Plain Bearings pv value

[umatrix]

Hello All,

From Article :

https://www.machinedesign.com/bearings/how-pinpoint-best-plain-bearing

Know Your pV Value

The pV value—the pressure (p) multiplied by the speed of operation (V)—measures the ability of the bearing material to accommodate the temperature limit generated by the
frictional energy during operation. The pV value alone is only one-half of what is needed to achieve a stable temperature limit. Therefore, the solution pV will be multiplied
by two for a design pV value before comparing with a material’s pV rating.

Why is pV value one-half of what is needed to achieve a stable temperature limit?

 

[Pete_K]

That passage in the article is strangely-worded. I think they are just putting a safety factor on it...later on they say that if you run too close to the pv limit, the generated heat may have some undesired effect on the dimensions of the bushing.

To mention one-half of something, and then not explain what the other half is, is not great writing.

 

[umatrix]

Thanks Pete K.

I agree the writing could be improved. I also suspected a safety factor, i.e, doubling of the pv value.

However I found a source that added some confusion.
In the book:
Engineering Design with Polymers and Composites, Volume 1
By James C. Gerdeen, PhD, PE, James C. Gerdeen, Harold W. Lord, Ronald A.L. Rorrer, PhD, PE, Ronald A.L. Rorrer
P. 282

States: PV limit was determined by utilization of a shaft rotating in a half bearing.
The article goes on to say that currently, the PV limit is often determined by the use of
a thrust washer configuration.

This made me think that the Machine Design article could be referencing an older test method.

Thoughts ?

https://books.google.com/books?id=L...6AEIKDAA#v=onepage&q=pv value bushing&f=false