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The machine tool spindle supported by oil-lubricated hydrostatic bearings suffers from high temperature rise when running at high speed. To overcome this issue, an improved motorized spindle supported by water-lubricated hydrodynamic spiral groove bearings is proposed in this study. The thermal model for the motorized spindle including heat generation model and heat dissipation model is established by aid of finite element method. A test prototype for the motorized spindle and an experimental device are developed to carry out the test study of the spindle thermal behavior. The temperature field and thermal deformation field of the motorized spindle are investigated by numerical simulation and experimental measurement. Finally, a comparative study is made from the thermal behavior of the proposed spindle with herringbone groove journal bearings (HGJB) and the replacement spindle with plain journal bearings (PJB), and a comparative study of HGJB lubricated by the water and by the oil is carried out. The result indicates that using the water-lubricated hydrodynamic spiral groove bearings can decrease the temperature rise of motorized spindle, and the thermal design for the proposed motorized spindle can reduce the axial thermal displacement of the spindle front end to a low level. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the implementation of the finite difference method on arbitrary meshes in conjunction with a fixed-point algorithm for the lubrication problem of a journal bearing with cavitation, considering the Elrod-Adams model. We establish numerical properties of the generalized finite difference scheme and provide several illustrative examples. [ABSTRACT FROM AUTHOR]

There is still a lack of effective lubrication condition monitoring methods in the field of diesel engines. The paper proposes a novel thermoelectric approach to divide the lubrication state of bearings. First, the generation mechanism of thermoelectric potential on bearings is clarified. Then, both experimental and simulation studies are done, and a strong correlation between lubrication and thermoelectric potential is shown. The film thickness and temperature are further confirmed as significant factors influencing thermoelectric potential. Generally, the thermoelectric potential increases with temperature. However, a small film thickness ratio (when the film thickness ratio is less than 4) will suppress the thermoelectric potential. Three typical lubrication states of bearings are distinguished through thermoelectric potential and supported by the Stribeck curve results. Moreover, the significant influence of lubrication on the bearing is confirmed through the analysis of surface morphology and composition. [ABSTRACT FROM AUTHOR]

The disturbance of the coal caving mechanism is the main method to solve the problem of coal falling into an arch during the top coal caving process, and the clearance in the caving mechanism is an important factor affecting its disturbance. To study the influence of clearance on the hydraulic supports, the dynamic analysis of hydraulic supports with two-level and three-level caving mechanisms is conducted considering the clearance. Based on Lagrange's equations of first kind, the mathematical model is constructed, and the equivalent spring stiffness of the oil cylinder is solved. The dynamic response of hydraulic support is studied by solving the mathematical model, and the relative position changes of the journal and bearing are compared. The research results prove that clearance has a better disturbance effect on the three-level caving mechanism. At the same time, the influence of clearance size and motion process on the motion error of the three-level caving mechanism is analyzed. Using the Kriging surrogate model and polynomial interpolation, the motion prediction model for the secondary tail beam with different clearance sizes is proposed, and the predicted values of the test samples are compared with the numerical solution values to prove the feasibility. [ABSTRACT FROM AUTHOR]

Mechanical systems are expected to operate under various load conditions, and it is necessary to use a lubrication system to achieve reliability and stable performance. Journal bearings, which are used to achieve such stable lubrication, are representative of hydrodynamic lubrication bearings. In this study, groove-shaped structures and rubber were applied to the ends of the bearings to ensure stable lubrication performance under conditions where, for various reasons, shock loads are applied in addition to static loads under misaligned conditions. The groove structure and rubber contribute to stable lubrication performance by preventing contact between the shaft and bearing as well as absorbing shock loads through elastic deformation of the groove's end due to oil film pressure. This novel design, which utilizes groove-type flexible structures and rubber, led to journal bearings that exhibited improved lubrication performance under various shock load conditions. When a shock load is applied to a mechanical system, the design proposed in this study contributes to improving the reliability of the mechanical system by enhancing its lubrication performance. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigates the impact of oil additives on the performance of hydrodynamic journal bearings using hazelnut oil. Various additives, including titanium dioxide, hexagonal boron nitride and graphite, are mixed with hazelnut oil in specific concentrations. Experimental tests are conducted in boundary and mixed lubrication regimes using a specialised rig to simulate bearing operating conditions. The friction performance of these oil‐additive combinations is evaluated in terms of bearing load, rotating speed and oil temperature. The findings contribute to understanding hazelnut oil as a potential lubricant and optimising its formulation for specific applications, promoting environmentally friendly lubricants and sustainability. [ABSTRACT FROM AUTHOR]

Bearings are common components used in the transmission system of tool machinery and linear drive equipment. With increasing demand for higher efficiency and faster production under the required accuracy, the control of bearing temperature rise under high operational speed becomes a critical issue. The improper control of temperature rise can lead to the thermal deformation and life reduction of the machinery. Conventionally, a circulating oil lubrication system is utilized with journal bearings. In this study, a similar lubrication system was adopted for the ball bearing with a retrofit design. Three control factors, i.e., rotational speed, bearing preload, and the viscosity of the lubricant used, were chosen to study their effects on the temperature performance of the proposed lubrication system. Experimental measurements showed that the lubrication system was able to lower the temperature rise of the bearing considerably compared with its unlubricated counterpart, especially at high rotational speeds. Even with the enhanced cooling from the oil circulation system, temperature rise still increased with rotational speed. However, with increased preload, the temperature rise first dropped and then increased owing to the different contact characteristics of the balls and rings of the bearing. A fitted function for the temperature rise of the bearing under different operational conditions was demonstrated to have a prediction accuracy within 3%. Therefore, the retrofitted bearing oil cooling system should be applicable in the design of high-speed machinery for industry. [ABSTRACT FROM AUTHOR]

Introduction: The demand to increase reliability and reduce maintenance costs drives the search for new condition monitoring solutions of machines. Bearings are of special interest in this matter as they are main contributors to machine downtime. Therefore, this article investigates the electric behavior of a hydrodynamic journal bearing using impedance measurement. Methods: For that purpose measurements are taken in boundary lubrication, mixed lubrication and hydrodynamic lubrication of a hydrodynamic journal bearing. In order to interpret the behaviour observed in these measurements, a phenomenological model is developed using the quantitative working space model. The measurement results are also interpreted using analogies to the Stribeck curve as a known tribological model. Additionally, measurements in mixed lubrication are analysed in detail. Results: These measurements show that the electric behaviour of journal bearings changes significantly within the mixed lubrication regime. This change in behaviour shows three distinct states within mixed lubrication which helps to identify destructive operating conditions. Furthermore, the measurements potentially allow the detection of deformation or damage of the bearing in mixed lubrication. Discussion: The quantitative analysis of the electric behaviour of journal bearings is possible in the mixed lubrication regime and can be used in future to extract condition and operating information from a system during operation. [ABSTRACT FROM AUTHOR]

In this work, the influence of magneto-rheological fluid embedded on journal bearings in the dynamic behavior of rotors is considered. The modified Reynolds equations for Bingham viscoplastic materials are used for calculation of the nonlinear hydrodynamic forces. Flexible rotors are modeled by the finite element method. The static weight of the rotor, unbalance and bearing hydrodynamic forces are included in the equations of motion. Non-linear hydrodynamic forces calculation depends on the relative positions of the journal bearings. The dynamic system response is computed by the Newmark method modified to obtain the calculation of the differential displacements and velocities for each time step. By incorporating the Newton-Raphson method the necessary corrections are included in the equations of motion. Time and frequency responses are presented for two of the case studies. The sudden elevation in oscillation magnitudes due to the oil whip phenomenon is not observed in the 1-un-up test after the application of electromagnetic induction on the MR fluid. Furthermore, the controlled variation in the viscosity of the MR fluid causes significant changes in the bearing movements, as demonstrated by the orbit graphs. [ABSTRACT FROM AUTHOR]

The rotor-bearing system is a crucial component of rotating machinery, such as turbines, pumps, compressors, and turbogenerators, which are widely used in various advanced engineering fields. This work presented a methodology for studying the behavior of an elastic Jeffcott rotor supported by two similar fluid film journal bearings. A finite element model using consistent matrix formulation was employed to simulate the shaft, including the external load, with four degrees of freedom per node. The small perturbation method was used to evaluate the second-order bearing coefficients of a journal bearing of finite length. These coefficients were further integrated with the finite element model to evaluate the dynamic response of the flexible rotors. Moreover, the system equations of motion were presented in dimensional form. The results of the second-order bearing coefficients analysis agreed with nonlinear analysis when the speed was less than the threshold speed, while there was a pronounced difference in second-order analysis when the speed was above the threshold speed. The behavior of the rotor-bearing system was studied using dynamic response and orbit diagrams, revealing that changes in rotational speed significantly affected the rotor's stability. [ABSTRACT FROM AUTHOR]

Water lubricated bearings can be used to reduce contamination due to lubricant leakage in heavy machinery such as power positioning systems of offshore platforms and ship propulsion systems. The lubrication model of a textured twodimensional parallel friction pair and a textured water-lubricated journal bearing are developed to investigate the lubrication performance. The governing equation is solved, and the fluid cavitation is analyzed using the Zwart-Gerber- Belamri (ZGB) model. A multi-objective optimization method combining the response surface and Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is used to optimize the textured journal bearings. The results indicate that a small texture width will inhibit the occurrence of liquid film cavitation. With the rise in the texture width, the cavitation effect gradually rises and stabilizes. As the texture depth deepens, the micro dynamic pressure effect is enhanced and liquid film pressure rises. Through the tests, it is found that the optimized texture parameters can be implemented to effectively diminish the friction and wear volume, also the optimized textured bearing hydrodynamic pressure effect is enhanced at the same speed. [ABSTRACT FROM AUTHOR]

The performance of the porous gas bearing depends on the geometric characteristics, material, fluid properties, and the properties of the porous media, which is a restrictor that controls the gas flow. Its application in industrial environments must support higher loads, higher supply pressure, and, consequently, higher pressure in the lubricant fluid film. Because porous media has a relatively low elastic modulus, it is necessary to consider its deformation when designing porous gas bearings. The design of porous gas bearings is a multi-objective problem in engineering because the optimization objectives commonly are to maximize the load capacity or static stiffness coefficient and minimize the airflow; these objectives conflict. This work presents a multi-objective optimization algorithm based on the nature-inspired Flower Pollination Algorithm enhanced with Non-Dominated Sorting Genetic Algorithm II. The algorithm is applied to optimize the design of a porous gas bearing, maximizing the resultant force and the static stiffness coefficient and minimizing the airflow. The results indicate a better performance of the Multi-Objective Flower Pollination Algorithm than the Multi-Objective Cuckoo Search. The results show a relatively short running time of 6 min for iterations and a low number of iterations of 50. [ABSTRACT FROM AUTHOR]

Lead-Bismuth Eutectic (LBE) is an interesting candidate as a coolant for Generation IV nuclear power plants. Lead-bismuth lubricated radial guide bearing is the key component of the mechanical pump in a lead-bismuth coolant system. In this paper, the transient calculation model of multiphase lubrication flow field of journal bearing is established by using Singhal full cavitation model and structured dynamic grid technique. Due to the saturated vapors of LBE being very low, the effects of different Non-Condensable Gas (NCG) contents on the characteristics of lead-bismuth lubricated journal bearing systems were analyzed. The results show that the NCG content has an obvious influence on the working state of the bearing. With the increase in NCG content, the bearing load capacity decreases. Under the same load, with the increase in NCG content, the eccentricity of the static equilibrium position will be larger, which will increase the risk of bearing contact with the bearing bush. Moreover, the increase of NCG content will lead to the increase of tangential oil film force work, which is helpful to improve rotor stability. [ABSTRACT FROM AUTHOR]

Methods for determining the characteristics of self-acting (aerodynamic) gas bearings have been developed for many years, but many researchers and engineers still question how sophisticated a model of such bearings should be to obtain reliable results. This is the subject of this article, which presents a numerical analysis of aerodynamic gas bearings using two alternative methods: a specialized program based on the finite difference method, and a universal CFD program using the finite volume method. Gas bearings with a nominal diameter of 49 mm, designed for a 10 kW turbogenerator operating at a rotational speed of 40,000 rpm, are analyzed. The vapor of the low-boiling medium, designated HFE-7100, is used as the bearing lubricant. The calculations focus on determining the position of the bearing journal where the bearing achieved the required load capacity and checking the bearing characteristics beyond the nominal operating point. The most important results obtained by the two independent methods are compared, and recommendations are made for those interested in the numerical analysis of self-acting gas bearings. [ABSTRACT FROM AUTHOR]

As the transmission component in mechanical systems, hydrodynamic journal bearing is widely used in large electromechanical equipment. The instability of the hydrodynamic journal bearing often results in mechanical wear and damage, which may cause maintenance shutdowns and significant financial losses. Accordingly, assessing the hydrodynamic journal bearing online is a highly effective approach to guaranteeing reliability. To analyze oil film thickness distribution under various assembly characteristics, this paper proposes a Fluid–Solid coupling analysis method based on hydrodynamic lubrication theory and Hertzian elastic deformation theory. The novelty is that the difference between the oil film thicknesses at the same measuring angle within the two opposing faces of the bearing shell is taken as the assessment parameter, which can directly indicate the deviation degree of the stator axis. Comparison of simulation and experimental results validated that the proposed method exhibits exceptional accuracy in practical applications. [ABSTRACT FROM AUTHOR]

This research aimed to determine the impact of varying loads on a hydrodynamic journal-bearing assembly, the speed of the journal corresponding to the bearing, and the influence of different grades of lubricant on the developed oil film. The critical response parameters, such as peak pressure, the direction of the journal's elevation relative to the bearing on the oil film, also known as peak pressure angle, and the frictional torque generated between the journal and bearing, has been demonstrated in this study. This work demonstrated a technique for developing an SIT capable of predicting peak pressure at various angles and frictional torque within the bearing using response surface methodology (RSM) in conjunction with a nDoE (novel design of experiment) optimization approach for an energy-efficient running condition. By overcoming the central composite design (CCD) and Box–Behnken (BB) restrictions, this robust nDoE may produce a robust prediction model for robust optimization. Both the nDoE and the generated SIT have been subjected to several fitness test matrices to ensure their resilience in qualitatively predicting response parameters without incurring any experimental expense or effort. The optimization findings indicated that a distinct tread-off between peak pressure and frictional torque was obtained at a given pressure angle. The optimal compromise of the input parameters results in the highest desirability of 90.8% for a maximum pressure of 269.969 psi and a minimum frictional torque of -2.505 N-mm at a peak pressure angle of 270°. [ABSTRACT FROM AUTHOR]

The present study aims to efficiently predict the wear volume of a journal bearing under start–stop operating conditions. For this purpose, the wear data generated with coupled mixed-elasto-hydrodynamic lubrication (mixed-EHL) and a wear simulation model of a journal bearing are used to develop a neural network (NN)-based surrogate model that is able to predict the wear volume based on the operational parameters. The suitability of different time series forecasting NN architectures, such as Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), and Nonlinear Autoregressive with Exogenous Inputs (NARX), is studied. The highest accuracy is achieved using the NARX network architectures. [ABSTRACT FROM AUTHOR]

In high-speed and heavy-load conditions, ordinary rigid tilting pad journal bearings experience significant contact stress at the pad pivot points, leading to severe pad deformation and increased wear. A flexible structure tilting pad bearing (FSTPB) is presented in this paper, using spring supports to replace the traditional pivot supports and flexible hinge supports. A theoretical calculation model for tilting pad radial journal bearings considering flexible structure deformation is established, and the impact of elastic deformation on the performance of the flexible structure tilting pad bearings is discussed. Based on theoretical research, vibration experiments on flexible tilting pad bearings under different loading conditions were conducted. The influence of various structural parameters on the vibration characteristics of the flexible tilting pad radial bearings was studied. The results indicate that, compared to ordinary tilting pad bearings, flexible structure tilting pad bearings exhibit excellent vibration reduction characteristics at high speeds. Reducing the bearing clearance, lowering the stiffness of the flexible structure, and increasing the offset angle of the flexible structure contribute to enhancing the operational stability of the bearing–rotor system. [ABSTRACT FROM AUTHOR]

Durability and reliability have been studied for decades through intensive trial-error experimentation. However, there are numerous fields of application where the costs associated with this approach are not acceptable. In lubricated machines with severe dynamic loads, such as high-power-density engines, simulation tools offer clear advantages over intensive testing. Prototypes and multiple scenarios can be cost-effectively simulated to assess different lubricants and engine configurations. The work presented here details the study of wear based on a validated elastohydrodynamic (EHD) simulation model of the connecting rod journal bearing. This model accounts for elastic deformation through a connecting rod finite element model (FEM). In addition, multiple lubricant rheological and tribological dependences, determined by specific experimental tests, are applied in the model through their interaction with the simulation software. Correspondingly, a novel wear algorithm is proposed to predict wear depth over time evolution along a proposed wear cycle based on the typical working ranges of high-performance engines. A final assessment is presented to compare 4 different ultralow-viscosity lubricants in their protective performance under severe conditions. The results show the evolution of the wear load and wear depth over the wear cycle. This evaluation is key to describing a lubricant selection procedure for high-power-density engines. [ABSTRACT FROM AUTHOR]

The following study investigates the effects of Rabinowitsch fluid on journal bearing lubrication under the influence of velocity slip and variable viscosity. The finite difference method is used to produce a numerical solution to the 2D Modified Reynolds equation. The findings verify the previous results, which indicate that the dilatant (shear-thickening) fluid pressure is higher than the Newtonian and pseudo-plastic (shear-thinning) fluids. The results show that in the presence of slip, the pressure distribution rises with the piezo- viscosity parameter (variable viscosity) by up to 75%. Compared to the Newtonian, and pseudo-plastic (shear thinning) fluid, the dilatant (shear-thickening) fluid produces the highest pressure. A higher eccentricity ratio, slip-velocity, piezo-viscosity parameter, and dilatant fluid enhances the load-carrying capacity. The reduction in the attitude angle plays an integral part in the load-carrying capacity of the journal bearing. The attitude angle decreases for all values of the bearing ratio; the dilatant fluid has the most significant reduction in attitude angle compared to the Newtonian and pseudo-plastic fluids. Slip effects reduce the attitude angle, and a further reduction occurs when the piezo-viscosity and slip factors are combined. The slip-velocity, lower values of the bearing's length to diameter ratio, greater piezo-viscosity, higher values of the eccentricity ratio, and the dilatant fluid minimize friction. The Rabinowitsch fluid properties and the addition of both slip and variable viscosity increase bearing performance by increasing the pressure distribution, load-carrying capacity of the journal bearing and reduction of the frictional parameter, and should be considered when optimizing pressure, load, and friction for the creation of the ideal journal bearing. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to identify the dynamic parameters of journal bearings in asymmetric rotor systems without additional test runs or excitations. Design/methodology/approach: An asymmetric rotor-bearing test rig was set up for the identification experiment. Comparations were made between the measured response of the asymmetric rotor and the symmetric rotor. The mathematical model of the asymmetric rotor is established by the finite element method. The identification algorithm is based on the model of the rotor and the measured vibration response to identify bearing parameters. The influence of modeling error and measurement noise on the identification results are numerically analyzed. The dynamic parameters of the journal bearings under different rotational speeds are identified and compared with the theoretical values calculated by the perturbation method. Findings: The experiment results show that the vibration characteristics of the asymmetric rotor and the symmetric rotor are different. The numerical evaluation of the identification algorithm shows that the algorithm is accurate and has good robustness to modeling error and measurement noise. The identified dynamic parameters agree reasonably well with the parameters derived from the theoretical bearing model. Originality/value: The proposed identification method uses the unique vibration characteristics of asymmetric rotors to identify the bearing dynamic parameters. As the method does not require excitations or additional test runs, it is suitable for the field test. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0096/ [ABSTRACT FROM AUTHOR]

Purpose: This study aims to find the dynamic performance parameters of the journal bearing with micro geometries patterning the arc (crescent) shape textures provided in three specific regions of the journal bearing: the full, the second half and the increasing pressure region. The dynamic behavior of textured journal bearings has been analyzed by computing dynamic parameters and linear and non-linear trajectories. Design/methodology/approach: The lubricant flows between the bearing and journal surface are governed by Reynold's equation, which has been solved by finite the element method. The dynamic performance parameters such as stiffness, damping, threshold speed, critical mass and whirl frequency ratio are examined under various operating conditions by considering various ranges of eccentricity ratios and texture depths. Linear and non-linear equations of motion have been solved with Ranga–Kutta method to get journal motion trajectories. Also, the impact of adding aluminum oxide and copper oxide nanoparticles to the base lubricant in combination with arc-shaped textures is analyzed to further see any enhancement in the performance parameters. Findings: The findings demonstrated that direct stiffness and damping parameters increased to their maximum level with six textures in the pressure-increasing region when compared with the untextured surface. Also, nanoparticle additives showed improvements above the highest value attained with no inclusion of additives in the same region or quantity of textures. Originality/value: Engineers may design bearings with improved stability and overall performance if they understand how texture form impacts dynamic properties. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The water-lubricated hydrodynamic spiral grooved bearings have been utilized to support the high-speed motorized spindle. However, the viscous damping effect of water is much weaker than that of the oil, so the dynamic behavior and the stability of the motorized spindle with the water-lubricated spiral grooved bearings need to be studied thoroughly. This paper established an improved rotor-bearing dynamic model for the motorized spindle by incorporating both the distributed effect of journal bearing and the tilting effect of thrust bearing into a turbulent thermohydrodynamic lubrication model. An experimental setup for the motorized spindle was developed to measure the spindle dynamic behaviors and verify the established dynamic model. The critical speeds, the transient dynamics, and the stability of the motorized spindle are studied theoretically and experimentally. The results show that the motorized spindle with the water-lubricated spiral grooved bearings can operate at high speeds with a satisfactory supporting stiffness and exhibits an excellent operational stability. [ABSTRACT FROM AUTHOR]

This article investigates the influence of textured shapes and electrorheological fluid (ERF) behavior on slot entry hybrid conical journal bearing system (HCJBs). The slot entry restrictor is used as a compensating element to supply the lubricant in the clearance space. Spherical, rectangular, and triangular textured shapes over the surface of conical bearings have been employed. Furthermore, the intelligent properties of ERF on the behavior of textured slot entry HCJBs have been analyzed. The finite element method (FEM) and the successive iteration-based Gauss-Seidel method have been used to solve the modified Reynolds equation. The results drawn from this study show different influences on the bearing performance for different textured shapes. Using textured surfaces and ERF improves the minimum fluid film thickness, stability, and bearing stiffness compared to the non-textured bearing. [ABSTRACT FROM AUTHOR]

Resource and energy efficiency are of high importance in gearbox applications. To reduce friction and wear, an external lubricant supply like dip or injection lubrication is used to lubricate tribosystems in machine elements. This leads to the need for large lubricant volumes and elaborate sealing requirements. One potential method of minimizing the amount of lubricant and simplifying sealing in gearboxes is the self-lubrication of tribosystems using oil-impregnation of porous materials. Although well established in low-loaded journal bearings, self-lubrication of rolling-sliding contacts in gears is poorly understood. This study presents the self-lubrication method using oil-impregnated porous sinter material variants. For this, the tribosystem of gear contacts is transferred to model contacts, which are analyzed for friction and temperature behavior using a twin-disk tribometer. High-resolution surface images are used to record the surface changes. The test results show a significant increase in self-lubrication functionality of tribosystems by oil-impregnated porous sinter material and a tribo-performance comparable to injection-lubricated tribosystems of a sinter material with additionally solid lubricant added to the sinter material powder before sintering. Furthermore, the analyses highlight a significant influence of the surface finish, and in particular the surface porosity, on the overall tribosystem behavior through significantly improved friction and wear behavior transferable to gear applications. [ABSTRACT FROM AUTHOR]

Due to the complexity of lubricating characteristics in the variable-sectional and multiscale clearance, the absence of an effective prediction method and theoretical basis of multi-foil aerodynamic journal bearing with bump-backing foils needs to be further developed. Hence, a modified efficient static characteristics model has been established, of which the one-dimensional curved beam theory is integrated and the elasto-hydrodynamic influence is intelligently concerned. It can be used to well predict the influential mechanisms of operational, geometric, and physical parameter effects on the static characteristics, and the important variation laws are systemically clarified. It aims to furnish a more effective and computationally efficient method and theoretical foundation for this significant type of bearing and promote its engineering design and performance optimization. [ABSTRACT FROM AUTHOR]

In this paper, the effect of micro-dimple textures (produced by a laser) on the tribological properties of bearings is investigated. This study offers guidelines to reduce the friction torque of the bearing pair and addresses the problem of difficult start-ups after shutdowns. Micro-pits with different texture diameters and depths were machined on the surface of journal bearings. Then, the impact of several different texture parameters on the tribological performance of the bearing pairs was studied using an orthogonal experimental design. Subsequently, the surface morphology of the bearings before and after the friction and wear test was observed using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). These observations were then used to determine the type/state of friction and wear, which also improves our understanding of how texture affects the service life of bearings. The results indicate that the bearings' micro-pit surface hardness follows an approximate parabolic spatial distribution that decreases along the micro-pit wall. Furthermore, the laser processing of surface textures was found to cause hardening in certain areas, and the chemical composition of elemental carbon and oxygen at the inner surface of processed bearings increased by 31.1% and 7.9%, respectively. Moreover, abrasive wear was identified as the primary form of wear. The textured surface's antifriction mechanism primarily functioned to trap particles, which acted as a secondary lubrication source and altered the lubrication states by serving as a medium for supplied lubricants. The results confirm that a suitable selection of texture parameters can not only effectively reduce the friction coefficient without shortening the service life of the bearing pair but also facilitate the smooth start-up of the rotor–bearing system. [ABSTRACT FROM AUTHOR]

Copyright of AIN Journal is the property of Arab Institute of Navigation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Linearized dynamic bearing coefficients are commonly used to determine the vibration response of rotors supported by journal bearings. Journal bearings can, however, behave nonlinearly, particularly in the presence of bearing wear. This work was undertaken to examine the effect of bearing wear severity on the linear and nonlinear responses of a rigid rotor at low, moderately, and highly loaded operating regime. Numerical results showed that the center of the nonlinear orbit coincides with the center of the linear orbit for all three operating regimes in non-worn bearing. However, in worn bearings, the center of the nonlinear orbit shifts away from the center of the linear orbit for all three operating regimes. The nonlinear analysis also showed that super-synchronous vibration response may occur, particularly at highly loaded operating regimes and at the maximum wear depth investigated in this work. [ABSTRACT FROM AUTHOR]

In this paper, a load-sharing performance analysis method of the planetary gear system is proposed considering the coupling effects of double-helical gear and journal bearing. Firstly, the coupling effects between the meshing characteristics of the double-helical gear pair and the dynamic characteristics of journal bearing under the actual operation state are studied, the dynamic model of the double-helical gear planetary transmission system is established, and the load sharing coefficient before and after considering the coupling effects are calculated; secondly, the load sharing characteristic test rig of planetary transmission system is built, and the load sharing coefficient of gear system under the test condition is measured to verify the accuracy of the proposed method; finally, the effects of operating parameters and structural parameters on the load sharing characteristic of gear system are discussed. [ABSTRACT FROM AUTHOR]

To investigate the variation of carrying capacity of a spiral-groove gas radial bearing under different Reynolds numbers,a gas bearing lubrication model modified by Ng-Pan theory was established.The model was solved using the finite difference method to obtain the bearing characteristics under different Reynolds numbers.The effects of geometric parameters and groove parameters on carrying capacity were analyzed.The results show that the carrying capacity of the spiral-groove gas radial bearing in non-laminar lubrication state is greater than that in the laminar lubrication state .The geometric parameters of the bearing have a significant influence on the bearing characteristics. As the eccentricity increases,the bearing capacity increases divergently, and the difference between the bearing capacity in the non-laminar lubrication state and the laminar lubrication state increases.As the aspect ratio increases,the bearing capacity increases convergently.Among the groove parameters,groove width ratio and groove depth ratio have a significant impact on the bearing characteristics, and the bearing bearing capacity increases with the increase of groove width ratio and groove depth ratio.While the influence of the number of grooves on bearing bearing capacity is not significant,and the helix angle only has a significant impact on bearing capacity in non-laminar lubrication state.The inlet pressure of bearing has obvious influence on carrying capacity. As the inlet pressure increases,the bearing capacity increases in laminar lubrication state and fluctuates greatly in non-laminar lubrication state. [ABSTRACT FROM AUTHOR]

This paper introduces a rigorous and comprehensive approach to the assessment of marine shafting systems through the utilization of an advanced π-Theorem-based scaling methodology. Integrating journal-bearing similarity assessment and shaft-line scaling methodology with advanced dimensional analysis, the study aims to provide a methodology foundation for systematic replication and analysis of marine shafting systems through scaled models. The proposed scaling methodology ensures geometric and mechanical similarity in terms of shaft-line deflection, considering key scaling parameters such as shaft length, diameter, weight, loads, rotational speed, material properties, bearing locations, and offsets. The advanced dimensional analysis computes specific non-dimensional ratios to guarantee a close resemblance between a real-size system and a scaled lab model. The methodology is analytically derived and validated with numerical simulations for a case study, conducting comparative analysis, evaluating discrepancies, and utilizing the integrated framework for experimentation. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the 3D-printed textured journal bearings (TJBs) are developed by fused deposition modelling (FDM) process with three different polymers such as ABS, PLA and nylon. For the study, the process parameters such as texture depth (TD), rotor speed (S) and load (L) are considered as input parameters. The experimental analysis of 3D-printed TJB is performed based on the response surface methodology (RSM). With the RSM technique, the influence of these input parameters on the tribological performance of 3D-printed TJBs. The tribological performance of 3D-printed TJBs are wear resistance (WR) and wear temperature (WT). Further, the GRA analysis is performed to evaluate the optimum value of these process parameters for ABS, PLA and nylon polymer. These results demonstrate that the wear resistance (WR) of TJBs is first increases with the texture depth and then starts decreasing. Among all the polymers, the ABS polymer is the most significant, and nylon is the least significant polymer for the 3D-printed TJBs. The maximum WR (i.e. 76.576 m/mm3) of 3D-printed TJBs is observed for the PLA polymer. Whereas, nylon provides the least WR (i.e. 9.572 m/mm3) of 3D-printed TJBs. At the optimal value of process parameters (TD = 1.5 mm, S = 500 r/min and L = 10N), the WR and WT of 3D-printed TJBs (for ABS polymer) are 62.126 m/mm3 and 323.75 K respectively. [ABSTRACT FROM AUTHOR]

Polymer based additives with long chain of suspended particles in oil retain polarity effect in the presence of couple stresses. Further, at high speed of journal bearing, the oil film experiences substantial agitation due to pressure-viscosity interaction which evolve piezo-viscous dependency of the lubricant. The present article addresses the combined effects of piezo-viscous dependency and couple stresses of lubricant on the characteristics of multi-recessed hybrid journal bearing under misaligned operation. To govern the flow of piezo-viscous-polar lubricant in clearance space of the journal bearing, a piezo-polar function is used to obtain the modified form of Reynolds equation. Galerkin's technique is employed to obtain the finite element formulation in the form of algebraic equation, which is solved to determine the unknown pressure field in the bearing system. The present results reveal that the use of piezo-viscous-polar lubricant offers an enhancement in performance characteristics of bearing system, i.e., a significant hike of 13–36%, 27–30% and 7–10% in the values of S ¯ ij , C ¯ ij and ω ¯ th respectively vis-à-vis Newtonian lubricant. The numerically simulated non-dimensional results presented in the article may be useful to generate the bearing design data of the hybrid journal baring system functioning in realistic and stringent operating conditions. [ABSTRACT FROM AUTHOR]

This study aims to analyze the impact of uniform and eccentric load conditions on the performance of internal feedback hydrostatic thrust and journal bearing. Two distinct models are established: a three-degrees-of-freedom uniform load model and a five-degrees-of-freedom eccentric load model. The support stiffness, overturning stiffness, and flow rate for both thrust and journal bearings are calculated. Additionally, numerical analysis is conducted to examine the influence of oil film thickness, inlet pressure, and restrictor size on the operational characteristics of the bearings, revealing the interplay between an eccentric load and journal bearing speed. The validity of the theoretical algorithm is verified through finite element simulation. The research outcomes hold significant guiding implications for the design and application of internal feedback hydrostatic bearings. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the performance of bio-based lubricants (BBL), namely, palm mid-olein (PMO) enriched with an antioxidant agent, tertiary-butylhydroquinone (TBHQ) and a viscosity improver, ethylene-vinyl acetate (EVA), in journal bearing (JB) applications. Design/methodology/approach: Samples of the BBL were prepared by blending it with TBHQ and EVA at various blending ratios. The oxidative stability (OS) and viscosity of the BBL samples were examined using differential scanning calorimetry and a viscometer, respectively. Meanwhile, their performance in JB applications was evaluated through the use of a JB test rig with a 0.5 length-to-diameter ratio at various operating conditions. Findings: It was found that the combination of PMO + TBHQ + EVA demonstrated a superior oil film pressure and load-carrying capacity, resulting in a reduced friction coefficient and a smaller attitude angle compared to the use of only PMO or VG68. However, it was observed that the addition of TBHQ and EVA to the PMO did not have a significant impact on the minimum oil film thickness. Practical implications: The results would be quite useful for researchers generally and designers of bearings in particular. Originality/value: This study used PMO as the base stock, and its compatibility with TBHQ and EVA was investigated in terms of its OS and viscosity. The performance of this treated BBL was evaluated in a hydrodynamic JB. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2023-0363/ [ABSTRACT FROM AUTHOR]

Purpose: To guide the stable radius clearance choice of water-lubricated bearings for single screw compressors, this paper aims to analyze the effects of turbulence and cavitation on bearing performance under two conditions of specified external load and radius clearance. Design/methodology/approach: A modified Reynolds equation considering turbulence and cavitation is adopted, based on the Jakobsson–Floberg–Olsson boundary condition, Ng–Pan model and turbulent factors. The equation is solved using the finite difference method and successive over-relaxation method to investigate the bearing performance. Findings: The turbulent effect can increase the hydrodynamic pressure and cavitation. In addition, the turbulent effect can lead to an increase in the equilibrium radius clearance. The turbulent region exhibits a higher load capacity and cavitation rate. However, the increased cavitation negatively impacts the frictional coefficient and end flow rate. The impact of turbulence increases as the radius clearance decreases. As the rotating speed increases, the turbulence effect has a greater impact on the bearing characteristics. Originality/value: The research can provide theoretical support for the design of water-lubricated journal bearings used in high-speed water-lubricated single screw compressors. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0029/ [ABSTRACT FROM AUTHOR]

The current paper is aimed to investigate the deformability effects of the bearing surface on the lubrication performance of cylindrical journal bearing with finite length under turbulent conditions. The bush is coated with a thin resilient layer with a smooth surface, the radial distortions of which are of the same order of magnitude as the film thickness. The elastohydrodynamic problem is studied under elasticity conditions in accordance with the plain strain hypothesis (Winkler model). The modified Reynolds equation is carried out on the base of the turbulent lubrication model of Hirs (bulk flow model). The partial differential equation is solved numerically by successive over-relaxation technique on a finite difference grid, considering different values of coating materials, lubricant viscosity, and journal speed. Results for the performance characteristics of the bearing are given for several selected values of Reynolds number and elasticity parameters of the soft liner on the bush. [ABSTRACT FROM AUTHOR]

The purpose of this work is to examine the effects of wear severity on the static and dynamic characteristics of journal bearings, and on the vibration response of a rigid rotor supported by journal bearings. Numerical simulations using MATLAB was conducted for three different operating regimes, namely low loaded operating regime ( ϵ 0 = 0.15 ), moderately loaded operating regime ( ϵ 0 = 0.45 ) and highly loaded operating regime ( ϵ 0 = 0.75 ) with wear depth parameter ratio (δ ) varied from 0 to 0.5 at increments of 0.1. Numerical results showed that the vibration response of the rotor generally increases with the increase of the wear depth for all cases of low, moderately and highly loaded operating regimes of the bearings. For the values of parameters considered in this work, it was shown that the vibration response amplitude of the rotor in worn journal bearings may be six times larger compared to the response amplitude of the rotor in non-worn bearings. [ABSTRACT FROM AUTHOR]

This study aims to verify the effectiveness of the 250 HP class compressor system to which the integrated hybrid air-foil magnetic thrust bearing (i-HFMTB) proposed in (Ha et al., 2023, "Integrated Hybrid Air Foil-Magnetic Thrust Bearing (i-HFMTB) Part I: Preliminary Experimental Test for Rotordynamic Parameter Identification and Behavior With PD Control," ASME Paper No. GT2023-102860) [1] is applied, and the vibration and instability problems of air-foil journal bearing (AFJB) occurring in the rigid mode are controlled by i-HFMTB. The compressor rotor is supported by two AFJB (journal diameter = 60 mm) and an i-HFMTB, and the length and mass of the rotor are 550 mm and 15.24 kg, respectively. i-HFMTB has a structure in which air-foil thrust bearing (AFTB) pads are inserted into eight slotted active magnetic thrust bearings (AMTB), and PD control (proportional gain: 4000; differential gain: 10) is applied. The operating area was identified through AFJB's dynamic coefficients and rotordynamic analysis. As a result, in the experiment with the 250 HP compressor system supported only by two AFJB, sub- and super-synchronous vibrations were generated owing to the AFJB's insufficient load capacity and damping in the rigid mode (7000 rpm) region, and this instability did not disappear even upon increasing the speed to 15,000 rpm. However, when i-HFMTB was turned on in rigid mode, it was confirmed that the sub- and super-synchronous vibrations were significantly reduced. The thrust collar tilt angle was calculated through orbit trajectory analysis of the impeller and cooling side, and it was confirmed that the tilt angle of the thrust collar was reduced during i-HFMTB operation. [ABSTRACT FROM AUTHOR]

This research aims to examine the compound impact of adding rectangular textures to various zones on the surface of the bearing and nanoparticles in the lubricant on the properties of journal bearing. A lubrication models with various texture depths and eccentricity ratios of journal bearing are created and simulated using CFD-FSI method to get static properties like load capacity and frictional force. Aluminum oxide nanoparticles were added in weight ratios ranging from 0.1 to 0.5 %, and the change in viscosity due to these additives in the lubricant was considered. Cavitation and the dependence of viscosity on temperature effects are also considered. The validation results show that the acquired results from the current simulation method agree well with the experimental results in the reference. The outcomes indicated that the highest load capacity and the lowest frictional force are found in the high-pressure region. It was noted that the maximum rise in load capacity was 16.51% without nanoparticles at a texture depth of 0.5 mm and eccentricity ratio of 0.1, and with the adding of 0.5 wt. % of nanoparticles to the lubricant in the same region, the load carrying capacity increased to 40.87 % compared to a bearing without textures. [ABSTRACT FROM AUTHOR]

In this paper, we develop a method for the estimation of airgap spatial variation from the harmonics that appear in the stator's current under static eccentricity conditions. We move beyond the detection of the eccentricity fault and endeavour to quantify the severity of this fault. To achieve this, we formulate the problem as a mathematical inverse problem and attempt to solve it in the Bayesian framework using the so-called Bayesian approximation error approach. The solution takes the form of an algorithm capable of estimating the parameter(s) that characterize the spatial variation of the airgap length from noisy and limited data. Furthermore, it can quantify the uncertainty associated with the results as a byproduct of the Bayesian analysis approach employed in this paper. The results demonstrate that with each iteration of the algorithm, estimation accuracy improves, and the uncertainty of the estimated results reduces. • Bayesian approximation error analysis shows promise in monitoring electrical machines with eccentric rotors. • The paper applies Bayesian inversion for online estimation of airgap length in induction machines with eccentric rotors. • The study estimates static eccentricity ratio from limited data on harmonics of the machine line currents. • This paper gives an analytical method for calculating all inductances of induction machines under static eccentricity. [ABSTRACT FROM AUTHOR]