ESDU 00015:2010

INTRODUCTION

This Data Item describes the use of ESDUpac A0015 which provides
a computer program for analysing a disc cam/follower system. The
program allows the following tribological aspects to be
examined.

• The surface and sub-surface stresses at the contact between
the cam and follower.

• The lubricant film thickness generated between the cam and
follower.

• The transient temperature rise ("flash" temperature) in the
contact between the cam and follower.

• The driving torque and power loss of the cam.

• The life of a rolling element bearing follower.

The program determines the contact loads, with or without
friction, in the operating cam/follower system and then determines
the instantaneous contact dimensions, gross deflection (normal
closure) and contact stresses. The program locates the critical
stress points with respect to three criteria involving yield
failure, brittle failure and fatigue failure.

Where a Newtonian liquid lubricant is present, the program can
be used to predict the film thickness of the lubricant entrained
into the contact. Computation of this lubricant film thickness
includes an allowance for squeeze film effects at the points in the
cam cycle where the entrainment velocity reverses.

Six types of cam follower are considered including both
translating and swinging versions of flat-faced, domed, and roller
followers. Also, follower motions involving any number of blended
cam law portions can be analysed. The cam law of each portion can
be selected from a supplied database of cam law expressions or can
be specified by the user. The follower load, arising from spring
closure or a process load, can similarly be selected from a
database or be specified by the user.

Computer parameters of interest can be logged over a full, or
partial, cycle of cam rotation and the values recorded in a file
suitable for plotting. Alternatively, a single instantaneous point
in the cycle can be examined in more detail and stress distribution
contours, for example, examined.

This Data Item documents the specification of input data for the
program and describes the various output data that can be obtained.
Guidance on interpretation of the output data is given in further
Data Items devoted to specific tribological aspects. Guidance on,
and methods for, the design of cams can be found in the ESDU
Mechanisms Series (see Section 11). ESDUpac A0015 allows the direct
import of motion data from many of the Mechanisms Series computer
programs (see Section 4.2).

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