Search Results (1,726)

When hydrogen is transported in a pipeline, the fatigue loading in the pipeline will enhance hydrogen accumulation and diffusion, thus increasing the risk of hydrogen-induced fracture. In this study, specimens are subjected to cyclic loading within an autoclave, where hydrogen gas pressure is varied to examine its impact on fatigue crack growth. The influence of hydrogen pressure and stress variations on the fatigue crack growth rate is investigated. The findings show that as hydrogen pressure increases, the crack growth rate also rises, and at 3 MPa hydrogen pressure the rate is elevated by one order of magnitude compared to that in air, reaching 10⁻² mm/cycle. In hydrogen, the fatigue crack propagation rate decreases with increasing loading frequency. When the frequency is 0.02 Hz, the crack propagation rate reaches a maximum of 10⁻² mm/cycle, whereas at 0.5 Hz, the fatigue crack propagation rate is generally below 10⁻³ mm/cycle. With the maximum stress held constant during cyclic loading, the fatigue crack growth rate increases as the stress range widens, and when the stress ratio reaches 0.5, the crack propagation rate can increase to a maximum of 10⁻¹ mm/cycle. Based on these experimental results, a predictive model is proposed to estimate the crack growth rate under different hydrogen pressures and loading conditions, and the average relative errors of predictive values and experimental data are limited below 10%. Full article

Background: After the start of the COVID-19 pandemic, general fatigue in patients with long COVID and post-COVID-19 conditions (PCC) became a medical issue. Although there is a lack of evidence-based treatments, Kampo medicine (traditional Japanese medicine) has gained attention in Japan. At an outpatient clinic in Japan specializing in long COVID, 24% of all prescriptions were Kampo medicines, and 72% of Kampo medicine prescriptions were hochuekkito. However, there has been no prospective, quantitative study on the course of fatigue in patients with long COVID and PCC who were prescribed hochuekkito. The aim of this study was to clarify the course of fatigue in those patients. Methods: This study included patients aged 18 years or older with general fatigue who visited the long COVID specialized outpatient clinic at Okayama University Hospital and consented to participate after being prescribed hochuekkito. We reviewed the backgrounds of the patients, and we evaluated the patients’ fatigue assessment scale in person or online. Results: Twenty patients were enrolled in this study from September to December in 2023. The average age of the patients was 42.9 years (SD: 15.8 years) and 12 patients (60%) were female. After hochuekkito administration, the fatigue assessment scale score decreased from 35.9 (SD: 5.9) at the initial visit to 31.2 (SD: 9.4) after 8 weeks, indicating a trend for improvement in fatigue (difference: 4.7; 95% CI: 0.5–8.9). Conclusions: A trend for improvement in fatigue was observed in patients with long COVID and PCC who were prescribed hochuekkito, indicating a potential benefit of hochuekkito for general fatigue in such patients. General fatigue in patients with long COVID or PCC can be classified as post-infectious fatigue syndrome and is considered a condition of qi deficiency in Kampo medicine, for which hochuekkito is appropriately indicated. Full article

The VITAL-E (Versatile Innovative Testing Low-Cycle Fatigue for Elastomers) project introduces a shift in low-cycle fatigue (LCF) testing by replacing traditional hydraulic systems with an electromechanical solution. Hydraulic machines, although widely used, present issues such as fluid leakage, environmental impact, high maintenance, and complex feedback control. In contrast, VITAL-E incorporates a zero-backlash linear actuator, addressing a key challenge in electromechanical systems: backlash. This issue, caused by axial movement between the nut and screw during load reversals, can disrupt load application and compromise test accuracy. By eliminating backlash, the chosen actuator ensures continuous and precise load application, especially during critical cycle reversals, enhancing both the accuracy and reliability of LCF testing. Beyond technical improvements, the electromechanical system reduces component complexity, wear, and maintenance needs while offering easier upgrades and adaptability to evolving testing demands. Compared to conventional hydraulic systems, VITAL-E’s design offers an innovative industrial solution, promoting a new generation of LCF test machines that excel in accuracy, reliability, and operational efficiency. This innovation aligns with the growing demand for sustainable and adaptable testing solutions, particularly in the automotive industry, ensuring that LCF testing remains relevant for future research and industrial needs. Full article

Vinegar, frequently distilled by solid fermentation or liquid processes, was generated through the synergistic effect of a microbial community in open or semi-open environments. Based on the studied raw materials, researchers distributed the vinegar into three classes: grain, fruit and animal, with lactic acid bacteria (LAB) playing a pivotal role in their fermentation and contributing significantly to their functional and sensory qualities. Typically, the natural maturation of fresh vinegar necessitates a long period and vast space, engendering a reduced efficiency. To accelerate the vinegar aging process, some physical methods, viz. micro-oxygenation, ozone, ultrasound, microwave, gamma rays, infrared, electric fields and high pressure, have been developed. Produced or enriched by LAB, key bioactive vinegar components are organic acids, phenolic compounds, melanoidins, and tetramethylpyrazine. These active compounds have antibacterial, antioxidant, anti-inflammatory functions; aid in the regulation of liver protection metabolism and glucose control; and have blood pressure, anti-tumor, anti-fatigue and metabolic regulatory effects. The review explores advancements in vinegar production, including modernized fermentation processes and optimized aging techniques, which enhance these beneficial compounds and ensure product consistency and safety. By examining the LAB variety strains and the bioactive profiles of different vinegar types, this study highlights vinegar’s value beyond a culinary product, as a potential therapeutic agent in human nutrition and health. The findings underscore vinegar’s relevance not only in dietary and preventive healthcare but also as a potential functional food ingredient. Further research is needed to explore the mechanisms of action through which LAB contribute to the development of several new healthy vinegars. Full article

In the context of the automotive industry, this paper proposes an enhancement of the numerical simulation using FEM and performing material choosing with the Ashby method for automotive brake discs, using the symmetric shape of the disc. Automotive braking involves the dissipation of kinetic energy through heat generation due to friction, a physical phenomenon that alters the mechanical properties of brake discs. This prompts automotive development engineers to investigate new materials capable of absorbing heat while maintaining their mechanical properties. A thermomechanical study of a ventilated front brake disc has successfully demonstrated a good performance of cast iron because the equivalent stress is significantly lower than the elastic limit, with a margin of approximately 73 MPa. Compared to validated results extracted from the state of the art, the adopted methodology gives more realistic results with minimum CPU requirements, where the total time of calculation is around 40 min. More than that, the results are suitable to be used for studying durability and other properties like mechanical impact and fatigue. Full article

To reduce the computational cost of the multi-objective optimization process and improve the accuracy of fatigue life prediction for the lower control arm (LCA) of a vehicle under multiaxial random vibration, this paper focuses on the LCA of a MacPherson suspension in a specific vehicle model and proposes a multi-objective lightweight design method based on multiaxial random vibration fatigue. This method combines the Latin hypercube sampling (LHS) technique, Kriging surrogate modeling, and the second-generation non-dominated sorting genetic algorithm (NSGA-II). First, static and dynamic analyses are conducted to extract the design parameters required to meet the design specifications of the reference LCA. Subsequently, the LHS technique is employed to obtain 50 sample points, which are used to construct the sample space. The Kriging method is then applied to build surrogate models that capture the relationship between design variables and various responses. Finally, the NSGA-II multi-objective genetic algorithm is utilized to obtain the optimized solution. Considering 1.2 times the safe driving distance, the optimal solution with the minimum LCA mass is selected from the Pareto frontier. The optimization results show that compared to the initial LCA model, the mass of the optimized model is reduced by 13.06%, the fatigue life is increased by 47.48%, and the maximum displacement and maximum stress are reduced by 1.78% and 4.31%, respectively. Additionally, the first-order modal frequency decreases by 4.60%. Full article

As advanced structural materials, titanium alloys have found extensive applications in aerospace, medical devices, and precision electronics industries, serving as critical components for achieving lightweight designs in high-end equipment. In aerospace applications, titanium alloy components are frequently subjected to complex thermo-mechanical loading conditions involving varying temperature levels and multiaxial stress states, which may induce progressive fatigue damage accumulation and ultimately lead to premature fracture failures. This study conducts a systematic investigation into the fatigue damage mechanisms of aerospace-grade titanium alloys under service conditions, with particular emphasis on elucidating the synergistic effects of microstructural characteristics, surface integrity parameters, and operational temperature variations on fatigue behavior. Through comprehensive analysis, the research reveals that surface modification techniques, including shot peening (SP), ultrasonic surface polling process (USRP), and laser shock peening (LSP), significantly enhance fatigue performance through two primary mechanisms: (1) the generated residual compressive stress fields effectively inhibit crack initiation and retard propagation rates; (2) improved surface integrity characteristics, such as reduced roughness and work-hardened layers, contribute to enhanced oxidation resistance thereby preserving structural integrity. Full article

High-strength steel (HSS) plates are widely used due to their superior performance. However, residual stresses generated during welding can exacerbate the initiation of fatigue cracks, and the accurate prediction of residual stresses is crucial. Therefore, thermo-mechanical behavior analysis of the EH40 joints was completed based on the proposed new heat source model. The thermo-elastoplastic finite element analysis was determined via thermo-mechanical coupling with fully parametric programming. The influence of laser welding power and joint thickness on peak temperature and gradient was clarified. Meanwhile, it was found that when the laser welding power increased from 9 kW to 22.5 kW and the joint thickness increased from 6 mm to 15 mm, the distribution trend of longitudinal residual stress in the weld zone was gradually altered from a “U” shape to a “W” shape, while the transverse stress was transformed from a “U” shape to an “M” shape. It was determined that the amplitude of longitudinal and transverse stress changed along the thickness direction of nodes and was directly proportional to the peak temperature. The above results imply that the peak temperature, maximum temperature gradient longitudinal, and transverse residual stress distribution in the weld zone and its vicinity were remarkably affected by laser welding power and joint thickness. Full article

This study addresses the problem of parameter estimation and prediction for type-II censored data from the two-parameter Birnbaum–Saunders (BS) distribution. The BS distribution is commonly used in reliability analysis, particularly in modeling fatigue life. Accurate estimation and prediction are crucial in many fields where censored data frequently appear, such as material science, medical studies and industrial applications. This paper presents both frequentist and Bayesian approaches to estimate the shape and scale parameters of the BS distribution, along with the prediction of unobserved failure times. Random data are generated from the BS distribution under type-II censoring, where a pre-specified number of failures (m) is observed. The generated data are used to calculate the Maximum Likelihood Estimation (MLE) and Bayesian inference and evaluate their performances. The Bayesian method employs Markov Chain Monte Carlo (MCMC) sampling for point predictions and credible intervals. We apply the methods to both datasets generated under type-II censoring and real-world data on the fatigue life of 6061-T6 aluminum coupons. Although the results show that the two methods yield similar parameter estimates, the Bayesian approach offers more flexible and reliable prediction intervals. Extensive R codes are used to explain the practical application of these methods. Our findings confirm the advantages of Bayesian inference in handling censored data, especially when prior information is available for estimation. This work not only supports the theoretical understanding of the BS distribution under type-II censoring but also provides practical tools for analyzing real data in reliability and survival studies. Future research will discuss extensions of these methods to the multi-sample progressive censoring model with larger datasets and the integration of degradation models commonly encountered in industrial applications. Full article

Background: Parkinson’s disease (PD) is a neurodegenerative disorder characterized by motor symptoms like bradykinesia, tremor, rigidity, and postural instability. Additionally, PD severely impacts physical abilities and independence. Chronic pain, affecting 67.6% of PD patients, varies in form and presentation, and it is often underdiagnosed. Objectives: This study investigated the association between chronic pain and motor symptom severity in PD patients. Methods: This analysis used data from a cross-sectional study on 52 Parkinson’s disease (PD) patients conducted at Jena University Hospital, Germany. The dataset, available on Dryad, included demographics; clinical reports; and assessments of coping strategies, quality of life, and pain. Descriptive statistics, a bivariate analysis, and an ordinal logistic regression model were executed to explore the association between pain and motor symptom severity (MSS). A direct acyclic graph was used to represent the relationship between variables and identify potential confounders, and an outcomes definition sensitivity analysis was used to assess the impact of using pain intensity as an outcome. The E-value was calculated to evaluate the strength of association needed by an unmeasured confounder to nullify the observed association. Results: A total of 50 Parkinson’s disease (PD) patients were included, with 64% being male, with an average age of 76.1 years. The sample included 20 patients without pain and 30 with chronic pain. The bivariate analysis did not identify significant differences in disease duration, cognitive function, and non-motor symptoms between pain and no-pain groups. However, significant differences (p-value < 0.05) emerged in motor symptom severity, coping strategies, and several SF-36 domains (Physical and Social Functioning, Role Functioning, Energy/Fatigue, Pain, General Health, and Health Change). The ordinal logistic regression showed a substantial association between chronic pain and MSS: patients with chronic pain had 3.52 times higher odds (95% CI: 1.40–8.84, effect size d ≈ 0.70, p = 0.02) of low to medium MSS and 5.44 times higher odds (95% CI: 2.03–14.60, effect size d ≈ 0.94, p = 0.01) of medium to severe MSS, indicating a dose–response relationship. Additionally, male patients had increased odds of higher MSS (OR 4.63, 95% CI: 1.15–18.58, effect size d ≈ 0.85, p = 0.03). Conclusions: Chronic pain is strongly associated with MSS in PD patients, with a more pronounced effect as MSS progresses from medium to severe, supporting a dose–response relationship. Effect sizes suggest a robust association, emphasizing the need for pain assessment in managing motor symptoms in PD. Full article

Laser powder bed fusion (LPBF) has emerged as a transformative additive manufacturing technique for fabricating architected cellular metallic structures, offering tailored properties for diverse biomedical applications. These structures are particularly well-suited for bone implants, scaffolds, and other load-bearing medical devices due to their ability to achieve lightweight designs, enhanced mechanical properties, and customized geometries. However, the complex interactions between LPBF process parameters and the resulting structural and mechanical properties pose significant challenges in achieving the precision and reliability required for clinical applications. This review provides a comprehensive analysis of the effects of LPBF process parameters, including laser power, scanning speed, and layer thickness, on key attributes such as dimensional accuracy, density, surface roughness, and microstructure. Their influence on the mechanical performance, including strength, fatigue resistance, and functional properties, is critically examined, with specific attention to biomedical relevance. The impact of lattice design factors, such as topology, unit cell size, and orientation, is also discussed, underscoring their role in optimizing biocompatibility and structural integrity for medical applications. Challenges such as surface defects, geometric inaccuracies, and microstructural inconsistencies are highlighted as key barriers to the broader adoption of LPBF in biomedical fields. Future perspectives focus on advancing LPBF technologies through process optimization and integration with advanced computational tools, such as machine learning, to enable efficient manufacturing of complex, patient-specific architectures. By addressing these challenges, LPBF has the potential to revolutionize the development of next-generation biomaterials, tailored to meet evolving clinical needs and improve patient outcomes. Full article

Background and Objectives: Fibromyalgia (FM), through the presence of widespread chronic pain, stiffens the musculoskeletal system and causes sleep disturbances and fatigue. Through this study, we aimed to compare the effectiveness of two different recovery interventions for improving sleep quality: a standard, multidisciplinary intervention in a recovery hospital versus a therapy focused on intrinsic relaxation at home. Materials and Methods: This study included 60 adult patients who participated voluntarily and were diagnosed with FM by a rheumatologist, randomly divided into two groups. During this study, 30 patients out of the 60 were randomly assigned to experimental group 1 and underwent treatment at the Recovery Clinical Hospital in Băile Felix. The other 30 patients were assigned to experimental group 2 and underwent treatment at home. They were assessed on the first and last day of the recovery program using the Fatigue Severity Scale (FSS) and the Pittsburgh Sleep Quality Index (PSQI). Results: In experimental group 1, where by patients underwent hospital recovery (EG1), the results show that the severity of fatigue (FSS) was significantly reduced, with p = 0.00 and an effect size of 0.77, which suggests a general improvement in the state of fatigue, as well as in the quality of sleep evaluated with the PSQI (p = 0.00, effect size = 0.55). In experimental group 2 (EG2), no change was observed between assessments in terms of the FSS, but in terms of the quality of sleep, there was a small decrease in the PSQI score (p = 0.083), with a small effect size of 0.09. Conclusions: The results show that, from a clinical point of view, a complex treatment carried out daily improves sleep quality and reduces fatigue. Full article

A numerical simulation investigating the frequency dependence of fatigue damage progression in carbon fiber-reinforced plastics (CFRPs) is conducted in this study. The initiation and propagation of transverse cracks under varying fatigue test frequencies are successfully simulated, consistent with experiments, using an enhanced degradable Hashin failure model that was originally developed by the authors in 2022. The results obtained from the numerical simulation in the present study, which employs adjusted numerical values for the purpose of damage acceleration, indicate that the number of cycles required for the formation of three transverse cracks was 174 cycles at 0.1 Hz, 209 cycles at 1 Hz, and 165 cycles at 10 Hz. Based on these results, it is demonstrated that under high-frequency cyclic loading, internal heat generation caused by dissipated energy from mechanical deformation, attributed to the viscoelastic and/or plastic behavior of the material, exceeds thermal dissipation to the environment, leading to an increase in specimen temperature. Consequently, damage progression accelerates under high-frequency fatigue. In contrast, under low-frequency fatigue, viscoelastic dissipation becomes more pronounced, reducing the number of cycles required to reach a similar damage state. The rate of damage accumulation initially increases with test frequency but subsequently decreases. This observation underscores the importance of incorporating these findings into discussions on the fatigue damage of real structural components. Full article

From learning environments to battlefields to marketing teams, the desire to measure cognition and cognitive fatigue in real time has been a grand challenge in optimizing human performance. Near-infrared spectroscopy (NIRS) is an effective optical technique for measuring changes in subdermal hemodynamics, and it has been championed as a more practical method for monitoring brain function compared to MRI. This study reports on an innovative functional NIRS (fNIRS) sensor that integrates the entire system into a compact and wearable device, enabling long-term monitoring of patients. The device provides unrestricted mobility to the user with a Bluetooth connection for settings configuration and data transmission. A connected device, such as a smartphone or laptop equipped with the appropriate interface software, collects raw data, then stores and generates real-time analyses. Tests confirm the sensor is sensitive to oxy- and deoxy-hemoglobin changes on the forehead region, which indicate neuronal activity and provide information for brain activity monitoring studies. Full article

Concomitant administration may improve vaccination rates. This analysis of a phase 1/2 randomized study included 1073 healthy ≥65-year-olds who previously received ≥3 mRNA COVID-19 vaccine doses. Participants received concomitantly administered RSVpreF and bivalent BA.4/BA.5-adapted BNT162b2 vaccine (concomitant administration) with or without quadrivalent influenza vaccine (QIV), admixed combined RSVpreF + BNT162b2 vaccine (combined vaccine) with or without QIV, RSVpreF, BNT162b2, or QIV. Immunogenicity objectives included demonstrating the noninferiority of neutralizing antibody titers elicited by concomitant administration and combined vaccine compared with RSVpreF or BNT162b2 administered alone, and by concomitant administration and combined vaccine given with QIV compared with RSVpreF, BNT162b2, and QIV alone. Reactogenicity (≤7 days) and safety ≤1 month (adverse events (AEs)) and ≤6 months (serious AEs (SAEs)) after vaccination were assessed. Noninferiority for all immunogenicity comparisons was demonstrated. All vaccine groups were well tolerated; no new safety concerns were identified. Reactogenicity was mostly mild/moderate with rates generally similar across groups, except injection site pain and fatigue, which were less frequent with RSVpreF + placebo vs. other groups. AEs were infrequent, mostly mild/moderate, occurring at similar frequencies across groups. No AEs leading to study withdrawal or vaccine-related SAEs were reported. Favorable safety and tolerability alongside similar immunogenicity provide support for concomitant or combined use of RSVpreF and BNT162b2, with or without QIV, to help protect older adults from these important respiratory pathogens (NCT05886777). Full article