Maintenance, Reliability and Condition Monitoring
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Random vibration analysis and mechanical performance research of large-span spatial structures using new building materials
Get PDFIn order to analyze the performance of large-span spatial structures made of new building materials, improve the seismic resistance of large-span spatial structures made of new building materials, analyze the random vibration of large-span spatial structures made of new building materials, and determine the mechanical properties of large-span spatial structures made of new building materials. The paper takes carbon fiber reinforced polymer (CFRP) as an example, and prepares CFRP large-span structural specimens through surface coating treatment of carbon fiber and composite material preparation process; Enhancement effect of interfacial bonding strength of CFRP large-span spatial structures through bidirectional shear experiments; Design large-span spatial structures of carbon fiber composite buildings and establish multi-scale finite element models of vibration reduction systems; Analyze the random vibration of large-span spatial structures, improve the Kanai Tajimi model through the random vibration power spectral density function, calculate the structural response power spectrum, analyze the response of CFRP large-span spatial structures through the H-V coherence function model, and verify the mechanical properties of CFRP material large-span spatial structure specimens through experiments. The test results show that after the tensile test, the CFRP specimen connecting plate did not fail, indicating that the CFRP specimen has a significant impact on its connection strength in this situation. However, the compression and shear failure of the CFRP large-span spatial structure specimen will occur in local areas due to the compressive action of the specimen
Research on fault diagnosis of rolling bearings based on multi-method fusion
Get PDFTo address the limitation that Variational Mode Decomposition (VMD) relies on empirical settings for the mode decomposition number K and penalty factor α, this paper proposed the RIME-VMD-KNN method for bearing fault diagnosis. Specifically, the RIME algorithm was used to intelligently optimize K and α of VMD, breaking the reliance on experience; Pearson Correlation Coefficient (PCC) was adopted to screen Intrinsic Mode Functions (IMFs) with high fault correlation for signal reconstruction, preserving key features; and the sample entropy of the reconstructed signal was input into KNN for fault identification. Experiments show that the optimization performance of RIME is superior to that of GA, GWO and AOA; the generalization ability is verified by supplementary tests on the XJTU-SY dataset; KNN is simpler and more efficient than SVM, proving the rationality of its selection; the confusion matrix and multiple random cross-validation confirm stability; and computing time and resource data are provided to verify the feasibility of embedded deployment. This method improves the reliability and real-time performance of diagnosis and has engineering value
Analysis of dynamic response characteristics of vehicle-mounted tank based on the finite element method
Get PDFThe vehicle-mounted tanks face prominent challenges in balancing dynamic safety, including vibration resistance and fatigue durability under complex transportation conditions. A rigid-flexible coupled finite element model, consisting of the base, tank body, and frame, was established. Vibration response analysis was conducted in accordance with ride comfort standards and road excitation requirements. Rigid-flexible coupled simulations were implemented with consideration of vertical acceleration inputs and road unevenness. For random vibration, power spectral density analysis demonstrated that the tank structure was prone to resonance in specific frequency bands. For structural optimization, key dimensions were selected as design variables, including vertical thickness, longitudinal thickness, middle width, and lateral width. An optimization mathematical model was established, and the Sequential Quadratic Programming (SQP) algorithm was adopted to solve the constrained nonlinear multi-objective optimization model. Through optimization calculations, the structure achieved 4.93 % reduction in mass, 37.3 % decrease in stress, and 37.1 % increase in the first-order natural frequency, thereby effectively balancing the requirements of lightweight design, structural strength safety, and anti-resonance performance. This study provided a comprehensive methodology for the dynamic analysis and optimization of vehicle-mounted tank containers, offered key technical support for advancing innovative studies in transportation and vibration engineering
Modal and optimization analysis of a 12-degree-of-freedom engine mount system considering engine elasticity
Get PDFThe multi-degree-of-freedom engine mount system presents a coupling issue that significantly impacting its vibration isolation performance. Although the optimization theories for decoupling 6-degree-of-freedom (6-DOF) and 12-degree-of-freedom (12-DOF) engine mount systems are relatively well-developed, previous studies have predominantly focused on engine response and often overlook the impact of car body vibrations. To address this gap, this article conducts an in-depth investigation into how the elasticity of the car body affects the vibration isolation performance of the engine mount system. Initially, the dynamics of the engine mount system are modeled with 6 degrees of freedom, incorporating an elastic base with 9 and 12 degrees of freedom, respectively. The study then analyzes how body elasticity influences the natural frequencies and modal shapes of the engine mount system. Subsequently, the sensitivity of the engine mount system is assessed using Isight analysis to evaluate the three directional stiffnesses of the mount. Finally, the decoupling optimization of the 12-degree-of-freedom engine mount system is performed using the NLPQL (Sequential Quadratic Programming) method. The findings indicate that: (1) considering the car body’s influence directly affects the natural characteristics and decoupling efficiency of the engine mount system; (2) body elasticity in the Z-direction has the greatest impact on the system’s vertical natural frequency; and (3) the NLPQL method effectively enhances the decoupling rate of the engine mount system
Dynamic behaviors and double-frequency synchronization analysis of a dynamic vibration absorption system driven by three co-rotating exciters
Get PDFThe recovery efficiency of drilling fluid is directly affected by working performance of the vibration screen. Therefore, a newly dynamic vibration absorption system driven by different excitation frequencies is designed through double-frequency synchronization theory to improve the mechanical performance of screening equipment. Firstly, the differential equations of motion of vibration system are deduced by Lagrange method. Then, the theoretical conditions of the system implementing double-frequency synchronization are obtained based on asymptotic method, and stability criterion of the synchronization is revealed according to Routh-Hurwitz criterion. Subsequently, the effects of structure parameters on vibration isolation ability, synchronous state, and stability of synchronization are numerically discussed. Finally, the feasibility of the theoretical method and the obtained results is further verified by simulation and experiment. It is found that the vibration isolation and synchronization performance of the system is influenced by the motor parameters and system structure. The system has the best vibration isolation ability when ωm0= 157 rad/s, which is considered as the best operating frequency of the present vibration system. Meanwhile, when the mass ratio κ between the high-frequency co-rotating rotor and the low-frequency co-rotating rotor is smaller, the absolute value of the stability coefficient Si is larger, and the stability phase difference is smaller, and the system is more stable. The present work can provide theoretical direction for the design of new screening equipment
Study on the effect of suspension system friction of heavy-haul freight vehicles on the operation performance
Get PDFDuring the operational life of heavy-haul freight vehicles, the long-term wear between components can affect the suspension parameters. Suspension system wear has a significant effect on the dynamic performance and wheel wear. Experimental tests are performed to measure the changes in suspension system parameters after wear. A dynamic model and wheel wear model of the heavy-haul freight vehicles were established to analyze their dynamics and wheel wear performance. The results showed that with the wear of the suspension system, the stiffness parameters further increase. The dynamic performance of the vehicle system deteriorates after suspension system wear, with a decrease in the critical speed and an increase in safety and ride indexes. The analysis also reveals that the wheel wear increases as the stiffness parameters increase after the suspension system wear. This paper provides a basis for maintaining heavy-haul freight vehicle suspension systems
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
Numerical simulation of chloride ion transport in concrete based on a random aggregate model
Get PDFA three-dimensional stochastic aggregate model of concrete was established using the Monte Carlo method, and a numerical simulation of chloride ion diffusion at the microscopic level was conducted. The study investigated the migration behaviour of chloride ions in concrete regarding mixing proportions and temperature. The results showed that compared to the simulation results at an ambient temperature of 20 ℃, the chloride ion diffusion coefficient increased by 31 % and 70.5 % for concrete at 25 ℃ and 30 ℃ at 28 days, respectively. The chloride ion penetration depth increased by 17.3 % and 34.9 % for concrete at 25 ℃ and 30 ℃, respectively. With a slag content of 10.4 %, 20.8 %, and 27.1 %, the chloride ion diffusion coefficient at 28 days decreased by 1.4 %, 2.7 %, and 4.1 %, respectively. With a fly ash content of 8.3 %, 16.7 %, and 25 %, the chloride ion diffusion coefficient at 28 days decreased by 2.1 %, 5.4 %, and 9.2 %, respectively. Both slag and fly ash can reduce the chloride ion diffusion coefficient in concrete, with fly ash showing better effectiveness than slag. A water-to-binder ratio of 0.4, combined with 27.1 % slag and 25 % fly ash as cement replacements, can effectively improve the resistance of concrete to chloride ion attack. The micro-scale finite element model of concrete, developed through Monte Carlo simulation, offers enhanced visualization of chloride ion penetration processes under varying mix proportions and temperature conditions
Enhancing sound absorption of Helmholtz resonance metamaterials with extended microperforated neck
Get PDFTo enhance sound absorption of Helmholtz resonance metamaterials in low frequency region with simple structure and engineering practicability, according to the well-established acoustic absorption theory of micro-perforated panel, a novel designed Helmholtz resonance metamaterial with extended microperforated neck is proposed, and a theoretical modelling method is developed by using the transfer matrix method which is validated by finite element simulation. Both theoretical calculation and finite element simulation results show that sound absorption performance of proposed Helmholtz resonance metamaterial is improved significantly compared to that of Helmholtz resonator with normal neck, and the resonant absorption coefficient is close to 1. The influence of geometric parameters of microperforated neck is also investigated in detail, and some meaningful conclusions are drawn. This work provides a perfect solution for low-frequency noise control with Helmholtz resonance metamaterials
Enhancing loess deformation resistance using waste tire rubber particles
Get PDFLoess, characterized by its large pore structure and vertical joints, is prone to collapsible deformation upon moisture infiltration and significant settlement under load, threatening the stability of buildings and infrastructure. This study systematically investigates the effects of rubber particle size (10, 20, 40, and 100 mesh), content (0 %, 5 %, 10 %, 15 %, and 20 % by volume), moisture content, and freeze-thaw cycles on the deformation properties of loess. This systematic investigation distinguishes itself by using waste tire rubber particles as the sole amendment to elucidate both the individual and coupled effects of these factors. Results demonstrate that incorporating rubber particles significantly reduces the compression coefficient of loess, with optimal compressibility achieved at a 5 % rubber particle content and 40 mesh particle size. The collapsibility coefficient is minimized at a 20 mesh particle size with the same 5 % content. Moisture content significantly influences deformation behavior, with both high and low levels increasing the compression and collapsibility coefficients. The study also reveals that rubber particle-loess mixtures exhibit superior freeze-thaw resistance, with smaller increases in deformation coefficients after multiple freeze-thaw cycles compared to remolded loess. The particle size and content of rubber particles are identified as the most important factors influencing the compressibility and collapsibility of loess. This research provides specific guidelines for optimizing rubber particle size and content, controlling moisture levels, and evaluating freeze-thaw impacts to enhance the engineering performance of loess. The findings offer a scientific basis for sustainable waste tire management and advance the application of rubber particles in geotechnical engineering