This article describes how more sophisticated
modeling techniques allow
the latest software to identify design
issues with bearings, shafts, gears and
complicated multi-body systems.
Bearings play an important role in
powertrain design. For example, in
modern transmission systems, there
are three major bearings that support
the main shaft from front to back. They
include the pilot bearing, the input
shaft bearing, and the rear support
(angular) bearing. The role of a pilot
bearing is to stabilize the nose end of
the main shaft and clutch disc with the
flywheel. If this bearing fails, this portion
of the shaft will be able to vibrate/
thrust up and down as the disc rotates.
This new clearance will allow the
clutch to engage at an axis that is no
longer centered along the line of power
flow, which can cause catastrophic
transmission element failure.
Because of the importance of the
bearing, the prediction and control of
rolling-element bearings on system
performance are becoming some of
the major concerns in powertrain design.
Important considerations include
how bearing clearance could affect the
gear mesh, how bearing stiffness could
impact the system natural frequency,
or how different bearing parameters
could change the stress distribution of
the rotating main shaft.

Multi-body dynamics software is
used to study the dynamics of moving
parts and to determine how loads and
forces are distributed throughout mechanical
systems. Multi-body dynamic
software like MSC Software’s Adams is
usually applied to model and analyze
the powertrain systems by engineers
at major OEMs. However, due to the
complication of the bearing model itself,
a “bushing element” is usually applied
to represent the bearing model.
While the bushing element plays a decent role in constraining relative motion
between different parts, it lacks
the fidelity of incorporating most of
the bearing properties and limits engineers’
ability to study how different
bearings would impact the transmission
system performance.

MSC Software has recently released
a new member of the Adams family,
Adams/Machinery, which is a set
of productivity modules with the capability
for wizard-based modeling
and adjustable-fidelity simulation of
common mechanical subsystems and
components, including belts, chains,
gears and bearings.