Abstract:This study addresses the vibration problems in high-speed long-shaft rotor system of an aerial UAV by developing a computational model that incorporates various forms of bearing support and damping. Using Ansys Workbench, the effects of bearing support forms and bearing damping on the critical speed of the rotor system are analyzed. Results indicate that the critical speed is significantly higher with rigid support than with flexible support. When rigid support is combined with bearing damping, the critical speed decreases with the increase of damping, and the influence of bearing damping decreases in higher-order modes. Additionally, the harmonic responses of the system are consistent across different positions, with the response amplitude increasing as the unbalanced load rises. Furthermore, the response amplitude shows an upward trend with increased damping.

Abstract:This study investigates the vibration characteristics of planetary gear transmissions subjected to pitting faults. Gear contacts are modeled using the Hertzian contact theory, and multi-flexible body dynamics models are established and simulated for gears in healthy, mild, moderate and severe states of pitting damage. The time-frequency domain vibration responses of planetary gears are analyzed under these different conditions of pitting corrosion. A vibration test platform for planetary gearboxes is built to capture the vibration response signals, which are used to verify the accuracy and reliability of the dynamic model of pitting-induced vibrations. The results show that both the effective and peak-to-peak values of vibration velocity in the Y-direction increase with the severity of the pitting damage. The vibration velocity and acceleration of the slightly corroded model show distinct sideband frequencies, and the experimental results are basically in agreement with the simulation results. Additionally, the study identifies variations in the width and depth of micro-pitting and macro-pitting during their expansion.

Abstract:Crown gear couplings are primarily manufactured using two tooth surface forming methods. In Forming Method I, the hob centre makes circular motion around the displacement circle center, while in Forming Method II, the gear shaper centre follows the same motion. However, the differences in tooth profiles and the mechanisms influencing their contact performance between these two methods remain unclear. To address this, simulations of the tooth surface machining processes for both forming methods were conducted, and the resulting hub tooth surfaces were modeled. Geometric tooth contact analysis and loaded tooth contact analysis models were established using meshing theory and the finite element method. Comparative analyses of tooth profiles, unloaded, and loaded contact characteristics were performed. Results show that, under identical displacement circle radii, the tooth profile deviations between the two forming methods gradually decreases as the radius increases, with a maximum deviation of 251 μm. Moreover, load sharing among teeth is notably less uniform in Forming Method I than in Forming Method II, with maximum loads exceeding minimum loads by 702.8% and 451.2%, respectively. For equal crowning amounts, Forming Method II requires a larger displacement circle radius than Method I, with a difference of 200 mm. Despite this, the load-sharing performance of both methods becomes comparable under these conditions.

Abstract:This study focuses on the boom luffing hydraulic system of boom-type aerial work platforms. A hydraulic simulation model is developed using AMESim software, and its accuracy is verified through mechanical-hydraulic co-simulation. To optimize the model for real-time simulation, a linear frequency domain analysis method, supplemented by active energy index analysis, is used to simplify and reduce the model’s order. Components with higher natural frequencies and lower activity indices are either removed or modified, and parameters of certain high-frequency models that could not be removed are adjusted to achieve real-time simulation compatibility. The reduced-order hydraulic system model significantly reduces computational time while maintaining a high level of fidelity, meeting real-time simulation requirements effectively.

Abstract:To achieve a low-cost, high-precision indoor location system, this study designs a method using simple visual labels while balancing computation complexity and practical requirements. Only color and shape features are used for label detection, minimizing both detection complexity and data storage needs. To deal with the issue of nonunique solutions caused by simplified label features, a rapid query and matching method is proposed by incorporating the camera’s field of view and the label's azimuth. Furthermore, a pose and position estimation method using a weighted least square algorithm is developed. This method is integrated with an interactive algorithm guided by a designed switching strategy. These techniques strike an effective balance between algorithm complexity and location accuracy. Simulation and experimental results show that the proposed method effectively resolves singularity issues in overdetermined equations and attenuates the negative effects of poorly distributed label groups. Compared with ultra-wideband technology, the proposed approach reduces location error by more than 62%.

Abstract:Air infiltration through building entrances significantly affects the energy consumption and occupant comfort of commercial buildings. To improve the resistance of entrances to air infiltration, this study identifies and evaluates four typical entrance exterior entrance forms of commercial buildings in cold regions. With utilizing the FLUENT platform, multi-directional wind simulations are conducted to assess the performance of these entrance types. A novel metric, “comprehensive velocity” , is introduced to quantify and compare their effectiveness under different wind conditions. Results show that under windward conditions, a concave entrance is more effective than a flat entrance, whereas under leeward conditions, a semi-convex-near entrance is preferable to a semi-convex-far entrance. When the dominant wind directions are 90°, 180° and 270°, any entrance form may be selected; however, under variable wind directions, the concave entrance demonstrates the best performance, with the flat entrance performing the worst. Based on these findings, this study proposes optimization strategies and improvement methods for the exterior design of entrances to enhance their performance under diverse wind conditions.

Abstract:Traditional shallow neural networks exhibit low prediction accuracy and poor generalization when handling high-dimensional data. To solve these problems, this study proposes an intelligent control algorithm for high-rise buildings based on one-dimensional convolutional neural networks(1D-CNN) and the deep dream visualization algorithm. The proposed method enables high-precision network model training and visualizes data features through 1D-CNN. Using a 20-story benchmark model as a case study, the damping performance of the 1D-CNN-based intelligent control algorithm was analyzed under different conditions and compared with back propagation(BP) and radial basis function(RBF) algorithms. Results show that 1D-CNN can effectively extract deep data features and reduce the dimensionality of massive datasets by virtue of one-dimensional convolution and pooling operations. Under external excitation, the maximum damping rates for acceleration and displacement achieved by the 1D CNN controller were 69.0% and 55.6% respectively, significantly outperforming BP and RBF. Although the control performance of all algorithms decreased under modified excitation conditions, the 1D-CNN consistently exhibited superior performance and the best generalization capability.

Abstract:In the damage detection of composite blade, it is very important to accurately and rapidly obtain the dynamic characteristics of blade before and after blade damage. Therefore, an efficient numerical calculation method for composite blade damage simulation was proposed under the finite element framework based on the homogenization of composite materials, extended Bredt-Batho shear flow theory and damage stiffness degradation theory, and the corresponding finite element program is developed based on Python language. On this basis, the composite sandwich cantilever beam is taken as the research object and compared with ANSYS calculation results to verify the rationality of the composite material homogenization method. At the same time, it is applied to simulate the modal calculation of NREL 5MW fan blade under different damage conditions. The results show that the numerical calculation method can simulate the blade leading edge crack damage well. The blade frequency gradually decreases with the deepening of damage degree. The leading edge crack has more influence on blade flapping direction. Under the same damage degree, the frequency of blade leading edge crack decreases more as it gets closer to the root. The leading edge crack at the blade root has a great influence on the blade oscillation direction, while the leading edge crack at the blade tip has a great influence on the blade oscillation direction. The blade leading edge crack has little effect on the natural frequency, and the curvature damage factor calculated by the mode displacement of the flapping direction can be used as the damage identification index to identify the blade leading edge crack damage effectively.

Abstract:This study investigates the bond failure mechanism between engineered cementitious composite (ECC) and corroded rebars through pull-out experiments. The effects of corrosion rate, bond anchorage length, rebar diameter, and fiber content on bond performance are analyzed. The results show that the bond stress-slip curve can be divided into: micro-slip, slip, failure and residual phases. All specimens exhibit shear pull-out failure as the primary failure mode. The bond strength initially increases and then decreases with the corrosion rate and there is a critical corrosion rate resulting in the warimized bond strength. For rebars with a 10% corrosion rate, bond strength decreases as anchorage length and rebar diameter increase. Additionally, increasing the fiber content enhances the bond toughness index and bond strength initially, followed by a decline. The optimum performance, including maximum toughness and crack resistance, is observed at a fiber content of 2%.

Abstract:To enhance the adhesion of bio-asphalt to aggregates and improve its practical application in engineering, this study investigates the effects of diatomite modification on bio-asphalt. The physical properties of diatomite-modified bio-asphalt are evaluated using standard index tests and rotational viscosity experiments. Adhesion to limestone is evaluated using an improved boiling method, Based on surface free energy, contact angles between the diatomite-modified bio-asphalt and test liquids are measured by the lying drop method, enabling the calculation of surface energy, cohesion work, adhesion work and spalling work. The results show that diatomite improves the physical properties of bio-asphalt, increases the softening point, reducces needle penetration, initially decreases ductility, and then slightly increases. Viscosity increases with diatomite content but stabilizes when the content exceeds 17%. When diatomite content is 17%, the asphalt quality loss during the boiling test is minimized, showing a decrease of 36.44% compared with unmodified bio-asphalt. Additionally, diatomite significantly improves the surface energy, adhesion and cohesion of bio-asphalt, and reduces spalling work. The dimensionless energy parameter (ER) reaches its peak at a diatomite content of 17%.