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Classical non-contact bearings are already used in a number of specialist applications. However, there are some specialist areas where they cannot be used for variety of reasons. The paper presents the search for an optimal configuration of an acoustic journal bearing and shows that the overall shape of the bearing and its geometry are of a vital importance for the load capacity of the bearing. The results presented and discussed in the paper clearly demonstrate that the acoustic journal bearing with appropriate geometry can develop a load capacity of magnitude that can be sufficient for some practical applications. Dear Editor-in Chief, I should be grateful for initiating the assessment procedure of our paper entitled 'Acoustic journal bearing -a search for adequate configuration'.Please let me know the outcome of the review in due time. The paper has not been published and is not under consideration for publication. 2The paper does not contain material which could create any issue of copy write or require permission for reproduction. *Statement of Originality Highlights (i)The paper demonstrates practical feasibility of an acoustic air bearing.(ii) It stresses the importance of the geometrical configuration of the bearing for the acoustic levitation effect.(iii) It contains experimental results showing the load capacity of the pressure generated by squeeze film acoustic levitation.(iv) Ranks three different geometries of the bearing in accordance with the magnitude of the torque required to initiate motion of the shat for a number of loads on the bearing. *Highlights (for review)Acoustic journal bearing -a search for adequate configuration R Gawarkiewicz, T A Stolarski 1) , K Tesch Gdansk University of Technology, Gdansk, Poland 1) also Brunel University London, United Kingdom e-mail: mesttas@brunel.ac.ukTel: +44 (0)1895266693 Abstract: Classical non-contact bearings are already used in a number of specialist applications. However, there are some specialist areas where they cannot be used for variety of reasons. The paper presents the search for an optimal configuration of an acoustic journal bearing and shows that the overall shape of the bearing and its geometry are of a vital importance for the load capacity of the bearing. The results presented and discussed in the paper clearly demonstrate that the acoustic journal bearing with appropriate geometry can develop a load capacity of magnitude that can be sufficient for some practical applications.

Traditional non-contact bearings, such as air bearings (aerostatic and aerodynamic) and magnetic bearings are commonly used in a number of practical specialist applications. However, magnetic bearings are unacceptable where a strong magnetic flux is harmful to the surrounding environment while a continuous supply of a large volume of clean air, never sufficiently clean for food and medical applications, from external auxiliary devices is required for air bearings (for example batteries of drilling spindles used in mass scale manufacturing), which increases the cost of their use. Also, aerodynamic air bearings are known to become unstable when lightly loaded and operating at high speeds. Therefore, alternative and radically new concepts, such as acoustic bearings, offer an exciting solution. Acoustic levitation, being at the heart of an acoustic bearing concept, uses an acoustic wave to exert a force on objects immersed in the wave field. These forces are normally weak but can become quite large when using high frequency and high intensity waves, large enough to suspend substances against gravity force. Ultrasonic levitation (frequencies higher than 20 kHz) has been used initially for levitating small objects using a standing wave field between a sound radiator and a reflector. In standing wave acoustic levitation, the size of the levitated object is limited to less than a wavelength. Standing wave type ultrasonic levitators have been *Manuscript Click here to view linked References designed for applications in various scientific disciplines such as material processing and space engineering [1]. Kundt's in his tube experiment [2] in 1866, in which small dust particles moved towards the pressure nodes of a standing wave created in a horizontal tube, was the first to observe standing wave levitation. The first detailed theoretical description of standing wave levitation was given by King [3] in 1934, which was extended by Hasegawa [4] to include the effects of compressibility. Embleton [5] adopted King's approach to fit to the case of a rigid sphere in a progressive spherical or cylindrical wave field. Westervelt [6,7,8] derived a general expression for the force owing to radiation pressure acting on an object of arbitrary shape and normal boundary impedance to show that a boundary layer with a high internal loss can lead to forces that are several orders of magnitude greater than those predicted by the classical theory. Another type of levitation is the squeeze-film (or near field acoustic) levitation in which an object (not limited by wavelength) is brought very close to a radiation surface vibrating at high frequency. The gap is smaller than the wavelength of the generated sound, which means that the standing wave is replaced by a gas film with pressure that varies according to the motion of the radiation surface. Squeeze film levitation can carry higher loads than standing wave levitation and has been widely investigated for building non-contact linear and rotational bearings [9-13]. A contribution to the analys...

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A system of two taper roller bearings can carry loads with a high ratio of axial load to radial load. Such a system was proposed for a wind turbine gearbox following the poor durability of original bearing design with the aim of increasing durability. Because of size limits, a proposed system is composed of two different taper roller bearings. Standard manufacturers’ catalogues do not provide information on recommended preload or clearance conditions or the durability as a function of pre-load. That was the reason why durability was calculated on the basis of software provided by one of the manufacturers. The analysis presented in the paper shows the relationship between bearing fits, preload values, and the theoretical durability of the bearing.

Polyetheretherketone (PEEK) was investigated using a modified version of the four-ball tester in which the upper forth ball was replaced by a cone in such a way that kinematics of the four-ball configuration were fully preserved. In this apparatus, a polymer cone was spinning against three nested ceramic balls in a cup with polymer side walls and bottom. Rotation of the cone enforced orbiting and rolling of the ceramic balls around the polymer cup. The results produced some unexpected peculiarities in the wear of ceramic balls which, in principle, should not take place. It is postulated that the wear of ceramic balls was due to the viscoelastic nature of the PEEK. On behalf of my co-author, I submit the manuscript of our paper entitled "Peculiarities associated with testing polyetheretherketone (PEEK) in a model rolling contact" with the hope that you will be kind enough to consider it for publication in Tribology International.Please let me know the outcome of the assessment in due time. Yours sincerely, T A Stolarski Brunel UniversityCover Letter Novelty Statement I, on behalf of my co-author, declare that the work described in the manuscript "Peculiarities associated with testing polyetheretherketone (PEEK) in a model rolling contact" has not been published previously in any other journal and neither is under consideration for publication in any other journal.T A Stolarski, PhD, DSc(Eng) Brunel University *Statement of Originality HighlightsThe paper reports experimentally observed phenomenon of direct contact between three lower ceramic balls in the four-ball configurations when in contact with polyetheretherketone (PEEK) elements of the assembly. This is rather unprecedented as it is well known that direct contact between lower three ball normally does not take place when nominally elastic materials are tested. It is argued that the viscoelastic nature of the polymer is responsible for the occurrence of direct contact between three lower ceramic balls. A caution is recommended when testing viscoelastic materials in the four-ball configuration.*Highlights (for review) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Polyetheretherketone (PEEK) was investigated using a modified version of the fourball tester in which the upper forth ball was replaced by a cone in such a way that kinematics of the four-ball configuration were fully preserved. Rotation of the cone enforced orbiting and rolling of the ceramic balls around the polymer cup. The results produced some unexpected peculiarities in the wear of ceramic balls which, in principle, should not take place. It is postulated that the wear of ceramic balls was due to the viscoelastic nature of the PEEK.

The literature describes acoustic levitation phenomena with the utilization of air squeeze film between the vibrating inducer and the lifted object. The objective of the study is to determine the shape of the inducer with vibration characteristics that would allow the levitation of an object of the assumed geometry. In this paper, the influence of the dimension ratio of the inducer on the frequency of the first mode of vibration was presented. CFD calculations for a selected dimension series were performed with the goal of the determination of lifting conditions. The data obtained from the analysis will be used to manufacture an inducer that will serve as an experimental verification for the fluid dynamics calculation.