EHL

[MolaKule]

Before the new Semester shifts into high gear, here is a new QOTD:

EHL, or ElastoHydrodynamic Lubrication films, less than 1 micron thick, are the main lubricant regimes in non-conformal contacts common in Wind Turbines.

EHL films are less effective under transient loading, start-stop operations, and slow speed.

Define EHL:

This Question of the Day is open only to non-scientific disciplines so regular membership will have a chance to research it and respond.

 

[blingo]

EHL is where the MOFT ideas are more precarious than usual, the metal crusts creak and the PIB as always shines.

 

[MolaKule]

Hint.

A potential response might include the effect of mechanical deformation on materials such as bearings.

 

[bruce381]

As the name suggests EHL is lubrication regime that occurs only in very high contact areas such as roller bearings or gear teeth.
With loads so high that deformation of the metal elements can occur.

Under this condition an oil film that is trapped in such contact zones will increase in viscosity to perhaps almost a solid, keeping surfaces from touching.

This was drilled into me 30-40 years ago By Douglas Godfrey STLE Fellow and Chevron researcher.

 

[bruce381]

EHL I thought was conterintuitive is that you would think a oil would squish out under high loads but EHL regime the oil could impart the load enough to dent roller bearing races

 

[DriveHard]

EHL I thought was conterintuitive is that you would think a oil would squish out under high loads but EHL regime the oil could impart the load enough to dent roller bearing races

Bruce, I think you are on the right track, but not entirely accurate. As a former Timken engineer, I can't comment on the answer as per MolaKule's rules, but the definition is simpler, and you won't dent a bearing race surface if you have true EHL. Yes, the roller and race surface will elastically deform under this regime, but there is not permanent damage or dents.

 

[bruce381]

I remmeber some deformation perhaps micro cracks?

 

[MolaKule]

The Question of the Day (QOTD) was limited to non scientific disciplines to allow members to do their own research and to respond.

Many times the QOTD is open to all so those with scientific or engineering backgrounds can also respond.

People with scientific backgrounds often jump in with answers before non-technical people can answer, so some QOTD questions have to be limited to a specific group.

Here is a good reference to EHL:

Elastohydrodynamic Lubrication (EHL): Theory and Definition - About Tribology

www.tribonet.org