Robotic Systems and Applications
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Current research status on the occupational hazards of hand-transmitted vibration: a case study in China
Get PDFThe hazards arising from long-term hand-transmitted vibration operations can cause significant damage to the human body. As China is a populous country, understanding the current situation of vibration exposure among workers in various related fields in China holds significant reference value. To this end, this paper analyzes data from core journal literature in China from the 1980s to the present based on the keywords hand-arm vibration disease, hand-transmitted vibration, and occupational exposure. This paper provides an overview of the current status of hand-transmitted vibration hazards, including the distribution characteristics, hazards, and diagnostic methods of hand-arm vibration disease, as well as the deficiencies in these diagnostic methods. It also integrates data on the vibration intensity, frequency, and prevalence of vibration tools to analyze the relationship between the prevalence of hand-arm vibration disease and the vibration intensity and frequency of vibration tools. The results indicate that the vibration tools causing occupational hand-arm vibration disease are primarily found in the mining and manufacturing industries, with rock drilling jobs and positions being dominant in the mining industry and grinding jobs and positions being dominant in the manufacturing industry. The A(4) values of grinding tools, jobs, or positions are significantly higher than China’s limit value of 5 m/s2 for hand-transmitted vibration. The A(4) distribution of rock drilling tools is more concentrated, while the A(4) distribution of grinding tools is broader. The current diagnostic methods have poor specificity and sensitivity. There is insufficient awareness of the hazards of hand-transmitted vibration. There is no significant correlation between A(4) and the prevalence of vibration white finger (P>0.05), and A(4) alone is insufficient to reflect the extent of harm caused by hand-transmitted vibration operations to the human body. Both low-frequency and high-frequency vibrations may be harmful to the human body, and there may be a positive correlation between the fundamental frequency of vibration tools and the prevalence of disease (r>0,P<0.05)
Construction of a mathematical model of the motion of a vibrating separator with pneumatic suspension
Get PDFThe mathematical model of the movement of an arbitrary point of the container of a vibrating separator with a pneumatic suspension is built in the article. For modeling, a vibrating separator with two independently driven unbalances and a pneumatic suspension was chosen, which has a number of advantages over other separators, is characterized by simplicity of construction and maintenance, and low sensitivity to the properties of the medium being separated. The developed unified parameterized model of a vibrating separator can be used by changing its parameters or zeroing them for a wide range of designs of vibrating separators. The use of data from ready-made unified mathematical models allows you to reduce the duration of research and design of vibrating separators, and reduce material costs in general
Permeability test of geotextile-soil system under different sand filling heights
Get PDFGeotube dams are constructed by stacking geotubes, which are non-homogeneous structures composed of geotextiles and filled sand. Therefore, studying the permeability characteristics of the geotextile-soil system is of great significance for seepage analysis in geotube dams. While the permeability characteristics of geotextiles and filled sand have been extensively studied individually, there has been relatively little research on the permeability characteristics of the geotextile-soil system formed by the combination of geotextiles and soil. In this study, a self-designed permeameter was used to investigate the permeability characteristics of the geotextile-soil system under different sand filling heights. The test results indicate that the permeability coefficient of the geotextile-soil system decreases continuously with the increase in permeation time and eventually stabilizes. The permeability coefficient of the geotextile-soil system increases with the sand-filling height and finally approaches but remains slightly smaller than that of pure sand with the same gradation. The influence of geotextiles on the permeability of the geotextile-soil system is significant within the range of 0 to 5 cm. Additionally, the water permeability of geotextiles affects the permeability performance of the geotextile-soil system. Specifically, a larger porosity corresponds to higher water permeability, and a greater permeability coefficient of the geotextile leads to a higher permeability coefficient of the geotextile-soil system
Study on the impact of wheel roundness defects on axle fatigue damage
Get PDFWith the continuous increase in the operating mileage of China’s high-speed railway network, wheel out-of-roundness has become increasingly common in electric multiple unit (EMU) vehicles. Wheel out-of-roundness directly increases the vibration level of the axle, affects various vehicle components, and in severe cases, may lead to fatigue fracture of the axle – a key load-bearing component – thereby causing major safety incidents. To investigate the influence of wheel out-of-roundness on axle dynamic stress and to evaluate the fatigue strength of the axle under such conditions, this study analyzes the effects of different wheel flat lengths, polygon orders and depths, as well as various operating speeds on the dynamic stress of EMU axles. Based on numerical simulation results, the fatigue damage of the axle under wheel out-of-round conditions and the impact of wheel polygonal wear over one development cycle are calculated. The findings show that within a single re-profiling cycle, wheel flats shorter than 50 mm have a negligible effect on axle fatigue damage. Furthermore, a reference limit for polygonal wear depth is proposed, providing theoretical guidance for wheel maintenance and safety assessment of EMU vehicles
Energy analysis of living stumps slope based on Hilbert-Huang Transform and marginal spectrum
Get PDFA large-scale shaking table model test on a slope with living stumps was designed and conducted. Under various types of seismic waves and excitation intensities, acceleration data from monitoring points on both sides of the living stumps were collected. Hilbert-Huang Transform (HHT) was innovatively applied to study the dynamic response of slopes with living stumps under seismic loading, overcoming the limitations of traditional Fourier Transform and Wavelet Transform. The variation patterns of Hilbert energy and marginal spectral characteristics under different seismic excitations were analyzed, providing new insights from both time-frequency domain and energy perspectives. The research conclusion showed that: (1) Under different seismic waves, the horizontal peak acceleration inside the living stumps slope shows the elevation amplification effect, and increases with the intensity of excitation. Additionally, the existence of living stumps causes a difference in horizontal acceleration on both sides, and the absolute value of the difference is positively correlated with elevation and excitation intensity. (2) Under different seismic waves, Peak of Hilbert energy spectrum (PSHEA) is positively correlated with excitation intensity and elevation. With the increase of elevation, the increase of PSHEA increases gradually when the excitation intensity increases. PMSA is positively correlated with excitation intensity, but at low frequencies (1-3 Hz), Peak of marginal spectrum (PMSA) is negatively correlated with elevation; while at high frequencies (7-11 Hz), PMSA is positively correlated with elevation. (3) With increasing elevation and excitation intensity, the total seismic Hilbert energy continues to accumulate and reaches the maximum at the top of the slope. During the propagation of seismic waves, the living stumps and the rock-soil composite play the characteristics of filtering the low-frequency components and amplifying the high-frequency components, causing the total seismic Hilbert energy in the low-frequency (1-3 Hz) component to gradually decrease and transfer to the high-frequency (7-11 Hz) component, resulting in a significant increase in seismic Hilbert energy in the high-frequency component. (4) The superposition of incident wave and reflected wave near the living stumps, and the absorption of seismic Hilbert energy by the living stumps make the PSHEA, PMSA, and total seismic Hilbert energy on the outside of the living stumps always smaller than the inside, resulting in different dynamic responses on either side of the living stumps. The living stumps show attenuation effect on seismic Hilbert energy, and the attenuation degree increases with the increase of excitation intensity and elevation. The study provides a theoretical basis for the seismic design of living stumps slopes
A vision-based deep learning approach for non-contact vibration measurement using (2+1)D CNN and optical flow
Get PDFThis paper introduces a proof-of-concept vision-based deep learning approach for vibration measurement, proposing a factorized (2+1)D Convolutional Neural Network (CNN) model to predict four vibration metrics: acceleration, velocity, displacement, and frequency, with a focus on rigid body motion. Unlike conventional neural network models that primarily focus on frequency prediction alone, this approach uniquely enables the simultaneous estimation of four critical vibration metrics, offering a comprehensive and cost-effective alternative to traditional contact-based sensors such as accelerometers. The framework relies on the visibility of a training fiducial marker, eliminates the need for calibration in controlled settings, enhancing scalability across specific environments. A curated dataset was generated using a controlled experimental setup comprising a single object in a lab-scale environment, augmented synthetically to enhance frequency diversity. An optical flow-based preprocessing algorithm synchronized motion features in recorded video inputs with measured vibration labels, improving measurement accuracy. The proposed model achieved an average Mean Absolute Percentage Error (MAPE) of 7.51 %, with acceleration predictions exhibiting the lowest error at 4.84 % and displacement the highest at 8.80 % across varying brightness levels and object-camera distances. Techniques such as Region of Interest (ROI) cropping and multi-section frame extraction were implemented to reduce computational complexity while further enhancing accuracy. These results highlight the framework’s potential for non-invasive vibration analysis, though its generalizability is limited by the single-object dataset. Future work will expand the dataset, integrate multi-sensor inputs, explore marker-less tracking methods, and enable real-time deployment for predictive maintenance and structural health monitoring
Random parametric nonlinear vibrations of a discrete mechanical system protected from vibration
Get PDFIn this work, the issue of checking the dynamics of nonlinear vibrations of a mechanical system protected from vibrations in case of random parametric excitations is considered. Using the Ito method, the analytical expressions of the mean square values of the absolute accelerations of the mechanical system and the dynamic absorber were determined. Statistical linearization method based on Davidenko's hypothesis was used to determine mean squared values. The average square value change of the random parametric vibration of the mechanical system protected against vibrations with the dynamic absorber at different values of the parameter describing the width of the vibration spectrum was analysed. It is shown that if the parameter describing the width of the vibration spectrum is taken smaller, the mean square value of the random parametric vibration of the protected object combined with the dynamic absorber will have a smaller vibration. At different values of the parameter of the hysteresis loop, the change of the mean square value of the random parametric vibration was analysed and appropriate conclusions were drawn
Analysis of modal and vibration response characteristics of high-pressure storage tanks
Get PDFAnalysis of dynamic characteristic was conducted focusing on the transportation of high-pressure storage tanks, covering two scenarios: independent transportation and mixed transportation. For independent transportation, analysis of free modal was carried out to obtain the first four orders of modal shapes. Additionally, the influence of two constraint methods on the modal characteristics and stress distribution was studied, including fixed at both ends and fixed at the cylinder body. Results show that when the tank was fixed at the cylinder body, it had a higher natural frequency and a lower stress level, making it safer. For mixed transportation, a finite element model was built for 6 high-pressure storage tanks, and analysis of random vibration was performed. The results showed that stress was mainly concentrated on the crossbeams and connection nodes, while the stress on the main body of the storage tanks was relatively low. The overall structure exhibited excellent fatigue performance and met the mechanical and safety requirements under random vibration conditions
Experimental method for determining the vibrodynamic state of embankments on high-speed railways
Get PDFThe article presents modern methods for reinforcing the embankment in the zone of the interface between the coastal bridge piers and the earth bed of the high-speed railway section. It has been established that as a result of driving reinforced concrete piles into the railway embankment, the natural vibrations of the earthwork decrease by up to 15 %. A frequency equal to the frequency of vibrations arising from the speed of high-speed railways with the help of vibrators on models of the earth bed for determining the amplitude-frequency characteristics of various design points has been created and the values of this frequency have been processed by fixing them with the help of seismometric sensors SM-3 in all design points. A significant decrease of shear at the main site after driving of reinforced concrete piles and approaching of this value to microseismic value based on the values of sensors located at the main site and at a distance of 1.5 m from the foundation is determined. It has been established that by driving reinforced concrete piles into the railway embankment, the vertical settlement of the earthwork decreases by 33 % and 50 % depending on the soil type. Also, the methodology of experimentation for the study of vibrations of the earth bed piled from different soils on high-speed railroads is given
Lightweight design of double-head machine tool beam based on the adaptive multi-objective method
Get PDFDouble-head machine tool has the advantages of high efficiency and high degree of automation. In order to reduce the weight of double-head machine tool and improve the stiffness of the entire machine. An optimization design method combining topology optimization, sensitivity analysis and adaptive multi-objective method is used. Firstly, simplify the model in SolidWorks and import it into ANSYS Workbench software to carry out finite element analysis on the entire double-head machine tool to find out the weak component as the beam. Afterwards, carry out topological optimization on the beam and redesign the beam structure, and complete the first optimization. Then, through sensitivity analysis of the input parameters, key parameters that significantly impact the objective function are identified. Subsequently, a multi-objective optimization function is constructed for these key parameters and the objective function. Finally, an adaptive multi-objective method is used to solve the problem and obtain a Pareto optimal solution set, completing the second optimization. The results show that the weight of the beam is reduced by 8.88 %, the deformation of the beam is reduced by 11.29 %, and the equivalent stress of the entire machine is reduced by 28.33 %. This design not only yields significant economic benefits but also serves as a valuable reference for the lightweight design of large machine tool crossbeams