Sliding Bearing System Research Articles

Numerical Analysis on Frictional Heat Effect in Polyether-Ether-Ketone (PEEK)/Steel Pair by using OpenFOAM Model

The PEEK material has been applied to a sliding bearing system in a power plant system because of its high mechanical durability. In the solid friction of the PEEK materials, the frictional heat becomes the important factor because the temperature increase due to the frictional heat causes the rapid increase of the frictional coefficient of the specimen. To maintain the low frictional coefficient of the PEEK materials, an effective cooling method for the PEEK materials needs to be developed. In this study, the passive cooling method, which attaches the heat sink to the PEEK materials, was suggested. For evaluating the suggested cooling method of the PEEK materials, the calculation model adopting OpenFOAM, which is open-source software, has been developed. Adopting some functions and libraries of OpenFOAM, the frictional heat, heat resistance, and heat transfer coefficient on the heat sink were modelled. The sliding bearing experiment was conducted and time variation of the temperature and friction coefficient in the ring specimen were measured. The temperature variation in the ring specimen was compared with the calculation result. From the numerical calculation results, the developed calculation model could simulate the temperature-time variation of the ring obtained in the experiment, when the variation of the frictional coefficient, heat resistance, and heat transfer coefficient was modelled appropriately. Based on the friction and wear test results, by applying a heat dissipation mechanism to the ring test piece, the calorific value of the PEEK material can be reduced, and it is stable. It was suggested that the friction was maintained.

Experimental Investigation of the Dynamic Response of a Sliding Bearing System under Different Oil Pressure Levels

A sliding bearing system performs a critical function in a rotating machinery system and provides support for the rotating components. In this paper, a single-rotor experimental rig and a dual-rotor sliding bearing experimental rig were independently established, and the dynamic response of the test systems are investigated. To study the effect of oil pressure levels on the dynamic response of the test systems under the single-rotor system and the dual-rotor system, the vibration response of single-rotor and dual-rotor systems ware analyzed by different oil inlet pressures to study the effect of oil pressure levels on the dynamic response of the test systems under the single-rotor system and the dual-rotor system. Among them, the single rotor system under a large oil pressure system is mostly periodic and more stable. While under different inlet oil pressure conditions applied in the experiments, the dynamic motion of the dual-rotor bearing system is relatively stable in both the subcritical and supercritical speed regions. However, the oil whirl and oil whip of the dual-rotor system were observed at the critical speed, which causes the system into unstable multiperiodic motions. In general, this paper can give some insight into the dynamic response of the sliding bearing system influenced by different oil pressure levels.

Condition Assessment of Railway Bridge Sliding Bearing Using Alternating Vehicle Longitudinal Excitation

The identification of maximum bearing friction is critical to working performance assessment of bridge sliding bearings. The friction-displacement hysteresis model was used for the bearing working performance (BWP) assessment. In this study, the bearing longitudinal displacement (BLD) hysteresis model is established for the sliding bearing system, introducing bearing friction and vehicle longitudinal effect. A novel approach for BWP assessment is presented using alternating vehicle longitudinal excitation. First, bearing friction and vehicle longitudinal effect were introduced to establish the hysteresis model of BLD. Subsequently, the evaluation index and the assessment approach were proposed for BWP assessment using the alternating vehicle longitudinal excitation. Finally, the assessment approach for BWP was applied to a real-world railway bridge. The results show that temperature-displacement relationship model for BWP assessment is unapplicable under significant vehicle longitudinal effects. On the contrary, the BLD induced by alternating vehicle longitudinal excitation can identify the degradation of the BWP when vehicle longitudinal excitation overcomes maximum bearing friction.

Shape memory alloy (SMA)-cable-controlled sliding bearings: development, testing, and system behavior

This paper presents an innovative type of friction sliding bearing system incorporating shape memory alloy (SMA) cables. The study commences with cyclic tests on individual SMA cables to understand their fundamental mechanical properties. The working principle of the proposed SMA-cable-controlled friction sliding bearing (SMA-sliding bearing) is subsequently described, followed by physical tests on two SMA-sliding bearing specimens. The bearing specimens show rectangular hysteresis loops induced by Coulomb friction before the SMA cables are stretched, and afterward the load resistance and energy dissipation capacity of the bearings are increased accompanied by certain self-centering capability due to the engagement of the SMA cables. Such action is expected to effectively restrict excessive displacements of the bearings and to help reduce the residual displacement. Following the experimental study, a theoretical model of the new bearing is developed and numerical simulation is carried out. The theoretical and numerical results agree very well with the experimental results. A case study focusing on a three-span continuous bridge subjected to pulse-like near-fault (NF) ground motions is subsequently conducted, where three types of bearing system, namely, conventional sliding bearing system, SMA-sliding bearing system, and steel-cable-controlled (steel-sliding) bearing system are compared. The system-level analysis results show that the proposed SMA-sliding bearing has its superiority in superstructure displacement control, with a limited increase in the curvature ductility of the pier.

SOM-Based High-Dimensional Design Spaces Mapping for Multi-Objective Optimization

Multi-objective optimization can reveal the complex parameter-objective relationships in the high-dimensional design problems. However, the data-extraction and data-presentation of the high-dimensional complex nonlinear system suffers from the increasing dimensionality. Key features and data-distribution of high-dimensional design spaces:parameter and objective spaces could be obtained by using Self-Organizing Maps (SOM) method, which re-clusters the high-dimensional multi-attribute data existing on the Pareto front into several low-dimensional maps. Correlations among all the design variables can be drawn according the colorized topological structure of the maps. Under the constraints including geometric structure and operating parameters, a low-cost and high accurate Kriging surrogate model was established to optimize a hybrid sliding bearing based on the sequential design method. Correlations between 3 objectives:"friction-to-load" ratio, temperature rise, instability threshold speed and 4 design parameters were extracted by SOM. Optimal feature regions were captured and analyzed. Results show that, within the specific feasible design space, supply pressure, axial bearing land width have important impact on the selected objectives, whereas the other parameters such as deep pocket depth and shallow pocket angle have relatively limited impact. A series of corresponding design decisions and optimization results help to understand the mechanism of the hybrid sliding bearing system in a much more intuitive way.

Dynamic wear sensor array based on single-electrode triboelectric nanogenerators

Smart sensor is the foundation and core of intelligent manufacturing, which is developing for miniaturization, integration and self-powering. Here, we report an active sensor array based on single-electrode triboelectric nanogenerators (TENGs) for dynamic wear monitoring and positioning. The sensor unit is fabricated by embedding the electrode into the core-shell composite with polytetrafluoroethylene (PTFE) as the core and polymethylmethacrylate (PMMA) as the shell. The working mechanism and performances of the sensor unit with different parameters including the thickness of PTFE@PMMA layer, reciprocating frequency, sliding displacement, electrode width and the diameter of copper bar are systematically investigated and discussed. By integrating into the sensor array, the dynamic wear monitoring and positioning have been realized, which can be used to detect the wear states of multiple regions in the sliding bearing system. This work has extended the application of the TENGs to determine the wear states of polymer interface and may promote the great development of intelligent bearing.

Effects of heat sink on frictional heat effect in PEEK/Steel Pair（Numerical calculation using OpenFOAM model and experiments）

The PEEK material has been applied to a sliding bearing system in a power plant system because of its high mechanical durability. In the solid friction of the PEEK materials, the frictional heat becomes the important factor because the temperature increasing due to the frictional heat causes the rapidly increasing of the frictional coefficient of the specimen. In order to maintain the low frictional coefficient of the PEEK materials, the effective cooling method for the PEEK materials needs to be developed. In this study, the passive cooling method, which attaches the heat sink to the PEEK materials, was suggested. For evaluating the suggested cooling method of the PEEK materials, the calculation model adopting OpenFOAM, which is the open source software, has been developed. Adopting some functions and library of OpenFOAM, the frictional heat, heat resistance, and heat transfer coefficient on the heat sink were modeled. The sliding bearing experiment was conducted and time variation of the temperature and friction coefficient in the ring specimen were measured. The temperature variation in the ring specimen was compared with the calculation result. From the numerical calculation results, the developed calculation model could simulate the temperature time variation of the ring obtained in the experiment, when variation of the frictional coefficient, heat resistance, and heat transfer coefficient were modeled appropriately. Finally, the calculation predict ability using OpenFOAM in the considered situation was evaluated.

Seismic performance of Transverse Steel Damper seismic system for long span bridges

To provide seismic resistance of long span bridges in transverse direction, fixed bearings are often installed between girders and piers (or towers). Although the fixed bearings and substructures can be designed extraordinarily strong to resist the design seismic loads, they may still be vulnerable when the design seismic loads are exceeded. To address this issue, this paper proposes a novel seismic system, which combines Transverse Steel Dampers (TSDs) with conventional sliding bearings, and is named the TSD seismic system. A TSD consists of several triangular steel plates outfitted with steel hemispheres at their upper vertices. The steel hemispheres not only allow free movements of the superstructures with respect to the piers in the longitudinal direction, but also provide reliable load paths in the transverse direction. Quasi-static tests have been conducted to investigate seismic behaviors of the TSD using two scaled and two prototype specimens. Test results show that the TSD has excellent performance in energy dissipation, large displacements, and synchronization of triangular plates under complex contact conditions. The load-displacement constitutive model of the TSD has been established using a bilinear model in ABAQUS, followed by a design method for the TSD seismic system. A 620m long-span cable-stayed bridge was selected for a case study of the TSD seismic system. Ground motions recorded at various site conditions were used as seismic inputs. Numerical results show that: (1) the TSD seismic system can achieve a desired balance of transverse seismic displacements and forces, which is not the case when a sliding bearing system (without TSDs) or a fixed bearing system is used; (2) TSDs contribute to most of the energy dissipation capacity of a TSD seismic system while the contribution of sliding bearings is negligible; and (3) the proposed TSD seismic system, compared with a sliding system, tends to be less sensitive to seismic input properties, such as peak ground accelerations and site conditions.

Seismic vulnerability mitigation of liquefied gas tanks using concave sliding bearings

The aim of this paper is to evaluate the effectiveness of a concave sliding bearing system for the seismic protection of liquefied gas storage tanks through a seismic fragility analysis. An emblematic case study of elevated steel storage tanks, which collapsed during the 1999 Izmit earthquake at Habas Pharmaceutics plant in Turkey, is studied. Firstly, a fragility analysis is conducted for the examined tank based on a lumped-mass stick model, where the nonlinear shear behaviour of support columns is taken into account by using a phenomenological model. Fragility curves in terms of an efficient intensity measure for different failure modes of structural components demonstrate the inevitable collapse of the tank mainly due to insufficient shear strength of the support columns. A seismic isolation system based on concave sliding bearings, which has been demonstrated a superior solution to seismically protect elevated tanks, is then designed and introduced into the numerical model, accounting for its non-linear behaviour. Finally, a vulnerability analysis for the isolated tank is performed, which proves a high effectiveness of the isolation system in reducing the probability of failure within an expected range of earthquake intensity levels.

Response simulation of hybrid base isolation systems under earthquake excitation

In the present work, we investigate the response of a hybrid base isolation system under earthquake excitation. The physical parameters of the hybrid base isolation system are identified from dynamic tests performed during a parallel project involving two residential buildings in the town of Solarino, Sicily, using the well-established optimization procedure ‘covariance matrix adaptation-evolution strategy’ as dynamic identification algorithm in the time domain. The base isolation system consists of high damping rubber bearings and low friction sliding bearings. Two separate models are employed for the numerical simulation of the high damping rubber bearing component, namely a bilinear system and a trilinear system, both in parallel with a linear viscous damper. In addition, a linear Coulomb friction model is used to describe the behavior of the low friction sliding bearing system. Analytical solutions are provided, in compact form, for all possible phases of motion of the hybrid base isolation system under earthquake excitation. A series of numerical simulations are carried out to highlight the behavior of the considered hybrid base isolation system under different excitation and site conditions.

Stiffness and damping of liquid crystal lubricating film under electric field

In this paper, a controllable sliding bearing system, in which a liquid crystal was applied as a lubricant, was constructed, and experiments were conducted to study its controllability and dynamic properties. In the present system, a sinusoidal load was applied to the bearing pad by a magnetic exciter and the equivalent spring and damping constants were identified under various electric fields, sliding velocities, and film thicknesses. Results show that the applied electric field strength had a great effect on the damping properties of the liquid crystal film, whereas it had less effect on the equivalent spring constant.

DESIGN AND TRIAL OF INTELLIGENT SLIDING BEARING SYSTEM

A patented intelligent sliding bearing system of roller cone bit is invented to monitor radial wear and to stop the running of bearing automatically when the wear reaches the predetermined limit so as to prevent the wear-induced cone loss by early warning. In this paper, the basic operating mechanism of new bearing is stated and discussed. A series of tests are conducted to investigate the mechanical features and the reliability of the new bearing system. The performance of the system is proven to be adequate by the test results.

Vibration analysis of cracked rotor sliding bearing system with rotor–stator rubbing by harmonic wavelet transform

In this paper, the vibration of a cracked rotor sliding bearing system with rotor–stator rubbing is investigated using harmonic wavelet transform (HWT). Three non-linear factors, non-linear oil film forces, rotor–stator rubbing and the presence of crack, are taken into account. So the non-linear behavior of the rotor will be much more complex. According to Newmark method, the dynamic response of the rotor is calculated. Using HWT method, the effect of these non-linear factors is analyzed simultaneously in both time and frequency domain. The numerical simulated result shows that HWT will be available to analyze this multi-non-linear factors rotor effectively and can reveal the exact fault characteristics in detail.

Toward a durable impeller pump with mechanical bearings.

Our former work demonstrated that our impeller pump could support the circulation of experimental animals for several months without harm to blood elements or organ function. The termination of the experiments was mostly related to wear of the mechanical bearing and thrombosis along the bearing. To solve the bearing problem, we investigated a magnetic bearing in our lab, which resulted in some new problems, such as complicated design and control, considerable energy consumption, and lesser reliability. Progress in developing an impeller pump for long-term application has recently been achieved. Instead of using a sliding bearing system, we devised a rolling bearing system. Its service life is more than 10 years because of a wearproof roller made of ultra high molecular weight polythene. To avoid thrombus formation, we introduced a special purge system to the bearing, allowing the saline with heparin to be infused through the bearing into the pump. The bearing, therefore, keeps working in the saline, and no thrombus will be formed. Animal experiments demonstrated that a 30 ml fluid infusion per hour is enough to prevent thrombus formation. With these improvements, the impeller pump has continuously run for 8 months, and no bearing wear can be measured. The device, weighing 150 g, is fully implantable, consumes approximately 9.6 watts, and delivers a 9L/min blood flow against a 120 mm Hg mean pressure and reaches a highest total efficiency of 24.7% for the motor (including the controller) and pump. The system can produce both pulsatile and nonpulsatile flow according to requirements.