Journal of Engineering and Thermal Sciences
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Identification and analysis of pavement structure features based on vibration behavior parameters
Full text linkTo clarify the correlation between the service performance of asphalt pavement structures and their vibration behavior parameters, this study focuses on asphalt pavement structures as the primary research subject. A quarter-vehicle two-degree-of-freedom model of a standard vehicle was selected as the simplified vehicle dynamics model, while a semi-rigid asphalt pavement was adopted as the simplified pavement model. Based on the elastic layered system theory, a three-dimensional finite element model of the asphalt pavement was constructed by using the software of Abaqus. The effects of modulus variations in asphalt pavement structural layers on modal frequencies were analyzed. The impacts of coupled working conditions, such as structural layer cracking positions and interlayer failure, on the modal frequencies of asphalt pavement were investigated. Additionally, the attenuation process of dynamic responses in asphalt pavement structures under transient impact loads was examined. Building on this, the dynamic response behaviors of asphalt pavement structures under working conditions including structural layer cracking and interlayer failure were studied. The results demonstrate that as the vertical depth of the asphalt pavement structure increases, the modulus attenuation of structural layers significantly affects the overall modal frequencies and vibrational effects. When internal cracking and interlayer failure coexist in the asphalt pavement structure, the vibration acceleration characteristics under load align more closely with those of interlayer failure, while the vibration displacement exhibits greater magnitudes
Research on fault diagnosis of electric motor rolling bearings based on CMFSE-SVM
Full text linkRolling bearings are key components of rotating machinery such as electric motors, and their health status directly affects the reliability and safety of the equipment. In order to improve the fault classification accuracy of electric motor rolling bearing, this paper proposes a diagnostic method based on CMFSE-SVM. Firstly, the composite multi-scale fuzzy slope entropy (CMFSE) method proposed in this paper is used to extract the characteristics of the vibration signal of the motor rolling bearings. Finally, the obtained feature vectors are sent to the support vector machine (SVM) for fault classification. This paper verifies the classification accuracy of the method proposed in this paper on two publicly available datasets of electric motor rolling bearing faults. The experimental results show that the method proposed in this paper achieves average classification accuracies of 100 % and 99.6 % respectively on all working conditions corresponding to these two datasets. And the classification accuracies were 2.4 % and 2.8 % higher respectively than those of the compared methods
Impact of underground near surface ore body mining on the stability of overburden and dangerous rock masses
Full text linkIn order to explore the impact of near surface ore body mining on the stability of overburden and surface dangerous rock masses, a Phosphate Mine was used as the engineering background. On-site investigation method was adopted to clarify the stability conditions of the surface dangerous rock. Numerical analysis software was used to simulate the evolution laws of overburden deformation, stress, and plastic zone. The research results indicate that the development of interlayer structural planes in the surrounding rock of the roof of the mining area can easily cause the collapse of the roof slab or sheet. The strata are hard and brittle in lithology, with developed rock fractures. Dangerous rock blocks are formed under the combination of fissures and rock layers. The mining disturbance generated during the mining process is relatively small. The impact on the rock layers, adjacent mining sites, and surface stability is weak. The surface is less affected by the mining of underground ore bodies and has not reached the maximum allowable value. Under the condition of first mining the ph1# ore body and then mining the ph2# ore body, the displacement of the overburden is relatively small. There is no distribution of connectivity in the plastic zone in the mining pillars, mining areas, and overburden. The research results can provide theoretical reference for the feasibility analysis of near surface ore body mining in similar mines
A method for automatically extracting harmonic features and its application in fault diagnosis of rolling bearing
Full text linkWith regard to fault diagnosis of rolling bearing, the envelope demodulation method is usually used to analyze the original vibration signal of faulty bearing, then the fault location of the bearing is determined by examining the distributions of fault characteristic frequencies, harmonics and sideband on the envelope demodulation spectral. The fault characteristic frequency with its harmonics could not be extracted by this traditional method when the original vibration signal is contaminated heavily by background noise. Besides, this method needs high professional knowledge and will expose drawbacks such as complex work, low diagnostic efficiency and so on while dealing with a large number of faulty bearings in engineering application. To solve the above problems, this paper proposes an automatic harmonic feature extraction method. Firstly, a series of bandpass filters are obtained based on fast Kurtogram, and then the original signal is filtered by the series of bandpass filters. The series of filtered signals are subjected to envelope analysis and noise reduction processing. Finally, the denoised series of envelope results are processed by the proposed algorithm for extracting the number of harmonics, harmonic intensity, and harmonic intensity index, and the target feature frequency and its harmonic components hidden in the original signal is extracted automatically. A simulation case and an engineering case verify that the proposed method can not only automatically calculate the number of harmonics of the characteristic frequencies, but also calculate the corresponding harmonic intensity, providing more effective and efficient feature support for fault diagnosis of bearing
Simulation and experimental study on dynamic response characteristics of vertical pipeline assembly
Full text linkThe preload of bolt connection affects the dynamic response of vertical pipeline structures, which has an important influence on the vibration and noise of hydraulic systems. Based on ANSYS, the finite element analysis model of the prestressed modal of the vertical pipeline connection unit was established. The clamp model was simplified by the equivalent stiffness test and fitting method. Under different preload torque conditions, the natural frequency and mode shape of the pipeline were solved. The modal test platform was established based on the hammering method to verify the error of modal calculation. The harmonic response analysis of the vertical pipeline was carried out, and the accuracy of the simulation analysis was verified by the frequency response test of the power flow parameters. The research results show that the preload load of the bolt has a limited influence on the modal characteristics of the connected pipeline. When the preload torque is about 8 N·m, the structural stiffness tends to be balanced, and under external excitation conditions, no large resonance amplitude will occur
Analysis of a 10 kW mini pumped hydro storage plant with solar integration in Uzbekistan
Full text linkThis paper presents the design and performance evaluation of a 10 kW mini pumped hydro storage (PSH) system integrated with solar photovoltaic (PV) energy for rural electrification in Uzbekistan. The system stores excess solar energy during the day and generates 60 kWh electricity during evening hours at a rated power of 10 kW, with an overall efficiency of about 75 %. The optimized design includes a Cross-Flow turbine (200 mm diameter, 600 rpm), a 10 m head, and 58 solar panels of 400 W. The study demonstrates that such small PSH systems can provide a cost-effective, long-lifetime alternative to chemical batteries in rural power applications
Design and simulation of a cable-driven elbow rehabilitation device
Full text linkWith the increasing prevalence of neurological and musculoskeletal disorders, the demand for effective rehabilitation technologies has grown. This study presents the AlmatyExoElbow system with a cable-driven exoskeleton for elbow rehabilitation with two degrees of freedom. The device was designed in SolidWorks CAD and tested in SolidWorks Motion to evaluate flexion/extension and pronation/supination trajectories. The design is simple, adaptable, and cost-effective, making it a promising candidate for future clinical integration and personalized therapy
Almaty ankle exoskeleton: comparative analysis and structural improvements of versions V.1 and V.2
Full text linkThis paper presents a comparative analysis of the V.1 and V.2 versions of the Almaty Ankle Exoskeleton. The main objective of the study is to identify the structural and functional shortcomings observed in the first version (V.1) and to develop an improved prototype in the second version (V.2) by addressing these issues. The paper compares the kinematic schemes, CAD models, and physical prototypes of both versions, highlighting their structural differences and technical advancements. In addition, the results of a static structural analysis performed on the V.2 prototype using the Finite Element Analysis (FEA) method are presented. This analysis allowed for the evaluation of stress, strain, and displacement distribution within the structure. The results demonstrated that the exoskeleton can effectively handle applied loads, although additional reinforcement is required in certain critical regions. Overall, the findings provide a foundation for engineering solutions aimed at enhancing the functional performance of the ankle exoskeleton and its application in rehabilitation processes
Advanced design strategies and applications for enhanced higher-order multisegment denatured pascal curve gears
Full text linkThe existing Pascal curve gears suffer from limited flexibility in pitch curves and restricted changes in transmission ratios. This has impeded the application in a range of mechanical systems that require more adaptable gear solutions. For this, a design procedure for higher-order multisegment denatured Pascal curve gear is proposed. This innovative design offers greater flexibility in pitch curves and allows for a broader range of transmission ratios. The analysis of the transmission ratio confirms the theoretical predictions and highlights the effectiveness of the proposed gear design in achieving variable transmission ratios. The transmission mechanism of the higher-order multisegment denatured Pascal curve gear is analyzed and the unified mathematical expression of the families of Pascal curve gear is derived. The non-circular gears with free-form pitch curves can be obtained from higher-order multi-segment denatured Pascal curves by adjusting design parameters to unify different types of pitch curves. This approach provides significant flexibility in achieving specific transmission characteristics. Then the transmission characteristics are discussed. To further validate the design, the visual analysis and design software of the higher-order multisegment denatured Pascal curve gear is compiled based on Visual Basic, and is verified with the example. The novelty Pascal curve gears is applied to drive the differential velocity vane pump. The displacement, instantaneous flow rate, and pulsation rate of the differential velocity vane pump are calculated. The novelty drive mechanism could meet the requirements and have good performance. The application shows that the higher-order multisegment denatured Pascal curve gear is feasible in practice
Dynamics analysis and experiment of banana-shaped vibrating-dewatering screen
Full text linkBanana-shaped Vibrating-Dewatering Screen (BVDS) is effective for dehydrate and demud sand aggregate, fine coal slime, ore and other materials. In this paper, the mechanical structure of the BVDS was revealed by means of theoretical modeling, simulation research and experimental test, and its dynamic and vibration characteristics were studied. The mathematical model was established, and the dynamic curve and spatial trajectory of the BVDS were obtained by MATLAB/Simulink software. Lissajous displacement diagram shows that the spatial motion trajectory of the shaker is an oblique line. The vibration test was carried out by using dynamic characteristic test system, and the dynamic characteristics of displacement, velocity and acceleration of the BVDS were revealed. Finally, through theoretical analysis, the changing trend of vibration characteristics of the BVDS with the increase of rotating velocity was obtained. The results show that the experimental data is basically consistent with the theoretical data, and the deviation is less than 6.58 %, which verifies the accuracy of the theoretical model. This paper provides a reference for the design and efficient operation of the BVDS