A review of the design and optimization of large-scale hydrostatic bearing systems

Research in the field of tribo-mechatronics has been gaining popularity in recent decades. The objective of the current research is to improve static/dynamics characteristics of hydrostatic bearings. Hydrostatic bearings always work in harsh environmental conditions that effect their performance, and which may even result in their failure. The current research proposes a mathematical model-based system for hydrostatic bearings that helps to improve its static/dynamic characteristics under varying conditions of performance-influencing variables such as temperature, spindle speed, external load, and clearance gap. To achieve these objectives, the capillary restrictors are replaced with servo valves, and a mathematical model is developed along with robust control design systems. The control system consists of feedforward and feedback control techniques that have not been applied before for hydrostatic bearings in the published literature. The feedforward control tries to remove a disturbance before it enters the system while feedback control achieves the objective of disturbance rejection and improves steady-state characteristics. The feedforward control is a trajectory-based controller and the feedback controller is a sliding mode controller with a PID sliding surface. The particle swarm optimization algorithm is used to tune the 6-dimensional vector of the tuning parameters with multi-objective performance criteria. Numerical investigations have been carried out to check the performance of the proposed system under varying conditions of viscosity, clearance gap, external load and the spindle speed. The comparison of our results with the published literature shows the effectiveness of the proposed system.

https://www.mdpi.com/2227-7390/9/4/388/pdf

Model-Based Design Approach to Improve Performance Characteristics of Hydrostatic Bearing Using Multivariable Optimization

Investigation of the deformation characteristics of adaptive hydrostatic thrust bearings has been performed under extreme conditions, considering the relationship between viscosity and temperature of lubricating oil. A 3D model is generated, including the oil pad, the oil film and friction pairs. The oil film temperature field and the oil cavity pressure field have been calculated based on CFD. According to the lubrication theory and tribology principle, the force deformation, the thermal deformation, the force and thermal coupling deformation have been studied by using workbench simulation software, and the best working condition of adaptive hydrostatic thrust bearing is obtained. The results show that the load causes the table and the base to undergo inward elastic deformation, and the temperature causes them to undergo outward thermal deformation. The two deformations have opposite directions, and the deformations compensate each other. When the load is between 28 and 32t, the possibility of dry friction generated by the friction pair is low. The research results provide a theoretical basis for the stability of adaptive hydrostatic thrust bearings under extreme working conditions.

Deformation characteristics of adaptive hydrostatic thrust bearing under extreme working conditions

Effects of oil recess structural parameters on comprehensive tribological properties in multi-pad hydrostatic thrust bearing for CNC vertical processing equipment based on low power consumption

Perovskite Light‐emitting diodes (PeLEDs) have emerged as a promising technique for future high‐definition displays due to their outstanding electroluminescent characters. However, the development of blue PeLEDs toward practical applications is seriously hindered by their inferior performance, which mainly arises from the detrimental halide ionic behavior and thus severe nonradiative recombination in mixed‐halide blue perovskite materials. Herein, efficient sky‐blue PeLEDs featuring spectrally stable emission at 483 nm are realized by employing bifunctional passivators of Lewis‐base benzoic acid anions and alkali metal cations to simultaneously passivate the under‐coordinated lead atoms and suppress halide ion migration. A decent external quantum efficiency (EQE) of 16.58% and a maximum EQE of 18.65% are achieved, which is further boosted to 28.82% through the optical outcoupling enhancement. This work demonstrates unique insight into the generality and individuality of this category of benzoates and puts forward a feasible guidance in choosing appropriate additives for efficient perovskite materials.

Manipulating Ionic Behavior with Bifunctional Additives for Efficient Sky‐Blue Perovskite Light‐Emitting Diodes

Purpose




The purpose of this paper is to study thermal-fluid-solid coupling deformation and friction failure mechanism of bearing friction pairs under the working conditions of high speed and heavy load.




Design/methodology/approach




The deformation is simulated based on thermal-fluid-solid coupling method, its deformation distribution law is revealed and the relationships of deformation of friction pairs, rotational speed and bearing weight are obtained.




Findings




The results prove that the oil film temperature rises sharply, the lubricating oil viscosity decreases rapidly, the film thickness becomes thinner, the deformation increases, the whole deformation is uneven and the boundary lubrication or dry friction are caused with the increase in rotational speed and bearing load.




Originality/value




The conclusions provide theoretical method for deformation solution and friction failure mechanism of hydrostatic thrust bearing.

Thermal-fluid-solid coupling deformation of hydrostatic thrust bearing friction pairs

This paper aims to describe a theoretical and experimental research concerning influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing with a constant flow.,The lubrication performance of a hydrostatic thrust bearing with different recess shape under the working conditions of high speed and heavy load has been simulated by using computational fluid dynamics and finite volume method.,It is found that the comprehensive lubrication performance of a hydrostatic thrust bearing with circular recess is optimal. The results demonstrate that recess shape has a great influence on the lubrication performance of the hydrostatic thrust bearing.,The simulation results indicate that to get an improved performance from a hydrostatic thrust bearing with constant flow, a proper selection of the recess shape is essential.

Influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing

Modulating Phase Distribution and Passivating Surface Defects of Quasi-2d Perovskites Via Potassium Tetrafluoroborate for Light-Emitting Diodes

Colloidal Quantum Dot Solids with a Diminished Epitaxial PbI2 Matrix for Efficient Infrared Solar Cells

Inorganic cesium lead triiodide (CsPbI3) perovskites show high potential for photovoltaic applications due to their suitable bandgap and excellent thermal stability. However, the photovoltaic performance of CsPbI3 perovskite solar cells (PSCs) is significantly restricted by unsatisfactory crystal quality and serious nonradiative recombination. Herein, chloride additives, such as dimethylammonium chloride (DMACl), ammonium chloride (NH4Cl), and methylammonium chloride (MACl), are applied to ameliorate the crystallization of CsPbI3 perovskite films. The results reveal that DMACl could form a low-solubility complex (Cs4PbI6-Cl) in the precursor as seeds to induce crystallization during solvent evaporation and simultaneously passivate perovskite surface with residual DMA+. Consequently, the DMACl-CsPbI3 perovskite film with highly oriented crystals and suppressed nonradiative recombination is realized. With these advantages, the inorganic PSC with high efficiency of 18.62% is demonstrated and exhibits good stability. This work provides insight into the crystallization of CsPbI3 perovskite films for the development of high-performance all-inorganic PSCs. 

Mubing Yu

Papers

Thermal-fluid-solid coupling deformation of hydrostatic thrust bearing friction pairs

Influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing

Modulating Phase Distribution and Passivating Surface Defects of Quasi-2d Perovskites Via Potassium Tetrafluoroborate for Light-Emitting Diodes

Colloidal Quantum Dot Solids with a Diminished Epitaxial PbI2 Matrix for Efficient Infrared Solar Cells

Cs4PbI6-Cl Nucleation Seeds Assisted Highly-Oriented Inorganic CsPbI3 Perovskites for Efficient Perovskite Solar Cells