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Reduced-order modeling of digital twins for a high-voltage circuit breaker
Get PDFThe 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
Impact of underground near surface ore body mining on the stability of overburden and dangerous rock masses
Get PDFIn 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
Direct writing and parameter optimization of microchannels in glass microfluidic chips using RF CO2 laser
Get PDFMicrofluidic chips, featuring microchannels as key components, are crucial in chemistry, biology, and medical diagnostics. This study uses an RF CO₂ laser for direct writing on glass substrates, offering a cost - effective and fast fabrication method for microfluidic chip development. We investigated the RF CO2 laser’s energy distribution to set guidelines for processing line widths. Key parameters, laser power, processing speed, PPI, and repetition frequency, were studied for their effects on microchannel surface width and depth. We also examined how processing speed, laser power, and surface water films affect edge chipping on glass. Findings show that when PPI exceeds 2000 and processing speed is above 2000 mm/s, microchannel surfaces are smoother. There is a linear relationship between microchannel surface width/depth and laser power/repetition count. To minimize edge chipping, glass processing should remove internal stress, use high speeds, and apply low laser power. Edge chipping can undermine microchannel quality; thus, controlling processing parameters to reduce it is vital for high-quality microfluidic chip fabrication
A method for automatically extracting harmonic features and its application in fault diagnosis of rolling bearing
Get PDFWith 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
Implementation of lookup tables for different optimization strategies of semi-active car suspension system
Get PDFRoad irregularities and various vehicle loads influence comfort and safety levels. Owing to these changes, the driver cannot quickly and easily find the best driving parameters. Control of damping in a semi-active suspension adjusts the damping process in the vehicle to minimize the acceleration of the crew. This ensures comfort for them, influencing the level of fatigue of the driver and safe driving. A theoretical analysis was implemented using a mathematical full-car model in Simulink/MATLAB. We performed a simulation of a vehicle with all passengers passing various artificially generated road profiles at different velocities. We optimized the damping coefficient for the maximum comfort level using one, two, or four damping values, implementing different optimization strategies. The obtained research results were finalized by the conclusions
Research on modeling and dynamic characteristics of GTF transmission gearbox
Get PDFTaking a GTF star transmission gearbox as the research object, this paper innovatively introduces the Westgard decision diagram, which is widely used in medical clinical trials, and combines "relative error distance method of speed, transmission ratio and meshing force" to build a performance evaluation method of gearbox model based on multi-body dynamics. At the same time, the translation-torsional dynamics model of the gearbox is established by using the lumped mass theoretical method, and the key parameters such as output speed, gear meshing force and bearing vibration acceleration are obtained by the analysis of the two models. Comparing the simulation results of the multi-body dynamics model selected by the performance evaluation method with the analysis results of the concentrated parameter method, it can be seen that the performance of the multi-body dynamics model selected by the performance evaluation method is reliable and effective, and the analysis accuracy and analysis efficiency can be taken into account. The maximum absolute error of meshing force is 2.5771 N, and the absolute error of vibration acceleration at the bearing of input shaft and output shaft is controlled within 0.08 m·s-2 and 0.1 m·s-2, respectively. The model performance evaluation method proposed in this paper effectively solves the problem of the balance between simulation efficiency and accuracy of the traditional gearbox dynamics model, provides a new technical path for the performance evaluation of complex gear transmission systems, and provides a reliable theoretical basis and technical support for the design and optimization of gear transmission systems of high-end equipment such as aeroengines, and has important engineering application value
Research on rockfall scratch damage of FRP-coated oil and gas pipelines based on finite element method
Get PDFOil and gas pipelines, as vital arteries for energy transportation, play a crucial role in ensuring the supply of energy. However, under harsh geological conditions and external forces, the pipeline's anti-corrosion layer is susceptible to damage, particularly the destruction caused by external forces such as rockfall. This study focuses on the performance of a new type of anti-corrosion material-Fiber Reinforced Polymer (FRP) coating-under rockfall scratch, and compares it with Polyethylene (3PE) coating. By establishing a three-dimensional finite element model of the pipeline and rockfall, the study simulates the scratch process of rockfall on FRP and 3PE coated pipelines, analyzing the impact of various parameters on the coating damage. The results indicate that the FRP coating has a significant advantage in resisting rockfall damage, effectively dispersing and absorbing the impact force, thereby reducing damage. Moreover, parameters such as rockfall moving velocity, angle, penetration depth, and coating thickness significantly affect the degree of damage to the FRP coating. This research provides theoretical basis and technical support for the protection of oil and gas pipelines, which is of great importance for enhancing the safety and reliability of pipelines
Simulation and experimental study on dynamic response characteristics of vertical pipeline assembly
Get PDFThe 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
Vibration-resistant mixed binders using man-made burnt rocks for transport infrastructure
Get PDFThis study presents the characteristics of man-made wastes, specifically burnt rocks formed by the self-combustion of coal-bearing waste dumps, whose chemical and mineralogical composition depends on the origin of the basin. The aim of this research is to assess the feasibility of using these burnt rocks as components of mixed mineral binders and to evaluate their influence on mechanical and dynamic performance parameters. A comprehensive analysis of their physical, chemical, and structural properties was carried out, demonstrating their compatibility with conventional binder materials. The novelty of this study lies in the first systematic use of locally available burnt rocks (glyage) in vibration-resistant binder compositions for transport infrastructure, expanding the raw material base of construction materials while reducing environmental impact. The developed binders achieved compressive strengths up to 17.6 MPa, sufficient for structural layers of pavement bases and subgrade stabilization. Moreover, these mixed binders can modify the dynamic stiffness and damping behavior of pavement structures under moving vehicle loads, establishing a scientific link between binder composition and vibration control in transport engineering. These results are directly relevant to vibration engineering, as the dynamic stiffness and damping behavior of the developed binders influence vibration propagation and attenuation in transport pavements, ensuring longer service life and reduced noise and deformation under dynamic traffic loads
Kinematic synthesis of a cam-follower mechanism of a novel internal combustion engine
Get PDFThis paper presents a kinematic synthesis of a groove-type disk cam that directly drives sliders in a novel internal-combustion engine architecture. The synthesis is formulated in an invariant (normalized) space and enforces zero acceleration at phase boundaries while embedding a quasi-constant-velocity segment in the mid-portion of the compression (retraction) phase. An arbitrary shaping function is introduced to generate a family of admissible motion laws; a constrained optimization (series truncated to four terms) minimizes the peak acceleration under a prescribed bound on velocity, yielding a PLM with a quasi-constant-velocity interval of approximately 39 % of the kinematic cycle (±5 %). The synthesized retraction law is paired with a sinusoidal approach (power) law to ensure zero endpoint accelerations for both phases. Cam profiles for the working and return strokes are constructed; maximum pressure angles remain within admissible limits across examined phase splits, including an experimental 65°/25° case. Compared with the sinusoidal baseline, the synthesized law retains a similar acceleration constant but reduces the velocity constant by approximately 31 %, indicating lower inertial loading and milder end-conditions that are favorable for mixture preparation and bearing lubrication. The results provide a compact, implementable route to motion programming for cam-driven reciprocators in internal-combustion engines and establish feasibility for multi-cylinder layouts