Search Results (1,326)

As a critical component of demolition robots, the rotary joint supports the entire manipulator arm and operates under severe loading conditions, rendering it highly susceptible to fatigue failure. To address this challenge, topology optimization is integrated into the structural design to simultaneously enhance fatigue life and achieve lightweighting. In this work, multiple working conditions of the demolition robot are considered and analyzed to identify the extreme operating condition. By extracting the resultant stress on the rotary joint from the assembled structure under the extreme condition, an equivalent model of the independent rotary joint is established. Given that topology optimization based on the original structure could not yield a usable structure, two topology optimization strategies based on resetting the design space are proposed, including topology optimization based on the partially filled design space and topology optimization within the fully filled design space. By performing topology optimization under different schemes, the optimized rotary joint models are reconstructed through geometric fusion. Numerical results demonstrate that the optimized rotary joints exhibit significant improvements in fatigue performance, with fatigue life doubled compared to the original design. Concurrently, the structural mass is effectively reduced. This proposed method achieves the dual objectives of fatigue life enhancement and lightweight design. Furthermore, the results reveal that resetting the design space when topology optimization fails to obtain a usable structure yields superior topology optimization outcomes, providing a valuable new insight for future structural optimization design processes in similar engineering scenarios. Full article

High-pressure plunger-cylinder pairs in axial piston pumps are prone to brittle failure due to local contact stress, time-dependent material degradation, and cyclic loading, which complicates long-term reliability assessment. To address this issue, an integrated reliability analysis framework is proposed for SiC ceramic plunger pairs, combining local stress identification, strength degradation, and fatigue damage modeling. A three-dimensional finite element model identifies the critical contact region, where the maximum equivalent stress reaches 1291.5 MPa. An exponential strength degradation model and a time-variant stress-strength interference approach based on lognormal stress and Weibull strength distributions are adopted, with 10⁵ Monte Carlo simulations used to evaluate failure probability. The results indicate that although the initial static reliability is close to 1.0, it decreases nonlinearly with service time, reaching 0.9663 at 10,000 h under moderate degradation. In addition, fatigue reliability is assessed by integrating the S-N curve of SiC with a cumulative damage model, enabling reliability-cycle curve construction and fatigue life prediction. The proposed method provides a quantitative framework for static, degradation-driven, and fatigue reliability assessment of high-pressure ceramic tribological structures. Full article

Contra-rotating propellers (CRPs) have promising applications in stratospheric airships. However, the aerodynamic interference caused by the airship envelope could lead to thrust loss, efficiency decrease, and even structure fatigue. This paper constructed parameterized computational fluid dynamic (CFD) models to simulate the aerodynamic performance of CRPs at different positions relative to the airship envelope. The total thrust, torque, efficiency, and thrust generated by a single propeller blade all show different degrees of interference. It is advised that such interference be considered in the layout design of stratospheric airships to improve propeller efficiency and ensure a longer structure fatigue life. Full article

Background: Spondyloarthritis (SpA) typically develops before 40 years of age, but increasing life expectancy has led to a growing number of cases in older adults. It is well known that age at onset may influence disease presentation, comorbidities, and patient outcomes. Objectives: To assess whether age at onset influences SpA clinical presentation. Methods: We analyzed clinical, demographic, clinimetric, and imaging data in 272 SpA patients, grouped by onset age: early (≤40, n = 119), intermediate (41–59, n = 127), and late (≥60, n = 26). All patients had a minimum follow-up duration of 12 months. Their epidemiologic, clinic, and clinimetric data were collected, as well as patient-reported outcome measures (PROs) [Patient Global Assessment (PGA), Health Assessment Questionnaire (HAQ), FACIT-Fatigue (FACIT-F), SHORT-FORM 36 (SF-36), Hospital Anxiety and Depression Scale (HADS), Work Productivity and Activity Impairment Questionnaire (WPAI), CSI (Central Sensitization Inventory), and Psoriatic Arthritis Impact of Disease (PsAID) questionnaire]. In univariate analyses, differences in categorical variables across onset groups were assessed using Fisher’s exact test; for continuous variables, between-group comparisons were performed using the Mann–Whitney U test (two-tailed) or the Kruskal–Wallis test, as appropriate, with Bonferroni correction for post hoc analyses. Multivariable regression models were subsequently fitted, adjusting for sex, diagnosis, and disease duration. For binary outcomes, multivariable logistic regression models were used, while multivariable linear regression models (ANCOVA) were applied for continuous outcomes. The overall association between onset group and each outcome was formally tested using likelihood ratio tests, comparing models including the onset variable with nested models excluding it. A p-value < 0.05 was considered statistically significant. Results: Patients’ mean age was 60.0 ± 13.7 years; 55.9% of them were males; and there were 188 cases (69.1%) of psoriatic arthritis (PsA) and 84 cases (30.9%) of ankylosing spondylitis (AS). In early-onset patients, inflammatory back pain (IBP) was more frequent, whereas late-onset patients more often presented with joint swelling. A family history of SpA and psoriasis was less common in late-onset forms. Comorbidities, including osteoporosis, osteoarthritis, hypertension, hyperuricemia, and diabetes, were more prevalent in older-onset patients, resulting in a higher overall comorbidity burden in Groups 2 and 3. Patient-reported outcomes were largely similar across age groups, although work activity limitation was more pronounced in younger patients. Conclusions: Age at onset seems to influence SpA phenotypes: early-onset could favor axial involvement, while late-onset may associate with peripheral arthritis. Late-onset forms are associated with a more severe comorbidity burden, in particular for cardiovascular risk factors. Lung involvement proved to be more prevalent with respect to the general population, so it should be checked in the routinary assessment of SpA patients. These findings suggest that rheumatologists could tailor their routine assessments based on patients’ age at disease onset. Interestingly, work productivity seems more impacted in early-onset patients. All these points highlight the importance of age at disease onset in SpA, guiding toward personalized medicine in terms of follow-up, therapy, and more holistic patient management. Full article

This study investigated a 460 MPa marine engineering steel’s microstructure and low-cycle fatigue (LCF) behavior along the thickness direction. The results showed that the low-cycle fatigue life was reduced from 9681, 4395, 2107, 1020, 829 to 7222, 1832, 1015, 630, 242 with the specimen taken from the surface to the middle of steel plate, increasing grain size and decreasing the content of high-angle grain boundaries (HAGBs). All specimens showed notable cyclic hardening and softening. This was related to the dislocation movement, interaction, accumulation, annihilation, and dynamic recovery during fatigue tests. Furthermore, the crack propagation paths in the fatigue specimens were also observed and discussed. Finally, the Basquin and Coffin–Manson relationships were used to suggest a prediction model for the LCF life at strain amplitudes ranging from 0.4% to 1.2%, and the anticipated outcomes agreed well with the test results. Full article

Intense thermo-mechanical coupling effects during cutting generate residual stress within the surface layer of a workpiece. This residual stress is a critical factor influencing the fatigue life, corrosion resistance, and dimensional stability of mechanical components, making its accurate prediction and control essential for improving product performance. To address the often generalized treatment of residual stress prediction modeling in existing literature, this paper presents a systematic review of recent advances in surface residual stress prediction for cutting operations. It details the formation mechanisms and significance of residual stress, focusing on four primary modeling approaches: empirical models based on experimental data, analytical models founded on metal cutting and elastoplastic theory, finite element models that simulate actual machining conditions, and hybrid models. A comprehensive analysis and comparison of these four model types is provided, summarizing their respective advantages and limitations. Furthermore, this paper identifies potential future research directions and development trends in residual stress prediction modeling, serving as a valuable reference for work in this field. Full article

Silicon nitride (Si₃N₄) ceramic bearings inevitably contain crack-like defects, yet their compressive capacity degradation and crack-driven failure mechanisms remain unclear. This study proposes a discrete element method (DEM) numerical framework within PFC2D to simulate a bearing containing a single prefabricated crack. First, a bearing DEM model was established and calibrated to reproduce the compressive mechanical response. Then, particle deletion introduced controllable central cracks in the ball and raceway with prescribed inclination angles. Finally, displacement-controlled compression-splitting simulations, serving as a surrogate for a quasi-static overload scenario relevant to quality screening, tracked crack initiation, propagation, and failure modes; under a fixed raceway-crack inclination, crack length was varied to quantify size effects. Results show that a single crack markedly reduces compressive strength. Failure progresses through elastic deformation, crack propagation, and final fracture, with cracks initiating at stress concentrators near crack tips. Crack inclination significantly regulates capacity: raceway cracks are most detrimental near 45°, while ball cracks exhibit an overall decrease in initiation and peak stresses with increasing inclination (with local non-monotonicity). Crack length has a stronger weakening effect than inclination, with accelerated capacity loss beyond 0.3 mm and a pronounced drop in initiation stress beyond 0.6 mm. The framework enables controllable defect parametrization and micro-scale failure interpretation for defect sensitivity assessment under compressive overload. Thus, this study focuses on simulating monotonic fracture events to elucidate fundamental defect–property relationships, which provides a foundation distinct from the prediction of rolling contact fatigue life under cyclic service conditions. Full article

Addressing the challenge of optimizing the fatigue life of cylindrical roller bearings under high-speed and heavy-duty conditions, a collaborative multi-parameter optimization design method is proposed. First, a novel five-parameter profiling equation is introduced to overcome the limitations of traditional profiling methods based on the elastohydrodynamic lubrication property of the roller–raceway contact pair. Second, a nonlinear constrained optimization model that comprehensively considers key bearing structural parameters and the new profiling characteristics is constructed. In this model, the fatigue life is taken as the direct optimization objective, and geometric constraints, strength conditions, and lubrication performance are contained. Finally, using a NU2218E cylindrical roller bearing as the study case, the synchronous optimization achieved about a 196% enhancement in fatigue life over that of optimizing structural or profiling parameters alone. The proposed multi-parameter collaborative optimization framework and the innovative profiling approach provide new technical approaches and theoretical foundations for the design of high-performance rolling bearings. Full article

Reverse engineering (RE) has been increasingly adopted in metal manufacturing to digitize legacy parts, connect “as-is” geometry to mechanical performance, and enable agile repair and remanufacturing. This review consolidates scan-to-simulation workflows that transform 3D measurement data (optical/laser scanning and X-ray computed tomography) into simulation-ready models for structural assessment and manufacturing decisions, with an explicit focus on sustainability. Key steps are reviewed, from acquisition planning and metrological error sources to point-cloud/mesh processing, CAD/feature reconstruction, and geometry preparation for finite-element analysis (watertightness, defeaturing, meshing strategies, and boundary condition transfer). Special attention is given to uncertainty quantification and the propagation of geometric deviations into stress, stiffness, and fatigue predictions, enabling robust accept/reject and repair/replace choices. Sustainability is addressed through a lightweight reporting framework covering material losses, energy use, rework, and lead time across the scan–model–simulate–manufacture chain, clarifying when digitalization reduces scrap and over-processing. Industrial use cases are discussed for high-value metal components (e.g., molds, turbine blades, and marine/energy parts) where scan-informed simulation supports faster and more reliable decision making. Open challenges are summarized, including benchmark datasets, standardized reporting, automation of feature recognition, and integration with repair process simulation (DED/WAAM) and life-cycle metrics. A checklist is proposed to improve reproducibility and comparability across RE studies. Full article

Long-distance natural gas pipelines with internal corrosion defects are susceptible to fatigue failure under operational pressure fluctuations, posing significant risks to infrastructure integrity and safety. To address this, the present study employs a finite element methodology, utilizing Ansys Workbench to model pipelines of various specifications with parametrically defined corrosion defects, and nCode DesignLife to predict fatigue life based on Miner’s linear cumulative damage theory. The S-N curve for X70 steel was directly adopted, while a power-function model was fitted for X80 steel based on standards. A cleaned real-world pressure-time history was used as the load spectrum. Parametric analysis reveals that defect depth is the most influential factor, with a depth coefficient increase from 0.05 to 0.25, reducing fatigue life by up to 67.5%, while the influence of defect width is minimal. An empirical formula for fatigue life prediction was subsequently developed via multiple linear regression, demonstrating good agreement with simulation results and providing a practical tool for the residual life assessment and maintenance planning of in-service pipelines. Full article

This study investigated the effects of rubber substitution ratios (0%, 5%, 10%, 15%) on the frost resistance of rubber concrete with recycled brick–concrete aggregate (BRC). The freeze–thaw (F–T) damage model was established and improved, and the damage mechanism was revealed. The results showed that with the increase in rubber substitution ratio, the frost resistance indices of BRC did not improve or decline synchronously. An increase in rubber content could enhance one index, such as the relative compressive strength, but was often achieved at the expense of reductions in other indices, such as the relative dynamic elastic modulus (RDEM) and relative quality. Consequently, a single indicator was insufficient for evaluating the overall frost resistance. To address this limitation, an entropy weight-based evaluation system was developed. This system integrated the multiple indices into a unified damage score. When combined with defined damage grades, it enabled a holistic assessment of the damage state. For the nonlinear accelerated damage stage during freeze–thaw cycles, the Weibull distribution-based freeze–thaw damage model demonstrated higher prediction accuracy (R² > 0.85) compared to the conventional freeze–thaw fatigue model. The freeze–thaw damage in BRC originated from the competition between “pore deterioration and crack propagation at weak interfaces” and “the elastic buffering effect of rubber.” This study provided a reference for the frost-resistance design and freeze–thaw life prediction of BRC in cold regions. Full article

During deepwater completion and testing, the platform and riser system are subjected to long-term motions induced by ocean currents, which may cause structural damage and potential failure of the landing string. This study investigates the mechanical and fatigue performance of a subsea Christmas tree and landing string under environmental conditions of the LH11-1 Oilfield in the South China Sea. A global–local simulation framework is used to build a coupled dynamic model of the riser–landing string system and a local model for the landing string, considering load-transfer characteristics, current profiles, periodic features, and two representative environmental conditions (typhoon and non-typhoon). For seventeen typical operating scenarios, the strength of the riser–landing string system is evaluated, and wave-induced and vortex-induced fatigue analyses are performed for the key components. The stress distribution strongly depends on operating conditions, but local strength results confirm that stresses in the primary landing string components remain below allowable limits in all scenarios. Fatigue analysis indicates that the most severe wave-induced damage in the riser occurs at its bottom section, with a fatigue life of about 15.12 years, while in the landing string, it is concentrated near the lower end, with an estimated life of about 52.68 years. The maximum vortex-induced fatigue damage occurs near the riser surface region, with a corresponding fatigue life of about 18.52 years. Full article

Background: Multiple sclerosis (MS) involves complex physical, cognitive and behavioral challenges that collectively affect quality of life. Integrating lifestyle components such as sleep optimization, dietary behaviors, stress management, and self-management strategies into rehabilitation may enhance outcomes beyond traditional approaches. This scoping review aimed to map rehabilitation interventions that combine psychomotor, cognitive, lifestyle-focused, or multimodal elements and assess quality of life in adults with MS. Methods: This scoping review was conducted in accordance with the PRISMA-ScR guidelines, which guided the identification, screening, and selection of studies. Screening and data extraction were conducted independently by two reviewers. From 135 records, nine primary studies and four secondary evidence sources were included. Results: Most studies involved adults with mild-to-moderate disability and predominantly relapsing–remitting multiple sclerosis. Physical or motor rehabilitation interventions were examined in five studies, while two studies evaluated multimodal rehabilitation programs, one study focused on cognitive rehabilitation, and one study investigated lifestyle-oriented or self-management-integrated approaches. Quality of life was assessed in all included studies, with improvements reported across multiple domains. Fatigue-related outcomes were reported in four studies, sleep-related outcomes in three studies, and digitally delivered or hybrid rehabilitation interventions were implemented in three studies, indicating an emerging trend toward technology-supported rehabilitation approaches. Conclusions: Contemporary MS rehabilitation is moving toward multidimensional, holistic models that integrate lifestyle components. Standardized outcomes, inclusion of more diverse MS phenotypes, and rigorous evaluation of integrated frameworks are required to strengthen the evidence base and inform clinical practice. Full article

To improve the computational efficiency of complex fatigue assessments, this study proposes a framework that integrates high-fidelity finite element analysis (FEA)with ensemble learning for evaluating the fatigue performance of weathering steel welded joints. First, a three-dimensional crack propagation model for cruciform fillet welds was developed on the ABAQUS-FRANC3D platform, with a validation error of less than 20%. Subsequently, a large-scale parametric analysis was conducted. The results indicate that as the stress amplitude increases from 67.5 MPa to 99 MPa, the fatigue life decreases to 40.29% of the baseline value. When the stress amplitude reaches 180 MPa, the fatigue life drops sharply to 14.28% of the baseline. Within the stress ratio range of 0.1 to 0.7, increasing the initial crack size from 0.075 mm to 0.5 mm reduces the fatigue life to between 85.78% and 86.48% of the baseline. Edge cracks, influenced by stress concentration, exhibit approximately 15.2% shorter fatigue life compared to central cracks, while the maximum variation in fatigue life due to crack geometry is only 10.25%. Second, an Extremely Randomized Trees surrogate model constructed based on the simulation data demonstrates excellent performance. Finally, by integrating this model with Paris’s law, the developed prediction framework achieves high consistency with numerical simulation results, with all predicted values falling within the two-standard-deviation interval. This data-driven approach can effectively replace computationally intensive finite element analysis, enabling efficient structural safety assessments. Full article

Fatigue strength is vital for engineering applications of aluminum alloys. Accurate models incorporating mesoscopic defect-representing features are one of the issues for accurate fatigue strength prediction. A fatigue life prediction method based on meso-defect-representing features is proposed in this study. Based on staged fatigue damage, meso-defect data was obtained by X-ray CT. After 3D reconstruction and simplification, porosity, shape, and location were selected as the meso-defect-representing features using correlation coefficient analysis. Weights of meso-defect features were determined through FEM simulation. A mesoscopic damage variable incorporating the weights of porosity, shape, and location for meso-defect was defined. Correlation between fatigue life and meso-defect features was established through the mesoscopic damage variable. Experimental verification results showed that the prediction method is an effective method for fatigue life assessment. Full article