Creep is a dominant failure mode for high-temperature structural components and is inherently characterized by pronounced scatter. However, creep constitutive models capable of describing probabilistic creep rupture remain limited. In this work, the microvoid growth mechanism and statistical distribution characteristics are incorporated into the creep damage accumulation process, then a probabilistic creep damage model is developed. Combined with a Monte Carlo simulation strategy, the proposed model is applied to investigate the scatter in small punch creep tests (SPCT) and uniaxial tensile creep tests of P91 steel. It is found that the 95 % confidence interval of the rupture life predicted for SPCT agrees closely with the experimentally measured 95 % confidence interval from the European Union Joint Research Centre Materials Database engineering materials database, demonstrating that this model can effectively quantify the uncertainty in SPCT rupture life. In addition, the model successfully reproduces the statistical difference in scatter between the two test types, showing that the 95 % confidence interval width of SPCT rupture life is approximately 1.3 times that of uniaxial tensile creep tests data. The proposed probabilistic creep damage model and the associated simulation methodology provide a new theoretical tool for creep data analysis and life prediction, and are of significant engineering value for ensuring highly reliable service of high-temperature components.
{"title":"A probabilistic creep damage model for studying the dispersion of small punch creep test and uniaxial tensile creep test","authors":"Manlin Huang , Jinyuan Wu , Yihan Wang , Jiru Zhong , Kaishu Guan , Bintao Yu","doi":"10.1016/j.ijpvp.2026.105764","DOIUrl":"10.1016/j.ijpvp.2026.105764","url":null,"abstract":"<div><div>Creep is a dominant failure mode for high-temperature structural components and is inherently characterized by pronounced scatter. However, creep constitutive models capable of describing probabilistic creep rupture remain limited. In this work, the microvoid growth mechanism and statistical distribution characteristics are incorporated into the creep damage accumulation process, then a probabilistic creep damage model is developed. Combined with a Monte Carlo simulation strategy, the proposed model is applied to investigate the scatter in small punch creep tests (SPCT) and uniaxial tensile creep tests of P91 steel. It is found that the 95 % confidence interval of the rupture life predicted for SPCT agrees closely with the experimentally measured 95 % confidence interval from the European Union Joint Research Centre Materials Database engineering materials database, demonstrating that this model can effectively quantify the uncertainty in SPCT rupture life. In addition, the model successfully reproduces the statistical difference in scatter between the two test types, showing that the 95 % confidence interval width of SPCT rupture life is approximately 1.3 times that of uniaxial tensile creep tests data. The proposed probabilistic creep damage model and the associated simulation methodology provide a new theoretical tool for creep data analysis and life prediction, and are of significant engineering value for ensuring highly reliable service of high-temperature components.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"222 ","pages":"Article 105764"},"PeriodicalIF":3.5,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-03DOI: 10.1016/j.ijpvp.2025.105740
M.D. Mathew , J. Ganesh Kumar , K. Linga Murty
The ball indentation (BI) technique is a versatile and efficient small-scale testing method employed to assess the mechanical properties of metallic materials. In this method, a compressive force is gradually applied to a spherical indenter, which is pressed onto the material’s surface until a predetermined indentation depth is achieved. The indenter is then partially unloaded and reloaded. This loading-unloading cycle is repeated several times at incrementally increasing depths. Throughout the test, the indentation depth and the corresponding load are measured. This data is used to generate a load-depth curve. By combining semi-empirical relationships with elasticity and plasticity theories, this analysis yields the stress-strain curve that is characteristic of the material’s response to multiaxial indentation loading.
Key mechanical properties derived from the BI tests include hardness, flow curve, yield strength, ultimate tensile strength, and indentation energy to fracture. This testing method facilitates localized, point-to-point assessment of the mechanical properties of metallic materials. The technique is advantageous in evaluating narrow microstructural zones within weldments. The test method is minimally invasive as well. This makes ball indentation testing attractive for assessing the mechanical properties of structural components in service and for extending their life without compromising component integrity. The paper discusses a range of BI applications. Theoretical models, AI-assisted data analysis, portable in-situ BI system, and other critical issues, as well as future scenarios, are also discussed.
{"title":"Ball indentation test: A versatile small-scale testing method for evaluating mechanical properties of materials","authors":"M.D. Mathew , J. Ganesh Kumar , K. Linga Murty","doi":"10.1016/j.ijpvp.2025.105740","DOIUrl":"10.1016/j.ijpvp.2025.105740","url":null,"abstract":"<div><div>The ball indentation (BI) technique is a versatile and efficient small-scale testing method employed to assess the mechanical properties of metallic materials. In this method, a compressive force is gradually applied to a spherical indenter, which is pressed onto the material’s surface until a predetermined indentation depth is achieved. The indenter is then partially unloaded and reloaded. This loading-unloading cycle is repeated several times at incrementally increasing depths. Throughout the test, the indentation depth and the corresponding load are measured. This data is used to generate a load-depth curve. By combining semi-empirical relationships with elasticity and plasticity theories, this analysis yields the stress-strain curve that is characteristic of the material’s response to multiaxial indentation loading.</div><div>Key mechanical properties derived from the BI tests include hardness, flow curve, yield strength, ultimate tensile strength, and indentation energy to fracture. This testing method facilitates localized, point-to-point assessment of the mechanical properties of metallic materials. The technique is advantageous in evaluating narrow microstructural zones within weldments. The test method is minimally invasive as well. This makes ball indentation testing attractive for assessing the mechanical properties of structural components in service and for extending their life without compromising component integrity. The paper discusses a range of BI applications. Theoretical models, AI-assisted data analysis, portable in-situ BI system, and other critical issues, as well as future scenarios, are also discussed.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105740"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
5 %Ni steel is a key material for manufacturing cryogenic storage tanks, which are designed to serve in low-temperature environments. However, welding reduces the low-temperature toughness of the structure, making it particularly important to improve the low-temperature impact toughness of welded joints. In this study, post-weld heat treatment tests were performed on MAG-welded joints of 5 % Ni steel employed in the tanks of very large ethane carriers. The effects of tempering temperatures (200–600 °C) on the microstructural evolution and changes in mechanical properties of the weld metal and heat-affected zone of the welded joint were investigated. The results indicate that weld metal consists of austenitic dendrites. Heat-affected zone primarily consists of bainite-ferrite, M-A constituents, and carbides. The fracture location of the welded joint was within the heat-affected zone. The yield strength, ultimate tensile strength, and elongation were 506 MPa, 679 MPa, and 20 %, respectively. The impact energy of the FL microregion at −140 °C is only 39 J. As the tempering temperature increases, BF undergoes recovery in the heat-affected zone. The redistribution of C leads to the gradual decomposition of the M-A constituent. Within the tempering temperature range of 200–500 °C, no significant changes were observed in the microhardness and tensile properties of the heat-affected zone. At a tempering temperature of 600 °C, the microhardness of the HAZ decreased by 5 % compared to the as-welded condition. Yield strength and ultimate tensile strength decreased by 7 % and 4 %, respectively. The impact toughness of the FL microregion increased by 215 % compared to the as-welded condition. This improvement is attributed to tempering enhancing the plasticity and toughness of the bainite-ferrite matrix while simultaneously reducing stress concentration caused by M-A constituents. Post-weld heat treatment improves the overall properties of welded joints. At a tempering temperature of 600 °C, the strength of the welded joint decreases slightly, but low-temperature impact toughness is significantly enhanced. According to the study, the optimal post-weld heat treatment temperature for MAG welded joints in 5 % Ni steel was determined to be 600 °C.
{"title":"Effects of PWHT on microstructure and mechanical properties of the 5 % Ni steel MAG welded joints","authors":"Zhiwei Zeng , Zhiqiang Zhang , Dongxue Jiang , Jialu Sun , Zhimeng Tian , Luyun Zhang , Henan Huang , Junwei Zhang","doi":"10.1016/j.ijpvp.2026.105754","DOIUrl":"10.1016/j.ijpvp.2026.105754","url":null,"abstract":"<div><div>5 %Ni steel is a key material for manufacturing cryogenic storage tanks, which are designed to serve in low-temperature environments. However, welding reduces the low-temperature toughness of the structure, making it particularly important to improve the low-temperature impact toughness of welded joints. In this study, post-weld heat treatment tests were performed on MAG-welded joints of 5 % Ni steel employed in the tanks of very large ethane carriers. The effects of tempering temperatures (200–600 °C) on the microstructural evolution and changes in mechanical properties of the weld metal and heat-affected zone of the welded joint were investigated. The results indicate that weld metal consists of austenitic dendrites. Heat-affected zone primarily consists of bainite-ferrite, M-A constituents, and carbides. The fracture location of the welded joint was within the heat-affected zone. The yield strength, ultimate tensile strength, and elongation were 506 MPa, 679 MPa, and 20 %, respectively. The impact energy of the FL microregion at −140 °C is only 39 J. As the tempering temperature increases, BF undergoes recovery in the heat-affected zone. The redistribution of C leads to the gradual decomposition of the M-A constituent. Within the tempering temperature range of 200–500 °C, no significant changes were observed in the microhardness and tensile properties of the heat-affected zone. At a tempering temperature of 600 °C, the microhardness of the HAZ decreased by 5 % compared to the as-welded condition. Yield strength and ultimate tensile strength decreased by 7 % and 4 %, respectively. The impact toughness of the FL microregion increased by 215 % compared to the as-welded condition. This improvement is attributed to tempering enhancing the plasticity and toughness of the bainite-ferrite matrix while simultaneously reducing stress concentration caused by M-A constituents. Post-weld heat treatment improves the overall properties of welded joints. At a tempering temperature of 600 °C, the strength of the welded joint decreases slightly, but low-temperature impact toughness is significantly enhanced. According to the study, the optimal post-weld heat treatment temperature for MAG welded joints in 5 % Ni steel was determined to be 600 °C.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105754"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-10DOI: 10.1016/j.ijpvp.2026.105758
Dejia Liu , Haitao Xiao , Guodong Lv , Yanchuang Tang , Shanguo Han
The welding of titanium/steel bimetallic sheets exhibits a great challenge owing to the formation of Fe-Ti intermetallic compounds, which can severely degrade the mechanical properties of the welded joint. In this paper, a FeCrNiCu filler metal was used for laser welding TA2/Q235 bimetallic sheets. The strength-ductility synergy and fracture behavior of the welded joint were investigated. A noteworthy finding was that the FeCrNiCu filler metal could generate a high mixing entropy value in the weld seam, which promoted the formation of a primarily face-centered cubic (FCC) phase and coarse grains within the weld seam. The negative enthalpy variation in the transition zones (TZs) on the TA2 layer resulted in phase structures predominantly composed of Fe2Ti, FCC, and α-Ti phases, accompanied by fine grains. Consequently, extremely high hardness values, ranging from 600 to 764 HV0.2 were observed in the TZ. The fragile zones of the welded joint shifted from the weld seam to the TZ, which played a significant role in promoting crack initiation and propagation in the welded joint during mechanical testing. The welded joint fabricated with the FeCrNiCu filler metal exhibited a favorable strength-ductility synergy. The strength coefficient of the welded joint was up to 92.5 %, with a fracture elongation of 6.9 %. Additionally, the welded joint demonstrated promising bending properties. A bending angle of 180° was achieved with no surface cracks observed on the weld seam during root bending tests (compressive stress on the TA2 layer).
{"title":"Investigation on the strength-ductility synergy in the laser-welded titanium/steel bimetallic sheets used for pressure vessels","authors":"Dejia Liu , Haitao Xiao , Guodong Lv , Yanchuang Tang , Shanguo Han","doi":"10.1016/j.ijpvp.2026.105758","DOIUrl":"10.1016/j.ijpvp.2026.105758","url":null,"abstract":"<div><div>The welding of titanium/steel bimetallic sheets exhibits a great challenge owing to the formation of Fe-Ti intermetallic compounds, which can severely degrade the mechanical properties of the welded joint. In this paper, a FeCrNiCu filler metal was used for laser welding TA2/Q235 bimetallic sheets. The strength-ductility synergy and fracture behavior of the welded joint were investigated. A noteworthy finding was that the FeCrNiCu filler metal could generate a high mixing entropy value in the weld seam, which promoted the formation of a primarily face-centered cubic (FCC) phase and coarse grains within the weld seam. The negative enthalpy variation in the transition zones (TZs) on the TA2 layer resulted in phase structures predominantly composed of Fe<sub>2</sub>Ti, FCC, and α-Ti phases, accompanied by fine grains. Consequently, extremely high hardness values, ranging from 600 to 764 HV<sub>0.2</sub> were observed in the TZ. The fragile zones of the welded joint shifted from the weld seam to the TZ, which played a significant role in promoting crack initiation and propagation in the welded joint during mechanical testing. The welded joint fabricated with the FeCrNiCu filler metal exhibited a favorable strength-ductility synergy. The strength coefficient of the welded joint was up to 92.5 %, with a fracture elongation of 6.9 %. Additionally, the welded joint demonstrated promising bending properties. A bending angle of 180° was achieved with no surface cracks observed on the weld seam during root bending tests (compressive stress on the TA2 layer).</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105758"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2025-12-31DOI: 10.1016/j.ijpvp.2025.105744
Kai Liu, WeiWei Liu, ShaoWei Wu, BoQun Xie, Xin Liu
The reactor pressure vessels (RPVs) are key components in nuclear power plants, and their structural integrity assessment is of great significance for the safe and stable operation of nuclear power plants. To address issues such as low computational efficiency and limited applicability of existing assessment methods, this study proposes an innovative collaborative prediction method based on the extended finite element method (XFEM) and the particle swarm optimization neural network (PSONN). This method enables rapid and accurate prediction of stress intensity factors (SIFs) under the combined influence of multiple parameters including crack geometric parameters, container structure dimensions and internal pressure. Firstly, a parametric model including typical crack configurations such as beltline shells and nozzle corners is established using XFEM, and a comprehensive database of SIFs is constructed. By systematically comparing the predictive performance of eight machine learning (ML) algorithms, a neural network model based on Particle Swarm Optimization is developed. And K-fold cross-validation and grid search techniques are adopted to optimize the model's hyperparameters. The interpretability analysis of SHAP indicates that internal pressure and crack inclination Angle are the most critical parameters affecting the prediction accuracy. By effectively integrating the physical accuracy of XFEM with the computational efficiency of PSONN, the proposed method provides a practical tool for rapid and accurate safety assessment upon crack detection in in-service inspections.
{"title":"Intelligent prediction of crack stress intensity factors for nuclear-grade pressure vessels based on XFEM-PSONN collaboration","authors":"Kai Liu, WeiWei Liu, ShaoWei Wu, BoQun Xie, Xin Liu","doi":"10.1016/j.ijpvp.2025.105744","DOIUrl":"10.1016/j.ijpvp.2025.105744","url":null,"abstract":"<div><div>The reactor pressure vessels (RPVs) are key components in nuclear power plants, and their structural integrity assessment is of great significance for the safe and stable operation of nuclear power plants. To address issues such as low computational efficiency and limited applicability of existing assessment methods, this study proposes an innovative collaborative prediction method based on the extended finite element method (XFEM) and the particle swarm optimization neural network (PSONN). This method enables rapid and accurate prediction of stress intensity factors (SIFs) under the combined influence of multiple parameters including crack geometric parameters, container structure dimensions and internal pressure. Firstly, a parametric model including typical crack configurations such as beltline shells and nozzle corners is established using XFEM, and a comprehensive database of SIFs is constructed. By systematically comparing the predictive performance of eight machine learning (ML) algorithms, a neural network model based on Particle Swarm Optimization is developed. And K-fold cross-validation and grid search techniques are adopted to optimize the model's hyperparameters. The interpretability analysis of SHAP indicates that internal pressure and crack inclination Angle are the most critical parameters affecting the prediction accuracy. By effectively integrating the physical accuracy of XFEM with the computational efficiency of PSONN, the proposed method provides a practical tool for rapid and accurate safety assessment upon crack detection in in-service inspections.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105744"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145877098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2025-12-30DOI: 10.1016/j.ijpvp.2025.105742
Ruiyuan Xue , Xuezong Zhang , Juyin Zhang , Xueping Wang , Yongnan Zhang , Linbin Li , Yongzhi Luo
A digital twin-driven online stress prediction method is proposed to address the stress monitoring requirements for multi-layer wrapped high-pressure hydrogen storage vessels. This method establishes a phased computational framework (offline/online): During the offline phase, the global stress field is computed using the Finite Element Method (FEM), and a random forest hybrid regression prediction model incorporating the whale optimization algorithm (WOA-RF) is trained to establish the mapping relationship between container load, structural features, node coordinates, and stress. During the online phase, the deviation between measured local stresses and offline-predicted stresses is first calculated. Subsequently, a K-Nearest Neighbors (KNN) algorithm constructs a surrogate model linking load-node coordinates to stress deviation. Ultimately, the KNN model is driven by locally acquired real-time measurement data, utilizing its output stress deviation to perform real-time corrections on WOA-RF prediction results, thereby achieving global twin stress prediction for the monitored vessel. To establish a more accurate finite element model during the offline phase, this paper innovatively derives a method for inverting interlayer preload in multilayer vessels based on measured data. Verification conducted on a multi-layer wrapped high-pressure reactor demonstrated that the proposed stress monitoring method achieved prediction errors ranging from 0.4 % to 10 %. Furthermore, the findings elucidate the random and non-uniform stress distribution characteristics exhibited by multi-layer wrapped vessels under loading, which stem from the complex interlayer preload generated during the manufacturing process.
{"title":"Stress distribution characteristics and intelligent online monitoring methods for multilayer wound pressure vessel","authors":"Ruiyuan Xue , Xuezong Zhang , Juyin Zhang , Xueping Wang , Yongnan Zhang , Linbin Li , Yongzhi Luo","doi":"10.1016/j.ijpvp.2025.105742","DOIUrl":"10.1016/j.ijpvp.2025.105742","url":null,"abstract":"<div><div>A digital twin-driven online stress prediction method is proposed to address the stress monitoring requirements for multi-layer wrapped high-pressure hydrogen storage vessels. This method establishes a phased computational framework (offline/online): During the offline phase, the global stress field is computed using the Finite Element Method (FEM), and a random forest hybrid regression prediction model incorporating the whale optimization algorithm (WOA-RF) is trained to establish the mapping relationship between container load, structural features, node coordinates, and stress. During the online phase, the deviation between measured local stresses and offline-predicted stresses is first calculated. Subsequently, a K-Nearest Neighbors (KNN) algorithm constructs a surrogate model linking load-node coordinates to stress deviation. Ultimately, the KNN model is driven by locally acquired real-time measurement data, utilizing its output stress deviation to perform real-time corrections on WOA-RF prediction results, thereby achieving global twin stress prediction for the monitored vessel. To establish a more accurate finite element model during the offline phase, this paper innovatively derives a method for inverting interlayer preload in multilayer vessels based on measured data. Verification conducted on a multi-layer wrapped high-pressure reactor demonstrated that the proposed stress monitoring method achieved prediction errors ranging from 0.4 % to 10 %. Furthermore, the findings elucidate the random and non-uniform stress distribution characteristics exhibited by multi-layer wrapped vessels under loading, which stem from the complex interlayer preload generated during the manufacturing process.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105742"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2025-12-26DOI: 10.1016/j.ijpvp.2025.105738
Fuhai Gao , Cheng Li , Rou Du , Jianguo Gong , Xiaoming Liu , Fuzhen Xuan
2.25Cr–1Mo steel is widely used in high-temperature components of nuclear and fossil power plants. Accurate modelling of its cyclic behavior over a wide temperature range is essential for structure integrity assessment. In this study, a Chaboche-type constitutive model is employed to describe the cyclic response of 2.25Cr–1Mo steel under various strain amplitudes and temperatures. The isotropic hardening parameter , defined as the difference between the initial and the stabilized peak stresses, plays a key role in characterizing cyclic softening. To capture the coupled dependence of on strain amplitude and temperature, a physics-constrained neural network was developed. The approach incorporates experimental scatter into the calibration process. The predicted parameters are expressed as logarithmic functions of temperature, enabling smooth interpolation and direct implementation in finite element simulations. The proposed model reproduces the experimental cyclic softening behavior with good accuracy. This framework provides a practical and reliable tool for fatigue and inelastic analysis of high-temperature structural components.
{"title":"Neural network-aided constitutive modeling of cyclic softening in 2.25Cr–1Mo steel across temperatures and strain amplitudes","authors":"Fuhai Gao , Cheng Li , Rou Du , Jianguo Gong , Xiaoming Liu , Fuzhen Xuan","doi":"10.1016/j.ijpvp.2025.105738","DOIUrl":"10.1016/j.ijpvp.2025.105738","url":null,"abstract":"<div><div>2.25Cr–1Mo steel is widely used in high-temperature components of nuclear and fossil power plants. Accurate modelling of its cyclic behavior over a wide temperature range is essential for structure integrity assessment. In this study, a Chaboche-type constitutive model is employed to describe the cyclic response of 2.25Cr–1Mo steel under various strain amplitudes and temperatures. The isotropic hardening parameter <span><math><mrow><mi>Q</mi></mrow></math></span>, defined as the difference between the initial and the stabilized peak stresses, plays a key role in characterizing cyclic softening. To capture the coupled dependence of <span><math><mrow><mi>Q</mi></mrow></math></span> on strain amplitude and temperature, a physics-constrained neural network was developed. The approach incorporates experimental scatter into the calibration process. The predicted parameters are expressed as logarithmic functions of temperature, enabling smooth interpolation and direct implementation in finite element simulations. The proposed model reproduces the experimental cyclic softening behavior with good accuracy. This framework provides a practical and reliable tool for fatigue and inelastic analysis of high-temperature structural components.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105738"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-19DOI: 10.1016/j.ijpvp.2026.105762
Chenshuo Cui , Jiaxu Liu , Xin Wang , Fei Teng , Guolin Guo , Tao Meng , Zhengbing Lv , Xuezhi Li , Lijia He , Xiaonan Wang , Xiuhua Gao
With the development of ultra-supercritical units toward higher operating temperatures and pressures, fourth-generation heat-resistant steels have become critical materials for enhancing the service life of key pressure-bearing components. This study investigated the high-temperature oxidation behavior of a novel martensitic heat-resistant steel exposed to air at temperatures ranging from 600 °C to 900 °C for 8 h. The oxidation behavior and mechanisms were analyzed through thermodynamic analysis, weight gain assessment, and microstructural characterization. At different temperatures, the oxidation weight gain curves followed linear, parabolic, and logarithmic patterns. With the increase of temperature, the oxide film gradually changes from thin and continuous dense to discontinuous and loose, covering the whole substrate surface. The increase in oxide layer thickness significantly hindered the mutual diffusion of Fe and O. At 900 °C, the porous oxide layer stratified into a Cr- and Fe-rich inner layer and an Fe-rich outer layer. Fe and O were uniformly distributed in the oxidation products, while Cr tended to enrich in the inner oxide layer. The thickening of the oxide layer and its morphological transformation from granular to dense layered significantly enhance the high-temperature oxidation resistance of heat-resistant steels.
{"title":"High-temperature oxidation behavior of novel martensitic heat-resistant steel exposed to an ambient air atmosphere","authors":"Chenshuo Cui , Jiaxu Liu , Xin Wang , Fei Teng , Guolin Guo , Tao Meng , Zhengbing Lv , Xuezhi Li , Lijia He , Xiaonan Wang , Xiuhua Gao","doi":"10.1016/j.ijpvp.2026.105762","DOIUrl":"10.1016/j.ijpvp.2026.105762","url":null,"abstract":"<div><div>With the development of ultra-supercritical units toward higher operating temperatures and pressures, fourth-generation heat-resistant steels have become critical materials for enhancing the service life of key pressure-bearing components. This study investigated the high-temperature oxidation behavior of a novel martensitic heat-resistant steel exposed to air at temperatures ranging from 600 °C to 900 °C for 8 h. The oxidation behavior and mechanisms were analyzed through thermodynamic analysis, weight gain assessment, and microstructural characterization. At different temperatures, the oxidation weight gain curves followed linear, parabolic, and logarithmic patterns. With the increase of temperature, the oxide film gradually changes from thin and continuous dense to discontinuous and loose, covering the whole substrate surface. The increase in oxide layer thickness significantly hindered the mutual diffusion of Fe and O. At 900 °C, the porous oxide layer stratified into a Cr- and Fe-rich inner layer and an Fe-rich outer layer. Fe and O were uniformly distributed in the oxidation products, while Cr tended to enrich in the inner oxide layer. The thickening of the oxide layer and its morphological transformation from granular to dense layered significantly enhance the high-temperature oxidation resistance of heat-resistant steels.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105762"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The last stage low pressure LP steam turbine blade operated for 3000 rpm was failed after 42000 equivalent hours of operation from 600 MW thermo electric plant. The fractured blade was investigated and compared with virgin blade to determine the failure mode. Visual examination, chemical analysis, uni-axial tensile, V-notch impact tests, bulk hardness, EDX, fractography and microstructural characterization were conducted on the fractured blade. Further, wet fluorescent magnetic particle inspection and surface roughness measurement conducted on virgin blade as well. Initial visual analysis suggested that chevron cracking accompanied with several ratchet marks. Moreover, dynamic analysis of last stage virgin blade was performed and evidenced that natural frequency was stable. Modal analysis had predicted using Finite Element Analysis. Both experimental and theoretical frequencies had been closely matched, and natural frequencies were well below the resonant frequency, thus, vibration had not induced fatigue fracture. Moreover, fractured blade was fractographic and metallographic analyzed for fatigue fracture characterization. An engineering failure analysis suggested that several non-metallic inclusions have been de-bonded at crack origin zone. Multiple source of fatigue cracks have been initiated adjacent to material anomalies and fatigue fracture propagated by alternating centrifugal induced tensile stress. Fine curved striations have been evidenced on fatigue crack initiation and propagation zones. The blade exhibited tempered martensite and tensile properties including hardness were within the specifications. The presence of anomalies including non-metallic inclusions and internal volumetric material defects has been linked with poor blade toughness which had reduced the fatigue resistance of last stage blade. Interaction of manganese sulfide inclusions with complex alternating centrifugal and bending stress had induced fatigue fracture. Several recommendations including blade manufacturing by clean steel technology are suggested based on various obtained evidences to prevent LPT blade failures in power plants.
{"title":"Fatigue fracture of last stage X20Cr13 low pressure turbine (LPT) blade from 600 MW thermal power station","authors":"Chidambaram Subramanian , Swarup Kr Laha , Sourav Kansabanik , Biplab Swarnakar , Debashis Ghosh","doi":"10.1016/j.ijpvp.2026.105751","DOIUrl":"10.1016/j.ijpvp.2026.105751","url":null,"abstract":"<div><div>The last stage low pressure LP steam turbine blade operated for 3000 rpm was failed after 42000 equivalent hours of operation from 600 MW thermo electric plant. The fractured blade was investigated and compared with virgin blade to determine the failure mode. Visual examination, chemical analysis, uni-axial tensile, V-notch impact tests, bulk hardness, EDX, fractography and microstructural characterization were conducted on the fractured blade. Further, wet fluorescent magnetic particle inspection and surface roughness measurement conducted on virgin blade as well. Initial visual analysis suggested that chevron cracking accompanied with several ratchet marks. Moreover, dynamic analysis of last stage virgin blade was performed and evidenced that natural frequency was stable. Modal analysis had predicted using Finite Element Analysis. Both experimental and theoretical frequencies had been closely matched, and natural frequencies were well below the resonant frequency, thus, vibration had not induced fatigue fracture. Moreover, fractured blade was fractographic and metallographic analyzed for fatigue fracture characterization. An engineering failure analysis suggested that several non-metallic inclusions have been de-bonded at crack origin zone. Multiple source of fatigue cracks have been initiated adjacent to material anomalies and fatigue fracture propagated by alternating centrifugal induced tensile stress. Fine curved striations have been evidenced on fatigue crack initiation and propagation zones. The blade exhibited tempered martensite and tensile properties including hardness were within the specifications. The presence of anomalies including non-metallic inclusions and internal volumetric material defects has been linked with poor blade toughness which had reduced the fatigue resistance of last stage blade. Interaction of manganese sulfide inclusions with complex alternating centrifugal and bending stress had induced fatigue fracture. Several recommendations including blade manufacturing by clean steel technology are suggested based on various obtained evidences to prevent LPT blade failures in power plants.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105751"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-17DOI: 10.1016/j.ijpvp.2026.105756
Yong Gyun Shin, Yoon-Suk Chang
Ensuring the integrity of spent nuclear fuel (SNF) transport cask during extreme accident as well as normal conditions is essential for public and environmental safety. In this study, a series of explosion analyses were conducted for an SNF transport cask and fuel cladding based on a representative hypothetical explosion scenario. First, three numerical methods, namely the conventional weapons effects program, smoothed particle hydrodynamics and coupled Eulerian-Lagrangian, were benchmarked against experimental data from a steel pipe explosion to identify the most reliable one. Finite element (FE) analyses of the transport cask were then primarily performed by considering different detonation angles and configurations with and without the impact limiters. The influence of explosive shapes including cube, cylinder, and sphere was also examined by comparing the resulting shock wave propagation in each cask component. The structural integrity assessment revealed that the factor of safety for all cask components exceeded 1.5 except in the case of a 0° detonation angle. Accordingly, the detailed FE model of an SNF assembly was developed and its integrity was assessed. The subsequent FE analyses showed that the resulting strains remained well below the strain-based failure criterion for all detonation angles in both configurations, suggesting that the limited damage to the cask would not compromise the integrity of the SNF fuel cladding.
{"title":"Structural integrity assessments of SNF transport cask and fuel cladding under hypothetical explosion scenario","authors":"Yong Gyun Shin, Yoon-Suk Chang","doi":"10.1016/j.ijpvp.2026.105756","DOIUrl":"10.1016/j.ijpvp.2026.105756","url":null,"abstract":"<div><div>Ensuring the integrity of spent nuclear fuel (SNF) transport cask during extreme accident as well as normal conditions is essential for public and environmental safety. In this study, a series of explosion analyses were conducted for an SNF transport cask and fuel cladding based on a representative hypothetical explosion scenario. First, three numerical methods, namely the conventional weapons effects program, smoothed particle hydrodynamics and coupled Eulerian-Lagrangian, were benchmarked against experimental data from a steel pipe explosion to identify the most reliable one. Finite element (FE) analyses of the transport cask were then primarily performed by considering different detonation angles and configurations with and without the impact limiters. The influence of explosive shapes including cube, cylinder, and sphere was also examined by comparing the resulting shock wave propagation in each cask component. The structural integrity assessment revealed that the factor of safety for all cask components exceeded 1.5 except in the case of a 0° detonation angle. Accordingly, the detailed FE model of an SNF assembly was developed and its integrity was assessed. The subsequent FE analyses showed that the resulting strains remained well below the strain-based failure criterion for all detonation angles in both configurations, suggesting that the limited damage to the cask would not compromise the integrity of the SNF fuel cladding.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105756"},"PeriodicalIF":3.5,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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