I was invited by Tom Astrene of TLT to write a response to the July 2010 TLT article (Ref. 1). My rebuttal — “In Search of a Fatigue Limit: A Critique of ISO Standard 281:2007” — was published in Tribology and Lubrication Engineering, TLT, August 2010 edition (Ref. 10). While this article is also available online, I will attempt to summarize the essence of my response.

Until now the estimation of rolling bearing life has been based on engineering models that consider an equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the rolling contact. Through the years, fatigue surface–originated failures, resulting from reduced lubrication or contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific failure modes originated directly at the surface of the rolling contact can be challenging. In the present article, this issue is addressed by developing a general approach for rolling contact life in which the surfaceoriginated damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is achieved by introducing a function to describe surface-originated failures and coupling it with the traditional, subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the new model and its general behavior. The ability of the present general method to provide an account for the surface–subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with reference to endurance testing data.

A nose-in-the-tent peek at the booths featuring mechanical motion components.

End users and OEMs frequently specify "lubed-for-life" mounted bearings, thinking the lubed-for-life bearings will deliver the same life — without lubrication — as bearings that currently require periodic lubrication. The truth is it depends on many factors, and only a detailed review of the application and testing will provide a more accurate answer.

Although David Korins had an impressive resume of Broadway, film, television and music credits, the New York-based production designer had something to prove when interviewing for the pop culture phenomenon Hamilton. “I prepped for the interview like crazy, sketching out my ideas, presenting a scene breakdown, basically doing everything I could short of begging for the job,” Korins said. “Lin Manuel Miranda (the show’s creator and star) had developed an incredibly effective blueprint. I just wanted the opportunity to help tell his story.”

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Often I get asked the generic question — “Which motor should I use?” But the answer is not quick or easy. The proper choice of the motor may ...