There exists an ongoing, urgent need for a rating method to assess micropitting risk, as AGMA considers it a "a very significant failure mode for rolling element bearings and gear teeth - especially in gearbox applications such as wind turbines."

This review of elastohydrodynamic lubrication (EHL) was derived from many excellent sources (Refs. 1–5). The review of Blok’s flash temperature theory was derived from his publications (Refs. 6–9). An excellent general reference on all aspects of tribology is the Encyclopedia of Tribology (Ref. 10).

I have heard that X-ray diffraction does not tell the whole story and that I should really run a fatigue test. I understand this may be the best way, but is there another method that gives a high degree of confidence in the residual stress measurement?

I must confess I sometimes find myself a bit dazed when discussing lubrication issues with either staff or vendors. The terminology seems to be all over the lot, with some terms having double meanings. Can you help cut through the confusion?

For maximum life in carburized and ground gearing, I have been advised that fully grinding a radius into the root gives maximum resistance against fatigue failures. Others have advised that a hobbed and unground radius root form is best. Which is best, and why?

A reader asks about how to specify a method of lubrication for a speed reducer with a three-stage helical gear with a low peripheral speed.

Understanding the morphology of micropitting is critical in determining the root cause of failure. Examples of micropitting in gears and rolling-element bearings are presented to illustrate morphological variations that can occur in practice.

Review of "Gigacycle Fatigue in Mechanical Practice," by Claude Bathias and Paul C. Paris

I. Inspect failed components as soon as possible. If an early on-site inspection is not possible, someone at the site must preserve the evidence based on your instructions.

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