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The next few years will be marked by major changes in the mobility sector in order to come closer to CO 2 neutrality. Especially in the commercial vehicle sector, fuel cells can make an important contribution. In order to achieve this, the efficiency of all subcomponents of a vehicle has to be improved. This also includes the bearings in the electrical air compressors. The frequent start–stop cycles are critical, as they can lead to higher wear and thus a shorter service life. One solution is a prototype that can actively switch between a triangular profile and a round bearing shape. In this work, the two switching states are investigated experimentally. Instead of the thin bearing sleeve of the prototype, rigid sleeves are used for each switching shape. This allows the shape itself to be studied without the contribution of the stiffness of the thin bearing sleeve along with the actuators. The examination includes static load tests and run-out tests in the range of the lift-off speed. Alongside this, the difficulties of the bearing production and the improvement of the test rig used are pointed out. [ABSTRACT FROM AUTHOR]

The traditional dynamic characteristic analysis of the multi-stage centrifugal pump rotor system is developed assuming the bearing structural parameters with constant values. However, the manufacturing errors will cause the structural parameters to vary around their nominal values and then affect the dynamic characteristics of the bearing-rotor system. Thus, this paper proposes a method for analyzing the dynamic characteristics of the bearing-rotor system with uncertain bearing structural parameters. First, dynamic characteristic coefficients of the sliding bearing are identified to establish the dynamic model of the rotor system, and its dynamic characteristics are analyzed through finite element simulations. Next, the sliding bearing structural parameters are taken as the variables to establish an optimization model, which is solved by the improved particle swarming optimization algorithm to obtain the extreme critical speed of the rotor system. A case study was carried out on a multi-stage centrifugal pump. The obtained extreme values of the critical speeds were close to those calculated using the multiple samples generated by the Monte Carlo method, indicating that the proposed method can provide accurate variation ranges of critical speeds efficiently and lay a theoretical basis for selecting robust operational speeds and designing the rotor system of the multi-stage centrifugal pump. [ABSTRACT FROM AUTHOR]

An expanding pin locks the pin assembly to its supports and bearings and prevents any relative movements between the surfaces in contact. In this study, the diameter changes of the bearing inner ring as a function of the expanding pin's tightening torque were studied. In addition, the required rotational moment of a set of complete bearings locked to an expanding pin solution was studied by exposing the assembly to a combination of an increasing radially outwards directed load from the bolt torquing and a radially external inwards directed load from a hydraulic jack. The bearings were of type Radial Spherical Plain Bearings (RSPBs), GE 80 ES, steel/steel, and loaded externally up to their maximum dynamic limit of 400 kN. The results indicate a major reduction in the required rotation moment of the bearing when the bearing inner ring is expanded by use of an expanding pin. The reduction of rotation moment indicates reduced contact pressure and friction force between the two bearing rings, which ultimately can have a reduced effect on ring surface wear and a positive effect on the bearing operational lifetime. [ABSTRACT FROM AUTHOR]

The development of modern energy is moving towards distributed generation, in which numerous sources of different capacities are connected into a single network. This makes it possible to increase the reliability of the entire system, since the probability of the failure of several energy sources at the same time is small. One of the major possibilities of distributed generation is the generation of electric energy based on high-speed gas turbines. The main advantage of these sources are high specific energy indicators, which improve with increasing rotation speed. However, it is technically difficult to realize the advantages of high-speed devices. It is necessary to abandon the step-down gearbox for the generator and directly connect it to a high-speed turbine, use high-strength materials that can withstand the load from centrifugal forces, abandon traditional plain bearings, and use special supports. Installations with generators that have a radial rotor design are the most widespread. The main problem with generators of this type is that the rotor diameter is limited by the mechanical strength from centrifugal forces and the power can be increased only by increasing the axial length. At the same time, only two supports can be used for a radial structure; this leads to a decrease in the rigidity of the shaft and the occurrence of resonant frequencies during acceleration. In addition, radial generators have unreasonably large losses in the stator magnetic circuit, which increase with increasing speed and are difficult to remove from a limited volume. For this reason, radial structures have exhausted their reserves and cannot develop further in the direction of increasing the speed of rotation. This article proposes the design of a high-speed gas turbine installation based on a generator of a fundamentally different design. This is a multi-section generator with an axial air gap. The electric machine has a diamagnetic armature, which eliminates magnetic losses and allows for increased efficiency and simplification of the design. A large number of rotor sections can be used as supports for a gas-dynamic bearing, which greatly increases the rigidity of the structure and eliminates resonant frequencies during acceleration. The main structural difference from existing designs is the use of two types of bearings at the same time: magnetic bearings and gas-dynamic bearings. Magnetic bearings ensure operation at low speeds during acceleration, and gas-dynamic bearings ensure the rotation of the rotor and its rigidity at high speeds. Analysis of developments in this area shows that this solution is innovative. The proposed design required study of both the power part, including the axial inductor and the diamagnetic armature, and the combined support. This article shows the results of the development of a combined suspension and provides calculations of magnetic and gas-dynamic bearings for a gas turbine installation of 100 kW and 70,000 rpm. The results of the study can be applied to a number of gas turbine installations from 10 kW to 500 kW. The authors consider this concept to be competitive with modern analogues that have a radial generator design. [ABSTRACT FROM AUTHOR]

Bearings are the critical parts that support the rotating of rotor of wind turbine generators. Due to high speed revolution and affected by potential misalignment between rotor and the high speed shaft in wind turbine gearbox, the fault ratio in wind turbine generator bearings is high. Once the bearings fail, it will cause gap eccentricity, even rub, or sweeping chamber between rotor and stator. Under fault conditions, the vibration signals from rotating machinery exhibits distinct second cyclostationarity. In the light of this, the fast spectral correlation based method is applied to the fault extraction of bearings in wind turbine generators. Through converting conventional correlation into summation algorithm, the computational cost is reduced largely, meanwhile, the diagnosis accuracy is guaranteed. The effectiveness of the method in this paper is verified by two fault cases from on-site wind turbines. [ABSTRACT FROM AUTHOR]

To improve the tribodynamic performance of ball bearings, micro-texturing has been widely used on bearing components and significant beneficial effects by using different shape, size and density of dimples at their contact zone has been reported in literature. However, behaviour of textures in vicinity of the contact zone in machine components particularly in ball bearings, where lubricant/grease is push aside from the contact zone has not been explored yet. Hence, two different configurations of micro-textured inner races (i.e., inner races with large number of circular micro-dimples circumferentially on both sides of the central non-textured zones of 2.2 and 1.0 mm) of a deep groove ball bearing have been fabricated by employing a low power laser marking machine. The performance of these micro-textured bearings (MTBs) possessing textured inner races and conventional outer race have been evaluated by conducting experiments in a test rig designed and fabricated inhouse. Capacitance based electrical method, load sensor, thermocouple and miniature type accelerometer have been employed for measuring film thickness, frictional torque, temperature rise and vibrations respectively at realistic bearing loads (speed: 1.4–5.6 m/s, and loads: p H =1.07–1.70 GPa) and the results were compared with that of a same size conventional bearing (SKF: BB1B 420 206). About 8–27 % improvement in film formation, reductions in overall vibration level (5–36 %), frictional torque (10–35 %) and bulk temperature rise (14–37 %) has been recorded in case of MTBs as compared to the conventional bearing (CB) cases at identical load conditions. Moreover, study on the effect of the positioning of the textures with respect to the contact zone on performance behavior of bearings indicated that the tribological and vibration behavior of MTB-2 (bearing with a micro-textured inner race where, textures were created in vicinity of 1.0 mm central non-textured zone) is better than that of the MTB-1 (bearing with a micro-textured inner race, where textures were created in vicinity of 2.2 mm central non-textured zone) and CB at tested loads and speed range. [ABSTRACT FROM AUTHOR]

• 88% vibration reduction was achieved by adjusting the radial clearance of the bearings. • The frequency "locked-up" phenomenon was observed in the experiments. • The mechanism of vibration reduction and frequency "locked-up" were deduced. To investigate the impact of radial internal clearance of rolling bearings on the dynamic response of a flexible rotor system in a turbo-shaft engine, a dynamic similarity model of the power turbine rotor was established. Experimental research was then conducted. Four rolling bearings supporting the rotor were examined, with dynamic response tests carried out under varying radial internal clearances. The influence of the radial internal clearance on the dynamic characteristics of the rotor system was studied using the controlled variable method. The amplitude, orbit, and asynchronous vibration were analyzed through time-domain signal comparison, waterfall diagrams, and spectral analysis. The experimental results demonstrate that: (1) Adjusting the radial internal clearance of the bearings can significantly reduce the dynamic response of the flexible rotor system, with a maximum observed displacement response reduction of 88%. (2) The efficiency of vibration reduction is closely related to the axial location of the bearing. (3) Optimal radial internal clearance is not necessarily achieved at the maximum or minimum values. (4) The "locked-up" frequency phenomenon, which increases the resonance opportunities of the rotor system, can be mitigated by adjusting the radial internal clearance of different bearings. This research is of great significance and engineering value for understanding, diagnosing, and preventing excessive vibration in flexible rotor systems. [ABSTRACT FROM AUTHOR]

To investigate potential mechanisms of behavior interference between the gearbox components, based on the modeling method of flexible rotors, an analytical model for the gear-rotor-bearing coupled system with semi-flexible body elements is developed. Through simulation investigation and experimental observation, the interference mechanisms between system components are unveiled, and the response characteristic is discussed. Then, to underscore that alterations in the motion state of a single component can initiate a cascade of reactions in the behavior response of system components, the tooth root crack faults, race faults, and misaligned rotors are introduced. In addition to the general focus on the dynamic response of the coupled system, more attention is devoted to the system coupling mechanism. Pioneering discoveries of hitherto unreported phenomena are implemented. The deformation of the flexible rotor is induced by the mesh force, leading to the gear pair and bearings consistently operating under misaligned conditions. The contact angle of ball bearings and the eccentric load distribution on tooth surface are generated. Local failures scarcely alter the vibration mode of the rotor, which intensifies the behavior interference between system components. [ABSTRACT FROM AUTHOR]

The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are compared and agreed well with each other. This study combines the experimental and theoretical analyses and provides a deep understanding of the physical phenomenon of the nonlinear vibration and is meaningful for the vibration control of the relevant applications. [ABSTRACT FROM AUTHOR]

This paper presents a method for passively compensating thermal bending distortions of the thrust disk in gas thrust bearings by passive approaches. Thermal bending displays a prominent problem in hydrodynamic thrust bearings, especially in connection with air bearings. Axial temperature gradients cause the rotor disk to dish which in turn diminishes the lubricating gap topology and reduces the load capacity of the bearing. Consequently, the bearing performance is decreased and the bearing may even fail. The here proposed straightforward solutions are small changes in the rotor and runner disk design and are therefore rather simple and inexpensive to adopt. They comprise asymmetric mass distributions, recesses, disk cuts, and dual-material rotor disks. In order to show the benefit for the thrust bearing performance, detailed multiphysical numerical simulations of a representative rotor assembly with a foil thrust bearing are presented. The fully coupled finite element model calculates the deformations of the foil package (2D Reissner–Mindlin type shell equations), lubricating air film pressure (2D compressible Reynolds equation), air film temperatures (3D energy equation), and thermo-elastic deformations of the rotor and rotor disk (2D Navier-Lamé equations including centrifugal forces and thermal stresses). When the proposed design changes are applied, the model predicts reduced thermal bending, marked improvements in load capacity as well as decreased temperatures. The load capacity increase ranges up to 43% for an optimized design when compared against a standard symmetric design. Also, the sensitivity of different design parameters is discussed in detail. The suggested disk design changes may be applied to a broad variety of rotor-bearing systems. However, the design has to be tailored to the specific and individual machine operating conditions. [ABSTRACT FROM AUTHOR]

Among the existing bearing fault diagnosis algorithms, the diagnosis time of algorithms with high accuracy is relatively long, and the accuracy of some lightweight methods is low compared to other methods. This work proposes a bi-level binary coded fully connected classifier based on residual network 50 with bottom and deep level features (Bi-BUR) for bearing fault diagnosis, enabling both high accuracy and high-speed characteristics. The Bi-BUR has two levels of classifiers. The first level begins with a signal-to-picture method based on integer binary coding to convert the bearing fault signals into binary pictures; then, the first classification of the converted pictures is performed by the underlying feature extraction-residual network 50, which can extract both the underlying and the advanced features. The second level performs modal decomposition of the signals that are not classified successfully in the first level, performs the second classification with a fully connected classifier inserted into the underlying feature extraction module, and exports the final classification results after weighted summation of the results of each type. The Bi-BUR is simulated on the Case Western Reserve University motor, the self-priming centrifugal pump, and the axial piston hydraulic pump bearing failure datasets. All three experiments achieved more than 95% accuracy in the first level of categorization and 100% diagnosis after the second level of categorization. And the Bi-BUR is faster than other high-accuracy methods. • A bearing fault diagnosis method with fusion of speed and accuracy is considered. • A two-layer bearing fault diagnosis method is proposed. • A signal-to-picture method based on integer binary coding is proposed. • A method to extract both bottom and deep level features is proposed. • The method fills the gap of bearing fault diagnosis with high speed and accuracy. [ABSTRACT FROM AUTHOR]

• A damage coupling fatigue simulation model, considering residual stress (RS) and surface hardness effect, was constructed for pitch bearing. • Different ultimate loading conditions for pitch bearing are calculated on an integrated load simulation platform. • The effects of ultimate loading conditions, RS, and surface hardness on pitch bearing rolling contact fatigue (RCF) are revealed. Pitch bearing is the critical component that are widely used to ensure the operation of offshore wind turbine blades and enable efficient capture of wind energy. Uncertain environmental factors and extreme load conditions can induce early fatigue failure in pitch bearings, and lead to major accidents such as blade detachment. In this study, a damage coupling fatigue simulation model, considering residual stress (RS) and surface hardness effect, was constructed following the continuum damage mechanics (CDM) to investigate the rolling contact fatigue (RCF) of pitch bearing under ultimate loading conditions. Different ultimate loading conditions were calculated on an integrated load simulation platform established using Python script. The damage-coupled elastoplastic constitutive equation and damage-controlling equations considering RS and surface hardness were derived and programmed in the material user subroutine UMAT. The effects of ultimate loading conditions, RS, and surface hardness on RCF were studied. Results show that increasing the surface hardness or increasing the compressive RS enhances the anti-fatigue performance of pitch bearing. [ABSTRACT FROM AUTHOR]

In order to analyse the system spatial vibration of compound biaxial and inter-shaft bearings during unbalanced excitation, the theory of rotor dynamics and bearing contact deformation are combined to establish a coupling system model of compound biaxial and inter-shaft bearings. Considering the moment of inertia, gyro effect, and structural damping, a one-dimensional beam model is used to perform the MATLAB numerical calculation of the coupling system to obtain the modal characteristics of the system, and based on the ANSYS simulation analysis of the three-dimensional model, a modal test is used to obtain the system modal shape and test frequency response function to verify the rationality of the coupling system model. Based on the Runge-Kutta iterative method and Hamilton's principle, the nonlinear amplitude-frequency response of the system is calculated while taking into account the influence of the compound biaxial eccentricity, as well as the stiffness and radial clearance of the inter-shaft bearing. The results show that the changes in the eccentricity of the compound biaxial and the structural parameters of the inter-shaft bearing cause the unbalanced excitation of the system, additional external load changes, and different coupled vibrations between the composite compound biaxial and inter-shaft bearings. Therefore, it is reasonable to match the structural parameters of the coupling system and improve the dynamic performance to avoid system resonance. [ABSTRACT FROM AUTHOR]

In this study, a novel optimization-based method is proposed to determine the parameters of a rotating unbalance in a rotor-bearing system. For that purpose, the weighted sum of squared difference between the analytical and predicted unbalance response due to rotational unbalance is considered as the objective function. A hybrid algorithm integrating salp swarm algorithm and Nelder–Mead algorithms is presented for detecting unbalance magnitude and phase as the unbalance parameters. Parameters of the aforementioned optimization algorithm are determined systematically using the Taguchi design of experiments method. The efficiency of the proposed method is compared with various optimization algorithms in the literature. The optimization method is validated with different unbalances experimentally to consider the real-world conditions. The results show the superiority of the proposed hybrid algorithm in terms of the accuracy of the unbalance parameters and computational efficiency. [ABSTRACT FROM AUTHOR]

The technology of fault diagnosis is helpful to improve the reliability of wind turbines, and further reduce the operation and maintenance cost at wind farms. However, in reality, wind turbines are not allowed to operate with faults, so few fault samples could be obtained. With a small amount of training data, traditional fault diagnosis models that need huge samples under a deep learning framework are difficult to maintain with high accuracy and effectiveness. Few-shot learning can effectively solve the problem of overfitting caused by fewer fault samples in model training. In view of model-agnostic meta-learning (MAML), this paper proposes a model for few-shot fault diagnosis of the wind turbines drivetrain, which is named model-agnostic meta-baseline (MAMB). The training data is input to the base classification model for pre-training, then, some data is randomly selected from the training set to form multiple meta-learning tasks that are utilized to train the MAML to finally fine-tune the later layers of the model at a smaller learning rate. The proposed model was analyzed by the small samples of the bearing data from Case Western Reserve University (CWRU) data, the generator bearings, and gearboxes vibration data in wind turbines under randomly changing operating conditions. The results verified that the proposed method was superior in one-shot, five-shot, and ten-shot tasks of wind turbines. [ABSTRACT FROM AUTHOR]

Hydrostatic bearings offer numerous advantages in large-scale moving mechanisms and structures. Nonetheless, the limits of manufacturing, transportation, and assembly in such scales are often encountered. The manufacturing and assembly errors significantly influence the hydrostatic bearing's overall performance. Therefore, it is desirable to compensate the resulting errors and pad misalignment of the hydrostatic multi-pad bearing. Previous research dealt with accuracy improvement and error prediction of small hydrostatic guideways. A little attention was aimed at the use of compliant materials for pads, but this area did not develop any further. The present study offers a methodology on how to estimate allowed assembly errors based on the analysis of the influence of manufacturing errors on the bearing's performance. Additionally, this article describes effects of the compliant support on assembly errors of hydrostatic multi-pad bearings. The proposed prediction is compared with experimental measurements on a hydrostatic bearing experimental rig. The effects of compliant support for a hydrostatic bearing can significantly increase the allowed error as compared to the usual rigid support. Furthermore, the experimental results indicate that the prediction of performance influence based on a known manufacturing error could be used for the hydrostatic bearing's performance improvement. The obtained results might help to enhance the design process of a hydrostatic bearing and improve its performance and extend the lifetime. • The influence of compliant support for hydrostatic bearing pad misalignment compensation is analysed. • The compliant support stiffness design procedure is suggested and experimentally verified. • A methodology for allowable errors estimation for hydrostatic bearings is proposed. [ABSTRACT FROM AUTHOR]

The international standard ISO 7902: Hydrodynamic plain journal bearing under steady-state conditions -- Circular cylindrical bearings, is widely used for the evaluation of plain bearings in different operation conditions. In Cuba, the procedure proposed by this document has been used to evaluate plain bearings in different working conditions and productive sectors of the national economy, both by Universidad Tecnológica de La Habana researchers, and from other universities. The objective of this research is to demonstrate the relevance and feasibility of applying ISO 7902 standard. In this work research, a study of the load capacity calculation for plain bearings, according to the third edition of ISO standard 7902: 20202 is presented. The Cómo citar este artículo: mentioned procedure was used to simulate the operating conditions and work capacity of a plain bearing support in an HSR7 637-8P generator of a Hyundai Himsen 9H 25/33 engine in a fuel-oil thermal power plant. The results show evidence of similarity between the simulation and the real operating conditions in the plain bearing. In this work, it could be concluded ISO standard 7902:2020 allows establishing a feasible procedure to apply to prevent the effects caused by control actions, working conditions and modification in the design of plain bearing. [ABSTRACT FROM AUTHOR]

The paper presents the multiscale analysis for the hydrodynamic step bearing with ultra low surface clearances where only the physical adsorbed layer is present in the outlet zone and the continuum fluid flow mainly occurs in the inlet zone. This bearing can occur under heavy loads. The flow in the outlet zone is described by the nanoscale flow equation, while the flow in the inlet zone is described by the multiscale flow equation incorporating both the adsorbed layer flow and the intermediate continuum fluid flow. The pressure and carried load of the bearing were derived. Exemplary calculations show that the fluid-bearing surface interaction has the strongest influence on the pressure and carried load of this bearing when the bearing surface clearance is as small as possible, the bearing step size is close to the surface clearance in the outlet zone and the value of the geometrical parameter is the optimum one, which depends on the fluid-bearing surface interaction. For the strong fluid-bearing surface interaction, the carried load of the bearing can be 10 times higher than that calculated from the classical hydrodynamic lubrication theory. [ABSTRACT FROM AUTHOR]

The classical theory of centralized dynamic characteristics with eight coefficients is adopted for traditional journal bearings. However, under cantilevered load, distributed dynamic characteristics along the axial direction will be generated for the journal bearing with a large aspect ratio (L/D). A double-section loading method simulating shaft bending and excitation was developed, a dynamic characteristic test-rig of a large-aspect-ratio bearing was set-up, the novel four-time vertical excitation method and eight-time cross excitation method were put forward, and the equations of 16 dynamic characteristic coefficients of the bearing were deduced. The dynamic characteristic test was carried out. The results showed that the four-time vertical excitation method had a small response amplitude in the horizontal direction, and was vulnerable to interference by the vibration of the test-rig. The eight-time cross excitation method had a higher SNR with more accurate identification results. When the cantilevered load was not applied, the dynamic characteristic coefficients were evenly distributed along the axial direction, the stiffness coefficients fluctuated slightly as the rotation rate increased, while the main damping coefficients decreased significantly. Shaft bending resulted in a significant increase in local dynamic characteristic coefficients, in which the relative increase in the stiffness coefficients was greater than that of the damping coefficients. Increasing the rotational speed can weaken the effect of shaft bending, and key factors that cause the axially nonuniform distribution of dynamic characteristic coefficients of the bearing are shaft bending and large aspect ratio under low speed and cantilevered load. [ABSTRACT FROM AUTHOR]

Condition monitoring of components in internal combustion engines is an essential tool for increasing engine durability and avoiding critical engine operation. If lubrication at the crankshaft main bearings is insufficient, metal-to-metal contacts become likely and thus wear can occur. Bearing temperature measurements with thermocouples serve as a reliable, fast responding, individual bearing-oriented method that is comparatively simple to apply. In combination with a corresponding reference model, such measurements could serve to monitor the bearing condition. Based on experimental data from an MAN D2676 LF51 heavy-duty diesel engine, the derivation of a data-driven model for the crankshaft main bearing temperatures under steady-state engine operation is discussed. A total of 313 temperature measurements per bearing are available for this task. Readily accessible engine operating data that represent the corresponding engine operating points serve as model inputs. Different machine learning methods are thoroughly tested in terms of their prediction error with the help of a repeated nested cross-validation. The methods include different linear regression approaches (i.e., with and without lasso regularization), gradient boosting regression and support vector regression. As the results show, support vector regression is best suited for the problem. In the final evaluation on unseen test data, this method yields a prediction error of less than 0.4 °C (root mean squared error). Considering the temperature range from approximately 76 °C to 112 °C, the results demonstrate that it is possible to reliably predict the bearing temperatures with the chosen approach. Therefore, the combination of a data-driven bearing temperature model and thermocouple-based temperature measurements forms a powerful tool for monitoring the condition of sliding bearings in internal combustion engines. [ABSTRACT FROM AUTHOR]

Identification of bearings' stiffness and damping coefficients, which strongly affects the dynamic characteristics of rotors, is another inverse problem of Rotor Dynamics. In this paper, aiming at multi-disc and multi-span rotors, two novel algorithms are proposed for identifying each bearing's coefficients based on the continuous rotor dynamic analysis method. A linear functional relationship between the main complex coefficients and the cross-coupled complex coefficients is obtained, which eliminates the coupling between the coefficients and the rotor unbalance in the forward problem. Then, Algorithm I is proposed. However, it is only suitable for rolling-bearing. To solve the problem, changing the rotating speed slightly is proposed to solve the difficulty that another set of equations cannot be developed because the slope of the proposed linear function is constant when the rotating speed is maintained at a fixed speed. Then, Algorithm II, which can be applied to both rolling-bearing and oil-journal bearing, is provided. Numerical investigations are conducted to study the two methods. It is indicated that there should be a measuring point, called an adjustment point, near each bearing, whose coefficients should be identified, to obtain high identification accuracy. Moreover, the identification accuracy of the two algorithms is strongly related to sensor resolution. When the measuring errors of all the required unbalance responses are zero or the same, the identification errors are almost equal to zero. In conclusion, the proposed algorithms provide a method for monitoring the stiffness and damping coefficients of all bearings in a multi-disc and multi-span rotor under operation conditions to predict rotor dynamic behavior for the safe and steady running of rotating machines. [ABSTRACT FROM AUTHOR]

Bearings are one of the most common causes of failure for rotating electric machines. Intelligent condition-based monitoring (CbM) can be used to predict rolling element bearing fault modes using non-invasive and inexpensive sensing. Strategically placed accelerometers can acquire bearing vibration signals, which contain salient prognostic information regarding the state of health. Machine learning (ML) algorithms are currently being investigated to accurately predict the health of machines and equipment in real time. This is highly advantageous towards reducing unscheduled maintenance, increasing the operational lifetime, as well as mitigation of the associated health risks caused by catastrophic machine failure. Motivated by this, a robust CbM system is presented for rotating machines that is suitable for various industrial applications. Novel non-linear methods for both feature engineering (one-third octave bands) and wear-state modelling (exponential) are investigated. The paper compares two main types of feature extraction, which are derived from Short-Time Fourier Transform (STFT) and Envelope Analysis (EA). In addition, two types of supervised learning, Support Vector Machines (SVM) and k-Nearest Neighbour (k-NN) are explored. The work is tested and validated on the PRONOSTIA platform dataset, with remaining useful life (RUL) classification results of up to 74.3% and a mean absolute error of 0.08 achieved. [ABSTRACT FROM AUTHOR]

This work considers the characteristics and drivers of the loads experienced by wind turbine main bearings. Simplified load response models of two different hub and main-bearing configurations are presented, representative of both inverting direct-drive and four-point-mounted geared drivetrains. The influences of deterministic wind field characteristics, such as wind speed, shear, yaw offset, and veer, on the bearing load patterns are then investigated for similarity scaled 5, 7.5, and 10MW reference wind turbine models. Main-bearing load response in cases of deterministic gusts and extreme changes in wind direction are also considered for the 5MW model. Perhaps surprisingly, veer is identified as an important driver of main-bearing load fluctuations. Upscaling results indicate that similar behaviour holds as turbines become larger, but with mean loads and load fluctuation levels increasing at least cubically with the turbine rotor radius. Strong links between turbine control and main-bearing load response are also observed. [ABSTRACT FROM AUTHOR]

Because of the nonlinearity and nonstationarity in the vibration signals of some rotating machinery, the analysis of these signals using conventional time- or frequency-domain methods has some drawbacks, and the results can be misleading. In this paper, a couple of features derived from multivariate empirical mode decomposition (MEMD) are introduced, which overcomes the shortcomings of the traditional features. A wind turbine gearbox and its bearings are investigated as rotating machinery. In this method, two types of feature structures are extracted from the decomposed signals resulting from the MEMD algorithm, called intrinsic mode function (IMF). The first type of feature vector element is the energy moment of effective IMFs. The other type of vector elements is amplitudes of a signal spectrum at the characteristic frequencies. A correlation factor is used to detect effective IMFs and eliminate the redundant IMFs. Since the basic MEMD algorithm is sensitive to noise, a noise-assisted extension of MEMD, NA-MEMD, is exploited to reduce the effect of noise on the output results. The capability of the proposed feature vector in health condition monitoring of the system is evaluated and compared with traditional features by using a discrimination factor. The proposed feature vector is utilized in the input layer of the classical three-layer backpropagation neural network. The results confirm that these features are appropriate for intelligent fault detection of complex rotating machinery and can diagnose the occurrence of early faults. [ABSTRACT FROM AUTHOR]

To meet the requirements of crashworthiness design of electric vehicle power battery packs, the failure mechanism of lithium-ion batteries was studied under different mechanical abuse conditions. Based on local indentation and plane compression loading tests on three different capacity NCR18650 cylindrical lithium-ion batteries, the force-electric-thermal responses of lithium-ion batteries were analyzed and the cross-section failure modes of the compressed battery samples were given. Then the effects of loading types and battery capacity on the failure mechanism of cylindrical batteries were discussed. The results show that internal short circuit and external short circuit failure modes of batteries may be caused by local indentation and plane compression, respectively. With the increase of battery capacity, the bearing performances of the batteries may reduce, which leads to the failure displacements decrease. Loading types and rated capacity also have an effect on the surface temperature changes of the batteries. The maximum surface temperature of the batteries after the local indentation is higher, and the surface temperature changes of the medium-capacity batteries are relatively smooth. [ABSTRACT FROM AUTHOR]

The existence of residual stresses in unloaded arteries has long been known. However, their effect is often neglected in experimental studies. Using a recently developed modelling framework, we aimed to investigate the role of residual stresses in the mechanical behaviour of the tri-layered wall of the pig thoracic aorta. The mechanical behaviour of the intact wall and isolated layers of n = 3 pig thoracic aortas was investigated via uniaxial tensile testing. After modelling the layer-specific mechanical data using a hyperelastic strain energy function, the layer-specific deformations in the unloaded vessel were estimated so that the mechanical response of the computationally assembled tri-layered flat wall would match that measured experimentally. Physiological tension–inflation of the cylindrical tri-layered vessel was then simulated, analysing changes in the distribution of stresses in the three layers when neglecting residual stresses. In the tri-layered model with residual stresses, layers exhibited comparable stresses throughout the physiological range of pressure. At 100 mmHg, intimal, medial, and adventitial circumferential load bearings were 16 ± 3%, 59 ± 4%, and 25 ± 2%, respectively. Adventitial stiffening at high pressures produced a shift in load bearing from the media to the adventitia. When neglecting residual stresses, in vivo stresses were highest at the intima and lowest at the adventitia. Consequently, the intimal and adventitial load bearings, 23 ± 2% and 18 ± 3% at 100 mmHg, were comparable at all pressures. Residual stresses play a crucial role in arterial mechanics guaranteeing a uniform distribution of stresses through the wall thickness. Neglecting these leads to incorrect interpretation of the layers' role in arterial mechanics. [ABSTRACT FROM AUTHOR]

High vibration in the horizontal motor causes damage in the shaft and bearing and it leads to a reduction in the lifetime and performance of the motor. A proper bearing preload and frame design can reduce some of the causes of high vibration. Preload increases the stiffness of the bearing and leads to a change in the natural frequency of the rotor. The frame also affects the natural frequency of the rotor as the bearing is supported by the frame. The heat generated during the operation leads to large and imbalanced thermal deformation in the frame, and it can result in high vibration. This paper presents a proper way to consider bearing preload, stiffness, and thermal deformation of the frame. A coil spring is applied to impose preload and its effect on axial rigidity is calculated by FEA (finite element analysis). Frame stiffness and thermal deformation are also calculated by FEA, and reinforcement is made to increase the stiffness of the bearing support structure and to reduce thermal deformation. The countermeasure was verified by measurement and the result showed a 50 % vibration reduction. [ABSTRACT FROM AUTHOR]

The flexural performance of three SCFRC ribbed slabs with different fibre provision area were investigated in this paper; in both ribs and flange (SFWS), ribs only with additional welded mesh in flange (SFT) and in ribs only (SFR). Short hooked end fibres of 35 mm length of 1% volume fraction was blended with the flowable self-compacting concrete (SCC) were used as the material for the slabs. Slab samples of 2.8 × 1.2 × 0.2 m were constructed and loaded until failure under fourpoint bending. Investigation was carried out in view of the load bearing capacity, deflection, energy absorption capacity as well as the failure modes. The influence of the steel fibre provision on the strain distribution was also examined. [ABSTRACT FROM AUTHOR]

Laser surface hardening is used to improve the fatigue performance of the large diameter pitch bearing. Determination of the process parameters by a trial and error method, depending on the experience of the technician, by changing the parameters repeatedly for each laser surface hardening process is time-consuming and costly. In this paper, a method of analyzing the maximum temperature and depth of a hardened layer during the laser surface hardening process for a pitch bearing raceway of a wind turbine is proposed, which combines finite element simulation and the Kriging model. A three-dimensional finite element model of a pitch bearing ring was established using ABAQUS. The temperature field analysis was performed. The effects of process parameters including laser power, scanning speed, and laser spot radius on the depth of the hardening layer were investigated. Then, taking into account the interactional effects of different process parameters, Kriging models were constructed to reflect the relationship between input process parameters and output responses. The results show that the Kriging approximation model has a small relative error compared with the simulated results and can be used to predict the hardened layer depth. [ABSTRACT FROM AUTHOR]

Vibration analysis for conditional preventive maintenance is an essential tool for the industry. The vibration signals sensored, collected and analyzed can provide information about the state of an induction motor. Appropriate processing of these vibratory signals leads to define a normal or abnormal state of the whole rotating machinery, or in particular, one of its components. The main objective of this paper is to propose a method for automatic monitoring of bearing components condition of an induction motor. The proposed method is based on two approaches with one based on signal processing using the Hilbert spectral envelope and the other approach uses machine learning based on random forests. The Hilbert spectral envelope allows the extraction of frequency characteristics that are considered as new features entering the classifier. The frequencies chosen as features are determined from a proportional variation of their amplitudes with the variation of the load torque and the fault diameter. Furthermore, a random forest-based classifier can validate the effectiveness of extracted frequency characteristics as novel features to deal with bearing fault detection while automatically locating the faulty component with a classification rate of 99.94%. The results obtained with the proposed method have been validated experimentally using a test rig. [ABSTRACT FROM AUTHOR]

Bearings as the key component of most rotating machinery, responsible for major breakdowns. Therefore, this paper addresses intelligent prognostics involving remaining useful life estimation. The proposed framework is based on a deep learning model to learn the bearing degradation from vibration responses. A comprehensive feature selection strategy involving PSO (particle swarm optimization) optimization technique and feature transformations is carried out. The sensitive prognostic features set are then input to BiLSTM (bi-directional long short-term memory) network to learn long-term time dependencies in two directions. Furthermore, the attention mechanism is integrated with BiLSTM enables selective processing of information. The experimental validation is carried out by acquiring data from a high-speed rotor supported on the bearings. The results achieved higher prediction accuracy. Also, the generalization on IEEE PHM data achieves higher RUL (remaining useful life) prediction accuracy as compared to state-of-art methods. Hence, the results proved the high performance and feasibility of the proposed RUL prognostic method. [ABSTRACT FROM AUTHOR]

We tested two types of ball bearings with an outer diameter of 750 mm to learn more about the challenges of oscillating motions for pitch bearings. The experimental conditions are derived from aero‐elastic simulations, long‐term wind speed measurements and a scaling method that considers loads and pitch angles. As a result, the parameters relevant for pitch bearings are represented appropriately, and the findings are transferable to other bearing sizes. For the tested parameter sets, severe wear occurred for over 90% of the exposed contact areas after 12 500 oscillating cycles. Decreasing the number of cycles to 1250 leads to a mix of exposed areas with 13% severe wear, 32% mild wear and 55% no wear, with no apparent pattern. The results demonstrate that a comparatively small amount of consecutive cycles can lead to severe wear. A new type of bearing tested showed less wear for the selected operating conditions. [ABSTRACT FROM AUTHOR]

The In process industries, various types of machines with rotary components are linked together to perform the manufacturing process. Bearings are the most common and important components of rotating machinery used in industries. In the event that a defect occurs in any bearing in the machine while it is operating, severe consequences will occur; therefore, the diagnosis of the fault in the bearing is critical to avoid a device failure that could cause damage to the entire system. The bearing's fault diagnosis has undergone extensive research until recently and several studies have been performed. Proper maintenance of the systems is very important to avoid cateroscopic failure of the machines. The fault diagnosis uses the vibration signal at the early stage of fault occurrence. Machine Learning concepts are gradually applied for the fault diagnosis and classification in rotating machinery's condition monitoring. Vibration signals for diagnosis of bearing fault were collected for healthy, fault at inner race and fault at outer race conditions under constant motor speed, constant load and varying speed, varying load conditions. All these fault conditions are artificially induced on the components similar to early stage of fault occurrence and signals were extracted separately. These signals are to be processed by techniques such as Wavelet analysis. Later the features are extracted from the time domine signal. The time domine statistical features are proposed to the machine learning classifiers such as K-Nearest Neighbour (KNN) and Support Vector Machines (SVM). The results show that the proposed method can reliably separate bearing fault conditions). [ABSTRACT FROM AUTHOR]

The bearing-rotor-gear system is an important mechanical component for transmitting motion and power. Due to the complex responses, the condition assessment of the transmission system becomes more difficult. Thus, a model of the bearing-rotor-gear system with a misaligned rotor is built for implementing the complex response analysis. The misalignment rotor is realized by offset connection of couplings, and the creative excitation force is transferred to the bearing inner ring through the rotor. The constructed model is checked by the corresponding experiment. From the simulation results, it is found that vibration responses are modulated by rotor frequencies, and there are rotor frequencies, harmonic frequencies of bearings, and gear pairs in the spectrum. When the misalignment defect is deepening, the high-order harmonic responses are excited. If the revolving speed increases, the modulation of the rotor frequencies is accentuated, the vibration intensity generated by gear pairs is attenuated, while the harmonic response and super-harmonic response of bearings can be suppressed, and the system vibrates mainly at the low-frequency band. When the load becomes higher, the amplitudes of the rotor frequencies, meshing frequencies, and defect frequencies are all increased. [ABSTRACT FROM AUTHOR]

Gear-shaft-bearing systems are commonly used in transmission mechanisms of modern industry. Because of the coupling relationship of the gear pair system and the bearing system, complex vibration signals will be generated when there are localized defects on the transmission system, which makes the defect diagnosis more difficult. Thus, for explaining the vibration signals, a model of gear-shaft-bearing coupling system with 36 DOFs is established. In the proposed model, the model of gear pair with spalling defects and the model of ball bearing with localized defects are combined, and the center distance error and misalignment of the shafts caused by the displacement of bearings' inner raceways are used as a connection, then the coupling relationship between the gear pair system and the bearing system is established, and the changing laws of the meshing stiffness are studied. The results show that the decrease of meshing stiffness will also be excited by the center distance error and the misalignment angle caused by system vibration. And when there are localized defects on the gear and bearing, the sudden change of actual center distance and misalignment angle will be caused, which results in a further reduction in the meshing stiffness of the gear pair as the failure zone is loaded and a short time after the failure zone. There are obvious signs of the coupling relationship between gears and bearings on the vibration spectrogram of the gear-shaft-bearing. When there is a single defect on the gear pair or bearing, the defect frequencies of the gear pair and bearing can be found at the same time on the spectrogram. Finally, the established model and the analysis of the results are verified by experiments. The established model is closer to engineering practice, and it provides a theoretical basis for fault diagnosis of rotating machinery. [ABSTRACT FROM AUTHOR]

The phenomenon of occurrence of a hydrodynamic oil film on the bearing system is analyzed. A theoretical model of the radial slide bearing system that takes into account the normal and static stresses as well as the deformations is proposed. The values of stress and deformation in the contact area are established. They are compared with the values obtained using the Hertz model. Moreover, the results of the analysis of the bearing system in thermodynamic equilibrium are presented. In this case, the journal and the bushing are separated by an oil layer. [ABSTRACT FROM AUTHOR]

In this article, the coupling effects of the unbalanced magnetic pull and ball bearing on nonlinear vibration of the three-phase asynchronous motor are investigated with the experimental and numerical methods. A test rig of a motor whose rotor supported by ball bearings is used and a 2 degrees of freedom magnetic solid coupling dynamic model of the motor rotor system is presented. The nonlinear dynamic response and spectrum are obtained from experiments and numerical analysis. The numerical results are in good agreement with test data, thus validating the presented model. It is found that the unbalanced magnetic pull and ball bearing forces possess the significantly interactional and nonlinear influences on the rotor dynamic characteristics. Small magnetic pull could impact the nonlinear bearing-rotor system, resulting in remarkable changes in the dynamic characteristics of the system. The effects of rotational speed and the rotor mass eccentricity on dynamic behaviors of the motor are discussed, and the results show that the magnetic pull gradually increases the amplitude of the ball bearing-rotor system, and its effect decreases with the increment of the rotational speed and mass eccentricity. [ABSTRACT FROM AUTHOR]

Combined bearings are made of spherical roller and thrust spherical roller bearings that are two important supports in different low-speed heavy-duty mechanisms, and the stability of their running state is the key to ensure supporting the normal operation of the mechanism. Based on the functionality of wellbore trajectory control tool, the loading distribution of the combined bearing under pure radial and axial forces is theoretically studied. Two kinds of the limit state of the rolling elements movement called "Odd press" state and "Even press" state are considered, and the Hertzian line elastic contact model is used to deal with the contact between roller and raceway. The calculation results of the contact stress and radial displacement are very close to the analysis results, and the accuracy of the analysis results is verified by the radial displacement experiment. The results indicate that the radial load causes the radial displacement of the combined bearing axis, which is about 5:81 x 10-3 mm. The radial displacement can affect the guiding accuracy of the tool to a certain extent. The radial displacement can be reduced by adjusting the structural dimensions of the combined bearing. The findings of this research can be employed to design combined Spherical Roller Bearing (SRB) and Thrust Spherical Roller Bearing (TSRB) combined bearings in actual engineering problems. [ABSTRACT FROM AUTHOR]

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The vibrations of a shaft in rotary mechanical systems supported by angular contact ball bearings are investigated theoretically and experimentally for various preloads in this paper. In the theoretical part of the study, a dynamic bearing model is presented, a rigid shaft supported by EHL angular contact bearing has been modelled as 5 DoF. Non-linear equations of motion are solved numerically by the Runge–Kutta method. In the second part of the study, an experimental setup that enables performing different operating cases has been designed to validate the theoretical results. Theoretical and experimental data are investigated and compared in both time and frequency domains and the results are compared. It is observed from both the theoretical and experimental studies that preload has a significant effect on the vibration behaviour. Results show that the increase in preload reduces the amplitude of the variable compliance frequencies of bearing, the natural frequency of system is shifted to a higher value, and using signal processing with an envelope spectrum gives better results in spectral analysis; small deviations occur between the theoretical and the experimental data due to modulation and noise from machine elements such as gear, motor, misalignment, waviness, etc. Therefore, the presented dynamic bearing model can be used with a reasonable accuracy to examine effect of preload on the vibration of shaft-bearing system. [ABSTRACT FROM AUTHOR]

Several theoretical models for predicting the performance of tilting pad journal bearings (TPJB) have been developed by the scientific community over the years. However, reliable validation of the predictions based on the theoretical models, taking into account the complexity of TPJBs, demands robustness in the design and assembly of an improved test rig. Test bench designs for testing hydrodynamic bearings must carefully consider construction details as much as possible to observe the effect from the journal bearing and, consequently, improve the predictability of its dynamical behavior. In this context, there are still relatively few test rigs in the specific literature devoted to isolating the dynamic effects from hydrodynamic bearings for analysis purposes. Therefore, a novel test rig project is described in this work, also involving the design versatility characterized by measurement feasibility in rolling-element bearings and fixed-geometry, hydrodynamic journal bearings. This test rig aims to reproduce the most diverse operating conditions in order to measure the involved physical responses and validate the different models applied to the bearings. Therefore, the bearing performance can be properly evaluated, especially when operating under critical operating conditions, thus providing important contributions to the area of lubrication and rotor dynamics. [ABSTRACT FROM AUTHOR]