Journal of Engineering and Thermal Sciences
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Modernization of the electromagnetic vibration stand for testing aviation industry products
Get PDFThe article presents a methodology for modernizing a two-mass resonant electromagnetic vibration stand for testing parts of the aviation industry for vibration resistance. The main goal of the modernization is to provide a significantly lower disturbance force from electromagnetic vibration exciters to set the working body in motion. For this purpose, by introducing a third oscillating mass into the two-mass mechanical system, the interresonant mode of operation of the vibration stand is ensured. Analytical dependencies are presented that reveal the methodology for calculating inertial and stiffness parameters that ensure the transformation of a two-mass resonant vibration system into a three-mass interresonant vibration system. A specific example demonstrates the implementation of the proposed approach in the modernization of the design. The amplitude-frequency characteristics of the basic two-mass resonant and modernized three-mass interresonant vibration systems are constructed. It has been confirmed that to ensure the specified amplitude of oscillations of the working body in the modernized design, 4 times less disturbing force from electromagnetic vibration exciters (400 N) is required
Multi-scale information distillation attention network for super-resolution reconstruction of remote sensing images
Get PDFSuper-resolution (SR) is an effective and reasonable way to improve the spatial resolution of remote sensing images, which serve as an important information carriers for Earth observations. Compared to natural images, the more complex spatial distributions and more detailed ground information contained within remote sensing data place higher demands on the feature-representation ability of the model. Moreover, considering the deployment of these systems on mobile hardware, the complexity of the model is also an urgent issue. To overcome these problems, this study proposes the multi-size information distillation attention network (MSIDAN) for super-resolution reconstruction of remote sensing images. In the designed residual block, a multi-size information-distillation module is designed to distill and fuse multi-level semantic features step-by-step while reducing the number of model parameters. After this, an enhanced contrast-aware channel attention mechanism is employed to perceive high-frequency information by automatically encoding the weight values of candidate features. A large number of comparative experiments on four typical remote sensing image datasets demonstrate that MSIDAN outperforms other state-of-the-art approaches in both quantitative metrics and visual qualities. Compared to the information multi-distillation network (IMDN), MSIDAN improves the Peak Signal-to-Noise Ratio (PSNR) by 0.03312 dB, 0.06031 dB, 0.05319 dB, and 0.03812 dB on the RSSCN7, WHU-RS19, NWPU VHR-10, and COWC datasets, respectively. Moreover, in comparison to other comparable CNNs-based approaches, MSIDAN achieves a more favorable balance by jointly considering SR performance and model size. This technology provides valuable support for small target measurement and opens new opportunities in the field
Structural instability motion and optimization of the demolition and blasting scheme for complex continuous multi-span frame-shear structure
Get PDFDue to challenges faced during demolition and blasting processes such as conducting prototype monitoring tests on large continuous multi-span structures or carrying out full-area dynamic monitoring of overall structural stress; This paper takes the demolition of the Ruzhou Unicom building as the background, optimizes the design of the demolition and blasting program through theoretical analysis and simulation monitoring, and also studies the form of structural instability movement and the deformation of the key parts of the damage and internal force characteristics, and obtains the following conclusions: the axial force reaches the maximum value when the building is not deflected; when the first-order derivative of the shear force is 0, the maximum shear stress occurs at the position of 2/3 of the height of the building; When the first-order derivative of bending moment is 0, the maximum bending moment occurs at 1/3 of the building height. In Mushroom Pavilion incision formation, the support part of the main structure produces a downward force, exacerbating the disintegration of the main part of the damage; the main structure of the collapse process, the back row of columns are mainly presented as bending shear damage, the upper side beams are mainly presented as tensile damage, the central and lower side beams are mainly presented as compression shear damage. Notably, the bidirectional notch configuration results in a forward displacement of 9.5 meters and a subsequent recoil of 4.6 meters, providing effective shielding for the military fiber-optic cables positioned at the forefront and the adjacent deep excavation pits. Additionally, this configuration facilitates the rapid establishment of a stable collapse pattern between the Mushroom Pavilion structure and its main body, ultimately accelerating the disintegration of the overall building structure during the collapse event
Research on bearing equipment fault diagnoses via SAWOA-LSTM
Get PDFTo address the current low fault diagnosis accuracy problem for bearing equipment, and improve the detection methods, in this paper a sine-adapted whale optimization algorithm (SAWOA)-based optimization of a long short-term memory (LSTM) network is proposed as the equipment fault diagnosis method (SAWOA-LSTM). First, an optimization strategy based on sinusoidal population initialization and adaptive optimization is proposed for the whale optimization algorithm, which has the two drawbacks of slow convergence and easily falling into a local optimum. Second, to improve the accuracy and efficiency of fault diagnoses, the SAWOA is used to optimize the number of hidden units and the learning rate parameter of the LSTM. Compared with ACO-, PSO-, and WOA-based LSTM models, the proposed method improves diagnostic accuracy by 14.17 %, 15.03 %, and 4.32 %, respectively. In tests on 50 bearing samples, SAWOA-LSTM further improves accuracy for RBD, IRA, and ORD by 1.08 %, 1.62 %, and 1.10 %, respectively. Our algorithm provides an innovative solution for the health management of complex industrial bearing equipment
Fault diagnosis of time-varying speed gearbox based on gated recurrent dropout attention unit
Get PDFIn response to the difficulty of fault diagnosis of gearbox under time-varying speed conditions, this paper presents a novel approach for diagnosing gearbox faults in time-varying speed, utilizing an improved gate recurrent unit (GRU), which adds attention gate mechanism and cyclic dropout learning strategies on the basis of the GRU, and constructs a new model named as gated recurrent dropout attention unit (GRDAU). By introducing attention gate mechanism to realize allocating weights dynamically, focusing on key features, and enhancing GRU’s ability to capture important information. In addition, the designed cyclic dropout learning strategy reduces excessive dependence on specific hidden states by randomly discarding some hidden state information. Finally, the robustness and excellent interference suppression ability of the proposed method were verified through case analysis of a gearbox under time-varying speed, and the diagnostic accuracy of the method is as high as 99.78 %. Comparative experiments were conducted to validate its superior performance and stronger generalization ability compared to existing advanced diagnostic methods
Dual-stator ultrasonic motor achieving 2-DOF linear and rotary motion with single-phase excitation
Get PDFThis study proposes a novel dual-stator linear-rotary ultrasonic motor. The piezoelectric ceramic excites both out-of-plane and in-plane vibration modes within the stator. These distinct vibration modes independently drive the slider (rotor), generating reciprocating linear and rotational motions, respectively. Finite element analysis and laser vibrometer-based vibration testing validated the motor's operational principle. The close agreement between simulated and measured resonant frequencies for both vibration modes, with mere discrepancies of 3 % and 4 %, respectively, underscores the accuracy of the stator’s vibrational characteristics. Subsequently, two stators are fabricated and assembled to the ultrasonic motor prototype. Experimental results demonstrate the motor’s impressive performance, achieving a maximum linear velocity of 265 mm/s and a peak rotational speed of 1600 rpm. Furthermore, the motor delivers a maximum thrust force of 0.18 N and a stalling torque of 1.8 mN·m
Anomaly detection method of traction motor bearing based on multi-scale sub-band fuzzy entropy manifold fusion index
Get PDFDetecting early faults in traction motor bearings poses significant challenges due to weak signals and difficulties in identifying fault initiation points with sufficient sensitivity. This paper introduces a novel anomaly detection method based on a multi-scale sub-band fuzzy entropy manifold fusion index (MFMI). The proposed method decomposes vibration signals across multiple scales to capture local features of bearing health, calculates sub-band fuzzy entropy to quantify fault characteristics, and uses locality preserving projection to retain nonlinear structural features while reducing dimensionality. Validation experiments using full-cycle acceleration life vibration signals demonstrate the superior performance of the proposed method. For instance, in the traction motor case, the proposed index detected early damage at the 189th time point, outperforming other indicators that detected damage after the 200th time point. The proposed method also shows higher sensitivity to early degradation trends while maintaining stability during normal operation. These results highlight the practical applicability of the method for early anomaly detection in traction motor bearings, offering earlier and more reliable fault detection compared to traditional methods
Numerical analysis and experimental research on Acoustic-vibration characteristic of 110 kV transformer tank
Get PDFA vibroacoustic coupling model of the 110 kV transformer tank is constructed by using the finite element method. The structural vibration response under 100 Hz and 200 Hz sound source excitation is analyzed. Radiated sound field characteristics and sound transmission loss performance across the 0-400 Hz frequency range are evaluated. Then, a test system is established to measure vibration response and sound transmission loss through experiments. Simulation analysis and experimental test results show that the average sound transmission loss of the 110 kV transformer tank ranges from 30 dB to 40 dB. The simulation calculation results show good agreements with experimental test results, which prove the correctness of the vibroacoustic coupling model of the 110 kV transformer tank
Mechanics of composite fiber pull-out from concrete with fly ash using the DCB test
Get PDFThis study explores novel concretes where cement is partially replaced by oil shale ash (OSA), reducing CO2 emissions, and incorporates patented composite fibers for enhanced mechanical performance. The mechanics of fiber pull-out and interfacial bond strength in concrete reinforced with short fibers, where cement is partially replaced by either fly ash or OSA, using the Double Cantilever Beam (DCB) test. The research aims to assess how these eco-friendly additives impact the fiber-matrix bond and crack propagation resistance in fiber-reinforced concrete. In the experimental setup, two partially sawn concrete beams were joined along their length by a thin, fiber-reinforced concrete layer and subjected to a tensile force, simulating crack opening. Concrete specimens (400×210×100 mm) with varying ash contents were tested, focusing on key parameters such as peak load, energy absorption, and interfacial toughness. Findings indicate that both fly ash and basalt enhance the mechanical properties of the concrete, with significant improvements in load transfer and fiber pull-out resistance observed, particularly at higher ash contents. Analysis of force-displacement curves and fracture surfaces demonstrated a shift from brittle to more ductile behavior as ash content increased, enhancing the fracture resistance of the composite. This research supports the use of alternative cementitious materials like fly ash and basalt in developing sustainable, high-performance fiber-reinforced concrete, with potential applications in structural engineering and eco-friendly construction practices
Investigation of transient processes in auxiliary asynchronous electric motors of locomotives using differential equations
Get PDFThe aim of this research is to scientifically substantiate the operating conditions of small and medium-power auxiliary asynchronous electric motors currently in use on mainline electric locomotives of the VL60, VL80, and Ermak 3ES5K types. The goal is to draw conclusions based on scientific research, such as evaluating the operational efficiency of auxiliary asynchronous electric motors and creating the possibility to predict their service life based on the assessment results. This, in turn, will enable timely maintenance of auxiliary engines in locomotives