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Keywords = fatigue-corrosion damage

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26 pages, 3943 KiB  
Article
Effect of Corrosion-Induced Damage on Fatigue Behavior Degradation of ZCuAl8Mn13Fe3Ni2 Nickel–Aluminum Bronze Under Accelerated Conditions
by Ruonan Zhang, Junqi Wang, Pengyu Wei, Lian Wang, Chihui Huang, Zeyu Dai, Jinguang Zhang, Chaohe Chen and Xinyan Guo
Materials 2025, 18(15), 3551; https://doi.org/10.3390/ma18153551 - 29 Jul 2025
Viewed by 305
Abstract
Corrosion fatigue damage significantly affects the long-term service of marine platforms such as propellers. Fatigue testing of pre-corrosion specimens is essential for understanding damage mechanisms and accurately predicting fatigue life. However, traditional seawater-based tests are time-consuming and yield inconsistent results, making them unsuitable [...] Read more.
Corrosion fatigue damage significantly affects the long-term service of marine platforms such as propellers. Fatigue testing of pre-corrosion specimens is essential for understanding damage mechanisms and accurately predicting fatigue life. However, traditional seawater-based tests are time-consuming and yield inconsistent results, making them unsuitable for rapid evaluation of newly developed equipment. This study proposes an accelerated corrosion testing method for ZCuAl8Mn13Fe3Ni2 nickel–aluminum bronze, simulating the marine full immersion zone by increasing temperature, adding H2O2, reducing the solution pH, and preparing the special solution. Coupled with the fatigue test of pre-corrosion specimens, the corrosion damage characteristics and their influence on fatigue performance were analyzed. A numerical simulation method was developed to predict the fatigue life of pre-corrosion specimens, showing an average error of 13.82%. The S–N curves under different pre-corrosion cycles were also established. The research results show that using the test solution of 0.6 mol/L NaCl + 0.1 mol/L H3PO4-NaH2PO4 buffer solution + 1.0 mol/L H2O2 + 0.1 mL/500 mL concentrated hydrochloric acid for corrosion acceleration testing shows good corrosion acceleration. Moreover, the test methods ensure accuracy and reliability of the fatigue behavior evaluation of pre-corrosion specimens of the structure under actual service environments, offering a robust foundation for the material selection, corrosion resistance evaluation, and fatigue life prediction of marine structural components. Full article
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15 pages, 1929 KiB  
Article
A Stochastic Corrosion Fatigue Model for Assessing the Airworthiness of the Front Flanges of Fleet Aero Engines Using an Automated Data Analysis Method
by Govindarajan Narayanan and Andrej Golowin
Corros. Mater. Degrad. 2025, 6(3), 32; https://doi.org/10.3390/cmd6030032 - 15 Jul 2025
Viewed by 213
Abstract
Corrosion, combined with cyclic loading, is inevitable and becomes a challenging problem, even when inherently corrosion-protected materials have been selected and applied based on established in-house experience. Aero engine mount structures are exposed to dusty and salty environmental conditions during both operational and [...] Read more.
Corrosion, combined with cyclic loading, is inevitable and becomes a challenging problem, even when inherently corrosion-protected materials have been selected and applied based on established in-house experience. Aero engine mount structures are exposed to dusty and salty environmental conditions during both operational and non-operational periods. It is becoming tough to predict the remaining useful corrosion fatigue life due to the unascertainable material strength degradations under service conditions. As such, a rationalized approach is currently being used to assess their structural integrity, which produces more wastages of the flying parts. This paper presents a novel approach for predicting corrosion fatigue by proposing a random-parameter model in combination with validated experimental data. The two-random-parameter model is employed here with the probability method to determine the time-independent corrosion fatigue life of a magnesium structural casting, which is used heavily in engine front-mount aircraft systems. This is also correlated with experimental data from the literature, validating the proposed stochastic corrosion fatigue model that addresses the technical variances that occur during service to increase optimal mount structure usage using an automated data system. Full article
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20 pages, 3583 KiB  
Article
Bridge Cable Performance Warning Method Based on Temperature and Displacement Monitoring Data
by Yan Shi, Yan Wang, Lu-Nan Wang, Wei-Nan Wang and Tao-Yuan Yang
Buildings 2025, 15(13), 2342; https://doi.org/10.3390/buildings15132342 - 3 Jul 2025
Viewed by 323
Abstract
Cable-stayed bridge cables experience significant tension over time, making the bridge cables prone to corrosion and fatigue. The direct measurement of cable length is not a standard capability in most current structural health monitoring systems, nor is long-term monitoring of cable changes. Bridge [...] Read more.
Cable-stayed bridge cables experience significant tension over time, making the bridge cables prone to corrosion and fatigue. The direct measurement of cable length is not a standard capability in most current structural health monitoring systems, nor is long-term monitoring of cable changes. Bridge displacements are caused by both dynamic loads (wind and traffic) and quasi-static factors, primarily temperature. This study filtered out dynamic responses by the three-sigma rule, multiple linear regression, interpolation method, and not-a-number calibration. Monitoring data were used to analyze the bridge’s thermal field distribution and the time-dependent variation of tower displacements. Correlation analysis revealed a strong linear correlation between air temperature and quasi-static tower-girder displacements. This research proposes to use the tower-girder distance (effective cable length) to represent the length of the cable, take the thermal expansion coefficient of the effective length of the cable as the quantitative index for long-term monitoring, and take its error as the performance early warning indicator. This method effectively monitors cable health and provides damage warnings. Full article
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26 pages, 7829 KiB  
Article
Vortex-Induced Vibration Analysis of FRP Composite Risers Using Multivariate Nonlinear Regression
by Lin Zhang, Chunguang Wang, Wentao He, Keshun Ma, Run Zheng, Chiemela Victor Amaechi and Zhenyang Zhang
J. Mar. Sci. Eng. 2025, 13(7), 1281; https://doi.org/10.3390/jmse13071281 - 30 Jun 2025
Viewed by 246
Abstract
Marine risers are essential for offshore resource extraction, yet traditional metal risers encounter limitations in deep-sea applications due to their substantial weight. Fiber-reinforced polymer (FRP) composites offer a promising alternative with advantages including low density and enhanced corrosion/fatigue resistance. However, FRP risers remain [...] Read more.
Marine risers are essential for offshore resource extraction, yet traditional metal risers encounter limitations in deep-sea applications due to their substantial weight. Fiber-reinforced polymer (FRP) composites offer a promising alternative with advantages including low density and enhanced corrosion/fatigue resistance. However, FRP risers remain susceptible to fatigue damage from vortex-induced vibration (VIV). Therefore, this study investigated VIV behavior of FRP composite risers considering the coupled effect of tensile-flexural moduli, top tensions, slenderness ratios, and flow velocities. Through an orthogonal experimental design, eighteen cases were analyzed using multivariate nonlinear fitting. Results indicated that FRP composite risers exhibited larger vibration amplitudes than metal counterparts, with amplitudes increasing to both riser length and flow velocity. It was also found that the optimized FRP configuration demonstrated enhanced fiber strength utilization. Parameter coupling analysis revealed that the multivariate nonlinear fitting model achieved sufficient accuracy when incorporating two coupled parameters, with the most significant interaction occurring between flexural modulus and top tension. Full article
(This article belongs to the Section Ocean Engineering)
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15 pages, 7975 KiB  
Article
Microstructural and Mechanical Characterization of Corroded Aluminum Wires from ACSR Strand
by Laurent Gaillet, Alan Rondineau, Sébastien Langlois, Marc Demers and Lamine Dieng
Corros. Mater. Degrad. 2025, 6(2), 25; https://doi.org/10.3390/cmd6020025 - 17 Jun 2025
Viewed by 329
Abstract
Aluminum Conductors Steel-Reinforced (ACSR) conductors are typically used in overhead transmission lines. Corrosion is an important degradation mechanisms that might affect the lifetime of this essential electricity network component. Considering the complexity of conductors, it is difficult to predict the damage of these [...] Read more.
Aluminum Conductors Steel-Reinforced (ACSR) conductors are typically used in overhead transmission lines. Corrosion is an important degradation mechanisms that might affect the lifetime of this essential electricity network component. Considering the complexity of conductors, it is difficult to predict the damage of these conductors in corrosive environments. The objective of this paper is to evaluate the effect of grease and conductor geometry on the mechanical properties of aluminum strand composing the envelope of ASCR conductors. Thus, ACSR wires and strands have been evaluated in corrosion by the mean of accelerated corrosion tests. Tensile, fatigue and torsion test results are presented to examine the effect of corrosion on aluminum strands. The influence of corrosion on mechanical characteristics is established by a decrease in ductility, maximum elongation and tensile strength for the longest exposition (336 days). This significant reduction in the internal layer of ungreased wires confirms the importance of the galvanic corrosion mechanism of aluminum wires. This evolution concerns only aluminum wires of non-greased conductors, confirming the crucial role of grease as protection against corrosion. Full article
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24 pages, 14794 KiB  
Article
Development of Laser AM Process to Repair Damaged Super Duplex Stainless Steel Components
by Abdul Ahmad, Paul Xirouchakis, Alastair Pearson, Frazer Brownlie and Yevgen Gorash
Sustainability 2025, 17(12), 5438; https://doi.org/10.3390/su17125438 - 12 Jun 2025
Viewed by 580
Abstract
The escalating demands of industrial applications, particularly those involving severe wear, temperature, and corrosive environments, present significant challenges for the long-term strength of critical components, often fabricated from high-value materials such as super duplex stainless steel alloys. Super duplex can withstand the corrosive [...] Read more.
The escalating demands of industrial applications, particularly those involving severe wear, temperature, and corrosive environments, present significant challenges for the long-term strength of critical components, often fabricated from high-value materials such as super duplex stainless steel alloys. Super duplex can withstand the corrosive environment (in particular, crevice corrosion and pitting damage) and maintain mechanical integrity sufficient for high-pressure pumping applications such as seawater injection and crude oil. Conventional repair methodologies frequently result in component rejection due to process-induced distortions or detrimental phase transformations, contributing to substantial material waste and hindering the adoption of circular economy principles. This research addresses this issue by developing and validating a novel repair process utilizing laser metal deposition (LMD) additive manufacturing. The research focuses on establishing optimized process parameters to ensure the salvaging and restoration of damaged super duplex components while preserving their requisite mechanical integrity and corrosion resistance, in accordance with industry standards. Comprehensive characterization, including microstructural analysis, chemical composition verification, hardness profiling, and mechanical fatigue testing, confirms the efficacy of the LMD repair process. This work demonstrates the potential for extending the service life of critical components, thereby promoting resource efficiency and contributing to a more sustainable and resilient industrial paradigm. Full article
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15 pages, 2026 KiB  
Article
The Multistate Reliability Assessment of Ship Hull Girders
by Joanna Soszyńska-Budny and Špiro Ivošević
Appl. Sci. 2025, 15(11), 6218; https://doi.org/10.3390/app15116218 - 31 May 2025
Viewed by 306
Abstract
Ships are designed to withstand various types of hull structure damage, including corrosion, fatigue, damage, crack, fouling, etc., throughout their projected life cycle of 25 years. In this study, we used a database of 25 different bulk carriers aged from five to twenty-five [...] Read more.
Ships are designed to withstand various types of hull structure damage, including corrosion, fatigue, damage, crack, fouling, etc., throughout their projected life cycle of 25 years. In this study, we used a database of 25 different bulk carriers aged from five to twenty-five years, consisting of a total of 1920 thickness measurements of girder plate damage across 110 fuel tanks. Thickness measurements of longitudinal girder plate were conducted by certified technicians and approved company. Ultrasound thickness gauging equipment was used to collect data in accordance with the developed methodology and gauging scheme. Based on the classification societies’ rules, the values of the reduction in steel plate thickness due to corrosion over time fall into three categories: acceptable corrosion, substantial corrosion, and extensive corrosion. While classification societies prescribe permissible thickness reductions between 15 and 30%, in this study, the authors considered the excessive corrosion values to be above 20% reduction in initial thickness. Measurements indicating more than 20% reduction were classified as failures, necessitating the replacement of the corroded surfaces. After applying the multistate approach to the reliability analysis of longitudinal girder plates and improving reliability after reaching the critical state, the results show that usability dropped significantly between ten and fifteen years of service for upper girder plating and between twenty and twenty-five years of service for lower girder plates. These findings highlight the crucial impact of gauging location on reliability analysis. Full article
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25 pages, 7210 KiB  
Article
Determination of Interface Fracture Parameters in Thermoplastic Fiber Metal Laminates Under Mixed-Mode I+II
by Michał Smolnicki and Szymon Duda
Polymers 2025, 17(11), 1462; https://doi.org/10.3390/polym17111462 - 24 May 2025
Viewed by 557
Abstract
Thermoplastic fiber metal laminates (FMLs) are hybrid material systems that consist of a thin aluminum alloy sheet bonded to plies of fiber-reinforced adhesive. They provide excellent properties like fatigue strength, damage-tolerant properties, and inherent resistance to corrosion. However, they are still challenging materials [...] Read more.
Thermoplastic fiber metal laminates (FMLs) are hybrid material systems that consist of a thin aluminum alloy sheet bonded to plies of fiber-reinforced adhesive. They provide excellent properties like fatigue strength, damage-tolerant properties, and inherent resistance to corrosion. However, they are still challenging materials in terms of the metal–composite interface, which is the weakest link in this material system. In this paper, an experimental–numerical method for the determination of the fracture stress and energy for metal–composite interlayer is presented and verified. The proposed method utilizes four different experimental tests: DCB test (interface opening—mode I), ENF test (interface shearing—mode II), MMB test (mixed-mode I+II—opening with the shearing of the interface) and three-point bending test (3PB). For each test, digital twin in the form of a numerical model is prepared. The established numerical models for DCB and ENF allowed us to determine fracture stress and energy for mode I and mode II, respectively. On the basis of the numerical and experimental (from the MMB test) data, the B-K exponent is determined. Finally, the developed material model is verified in a three-point bending test, which results in mixed-mode conditions. The research is conducted on the thermoplastic FML made of aluminum alloy sheet and glass fiber reinforced polyamide 6. The research presented is complemented by fundamental mechanical tests, image processing and Scanning Electron Microscopy (SEM) analysis. As an effect, for the tested material, fracture parameters are determined using the described method. Full article
(This article belongs to the Special Issue Advances in Fatigue and Fracture of Fiber-Reinforced Polymers)
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16 pages, 18412 KiB  
Article
Research on the Influence of Surface Defects Under the Influence of Rail Corrosion on the Fatigue Damage of Wheel Rolling Contact
by Longzhi Zhao, Minghui Mou, Daoyun Chen and Minshi Zhong
Coatings 2025, 15(5), 589; https://doi.org/10.3390/coatings15050589 - 15 May 2025
Cited by 1 | Viewed by 457
Abstract
Heavy rolling contact fatigue (RCF) may be caused by wheel surface defects under the influence of rail corrosion, which threatens the operational safety of rail vehicles. To investigate the role of surface defects on wheel RCF damage under the influence of rail corrosion, [...] Read more.
Heavy rolling contact fatigue (RCF) may be caused by wheel surface defects under the influence of rail corrosion, which threatens the operational safety of rail vehicles. To investigate the role of surface defects on wheel RCF damage under the influence of rail corrosion, a salt spray tester was used to corrode the rails, an impact testing machine was employed to create surface defects, and RCF tests were completed. The role of surface defects on wheel RCF damage was studied by monitoring the wheel defect surface and cross-section. The results indicate that the tendencies of the RCF crack extension of surface defects of different sizes are similar, and they all extend in a C-shape along the tangential force direction. However, the larger the defect size, the later the crack is initiated. The leading edge material is continuously squeezed into the defect by the tangential force, and a larger plastic deformation layer is formed, which causes the RCF at the leading edge to crack more severely. Meanwhile, under the effect of combined normal force and shear stress, the leading edge crack intersects with the middle edge crack, and the leading edge material is spalled off first. Wheel RCF damage and wear are aggravated by rail corrosion, the longer the corrosion time, the more serious the RCF damage and wear, and the earlier the material spalling time, the lower the fatigue life. Full article
(This article belongs to the Special Issue Advancements in Surface Engineering, Coatings and Tribology)
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14 pages, 3035 KiB  
Article
Experimental Study on the Effect of Impactor Hardness and Shape on the Impact Response of Composite Panels
by Zoe E. C. Hall, Yuancheng Yang, James P. Dear, Jun Liu, Richard A. Brooks, Yuzhe Ding, Haibao Liu and John P. Dear
J. Compos. Sci. 2025, 9(5), 230; https://doi.org/10.3390/jcs9050230 - 2 May 2025
Viewed by 535
Abstract
In recent decades, the application of composite materials in aerostructures has significantly increased, with modern commercial aircraft progressively replacing aluminum alloys with composite components. This shift is exemplified by comparing the material compositions of the Boeing 777 and the Boeing 787 (Dreamliner). The [...] Read more.
In recent decades, the application of composite materials in aerostructures has significantly increased, with modern commercial aircraft progressively replacing aluminum alloys with composite components. This shift is exemplified by comparing the material compositions of the Boeing 777 and the Boeing 787 (Dreamliner). The Boeing 777 incorporates approximately 50% aluminum alloy and 12% composite materials, whereas the Dreamliner reverses this ratio, utilizing around 50% composites and 12% aluminum alloy. While metals remain advantageous due to their availability and ease of machining, composites offer greater potential for property tailoring to meet specific performance requirements. They also provide superior strength-to-weight ratios and enhanced resistance to corrosion and fatigue. To ensure the reliability of composites in aerospace applications, comprehensive testing under various loading conditions, particularly impact, is essential. Impacts were performed on quasi-isotropic (QIT) carbon-fiber reinforced epoxy panels with stainless steel, round-nosed and flat-ended impactors with rubber discs of 1-, 1.5- and 2 mm thickness, adhered to the flat-ended impactor to simulate the transition between hard and soft impact loading conditions. QIT composite panels were tested in this research employing similar lay-ups often being implemented in aircraft wings and other structures. The rubber discs were applied in the flat-ended impactor case but not for the round-nosed impactor due to the limited adhesion between the rubber and the rounded stainless-steel surface. Impact energies of 7.5, 15 and 30 J were investigated, and the performance of the panels was evaluated using force-time and force-displacement data alongside post-impact ultrasonic C-scan imaging to assess the damaged area. Damage was observed at all three energy values for the round-nosed impacts but only at the highest impact energy when using the flat-ended impactor, leading to the hardness study with adhered rubber discs being performed at 30 J. The most noticeable difference with the addition of rubber discs was the reduction in the damage in the plies nearest the top (impacted) surface. This suggests that the rubber reduces the severity of the impact, but increasing the thickness of the rubber from 1 to 2 mm does not notably increase this effect. Indentation clearly plays a significant role in promoting delamination at low-impact energies for the round-nosed impactors. Full article
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22 pages, 10465 KiB  
Article
Effect of Foreign Object Damage on the Fatigue Performance of Stainless Steel Blades Under Pre-Corrosion Conditions
by Taidou Zhang, Kainan Lu, Lingfeng Wang, Zhenhua Zhao and Guangdong Zheng
Metals 2025, 15(4), 357; https://doi.org/10.3390/met15040357 - 24 Mar 2025
Viewed by 463
Abstract
Aeroengine blades are prone to corrosion and foreign object damage (FOD) during service, leading to the risk of premature fatigue failure and impacting flight safety. The size of the blade’s damage depends mainly on the impact velocity and the size of the foreign [...] Read more.
Aeroengine blades are prone to corrosion and foreign object damage (FOD) during service, leading to the risk of premature fatigue failure and impacting flight safety. The size of the blade’s damage depends mainly on the impact velocity and the size of the foreign object. Therefore, this paper studies the influence of foreign object damage on the fatigue performance of 13Cr stainless steel blades under corrosive conditions by means of experimental exploration. The results are as follows. Pre-corrosion did not alter the blade’s damage mechanism, but only reduced its impact resistance. The longer the corrosion time, the more the impact resistance of the blade decreased. Pre-corrosion leads to an increase in damage when the simulated blade is impacted, resulting in decreased fatigue performance of the blade. The fatigue limits of the simulated blades pre-corroded for 24 h, 48 h, and 96 h are reduced by approximately 22%, 23%, and 29%, respectively. The research results of this paper can provide data support for the detection of external field damage of aeroengine blades and provide reference for the design of anti-foreign object damage aeroengine blades. Full article
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25 pages, 6918 KiB  
Review
A Review of Material-Related Mechanical Failures and Load Monitoring-Based Structural Health Monitoring (SHM) Technologies in Aircraft Landing Gear
by Kailun Deng, Agusmian Partogi Ompusunggu, Yigeng Xu, Martin Skote and Yifan Zhao
Aerospace 2025, 12(3), 266; https://doi.org/10.3390/aerospace12030266 - 20 Mar 2025
Cited by 2 | Viewed by 1953
Abstract
The aircraft landing gear system is vital in ensuring the aircraft’s functional completeness and operational safety. The mechanical structures of the landing gear must withstand significant operational forces, including repeated high-intensity impact loads, throughout their service life. At the same time, they must [...] Read more.
The aircraft landing gear system is vital in ensuring the aircraft’s functional completeness and operational safety. The mechanical structures of the landing gear must withstand significant operational forces, including repeated high-intensity impact loads, throughout their service life. At the same time, they must resist environmental degradation, such as corrosion, temperature fluctuations, and humidity, to ensure structural integrity and long-term reliability. Under this premise, investigating material-related mechanical failures in the landing gear is of great significance for preventing landing gear failures and ensuring aviation safety. Compared to failure investigations, structural health monitoring (SHM) plays a more active role in failure prevention for aircraft landing gears. SHM technologies identify the precursors of potential failures and continuously monitor the operational or health conditions of landing gear structures, which facilitates condition-based maintenance. This paper reviews various landing gear material-related failure investigations. The review suggests a significant portion of these failures can be attributed to material fatigue, which is either induced by abnormal high-stress concentration or corrosion. This paper also reviews a series of load monitoring-based landing gear SHM studies. It is revealed that weight and balance measurement, hard landing detection, and structure load monitoring are the most typical monitoring activities in landing gears. An analytical discussion is also presented on the correlation between reviewed landing gear failures and SHM activities, a comparison of sensors, and the potential shift in load-based landing gear SHM in response to the transition of landing gear design philosophy from safe life to damage tolerance. Full article
(This article belongs to the Special Issue Advances in Landing Systems Engineering)
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23 pages, 11405 KiB  
Review
An Overview of the Main Types of Damage and the Retrofitting of Reinforced Concrete Bridges
by Andrii Klym, Yaroslav Blikharskyy, Volodymyr Gunka, Olha Poliak, Jacek Selejdak and Zinoviy Blikharskyy
Sustainability 2025, 17(6), 2506; https://doi.org/10.3390/su17062506 - 12 Mar 2025
Cited by 4 | Viewed by 1012
Abstract
Restoring and strengthening existing bridges is more economically and environmentally feasible, as cement production in new RC bridges significantly contributes to CO2 emissions. Additionally, the production of composite carbon materials for strengthening RC structures does not require a large amount of energy, [...] Read more.
Restoring and strengthening existing bridges is more economically and environmentally feasible, as cement production in new RC bridges significantly contributes to CO2 emissions. Additionally, the production of composite carbon materials for strengthening RC structures does not require a large amount of energy, unlike the production of steel for reinforcement, which requires a significant amount of electricity and, accordingly, causes a significant amount of CO2 emissions. This is why this article presents a comprehensive review of the damage, calculations, and strengthening of RC bridge structures. It examines the main types of damage, including mechanical impacts, material fatigue, corrosion processes, seismic actions, and thermal loads. The mechanisms of their formation, correlations with environmental factors, and operational conditions are detailed. Examples of damage from real engineering objects are provided to assess the scale of the problem. Approaches to the calculation of RC bridge structures are analyzed, particularly methods for modeling the stress–strain state, considering crack formation and material degradation. Key studies by Ukrainian and foreign researchers are highlighted, identifying areas for further methodological improvement. Special attention is given to traditional and modern strengthening methods, including the use of steel elements, composites, and carbon strips. A comparative analysis of the effectiveness of different strengthening approaches is conducted. The conclusion emphasizes the need for further development of existing diagnostic, calculation, and strengthening methods. The integration of innovative materials and technologies is particularly relevant for enhancing the durability of bridges under modern operational loads. Full article
(This article belongs to the Special Issue Sustainable Road Construction Materials: Challenges & Innovations)
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21 pages, 5078 KiB  
Article
Innovative Approach Integrating Machine Learning Models for Coiled Tubing Fatigue Modeling
by Khalil Moulay Brahim, Ahmed Hadjadj, Aissa Abidi Saad, Elfakeur Abidi Saad and Hichem Horra
Appl. Sci. 2025, 15(6), 2899; https://doi.org/10.3390/app15062899 - 7 Mar 2025
Viewed by 922
Abstract
Coiled tubing (CT) plays a pivotal role in oil and gas well intervention operations due to its advantages, such as flexibility, fast mobilization, safety, low cost, and its wide range of applications, including well intervention, cleaning, stimulation, fluid displacement, cementing, and drilling. However, [...] Read more.
Coiled tubing (CT) plays a pivotal role in oil and gas well intervention operations due to its advantages, such as flexibility, fast mobilization, safety, low cost, and its wide range of applications, including well intervention, cleaning, stimulation, fluid displacement, cementing, and drilling. However, CT is subject to fatigue and mechanical damage caused by repeated bending cycles, internal pressure, and environmental factors, which can lead to premature failure, high operational costs, and production downtime. With the development of CT properties and modes of application, traditional fatigue life prediction methods based on analytical models integrated in the tracking process showed, in some cases, an underestimate or overestimate of the actual fatigue life of CT, particularly when complex factors like welding type, corrosive environment, and high-pressure variation are involved. This study addresses this limitation by introducing a comprehensive machine learning-based approach to improve the accuracy of CT fatigue life prediction, using a dataset derived from both lab-scale and full-scale fatigue tests. We incorporated the impact of different parameters such as CT grades, wall thickness, CT diameter, internal pressure, and welding types. By using advanced machine learning techniques such as artificial neural networks (ANNs) and Gradient Boosting Regressor, we obtained a more precise estimation of the number of cycles to failure than traditional models. The results from our machine learning analysis demonstrated that CatBoost and XGBoost are the most suitable models for fatigue life prediction. These models exhibited high predictive accuracy, with R2 values exceeding 0.94 on the test set, alongside relatively low error metrics (MSE, MAE and MAPE), indicating strong generalization capability. The results of this study show the importance of the integration of machine learning for CT fatigue life analysis and demonstrate its capacity to enhance prediction accuracy and reduce uncertainty. A detailed machine learning model is presented, emphasizing the capability to handle complex data and improve prediction under diverse operational conditions. This study contributes to more reliable CT management and safer, more cost-efficient well intervention operations. Full article
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22 pages, 6301 KiB  
Article
Mechanical Properties and Constitutive Model of Steel Under Temperature–Humidity Cycles
by Qianying Ma, Dingyu Feng, Yu Li, Boxiang Yao and Lu Wang
Buildings 2025, 15(5), 732; https://doi.org/10.3390/buildings15050732 - 24 Feb 2025
Viewed by 981
Abstract
Through alternating high–low temperature and humid heat tests, six sets of different humidity cycle numbers were applied to Q235B low-carbon steel and Q345B low-alloy steel. Monotonic tensile tests were conducted to compare the differences in monotonic performance degradations. The influence of humidity cycle [...] Read more.
Through alternating high–low temperature and humid heat tests, six sets of different humidity cycle numbers were applied to Q235B low-carbon steel and Q345B low-alloy steel. Monotonic tensile tests were conducted to compare the differences in monotonic performance degradations. The influence of humidity cycle numbers on the hysteretic and fatigue performance of Q235 steel was investigated through cyclic loading tests. A cyclic constitutive model based on the mixed hardening model was established and validated. The results show that the humid heat environment causes corrosion of the steel, and the degree of corrosion follows a power-law relationship with the number of humid heat cycles. Under monotonic loading, as the number of humid heat cycles increases, the strength and deformation performance of both steels degrade linearly, with Q345 low-alloy steel exhibiting more significant performance deterioration. The corrosion damage induced by the humid heat environment greatly reduces the low-cycle fatigue life of Q235 steel, and the more severe the corrosion, the lower the fatigue life. However, there is no significant effect on the development of the hysteretic curve shape. Under variable amplitude cyclic loading, as the corrosion degree increases, the hysteretic energy dissipation and energy dissipation rate continuously decrease. The two-segment backbone curve considering mass loss rate and the material hardening parameters based on the mixed hardening model can accurately describe the hysteretic characteristics of Q235 low-carbon steel under the humid heat environment. Full article
(This article belongs to the Section Building Structures)
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