Friction coefficient for steel on steel with a water film between
Friction coefficient for steel on steel with a water film between
(OP)
Hi there,
I'm looking to find the friction coefficient for steel on steel with a water film between .
Any references ?
Thanks
I'm looking to find the friction coefficient for steel on steel with a water film between .
Any references ?
Thanks





RE: Friction coefficient for steel on steel with a water film between
Look up the "Inclined Plane Method" of measuring frictional coefficients in a statics reference book.
RE: Friction coefficient for steel on steel with a water film between
Some variables
1. smoothness(grove pattern from previous wear)
2. water content in steel wear groves
3. water viscosity - function of temperature of steel which will be a function of the energy in the friction which has already occured (time dependent).
4. steel to steel pressure
When automobile brakes are wet there is not much stopping power at all even with hydraulic assist.
Maybe the guys at www.cfd-online.com and the fluids group at eng-tips could help you further.
RE: Friction coefficient for steel on steel with a water film between
Actually, the coefficient is independent of force. The very nature of the inclined plane method shows this.
RE: Friction coefficient for steel on steel with a water film between
Do you mean dynamic friction? Seems like you could look at shear forces on water to determine the friction. Are you making water lubricated bearings?
RE: Friction coefficient for steel on steel with a water film between
oh yeah... I do that all the time...second time in here actually.
RE: Friction coefficient for steel on steel with a water film between
I'm asking for a co-worker and he wants this to calculate the force to move a piece of equipment made of steel piled on top of a similar piece of equipement stored underwater.
We understand that the steel/steel coefficient of friction will be different underwater because of the water film who act as a lubricant.
But we want to know how much it will affect !
RE: Friction coefficient for steel on steel with a water film between
Other than pumping a liquid film (hydrostatic similar to an air cushion vehicle)for this case
or depending on the geometery between the surfaces as in some bearings (where the rotating surface acts as a pump to maintain the film---
I don't believe you will be able to calculate that film thickness.
RE: Friction coefficient for steel on steel with a water film between
Force to move = .75 x weight of the top part.
This is form Standard Handbook for Mechanical Engineers, seventh edition, Baumeister & Marks
RE: Friction coefficient for steel on steel with a water film between
How thin is the film? Less than 0.05mm. Once fluid film state is reached, the friction approaches that achieved with ball bearings.
RE: Friction coefficient for steel on steel with a water film between
Your data point is for parts in vacuum, which is not applicable here. I question using a single data point with two decimal precision when there is no supporting specifications, testing, etc. for this precise condition.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Friction coefficient for steel on steel with a water film between
RE: Friction coefficient for steel on steel with a water film between
Friction is a very subject value. There is an error: Force to move =.74 x weight. In many cases when two item set any film between them migrates out leaving dry metal contact. We used this calculation with two decimal point precision when designing a 50,000 ft lb brake and were within 5% of design torque. This brake has aluminum bronze running against 4150 in an oil filled housing. The oil is forced out with the clamping pressure so a dry value was used.
RE: Friction coefficient for steel on steel with a water film between
Coef. of static friction
Iron iron - clean 1.0
- lubricated 0.08
Brake material on cast iron dry 0.4
wet 0.2
which references
The "Friction and Lubrication of Solids",Vol. I,by Bowden and Tabor, Clarendon Press,Oxford, 1950
RE: Friction coefficient for steel on steel with a water film between
RE: Friction coefficient for steel on steel with a water film between
Do some tests.
A few square inches of steel sections, with whatever surface treatment (or corrosion) is on the prototype, and a scaled load. A piece of string and a spring balance - voila!
Worth any amount of theoretical conjecture when there isn't enough data or the working environment is indeterminate.
Your wife may object to bits of rusty metal in the bath, though. (Sorry, that's not very PC)
Cheers - John