1. A Project presentation on
Characterization of Anticlastic Effect
in Foil Air Bearings
Under the guidance of Mr. V. Ravi
Kumar
Kartik Babu BL.EN.U4MEE09027
Linto P Lalu BL.EN.U4MEE09031
Mohit Jain BL.EN.U4MEE09034
N M Amit BL.EN.U4MEE09035
2. What is a Bearing?
A bearing is a machine element which supports another moving
machine element (known as journal). It permits a relative motion
between the contact surfaces of the members, while carrying the load.
3. Introduction to Foil Air Bearings
Foil bearings were first developed in
the late 1950s by AiResearch Mfg. Co.
They were first tested for commercial
use in United Airlines Boeing
727 and Boeing 737 cooling turbines.
Most commonly used for high speed,
high temperature applications.
5. Disadvantages
Lower load carrying capacity than roller or oil bearings
Wear during start-up and stopping
High speed required for operation
Wobbling of the rotating element
6. Concept and Working
When shaft rotates, air pushes the
foil away from the shaft, so there is
no more contact.
The shaft and foil are separated by
the formation of air wedge.
No external pressurization system
required (i.e. Aerodynamic bearings).
7. Air Wedge Formation
For most fluids, with increase in operational
temperature there is a drop in viscosity.
Viscosity of air increases with increase in
temperature.
Air becomes viscous at the journal - foil
interface, increasing the load carrying
capacity.
8. Anticlastic Effect
When a plate is subjected to pure bending, the
strains developed in the direction of the load
develops a negative strain in the perpendicular
direction which is proportional to Poisson’s ratio
of the material. This negative strain develops a
bending moment in the direction perpendicular
to that of the applied bending. This bending in
the perpendicular direction to that of the applied
bending is termed as anticlastic effect. This
effects are also observed in beams.
9. Problem Definition
The foils on the bearing
can be modeled as a
cantilever with a UDL in
the direction perpendicular
to the surface of the
screen.
At high speed operation, the side profile of the foil gets
deformed which causes eccentric rotation of the journal in
the bearing resulting in shaft/journal wobbling.
11. The anticlastic effect on the bearing foil gets affected by
varying the following parameters:
Length
Width
Thickness
Parameters Effecting Anticlastic Effect
12. Analytical Simulation
Using the CAE software package ‘Ansys’ the model was simulated in the
following steps:
Preferences
Preprocessor
Element type
Material Properties
Sections
Modelling
Meshing
Loads
Solution
General Post Processor
31. Inference
Minimum deflections occur when the width is taken to be
equal to the length, i.e., when it approaches a ‘Square Profile’
Confirming results observed in length variation discussed
previously
37. Inference
When two separate bearings are utilized, the anti-clastic
deflection reduces drastically
Reduces wobbling of the journal.
38. Future Scope
Giving negative anticlastic curvature to the edge of foil plate.
Conducting fluid flow analysis to analyze the formation of air
wedge.
Using alternative alloys of superior properties to develop new
generation of foil air bearings
