Optimum design of short journal bearings by enhanced artificial life optimization algorithm

This paper presents an optimum design of high-speed short journal bearing using an enhanced artificial life algorithm (EALA) to compute the solutions of optimization problem. The proposed hybrid EALA algorithm is a synthesis of an artificial life algorithm (ALA) and the random tabu search method (R-tabu method) to solve some demerits of the ALA. The emergence is the most important feature of the artificial life which is the result of dynamic interaction among the individuals consisting of the system and is not found in an individual. The artificial life optimization algorithm is a stochastic searching algorithm using the feature of artificial life. The feature of R-tabu method, which prevents converging to the local minimum, is combined with the ALA. One of the features of the R-tabu method is to divide any given searching region into several sub-steps. As the result of the combination of the two methods, the EALA not only converges faster than the ALA, but also can lead to a more accurate solution. In addition, this algorithm can also find all global optimum solutions. We applied the hybrid algorithm to the optimum design of a short journal bearing. The optimized results were compared with those of ALA and successive quadratic programming, and identified the reliability and usefulness of the hybrid algorithm.     

Optimum computerized design of hydrodynamic journal bearings

Solutions of the Reynolds equation have been computed for a bearing configuration which, previously, has received little attention theoretically. Operating characteristics evaluated from the computed solutions are presented graphically, and also form the basis for the development of a computerized optimum design technique. The optimum design objective is stated explicitly in terms of the operating characteristics and is minimised within both design and operative constraints.Optimum designs are given for a range of running conditions for minimum power loss. A comparison is made of the optimum designs obtained for three differing design objectives. Results from the computerised design technique are also compared with the solution given by a long-hand design procedure.     

Metal-on-metal bearings surfaces: materials, manufacture, design, optimization, and alternatives

When first introduced, total hip replacements offered pain relief and improved mobility in elderly patients. The success of this procedure in terms of long-term durability and restoration of function has led to its use in younger, more active patients. This has resulted in a commensurate increase in patient expectation regarding longevity and the degree to which function and lifestyle is restored. The bearing surface is a key feature of the performance of replacement joints. It is generally accepted that excessive amounts of wear debris preclude their long-term survivorship and hence there is an ongoing requirement for bearing surfaces which minimize debris generation. The purpose of this paper is to review the factors which affect the performance of so-called metal-on-metal bearings, to compare their performance with that of the other commonly used contemporary alternatives, metal and ceramic articulating against highly cross-linked polyethylene, and ceramic-on-ceramic, and finally to consider the potential solutions offered by new developments such as ceramic-on-metal and coatings applied to metal-on-metal bearings.     

On the design and development of hybrid journal bearings: a review

This paper presents a comprehensive review of developments in the design and application of hydrostatic and hybrid journal bearing systems during the last few decades. Revolutionary changes have taken place in the applications of hydrostatic and hybrid journal bearings, from very low‐speed radar to very high‐speed turbo‐machinery and ultra‐precision machine tools requiring high stiffness to improve accuracy. Hydrostatic and hybrid bearings are of interest because of their potential at very high operating speed and heavy load‐carrying capacity. This paper also outlines the analyses done of these types of journal bearings in practical application, which has led to improved bearing design. This review critically discusses the parameters that significantly affect the static and dynamic performance of a journal bearing. This review includes coverage of recent publications in the literature pertaining to hydrostatic and hybrid journal bearings focusing on the influence of parameters such as bearing geometry, supply pressure, flow control devices, fluid compressibility, fluid inertia, journal misalignment, bearing flexibility, surface roughness, and thermal effects. Copyright © 2006 John Wiley & Sons, Ltd.     

A new basis for the optimization of hybrid journal bearings

A design strategy is presented for hybrid hydrodynamic/hydrostatic journal bearings which maximizes the hybrid load for minimum total power dissipation. It is shown that the detailed design of hybrid bearings is quite different from the design of recessed hydrostatic bearings. It is found that design for hybrid operation may lead to substantial increases in load support with significantly less total power dissipation than would be required if the designs were developed from hydrostatic bearing procedures.A new technique for optimizing hybrid journal bearings is presented. The method involves the comparison of the bearings to be optimized with a reference bearing on the basis of load/total power, load/pumping power and load/flow.     

Optimum design of hydrostatic journal bearings Part I: Maximum load capacity

The optimization problem is formulated with a view to maximizing the load-carrying capacity of hydrostatic journal bearings. Equations governing the performance of multi-recess hydrostatic journal bearings are summarized. Practical design limits and operational constraints are also defined. The optimization process is based on the well known Rosenbrock method. Results illustrating the effect of area ratio, axial land width and circumferential land width on load capacity, flow rate and power ration are reported. In conclusion precision bearings with small clearances and low pressure ratios are recommended for applications involving low supply pressures, while bearings with large clearances and pressure ratios close to 0.5 are recommended for applications involving high supply pressures     

Reliability-based design optimization of slider air bearings

This paper presents a design methodology for determining configurations of slider air bearings considering the randomness of the air-bearing surface (ABS) geometry by using the iSIGHT. A reliability-based design optimization (RBDO) problem is formulated to minimize the variations in the mean values of the flying heights from a target value while satisfying the desired probabilistic constraints keeping the pitch and roll angles within a suitable range. The reliability analysis is employed to estimate how the fabrication tolerances of individual slider parameters affect the final flying attitude tolerances. The proposed approach first solves the deterministic optimization problem. Then, beginning with this solution, the RBDO is continued with the reliability constraints affected by the random variables. Reliability constraints overriding the constraints of the deterministic optimization attempt to drive the design to a reliability solution with minimum increase in the objective. The simulation results of the RBDO are listed in comparison with the values of the initial design and the results of the deterministic optimization, respectively. To show the effectiveness of the proposed approach, the reliability analyses are simply carried out by using the mean value first-order second-moment (MVFO) method. The Monte Carlo simulation of the RBDO’s results is also performed to estimate the efficiency of the proposed approach. Those results are demonstrated to satisfy all the desired probabilistic constraints, where the target reliability level for constraints is defined as 0.8.     

Optimum design of short journal bearings by artificial life algorithm

This paper presents an enhanced artificial life algorithm for optimum design of short journal bearing. As artificial life organisms have a sensing system, they can find the resource they want and metabolize it. The characteristics of artificial life are emergence and dynamic interaction with the environment. In other words, the micro-interaction with each other in the artificial life's group results in emergent colonization in the whole system. In this paper, artificial life algorithm by using the above characteristics is applied to the optimum design of short journal bearing. The optimized results were compared with those of genetic algorithm and successive quadratic programming, and identified the optimizing ability.     

Computer-aided design of hydrostatic journal bearings including shaft bending effect

Most analyses of hydrostatic journal bearings assume that there is no deflection of the shaft. This paper shows that prediction of bearing performance from ‘no bending’ theory would underestimate the eccentricity ratio, power ratio, and lubricant flow rate. The computerised iteration technique developed gives full performance data for multi-pocket hydrostatic bearings once the dimensions and operating conditions are known.     

Optimum design of hydrostatic journal bearings Part II. Minimum power

The optimization problem is formulated with a view to maximizing the load-carrying capacity of hydrostatic journal bearings. Equations governing the performance of multi-recess hydrostatic journal bearings are summarized. Practical design limits and operational constraints are also defined. The optimization process is based on the well known Rosenbrock method. Results illustrating the effect of area ratio, axial land width and circumferential land width on load capacity, flow rate and power ration are reported. In conclusion precision bearings with small clearances and low pressure ratios are recommended for applications involving low supply pressures, while bearings with large clearances and pressure ratios close to 0.5 are recommended for applications involving high supply pressures     

Boundary slip surface design for high speed water lubricated journal bearings

This paper presents the development of a numerical model for high speed and water lubricated journal bearings with different boundary slip arrangements. The effect of boundary slip and its possible mechanism are analyzed and discussed. The results suggest that a suitable combination of slip/no-slip surfaces on the sleeve of a journal bearing enables improvement of the tribological performance through (i) suppressing the occurrence of cavitation, (ii) enhancing the load bearing capacity, and (iii) reducing the interfacial friction between bearing sleeve and shaft. Such improvement becomes more significant for the bearings with smaller eccentricity ratio, smaller width and larger diameter.     

基于遗传算法的轿车轮毂轴承数值优化

为了提高设计效率和质量,优化系统性能指标,在给定的装配空间条件下满足几何和性能约束,以获得最大的疲劳寿命为目的,运用遗传算法对双列角接触球轴承结构的轿车轮毂轴承进行数值优化设计。并基于一个实际例子编制了优化程序,给出了运算结果。结果表明,遗传算法能够有效地解决离散变量全局寻优问题,全部约束得到满足并且优化设计方案在系统疲劳寿命方面显著优于当前设计方案。     

Comparison of slot-entry and orifice-compensated gas journal bearings

Controversy concerning the relative merits of gas journal bearings employing slot and orifice restrictors led to an experimental and theoretical study to determine the relative merits of the two types of bearing. This paper is an interim report on the programme and shows that slot-entry bearings yield greater load capacity at high eccentricity ratios, whilst orifice-compensated bearings have greater stiffness up to ? = 0.35.     

Wear numbers for ball cup and journal bearings

A wear number is defined for ball cup bearings and for journal bearings where the cup and the cylindrical bearing are made of soft material. This dimensionless wear number provides a relation between the following five quantities: the radius of the ball or the length of the journal bearing in millimetres, the wear modulus in newtons per square millimetre, the maximum wear depth rate of the cup or the cylindrical bearing in millimetres per second, the force between the mating surfaces in newtons and the angular angular speed of the ball or the journal in radians per second. The wear volume of the plastic cup of a hip joint prosthesis was calculated and from the point of view of wear the Charnley prosthesis is probably superior to the Charnley-Muller prosthesis.     

基于MATLAB的动压轴承压力分布计算和优化设计

运用MATLAB编制的有限差分程序对动压轴承的内部压力分布求解及对动压轴承进行结构优化设计,通过MATLAB图示可以形象直观地反映出动压轴承内部的压力分布情况以及优化后的动压轴承承载能力的提高.     

Comparison of power loss and pad temperature for leading edge groove tilting pad journal bearings and conventional tilting pad journal bearings

A study was undertaken to compare power loss and pad temperature characteristics between LEG (leading edge groove) tilting pad journal bearings and conventional tilting pad journal bearings with and without a seal tooth. All test bearings were double tilting type with six-pad LOP (Load On Pad), 300.6 mm inner diameter, and 120.0 mm effective length. Pad temperatures and power losses were compared and evaluated versus rotor rotational speed, oil flow rate, and static load. Four kinds of tilting pad journal bearings were evaluated, conventional tilting pad journal bearings with and without a seal tooth and LEG tilting pad journal bearings with and without a seal tooth.Test results indicate that tilting pad journal bearings without a seal tooth have lower power loss and pad temperature than tilting pad journal bearings with a seal tooth. Especially, conventional tilting pad journal bearing without a seal tooth has the lowest power loss and pad temperature among the test bearings.     

Steadily loaded journal bearings: Quasi-3D mass-energy-conserving analysis

A finite-element approach to thermoelastohydrodynamic lubrication analysis is developed by extending a previous mass- and energy-conserving algorithm to include wall-convection boundary conditions, groove-mixing theory, and thermo-mechanical deformations. To this end, the cross-film-averaged energy equation is coupled with the heat conduction equations relevant to the bearing sleeve and the journal by fitting the temperature profile across the film thickness with a fourth-order polynomial. A finite-element condensation technique is used to reduce the unknowns in heat conduction equations in the bush and in the journal to the temperatures of the sleeve surface and journal axis, respectively. Applied to the analysis of steadily loaded journal bearings, the proposed method shows good agreement with published experimental results and incurs low computational cost.     

Inertia and thermal effects in turbulent flow journal bearings

A semi-analytical study of the influence of inertia terms and the effects of convection and dissipation on an infinitely long bearing is presented. The distribution of the effective viscosity is assumed to be dependent on local shear stress and temperature. The momentum and energy equations are evaluated by assuming that the shape of the velocity profiles is not strongly affected by the presence of the inertia forces. Approximate integral momentum equations are thus obtained. The results show that inclusion of inertia terms has a pronounced effect on the dimensionless load capacity of the bearing. The inclusion of thermal effects results in a smaller dimensionless capacity.