Precise estimation of the maximum load capacity of wind turbine blades remains a significant challenge in wind energy engineering. This study provides a detailed assessment of the mechanical behavior of a composite wind turbine blade through using a blade sub-model approach. To evaluate its structural resistance, the blade sub-model was subjected to progressively increasing maximum loads in the flapwise direction. This numerical investigation allowed a thorough analysis of the onset of damage as a function of the applied loading conditions. The simulations were carried out using ANSYS Workbench and ANSYS Composite PrepPost. The adopted sub-model corresponds to the upper section of the wind turbine blade, which was extracted from the full geometry to reduce computational cost and simulation time. The obtained numerical results indicate that the initial failure tends to occur near the blade root region. Consequently, a wind blade reinforcement strategy was implemented to evaluate how reinforcement influences the structural strength of the blade, leading to a significant reduction in damage initiation. These findings provide valuable insight into the blade’s structural integrity and its dynamic behavior during operation. Furthermore, the results contribute to improvements in manufacturing practices, helping ensure that the final blade structures comply with strict safety and reliability requirements when operating under demanding environmental conditions.
Micro-scratches are unavoidable surface defects that act as stress raisers under mechanical loading. In this unorthodox work, the stress concentration induced by such defects is quantified using a parameter termed the F-factor. The micro-scratches are modelled as semi-cylindrical grooves on a free surface. Under uniaxial tensile loading, the F-factor is found to be approximately 3.1. This value remains essentially independent of the scratch radius over a wide range from 0.1 µm to 500 µm. Because of this high stress concentration, yielding initiates at the critical point of the scratch even when the stress is well below the material’s yield strength. Under repeated fatigue loading, plastic deformation accumulates progressively at the scratch root. This accumulation ultimately leads to the nucleation of a fatigue crack. To reduce this effect, a thin unidirectional fibre-reinforced polymer (FRP) patch is adhesively bonded over the scratched region. The presence of the patch significantly reduces the F-factor. Three types of FRP patches—GFRP, CFRP, and BFRP- are examined in combination with three substrate materials: aluminium, titanium alloy, and mild steel. The patch thickness is varied from 0.1 mm to 0.4 mm. The extent of reduction in the F-factor depends primarily on the relative stiffness of the patch and the substrate. Low-stiffness patches, such as UD-GFRP, produce only marginal reduction when bonded to high-modulus substrates like mild steel. In contrast, high-stiffness patches, such as UD-BFRP, result in substantial reductions, particularly when applied to low-stiffness substrates such as aluminium.
Isomorphism detection in epicyclic gear trains (EGTs) is an important step in mechanism topological analysis and structural synthesis because it enables the identification and elimination of duplicate or structurally equivalent mechanisms. Although several graph-theoretic and matrix-based approaches have been developed for EGT isomorphism detection, their relative computational characteristics, implementation requirements, and suitability for automated structural synthesis have not been systematically compared under a common framework. This study presents a comparative assessment of four approaches: the Modified path matrix method (MPM), Bocher’s method (BM), Modified gradient method (MGM), and Wiener number technique (WNT). The methods are evaluated using representative EGT configurations with different numbers of links and degrees of freedom, considering computational effort, calculation procedure, classification capability, reliability, and potential for computer-based automation. The results show that all four methods can effectively distinguish the isomorphic and non-isomorphic EGT configurations investigated, although their computational requirements differ considerably. MPM provides detailed structural information but involves relatively extensive manual calculations, while BM offers a matrix-based computational approach with moderate implementation requirements. MGM provides reliable classification but involves several intermediate calculations and comparatively greater manual effort. WNT requires relatively simple calculations based on graph connectivity and pairwise distances and demonstrates strong computational efficiency and automation potential for the benchmark EGT configurations considered. The study therefore provides a systematic comparative framework for assessing EGT isomorphism-detection methods and identifying their respective computational advantages and limitations. The findings suggest that WNT can serve as an efficient invariant-based screening approach for the investigated EGT cases; however, equality of a Wiener number alone should not be interpreted as a universal proof of graph isomorphism. The study provides a basis for future development of larger automated EGT databases and hybrid screening–verification frameworks for computer-aided structural synthesis.
Due to high energy density and localized heat input, laser beam welding (LBW) is getting more and more used in connection with advanced engineering alloys. In this study, laser beam welding was used to join the similar and dissimilar weldments of Inconel 718 and steel 321. The weldability of similar and dissimilar joints produced by laser beam welding (LBW) was assessed through macrostructural and microstructural examination, tensile testing, Vickers microhardness measurements, and fracture characterization using scanning electron microscopy (SEM). Macrostructural examination confirmed sound weld formation with full penetration, while optical observations indicated a clear grain boundaries. The weld zone exhibited cellular–dendritic microstructures, which are commonly formed at high cooling rates during laser welding. The dendritic morphology of the dissimilar joint exhibited a mixed cellular–dendritic structure, suggesting the interaction of the two base materials during weld solidification. The Inconel 718–Inconel 718 joint exhibited the highest tensile strength (922 MPa), whereas the AISI 321–AISI 321 joint showed superior ductility. The weld region adjacent to the Inconel 718 side exhibited higher microhardness than the AISI 321 side. SEM fractography revealed predominantly ductile fracture characterized by dimples, consistent with the tensile properties of the welded joints.
The performance, efficiency, and operational safety of multirotor unmanned aerial vehicles or unmanned vehicles are strongly influenced by propeller aerodynamic characteristics, structural integrity, and power requirements. The high-fidelity computational approaches such as CFD and FEA, although accurate, are often unsuitable for early stage design due to high computational cost. This study presents an integrated, low fidelity computational framework that combines a Blade Element Momentum Theory based propeller aerodynamics, quad rotor rigid body flight dynamics, light weight structural screening, and composite safety assessment methodology within an unified environment. The framework enables rapid, Excel driven parametric evaluation of blade geometry, material properties, motor-battery configurations, and operating conditions. Thrust generation and power consumptions, and trajectory tracking are simulated under nominal and disturbed wind condition through dynamic coupling between propulsion and flight model. The structural feasibility is ensured through centrifugal, bending, and torsional stress evaluation, tip deflection estimation, and safety factor assessment. A novel composite safety index is introduced to quantify the thrust margin, actuator saturation, and control robustness, under gusts, power loading, torque limits, and structural integrity. Aerodynamics predictions are validated against the experimental data from the UIUC low Reynolds number propeller data base, yielding mean thrust and power errors below 8
