effect of temperature on friction force or coefficient of friction 2

[yogidhanpal]

Hello,

i am working on modelling of friction in fem, i would like to know the exact influence of temperature on friction force. i.e how friction force varies with temperature. i will be thankful if u can provide me with some formula and graph.

if it is dificult to find with friction force, help me out with coefficient of friction.

thank you

 

[ione]

I think you'll have hard time to define a correlation being universally valid whatever couple of materials you take, at least from a quantitative point of view. One should carry out experiments over the temperature range of interest and for the specific couple of materials involved. Anyway, from a qualitative point of view, friction factor, and friction force accordingly, should increase with temperature up to a maximum and then decrease.

 

[zdas04]

I've got several points:
1. You are more likely to get meaningful answers if you ask meaningful questions. From your post I can't tell if you are interested in sliding friction between two solids, fluid friction lubricating two solids, or fluid friction in a conduit. The answer is different for each.
2. Posts on eng-tips.com are not limited to 160 characters--using text-speak and omitting capitalization really annoys many of the people most able to help you. You need to ask yourself "why risk the alienating the old farts with text-speak?". We may be dinosaurs, but we're the people who know what you need to find out.
3. Your post reads like a student question. Is it?

David

 

[bradleyelwood]

zdas04,

Let go easy on the issue of punctuation and capitals...but you are right about needing a little more information to give a meaningful answer.

The coefficient of friction changes quite a bit between 33 degrees F and 31 degrees F when there is water on the road, but I think all of us knew this already.

 

[Cockroach]

This is really a tough question, friction coefficient as a function of temperature. It is somewhat common place here in Canada, where seasonal variation has an enormous effect on something as simple as driving down the road.

From everyday experience, I think the relationship would be nonlinear and dependent somewhat on lubricity of materials at the contact point. For example, our drive down the roadway, suppose we enter a gradual turn like a turnpike entrance to a freeway. How would your speed vary with temperature, i.e. fish tail impending?

I would expect that in warm weather, you could probably do the posted limit, 60 km/hrs. But with dropping temperatures, your speed would need to be reduced because of the influence of rubber/road variations at the contact point. You would definitely need a handle on material behavior with temperature, i.e. rubber properties at temperature, pavement properties with temperature. That would be complex. Perhaps you could model it as an exponential decay, something along the lines as the rate of change is proportional to a percentage of friction coefficient at room temperature. That percentage could then be modeled experimentally with temperature, say a block on an incline plane, thermally controlled, vary inclination until motion impends.

Probably setting up an experiment for raw datum would be the best approach. I think it would be tough otherwise.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[corus]

It is a good question and is relevant to steel manufacture where particularly high temperatures can signifcantly affect mechanical behaviour. The only reference I found was Gwidon W. Stachowiak, Andrew William Batchelor, Engineering Tribology, Elsevier Publisher, 750 pages (2000), where it's claimed that an increase in temperature increases the friction coefficient. I think it may refer to tyres, or tires, where ever you come from.

Tara

http://tinyurl.com/4ydjg7m

 

[dvd]

Depending on the arrangement, increased friction as a function of temperature may really be more of a result of increased length/area/volume from thermal growth. If parts are constrained and there is thermal growth, there will be increased loading thus the friction coefficient may appear to increase.

 

[flash3780]

The topic of friction, in general, is a huge can of worms. The seemingly simple equation F = mu*N turns out to be quite complicated when you consider all of the things that can affect mu. The coefficient of friction will differ based on the lubricant (dry vs boundary lubrication), the load, the speed, the size of the contact area, the surface roughness, etc.

The best thing to do in a friction critical application is to match the variables to your situation and do a test. I think that there is some good information out there by Kraghelsky, but I don't have a copy. But, for what it's worth, I've been meaning to add the Handbook of Frictional Units of Machines to my library.

http://www.asme.org/products/books/handbook-of-frictional-units-of-machines

 

[racookpe1978]

And the response/feedback from the original poster is ...?

What would the effect then be between two (dry/lubricated) sliding surfaces between (identical/different) metals over a (small/very large) temperature difference? (I'm thinkning of Combustion Turbine mounts at ambient and 1300 operating temps for example, compared to a machines sliding lathe surface only raised 10 or 20 degrees?)