Pub Date : 2026-02-01Epub Date: 2025-09-26DOI: 10.1016/j.ijpvp.2025.105664
Daniela V. Klein , Pål Efsing , Jonas Faleskog
Fracture toughness testing was conducted on 81 SE(B)-specimens extracted from the weld metal of an aged pressurizer weld, of which 42 were deep-cracked and 39 shallow-cracked specimens. The crack tips were positioned in distinct zones in the weld metal, which was achieved by polishing and etching the material to reveal prior-austenite grain boundaries prior to specimen manufacturing. Deep-cracked specimens with crack tips located in the as-welded zone and where dendrites exhibit a low inclination to the pre-crack plane, frequently showed pop-in events during testing. The length of these pop-ins correlated directly with the length of the weld zone in front of the crack tip. Toughness was evaluated both at the pop-in and at final failure, and values were assigned to the corresponding weld zones. The ductile-to-brittle transition temperature was determined separately for each zone, confirming that the as-welded zone with low dendrite inclination is the most critical in the aged weld.
{"title":"The role of heterogeneity and pop-in events when assessing brittle fracture in the weld metal of multi-pass welds","authors":"Daniela V. Klein , Pål Efsing , Jonas Faleskog","doi":"10.1016/j.ijpvp.2025.105664","DOIUrl":"10.1016/j.ijpvp.2025.105664","url":null,"abstract":"<div><div>Fracture toughness testing was conducted on 81 SE(B)-specimens extracted from the weld metal of an aged pressurizer weld, of which 42 were deep-cracked and 39 shallow-cracked specimens. The crack tips were positioned in distinct zones in the weld metal, which was achieved by polishing and etching the material to reveal prior-austenite grain boundaries prior to specimen manufacturing. Deep-cracked specimens with crack tips located in the as-welded zone and where dendrites exhibit a low inclination to the pre-crack plane, frequently showed pop-in events during testing. The length of these pop-ins correlated directly with the length of the weld zone in front of the crack tip. Toughness was evaluated both at the pop-in and at final failure, and values were assigned to the corresponding weld zones. The ductile-to-brittle transition temperature was determined separately for each zone, confirming that the as-welded zone with low dendrite inclination is the most critical in the aged weld.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105664"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221030","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 : 2026-02-01Epub Date: 2025-10-08DOI: 10.1016/j.ijpvp.2025.105670
Gopal Ji Rai, Suhrit Mula, Gautam Agarwal
Increasing energy consumption brings significant challenges, including increased greenhouse gas emissions and rising costs. To overcome these issues, Advanced Ultrasupercritical (AUSC) thermal power plants are proposed to operate at high steam temperatures (983 K) and pressures (310 bar). To meet this demand, materials should be able to withstand the harsh environments during service life. Considering cost-effectiveness, cast Superni 625, an Indian equivalent of Inconel 625, is proposed for high-temperature applications, whereas 304H austenitic stainless steel is recommended for moderately high temperatures. Joining these two alloys, thus, assumes importance, and integrity of the dissimilar welds at high service temperatures becomes critical. In this work, 304H ASS and Superni 625 alloy were welded using ERNiCrMo-3, a Mo-rich filler metal, by multi-pass gas tungsten arc welding (GTAW). Macro & microstructural analyses demonstrated the formation of a sound joint. The weld metal (WM) predominantly comprised an austenite phase, exhibiting distributions of Mo and Ti/Nb carbides within interdendritic areas. The micro-hardness assessment indicated the highest hardness at the filling area of the weld metal, whereas 304H base metal is the weakest zone. Tensile tests at 923 K on transverse specimens of the welded plates revealed failure within the 304H base metal, indicating superior weld metal tensile strength. Furthermore, tensile tests at 923 K on longitudinal specimens revealed the weld metal strength to be higher than either of the base metals. The higher strength of the weld metal than the Superni 625 base metal at high temperature is attributed to the absence of Laves phase in the weld metal and a more pronounced PLC effect. In addition, at high temperature, the strength of the heat-affected zone near the 304H base metal side was found to be higher than the 304H base metal, which is attributed to dynamic strain aging in the heat-affected zone. The V-notch Charpy impact toughness of the weld metal was found to be significantly higher (79.7 ± 4.04 J) than the acceptable value (47 J) as per the existing standard (EN ISO 3580:2017). Fractography showed dimples at room temperature that elongated with increased temperature. At 923 K, the fracture mode was primarily mixed, exhibiting dimples from micro-voids coalescence alongside faceted features. Through extensive weld metal characterization, it is concluded that the chosen welding method for dissimilar welding was performed successfully, which has applications at high temperatures, including AUSC.
{"title":"Investigating metallurgical integrity and temperature-dependent mechanical performance of multi-pass dissimilar welds between a cast nickel-based 625 superalloy and 304H stainless steel","authors":"Gopal Ji Rai, Suhrit Mula, Gautam Agarwal","doi":"10.1016/j.ijpvp.2025.105670","DOIUrl":"10.1016/j.ijpvp.2025.105670","url":null,"abstract":"<div><div>Increasing energy consumption brings significant challenges, including increased greenhouse gas emissions and rising costs. To overcome these issues, Advanced Ultrasupercritical (AUSC) thermal power plants are proposed to operate at high steam temperatures (983 K) and pressures (310 bar). To meet this demand, materials should be able to withstand the harsh environments during service life. Considering cost-effectiveness, cast Superni 625, an Indian equivalent of Inconel 625, is proposed for high-temperature applications, whereas 304H austenitic stainless steel is recommended for moderately high temperatures. Joining these two alloys, thus, assumes importance, and integrity of the dissimilar welds at high service temperatures becomes critical. In this work, 304H ASS and Superni 625 alloy were welded using ERNiCrMo-3, a Mo-rich filler metal, by multi-pass gas tungsten arc welding (GTAW). Macro & microstructural analyses demonstrated the formation of a sound joint. The weld metal (WM) predominantly comprised an austenite phase, exhibiting distributions of Mo and Ti/Nb carbides within interdendritic areas. The micro-hardness assessment indicated the highest hardness at the filling area of the weld metal, whereas 304H base metal is the weakest zone. Tensile tests at 923 K on transverse specimens of the welded plates revealed failure within the 304H base metal, indicating superior weld metal tensile strength. Furthermore, tensile tests at 923 K on longitudinal specimens revealed the weld metal strength to be higher than either of the base metals. The higher strength of the weld metal than the Superni 625 base metal at high temperature is attributed to the absence of Laves phase in the weld metal and a more pronounced PLC effect. In addition, at high temperature, the strength of the heat-affected zone near the 304H base metal side was found to be higher than the 304H base metal, which is attributed to dynamic strain aging in the heat-affected zone. The V-notch Charpy impact toughness of the weld metal was found to be significantly higher (79.7 ± 4.04 J) than the acceptable value (47 J) as per the existing standard (EN ISO 3580:2017). Fractography showed dimples at room temperature that elongated with increased temperature. At 923 K, the fracture mode was primarily mixed, exhibiting dimples from micro-voids coalescence alongside faceted features. Through extensive weld metal characterization, it is concluded that the chosen welding method for dissimilar welding was performed successfully, which has applications at high temperatures, including AUSC.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105670"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145320565","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 : 2026-02-01Epub Date: 2025-09-16DOI: 10.1016/j.ijpvp.2025.105659
Van Thao Le , Duc Manh Dinh , Van-Chau Tran , Quang Huy Mai , Quoc Hoang Pham
Currently, wire arc additive manufacturing (WAAM) is widely investigated to manufacture large-scale parts in various industry sectors - e.g., shipbuilding, aeronautics, and tooling. In WAAM processes, single weld beads (SWBs) are considered as basic elements in deposition path planning, and their attributes remarkably impact on the stability and quality of as-deposited parts. The SWB size, including bead width (W) and height (H), directly involves the deposition path planning. Meanwhile, the aspect ratio H/W and the penetration depth (D) relate to the process stability and adhesive strengths between layers, respectively. As a result, predicting SWB attributes in function of process parameters - e.g., wire feeding speed (WFS) and traveling speed (TS) is essential. In this research, models for predicting SWB attributes in WAAM of Inconel 625 superalloy are developed, using popular machine learning (ML) models - linear regression (LR), neural network regression (NNR), support vector regression (SVR), and gaussian process regression (GPR). The performance of ML models is assessed and compared to selecting the best one for each attribute (H, W, H/W, and PD). The relations between the SWB attributes and process variables are also discussed. The results indicate that the effects of process variables on the SWBs’ attributes are complex and nonlinear. WFS shows the most contribution to the bead width W and the aspect ratio H/W with a contribution of 74.61 % and 60.55 %, respectively, while the travel speed TS reveals the greatest effect contribution to the bead height H and the penetration depth PD with a contribution of 90.46 % and 58.20 %, respectively. All the SVR, NNR and GPR models reveal greater performance than the LR model in predicting H, W, H/W, and PD. Compared to other ones, the GPR models feature the highest accuracy when predicting H, W, H/W, and PD. Their evaluation metrics {MAE, MSE, R2} in prediction of H, W, H/W, and PD are {0.097, 0.013, 0.95}, {0.125, 0.025, 0.98}, {0.018, 0.00051, 0.90}, and {0.075, 0.007, 0.93}, respectively. Based on the developed GPR models, process maps describing relationships between the process variables and responses are built for operators to select proper process parameters that enable producing the desirable SWBs coherent to specific applications.
{"title":"Machine learning-based prediction models of single weld bead attributes in wire arc additive manufacturing of Inconel 625 superalloy and process map generation","authors":"Van Thao Le , Duc Manh Dinh , Van-Chau Tran , Quang Huy Mai , Quoc Hoang Pham","doi":"10.1016/j.ijpvp.2025.105659","DOIUrl":"10.1016/j.ijpvp.2025.105659","url":null,"abstract":"<div><div>Currently, wire arc additive manufacturing (WAAM) is widely investigated to manufacture large-scale parts in various industry sectors - e.g., shipbuilding, aeronautics, and tooling. In WAAM processes, single weld beads (SWBs) are considered as basic elements in deposition path planning, and their attributes remarkably impact on the stability and quality of as-deposited parts. The SWB size, including bead width (<em>W</em>) and height (<em>H</em>), directly involves the deposition path planning. Meanwhile, the aspect ratio <em>H/W</em> and the penetration depth (<em>D</em>) relate to the process stability and adhesive strengths between layers, respectively. As a result, predicting SWB attributes in function of process parameters - e.g., wire feeding speed (<em>WFS</em>) and traveling speed (<em>TS</em>) is essential. In this research, models for predicting SWB attributes in WAAM of Inconel 625 superalloy are developed, using popular machine learning (ML) models - linear regression (LR), neural network regression (NNR), support vector regression (SVR), and gaussian process regression (GPR). The performance of ML models is assessed and compared to selecting the best one for each attribute (<em>H</em>, <em>W</em>, <em>H/W</em>, and <em>PD</em>). The relations between the SWB attributes and process variables are also discussed. The results indicate that the effects of process variables on the SWBs’ attributes are complex and nonlinear. <em>WFS</em> shows the most contribution to the bead width <em>W</em> and the aspect ratio <em>H/W</em> with a contribution of 74.61 % and 60.55 %, respectively, while the travel speed <em>TS</em> reveals the greatest effect contribution to the bead height <em>H</em> and the penetration depth <em>PD</em> with a contribution of 90.46 % and 58.20 %, respectively. All the SVR, NNR and GPR models reveal greater performance than the LR model in predicting <em>H</em>, <em>W</em>, <em>H/W</em>, and <em>PD</em>. Compared to other ones, the GPR models feature the highest accuracy when predicting <em>H</em>, <em>W</em>, <em>H/W</em>, and <em>PD</em>. Their evaluation metrics {MAE, MSE, R<sup>2</sup>} in prediction of <em>H</em>, <em>W</em>, <em>H/W</em>, and <em>PD</em> are {0.097, 0.013, 0.95}, {0.125, 0.025, 0.98}, {0.018, 0.00051, 0.90}, and {0.075, 0.007, 0.93}, respectively. Based on the developed GPR models, process maps describing relationships between the process variables and responses are built for operators to select proper process parameters that enable producing the desirable SWBs coherent to specific applications.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105659"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106639","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 : 2026-02-01Epub Date: 2025-10-27DOI: 10.1016/j.ijpvp.2025.105693
Chih-Hsuan Lee
The nozzles in RPV systems are critical components due to their high-stress concentrations, which can significantly affect the system's structural integrity. Despite the relatively minor impact of material radiation embrittlement, the stress concentration at nozzle corners should be closely monitored and precisely evaluated to ensure long-term operational safety. As different RPV nozzle geometries result in varying stress distributions and stress intensity factors (SIFs) for specific crack depths along a 45° path from the high-stress concentration point, identifying the geometry with the lowest SIFs represents the optimal design. Recently, artificial intelligence (AI) algorithms have been used to assist in calculating the stress distribution in finite element analysis (FEA), which can rapidly acquire a solution without any convergence issues during FEA. In this work, the verified finite element models (FEMs) of the RPV nozzle are established to generate extensive datasets, which correspond to various geometry sizes with the SIFs. These results are then applied to a machine learning model, support vector regression (SVR), which includes a kernel function that is suitable for high-dimensional cases. After training the SVR model, it was applied to particle swarm optimization (PSO) to identify the optimal design for the RPV nozzle geometry. The results demonstrate that the PSO with the trained SVR model can find an optimal design of nozzle geometry, which is better than the FEA results.
{"title":"Prediction and optimization of stress intensity factors for reactor pressure vessel nozzles using support vector regression and particle swarm optimization","authors":"Chih-Hsuan Lee","doi":"10.1016/j.ijpvp.2025.105693","DOIUrl":"10.1016/j.ijpvp.2025.105693","url":null,"abstract":"<div><div>The nozzles in RPV systems are critical components due to their high-stress concentrations, which can significantly affect the system's structural integrity. Despite the relatively minor impact of material radiation embrittlement, the stress concentration at nozzle corners should be closely monitored and precisely evaluated to ensure long-term operational safety. As different RPV nozzle geometries result in varying stress distributions and stress intensity factors (SIFs) for specific crack depths along a 45° path from the high-stress concentration point, identifying the geometry with the lowest SIFs represents the optimal design. Recently, artificial intelligence (AI) algorithms have been used to assist in calculating the stress distribution in finite element analysis (FEA), which can rapidly acquire a solution without any convergence issues during FEA. In this work, the verified finite element models (FEMs) of the RPV nozzle are established to generate extensive datasets, which correspond to various geometry sizes with the SIFs. These results are then applied to a machine learning model, support vector regression (SVR), which includes a kernel function that is suitable for high-dimensional cases. After training the SVR model, it was applied to particle swarm optimization (PSO) to identify the optimal design for the RPV nozzle geometry. The results demonstrate that the PSO with the trained SVR model can find an optimal design of nozzle geometry, which is better than the FEA results.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105693"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465517","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 : 2026-02-01Epub Date: 2025-10-16DOI: 10.1016/j.ijpvp.2025.105682
Gang Li , Yichao Zhu
The study of the stress corrosion cracking (SCC) behaviour of pipeline steel is of great significance for the safe operation in the oil and gas industry. However, current experimental studies, being costly in both economic and temporal terms, can only deliver data suggesting the instantaneous SCC behaviour of pipeline steel, while quantities of actual interest, such as the lifespan against SCC, cannot be measured directly. To address this issue, a semi-analytical model based on partial differential equations is developed to model the SCC kinetics for steels making oil and gas pipeline. With the effect of stress gradient on ion transportation near crack tips taken into account, the mechanism of repeated rupture of the oxide film can be mimicked. With only one parameter needing calibration, the model proposed in this study is shown to make predictions, within a few seconds on a laptop computer, over SCC indices that are difficult to experimentally measure, such as the crack incubation period under various mechanical and chemical environments. It is predicted by the model that for a 56 mm-thick API 5L X70 steel segment with a 2 mm surface scratch, it takes roughly 90 years for the scratch to become an active crack under a tensile load of 120 MPa and with an environmental pH value of 6.8 and a chloride ion concentration of 0.004 mol/L, and it takes another 30 years for SCC evolution before the final material failure.
{"title":"Full-life simulation of the stress corrosion cracking behaviour of the pipeline steel for oil and gas","authors":"Gang Li , Yichao Zhu","doi":"10.1016/j.ijpvp.2025.105682","DOIUrl":"10.1016/j.ijpvp.2025.105682","url":null,"abstract":"<div><div>The study of the stress corrosion cracking (SCC) behaviour of pipeline steel is of great significance for the safe operation in the oil and gas industry. However, current experimental studies, being costly in both economic and temporal terms, can only deliver data suggesting the instantaneous SCC behaviour of pipeline steel, while quantities of actual interest, such as the lifespan against SCC, cannot be measured directly. To address this issue, a semi-analytical model based on partial differential equations is developed to model the SCC kinetics for steels making oil and gas pipeline. With the effect of stress gradient on ion transportation near crack tips taken into account, the mechanism of repeated rupture of the oxide film can be mimicked. With only one parameter needing calibration, the model proposed in this study is shown to make predictions, within a few seconds on a laptop computer, over SCC indices that are difficult to experimentally measure, such as the crack incubation period under various mechanical and chemical environments. It is predicted by the model that for a 56 mm-thick API 5L X70 steel segment with a 2 mm surface scratch, it takes roughly 90 years for the scratch to become an active crack under a tensile load of 120 MPa and with an environmental pH value of 6.8 and a chloride ion concentration of 0.004 mol/L, and it takes another 30 years for SCC evolution before the final material failure.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105682"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362499","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 : 2026-02-01Epub Date: 2025-10-04DOI: 10.1016/j.ijpvp.2025.105674
S. Chapuliot, C. Sénac
This paper presents the development of a semi-analytical version of the industrial variation of the Beremin model for brittle fracture exclusion. Such an approximate expression is needed for two branches of safety analysis: on the one hand, for probabilistic studies which cover a large set of material, loadings, and geometrical conditions, and on the other hand, for the severity ranking of thermomechanical transients in deterministic studies. First, this article offers a short synthesis on the industrial variation of the Beremin model. Then, the physical foundations of the semi-analytical formulation are detailed. Indeed, the latter is based on analytical developments of the stress field at the tip of a crack combined with simplifying assumptions that are checked on fracture mechanics specimen of various geometry and on reactor pressure vessels’ surface defects. Owing to these prior analyses, a simple formulation relying on three geometrical parameters and one material-dependent parameter is finally proposed. The accuracy of this semi-analytical formulation is established by a comparison to the detailed industrial variation of the Beremin model on two complex industrial applications.
{"title":"Simplified formulation of the Beremin model's industrial variation for pressurized thermal shocks","authors":"S. Chapuliot, C. Sénac","doi":"10.1016/j.ijpvp.2025.105674","DOIUrl":"10.1016/j.ijpvp.2025.105674","url":null,"abstract":"<div><div>This paper presents the development of a semi-analytical version of the industrial variation of the Beremin model for brittle fracture exclusion. Such an approximate expression is needed for two branches of safety analysis: on the one hand, for probabilistic studies which cover a large set of material, loadings, and geometrical conditions, and on the other hand, for the severity ranking of thermomechanical transients in deterministic studies. First, this article offers a short synthesis on the industrial variation of the Beremin model. Then, the physical foundations of the semi-analytical formulation are detailed. Indeed, the latter is based on analytical developments of the stress field at the tip of a crack combined with simplifying assumptions that are checked on fracture mechanics specimen of various geometry and on reactor pressure vessels’ surface defects. Owing to these prior analyses, a simple formulation relying on three geometrical parameters and one material-dependent parameter is finally proposed. The accuracy of this semi-analytical formulation is established by a comparison to the detailed industrial variation of the Beremin model on two complex industrial applications.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105674"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267755","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 : 2026-02-01Epub Date: 2025-11-16DOI: 10.1016/j.ijpvp.2025.105705
Hye-Won Jeong , Jae-Yoon Kim , Yun-Jae Kim , Nam-Su Huh , Do-Jun Shim
For LBB analysis of small-diameter piping in small modular reactors, elastic-plastic J and COD needs to be estimated potentially for long circumferential through-wall cracks larger than 50 % of the circumference. This paper proposes improved J and COD estimation equations for circumferential thorough-wall cracked pipes in bending, covering short-to-long cracks over 50 % of the circumference. The proposed equations are based on extensive FE analysis. Comparisons with FE J and COD results confirmed that the proposed equations improves the accuracy of estimated J and COD not only for short cracks but also for long cracks, compared to existing estimation equations.
{"title":"Improved J and COD estimation equations covering long circumferential through-wall cracks in pipes: I- bending","authors":"Hye-Won Jeong , Jae-Yoon Kim , Yun-Jae Kim , Nam-Su Huh , Do-Jun Shim","doi":"10.1016/j.ijpvp.2025.105705","DOIUrl":"10.1016/j.ijpvp.2025.105705","url":null,"abstract":"<div><div>For LBB analysis of small-diameter piping in small modular reactors, elastic-plastic <em>J</em> and COD needs to be estimated potentially for long circumferential through-wall cracks larger than 50 % of the circumference. This paper proposes improved <em>J</em> and COD estimation equations for circumferential thorough-wall cracked pipes in bending, covering short-to-long cracks over 50 % of the circumference. The proposed equations are based on extensive FE analysis. Comparisons with FE <em>J</em> and COD results confirmed that the proposed equations improves the accuracy of estimated <em>J</em> and COD not only for short cracks but also for long cracks, compared to existing estimation equations.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105705"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578706","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}
This study presents a comprehensive life assessment of a Process Water Boiler affected by High-Temperature Hydrogen Attack (HTHA) after over 27 years of continuous operation. Constructed primarily from C-0.5Mo steel and subjected to elevated hydrogen partial pressures and temperatures up to 346.5 °C, the boiler was evaluated using a combination of advanced Non-Destructive Testing (NDT) techniques—Phased Array Ultrasonic Testing with Total Focusing Method (PAUT-TFM) and Magnetic Particle Inspection (MPI)—alongside hardness measurements and metallographic analysis. The PAUT-TFM revealed progressive HTHA damage in critical regions, with estimated damage progression rates ranging from 0.1 to 7.6 mm/year over a 10-month monitoring period. MPI confirmed the presence of a surface-breaking crack in the longitudinal weld near the inlet, accompanied by subsurface blistering and microcracking. Hardness testing identified significant softening, particularly at the inlet, with values falling below the typical hardness threshold for C-0.5Mo steel (157 HV), indicative of decarburization. Metallographic analysis corroborated these findings, revealing increased ferrite content and carbide depletion in HTHA-prone zones. The integration of destructive and non-destructive assessments confirms that the material has entered an advanced and irreversible degradation phase. Given the high structural risk and limited feasibility of repairs, the study recommends targeted component replacement using hydrogen-resistant alloys such as 1.25Cr-0.5Mo, guided by thermal exposure assessments and Nelson Curves. These findings emphasize the critical importance of early detection, informed material selection, strategic maintenance, and replacement planning to ensure long-term operational safety and reliability in hydrogen-intensive environments.
{"title":"HTHA-induced degradation in boilers: A life assessment approach using advanced NDT, metallography, and strategic maintenance","authors":"Nugroho Karya Yudha , Nosal Nugroho Pratama , Dwipa Fattamonas , Wahyuda Prakasa , Eka Wijayanto , Saiful Bahri , Akmal Irfan Majid , Deendarlianto , Muhammad Akhsin Muflikhun","doi":"10.1016/j.ijpvp.2025.105666","DOIUrl":"10.1016/j.ijpvp.2025.105666","url":null,"abstract":"<div><div>This study presents a comprehensive life assessment of a Process Water Boiler affected by High-Temperature Hydrogen Attack (HTHA) after over 27 years of continuous operation. Constructed primarily from C-0.5Mo steel and subjected to elevated hydrogen partial pressures and temperatures up to 346.5 °C, the boiler was evaluated using a combination of advanced Non-Destructive Testing (NDT) techniques—Phased Array Ultrasonic Testing with Total Focusing Method (PAUT-TFM) and Magnetic Particle Inspection (MPI)—alongside hardness measurements and metallographic analysis. The PAUT-TFM revealed progressive HTHA damage in critical regions, with estimated damage progression rates ranging from 0.1 to 7.6 mm/year over a 10-month monitoring period. MPI confirmed the presence of a surface-breaking crack in the longitudinal weld near the inlet, accompanied by subsurface blistering and microcracking. Hardness testing identified significant softening, particularly at the inlet, with values falling below the typical hardness threshold for C-0.5Mo steel (157 HV), indicative of decarburization. Metallographic analysis corroborated these findings, revealing increased ferrite content and carbide depletion in HTHA-prone zones. The integration of destructive and non-destructive assessments confirms that the material has entered an advanced and irreversible degradation phase. Given the high structural risk and limited feasibility of repairs, the study recommends targeted component replacement using hydrogen-resistant alloys such as 1.25Cr-0.5Mo, guided by thermal exposure assessments and Nelson Curves. These findings emphasize the critical importance of early detection, informed material selection, strategic maintenance, and replacement planning to ensure long-term operational safety and reliability in hydrogen-intensive environments.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105666"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145320566","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 finite element analysis with Gurson-Tvergaard-Needleman (GTN) damage model has been performed to investigate ductile fracture of X70 pipeline steel and weld. Uniaxial tensile tests and single edge notch bend tests with and in-plane constraints were tested. The inverse approach of GTN parameter identification was applied. The SENB samples were prepared with precise electric-discharge machining. Digital image correlation was used for crack mouth opening displacement. The calibrated GTN parameters with critical element size were validated on and flat-notch tensile test results. The pop-in behavior of weld SENB was simulated by assigning brittle material properties in the fracture process zone at a definite interval. The modified fracture process zone combined with the GTN model has shown better agreement with load-CMOD results. The simulation of single edge notch bend tests of EDM cut crack and sharp crack shows that initial fracture toughness increases for EDM cut crack.
{"title":"Experimentally Informed GTN model to predict ductile fracture in API X70 steel and weld using finite element analysis","authors":"Aditya Kumar , Harpreet Singh , Sandip Haldar , Rahul Chhibber","doi":"10.1016/j.ijpvp.2025.105633","DOIUrl":"10.1016/j.ijpvp.2025.105633","url":null,"abstract":"<div><div>The finite element analysis with Gurson-Tvergaard-Needleman (GTN) damage model has been performed to investigate ductile fracture of X70 pipeline steel and weld. Uniaxial tensile tests and single edge notch bend tests with <span><math><mrow><msub><mi>a</mi><mi>o</mi></msub><mo>/</mo><mi>W</mi><mo>=</mo><mn>0.50</mn></mrow></math></span> and <span><math><mrow><msub><mi>a</mi><mi>o</mi></msub><mo>/</mo><mi>W</mi><mo>=</mo><mn>0.25</mn></mrow></math></span> in-plane constraints were tested. The inverse approach of GTN parameter identification was applied. The SENB samples were prepared with precise electric-discharge machining. Digital image correlation was used for crack mouth opening displacement. The calibrated GTN parameters with critical element size were validated on <span><math><mrow><msub><mi>a</mi><mi>o</mi></msub><mo>/</mo><mi>W</mi><mo>=</mo><mn>0.25</mn></mrow></math></span> and flat-notch tensile test results. The pop-in behavior of weld SENB was simulated by assigning brittle material properties in the fracture process zone at a definite interval. The modified fracture process zone combined with the GTN model has shown better agreement with load-CMOD results. The simulation of single edge notch bend tests of EDM cut crack and sharp crack shows that initial fracture toughness increases for EDM cut crack.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105633"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050107","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 : 2026-02-01Epub Date: 2025-10-08DOI: 10.1016/j.ijpvp.2025.105672
Wang Hao , Zhan Ming , Li Yongsheng , Wang Lihui
Moderately thick composite cylindrical shells are widely used in submarine pressure-resistant structures. This study employed machine learning to analyse the failure of moderately thick composite cylindrical shells under hydrostatic pressure. Ten moderately thick composite cylindrical shells were fabricated, and their failure behaviour was examined through hydrostatic experiments and finite element analysis (FEA). Subsequently, their failure modes were analysed using FEA. Furthermore, this study trained a TabNet model for predicting the failure pressure of moderately thick composite cylindrical shells, and the model's accuracy and interpretability were validated. The trained TabNet was used to analyse the interaction effects of a shell's length-to-radius ratio (L/R), thickness-to-radius ratio (T/R), and ply angle (θ) on failure pressure. The experimental failure pressures were consistent with the FEA predictions (average error = 1.53 %). The T/R threshold at which the failure mode changes from buckling instability to strength failure varied with the ply angle. The threshold was lowest for shells with ply angles of ±20° and ±30°, and shells with ±10° and 0°/90° ply angles consistently exhibited buckling instability. The TabNet model, which achieved an R2 of 0.986 on the test set, had higher accuracy for failure pressure prediction than benchmark models did. Interpretability analysis revealed that θ and T/R are the dominant factors affecting a shell's failure pressure. Failure pressure increases to the greatest degree as T/R increases for shells with ply angles of ±60° to ±80°. Conversely, failure pressure decreases most markedly with increasing L/R within the same ply angle range. Moreover, if L/R or T/R is increased, the optimal alternating ply angle for maximising failure pressure tends to slightly decrease. The findings of this study offer guidance for the design of pressure-resistant composite shells used in submarine applications.
{"title":"Explainable machine-learning-assisted failure analysis of moderately thick composite cylindrical shells under hydrostatic pressure","authors":"Wang Hao , Zhan Ming , Li Yongsheng , Wang Lihui","doi":"10.1016/j.ijpvp.2025.105672","DOIUrl":"10.1016/j.ijpvp.2025.105672","url":null,"abstract":"<div><div>Moderately thick composite cylindrical shells are widely used in submarine pressure-resistant structures. This study employed machine learning to analyse the failure of moderately thick composite cylindrical shells under hydrostatic pressure. Ten moderately thick composite cylindrical shells were fabricated, and their failure behaviour was examined through hydrostatic experiments and finite element analysis (FEA). Subsequently, their failure modes were analysed using FEA. Furthermore, this study trained a TabNet model for predicting the failure pressure of moderately thick composite cylindrical shells, and the model's accuracy and interpretability were validated. The trained TabNet was used to analyse the interaction effects of a shell's length-to-radius ratio (<em>L</em>/<em>R</em>), thickness-to-radius ratio (<em>T</em>/<em>R</em>), and ply angle (<em>θ</em>) on failure pressure. The experimental failure pressures were consistent with the FEA predictions (average error = 1.53 %). The <em>T</em>/<em>R</em> threshold at which the failure mode changes from buckling instability to strength failure varied with the ply angle. The threshold was lowest for shells with ply angles of ±20° and ±30°, and shells with ±10° and 0°/90° ply angles consistently exhibited buckling instability. The TabNet model, which achieved an <em>R</em><sup>2</sup> of 0.986 on the test set, had higher accuracy for failure pressure prediction than benchmark models did. Interpretability analysis revealed that <em>θ</em> and <em>T</em>/<em>R</em> are the dominant factors affecting a shell's failure pressure. Failure pressure increases to the greatest degree as <em>T</em>/<em>R</em> increases for shells with ply angles of ±60° to ±80°. Conversely, failure pressure decreases most markedly with increasing <em>L</em>/<em>R</em> within the same ply angle range. Moreover, if <em>L</em>/<em>R</em> or <em>T</em>/<em>R</em> is increased, the optimal alternating ply angle for maximising failure pressure tends to slightly decrease. The findings of this study offer guidance for the design of pressure-resistant composite shells used in submarine applications.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"219 ","pages":"Article 105672"},"PeriodicalIF":3.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267000","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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