Search Results (369)

This paper presents a numerical assessment of bending-fatigue durability in the tooth root region of cylindrical involute gears. Multiple gear pairs were modelled with different numbers of teeth and varying gear rim thicknesses. The generated geometry was implemented in the ANSYS 2025 R2 software suite, where the maximum normal stresses at critical locations in the tooth root region were determined through numerical simulation. A deformation-based method derived from Socie’s models was applied to estimate the duration of the phase leading up to fatigue crack formation in terms of load cycle accumulation. The gear geometry, together with the generated finite element mesh, was transferred to the FRANC2D/L version 4 software suite, where fatigue crack propagation was numerically simulated. Numerical analysis provided effective stress intensity factors, which then enabled an estimation of the number of load cycles required for an initiated crack to grow to the critical length associated with tooth failure. The total fatigue life in the tooth root region was evaluated as the sum of load cycles in the crack initiation phase and the crack propagation phase up to the critical crack length. The results show that all analysed factors exhibit very high resistance to fatigue fractures in the tooth root region. Furthermore, for gears with a rim thickness ratio greater than 0.7, the fatigue crack propagates through the tooth and reaches the fracture toughness limit of the material (K_Ic), whereas for lower rim thickness ratios, crack propagation occurs through the gear rim itself. Full article

This paper investigates whether event-level pitch-bearing fatigue damage can be estimated directly from turbine measurements, and whether these mechanical damage metrics leave measurable fingerprints in the generator DC-link voltage and current. To achieve this, a case study was performed using SCADA and structural load data from the 45 kW Chalmers (Björkö) research turbine. This data was segmented into 223 park-run-park pitch events. For each event, blade-root flapwise and edgewise bending moments were converted into radial and axial loads at the pitch bearing; an equivalent dynamic bearing load $P_{\mathrm{eq}}\left(t\right)$ was reconstructed using SKF and DG03 formulations; and rainflow counting with an S–N curve and Palmgren–Miner’s rule was used to compute event-level damage indices compatible with the International Standard Organization basic rating life concepts. In parallel, DC-link voltage and current were summarized into time-domain features, combined with operating-condition descriptors, and clustered using PCA-based k-means. The resulting clusters captured distinct electrical regimes that, across several event batches, corresponded to different levels of accumulated fatigue damage: regimes with sustained high DC-link voltage and longer duration tended to exhibit higher mean damage indices than lower, steadier DC regimes, indicating an electromechanical link. The results show that physics-based lifetime estimation and unsupervised analysis of existing electrical traces can be combined into a hybrid workflow for pitch-bearing condition assessment without additional sensors. Full article

Loading fluctuations and fatigue-related structural demand under turbulent wind conditions are important factors that limit the reliability of small wind turbines. This study investigates the separate effects of turbulence intensity and pitch angle on a 5 kW distributed variable-pitch wind turbine prototype using an OpenFAST-based aeroelastic model validated against field measurements. Under the adopted simulation setup and selected operating conditions, increasing turbulence intensity from 5% to 20% leads to a pronounced increase in the extreme blade-root flapwise bending moment and a substantial reduction in the estimated comparative fatigue life. The analysis also reveals a clear trade-off between aerodynamic efficiency and structural durability: among the tested pitch settings, the 6° case yields the highest power output, but also exhibits the largest load fluctuations and the shortest estimated comparative fatigue life. Adjusting the pitch angle to 0° or 12°, while reducing power to some extent, alleviates fatigue-related structural demand and increases the estimated comparative fatigue life. Overall, the results provide a validated prototype-level comparative assessment of how turbulence intensity and pitch angle influence aerodynamic performance, structural response, and fatigue-related demand in the studied turbine. Because the present work focuses on one prototype and does not include cross-turbine comparison or a full stochastic convergence study, the reported quantitative results should not be interpreted as directly generalizable to other turbine configurations. These findings may nevertheless provide a useful basis for future studies on load-aware pitch regulation under turbulent inflow. Full article

Solid oxide fuel cells (SOFCs) are a promising near-zero-emission propulsion source for Northern Sea Route (NSR) vessels, but their yttria-stabilized zirconia (YSZ) electrolyte and Ni-cermet anode are susceptible to thermomechanical degradation under repetitive start–stop thermal cycling. We develop a hierarchical Bayesian competing-risk framework built on a dual degradation model that decomposes area-specific resistance (ASR) growth into cycle-induced fatigue and time-dependent electrochemical aging and apply it across six NSR duty-cycle scenarios spanning f = 1–27 cycles/month. Posterior inference via the No-U-Turn Sampler (NUTS) yields 17 estimated parameters meeting standard convergence criteria (R^ ≤ 1.01, ESS_bulk ≥ 479, zero divergent transitions). The analysis identifies a failure-mode transition at f ≈ 3–6 cycles/month: high-frequency routes are crack-dominated (S1a: 10/15 cells fail by crack within the 600-cycle window with 5/15 right-censored), whereas low-frequency routes are ASR-dominated (S3b: 100% ASR). Global sensitivity analysis indicates the time-dependent rate coefficient k_time as the primary remaining-useful-life driver (S_T = 0.37–0.46). Cycle-based maintenance thresholds span 160 cycles (S3b) to ≥600 cycles (S2b), bracketed by S1a (270 cycles, 10.0 months, crack-dominant) and S3a (480 cycles, 160 months, transition regime); qualitative consistency with published experimental data supports physical plausibility. Full article

Background: Emotional distress (ED) is common among patients with gynecological malignancies and is associated with reduced quality of life and suboptimal health outcomes. Total-score approaches may overlook the complex interrelationships among individual emotional symptoms. Objective: This study provides a theory-informed contextual application and empirical boundary test of symptom network analysis, organized by the Stress Process Model (SPM), to examine not only how ED symptoms cluster and connect with psychosocial correlates and quality-of-life domains, but also whether psychosocial stratification is reflected in altered symptom topology or primarily in differences in distress burden. Methods: A cross-sectional study was conducted among 415 patients with gynecological malignancies recruited from a tertiary hospital in China. ED was assessed using the Brief Profile of Mood States-Short Form (BPOMS-SF30). An exploratory three-track screening strategy was used to derive a focused 16-node set of frequent negative mood symptoms. Gaussian graphical models with EBICglasso regularization were estimated for the symptom network and for extended networks including demographic/clinical variables, SPM-related psychosocial variables, and quality-of-life indicators. Results: The ED network showed dense positive connectivity, with strong within-domain clustering and several cross-domain associations. Exhaustion, restlessness, and irritability were relatively more relationally prominent in the primary network, although centrality stability was low to moderate across models. Fatigue-related symptoms were closely connected with anxiety, depressive symptoms, and impaired quality of life. Among psychosocial variables, self-perceived burden showed the strongest conditional association with fatigue. Adjusting for demographic and clinical variables did not materially alter the core symptom network, and no significant subgroup differences in global strength or overall structure were observed across psychosocial strata. Conclusions: In this sample, psychosocial risk stratification appeared to relate more to the overall severity and burden of distress than to major reorganization of symptom topology. The study therefore contributes primarily as a theory-informed contextual application of network methods and as an empirical boundary test showing that several psychosocial strata did not exhibit major topological differences. Because the retained nodes were selected for prevalence, association strength, and selection stability, the observed prominence of fatigue- and activation-related symptoms should be interpreted as conditional on this focused symptom subset. Overall, the findings are correlational, exploratory, and hypothesis-generating. Full article

Background/Objectives: To evaluate the short-term effects of structured physical activity (PA), alone or combined with dietary counselling, in early-stage chronic kidney disease (CKD) patients managed in primary healthcare (PHC). Methods: This non-randomised controlled study was conducted in Croatia from 1 September to 30 November 2025. Ninety adults aged 40–75 years with early-stage CKD were allocated to three groups: structured PA, combined PA and dietary counselling, or control. Interventions included kinesiologist-led PA and, in the combined group, dietitian-led Mediterranean/plant-based counselling. Outcomes included estimated glomerular filtration rate (eGFR), urinary albumin-to-creatinine ratio (ACR), cardiometabolic risk factors, behavioural measures, quality of life, and sleep quality. Statistical significance was set at p < 0.01. Results: Seventy-eight participants completed follow-up. Changes in eGFR did not differ between groups (p = 0.310). Mean ± standard deviation changes in ACR were −1.10 ± 6.37, −0.86 ± 2.88, and +1.18 ± 3.13 in the PA, combined, and control groups, respectively (p = 0.017, not meeting the prespecified significance threshold). Significant between-group differences were observed for selected patient-reported and PA outcomes, including emotional well-being, energy/fatigue, role limitations due to emotional problems, sedentary time, and total PA (all p ≤ 0.006). Conclusions: Structured PA, with or without dietary counselling, improved PA behaviour and selected patient-reported outcomes in early-stage CKD managed in PHC but did not demonstrate significant short-term effects on kidney-related outcomes. These findings support the feasibility of integrating lifestyle-oriented interventions into PHC as part of integrated CKD care, while larger, longer-term studies are needed. Full article

At present, most of the research methods for vibration fatigue of welded structures mainly focus on uniaxial stress, ignoring the influence of shear stress. To this end, by combining the ASME structural stress method with the random and vibration analysis theory outlined in the IEC 61373 standard, a new method for evaluating the fatigue life of multi-axis random vibration problems in the frequency domain has been proposed. This method extends the structural stress method to multi-axis scenarios to accurately extract the local multi-axis structural stress state at the weld toe. Its advantage lies in the fact that it not only accounts for the influence of load frequency distribution and structural modal vibrations on fatigue life, but also incorporates the effect of local multiaxial stress conditions in the weld on fatigue life. Additionally, it includes corrections for non-proportional multiaxial stress conditions, resulting in fatigue assessment results that more closely reflect actual conditions. It was validated by comparing the local multiaxial stress, phase difference between shear and normal stress, and equivalent structural stress power spectrum of 0° and 30° fillet welded specimens with test results. Subsequently, it was applied to a multiaxial random vibration fatigue assessment of a vehicle-mounted electrical cabinet with experimental verification. The results indicate that fatigue life estimates based on a multi-axis stress state are lower than those obtained using a uniaxial method. Compared to traditional uniaxial methods, the multi-axis fatigue life estimates show a significant reduction ranging from 4.20% to 88.35%, effectively accounting for damage caused by shear stress. The fatigue assessment results are more closely aligned with experimental data, thereby validating the effectiveness of the proposed new method. The frequency-domain multiaxial random vibration fatigue assessment method proposed in this article provides a new technology for the design and evaluation of welded structures of vehicle-mounted equipment in rail vehicles. This method reduces costs during the design phase of rail vehicles, offering positive economic implications. Full article

The present study investigates the thermo-mechanical behaviour and fatigue life associated with the shrink-fit process of shrink-fit tool holders. These holders are an indispensable component of high-precision and high-speed machining processes in modern manufacturing industries. Shrink-fit holders are subjected to elevated levels of stress as a consequence of repeated heating and cooling cycles, which can result in clamping fatigue over time. In this study, a three-dimensional finite element model (FEM) of a holder manufactured from H13 tool steel in accordance with BT40 standards was created using ANSYS software. The numerical analyses included transient thermal and structural analyses, consisting of a 4.5-s induction heating stage at 10 kW power, followed by a 1200-s cooling process. The analysis yielded results that were corroborated by the experimental data. It was established that, upon the conclusion of the heating process, the temperature in the conical region of the holder attained a range of approximately 388–417 °C. Furthermore, it was ascertained that a radial expansion of approximately 17.2–22 µm, which is required for the successful insertion of the cutting tool into the inner bore, was achieved. The fatigue life prediction, which constitutes the main focus of the study, applied the Soderberg criterion and evaluated two basic loading scenarios: the first tool assembly and repeated tool assembly cycles. The calculations yielded a life estimate of approximately 12,407 cycles for the first tool assembly cycle and approximately 19,400 cycles for the repeated tool assembly cycle. Accordingly, the repeated tool assembly condition exhibited a longer fatigue life than the first tool assembly condition. The enhanced longevity observed in the repeated tool assembly scenario is attributed to the stress cycle not fully reaching zero during this process, resulting in a lower stress amplitude. Full article

This study explores the use of spectral methods for fatigue life assessment, considering the effects of material plasticity. While these methods are widely used for high-cycle fatigue in the linear elastic regime, their application to low-cycle fatigue remains more complex due to nonlinear material behaviour. By incorporating models such as Neuber’s rule and the Ramberg-Osgood formulation, this work examines how spectral methods can be adapted to account for elastic-plastic effects. A comparison is made between fatigue life estimations obtained with spectral approaches and results from time-domain nonlinear simulations. The study provides insights into the applicability of strain-based spectral methods, contributing to a better understanding of their potential and limitations in fatigue assessment. Full article

TC4 titanium alloy bolted structures are extensively utilized in aerospace engineering, particularly within the heat-affected zones of aircraft engines. However, current studies have predominantly focused on fatigue fracture of titanium alloys at temperatures exceeding 400 °C, leaving a gap in accurate fatigue life prediction for TC4 bolted structures subjected to moderate elevated temperatures up to 400 °C. To address this limitation, this study proposes an enhanced detail fatigue rating (DFR) method that is applicable to fatigue life prediction of TC4 bolted structures under thermal environments not exceeding 400 °C. Firstly, fatigue life data were acquired from base material specimens of TC4 titanium alloy tested at 20 °C, 200 °C, and 400 °C. Secondly, an enhanced DFR method that considered the temperature-dependent thermal influence was established based on the experimental results. The enhanced DFR approach was then applied to predict the fatigue life of double-shear TC4 bolted structures, and the results were compared with those obtained via the conventional DFR method. The findings demonstrate that the enhanced DFR method improves the average fatigue life estimation accuracy by 9.29% over the conventional DFR method within the 20~400 °C range. This establishes the proposed model as a highly promising tool for evaluating the fatigue performance of TC4 bolted structures under elevated thermal conditions below 400 °C. Full article

The fatigue behaviour of a 90° long radius elbow, which is adjacent to the feedwater nozzle in a BWR, was analyzed. The start-up and shutdown transients were considered. A thermo-mechanical finite element analysis was carried out to determine the stresses induced by thermal transients, considering the environmental conditions in the reactor feedwater pipe. In addition, the Palmgren–Miner methodology and the ASME B&PVC code fatigue curve were applied to evaluate the accumulated damage and service life of the component. Environmental correction factors were considered to estimate environmentally assisted fatigue. Reductions in fatigue life were observed. In the second part of this paper, a part-through thickness semielliptical crack was also postulated in the internal surface of the elbow. It was aligned along the axial direction at the crown zone. Its growth was modelled using the Paris equation, evaluating the risk of failure using fracture parameters. It was found that the vulnerable area is located on the inner surface of the elbow, due to the concentration of stress caused by the curved geometry. Failure assessment diagrams (FADs) were plotted. It was found that the crack depth is the main factor governing crack behaviour under the conditions studied. The results provide a methodology for assessing the integrity of pipes subjected to specific environmental and operating conditions. Full article

Fatigue failure constitutes an issue that cannot be ignored when designing welded steel structures due to the initiation of cracks at weld toes and defects under cyclic loading conditions. Traditional methods, such as the notch stress approach, estimate fatigue life by modeling local stress distributions using idealized weld geometries. While these methods are widely accepted in design codes, they can be limited by complexity and reduced accuracy in real-world applications. This study explores the use of artificial neural networks (ANNs) to enhance fatigue life prediction through data-driven modeling. The proposed method involves training an ANN using synthetic data generated through finite element simulations of S355 steel weldments under various loading histories, rates, and frequencies. The objective is to capture the influence of local geometric and stress features without relying solely on assumptions used in conventional approaches. The FEM-based training data incorporate both classical experimental findings and validated modeling practices. While performance evaluation of the ANN model is reserved for future work, this study lays the groundwork for replacing or supplementing the notch stress approach with a more adaptable and efficient predictive tool. The integration of machine learning into fatigue assessment has the potential to improve reliability, reduce computational burden, and support more informed maintenance and design decisions. Full article

The durability characteristics of inorganic mixtures incorporating recycled aggregates from rural residential construction and demolition waste with high red brick content remain inadequately elucidated. To illuminate their long-term serviceability, two types of recycled aggregate inorganic mixtures (RAIMs) were formulated and implemented in a test road section, with their mechanical properties and fatigue resistance systematically monitored and assessed. Comparative analysis indicated that RAIMs exhibit comparable resistance to permanent deformation and analogous fracture failure mechanisms to natural aggregate inorganic mixtures (NAIMs), yet their elastic deformation recovery capability is compromised. Specifically, RAIMs attained parity with NAIMs in terms of unconfined compressive strength, indirect tensile strength, flexural tensile strength, and static compressive resilient modulus. However, their dynamic compressive resilient modulus, indirect tensile resilient modulus, and flexural tensile resilient modulus were lower than those of NAIMs by over 30%. Furthermore, probabilistic fatigue prediction models for RAIMs were established, facilitating reliable estimation of the service life of RAIMs under various stress intensity levels. This study holds considerable significance for dispelling the inherent perception of RAIMs’ inferior service performance and augmenting the theoretical foundation for their resourceful utilization in road engineering. Full article

Surface cracks in integral structures of aircraft pose a significant threat to structural integrity. This paper investigates the three-dimensional propagation behavior and crack-arrest characteristics of surface-initiated cracks in the web of an integral wing spar manufactured from 7050-T7451 aluminum alloy. A three-dimensional finite element model is developed in ANSYS 2024R2 to evaluate the stress intensity factors (SIFs) along the crack front under representative displacement-controlled loading conditions. This paper focuses on comparing the crack-arrest effectiveness of different tear strap configurations by varying their height-to-thickness (H/T) ratios while maintaining a constant mass. The results indicate that surface crack propagation in the spar web is dominated by Mode I (opening mode). Among the investigated designs (H/T = 0.5, 2.0, and 8.0), the configuration with the smallest ratio (H/T = 0.5) exhibits the most effective crack-arrest capability, yielding the lowest crack-driving force as the crack approaches the strap. Furthermore, fatigue life estimates based on Paris’ law illustrate the dependence of remaining service life on the evaluated stress intensity factor evolution. These findings provide a comparative basis for the damage-tolerant design of integral metallic aircraft structures, suggesting that selecting appropriate geometric proportions for crack-arrest features can enhance resistance to surface crack propagation. Full article

This study investigates the fatigue behaviour of carbon fibre–aluminium adhesively bonded tubular joints, representative of the suspension arm of a Formula SAE racing car, under both constant- and variable-amplitude fatigue loading. A linear elastic stress analysis was conducted using two-dimensional axisymmetric finite element models to determine the singular stress field parameters—specifically the Generalised Stress Intensity Factor (H₀) and the stress singularity exponent (s)—at critical adhesive–adherend interfaces. Experimental tests under quasi-static loading and constant amplitude, as well as variable-amplitude fatigue conditions, were performed. The constant-amplitude fatigue data were reanalysed in terms of both nominal maximum shear stress and H₀. The results show that the scatter index of the fatigue data was reduced by a factor of 1.46 when H₀ was used as the fatigue-driving parameter, indicating an improved correlation of the experimental results. Variable-amplitude fatigue tests were interpreted using Miner’s cumulative damage rule, confirming the suitability of H₀-based life estimation models even under realistic, variable-amplitude loading conditions. The results demonstrate that H₀ is an effective parameter for rationalising fatigue performance of tubular bonded joints and highlight its potential for fatigue design in composite–metal structural applications. Full article