measured stains during operation in the LCF regime, a non-linear fracture mechanics based concept was chosen. For the development and validation of the model, different experiment types are carried out using various types of specimens. To consider the influence of different microstructures within a welded component, specimens made of X6CrNiNb18-10 (AISI 347) with the microstructure found in the base material on the one side, and as found in the HAZ on the other side are used. To take the influence of a mechanical and microstructural notch into account, notched specimens of X6CrNiNb18-10 (AISI 347), and welded specimens made of X6CrNiNb18-10 (AISI 347, base material) and X5CrNiNb19-9 (weld material) are used. Experiments are performed with all types of specimens with an increasing complexity from constant amplitude loading to operational loading. The developed nonlinear fracture mechanics based lifetime model uses the effective cyclic J-Integral normalized to the crack length to replace crack growth calculation by a linear damage accumulation. To consider the loading history an algorithm for the calculation of crack opening and crack closure is used. The advantages of this approach are shown by a comparison with damage calculations based on the damage parameter by Smith, Watson and Topper and based solely on the strain ranges. The differences in the concepts will be highlighted and used for further considerations of how to advance the lifetime prediction model for variable amplitudes.\u0000 The presented work gives an overview of the preliminary results of the current work on the AiF research project 18842 N ‘Extended damage concepts for thermomechanical loading under variable amplitudes and plastic deformation’.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130238943","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 the core meltdown severe accident, in-vessel retention (IVR) of molten core debris by external reactor vessel cooling (ERVC) is an important mitigation strategy. During the IVR strategy, the core debris forming a melt pool in the reactor pressure vessel (RPV) lower head (LH) will produce extremely high thermal and mechanical loadings to the RPV, which may cause the failure of RPV due to over-deformation of plasticity or creep. Therefore, it is necessary to study the thermomechanical behavior of the reactor vessel LH during IVR condition. In this paper, under the assumption of IVR-ERVC, the thermal and structural analysis for the RPV lower head is completed by finite element method. The temperature field and stress field of the RPV wall, and the plastic deformation and creep deformation of the lower head are obtained by calculation. Plasticity and creep failure analysis is conducted as well. Results show that under the assumed conditions, the head will not fail due to excessive creep deformation within 200 hours. The results can provide basis for structural integrity analysis of pressure vessels.
{"title":"Thermal and Structural Analysis of Reactor Vessel Lower Head Considering Core Meltdown Accident","authors":"Juan Luo, Jia-cheng Luo, Lei Sun, Peng Tang","doi":"10.1115/PVP2018-85101","DOIUrl":"https://doi.org/10.1115/PVP2018-85101","url":null,"abstract":"In the core meltdown severe accident, in-vessel retention (IVR) of molten core debris by external reactor vessel cooling (ERVC) is an important mitigation strategy. During the IVR strategy, the core debris forming a melt pool in the reactor pressure vessel (RPV) lower head (LH) will produce extremely high thermal and mechanical loadings to the RPV, which may cause the failure of RPV due to over-deformation of plasticity or creep. Therefore, it is necessary to study the thermomechanical behavior of the reactor vessel LH during IVR condition. In this paper, under the assumption of IVR-ERVC, the thermal and structural analysis for the RPV lower head is completed by finite element method. The temperature field and stress field of the RPV wall, and the plastic deformation and creep deformation of the lower head are obtained by calculation. Plasticity and creep failure analysis is conducted as well. Results show that under the assumed conditions, the head will not fail due to excessive creep deformation within 200 hours. The results can provide basis for structural integrity analysis of pressure vessels.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"33 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121270781","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}
For equipment designed to ASME or API standards, it is common practice to perform impact testing of base material and/or weldments to establish the Minimum Design Metal Temperature (MDMT). The impact test is typically a Charpy V-Notch (CVN) test and the test temperature is set equal to the MDMT. The required Charpy energy at MDMT can vary anywhere from 10 ft-lbs to 40 ft-lbs depending on material specification, thickness, and the ASME/API standard. The detailed historical background behind the Charpy energy requirements of different ASME/API standards is not well documented. Additionally, no credit is given for post weld heat treatment (PWHT) of impact tested materials. The CVN tests are used because they are quick and economical for quality control, but the tests only provide a relative indication of material toughness. Consequently, the current impact test requirements lead to inconsistent results in brittle fracture assessments, conducted through explicit fracture mechanics. In this paper, two examples are presented to highlight the inconsistencies of the current impact test requirements. A methodology of estimating MDMT for impact tested materials based on fracture mechanics, consistent with Welding Research Council (WRC) Bulletin 562 [1] is also presented. Furthermore, this methodology explicitly accounts for the effects of PWHT (and the influence of weld residual stress on crack driving force) for impact tested materials. A methodology of adjusting MDMT for in-service impact tested materials is also presented. In the interest of moving towards harmonizing the impact test requirements, an alternative procedure for establishing impact test requirements is presented for ASME/API consideration.
{"title":"Proposed Methodology Changes to Determine Minimum Design Metal Temperature of ASME/API Impact Tested Materials Based on Fracture Mechanics","authors":"S. R. Kummari, Brian Macejko, P. E. Prueter","doi":"10.1115/PVP2018-84795","DOIUrl":"https://doi.org/10.1115/PVP2018-84795","url":null,"abstract":"For equipment designed to ASME or API standards, it is common practice to perform impact testing of base material and/or weldments to establish the Minimum Design Metal Temperature (MDMT). The impact test is typically a Charpy V-Notch (CVN) test and the test temperature is set equal to the MDMT. The required Charpy energy at MDMT can vary anywhere from 10 ft-lbs to 40 ft-lbs depending on material specification, thickness, and the ASME/API standard. The detailed historical background behind the Charpy energy requirements of different ASME/API standards is not well documented. Additionally, no credit is given for post weld heat treatment (PWHT) of impact tested materials. The CVN tests are used because they are quick and economical for quality control, but the tests only provide a relative indication of material toughness. Consequently, the current impact test requirements lead to inconsistent results in brittle fracture assessments, conducted through explicit fracture mechanics.\u0000 In this paper, two examples are presented to highlight the inconsistencies of the current impact test requirements. A methodology of estimating MDMT for impact tested materials based on fracture mechanics, consistent with Welding Research Council (WRC) Bulletin 562 [1] is also presented. Furthermore, this methodology explicitly accounts for the effects of PWHT (and the influence of weld residual stress on crack driving force) for impact tested materials. A methodology of adjusting MDMT for in-service impact tested materials is also presented. In the interest of moving towards harmonizing the impact test requirements, an alternative procedure for establishing impact test requirements is presented for ASME/API consideration.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121439063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Liu, E. Xiao, Gregory D. Westwater, C. R. Johnson, J. Mann
The total strain, elastic plus plastic, was measured with strain gages on valve bodies with internal pressure that caused surface yielding. The correlation of the simulated maximum principal strain was compared to strain gage data. A mesh sensitivity study shows that in regions of large plastic strain, mesh elements are required that are an order of magnitude smaller than what is used for linear elastic stress analysis for the same structure. A local mesh refinement was adequate to resolve the local high strain values. Both the location and magnitude of the maximum strain changed with a local mesh refinement. The local mesh refinement requirement was consistent over several structures that were tested. The test and simulation work will be presented along with the mesh sensitivity study. Some results on using an energy stabilization technique to aid convergence will be presented in terms of the impact on the predicted plastic strain.
{"title":"Local Mesh Refinement for Correlation of FEA Estimated Plastic Strain to Tests in Areas of High Plastic Strain","authors":"K. Liu, E. Xiao, Gregory D. Westwater, C. R. Johnson, J. Mann","doi":"10.1115/PVP2018-84630","DOIUrl":"https://doi.org/10.1115/PVP2018-84630","url":null,"abstract":"The total strain, elastic plus plastic, was measured with strain gages on valve bodies with internal pressure that caused surface yielding. The correlation of the simulated maximum principal strain was compared to strain gage data. A mesh sensitivity study shows that in regions of large plastic strain, mesh elements are required that are an order of magnitude smaller than what is used for linear elastic stress analysis for the same structure. A local mesh refinement was adequate to resolve the local high strain values. Both the location and magnitude of the maximum strain changed with a local mesh refinement. The local mesh refinement requirement was consistent over several structures that were tested. The test and simulation work will be presented along with the mesh sensitivity study. Some results on using an energy stabilization technique to aid convergence will be presented in terms of the impact on the predicted plastic strain.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128946144","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}
Codified fitness for service methods such as API 579 or BS 7910 require consideration of residual stresses in fracture assessments, and guidance is given for upper bound residual stress distributions in common weld geometries. However, these distributions are not appropriate for some welding processes currently or historically used in the manufacture of linepipe, such as high frequency induction welding or flash butt welding. In addition, some linepipe manufacturing routes generate large plastic strains which result in high residual forming stresses, or mechanically relax residual stresses generated in earlier stages of production. This paper first reviews the code recommendations for the effects of plastic strains and stresses from high level pressure testing on residuals stresses. The paper then briefly describes the major methods of producing carbon steel linepipe and provides recommended residual stress levels for the seam weld and parent material of linepipe using the code recommendations. These are based on assumed uniform residual stresses combined with mechanical stress relaxation due to manufacturing steps such as cold expansion and hydrostatic testing. The recommendations are compared with measured residual stress levels from the open literature. Proposals are given for reduced residual stress levels when assessing axial cracks in carbon steel linepipe.
API 579或BS 7910等服务方法的规范适用性要求在断裂评估中考虑残余应力，并对常见焊缝几何形状的上限残余应力分布给出了指导。然而，这些分布不适用于目前或历史上用于制造管道的一些焊接工艺，例如高频感应焊或闪光对焊。此外，一些管道制造路线会产生较大的塑性应变，从而导致较高的残余成形应力，或者机械地放松在生产早期阶段产生的残余应力。本文首先回顾了高水平压力试验中塑性应变和应力对残余应力影响的规范建议。然后简要介绍了碳钢管道的主要生产方法，并根据规范建议提供了焊缝和管道母材的推荐残余应力水平。这些都是基于假设的均匀残余应力结合机械应力松弛，由于制造步骤，如冷膨胀和流体静力测试。将建议与公开文献中测量的残余应力水平进行比较。提出了降低碳钢管道轴向裂纹残余应力水平的建议。
{"title":"Estimation of Residual Stress Levels in Fitness for Service Evaluations of Linepipe","authors":"R. Andrews, S. Slater","doi":"10.1115/PVP2018-84973","DOIUrl":"https://doi.org/10.1115/PVP2018-84973","url":null,"abstract":"Codified fitness for service methods such as API 579 or BS 7910 require consideration of residual stresses in fracture assessments, and guidance is given for upper bound residual stress distributions in common weld geometries. However, these distributions are not appropriate for some welding processes currently or historically used in the manufacture of linepipe, such as high frequency induction welding or flash butt welding. In addition, some linepipe manufacturing routes generate large plastic strains which result in high residual forming stresses, or mechanically relax residual stresses generated in earlier stages of production.\u0000 This paper first reviews the code recommendations for the effects of plastic strains and stresses from high level pressure testing on residuals stresses. The paper then briefly describes the major methods of producing carbon steel linepipe and provides recommended residual stress levels for the seam weld and parent material of linepipe using the code recommendations. These are based on assumed uniform residual stresses combined with mechanical stress relaxation due to manufacturing steps such as cold expansion and hydrostatic testing. The recommendations are compared with measured residual stress levels from the open literature. Proposals are given for reduced residual stress levels when assessing axial cracks in carbon steel linepipe.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116776697","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 piping support or restraint design and analysis must meet or exceed requirements of the applicable ASME Codes and standards specified for loading conditions of nuclear power plants such as ASME Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF. In the piping industry, various restraint types such as shock and energy absorbers, struts, dynamic clamps, etc., are used in the field to provide support between piping and building structures. This work primarily focuses on dynamic clamps, specifically, variations such as traditional 3-bolt dynamic clamps and dynamic yoke clamps. Dynamic yoke clamps have a close fit around the pipe and can be used in more applications than 3-bolt dynamic clamps such as instances of limited space, due to the smaller size of the clamps (distance from center of pipe to center of pin), and connections with larger binding angles. Additionally, finite element analysis is utilized to demonstrate superior performance of the yoke style clamp. Therefore, this study yields results that provide a strong substitute for the 3-bolt clamp. Previously, a 3-bolt clamp was the clamp of choice but the state-of-the-art design of a yoke style clamp makes it a better piping support for the dynamic application.
{"title":"A Study of Dynamic Pipe Clamp Design","authors":"P. Wiseman, A. Mayes","doi":"10.1115/PVP2018-84312","DOIUrl":"https://doi.org/10.1115/PVP2018-84312","url":null,"abstract":"The piping support or restraint design and analysis must meet or exceed requirements of the applicable ASME Codes and standards specified for loading conditions of nuclear power plants such as ASME Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF. In the piping industry, various restraint types such as shock and energy absorbers, struts, dynamic clamps, etc., are used in the field to provide support between piping and building structures. This work primarily focuses on dynamic clamps, specifically, variations such as traditional 3-bolt dynamic clamps and dynamic yoke clamps. Dynamic yoke clamps have a close fit around the pipe and can be used in more applications than 3-bolt dynamic clamps such as instances of limited space, due to the smaller size of the clamps (distance from center of pipe to center of pin), and connections with larger binding angles. Additionally, finite element analysis is utilized to demonstrate superior performance of the yoke style clamp. Therefore, this study yields results that provide a strong substitute for the 3-bolt clamp. Previously, a 3-bolt clamp was the clamp of choice but the state-of-the-art design of a yoke style clamp makes it a better piping support for the dynamic application.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122291481","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}
Ancillary exhaust system structural design for turbines typically employs a separation of responsibilities between the design and installation functions. The design expectations must be implemented correctly during the installation phase to allow long-term serviceability and success of the turbine exhaust system. This paper will explore a case study reviewing bolt tightening of duct structural angle and plate flange joints using compressible high temperature fiberglass gasket material, as well as design suggestions for metal-on-metal duct sliding support joints to structural steel. Improper design and operation can lead to failure, downtime, warranty cost and reduced design life of the exhaust system. It is not uncommon for field installation personnel to modify key system design requirements during the installation phase; typically out of habit, perceived best practice, missed installation instructions and/or misunderstanding the system behavior. In addition, maintenance recommendations are often overlooked. Literature provides extensive background for bolting of stationary metal-to-metal plate joints, rigid gaskets and pressure vessel joints. There is a gap with respect to structural angle and plate flange joint bolt tensioning using compressible fiberglass gaskets at low pressures and high temperatures. Much of the industry standard tightening philosophy is useful, but has not been extensively studied and written about with respect to flanges under high exhaust temperatures or for sliding joints exposed to thermal expansion. This paper summarizes current industry practice, presents relevant test data and a case study, analyzes the effects of high thermal stresses, and recommends a tightening procedure for typical field applications of flange joints using high temperature gaskets, and the design of metal-to-metal sliding support joints.
{"title":"Assembly of Bolted Flanged and Support Joints for Use in Elevated Temperature Exhaust Systems","authors":"Jason E. Dorgan, A. Gjinolli","doi":"10.1115/PVP2018-84159","DOIUrl":"https://doi.org/10.1115/PVP2018-84159","url":null,"abstract":"Ancillary exhaust system structural design for turbines typically employs a separation of responsibilities between the design and installation functions. The design expectations must be implemented correctly during the installation phase to allow long-term serviceability and success of the turbine exhaust system.\u0000 This paper will explore a case study reviewing bolt tightening of duct structural angle and plate flange joints using compressible high temperature fiberglass gasket material, as well as design suggestions for metal-on-metal duct sliding support joints to structural steel. Improper design and operation can lead to failure, downtime, warranty cost and reduced design life of the exhaust system. It is not uncommon for field installation personnel to modify key system design requirements during the installation phase; typically out of habit, perceived best practice, missed installation instructions and/or misunderstanding the system behavior. In addition, maintenance recommendations are often overlooked.\u0000 Literature provides extensive background for bolting of stationary metal-to-metal plate joints, rigid gaskets and pressure vessel joints. There is a gap with respect to structural angle and plate flange joint bolt tensioning using compressible fiberglass gaskets at low pressures and high temperatures. Much of the industry standard tightening philosophy is useful, but has not been extensively studied and written about with respect to flanges under high exhaust temperatures or for sliding joints exposed to thermal expansion.\u0000 This paper summarizes current industry practice, presents relevant test data and a case study, analyzes the effects of high thermal stresses, and recommends a tightening procedure for typical field applications of flange joints using high temperature gaskets, and the design of metal-to-metal sliding support joints.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115030087","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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