Journal of Engineering and Thermal Sciences
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LSGAN-Transformer life prediction method for rolling bearings under few samples
Get PDFAiming at the problem that it is difficult to obtain a large amount of data for bearings with complex working conditions, which leads to the inability to accurately predict their life, a rolling bearing life prediction method based on few samples, LSGAN-Transformer, is proposed. A dropout layer is added to the LSGAN generator to avoid the overfitting phenomenon that often occurs during few-sample training. The normalization of each layer in the traditional Transformer model is moved forward to the input of the decoder and encoder submodules before the residual network, forming a direct gradient path from input to output, avoiding the problem of excessive expected gradient near the output layer that often occurs in the traditional Transformer network. Verification on the PHM2012 dataset and the XJTY-SY dataset shows that the MAE and RMSE of the proposed method are greatly improved; compared with other common prediction models, the MAE and RMSE of the proposed method are improved by 30.61 % and 35.93 % respectively
Modal analysis of harmonic drive reducer based on ANSYS
Get PDFModal characteristics are critical indicators for assessing the stability of harmonic reducer and serve as an essential basis for structural optimization. Based on the structure and working principle, the finite element model of harmonic reducer was systematically established and appropriately simplified. According to Block Lanczos method, the natural frequencies and mode shapes of the flexible gear and rigid gear under free boundary conditions were obtained by ANSYS. The single-factor analysis method was employed to investigate the influence of structural parameters of the flexible gear on its natural frequency and torsional stiffness. Results indicate that the natural frequency of the flexible gear increases with the length and wall thickness of the cylindrical section. Although the natural frequency of the flexible gear is lower than that of the rigid gear, it remains higher than the working excitation frequency, thus avoiding resonance. Additionally, the maximum stress in the flexible gear decreases with increasing tube length and wall thickness, which contrasts with the trend observed for torsional stiffness
Aeroelastic stability analysis and optimal PID control strategy simulation for large-scale HAWT blades
Get PDFAiming at the classical flutter problem of wind turbine blades, a wind turbine blade aeroelastic model is constructed based on the typical leaf cross-section model of spring-mass-damper and the classical flutter aerodynamic model. The stability analysis of the wind turbine aeroelastic model is carried out using the Liapunov indirect method, and the effects of different parameters on stability are compared. Combining the aeroelastic model with the second-order model of pitch exciter, the pitch aeroelastic equation of the system is given, and the system controllability is analyzed. The optimal PID pitch control is designed, and the Simulink simulation is performed to explore the optimal combination under different combinations by selecting the torsion angle and waving displacement as the error signals, and different combinations of the torsion angle, waving displacement, and pitch angle as the optimal control objectives, respectively. The simulation results show that when the torsional angle is used as the error feedback signal and the torsional angle is set as the optimal control objective, it is the only scenario without overshoot. The overshoot in other cases ranges from 30 % to 500 %. In terms of adjustment time, this scenario also demonstrates good performance. Although it is not the fastest, the gap from the fastest is no more than 20 %. Therefore, using the torsional angle as the error feedback signal and the torsional angle as the optimal control objective is the best choice
Dynamic detection and evaluation of wheel flats in heavy-haul railway wheelsets using wayside monitoring systems
Get PDFIn recent years, heavy-haul railways have become a critical direction for freight transport in China, with wheel flats in wheelsets posing significant threats to operational safety and infrastructure integrity. Traditional detection methods (e.g., manual inspection, TPDS) suffer from low efficiency or limited accuracy in characterizing flat features. To address this, this study develops a rigid-flexible coupling dynamic model for C80 wagons with K6 bogies, uniquely integrated with field data from the Truck Operation Detection System (TODS) to bridge simulation and engineering application gaps. Focusing on wheel-rail force responses under wheel flat conditions, we establish a quantitative mapping relationship between flat length, vehicle speed, and impact force through polynomial fitting of simulation data (10-80 km/h for empty/loaded vehicles). To validate feasibility, a 56-channel wayside monitoring system (TODS) is installed on a heavy-haul railway, calibrated via hydraulic loading to ensure measurement accuracy. Field tests (80,541 vehicles monitored) confirm that TODS can infer flat length from detected impact forces, with results consistent with TPDS alarms but offering finer characterization of flat dimensions. This work provides a practical solution for real-time wheel flat detection, enhancing maintenance efficiency and safety in heavy-haul operations
Experimental and finite element analysis of the structural durability of special self-propelled rolling stock frames
Get PDFThe study presents an experimental-numerical assessment of the structural durability and residual life of the ADM-1 self-propelled railcar frame operating under cyclic and static loading conditions. A combined methodology integrating full-scale cyclic bench testing and finite element modeling (FEM) was developed to determine the frame’s stress–strain state and fatigue resistance. The experimental tests, performed at the accredited laboratory of “Quyuv Mexanika Zavodi” JSC using the ISRB-1000 hydraulic loading stand, simulated real operational loads up to 2×106 cycles, equivalent to approximately ten years of service. A detailed FEM model was created in SOLIDWORKS Simulation to replicate these loading conditions, analyze stress distribution, and validate experimental data. The numerical and experimental results showed strong correlation (r > 0.9) with a deviation below 8 %, confirming the accuracy of the proposed approach. The maximum equivalent (von Mises) stresses remained below 0.6σ0.2 for St3sp steel, indicating that the structure operated entirely within the elastic range and met the strength requirements of GOST 31846-2012. Fatigue life estimation using Miner’s cumulative damage rule yielded a damage factor of D= 0.72, corresponding to 8-12 years of effective service life, with a residual fatigue resource of approximately 35-40 %. The developed hybrid methodology provides a reliable framework for condition-based maintenance and life-extension of special self-propelled rolling stock
The technology of non-stop passage of high-speed passenger and freight trains on double-track sections and its impact on operational performance
Get PDFCurrently, a mixed system of high-speed passenger and freight trains has been implemented on the railways of Uzbekistan. During the movement of high-speed passenger trains on double-track main line sections, the movement of freight trains at all stations and segments is temporarily suspended for a specific period. From this perspective, in the present time, the suspension of freight train traffic is leading to numerous technical and economic expenses. In this article, based on experimental runs using the technology of passing freight trains without stopping, train movement schedules have been drawn up, and train operations have been organized without unnecessary stops. This research paper provides a restructured overview of the introduction and practical implementation of non-stop train operation technology for double-track railway lines where both high-speed passenger and freight trains operate simultaneously. Using real operational schedules, comparative experimental charts were developed to evaluate the new approach. The outcomes of this analysis demonstrate how the proposed technology influences efficiency and key performance indicators of train movements. A regression-based analytical model was also constructed to determine the relation between freight train waiting time and average section speed, ensuring reliability through statistical verification. Furthermore, the application of innovative solutions and technologies mentioned in this article to sections of high-speed highways creates an opportunity to increase transport transit potential and improve economic indicators
Performance assessment of network system network comprising four subsystems via multi failure and multi repair methodology
Get PDFA multi-dimensional repair approach is the most effective policy for restoring repairable systems. This research study analyzes a complex repairable system that consists of four subsystems with different configurations. The system consists of four subsystems: Subsystem 1 contains a single unit, Subsystem 2 includes n identical units operating under a k-out-of-n: G policy, Subsystem 3 features two identical load balancers responsible for distributing the load (with at least one required for operation), and Subsystem 4 consists of four identical units functioning under a 3-out-of-4: G policy. It is assumed that all subsystems have constant failure rates that are distributed exponentially. General repair, which is utilized while the system continues to function in accordance with the established operating policy, and copula-based repair, which is employed when the system stops completely, are the two types of repair techniques that are put into practice. A supplementary variable approach is incorporated to analyses system performance. Various reliability measures are computed using Maple 18, software, and future behaviour of system have been predicted in long run operation. By means of illustrations in the tables and graph it clearly shown how the copula repair is beneficial over ordinary repair
The relationship between shaft vibration and bearing vibration under imbalanced state based on homologous information fusion under imbalanced state
Get PDFShaft vibration and bearing vibration are important parameters reflecting the dynamic behavior of the rotor-bearing-supporting system, and they have a significant impact on the operating state and safety of equipment. However, obtaining relevant signals of shaft vibration or bearing vibration often faces many challenges in actual working conditions, mainly due to the limitations of measuring equipment, environmental interference, and the complexity of operating conditions. Therefore, understanding the correlation between shaft vibration and bearing vibration can not only realize signal complementarity and improve the comprehensiveness and accuracy of data, but also provide a more accurate basis for fault diagnosis and condition monitoring. Therefore, this study constructs an unbalanced fault dynamics model based on the short-bearing theory. The shaft vibration and bearing vibration signals predicted by the model are obtained through the numerical integration technique. Secondly, the full-vector spectrum technology based on homologous information fusion is adopted to conduct a two-channel fusion analysis of these signals. Finally, a rotor experimental platform is constructed and corresponding experimental verifications are carried out to verify the accuracy of these analysis results. The experimental results confirm that obtaining this complementary relationship enables us to infer the operation health state of equipment through the changing trend of some parameters even in the absence of a certain measurement signal, and then formulate corresponding maintenance and management strategies, thereby improving the reliability and operating efficiency of equipment
Improving the technical and economic performance of diesel engines for shunting locomotives
Get PDFAn experimental verification of the effectiveness of applying a compromise fuel injection advance angle (FIAA) was conducted on a test stand for a PD1M type diesel generator unit. The study included an analysis of injection pressure changes at various FIAA values, as well as tests of the installation with the ESUVT.01 electronic fuel injection control system under load. Additionally, modeling of the diesel engine’s working process was performed using the “Diesel-RK” software package, followed by processing of the obtained data. Comparison of test results in locomotive characteristic modes at fuel injection advance angles of 14° and 29° crankshaft rotation showed that using a compromise FIAA value ensures a reduction in the locomotive’s average operational fuel consumption by 7-10 %, depending on operating conditions. Furthermore, decreasing the advance angle positively affects the reduction of maximum cylinder pressure and exhaust gas temperature, indicating an increase in the overall effectiveness of this approach
Analysis of progressive collapse of low-rise concrete frame structure under double earthquake in Türkiye
Get PDFThe double earthquake that struck Türkiye on February 6, 2023 killed over 50,000 people. It also caused the collapse of thousands of low-rise reinforced concrete structures in the seismic area, resulting in incredible damage. To study the reasons for the progressive collapse of numerous buildings, a nine-story concrete frame structure was established in this study, and the elastic-plastic time-history analysis under the double earthquake was performed. The element failure criterion was defined using the max equivalent compressive strain, refining the damage initiation point and transmission path of the proposed structure. The results showed that: 1. The natural period of vibration of the low-rise concrete frame structure in the seismic area is in the peak spectral acceleration region of the first earthquake, which maximizes the earthquake damage force. 2. The first strong earthquake disabled the main load-bearing columns on the ground floor of the structure, resulting in collapse within a few seconds of the second earthquake. 3. The seismic damage investigation showed that the low-rise frame structure had insufficient longitudinal reinforcement laps, insufficient transverse reinforcement and stirrups, and weak embeddedness between longitudinal bars and concrete. These issues have amplified the damage degree. 4. Despite the comprehensive building seismic regulations in Türkiye, the most pressing problem may be the long-term regulatory failure of the authorities