Search Results (1,099)

This study investigates the influence of temperature on the bending properties, fatigue life, and breakdown voltage of glass fiber/epoxy composites (EPGF). The three-point bending tests were conducted at room temperature (RT) and 60 °C, and the bending fatigue tests were carried out under three displacement amplitudes (0.80, 0.75, 0.70). At the same time, fatigue life prediction was conducted using the Weibull distribution fitting, microscopic structure analysis by scanning electron microscopy (SEM), and breakdown voltage tests in accordance with the GB/T1408-2006 standard. The results show that at 60 °C, the ultimate bending strength and flexural modulus of EPGF decreased by 52.67% and 65.45%, respectively. At high displacement amplitudes (S = 0.80, 0.75), 60 °C leads to a sharp rise in data dispersion with the coefficient of variation (CV) surging by 1.56 and 2.32 times separately. S and temperature exert a significant synergistic degradation effect on fatigue life, and the two-parameter Weibull distribution (R² > 0.85) can well characterize the fatigue life of EPGF. In terms of dielectric properties, 60 °C reduces the initial breakdown voltage of EPGF by 4.23% (p < 0.05). Fatigue damage causes a continuous drop in breakdown voltage. At RT with 80% damage, the reduction rate increases from 16.28% to 26.95% as S rises, showing a synergistic characteristic between amplitude and fatigue damage. Moreover, 60 °C only affects the initial breakdown voltage and has no significant effect on the fatigue-induced decrease in breakdown voltage. SEM observations indicate that 60 °C induces matrix cracking, fiber curling and interfacial debonding in EPGF. This study provides key experimental data and theoretical support for the fatigue life prediction and insulation performance evaluation of EPGF under different temperature fatigue conditions. Full article

The low-cycle fatigue failure of drive shafts under complex service conditions constitutes a critical issue that undermines the structural integrity and service safety of the transmission system in special vehicles. To improve the prediction accuracy of the low-cycle fatigue life of drive shafts, a low-cycle fatigue life prediction method for the drive shaft that accounts for load effects and strength degradation is proposed. A fatigue life prediction model that accounts for the mean stress effect and fatigue strength degradation is proposed by introducing dynamically degrading fatigue strength into the mean stress-refined SWT (Smith–Watson–Topper) model. A fatigue cumulative damage model that considers load interactions and fatigue strength degradation is also proposed, in which the load ratio is introduced to quantitatively describe the extent of the influence of load interactions on the damage process. Furthermore, the dynamically degrading fatigue strength is incorporated into the M-H (Manson–Halford) model. Finally, the stress–strain responses at the critical locations of the drive shaft are analyzed using the finite element model, and the fatigue life of the drive shaft under the load spectrum is calculated using the improved fatigue life prediction model and the improved fatigue cumulative damage model. The results indicate that the improved life prediction method, which considers load effects and strength degradation, can effectively enhance the accuracy of fatigue life prediction for the drive shaft. Full article

Investigating the effects of corrosion on the mechanical and fatigue properties of steel wires is critical for the safety assessment of bridge cable structures.This study focuses on high-strength galvanized steel wires used for bridge cables, with a diameter of 7 mm and a strength grade of 1770 MPa. Specimens with varying mass loss rates η were prepared by electrochemical corrosion method, and systematic tensile and fatigue tests were conducted to study the effects of corrosion on the fundamental mechanical properties and fatigue life of the steel wires. The results indicate that the elastic modulus of the steel wires decreases slightly with the increase of η but still meets the requirements of relevant standards. In contrast, the yield strength and tensile strength degrade significantly, while ductility is particularly susceptible to corrosion, showing more severe deterioration. When η is less than 2.75%, the corroded steel wires still maintain favorable fatigue resistance at a nominal stress amplitude of 360 MPa. Once η exceeds this threshold, their fatigue life decreases significantly in a nonlinear manner with increasing η. The fatigue life predicted by a finite element model (FEM) reconstructed based on the 3D scanning geometry of corroded steel wires and combined with the Abaqus/fe-safe module shows good agreement with the experimental results, indicating that this approach can provide a valuable reference for the durability assessment of bridge cables. Full article

In high-cycle fatigue, the majority of fatigue life is spent in the crack initiation stage. However, current models fail to accurately capture the fatigue life consumed in the crack initiation stage, resulting in discrepancies in predictions. Here, we propose a fatigue life prediction model based on the crack tip plastic zone, combined with a multi-stage crack growth approach. To quantify the crack initiation life, a modified Tanaka–Mura model is developed by incorporating the effects of localized plastic deformation at the crack tip. The proposed model demonstrates good agreement with experimental observations. Furthermore, a reliability-based fatigue evaluation framework is established by introducing a fatigue safety factor formulation. The results show that the safety factor decreases with increasing applied stress levels, attributed to the reduced standard deviation and lower scatter of fatigue life at higher stresses. The findings provide a practical and physics-informed methodology for fatigue life and safety assessment of aluminum alloy components under complex cyclic loading conditions. Full article

This study evaluates fatigue crack growth in marine high-manganese steel LNG (Liquefied Natural Gas) storage tanks under cryogenic conditions. A 3D simulation framework using the M-integral for stress intensity extraction and the VCTD (Vertical Crack Tip Displacement) criterion for path prediction was developed. Parametric simulations showed that crack propagation is strongly directional, with the surface growth rate exceeding the depthwise rate. Fatigue life decreased with increasing initial crack surface length and maximum load but increased with crack inclination angle. In addition, the Mode I stress intensity factor along the depthwise path converged during propagation and rose sharply when the crack depth approached 90% of the wall thickness. An XGBoost-based dual-target model further achieved accurate prediction of crack depth and residual life. Full article

Metal magnetic memory (MMM) is a promising non-destructive evaluation method for ferromagnetic materials, allowing early detection of stress concentration and micro-defects under weak geomagnetic excitation. However, current magneto-mechanical coupling models are computationally complex and insufficient to characterize the full-cycle evolution of mesoscale physically short cracks. This work proposes a magnetic dipole model and its decomposed formulation for V-shaped cracks. Combined with theoretical derivation, finite element simulation, and in situ three-point bending tests on Q345 steel, the magneto-mechanical coupling mechanism and magnetic signal evolution during crack propagation are investigated. Results show that the MMM normal component exhibits obvious peak-peak features at the crack tip, while the tangential component shows a single-peak characteristic. Two critical signal mutations are observed at crack lengths of about 100 μm and 3000 μm, corresponding to micro-meso and meso-macro crack transitions, respectively. The model is verified with relative errors of 15.2% for H_x and 17.6% for H_y. This study reveals the quantitative correlation between MMM signals and full-lifecycle crack growth, supporting damage assessment and fatigue life prediction for ferromagnetic engineering structures. Full article

Accurate assessment of cumulative fatigue damage in container gantry cranes under long-term cyclic loading is hindered by the inability of traditional single-model methods to capture real-time structural conditions. This paper proposes a digital twin-driven framework that fuses multi-source data for dynamic fatigue life prediction. The framework’s core is an improved Extended Hyper-Heuristic Neural Network (EHH-NN), which incorporates regularization optimization, a split node structure, and ANOVA-based function decomposition to model complex stress responses under limited training data. The improved model achieves a goodness of fit (R²) of 0.942 and a mean relative error of 4.4%, outperforming standard BP and LSTM models while maintaining a prediction time of 42 ms. A closed-loop correction mechanism driven by measured stress feedback is designed to dynamically adjust model outputs, and a prototype system integrating PLC-based data acquisition with Unity3D 2022.3 visualization is developed to demonstrate engineering applicability. Full article

In high-speed train traction power supply systems, compensation ropes serve as critical transmission components to ensure system stability. These ropes are specially designed as right-hand alternating lay wire ropes. During tension compensation of the contact wire, the compensation rope undergoes repeated bending around the ratchet device, making it susceptible to fatigue fracture. This study conducted bending fatigue tests on compensation ropes with complete structural configurations in accordance with GB/T 12347-2008. The stress distribution and deformation evolution induced by bending were simulated using the finite element method, enabling fatigue life prediction under cyclic bending conditions. Given the significant convergence difficulties encountered in large-deformation bending simulations of the full structural model, this study innovatively adopts Love’s elastic thin-rod theory as an alternative approach, which avoids the computational prohibitions of full-scale helical modeling while preserving critical bending stiffness characteristics. The results demonstrate that the equivalent elastic modulus derived from Love’s elastic thin-rod theory closely matches the modulus obtained through stress–strain curve fitting from strand tensile tests. Furthermore, under identical axial tensile loads, the equivalent diameter model and the full-structure finite element model exhibit nearly identical end elongations. The predicted bending fatigue life using the equivalent diameter model agrees well with experimental results, and the fatigue fracture mechanisms are further revealed through microscopic morphology analysis, collectively confirming that the proposed equivalent modeling strategy provides an efficient and reliable solution for fatigue life prediction of complex wire rope structures under coupled tension–bending conditions. Full article

This study tested the mechanical properties of sugarcane bagasse fiber-reinforced recycled aggregate concrete (SFRAC) with sugarcane bagasse fiber (SF) volume fractions of 0.5%, 1.5%, and 3%, and recycled coarse aggregate (RCA) replacement rates of 20%, 40%, and 60% by the mass of coarse aggregate. Evaluated parameters included compressive strength and flexural strength. Based on the mechanical performance test results, seven specimens with superior performance were selected for further flexural fatigue testing. This identified the optimal SF and RCA replacement ratios that balance mechanical performance, fatigue resistance, and economic/environmental considerations. The study concluded that sugarcane bagasse fiber significantly enhances the mechanical properties of recycled aggregate concrete (RAC). At a fiber volume concentration of 1.5%, compressive strength increased by up to 15.1%, while flexural strength improved by up to 24.6%. Regarding fatigue performance, the flexural fatigue life of SFRAC increased synchronously with rising SF content, with test results highly consistent with the three-parameter Weibull distribution. Based on this, the P-lgS-lgN equation and the S-${\lambda }_f$-N equation incorporating failure probability and fiber parameters were derived. A fatigue strain-based damage evolution model was established to predict damage levels and remaining life of SFRAC. SEM experiments confirmed SF’s reinforcing effect on SFRAC at the microstructural level. These studies demonstrate that SFRAC with a 1.5% SF content and 40% RCA substitution offers optimal performance and environmental sustainability. Full article

The operation and maintenance (O and M) phase of offshore wind farms is often simplified in life cycle assessments (LCA), especially with respect to scour-related activities. This study develops a refined O and M–LCA model that explicitly includes scour monitoring, repair, and protection measures, and applies it to a 202 MW offshore wind farm in China. The analysis focuses on the environmental burdens of scour-related O and M activities under predefined engineering scenarios, rather than on the prediction of structural fatigue life or reliability-based intervention timing. Two representative scour-protection strategies were compared: rock dumping (S1) and cement-stabilized soil (S2). The results show that scour protection can substantially increase the environmental burdens of the O and M phase. Relative to the baseline O and M carbon intensity of 4.36 kg CO₂-eq/MWh, S1 causes only a slight increase in global warming potential but greatly increases air pollution- and resource-related impacts because of large-scale rock extraction and transport. In contrast, S2 reduces mineral resource scarcity from 2.14 to 0.042 kg Cu-eq/MWh, corresponding to a 98% reduction compared with S1, but raises the global warming potential to 9.94 kg CO₂-eq/MWh, mainly because of cement production and offshore treatment. Sensitivity analysis shows that S1 is more affected by hydrodynamic-driven intervention frequency in air pollution-related categories, whereas S2 is more sensitive to seabed conditions and stabilization efficiency in terms of GWP. A site-specific screening framework is proposed by integrating geotechnical and hydrodynamic constraints, regional environmental concerns, and targeted mitigation options. The results provide O and M-stage environmental evidence for the site-specific screening of scour-protection strategies and for improving the environmental performance of offshore wind O and M. Full article

Subsurface rolling contact fatigue (RCF) failure is one of the primary failure modes in properly installed and lubricated rolling bearings. Its actual service life often exhibits significant scatter, posing a formidable challenge to the reliable life prediction and operational safety of bearings. This study establishes a macro-meso-coupled rolling contact fatigue model that accounts for crystalline anisotropy and grain topological structures. This model utilizes Voronoi tessellations and random Euler angles to construct a polycrystalline mesoscopic model, which is subsequently integrated with a macroscopic Hertzian contact finite element analysis to simulate the roller bearing loading cycles and determine the localized stress responses within the material. The results indicate that variations in macroscopic structural and operating parameters primarily affect the overall stress level of the subsurface RCF failure. The relative fatigue life of the bearing exhibits an exceptionally high sensitivity to changes in macroscopic and operating parameters. Specifically, an increase in radial load leads to an exponential decrease in relative life, with the Weibull slope ranging between 1.001 and 1.129, which is broadly consistent with the classical Lundberg–Palmgren experimental value of 1.125. Conversely, the heterogeneity of the mesoscopic crystalline structure strongly influences the statistical variance of localized extreme stresses. The scatter in bearing fatigue life demonstrates a much more pronounced sensitivity to mesostructural alterations; as the grain size increases from 10 μm to 40 μm, the Weibull slope drops from 1.041 to 0.784. This study provides an analytical basis for the reliable life prediction of rolling bearings. Full article

With the increasing penetration of wind power, the participation of wind farms in primary frequency regulation has become important for maintaining power system frequency stability. However, virtual inertia and droop control, while providing frequency support, can increase structural fatigue loads in wind turbines and shorten their service life. To address this issue, this study proposes a coordinated optimization method for wind farm primary frequency control parameters based on fatigue load prediction. First, damage equivalent load (DEL) data under different power disturbances, wind speeds, and control parameter settings are generated through OpenFAST–Simulink co-simulation. Then, a multilayer perceptron (MLP) neural network is developed to establish the mapping from power disturbance, wind speed, and control parameters to turbine DEL. Based on the trained model, an optimization framework is constructed to minimize the total DEL of the wind farm, improve the uniformity of DEL distribution among turbines, and satisfy grid frequency support constraints. Simulation results show that the proposed method effectively reduces the overall fatigue load of the wind farm while ensuring system frequency security and improving load distribution uniformity among turbines. Full article

This study addresses, within the framework of fracture mechanics, the structural analysis of the DEMO (demonstration power plant) divertor—a key component in fusion reactors—subjected to particularly severe loading conditions. A global model of the divertor was developed using Finite Element Method (FEM) analysis through the software ANSYS Workbench 2024, including all structural subcomponents. Thermal and internal pressure load cases were considered. The FEM analysis enabled the identification of critical areas prone to stress concentration. Based on the global results, a submodeling technique was applied to analyze locally critical components with higher resolution. On these submodels, a Linear Elastic Fracture Mechanics (LEFM) analysis was performed using the FRANC3D (v 8.6.2) software. Static semi-elliptical cracks were introduced in various configurations, and the stress intensity factor was evaluated to assess their criticality. Subsequently, an incremental crack growth analysis was conducted to simulate crack propagation based on the local stress field, also accounting for directional variations. Finally, a lifetime analysis was carried out using Paris’ law, estimating the fatigue cycles for an arbitrary crack propagation under the given loading conditions. The entire procedure was repeated for each subcomponent and loading condition, resulting in a broad and detailed understanding of the fracture response of the system. This approach provides crucial insights for the design, inspection, and long-term maintenance of the divertor. Full article

Background: Critical care nurses are frequently exposed to traumatic clinical events and occupational stress, increasing the risk of post-traumatic stress disorder (PTSD), compassion fatigue, and compromised psychological well-being. However, the interrelationships among these variables in Saudi Arabia remain unclear. This study investigated the associations between PTSD symptoms, compassion fatigue, and psychological well-being among critical care nurses. Methods: A descriptive cross-sectional study was conducted between October and December 2025 with 210 critical care nurses from the Eastern and Riyadh regions of Saudi Arabia. Data were collected using the PTSD Checklist for DSM-5 (PCL-5), the Professional Quality of Life Scale, and the WHO-5 Well-Being Index. Data analysis included descriptive statistics, t-tests, one-way analysis of variance, Pearson’s correlation coefficients, and multiple linear regression. Results: The mean PCL-5 score was 27.44, with 38.1% of participants meeting the cutoff for probable PTSD. Compassion fatigue was moderate. The mean WHO-5 score was 54.60, indicating moderate well-being, though a substantial proportion reported poor well-being. Psychological well-being was negatively correlated with both PTSD symptoms and compassion fatigue, while PTSD symptoms were strongly positively correlated with compassion fatigue. Both PTSD and compassion fatigue independently predicted lower well-being, explaining 21% of the variance. Sociodemographic variables were not significant predictors after adjustment. Conclusions: Critical care nurses experience moderate PTSD symptoms and compassion fatigue, adversely affecting psychological well-being. These findings underscore the interconnected nature of trauma-related distress and professional quality of life, highlighting the need for routine psychological screening, trauma-informed support, and resilience-focused interventions. Full article

Geometric discontinuities in aero-engine turbine blades generate multiple stress concentrations along the airfoil, rendering life prediction exceptionally challenging. While conventional skeletal point method (SPM) offers reasonable accuracy in predicting creep-fatigue-interaction (CFI) life for simple structural specimens, they prove inadequate for geometries with poor symmetry. This study introduces a novel two-dimensional skeletal point method (2D SPM) to analyze stress evolution characteristics, identify representative stresses, and predict CFI life in complex structures. Leveraging the film-cooling hole (FCH) features of a representative turbine blade, three perforated plate specimens were designed, manufactured, and subjected to CFI testing. Failure analysis confirmed crack initiation at hole-edge stress concentration zones, followed by inward propagation. Specimen fracture surfaces exhibited predominantly ductile dimpling features, with multi-origin fatigue characteristics observed only near hole-edges, collectively indicating creep-damage-dominated failure mechanisms. Five life prediction methodologies were comparatively evaluated. The results demonstrate that the 2D-SPM achieved the highest accuracy (all predictions within twofold scatter bands), followed by the conventional SPM (also within twofold scatter bands). The nominal stress method showed moderate accuracy (within fivefold scatter bands), while both hot point method and TCD methods proved unsuitable for creep-fatigue scenarios with significant stress evolution. Full article