Inertia and couple‐stress effects on squeeze‐film characteristics with reference to biological bearings

Couple stresses affect lubrication when additives are used or the lubricant contains long‐chain molecules. Such couple stresses may have a considerable effect on the behaviour of bearings in practice. The influence of couple stresses and lubricant inertia on the mechanical parameters of a curvilinear thrust bearing with a squeeze film is considered in this paper. Simulation of the squeeze‐film behaviour of a human joint modelled as a spherical bearing is discussed as an example.     

Sliding thrust bearings in a centrifugal compressor with a semiclosed impeller

The equipment for dynamic tests of sliding thrust bearings is considered. The test data are analyzed for a thrust bearing with motionless pads in a centrifugal compressor with a semiclosed impeller in pumping mode.     

On the Development of a Design Procedure of the Hydrodynamic Characteristics of Hydrogenerator Thrust Bearings Taking into Account the Heat Exchange

The problem solution for the thrust sector bearing of a hydrogenerator with oil lubrication is considered. The value of the most important hydrodynamic characteristic of the thrust bearing, which is the lifting force, is defined. The pressure field is determined by the direct numerical integration of the Navier-Stokes equations for a lubricating oil layer. The case of the absence of heat exchange between the lubrication layer and solid-state components of the thrust bearing and the case when the heat exchange is taken into account are considered. The calculation results, which are compared with an experiment, are presented. The research results can serve as the basis to develop automation systems for designing hydrogenerator thrust bearings.     

Curvilinear cutting edge of a helical bit with uniform life

The geometry of the curvilinear cutting edge of a helical bit such that the life is uniform over its length is considered, on the basis of a mathematical model.     

Rotordynamic modelling of a hydrodynamic pivoted-pad thrust bearing

The rotordynamic characteristics of a hydrodynamic pivoted-pad thrust bearing are investigated in this paper. Firstly, the rotordynamic coefficients of a single pad are defined in the case of small perturbation. The Reynolds equation and its perturbed forms are solved by using the boundary element method (BEM). An iterative procedure is proposed to determine the static positions of the thrust pads when the static tilt of the runner is considered by using the Newton–Raphson method. The characteristics of the thrust bearing are obtained by using an approach based on a coordinate transformation principle.     

Theory of constrained motion of materials: Chip formation with a single conditional shear surface

Orthogonal constrained cutting is considered. The initial direction of chip flow for a curvilinear blade with an inclined cutting face is analyzed, in static coordinates.     

环境因素对推力轴承润滑膜超声检测精度的影响

核主泵推力轴承摩擦副采用的润滑介质黏度较低且轴承工作于高温高压等极端工况下,采用超声技术对润滑膜分布进行精确测量时,要考虑环境因素的影响。建立核主泵推力轴承润滑膜分布的超声检测模型,并在模拟试验台上进行推力润滑状态的实测。在对测试结果的分析中考虑测量时温度和压力等环境因素的影响,分析环境因素对超声检测精度的影响程度。结果表明:在启、停阶段推力轴承处于边界润滑状态,考虑温度和压力影响时润滑膜厚值最大会增大加38.5%;在额定转速下推力轴承处于流体润滑状态,考虑温度和压力影响时润滑膜厚值最大会增大加39.8%。     

Hydrodynamic Calculation of a Thrust Bearing with an Adapted Profile

Russian Engineering Research - Hydrodynamic models are considered for thrust bearings with a profile adapted to the frictional conditions, when operating in incompressible electrically conducting...     

止推滑动轴承的温度场和热变形分析

通过对止推滑动轴承的传热学、摩擦学研究，建立了该轴承相应的稳态温度场和热变形的三维热分析有限元模型，并运用ANSYS分析了轴承处于热平衡状态时的温升和热变形。研究结果表明，对于井下用止推滑动轴承，由于其摩擦产生的热量很大，在地面常温下设计时应考虑到热变形对轴承间隙的影响。     

Flow Visualization in a Pocketed Thrust Washer

The objectives of this study were to experimentally and numerically investigate oil flow in surface-pocketed thrust washers. In order to achieve the experimental aspects of this investigation, a thrust washer test rig was designed and developed to visualize the lubricant flow at the contact interface. A novel approach for creating the pockets was developed to allow optical inspection of the lubricant during thrust washer operation. The thrust washers were fabricated using a glass disk with a thin layer of steel shim stock adhered to the surface. The micrometer-thick shim stock was machined using an Nd:YAG laser to create the circular pocket geometries and then glued to the glass disk. A mirror and camera were placed below the semitransparent washer to observe the lubricant flow in the pocket. The results obtained from this configuration illustrate a cavitation bubble forming on the leading edge of the pocket followed by a sharp transition back to liquid. The size of the cavitation area was found to be a function of rotational speed, nominal bearing pressure (NBP), viscosity, and pocket geometry. The cavitation area ratio (gaseous region divided by the pocket area) increased for greater speeds and higher viscosities and decreased for larger pocket diameters, deeper pockets, and higher NBPs. The friction force for various thrust washer designs was also measured as a function of load, speed, and lubricant. The results showed that shallower, wider pockets provided the lowest friction. It was found that, generally, the conditions that minimize friction also result in a stable cavitation region. ANSYS Fluent computational fluid dynamics software was used to develop a three-dimensional model of the pocketed thrust washer utilizing the full Navier-Stokes equations to investigate the cavitation and pressure distribution occurring at the contact and corroborate the experimental results.     

Acoustic-emission testing of curvilinear fuselage panels of an RRJ airplane in life tests

The technique of acoustic-emission testing of curvilinear fuselage panels of an RRJ airplane in life tests is considered. Specimens are loaded with a distributed mechanical load and pressurization with an air overpressure.     

Stresses around reinforced curvilinear holes in spherical shells

A perturbation technique is used to determine the stress concentration around reinforced curvilinear holes in thin pressurized spherical shells. Starting from the governing differential equations for thin shallow spherical shells, a solution is first obtained for a circular hole. The solution for an arbitrary shaped curvilinear hole is then obtained as a first-order perturbation over the circular hole solution using the conformal mapping technique. The effects of a large number of parameters involved in the design of a reinforcement around cutouts in shells are studied. The problems of symmetric and eccentric reinforcements are also considered. The results obtained would be very helpful in the design of an efficient reinforcement for elliptical and square holes in thin shallow spherical shells.     

Development of a two-dimensional dual pendulum thrust stand for Hall thrusters

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors [axial and horizontal (transverse) direction thrusts] of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25 mN (1.4%) in the main thrust direction and 0.09 mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of +/-2.3 degrees was measured with the error of +/-0.2 degrees under the typical operating conditions for the thruster.     

Measurement and analysis of thrust force in drilling of particle board (PB) composite panels

Particleboard is a wood based composite extensively used in wood working. Drilling is the most commonly used machining process in furniture industries. The surface characteristics and the damage free drilling are significantly influenced by the machining parameters. The thrust force developed during drilling play a major role in gaining the surface quality and minimizing the delamination tendency. The objective of this study is to measure and analyze the cutting conditions which influences the thrust force in drilling of particle board panels. The parameters considered are spindle speed, feed rate and point angle. The drilling experiments are performed based on Taguchi’s design of experiments and a response surface methodology (RSM) based mathematical model is developed to predict the influence of cutting parameters on thrust force. The results showed that high spindle speed with low feed rate combination minimizes the thrust force in drilling of pre-laminated particle board (PB) panels.     

Analysis of a hydrodynamic thrust bearing with elastic deformation using a recurrent neural network

A theoretical analysis on the general behaviour of a thrust bearing is presented in this paper. The model programme using a method adaptation of finite differences was developed to solve the Reynolds equation for lubrication. The model in the theoretical analysis uses a single one-dimensional grid. The altering of total lubrication load obtained in the result of under-cutting in the thrust bearing have been determined together with the parameters such as oil film thickness and pressure. Parameters such as the pressure and thickness of the oil film were determined. The hydrodynamic behaviour of thrust bearing was analysed by considering of different dimensionless system pressure, speed and geometry of the bearing. The effect of the elastic load due to elastic deflection is taken into account as on the load-bearing characteristics is included. Also, a proposed neural network predictor is utilised to analyse of the general behaviour of thrust bearing. The results of the proposed neural network predictor gives superior performance for analysing of the behaviour of a thrust bearing undergoing in elastic deformation.     

Inertia effect of micropolar fluid in squeeze bearings and thrust bearings

A theoretical study is made of squeeze films between two infinitely long rectangular plates and between circular plates, and of a thrust bearing, assuming the lubricant to be a micropolar fluid. The effect of inertia is considered and the effects of the material constants of the fluid on the bearing characteristics are discussed. The effect of inertia is to increase the time of approach for squeeze bearings and to diminish the load capacity for thrust bearings. For squeeze bearings, the time of approach is greater with a micropolar fluid than with a Newtonian fluid and, for thrust bearings, the load capacity is greater with a micropolar fluid than with a Newtonian fluid.     

Structural design of transom pod for outboard motor in polyethylene boat

In a polyethylene boat, a transom pod is subjected to repeated thrust forces generated by an outboard motor. The structural design of the transom pod for the outboard motor must be considered because it is subjected to cyclic bending moments causing thrust forces of the outboard motor. We designed a transom pod reinforced with aluminum alloy plate inside the transom pod in a polyethylene boat and obtained an optimal thickness of the Al alloy plate to ensure the transom pod durability. We then performed a structural analysis for the transom pod reinforced with Al alloy plate and estimated the fatigue life using modified Goodman diagram. The optimal thickness of Al alloy plate was 7 mm.     

抽水蓄能机组推力头的强度与寿命分析

在抽水蓄能机组运行过程中推力头承受着交变应力,容易出现疲劳磨损从而影响机组正常运行。以江西洪屏抽水蓄能电站的推力头模型为研究对象,基于流固耦合理论并运用CFD技术,分析机组转速、油膜厚度对油膜压力分布的影响,研究推力头在不同转速和不同油膜厚度下的应变和疲劳寿命。结果表明:随着机组转速的升高,油膜压力也随之升高;随着油膜厚度的增加,油膜压力先增加后减小;推力头形变量随着转速的升高不断增加,然而形变量相比较推力头的尺寸仍属于小变形范围;在转速一定和不同油膜厚度下,推力头的最大形变均大于油膜厚度进而影响了油膜的均匀分布;推力头的应力循环次数随着转速升高,在应力集中处不断降低;随着油膜厚度的增加,应力循环次数先减小后增加。因此,为延长推力头寿命,应考虑对推力头应力集中处进行表面强化或改善其结构,同时为保证机组安全稳定运行,油膜厚度和推力头最大形变应尽量接近。     

Analysis of thrust force in a work roll shifting mill

In a work roll shifting mill, thrust force can cause troubles in the operation of the mill. Based on theoretical analysis and practical application, the mechanics and control approach of the thrust force have been analyzed. Research shows that the relative displacement vector of friction pair is a criterion for controlling the thrust force during work roll shifting. This friction pair is caused by contact between the work roll and the backup roll in the deformation zone. The thrust force is determined by relative displacement vector, and it can be controlled effectively through decreasing the relative displacement vector. Using vector analysis, the effects of the work roll shifting and crossing on mechanics and practical application are also discussed. The experiment shown in this paper verifies that the work roll crossing can decrease the thrust force which is caused by its shifting during rolling.     

Simulation-based fabrication of micro-helical grooves in a hydrodynamic thrust bearing by using ECMM

In hydrodynamic thrust bearing, common micro-grooves with helical or herringbone forms are generally to ensure the bearing load capacity and reduce leakage of lubricant, consistent with the design or size requirements of grooves. In this investigation, the electrical field distribution and anodic dissolution of helical grooves in electrochemical micro-machining process can be predicted by using COMSOL Multiphysics^TM software. The processing equivalent is based on the chemical composition of the workpiece. The micro-helical grooves are hollowed out of hydrodynamic thrust bearing using a DC and pulse power supply, and experiment results are compared with simulation results. The experimental results demonstrate that the fine surface of helical grooves can be obtained with a depth of 4.9 μm in machining time of 3 s by using a pulse power supply of 5 kHz. To eliminate the effect of such factors as flush flow, temperature difference between workpiece and tool, and formation of hydrogen bubble barriers, the k values of these factors are considered for amendment to get more accurate simulation results.