In order to develop new design fatigue curves for austenitic carbon steels & low alloy steels and stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society. The study on design fatigue curves was actively performed in the subcommittees. In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database was constructed. Using this fatigue database, the accurate best-fit curves of austenitic carbon steels & low alloy steels and stainless steels were developed by applying tensile strength to a parameter of the curve. Regarding design factors on design fatigue curves, data scatter, mean stress correction, surface finishing effect, size effect and variable loading effect were investigated and each design factor was decided to be individually considered on the design fatigue curves. A Japanese utility project performed large scale fatigue tests using austenitic stainless steel piping and carbon and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect and surface finishing effect. Those test results were provided to the subcommittee and utilized the above studies. In this paper, the large scale fatigue tests using austenitic stainless steel piping and the best-fit curve of austenitic stainless steel are discussed.
{"title":"Development of New Design Fatigue Curves in Japan: Discussion of Best Fit Curves Based on Fatigue Test Data With Large Scale Piping","authors":"M. Bodai, Y. Fukuta, S. Asada, K. Hayashi","doi":"10.1115/PVP2018-84436","DOIUrl":"https://doi.org/10.1115/PVP2018-84436","url":null,"abstract":"In order to develop new design fatigue curves for austenitic carbon steels & low alloy steels and stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society. The study on design fatigue curves was actively performed in the subcommittees.\u0000 In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database was constructed. Using this fatigue database, the accurate best-fit curves of austenitic carbon steels & low alloy steels and stainless steels were developed by applying tensile strength to a parameter of the curve.\u0000 Regarding design factors on design fatigue curves, data scatter, mean stress correction, surface finishing effect, size effect and variable loading effect were investigated and each design factor was decided to be individually considered on the design fatigue curves.\u0000 A Japanese utility project performed large scale fatigue tests using austenitic stainless steel piping and carbon and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect and surface finishing effect. Those test results were provided to the subcommittee and utilized the above studies.\u0000 In this paper, the large scale fatigue tests using austenitic stainless steel piping and the best-fit curve of austenitic stainless steel are discussed.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"10 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":"126327613","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 case of cyclic loading, strain may accumulate due to a ratcheting mechanism until the state of shakedown is possibly achieved. Design Codes frequently require strain limits to be satisfied at the end of the specified lifetime of the structure. However, this requirement is sometimes tied to misleading prerequisites, and little guidance is provided on how the strains accumulated in the state of shakedown can be calculated. Incremental elastic-plastic analyses which require to go step-by-step through many cycles of a given load histogram are rather costly in terms of engineering time and numerical effort. As an alternative, the Simplified Theory of Plastic Zones (STPZ) is used in the present paper. Being a direct method, effects from load history are disregarded. The theory is described shortly and exemplarily applied to a simplification of a pipe bend and a straight pipe, both subjected to combinations of several loads which vary independently from each other so that a multidimensional load domain is represented. It is shown that the Simplified Theory of Plastic Zones is well suited to provide reasonable estimates of strains accumulated in the state of elastic shakedown at the cost of few linear elastic analyses.
{"title":"Simplified Analysis of Strains Accumulated in the State of Elastic Shakedown Considering Multi-Parameter Loadings","authors":"H. Hübel, B. Vollrath","doi":"10.1115/PVP2018-84070","DOIUrl":"https://doi.org/10.1115/PVP2018-84070","url":null,"abstract":"In case of cyclic loading, strain may accumulate due to a ratcheting mechanism until the state of shakedown is possibly achieved. Design Codes frequently require strain limits to be satisfied at the end of the specified lifetime of the structure. However, this requirement is sometimes tied to misleading prerequisites, and little guidance is provided on how the strains accumulated in the state of shakedown can be calculated. Incremental elastic-plastic analyses which require to go step-by-step through many cycles of a given load histogram are rather costly in terms of engineering time and numerical effort. As an alternative, the Simplified Theory of Plastic Zones (STPZ) is used in the present paper. Being a direct method, effects from load history are disregarded. The theory is described shortly and exemplarily applied to a simplification of a pipe bend and a straight pipe, both subjected to combinations of several loads which vary independently from each other so that a multidimensional load domain is represented. It is shown that the Simplified Theory of Plastic Zones is well suited to provide reasonable estimates of strains accumulated in the state of elastic shakedown at the cost of few linear elastic analyses.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"42 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":"130908119","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}
Operation flexibility and the high efficiency of thermal cycle are the two hot research topics for the steam turbine unit. For the operation flexibility, it requires the turbine unit be able to start up quickly and frequently, and good thermal fatigue properties of the components are a must. On the other hand, the trend to higher temperature with ultra supercritical (USC) steam is the key drive of ongoing development for the validation of a method to improve the thermal cycle efficiency, but the application of the higher steam temperature will intensify the component’s thermal fatigue. In this paper, a high pressure inner casing for the new designed solar steam turbine was studied, and the Finite Element Method (FEM) combined with linear elastic material was applied to simulate the transient stress and temperature fields during the daily warm/hot startup process. On the basis of the stress spectrum in the critical zone, the standard DIN EN-12952-3 and the fatigue curve were used to evaluate the low cycle fatigue life consumption in the transient process.
{"title":"Numerical Study on the Startup Performance for the High Pressure Inner Casing of the Solar Steam Turbine","authors":"Peng Wang, Gang Chen, Wenfu Li","doi":"10.1115/PVP2018-84418","DOIUrl":"https://doi.org/10.1115/PVP2018-84418","url":null,"abstract":"Operation flexibility and the high efficiency of thermal cycle are the two hot research topics for the steam turbine unit. For the operation flexibility, it requires the turbine unit be able to start up quickly and frequently, and good thermal fatigue properties of the components are a must. On the other hand, the trend to higher temperature with ultra supercritical (USC) steam is the key drive of ongoing development for the validation of a method to improve the thermal cycle efficiency, but the application of the higher steam temperature will intensify the component’s thermal fatigue.\u0000 In this paper, a high pressure inner casing for the new designed solar steam turbine was studied, and the Finite Element Method (FEM) combined with linear elastic material was applied to simulate the transient stress and temperature fields during the daily warm/hot startup process. On the basis of the stress spectrum in the critical zone, the standard DIN EN-12952-3 and the fatigue curve were used to evaluate the low cycle fatigue life consumption in the transient process.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"249 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":"124744604","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}
Corrosion under insulation (CUI) is an aging degradation issue in long-term service vessels and pipes made of carbon steel and low-alloy steel. One of the problems in managing CUI is an equivocal evaluation technique of thinning detected by inspection. A replacement period with more accuracy can be evaluated more appropriately by performing fitness-for-service (FFS) assessment in this equipment. It is important to verify the validity of the FFS assessment using actually corroded pipes in order to promote the spread of FFS assessment in the domestic industry. In the present paper, pipes with complicated metal-loss due to CUI that were used in a chemical plant are burst in burst tests. An estimated burst pressure, which is calculated based on the assessment of metal-loss and through finite element analysis (FEA) based on FFS assessment, is compared with experimentally obtained burst pressures in order to validate the integrity evaluation. The burst pressure is then estimated by FEA, in which the ductile fracture under the multiaxial stress condition is considered. The burst pressure estimated by FFS approximately matched the burst pressure obtained based on experimental results. Fitness-for-service is sufficiently valid for investigating the remaining strength or burst pressure of corroded pipe. In addition, the burst pressure estimated by FEA that considered the ductile fracture under the multiaxial stress condition agreed with the experimental results and is valid so long as the remaining strength factor (RSF) is less than 0.6.
{"title":"Evaluation of Strength of Pipe With Metal-Loss due to CUI by FFS and FEA Which Considered the Fracture Ductility","authors":"A. Yamaguchi, N. Yoshida","doi":"10.1115/PVP2018-84741","DOIUrl":"https://doi.org/10.1115/PVP2018-84741","url":null,"abstract":"Corrosion under insulation (CUI) is an aging degradation issue in long-term service vessels and pipes made of carbon steel and low-alloy steel. One of the problems in managing CUI is an equivocal evaluation technique of thinning detected by inspection. A replacement period with more accuracy can be evaluated more appropriately by performing fitness-for-service (FFS) assessment in this equipment. It is important to verify the validity of the FFS assessment using actually corroded pipes in order to promote the spread of FFS assessment in the domestic industry. In the present paper, pipes with complicated metal-loss due to CUI that were used in a chemical plant are burst in burst tests. An estimated burst pressure, which is calculated based on the assessment of metal-loss and through finite element analysis (FEA) based on FFS assessment, is compared with experimentally obtained burst pressures in order to validate the integrity evaluation. The burst pressure is then estimated by FEA, in which the ductile fracture under the multiaxial stress condition is considered. The burst pressure estimated by FFS approximately matched the burst pressure obtained based on experimental results. Fitness-for-service is sufficiently valid for investigating the remaining strength or burst pressure of corroded pipe. In addition, the burst pressure estimated by FEA that considered the ductile fracture under the multiaxial stress condition agreed with the experimental results and is valid so long as the remaining strength factor (RSF) is less than 0.6.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"33 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":"125330183","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 cyclic loading and when plastic flow occurs, discontinuities grow. In this research, interaction diagram of Bree has been developed when the spherical pressure vessel contains discontinuities such as voids and microcracks. Bree’s diagram is used for ratcheting assessment of pressurized equipment in ASME III NH. Nature of these defects leads to an anisotropic damage. Anisotropic Continuum Damage Mechanics (CDM) is considered to account effects of these discontinuities on the behavior of the structure. Shakedown – ratcheting response of a hollow sphere under constant internal pressure and cyclic thermal loadings are studied by using anisotropic CDM theory coupled with nonlinear kinematic hardening of Armstrong-Frederick m’s model (A-F). Return mapping method is used to solve numerically the developed relations. Elastic, elastic shakedown, plastic shakedown and ratcheting regions are illustrated in the modified Bree’s diagram. Influence of anisotropic damage due to the plastic deformation is studied and it was shown that the plastic shakedown region is diminished because of the developed damage.
在循环加载和塑性流动发生时，不连续面增大。本研究绘制了球形压力容器中存在空隙、微裂纹等不连续时的Bree相互作用图。布里图用于ASME III NH中加压设备的棘轮评估。这些缺陷的性质导致了各向异性损伤。各向异性连续损伤力学(CDM)被认为是考虑这些不连续性对结构行为的影响。采用各向异性CDM理论，结合Armstrong-Frederick m模型(a - f)的非线性运动硬化，研究了空心球体在恒内压和循环热载荷作用下的安定棘轮响应。采用返回映射法对已开发的关系进行数值求解。弹性，弹性安定，塑料安定和棘轮区域在修改后的布里图中说明。研究了各向异性损伤对塑性变形的影响，结果表明，损伤的发展使塑性安定区减小。
{"title":"Shakedown-Ratcheting Analysis of a Spherical Pressure Vessel by Anisotropic Continuum Damage Mechanics","authors":"A. Nayebi, Azam Surmiri, H. Rokhgireh","doi":"10.1115/PVP2018-84065","DOIUrl":"https://doi.org/10.1115/PVP2018-84065","url":null,"abstract":"In cyclic loading and when plastic flow occurs, discontinuities grow. In this research, interaction diagram of Bree has been developed when the spherical pressure vessel contains discontinuities such as voids and microcracks. Bree’s diagram is used for ratcheting assessment of pressurized equipment in ASME III NH. Nature of these defects leads to an anisotropic damage. Anisotropic Continuum Damage Mechanics (CDM) is considered to account effects of these discontinuities on the behavior of the structure. Shakedown – ratcheting response of a hollow sphere under constant internal pressure and cyclic thermal loadings are studied by using anisotropic CDM theory coupled with nonlinear kinematic hardening of Armstrong-Frederick m’s model (A-F). Return mapping method is used to solve numerically the developed relations. Elastic, elastic shakedown, plastic shakedown and ratcheting regions are illustrated in the modified Bree’s diagram. Influence of anisotropic damage due to the plastic deformation is studied and it was shown that the plastic shakedown region is diminished because of the developed damage.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"92 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":"126201388","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 fracture toughness Jc of a material in the ductile-to-brittle transition temperature region shows a test specimen thickness (TST) effect and temperature dependence, and apparently increases when a compressive residual stress is applied. Many models to explain these phenomena have been proposed that can also consider the large scatter of Jc. On the contrary, the authors have focused on the mean Jc and have demonstrated that the TST effect on Jc and temperature dependence of Jc are due to “the loss of the one-to-one correspondence between J and the crack-tip stress distribution” and that the “scaled” crack-tip stress distribution at fracture is independent of the TST effect on Jc or temperature. The T-scaling method was proposed and validated for this purpose. In this study, the fracture prediction of a specimen with compressive residual stress was performed using the T-scaling method, and its validity was confirmed for high-strength steel of 780-MPa class and 0.45 % carbon steel JIS S45C.
{"title":"Application of the T-Scaling Method to Predict Fracture Toughness Under Compressive Residual Stress in the Transition Temperature Region","authors":"T. Meshii, K. Ishihara","doi":"10.1115/PVP2018-84151","DOIUrl":"https://doi.org/10.1115/PVP2018-84151","url":null,"abstract":"The fracture toughness Jc of a material in the ductile-to-brittle transition temperature region shows a test specimen thickness (TST) effect and temperature dependence, and apparently increases when a compressive residual stress is applied. Many models to explain these phenomena have been proposed that can also consider the large scatter of Jc. On the contrary, the authors have focused on the mean Jc and have demonstrated that the TST effect on Jc and temperature dependence of Jc are due to “the loss of the one-to-one correspondence between J and the crack-tip stress distribution” and that the “scaled” crack-tip stress distribution at fracture is independent of the TST effect on Jc or temperature. The T-scaling method was proposed and validated for this purpose. In this study, the fracture prediction of a specimen with compressive residual stress was performed using the T-scaling method, and its validity was confirmed for high-strength steel of 780-MPa class and 0.45 % carbon steel JIS S45C.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"75 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":"126986074","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}
G. Vivas, Armando J. Moret, R. Bello, Luis M. Melian, J. Bedoya
Coke drums are thin-walled pressure vessels that experience low cycle fatigue due to thermal loadings. The delayed coking process is comprised by three major stages: heating, coking and cooling, which repeat at intervals between 20 and 48 hours. The cyclic changes of temperature increase the growth of bulges and cracks which with the passing of time, propagate and eventually cause failures due to the loss of containment. A better understanding of the phenomena of the thermal gradients and their influence on the generated stresses would reduce the effects of the damage mechanisms afflicting coke drums, for example; a continuous monitoring system could be implemented in order to control the cooling ramp to obtain a more homogeneous quenching around the cylinder of the coke drum and consequently increase its lifetime. It is been widely accepted that there is a relationship between high cooling rates in isolated zones and high axial stresses. However, this relationship has not been fully validated, since there are also been reported events of low cooling rates and high stresses. This study shows a predictable behavior (trend) that relates the spatial thermal gradients and the axial and circumferential stresses generated. A coke drum in an upgrader facility was instrumented with two arrays or grids, each of them having 24 thermocouples and 2 strain gauges in zones with distinct bulges. One arrangement was located at an inward bulge while the other was located at an outward bulge. Computational models were carried out to reproduce the behavior of the instrumented zones with their actual deformations obtained from laser scanning. Finite element models were developed using a sequentially coupled thermo-mechanical analysis to determine the transient temperature and stress distributions. The effect of the circumferential thermal gradients on the stress levels in the instrumented cylindrical sections were analyzed, considering two cases; the first of them a perfect cylinder (without deformation) and the second one considering the presence of bulges in the area of interest. The results indicate that there is a relationship between the circumferential thermal gradients [°C/m] or [°F/ft] and the axial stress levels, i.e., cold zones generate axial tensile stresses, and hot zones produce compressive axial stresses. This relationship is affected — exacerbated or counteracted — by the presence of the bulges. Additionally, the results obtained in this paper confirm those of previous investigations showing that outward bulges subject to pressure and thermal loading generate high stresses on its internal surface and low stresses on its external face whereas inward bulges produce the opposite effect.
{"title":"Analysis of the Influence of the Cooling Patterns and the Shape of the Bulges on the Levels of Stress in the Cylindrical Section of Delayed Coke Drums","authors":"G. Vivas, Armando J. Moret, R. Bello, Luis M. Melian, J. Bedoya","doi":"10.1115/PVP2018-85009","DOIUrl":"https://doi.org/10.1115/PVP2018-85009","url":null,"abstract":"Coke drums are thin-walled pressure vessels that experience low cycle fatigue due to thermal loadings. The delayed coking process is comprised by three major stages: heating, coking and cooling, which repeat at intervals between 20 and 48 hours. The cyclic changes of temperature increase the growth of bulges and cracks which with the passing of time, propagate and eventually cause failures due to the loss of containment. A better understanding of the phenomena of the thermal gradients and their influence on the generated stresses would reduce the effects of the damage mechanisms afflicting coke drums, for example; a continuous monitoring system could be implemented in order to control the cooling ramp to obtain a more homogeneous quenching around the cylinder of the coke drum and consequently increase its lifetime. It is been widely accepted that there is a relationship between high cooling rates in isolated zones and high axial stresses. However, this relationship has not been fully validated, since there are also been reported events of low cooling rates and high stresses. This study shows a predictable behavior (trend) that relates the spatial thermal gradients and the axial and circumferential stresses generated.\u0000 A coke drum in an upgrader facility was instrumented with two arrays or grids, each of them having 24 thermocouples and 2 strain gauges in zones with distinct bulges. One arrangement was located at an inward bulge while the other was located at an outward bulge. Computational models were carried out to reproduce the behavior of the instrumented zones with their actual deformations obtained from laser scanning. Finite element models were developed using a sequentially coupled thermo-mechanical analysis to determine the transient temperature and stress distributions. The effect of the circumferential thermal gradients on the stress levels in the instrumented cylindrical sections were analyzed, considering two cases; the first of them a perfect cylinder (without deformation) and the second one considering the presence of bulges in the area of interest.\u0000 The results indicate that there is a relationship between the circumferential thermal gradients [°C/m] or [°F/ft] and the axial stress levels, i.e., cold zones generate axial tensile stresses, and hot zones produce compressive axial stresses. This relationship is affected — exacerbated or counteracted — by the presence of the bulges. Additionally, the results obtained in this paper confirm those of previous investigations showing that outward bulges subject to pressure and thermal loading generate high stresses on its internal surface and low stresses on its external face whereas inward bulges produce the opposite effect.","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":"134087886","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 Elastic-Plastic Fracture Mechanics, several J-estimation schemes are based on the reference stress approach. This approach has been developed initially for creep analyses and later on for elasto-plastic fracture assessments in 1984, then included in the R6 rule. Much later, other methods, based on the reference stress concept, were derived for 3D applications like the Js method introduced in the French RSE-M code in 1997 and the Enhanced Reference Stress (ERS) method in Korea around 2001. However, these developments are based on the J2 deformation plasticity theory and well established for a pure power hardening law. Js and ERS schemes propose some corrections for recorded behavior laws which cannot be fitted by a power law. Nevertheless, their application to materials governed by a bilinear hardening law has been called into question by several studies. One of these, carried out by M. T. Kirk and R. H. Dodds [1, 2] is of great interest since addressing the practical case of a surface cracked plate.
在弹塑性断裂力学中，有几种基于参考应力法的j估计方法。该方法最初用于蠕变分析，后来在1984年用于弹塑性断裂评估，然后纳入R6规则。很久以后，基于参考应力概念的其他方法被衍生出来用于3D应用，如1997年法国RSE-M代码中引入的Js方法和2001年左右韩国的增强参考应力(ERS)方法。然而，这些发展都是基于J2变形塑性理论，并建立了纯粹的功率硬化规律。Js和ERS方案对幂律不能拟合的记录行为规律提出了一些修正。然而，它们在双线性硬化规律支配下的材料上的应用受到了一些研究的质疑。其中一项是由M. T. Kirk和R. H. Dodds[1,2]进行的，由于解决了表面裂纹板的实际情况，因此引起了极大的兴趣。
{"title":"Improvement of J Estimation Schemes Based on Reference Stress for Linear Hardening Behavior","authors":"P. Gilles","doi":"10.1115/PVP2018-84410","DOIUrl":"https://doi.org/10.1115/PVP2018-84410","url":null,"abstract":"In Elastic-Plastic Fracture Mechanics, several J-estimation schemes are based on the reference stress approach. This approach has been developed initially for creep analyses and later on for elasto-plastic fracture assessments in 1984, then included in the R6 rule. Much later, other methods, based on the reference stress concept, were derived for 3D applications like the Js method introduced in the French RSE-M code in 1997 and the Enhanced Reference Stress (ERS) method in Korea around 2001. However, these developments are based on the J2 deformation plasticity theory and well established for a pure power hardening law. Js and ERS schemes propose some corrections for recorded behavior laws which cannot be fitted by a power law. Nevertheless, their application to materials governed by a bilinear hardening law has been called into question by several studies. One of these, carried out by M. T. Kirk and R. H. Dodds [1, 2] is of great interest since addressing the practical case of a surface cracked plate.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"21 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":"134300003","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}
Sulfidation corrosion of the carbon steel tubes at the tube-to-tubesheet joint often governs the life of waste heat boilers in sulphur recovery plants. Conventional tube joints typically have a welded joint located at the hot-side face of the tubesheet. An alternative design involves welding the tubesheet joint at the cold-side face of the tubesheet, close to the boiler feed water. The alternative design also employs stainless steel cladding on the tubesheet face and a tube-hole sleeve selectively at high-temperature locations. Finite element heat transfer analysis is used to establish the thermal profiles of the conventional and the alternative designs. From the worked example, the alternative design provided a lower metal temperature by approximately 80 °F at the joint, as compared to the conventional tube joint. Sulfidation rate prediction based on a sample gas composition using ASSET (Alloy Selection System for Elevated Temperatures) Software predicts that the alternative design can reduce the sulfidation rate by 35% because of the lower metal temperature.
{"title":"Sulfidation Rate Prediction on Tube-to-Tubesheet Joints in a Waste Heat Boiler in a Sulphur Plant","authors":"F. Ju, Allen Miller, Simon Yuen, Brian Tkachyk","doi":"10.1115/PVP2018-85070","DOIUrl":"https://doi.org/10.1115/PVP2018-85070","url":null,"abstract":"Sulfidation corrosion of the carbon steel tubes at the tube-to-tubesheet joint often governs the life of waste heat boilers in sulphur recovery plants. Conventional tube joints typically have a welded joint located at the hot-side face of the tubesheet. An alternative design involves welding the tubesheet joint at the cold-side face of the tubesheet, close to the boiler feed water. The alternative design also employs stainless steel cladding on the tubesheet face and a tube-hole sleeve selectively at high-temperature locations. Finite element heat transfer analysis is used to establish the thermal profiles of the conventional and the alternative designs. From the worked example, the alternative design provided a lower metal temperature by approximately 80 °F at the joint, as compared to the conventional tube joint. Sulfidation rate prediction based on a sample gas composition using ASSET (Alloy Selection System for Elevated Temperatures) Software predicts that the alternative design can reduce the sulfidation rate by 35% because of the lower metal temperature.","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":"131741621","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 determination of stress intensity factors (SIF) and crack opening area or displacements (COA or COD) is important constituent when performing the “leak before break” analysis of piping systems in NPPs. The tabulated parametrical results of their calculation are widely presented in modern scientific and normative literature. Nevertheless, there is one aspect of crack behavior, at least in thin walled pipes, which still had not obtained its due attention. We mean here the geometrically nonlinear effect, which can be the big enough to be accounted for in practical applications. It is considered in geometrically linear analysis that only the inner pressure opens the crack, and COA and SIF are directly proportional to it. SIF is presented usually as solution for infinite plate multiplied by so-called bulging factor, BF, which depends on dimensionless crack length, i.e. ratio of crack length divided on square root of product of radius, R, and wall thickness, t. Two loading factors in thin walled pipes can contribute to geometrically nonlinear behavior. The first one is axial stresses induced by value of axial force or bending moment. The second one – is the inner pressure itself. The most attention in present paper is given to influence of the axial force. With this goal the numerical models were created for pipes with different ratios of R/t (20, 30, 40, 50) and different dimensionless crack length (2, 4, 6, 8). To exclude the nonlinearity due to circumferential stress the inner pressure is kept as a very small value and dimensionless SIF and COD values are calculated with respect to axial force. To prove the correctness of choosing the finite element types, meshing, number of elements along the thickness, loading steps the auxiliary problem of nonlinear modeling of transverse beam loaded additionally by very big axial force is considered. The very good correspondence was attained. For the pipe with axial crack the careful verification of numerical model was performed by comparison with linear results existing in literature. The results obtained are presented as a percentage of difference between the linear and nonlinear results. They show that influence of geometrical nonlinearity is fairly essential to be accounted in practice and can reach for practically real cases almost 3–10%. The change of SIF in percentages due to geometrical nonlinearity for different axial stress levels and for different crack lengths can be fairly well presented as unique dependence from product of stresses, radius to thickness ratio, and square root of dimensionless crack length. The change COD in central point of crack is slightly bigger than for SIF and the same unique dependence can be formulated for COD with only exception for small cracks λ < 3.
{"title":"FEM Calculations of SIF and COA for Through Axial Cracks in Pipes in Geometrically Nonlinear Formulation","authors":"A. Oryniak, I. Orynyak","doi":"10.1115/PVP2018-85033","DOIUrl":"https://doi.org/10.1115/PVP2018-85033","url":null,"abstract":"The determination of stress intensity factors (SIF) and crack opening area or displacements (COA or COD) is important constituent when performing the “leak before break” analysis of piping systems in NPPs. The tabulated parametrical results of their calculation are widely presented in modern scientific and normative literature. Nevertheless, there is one aspect of crack behavior, at least in thin walled pipes, which still had not obtained its due attention. We mean here the geometrically nonlinear effect, which can be the big enough to be accounted for in practical applications.\u0000 It is considered in geometrically linear analysis that only the inner pressure opens the crack, and COA and SIF are directly proportional to it. SIF is presented usually as solution for infinite plate multiplied by so-called bulging factor, BF, which depends on dimensionless crack length, i.e. ratio of crack length divided on square root of product of radius, R, and wall thickness, t.\u0000 Two loading factors in thin walled pipes can contribute to geometrically nonlinear behavior. The first one is axial stresses induced by value of axial force or bending moment. The second one – is the inner pressure itself.\u0000 The most attention in present paper is given to influence of the axial force. With this goal the numerical models were created for pipes with different ratios of R/t (20, 30, 40, 50) and different dimensionless crack length (2, 4, 6, 8). To exclude the nonlinearity due to circumferential stress the inner pressure is kept as a very small value and dimensionless SIF and COD values are calculated with respect to axial force.\u0000 To prove the correctness of choosing the finite element types, meshing, number of elements along the thickness, loading steps the auxiliary problem of nonlinear modeling of transverse beam loaded additionally by very big axial force is considered. The very good correspondence was attained.\u0000 For the pipe with axial crack the careful verification of numerical model was performed by comparison with linear results existing in literature.\u0000 The results obtained are presented as a percentage of difference between the linear and nonlinear results. They show that influence of geometrical nonlinearity is fairly essential to be accounted in practice and can reach for practically real cases almost 3–10%. The change of SIF in percentages due to geometrical nonlinearity for different axial stress levels and for different crack lengths can be fairly well presented as unique dependence from product of stresses, radius to thickness ratio, and square root of dimensionless crack length. The change COD in central point of crack is slightly bigger than for SIF and the same unique dependence can be formulated for COD with only exception for small cracks λ < 3.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"36 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":"125229998","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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