Anton van Beek

Film Height Optimization of Hydrodynamic Slider Bearings

The film height distribution which yields the maximum load carrying capacity for the rectangular slider is determined using a PDE-constrained optimization solver. The gradient of the objective function, i.e. the load, with respect to the design variable, i.e. the film height distribution, is calculated using a discrete adjoint approach. It is shown that, in contrast to the linear slider, the load carrying capacity per unit length and at constant width of the optimized slider steadily increases with increasing length over width ratio.Copyright

Thermal analysis of an LPV test-rig

Abstract A material property which is often used in the comparison and selection of polymer based materials used for dry rubbing journal bearings is the Limiting Pressure-Velocity (LPV) value. In a large pressure and velocity range this value is determined by the maximum temperature and compressive strength in the contact area. The temperature is related to the amount of heat generated in the contact area between shaft and bearing and the total thermal resistance from that contact area to the ambient atmosphere. This thermal resistance is therefore not only determined by the bearing itself but also by the assembly as a whole in which that bearing has been used. The LPV-value for a particular material measured on a particular test-rig is therefore dependent on the thermal resistance of that test-rig and cannot be compared directly with an LPV curve for that same material measured on another test-rig which has a different thermal resistance. In this paper a thermal model is used to calculate the heat generation and transport in an LPV test-rig and the results of this model are verified with some experiments. Furthermore it is shown how the material properties such as friction coefficient and melting temperature obtained by another material testing method viz the so-called Finger Print (FP), in combination with the calculated thermal resistance of the test-rig, can be used to predict LPV-values for a material on that test-rig.

Prototype Design of a High-Speed Viscous Air Spindle

In this paper an innovative air driven spindle for micro cutting applications is presented. The spindle uses a viscous traction concept which has the advantage that the viscous traction forces can act directly on the cylindrical part of the tool, which makes the tool-holder redundant. Furthermore, the tool can be actuated in the axial direction within the housing. In this paper the concept of the viscous turbine, a design of a prototype spindle along with the traction and load-capacity of the spindle are discussed.Copyright

Thermal network modelling of an LPV test-rig

A material property which is often used in the comparison and selection of polymer based materials used for dry rubbing journal bearings is the limiting pressure-velocity (LPV) value. In this paper the thermal network method (TNM) is used to model an LPV test-rig and the results of this model are verified with some experiments.

Optimization of Hydrodynamic Sliders for Multiple Operating Conditions

We present a new method to determine the film height distribution of the load-optimal hydrodynamic slider for multiple operating conditions. The use of the method is demonstrated in two examples, the second of which is based on the load conditions in an artificial hip-joint during a standard walking cycle. The results of this optimization may lead to an improved design of the replacement hip-joint, resulting in less wear and an improved lifespan.Copyright

An Investigation to the Effect of Elastic Deformations of the Bearing Surface of EP Air Bearings

In this paper a study is presented towards the effect of elastic deformation of the bearing surface of axial externally pressurized centrally pivoted modular air bearings. To this purpose shallow pocket, tapered and grooved air bearings are selected, which look the most promising to apply in small dimensions and with very small film thickness. The elastic deformation is calculated numerically by simultaneously solving the 2D-Reynolds equation for compressible fluids and the 3D-elasticity equation. The effect of the elastic distortion on the bearing performance is visualized in graphs presenting the load capacity and flow as a function of the film thickness. The results obtained from numerical calculation are verified experimentally.Copyright

An Investigation to the Design of Vacuum Preloaded Air Bearings With Respect to Reproducibility

Vacuum preloaded (VPL-) air bearings are generally designed by combining a collar bearing and a central area where vacuum is drawn (Figure 1). Sometimes the bearing area and vacuum area are separated by a groove which is connected to ambient pressure in order to prevent flow from the pressurized area to the vacuum ejected area. The collar bearing around the vacuum area is generally orifice compensated, compensated by a porous surface or by shallow grooves applied in the bearing surface. In this paper a study is presented towards the design of bearing configurations with the highest axial bearing stiffness that can be machined with good reproducibility. Various bearing configurations are analyzed analytically and numerically and the performance of the analyzed bearings are compared to each other.Copyright

Comparison Between Plain and Herringbone-Grooved Aerodynamic Journal Bearings

Aerodynamic journal bearings are commonly used to support high-speed rotors. In applications where the shaft rotates concentric, like turbines and high-speed spindles, grooved aerodynamic bearings are used because they can run concentric. Plain aerodynamic journal bearings are unstable in the concentric position and are therefore not used for these applications. The instability is caused by the 90° attitude angle of the plain bearing at low rotational speeds. However by increasing the rotational speed the attitude angle of the plain bearing approaches the attitude angle of the grooved bearing. Moreover up to a certain speed the load capacity of the plain bearing is higher than the load capacity found for grooved bearings. In certain circumstances plain bearings might be preferable, since the plain bearing is much easier to manufacture. In this work a comparison is outlined for the plain and herringbone grooved bearings.Copyright