In this paper, limiting the damage zone length in mode II during the interaction between a main crack and a surrounding dislocation in a brittle material is considered. This study is mainly based on the strain and stress field generated by varying the distance between the dislocation and a main crack by taking into consideration several cracks’ length.The proposed model is a dish element having an edge crack surrounded by an arbitrarily dislocation anduniformly loaded under the shearing mode II. The problem is then analyzed using Finite Element Method (FEM) along with the software ABAQUS. For each distance between the main crack and the dislocation, stress and strains fields are determined and then, the limiting length of damage zone is drawn. The results are compared with those found for the opening mode I.
{"title":"Damage zone length limit during the dislocation-crack interaction under shearing mode","authors":"Hamid Hamli Benzahar, M. Chabaat","doi":"10.3233/sfc-220290","DOIUrl":"https://doi.org/10.3233/sfc-220290","url":null,"abstract":"In this paper, limiting the damage zone length in mode II during the interaction between a main crack and a surrounding dislocation in a brittle material is considered. This study is mainly based on the strain and stress field generated by varying the distance between the dislocation and a main crack by taking into consideration several cracks’ length.The proposed model is a dish element having an edge crack surrounded by an arbitrarily dislocation anduniformly loaded under the shearing mode II. The problem is then analyzed using Finite Element Method (FEM) along with the software ABAQUS. For each distance between the main crack and the dislocation, stress and strains fields are determined and then, the limiting length of damage zone is drawn. The results are compared with those found for the opening mode I.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45756836","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}
{"title":"Special Issue of the HIDA-8 Conference, 20–22 April 2021","authors":"A. Shibli","doi":"10.3233/sfc-228000","DOIUrl":"https://doi.org/10.3233/sfc-228000","url":null,"abstract":"","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43159374","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 Wilshire creep equations were introduced around fifteen years ago. Their aim was to address the non-physical extrapolation of power-law models, especially to high stresses, and the unrealistic values for activation energy and stress exponent that often arise from simple fits to data. In application they have met with some success, also with some difficulties which have largely been addressed empirically. No detailed mathematical analysis of the model seems to have been performed. This paper considers the fundamental characteristics of the Wilshire equations, as originally given, commencing with their internal consistency. It is found that the strain-time equation is incompatible with those for minimum creep-rate and rupture life. A consistent rate equation is derived, enabling the model to address the creep process rather than merely its results. Predictions made using the original and developed models are compared with actual materials behaviour; this reveals aspects of the approach which require reconsideration. The upper limit imposed by the ultimate tensile strength, and departures from a simple power law emerge as the key characteristics to be preserved and considered further.
{"title":"A perspective on the Wilshire creep equations","authors":"J. Brear","doi":"10.3233/sfc-228006","DOIUrl":"https://doi.org/10.3233/sfc-228006","url":null,"abstract":"The Wilshire creep equations were introduced around fifteen years ago. Their aim was to address the non-physical extrapolation of power-law models, especially to high stresses, and the unrealistic values for activation energy and stress exponent that often arise from simple fits to data. In application they have met with some success, also with some difficulties which have largely been addressed empirically. No detailed mathematical analysis of the model seems to have been performed. This paper considers the fundamental characteristics of the Wilshire equations, as originally given, commencing with their internal consistency. It is found that the strain-time equation is incompatible with those for minimum creep-rate and rupture life. A consistent rate equation is derived, enabling the model to address the creep process rather than merely its results. Predictions made using the original and developed models are compared with actual materials behaviour; this reveals aspects of the approach which require reconsideration. The upper limit imposed by the ultimate tensile strength, and departures from a simple power law emerge as the key characteristics to be preserved and considered further.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45148726","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 the evaluation of the fraction of life consumed due to creep damage in martensitic materials, unlike what happens for ferritic materials for which there is a consolidated method, there are currently several usable methods. Therefore, laboratory tests and in-depth microstructural analyses were carried out on Grade 91 and 92 steels for the realization of a reference atlas on microstructural modification and precipitates state evolution during isothermal ageing and thermal creep.
{"title":"New Italian standard for the creep assessment of martensitic steels","authors":"A. Tonti, C. Delle Site, L. Campanile","doi":"10.3233/sfc-228005","DOIUrl":"https://doi.org/10.3233/sfc-228005","url":null,"abstract":"For the evaluation of the fraction of life consumed due to creep damage in martensitic materials, unlike what happens for ferritic materials for which there is a consolidated method, there are currently several usable methods. Therefore, laboratory tests and in-depth microstructural analyses were carried out on Grade 91 and 92 steels for the realization of a reference atlas on microstructural modification and precipitates state evolution during isothermal ageing and thermal creep.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46761718","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}
High-temperature components in power generation plant are exposed to creep, fatigue, and creep-fatigue environment during service. The components are usually under multiaxial state of stress condition. Understanding how the material behaves under these loading and environment is essential in order to sustain and keep the plant safe. The present paper aims to investigate the creep rupture and crack growth behaviours of P92 steel at 600 °C. For creep rupture test, notched bars with two different notch radii were prepared and tested under creep condition between 250 and 3500 hours at 600 °C, while the C-shaped specimen was prepared for fatigue and creep-fatigue crack growth tests. The material tested under creep condition showed notch strengthening effect where the life of notched bar specimen increased compared to smooth specimens when the net stress against creep time data was plotted. The effect was more significant as the notch radius decreased. It was also observed that the rupture life of all specimens was von-Mises stress controlled. Based on the fatigue test, it was found that the frequency in a range of 0.1 Hz–10 Hz was insignificantly affecting the crack growth rate. Under creep-fatigue, however, the material showed frequency-dependent behaviour. Observation on the fracture surface revealed that the ductile dimple associated with plasticity was dominant for all creep specimens. In addition, frequency independent specimen was associated with the transgranular fracture, thus flat appearance was evident, while fracture surface of frequency dependent specimen was roughly associated with intergranular fracture.
{"title":"Creep, fatigue, and creep-fatigue crack growth behaviours of P92 steel at 600 °C","authors":"N. Alang, K. Nikbin","doi":"10.3233/sfc-228003","DOIUrl":"https://doi.org/10.3233/sfc-228003","url":null,"abstract":"High-temperature components in power generation plant are exposed to creep, fatigue, and creep-fatigue environment during service. The components are usually under multiaxial state of stress condition. Understanding how the material behaves under these loading and environment is essential in order to sustain and keep the plant safe. The present paper aims to investigate the creep rupture and crack growth behaviours of P92 steel at 600 °C. For creep rupture test, notched bars with two different notch radii were prepared and tested under creep condition between 250 and 3500 hours at 600 °C, while the C-shaped specimen was prepared for fatigue and creep-fatigue crack growth tests. The material tested under creep condition showed notch strengthening effect where the life of notched bar specimen increased compared to smooth specimens when the net stress against creep time data was plotted. The effect was more significant as the notch radius decreased. It was also observed that the rupture life of all specimens was von-Mises stress controlled. Based on the fatigue test, it was found that the frequency in a range of 0.1 Hz–10 Hz was insignificantly affecting the crack growth rate. Under creep-fatigue, however, the material showed frequency-dependent behaviour. Observation on the fracture surface revealed that the ductile dimple associated with plasticity was dominant for all creep specimens. In addition, frequency independent specimen was associated with the transgranular fracture, thus flat appearance was evident, while fracture surface of frequency dependent specimen was roughly associated with intergranular fracture.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47311666","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}
Creep crack growth rates originally gathered for the 𝛾′ strengthened cast nickel based superalloy Alloy-939 in terms of apparent stress intensity factor are re-evaluated as a function of the time dependent C* parameter, with crack propagation rates being insensitive to grain size at 750 and 850 °C. However, whereas a˙C(Ka) rates at 750 °C are significantly lower than those at 850 °C, equivalent a˙C(C*) rates are relatively insensitive to temperature, comparing well with the plane strain a˙C(C*) rates predicted using an approximate reference stress based C* model. While overall CT-specimen creep crack growth times for Alloy-939 can be predicted using uniaxial creep-rupture strength data when expressed in terms of reference stress at 850 °C, this appears not to be possible at 750 °C. The observation is explained with respect to evidence provided by a modified time dependent failure assessment diagram. The influence is examined of thermal transient durations at 850 °C (from 750 °C), or at 750 °C (from 850 °C) on a˙C(Ka) creep crack growth rates and tR(𝜎ref) overall lives.
{"title":"Factors influencing the analytical representation of creep crack development in Alloy 939","authors":"S. Holdsworth","doi":"10.3233/sfc-228001","DOIUrl":"https://doi.org/10.3233/sfc-228001","url":null,"abstract":"Creep crack growth rates originally gathered for the 𝛾′ strengthened cast nickel based superalloy Alloy-939 in terms of apparent stress intensity factor are re-evaluated as a function of the time dependent C* parameter, with crack propagation rates being insensitive to grain size at 750 and 850 °C. However, whereas a˙C(Ka) rates at 750 °C are significantly lower than those at 850 °C, equivalent a˙C(C*) rates are relatively insensitive to temperature, comparing well with the plane strain a˙C(C*) rates predicted using an approximate reference stress based C* model. While overall CT-specimen creep crack growth times for Alloy-939 can be predicted using uniaxial creep-rupture strength data when expressed in terms of reference stress at 850 °C, this appears not to be possible at 750 °C. The observation is explained with respect to evidence provided by a modified time dependent failure assessment diagram. The influence is examined of thermal transient durations at 850 °C (from 750 °C), or at 750 °C (from 850 °C) on a˙C(Ka) creep crack growth rates and tR(𝜎ref) overall lives.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47849544","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 electrical potential drop (EPD) technique has previously shown promising results using a combination of AC and DC EPD (or DCPD) on large pressure vessel creep tests, detecting final cracking as well as incipient creep cavitation damage in welded P91 steel, with DCPD showing subtle but steady rises of around 5% over ca 10,000 h of testing before rising exponentially at failure. The work presented here has attempted to shed light upon this using a simple numerical model. The model uses an array of spherical cavities to constrain the current path and hence raise the DCPD, however it was only able to show a modest rise in DCPD, and not match experimentally determined rises. Modelled DCPD values were a fifth of those experimentally observed, but both the nature of the model (simplified to aid timely computation) and the assumption that only cavitation is responsible for the changes seen, could be the reason for the discrepancies reported here. The possibility remains that other mechanisms are at play, which could magnify the measured DCPD – particularly those mechanisms that could be associated with embryonic or micro-crack formation, and these are discussed herein.
{"title":"Understanding signal changes when monitoring creep damage in high temperature plant using DCPD","authors":"A. Wojcik, A. Santos, M. Waitt, A. Shibli","doi":"10.3233/sfc-228004","DOIUrl":"https://doi.org/10.3233/sfc-228004","url":null,"abstract":"The electrical potential drop (EPD) technique has previously shown promising results using a combination of AC and DC EPD (or DCPD) on large pressure vessel creep tests, detecting final cracking as well as incipient creep cavitation damage in welded P91 steel, with DCPD showing subtle but steady rises of around 5% over ca 10,000 h of testing before rising exponentially at failure. The work presented here has attempted to shed light upon this using a simple numerical model. The model uses an array of spherical cavities to constrain the current path and hence raise the DCPD, however it was only able to show a modest rise in DCPD, and not match experimentally determined rises. Modelled DCPD values were a fifth of those experimentally observed, but both the nature of the model (simplified to aid timely computation) and the assumption that only cavitation is responsible for the changes seen, could be the reason for the discrepancies reported here. The possibility remains that other mechanisms are at play, which could magnify the measured DCPD – particularly those mechanisms that could be associated with embryonic or micro-crack formation, and these are discussed herein.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48770152","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}
Applied loads in bolted geometries of safety critical components can vary with time and operating conditions. Structural integrity and remaining life assessments of such components in aging industrial plants must consider the resultant changes in damage accumulation rates and acceptable defect sizes. Two case studies are presented that demonstrate the effect of bolt pre-load on creep and fatigue lives as well as on the acceptability assessments of defects. In the first case the sensitivity of creep damage accumulation and crack propagation rates to bolt pre-load in high temperature flanged connections are considered. Predicted results were found to compare well with actual damage quantified on a high pressure turbine loop pipe flange connection. It was shown that decreased pre-loads, in this case, leads to an increase the allowable safe defect size during assembly at room temperature. In contrast to this the second case study of corrosion fatigue cracking in a boiler water circulating pump illustrates that an increase in bolt pre-load leads to an increase in fatigue initiation life, a decrease in fatigue crack propagation rate and an increase in the acceptable defect size. Strain gauge measurements of bolt and casing strain, which correlated well with finite element calculations, indicated the necessity for close control of bolt pre-load during assembly to ensure specified levels are attained. In both cases metallurgical analysis and structural integrity assessments of cracked and excavated geometries were conducted which enabled limited continued operation of the components after which repairs and/or replacements will be implemented.
{"title":"Bolt loading effects on the structural integrity assessment of defects in industrial components","authors":"R. Scheepers, M. Bezuidenhout","doi":"10.3233/sfc-228009","DOIUrl":"https://doi.org/10.3233/sfc-228009","url":null,"abstract":"Applied loads in bolted geometries of safety critical components can vary with time and operating conditions. Structural integrity and remaining life assessments of such components in aging industrial plants must consider the resultant changes in damage accumulation rates and acceptable defect sizes. Two case studies are presented that demonstrate the effect of bolt pre-load on creep and fatigue lives as well as on the acceptability assessments of defects. In the first case the sensitivity of creep damage accumulation and crack propagation rates to bolt pre-load in high temperature flanged connections are considered. Predicted results were found to compare well with actual damage quantified on a high pressure turbine loop pipe flange connection. It was shown that decreased pre-loads, in this case, leads to an increase the allowable safe defect size during assembly at room temperature. In contrast to this the second case study of corrosion fatigue cracking in a boiler water circulating pump illustrates that an increase in bolt pre-load leads to an increase in fatigue initiation life, a decrease in fatigue crack propagation rate and an increase in the acceptable defect size. Strain gauge measurements of bolt and casing strain, which correlated well with finite element calculations, indicated the necessity for close control of bolt pre-load during assembly to ensure specified levels are attained. In both cases metallurgical analysis and structural integrity assessments of cracked and excavated geometries were conducted which enabled limited continued operation of the components after which repairs and/or replacements will be implemented.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43510003","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}
Weld repairs of castings during manufacture is a well-known and acceptable practice if conducted in accordance with approved standards and procedures. However, either original casting induced cracks or cracking of these weld repairs in high temperature and aging plant is not uncommon. Structural integrity assessments of such components must not only consider reduced material toughness, due to temper embrittlement, but also the stress intensities generated during transient thermal events such as start/stops and quenching incidents. In the first of two case studies the acceptability of weld repair defects in a high pressure turbine outer casing is presented. Metallurgical assessments concluded significant temper embrittlement had occurred which was taken into account in a finite element based structural integrity assessment that considered design operating conditions as well as a hypothetical quenching event. Low pressure turbine bypass valves are considered in the second case study. In this case the material temper embrittlement was found not to be as severe but the criticality of pre-warming to reduce transient thermal stress and by extension crack stress intensities during trips or shutdowns was clearly demonstrated. Remaining life assessments concluded the defects to be acceptable for operation to the next planned outage.
{"title":"Acceptability assessment of casting defects under transient thermal loading","authors":"R. Scheepers, M. Bezuidenhout","doi":"10.3233/sfc-228008","DOIUrl":"https://doi.org/10.3233/sfc-228008","url":null,"abstract":"Weld repairs of castings during manufacture is a well-known and acceptable practice if conducted in accordance with approved standards and procedures. However, either original casting induced cracks or cracking of these weld repairs in high temperature and aging plant is not uncommon. Structural integrity assessments of such components must not only consider reduced material toughness, due to temper embrittlement, but also the stress intensities generated during transient thermal events such as start/stops and quenching incidents. In the first of two case studies the acceptability of weld repair defects in a high pressure turbine outer casing is presented. Metallurgical assessments concluded significant temper embrittlement had occurred which was taken into account in a finite element based structural integrity assessment that considered design operating conditions as well as a hypothetical quenching event. Low pressure turbine bypass valves are considered in the second case study. In this case the material temper embrittlement was found not to be as severe but the criticality of pre-warming to reduce transient thermal stress and by extension crack stress intensities during trips or shutdowns was clearly demonstrated. Remaining life assessments concluded the defects to be acceptable for operation to the next planned outage.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44743777","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. Yokobori, Haruki Ishikawa, R. Sugiura, T. Ohmi, M. Tabuchi
Research concerning heat-resistant steels for the application in fossil-fired power plants has progressed remarkably during the past 60 years. This has resulted in improvements in the electrical efficiency of fossil-fired power plants. Currently, there are plans and programs to develop ultra-supercritical plants designed to operate at steam temperature and pressure conditions of 600/650 °C and 32 MPa. The W-added 9%Cr ferritic heat-resistant steel, that is, ASME grade P92, has been developed as a boiler material for this ultra-supercritical plant. Boiler materials, whose performance is critical for ultra-supercritical plant, are required to possess high creep resistant properties. In addition, these materials are exposed to fatigue induced by thermal stresses, that is, they are operated under creep-fatigue interacting conditions. In this study, mechanical tests under the condition of high temperature creep-fatigue interaction were conducted for P92 steel under stress-controlled and various load frequency conditions using the in-situ observational creep-fatigue testing machine to observe the damage formation behavior around a notch tip composed of voids in mesoscale. On the basis of these results, the effects of damage formation behavior on crack growth life were clarified. Furthermore, for the case of creep deformation, the numerical analyses of vacancy diffusion and concentration around a notch tip were conducted using our proposed numerical method of local stress-induced vacancy diffusion behavior, which is a nanoscale phenomenon to relate these behaviors to the damage formation behavior in mesoscale (μm scale).
{"title":"Correlation of deformation with damage progression behavior around a notch tip under creep and fatigue conditions for W-added 9Cr steel including weld joint","authors":"A. Yokobori, Haruki Ishikawa, R. Sugiura, T. Ohmi, M. Tabuchi","doi":"10.3233/sfc-228010","DOIUrl":"https://doi.org/10.3233/sfc-228010","url":null,"abstract":"Research concerning heat-resistant steels for the application in fossil-fired power plants has progressed remarkably during the past 60 years. This has resulted in improvements in the electrical efficiency of fossil-fired power plants. Currently, there are plans and programs to develop ultra-supercritical plants designed to operate at steam temperature and pressure conditions of 600/650 °C and 32 MPa. The W-added 9%Cr ferritic heat-resistant steel, that is, ASME grade P92, has been developed as a boiler material for this ultra-supercritical plant. Boiler materials, whose performance is critical for ultra-supercritical plant, are required to possess high creep resistant properties. In addition, these materials are exposed to fatigue induced by thermal stresses, that is, they are operated under creep-fatigue interacting conditions. In this study, mechanical tests under the condition of high temperature creep-fatigue interaction were conducted for P92 steel under stress-controlled and various load frequency conditions using the in-situ observational creep-fatigue testing machine to observe the damage formation behavior around a notch tip composed of voids in mesoscale. On the basis of these results, the effects of damage formation behavior on crack growth life were clarified. Furthermore, for the case of creep deformation, the numerical analyses of vacancy diffusion and concentration around a notch tip were conducted using our proposed numerical method of local stress-induced vacancy diffusion behavior, which is a nanoscale phenomenon to relate these behaviors to the damage formation behavior in mesoscale (μm scale).","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46094400","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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