Search Results (1,469)

This study investigates the design of bio-hybrid sandwich composites by combining polyester/glass skins with cores reinforced by continuous Musa paradisiaca fibres. The aim is to quantify how fibre weight fraction and alkaline surface treatment control the Charpy impact performance of these systems. Sandwich laminates were manufactured with three fibre loadings in the core (20, 25 and 30 wt.%), using fibres in the as-received condition and after alkaline treatment in NaOH solution. Charpy impact specimens were machined from the laminates and tested according to ISO 179-1. Fibre morphology and fracture surfaces were examined by scanning electron microscopy, while Fourier-transform infrared spectroscopy was used to monitor changes in surface chemistry after alkaline treatment. The combined effect of fibre content and treatment on absorbed energy was assessed through a two-way analysis of variance. Increasing Musa paradisiaca fibre content up to 30 wt.% enhanced the impact energy of the sandwich composites, and alkaline treatment further improved performance by strengthening fibre–matrix adhesion and promoting fibre pull-out, crack deflection and bridging mechanisms. The best Charpy impact response was obtained for cores containing 30 wt.% NaOH-treated fibres, demonstrating that surface modification and optimised fibre loading are effective design parameters for toughening polyester/glass bio-hybrid sandwich composites. Full article

Module-level free-space optical interconnects require actuators to combine both large stroke and high stability. To address this core trade-off that plagues traditional folded-beam actuators, we have developed a millimeter-scale MEMS electromagnetic actuator integrating a Differential Motion Rejection (DMR) unit with a rigid frame. Its performance was systematically evaluated through magnetic–structural coupling modeling, finite element simulation, and experiments. The actuator achieved millimeter-scale stroke under sinusoidal drive, with a primary resonant frequency of approximately 31 Hz. The introduction of the DMR and frame proved highly effective: the out-of-plane displacement at resonance was reduced by about 97%, the static Z-direction stiffness increased by over 50 times, and the displacement crosstalk decreased to 0.265%. Optical testing yielded a stable deflection angle of approximately ±21°. These results demonstrate that this design successfully combines large stroke with high stability, significantly suppressing out-of-plane parasitic motion and crosstalk, making it suitable for module-level optical interconnect systems with stringent space and stability requirements. Full article

Slender, lightweight and modern footbridges are particularly susceptible to vibrations induced by pedestrian activity. While extensive research has focused on vertical and lateral forces produced by walking, torsional moments generated by eccentrically walking pedestrians remain largely overlooked. Traditional assessments typically neglect these torsional effects, which can be critical when eccentric pedestrian loading excites torsional modes, especially in footbridges with asymmetric geometries. To address this, the paper considers the coupling between bending and torsional effects in both the pedestrian action and structure reaction, including pedestrian forces and moments, as well as bending-induced deflections and torsion-induced rotations of the cross-sections. A simplified method is also presented, allowing standard bending-only analyses to be easily adapted to include torsional effects using analytically derived correction factors. For validation, several experimental tests are conducted on an asymmetric curved footbridge located in Modena, Italy, characterised by coupled bending-torsional vertical modes and hosting different pedestrian densities, pacing frequencies, and crowd distributions (both uniform and eccentric). Experimental and numerical analyses demonstrate that neglecting torsional effects oversimplifies the assessment, highlighting the importance of accounting for bending-torsion coupling for the serviceability of asymmetric footbridges under eccentric near-resonance loading. Full article

With the continuous development of global intelligent shipping technology, in fields such as virtual testing of intelligent ships and crew training and assessment, there is an urgent need for a highly realistic model to reproduce the driver’s bumpy feeling of ship drivers. Due to the limited travel of the six-degree-of-freedom platform, the platform is unable to provide continuous acceleration during the simulation of the driver’s body sensation in the three degrees of freedom of the ship, namely, sway, surge, and yaw. To overcome the above problems, a six-degree-of-freedom motion model of ships is constructed under low sea conditions based on the MMG-separated ship motion model and the FFT wave simulation method. Secondly, the otolith model and the semicircular canal model are introduced to establish a human body perception deception mechanism. The gravity is transferred by using the deflection angles of roll and pitch to extend the acceleration sensation in the three degrees of freedom of sway, surge, and yaw. Finally, through the real ship rotation and Z-shaped test experiments, the simulation trajectory, real ship attitude, and platform motion data are compared to verify the effectiveness of the established method. To simplify the research, under the low sea conditions where the three degrees of freedom of heave, roll, and pitch are ignored, the virtual ship simulation trajectory based on the above method is basically consistent with the real ship, and the correlation between the platform and the real ship body-sensing data is at least 81.2%. Through scoring the simulation driving body-sensing reproduction experience, it is proven that the above method can achieve a better body-sensing reproduction effect on the six-degree-of-freedom platform. Full article

This study investigates the hydrodynamic characteristics of supercavitating flows near boundaries through numerical simulations, focusing on the influence of free surfaces and solid walls. A validated numerical framework combining the Realizable k-ε turbulence model with the VOF multiphase approach and Schnerr–Sauer cavitation model is employed to capture complex phase interfaces and turbulent cavitating flows. Systematic validation against existing experimental data and dedicated underwater launch tests confirms the reliability of the methodology. The results demonstrate significant boundary effects on supercavitation dynamics. Near a free surface, the cavity tail deflects away from the interface, whereas it bends toward the wall when in close proximity to a solid boundary. Simultaneous presence of both boundaries causes combined torsional deformation and deflection. The cavity interface exhibits progressive indentation toward the tail, with indentation angle following a power–law relationship to axial position. Boundary interactions create distinct effects: free surfaces suppress cavity elongation, whereas solid walls promote extension, with cavity length remaining bounded within predictable limits. A notable torque reversal phenomenon occurs at $x=D$ from the cavitator tip, creating positive torque upstream (x < D) and negative torque downstream (x > D). Full article

There are almost no studies that investigate the flexural behavior of existing reinforced concrete (RC) beams with insufficient concrete strength using machine learning methods. This study investigates the flexural response of low-strength concrete (LSC) RC beams reinforced exclusively with steel rebars, focusing on the effectiveness of three different longitudinal reinforcement configurations. Nine beams, each measuring 150 × 200 × 1100 mm and cast with C10-grade low-strength concrete, were divided into three groups according to their reinforcement layout: Group 1 (L2L) with two Ø12 mm rebars, Group 2 (L3L) with three Ø12 mm rebars, and Group 3 (F10L3L) with three Ø10 mm rebars. All specimens were tested under three-point bending to evaluate their load–deflection characteristics and failure mechanisms. The experimental findings were compared with ML approaches. To enhance predictive understanding, several ML regression models were developed and trained using the experimental datasets. Among them, the Light Gradient Boosting, K Neighbors Regressor and Adaboost Regressor exhibited the best predictive performance, estimating beam deflections with R² values of 0.89, 0.90, 0.94, 0.74, 0.84, 0.64, 0.70, 0.82, and 0.72, respectively. The results highlight that the proposed ML models effectively capture the nonlinear flexural behavior of RC beams and that longitudinal reinforcement configuration plays a significant role in the flexural performance of low-strength concrete beams, providing valuable insights for both design and structural assessment. Full article

Accurate determination of a vehicle’s centre of gravity (CoG) is fundamental to driving dynamics, safety, and engineering design. However, existing static CoG estimation methods often neglect tyre deflection and detailed wheel geometry, which can introduce significant errors, particularly in electric vehicles, where the low and concentrated mass of the battery pack increases the sensitivity of vertical CoG calculations. This study presents a refined static axle-load-based method for electric vehicles, in which the influence of tyre deformation and lifting height on the accuracy of the vertical centre of gravity coordinate is explicitly considered and quantitatively justified. To minimise human error and accelerate the evaluation process, a custom-developed Python (Python 3.13.2.) software tool automates all calculations, provides an intuitive graphical interface, and generates visual representations of the resulting CoG position. The methodology was validated on a Volkswagen e-Golf, demonstrating that the proposed approach provides reliable and repeatable results. Due to its accuracy, reduced measurement complexity, and minimal equipment requirements, the method is suitable for design, educational, and diagnostic applications. Moreover, it enables faster and more precise preparation of vehicle dynamics tests, such as rollover assessments, by ensuring that sensor placement does not interfere with vehicle behaviour. Full article

This study presents an experimental and numerical investigation into the mechanical behavior of corrugated steel–concrete composite bridge decks with composite dowel shear connectors. Four full-scale specimens were fabricated and subjected to flexural tests to obtain and analyze the load–deflection and load–strain curves. A finite element model was developed and validated against the experimental results. The validated model was subsequently applied to analyze the load-carrying process and to perform parametric sensitivity analysis. The effects of the concrete strength grade, steel strength, corrugated steel plate thickness, concrete slab thickness, and corrugated steel plate height on the ultimate bearing capacity were evaluated. The results indicate that corrugated steel–concrete composite bridge decks were subjected to concrete shear failure. The ultimate bearing capacity of the bridge deck reached approximately 3.36 times the design value, demonstrating a high safety reserve. Throughout the entire flexural failure process, the shear connectors performed effectively, with only minimal relative slip observed at the steel–concrete interface. At the instance of failure, only partial areas of the corrugated steel plate yielded. To fully exploit the structural potential, the key design parameters require rational coordination. Full article

This study investigates the differences in flexural behavior of ultra-high-performance concrete (UHPC) arising from variations in test methods and key experimental parameters. Flexural tensile tests were conducted on 51 specimens representing 17 combinations of test variables, including steel fiber length (13 mm and 19.5 mm), specimen cross-sectional dimensions (75 × 75 mm, 100 × 100 mm, and 150 × 150 mm), presence or absence of a notch, and loading configuration (three-point and four-point loading). The tests were performed in accordance with ASTM C1609 and EN 14651, and both deflection and crack mouth opening displacement (CMOD) were normalized by the span length to compare the influence of each parameter. The notched specimens demonstrated significantly improved reliability, exhibiting up to an 8.4-fold reduction in standard deviation due to the consistent initiation of cracking. Regarding size effects, the 75 × 75 mm specimens showed an overestimation of flexural performance due to the wall effect of fiber distribution, whereas the 100 × 100 mm and 150 × 150 mm specimens exhibited similar flexural responses. The comparison of loading configurations revealed that three-point loading produced up to 11.7% higher flexural tensile strength than four-point loading, attributable to concentrated moment–shear interaction and the combined effects of fiber bridging and shear resistance mechanisms. In addition, specimens with longer steel fibers (19.5 mm) exhibited 5.2–9.7% higher flexural performance than those with shorter fibers (13 mm), which is attributed to enhanced interfacial bonding and improved crack dispersion capacity. Full article

This paper presents an experimental and numerical investigation of continuous reinforced concrete (RC) beams made of self-compacting concrete (SCC) strengthened with fiber-reinforced polymer (FRP) bars using the Near-Surface Mounted (NSM) method. While the majority of previous studies have focused on simply supported beams, this work examines two-span continuous beams, which are more representative of real structural behavior. Four SCC beams were tested under static loading to evaluate the influence of the FRP reinforcement position on flexural capacity and deformational characteristics. The beams were strengthened using glass FRP (GFRP) bars embedded in epoxy adhesive within pre-cut grooves in the concrete cover. Experimental results showed that FRP reinforcement significantly increased the ultimate load capacity, while excessive reinforcement reduced ductility, leading to a more brittle failure mode. A three-dimensional finite element model was developed in Abaqus/Standard using the Concrete Damage Plasticity (CDP) model to simulate the nonlinear behavior of concrete and the bond–slip interaction at the epoxy–concrete interface. The numerical predictions closely matched the experimental load–deflection responses, with a maximum deviation of less than 3%. The validated model provides a reliable tool for parametric analysis and can serve as a reference for optimizing the design of continuous SCC beams strengthened by the NSM FRP method. Full article

Wind-assisted ship propulsion (WASP) has gained considerable interest as a means of reducing fuel consumption and Greenhouse Gas (GHG) emissions, with further benefits when combined with weather-optimized routing. This study employs and extends a National Technical University of Athens (NTUA) weather-routing optimization tool to more realistically assess WASP performance through integrated modeling. The original tool minimized fuel consumption using forecasted weather data and a physics-based performance model. A previous extension to account for the WASP effect introduced a 1-Degree Of Freedom (DOF) model that accounted only for longitudinal hydrodynamic and aerodynamic forces, estimating the reduced main-engine power required to maintain speed in given conditions. The current study incorporates a 3-DOF model that includes side forces and yaw moments, capturing resulting drift and rudder deflection effects. A Kamsarmax bulk carrier equipped with suction sails served as the case study. Initial simulations across various operating and weather conditions compared the two models. The 1-DOF model predicted fuel-saving potential up to 26% for the tested apparent wind speed and the range of possible headings, whereas the 3-DOF model indicated that transverse effects reduce WASP benefits by 2–7%. Differences in Main Engine (ME) power estimates between the two models reached up to 7% Maximum Continuous Rating (MCR) depending on the speed of wind. The study then applied both models within a weather-routing optimization framework to assess whether the optimal routes produced by each model differ and to quantify performance losses. It was found that the revised optimal route derived from the 3-DOF model improved total Fuel Oil Consumption (FOC) savings by 1.25% compared with the route optimized using the 1-DOF model when both were evaluated with the 3-DOF model. Full article

This paper presents an experimental investigation on the flexural performance of continuous two-span reinforced concrete beams made with self-compacting concrete (SCC) incorporating natural and recycled coarse aggregates. A total of nine beams were tested under static loading conditions. The beams were divided into three groups based on different reinforcement ratios, and within each group, three aggregate replacement levels were used: 0%, 50%, and 100% recycled coarse aggregate. All beams were designed with identical cross-sections and subjected to two-point loading to simulate continuous support conditions. The study focused on evaluating cracking behavior, load–deflection response, and failure modes. The experimental results highlight that partial replacement with recycled aggregates (RAC50) can achieve comparable or even improved mechanical performance compared to natural aggregate beams, including enhanced compressive strength and ductility. Beams with 100% recycled aggregates (RAC100) showed slightly higher deflections and earlier crack initiation, particularly at lower reinforcement ratios, although overall flexural behavior remained consistent with natural aggregate concrete (NAC) beams. It was also observed that as reinforcement ratio increases, the influence of aggregate type diminishes, indicating that steel reinforcement predominantly governs the structural response at higher ratios. Crack widths and propagation patterns were systematically monitored, confirming that RAC beams maintain acceptable deformation and ductility under load. These findings emphasize the feasibility of using high-quality recycled aggregates in structural SCC elements, providing a sustainable alternative without compromising performance, and offering guidance for the design of continuous RAC beams. Full article

The use of miniscrews as Temporary Skeletal Anchorage Devices (TSAD) in orthodontics has allowed clinicians to perform challenging tooth movements by dissipating undesired forces into the bone structure; thus, avoiding unwanted movement of the adjacent teeth. It is essential for miniscrews to be highly resistant to fracture during clinical use. While many studies have analysed torsional loads, none have measured the changes in flexural and bending strength of miniscrews before and after an ageing process. This study aims to analyse the resistance to orthogonal forces of miniscrews with different diameters, focusing on both new and aged materials, the latter subjected to thermocycling and autoclaving laboratory processes to simulate a 3- and a 6-month exposure to the oral environment. A total of 105 pristine miniscrews have been tested; specimens were divided into seven groups based on the different endosseous body diameters. Each group was further subdivided into three subgroups, according to the simulated ageing of the miniscrews (intact, 3 months of ageing and 6 months of ageing, respectively). An Instron Universal Testing Machine has been used to measure deflection at 0.1 mm and 0.2 mm, as well as maximum load at fracture. The results evidenced that miniscrews respond differently to cutting forces; in particular, the resistance to orthogonal loads increases as the diameter of the miniscrews increases. Linear regression analysis revealed a significant influence between all the dependent variables—maximum load, 0.1 mm deflection load, and 0.2 mm deflection load—and the independent variables, such as diameter and thermocycling (p < 0.05). Both new and aged miniscrews are suitable for orthodontic and orthopaedic loads; moreover, ageing up to 6 months does not seem to significantly decrease the resistance to shear forces for the same diameter. Linear regression analysis of the miniscrews subjected to experimental ageing showed a slight but significant decrease in resistance to orthogonal loading. Full article

This work proposes a general methodology for the design and experimental validation of dual-arm robotic platforms intended for intelligent manipulation tasks in real-world environments. The proposed framework formalizes the complete engineering process, from the definition of functional requirements to the structural validation of the final prototype, ensuring reproducibility and adaptability across different applications. The methodology is organized into five main stages: (i) requirement analysis and context characterization; (ii) conceptual architecture definition; (iii) detailed mechanical design and structural analysis; (iv) prototype construction and integration; and (v) experimental validation and iterative refinement. Each stage defines its expected deliverables, evaluation metrics, and decision criteria to support systematic design progression. The approach is demonstrated through its implementation within the European project MANiBOT, where the framework guided the development of a modular bimanual robotic platform capable of integrating collaborative manipulators and conveyor subsystems for dual-arm manipulation. Structural testing, deflection measurements, and stability analyses confirmed the robustness and safety of the resulting design. Beyond this specific case, the proposed methodology provides a replicable and extensible design reference for research and industrial teams developing modular robotic structures, supporting the standardization of engineering practices in bimanual mobile robotics. Full article

This study investigates the flexural performance of geopolymer (zero-cement) concrete (ZCC) beams compared to normal concrete (NC) under monotonic and cyclic loading. Sixteen reinforced beams with compressive strengths of 20 and 30 Mpa and reinforcement configurations of 2Ø10 and 3Ø12 were tested to evaluate load–deflection behavior, ductility, energy absorption, and cracking characteristics. Under monotonic loading, ZCC beams achieved 9–17% higher ultimate strength and 5–30% greater mid-span deflection than NC beams, indicating superior ductility and energy dissipation. Under cyclic loading, ZCC beams demonstrated more stable hysteresis loops, slower stiffness degradation, and 8–32% higher cumulative energy absorption. ZCC specimens also sustained 8–12 cycles, corresponding to 70–90% of the monotonic displacement, whereas NC beams generally failed earlier at lower displacement levels. Increasing reinforcement ratio enhanced stiffness and load capacity but reduced deflection for both materials. Crack mapping showed finer and more uniformly distributed cracking in ZCC beams, confirming improved bond behavior between steel reinforcement and the geopolymer matrix. In addition, geopolymer concrete beams exhibited a significant enhancement in ductility, with the ductility coefficient increasing by nearly 50% compared to normal concrete under cyclic loading. Overall, the findings indicate that ZCC provides comparable or superior structural performance relative to NC, supporting its application as a sustainable, low-carbon material for flexure- and shear-critical members subjected to static and cyclic actions. Full article