The quantitative diagnosis of rolling bearings is essential to automating maintenance decisions. Over recent years, Lempel-Ziv complexity (LZC) has been widely used for the quantitative assessment of ...mechanical failures as one of the most valuable indicators for detecting dynamic changes in nonlinear signals. However, LZC focuses on the binary conversion of 0-1 code, which can easily lose some effective information about the time series and cannot fully mine the fault characteristics. Additionally, the immunity of LZC to noise cannot be insured, and it is difficult to quantitatively characterize the fault signal under strong background noise. To overcome these limitations, a quantitative bearing fault diagnosis method based on the optimized Variational Modal Decomposition Lempel-Ziv complexity (VMD-LZC) was developed to fully extract the vibration characteristics and to quantitatively characterize the bearing faults under variable operating conditions. First, to compensate for the deficiency that the main parameters of the variational modal decomposition (VMD) have to be selected by human experience, a genetic algorithm (GA) is used to optimize the parameters of the VMD and adaptively determine the optimal parameters
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of the bearing fault signal. Furthermore, the IMF components that contain the maximum fault information are selected for signal reconstruction based on the Kurtosis theory. The Lempel-Ziv index of the reconstructed signal is calculated and then weighted and summed to obtain the Lempel-Ziv composite index. The experimental results show that the proposed method is of high application value for the quantitative assessment and classification of bearing faults in turbine rolling bearings under various operating conditions such as mild and severe crack faults and variable loads.
Double-row tapered roller bearings have been widely used in various equipment recently due to their compact structure and ability to withstand large loads. The dynamic stiffness is composed of ...contact stiffness, oil film stiffness and support stiffness, and the contact stiffness has the most significant influence on the dynamic performance of the bearing. There are few studies on the contact stiffness of double-row tapered roller bearings. Firstly, the contact mechanics calculation model of double-row tapered roller bearing under composite loads has been established. On this basis, the influence of load distribution of double-row tapered roller bearing is analyzed, and the calculation model of contact stiffness of double-row tapered roller bearing is obtained according to the relationship between overall stiffness and local stiffness of bearing. Based on the established stiffness model, the influence of different working conditions on the contact stiffness of the bearing is simulated and analyzed, and the effects of radial load, axial load, bending moment load, speed, preload, and deflection angle on the contact stiffness of double row tapered roller bearings have been revealed. Finally, by comparing the results with Adams simulation results, the error is within 8%, which verifies the validity and accuracy of the proposed model and method. The research content of this paper provides theoretical support for the design of double-row tapered roller bearings and the identification of bearing performance parameters under complex loads.
The abnormal wear of a rolling element bearing caused by early failures, such as pitting and spalling, will deteriorate the running state and reduce the life. This paper demonstrates the importance ...of oil debris monitoring and its effective feature extraction for bearing health assessment. In this paper, a rolling bearing-rotor test rig with forced lubrication is set up and the nonferrous contaminants with higher hardness were introduced artificially to accelerate the occurrence of pitting and spalling. The early failure and abnormal wear of rolling bearings cannot be effectively detected only through the vibration signal; the temperature and oil debris monitoring data are also collected synchronously. Two features regarding the ferrous particle size distribution are extracted and fused with vibration based-features to form a feature set. The sensitive features are extracted from the features set using the Neighborhood Component Analysis method to avoid feature redundancy. Finally, the importance of the oil debris based-features for the diagnosis of abnormal bearing wear is analyzed with different machine learning algorithms. Taking SVM classifier as an example, the experiment results show that the introduction of oil debris based-features increases the diagnostic accuracy by 15.7%.
A measurement method for temperature distribution of bearing inner and outer rings based on fiber Bragg grating is proposed, and a bearing test rig has been established to measure the temperature of ...bearing rings at multiple points. Then, a calculation method is developed to research the temperature and its distribution of the bearing, which is consistent with the experiment result. The influence of applied load and rotating speed on the temperature distribution of the inner and outer rings is investigated as well. The results indicate that the temperature of the inner ring is higher than the outer ring and the circumferential temperature difference of the stationary ring is greatly affected by the radial load and rotating speed.
•Multi-point and in-situ measurement of bearing temperature is achieved.•Circumferential temperature distribution of the outer ring is related to the azimuth angle.•The temperature of the inner ring is higher than the outer ring.
In this paper, a parameter sensitivity analysis of mounting pedestals and a multi-objective optimization design for vibration reduction in a multi-support rigid body system, taking an ...aeroengine-lubricating oil tank supported by multiple mounting pedestals as an example, are conducted based on the third version of non-dominated sorting genetic algorithm (NSGA-Ⅲ) combined with Sobol’s sensitivity analysis method (SSAM). An aeroengine-lubricating oil tank with three mounting pedestals is simplified as a three-support dynamic system, and its dynamics model is established. Several structural parameters of mounting pedestals are taken as the design variables, and the system vibration response and the reaction force of the front and rear mounting pedestals are considered as the objective functions. The first-order results and total sensitivity index of different design parameters for each objective function are obtained via SSAM, and the five most sensitive parameters are selected. Based on the above five design parameters, multi-objective optimization designing for vibration reduction in a simplified lubricating oil tank system is conducted based on NSGA-Ⅲ, and the results of the above triple-objective optimization are obtained as a Pareto-front surface with an obvious frontier. It can be observed from the simulation results that the oil tank vibration of the optimized system is effectively suppressed under the unbalanced excitation of two typical engine speeds. The established method and the main results can provide guidance for designers of aeroengine external structural systems, which can help to achieve superior system dynamic performances in engineering applications.
In this paper, the thermomechanical characteristics of microturbine bearing during the process of bearing performance decay due to abrasive particles are theoretically and experimentally researched, ...such as contact characteristic, temperature characteristics, and stiffness characteristic, are illustrated. The results is that the evolution law of contact deformation and contact stiffness over the whole life of bearing is the same, whose amplitude is slightly different. The curve shape and amplitude of contact angular between ball and outer/inner ring has the obvious diversity.
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are dominant in heat production of bearing, the temperature of inner ring and contact zone between ball and inner ring is the maximum. The variation curve of bearing dynamic stiffness agrees with that of temperature in general.
In this paper, the roller bearings partial wear due to extreme inclined load caused by poor installation is investigated. First, based on non-Hertz contact theory, a quasi-static model of roller ...bearing with inclined load is established by the influence coefficient method. The influence of deflection angle between the inner ring and outer ring on the non-uniform contact characteristics is discussed. The finite element model of roller bearing housing is established and optimized by the theoretical results. The double-loading zones characteristic of roller bearings caused by the inclined installation of the housing is analyzed. The influence of the extreme position of the rollers on the deformation of the bearing is also considered. The partial wear experiment of the bearing is carried out. The contact surface roughness and deformation of the outer ring are measured. Fusing the analytical analysis, finite element analysis, and experiment, the effects of external inclined loads, rollers extreme positions, and wear on the deformation of the contact surface of the outer ring are systematically studied to reveal the mechanism of partial wear.
Aiming at the problem of incomplete information covered by the bearing state discrimination using a single physical quantity as the data source, a characterization method based on the feature ...information fusion of multi-physical quantities including acceleration RMS and stiffness that are sensitive to the bearing operating state is proposed. The accelerated life test of the bearing is carried out through the bearing experiment bench, and the effect of different feature information fusion schemes to characterize the bearing state is compared, and the effectiveness of the method is verified. This paper also analyzes the different characteristics of the state evolution law between the bearing early failure caused by specific factors and the bearing reaching normal fatigue life, which provides a new method and idea for the maintenance strategy of rolling bearing such as condition-based maintenance.
This study analyzes and predicts the vibration characteristics of fiber-reinforced composite sandwich (FRCS) cylindrical-spherical (CS) combined shells with hexagon honeycomb core (HHC) for the first ...time based on an analytical model developed, which makes good use of the advantage of the first-order shear deformation theory (FSDT), the multi-segment decomposition technique, the virtual spring technology, the Jacobi-Ritz approach, and the transfer function method. The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula, and the related energy equations are derived for the HHC-FRCS-CS combined shells, from which the fundamental frequencies, the mode shapes, and the forced vibration responses are solved. The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element (FE) results. The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model. It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius, and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.
In this study, the molecular dynamics method was used to study the damping mechanism in Mg alloys at the atomic scale. The energy dissipated by the nucleation and motion of dislocations and by ...defects friction, and the effect of defects, such as vacancies, cracks, and grain boundaries, on them were studied. The study shows that different kinds of defect have different effects on the dislocation damping and defect friction damping. And then, the effect of strain amplitude and temperature on damping capacity of Mg was studied. The result shows that the amplitude independent damping is caused by defect friction and the amplitude dependent damping is mainly caused by the nucleation and motion of dislocation; the damping of Mg increased exponentially with the temperature, and the damping peck appeared at 440 K is attributed to the appearance of dislocations at the grain boundaries which may be caused by boundaries self-diffusion.
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