Rolling-Element Bearing Analysis

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.