The failure of coke drum anchor bolts is a demanding and recurring maintenance item for many delayed coking operators. While there are several factors that can contribute to these failures, some studies have demonstrated that significant stresses may result from thermal expansion of the drum under non-uniform thermal gradients. To address bolt failures, a restraint system that utilizes non-contacting anchor blocks has been developed and implemented for the first time on a set of operating coke drums. In this paper, the background of anchor bolt failures as well as the design and first implementation of the new restraint system are discussed.
{"title":"A Non-Bolted Restraint for Coke Drums","authors":"M. Samman, A. Kaye","doi":"10.1115/PVP2018-84734","DOIUrl":"https://doi.org/10.1115/PVP2018-84734","url":null,"abstract":"The failure of coke drum anchor bolts is a demanding and recurring maintenance item for many delayed coking operators. While there are several factors that can contribute to these failures, some studies have demonstrated that significant stresses may result from thermal expansion of the drum under non-uniform thermal gradients. To address bolt failures, a restraint system that utilizes non-contacting anchor blocks has been developed and implemented for the first time on a set of operating coke drums. In this paper, the background of anchor bolt failures as well as the design and first implementation of the new restraint system are discussed.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"28 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":"130751240","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}
Printed Circuit Heat Exchangers (PCHEs) have high compactness and efficiency for heat transfer, which makes them an attractive option for the Very High Temperature Reactors (VHTRs). Design methodology of PCHE for non-nuclear service is well established in the ASME Code, Section VIII; however, ASME Code rules for PCHE nuclear services are yet to be developed. Towards developing the ASME Section III code rules for PCHE, the study started with the design of PCHE core specimens for testing following the ASME section VIII methodology. The failure responses of these PCHE specimens are investigated by using Finite Elements Analyses (FEA). Two dimensional isothermal plane strain analyses are performed using an uncoupled constitutive material model. Parametric studies by varying shape and size of semicircular channels, PCHE core size, and loading cases are performed to quantify the critical parameters which influence the PCHE failure responses under pressure creep and pressure burst loadings. Results indicate that the maximum creep strain and its location are dependent on the PCHE core size. Significant reduction in creep strains are observed at the channel sharp corners by considering a realistic semielliptical channel shape instead of a semicircular channel in the analysis.
{"title":"Finite Element Analysis of Printed Circuit Heat Exchanger Core for High Temperature Creep and Burst Responses","authors":"Heramb P. Mahajan, U. Devi, T. Hassan","doi":"10.1115/PVP2018-84748","DOIUrl":"https://doi.org/10.1115/PVP2018-84748","url":null,"abstract":"Printed Circuit Heat Exchangers (PCHEs) have high compactness and efficiency for heat transfer, which makes them an attractive option for the Very High Temperature Reactors (VHTRs). Design methodology of PCHE for non-nuclear service is well established in the ASME Code, Section VIII; however, ASME Code rules for PCHE nuclear services are yet to be developed. Towards developing the ASME Section III code rules for PCHE, the study started with the design of PCHE core specimens for testing following the ASME section VIII methodology. The failure responses of these PCHE specimens are investigated by using Finite Elements Analyses (FEA). Two dimensional isothermal plane strain analyses are performed using an uncoupled constitutive material model. Parametric studies by varying shape and size of semicircular channels, PCHE core size, and loading cases are performed to quantify the critical parameters which influence the PCHE failure responses under pressure creep and pressure burst loadings. Results indicate that the maximum creep strain and its location are dependent on the PCHE core size. Significant reduction in creep strains are observed at the channel sharp corners by considering a realistic semielliptical channel shape instead of a semicircular channel in the analysis.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"34 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132399323","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 objective of the current work is to model a stainless steel SA 316L autoclave explosion and rupture that occurred during a research laboratory experiment designed to study the thermal decomposition of ammonium tetrathiomolybdate in the presence of dimethyl sulfoxide (DSMO) in an autoclave. The explosion was believed to have occurred because DMSO was used in excess in the experiment and heated beyond its decomposition temperature. The aim of the current study is to investigate the effect of internal blast load on a pressure vessel made of stainless steel AISI 316L through finite element analysis. Numerical simulation using FEA is performed to better understand the cause of failure of the pressure vessel. The finite element model predicts very well the structural response and subsequent failure of the actual incident and the results reveal that the root cause to failure was an internal blast load, which arose from the decomposition of DMSO at high temperature.
{"title":"Finite Element Analysis of a Pressure Vessel Subjected to an Internal Blast Load","authors":"I. Barsoum, L. Sadiq","doi":"10.1115/PVP2018-84012","DOIUrl":"https://doi.org/10.1115/PVP2018-84012","url":null,"abstract":"The objective of the current work is to model a stainless steel SA 316L autoclave explosion and rupture that occurred during a research laboratory experiment designed to study the thermal decomposition of ammonium tetrathiomolybdate in the presence of dimethyl sulfoxide (DSMO) in an autoclave. The explosion was believed to have occurred because DMSO was used in excess in the experiment and heated beyond its decomposition temperature. The aim of the current study is to investigate the effect of internal blast load on a pressure vessel made of stainless steel AISI 316L through finite element analysis. Numerical simulation using FEA is performed to better understand the cause of failure of the pressure vessel. The finite element model predicts very well the structural response and subsequent failure of the actual incident and the results reveal that the root cause to failure was an internal blast load, which arose from the decomposition of DMSO at high temperature.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"29 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":"133596391","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}
With the life extension of NPPs world-wide, new challenges have emerged in engineering calculations. These challenges often stem from the difficulty to demonstrate an adequate margin for some key components, which have gradually been ageing during the operation of the plant. In particular, the Reactor Pressure Vessel (RPV) is impacted by the irradiation, and the risk of brittle fracture under severe cold shocks must be assessed. Over the past decades, the RSE-M code [1], which is used in France and internationally for in-service inspection, has been developing methods using a conventional approach to brittle fracture. Analyses are typically performed either using tabulated indices to evaluate analytically the stress intensity factor, or using more advanced approaches which require more complex and time-consuming FEA calculations. Recently, the ongoing trend has been to rely on the latter to demonstrate an adequate margin on the RPV for potential operation beyond 40 years: the question today is whether these existing methods will still provide adequate margins after 50 or 60 years of operation. In parallel to the conventional approach, a significant amount work has been performed over the past 20 years in France to adapt the historic Griffith energy release-rate approach [2] to engineering space. The work was initiated by Francfort and Marigo [3] who set up a new elastic fracture theory, extended from the Griffith approach. Within EDF R&D, Lorentz et al. [4] and Wadier et al. [5] have then relied on some of their ideas and applied them to the easier case of the propagation onset of a preexisting crack along a given crack path. Several ingredients are involved in this reduced formulation: the application of an energy minimization principle, the definition of a specific damage model and the use of a notch to represent the crack. Among other advantages, the Gp method has been developed as a true engineering approach, i.e. not relying on difficult and time-consuming models to set up. It is hence easy to implement in a FE software as a postprocessing of a mechanical calculation. The method has also been applied to various test cases and has shown the potential to increase margins. The drawbacks are that the method is likely restricted to 2D cases for practical reasons. The paper also provides an overview of the methods implemented in the EDF open source tool code_aster with a specific focus on the Gp approach.
{"title":"Brittle Fracture Prediction Using Code_Aster: Review of Available Models and Focus on the GP Energy Approach","authors":"S. Jules, T. Métais, E. Lorentz, S. Géniaut","doi":"10.1115/PVP2018-84096","DOIUrl":"https://doi.org/10.1115/PVP2018-84096","url":null,"abstract":"With the life extension of NPPs world-wide, new challenges have emerged in engineering calculations. These challenges often stem from the difficulty to demonstrate an adequate margin for some key components, which have gradually been ageing during the operation of the plant. In particular, the Reactor Pressure Vessel (RPV) is impacted by the irradiation, and the risk of brittle fracture under severe cold shocks must be assessed.\u0000 Over the past decades, the RSE-M code [1], which is used in France and internationally for in-service inspection, has been developing methods using a conventional approach to brittle fracture. Analyses are typically performed either using tabulated indices to evaluate analytically the stress intensity factor, or using more advanced approaches which require more complex and time-consuming FEA calculations. Recently, the ongoing trend has been to rely on the latter to demonstrate an adequate margin on the RPV for potential operation beyond 40 years: the question today is whether these existing methods will still provide adequate margins after 50 or 60 years of operation.\u0000 In parallel to the conventional approach, a significant amount work has been performed over the past 20 years in France to adapt the historic Griffith energy release-rate approach [2] to engineering space. The work was initiated by Francfort and Marigo [3] who set up a new elastic fracture theory, extended from the Griffith approach.\u0000 Within EDF R&D, Lorentz et al. [4] and Wadier et al. [5] have then relied on some of their ideas and applied them to the easier case of the propagation onset of a preexisting crack along a given crack path. Several ingredients are involved in this reduced formulation: the application of an energy minimization principle, the definition of a specific damage model and the use of a notch to represent the crack.\u0000 Among other advantages, the Gp method has been developed as a true engineering approach, i.e. not relying on difficult and time-consuming models to set up. It is hence easy to implement in a FE software as a postprocessing of a mechanical calculation. The method has also been applied to various test cases and has shown the potential to increase margins. The drawbacks are that the method is likely restricted to 2D cases for practical reasons.\u0000 The paper also provides an overview of the methods implemented in the EDF open source tool code_aster with a specific focus on the Gp approach.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"167 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":"132877984","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-Vessel Retention (IVR) is one of appropriate severe accident mitigation strategies for AP1000 Nuclear Power Plant (NPP), and assurance of prevention against to thermal failure and structural failure of Reactor Pressure Vessels (RPV) is the prerequisite of IVR. A Finite Element Model fora RPV considering lower head melting was established, the creep calculation was carried out after the temperature field analysis, and the stress-strain responses for different times were obtained. By means of choosing representative evaluation sections and applying the Accumulative Damage Theory based on Larson-Miller Parameter, the Creep Damage calculations and evaluations were conducted. The results showed that the failure modes associated with creep rupture would not happen under IVR condition when a certain amount of internal pressure sustained. The approaches employed in this paper could be utilized in structural integrity evaluation of RPV under IVR for other new type NPPs.
{"title":"Creep Evaluation for a PWR Reactor Pressure Vessel Lower Head Under Severe Accident Conditions Considering Sustained Internal Pressure","authors":"Yongjian Gao, M. Cao, Yinbiao He","doi":"10.1115/PVP2018-84375","DOIUrl":"https://doi.org/10.1115/PVP2018-84375","url":null,"abstract":"In-Vessel Retention (IVR) is one of appropriate severe accident mitigation strategies for AP1000 Nuclear Power Plant (NPP), and assurance of prevention against to thermal failure and structural failure of Reactor Pressure Vessels (RPV) is the prerequisite of IVR. A Finite Element Model fora RPV considering lower head melting was established, the creep calculation was carried out after the temperature field analysis, and the stress-strain responses for different times were obtained. By means of choosing representative evaluation sections and applying the Accumulative Damage Theory based on Larson-Miller Parameter, the Creep Damage calculations and evaluations were conducted. The results showed that the failure modes associated with creep rupture would not happen under IVR condition when a certain amount of internal pressure sustained. The approaches employed in this paper could be utilized in structural integrity evaluation of RPV under IVR for other new type NPPs.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"65 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":"127105293","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}
Whenever undesirable dynamic events occur within power plant, refinery, or process piping systems, specialty supports and restraints have the task of protecting the mechanical equipment and connecting piping from damaging loads and displacements. The array of components that may be affected include, but are not limited to, piping systems, pumps, valve assemblies, pressure vessels, steam generators, boilers, and heat exchangers. In particular, the dynamic events can be classified into two distinct types that originate from either internal events or external events. The internal dynamic load generating events include plant system start-up and shut-down, pressure surges or impacts from rapid valve closures such as steam and water hammer, boiler detonations, pipe rupture, and operating vibratory displacements that may be either low frequency or high frequency vibrations. The external dynamic load generating events include wind loads, earthquake, airplane impact to supporting structures and buildings, and explosions. Most of the aforementioned dynamic load generating events can be defined quite simply as impact loads, i.e., forces and moments that are applied over very short periods of time, for example, less than one second. While earthquake loads may be applied over a total time period of an hour or so, the peak loads and resulting displacements occur on a more sinusoidal basis of peak-to-peak amplitudes. One of the most common specialty restraint components utilized in the piping industry to absorb and transfer the dynamic load resulting from impact events is the hydraulic shock suppressor, otherwise known as the snubber. The snubber is a formidable solution to protecting plant piping systems and equipment from impact loading while not restricting the thermal displacements during routine operations. In the dynamic events that may be characterized by an impact type loading, snubbers provide an instantaneous, practically rigid, axial connection between the piping or other component to be secured and the surrounding structure whether it be concrete or steel (for example). In this way, the kinetic energy can be transmitted and harmlessly dissipated. In the vibratory environment, however, neither the impact load scenario nor the rapid translations are imposed upon snubbers, thereby presenting the competing intended application of the snubber to protect against impact loads versus, in many cases, the improper selection of the snubber to dampen vibratory (other than seismic) loads. The details of the hydraulic shock suppressor design are reviewed and discussed to exemplify why a case can and should be made against the use of snubbers in piping systems within an operating vibratory environment.
{"title":"A Case for Avoiding Hydraulic Shock Suppressors (Snubbers) in the Vibratory Environments","authors":"Kshitij P. Gawande, P. Wiseman, A. Mayes","doi":"10.1115/PVP2018-85035","DOIUrl":"https://doi.org/10.1115/PVP2018-85035","url":null,"abstract":"Whenever undesirable dynamic events occur within power plant, refinery, or process piping systems, specialty supports and restraints have the task of protecting the mechanical equipment and connecting piping from damaging loads and displacements. The array of components that may be affected include, but are not limited to, piping systems, pumps, valve assemblies, pressure vessels, steam generators, boilers, and heat exchangers. In particular, the dynamic events can be classified into two distinct types that originate from either internal events or external events. The internal dynamic load generating events include plant system start-up and shut-down, pressure surges or impacts from rapid valve closures such as steam and water hammer, boiler detonations, pipe rupture, and operating vibratory displacements that may be either low frequency or high frequency vibrations. The external dynamic load generating events include wind loads, earthquake, airplane impact to supporting structures and buildings, and explosions. Most of the aforementioned dynamic load generating events can be defined quite simply as impact loads, i.e., forces and moments that are applied over very short periods of time, for example, less than one second. While earthquake loads may be applied over a total time period of an hour or so, the peak loads and resulting displacements occur on a more sinusoidal basis of peak-to-peak amplitudes. One of the most common specialty restraint components utilized in the piping industry to absorb and transfer the dynamic load resulting from impact events is the hydraulic shock suppressor, otherwise known as the snubber. The snubber is a formidable solution to protecting plant piping systems and equipment from impact loading while not restricting the thermal displacements during routine operations. In the dynamic events that may be characterized by an impact type loading, snubbers provide an instantaneous, practically rigid, axial connection between the piping or other component to be secured and the surrounding structure whether it be concrete or steel (for example). In this way, the kinetic energy can be transmitted and harmlessly dissipated. In the vibratory environment, however, neither the impact load scenario nor the rapid translations are imposed upon snubbers, thereby presenting the competing intended application of the snubber to protect against impact loads versus, in many cases, the improper selection of the snubber to dampen vibratory (other than seismic) loads. The details of the hydraulic shock suppressor design are reviewed and discussed to exemplify why a case can and should be made against the use of snubbers in piping systems within an operating vibratory environment.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"97 16 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":"127467643","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}
Inelastic analysis considering individual material behavior is expected to play a more and more important role in design and fitness-for-service assessment of various pressure-retaining components. Constitutive model is a fundamental element of such an analysis and modeling of stress-strain relations under uniaxial loading constitutes its basis. Some formulae for describing stress-strain relations under monotonically increasing loading have been developed and incorporated in some codes to provide a guidance for elastic-plastic analysis. The author has been trying to find alternative formulae to improve the accuracy and widen the applicability. A simple formula based on the Swift-type equation was derived as a result of systematic analysis of the test data on a number of materials used in nuclear power plants. An alternative expression was also developed in order to circumvent the deficiency observed in ferritic steels. All the constants in these expressions were represented by the functions of temperature, yield stress and tensile strength to make it possible to apply them without further information. Formulae were found to be applicable to various materials such as austenitic stainless steels, high- and medium-strength ferritic steels and some of Nicked based alloys.
{"title":"Trial for United Representation of Monotonic Stress-Strain Relations of Various Alloys","authors":"Yukio Takahashi","doi":"10.1115/PVP2018-85041","DOIUrl":"https://doi.org/10.1115/PVP2018-85041","url":null,"abstract":"Inelastic analysis considering individual material behavior is expected to play a more and more important role in design and fitness-for-service assessment of various pressure-retaining components. Constitutive model is a fundamental element of such an analysis and modeling of stress-strain relations under uniaxial loading constitutes its basis. Some formulae for describing stress-strain relations under monotonically increasing loading have been developed and incorporated in some codes to provide a guidance for elastic-plastic analysis. The author has been trying to find alternative formulae to improve the accuracy and widen the applicability. A simple formula based on the Swift-type equation was derived as a result of systematic analysis of the test data on a number of materials used in nuclear power plants. An alternative expression was also developed in order to circumvent the deficiency observed in ferritic steels. All the constants in these expressions were represented by the functions of temperature, yield stress and tensile strength to make it possible to apply them without further information. Formulae were found to be applicable to various materials such as austenitic stainless steels, high- and medium-strength ferritic steels and some of Nicked based alloys.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"58 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":"123094672","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}
R. Lacroix, A. Caron, Sandrine Dischert, H. Deschanels, M. Pignol
Stress intensity factors (SIFs) are a major feature in regulatory analyses of Nuclear Power Plants (NPP) components, as they allow to rule on the acceptability of defects when compared to a critical experimental value (K1c). Simplified and robust evaluations of SIFs have been provided in major regulations standards for cracks having usual geometries and locations in major components. However, their evaluations still require a significant effort in the case of important deviations of the geometry of cracks regarding the usual semi-elliptical shape, or in the case of specific geometries of components, and specific locations of cracks in components. In these cases, time-consuming Finite Element meshes must be constructed, either manually or using semi-automatical tools, to represent the components and its defect(s). This method can become particularly costly, especially in the case of fatigue crack propagation. The eXtended-Finite Elements Method (X-FEM) has been proposed to overcome this issue. The representation of the defect is carried out by the level-set method, and specific enrichment functions are used to represent the solution near the crack surface and the crack front. This paper proposes a benchmark of numerical predictions of stress intensity factors using SYSTUS software [5]. It will be based on: a) Available analytical solutions; b) Classical Finite Element method; c) EXtended-Finite Elements Method. The classical case of a circular and elliptical crack in a semiinfinite body is first presented. Then the case of a circumferential crack in a valve under a thermo-mechanical loading is analyzed. The accuracy of the different methods is then compared and discussed.
{"title":"Benchmark of Finite Elements and Extended-Finite Elements Methods for Stress Intensity Factors and Crack Propagation","authors":"R. Lacroix, A. Caron, Sandrine Dischert, H. Deschanels, M. Pignol","doi":"10.1115/PVP2018-84401","DOIUrl":"https://doi.org/10.1115/PVP2018-84401","url":null,"abstract":"Stress intensity factors (SIFs) are a major feature in regulatory analyses of Nuclear Power Plants (NPP) components, as they allow to rule on the acceptability of defects when compared to a critical experimental value (K1c). Simplified and robust evaluations of SIFs have been provided in major regulations standards for cracks having usual geometries and locations in major components.\u0000 However, their evaluations still require a significant effort in the case of important deviations of the geometry of cracks regarding the usual semi-elliptical shape, or in the case of specific geometries of components, and specific locations of cracks in components. In these cases, time-consuming Finite Element meshes must be constructed, either manually or using semi-automatical tools, to represent the components and its defect(s). This method can become particularly costly, especially in the case of fatigue crack propagation.\u0000 The eXtended-Finite Elements Method (X-FEM) has been proposed to overcome this issue. The representation of the defect is carried out by the level-set method, and specific enrichment functions are used to represent the solution near the crack surface and the crack front.\u0000 This paper proposes a benchmark of numerical predictions of stress intensity factors using SYSTUS software [5]. It will be based on:\u0000 a) Available analytical solutions;\u0000 b) Classical Finite Element method;\u0000 c) EXtended-Finite Elements Method.\u0000 The classical case of a circular and elliptical crack in a semiinfinite body is first presented. Then the case of a circumferential crack in a valve under a thermo-mechanical loading is analyzed. The accuracy of the different methods is then compared and discussed.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"98 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":"127240790","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}
We present an iterative method to solve static piping analysis including Coulomb friction between pipes and supports. It is known that the most stable method to find the solution of this problem is to look for the correct stiffness to add in the plane orthogonal to the direction of the restraints for the resulting forces to be of correct intensity. The naivest way to pick the stiffnesses at each step is to choose the ones that would give the correct forces intensities if the displacements were correct. It is very effective in term of precision, but sometimes slow in term of execution. The penalty comes from the fact that the stiffness matrix is different at each iteration and thus that it must be factorized again. In this article we propose a way to increase the speed of convergence: selecting a subset of supports among the ones where convergence is the worst, and introducing sub-iterations focusing only on those supports can reduce the number of main iterations. Those sub-iterations can be calculated at a much lesser cost than the main ones by using the generalized Sherman-Morrison formula. This algorithm was successfully implemented into the piping analysis software PIPESTRESS version 3.9.1 developed by DST Computer Services SA (the version number is temporary, the release date is Q3/Q4 of 2018).
{"title":"An Iterative Method for Solving Static Piping Analysis Including Friction Between Pipes and Support","authors":"M. Anderegg","doi":"10.1115/PVP2018-84645","DOIUrl":"https://doi.org/10.1115/PVP2018-84645","url":null,"abstract":"We present an iterative method to solve static piping analysis including Coulomb friction between pipes and supports. It is known that the most stable method to find the solution of this problem is to look for the correct stiffness to add in the plane orthogonal to the direction of the restraints for the resulting forces to be of correct intensity. The naivest way to pick the stiffnesses at each step is to choose the ones that would give the correct forces intensities if the displacements were correct. It is very effective in term of precision, but sometimes slow in term of execution. The penalty comes from the fact that the stiffness matrix is different at each iteration and thus that it must be factorized again. In this article we propose a way to increase the speed of convergence: selecting a subset of supports among the ones where convergence is the worst, and introducing sub-iterations focusing only on those supports can reduce the number of main iterations. Those sub-iterations can be calculated at a much lesser cost than the main ones by using the generalized Sherman-Morrison formula.\u0000 This algorithm was successfully implemented into the piping analysis software PIPESTRESS version 3.9.1 developed by DST Computer Services SA (the version number is temporary, the release date is Q3/Q4 of 2018).","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"15 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":"114968296","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 crack was observed on the tube of radiation section of ethylene cracking furnace during operation. The material of the tube is KHR35CT-HiSi. This paper details the investigation into the failure and highlights the most probable cause of the failure based on available documents and experimental analysis, visual examination, chemical composition analysis, metallographic examination, scanning electron microscope analysis, energy spectrum analysis, X-ray diffraction analysis, fracture morphology observation was performed. Comprehensive data access, macro examination and the results of analysis, the failure of the furnace pipe is due to brittle fracture. The main reason for embrittlement of furnace tube is serious carburization of the pipe inside. Carburization can lead to two consequences. The first is to make the pipe become brittle; the second is the difference of the thermal expansion coefficient between carburization layer and non-carburization layer, which makes the pipe produce a large thermal stress, that can produce a micro crack in the Transitional position of the carburization layer and the non–carburization layer. The above two points are confirmed by experiments. The brittle fracture of tube is produced by the combined action of the micro crack and carburization.
{"title":"Failure Analysis of Furnace Tube in the Radiation Section of Ethylene Cracking Furnace","authors":"Wen Liu, Guodong Sun, Jian Xing, Zhenlong Hu, Luowei Cao, Fakun Zhuang","doi":"10.1115/PVP2018-84037","DOIUrl":"https://doi.org/10.1115/PVP2018-84037","url":null,"abstract":"A crack was observed on the tube of radiation section of ethylene cracking furnace during operation. The material of the tube is KHR35CT-HiSi. This paper details the investigation into the failure and highlights the most probable cause of the failure based on available documents and experimental analysis, visual examination, chemical composition analysis, metallographic examination, scanning electron microscope analysis, energy spectrum analysis, X-ray diffraction analysis, fracture morphology observation was performed. Comprehensive data access, macro examination and the results of analysis, the failure of the furnace pipe is due to brittle fracture. The main reason for embrittlement of furnace tube is serious carburization of the pipe inside. Carburization can lead to two consequences. The first is to make the pipe become brittle; the second is the difference of the thermal expansion coefficient between carburization layer and non-carburization layer, which makes the pipe produce a large thermal stress, that can produce a micro crack in the Transitional position of the carburization layer and the non–carburization layer. The above two points are confirmed by experiments. The brittle fracture of tube is produced by the combined action of the micro crack and carburization.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"34 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":"115267443","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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