最新刊期
卷 47 ， 期 6 ， 2025
- 摘要：When the gear system starts or stops in non-stationary working conditions, a sharp change of the speed can cause it to exhibit complex vibration characteristics which has a significant impact on the performance and lifespan of the gear. Considering the influence of time-varying meshing stiffness, backlash and gear meshing error, a dynamics model of spur gear system was established. The influence of external load and angular acceleration on the vibration characteristics of the start-stop process was studied. At the same time, the time-frequency analysis of the non-stationary vibration signal of the gear system was carried out by using the short-time Fourier transform. The results show that increasing the load and angular acceleration during the start and stop processes will exacerbate the degree of vibration and impact of the gear pair, and both will make the unstable motion process in the early start period end earlier, and the unstable motion process in the late stop period appear later, but the impact components in the late start period (the early stop period) will increase (decrease). In the frequency domain, increasing the external load will enhance the energy of the harmonic component of the gear system’s meshing frequency, but it has no effect on the fundamental energy of the meshing frequency. However, increasing the angular acceleration will enhance the energy of both the fundamental and harmonic components of the meshing frequency.关键词：Gear system;Dynamics;Start-stop process;Short-time Fourier transform;Vibration characteristic2|0|0更新时间：2025-06-09
- 摘要：Gear’s Circular plot is a result presentation method which needs to be combine with time synchronous averaging (TSA), which can clearly display gear meshing vibration waveform extracted by TSA. Aiming at the problem of parameter setting of gear’s Circular plot and lack of the quantitative index, Fi index for waveform edge recognition and Yi index based on Hu-moments were proposed. Firstly, TSA algorithm was used to extract the gear meshing vibration signal, and the upper and lower edges of the vibration signal waveform were determined by calculating the minimum Fi index.Secondly, Circular plot of gears were drawn by the upper and lower edge parameters. Then, the Circular plot of the gear was divided into four parts, and Yi index of the Circular plot was obtained by calculating Hu-moments of the picture after segmentation. Finally, based on the Yi and Fi indices extracted from the gear Circular plot, a K-nearest neighbors (KNN) classifier was utilized to classify the gear vibration signals. The results show that there is a significant difference between the Yi and Fi indices of the vibration signals of normal gears and those of abnormal gears. By combining with the KNN classifier， it is possible to distinguish between normal and abnormal gear signals， which proves the effectiveness of this method.关键词：Gearbox;Gear Circular plot;Characteristic index;Intelligent fault diagnosis2|0|0更新时间：2025-06-09
- 摘要：To overcome the difficulty in early fault diagnosis with weak fault characteristics of rolling bearings that are easily drowned out by noise in the complex operation environment, an early fault diagnosis method was proposed by integrating the improved artificial gorilla troops optimizer (IGTO) algorithm, the optimized resonance-based sparse signal decomposition (RSSD), multi-parameter and sparse maximum harmonics-to-noise-ratio deconvolution (SMHD) method. Firstly, taking the squared envelope spectrum correlated kurtosis (SE-SCK) negative value of the low resonance component as the objective function, IGTO was used to simultaneously optimize the quality factor
- 摘要：During the gear meshing process, the driving speed plays a crucial role in evaluating mesh stiffness, a factor that many scholars often overlook along with the accompanying centrifugal effects. Based on Euler beam theory,a original computational algorithm was proposed to calculate the dynamic mesh stiffness of spur gears considering driven-speed effects by introducing centrifugal effects into the velocity field. Using the driving speed as a control parameter, the dynamic mesh stiffness in relation to driving speed was investigated, and the nonlinear relation between centrifugal effects and dynamic mesh stiffness was demonstrated. The results indicate that, under the influence of a centrifugal field, both the natural frequency and the dynamic mesh stiffness of the gears increase with rising driving speed. Additionally, materials with a high elastic modulus tend to suppress the impact of driving speed on dynamic mesh stiffness, while higher density has the opposite effect. The research results provide reference for further analysis of gear vibration and noise under centrifugal effects.关键词：Dynamic mesh stiffness;Centrifugal effect;Driving speed;Gear material;Frequency analysis2|0|0更新时间：2025-06-09
- 摘要：In response to the problem of the gearbox fault diagnosis and analysis based on multi-sensor data under dataset imbalanced conditions, a gearbox fault diagnosis method based on a kurtosis index data fusion and a generative adversarial neural networks (GAN) was proposed. This method weighted the fusion of multiple sensor data based on signal kurtosis, highlighting the fault sensitive components of the gearbox in the fused signal. Then, a wavelet packet transform was used to extract the energy coefficients of each frequency band of the signal as signal features. Finally, the classification and recognition of signal features were implemented based on a back propagation (BP) neural network. Due to the fact that in actual working conditions, fault signals were more difficult to obtain than normal signals, GAN was used to expand the fault data section of the dataset, and the expanded dataset was used to train BP neural network. Through test analysis, it is shown that the fault accuracy of the described method is as high as 98%, which verifies the correctness of the proposed method and provides new ideas and methods for multi-sensor data fusion and fault diagnosis problems.关键词：Multi-sensor;Data fusion;Fault diagnosis;GAN2|0|0更新时间：2025-06-09
- 摘要：In response to challenges such as large sampling data, extended diagnosis time, and subjective fault feature selection in traditional bearing fault diagnosis, based on compressed sensing (CS) and deep multi-kernel extreme learning machine (D-MKELM) theory, a CS-DMKELM intelligent diagnosis model for rolling bearings was proposed. Firstly, sparse signals were obtained through threshold processing of transformed domain signals. A Gaussian random matrix was employed as the measurement matrix to compress the processed data. Secongly, the compressed data was used as the input signal for the D-MKELM. Particle swarm optimization (PSO) algorithm was applied to optimize critical parameters, enabling intelligent fault diagnosis. Results demonstrate that the proposed method, using only a small amount of bearing diagnostic data, automatically extracts feature information of bearings from a limited number of measurement signals through the D-MKELM. The proposed method enables rapid fault diagnosis of bearings. With a diagnostic time of 0.55 s, a final recognition accuracy of 99.29% was achieved. The proposed method reduces the diagnostic time and exhibits the high diagnostic accuracy, providing a new approach for handling massive bearing data in the fault diagnosis.关键词：Compressed sensing;Bearing;Kernel function;Extreme learning machine;Fault diagnosis29|23|0更新时间：2025-06-09
- 摘要：In order to solve the problem of difficult to accurately extract early faults of solar wheels under the strong noise background, an improved grey wolf algorithm (newGWO) was proposed to optimize and improve the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) and the maximum correlated kurtosis deconvolution (MCKD) for early fault feature extraction of solar wheels.NewGWO was used to optimize the selection of parameters of the white noise amplitude weight and noise addition times that affected the decomposition effect.The fault vibration signal was decomposed by newGWO-ICEEMDAN, and the minimum envelope entropy was selected as the fitness function to obtain several related modal components.Then, the envelope spectrum peak factor was selected as the best modal component index.MCKD signals optimized by newGWO were enhanced for the selected optimal intrinsic mode function （IMF） components. Finally, an envelope demodulation analysis was performed on the obtained signals to extract the solar wheel fault characteristic frequency and multiple frequency components. Simulation signals and experiments show that this method can make the early fault impact characteristics more obvious, and realize the early fault characteristic frequency extraction of solar wheels.关键词：Solar wheel;Early fault;Feature extraction;NewGWO;ICEEMDAN;MCKD2|0|0更新时间：2025-06-09
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RESEARCH ON FREE VIBRATION CHARACTERISTICS OF THIN PLATE STRUCTURES BASED ON IMPROVED FOURIER SERIES
摘要：Aiming at the problem of structural vibration modeling and characteristic analysis of rectangular sheets under arbitrary boundary conditions, an improved Fourier series method was proposed.Based on the Rayleigh-Ritz method, the allowable function of vibration displacement of thin plates was expressed as a linear combination of double Fourier cosine series function and auxiliary series function, which effectively avoided the possible discontinuities or singularities of the traditional Fourier series at the boundary. Firstly, the variational equation of the sheet vibration model was established by using the Hamilton energy variational principle, and the energy expressions in the equation were calculated and the displacement tolerance function was brought in. Secondly, the variational solution of the unknown Fourier coefficient was carried out to obtain the matrix equation of the model. The matrix equation was solved by numerical calculation method to obtain the free vibration frequency and eigenvector of the thin plate. Finally, the classical boundary conditions and elastic boundary conditions were used as examples to calculate and analyze. The calculation efficiency and accuracy of the proposed method were verified by comparison with the results of finite element simulation and existing literature. Additionally, the influence of the aspect ratio and constrained the spring stiffness coefficient on the vibration characteristics of the thin plate was discussed.关键词：Improved Fourier series;Elastic boundary;Thin plate structure;Hamilton principle;Rayleigh-Ritz method2|0|0更新时间：2025-06-09 - 摘要：To address the problem that it is difficult to label variable working condition gearbox fault samples and the significant data distribution discrepancies in practical engineering, which result in reduced accuracy of fault diagnosis models, a semi-supervised gearbox fault diagnosis method based on masked contrastive learning is proposed. Firstly, a random mask was used to hide part of the information in the unlabeled dataset, generating two different masked instances for each unlabeled sample. Secondly, a dynamic convolutional neural network was employed to dynamically weight and aggregate the masked instances, enabling discriminative feature modeling of different masked instances. Then, a contrastive learning framework was constructed with the optimization goal of maximizing the similarity between features of different masked instances. By enhancing the consistency of feature representations of masked instance pairs, the model's dependency on labels was reduced. Finally, during the fine-tuning phase, a domain-conditioned feature correction strategy was introduced to generate target domain feature corrections. By aligning source domain features and target domain corrected features according to the metric of minimizing domain feature distribution discrepancies, the method explicitly reduces the domain distribution differences caused by varying working conditions. Validation on a variable working condition gearbox fault dataset demonstrates the effectiveness of the proposed method.关键词：Gearbox;Variable working condition;Fault diagnosis;Contrastive learning;Semi-supervised2|0|0更新时间：2025-06-09
·Vibration·Noise·Monitoring·Diagnosis·
- 摘要：Based on Reddy’s layerwise theory (RLWT) and O(1) homogenization method, a three-scale layerwise multiscale analysis method (LMAM) for composite honeycomb sandwich structures was established. The macroscopic model of composite laminates was discretized by RLWT, and the microscopic unit cell model composed of fibers and matrix was established by three-dimensional finite element method. In the numerical example, the numerical simulation of the cubic block with inclusions was carried out, and the simulation results were compared with those of the direct numerical simulation (DNS) method, which verified the correctness of the LMAM. LMAM is also used to calculate and analyze the macroscopic, mesoscopic and microscopic stress distribution of composite honeycomb sandwich structures.关键词：Layerwise method;Multiscale analysis;Homogenization method;Honeycomb sandwich structure2|0|0更新时间：2025-06-09
- 摘要：Surface texture design is an effective way to achieve small leakage, long life and highly reliable operation of mechanical end seals. To investigate the characteristics of the interface film of guide groove texture, through the design and preparation of semi-circular, herringbone and E-shaped guide groove textures, experiments and theoretical research under high-speed operation conditions were carried out, the influence of different guide groove textures on the tribological properties of end face seals was explored. The results show that the existence of the guide groove can effectively improve the bearing capacity of the interface film and improve the tribological performance. In numerical calculations, the results show that the frictional performances of face seals varied with the configuration of guide groove. The herringbone textures and E-type ones show an obvious guide-aggregation effect. When the lubricant in E-type texture after being guide-aggregation through the groove, the pressure accumulates at the textured tail barrier, and fluid in the face seal clearance cannot escape from the guide groove boundary. As a result， the low energy loss in system, and an optimal liquid film bearing capacity achieves. Under different depths, the existence of guide groove promotes the hydrodynamic pressure. With the increase in depth, the bearing capacity of the liquid film increases first and then decreases. For the E-shape texture, the optimum bearing capacity of liquid film Pav=0.527 5 MPa is obtained at h1=10 μm. The bearing capacity of fluid film of E-shape texture has a 51.2% increase in comparison to the common grooved texture, the value of frictional torque has a 53.5% decrease. The analysis show that, the configuration of guide groove results in an accumulation of lubricant on the top of texture, which enhances the pressure convergence, thereby improving the bearing capacity of the lubricating fluid film and reducing friction（‘guide⁃aggregation effect’）. The geometric parameters of the guide groove have a significant impact on the fluid dynamic pressure in the end face sealing pair， which will influence the tribological performances of face seal. The research result provides theoretical support for the design of non-contact end face seal material surface texture in future.关键词：Guide-aggregation effect;Mechanical seal;Hydrodynamic lubrication;Surface texture;Friction reduction mechanism2|0|0更新时间：2025-06-09
- 摘要：To improve the accuracy and efficiency of load identification and structural response reconstruction, an improved Tikhonov regularization method that simultaneously considers transfer matrix error and measurement error was proposed. Firstly, the state space equation and transfer matrix were constructed through the structural dynamics model to obtain the reconstruction equation of the structural load and response. Secondly, the truncated randomized singular value decomposition method was used to calculate the approximate transfer matrix at the locations of the measurement points, while the total least squares method (TLSM) and the traditional Tikhonov regularization method were combined to identify the load, and then the unknown response was reconstructed by the transfer matrix at the locations. Finally, a numerical simulation and an experimental analysis were carried out for two-dimensional truss and simply supported beam to verify the proposed method. The results show that compared with the traditional Tikhonov regularization method, the proposed method can improve the reconstruction efficiency while guaranteeing the reconstruction accuracy.关键词：Structural response reconstruction;Load identification;Transfer matrix;Tikhonov regularization2|0|0更新时间：2025-06-09
- 摘要：In order to improve the carrying capacity of double curved beams negative stiffness structure composed of two curved beams arranged in parallel, the curved sandwich beam negative stiffness structure was proposed. The design idea was to array the sandwich straight beam between the upper and lower curved beams of the double curved beam negative stiffness structure, and the bearing capacity and energy absorption characteristics were studied systematically. Firstly, the negative stiffness structure model was fabricated using 3D printing technology and silicone emolding process, the compressive mechanical response of the curved sandwich beam and double curved beam negative stiffness structure was compared and analyzed by quasi-static compression experiment, and the reliability of the finite element simulation model was verified. Then, the influence of structural parameters (width, spacing, height and angle) of the sandwich straight beam on the bearing capacity and energy absorption characteristics of the negative stiffness structure was studied by simulation. The results indicate that the introduction of the sandwich significantly enhances the load-bearing capacity of the double curved beam negative stiffness structure. Compared with the spacing and angle of the sandwich straight beam, increasing the width and height of the sandwich straight beams can notably enhance the load-bearing capacity and energy absorption capacity of the structure.关键词：Curved sandwich beam;Negative stiffness structure;Quasi-static compression;Carrying capacity;Energy absorption characteristic2|0|0更新时间：2025-06-09
- 摘要：To explore the penetration resistance of aluminum alloy tubes under spherical steel projectile impact, focusing on the effects of varying tube radii and wall thicknesses on ballistic limit velocity, providing a foundation for tube protection design. A finite element model of spherical steel projectile penetration into 2024-T42 aluminum alloy targets was established using Ansys/Workbench software and the Johnson-Cook material model, which was then verified. Simulations of the response characteristics of aluminum alloy tubes with different radii and wall thicknesses under normal impact of spherical steel projectiles were conducted, along with an analysis of tube deformation and damage. The study found that the penetration resistance of the upper and lower walls of aluminum alloy tubes differs, with the upper convex structure outperforming the lower concave structure. A smaller tube radius enhances the penetration resistance of the upper wall, while for tubes of the same radius, increasing the wall thickness leads to a roughly linear increase in the ballistic limit velocity of both upper and lower walls.关键词：Aluminum alloy circular tubes;Spherical steel projectile;Penetration performance;Ballistic limit velocity;Numerical simulation18|10|0更新时间：2025-06-09
- 摘要：Elbows are an important component of oil and gas pipelines. The force state and the medium flow state are more complex than that of the straight pipe. Once the defect occurs at the elbow, the elbow pipe is more prone to fail. The high steel grade pipeline is the development trend of the long distance oil and gas pipeline construction, and it is urgent to evaluate the residual strength of the high steel grade bending pipe. Through the establishment of the finite element model, the defect size, relative position, bending radius, pipe parameters and pipe performance influence were studied on the ultimate internal pressure of the elbow, and finally the prediction formula of the bending was established. The results show that with the increase of defect length and defect depth, the ultimate internal pressure of the elbow is significantly reduced. The trench defect affects the ultimate internal pressure when the trench defect is located in the inner arch of the elbow. The bending radius, the wall thickness and the pipe material will affect the ultimate internal pressure. The error analysis shows that the prediction formula is more accurate, which can provide the basis for the residual strength evaluation of high steel grade elbows with trench defects.关键词：Elbows;Trence defect;Ultimate internal pressure;Finite element analysis;Prediction formula2|0|0更新时间：2025-06-09
- 摘要：In order to study the mechanical properties of high volume fraction ratio metal particle reinforced resin matrix composites, the elastic modulus of the composites was predicted based on the micromechanics theory and the meso-finite element method. Firstly, standard specimens of the composites were prepared, and their macroscopic elastic moduli were tested by uniaxial tensile experiments, and the microscopic properties were observed. Secondly, the elastic modulus of the composites was predicted by using Voigt, Reuss, Mori-Tanaka and Generalized means based on the micromechanics theory. Then, based on the microscopic particle size statistics of the specimens, the gradation of the metal particle size and its quantity were determined by using the Gaussian distribution law, and the random particle placement program was written by Python language to construct a two-dimensional representative volume element (RVE) finite element model consisting of the particles, the resin matrix, and the interface. Finally, the elastic modulus of resin matrix composites reinforced with high volume fraction metal particles was predicted by theoretical and finite element simulations. The analysis results show that the generalized means and finite element models predict the elastic modulus with less error from the experimental test results, and the elastic modulus of the composites increases with the increase of the volume fraction of the metal particles.关键词：High volume fraction ratio;Particle reinforced composite;Modulus of elasticity;Random distribution2|0|0更新时间：2025-06-09
- 摘要：The main purpose was to study the local cyclic plastic behavior of 3D printed titanium alloy notched parts. Firstly, the local stress and strain field near the 3D printed titanium alloy notch was analyzed in detail by finite element method， and the evolution of stress and strain field was deeply investigated. Then, the experimental study was carried out and the influence of the forming direction on the results was analyzed. The results show that ratcheting deformation occurs at the notch root, with the maximum ratcheting strain rate in the L3 direction and the minimum ratcheting strain rate in the L1 direction. The influence of the forming direction on the stress triaxiality is not too obvious. The elastic strain energy of different forming directions is almost no difference. However, the forming direction has a great influence on the plastic strain energy. With the increase of the number of cycles, the difference of plastic strain energy results for different notch radii also becomes larger.关键词：Notch;Ratcheting deformation;Stress triaxiality;Strain energy;3D printing;Forming direction2|0|0更新时间：2025-06-09
- 摘要：In order to improve the mechanical properties of three-dimensional negative Poisson ratio materials, and expand the application of negative Poisson ratio materials. A new unit cell of negative Poisson ratio structural material was proposed by introducing internal concave angles into the edges of tetrahedral porous structures, and 7 kinds of orthogonal isotropic and orthogonal anisotropic enhancement designs were carried out on it. The influence of cell geometry parameters on the dimension one equivalent elastic modulus and Poisson ratio of new and enhanced cells was studied by using the homogenized finite element method and periodic boundary conditions， and the 3D printed resin sample was used for experimental verification. Compared with the existing negative Poisson ratio unit cells, the novel unit cell can save 50% of materials while maintaining the negative Poisson ratio characteristics. The three reinforcement schemes in x-direction, y-direction and xy-direction can significantly improve the bearing-load capacity while improving the negative Poisson ratio characteristics.关键词：Negative Poisson ratio;Space cell;Finite element simulation;Mechanical property2|0|0更新时间：2025-06-09
·Experimental Research·Testing Technology·
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