Whiffletree based supports for self-adjustable hydrostatic bearings

Hydrostatic bearings are superior in terms of their friction and load carrying characteristics when compared to contact based bearings, but non-usable in applications with non-constant curvature counter surfaces. A possible solution to this limitation is the introduction of deformable hydrostatic bearings components that cope with these required deformations. To reduce the required deformation of a single bearing pad, multiple pads can be connected through a so-called whiffletree support system. In this work, a symmetric whiffletree based hydrostatic bearing embodiment is introduced. A 2D quasi-static model is introduced that allows for determining the kinetostatic and path following properties of such a type of bearing. Design considerations are given regarding the joint rotational-, normal-, and shear stiffness of each individual joint, as well as basic bearing layout. The potential of a whiffletree suspended bearing is presented through the use of a case study.

Study and analysis on some design aspects in single and multi-axis active magnetic bearing (AMB)

Active magnetic bearing (AMB) is a substitute of conventional bearing, which provides electromagnetic force to support the rotating part respecting the stator. The utilization of electromagnetic force makes this bearing “active”. The attraction force of an AMB system can be control by manipulating the input so that the rotor can be levitate at required position. As lot of limitation exist in passive magnetic bearing, the AMB is very useful in modern applications. Due to frictionless nature of magnetic bearing and non-necessity of lubricants, now-a-days AMB is taking place as the alternate of any other bearing in multiple applications of growing industry. Adequate knowledge of essential components is necessary for successful implementation of any active magnetic bearing design. So, In this paper, the magnetic analysis has been analyzed for the different types of single and multi-axis AMB using ANSYS Maxwell with extensively reviewed components.

Learning the theory, improving the practice? A case study of award-bearing leadership training among college principals from Bangladesh

Award-bearing transnational professional development training has received little attention in the literature. By taking a longitudinal mixed-methods approach, this project's researchers investigated the ways in which participants on a World Bank-funded programme practised leadership at the start of their training, before revisiting them a year later to find out what, if any, changes had resulted. It was discovered that the award-bearing design had been very influential in endowing the participants with concepts that they enthusiastically adopted, but that, over time, the concepts had undergone a process of simplification, largely driven by incongruities between the concepts and the cultural environments to which they had been applied. It is recommended that award-bearing programmes might more readily take into account the individual and contextual circumstances of their participants at the planning stage.

Bearing Design and Lubrication

High rotational speeds of the impeller call for careful bearing design and layout, not just those on the supercharger impeller shaft itself but also on any preceding shafts, which may run at lower speed. The question of whether to use plain (journal) bearings or rolling element bearings can only be decided after a complete evaluation of the overall design of the supercharger drive system in question. Journal bearings are in general smaller in outside diameter and despite the higher overall length have a lower weight than rolling element bearings. Journal bearings demand several times the lubricating oil flow rate than rolling element bearings, and they also exhibit high sensitivity to particulates in the oil and the overall quality thereof.

Failures of Sliding Bearings

A mechanical part, which supports the moving part, is termed a mechanical bearing and can be classified into rolling (ball or roller) bearings and sliding bearings. This article discusses the failures of sliding bearings. It first describes the geometry of sliding bearings, next provides an overview of bearing materials, and then presents the various lubrication mechanisms: hydrostatic, hydrodynamic, boundary lubrication, elastohydrodynamic, and squeeze-film lubrication. The article describes the effect of debris and contaminant particles in bearings. The steps involved in failure analysis of sliding bearings are also covered. Finally, the article discusses wear-damage mechanisms from the standpoint of bearing design.

Fixed-bearing vs mobile-bearing prostheses for total knee arthroplasty after approximately 10 years of follow-up: a meta-analysis

Background The benefits and risks of fixed-bearing and mobile-bearing designs for total knee arthroplasty (TKA) were compared, and long-term functional, clinical and radiological outcomes were analysed. Methods A comprehensive search in the PubMed, EMBASE, Web of Science and Cochrane Central databases was conducted to identify randomized controlled trials (RCTs) comparing fixed-bearing and mobile-bearing designs with no less than 9 years of follow-up. Primary outcome measures were Knee Society Scores (KSSs), range of motion (ROM) in knee joint values, complication rates and revision rates. The final search was performed on 23 April 2021. Results Six RCTs were included. A total of 451 patients with 612 knees met the inclusion criteria. The mobile-bearing design, in contrast to the fixed-bearing design, can clearly increase the KSFSs, especially with posterior cruciate retention. There was no significant difference in the KSKSs, ROM values, revision rates or complication rates between the two bearing design groups. Conclusion After approximately 10 years of follow-up, the mobile-bearing design has advantages in KSFSs over the fixed-bearing design. The mobile-bearing design may also have advantages in the revision rates over the fixed-bearing design when the posterior cruciate ligament is substituted. There may be no clear difference in KSKSs, ROM values or complication rates between these two designs.

Macro and Micro-Geometric Robust Design of Cylindrical Roller Bearings Using Fatigue and Wear Considerations

Cylindrical roller bearings have been chosen for the optimization using a robust design because tolerances are always provided during manufacturing. For rolling element bearings, a measure of satisfactory performance is a long life, lubrication and thermal characteristics. Hence, the first two objectives have been optimized simultaneously using the robust design. For bearing design, variables chosen include four basic internal dimensions and five design constraint factors. Genetic algorithm is implemented for solving the problem by considering both the objective functions, simultaneously. The lives of the bearing are found to be improved at least two times that of the standard bearings. It has been found that during manufacturing, designer should have more attention on the roller diameter compared to others dimensions.

Influence of the cage on the migration and distribution of lubricating oil inside a ball bearing

The migration and distribution of lubricant oil in a rolling bearing strongly affect the elastohydrodynamic lubrication performance between the balls and rings. However, oil re-lubrication is highly dependent on the bearing design, which is different from the ball-on-disc model. This study directly observed the distribution of the lubricant film in a custom-made model-bearing rig, with an outer ring replaced by a glass ring to allow full optical access. The influence of the cage type and surface properties were presented. The physical origin of the re-lubrication mechanism, including capillary flow and mechanical redistribution, was discussed.