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The demystification of bearing technology

The demystification of bearing technology

Dr. Henning Wittmeyer joined the SKF Engineering and Research Centre in 1978, serving as manager of process control, chief engineer of product development and quality, and managing director. He assumed the position of senior vice president, SKF Group Technology Development in 1998. Henning received a Master of Science in engineering physics from Chalmers University of Technology, Sweden in 1966 and obtained additional qualifications in mechanics and solid mechanics in 1971. He is a member of the Swedish Academy of Engineering Sciences, and a board member of the Association for Surface Chemistry Research.

Bearings were once a kind of black box for engineers-but not anymore. SKF's Henning Wittmeyer looks at some of the recent advancements in analysis tools and bearing development that are helping engineers more effectively apply the technology.

Design News: With new bearing analysis tools, are bearings becoming less of a mystery for engineers? How do these tools benefit design engineers?

Wittmeyer: Modeling and simulation are already shedding light on the internal workings of the bearings at impressive levels of detail that were hitherto not available because observation and measurements are notoriously difficult in the internal confines of the bearing. The BEAST is a dynamic bearing computer program that uses multibody models to compute the motions, forces, and stresses of the bearing components. This capability is exploited in designing optimum bearing geometries and cages, cage pockets, etc., as well as analyzing bearing behavior in real applications to optimize the bearing performance in the specific application.

Orpheus complements this capability in so far as it addresses, albeit with a somewhat simpler internal bearing model and no explicit cage model, the dynamic simulation of the bearing and the rest of the system together.

Q: What are the long-term implications for research SKF is conducting on the surface conditions of bearings, in particular the presence of grooves?

A: The long term implication of surface condition can be described as a dual approach to optimize the material in the surface region, notably through coatings, and to optimize the detailed topography of the surface for use in adverse lubrication conditions.

Q: Please describe some of the specific bearing materials research currently underway at ERC.

A: Specific bearing materials research is carried out in the modeling of the behavior of bearing steel in rolling contact fatigue. Here, the "aging," loss of strength, of the steel under the combined effects of temperature and stress is introduced, which is manifested by the observed microstructural alterations, and the reduction of bearing life due to different temperature and load can be calculated. The effects of the steel inclusions (i.e. steel cleanliness) are also accounted for, and application of this methodology allows for more advanced predictions of the bearing life. Spin-offs of this research are the prediction of the remaining bearing life in a specific application, and the future "design" of optimized steel for an application.

Q: How much do engineers need to know about bearings in order to apply them successfully?

A: All design work is a combination of technical and economical processes that will maximize some machinery performance parameters whilst certain constraints are fulfilled. Consequently, what engineers need to know about the bearings varies considerably-from the simple, standardized or bearing manufacturer catalogue bearing life calculations, in a non-demanding application for the bearing, to rather sophisticated knowledge of the effects of housing deformation on bearing life, or dynamic behavior in an application where the bearing is a critical component.

Q: What can we expect to see down the road?

A: The trend in increasing modeling capability, supported by better understanding of mechanisms that affect bearing performance, and computer power, will facilitate the future optimization of bearings in a customized application (e.g. steel selection, surface design), but one challenge here is that manufacturing delivers these bearings at a price that provides value to the customer and to SKF. A further challenge in the modeling is the integration of all the elements that make up a system, e.g. gearbox, to provide the overall optimal design as the interaction of the different parts is an inseparable part of the optimization.

This is just at the edge of the state of the art today. The effect of electronics on the traditional bearing is also an exciting prospect where sensors and intelligence will be used to relay information about the bearing, the machine the bearing is in, or the conditions being experienced in the application.

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