ESDU 85027:2010

INTRODUCTION

This Item provides charts and calculation methods for
determining the minimum lubricant film thickness in concentrated
contacts that occur, for example, in rolling bearings and gears; in
such contacts, often called Hertzian contacts, the nominal contact
area increases with applied load.

For the purpose of calculating the lubricant film thickness,
Hertzian contacts are regarded as either two-dimensional, with
nominally line contact, or three-dimensional, with nominally point
contact. Nominally line contact occurs in, for example, roller
bearings, roller followers on cams and spur gears while
three-dimensional contacts occur in, for example, ball bearings.
The charts and calculation methods presented in this Item apply to
two-dimensional contacts. It is frequently possible to obtain
guidance on some three-dimensional contacts using these methods
(see Section 4).

The text of this Item is divided into three main parts. The
first part (Section 3) describes the operation of a lubricated
Hertzian contact. The second part (Sections 4 and 5) gives guidance
on the specification of the design parameters, identification of
the regime of operation and determination of the film thickness.
The final part gives guidance on ensuring that the contact will
operate with an adequate margin of safety.