Maintenance, Reliability and Condition Monitoring
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Mathematical modeling of the possibility of creating interresonance discrete-continuous vibration technological equipment without a spring
Get PDFIn the article is implemented interresonance mechanical oscillating system vibrational technological equipment, which provides using two continuous of connected area successively to working body vibrational machines. Disturbance of the structure is carried out by applying a variable-sign power supply voltage to the reactive continuous section, where in interaction with the magnetic field from the permanent magnets, a variable-sign disturbance force occurs. Inertial forces from the reactive continuous section are transferred to the intermediate continuous section, which resonates with the working body. In fact, an interresonance discrete-continuous oscillating system is obtained in which there are no springs. The function of springs is performed by bodies with distributed parameters that have elastic properties. Based on the Krylov-Duncan functions, a system of equations was formed that establishes the amplitude of oscillations of the working body. The amplitude-frequency characteristic of the discrete-continuous system was studied, which confirms the possibility of creating interresonance oscillating systems of vibrating technological equipment without springs
Numerical analysis of the influence of air flow channel on ear pressure during door closure
Get PDFIn this paper, Numerical simulation analysis was conducted on the ear pressure of a certain vehicle model during door closing process. Firstly, relevant airflow channel parameters are formulated based on the benchmark vehicle data, and transient closing ear pressure simulation calculation is carried out using overset grid technology. Then, the impact of key structural parameters on the interior ear pressure of the car was analyzed. Finally, based on the requirements of actual engineering design, the design scheme for the peak pressure of the car was determined, and the results will be a reference for the development and design of later vehicle
Dynamics analysis and collaborative optimization of vehicle steering mechanism
Get PDFIn order to improve the dynamic response characteristics of the steering mechanism, a research scheme for increasing the natural frequency based on lightweight design was proposed. Based on the finite element method and the collaborative optimization method, the modal characteristics and harmonic response characteristics of the model were studied and analyzed to verify the strength and stiffness performance of the optimized structure. The modal shapes between the free mode and the constrained mode were compared and analyzed. With the second-order natural frequency as the optimization objective, the response surface function of the equivalent stiffness was constructed. Through optimization calculation, the design variables that satisfy the constraint conditions can be obtained. The results show that the optimized structure can increase the second-order natural frequency by 14.4 % on the premise of reducing the mass by 5.2 %, effectively avoiding the excitation frequency of the engine
Finite element analysis of rockfall impact on pipelines with different erosion resistant coatings
Get PDFIn this paper, the finite element analysis method is used to extensively study the response of rockfall impact on pipelines with different erosion resistant coating. Based on the numerical results, the safety of the pipeline is comprehensively evaluated. Firstly, through the establishment of detailed pipeline and rockfall models, the impact of different rockfall materials and speeds on the pipeline is simulated. The results of the finite element analysis indicate that rockfall impact can cause significant stress concentration and deformation in the pipelines and damage to the coating. With the increment of impact speed, the damage to the pipeline also increases significantly, and different rockfall materials exhibit varying damage conditions, and it is found that fibreglass reinforced epoxy is better than the polyethylene coating. By comparing the analysis results under different conditions, the safety threshold of the pipeline under various rockfall impact scenarios is obtained. This provides an important theoretical basis and reference for the protection design and safety maintenance of the pipeline. The research in this paper not only aids in deepening the understanding of the mechanism of rockfall impact on pipelines but also serves as a valuable reference for improving the safety and reliability of pipeline engineering
Experimental study on the influence of different curing methods on the performance of concrete
Get PDFCuring concrete is an effective method to ensure concrete’s mechanical and durability performance. This article experimentally investigates the impact of various curing methods (air curing, sprinkler curing, geotextile curing, and composite geotextile curing) on the compressive strength of concrete at 7, 14, and 28 days, as well as the carbonation depth and chloride ion diffusion coefficient at 28, 56, and 90 days. The effects of different curing methods on concrete performance are compared. The experimental results demonstrate that sprinkler, geotextile, and composite geotextile curing at 7 and 14 days effectively enhance concrete’s mechanical and durability performance. Compared to air curing concrete at 28 days, sprinkler, geotextile, and composite geotextile curing reduced by 17.75 %, 25.11 %, and 31.51 %, respectively, but the average absolute deviation is reducing. From 28 to 90 days, air curing concrete’s chloride ion diffusion coefficient decreases by 8.5 %. For concrete specimens under sprinkler curing, geotextile curing, and composite geotextile curing, the chloride ion diffusion coefficient decreases by 20.4 %, 8.3 %, and 6.0 %, respectively. Beyond 28 days, the durability performance of concrete under composite geotextile curing, including carbonation depth and chloride ion diffusion coefficient, tends to stabilize. The optimal curing period of 28 days is determined based on comprehensive mechanical and durability performance. Composite geotextile curing retains moisture on the concrete surface, slows evaporation, reduces watering frequency and labour costs, and promotes long-term concrete performance development. Carbonation tests and durability performance, such as chloride ion diffusion coefficient, are more sensitive to concrete curing effects. Single indicators like mechanical or durability performance cannot comprehensively evaluate concrete’s long-term performance. Concrete quality should be comprehensively evaluated by considering strength, carbonation depth, chloride ion diffusion coefficient, and other indicators
Research on the relationship between feature extraction time and training samples of hyperspectral image based on spatial domain
Get PDFHyperspectral image (HSI) feature extraction is an important means to improve the classification of different ground features. According to the structural characteristics of hyperspectral data, the general feature extraction scheme can extract features from the point of view of spectral dimension, spatial and spatial spectrum. And the feature extraction time is also an index to measure the feature extraction method. Therefore, from the perspective of spatial dimension, this paper explores the relationship between HSI feature extraction time and training sample ratio. Three groups of HSIs sets were used for correlation test and analysis in the experiment. According to the characteristics of different data sets, the best selection scheme between spatial domain feature extraction method and training samples is given
Constructing the schematic and mathematical model of the dynamics of a vibratory drum separator
Get PDFA structural diagram of a vibratory drum separator has been developed, and based on it, a mathematical model of the separator’s oscillatory motion has been constructed. The mathematical model was built using nonlinear mechanics methods and Lagrange equations. The obtained dependencies allow for determining the influence of geometric and physico-mechanical parameters on various factors affecting the intensity of the separation process. The research results should be used both at the design stages of vibratory separators and when selecting their parameters and operational modes
A broadband variable fluid damper with frequency selective valves for spacecraft micro-vibration isolation
Get PDFIn order to improve the vibration isolation performance of current three-parameter damper using bellow and fluid damping, a concept of fluid damper with variable damping and secondary variable stiffness was proposed, a prototype has been designed with several frequency selective valves to adjust the damping characteristics at specific frequency bands, especially that in the low-frequency range. Followed mathematical modelling and simulation of the damper have been carried out, the results show that the designed damper has obtained excellent damping characteristics both in the high- and low-frequency ranges, the micro-vibration isolation efficiency of the damper under realistic excitation of a Control Moment Gyroscope used in a manned spacecraft reaches a significant 71.03 %.The proposed damper concept and designed prototype have laid the foundation for further testing and optimization of high-end isolators for modern spacecrafts
Application of modal analysis to multi-objective optimization of gear box
Get PDFThe high stiffness and low mass gearbox structure design requirements were met through multi-objective optimization based on finite element modal analysis. The correlation between structural parameters and optimization objectives was identified, providing guidance for optimal design. A parametric finite element model of the box cover was established to calculate the first-order modal shape and equivalent stiffness. By using mass and equivalent stiffness as optimization objectives, a discrete data set was constructed with key dimensions of the box cover as design variables, from which a surrogate model was obtained. Standard response surface and full second-order polynomial fitted response surface function were applied after error verification. Different optimization algorithms were employed to search for the optimal value, resulting in obtaining design variables meeting the optimization objectives. The results indicated a reduction in optimized mass by approximately 6.8 %, with an error of less than 1 %
Investigation of the propagation characteristics of train-induced vibration at Guangzhou Baiyun railway station
Get PDFIn densely populated cities, the increasing popularity of railways and urban rail transit interchange hubs has led to the extensive use of land resources and raised concerns about the environment, especially the inevitable noise and vibration impact. This study aims to identify the propagation patterns of roof structure vibrations in railway complexes through experimental research, with the premise of maintaining normal train operation and safety, in order to lay a foundation for developing vibration mitigation strategies and optimizing functional layout. The results found that the train-induced vibrations are strongest at track level, but decrease as they move vertically and horizontally. Vibrations from passing trains are most noticeable within a single floor slab and beams, with minimal transmission at the base of columns