1,721,060 research outputs found
Solar Energy-Powered Boats: State of the Art and Perspectives
Full text linkThis paper presents an examination of the primary applications of solar energy as the main power source in the maritime sector, focusing on recent developments. A comprehensive review of the existing literature, including journal articles, proceedings, and patents, is conducted to identify three prominent areas for advancing solar energy-powered boats: maritime drones, sporting boats, and short-range touristic vessels. Maritime drones primarily serve as small autonomous boats for research, conservation, or military operations. On the other hand, sporting boats include nautical and energy design competitions involving students and enthusiasts. In terms of commercial interest, there is a growing demand for environmentally friendly and low-noise boats suitable for tourist activities, particularly in protected areas. Furthermore, specific and illustrative cases are explored in a dedicated section. Lastly, potential future perspectives are discussed and elucidated
An advanced mean value method for the treatment of uncertainties in Reliability calculations
No full textThe problem of uncertainties managing in Reliability calculations is stressed.Parametric uncertainties on the failure rate of mechanical components are considered and an approximated method for the determination of the cumulate probability function of the Reliability is shown
FEM-SPH Numerical Simulation of Impact Loading on Floating Laminates
Full text linkThe study of dynamic events such as impact and hydroelastic slamming is of great importance in determining the structural integrity of naval or maritime structures, particularly those made of composite materials. This topic has been investigated by numerous researchers using analytical, experimental, and numerical approaches. In this study, we propose using a hybrid numerical model combining smoothed-particle hydrodynamics (SPH) and the finite element method (FEM) to investigate the impact of external objects on floating laminates. The results show a good agreement with the available experimental data regarding the impact dynamic and some limitations in the damage determination
Numerical Investigation of Low-Velocity Ice Impact on a Composite Ship Hull Using an FEM/SPH Formulation
No full textIn cold climate regions, ships navigate through diverse ice conditions, making the varied interaction scenarios between hulls and ice critically important. It is crucial to consider the safety and integrity of the hull during an ice-hull interaction, especially in the presence of lightweight structures. Proper design and material selection can help improve the structure's ability to withstand ice forces. Within the scope, understanding the behavior of ice and its interaction with the structure can inform the development of appropriate measures to minimize possible damage or failure. The current study focuses on the interactions occurring during the impact loading phases, which are characteristic of thin first-year ice. A sandwich structure made with carbon fiber-reinforced epoxy prepreg and PVC core was investigated. Low-velocity ice impact was modelled using the Ansys Workbench 2023 R2 and LS-DYNA R11 explicit solver. As the material model, the *MAT055 was chosen based on the literature, while ice was represented with its equation of state. The Tsai Wu criterion was adopted to identify tensile and compressive failure in the matrix and fibers. This simulation allowed us to evaluate how the composite material responds to ice impacts, considering factors such as the speed of the impact, the shape and thickness of the ice, and the properties of the composite material itself
An innovative processing method for the direct bathtub calculation
No full text\In many plants, industries, etc. unavailability, often due to neglected or not well performed maintenance, results in reduced revenue and decreasing profitability. It is proved that with good maintenance management methods (usually called Computer Maintenance Management Systems, CMMS) these economic losses can be reduced and the availability improved. But a better result may be obtained intervening at level of maintenance planning. For its improvement, an optimal compromise between the costs of failures repairs and of maintenance operations, carried-out to avoid such failures, has to be found in respect of prefixed constraints on the system availability, reliability, etc. To this aim, reliability criteria must be considered. In this frame, the knowledge of the failure rate of the single components (suitably obtained by the processing of exploitation data previously collected) and, in particular, of its variation in the time has a particular importance. The present paper describes a now method for the processing of the much less than total much greater than failure rate of each component type of an industrial system on the basis of historical data previously collected on it and its possible use for the selection of the only components on which maintenance must be applied and its preliminary definition
Buckling analysis of telescopic boom: Theoretical and numerical verification of sliding pads
Full text linkWith the aim at improving the highest performances, materials in mechanical structures are constantly pushed closer and closer to their critical limits. Consider, for example, how the progressive reduction in thickness may lead to unforeseen effects in the instability of metal sheets, until the rapid collapse of the whole structure. This risk is specially known by designers of telescopic booms, used for moving aerial platforms. In this paper, by a numerical approach and ANSYS code, structural resistance and stability of a telescopic boom were verified. After a preliminary theoretical analysis, different loads and boundary configurations were considered in accordance with the most common conditions of real utilisation. As general result, it was confirmed that stresses were under the elastic limit of materials, except in a very limited number of contact zones, where specific connecting solutions have to be installed to prevent failures. Furthermore, linear buckling techniques showed that critical loads and corresponding buckling modes were higher than the most extreme working conditions; thus, structural stability was also confirmed. Finally, the large adoption of FEM simulations permitted to reduce the experiments, offering a fast methodology for improvements in design
Delamination analysis of laminated composites in drilling and quasi-static penetration
No full textDrilling of composite materials is highly important from aspects of operation capacity and safety of structures; especially because these materials are mostly used in transportation industry. One of the main damages observed after drilling composite materials is the delamination, which refers to a damage bonder around the machined holes. This type of damage causes poor assembly tolerance, reduce the structural integrity and has the potential for long-term performance deterioration under fatigue loads. Drilling-induced delamination occurs both at the entry and the exit of the drilled holes and accounts for 60% of all part rejections during final assembly of composite products. In this paper, the effect of machining parameters, feed rate and cutting speed, on delamination in drilling process and quasi-static penetration were investigated. For this purpose, two sets of experiments, drilling and quasi static penetration, were designed based on full factorial design. Using analysis of variance, optimum cutting condition for minimum delamination was determined. A correlation between feed rate and cutting speed with the delamination factor was established by second order linear regression. According to the results, delamination increases with feed rate; whereas it decreases with cutting speed. Finally, a comparison between the delamination in drilling process and quasi-static penetration by conical-nosed projectile was made. According to the results, the difference is significant so that the average value of delamination for each level in quasi-static penetration is about two times greater than drilling process
Effects of Moisture Absorption on the Mechanical and Fatigue Properties of Natural Fiber Composites: A Review
Full text linkThis review critically examines the effects of moisture absorption on the mechanical and fatigue properties of natural fiber composites (NFCs), with a focus on tensile strength, elastic modulus, and long-term durability. Moisture uptake can cause reductions in tensile strength of up to 40% and in elastic modulus by 20-30% depending on fiber type, mass fraction (typically in the range of 30-60%), and surface treatments. The review highlights Ithat while surface modifications (e.g., alkaline and silane treatments) significantly mitigate moisture-induced degradation, their effectiveness is highly sensitive to the processing conditions. Additionally, hybridization strategies and optimized fiber orientations show promise in enhancing fatigue resistance under humid environments. Despite substantial progress, major challenges remain, including the lack of standardized testing protocols and the limited understanding of multiscale aging mechanisms. Future research directions include developing predictive models that couple moisture diffusion and mechanical deterioration, implementing advanced in situ monitoring of damage evolution, and exploring novel bio-based treatments. By addressing these gaps, NFCs can become more reliable and widely adopted as sustainable alternatives in structural applications
Probabilistic first-ply failure analysis of a symmetric-equilibrate laminate in composite material
No full textA general procedure to develop a probabilistic analysis of composite materials is presented. The second order of the Taylor series was used to determine the statistics of the first ply failure for a symmetric equilibrate composite. The Monte Carlo Method was used to validate the accuracy of the procedure
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