Search Results (1,531)

The work aimed to investigate the possibility of improving the mechanical properties, and therefore the wear resistance, of coated tools in manufacturing processes with continuous or interrupted cutting loads through appropriate annealing. In this context, PVD CrAlN coatings were deposited on cemented carbide inserts. A part of these coated tools was annealed at a temperature of 400 °C, which was close to the deposition temperature, in an inert gas atmosphere. The annealing duration ranged up to 60 min. Nanoindentations and repeated perpendicular and inclined impact tests were carried out to characterize the strength, fatigue, and adhesion of the tool coatings before and after annealing. According to the results, the mechanical properties of the coating and the fatigue resistance were maximized after a short annealing period of about 15 min, while the adhesion of the coating remained unchanged. These facts led to a large increase in tool life in milling 42CrMo4 QT, when annealed coated tools were applied at 400 °C for 15 min. Furthermore, turning experiments using the mentioned hardened steel as well as GG30 cast iron to produce continuous or interrupted chips, respectively, confirmed the obtained results in milling. Therefore, annealing of coated cutting tools at an optimized duration is recommended as an effective method to extend tool life. Full article

Navigable waterways play a vital role in the efficient transportation of millions of tons of cargo annually. Inland traffic must pass through a lock, which consists of miter gates. Failures and closures of these gates can significantly disrupt waterborne commerce. Miter gates often experience fatigue cracking due to their loading and welded connections. Repairing every crack can lead to excessive miter gate downtime and serious economic impacts. However, if the rate of crack growth is shown to be sufficiently slow, e.g., using Paris’ law, immediate repairs may be deemed unnecessary, and this downtime can be avoided. Paris’ law is often obtained from laboratory testing with detailed crack measurements of specimens with relatively simple geometry. However, Paris’ law parameters for an in situ structure will likely deviate from those predicted from physical testing due to variations in loading and materials and a far more complicated geometry. To improve Paris’ law parameter prediction, this research proposes a framework that utilizes (1) convenient vision-based tracking of crack evolution both in the laboratory and the field and (2) numerical model estimation of stress intensity factors (SIFs). This study’s methodology provides an efficient tool for Paris’ law parameter prediction that can be updated as more data become available through vision-based monitoring and provide actionable information about the criticality of existing cracks. Full article

Breast cancer survivors experience numerous chronic symptoms linked to autonomic dysfunction including anxiety, stress, insomnia, menopausal symptoms, and cognitive impairment. Effective non-pharmacological solutions to address these are currently lacking. Methods: Our three-armed longitudinal randomized controlled trial assessed the effectiveness of a 4-week remote smartphone-based heart rate variability biofeedback intervention which involved daily paced breathing at 6 breaths p/min; active (12 breaths p/min) and waitlist controls were included. Heart rate variability and self-reported cancer-related symptoms were assessed at baseline, post-, and 6 months-post intervention. Participants were 60 UK-based women with primary breast cancer history (6 to 60 months post-active treatment). Results: The intervention group showed significant increases in low-frequency heart rate variability over time (F (4, 103.89) = 2.862, p = 0.027, d = 0.33), long-lasting improvement in sleep quality (F (4, 88.04) = 4.87, p = 0.001, d = 0.43) and cessations in night sweats (X² (2, N = 59) = 6.44, p = 0.04, Cramer’s V = 0.33), and reduced anxiety post-intervention compared to the active and waitlist controls (F (4, 82.51) = 2.99, p = 0.023, d = 0.44). Other findings indicated that the intervention and active control participants reported lasting improvements in cognitive function, fatigue, and stress-related symptoms (all ps < 0.05). The waitlist group reported no symptom changes across time. Conclusion: Heart rate variability biofeedback is a feasible intervention for addressing diverse chronic symptoms commonly reported by breast cancer survivors. Full article

An analysis of the time evolution of fatigue break prediction shows increasingly shorter developmental stages. The experimental period was the longest; the combination of more powerful mathematical methods led to a leap in evolution and a shortening of implementation time. All fatigue rupture prediction methods have proven to have limitations due to the multitude of influencing factors and the insufficient number of practical factors considered. Recently, attempts have been made to increase prediction accuracy by combining methods based on the physical mechanisms of the fatigue failure process with data-driven methods assisted by artificial intelligence. We attempt to present this evolution herein. There are several methods of review suitable for analyzing this subject: systematic, semi-systematic, and integrative. From these, a combination of semi-systematic and integrative was chosen precisely because the two methods complement each other. Full article

Lightweight and high-strength alloys such as Al and Ti alloys are commonly employed materials for aviation structural components. A “hole-fastener” is commonly used for their connection, and DMCE (direct mandrel cold expansion) is a reliable technique in industries to enhance the fatigue properties of hole-involved components due to its advantages, i.e., convenient, efficient and cost-effective. However, an inadequate understanding of the DMCE process leads to a vast amount of waste in industries when any materials or structural parameters are changed. In order to promote the application efficiency of the DMCE process in aviation industries and reduce the energy and resource waste caused by repeated attempts, taking Al7050 and TB6 as examples, this paper comprehensively investigates the fatigue enhancement mechanism of the DMCE process on lightweight and high-strength alloys. Numerical models with 12.9%, 36.9% residual stress prediction errors and 9.98%, 14.8% radial plastic deformation prediction errors for Al and Ti holes were established, and then simulations were performed to screen out five significant influence parameters from eleven independent parameters. On this basis, DMCE experiments with significant parameters were carried out, and the improvement mechanisms of the DMCE process on the tangential residual stress, radial plastic deformation and surface morphology of Al and Ti hole walls were comparatively analyzed. Furthermore, fatigue life prediction models for two-hole-involved specimens were generated via multiple linear regression, which exhibit, respectively, 13.5% and 33.9% mean prediction errors for Al and Ti alloys. Moreover, the optimal DMCE schemes were obtained and 2.33 and 4.12 times fatigue lifetime improvements were achieved for the Al and the Ti specimens. Full article

This study explores the integration of a custom-designed pneumatic spring into a car-seat cushion and its interaction with a simplified human body model using the Finite Element Method (FEM). A 3D half-symmetry FEM framework, developed from experimental data, ensured computational efficiency and convergence. This research bridged experimental and numerical approaches by analyzing the contact pressure distributions between a seat cushion and a volunteer with representative biometric characteristics. The model incorporated two material groups: (1) human body components (bones and muscles) and (2) seat cushion materials (polyurethane foam, latex, and fabric tape). Mechanical properties were obtained from both the literature and experiments, and simulations were conducted using MSC.Marc software under realistic boundary and initial conditions. The simulation results exhibited strong agreement with experimental data, validating the model’s reliability in predicting contact pressure distribution and optimizing seat cushion designs. Contrary to the conventional notion that uniformly distributed contact pressure inherently enhances comfort, this study emphasizes that the precise localization of pressure plays a crucial role in static and long-term seating ergonomics. Both experimental and simulation results demonstrated that modulating the pneumatic spring’s internal pressure from 0 kPa to 25 kPa altered peak contact pressure by approximately 3.5 kPa (around 20%), significantly influencing pressure redistribution and mitigating high-pressure zones. By validating this FEM-based approach, this study reduces dependence on physical prototyping, lowering design costs, and accelerating the development of ergonomically optimized seating solutions. The findings contribute to a deeper understanding of human–seat interactions, offering a foundation for next-generation automotive seating innovations that enhance comfort, fatigue reduction, and adaptive pressure control. Full article

To enhance the erosion resistance of typical Cr₃C₂-NiCr coatings, the Cr₃C₂-TiC-NiCrCoMo (NCT) coating was developed and deposited by high-velocity oxygen fuel spray (HVOF). The erosion resistance and mechanisms of the coating were investigated using numerical simulations and experimental methods. A comprehensive calculation model for the coating erosion rate was developed, incorporating factors such as the properties of the eroded particles, the characteristics of the coating, and the conditions of erosion. The erosion rate of the NCT coating was calculated and predicted by the model, and the accuracy of these predictions was validated through experiments. The NCT1 (87.3 wt.% Cr₃C₂-NiCrCoMo/3 wt.% TiC)coating demonstrated exceptional erosion resistance compared to the original Cr₃C₂-NiCrCoMo (NCC) coatings with reduced erosion rates of 23.64%, 20.45%, and 16.22% at impact angles of 30°, 60°, and 90°, respectively. The addition of nano-TiC particles into the NCT1 coating enhances the yield strength, impeding the intrusion of erosive particles at low angles and supporting the metal binder phase, eventually reducing fatigue fracture under repeated erosion. However, excessive nano-TiC content degrades the erosion resistance due to the increase in pores and cracks within the coating. Full article

In significant infrastructure, it takes more than simple fatigue load capacity calibration to meet design and analysis requirements; more importantly, fatigue damage evolution and remaining life assessments should be undertaken. Therefore, this paper proposes a dynamic fatigue damage analysis method for concrete infrastructures based on an extended microplane model. This study extends the original microplane model to encompass steel fiber-reinforced concrete, fatigue, and dynamic analysis. In particular, the influence of the material rate-dependent effect (usually related to loading frequency) on the material’s properties is considered. The model’s validity is corroborated through benchmark tests and illustrative examples. Subsequently, the model is employed for the dynamic fatigue analysis of concrete members and concrete infrastructure, with a particular focus on the material rate-dependent effects and the influence of steel fiber on the fatigue behavior of concrete. It is demonstrated that incorporating steel fiber into concrete can markedly enhance its fatigue resistance, a phenomenon that can be reflected in the present model. Furthermore, accelerated fatigue experiments may overestimate the fatigue life of concrete materials. However, when conducting dynamic fatigue analysis of structures, incorporating rate-dependent materials may result in underestimating the fatigue damage experienced by concrete infrastructures. The model provides a helpful predictive tool for assessing progressive fatigue damage in concrete infrastructure under a complex range of loading scenarios, contributing to structural resilience and promoting sustainability. Full article

Adhesive joints in real-world conditions often experience variable or step loading rather than constant-amplitude fatigue. This study addresses this gap by examining the influence of load sequence and block loading on fatigue damage in adhesive joints of fiber-reinforced polymer (FRP) composites. A novel bilinear traction-separation law based on the Fatigue Crack Growth Rate (FCGR) rule is introduced to predict fatigue failure under step/variable loads, accounting for load history, sequence, and interaction effects. This model was validated using a double-lap joint model under step/variable loading across four experimental scenarios. The proposed model outperformed existing fatigue damage-accumulation models, significantly reducing the Relative Error of Prediction ($REP$). Notably, the proposed model significantly reduced the Relative Error of Prediction ($REP$), achieving reductions from 81.10% to as low as 0.013% in certain cases. The proposed bilinear law exhibited an accelerated damage accumulation rate per cycle for low-to-high loading situations and a decelerated rate for high-to-low loading scenarios, aligning more closely with experimental observations. The proposed model offers practical benefits by improving fatigue life predictions, enabling optimized FRP composite designs, and minimizing overengineering. These advancements are particularly relevant in industries such as aerospace, automotive, and wind energy, where structural durability and safety are paramount. This research represents a significant step forward in the fatigue analysis of composite adhesive joints, paving the way for more reliable engineering solutions. Full article

During use, titanium alloy structural components may experience sudden overloads or occasional loads, which can reduce their fatigue life and accelerate structural failure. To study the fatigue behavior of TC4/Ti60 joints, this paper uses electron beam welding technology to obtain TC4/Ti60 dissimilar joints. The results show that the microstructure changes during the welding process, with the weld zone being relatively uniform, primarily consisting of coarse α′ phase. The near heat-affected zone on the TC4 side consists of α′, while on the Ti60 side, in addition to the α′ phase, there is a small amount of residual α phase. Fatigue tests reveal that as the pre-deformation increases, the fatigue life gradually decreases. During the early stages of fatigue, the joint exhibits cyclic hardening, which transitions to cyclic softening as the test progresses, ultimately leading to failure. Fatigue fracture analysis reveals that all fatigue samples failed on the TC4 side, with no failure observed in the weld zone. This is likely due to the presence of martensite, which gives the weld zone higher strength than the TC4 base materials. Additionally, fatigue cracks initiated from surface or near-surface defects, with ductile fractures being predominant. Full article

Following cancer treatment, individuals experience a range of physical, mental and social health difficulties that interfere with their ability to resume participation in pre-cancer activities. In Ireland, the National Cancer Strategy recommends community-based services to address post-treatment difficulties. Social prescribing is a community-based, non-medical service that links individuals with health-related activities and supports in their community. This study explored the feasibility and acceptability of social prescribing for cancer survivors. A mixed methods study was undertaken with individuals who had completed curative treatment for any cancer type. Recruitment was carried out in a national cancer centre. Quantitative outcomes included feasibility metrics (recruitment, intervention adherence and retention), the Frenchay Activities Index (FAI), the Hospital Depression and Anxiety Scale (HADS), the Multidimensional Assessment of Fatigue (MAF), and EORTC QLQ-C30. Qualitative interviews explored acceptability of social prescribing. Data were analysed using descriptive statistics (quantitative data) and content analysis (qualitative data). Out of 131 individuals identified as eligible to participate, 43 agreed to participate (32.8% recruitment) and 27 met a link worker and were connected to a local activity (62.7% adherence) and completed follow-up outcome measures (62.7% retention). Improvements were observed in all health-related outcomes and those interviewed identified the intervention as acceptable. Study participants attended a range of community-based activities as a result of link worker support. They also reported increased confidence, improved mental health and reduction in fatigue following attendance at community-based activities. The findings of this study indicate that social prescribing is a feasible and acceptable community-based intervention to improve the physical, mental and social health of individuals living with and beyond cancer. A pilot randomised trial is indicated to inform a definitive intervention trial. Full article

The development of innovative technologies and the employment of diverse material compositions have contributed to the enhancement of wear prediction methods. However, the accurate forecasting of service life and the identification of critical influencing factors remain challenging due to the complex interactions governing wear behaviour. Throughout history, various methodological approaches have been developed to model wear, primarily categorised into analytical calculations and experimental investigations. Analytical methods, including Archard’s equation and its variations, provide a theoretical basis for wear estimation. However, these models frequently depend on empirical coefficients derived from extensive experimentation, which restricts their predictive accuracy. Moreover, classical wear models do not fully account for material fatigue effects and 3D surface texture parameters, which are critical for solving complex engineering problems. Recent advancements have sought to address these limitations by integrating probabilistic surface modelling, fatigue-based degradation theories, and numerical simulations to enhance wear predictions. Experimental investigations remain essential for validating analytical models, as they provide empirical data necessary for parameter calibration. However, these experiments require specialised equipment and are often time-consuming and costly. The integration of modern measurement tools and numerical simulations, such as finite element analysis (FEA) and machine learning-based models, presents a promising direction for improving wear predictions. This review highlights the strengths and limitations of existing wear models and emphasises the need for further refinement of analytical approaches to incorporate fatigue wear mechanisms, real surface roughness effects, and environmental influences for more accurate and reliable wear assessments. Full article

The influence of residual stresses as a result of the welding process in the overall stress state of the weld joint is of great importance because they significantly affect the creation and growth of cracks, the occurrence of brittle fracture, and material fatigue. Previous experiences indicate that it would be necessary to provide an assessment of the deformation and stress state in the critical zones of the weld joints using a suitable test method, which will not endanger the structural integrity of the tested places. There are different methods for measurement of residual stress in welded constructions: destructive, semi-destructive and non-destructive. To choose one method over another, it is necessary to take into account the advantages and limitations of these techniques for practical application. This paper considers and analyzes the residual stresses in the welded joint of high-strength steel S960QL. MAG welding was performed by a robot. Three methods were used to measure the residual stresses: the magnetic method (MAS), the X-ray diffraction method (XRD), and the hole drilling method (HD). By all three methods, the highest residual stresses were measured in the weld metal and in the heat-affected zones. Nevertheless, the measured values differed considerably. The differences can be contributed to (a) the kind of stress that the individual method measures, (b) to the volume of material from which each method captures the signal and averages it, and (c) to the different sensitivities of the applied methods to coarse-grained microstructure and microstructural gradients. Full article

In order to investigate the relationship between the strain of prestressed concrete girders under fatigue loading and the corrosion degree of prestressed steel reinforcements, four 12.4-m-long large-size post-tensioned prestressed concrete box girders were designed and fabricated in this study, and prestressed steel reinforcements were corroded at different degrees by the Electric Accelerated Corrosion Method. The same equal-amplitude loads were used during fatigue loading. The relationship between the strain of different materials (strains of the plain reinforcements and prestressed steel reinforcements, as well as concrete strains in compression zones) and the corrosion degree was investigated. Then, the calculation method for the cumulative residual strain of concrete in the compression zone of the test beam was obtained. The test results show the following: the strains of the test beams under different corrosion degrees all show a three-stage development law; the ratio of the strain amplitude of the prestressed steel reinforcement to that of the regular steel reinforcement during fatigue loading basically stays in the range of 0.65–0.75, and the ratio rises with the corrosion degree of the prestressed steel reinforcement; the increase in strain of the compressed concrete is due to the accumulation of the residual strain of the concrete, and the increase in material strain is almost directly proportional to the growth of corrosion degree under the same fatigue load; the calculated values of the accumulated residual strain of the concrete agree well with the test values and satisfy the accuracy requirements of engineering. Full article

Objectives: this study aimed to explore the effects of different intake levels (20–80%) of highland barley on the anti-fatigue capacity of ICR mice, focusing on energy metabolism, metabolite accumulation, oxidative stress, and changes in the gut microbiota. Methods: male ICR mice were assigned to five groups: control (normal diet) and four experimental groups with highland barley supplementation at 20%, 40%, 60%, and 80% of total dietary energy. Anti-fatigue performance was assessed by behavioral experiments (rotarod, running, and exhaustive swimming tests), biochemical markers, and gut microbiota analysis. Results: the results showed that moderate supplementation (20%) significantly enhanced exercise endurance and anti-fatigue capacity, as evidenced by increased liver glycogen (134.48%), muscle glycogen (87.75%), ATP content (92.07%), Na⁺-K⁺-ATPase activity (48.39%), and antioxidant enzyme activities (superoxide dismutase (103.31%), catalase (87.75%), glutathione peroxidase (81.14%). Post-exercise accumulation of blood lactate, quadriceps muscle lactate, serum urea nitrogen, and the oxidative stress marker malondialdehyde was significantly reduced, with differences of 31.52%, 21.83%, 21.72%, and 33.76%, respectively. Additionally, 20% supplementation promoted the growth of beneficial gut microbiota associated with anti-fatigue effects, including unclassified_f_Lachnospiraceae, g_norank_f_Peptococcaceae, Lachnospiraceae NK4A136, Colidextribacter, and Turicibacter. However, when intake reached 60% or more, anti-fatigue effects diminished, with decreased antioxidant enzyme activity, increased accumulation of metabolic waste, and a rise in potentially harmful microbiota (Allobaculum, Desulfovibrio, and norank_f_norank_o_RF39). Conclusions: moderate highland barley supplementation (20% of total dietary energy) enhances anti-fatigue capacity, while excessive intake (≥60%) may have adverse effects. Full article