Journal of Engineering and Thermal Sciences
Not a member yet
1200 research outputs found
Sort by
An ensemble model with convolutional neural network by DS evidence fusion for bearing fault diagnosis
Full text linkBearing fault diagnosis is crucial for ensuring the safety and reliability of rotating machinery. In recent years, artificial intelligence technology based on machine learning has made substantial progress in the field of bearing fault diagnosis. Most existing models for bearing fault diagnosis are built using big data and deep learning algorithms and can achieve high diagnostic accuracy with sufficient fault data. However, there still exist two open issues, 1) in practical engineering, acquiring fault sample data is challenging, and it is difficult to obtain a sufficient number of samples to train the hyperparameters of deep learning models. 2) Fault diagnosis models based on individual classifiers rely heavily on prior knowledge for signal feature extraction and the selection of network structures and parameters, making it difficult to guarantee the model’s effectiveness. This paper proposes an integrated diagnostic model called DS-ELM that employs multiple extreme learning machine modules with different parameters as subclassifiers. The outputs of these modules are then fused via DS evidence fusion theory to obtain the final diagnostic result. This ensemble model has better flexibility and robustness which significantly improves the accuracy and stability of the diagnostic model. Overall, the proposed DS-ELM provides a new solution for bearing fault diagnosis. In addition, the superiority of the reported technique is confirmed via experimental bearing fault data from Case Western Reserve University
Reduced-order modeling of digital twins for a high-voltage circuit breaker
Full text linkThe dynamic characteristics of operating mechanisms are of great significance to the reliability of high-voltage circuit breakers (HVCBs). To achieve dynamic analysis and optimization design of HVCBs, this paper presents a reduced-order digital twin model for a 252 kV HVCB under the OpenModelica simulation platform. To validate the effectiveness of the model, simulated closing and opening stroke curves are compared with experimental results, demonstrating the high efficiency and accuracy of the reduced-order digital twin model. Furthermore, a simulation analysis is performed to examine the mechanical dynamics of the HVCB under potential fault conditions, such as abnormal spring driving force. The analysis reveals that a reduction in the preload of the closing spring slows the operating mechanism’s movement, increases closing time, and may even cause closing failure. Similarly, a decrease in the preload of the opening spring reduces the moving contact’s speed, prolongs the opening time, and may result in opening failure. The proposed digital twin modeling method offers designers a systematic method for quantifying the dynamic responses of HVCBs
Anomaly detection method of traction motor bearing based on multi-scale sub-band fuzzy entropy manifold fusion index
Full text linkDetecting 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
Full text linkA 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
Full text linkThis 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
Energy analysis of living stumps slope based on Hilbert-Huang Transform and marginal spectrum
Full text linkA large-scale shaking table model test on a slope with living stumps was designed and conducted. Under various types of seismic waves and excitation intensities, acceleration data from monitoring points on both sides of the living stumps were collected. Hilbert-Huang Transform (HHT) was innovatively applied to study the dynamic response of slopes with living stumps under seismic loading, overcoming the limitations of traditional Fourier Transform and Wavelet Transform. The variation patterns of Hilbert energy and marginal spectral characteristics under different seismic excitations were analyzed, providing new insights from both time-frequency domain and energy perspectives. The research conclusion showed that: (1) Under different seismic waves, the horizontal peak acceleration inside the living stumps slope shows the elevation amplification effect, and increases with the intensity of excitation. Additionally, the existence of living stumps causes a difference in horizontal acceleration on both sides, and the absolute value of the difference is positively correlated with elevation and excitation intensity. (2) Under different seismic waves, Peak of Hilbert energy spectrum (PSHEA) is positively correlated with excitation intensity and elevation. With the increase of elevation, the increase of PSHEA increases gradually when the excitation intensity increases. PMSA is positively correlated with excitation intensity, but at low frequencies (1-3 Hz), Peak of marginal spectrum (PMSA) is negatively correlated with elevation; while at high frequencies (7-11 Hz), PMSA is positively correlated with elevation. (3) With increasing elevation and excitation intensity, the total seismic Hilbert energy continues to accumulate and reaches the maximum at the top of the slope. During the propagation of seismic waves, the living stumps and the rock-soil composite play the characteristics of filtering the low-frequency components and amplifying the high-frequency components, causing the total seismic Hilbert energy in the low-frequency (1-3 Hz) component to gradually decrease and transfer to the high-frequency (7-11 Hz) component, resulting in a significant increase in seismic Hilbert energy in the high-frequency component. (4) The superposition of incident wave and reflected wave near the living stumps, and the absorption of seismic Hilbert energy by the living stumps make the PSHEA, PMSA, and total seismic Hilbert energy on the outside of the living stumps always smaller than the inside, resulting in different dynamic responses on either side of the living stumps. The living stumps show attenuation effect on seismic Hilbert energy, and the attenuation degree increases with the increase of excitation intensity and elevation. The study provides a theoretical basis for the seismic design of living stumps slopes
Effect of Si addition on phase structure and wear resistance of CoCrFeMoNi alloy coatings
Full text linkCoCrFeMoNi high entropy alloy coating was prepared on Q235 substrate by plasma cladding method. The phase structure, morphology characteristics, element distribution, microhardness, and wear resistance for this alloy without and with Si doping were investigated by XRD, OM, SEM, EDS, microhardness tester, and friction-wear tester, respectively. The results show that CoCrFeMoNi alloy is composed of a single FCC phase, while Si-containing alloy is composed of FCC main phase and HCP phase. Both alloys have a typical dendritic structure. There is a layer of isotropic fine-grained region near the fusion line, and a columnar crystal region away from the fusion line. After adding Si element, the enrichment of Mo element in the interdendrite region and Co element in the dendrite region significantly decreased, which is related to the Si-containing alloy can provide a liquid environment with longer duration, lower viscosity, and greater fluidity. The change of Cr element enrichment from interdendrite region to dendrite region is the result of comprehensive competition of mixing enthalpy, atomic radius difference, electronegativity, density, and melt flowability between alloying elements. The friction coefficients of the two alloys show a rapid increase first and then gradually stabilize with the increase of time. After adding Si element, the hardness and wear resistance of the alloy are greatly improved, which is mainly related to the increase of the lattice distortion of FCC phase, the formation of high-strength HCP phase and the reduction of internal defects
Structure design and sensitivity analysis of flexible ultrasonic transducer array
Full text linkTo investigate the influence of element parameters on the performance and acoustic field of flexible ultrasonic transducer arrays, this study employs finite element multiphysics simulation software to analyze various parameters of flexible ultrasonic transducers within a multiphysics coupled field. The analysis begins with simulating the width and thickness of piezoelectric materials in a single-element ultrasonic transducer structure. Simulation results indicate that the electromechanical coupling coefficient of the ultrasonic transducer exhibits a quasi-sinusoidal relationship with width. When the piezoelectric material width is 1.8 mm, the electromechanical coupling coefficient reaches its maximum at a thickness of 0.4 mm. Subsequently, simulations were conducted on various parameters of the flexible ultrasonic transducer array. Key investigations included the effects of piezoelectric unit count, inter-unit spacing, and frequency on the ultrasonic focusing performance of linear phased array transducers. Findings indicate that the focusing capability of flexible ultrasonic transducer arrays improves with reduced spacing and increased unit count. However, due to varying practical application requirements and manufacturing precision constraints, array parameters should be selected by comprehensively considering real-world factors. Overall, this study employs multiphysics coupling simulation to visually demonstrate how array element parameters influence the performance of flexible ultrasonic transducers. It provides valuable reference for advancing flexible ultrasonic technology from laboratory research toward commercial application
Improvement of the system for reporting the state of the electrified railway contact line
Full text linkEnsuring the stable and reliable operation of electrified railways requires continuous monitoring of the overhead contact line (CL), whose mechanical displacement under wind loads can lead to interruptions in power transmission, pantograph detachment, and safety hazards. Traditional inspection and monitoring systems are limited in responsiveness and cannot provide real-time information about the dynamic state of the CL. This study presents an improved contact line deviation reporting system based on distributed Signal Processing and Transmission Modules (SPTM) and Signal Reception Modules (SRM) connected through a GSM wireless communication network. Each vibration sensor installed on the catenary wire continuously measures the displacement amplitude, converts the analog signal into digital form, and transmits it to the dispatcher or driver in real time. The developed modules were implemented using microcontrollers with embedded wireless interfaces, allowing autonomous operation powered by solar-assisted batteries and ensuring electromagnetic protection under high-voltage (25 kV) conditions. Field experiments were carried out on an electrified railway test section near the Tashkent depot to evaluate the system’s performance in real environmental conditions – including wind speeds of 5-18 m/s, ambient temperatures from –10 °C to +38 °C, and during snow and rain. The results confirmed stable data transmission up to 1 km distance with signal delay below 0.8 s and detection accuracy above 95 %. The proposed system thus enables real-time monitoring, automatic warning, and high reliability of communication even under harsh weather conditions, significantly improving the safety and efficiency of train operation. The novelty of this work lies in the practical validation of a GSM-based monitoring network for contact line deviation detection that integrates autonomous power supply, environmental robustness, and real-field reliability testing – aspects that are rarely demonstrated in previous studies
Rocking responses of free-standing rigid blocks on flexible foundation with a slope under earthquakes: structure-foundation interaction effects
Full text linkTo simulate the dynamic rocking responses of free-standing rigid blocks on a flexible foundation with a slope, a modified concentrated spring model (CSM) is proposed. The shaking table model test of a rigid steel frame structure was conducted, and the test results indicated that the rocking response of the structure can be effectively predicted by the proposed model. Utilizing the modified CSM, the interaction effects between the structure and foundation on the rocking of the free-standing rigid blocks on a flexible foundation with a slope were investigated. The influences of spring stiffness, viscous damping, and the frictional coefficient on the rocking of the rigid blocks under pulse-type ground motions were analyzed numerically. The results indicated that decreasing the spring stiffness and increasing the viscous damping coefficient of the modified CSM can reduce the number of impacts and rocking duration, while the friction coefficient has a significantly non-linear effect on the rocking response